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KANG Donghyuk
| Mechanical Science Division | Associate Professor |
| Department of Mechanical Engineering and System Design |
- E-Mail：dhkang
mail.saitama-u.ac.jp - Home Page:
Performance information
■ Paper- 高速気流による単一液滴微粒化の時空間データ分析—Spatio-Temporal Data Analysis of Single Droplet Breakup by High Velocity Gas Flow—論文特集 混相流研究の進展(3)
岩崎 航大; 朝原 誠; 宮坂 武志; 姜 東赫
Volume：38, Number：3, First page：305, Last page：318, Sep. 2024, [Reviewed]
Japanese
ISSN：0914-2843, CiNii Books ID：AN10088286 - Experimental and Numerical Evaluations of Dynamic Transfer Matrix for a Three-Dimensional Centrifugal Impeller Based on Unsteady Energy Conservation
Kambayashi Izuru; Dou Chengye; Donghyuk Kang
Journal of Fluids Engineering, Transactions of the ASME, Volume：146, Number：9, Sep. 2024, [Reviewed]
Under unsteady operating conditions in turbomachinery, the performance is unable to respond rapidly enough to follow characteristic curves for the steady condition. To design a reliable turbomachinery under unexpected unsteady conditions, we evaluated the dynamic transfer matrix of a three-dimensional centrifugal impeller. The working fluid is incompressible air. To make the current results more applicable in a broader sense such as pumps, all parameters and results were normalized. The experimental results showed a more significant negative slope in the unsteady performance curve compared to that in the steady performance curve. This was mainly caused by the phase delay of the pressure rise to the pulsating flowrate. We clarified the changes in gain and phase delay under unsteady conditions by conducting numerical simulations. The numerical results showed that the unsteady pressure rise was primarily generated by inertia and power terms in the unsteady energy conservation equation. The power term was predominantly influenced by the angular momentum flowrate difference and the change rate of angular momentum. Each term was quantitatively evaluated, and its contribution to the unsteady pressure rise was discussed. Within the range of frequencies tested in this study, the transfer matrix for the threedimensional centrifugal impeller could be effectively approximated through a first-order lag approximation considering a series-connected derivative system. We believe that our findings can be extended to centrifugal pumps when disregarding the compressibility effects such as cavitation.
Scientific journal
DOI：https://doi.org/10.1115/1.4064996
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DOI ID：10.1115/1.4064996, ISSN：0098-2202, eISSN：1528-901X, SCOPUS ID：85189932164 - Effect of Plane Walls on Flow Characteristics of Primary Jets Controlled by Secondary Flow
H. Tezuka; K. Yabu; K. Nishibe; D. Kang; K. Sato
Journal of Research and Applications in Mechanical Engineering, Volume：12, Number：2, Jun. 2024, [Reviewed]
The method for controlling the direction of primary jets by secondary flow is called fluid thrust vectoring. It was originally studied for application in aircraft attitude control, where it was expected to reduce fuel consumption and improve motion performance. It has been demonstrated that the direction of the primary jet can be adjusted by adjusting the momentum of the secondary flow generated near a curved surface (Coanda surface), such as a cylinder. However, there is limited research applying the abovementioned method to fields such as aviation for flows other than external flows. To use this method for internal flows, such as airflow control in a room, knowledge of the geometric boundaries near the jet flow is required. That is, the interference problem between the jet and wall boundaries must be investigated to realize jet direction control using secondary flows in various fields. Thus, this study investigated the effects of wall length and step height (offset ratio) on the flow characteristics of jets controlled by secondary flow near the Coanda surface. Typical flow patterns are presented in this paper, and the jet deflection characteristics are discussed primarily through flow visualization and velocity distribution measurements.
Scientific journal
DOI：https://doi.org/10.14456/jrame.2024.24
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DOI ID：10.14456/jrame.2024.24, ISSN：2229-2152, eISSN：2697-424X, SCOPUS ID：85199424019 - Characterization of hydrogen jets considering leakage from high-pressure storage tanks using shadowgraphy
Makoto Asahara; Kazuma Iwatsuki; Donghyuk Kang; Izuru Kambayashi; Tei Saburi; Kodai Iwasaki; Takuma Uehara; Takeshi Miyasaka
International Journal of Hydrogen Energy, Volume：61, First page：1456, Last page：1472, Apr. 2024, [Reviewed]
The unsteady characteristics of pinhole-ejected ultrahigh-pressure hydrogen jets in the near field are investigated by the PIV and FFT-IFFT analysis of time-series shadowgraph images. Hydrogen stored at a maximum pressure of 99 MPa is ejected through pinholes of varying diameters. The fluctuating components caused by turbulence are removed to identify the barrel shock within the high-pressure hydrogen jets. The relationship between the Mach disk height and pressure ratios obtained through time averaging aligns with the Mach disk height measured in experiments involving non-hydrogen gases under low ambient pressure. The obtained results exhibit similarities to the time-averaged velocity observed in the far field, suggesting the feasibility of utilizing SIV to analyze jet velocity characteristics in the near field. By applying IFFT analysis, the spatiotemporal information of these components is reintegrated into the field, enabling separate identification and demonstration of the turbulent components comprising the high-pressure hydrogen jet.
Scientific journal
DOI：https://doi.org/10.1016/j.ijhydene.2024.02.074
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DOI ID：10.1016/j.ijhydene.2024.02.074, ISSN：0360-3199, SCOPUS ID：85187216786 - Flow deflection characteristics of two-dimensional synthetic jets generated from asymmetric stepped slots
Kaito SUZUKI; Takaya HIRUMA; Takumi ITO; Koichi NISHIBE; Donghyuk KANG; Kotaro SATO
Journal of Fluid Science and Technology, Volume：19, Number：3, First page：JFST0022, Last page：JFST0022, Apr. 2024, [Reviewed]
This study examines the behavior of two-dimensional synthetic jets generated from asymmetric stepped slots, focusing on the formation of recirculation regions and jet deflection near the slot. The effects of step length and frequency on the behavior of the jets were investigated. Experiments were conducted at a constant Reynolds number (Re = 1000), with varying frequencies. A speaker was used to generate the synthetic jet. Particle image velocimetry (PIV), which employed images captured via the smoke-wire method, was used to analyze flow patterns. To evaluate jet deflection, velocity distributions were measured using a hot-wire anemometer in selected cases. This study discusses the onset conditions of the recirculation region and the deflection mechanism, examining their relationship with jet deflection, dimensionless frequency, and dimensionless step length. The key findings indicate that jet deflection, associated with the recirculation region size, is influenced by both the dimensionless step length and frequency. The jet exhibits a straight flow when the dimensionless step length is either extremely small or large. Moreover, to minimize the size of the recirculation region, larger dimensionless step lengths require smaller dimensionless frequencies. Additionally, the study establishes a flow similarity rule within the tested conditions, employing the stroke length of the synthetic jet as a representative length.
The Japan Society of Mechanical Engineers, English, Scientific journal
DOI：https://doi.org/10.1299/jfst.2024jfst0022
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DOI ID：10.1299/jfst.2024jfst0022, eISSN：1880-5558, SCOPUS ID：85192965578 - On the interaction of two cavitation bubbles produced at different times: A jet from the primary bubble
Shingo Terasaki; Akihito Kiyama; Donghyuk Kang; Yukio Tomita; Kotaro Sato
Physics of Fluids, Volume：36, Number：1, Jan. 2024, [Reviewed]
The liquid jet formation upon the collapse of two interacting cavitation bubbles is a physics-rich complex problem, which has possible implications such as the membrane sonoporation. In this paper, we employed both experiment and numerical simulations to study the jet behavior in a bubble, which is affected by another one introduced at various time delays. We provided the regime diagram, which shows the transition of the jet direction as a function of time delay and distance between bubbles. The maximum velocity of the jet in the primary bubble was investigated. The highest velocity was achieved when the primary bubble split into two parts upon collapse. It was found that a high curvature on the rim of the collapsing primary bubble causes the lateral pinch-off, leading to the formation of a fast and thin vertical jet approaching the secondary bubble. The results would help design an effective sonoporation system. The physics depicted in this manuscript might also contribute to the deeper understanding of the jet in a bubble interacting with not only another bubble but also other boundaries.
Scientific journal
DOI：https://doi.org/10.1063/5.0180920
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DOI ID：10.1063/5.0180920, ISSN：1070-6631, eISSN：1089-7666, SCOPUS ID：85182279485 - Feedback Control of Unsteady Flow Around a Cylinder Located in Uniform Flow Using Dynamic Mode Decomposition with Control
KAMBAYASHI Izuru; KAWASAKI Narumichi; KANG Donghyuk
Turbomachinery, Volume：51, Number：12, First page：741, Last page：748, Dec. 2023, [Reviewed]
We conducted dynamic mode decomposition control (DMDc) to suppress the unsteady flow for a cylinder located in uniform flow and verified the results via computational fluid dynamics. The separation point was controlled by the blowing and suction generated from the cylinder surface, resulting in reduced lift oscillation. The unsteady flow around the cylinder located in uniform flow can be qualitatively estimated and controlled using DMDc.
Turbomachinery Society of Japan, Japanese
DOI：https://doi.org/10.11458/tsj.51.12_741
DOI ID：10.11458/tsj.51.12_741, ISSN：0385-8839, eISSN：1880-2338, CiNii Books ID：AN00004836 - Flow characteristics of two-dimensional impinging synthetic jets
Michiya YASUMIBA; Koichi NISHIBE; Donghyuk KANG; Kotaro SATO
Journal of Energy Systems, Volume：7, Number：4, First page：327, Last page：338, Dec. 2023, [Reviewed]
English, Scientific journal
DOI：https://doi.org/10.30521/jes.1316559
DOI ID：10.30521/jes.1316559, eISSN：2602-2052 - Unified Performance Model for S-Shaped Characteristics of Pump–Turbines Considering Reverse Flow
Donghyuk Kang; Wakana Tsuru; Ono Koudai; Kazuhiko Yokota
International Journal of Fluid Machinery and Systems, Volume：16, Number：1, First page：129, Last page：139, 2023, [Reviewed]
This study proposes a new unified performance model for the S-shaped characteristics of pump–turbines considering reverse flow. The turbine and reverse pump characteristic equations were unified using a sigmoid function considering the reverse flow. In the analysis, the torque coefficient is larger for small guide vane angles than for large guide vane angles due to an increase in the turbine Euler head. In the turbine mode, the runner shock loss and the circumferential discharge loss are directly proportional to the shock dynamic pressure and the circumferential dynamic pressure in the discharge section, respectively. In the reverse pump mode, the guide vane shock and friction losses are directly proportional to the shock dynamic pressure and the absolute dynamic pressure, respectively. The S-shaped characteristics of pump–turbines can be completely simulated using the proposed theoretical model.
Turbomachinery Society of Japan, Korean Society for Fluid Machinery, Chinese Society of Engineering Thermophysics, IAHR, English, Scientific journal
DOI：https://doi.org/10.5293/IJFMS.2023.16.1.129
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DOI ID：10.5293/IJFMS.2023.16.1.129, ISSN：1882-9554, eISSN：1882-9554, SCOPUS ID：85153566378 - Influence of Amplitude of Excited Secondary Flow on the Direction of Jets
Qiang ZHANG; Yu TAMANOI; Donghyuk KANG; Koichi NISHIBE; Kazuhiko YOKOTA; Kotaro SATO
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, Volume：66, Number：2, First page：37, Last page：45, 2023, [Reviewed]
In this research, a method for direction control of a primary jet with a Coanda surface is investigated as part of a fundamental study of fluidic thrust vectoring. The effect of the velocity amplitude ratio (i.e., ratio of time-averaged velocity to velocity fluctuation amplitude) of the secondary flow on the flow characteristics of the jet was experimentally investigated. It was determined that the jet deflection angle was maximized under the suction condition wherein the secondary flow exhibited velocity fluctuation. The relationship between the jet deflection angle and the momentum ratio between the primary jet and the secondary flow is presented, in which the dimensionless frequency of the secondary flow was used as a parameter. Although the jet deflection angle depended on the dimensionless frequency and the momentum ratio, it was difficult to adjust this parameter using only the momentum ratio in the hypothetical saturated region where this ratio is large. In addition, unsteady characteristics were also discussed for several conditions.
Japan Society for Aeronautical and Space Sciences, English, Scientific journal
DOI：https://doi.org/10.2322/tjsass.66.37
DOI ID：10.2322/tjsass.66.37, ISSN：0549-3811, eISSN：2189-4205 - 旋回キャビテーションの三次元数値計算—Three-Dimensional Calculation of Rotating Cavitation—特集 ターボ機械における流体力学的不安定現象の数値予測(2)
姜 東赫
Volume：50, Number：4, First page：214, Last page：221, Apr. 2022, [Reviewed]
Japanese
ISSN：0385-8839, CiNii Books ID：AN00004836 - Stability Analysis of Cavitation Surge in Hydraulic System Considering Response Delay of Cavitating Pump
Kanata Nemoto; Donghyuk Kang; Izuru Kambayashi; Wakana Tsuru; Satoshi Watanabe; Kazuhiko Yokota
International Journal of Fluid Machinery and Systems, Volume：15, Number：4, First page：401, Last page：410, 2022, [Reviewed]
Cavitation surge is a system instability caused by mutual interference between cavitation and a hydraulic system. A stability analysis for the cavitation surge was performed based on the unsteady characteristics of the cavitating pump, that is, the response delay of the pressure rise against the suction and discharge flow and suction pressure oscillations. Ordinary differential equations were derived from linear unsteady momentum and continuity equations, and the simplified-derived ordinary differential equations clearly show the onset criteria of stability and dynamic instabilities. The relatively short discharge and large suction pipe loss had a stabilizing effect on the cavitation surge. The positive quasi-steady suction and discharge flow gains as well as the negative quasi-steady suction pressure gain cause surge instability. The phase advance of the pressure rise against the flow and pressure oscillations also leads to surge instability.
Turbomachinery Society of Japan, Korean Society for Fluid Machinery, Chinese Society of Engineering Thermophysics, IAHR, English, Scientific journal
DOI：https://doi.org/10.5293/IJFMS.2022.15.4.401
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DOI ID：10.5293/IJFMS.2022.15.4.401, ISSN：1882-9554, eISSN：1882-9554, SCOPUS ID：85140368862 - Proposal of Design Method for Viscous Micropumps with a Rotating-Disk Using Theory and Simulation
Wakana Tsuru; Donghyuk Kang; Kotaro Sato; Kazuhiko Yokota
International Journal of Fluid Machinery and Systems, Volume：15, Number：1, First page：1, Last page：14, 2022, [Reviewed]
The aim of the present study is to treat circular-and spiral-shaped viscous micropumps unitarily and provide guidelines for determining the appropriate micropump for performance requirements. Three-dimensional theoretical equations applicable to circular-and spiral-shaped micropumps were derived. Numerical simulations were also performed, and the results were compared with the theoretical results. The results were qualitatively consistent. By comparing the performances of the two micropumps, the spiral-and the circular-shaped micropumps are suitable in the ratio of outermost diameter to channel width c* < 0.2, and c* > 0.2, respectively. The theoretical performance for rotating disk-type micropumps was expressed in a unified manner. Furthermore, the design guideline was provided based on the theoretical method.
Scientific journal
DOI：https://doi.org/10.5293/IJFMS.2022.15.1.001
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DOI ID：10.5293/IJFMS.2022.15.1.001, eISSN：1882-9554, SCOPUS ID：85124559398 - Theoretical, Numerical, and Experimental Study on an Unsteady Venturi Flowmeter for Incompressible Flows
Izuru Kambayashi; Donghyuk Kang; Naoki Nishimura
Journal of Fluids Engineering, Transactions of the ASME, Volume：143, Number：2, First page：021308, Feb. 2021, [Reviewed]
To examine the dynamic characteristics of turbomachinery and cavitation, the pulsating flow rates should be evaluated. As it is difficult to measure these pulsating flow rates quantitatively, systematic research has not been conducted on the dynamic characteristics of turbomachinery and cavitation. In this paper, an unsteady energy equation for a venturi tube has been proposed to measure pulsating flow rates. The pulsating flow rates were calculated using two methods based on the unsteady energy equation for incompressible flows. The first method calculated a pulsating flow rate by using the Euler method. The second one calculated the complex amplitude of a pulsating flow rate using a transfer function derived from the linearized unsteady energy equation. We analytically examined the order of magnitude for unsteady terms. The results indicated that the unknown unsteady loss was much smaller than the unsteady momentum. In the experiment, pulsating flows were generated by a reciprocating piston, and the given pulsating flow was measured using a hot wire anemometer. The pulsating flow rates evaluated by using the proposed methods were validated via numerical simulation and experiment. In particular, the influence of amplitudes on the evaluation of pulsating flow rates was numerically examined. Therefore, the nonlinear effect could be evaluated by using the proposed method, and the time-averaged loss coefficient was enough to evaluate the pulsating flow rate coefficient. The proposed unsteady venturi flowmeter can be applied to a wide range of research fields, such as analyzing dynamic characteristics of flows.
Scientific journal
DOI：https://doi.org/10.1115/1.4048689
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DOI ID：10.1115/1.4048689, ISSN：0098-2202, eISSN：1528-901X, SCOPUS ID：85101647544 - Validation of a super-resolution measurement using frequency filtering technique and optical displacement analysis of bubble surface in breathing mode oscillation
OKU Takao; HIRAHARA Hiroyuki; KANG Donghyuk
Transactions of the Visualization Society of Japan, Volume：41, Number：3, First page：1, Last page：10, 2021, [Reviewed]
A sound is generated when a bubble detaches from a nozzle installed in the water. The sound emission is known as a monopole sound source. This frequency is expressed by Minnaert's equation, and many studies have been conducted on bubble deformation, detachment, and coalescence. However, many physical processes still involve the unsettled phenomena regarding the mechanical behavior of the sound source. In this study, we report that the breathing mode was directly analyzed by an optical measurement, following the simulation of the breathing mode by CFD in the previous report. The present super-resolution measurement gives a sufficient result to discuss the oscillatory motion of bubble surface where the displacement of the bubble is so small that the normal observation cannot capture. In the present research, the numerical simulation of the measurement method was conducted, and measurement of the vibration disc were performed as the preliminary experiments. Thus, the optimum measurement parameters were extracted, and they were applied to the displacement measurement of the breathing mode of the bubble. The results show a good agreement with the CFD ones.
The Visualization Society of Japan, Japanese
DOI：https://doi.org/10.3154/tvsj.41.1
DOI ID：10.3154/tvsj.41.1, eISSN：1346-5260, CiNii Articles ID：130008031841 - Performance Degradation and Flow Instability of Axial-Flow Fan Due to Upstream Obstacle
Donghyuk Kang; Takeru Shinohara; Shinsaku Nakamura; Koichi Nishibe; Kotaro Sato; Kazuhiko Yokota; Hiroshi Ohue
Journal of Fluids Engineering, Volume：142, Number：9, Sep. 2020, [Reviewed]
Abstract
This paper elucidates the performance degradation and flow instability of an axial fan caused by the presence of disk-shaped obstacles upstream of the fan, such as wall surfaces. The increase in pressure loss and the decrease in shaft power coefficient due to inlet swirl flow, and the increase in pressure loss due to the outlet swirl flow, cause performance degradation. When the obstacle is closer to the fan, the strong swirl flow causes a negative pressure region between the fan and the obstacle, reversing the flow direction. This phenomenon is caused by the diffuser effect of the outward flow and the increase in pressure by acting as a multiblade centrifugal fan. At a low flow rate, a clockwise vortex is generated at the center of the obstacle and induces two counterclockwise rotating vortices. The vortices circumferentially separate the inward and outward flows along the fan's axis in a uniform manner, and their cores are circularly rotated by the clockwise vortex. These findings can contribute to the layout of fans under spatial restriction and suppression of flow instability due to obstacles.
ASME International, Scientific journal
DOI：https://doi.org/10.1115/1.4047535
DOI ID：10.1115/1.4047535, ISSN：0098-2202, eISSN：1528-901X - A Study on the Process of Low-Frequency Noise Generation in a Multi-Blade Centrifugal Fan
Kawasaki Masatoshi; Hirahara Hiroyuki; Kang Donghyuk
International Journal of Fluid Machinery and Systems, Volume：13, Number：2, First page：292, Last page：301, 2020, [Reviewed]
This study numerically investigates the flow characteristics of a multi-blade centrifugal fan in order to identify the process of low-frequency aerodynamic noise generation. Computational analysis has been carried out using the large eddy simulation (LES) model. In the preliminary study, it was confirmed that the present computational fluid dynamics simulation using LES shows good agreement with the experimental results of the performance curve, sound pressure spectra, and the flow field obtained by using a time-resolved particle image velocimetry (PIV) system. Consequently, it was found that the appearance of an unexpected significant flow, which recirculated from the scroll casing, passed through the impeller, and returned to the scroll casing again to exit the scroll casing in a specific region, was similar to the flow suggested in the experimental results, which were obtained utilizing PIV measurement. The fluid flow related to the fluctuation, which was remarkably not included in the impeller main flow, existed beside the outer main flow. A certain amount of fluctuated flow bifurcated near the scroll end, one regurgitating into the impeller, and another colliding with the tongue. The former became a driving source of noise and the latter a direct noise-generating factor. Consequently, it was demonstrated that a significant fluctuation owing to flow collision with the tongue propagated through the impeller and formed a loop.
Turbomachinery Society of Japan, Korean Society for Fluid Machinery, Chinese Society of Engineering Thermophysics, IAHR, English
DOI：https://doi.org/10.5293/ijfms.2020.13.2.292
DOI：https://doi.org/10.1115/1.4048689_references_DOI_MLNoIyQJmVuE0O2tG6yL1dVi0ll
DOI ID：10.5293/ijfms.2020.13.2.292, eISSN：1882-9554, CiNii Articles ID：130007834380 - Jet vectoring using secondary Coanda synthetic jets
Ryota KOBAYASHI; Yuki WATANABE; Yu TAMANOI; Koichi NISHIBE; Donghyuk KANG; Kotaro SATO
Mechanical Engineering Journal, Volume：7, Number：5, First page：20, Last page：00215, 2020, [Reviewed]
In recent years, studies on the fundamental principle of thrust vectoring using jets have been conducted to realize next-generation aircraft applications. Various methods for vector control of jet flow have been proposed, such as methods that achieve control via steady, continuous jets under the Coanda effect, steady suction flows near the Coanda surface, and synthetic jets from a neighbor slot as secondary jets. However, there are no studies on the flow direction control of jets using the secondary synthetic Coanda jet. In this study, the influence of synthetic jets near a circular cylinder on the flow characteristics of a primary jet was experimentally investigated. The main results obtained in the study were that the direction of the primary jet flow can be controlled using the secondary synthetic jet, and the degree of jet deflection depends on the frequency of the velocity oscillation for the secondary synthetic jet under an identical momentum ratio. Furthermore, when using the synthetic jet as the secondary flow, a controllable region larger than that obtained when using a steady and continuous injection or suction flow is expected. This is because secondary flow is generated using the ratio of the momentum between the primary jet and the secondary flow at the slot exit in conjunction with the dimensionless frequency of the synthetic jet based on the velocity of the primary flow at the slot exit.
Japan Society of Mechanical Engineers, English, Scientific journal
DOI：https://doi.org/10.1299/mej.20-00215
DOI ID：10.1299/mej.20-00215, eISSN：2187-9745, CiNii Articles ID：130007926527 - Experimental Investigation of Fluid Mixing Process with Newly Designed Conduit-Type Mixer and Fin-Type Mixer
Md. Tauhedul Azam; Donghyuk Kang; Hiroyuki Hirahara; Kazuhisa Murata; Yasufumi Shimoji
Volume：07, Number：02, First page：101, Last page：110, 2019, [Reviewed]
DOI：https://doi.org/10.4236/jfcmv.2019.72008
DOI：https://doi.org/10.1299/jfst.2019jfst0010_references_DOI_UP6skvCKpmO31bZrImZuIWGL82E
DOI ID：10.4236/jfcmv.2019.72008, ISSN：2329-3322, eISSN：2329-3330 - Enhancement of rotating jet by spirally structured vortex tube in centrifugal bladeless mixer flow
AZAM Md. Taurhedul; KANG Donghyuk; HIRAHARA Hiroyuki; MURATA Kazuhisa; SHIMOTSUKASA Yasufumi
Journal of Fluid Science and Technology, Volume：14, Number：2, First page：JFST0010, Last page：JFST0010, 2019, [Reviewed]
The flow characteristics in a centrifugal bladeless mixer were investigated by using particle image velocimetry (PIV) and large eddy simulation (LES). The numerical result is compared with experimental one in terms of the phase-averaged velocities in radial and tangential directions. The result was analyzed by comparing with that of a conventional flat-blade mixer. A spirally structured vortex tube pair was observed around the centrifugal bladeless rotor. In a vertical cross-section of the spirally structured vortex tube pair, a zigzag street of counter-rotating vortices like a reverse von Kármán vortex street was formed. It was found that the rotating jet flow was enhanced by the reverse von Kármán vortex street of the spirally structured vortex tube pair. Furthermore, the sustained rotating jet flow constructed a couple of large toroidal structured vortex tube near the tank wall. The large toroidal structured vortex caused a wider circulation in the stirred tank, which was advantage to stir the fluids over the whole field.
The Japan Society of Mechanical Engineers, English
DOI：https://doi.org/10.1299/jfst.2019jfst0010
DOI ID：10.1299/jfst.2019jfst0010, eISSN：1880-5558, CiNii Articles ID：130007732306 - Time Resolved PIV Analysis for Low Frequency Noise Generated at Low Flow Rate Mode of Multi-Blade Centrifugal Fan
KAWASAKI Masatoshi; HIRAHARA Hiroyuki; YAUCHI Yuki; KANG Donghyuk
Turbomachinery, Volume：47, Number：4, First page：208, Last page：218, 2019, [Reviewed]
A noise problem at a low flow rate of multi-blade centrifugal fan was investigated experimentally in terms of low frequency fluctuation in flow by using a time resolved PIV. The present PIV equipment makes blade by blade passing observation be possible to detect the low frequency velocity fluctuation without blade passing fluctuation, because the data acquisition rate was set equivalent to BPF. The experimental results show that the flow at the impeller outlet has a large fluctuation locally, in the present case, at the scroll angle θ=120°. This fluctuated flow was transported to the downstream in the scroll casing, which passed along the outside of the main flow exited from the impeller. This fluctuated flow was divided into a reverse flow to the impeller and a flow towards tongue in the vicinity of the scroll exit. The reverse flow returned again near θ=120° through the impeller towards the scroll casing. Thus, it was confirmed that the low frequency noise was generated due to this circulating fluctuation.
Turbomachinery Society of Japan, Japanese
DOI：https://doi.org/10.11458/tsj.47.4_208
DOI ID：10.11458/tsj.47.4_208, ISSN：0385-8839, eISSN：1880-2338, CiNii Articles ID：130007724316, CiNii Books ID：AN00004836 - Experimental and Numerical Evaluations of Helical Turbine Performance and Proposal for Theoretical Model
TSUTSUMI Hiromasa; KANG Donghyuk; HIRAHARA Hiroyuki
Turbomachinery, Volume：47, Number：6, First page：342, Last page：353, 2019, [Reviewed]
A helical wind turbine has been analyzed experimentally and numerically and a novel design protocol has been proposed by means of blade element and momentum theory. The subject of the present analysis is to discuss the effect of low tip speed ratio and high one, respectively. In the low tip speed ratio, the turbine is driven by the torque generated from the flow turning radially after colliding with the runner. On the other hand, in the high tip speed ratio, the turbine is operated by the torque generated from the flow passing through axially the turbine. The present helical turbine has a maximum power coefficient as 40%, which is larger than that of conventional multi-blade wind turbine and is competitive with Darrieus wind turbine. Also, the turbine has a maximum torque coefficient of 48%, which is slightly lower than that of Savonius wind turbine.
Turbomachinery Society of Japan, Japanese
DOI：https://doi.org/10.11458/tsj.47.6_342
DOI ID：10.11458/tsj.47.6_342, ISSN：0385-8839, eISSN：1880-2338, CiNii Articles ID：130007724351, CiNii Books ID：AN00004836 - Thermodynamic Effect of Tip-Leakage-Vortex Cavitation on Two-dimensional Hydrofoils with Tip Clearance for Hot Water
Donghyuk KANG; Daichi NAKAI; Yuka IGA
International Journal of Fluid Machinery and Systems, Volume：12, Number：4, First page：368, Last page：379, 2019, [Reviewed]
Investigation of the thermodynamic effect of tip-leakage-vortex cavitation on a two-dimensional hydrofoil designed with a tip clearance for hot water is reported herein. During unsteady cavitation of water maintained at 90 °C (hereinafter referred to as hot water), the observed decrease in temperature in the tip-leakage region was greater compared to that in the mid-span region. In contrast, during supercavitation of hot water, the situation was reversed (i.e., the temperature decrease in the tip-leakage region was smaller than that in the mid-span region). The cavitation-pattern map for hot water was observed to be largely similar to that for water maintained at 30 °C (hereinafter referred to as tepid water). On the other hand, the amplitude of the dominant frequencies of unsteady cavitation of the hot water was observed to be greater than that of the cavitation of tepid water owing to the sudden collapse of cloud cavitation.
Turbomachinery Society of Japan, Korean Society for Fluid Machinery, Chinese Society of Engineering Thermophysics, IAHR, English, Scientific journal
DOI：https://doi.org/10.5293/ijfms.2019.12.4.368
DOI ID：10.5293/ijfms.2019.12.4.368, eISSN：1882-9554, CiNii Articles ID：130007772830 - Flow Characteristics in a V-shaped Region of a Suction Performance Curve in a Double-suction Centrifugal Pump
Kang Donghyuk; Yamazaki Satoshi; Kagawa Shusaku; An Byungjin; Nohmi Motohiko; Yokota Kazuhiko
International Journal of Fluid Machinery and Systems (Web), Volume：12, Number：1, First page：89‐98(J‐STAGE), Last page：98, 2019, [Reviewed]
The present study investigated flow characteristics in the V-shaped region of the suction performance curve for a double-suction centrifugal pump based on the computational fluid dynamics (CFD). The V-shaped region in the time-averaged suction performance curve was simulated well. The CFD simulated the fluid oscillations due to cavitation surge and rotating cavitation well. The V-shaped region was observed in the absolute total pressure difference between the impeller inlet and outlet. The time histories showed that the cavity produced vorticity, resulting in an increase in a pressure loss, and a decrease in an impeller torque and an angular momentum flow rate. The time-averaged cavity volume, pressure loss between the impeller inlet and outlet, vorticity in the blade passage and impeller torque were examined. A Λ shape of a cavity volume curve caused a Λ shape of a vorticity curve, resulting in a Λ shape of a pressure loss curve and a V shape of an impeller torque curve. The Λ shape of the pressure loss curve and the V shape of the impeller torque curve caused the V shape of the suction performance curve.
Turbomachinery Society of Japan, Korean Society for Fluid Machinery, Chinese Society of Engineering Thermophysics, IAHR, English
DOI：https://doi.org/10.5293/IJFMS.2019.12.1.089
DOI ID：10.5293/IJFMS.2019.12.1.089, ISSN：1882-9554, eISSN：1882-9554, J-Global ID：201902236671692264, CiNii Articles ID：130007616389 - Three-Dimensional Theoretical Study on Flow Characteristics of a Spiral-Channel Viscous Micropump
Kang Donghyuk; Nishibe Koichi; Sato Kotaro; Yokota Kazuhiko
International Journal of Fluid Machinery and Systems (Web), Volume：12, Number：2, First page：169‐180(J‐STAGE), Last page：180, 2019, [Reviewed]
Technological developments have led to micropumps playing an ever-greater role at the heart of micro total analysis systems. Spiral-channel viscous micropumps have been studied theoretically, numerically, and experimentally. However, high-accuracy performance predictions have not been achieved over a wide range of operating conditions. The present study proposes three-dimensional and quasi-three-dimensional theoretical expressions for predicting the pressure performance of spiral-channel viscous micropumps in low-Reynolds-number environments. The theoretical analysis is validated through a series of comparisons with numerical simulation results for the pressure performance curves, velocity distributions, velocity gradient distributions, and channel internal pressure distributions. Furthermore, the influence of the channel aspect ratio on the performance characteristics is investigated.
Turbomachinery Society of Japan, Korean Society for Fluid Machinery, Chinese Society of Engineering Thermophysics, IAHR, English
DOI：https://doi.org/10.5293/IJFMS.2019.12.2.169
DOI ID：10.5293/IJFMS.2019.12.2.169, ISSN：1882-9554, eISSN：1882-9554, J-Global ID：201902278332184070, CiNii Articles ID：130007668915 - 大橋-秋元クライテリアに関する数値的考察(第1報)単純流体加振系の解析—Numerical Study of Criteria Proposed by Ohashi and Akimoto(First Report)A Case Study of a Simple Hydraulic Oscillating System—特集 荏原式オープンイノべーション
能見 基彦; 山﨑 賢; 香川 修作; 安 炳辰; 姜 東赫; 横田 和彦
Number：255, First page：19, Last page：23, Apr. 2018, [Reviewed]
コレクション : 国立国会図書館デジタルコレクション > 電子書籍・電子雑誌 > その他
Japanese
ISSN：0385-3004, CiNii Articles ID：40021590829, CiNii Books ID：AN1022883X - Two-Dimensional Theoretical Study on Flow Characteristics of a Spiral-Channel Viscous Micropump
Kang Donghyuk; Nishibe Koichi; Sato Kotaro; Yokota Kazuhiko
International Journal of Fluid Machinery and Systems (Web), Volume：11, Number：4, First page：374‐386(J‐STAGE), Last page：386, 2018, [Reviewed]
This study investigates the flow characteristics of a spiral-channel viscous micropump using two-dimensional theoretical analysis. The obtained results are compared to the results obtained from experiments, numerical simulations, and the theoretical analysis of Kilani et al., and the similarities and differences between these approaches are discussed. The present two-dimensional theoretical approach is validated. Its accuracy is improved as compared to previous work by setting the spiral-channel axis as the spiral-channel length from the pump inlet to the outlet and by considering the moving wall as a component in the spiral-channel direction of the circumferential velocity of the rotating disk. Furthermore, the present two-dimensional analysis can accurately predict pump performance, even though the actual flow in the micropump is three dimensional.
Turbomachinery Society of Japan, Korean Society for Fluid Machinery, Chinese Society of Engineering Thermophysics, IAHR, English
DOI：https://doi.org/10.5293/IJFMS.2018.11.4.374
DOI ID：10.5293/IJFMS.2018.11.4.374, ISSN：1882-9554, eISSN：1882-9554, J-Global ID：201902229571502997 - Experimental study on performance characteristics of a fin pump
KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Transactions of the JSME (in Japanese), Volume：82, Number：835, First page：15, Last page：00546-15-00546, 2016, [Reviewed]
A fin pump utilizing a forced vibration of a flexible sheet in the same way as a caudal fin motion was developed for a treatment of fetal hydrocephalus. This study conducted an experiment to investigate the performance characteristics of the fin pump. A link system was designed to generate a pitching motion of a silicon rubber sheet and to control a vibration frequency and an amplitude. The vibration modes were analyzed by visualization. The pressure rise of the fin pump was derived from the flexible sheet deformation equation. The relative pressure coefficients for all experimental results were distributed on a line. This implies that the relative pressure coefficient is determined by the frequency ratio. The pressure rise was almost constant when the flexible sheet vibrated in the standing modes. On the other hands, the pressure rise increased with an increase of the frequency ratio when the flexible sheet vibrated in the travelling modes. This means that the pressure rise of the fin pump is closely related with the vibration modes determined by the frequency ratio. The pressure performance curve, the flow rate versus the pressure rise, was obtained by controlling a booster pump and a valve. At lower flow rates, the performance characteristics were similar to the results at the zero flow rate.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/transjsme.15-00546
DOI ID：10.1299/transjsme.15-00546, ISSN：2187-9761, eISSN：2187-9761, CiNii Articles ID：130005140005 - Study on flow characteristics of a synthetic jet by using a vortex method
KANG Donghyuk; NISHIBE Kouichi; SATO Kotaro; YOKOTA Kazuhiko
Transactions of the JSME (in Japanese), Volume：82, Number：839, First page：16, Last page：00163-16-00163, 2016, [Reviewed]
A synthetic jet is generated by an oscillating flow that a time-averaged mass flow is zero, unlike continuous jets. Synthetic jets have been used for various applications such as mixing enhancement and active controls. The present study investigated flow characteristics of a synthetic jet by using the vortex method. Continuous and synthetic jets were simulated by distributed sources on a slot and vortex pairs discharged from slot lips and their images. The wall boundary was simulated by the images of vortices. The onset condition of the synthetic jet by the vortex method agrees well with the Holmans result. The mean velocity distribution on the x axis by the vortex method reasonably agrees with the experimental one. For the dimensionless stroke lengths larger than 3.14, vortices remain in the flow field after the period of the suction. The induced velocity of the vortex remaining in the flow field generates the synthetic jet. During the suction, the largest velocity is located near a pair of the vortex groups. The 2nd local maximum in the mean velocity distribution corresponds to that in the frequency distribution of the maximum velocity. The 2nd local maximum is caused by a pair of the vortex groups flowing between x=15 and x=25 slowly.
一般社団法人 日本機械学会, Japanese
DOI：https://doi.org/10.1299/transjsme.16-00163
DOI ID：10.1299/transjsme.16-00163, ISSN：2187-9761, J-Global ID：201602277577656103, CiNii Articles ID：130005166430 - Estimation of the Dynamic Characteristics of a Double-Suction Centrifugal Pump in Cavitation Surge
姜 東赫; 幡野 信哉; 横田 和彦
Volume：43, Number：3, First page：170, Last page：176, Mar. 2015, [Reviewed]
Japanese
ISSN：0385-8839, CiNii Articles ID：40020378208, CiNii Books ID：AN00004836 - Characteristic of viscous micropump using a rotating cylinder in an elbow duct
KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A, Volume：81, Number：830, First page：15, Last page：00326-15-00326, 2015, [Reviewed]
The model experiment, the numerical calculation and the theoretical analysis are performed to investigate the characteristic of a viscous micropump by using a rotating cylinder in an elbow duct. In the experiment, the low Reynolds flow in the centimeter-scale micropump is realized by using glycerin as working fluid. The flow is visualized by an aluminum powder for Particle Image Velocimetry (PIV) analysis. In the theoretical analysis, the 2D lubrication theory is adopted and the pressure performance formula of the viscous micropump in the elbow duct is proposed. The performance curves derived from the formula agree well with the numerical results. Therefore, the proposed formula can be used for the design of the viscous micropump in the elbow duct. The performance curve, the φ-ΨRe curve, becomes a straight line with a negative slope. In the experimental and numerical results, the two vortices which rotate in the opposite direction of the rotating cylinder are observed. With an increase of the angle of the elbow duct, the pressure dimensionless number at the zero flow coefficient increases and the flow coefficient at the zero pressure coefficient slightly decreases. The pressure performance is degraded at the normalized partition lengths smaller than 0.05.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/transjsme.15-00326
DOI ID：10.1299/transjsme.15-00326, ISSN：2187-9761, eISSN：2187-9761, CiNii Articles ID：130005105261 - Flagmill -A new power generator utilizing flexible sheet-
KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Journal of Fluid Science and Technology (Web), Volume：10, Number：1, First page：JFST0005-JFST0005 (J-STAGE), Last page：JFST0005, 2015, [Reviewed]
The present study proposes "a flagmill", which is a new power generator utilizing the flutter of a flexible sheet such as a flag. The sheet flutter causes the angular oscillation of the supporting pole. Since the supporting pole is connected to the power generator axis, the angular oscillation produces the electromotive power. The flutter and the power generation characteristics were investigated experimentally and analytically. The flutter occurs by decreasing the relative stiffness or increasing the mass ratio. The electromotive force cause the increase of the critical flutter speed. The higher flutter frequency and the larger amplitude of the angular oscillation of the sheet leading edge can generate the larger electromotive power.
The Japan Society of Mechanical Engineers, English
DOI：https://doi.org/10.1299/jfst.2015jfst0005
DOI ID：10.1299/jfst.2015jfst0005, ISSN：1880-5558, eISSN：1880-5558, J-Global ID：201502246596657344, CiNii Articles ID：130004942673 - 【展望・解説】キャビテーション不安定現象のシミュレーション
伊賀由佳; 姜東赫
ターボ機械, Volume：42, Number：12, First page：1, Last page：13, Dec. 2014, [Reviewed]
ターボ機械協会, Japanese, Scientific journal - Numerical Simulation of Cavitation Instabilities
伊賀 由佳; 姜 東赫
ターボ機械, Volume：42, Number：12, First page：737, Last page：749, Dec. 2014, [Reviewed]
日本工業出版, Japanese
ISSN：0385-8839, CiNii Articles ID：40020276075, CiNii Books ID：AN00004836 - Study of cavitation instabilities in double-suction centrifugal pump
Shinya Hatano; Donghyuk Kang; Shusaku Kagawa; Motohiko Nohmi; Kazuhiko Yokota
International Journal of Fluid Machinery and Systems, Volume：7, Number：3, First page：94, Last page：100, 2014, [Reviewed]
In double-suction centrifugal pumps, it was found that cavitation instabilities occur with vibration and a perio dic chugging noise. The present study attempts to identify cavitation instabilities in the double-suction centrifugal pump by the experiment and Computational Fluid Dynamics (CFD). Cavitation instabilities in the tested pump were classified into three types of instabilities. The first one,in a range of cavitation number higher than breakdown cavitation number, is cavitation surge with a violent pressure oscillation. The second one, in a range of cavitation number higher than the cavitation number of cavitation surge, is considered to be rotating cavitation and causes the pressure oscillation due to the interaction of rotating cavitation with the impeller. Last one, in a range of cavitation number higher than the cavitation number of rotating cavitation, is considered to be a surge type instability.
Turbomachinery Society of Japan, English
DOI：https://doi.org/10.5293/IJFMS.2014.7.3.094
DOI ID：10.5293/IJFMS.2014.7.3.094, ISSN：1882-9554, eISSN：1882-9554, J-Global ID：201402285638828525, CiNii Articles ID：130004679421, SCOPUS ID：84905569814 - Numerical evaluation of dynamic transfer matrix and unsteady cavitation characteristics of an inducer
Koichi Yonezawa; Jun Aono; Donghyuk Kang; Hironori Horiguchi; Yutaka Kawata; Yoshinobu Tsujimoto
International Journal of Fluid Machinery and Systems, Volume：5, Number：3, First page：126, Last page：133, Jul. 2012, [Reviewed]
The transfer matrix and unsteady cavitation characteristics, cavitation compliance and mass flow gain factor, of cavitating inducer were evaluated by CFD using commercial software. Quasi-steady values of cavitation compliance and mass flow gain factor were obtained first by using steady calculations at various flow rate and inlet cavitation number. Then unsteady calculations were made to determine the transfer matrix and the cavitation characteristics. The results are compared with experiments to show the validity of calculations.
Turbomachinery Society of Japan, Korean Society for Fluid Machinery, Chinese Society of Engineering Thermophysics, IAHR, English
DOI：https://doi.org/10.5293/IJFMS.2012.5.3.126
DOI ID：10.5293/IJFMS.2012.5.3.126, ISSN：1882-9554, eISSN：1882-9554, J-Global ID：201202271935636176, CiNii Articles ID：130004542488, SCOPUS ID：84870274589 - Suppression of Cavitation Instabilities by Applying Circumferential Groove and Study on the Cause of High-Frequency Pressure Fluctuation in an Inducer
KANG Donghyuk; ARIMOTO Yusuke; YONEZAWA Koichi; HORIGUCHI Hironori; KAWATA Yutaka; HAH Chunill; TSUJIMOTO Yoshinobu
Turbomachinery, Volume：39, Number：2, First page：65, Last page：78, Feb. 2011, [Reviewed]
The purpose of the present research is to suppress cavitation instabilities by using a circumferential groove. The circumferentialgroove was designed based on CFD so that the tip leakage vortex is trapped by the groove and does not interactwith the next blade. Experimental results show that the groove can suppress rotating cavitation, asymmetric cavitation andcavitation surge. However, weak instabilities with higher frequency occurred in a wide range of cavitation number. Fromthe analysis of pressure pattern similar to that for rotor-stator interaction, it was found that the higher frequency componentsare caused by the interaction of backflow vortices with the inducer blades.
Turbomachinery Society of Japan, Japanese
DOI：https://doi.org/10.11458/tsj.39.65
DOI ID：10.11458/tsj.39.65, ISSN：0385-8839, eISSN：1880-2338, CiNii Articles ID：10027781039, CiNii Books ID：AN00004836 - Suppression of Cavitation Instabilities in an Inducer by Circumferential Groove and Explanation of Higher Frequency Components
KANG Donghyuk; ARIMOTO Yusuke; YONEZAWA Koichi; HORIGUCHI Hironori; KAWATA Yutaka; HAH Chunill; TSUJIMOTO Yoshinobu
International Journal of Fluid Machinery and Systems (Web), Volume：3, Number：2, First page：137-149 (J-STAGE), Last page：169, 2010, [Reviewed]
On page 144, titles of Fig. 16 and Fig. 17 are not displayed correctly. The corrections are shown in PDF.
Turbomachinery Society of Japan, Korean Fluid Machinery Association, Chinese Society of Engineering Thermophysics, IAHR, English
DOI：https://doi.org/10.5293/IJFMS.2010.3.2.137
DOI ID：10.5293/IJFMS.2010.3.2.137, ISSN：1882-9554, eISSN：1882-9554, J-Global ID：201002208990605826, CiNii Articles ID：130006900208 - Inducer Design to Avoid Cavitation Instabilities
KANG Donghyuk; WATANABE Toshifumi; YONEZAWA Koichi; HORIGUCHI Hironori; KAWATA Yutaka; TSUJIMOTO Yoshinobu
Turbomachinery, Volume：37, Number：12, First page：749, Last page：762, Dec. 2009, [Reviewed]
Three inducers were designed to avoid cavitation instabilities. This was accomplished by avoiding the interaction of tip cavity with the leading edge of the next blade. The first one was designed with extremely larger leading edge sweep, the second and third ones were designed with smaller incidence angle by reducing the inlet blade angle or increasing the design flow rate, respectively. The inducer with larger design flow rate has larger outlet blade angle to obtain sufficient pressure rise. The inducer with larger sweep could suppress the cavitation instabilities in higher flow rates more than 95% of design flow rate, owing to weaker tip leakage vortex cavity with stronger disturbance by backflow vortices. The inducer with larger outlet blade angle could avoid the cavitation instabilities at higher flow rates owing to the extension of the tip cavity along the suction surface of the blade. The inducer with smaller inlet blade angle could avoid the cavitation instabilities at the flow rates larger than the design flow coefficient, owing to the occurrence of the cavity first in the blade passage and its development upstream. The cavity shape and suction performance were reasonably simulated by three dimensional CFD computations under the steady cavitating condition, except for the backflow vortex cavity. The difference in the growth of cavity for each inducer is explained from the difference of the pressure distribution on the suction side of the blades.
Turbomachinery Society of Japan, Japanese
DOI：https://doi.org/10.11458/tsj.37.749
DOI ID：10.11458/tsj.37.749, ISSN：0385-8839, eISSN：1880-2338, CiNii Articles ID：10026204011, CiNii Books ID：AN00004836 - LES Simulation of the Response of an Inducer to Flow Rate Fluctuations
KANG Donghyuk; YONEZAWA Koichi; UEDA Tatsuya; YAMANISHI Nobuhiro; KATO Chisachi; TSUJIMOTO Yoshinobu
Turbomachinery, Volume：37, Number：2, First page：94, Last page：103, Feb. 2009, [Reviewed]
A large eddy simulation (LES) of flow in an inducer is carried out under flow rate oscillations. The present study focuses on characteristics of dynamic responses of the backflow and the pressure performance to the flow rate fluctuations under non-cavitation conditions. Results show that the backflow response delays behind the flow rate fluctuation. The pressure performance curve exhibits a closed curve caused by the effect of inertia associated with the flow rate fluctuations. Comparing with one dimensional evaluation of the inertia effects, it was found that the inertial effects obtained by the LES are smaller. Additionally, the averaged negative slope of the performance curve becomes larger under unsteady conditions. From the conservations of angular momentum and energy, an expression useful for the evaluation of unsteady pressure rise was obtained. The examination of each term of this expression shows that the apparent decrease of inertia effects is caused by the response delay of Euler head and that the increase of negative slope is caused by the inertial term associated with the delay of backflow response.
Turbomachinery Society of Japan, Japanese
DOI：https://doi.org/10.11458/tsj.37.94
DOI ID：10.11458/tsj.37.94, ISSN：0385-8839, eISSN：1880-2338, CiNii Articles ID：10024744759, CiNii Books ID：AN00004836 - Inducer Design to Avoid Cavitation Instabilities
KANG Donghyuk; WATANABE Toshifumi; YONEZAWA Koichi; HORIGUCHI Hironori; KAWATA Yutaka; TSUJIMOTO Yoshinobu
International Journal of Fluid Machinery and Systems (Web), Volume：2, Number：4, First page：439-448 (J-STAGE), 2009, [Reviewed]
English
DOI：https://doi.org/10.5293/IJFMS.2009.2.4.439
DOI ID：10.5293/IJFMS.2009.2.4.439, ISSN：1882-9554, J-Global ID：200902256002007424 - Large Eddy Simulation of the Dynamic Response of an Inducer to Flow Rate Fluctuations
KANG Donghyuk; YONEZAWA Koichi; UEDA Tatsuya; YAMANISHI Nobuhiro; KATO Chisachi; TSUJIMOTO Yoshinobu
International Journal of Fluid Machinery and Systems (Web), Volume：2, Number：4, First page：431-438 (J-STAGE), 2009, [Reviewed]
English
DOI：https://doi.org/10.5293/IJFMS.2009.2.4.431
DOI ID：10.5293/IJFMS.2009.2.4.431, ISSN：1882-9554, J-Global ID：200902271003267917 - Cause of Cavitation Instabilities in Three Dimensional Inducer
KANG Donghyuk; YONEZAWA Koichi; HORIGUCHI Hironori; KAWATA Yutaka; TSUJIMOTO Yoshinobu
International Journal of Fluid Machinery and Systems (Web), Volume：2, Number：3, First page：206-214 (J-STAGE), Last page：214, 2009, [Reviewed]
Alternate blade cavitation, rotating cavitation and cavitation surge in rocket turbopump inducers were simulated by a three dimensional commercial CFD code. In order to clarify the cause of cavitation instabilities, the velocity disturbance caused by cavitation was obtained by subtracting the velocity vector under non-cavitating condition from that under cavitating condition. It was found that there exists a disturbance flow towards the trailing edge of the tip cavity. This flow has an axial flow component towards downstream which reduces the incidence angle to the next blade. It was found that all of the cavitation instabilities start to occur when this flow starts to interact with the leading edge of the next blade. The existence of the disturbance flow was validated by experiments.
Turbomachinery Society of Japan, Korean Society for Fluid Machinery, Chinese Society of Engineering Thermophysics, IAHR, English
DOI：https://doi.org/10.5293/IJFMS.2009.2.3.206
DOI ID：10.5293/IJFMS.2009.2.3.206, ISSN：1882-9554, eISSN：1882-9554, J-Global ID：200902289220387536, CiNii Articles ID：80020473730 - Choked Surge in a Cavitating Turbopump Inducer
WATANABE Toshifumi; KANG Donghyuk; CERVONE Angelo; KAWATA Yutaka; TSUJIMOTO Yoshinobu
International Journal of Fluid Machinery and Systems (Web), Volume：1, Number：1, First page：64-75 (J-STAGE), Last page：75, 2008, [Reviewed]
During an experimental investigation on a 3-bladed and a 4-bladed axial inducer, a severe surge instability was observed in a range of cavitation number where the blade passage is choked and the inducer head is decreased from non-cavitating value. The surge was stronger for the 4-bladed inducer as compared with a 3-bladed inducer with the same inlet and outlet blade angles. For the 4-bladed inducer, the head decreases suddenly as the cavitation number is decreased. The surge was observed after the sudden drop of head. This head drop was found to be associated with a rapid extension of tip cavity into the blade passage. The cause of surge is attributed to the decrease of the negative slope of the head-flow rate performance curve due to choke. Assuming that the difference between the 3 and 4-bladed inducers is caused by the difference of the blockage effects of the blade, a test was carried out by thickening the blades of the 3-bladed inducer. However, opposite to the expectations, the head drop became smoother and the instability disappeared on the thickened blade inducer. Examination of the pressure distribution on both inducers could not explain the difference. It was pointed out that two-dimensional cavitating flow analyses predict smaller breakdown cavitation number at higher flow rates, if the incidence angle is smaller than half of the blade angle. This causes the positive slope of the performance curve and suggests that the choked surge as observed in the present study might occur in more general cases.
Turbomachinery Society of Japan, Korean Fluid Machinery Association, Chinese Society of Engineering Thermophysics, IAHR, English
DOI：https://doi.org/10.5293/IJFMS.2008.1.1.064
DOI ID：10.5293/IJFMS.2008.1.1.064, ISSN：1882-9554, eISSN：1882-9554, J-Global ID：200902226507599133, CiNii Articles ID：130004953115
- Plane Jet Vectoring near a Flat Plate using Secondary Suction Flow
Kaito Yabu; Koichi Nishibe; Donghyuk Kang; Kotaro Sato
World Congress on Mechanical, Chemical, and Material Engineering, Aug. 2024
Avestia Publishing
DOI：https://doi.org/10.11159/htff24.189
DOI ID：10.11159/htff24.189, ISSN：2369-8136 - Influence of Interaction of Two Pulsating Jets with Phase on Flow Characteristics
Masahiro Takano; Donghyuk Kang; Kotaro Sato; Koichi Nishibe
World Congress on Mechanical, Chemical, and Material Engineering, Aug. 2024
Avestia Publishing
DOI：https://doi.org/10.11159/htff24.202
DOI ID：10.11159/htff24.202, ISSN：2369-8136 - 尿噴流の特異的な形状を利用した尿流測定法の開発
本間俊司; 兼子力; 木山景仁; 姜東赫; 竹下英毅
Volume：35, Number：1, 2024
ISSN：1347-6513, J-Global ID：202502245019115304 - 排尿音と排尿画像を組み合わせたハイブリッド式の尿流量推定法の提案
姜東赫; 下地倖輔; 上林出; 木山景仁; 本間俊司; 兼子力; 竹下英毅
Volume：35, Number：1, 2024
ISSN：1347-6513, J-Global ID：202502298036956111 - 楕円管ノズルから生成するジェットに対する流路狭窄の影響
高橋太陽; 兼子力; 竹下英毅; 小林拓央; 姜東赫; 木山景仁; 本間俊司
Volume：89th, 2024
J-Global ID：202402257737638371 - Two-Layer Liquid Sloshing Produced by Horizontal Excitation
Daiki Iwaya; Ryuichi Inoue; Akihito Kiyama; Donghyuk Kang; Kazuhiko Yokota; Kotaro Sato
Proceedings of the World Congress on Mechanical, Chemical, and Material Engineering, 2024
Many studies on single-layer sloshing have been carried out due to accidents involving damage to floating roofs in oil tanks caused by long-period earthquakes and technical issues in the transport of liquids by ships [1]. Research on two-layer sloshing is currently needed to examine seismic resistance and to ensure safety in situations in which two-layer liquids are mixed, such as floating production systems that are used in offshore resource development as well as tuned liquid dampers that are used as vibration control systems for buildings [2]. To study two-layer sloshing, Veletsos and Shivakumar [3] derived a linear analytical solution and showed that the natural frequency depends on the tank width, depth of the two liquids, and density ratio. Lin et al. [4] experimentally investigated the resonant and non-resonant responses of a two-layer liquid in a tank under pitch excitation and found that when the excitation frequency is equal to the natural frequency of the free surface, resonance occurs at the free surface, whereas the wave height at the liquid-liquid interface is much smaller than that at the free surface. However, the wave height at the liquid-liquid interface may show in-phase motion that follows the motion of the free surface, although the wave height is considerably smaller than that of the free surface. There have been few existing studies on the sloshing of bilayer liquids, and only fragmentary findings have been obtained thus far. Therefore, this study focuses on the effect of the depth ratio of the two liquids on the vibration characteristics of two-layer liquid sloshing. Horizontal excitation experiments using a two-dimensional rectangular tank are conducted, and visual observations are made. The main results show that when the depth ratio of the two liquids (=height of the upper liquid / height of the lower liquid) is small, the motions of the free surface and the liquid-liquid interface are in phase during resonance, and the wave heights of the two liquids are close. When the depth ratio of the two liquids is unity, the resonant responses of the upper and lower liquids are confirmed to be in the lower-order mode, but the wave height of the lower liquid is lower than that observed with a smaller depth ratio.
DOI：https://doi.org/10.11159/htff24.188
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DOI ID：10.11159/htff24.188, eISSN：2369-8136, SCOPUS ID：85205103026 - Observation of Two-Dimensional Bubble Motions near Various Boundaries
Ryuichi Inoue; Daiki Iwaya; Akihito Kiyama; Donghyuk Kang; Kotaro Sato
Proceedings of the World Congress on Mechanical, Chemical, and Material Engineering, 2024
In recent years, the environment surrounding cavitation bubbles has significantly changed. Because cavitation causes material damage and abnormal vibrations in turbomachinery, they are regarded as challenging, and research has focused on suppressing them. However, research on flow generation that actively utilizes the kinetic characteristics of bubbles, such as sonoporation using jet formation in the microregion of cavitation bubbles [1] and the generation of synthetic jets by the nonlinear volume fluctuations of bubbles [2], has recently attracted attention. The motion of a cavitation bubble is generally expressed by the upwelling and suction (without momentum) of a potential flow; therefore, it is necessary to restrict the motion of the bubble to generate a directional flow with momentum using bubbles. Therefore, the behavior of bubbles under various boundary conditions in addition to rigid plates and free surfaces should be clarified. Tomita et al. conducted experimental and theoretical studies on curved rigid boundaries and elucidated the effect of rigid-body curvature on bubble motion [3]. Li et al. performed numerical simulations on the collapse behavior of a single bubble and two bubbles in an inclined V-shaped corner and established the relationship between the angle of the V-shaped corner, the distance between the corner and cavitation bubbles, and the distance between bubbles by obtaining the temperature, density, velocity, and pressure fields [4]. Yin et al. generated laser-induced single bubbles at the tip of a conical rigid body and determined the relative distance between the bubbles from the tip of the conical rigid body; they also investigated the effect of the cone angle on the pressure peak and other parameters through experimental and numerical studies [5]. However, these studies were conducted on three-dimensional (3D, axisymmetric) bubbles but are unsuitable for generating two-dimensional (2D) flows. In this study, a roughly 2D bubble was generated in a liquid between flat plates by electrical discharge, and its behavior was filmed at high speed. The motion of 2D bubbles under rigid wall conditions with various geometries was clarified, focusing mainly on the relationship between the wall geometry and time characteristics, and the difference between 2D and 3D bubbles was analyzed. The results show that the dimensionless collapse period θθ=90° increases as the dimensionless distance llww∗ (the ratio of the distance between the wall and the bubble to the maximum bubble equivalent radius) decreases. The value of the dimensionless collapse period ττ∗ for θθ=90° exceeds that of θθ=180° when the rigid body boundary angle θθ=180° (flat wall) and θθ=90° (L-shaped wall) are compared for the dimensionless distance llww∗. The value of the dimensionless collapse period ττ∗ of θθ=90° exceeds that of θθ=180°.
DOI：https://doi.org/10.11159/htff24.199
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Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85205118673&origin=inward
DOI ID：10.11159/htff24.199, eISSN：2369-8136, SCOPUS ID：85205118673 - Investigation of Internal Flow near Return Guide Vane Using Jet and Suction Flow
Chihiro Sugiyama; Toshihiro Fujii; Koichi Nishibe; Donghyuk Kang; Kotaro Sato
Proceedings of the 9th World Congress on Mechanical, Chemical, and Material Engineering, Aug. 2023
Avestia Publishing
DOI：https://doi.org/10.11159/htff23.177
DOI ID：10.11159/htff23.177, ISSN：2369-8136 - Jet Vectoring by Suction Flows on Surface of Circular Cylinder
Kaito Suzuki; Minoru Nakagawa; Koichi Nishibe; Donghyuk Kang; Kotaro Sato
Proceedings of the 9th World Congress on Mechanical, Chemical, and Material Engineering, Aug. 2023
Avestia Publishing
DOI：https://doi.org/10.11159/htff23.159
DOI ID：10.11159/htff23.159, ISSN：2369-8136 - Jet Direction Control Using Active Switching Nozzle
Taisei Suzuoka; Koichi Nishibe; Kotaro Sato; Donghyuk Kang
Proceedings of the 9th World Congress on Mechanical, Chemical, and Material Engineering, Aug. 2023
Avestia Publishing
DOI：https://doi.org/10.11159/htff23.180
DOI ID：10.11159/htff23.180, ISSN：2369-8136 - 尿噴流のシミュレーション
兼子力; 小林拓央; 姜東赫; 竹下英毅; 本間俊司
Volume：88th, 2023
J-Global ID：202302233923690434 - 動的モード分解を用いたキャビテーションポンプの動特性推定方法の提案
姜東赫; 上林出; 横田和彦
Volume：88th, 2023
J-Global ID：202402232000397640 - 動的モード分解に基づく円柱周り流れのフィードバック制御の検討
上林出; 姜東赫
Volume：88th, 2023
J-Global ID：202402279273567008 - キャビテーションサージの能動制御に関する非線形解析
根本彼方; 姜東赫; 上林出
Volume：88th, 2023
J-Global ID：202402290584297770 - 動的モード分解制御を用いた遠心ファンの動特性の推定
丸山俊祐; 上林出; 姜東赫
Volume：89th, 2023
J-Global ID：202402227517347142 - 排気側障害物を有する軸流ファンの性能調査
松尾優輝; 杉山千紘; 松村威吹; 西部光一; 姜東赫; 横田和彦; 佐藤光太郎
Volume：89th, 2023
J-Global ID：202402241039159824 - 軸流ファンの性能に及ぼす多孔質フィルタの影響
杉山千紘; 松村威吹; 松尾優輝; 西部光一; 姜東赫; 横田和彦; 佐藤光太郎
Volume：89th, 2023
J-Global ID：202402242626958367 - 尿流測定のための噴流シミュレーション
兼子力; 小林拓央; 姜東赫; 竹下英毅; 本間俊司
Volume：54th, 2023
J-Global ID：202402234846528129 - Influence of Slot Geometry on the Behavior of Synthetic Jets
Kota Ishiwata; Koichi Nishibe; Donghyuk Kang; Kotaro Sato
Proceedings of the World Congress on Mechanical, Chemical, and Material Engineering, 2023
Synthetic jets have attracted considerable attention as alternatives to conventional continuous jets. It has been reported that the direction and jet structure of a two-dimensional planar jet can be tuned by its oscillation frequency, since the synthetic jets are oscillatory flows [1]. When controlling the jet direction using the oscillation frequency, the symmetry of the vortex pair is broken as the slot has an asymmetric beak or staircase shape, and the jet is considered to be deflected. In particular, it has been shown that there are cases where recirculation regions are generated near slots, and cases where staggered vortex rows in the form of inverse Kalman vortices are formed and deflected [2, 3]. Naturally, the deflection characteristics of a synthetic jet have been shown to depend on the asymmetric slot geometry. Although a number of reports have examined the behavior of synthetic jets generated by beak or staircase-shaped slots, no systematic studies have investigated the effect of slot geometry on synthetic jet behavior. The relationship between the flow characteristics and slot geometry remains unclear in many cases. It is therefore desirable to determine the optimal asymmetric slot geometry for jet angle adjustment. This study aims to investigate the geometry and flow characteristics of a beak-shaped slot via numerical simulations and smoke-wire flow visualization experiments. In particular, the effect of the beak tip angle, ββ, on the flow characteristics of synthetic jets was investigated. The jet outlet slot width bb0 was 0.50 m, the slot height ℎ was 0.10 m, and the aspect ratio was 20. The conditions in this study were as follows: the representative length was the slot width bb0, the representative speed UU0 was 3.0 m/s, the dimensionless stroke length LL0 was 10, and the dimensionless beak length, CC = cc⁄bb0, was approximately 3-12. When ββ= 11°, the alternating vortex trains moving downstream were barely entrained toward the slot outlet, and the deflection angle of the jet was small. Alternate vortex trains were generated at other beak tip angles. At ββ = 63°, the vortex trains were entrained toward the slot outlet side, confirming the deflection of the jet. Furthermore, at ββ = 79°, and ββ = 90°, vortex recirculation was observed and the jet was deflected significantly. Hence, it was shown that when the dimensionless beak length CC ~ 3 − 12, the jet was deflected to a greater extent when the beak tip angle ββ was increased. The closer the tip angle of the beak-shaped slot was to the 90°, the closer the slot resembled a staircase-shaped asymmetric slot. Therefore, a vortex did not develop at the top of the beak-shaped slot and the jet may have recirculated.
DOI：https://doi.org/10.11159/htff23.168
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DOI ID：10.11159/htff23.168, eISSN：2369-8136, SCOPUS ID：85188452398 - Visualization of rotating cavitation in a centrifugal pump
T. Yokoi; D. Kang; M. Nohmi; T. Tsuneda; J. Okajima; Y. Iga
Journal of Physics: Conference Series, Volume：2217, Number：1, 06 May 2022
In this study, unsteady cavitation in a centrifugal pump that had 3 blades was visualized in experiments. Cavitation behavior was photographed by using a high-speed camera from the axial direction. To observe rotating cavitation, its aspects were visualized using a high-speed camera. The experiment was performed at rotational speed of 825 rpm with a centrifugal pump under reduced pressure. Rotating cavitation occurred on the suction side of blades under the condition of flow rates lower than the best efficiency point. In addition, observed rotating cavitation was super-synchronous rotating cavitation, which rotates at a faster speed than the impeller in absolute coordinate form. As a result of frequency analysis of the brightness value on the channel, propagation velocity ratios, which is the ratio of the propagation velocity of the cavity to the rotational velocity of the impeller were 1.2-1.3. It was confirmed that the propagation velocity ratio of rotating cavitation in the centrifugal pump is close to that of rotating cavitation in the inducer even when the specific speed and Reynolds number are different.
DOI：https://doi.org/10.1088/1742-6596/2217/1/012019
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DOI ID：10.1088/1742-6596/2217/1/012019, ISSN：1742-6588, eISSN：1742-6596, SCOPUS ID：85130274535 - Interaction between a cavitation bubble and a gas bubble attached rigid surface
KUBOTA Yoshiki; SASAYAMA Hiroki; KANG Donghyuk; TOMITA Yukio; SATO Kotaro
The Proceedings of Conference of Kanto Branch, Volume：2022.28, First page：15G11, 2022
An experimental study was conducted focusing on the interaction between gas bubbles adhering to the surface of the rigid boundary and cavitation bubbles produced near the gas bubbles. In a sufficiently large water tank, gas bubbles of arbitrary size were placed on the surface of the boundary, discharge cavitation bubbles were produced, and the subsequent behaviors of the gas and cavitation bubbles were photographed with a high-speed camera using a halogen lamp as a light source. In this study, the interaction of bubbles was discussed, while focusing on the variation in the cavitation bubble centroid with time. The main parameters are the bubble size ratio and relative distance between the bubbles and rigid boundary, and the migration characteristics of the cavitation bubble were classified into three types based on the direction of centroid movement.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2022.28.15g11
DOI ID：10.1299/jsmekanto.2022.28.15g11, eISSN：2424-2691 - Study on a microjet generated by two laser-induced cavitation bubbles
TERASAKI Shingo; KANG Donghyuk; SATO Koutaro; TOMITA Yukio; Matsuura Keitaro
The Proceedings of the Fluids engineering conference, Volume：2022, First page：OS06-18, 2022
Two cavitation bubbles generated by laser irradiation in water generate microjets due to their mutual interference. The characteristics of microjets vary depending on the size and distance of the bubbles, as well as on the time difference between bubble generation and microjet generation. Therefore, the purpose of this study is to clarify the effect of the bubble generation time difference, T*D in dimensionless form, on the bubble motion and microjet by numerical calculations and experiments. Numerical calculations are performed using the boundary element method and the VOF method, both of which have conflicting characteristics, and two numerical methods are used for efficient analysis. In this study, cavitation bubbles are generated at the top and bottom, and the lower bubble that is generated first is bubble A, and the upper bubble that is generated after a delay is bubble B. When the distance between the bubbles and the bubble size ratio are kept constant and the bubble generation time difference is varied, it is found that there are three types of microjets generated in bubble A due to the mutual interference between the two cavitation bubbles. Upward microjets are generated in bubble A and penetrate upward when the bubble generation time difference is small. This occurs when the expansion of bubble A is slightly disturbed, causing the underside of bubble A to become concave. A downward microjet is generated in bubble A and penetrates downward when the bubble generation time difference is large. This is caused by the upper side of bubble A being pushed in due to the strong influence of the expansion of bubble B. When the bubble generation time difference is in the range of 0.16 ≤ T*D ≤ 0.20, bubble A is separated into two parts, resulting in the creation of upward and downward microjets. This is caused by the predominant horizontal nipping of bubble A.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2022.os06-18
DOI ID：10.1299/jsmefed.2022.os06-18, eISSN：2424-2896 - 流量変動時の遠心ファンの伝達関数に関する実験的・数値的研究
竇程よう; 上林出; 姜東赫
Volume：86th, 2022
J-Global ID：202202216286483323 - 動的モード分解制御(DMDc)を用いた円柱周りの流れ場の推定と制御
川崎成道; 上林出; 姜東赫
Volume：86th, 2022
J-Global ID：202202278787988050 - 機械学習を用いた流体機械内部流れ場の推定手法の検証
上林出; 姜東赫
Volume：86th, 2022
J-Global ID：202202278846593346 - 噴流/吸引流を利用した戻り案内羽根の開発
杉山千紘; 藤井俊宏; 姜東赫; 佐藤光太郎; 大上浩; 西部光一
Volume：87th, 2022
J-Global ID：202202214552993609 - ターボ機械の動特性測定システムの開発
竇程よう; 上林出; 姜東赫
Volume：85th, 2021
J-Global ID：202102238301774985 - 機械学習によるターボ機械内部流れ場の推定
上林出; 姜東赫
Volume：85th, 2021
J-Global ID：202102277048322688 - Clarification of the Transition Mechanism of Cavitation Instabilities
姜東赫; 伊賀由佳
東北大学流体科学研究所共同利用・共同研究拠点流体科学国際研究教育拠点活動報告書(CD-ROM), Volume：2020, 2021
J-Global ID：202202212258060961 - Clarification of the transition mechanism of cavitation instabilities
姜東赫; 伊賀由佳
東北大学流体科学研究所共同利用・共同研究拠点流体科学国際研究教育拠点活動報告書(CD-ROM), Volume：2021, 2021
J-Global ID：202302223823808454 - Fundamental Research on Drag Characteristics of Jet Impinging to Perforated Walls
村上元太郎; 吉岡瞬; KANG Donghyuk; 朝原誠; 宮坂武志; 平原裕行
日本機械学会流体工学部門講演会講演論文集(CD-ROM), Volume：99th, 2021
ISSN：1348-2882, J-Global ID：202302231561165154 - Clarification of the Transition Mechanism of Cavitation Instabilities
姜東赫; 伊賀由香; 胡ひん
東北大学流体科学研究所共同利用・共同研究拠点流体科学国際研究教育拠点活動報告書, Volume：2018, 2020
J-Global ID：202002222893527981 - 貫流羽根車に生じる渦の挙動に及ぼす壁面境界の影響
鶴若菜; 姜東赫; 佐藤光太郎; 横田和彦
Volume：83rd, 2020
J-Global ID：202002246271646781 - Numerical simulation of the influence of unsteady vortex motion on energy separation in a vortex tube
KOBAYASHI Yuta; HIRAHARA Hiroyuki; KANG Donghyuk
The Proceedings of the Fluids engineering conference, Volume：2020, First page：OS04-06, 2020
When a compressed air is supplied tangentially to a vortex tube, the total temperature separation is generated between the cold and hot air outlets by the swirling flow field formed inside the cylinder. By using the vortex tube, the industrial local coolers have been applied with the cold air of this device, such as called Ranque-Hilsch tube. Although this system has various advantages in terms of ease of maintenance and environmental protection, its practical application is limited due to the difficulty of temperature control. In this study, for the sake of the improvement of this device, we mainly focus on whistling and intermolecular heat transfer, so we engaged a CFD to investigate this total temperature separation mechanism. The characteristics of the temperature distribution and its change inside the device have been discussed.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2020.os04-06
DOI ID：10.1299/jsmefed.2020.os04-06, eISSN：2424-2896, CiNii Articles ID：130008043373 - Study on pressure performance of helical type viscous Micro pump
INAGAKI Miyu; KANG Donghyuk; HIRAHARA Hiroyuki
The Proceedings of the Fluids engineering conference, Volume：2020, First page：OS07-03, 2020
A micropump is a type of small and precise pump, which is mainly used for fuel supply for small fuel cells and liquid transport for biotechnology and medical equipment. However, viscous micropumps are one of the most suitable micropumps to be driven inside the body, and their features include continuous transport of liquid and simple structure, which is advantageous in terms of manufacturing. In this study, we develop a viscous micropump that can be driven inside the human body using a helical shape and evaluate its performance by experiments and numerical calculations. The experimental method uses a motor to rotate a helical-shaped pump in a pipe filled with silicone oil. Then, the mass change of the silicon oil flowing into the downstream tank is measured by a load cell at each time, and the flow rate ṁ and the pressure difference Δp are calculated. For numerical calculations, Ansys is used to calculate the maximum flow rate, ṁmax, and the maximum pressure difference, Δpmax, generated by the rotation of the two-wind helical geometry using a steady-state analysis with approximately 460000 meshes. Finally, in Re < 10, the maximum pressure coefficient has constant value. In Re > 10, the maximum pressure coefficient is increased with the increase of the Reynold number.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2020.os07-03
DOI ID：10.1299/jsmefed.2020.os07-03, eISSN：2424-2896, CiNii Articles ID：130008043489 - Study on the Thrust Characteristics of Synthetic Jets
HOSAKA Fumihiko; KANG Donghyuk; HIRAHARA Hiroyuki
The Proceedings of the Fluids engineering conference, Volume：2020, First page：OS03-26, 2020
A synthetic jet has a zero-net mass flow rate at the nozzle outlet but generates a net mass flow rate downstream. Considering the momentum conservation, we supposed that the synthetic jet produces the time-averaged thrust. Furthermore, the thrust induced by the synthetic jet would be unsteady. In order to use the synthetic jet as a thrust control, we experimentally and numerically investigated the unsteady thrust characteristics for the synthetic jet. For a pulsating flow generator, a reciprocating piston operated by a motor with an inverter was used. A torque induced by the synthetic jet was measured by a torque sensor and the thrust was evaluated by the torque based on the moment equilibrium. The unsteady flow around the chamber was calculated by using commercial numerical code and the unsteady thrust was evaluated by integrating the jet direction force acting on the chamber surface. The unsteady thrusts induced by the synthetic jet were confirmed in the experiment and the CFD. In the CFD, the two peaks and the one peak were observed during the blow and suction conditions, respectively. On the other hand, in the experiment, we could not observe two peaks during the blow condition. The discrepancy may be caused by fluid resistance due to the vibration of the thruster.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2020.os03-26
DOI ID：10.1299/jsmefed.2020.os03-26, eISSN：2424-2896, CiNii Articles ID：130008043363 - 非定常運動方程式を用いたベンチュリ式の流量計の評価
上林出; 姜東赫; 平原裕行
Volume：83rd, 2020
J-Global ID：202002272284740778 - Experimental Investigation of Unsteady Characteristics of Centrifugal Pump
Shunta TSUCHIYAMA; Junnosuke OKAJIMA; Donghyuk KANG; Motohiko NOHMI; Yuka IGA
16th International Conference on Flow Dynamics (ICFD2019), Number：OS18-33, Nov. 2019
English - Experimental and Numerical Studies of Unsteady Cavitation in a Centrifugal Pump for Visualization
Donghyuk Kang; Pin Hu; Junnosuke Okajima; Motohiko Nohmi; Yuka Iga
The 19th International Symposium on Advanced Fluid Information (AFI2019), Number：CRF-24, Nov. 2019
English - Experimental, Numerical and Analytical Evaluation of a Helical-Turbine Performance
Donghyuk Kang; Hiromasa Tsutsumi; Hiroyuki Hirahara
28 Jul. 2019
DOI：https://doi.org/10.1115/ajkfluids2019-5004
DOI ID：10.1115/ajkfluids2019-5004 - Cavitation CFD analyses considering the pressure wave propagation within the piping systems
Motohiko Nohmi; Shusaku Kagawa; Byungjin An; Tomoki Tsuneda; Kazuhiko Yokota; Donghyuk Kang
IOP Conference Series: Earth and Environmental Science, Volume：240, Number：6, 28 Mar. 2019
Cavitation surge is a typical unsteady phenomenon and can be a cause of severe noise and vibration problems in hydraulic systems. When the oscillation frequency of the piping systems surrounding the hydraulic devices under cavitation surge is high and/or the pipe length is long, the acoustic wave propagation within the piping systems must be considered. In this study cavitation is computed by two dimensional CFD with cavitation model and the pressure wave in the piping systems is computed by one dimensional distributed model of Method Of Characteristics (MOC). The cavitation CFD and MOC calculations are coupled through boundary conditions. The interactions of cavitation and pressure wave are observed in the computed results.
Institute of Physics Publishing, English
DOI：https://doi.org/10.1088/1755-1315/240/6/062025
DOI ID：10.1088/1755-1315/240/6/062025, ISSN：1755-1315, SCOPUS ID：85063945866 - Experiments and numerical simulations of a flow instability in a low-specific-speed pump-turbine
Koichiro Matsumura; Kazuhiko Yokota; Wakana Tsuru; Donghyuk Kang; Hayate Sugiyama
IOP Conference Series: Earth and Environmental Science, Volume：240, Number：7, 28 Mar. 2019
In order to clarify the mechanism of the fluid oscillation, which occurs for a shut-down sequence of a pump-turbine, the experiment and numerical simulation of the pump-turbine were performed. The pressure fluctuation is measured at inlet, outlet and four points between the runner and guide vanes. Parameters are flow rate, rotating speed and guide vane opening ratio. Results show that the characteristic curve shows so-called "S-shaped" and the pressure oscillation occurs in the "S-shaped" region.
DOI：https://doi.org/10.1088/1755-1315/240/7/072042
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DOI ID：10.1088/1755-1315/240/7/072042, ISSN：1755-1307, eISSN：1755-1315, SCOPUS ID：85063951478 - 粘着剤の高速塗布に関する研究
本間俊司; 中島遼太; 千葉匠; 姜東赫; 平原裕行; 大久保洋佑; 梅宮弘和; 小田純久
化学工学会年会研究発表講演要旨集(CD-ROM), Volume：84th, First page：ROMBUNNO.T302, 13 Mar. 2019
Japanese
J-Global ID：201902261701736238 - Thermodynamic Effect on Tip Leakage Vortex Cavitation
KANG Donghyuk; YUKA Iga
東北大学流体科学研究所共同利用・共同研究拠点流体科学国際研究教育拠点活動報告書, Volume：2017, First page：245‐246, Feb. 2019
English
J-Global ID：201902288550390058 - Spectral Decomposition and Reconstruction of Unsteady Flow in a Multi-blade Fan
KANAI Yutaro; KAWASAKI Masatoshi; KANG Donghyuk; HIRAHARA Hiroyuki
The Proceedings of the Fluids engineering conference, Volume：2019, First page：OS5-20, 2019
Multi-blade fan can achieve high pressure and flow rate despite of its small size. However, the fun has still has drawback on the noisegeneration. Although it is required to understand the cause of noise, it is difficult to understand the internal flow of a multi-blade fan because of its complexity. From the experimental results and analysis results, the multiblade fan in the present study was noisy around 1 kHz. The static pressure data obtained by CFD is filtered with narrow band pass filter, and only the frequency around 1kHz is extracted and analyzed. As a result of visualization, the change in static pressure is small at a location shifted by about 90 ° from the tongue rotation span of the blade, the positive / negative pressure changes at a location shifted by 270 °, and the static pressure change is large at other locations. Since the length of the scroll casing is close to the wavelength of the sound wave, it is assumed that the noise around 1kHz is due to the resonance phenomenon. The visualized result is similar to the behavior that assuming a resonance phenomenon. In the future, it will be important to conduct detailed acoustic analysis to clarify that 1kHz noise is a resonance phenomenon.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2019.os5-20
DOI ID：10.1299/jsmefed.2019.os5-20, eISSN：2424-2896, CiNii Articles ID：130007880293 - Visualization of breathing mode on releasing bubble
TSUCHIDA Daiki; OKU Takao; KANG Donghyuk; HIRAHARA Hiroyuki
The Proceedings of the Fluids engineering conference, Volume：2019, First page：OS2-26, 2019
Bubble oscillation in the breathing mode at the bubble release was investigated by flow visualization and image processing. The interface amplitude is usually a several micron meter with 1 kHz, so the direct observation is crucially difficult in the experiment. In this report, by means of direct optical observation with the special image processing, the interface displacement has been detected. With a Laplacian pyramid for the captured image group, decomposition, and frequency filtering, a target of fluctuations is able to extract in a sub-pixel order. We verify the method by Wu et al. (2012) and apply it to the breathing mode of bubbles The amplification procedure is as follows: 1) create a hierarchy of image at each time using the Laplacian pyramid method, 2) specify the frequency of the breathing mode, and apply a bandpass filter to each hierarchy, 3) multiply by the magnification and restore the image by overlaying each layer of the Laplacian pyramid, and 4) generate a new image at each time by overlaying the original image. After producing a calibration curve with a numerical simulation, the amplitude of the breathing mode is estimated.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2019.os2-26
DOI ID：10.1299/jsmefed.2019.os2-26, eISSN：2424-2896, CiNii Articles ID：130007880133 - Characteristics of heat transfer enhancement in low flow area heat exchanger tubes
UEMURA Tomotaka; KANG Donghyuk; HIRAHARA Hiroyuki
The Proceedings of the Fluids engineering conference, Volume：2019, First page：OS10-09, 2019
According to the downsizing of automotive equipment, the present report discussed the heat exchange efficiency in intercoolers used in turbochargers system, etc. Due to the downsizing, low-flow-rate heat exchanger such as installed in a sub-radiator, or the electronic devices in hybrid and electric vehicles. In a low flow rate regime, we can propose a method for promoting convective heat transfer by installing a protrusion on the surface to generate a calm swirling flow. In this study, we visualized the flow using a temperature-sensitive liquid crystal that promotes the heat transfer coefficient while suppressing the increase in pressure loss caused by the method of generating swirl flow with protrusions. In this study, experiments were conducted using a model of the tube part without cooling fins. The size of the channel is 16mm x 120mm x 1.2mm. We visualized the flow using the temperature-sensitive liquid crystal that promotes the heat transfer coefficient while suppressing the increase of pressure loss caused by the method of generating the swirl flow by the protrusion using the temperature-sensitive liquid crystal. From the results obtained in the temperature-sensitive liquid crystal experiment and the results obtained from the numerical analysis, it can be confirmed that the temperature distribution of the entire flow path is increased by installing V-shaped projections. Therefore, it can be said that it is necessary to improve the experimental apparatus in the future and compare the obtained temperature boundary layer with the approximate solution to confirm the validity of the experiment.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2019.os10-09
DOI ID：10.1299/jsmefed.2019.os10-09, eISSN：2424-2896, CiNii Articles ID：130007880106 - A study on separation flow around rotating and non-rotating cylinders with a vortex method
KOGURE Akihiro; KANG Donghyuk; HIRAHARA Hiroyuki
The Proceedings of the Fluids engineering conference, Volume：2019, First page：OS3-27, 2019
Separation of flows from a surface of an object is deeply related to aerodynamics itsself. In this study, a flow around a cylinder is considered as typical flow around the object. When a cylinder rotates, lift force is generated by the Magnus effect, meanwlie at a certain Reynolds number Re and spin ratio, it is reported that a negative Magnus effect (negative lift) is generated by the changes of separation points. And the behavior of the separation point is very important, however there are many unclear points on its fluctuations. Regarding to this, we assume the separations is closely related with the unsteady fluctuation of flow i.e. vortices. So we investigated flows around a cylinder by means of vortex method in order to clarify mechanisms of separations. Computations are performed at Re=2000, and agreements are obtained between the results with vortex method and a summary by Cantwell and Coles (1983). To estimate the location of flow separation we calculated velocity every π/180 rad on the circular arc whose radius is 1.02a (a is radius of the cylinder.). Then the angle θs at which the tangential velocity changes from positive to negative was detected on the condition that normal velocity is positive. As a result, the fluctuation of the separation point has been predicted. On the other hand, a relatively large velocity was observed behind the cylinder when vortices leave a cylinder. The influence of the velocity distribution and strength and position of vortices are discussed on the new vortices.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2019.os3-27
DOI ID：10.1299/jsmefed.2019.os3-27, eISSN：2424-2896, CiNii Articles ID：130007880249 - Study on characteristics of underwater expansion wave induced by pulsed laser irradiation
HAYASHI Toshiki; HIRAHARA Hiroyuki; KANG Donghyuk
The Proceedings of the Fluids engineering conference, Volume：2019, First page：OS2-22, 2019
In recent years, research on the use of underwater expansion waves in cell engineering and medical applications has attracted attention. Expansion waves can be generated by reflection at interfaces with large acoustic impedance differences, and research on expansion wave focusing using silicon materials is seen. However, there are still many unclear points regarding the characteristics of expansion waves. In this study, we generated underwater expansion wave by underwater shock wave reflection at the water-air interface and the PDMS-air interface. And we focused underwater expansion wave by reflection from an ellipsoidal reflector made of PDMS. The results showed that a large positive pressure appears behind the negative pressure in the expansion wave focused by the PDMS reflector. Then, when the propagation of the internal waves was observed with a two-dimensional reflector, a shock wave along the focusing expansion wave was observed.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2019.os2-22
DOI ID：10.1299/jsmefed.2019.os2-22, eISSN：2424-2896, CiNii Articles ID：130007880136 - Effect of accumulators on cavitation surge in hydraulic systems
Donghyuk Kang; Satoshi Yamazaki; Shusaku Kagawa; Byungjin An; Motohiko Nohmi; Kazuhiko Yokota
Open Archives of the 16th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC 2016, 2019
The analysis of cavitation surge was performed to investigate the effect of accumulators on cavitation surge. The accumulator was modeled by using the momentum equation with a mass and a damping and a stiffness coefficients. The mass, damping and stiffness coefficients were associated with a pipe length between an accumulator and a main pipe, a valve resistance and a compliance of fluid in an accumulator, respectively. The upstream accumulator with the valve resistance had the stability effect and caused the increase of the angular velocity of cavitation surge. The downstream accumulator had the stability effect at small mass flow gain factors and caused the increase/ decrease of the angular velocity of cavitation surge at low/ large cavitation compliances. The amplitudes of flow and pressure oscillations can be reduced by the installation of the upstream accumulator.
International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC 2016, English
SCOPUS ID：85083947143 - Numerical analyses for cavitation surge in a pump with the square root shaped suction performance curve
Motohiko Nohmi; Satoshi Yamazaki; Shusaku Kagawa; Byugjin An; Donghyuk Kang; Kazuhiko Yokota
Open Archives of the 16th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC 2016, 2019
The suction performance curves of the hydraulic pumps show several characteristics such as a sudden drop and gradual decay of pump head and so on. In some particular cases, suction performance curves have a square root shape of “” that shows a drop followed by a short term rise and another drop of pump head. In the present study cavitation surge under the square root shaped curve is analyzed by using numerical analyses Two methods of a lumped parameter system calculation and a distributed parameter system calculation that is in other words three dimensional computation of Navier Stokes Equations are applied. In the case of a lumped parameter system calculation, pump static pressure rise is assumed on the given square root shaped function. Dynamic behaviors of the pump cavitation are represented by the cavitation compliance and the mass flow gain factor. Ordinary Differential Equations are discretized by the second order Runge-Kutta method. In the case of 3D CFD, a commercial code of ANSYS-CFX with cavitation model is adopted. Intensive cavitation surges are observed from the computed results of both methods. Intensive cavitation surge exists around the operating point at the negative slope part of the suction performance curve in the case of the lumped parameter systemcalculation. It exists around the operating point at the positive slope part in the case of 3D CFD. Boundary conditions of the computation have significant effects on the characteristics of the cavitation surge.
International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC 2016, English
SCOPUS ID：85083946538 - Experimental study of thermodynamic effect of tip leakage cavitation in hot water
Daichi Nakai; Teppei Furusawa; Donghyuk Kang; Yuka Iga
Open Archives of the 16th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC 2016, 2019
Thermodynamic effect on cavitation appears in cryogenic fluids. The thermodynamic effect is considered to suppress the development of cavitation. The cavitation performance of inducer of liquid rocket turbopump with liquid hydrogen and oxygen is improved by the thermodynamic effect. The authors have conducted experimental studies about thermodynamic effect on cavitation around single hydrofoils in hot water in previous study, where sheet cavity and sheet/cloud cavity occurs. However, cavitation in inducer is not sheet cavity which is separation type but tip leakage cavity which is vortex type. Therefore, in the present study, experiment is conducted about tip leakage cavitation in order to clarify the intensity thermodynamic effect on vortex type cavitation. In the present study, cavitation experiments is conducted with high temperature and high pressure cavitation tunnel, NACA 0009 hydrofoil is chosen for a test body. In the experimental results, development of the pattern of the tip leakage cavitation did not change by the change of freestream temperature from room temperature up to 90 oC. The result of sheet cavitation is in our previous study. The effect of freestream temperature on a temperature reduction inside the cavity is investigated by the direct measurement technique of temperature inside the tip leakage cavity.
International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC 2016, English
SCOPUS ID：85083945351 - 軸流ファンの性能特性に及ぼす障害物の影響
篠原健; 西部光一; 姜東赫; 佐藤光太郎; 横田和彦; 大上浩
ターボ機械協会講演会(CD-ROM), Volume：81st, First page：ROMBUNNO.A1, 2019
Japanese
J-Global ID：201902235748930629 - 非定常運動方程式を用いたベンチュリ式の流量計の提案
西村尚樹; 姜東赫; 平原裕行
ターボ機械協会講演会(CD-ROM), Volume：82nd, First page：ROMBUNNO.2SHITSU10, 2019
Japanese
J-Global ID：201902244623325661 - 羽根なし撹拌機で発生するスパイラル渦による回転噴流の促進機構
姜東赫; AZAM Md. Tauhedul; 平原裕行; 村田和久; 下司泰史
ターボ機械協会講演会(CD-ROM), Volume：82nd, First page：ROMBUNNO.2SHITSU11, 2019
Japanese
J-Global ID：201902263236169463 - Effect of Obstacles on Premixed Combustion in a Rectangular Tube
TAKAHAMA Ryohei; FURUMOTO Kenichiro; YOKOTA Kazuhiko; KANG Donghyuk; SATO Kotaro
The Proceedings of Conference of Kanto Branch, Volume：2018.24, First page：OS0612, 2018
This study reports on the experiment about combustion wave propagating in the tube. In the experiment, hydrogen is used for fuel. the experimental tube has rectangular cross section and the cross-sectional area is 900mm2. The length is 1016mm. This tube has 5 holes. There are connected to pressure tube gage, fuel valve, vacuum drawing valve and piezometer. It is researched that the effect of the equivalence ratio and of the obstacles. In terms of the resarch on the effect of the equivalence ratio, the experiments are conducted on three conditions, 0.8, 1.0, 1.3. In the case of 0.8, pressure rises most gently in the three. In the case of 1.3, pressure rise most sharply. Judging from these results, the larger the equivalence ratio, more rapidly pressure rise. In terms of the research on the effect of the obstacles, the experiments are conducted using the angle of the block as a parameter. There are four kinds of angles, 0°,30°,60°and 90°. At each angle, pressure rise more rapidly with obstacle, than without obstacle. In addition to this, it is seen that the pressure wave arrives early as the angle increases. On the other hand, the maximum pressure does not depend on the angle.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2018.24.os0612
DOI ID：10.1299/jsmekanto.2018.24.os0612, eISSN：2424-2691, CiNii Articles ID：130007488829 - Effect of Downstream Wall on a Supersonic Jet
ANDO Ryo; YAMAGUCHI Hiroyoshi; YOKOTA Kazuhiko; KANG Donghyuk; YONEZAWA Kouichi
The Proceedings of Conference of Kanto Branch, Volume：2018.24, First page：OS0504, 2018
Dual-bell nozzle is one of the altitude compensation nozzle concepts, which consists of two bell types nozzle with different geometric area ratios. It can be used for the main engine of reusable vertical take-off and landing launch vehicles. Suppose vertical take-off and landing using the dual-bell nozzle, flow instabilities in dual-bell nozzle are examined with a wall simulating the ground downstream of the nozzle exit. Effects of the nozzle pressure ratio (NPR) and the distance of the wall from the nozzle exit, the angle against the wall and the nozzle exit are studied experimentally . In this study, nonsteady pressure change are measured and flow can be visualize. Reviaval the flow from high pressure chamber to low pressure chamber via the nozzle. FFT analysis are excuted with the result of pressure mesurement. Results shows that the operation modes are two types ,three types of periodic flow oscillation occur without impinging wall. With the wall, operation modes are one type, no or one type of flow oscillation occur. The number of fluid vibrations and vibration mode depend on the NPR and the distance between the nozzle and the wall. The frequencies of that depend on the angle. It is necessary to clarify the mechanism of flow oscillation with numerical calculation.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2018.24.os0504
DOI ID：10.1299/jsmekanto.2018.24.os0504, eISSN：2424-2691, CiNii Articles ID：130007485917 - Flow Characteristics of a Jet Using a Cylindrical Plasma Actuator
ITAGAKI Naoki; YOKOTA Kazuhiko; KANG Donghyuk; SATO Koutarou
The Proceedings of Conference of Kanto Branch, Volume：2018.24, First page：OS0515, 2018
In this study, experiments and numerical calculations of a plasma actuator (PA) were carried out. PA is a microfluidic device composed of two electrodes and dielectric, high voltage and high frequency power supply. Cylindrical PA was placed at the inside of the cylinder. Type A of cylindrical PA was opened inlet and outlet. Type B of cylindrical PA was opened outlet only. In the experiment, the flow field of the jet was visualized. Two types of cylindrical PA induced flow velocity were obtained from PIV. Type A of cylindrical PA tends to increase the flow velocity as the cylinder radius is decreased. Type B of cylindrical PA changes the state of the jet depending on the installation position of PA. Type A of cylindrical PA induced flow velocity is 450-650 mm/s. Type B of cylindrical PA induced maximum flow velocity is about 450 mm/s. In the numerical calculations, PA is modeled by body force. Type A of cylindrical PA gave a body force 50000-59000 N/m3 on the inside of the cylinder and obtained by steady calculation. Type B of cylindrical PA was gave a body force 50000 N/m3 on the inside of the cylinder and obtained by transient calculation. The induced flow velocity of numerical calculation is near to experiment.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2018.24.os0515
DOI ID：10.1299/jsmekanto.2018.24.os0515, eISSN：2424-2691, CiNii Articles ID：130007488761 - Influence of Backflow Prevention Plate on Unsteady Characteristics of Swirling Jet
ANAGUCHI Kaiki; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
The Proceedings of Conference of Kanto Branch, Volume：2018.24, First page：OS0517, 2018
The present research investigated effect of backflow prevention plate on unsteady characteristics of a swirling jet. The experimental facility was designed to control the swirl ratio adjusted by varying the angle of the guide vanes. For visualization, the swirling jet with a smoke was illuminated by a laser sheet. The circumferential velocities were measured by hot wire probes. The experimental results show that the swirling jet for the 0 degree of the guide vanes flows along the outside wall. When the angle of guide vanes is enlarged, the flow was emitted in the axial direction. When the guide vane angle is 30 degrees, backflow occurs toward the center of the jet outlet. In order to prevent the backflow, a cylinder and a disk are attached to the jet outlet. When the result was compared, the difference in the peak of the FFT analysis was seen by attaching the cylinder and the plate. By the FFT, one peak with the three rotating cells was observed with and without the cylinder. On the other hand, one peak with the four rotating cells was observed with cylinder and plate. Flow fluctuation occurs by backflow to the jet outlet at 30 degrees of the guide vane angle.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2018.24.os0517
DOI ID：10.1299/jsmekanto.2018.24.os0517, eISSN：2424-2691, CiNii Articles ID：130007488045 - Study on Behavior of Jet Generated in Underwater Explosion near Water Surface
AKIYAMA Goki; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
The Proceedings of Conference of Kanto Branch, Volume：2018.24, First page：OS0522, 2018
Although there is a lot of underwater explosion study to investigate impact on structures, there is very few study to investigate underwater explosion near surface. So in my study, we performed an experiment near surface with depth as a parameter. Underwater explosion was performed using a thin line explosive method. We used the boosting chopper circuit to make high voltage for a thin line explosive method. Under certain conditions, the peculiar shape like crown occurs to a jet. We investigated the flow field that occurs to underwater explosion by doing numerical calculation, and using this result, we investigated cause of generation with the crown shape. An explosion phenomenon was visualized with highspeed camera. Also we analyzed the resulting images to evaluate the results. We got the jet velocity from high-speed camera photos and we compared it every depth. When the depth was shallow, the jet velocity that occurs by underwater explosion was increase and the crown shape tended to become unstable. To imitate underwater explosion by numerical calculation, we made a high-pressure air bubble in the water. We used LES for turbulence model and grid with the same size as an experimental water tank. It was confirmed that numerical calculation is parallel with an experiment qualitatively.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2018.24.os0522
DOI ID：10.1299/jsmekanto.2018.24.os0522, eISSN：2424-2691, CiNii Articles ID：130007489642 - Characteristics of Geysering in a Vertical Heating Tube
KASAKURA Kenichi; ENDO Daiki; YOKOTA Kazuhiko; KANG Donghyuk
The Proceedings of Conference of Kanto Branch, Volume：2018.24, First page：OS0523, 2018
The present study investigated geysering in a vertical heat tube. In recent years, oscillation due to the boiling phenomenon of the same mechanism as Geysering is regarded as a problem at LNG base and nuclear power plant. Research on geysering has been done so far, but its characteristics are still unknown. In this research, experiments were conducted with the aim of understanding the fundamental characteristics of Geysering. The experimental apparatus is a closed loop type provided with a section for storing water and a section for heating. This system generates boiling and natural convection, and it is a mechanism that can measure and observe. In this experiment, the following conclusion was obtained. First, geysering occurs in a certain temperature region and has a frequency unique to the phenomenon. Second, As the inflow temperature rises, the frequency of the geysering also increases. Third, the pressure in the aquarium affects the occurrence of geyzering and its frequency. Fourth, the height of the liquid level also affects the occurrence of geizering and its frequency. Fifth, As the inflow temperature rises, the form of the flow instability phenomenon changes. Finally, even when the internal pressure and the liquid level are changed variously, the same phenomenon occurs if the hydrostatic pressure is adjusted to be equal.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2018.24.os0523
DOI ID：10.1299/jsmekanto.2018.24.os0523, eISSN：2424-2691, CiNii Articles ID：130007486954 - 112 The Study of Fluid Oscillation in Generating Mode about Pump-Turbine
SUGIYAMA Hayate; MATSUMURA Koichiro; YOKOTA Kazuhiko; Kang Donghyuk
The Proceedings of Conference of Tohoku Branch, Volume：2018.53, First page：23, Last page：24, 2018
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmeth.2018.53.23
DOI ID：10.1299/jsmeth.2018.53.23, eISSN：2424-2713, CiNii Articles ID：130007488389 - Influence of a Shape of Slit Nozzles on Atomization of a liquid Jet
TAKEUCHI Hitoshi; KANG Donghyuk; YOKOTA Kazuhiko; MIYAUCHI Hideki
The Proceedings of Conference of Kanto Branch, Volume：2018.24, First page：OS0516, 2018
In order to improve atomization characteristics, a steady jet experiment was conducted under atmospheric pressure atmosphere using a slit nozzle simulating a jet engine in two dimensions, and the spray characteristics associated with the influence of the groove on the nozzle wall surface were investigated. In this study, a steady jet experiment is performed on the wall surface of the nozzle injection port using a nozzle without grooves, a nozzles with a vertically grooved groove, and a nozzle with grooves inclined by 4 degrees, and the width of the jet is measured from the photographed image comparison was made. Water was used as the sample liquid, and pressurization and pressure adjustment were performed using a compressor and a regulator. As a result, comparing the nozzle without groove and the nozzle with grooves, the spread of the jet became larger in the grooved nozzle. In addition, when comparing the vertically grooved nozzles with the nozzles with grooves tilted by 4 degrees, the spread of jet widened in nozzles with grooves tilted 4 degrees. From those result, it was found that atomization is promoted by processing the groove on the wall surface inside the nozzle injection port, and further atomization is promoted by angle to the groove to be processed.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2018.24.os0516
DOI ID：10.1299/jsmekanto.2018.24.os0516, eISSN：2424-2691, CiNii Articles ID：130007490080 - 105 Visualization experiment and numerical calculation on cavitation vibration in centrifugal pump
YOSHINO Kazuki; YOKOTA Kazuhiko; Kang Donghyuk; Maeda Tomoshige
The Proceedings of Conference of Tohoku Branch, Volume：2018.53, First page：9, Last page：10, 2018
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmeth.2018.53.9
DOI ID：10.1299/jsmeth.2018.53.9, eISSN：2424-2713, CiNii Articles ID：130007488359 - On development in turbulence and energy transport over golf ball dimple
IKEDA Tsutomu; HIRAHARA Hiroyuki; KANG Donghyuk; MASAKI Kento
The Proceedings of the Symposium on sports and human dynamics, Volume：2018, First page：B-12, 2018
We prepared the computational domain, which 9 dimples of golf ball are linearly distributed on a flat plane. The Reynolds number based on dimple diameter is 22000 and a time step is 1×10-5s. We found out that the momentum thickness on a first dimple was also same value for different depth models and the momentum of the flow over 9 dimples didn’t change significantly after a fourth dimple. We think turbulence doesn’t develop after the fourth dimple. Observing the vortex structure visualized by lamda2-criterion (λ2=-6×108 /s2), there was no vortex on first dimple. Span axis vortices was generated on second dimple and it transformed to hairpin and streamwise vortices. After third dimple, there are almost only streamwise vortices except around dimple edges. These vortices help to transport a momentum from main flow to a turbulent boundary layer. Then, we measured vorticities for each directions ωx, ωy, ωz. The maximal value of ωx didn’t change after the fourth dimple, so that the momentum hardly change. As these results, we revealed that the vortex structure is completed over there dimples.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmeshd.2018.b-12
DOI ID：10.1299/jsmeshd.2018.b-12, eISSN：2432-9509, CiNii Articles ID：130007654514 - Rotordynamic Fluid Forces Operates to the Small Axial Fan
HASEGAWA Kodai; YOKOTA Kazuhiko; KANG Donghyuk
The Proceedings of Conference of Kanto Branch, Volume：2018.24, First page：OS0509, 2018
As the cause of vibration that be caused to the whirling motion at the rotating machine, It exists in the rotordynamic fluid forces. Vibration arisen by the forces is primarily called self-excited vibration. It is difficult to operate by the vibration more than natural frequency because it has the characteristics that amplitude is not reduced even if rotational speed is increased. In this study, the effect of pressure around the blades and fluid forces occurs to the whirling motion internally are investigated by making use of CFD. Also, it is enable to reproduce the whirling motion by producing rotating lattice between the casing and the axial fan. As the investigation of circumferential pressure, it is confirmed that pressure difference is increased by changing of eccentricity. Additionally, it is found that the changes of whirling speed ratio are gained the force which try to press fluid to the casing and pressure is increased. The investigation of normal and tangential fluid forces at the whirling speed ratio Ω/ω revealed that tangential fluid force tends to decrease linearly with increasing Ω/ω. Also, it is found that the tangential force works in the direction of promoting the whirling motion at the range of -0.1<Ω/ω<0.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2018.24.os0509
DOI ID：10.1299/jsmekanto.2018.24.os0509, eISSN：2424-2691, CiNii Articles ID：130007489727 - Consideration on development of turbulence in impulsive deceleration flow
工藤慎也; 吉崎翔; 姜東赫; 平原裕行
日本機械学会流体工学部門講演会講演論文集(CD-ROM), Volume：96th, 2018
ISSN：1348-2882, J-Global ID：202102240347778285 - Identification of Cells in Swirling Jets by Machine Learning
TAKAHASHI Hiroyuki; KANG Donghyuk; YOKOTA Kazuhiko
The Proceedings of Conference of Kanto Branch, Volume：2018.24, First page：OS0514, 2018
The present paper deals with identification and detection of cells. To identify the cells is useful for the investigation of the non-steady phenomenon and can consider its reason and measure. In the previous method, although it is done to detect the cells by using FFT, it does not detect the generation process and identification in real time. This paper investigated how can recognize the cells by learning a lot of the images by convolutional neural network (CNN) and evaluated where CNN pays attention to by Gradient-weighted Class Activation Mapping (Grad-CAM). Then it investigated to detect the cells by Single Shot Multibox Detector (SSD) by learning the own cell in itself. In this case, CNN seemed like learning the cells. In contrast, it estimated its based on unrelated information by Grad-CAM. It caused by the bias of the input data, for example, the rate of magnification of images, the range of the output value for computational fluid dynamics and the lack of the dataset and the conditions of CFD. Although CNN detected the cells by using SSD, detection accuracy is low. As a result, in order to get high detection accuracy, it is required for the quantitative and qualitative improvement of the dataset.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmekanto.2018.24.os0514
DOI ID：10.1299/jsmekanto.2018.24.os0514, eISSN：2424-2691, CiNii Articles ID：130007487428 - 103 Experiment and Numerical Simulation on Flow and Noise on Contra Rotating Propellers
TANIGUCHI Yuta; KANG Donghyuk; YOKOTA Kazuhiko
The Proceedings of Conference of Tohoku Branch, Volume：2018.53, First page：5, Last page：6, 2018
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmeth.2018.53.5
DOI ID：10.1299/jsmeth.2018.53.5, eISSN：2424-2713, CiNii Articles ID：130007487597 - Effect of volume exclusion rate on performance of screw-type turbine
TSUTSUMI Hiromasa; KANG Donghyuk; HIRAHARA Hiroyuki
The Proceedings of the Fluids engineering conference, Volume：2018, First page：OS6-4, 2018
Various wind power generators such as propeller, Darrius and Savonius types have been used. The present study proposed the new screw-type wind turbine. As compared to other power generators, the present one become simpler and more portable. By these advantages, the new applications of the wind power systems such as disaster areas and outdoor activities will be expected. The power characteristics of the screw-type wind turbine were clarified by using a Computational Fluid Dynamics (CFD) and a wind tunnel experiment. The CFD and experimental results show that the maximum-efficiency wind speed is about two times of the tip velocity. The angular momentum flow rates in a control planes surrounding the screw-type wind turbine were examined by the CFD. The results show that the angular momentum flow rate to the axial direction contributes to mainly the power coefficient in the wind speeds larger than the tip speed. On the other hands, the angular momentum flow rate to the radial direction becomes negative when the ratio of the tip speed to the wind velocity is high. That is, the energy of the flow to the radial direction was inversely supplied by the wind turbine. It was confirmed that the low velocity on the blade suction surface caused the negative angular momentum flow rate.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2018.os6-4
DOI ID：10.1299/jsmefed.2018.os6-4, eISSN：2424-2896, CiNii Articles ID：130007654156 - Flow Visualization of Stirred Tank Reactor with Rotating Jet
AZAM Md. Tauhedul; KANG Donghyuk; HIRAHARA Hiroyuki; MURATA Kazuhisa; SHIMOJI Yasufumi
Proceedings. International Conference on Flow Dynamics (CD-ROM), Volume：15th, First page：700‐701, 2018
English
J-Global ID：201902263072626798 - Fluid Dynamical Consideration on Signal Propagation in Creature Crowd with Molecular Kinetic Model
SULTANA Shirin; HASAN Mahmudul; KANG Donghyuk; HIRAHARA Hiroyuki
Proceedings. International Conference on Flow Dynamics (CD-ROM), Volume：15th, First page：98‐99, 2018
English
J-Global ID：201902283997760737 - 部分遮蔽の上流壁が小型軸流ファンの流れ場と騒音に与える影響
小澤諒; 横田和彦; 鶴若菜; 姜東赫
ターボ機械協会講演会(CD-ROM), Volume：79th, First page：ROMBUNNO.A03, 2018
Japanese
J-Global ID：201802267259389243 - 低比速度ポンプ水車の流体振動発生時の流れ場に関する実験及び数値計算
松村康一郎; 横田和彦; 鶴若菜; 杉山颯; 姜東赫
ターボ機械協会講演会(CD-ROM), Volume：79th, First page：ROMBUNNO.B06, 2018
Japanese
J-Global ID：201802277671911814 - 吐出配管アキュムレータによるポンプキャビテーションサージの抑制
前田智重; 鶴若菜; 横田和彦; 姜東赫; 常田智樹; 香川修作; 安炳辰; 能見基彦
ターボ機械協会講演会(CD-ROM), Volume：79th, First page：ROMBUNNO.B05, 2018
Japanese
J-Global ID：201802278345752844 - 多翼送風機のPIVによる特異変動解析
川埼真俊; 平原裕行; 箭内優樹; 姜東赫
ターボ機械協会講演会(CD-ROM), Volume：80th, First page：ROMBUNNO.B16, 2018
Japanese
J-Global ID：201902276503371876 - Thermodynamic Effect on Tip Leakage Vortex Cavitation
KANG Donghyuk; IGA Yuka
東北大学流体科学研究所共同利用・共同研究拠点流体科学国際研究教育拠点活動報告書, Volume：2016, First page：49‐50, Nov. 2017
English
J-Global ID：201802253527658708 - 翼端漏れ渦キャビテーションの熱力学的効果
姜東赫; 伊賀由佳
東北大学流体科学研究所共同利用・共同研究拠点流体科学研究拠点活動報告書, Volume：2015, First page：53‐54, Mar. 2017
Japanese
J-Global ID：201702233820369275 - 低流量領域に生じる軸流送風機の後ろ回り変動に関する研究
鈴木健仁; 姜東赫; 横田和彦; 佐藤光太郎
Volume：77th, 2017
J-Global ID：201702229052659395 - A study on a swirl flow instability induced by a rotating cylinder between coaxial two disks
KANG Donghyuk; SATO Kotaro; YOKOTA Kazuhiko
Transactions of the JSME (in Japanese), Volume：83, Number：850, First page：17-00038, Last page：17-00038, 2017
The present study investigates a swirl flow instability induced by a rotating cylinder between coaxial two disks as a model of a vaneless diffuser at zero flow rate. To begin with, the experiment and three-dimensional finite volume simulation were performed. The rotating cylinder was used to produce the swirl flow. Small vortices were generated from the cylinder surface. They were combing and forming one croissant-shaped toroidal vortex (CTV), which was rotating around the cylinder. Small vortices were separating from the CTV and flowing away from the cylinder. In order to investigate the cause of the swirl flow instability, a 2D stability analysis for an annular vortex street was performed. The annular vortex street became less unstable for the larger radial location and the fewer number of vortices. This implies that the vortices could be forming into one vortex as their radial locations increased. In order to validate the stability analysis, the vortex simulations were carried out. The vortices generated from the cylinder surface were forming into one cell as their radial locations increased. In order to validate the stability analysis and vortex simulation, the 2D finite volume simulation was performed. The vortices were generated from the cylinder surface. They were combining and forming one cell, which was rotating around the cylinder. The vortices were separating from one cell and flowing away from the cylinder. The frequencies of vortex rotation agreed in the experiment, the two and three-dimensional simulations. Therefore, it is considered that the 2D vortex transforms to the 3D CTV, similarly the Tayler vortex. Furthermore, all the results indicate that the 2D swirl flow instability causes the CTV, and the vortices combining to and separating from the CTV.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/transjsme.17-00038
DOI ID：10.1299/transjsme.17-00038, eISSN：2187-9761, CiNii Articles ID：130006943414 - FLOW CHARACTERISTICS OF AXIAL-FLOW FANS WITH AN UPSTREAM / DOWNSTREAM BLOCKAGE DISK
Keiichi Ochiai; Shinsaku Nakamura; Kotaro Sato; Donghyuk Kang; Kazuhiko Yokota
PROCEEDINGS OF THE ASME FLUIDS ENGINEERING DIVISION SUMMER MEETING, 2017, VOL 1A, 2017, [Reviewed]
Axial-flow fans have been used in various applications such as thermal control and ventilation. Fans are often used in narrow spaces around obstacles such as electric parts, areas near clogged of fan filters, and walls. These obstacles lead to decreased performance and increased noise and vibration in electric devices. This study attempts to experimentally clarify the influences of upstream/downstream-mounted blockage disks on the flow characteristics of an axial-flow fan. The important results are summarized as follows: (1) For the same relative distance, the pressure performance and efficiency curves of the fan owing to the upstream-mounted blockage disk completely differ from those owing to the downstream mounted blockage disk. (2) For a small relative distance, the pressure coefficient owing to the upstream and downstream mounted blockage disks decreases and increases, respectively. (3) The efficiency of the fan owing to the upstream-mounted blockage disk decreases. However, the efficiency owing to the downstream-mounted blockage disk increases for specific conditions.
AMER SOC MECHANICAL ENGINEERS, English
Web of Science ID：WOS:000417223800023 - NUMERICAL STUDY OF ONE DIMENSIONAL PIPE FLOW UNDER PUMP CAVITATION SURGE
Motohiko Nohmi; Satoshi Yamazaki; Shusaku Kagawa; Byungjin An; Donghyuk Kang; Kazuhiko Yokota
PROCEEDINGS OF THE ASME FLUIDS ENGINEERING DIVISION SUMMER MEETING, 2017, VOL 1A, 2017, [Reviewed]
Pump cavitation surge is highly coupled phenomenon with unsteady cavitation inside a pump and system dynamics of the pipe flow surrounding the pump. The piping system flow dynamics can be calculated under two kinds of assumptions; lumped parameter system (LPS) and distributed parameter system (DPS). In the lumped parameter system, the equations of motion of water columns inside pipes are calculated upstream and downstream of the pump. In the distributed parameter system, wave propagations along the pipes are calculated. In this study a simple system that consists of an upstream tank, an upstream pipe, a pump with cavitation, a downstream pipe and a downstream tank is analyzed by using two methods. Cavitation inside the pump is featured in the lumped parameters of cavitation compliance and mass flow gain factor. In the lumped parameter system case, equations of motion are calculated numerically by Runge-Kutta methods. In the distributed parameter system case, wave propagations are calculated by Method of Characteristics. From the comparison of two method results, appropriate criterion for practical piping system calculation is discussed.
AMER SOC MECHANICAL ENGINEERS, English
Web of Science ID：WOS:000417223800080 - クロスフローファン流れに生じる後ろ回り流体振動に関する片壁面半径の影響
日下部裕真; 姜東赫; 横田和彦; 佐藤光太郎
ターボ機械協会講演会(CD-ROM), Volume：77th, First page：ROMBUNNO.B02, 2017
Japanese
J-Global ID：201702286929016401 - Experimental Study of Thermodynamic Effect of Tip Vortex Cavitation in Hot Water
Daichi Nakai; Tepei Furusawa; Donghyuk Kang; Yuka Iga
International Symposium on Transport Phenomena and Dynamics of Rotating Machinery (ISROMAC2016), 15 Apr. 2016, [Reviewed]
English - GS0515 A Numerical Simulation on Flow Oscillations in a Transonic Compressor Cascade
SUZUKI Takehito; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2016, Number：22, First page："GS0515, Last page：1"-"GS0515-2", 10 Mar. 2016
In the flow of transonic compressor, shock waves occur around blades and cause instabilities. These shockwaves may become unstable at high pressure ratio near stall line. The purpose of the investigation was to determine the change in the flow around the three-dimensional blade row in transonic compressor. Two compressor wings were designed with changing length of span direction. With used the numerical simulations, determined how change these shock waves in the flow that several pressure ratio or circumference speed ratio. Compared to short span length, long span length can operate in wide-range condition at high circumference speed ratio. The shock wave and the expansion wave at leading edge become stronger at higher pressure ratio. The boundary layer develop from suction surface just behind the shock wave.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110010049977, CiNii Books ID：AA11902161 - GS0505 Effects of Position of Flexible Sheet Supported at Upstream on Wind Power Generation Utilizing Flutter
INOUE Shouta; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2016, Number：22, First page："GS0505, Last page：1"-"GS0505-2", 10 Mar. 2016
In this research, it's mentioned about investigations of effects of changing the position of sheet on the wind power generation utilizing flutter. A steel sheet is attached to the rotation axis. A flexible sheet is settled at the trailing edge of the plate. Displacement, the current and voltage of the generator were measured. Measuring values in a variety of wind speed. Calculating electric power from the value of the current and voltage, frequency and amplitude from the displacement. Moreover, the action of the flutter was observed with a high speed camera. Furthermore, it experimented by the seat which reduced the influence of the steel sheet. As a result, when the flexible sheet is settled at a distance from the rotation axis, the generated power increase.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110010049967, CiNii Books ID：AA11902161 - GS0514 Effects of a Blade Shape on a Cavitation Oscillation in a Centrifugal Pump
SEKI Kouta; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2016, Number：22, First page："GS0514, Last page：1"-"GS0514-2", 10 Mar. 2016
The present research investigates the cavitation instability in centrifugal pump with two dimensional impeller. In order to examine the cavitation instability, two types of two dimensional impeller are designed. These impellers that are simulated by CFD (Computational fluid dynamics) depend on the angle of the blade. Boundary conditions are total pressure at inlet and mass flow at outlet. Cavitation number is adjusted by total pressure. As a result, CFD shows that decreasing cavitation number in these impellers makes not only the pressure coefficient decreases but also the cavity volume increases.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110010049976, CiNii Books ID：AA11902161 - GS0520 A Numerical Simulation on the Effects of Guide Vane Opening on a Pump-Turbine Performance
NAGASHIKI Mayuko; YOKOTA Kazuhiko; KANG Donghyuk
Volume：2016, Number：22, First page："GS0520, Last page：1"-"GS0520-2", 10 Mar. 2016
In order to clarify the instability phenomena when the pump-turbine stops in case of necessity, the experiment and the numerical simulation were performed. The past research shows that these phenomena occur when the characteristic curve observed is the serpentine curve. Also, the inlet height and the outlet height of the pump-turbine's runner has no effect on this result. Therefore, this research focuses on how the inlet and blade angle of the guide vanes affects the characteristic curve observed when the blade thickness of pump turbine's runner is changed. Three different inlet and blade angles are used for the experiment and the numerical simulation. As a result, they show that the instability of the pump turbine is decreased by the guide vanes. Besides, the numerical simulation shows the vortex occurs at the trading edge of the runner.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110010049982, CiNii Books ID：AA11902161 - GS0522 The Experiment of influence of Guide Vane Opening about Pump-Turbine characteristics
MATSUSHIMA Naoto; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2016, Number：22, First page："GS0522, Last page：1"-"GS0522-2", 10 Mar. 2016
In order to clarify the mechanism of the vibration phenomenon which occurs when a pump-turbine stops suddenly, the experiment of the pump-turbine were performed in this research. The pressure are measured at inlet and outlet with changing flow rate, rotating speed and guide vane opening. "S-shape curve" was observed in the turbine characteristic curve. The past research clarifies that appearing "S-shape curve" means vibration phenomenon occurs. The experimental result shows that as the guide vane opening is smaller, ψ is larger. In the value of φ/φ_d from 0.3 to 0.6, the fluid vibration occurs with the 20 degree GV and the 34 degree GV. On the other hand, with the 8 degree GV, the fluid vibration doesn't occur.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110010049984, CiNii Books ID：AA11902161 - GS0521 A Backward-Propagating Flow Oscillation in a Multi-Blade Fan
YAMAGUCHI Yusuke; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2016, Number：22, First page："GS0521, Last page：1"-"GS0521-2", 10 Mar. 2016
The experimental studies were performed to clarify the fundamental flow characteristics of a fan with forward-inclined multi-blades. A crossflow fan is rotated in the open space, i.e. without casing. The crossflow fan simulates a Sirocco fan with a closed inlet. Using fan's height is 115mm, the inlet and outlet radii are 160 and 180mm, respectively. The inlet and outlet blade angles are 90 and 150 degrees, respectively. The impeller includes 52blades. The amplitude fluctuation at the impeller outlet are measured using a hot-wire anemometry. The experimental results show good agreements with respect to frequencies and cell numbers. The FFT spectra of the experimental results show one peak in the crossflow fan. The one-cell oscillations occur for the crossflow fan.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110010049983, CiNii Books ID：AA11902161 - GS0518 A Flow Oscillation in a Rotating Cylinder Between Two Circular Plates
TANIGUCHI Yuta; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2016, Number：22, First page："GS0518, Last page：1"-"GS0518-2", 10 Mar. 2016
This study presents the flow oscillation around a rotating cylinder between two coaxial stationary circular disks by experiment and numerical simulation. In the experiments and simulations, a cylinder is 55mm diameter and two coaxial stationary circular disks are 300mm diameter. This cylinder rotates with 7000rpm between two coaxial stationary circular disks. In conclusion, influence of two circular disks do not exist when the interval of two circular disks widen a certain level or more. FFT analysis results indicate the rotating instability of one cell rotating in the circumferential direction near the rotating cylinder in spite of interval of two circular disks.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110010049980, CiNii Books ID：AA11902161 - GS0506 Characteristics of Clearance Flow with Porous Plate
YAMAGISHI Hayato; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2016, Number：22, First page："GS0506, Last page：1"-"GS0506-2", 10 Mar. 2016
Porous aerostatic bearing are known to provide high stiffness and load capacity. It has been used to actually precision machine tools and precision measuring instruments However, it doesn't correspond to clearance internal pressure distribution and exhaust gas flow rate of measure result and FFT calculation result. The causes are thought to be due to various factors arising from features of porous material. In this paper, by performing experiments and theoretical analysis of the gap flow with a porous, it will approach the causes of disagreement of clearance internal pressure distribution and exhaust gas flow rate by experiment and numerical analysis.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110010049968, CiNii Books ID：AA11902161 - 多翼ファンに発生する後ろ回りの非定常流れに対するスパン高さの影響
山口裕介; 姜東赫; 横田和彦; 佐藤光太郎
Volume：76th, 2016
J-Global ID：201602269659918013 - Influence of Cavitation in a Double-Suction Centrifugal Pump on a Torque and a Pressure Loss
YAMAZAKI Satoshi; KANG Donghyuk; KAGAWA Shusaku; AN Byungjin; NOHMI Motohiko; YOKOTA Kazuhiko
The Proceedings of Mechanical Engineering Congress, Japan, Volume：2016, First page：J0520401, 2016
The present research investigated flow characteristics in a square-root-shaped region of a suction performance curve based on computational fluid dynamics (CFD). The square-root-shaped region observed in the experiment was well simulated by CFD. Cavitation surge and rotating cavitation occurred in the square-root-shaped region. The square-root-shaped region was observed only in the suction performance curve of the computational domain of the impeller. The square-root-shaped region is caused by the changes of the torque and the pressure loss due to cavitation. The torque fluctuation had the opposite phase to the cavity volume fluctuation. On the other hand, the pressure loss had the same phase as the cavity volume fluctuation. The vorticity was generated from the cavity and the generated vorticity led to the decrease of the torque and the increase of the pressure loss. The blockage of the blade passage due to cavitation decreased the torque and increased the pressure loss and vorticity.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmemecj.2016.j0520401
DOI ID：10.1299/jsmemecj.2016.j0520401, eISSN：2424-2667, CiNii Articles ID：130007063460 - Unsteady Characteristics in a Swirling Jet
FUJIWARA Akihiro; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
The Proceedings of Mechanical Engineering Congress, Japan, Volume：2016, First page：S0520401, 2016
The present study investigated unsteady characteristics of a swirling jet. The experimental facility was designed to control a swirl ratio which is the ratio of the averaged swirl velocity at the trailing edge of the impeller to the averaged axial velocity at the slot. The swirl ratio was adjusted by varying the rotational speed of the impeller and the mass flow rate. The swirling jet was visualized by smoke and a laser sheet. The visualization result showed that the swirling jet at the high swirl ratio leaned to the outside wall and flowed radially. The fluctuating circumferential velocities were measured by hot wire probes. By Fast Fourier Transform (FFT), it confirmed that the three cells rotated in the same direction as the rotating direction of the impeller. At higher swirl velocity ratios, the normalized frequencies of the rotating cells were not changed by the swirl velocity ratio. On the other hand, at lower swirl ratios, the normalized frequencies of the rotating cells increased with the decrease of the swirl ratio. The unsteady characteristics of the swirling jet observed in the experiment were simulated by the computation fluid dynamics (CFD) well.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmemecj.2016.s0520401
DOI ID：10.1299/jsmemecj.2016.s0520401, eISSN：2424-2667, CiNii Articles ID：130007069421 - Flow Characteristics of High-Speed Swirling Flow in a Circular Pipe
OHSHIMA Naoya; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
The Proceedings of Mechanical Engineering Congress, Japan, Volume：2016, First page：G0500804, 2016
A swirling flow has a high diffusibility and the high mixed efficiency, so it is used in a combustor, a boiler, a gas turbine and so on. The swirling flow is known that it has various unsteady, and in the case of unstable condition, the swirling flow causes fluid oscillation and it causes a vibration and a noise for fluid machinery. However, there is few reports of the research which is taken account of the high-speed swirling flow, that is, about compressibility flow. In this research, the unsteady behavior of the high-speed swirling flow was experimentally investigated. The high-speed swirl flow was generated by the inlet guide vane and the suction type wind tunnel. The various type of the unsteady flows was found in the large guide vane angles and the lower tank pressures. For 60 and 70 degrees of the inlet guide vane, the peaks near 2000Hz and 5000Hz observed in the large guide vane angles disappeared and the peak near the 3000Hz appeared.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmemecj.2016.g0500804
DOI ID：10.1299/jsmemecj.2016.g0500804, eISSN：2424-2667, CiNii Articles ID：130007063769 - ポンプキャビテーションサージにおけるバロクリニックトルクと損失の関係
岩田敏輝; 姜東赫; 山崎賢; 香川修作; 安炳辰; 能見基彦; 横田和彦
Volume：22nd, 2016
ISSN：2424-2691, J-Global ID：201702272667800430 - "Influence of Thermodynamic Effect on Growth and Collapse of Cavitation"
中井大地; 佐々木裕章; 姜東赫; 能見基彦; 安炳辰; 伊賀由佳
日本機械学会第94期流体工学部門講演会, 山口(2016.11.12-13(12)), OS9-1, No.0904, Volume：2016, Number：0, First page：904, Last page：904, 2016Cavitation experiments was conducted with high temperature and high pressure cavitation tunnel to investigate thermodynamic effect on tip leakage cavitation. NACA0009 hydrofoil with tip clearance is chosen for a test body. In the experiments results, at T∞ = 90 oC, the large amplitudes are observed at the higher frequencies than 50 Hz. These can be considered because collapse time of cavity was shortened by thermodynamic effect. Moreover, the temperature depression inside tip leakage cavity increases with the increase of the thermodynamic parameter.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmefed.2016.0904
DOI ID：10.1299/jsmefed.2016.0904, eISSN：2424-2896, CiNii Articles ID：130007133919 - 0211 Study on a circulation generation of a blade in a uniform flow
SUGIYAMA Hayate; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Fluids engineering conference ..., Volume：2015, First page："0211, Last page：1"-"0211-2", 07 Nov. 2015
The Kutta condition applied in the potential flow is the used for explanation of the lift mechanism. The present research experimentally and numerically investigated the transition process from the flow with the zero circulation to the flow satisfied with the Kutta condition. For visualization, glycerin solution with aluminum powder is used as the working fluid. In the numerical and experimental results, the downstream stagnation point is located at the upstream of the blade trailing edge, which is similar to the zero circulation flow. As the Reynolds number is increased, the stagnation point is moved to the blade trailing edge, finally the flow is satisfied with the Kutta condition.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110010047069, CiNii Books ID：AA11284390 - 0212 Investigations of Unsteady Flows Caused by Whirling Vortices in a Swirling Jet
FUJIWARA Akihiro; KANG Donghyuk; Yokota Kazuhiko; SATO Kotaro
Fluids engineering conference ..., Volume：2015, First page："0212, Last page：1"-"0212-2", 07 Nov. 2015
The present research investigated unsteady characteristics of a swirling jet. The experimental facility was designed to control the swirl ratio adjusted by varying the angle of the guide vanes. For visualization, the swirling jet with a smoke was illuminated by a laser sheet. The circumferential velocities were measured by hot wire probes. By the computational fluid dynamics (CFD), the swirling jet was simulated at the same conditions as the experiment. The CFD and experimental results show that the swirling jet for the 0 degree of the guide vanes flows along the outside wall. By the FFT, one peak with the four rotating cells observed in the pictures taken for the swirling jet is found in the experiment and the CFD results.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110010047070, CiNii Books ID：AA11284390 - G0501002 Flow Oscillation Occuring in an Impeller with Forward-Inclined Multi-Blades
WADA Nobuhiro; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Mechanical Engineering Congress, Japan, Volume：2015, First page："G0501002, Last page：1"-"G0501002-5", 13 Sep. 2015
The experimental and numerical studies were performed to clarify the fundamental flow characteristics of a fan with forward-inclined multi-blades. A Sirocco fan and crossflow fan are rotated in the open space, i.e. without casing. The crossflow fan simulates a Sirocco fan with a closed inlet. Using fan's height is 115mm, the inlet and outlet radii are 160 and 180 mm, respectively. The inlet and outlet blade angles are 90 and 150 degrees, respectively. The impller includes 52 blades. The rotational frequency is set to 24 Hz. The radial velocity fluctuations at the impeller outlet are measured using a hot-wire anemometry. The experimental and numerical results show good agreements with respect to frequencies and cell numbers. The FFT spectra of the experimental and numerical results show two peaks in the Sirocco fan and one peak in the crossflow fan. The two- and three-cell oscillations occur for the Sirocco fan, and the one-cell for the crossflow fan.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110010048367, CiNii Books ID：AA12588255 - 11003 The Flow around the Rotating Cylinder between Two Coaxial Stationary Circular Disks
Maruyama Satoshi; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2015, Number：21, First page："11003, Last page：1"-"11003-2", 20 Mar. 2015
The present paper presents the rotating instability around a rotating cylinder between two coaxial stationary circular disks experimentally and numerically. In the experiment, the hot-wire measurements were conducted. In the simulations, the calculations were performed which are corresponding to the experimental setup. Then, FFT analysis results indicate the rotating instability of one cell rotating hi the circumferential direction near the rotating cylinder. In the stability Analysis, some vorticities around a rotating cylinder between the stationary disks provided with a complex velocity potential. This system becomes neutrally stable for the stiffness is positive. While this system becomes unstable for damping ratio is negative.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009948253, CiNii Books ID：AA11902161 - 11004 Influence of the rotational center on the power generation characteristics of the flexible sheet flutter
FUJIMORI Yasuhiko; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2015, Number：21, First page："11004, Last page：1"-"11004-2", 20 Mar. 2015
In this research, investigations of effects of rotation center on the wind power generation utilizing flutter were conducted. A rigid plate is attached to the rotation axis. A flexible sheet is settled at the trailing edge of the plate. As the length of sheets was parameter, displacement, current and voltage of the generator were measured. Measuring values in a variety of wind speed. Calculating electric power from the value of the current and voltage, frequency and amplitude from the Displacement. Moreover, the action of the flutter was observed with a high speed camera. Moreover, it experimented by changing rotation center of the sheet. As for result, changing the position of the rotation center, flutter vibration becomes unstable and the generated power is reduced.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009948254, CiNii Books ID：AA11902161 - 21013 The aerodynamic characteristics of a wing in ground effect with propeller
FUKAZAWA Kosuke; YOKOTA Kazuhiko; KANG Donghyuk
Volume：2015, Number：21, First page："21013, Last page：1"-"21013-2", 20 Mar. 2015
WIG(Wing In Ground effect)can be improve their coefficient of lift by PAR(Power Augmented Ram), that blow air into lower side of a blade in order to increase a pressure in that space. To make their relation clear, we have evaluated such aerodynamic characteristics making some experiments and simulating by computation fluid dynamics. The wind tunnel we have used in the experiments is 600mm in width, and 600mm in height. It is capable of moving air at speeds up to about 20m/s. We cut a lower part of NACA6409 in order to raise a rate of increase in a coefficient of lift compared to it without modification. Aerodynamics characteristics of a WIG is effected by ground when h/c is 0.1 or less.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009948389, CiNii Books ID：AA11902161 - 21014 Influence of the blade leading edge on the supersonic flow in the two-dimensional cascade
SHIBASAKI Kazuki; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2015, Number：21, First page："21014, Last page：1"-"21014-2", 20 Mar. 2015
In the flow of a transonic compressor, shock waves occur around blades and cause instabilities. The present research investigates the instabilities caused by the shock waves. Four blades were designed with changing the blade leading edge in order to investigate the effect of the blade geometry on the two-dimensional supersonic flow of the blade row. The numerical calculation were carried out for various pressure ratios and circumferential speed ratios. The location of the shock wave in the blade passage are determined by the pressure ratio. The blade without the camber angle can obtain the high pressure ratio, but cannot operate in the wide-range condition. Compared to the original blade, the blade with the thin leading edge can operate in the higher mass flow rate.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009948390, CiNii Books ID：AA11902161 - 21009 Influence of Span on the Unsteady Flow in a Sirocco Fan
KONDO Yuma; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2015, Number：21, First page："21009, Last page：1"-"21009-2", 20 Mar. 2015
The two fans were designed with the span height of 7mm and 35mm to investigate the influence of the span height on the unsteady flow in a sirocco fan without a casing. The radial velocity oscillations were measured by hot wire probes, and the oscillating frequency and the phase delay of the radial velocity oscillation were obtained by using a fast fourier transform (FFT) analysis. The 3 or 4 peaks were observed in the experiment and the numerical calculation. The experimental result shows that the oscillating frequency and the number of rotating cells in the sirocco fan with the span height of 7mm are larger than those with the span height of 35mm. The rotating vortices caused by the backflow were found in the numerical results.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009948386, CiNii Books ID：AA11902161 - 21010 Experiment and Numerical Simulation for Porous Aerostatic Bearing Characteristics
KINOSHITA Takahiro; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2015, Number：21, First page："21010, Last page：1"-"21010-2", 20 Mar. 2015
Porous aerostatic bearing has high stiffness and load capacity. The present study experimentally investigates the vibration of a porous aerostatic bearing. A laser sensor was used for measuring the displacement of the porous aerostatic bearing. The flow through the porous aerostatic bearing was induced by a centrifugal blower. The volume flow rate was measured by a flow meter. The displacement and the volume flow meter were transferred to a personal computer. The experimental result shows that the displacement of the porous aerostatic bearing is increased with the increase of the volume flow rate. By using FFT, we confirmed that the oscillating frequency is decreased with the increase of the volume flow rate.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009948387, CiNii Books ID：AA11902161 - 21007 Experiment on the S-Curve Characteristic of the Pump-Turbine
MITSUHIRA Tatsurou; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2015, Number：21, First page："21007, Last page：1"-"21007-2", 20 Mar. 2015
In order to clarify the mechanism of the instability phenomenon in an abnormal operation of a pump turbine, the experiment of a pump-turbine was performed. The pressure at inlet and outlet are measured for the various flow rates and rotating speeds. "S-shape curve" was observed in the turbine characteristic curve. The experimental result shows that as the flow rate increases, the torque increases. "S-shape curve" was observed hi a vicinity of the runaway condition. "S-shape curve" in the pump turbine without the guide vane is more clearly observed than that with the guide vane. "S-shape curve" occurs when the increase ratio of the loss is larger than the decrease ratio of the torque.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009948384, CiNii Books ID：AA11902161 - 円管から放出された旋回流の非定常性に関する実験と数値計算
藤原章博; 姜東赫; 横田和彦; 佐藤光太郎
Volume：73rd, 2015
J-Global ID：201502282581191183 - 両吸込遠心ポンプに発生する√特性に関する研究
山崎賢; 姜東赫; 横田和彦; 能見基彦; 香川修作; 安炳辰
Volume：73rd, 2015
J-Global ID：201502292427056880 - 1024 Flow Characteristics of a Viscous Micropump using a Rotating Cylinder in a curved duct
Kang Donghyuk; Kishita Hiroyuki; Yokota Kazuhiko; Sato Kotaro
Fluids engineering conference ..., Volume：2014, First page："1024, Last page：1"-"1024-4", 25 Oct. 2014
With respect to a viscous micropump using a rotating cylinder in a curved duct, the influences of the angle of the curved duct on the pressure performance and flow field were investigated. The model experiment, the numerical simulation and the theoretical analysis were performed. The theoretical analysis has the qualitative agreement with the numerical simulation. With an increase of the angle of a curved duct, the pressure coefficient at the zero flow coefficient is increased and the flow coefficient at the zero pressure coefficient is slightly decreased. Near the zero pressure coefficient, the vortices at the upstream and downstream of the rotating cylinder are observed.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110009938739, CiNii Books ID：AA11284390 - 1018 Effect of the Shape of a Pump-Turbine's Runner on the Flow
SUGITA Toru; YOKOTA Kazuhiko; KANG Donghyuk
Fluids engineering conference ..., Volume：2014, First page："1018, Last page：1"-"1018-3", 25 Oct. 2014
In order to clarify the mechanism of the instability phenomenon which occurs when a pump-turbine stops suddenly, the experiment and the numerical simulation for the pump-turbine were performed in this research. The pressure are measured at inlet and outlet changing flow rate. Serpentine curve was observed on characteristic curve obtained from experimental and numerical result. The past research clarifies that appearing serpentine curve means instability phenomenon occurs. The numerical result shows that as the flow rate decreases, the torque coefficient decreases. The loss coefficient decreases when flow rate is more than design flow rate and it increases when flow rate is less than design flow rate. Serpentine curve appears when the torque coefficient's decrements exceeds rather than the loss coefficient's increments. Various losses which occur at pump-turbine's each parts calculated from numerical result are modeled mathematically.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110009938733, CiNii Books ID：AA11284390 - Analytical Study of Cavitation Surge in a Hydraulic System
Donghyuk Kang; Kazuhiko Yokota
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME, Volume：136, Number：10, First page：101103.1-101103.10, Oct. 2014
In order to clarify effects of an accumulator, pipe lengths and gradients of pressure and suction performances on cavitation surge, one-dimensional stability analyses of cavitation surge were performed in hydraulic systems consisting of an upstream tank, an inlet pipe, a cavitating pump, a downstream pipe, and a downstream tank. An accumulator located upstream or downstream of the cavitating pump was included in the analysis. Increasing the distance between the upstream accumulator and the cavitating pump enlarged the stable region. On the other hand, decreasing the distance between the downstream accumulator and the cavitating pump enlarged the stable region. Furthermore, the negative gradient of a suction performance curve and the positive gradient of a pressure performance curve cause cavitation surge.
ASME, English
DOI：https://doi.org/10.1115/1.4027220
DOI ID：10.1115/1.4027220, ISSN：0098-2202, eISSN：1528-901X, J-Global ID：201402299148543221, PubMed ID：25278638, Web of Science ID：WOS:000341759700003 - 20601 Flow Instabilities observed in Sirocco Fan Impeller in Open Space
WADA Nobuhiro; KANG Donghyunk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2014, Number：20, First page："20601, Last page：1"-"20601-2", 14 Mar. 2014
An experimental study was made to clarify the fundamental flow characteristics of Sirocco fans. Using fan's height is 115mm, inlet radius is 80mm, outlet radius is 90mm, vane angle is 150 degree, number of vanes is 52. This fan rotates with 23.75Hz. The oscillations of the radial velocity in the sirocco fan installed in the open space were measured by the hot wire probe. By FFT analysis, the two magnitude peaks of the radial velocity were found and the two significant peaks were found. The first peak was found at 19Hz and has the three cells rotating with the rotation of the impeller. The second peak was found at 33Hz and has the four cells rotating with the rotation of the impeller.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009949423, CiNii Books ID：AA11902161 - 20607 Study of Aerodynamic Characteristics of a Cylinder in a Shear Flow
OKUMURA Jun; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2014, Number：20, First page："20607, Last page：1"-"20607-2", 14 Mar. 2014
The self-excited vibration of a cylinder in a shear flow was investigated experimentally and numerically. The velocity downstream of the cylinder, the drug and the lift forces were measured by the hot wire and the load cell, respectively. The numerical simulation for the flow near the cylinder was performed and the drag and lift forces were obtained by the numerical results and compared with the experimental results. The effects of the gradient of the velocity and the Reynolds number on the drag coefficient are not significantly observed. The lift coefficient is increased by the decrease of the Reynolds number and the increase of the gradient of the velocity.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009949429, CiNii Books ID：AA11902161 - 20611 Operation Characteristics of a Pump-Turbine at Emergency Shutdown
ODA Ryu; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2014, Number：20, First page："20611, Last page：1"-"20611-2", 14 Mar. 2014
The present research clarifies the generating mechanism of the fluid vibration at emergency shutdown in a pump-turbine. The experiment and the numerical simulation for the pump-turbine were performed. The negative gradient of the pressure performance curve was observed in the experiment. The numerical result shows that the strong backflow and the second flow, observed at lower flow rates, cause the increase of the pressure loss in the blade passage, which leads to the negative gradient of the pressure performance curve. Furthermore, the angular momentum of the internal flow in the pump-turbine was examined. It was found that the region of the reverse pump in the blade passage exists in the turbine mode.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009949433, CiNii Books ID：AA11902161 - 20612 Evaluation of Supersonic Mixing of Flexible Sheet Flutter by the Water Jet
HATANO Fumiya; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2014, Number：20, First page："20612, Last page：1"-"20612-2", 14 Mar. 2014
In the supersonic combustion, supersonic mixing is one of the most important issues. The present research examined the supersonic mixing using by the flexible sheet flutter in order to find enhancement mixing methods. Water was injected from the pipe installed upstream of a flexible sheet. The pictures visualized by the schlieren method were used for the image processing to evaluate the flutter frequency, the flutter mode and the mixing effect. The results show that the amplitude of the sheet flutter is increased with the increase of the sheet length and decrease of Young modules. It was found that the displacement amplitude of the trailing edge of the flexible sheet is the most important for the supersonic mixing.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009949434, CiNii Books ID：AA11902161 - 20608 Effects of Duct Geometry on Pressure Performance of a Viscous Micropump Using a Rotating Cylinder in a Curved Duct
KISHITA Hiroyuki; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2014, Number：20, First page："20608, Last page：1"-"20608-2", 14 Mar. 2014
The micropumps have been used for the micro-machinery and they are needed to the accuracy and stability. The present research investigated the effects of the curved duct geometry on the pressure performance of the viscous micropump using by the rotating cylinder. The experiment and numerical simulation for the micropump with the curved duct were conducted. The experimental and numerical results show that the max pressure rise is increased but the max flow coefficient is somewhat decreased by using the curved duct. The vortex size is decreased by using the curved duct. This indicates that the vortex size is closely related with the pressure performance.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009949430, CiNii Books ID：AA11902161 - 10809 Effects of Loads on the Wind Power Generation Utilizing Flexible Sheet Flutter
YAMANAKA Kio; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2014, Number：20, First page："10809, Last page：1"-"10809-2", 14 Mar. 2014
In this research, the effect of load on the wind power generation utilizing flutter was investigated. A rigid plate is attached to the rotation axis and a flexible sheet is connected to the trailing edge of the rigid plate. The displacement, the frequency and the current and voltage of the generator for various wind speeds were measured. The result shows the electric power is significantly increased by the increase of the generator load. The critical flutter speed is increased as the generator load increases. However, at the longer sheet length, the effect of the generator load on the critical flutter wind speed was not observed. This indicates that the higher generator load and longer sheet length are suitable for the wind power generation using the sheet flutter.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009949315, CiNii Books ID：AA11902161 - 10308 Experiment and Numerical Calculation on Heat-Transfer Characteristic of Obliqueness Cylinder Group
FUKUMOTO Atsushi; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2014, Number：20, First page："10308, Last page：1"-"10308-2", 14 Mar. 2014
The present research investigated the effect of the obliqueness cylinder group on the heat transfer and pressure loss performances. The pressure loss and the temperature were measured by the pressure transducer and the thermal couple, respectively. The numerical simulation was performed to simulate the duct flow affected by the cylinder groups. The result shows that the heat transfer performance was improved by the obliqueness cylinder group as compared with the perpendicular cylinder group. Furthermore, the effect of the number of the cylinder row was examined. It was found that the cylinder group with the three rows is suitable for the heat transfer with minimum pressure loss.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009949299, CiNii Books ID：AA11902161 - S字特性発生領域におけるポンプ水車内部流に関する数値計算
姜東赫; 杉田徹; 横田和彦
Volume：71st, 2014
J-Global ID：201402221408749830 - A STUDY ON THE COANDA EFFECT AND THE THRUST CHARACTERISTICS OF SYNTHETIC JETS
Takahiro Iwasaki; Koichi Nishibe; Kotaro Sato; Kazuhiko Yokota; Donghyuk Kang
PROCEEDINGS OF THE ASME FLUIDS ENGINEERING DIVISION SUMMER MEETING - 2014, VOL 1B: SYMPOSIA, Volume：1B, 2014
Although there have recently been various studies on synthetic jets, many issues remain to be clarified, including details of the structure, Coanda effect and thrust characteristics. The present study clarifies some fundamental flow characteristics of synthetic jets near a rigid boundary by experiments and numerical simulations. In addition, a thruster model using the Coanda effect of synthetic jets is proposed and thrust characteristics are evaluated. As the main results, the flow of a synthetic jet near a rigid boundary is visualized and the trajectory of a vortex pair is demonstrated. It is confirmed that the flow patterns of the synthetic jets near a rigid boundary depend on H/b(0) (offset ratio, normalized step height). The behavior of the asymmetric synthetic jets caused by the presence of the rigid wall was observed experimentally and the results were compared with numerical data. Furthermore, typical flow patterns around the proposed synthetic jet thruster and its thrust characteristics curves are shown.
AMER SOC MECHANICAL ENGINEERS, English
DOI：https://doi.org/10.1115/FEDSM2014-21250
DOI ID：10.1115/FEDSM2014-21250, ISSN：0888-8116, SCOPUS ID：84919800639, Web of Science ID：WOS:000379635100016 - 0611 Study on Fundamental Flow Characteristics of Synthetic Jets Using Vortex Method
SHIMAMURAE Taisuke; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Fluids engineering conference ..., Volume：2013, First page："0611, Last page：01"-"0611-03", 09 Nov. 2013
The present study attempts to clarify flow characteristic in a synthetic jet by a discrete vortex method, particularly focusing on the streamwise mean velocity along the centerline of jets. The onset condition of the synthetic jet was simulated reasonably and depends on the normalized stroke length. The streamwise mean velocity distributions along the centerline of jets agree quantitatively well with the experimental results. The acceleration region, where the streamwise velocity is increasing partially, was observed downstream of slot lips. This is caused by the reductions of the decreasing rate of the induced velocity from the shedding circulations and the increasing rate of the induced velocity from the wall circulations. The upstream streamwise mean velocity is induced from the wall and shedding circulations and the downstream streamwise velocity is mostly supplied from the shedding circulations.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110009957440, CiNii Books ID：AA11284390 - 0607 Development of thruster using study on Synthetic Jets
IWASAKI Takahiro; NISHIBE Koichi; SATO Kotaro; YOKOTA Kazuhiko; KANG Donghyuk
Fluids engineering conference ..., Volume：2013, Number：0, First page：607, Last page：01"-"0607-05", 09 Nov. 2013, [Reviewed]
The present study clarifies some thrust characteristics of synthetic jets by conducting experiment and numerical simulations. In the paper type synthetic jet thruster is proposed for medical micro-machines or micro air vehicles. It is found that the fluid force and the velocity distribution around a synthetic jet thruster depend on the non -dimensional stroke of the synthetic jet.
一般社団法人日本機械学会, Japanese
DOI ID：10.1299/jsmefed.2013._0607-01_, ISSN：1348-0251, CiNii Articles ID：110009957436, CiNii Books ID：AA11284390, ORCID put code：40518619 - 1035 NUMERICAL SIMULATION OF SYNTHETIC JET BY DISCRETE VORTEX METHOD
Donghyuk Kang; Taisuke Shimamura; Marie Fujiwara; Kazuhiko Yokota; Kotaro Sato
Jets, wakes and separated flows : proceedings of International Conference on Jets, Wakes and Separated Flows, ICJWSF, Volume：2013, Number：4, First page："1035, Last page：1"-"1035-6", 16 Sep. 2013
The present study attempts to clarify flow characteristics in a synthetic jet by a discrete vortex method, particularly focusing on the streamwise mean velocity along the centerline of jets. The onset condition of the synthetic jet was simulated reasonably and the streamwise mean velocity distributions along the centerline of jets agree quantitatively well with the experimental results. For the synthetic jet, the acceleration region, where the streamwise velocity is increasing partially, is caused by the decrease of the negative velocity induced from the wall circulations and the reductions of the decreasing rate of the velocity induced from the shedding circulations.
The Japan Society of Mechanical Engineers, English
CiNii Articles ID：110009962644, CiNii Books ID：AA12113983 - 1043 ON SYNTHETIC JET ACTUATOR USING BUBBLE PRODUCED BY ELECTRIC DISCHARGE
Koichi Nishibe; Kotaro Sato; Hideki Takezawa; Donghyuk Kang; Kazuhiko Yokota
Jets, wakes and separated flows : proceedings of International Conference on Jets, Wakes and Separated Flows, ICJWSF, Volume：2013, Number：4, First page："1043, Last page：1"-"1043-8", 16 Sep. 2013
Over the last decade, synthetic jets adequate for micro machinery have received attention as substitutes for continuous jets. The development of synthetic jet actuators with, for example, a diaphragm, a piston, or a speaker cone, instead of mechanical drivers, is required for the downsizing of flow control systems in fluid machines. In this study, an experimental prototype of a synthetic jet actuator using the nonlinear oscillation of bubbles produced by iterative electric discharge is proposed. Numerical simulations clarify the fundamental flow characteristics of the synthetic jets produced by ideal bubble oscillation. The discharge conditions include the influence of the metal particle concentration in liquid on bubble generation. The onset condition based on the non-dimensional stroke of the synthetic jet and the relation between the bubble motion and the change of the jet velocity with time are discussed. Especially, the influence of T* (the ratio of driving time of a bubble to the down time) on the unsteady flow pattern and the time-averaged jet structure is investigated. In addition, the flow characteristics of a synthetic jet with down time are compared with that of a normal synthetic jet with equivalent velocity.
The Japan Society of Mechanical Engineers, English
CiNii Articles ID：110009962650, CiNii Books ID：AA12113983 - 1146 CHARACTERISTICS OF ROTATING FLOW DOWNSTREAM OF INLET GUIDE VANES
Masanori Kudo; Koichi Nishibe; Masayuki Takahashi; Kotaro Sato; Donghyuk Kang; Kazuhiko Yokota
Jets, wakes and separated flows : proceedings of International Conference on Jets, Wakes and Separated Flows, ICJWSF, Volume：2013, Number：4, First page："1146, Last page：1"-"1146-6", 16 Sep. 2013
The main objectives of the present study are: (1) to identify the dominant parameters responsible for the generation of unsteady flow, (2) to determine the conditions under which flow oscillations are produced and the relation between the flow characteristics and the number of vanes, and (3) to control the amplitude of the velocity fluctuation by means of tangential blowing. An attempt is made to clarify the flow instabilities downstream of the IGV by conducting experiments and a numerical simulation. The onset conditions, including the number of cells and the oscillation characteristics of the unsteady flow, are discussed based on the measured pressure and velocity fluctuations. The exit flow angle (α3) with identical solidity is presented as a function of the number of vanes. Furthermore, circular cylinders with tangential blowing are applied as IGV to generate the rotating flow. Flow characteristics downstream of circular cylinders with tangential blowing are discussed.
The Japan Society of Mechanical Engineers, English
DOI ID：10.1115/FEDSM2013-16102, CiNii Articles ID：110009962729, CiNii Books ID：AA12113983 - 20815 Numerical Calculation on Heat Transfer Characteristics in a Rectangular Channel with a Oscillating Sheet Flutter
SHISHIDO Takahiro; Donghyuk KANG; HIROI KIwako; YOKOTA Kazuhiko
Volume：2013, Number：19, First page：425, Last page：426, 14 Mar. 2013
The present research is to investigate the effects of the sheet flutter on the heat transfer coefficient in a rectangle channel. The two dimensional numerical simulation with the k-w turbulence model was performed to examine the flow in a rectangle channel with the sheet flutter. The sheet flutter was modeled by a rigid flat plate in forced vibration. The numerical results were validated by the experimental ones with the flexible sheet flutter. The results show that the turbulence kinetic energy produced by the oscillating sheet improves the heat transfer coefficient and that an increase of the frequency of the oscillating sheet also leads to the heat transfer enhancement
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954604, CiNii Books ID：AA11902161 - 10701 Simulations of Synthetic Jet using by the Discrete Vortex Method
FUJIWARA Marie; SHIMAMURAE Taisuke; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2013, Number：19, First page：95, Last page：96, 14 Mar. 2013
The present study attempts to clarify some of the fundamental flow characteristics of synthetic jet and continuous jet, based on method numerical simulations using the vortex. The flow pattern and the unsteady flow characteristics of the synthetic jet are compared with those of a continuous jet The numerical distributions of dimensionless mean velocities agree quantitatively with the experimental ones, which indicate the numerical simulation is valid. It is found that a vortex pair flowing downstream causes the synthetic jet. The accelerating domain of the jet which was confirmed in the synthetic jet experimentally is also observed in the numerical results.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954439, CiNii Books ID：AA11902161 - 10708 Experimental study for Supersonic Mixing Characteristics Using a Flexible Sheet Flutter
YAMANADA Yushi; NAGAOKA Hiroaki; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2013, Number：19, First page：107, Last page：108, 14 Mar. 2013
The SCRAM jet engine is characterized by the supersonic combustion. In the supersonic combustion, one of the most important issues is supersonic mixing. One method utilizing the flexible sheet flutter for the supersonic mixing was proposed and investigated. As flexible sheets, rubber thin sheets were examined with several Mach number and sheet lengths. The main purpose of the present study is to find enhancement mixing methods for the supersonic mixing. For the examination of the mixing effect, water was injected upstream of a flexible sheet in the supersonic flow. The flow and mixing fields were visualized by the schlieren method. The frequency and mode of flutter and the mixing effect were evaluated from the captured images. The results show that the displacement amplitude of the trailingedge of the flexible sheet is the most important for the supersonic mixing.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954445, CiNii Books ID：AA11902161 - 10707 Experimental study for self-vibration of a cylinder in a shear flow
NAKAMURA So; TAKEYAMA Atsushi; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2013, Number：19, First page：105, Last page：106, 14 Mar. 2013
Vibrations of a circular cylinder in the shear flow are investigated experimentally. The experiment is conducted by changing the velocity gradient and the mainstream speed. When the mainstream speed is between 2 m/s and 15 m/s, two kinds of different vibrations were observed. One was observed near the frequency of a von Karman's vortex street. The other was seen far from the one and its amplitudes are relatively large. The feature of the latter vibration is that the amplitude in the y direction is quite larger than that in the x direction. The mainstream speed hardly influences on the vibrations of a cylinder.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954444, CiNii Books ID：AA11902161 - 20708 Effect of Flow System-dependent boundary conditions on the unsteady cavitation
MURAO Mitsutaka; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2013, Number：19, First page：375, Last page：376, 14 Mar. 2013
The unsteady CFD for the cavitation in a throttle passage are carried out by using a commercial software ANSYS-CFX. The dynamic flow behavior of the closed loop system including the throttle are simulated by using the throttle cavitation CFD with the inlet and the outlet boundary conditions derived from The lumped parameter of the hydraulic system in the loop. the cavitation volume, inlet and outlet flow rate are oscillating. The time derivative of the cavitation volume shows relatively good agreement with the difference of the inlet and the outlet flow rate.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954579, CiNii Books ID：AA11902161 - 20711 Study on an unisteady flow appearing around a rotating cylinder in a pipe
SUGITA Toru; WATANABE Takumi; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2013, Number：19, First page：381, Last page：382, 14 Mar. 2013
The purpose of this study is to research the flow around a rotating cylinder in a stationary cylinder. In this study, flow velocity was measured by a hot-wire anemometry. A spectral peak was found when the Reynolds number is larger than 1948 in experiments and calculations. It was found that as the rotational speed increases, the frequency and amplitude of the spectral peak become higher and smaller, respectively. By the observation of numerical vorticity in a meridional plane, it was found that as the rotational speed increases, the magnitude of numerical vorticity fluctuations decreases. As a result, for the Reynolds number of 9740, the flow becomes almost steady and the amplitude of the spectral peak also becomes quite small.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954582, CiNii Books ID：AA11902161 - 20718 Measurement of an unsteady flow appearing around a rotating cylinder between two disks
KUROSAKI Yoshito; UCHIDA Masaya; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2013, Number：19, First page：395, Last page：396, 14 Mar. 2013
The present paper presents an experimental study on the rotating instability around a rotating cylinder between two coaxial stationary circular disks. The radial and circumferential flow velocities were simultaneously measured by a x-type hot-wire probe. The rotational speed and the disk interval between two stationary disks were varied. The FFT results of the velocity fluctuations show a typical spectrum peak. As the rotational speed increases, the frequency of the spectrum peak increase. Two-point simultaneous measurement prove that one cell is rotating in the circumferential direction.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954589, CiNii Books ID：AA11902161 - 20705 PIV Measurement of asymmetric channel flow excited by a reciprocating motion of a piston integrated on the side wall
KOSEMURA Tatsuya; KANQ Donghyuk; OKA Daichi; YOKOTA Kazuhiko; SATO Kotaro
Volume：2013, Number：19, First page：369, Last page：370, 14 Mar. 2013
The present research presents a new type of thruster that has a nozzle-like, or difluser-like, configuration, i.e., an asymmetric channel. The fluid in the channel is excited by the reciprocating piston integrated on the sidewall. The experiment and the one-dimensional (lD) analysis were conducted to investigate the flow characteristics in the asymmetric channels. In the experiment, the Particle Image Velocimetry (PIV) system was used. In the analysis, the one-dimensional analysis was performed with the continuity, the unsteady momentum and the quasi-steady loss equations. The experimental and analytical unsteady results agree qualitatively well. The mean flow runs from the wide to the narrow.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954576, CiNii Books ID：AA11902161 - 20712 Experiment on Heat Transfer Characteristics in a Rectangular Channel with a Oscillating Sheet Flutter
HIROI KIwako; KANG Donghyuk; SHISHIDO Takahioro; YOKOTA Kazuhiko
Volume：2013, Number：19, First page：383, Last page：384, 14 Mar. 2013
The present research is to examine the heat transfer coefficient utilizing the flexible sheet in a rectangle channel. The heat transfer and the pressure loss coefficients for various sheet lengths and widths were measured by the thermocouple and the differential pressure gauge, respectively. The heat transfer performances, e.g. the ratio 0f the pressure loss to the heat transfer, were evaluated. As the sheet length increases, the heat transfer and pressure loss coefficients were increased. As the sheet width increases, the heat transfer coefficient, decreases and pressure loss coefficient is, however, increased. When the sheet length and width arc 30mm and 100mm respectively, the heat transfer enhancement efficiency becomes larger than unity, which means the heat transfer is enhanced.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954583, CiNii Books ID：AA11902161 - 20717 Performance experiments of a disk-type viscous micropump in a curved pipe
GOTOH Takeshi; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2013, Number：19, First page：393, Last page：394, 14 Mar. 2013
The present research proposes a new type of viscous micropumps that has a rotating disk integrated on the upper wall of the elbow rectangular duct. The pressure performance of the viscous micropump was experimentally investigated. The performance of the micropump was evaluated from the flow rate and the pump head simultaneously measured by the electronic balance. The Reynolds effect was also estimated by changing the rotational speed. The pressure characteristics are represented as a straight line with a negative slope in the relation between the flow rate coefficient and the product of the pressure coefficient and the Reynolds number, which are the similar characteristics to the conventional viscous micropumps.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954588, CiNii Books ID：AA11902161 - 20714 Numerical calculation on "S" characteristics of pump-turbine under lower load turbine operating condition
TANOKURA Tsuyoki; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2013, Number：19, First page：387, Last page：388, 14 Mar. 2013
To clarify the cause of "S" instability, the three-dimensional simulation of the steady flow in a pump-turbine are performed using by the commercial CFD code. For lower flow rates and negative flow rates i.e., reverse pump region, the positive slope was observed in the performance curve and "S" curve is caused by the increase of the head width the decrease of flow rate. As the flow rate decreases, the backflow region near the pressure side of the leading edge of a blade is widened. For die reverse pump region, the high pressure region near the suction side of the trailing edge of a blade is observed.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954585, CiNii Books ID：AA11902161 - 20713 Experimental study for Wind power Characteristics utilizing a Rigid-Flexible sheet Flutters
ICHIHARA Yuto; TAGUCHI Yutaka; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2013, Number：19, First page：385, Last page：386, 14 Mar. 2013
In this research, investigation of the flutter characteristics and a power generation characteristics were conducted. A rigid plate is attached to the rotation axis. A flexible sheet is settled at the trailing edge of the plate. It experiments by changing the length of the rigid plate and the flexible sheet. Displacement, frequency, and the current and voltage of the generator were measured. Moreover, the action of the flutter was observed with a high speed camera. As for result, power generation, frequency, and amplitude become large with the rise of wind speed, and power generation is large when a rigid plate is short.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954584, CiNii Books ID：AA11902161 - 1203 Lift Characteristics of Circulation Control Wing with Simple Geometry
HIROSE Natsuho; KANG Donghyuk; SATO Kotaro; YOKOTA Kazuhiko
Volume：2013, Number：51, First page："1203, Last page：1"-"1203-2", 25 Feb. 2013
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954312, CiNii Books ID：AN00360626 - 1117 Fundamental study on oil mist separation by swirl flow
ITO Yuhei; HIWATA Akira; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2013, Number：51, First page："1117, Last page：1"-"1117-2", 25 Feb. 2013
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009954307, CiNii Books ID：AN00360626 - 両吸込遠心ポンプに発生するキャビテーション脈動の配管長さが及ぼす影響
幡野信哉; 姜東赫; 横田和彦; 能見基彦; 香川修作
Volume：70th, 2013
J-Global ID：201302265231289990 - Investigation on a synthetic jet actuator using bubble produced by electric discharge
Koichi Nishibe; Kotaro Sato; Donghyuk Kang; Kazuhiko Yokota
Int. Conf. on Jets, Wakes and Separated Flows September, 2013,Nagoya, 2013
DOI：https://doi.org/10.1299/jfst.2014jfst0033
DOI ID：10.1299/jfst.2014jfst0033 - シンセティックジェットを利用した推進器の開発
IWASAKI TAKAHIRO; NISHIBE KOICHI; SATO KOTARO; YOKOTA KAZUHIKO; KANG DONGHYUK
日本機械学会流体工学部門講演会講演論文集(CD-ROM), Volume：91st, First page：ROMBUNNO.0607, 2013
Japanese
ISSN：1348-2882, J-Global ID：201402224960359043 - Numerical Investigation of Dynamic Characteristics and Unsteady Cavitation Characteristics of an Inducer
YONEZAWA Koichi; AONO Jun; KANG Donghyuk; HORIGUCHI Hironori; KAWATA Yutaka; TSUJIMOTO Yoshinobu
Turbomachinery, Volume：40, Number：12, First page：735, Last page：744, 10 Dec. 2012
The transfer matrix and unsteady cavitation characteristics, cavitation compliance and mass flow gain factor, of cavitating inducer were evaluated by CFD using commercial software. Quasi-steady values of cavitation compliance and mass flow gain factor were obtained first by using steady calculations at various flow rate and inlet cavitation number. Then unsteady calculations were made to determine the transfer matrix and the cavitation characteristics. The results are compared with experiments to show the validity of calculations.
Turbomachinery Society of Japan, Japanese
DOI：https://doi.org/10.11458/tsj.40.735
DOI ID：10.11458/tsj.40.735, ISSN：0385-8839, eISSN：1880-2338, CiNii Articles ID：10031127498, CiNii Books ID：AN00004836 - 0910 Flagmill : A New Wind Power Generator Utilizing Flexible Sheet Flutter
TAGUCHI Yutaka; YOKOTA Kazuhiko; KANG Donghyuk; SATO Kotaro
Fluids engineering conference ..., Volume：2012, First page：351, Last page：352, 16 Nov. 2012
The research proposes a flagmill,which is a new wind power generator utilizing the flutter of a flexible sheet.The sheet is simply supported at the leading edge by a supporting pole which rotates around its axis.The flutter of sheet causes the rotational oscillation of the supporting pole around its axis.The rotational oscillation of the generator axis connected to the supporting pole induces the electric power.In the present research,the experiment and the two-dimensional stability analysis were performed.The flutter behaviors and power generation characteristic were investigated experimentally and analytically.Flutter flow speeds,modes,frequencies were investigated by varying uniform flow speeds,sheet lengths,and compared with the analytical results.The results mdicated that the angular amplitudes are the most important for the power generation and accordingly the first mode can generate the larger power than the second one.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110009951722, CiNii Books ID：AA11284390 - G510 Experimental, Numerical and Analytical Studies of Flows in Asymmetric Ducts Induced by a Reciprocating Piston Located in a Side Wall
OKA Daichi; KANG Donghyuk; KOSEMURA Tatsuya; YOKOTA Kazuhiko; SATO Kotaro
Fluids engineering conference ..., Volume：2012, First page：519, Last page：520, 16 Nov. 2012
The present research presents a new type of thruster that has a nozzle-like, or diffuser-like, configuration, i.e., an asymmetric channel. The fluid in the channel is excited by the reciprocating piston integrated on the sidewall. The experiment and the Computational Fluid Dynamics (CFD) and the one-dimensional(lD) analysis were conducted to investigate the flow characteristics in the asymmetric channels. In the experiment, the Particle Image Velocimetry (PIV) system was used. In the CFD, the ANSYS code was utilized. In the analysis, the one-dimensional analysis was performed with the continuity, the unsteady momentum and the quasi-steady loss equations. The experimental, CFD and analytical unsteady results agree qualitatively well. The mean flow runs from the wide to the narrow and the time-averaged thrusts acts in the opposite direction. The thrusts becomes larger for the 3mm width than for the 24mm one.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110009952133, CiNii Books ID：AA11284390 - 0307 Study on a rotating instability appearing around a rotating cylinder in a pipe
WATANABE Takumi; KANG Donghyuk; SUGITA Toru; YOKOTA Kazuhiko; SATO Kotaro
Fluids engineering conference ..., Volume：2012, First page：139, Last page：140, 16 Nov. 2012
The existence of rotating instability region of the flow around a cylinder rotating between two stationary disks was founded in the previous research. In this paper, the peripheral velocity around the rotating cylinder in pipe was measured. In order to investigate the rotating instability, the flow of rotating cylinder in the pipe was calculated by the three dimensional numerical simulation. It was found that higher peripheral velocity region rotates with 12Hz frequency in both the experiments and the calculation. The vortices in the meridional plane between the rotating cylinder and the outer static wall was found.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110009951616, CiNii Books ID：AA11284390 - 0306 Study on a rotating instability around a rotating cylinder between two coaxial circular disks
UCHIDA Masaya; KANG Donghyuk; KUROSAKI Yoshito; YOKOTA Kazuhiko; SATO Kotaro
Fluids engineering conference ..., Volume：2012, First page：137, Last page：138, 16 Nov. 2012
The present paper presents the rotating instability around a rotating cylinder between two coaxial stationary circular disks experimentally and numerically. In the experiment, the hot-wire measurements were conducted. In the simulations, the calculations were performed which are corresponding to the experimental setup. The experimental and numerical results shows qualitatively good agreements with respect to the velocity fluctuations. These results indicate the rotating instability of one cell rotating in the circumferential direction.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110009951615, CiNii Books ID：AA11284390 - 1202 Supersonic Mixing Using Flexible Sheet Flutter
NAGAOKA Hiroaki; KANG Donghyuk; SHIMAMURA Taisuke; YOKOTA Kazuhiko
Fluids engineering conference ..., Volume：2012, First page：441, Last page：442, 16 Nov. 2012
The SCRAM jet engine is characterized by the supersonic combustion.In the supersonic combustion,one of the most important issues is supersonic mixing.One method utilizing the flexible sheet flutter for the supersonic mixing was proposed and investigated.As flexible sheets,rubber thin sheets were examined with several elasticity moduli and sheet lengths.The main purpose of the present study is to find enhancement mixing methods for the supersonic mixing.For the examination of the mixing effect,water was injected upstream of a flexible sheet in the supersonic flow.The flow and mixmg fields were visualized by the schlieren method.The frequency and mode of flutter and the mixing effect were evaluated from the captured images.The results show that the displacement amplitude of the trailingedge of the flexible sheet is the most important for the supersonic mixing.
The Japan Society of Mechanical Engineers, Japanese
ISSN：1348-0251, CiNii Articles ID：110009952095, CiNii Books ID：AA11284390 - 104 Pressure Loss Characteristics of Rotating Perforated Cylinder
TSUNO Yutaro; WATANABE Takumi; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2012, Number：18, First page：129, Last page：130, 08 Mar. 2012
The pressure loss characteristics of the flow between the upstream and the downstream of the rotating perforated cylinder in the pipe were investigated experimentally. The effects of the flow rate, the number of holes and the rotational speed on the loss characteristics were examined. The Reynolds number was calculated based on the flow rate. The results show that the pressure loss coefficients decrease with an increase of the Reynolds number and the number of holes except the 8-hole case. The results for the 8-hole case indicate that, the rotational energy input given to the flow through holes on the rotational cylinder increases as the rotational speed increases, and consequently the loss decreases.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955250, CiNii Books ID：AA11902161 - 105 Numerical Calculation on The Flow around The Rotating Cylinder between The Circular Disks
TAKAHASHI Satoshi; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2012, Number：18, First page：131, Last page：132, 08 Mar. 2012
In the vaneless diffuser of centrifugal compressor or blower, the rotating stall occurs at the lower flow rate due the backflow from the diffuser. In this paper, the effect of swirl flow on the rotating stall was investigated by the three-dimensional numerical simulation. In order to investigate the effect of swirl flow on the rotating stall, the flow of rotating cylinder between the stationary disks without the rotating blades and inflow was calculated. The region of high circumferential velocity rotates with the frequency of 1.6Hz slightly higher than the frequency of 1.4Hz obtained from the experiments. The vortex found in the meridional plane between the stationary disks appears with the flow to the rotating cylinder from, and disappear with the flow to the outside.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955251, CiNii Books ID：AA11902161 - 1903 Supersonic Mixing Enhancement Using Sheet Flutter
SHIMAMURA Taisuke; NAGAOKA Hiroaki; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2012, Number：18, First page：67, Last page：68, 08 Mar. 2012
The SCRAM jet engine is characterized by supersonic combustion. In supersonic combustion, one of the most important issues is supersonic mixing. The main purpose of the present study is to find mixing enhancement methods in supersonic mixing. One method utilizing the flexible sheet flutter for supersonic mixing enhancement is proposed and investigated. As a flexible sheet, rubber thin sheets were examined with several elasticity moduli and flow direction lengths. Water was injected just upstream of a flexible sheet to in the supersonic flow. The flow and mixing fields were visualized by schlieren method and a high-speed camera. The frequency and modes of flutter and the mixing were calculated based on captured images. The results show that the flutter frequency decreases as sheet length increases. The flutter frequency decreases slightly with water injection compared to that without the injection. An increase of sheet length enlarges the diffusion region of water.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955219, CiNii Books ID：AA11902161 - 1906 Reduction of the Pressure Loss by the Addition of the Organic Nano Tube in the Circular Pipe Flow
INAIDA Yuki; TAKEYAMA Atsushi; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2012, Number：18, First page：73, Last page：74, 08 Mar. 2012
The pressure loss characteristics of a dispersion liquid flow containing the organic nanotube in the circular pipe are investigated experimentally. The volumetric flow rate and the pressure difference are measured. The dispersion concentrations of 1000 to 6000ppm are examined Up to the concentration of 3000ppm, the drag reduction increases with an increase of concentrations. At the concentration of more than 3000ppm, however, the drag reduction becomes almost constant, in spite of an increase of the concentration, i.e. saturated. As the Reynolds number increases, the drag reduction decreases. In addition, the electron microscope observation shows that the network structure of the organic nanotube in the dispersion liquid hardly alters after 42 days.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955222, CiNii Books ID：AA11902161 - 106 Measurement of the Valveless Asymmetric Channel Flow Induced by Reciprocal 0scillating Flow
KAWAMURA Naoto; OKA Daichi; YOKOTA Kazuhiko; SATO Kotaro
Volume：2012, Number：18, First page：133, Last page：134, 08 Mar. 2012
A fluid transport device utilizing a diffuser is investigated based on an experiment. The fluid in a diffuser was excited by the reciprocating motion of a piston integrated in the side wall. The flow fields was visualized by a laser sheet and a high-speed camera. The velocity fields are calculated by the particle image velocimetry based on the captured movies. Since the waveform of the sum of the inlet and the outlet flow rate agrees well with that of flow rate calculated based on the temporal displacement of the piston, the present PIV results can be said to be valid. Moreover, the amplitude of flow rate fluctuation at the outlet was larger about 3.5 times than that at the inlet. It implies the present device can transport fluid from an inlet to an outlet.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955252, CiNii Books ID：AA11902161 - 1907 Characteristics of Pressure Loss of Water Flow in Cavity of Rectangle Pipe
MURAO Masanori; SHISHIDO Takahiro; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2012, Number：18, First page：75, Last page：76, 08 Mar. 2012
The pressure loss characteristics were investigated for the water flow with the water and the air cavities in the rectangular duct. The pressure loss coefficients obtained by the experiments were compared with the total loss based on the typical minor losses. The semi-empirical losses of the friction, the sudden expansion, the sudden contraction and the hydraulic jump are considered as the typical minor losses. The semi-empirical total losses show differences of 24-27% from the experimental ones. For the case with the air cavity, the hydraulic jump loss increases as the Reynolds number increases. At relatively low Re, the loss coefficients with the air cavity become lower than those with the water cavity. On the other hand, at relatively high Re,the ones with the air cavity are almost same as those with the water cavity.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955223, CiNii Books ID：AA11902161 - 110 Measurement of The Flow Place between Rotation Disks
SHIBATA Yuki; UCHIDA Masaya; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2012, Number：18, First page：141, Last page：142, 08 Mar. 2012
The flow between coaxial double circular disks in an open space was investigated based on an experiment. The one disk was rotated and the other was set stationary. The diameter of the disks and the spacing between the two disks were 200 and 30 mm, respectively. The rotation speeds of 6000, 8000 and 10000 rpm were examined. The radial and azimuthal components of the flow velocity were measured by an X-type hot-wire anemometer on the periphery of the space between double circular disks. The fluid in the vicinity of the rotating disk was transported in the outer direction. On the other hand, the one in the middle region of two disks flowed in the inner direction. In addition, the fluid near the stationary disk was almost stationary.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955256, CiNii Books ID：AA11902161 - 1912 Measurement of the Flow Place of the Circumference of the Rotation Cylinder between Disks
KANAZAWA Hiroto; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2012, Number：18, First page：85, Last page：86, 08 Mar. 2012
In recent years, energy saving of fluid machinery, such as a centrifugal compressor, is desired, and the improvements of efficiency for each part are demanded. In a vaneless diffuser of a centrifugal fan and compressor, however, a rotating stall may occur and result in an unstable operation. Accordingly, various degradations may appear, e. g. a pressure performance drop, noise/vibration occurrences and damage of machines. The rotating stall is one of rotational flow instability, i.e. is induced by a rotating fluid. Therefore, in this research, the flow around the rotation circular cylinder between two stationary circular disks was investigated by experiments, which is a model of a centrifugal vaneless diffuser without discharge from and suction in an impeller. The experimental FFT results show several peaks with small frequencies, which indicates the flow instabilities can occur with neither discharge nor suction.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955228, CiNii Books ID：AA11902161 - 111 The performance characteristic of the VISCOUS micro pump using a rotation disk
NOMAKI Tsukasa; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2012, Number：18, First page：143, Last page：144, 08 Mar. 2012
In the present study, the viscous micropump using a rotating circular disk in an elbow duct is investigated based on the centimeter-scale model experiments. The low Reynolds number was realized by using glycerin as a working fluid. The flow is visualized by a lazer sheet and a high-speed camera. The velocity fields are calculated based on the captured movies using the particle image velocimetry. The head difference between the upstream and downstream tanks of 12 mm was obtained, which indicates the present viscous pump model using a rotating circular disk in an elbow duct can work as a micropump. The PIV results show that even fluid is still rotating even relatively far from rotating disk.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955257, CiNii Books ID：AA11902161 - 1902 The Characteristic of Wind Power Generation by Flexible Sheet Flutter
TAKAGI Shigeo; TAGUCHI Yutaka; KANG Donghyuk; YOKOTA Kazuhiko; SATO Kotaro
Volume：2012, Number：18, First page：65, Last page：66, 08 Mar. 2012
The characteristics of wind power generation by the flexible sheet flutter were investigated. In the present experiment, the effects of sheet length and wind velocity are examined. The sheet displacement, the angular frequency and the generated power were measured temporally to investigate the characteristics of power generation In addition, the high-speed camera was used to obtain the sheet behavior, especially modes and mode change. Power generation efficiency was roughly as a ratio of the measured electric power to the rotational kinetic energy calculated based on the moment of inertia, the rotational angular amplitude and the angular frequency. The results show that the rotational angular amplitude has the largest effect on the generated power.
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955218, CiNii Books ID：AA11902161 - 1933 Three Dimensional Incompressible Numerical Simulation of the Vortex in the Cavity Flow
YANASE Yoshihiro; KANG Donghyuk; YOKOTA Kazuhiko
Volume：2012, Number：18, First page：611, Last page：612, 08 Mar. 2012
The cavity flow is important issues for the practical engineer problems such as the heat fluid mechanics, the cavity noise and so on In the present paper, the effects of cavity geometries on the cavity flow structures were investigated using the three-dimensional numerical simulations The present numerical results were validated by the reference at the Reynolds number of 1500 At the Reynolds number of 1000, the two vortices were observed for the larger cavity The vortex size at the left bottom corner for the square cavity is increased with an increase of the cavity size The vortex structure are similar for the square cavity
The Japan Society of Mechanical Engineers, Japanese
CiNii Articles ID：110009955489, CiNii Books ID：AA11902161 - インデューサに生じるキャビテーション不安定現象の周方向溝による抑制と高周波数圧力変動の原因に関する考察
姜東赫; 有本悠祐; 米澤宏一; 堀口祐憲; 辻本良信; 川田裕; HAH Chunill
ターボ機械協会講演会, Volume：63rd, First page：31, Last page：36, 2010
Japanese
J-Global ID：201002214712730938 - Large Eddy Simulation of the Dynamic Response of an Inducer to Flow Rate Fluctuations
Donghyuk Kang; Koichi Yonezawa; Tatsuya Ueda; Nobuhiro Yamanishi; Chisachi Kato; Yoshinobu Tsujimoto
10TH ASIAN INTERNATIONAL CONFERENCE ON FLUID MACHINERY, Volume：1225, Number：4, First page：769, Last page：+, 2010
A large eddy simulation (LES) of the flow in an inducer is carried out under flow rate oscillations. The present study focuses on characteristics of dynamic responses of the backflow and the pressure performance to the flow rate fluctuations under non-cavitation conditions. The amplitude of angular momentum fluctuation evaluated by LES is larger than that evaluated by RANS. However, the phase delay of backflow is nearly the same as RANS calculation. The pressure performance curve exhibits a closed curve caused by the effect of inertia associated with the flow rate fluctuations. Compared with simplified one dimensional evaluation of the inertia component, the component obtained by the LES is smaller. The negative slope of averaged performance curve becomes larger under unsteady conditions. From the conservations of angular momentum and energy, an expression useful for the evaluation of unsteady pressure rise was obtained. The examination of each term of this expression show that the apparent decrease of inertia effects is caused by the response delay of Euler's head and that the increase of negative slope is caused by the delay of inertial term associated with the delay of backflow response. These results are qualitatively confirmed by experiments.
AMER INST PHYSICS, English
DOI：https://doi.org/10.1063/1.3464927
Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=78649276645&origin=inward
Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=78649276645&origin=inward
DOI ID：10.1063/1.3464927, ISSN：0094-243X, eISSN：1551-7616, J-Global ID：201202240683663962, CiNii Articles ID：130004542423, SCOPUS ID：78649276645, Web of Science ID：WOS:000283704700077 - Inducer Design to Avoid Cavitation Instabilities
Donghyuk Kang; Toshifumi Watanabe; Koichi Yonezawa; Hironori Horiguchi; Yutaka Kawata; Yoshinobu Tsujimotol
10TH ASIAN INTERNATIONAL CONFERENCE ON FLUID MACHINERY, Volume：1225, Number：4, First page：433, Last page：+, 2010
Three inducers were designed to avoid cavitation instabilities. This was accomplished by avoiding the interaction of tip cavity with the leading edge of the opposing blade. The first one applied extremely larger leading edge sweep, the second and third ones applied smaller incidence angle by reducing the inlet blade angle or increasing the design flow rate, respectively. The inducer with larger design flow rate has larger outlet blade angle to obtain sufficient pressure rise. The inducer with larger sweep could suppress the cavitation instabilities in wide ranges of cavitation number and flow rate, owing to weaker tip leakage vortex cavity with stronger disturbance by backflow vortices. The inducer with larger outlet blade angle could avoid the cavitation instabilities at higher flow rates owing to the extension of the tip cavity along the suction surface of the blade. The inducer with smaller inlet blade angle could avoid the cavitation instabilities at the flow rates larger than the design flow coefficient, owing to the occurrence of the cavity first in the blade passage and its extension upstream. The cavity shape and suction performance were reasonably simulated by three dimensional CFD computations under the steady cavitating condition, except for the backflow vortex cavity. The difference in the growth of cavity for each inducer is explained from the difference of the pressure distribution on the suction side of the blades.
AMER INST PHYSICS, English
DOI：https://doi.org/10.1063/1.3464890
Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=78549292101&origin=inward
Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=78549292101&origin=inward
DOI ID：10.1063/1.3464890, ISSN：0094-243X, eISSN：1551-7616, J-Global ID：201202246240438662, CiNii Articles ID：130004542424, SCOPUS ID：78549292101, Web of Science ID：WOS:000283704700044 - キャビテーション不安定現象を抑制するインデューサインペラ形状に関する実験的研究
KANG D; 渡邊俊文; 米澤宏一; 堀口祐憲; 辻本良信; 川田裕
ターボ機械協会講演会, Volume：61st, First page：33, Last page：38, 2009
Japanese
J-Global ID：200902254674749680 - J0501-4-1 Cause of Cavitation Instabilities in Three Dimensional Inducer
Kang Donghyuk; Yonezawa Koichi; Horiguchi Hironory; Kawata Yutaka; Tsujimoto Yoshinobu
The proceedings of the JSME annual meeting, Volume：2009, Number：0, First page：35, Last page：36, 2009
Rotating cavitation in rocket turbopump inducers was simulated by a three dimensional commercial CFD code. In order to clarify the cause of cavitation instabilities, the velocity disturbance caused by cavitation was obtained by subtracting the velocity vector under non-cavitating condition from that under cavitating condition. It was found that there exists a disturbance flow towards the trailing edge of the tip cavity. This flow has an axial flow component towards downstream which reduces the incidence angle to the next blade. It was found that all of the cavitation instabilities start to occur when this flow starts to interact with the leading edge of the next blade. The existence of the disturbance flow was validated by experiments.
The Japan Society of Mechanical Engineers, Japanese
DOI：https://doi.org/10.1299/jsmemecjo.2009.7.0_35
DOI ID：10.1299/jsmemecjo.2009.7.0_35, CiNii Articles ID：110007862674, CiNii Books ID：AA11461871 - インデューサに生じるキャビテーション不安定現象の3次元流れからの考察
姜東赫; 渡邊俊文; 米澤宏一; 堀口祐憲; 川田裕; 辻本良信
日本混相流学会年会講演会講演論文集, Volume：2008, First page：246, Last page：247, Aug. 2008
Japanese
J-Global ID：200902241244599590 - Effect of Blade Geometry on Tip Leakage Vortex of Inducer
Donghyuk Kang; Angelo Cervone; Koichi Yonezawa; Hironori Horiguchi; Yukata Kawata; Yoshinobu Tsujimoto
Proceedings of the 9th Asian International Conference on Fluid Machinery (AICFM9), First page：1, Last page：6, Oct. 2007, [Reviewed]
English
- Establishment of a cyber-physical system for smart safety management of hydrogen production equipment
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), 01 Apr. 2023 - 31 Mar. 2027
Gifu University
Grant amount(Total)：18850000, Direct funding：14500000, Indirect funding：4350000
Grant number：23H01646 - 圧縮センシング動的モード分解制御を用いたターボ機械のデジタルツイン
01 Apr. 2022 - 31 Mar. 2026
Grant amount(Total)：4290000, Direct funding：3300000, Indirect funding：990000
Grant number：22K03899 - 多孔板への噴流衝突を利用した高圧水素設備の安全性向上技術の評価
01 Apr. 2020 - 31 Mar. 2023
Grant amount(Total)：18200000, Direct funding：14000000, Indirect funding：4200000
Grant number：20H02396 - Dynamic characteristics and active control of turbomachinery using dynamic mode decomposition and proper fluctuation excitement
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), 01 Apr. 2019 - 31 Mar. 2023
Saitama University
Grant amount(Total)：4160000, Direct funding：3200000, Indirect funding：960000
Grant number：19K04188