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OBARA Tetsuro
Mechanical Science DivisionProfessor
Department of Mechanical Engineering and System Design
Center for English Education and DevelopmentDirector

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■ MISC
  • Reinitiation process of detonation wave behind a slit-plate               
    T. Obara; J. Sentanuhady; Y. Tsukada; S. Ohyagi
    SHOCK WAVES, Volume:18, Number:2, First page:117, Last page:127, Jul. 2008
    The propagation phenomenon of a detonation wave is particularly interesting, because the detonation wave is composed of a 3D shock wave system accompanied by a reaction front. Thus, the passage of a detonation wave draws cellular patterns on a soot-covered plate. The pressure and temperature behind the detonation wave are extremely high and may cause serious damages around the wave. Therefore, it is of great significance from a safety-engineering point of view to decay the detonation wave with a short distance from the origin. In the present study, experiments using high-speed schlieren photography are conducted in order to investigate the behaviors of the detonation wave diffracting from two slits. The detonation wave produced in a stoichiometric mixture of hydrogen and oxygen is propagated through the slits, and the behaviors behind the slit-plate are investigated experimentally. When a detonation wave diffracts from the slits, a shock wave is decoupled with a reaction front. Since the two shock waves propagate from the slits interact with each other at the center behind the plate, the detonation wave is reinitiated by generating a hot-spot sufficient to cause local explosions. Furthermore, it is clarified that the shock wave reflected from a tube-wall is also capable of reinitiating the detonation wave. The reinitiation distance of the detonation wave from the slit-plate is correlated using a number of cells emerged from each slit.
    SPRINGER, English
    DOI:https://doi.org/10.1007/s00193-008-0147-9
    DOI ID:10.1007/s00193-008-0147-9, ISSN:0938-1287, Web of Science ID:WOS:000257383600005
  • Propagation Behavior of Combustion Wave Induced by a Shock Wave Propagated into a Premixed Gas of Oxygen and Hydrogen               
    OBARA Tetsuro; KURIHARA Norihiro; OCHIAI Toshiyuki; OHYAGI Shigeharu
    Transactions of the Japan Society of Mechanical Engineers B, Volume:74, Number:740, First page:949, Last page:956, 2008
    In this paper, experimental results were reported to investigate a behavior of combustion wave when a shock wave was transmitted into a combustible premixed gas of oxygen and hydrogen. In general, phenomena occurring in the premixed gas would be classified into four types, i.e. (a) the shock wave was just transmitted without causing ignition for the shock wave propagated with low-Mach number, (b) the gas was ignited behind the shock wave and a deflagration wave was propagated following the shock wave, (c) the deflagration wave was transited to a detonation wave behind the shock wave, (d) a detonation wave was directly initiated just behind incident shock wave having high-propagation Mach number. In this study, a shock wave produced by a detonation-driven shock tube was transmitted into a premixed gas of oxygen and hydrogen varied with an equivalence ratio, initial pressure of premixed gas and Mach number of the shock wave. As a result, the phenomena of combustion wave were classified using a cell-size of steady-propagating detonation wave. For sensitive gases having small cell-size, the detonation wave was directly initiated behind the shock wave even though the Mach number of the shock wave was relatively low. Empirical equations to evaluate a Mach number and temperature behind shock wave were obtained, which are threshold parameters to cause detonation wave behind transmitted shock wave.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.74.949, ISSN:0387-5016, CiNii Articles ID:110006655833, CiNii Books ID:AN00187441
  • 酸水素予混合気体への衝撃波入射により生じる燃焼波の伝ぱ形態               
    小原哲郎; 栗原慶博; 落合俊幸; 大八木重治
    日本機械学會論文集. B編, Volume:74, Number:740, First page:949, Last page:956, 2008
    In this paper, experimental results were reported to investigate a behavior of combustion wave when a shock wave was transmitted into a combustible premixed gas of oxygen and hydrogen. In general, phenomena occurring in the premixed gas would be classified into four types, i.e. (a) the shock wave was just transmitted without causing ignition for the shock wave propagated with low-Mach number, (b) the gas was ignited behind the shock wave and a deflagration wave was propagated following the shock wave, (c) the deflagration wave was transited to a detonation wave behind the shock wave, (d) a detonation wave was directly initiated just behind incident shock wave having high-propagation Mach number. In this study, a shock wave produced by a detonation-driven shock tube was transmitted into a premixed gas of oxygen and hydrogen varied with an equivalence ratio, initial pressure of premixed gas and Mach number of the shock wave. As a result, the phenomena of combustion wave were classified using a cell-size of steady-propagating detonation wave. For sensitive gases having small cell-size, the detonation wave was directly initiated behind the shock wave even though the Mach number of the shock wave was relatively low. Empirical equations to evaluate a Mach number and temperature behind shock wave were obtained, which are threshold parameters to cause detonation wave behind transmitted shock wave.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.74.949, ISSN:0387-5016, CiNii Articles ID:110006655833, CiNii Books ID:AN00187441
  • デトネーション波の消炎および再開始現象の解明               
    小原哲郎
    Number:5(18年度), First page:580, Last page:581, 2007
  • Re-initiation Processes of Detonation Wave Behind Slit-Plate : Visualization of Re-initiation and Quenching Processes of Detonation Wave               
    OBARA Tetsuro; TSUKADA Yutaka; SENTANUHADY Jayan; OHYAGI Shigeharu
    Transactions of the Japan Society of Mechanical Engineers B, Volume:73, Number:735, First page:2354, Last page:2361, 2007
    A propagation of detonation wave shows particularly interesting phenomena, since the detonation wave is constituted from a three-dimensional shock wave system accompanied with a reaction front. Thus, the passage of a detonation wave draws cellular patterns on a soot-covered plate. Pressure and temperature behind the detonation wave are extremely high and have a potential to cause serious damages around it. Therefore, it is necessary from safety engineering point of view to quench the detonation wave with short distance from the origin. In this study, experiments applied high-speed schlieren photography are conducted to investigate behaviors of the detonation wave diffracting from two pieces of slits. The detonation wave produced in a stoichiometric mixture of hydrogen and oxygen is propagated through the slits and behaviors behind slit-plate are experimentally investigated. As a result, when the detonation wave diffracted from the slits, a shock wave is decoupled with a reaction front. Since two shock waves progagated from the slits interact each other at centre behind the plate, the detonation wave is re-initiated by generating a hot-spot enough to cause local explosion. It is also clarified that the shock wave reflected from a tube-wall induces detonation re-initiation.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.73.2354, ISSN:0387-5016, CiNii Articles ID:110006453745, CiNii Books ID:AN00187441
  • Re-initiation Processes of Detonation Wave Behind Slit-Plate : Influence of Slit-Plate Configuration               
    SENTANUHADY Jayan; OBARA Tetsuro; TSUKADA Yutaka; OHYAGI Shigeharu
    Transactions of the Japan Society of Mechanical Engineers B, Volume:73, Number:732, First page:1737, Last page:1744, 2007
    Pressure and temperature behind a detonation wave are extremely high and have a potential to cause serious damages around it. Therefore, it is necessary from safety engineering point of view to decay the detonation wave with short distance from a generation of it. In this study, experiments are conducted in order to investigate behaviors of the detonation wave propagating into two pieces of slits, since the detonation wave might be quenched behind the slits by expansion waves generated at a corner of the slits and this behavior might be applicable to a technique of detonation-arrester. The detonation wave produced in a stoichiometric mixture of hydrogen and oxygen is propagated through the slits and behaviors of it are experimentally investigated by using a technique of pressure measurement, soot track record and high-speed schlieren photography. As a result, when the detonation wave propagated through the slits, a shock wave is decoupled with a reaction front. Two shock waves diffracted from the slits interact each other at center behind the slits, then this shock wave interaction induces a hot-spot enough to cause local explosion. Since, the shock wave is reflected from a tube-wall eventually, the detonation wave is re-initiated by mechanisms of shock-shock interaction or shock-wall interactions.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.73.1737, ISSN:0387-5016, CiNii Articles ID:110006401679, CiNii Books ID:AN00187441
  • Behavior of Combustion Wave Induced by Propagation of Shock Wave into Premixed Gas of Hydrogen and Oxygen               
    OBARA Tetsuro; NARAHARA Yukiko; KURIHARA Norihiro; OHYAGI Shigeharu
    Transactions of the Japan Society of Mechanical Engineers B, Volume:73, Number:727, First page:871, Last page:878, 2007
    Experiments were conducted in order to investigate a behavior of comcustion wave when a shock wave was propagated into a combustible premixed gas of hydrogen and oxygen. A phenomenon occurring in the premixed gas can be classified into four types, i.e. (a) the shock wave just transmitted into the gas without causing ignition for the shock wave of low-Mach number, (b) the gas was ignited behind the shock wave and a deflagration wave was propagated following the shock wave, (c) the deflagration wave transited to a detonation wave behind the shock wave, (d) a detonation wave was directly initiated just behind incident shock wave of high-Mach number. In this study, a shock wave produced by a detonation-driven shock tube was transmitted into a hydrogen-oxygen premixed gas varied with an equivalence ratio 0, initial pressure p\ and Mach number of the shock wave Mst. As a result, the phenomena observed in the gas was classified using a cell-size A for steady detonation wave, since the cell-size was inversely proportional to a chemical reaction rate of the gas. For the case of sensitive gases having small cell-size, the detonation wave was directly initiated behind the shock wave even though the Mach number of the shock wave was relatively low. An empirical equation to evaluate a pressure was obtained, which is a threshold pressure to ignite the gas behind incident shock wave.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.73.871, ISSN:0387-5016, CiNii Articles ID:110006271376, CiNii Books ID:AN00187441
  • A study on multiple-cycle operation of pulse detonation engine               
    遠藤慎介; 中込大輔; 吉橋照夫; 小原哲郎; 大八木重治; 村山元
    Volume:8, Number:8, First page:64, Last page:67, 2007
    A Pulse detonation engine (PDE) is an internal combustion engine that generates power due to intermittent detonations. As an air supply method, many researchers used the solenoid valves. However, it is unsuitable for air breathing engines which use air from the atmosphere. Then, for practical use there, the PDE is expected to be equipped with some kind of rotary valves which can induce air intermittently from the atmosphere. Although some researchers reported the results using such valves for the PDE, a detailed study of the continuous operation PDE has not been reported yet, so it is meaningful to examine the behavior and the optimization of the PDE with the rotary valve. For this object, it is experimented to prove a certain, continuous operation of 40Hz by this device. The combustion test was performed for 30, 35, and 40Hz operations. The performance was evaluated by two parameters, i.e., thrust F [N] and impulse per unit area Icycle [Ns/m2]. As a result, a 120 cycle, 3 seconds operation was able to be achieved by 40Hz. The impulse was decreased as the operation frequency increased, although the thrust was slightly increased.
    Japanese
    ISSN:1347-4758, CiNii Articles ID:120001371278, CiNii Books ID:AA11808968
  • デトネーション波の消炎および再開始現象の解明               
    小原哲郎
    総合研究機構研究プロジェクト研究成果報告書, Number:5(18年度), First page:580, Last page:581, 2007
  • スリット板背後におけるデトネーション波の再開始過程 (デトネーション波の再開始と消炎過程の可視化)               
    小原哲郎; 塚田豊; Jayan Sentanuhady; 大八木重治
    日本機械学會論文集. B編, Volume:73, Number:735, First page:2354, Last page:2361, 2007
    A propagation of detonation wave shows particularly interesting phenomena, since the detonation wave is constituted from a three-dimensional shock wave system accompanied with a reaction front. Thus, the passage of a detonation wave draws cellular patterns on a soot-covered plate. Pressure and temperature behind the detonation wave are extremely high and have a potential to cause serious damages around it. Therefore, it is necessary from safety engineering point of view to quench the detonation wave with short distance from the origin. In this study, experiments applied high-speed schlieren photography are conducted to investigate behaviors of the detonation wave diffracting from two pieces of slits. The detonation wave produced in a stoichiometric mixture of hydrogen and oxygen is propagated through the slits and behaviors behind slit-plate are experimentally investigated. As a result, when the detonation wave diffracted from the slits, a shock wave is decoupled with a reaction front. Since two shock waves progagated from the slits interact each other at centre behind the plate, the detonation wave is re-initiated by generating a hot-spot enough to cause local explosion. It is also clarified that the shock wave reflected from a tube-wall induces detonation re-initiation.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.73.2354, ISSN:0387-5016, CiNii Articles ID:110006453745, CiNii Books ID:AN00187441
  • スリット板背後におけるデトネーション波の再開始過程 (スリット板形状の違いによる影響)               
    Jayan Sentanuhady; 小原哲郎; 塚田豊; 大八木重治
    日本機械学會論文集. B編, Volume:73, Number:732, First page:1737, Last page:1744, 2007
    Pressure and temperature behind a detonation wave are extremely high and have a potential to cause serious damages around it. Therefore, it is necessary from safety engineering point of view to decay the detonation wave with short distance from a generation of it. In this study, experiments are conducted in order to investigate behaviors of the detonation wave propagating into two pieces of slits, since the detonation wave might be quenched behind the slits by expansion waves generated at a corner of the slits and this behavior might be applicable to a technique of detonation-arrester. The detonation wave produced in a stoichiometric mixture of hydrogen and oxygen is propagated through the slits and behaviors of it are experimentally investigated by using a technique of pressure measurement, soot track record and high-speed schlieren photography. As a result, when the detonation wave propagated through the slits, a shock wave is decoupled with a reaction front. Two shock waves diffracted from the slits interact each other at center behind the slits, then this shock wave interaction induces a hot-spot enough to cause local explosion. Since, the shock wave is reflected from a tube-wall eventually, the detonation wave is re-initiated by mechanisms of shock-shock interaction or shock-wall interactions.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.73.1737, ISSN:0387-5016, CiNii Articles ID:110006401679, CiNii Books ID:AN00187441
  • 水素 酸素予混合気体への衝撃波入射により誘起される燃焼波の挙動               
    小原哲郎; 楢原由樹子; 栗原慶博; 大八木重治
    日本機械学會論文集. B編, Volume:73, Number:727, First page:871, Last page:878, 2007
    Experiments were conducted in order to investigate a behavior of comcustion wave when a shock wave was propagated into a combustible premixed gas of hydrogen and oxygen. A phenomenon occurring in the premixed gas can be classified into four types, i.e. (a) the shock wave just transmitted into the gas without causing ignition for the shock wave of low-Mach number, (b) the gas was ignited behind the shock wave and a deflagration wave was propagated following the shock wave, (c) the deflagration wave transited to a detonation wave behind the shock wave, (d) a detonation wave was directly initiated just behind incident shock wave of high-Mach number. In this study, a shock wave produced by a detonation-driven shock tube was transmitted into a hydrogen-oxygen premixed gas varied with an equivalence ratio 0, initial pressure p\ and Mach number of the shock wave Mst. As a result, the phenomena observed in the gas was classified using a cell-size A for steady detonation wave, since the cell-size was inversely proportional to a chemical reaction rate of the gas. For the case of sensitive gases having small cell-size, the detonation wave was directly initiated behind the shock wave even though the Mach number of the shock wave was relatively low. An empirical equation to evaluate a pressure was obtained, which is a threshold pressure to ignite the gas behind incident shock wave.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.73.871, ISSN:0387-5016, CiNii Articles ID:110006271376, CiNii Books ID:AN00187441
  • パルスデトネーション・エンジン連続作動特性の研究               
    遠藤慎介; 中込大輔; 吉橋照夫; 小原哲郎; 大八木重治; 村山元
    埼玉大学地域共同研究センター紀要, Volume:8, Number:8, First page:64, Last page:67, 2007
    A Pulse detonation engine (PDE) is an internal combustion engine that generates power due to intermittent detonations. As an air supply method, many researchers used the solenoid valves. However, it is unsuitable for air breathing engines which use air from the atmosphere. Then, for practical use there, the PDE is expected to be equipped with some kind of rotary valves which can induce air intermittently from the atmosphere. Although some researchers reported the results using such valves for the PDE, a detailed study of the continuous operation PDE has not been reported yet, so it is meaningful to examine the behavior and the optimization of the PDE with the rotary valve. For this object, it is experimented to prove a certain, continuous operation of 40Hz by this device. The combustion test was performed for 30, 35, and 40Hz operations. The performance was evaluated by two parameters, i.e., thrust F [N] and impulse per unit area Icycle [Ns/m2]. As a result, a 120 cycle, 3 seconds operation was able to be achieved by 40Hz. The impulse was decreased as the operation frequency increased, although the thrust was slightly increased.
    Japanese
    ISSN:1347-4758, CiNii Articles ID:120001371278, CiNii Books ID:AA11808968
  • Experimental study on the flow field behind a backward-facing step using a detonation-driven shock tunnel               
    TH Kim; T Obara; M Yoshikawa; S Ohyagi
    SHOCK WAVES, Volume:15, Number:1, First page:1, Last page:12, Mar. 2006
    The supersonic combustion RAM jet (SCRAM jet) engine is expected to be used in next-generation space planes and hypersonic airliners. To develop the engine, stabilized combustion in a supersonic flow field must be attained even though the residence time of flow is extremely short. A mixing process for breathed air and fuel injected into the supersonic flow field is therefore one of the most important design problems. Because the flow inside the SCRAM jet engine has high enthalpy, an experimental facility is required to produce the high-enthalpy flow field. In this study, a detonation-driven shock tunnel was built to produce a high-enthalpy flow, and a model SCRAM jet engine equipped with a backward-facing step was installed in the test section of the facility to visualize flow fields using a color schlieren technique and high-speed video camera. The fuel was injected perpendicularly to a Mach 3 flow behind the backward-facing step. The height of the step, the injection distance and injection pressure were varied to investigate the effects of the step on air/fuel mixing characteristics. The results show that the recirculation region increases as the fuel injection pressure increases. For injection behind the backward-facing step, mixing efficiency is much higher than with a flat plate. Also, the injection position has a significant influence on the size of the recirculation region generated behind the backward-facing step. The schlieren photograph and pressure histories measured on the bottom wall of the SCRAM jet engine model show that the fuel was ignited behind the step.
    SPRINGER, English
    DOI:https://doi.org/10.1007/s00193-005-0283-4
    DOI ID:10.1007/s00193-005-0283-4, ISSN:0938-1287, Web of Science ID:WOS:000235759200001
  • Experimental Study on Behavior of a Flame Entering into a Narrow Channel               
    OBARA Tetsuro; OHYAGI Shigeharu; NISHINA Yusuke; NARISAWA Nobuyuki
    Transactions of the Japan Society of Mechanical Engineers B, Volume:72, Number:720, First page:2018, Last page:2025, 2006
    A behavior of a flame propagating through a narrow channel is of importance, since this phenomenon is concerned with a quenching of the flame when heat losses by convective heat transfer or radiative one to a wall of channel are dominant and temperature behind the flame is not enough to increase that of unburned gases. Since, this phenomenon is also related to a safety-engineering problem where combustible gaseous mixture is handled, a device applying a narrow channel in a pipe might be one of useful technique to prevent the flame from propagating. Experiments were conducted to investigate a behavior of the flame propagating through a narrow channel, which connects two rectangular combustion chambers. The behavior of the flame was visualized using schlieren optical technique with an aid of high-speed video camera. In this study, an equivalence ratio of methane-air mixture, initial pressure and a width of the channel were varied in order to investigate effects of these parameters on characteristics of the flame propagation. As a result, the behavior of the flame entering into the narrow channel was classified into two phenomena, i.e. (i) the flame was quenched inside the narrow channel and combustion wave was not propagated into the downstream chamber, which results in just an emission of burned gaseous jet to the downstream chamber, (ii) the flame was propagated through the channel without quenching, which produced a high-pressure at both chambers.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.72.2018, ISSN:0387-5016, CiNii Articles ID:110004763450, CiNii Books ID:AN00187441
  • スリットに入射したデトネーション波の再開始過程<研究成果報告>               
    小原哲郎; 大八木重治
    Volume:39, First page:119, Last page:126, 2006
  • Combustion Processes in Model SCRAM Jet Combustor Using Detonation Driven Shock Tunnel               
    OBARA Tetsuro; ITO Takeaki; KIM Tae-Hwan; OHYAGI Shigeharu; TSUBOI Nobuyuki
    Transactions of the Japan Society of Mechanical Engineers B, Volume:72, Number:718, First page:1596, Last page:1604, 2006
    Experiments were conducted in order to investigate mixing and combustion processes in a model SCRAM (Supersonic Combustion RAM) jet combustor equipped with a backward-facing step. A detonation-driven shock tunnel was used to generate high-enthalpy flow of Mach number three. Firstly, an influence of installing a sidewall on the combustor model was investigated. Secondly, flow-fields around the step were visualized using high-speed video camera with an aid of schlieren technique. A hydrogen fuel was injected perpendicular to the supersonic flow behind the backward-facing step and a height of the step and an injection distance were varied in order to investigate the effects of these parameters on a characteristic of the combustion. As a result, the injected hydrogen was ignited behind the step and increasing the height of step became effective to the ignition and flame holding behaviors. Furthermore, a non-dimensional injection distance with respect to height of the step was considered to be an important parameter to influence an ignition and combustion processes in the model SCRAM jet combustor.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.72.1596, ISSN:0387-5016, CiNii Articles ID:110004758304, CiNii Books ID:AN00187441
  • A Study on Behavior of Detonation Wave Passing through Narrow Grooves               
    OBARA Tetsuro; SENTANUHADY Jayan; TSUKADA Yutaka; OHYAGI Shigeharu
    Transactions of the Japan Society of Mechanical Engineers B, Volume:72, Number:718, First page:1605, Last page:1612, 2006
    A detonation wave produced in a combustible gaseous mixture might cause serious damages by interacting with an artificial structure or human bodies because of an extremely high-pressure and high-temperature behind this wave. Therefore, the detonation wave produced in the gaseous mixture and propagated into a circumstance by accident should be attenuated or quenched within a short distance from its origin. Experiments were conducted in order to investigate behaviors of the detonation wave passing through narrow grooves, since the detonation wave was accompained with a cellular structure and no detonation wave could be propagated. In this study, the detonation wave produced in a gaseous mixture of hydrogen and oxygen was propagated through a grooved block and behaviors of the detonation wave were experimentally investigated by using techniques of pressure measurement and soot track record. As a result, the behavior of detonation wave propagating through the grooved block was classified into two categories, i. e. (i) the detonation wave was quenched, (ii) the detonation wave was once quenched behind the block but re-initiated again by focusing mechanisms of a reflected shock wave on a central axis.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.72.1605, ISSN:0387-5016, CiNii Articles ID:110004758305, CiNii Books ID:AN00187441
  • Laser Ablation with Water Micro-Drop for Dicing of Silicon Wafer               
    Volume:18, Number:2, First page:127, Last page:130, 2006
  • Re-Inititaion Processes of Detonation Wave behind Slit-Plate : Influence of Initial Test Gas Pressure               
    OBARA Tetsuro; SENTANUHADY Jayan; TSUKADA Yutaka; OHYAGI Shigeharu
    Transactions of the Japan Society of Mechanical Engineers B, Volume:72, Number:724, First page:3158, Last page:3165, 2006
    Experiments were conducted in order to investigate behaviors of a detonation wave propagating into two pieces of slit, since the detonation wave might be quenched behind a slit-plate by expansion waves generated at a corner of the plate and this technique might be applicable to a detonation arrestor. The detonation wave produced in a stoichiometric mixture of hydrogen and oxygen was propagated through the slits and behaviors of the detonation wave were experimentally investigated by using a technique of pressure measurement, soot track record and high-speed schlieren photography. As a result, when the detonation wave propagated through the slits, it was quenched and a schock wave was decoupled with a reaction front. Two shock waves diffracted from the slits interacted each other at centre of the tube, then this shock wave interaction induced a hot-spot enough to cause local explosions behind the slit-plate. Since the shock wave was reflected from the wall and interacted at centre of the tube, the detonation wave was re-initiated behind the slits.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.72.3158, ISSN:0387-5016, CiNii Articles ID:110006153443, CiNii Books ID:AN00187441
  • Effect of Injected Volume and Distribution of Purge-Air Regarding Stable Operation for a Pulse Detonation Engine               
    SAKURAI Takashi; OOKO Akinori; YUGI Satoshi; YOSHIHASHI Teruo; OBARA Tetsuro; OHYAGI Shigeharu
    JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, Volume:54, Number:628, First page:204, Last page:209, 2006
    For the development of Pulse Detonation Engine (PDE), effects of injected volume and distribution of purge-air gas on multiple-cycle operations of PDE were investigated. In order to improve the uniformity of a mixture, the experimental PDE had four sets of fuel and oxidizer injector in the opposite side at same axial location. In addition, an injector for the air purging was added on the thrust wall so that the direction of purging flow was discussed. In single cycle experiments, the air purging did not affect the pressure and propagation velocity of detonation wave, hence it is only effective for exhausting the burned gas. The amount of injected purging gas was varied in multiple-cycle experiments to find the optimum amount of purging for stable detonations. The results showed that the amount of air purging increased as the cycle frequency increased and the axial injection rather than the radial was effective to exhaust the burned gas.
    THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, Japanese
    DOI:https://doi.org/10.2322/jjsass.54.204
    DOI ID:10.2322/jjsass.54.204, ISSN:1344-6460, CiNii Articles ID:10018055331, CiNii Books ID:AA11307372
  • デトネーションアレスター技術の確立とメカニズムの解明               
    小原哲郎
    Number:4(17年度), 2006
  • 狭い間隙に進入する火炎の挙動に関する実験的研究(熱工学,内燃機関,動力など)               
    小原哲郎; 大八木重治; 仁科祐介; 成澤伸之
    日本機械学會論文集. B編, Volume:72, Number:720, First page:2018, Last page:2025, 2006
    A behavior of a flame propagating through a narrow channel is of importance, since this phenomenon is concerned with a quenching of the flame when heat losses by convective heat transfer or radiative one to a wall of channel are dominant and temperature behind the flame is not enough to increase that of unburned gases. Since, this phenomenon is also related to a safety-engineering problem where combustible gaseous mixture is handled, a device applying a narrow channel in a pipe might be one of useful technique to prevent the flame from propagating. Experiments were conducted to investigate a behavior of the flame propagating through a narrow channel, which connects two rectangular combustion chambers. The behavior of the flame was visualized using schlieren optical technique with an aid of high-speed video camera. In this study, an equivalence ratio of methane-air mixture, initial pressure and a width of the channel were varied in order to investigate effects of these parameters on characteristics of the flame propagation. As a result, the behavior of the flame entering into the narrow channel was classified into two phenomena, i.e. (i) the flame was quenched inside the narrow channel and combustion wave was not propagated into the downstream chamber, which results in just an emission of burned gaseous jet to the downstream chamber, (ii) the flame was propagated through the channel without quenching, which produced a high-pressure at both chambers.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.72.2018, ISSN:0387-5016, CiNii Articles ID:110004763450, CiNii Books ID:AN00187441
  • スリットに入射したデトネーション波の再開始過程<研究成果報告>
    小原哲郎; 大八木重治
    埼玉大学紀要, 工学部, 第1部論文集, Volume:39, First page:119, Last page:126, 2006
    Experiments were conducted in order to investigate behaviors of a detonation wave propagating into two pieces of slit, since the detonation wave might be quenched behind a slit-plate by expansion waves generated at a corner of the plate and this technique might be applicable to a detonation arrestor. The detonation wave produced in a stoichiometric mixture of hydrogen and oxygen was propagated through the slits and behaviors of the detonation wave were experimentally investigated by using a technique of pressure measurement, soot track record and high-speed schlieren photography. As a result, when the detonation wave propagated through the slits, it was quenched and a shock wave was decoupled with a reaction front. Two shock waves diffracted from the slits interacted each other at centre of the tube, then this shock wave interaction induced a hot-spot enough to cause local explosions behind the slit-plate. Since the shock wave was reflected from the wall and interacted at centre of the tube, the detonation wave was re-initiated behind the slits.
    Japanese
    ISSN:1880-4446, CiNii Articles ID:120001370439
  • デトネーション駆動型衝撃風洞を用いたスクラムジェット燃焼器モデル内の燃焼過程(熱工学,内燃機関,動力など)               
    小原哲郎; 伊藤豪明; 大八木重治; 金泰煥; 坪井伸幸
    日本機械学會論文集. B編, Volume:72, Number:718, First page:1596, Last page:1604, 2006
    Experiments were conducted in order to investigate mixing and combustion processes in a model SCRAM (Supersonic Combustion RAM) jet combustor equipped with a backward-facing step. A detonation-driven shock tunnel was used to generate high-enthalpy flow of Mach number three. Firstly, an influence of installing a sidewall on the combustor model was investigated. Secondly, flow-fields around the step were visualized using high-speed video camera with an aid of schlieren technique. A hydrogen fuel was injected perpendicular to the supersonic flow behind the backward-facing step and a height of the step and an injection distance were varied in order to investigate the effects of these parameters on a characteristic of the combustion. As a result, the injected hydrogen was ignited behind the step and increasing the height of step became effective to the ignition and flame holding behaviors. Furthermore, a non-dimensional injection distance with respect to height of the step was considered to be an important parameter to influence an ignition and combustion processes in the model SCRAM jet combustor.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.72.1596, ISSN:0387-5016, CiNii Articles ID:110004758304, CiNii Books ID:AN00187441
  • 狭い溝中を通過するデトネーション波の挙動に関する研究(熱工学,内燃機関,動力など)               
    小原哲郎; SENTANUHADY Jayan; 塚田豊; 大八木重治
    日本機械学會論文集. B編, Volume:72, Number:718, First page:1605, Last page:1612, 2006
    A detonation wave produced in a combustible gaseous mixture might cause serious damages by interacting with an artificial structure or human bodies because of an extremely high-pressure and high-temperature behind this wave. Therefore, the detonation wave produced in the gaseous mixture and propagated into a circumstance by accident should be attenuated or quenched within a short distance from its origin. Experiments were conducted in order to investigate behaviors of the detonation wave passing through narrow grooves, since the detonation wave was accompained with a cellular structure and no detonation wave could be propagated. In this study, the detonation wave produced in a gaseous mixture of hydrogen and oxygen was propagated through a grooved block and behaviors of the detonation wave were experimentally investigated by using techniques of pressure measurement and soot track record. As a result, the behavior of detonation wave propagating through the grooved block was classified into two categories, i. e. (i) the detonation wave was quenched, (ii) the detonation wave was once quenched behind the block but re-initiated again by focusing mechanisms of a reflected shock wave on a central axis.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.72.1605, ISSN:0387-5016, CiNii Articles ID:110004758305, CiNii Books ID:AN00187441
  • Laser Ablation with Water Micro-Drop for Dicing of Silicon Wafer               
    Journal of Laser Applications, Volume:18, Number:2, First page:127, Last page:130, 2006
  • スリット板背後におけるデトネーション波の再開始過程 (供試気体初期圧力の影響)               
    小原哲郎; Jayan Sentanuhady; 塚田豊; 大八木重治
    日本機械学會論文集. B編, Volume:72, Number:724, First page:3158, Last page:3165, 2006
    Experiments were conducted in order to investigate behaviors of a detonation wave propagating into two pieces of slit, since the detonation wave might be quenched behind a slit-plate by expansion waves generated at a corner of the plate and this technique might be applicable to a detonation arrestor. The detonation wave produced in a stoichiometric mixture of hydrogen and oxygen was propagated through the slits and behaviors of the detonation wave were experimentally investigated by using a technique of pressure measurement, soot track record and high-speed schlieren photography. As a result, when the detonation wave propagated through the slits, it was quenched and a schock wave was decoupled with a reaction front. Two shock waves diffracted from the slits interacted each other at centre of the tube, then this shock wave interaction induced a hot-spot enough to cause local explosions behind the slit-plate. Since the shock wave was reflected from the wall and interacted at centre of the tube, the detonation wave was re-initiated behind the slits.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.72.3158, ISSN:0387-5016, CiNii Articles ID:110006153443, CiNii Books ID:AN00187441
  • パルスデトネーションエンジンの安定作動に関するパージ空気の噴射量および分布の影響               
    桜井毅司; 大古壮了; 柚木聡; 吉橋照夫; 小原哲郎; 大八木重治
    日本航空宇宙学会論文集. B編, Volume:54, Number:628, First page:204, Last page:209, 2006
    For the development of Pulse Detonation Engine (PDE), effects of injected volume and distribution of purge-air gas on multiple-cycle operations of PDE were investigated. In order to improve the uniformity of a mixture, the experimental PDE had four sets of fuel and oxidizer injector in the opposite side at same axial location. In addition, an injector for the air purging was added on the thrust wall so that the direction of purging flow was discussed. In single cycle experiments, the air purging did not affect the pressure and propagation velocity of detonation wave, hence it is only effective for exhausting the burned gas. The amount of injected purging gas was varied in multiple-cycle experiments to find the optimum amount of purging for stable detonations. The results showed that the amount of air purging increased as the cycle frequency increased and the axial injection rather than the radial was effective to exhaust the burned gas.
    THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, Japanese
    DOI:https://doi.org/10.2322/jjsass.54.204
    DOI ID:10.2322/jjsass.54.204, ISSN:1344-6460, CiNii Articles ID:10018055331, CiNii Books ID:AA11307372
  • デトネーションアレスター技術の確立とメカニズムの解明               
    小原哲郎
    総合研究機構研究プロジェクト研究成果報告書, Number:4(17年度), 2006
  • Investigation of the purge process on the multi-cycle operations of a pulse detonation engine               
    T Sakurai; A Ooko; T Yoshihashi; T Obara; S Ohyagi
    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, Volume:48, Number:160, First page:78, Last page:85, Aug. 2005
    The pulse detonation engine (PDE) is a propulsion system that generates thrust by repetitive detonation. Performance of the PDE, such as specific impulse, has gained much attention, However, the details of operational conditions related to performance have not been clarified. In this Study, to investigate these issues. The hydrogen-air PDE was constructed and the effect of the purge process on multi-cycle operations was studied. The exhaust of the burned gas front the PDE was made by rarefaction waves so that it is expected not to create internal disturbance, such as, spiral in the tube so that the burned gas can be exhausted smoothly. A purge process using air was applied to assist the exhaust process in order to prevent failures in multi-cycle operations. The effects of the purge-volume fraction were investigated. As a result when a purge-air gas filled the region including the spark plug detonations occurred in a table manner. Using these conditions. multi-cycle experiments ranging from 10 to 50 Hz were conducted and profiles of wall thrust-wall pressure are discussed in detail.
    JAPAN SOC AERONAUT SPACE SCI, English
    DOI:https://doi.org/10.2322/tjsass.48.78
    DOI ID:10.2322/tjsass.48.78, ISSN:0549-3811, CiNii Articles ID:10016766214, Web of Science ID:WOS:000231206400004
  • 研究プロジェクト「マイクロ/ナノスケール計測制御テクノセンタ ー」活動報告<研究成果報告>               
    水野毅; 川橋正昭; 大八木重治; 加藤寛; 佐藤勇一; 堀尾健一郎; 豊岡了; 荒居善雄; 綿貫啓一; 池野順一; 小原哲郎; 高崎正也
    Volume:1, Number:38, First page:114, Last page:118, 2005
  • レーザダイシング技術の開発               
    Volume:12, Number:6, 2005
  • A study on detonative operation of PDE with rotary-valve               
    柚木聡; 桜井毅司; 笹森崇志; 小原哲郎; 大八木重治; 村山元英
    Volume:6, Number:6, First page:58, Last page:62, 2005
    A PDE equipped with the rotary-valve was constructed. Fuel, which is hydrogen, was injected by the solenoid valve. The porous plates was used to promote the mixing of fuel-air mixture. In this paper, multi-cycle operations for 20Hz, 4.5 second were conducted. It was investigated that what kind of porous shape and the fuel injection position were effective to the mixing and subsequent detonation process. As a result, the "IP2", which was downward injection to the air, was the best for the fuel injection position. The porous plate "P3" that has large open ratio and small aperture size was effective to the mixing and detonation. Detonations were not obtained at all cycles because the mixture could not be filled to the combustion tube uniformly.
    Japanese
    ISSN:1347-4758, CiNii Articles ID:120001371337, CiNii Books ID:AA11808968
  • スクラムジェットエンジンの開発を目指した基礎研究               
    小原哲郎
    Volume:16年度, 2005
  • 研究プロジェクト「マイクロ/ナノスケール計測制御テクノセンタ ー」活動報告<研究成果報告>               
    水野毅; 川橋正昭; 大八木重治; 加藤寛; 佐藤勇一; 堀尾健一郎; 豊岡了; 荒居善雄; 綿貫啓一; 池野順一; 小原哲郎; 高崎正也
    埼玉大学紀要, 工学部, 第1部論文集, Volume:1, Number:38, First page:114, Last page:118, 2005
  • レーザダイシング技術の開発               
    レーザ加工学会誌, Volume:12, Number:6, 2005
  • ロータリーバルブを装着したPDE のデトネーション作動に関する研究               
    柚木聡; 桜井毅司; 笹森崇志; 小原哲郎; 大八木重治; 村山元英
    埼玉大学地域共同研究センター紀要, Volume:6, Number:6, First page:58, Last page:62, 2005
    A PDE equipped with the rotary-valve was constructed. Fuel, which is hydrogen, was injected by the solenoid valve. The porous plates was used to promote the mixing of fuel-air mixture. In this paper, multi-cycle operations for 20Hz, 4.5 second were conducted. It was investigated that what kind of porous shape and the fuel injection position were effective to the mixing and subsequent detonation process. As a result, the "IP2", which was downward injection to the air, was the best for the fuel injection position. The porous plate "P3" that has large open ratio and small aperture size was effective to the mixing and detonation. Detonations were not obtained at all cycles because the mixture could not be filled to the combustion tube uniformly.
    Japanese
    ISSN:1347-4758, CiNii Articles ID:120001371337, CiNii Books ID:AA11808968
  • スクラムジェットエンジンの開発を目指した基礎研究               
    小原哲郎
    総合研究機構研究プロジェクト研究成果報告書, Volume:16年度, 2005
  • デトネーション波により駆動される衝撃波管の作動特性に関する実験的研究(熱工学,内燃機関,動力など)               
    金泰煥; 小原; 哲郎; 大八木重治; 吉川正人
    Volume:70, Number:691, First page:707, Last page:714, 2004
    DOI:https://doi.org/10.1299/kikaib.70.707
    DOI ID:10.1299/kikaib.70.707, ISSN:0387-5016, CiNii Articles ID:110004999317
  • A Study for Development of Hydrogen-fueled Pulse Detonation Engines               
    Sakurai T; Minagawa T; Yoshihashi T; Obara T; Ohyagi S
    Volume:65, Number:4, First page:125, Last page:133, 2004
  • デトネーション駆動型衝撃風洞を用いた後ろ向きステップ周りの流れ場に関する実験的研究               
    金泰煥; 小原哲郎; 大八木重治; 吉川正人
    Volume:52, Number:608, First page:385, Last page:392, 2004
    DOI:https://doi.org/10.2322/jjsass.52.385
    DOI ID:10.2322/jjsass.52.385, ISSN:1344-6460, CiNii Articles ID:10013578099
  • デトネーション波により駆動される衝撃波管の作動特性に関する実験的研究(熱工学,内燃機関,動力など)               
    金泰煥; 小原; 哲郎; 大八木重治; 吉川正人
    日本機械学會論文集. B編, Volume:70, Number:691, First page:707, Last page:714, 2004
    DOI:https://doi.org/10.1299/kikaib.70.707
    DOI ID:10.1299/kikaib.70.707, ISSN:0387-5016, CiNii Articles ID:110004999317
  • A Study for Development of Hydrogen-fueled Pulse Detonation Engines               
    Sakurai T; Minagawa T; Yoshihashi T; Obara T; Ohyagi S
    Science and Technology of Energetic Materials, Volume:65, Number:4, First page:125, Last page:133, 2004
  • デトネーション駆動型衝撃風洞を用いた後ろ向きステップ周りの流れ場に関する実験的研究               
    金泰煥; 小原哲郎; 大八木重治; 吉川正人
    日本航空宇宙学会論文集, Volume:52, Number:608, First page:385, Last page:392, 2004
    DOI:https://doi.org/10.2322/jjsass.52.385
    DOI ID:10.2322/jjsass.52.385, ISSN:1344-6460, CiNii Articles ID:10013578099
  • Diffraction and re-initiation of detonations behind a backward-facing step               
    S Ohyagi; T Obara; S Hoshi; P Cai; T Yoshihashi
    SHOCK WAVES, Volume:12, Number:3, First page:221, Last page:226, Nov. 2002
    Diffraction phenomena of gaseous detonation waves behind a backward-facing step in a tube are observed by using high-speed schlieren photography and soot-track records as well as by pressure measurements on the sidewall. Mixtures are stoichiometric oxyhydrogen and those diluted by argon at sub-atmospheric pressures. Three types of phenomena are observed, that is, continuous propagation of detonation, re-initiation after a temporal extinction of detonation and complete extinction of detonation. The continuous propagation means that the diffracted wave does not affect the main propagation although reflected shock waves from the bottom surface of the tube may affect it. The re-initiation occurs at a wall surface of the tube behind a reflected shock wave after the main detonation wave has been extinguished. Positions and conditions of the re-initiation are discussed. The complete extinction is defined as disappearance of detonation cells behind the step within a certain length of the tube. Cases exist where an ignition occurs after several reflections off the bottom and top surface of the tube.
    SPRINGER-VERLAG, English
    DOI:https://doi.org/10.1007/s00193-002-0156-z
    DOI ID:10.1007/s00193-002-0156-z, ISSN:0938-1287, Web of Science ID:WOS:000179514200006
  • Study on performance of detonation-driven shock tube               
    A Yamanaka; Y Ariga; T Obara; P Cai; S Ohyagi
    JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING, Volume:45, Number:2, First page:425, Last page:431, May 2002
    A detonation-driven shock tube firstly designed by H.R. Yu is considered to be a useful apparatus for producing high-enthalpy flow. In this apparatus, a strong shock wave is generated by detonating an oxygen-hydrogen mixture (oxy-hydrogen) and the driver gas temperature and pressure are extremely high compared with those of a conventional shock tube. However, the structure of the detonation wave is not uniform, e.g., the detonation wave has three-dimensional cellular structures and multiple transverse waves. Furthermore, the detonation wave is followed by a Taylor expansion fan and the performance of detonation-driven shock tube is not well understood. In this preliminary study, a detonation-driven shock tube is constructed and its performance is experimentally investigated by measuring pressure histories and the profile of the ionization current behind the detonation wave. As a result, (i) the pressure history of the detonation wave is clarified and shows reasonable agreement with the result obtained by the KASIMIR shock tube simulation code. (ii) The propagation velocity of the detonation wave coincides well with the theoretical prediction assuming a Chapman-Jouguet detonation wave. (iii) The equivalence ratio of the oxy-hydrogen mixture to produce the highest Mach number of the shock wave is evaluated to be phisimilar or equal to1.7.
    JAPAN SOC MECHANICAL ENGINEERS, English
    DOI:https://doi.org/10.1299/jsmeb.45.425
    DOI ID:10.1299/jsmeb.45.425, ISSN:1340-8054, Web of Science ID:WOS:000176689400025
  • Propagation of pressure waves initiated by flame and detonation in a tube               
    S Ohyagi; E Nohira; T Obara; P Cai; T Yoshihashi
    JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING, Volume:45, Number:1, First page:192, Last page:200, Feb. 2002
    Pressure waves produced by explosions of combustible mixtures formed by the accidental spillage of fuel gases have attracted considerable attention from the safety point of view. In order to assess damage caused by such explosion hazards, real-scale experiments are necessary. However, it is often difficult to perform such experiments because of space limitations and experimental safety. Small-scale experiments are preferred if an appropriate scaling law can be verified. The objectives of this study are to elucidate the decay processes of planar blast waves initiated by deflagration and detonation waves in a tube and to assess the applicability of the energy-based scaling law to these phenomena.
    JAPAN SOC MECHANICAL ENGINEERS, English
    DOI:https://doi.org/10.1299/jsmeb.45.192
    DOI ID:10.1299/jsmeb.45.192, ISSN:1340-8054, CiNii Articles ID:110003479029, Web of Science ID:WOS:000174734800031
  • 開放端から放出された衝撃波に関する実験と数値シミュレーション(流体工学,流体機械)               
    小原哲郎; 大八木重治; 加藤肇; 有賀洋介
    Volume:68, Number:668, First page:1036, Last page:1043, 2002
    DOI:https://doi.org/10.1299/kikaib.68.1036
    DOI ID:10.1299/kikaib.68.1036, ISSN:0387-5016, CiNii Articles ID:110002387082
  • 開放端から放出された衝撃波に関する実験と数値シミュレーション(流体工学,流体機械)               
    小原哲郎; 大八木重治; 加藤肇; 有賀洋介
    日本機械学會論文集. B編, Volume:68, Number:668, First page:1036, Last page:1043, 2002
    DOI:https://doi.org/10.1299/kikaib.68.1036
    DOI ID:10.1299/kikaib.68.1036, ISSN:0387-5016, CiNii Articles ID:110002387082
  • 回折する衝撃波の挙動に関する研究 : 第2報、溝付き開放端による衝撃波の減衰過程 : 流体工学,流体機械               
    小原哲郎; 大八木重治; 高藤亮一; 蔡品
    Volume:67, Number:659, First page:1680, Last page:1686, 2001
    DOI:https://doi.org/10.1299/kikaib.67.1680
    DOI ID:10.1299/kikaib.67.1680, ISSN:0387-5016, CiNii Articles ID:110002397664
  • 回折する衝撃波の挙動に関する研究 : 第2報、溝付き開放端による衝撃波の減衰過程 : 流体工学,流体機械               
    小原哲郎; 大八木重治; 高藤亮一; 蔡品
    日本機械学會論文集. B編, Volume:67, Number:659, First page:1680, Last page:1686, 2001
    DOI:https://doi.org/10.1299/kikaib.67.1680
    DOI ID:10.1299/kikaib.67.1680, ISSN:0387-5016, CiNii Articles ID:110002397664
  • A numerical simulation of reflection processes of a detonation wave on a wedge               
    S Ohyagi; T Obara; F Nakata; S Hoshi
    SHOCK WAVES, Volume:10, Number:3, First page:185, Last page:190, Jul. 2000
    A two dimensional numerical simulation has been performed to study reflection processes of detonation waves on a wedge. The numerical scheme adopted is the Aux corrected transport scheme and a two-step chemical reaction is assumed for a stoichiometric oxyhydrogen mixture diluted with argon. Transverse wave structures of the detonation are produced by artificial disturbances situated in front of a one-dimensional Chapman-Jouguet detonation wave. Numerical grids are generated by solving a Laplace equation. Results show that in the case where Mach reflection occurs, the cells in the Mach stem are smaller than those in the incident wave and are distorted in shape. There is also an initiating stage during which the cells in the Mach stem are created. The critical angle beyond which Mach reflection cannot occur is discussed.
    SPRINGER-VERLAG, English
    ISSN:0938-1287, Web of Science ID:WOS:000088471900005
  • デトネーション駆動形衝撃波管の作動特性               
    山中昭央; 有賀洋介; 小原哲郎; 蔡品; 大八木重治
    Volume:66, Number:651, First page:2992, Last page:2998, 2000
    DOI:https://doi.org/10.1299/kikaib.66.651_2992
    DOI ID:10.1299/kikaib.66.651_2992, ISSN:0387-5016, CiNii Articles ID:110002392687
  • 気体デトネーションの構造とその反射・回折現象               
    大八木 重治; 星 真太郎; 小原 哲郎
    Volume:7, Number:4, First page:249, Last page:263, 2000
    Japanese
    ISSN:0918-5712, CiNii Articles ID:40004994521, CiNii Books ID:AN10436291
  • デトネーション駆動形衝撃波管の作動特性               
    山中昭央; 有賀洋介; 小原哲郎; 蔡品; 大八木重治
    日本機械学會論文集. B編, Volume:66, Number:651, First page:2992, Last page:2998, 2000
    DOI:https://doi.org/10.1299/kikaib.66.651_2992
    DOI ID:10.1299/kikaib.66.651_2992, ISSN:0387-5016, CiNii Articles ID:110002392687
  • 気体デトネーションの構造とその反射・回折現象               
    大八木 重治; 星 真太郎; 小原 哲郎
    燃焼の科学と技術, Volume:7, Number:4, First page:249, Last page:263, 2000
    Japanese
    ISSN:0918-5712, CiNii Articles ID:40004994521, CiNii Books ID:AN10436291
  • 回折する衝撃波の挙動に関する研究 : 第1報, 衝撃波の回折と反射過程               
    高藤亮一; 山中昭央; 小原哲郎; 蔡品; 大八木重治
    Volume:65, Number:639, First page:3602, Last page:3607, 1999
    DOI:https://doi.org/10.1299/kikaib.65.3602
    DOI ID:10.1299/kikaib.65.3602, ISSN:0387-5016, CiNii Articles ID:110002395677
  • Numerical Study on a Planar Diffusion Flame Stabilized behind a Backward-facing Step               
    ROHMAT Tri agung; WANG Xiao; OBARA Tetsuro; OHYAGI Shigeharu
    Transactions of the Japan Society of Mechanical Engineers. Series B., Volume:65, Number:632, First page:1446, Last page:1451, 1999
    A numerical study on a planar diffusion flame stabilized behind a backward-facing step is performed. Computational model is set to simulate our experimental study where a fuel gas is supplied from a porous plate behind the backward-facing step. A flame sheet model is used because the simulation is focused on the stabilized flame. The computational scheme is the SIMPLE with the QUICK for convection terms. Although the model is restricted to two-dimensional, the results show that the flame deforms due to the Kelvin-Helmholtz instability arising from the density change due to combustion. Comparison with the experiment is succesfully performed by the schlieren photography and the temperature variation.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.65.1446, ISSN:0387-5016, CiNii Articles ID:110002395377, CiNii Books ID:AN00187441
  • 回折する衝撃波の挙動に関する研究 : 第1報, 衝撃波の回折と反射過程               
    高藤亮一; 山中昭央; 小原哲郎; 蔡品; 大八木重治
    日本機械学會論文集. B編, Volume:65, Number:639, First page:3602, Last page:3607, 1999
    DOI:https://doi.org/10.1299/kikaib.65.3602
    DOI ID:10.1299/kikaib.65.3602, ISSN:0387-5016, CiNii Articles ID:110002395677
  • 後向きステップ後方に安定化される平面的拡散火炎に関する数値解析               
    Tri Agung ROHMAT; Xiao WANG; Tetsuro OBARA; Shigeharu OHYAGI
    日本機械学會論文集. B編, Volume:65, Number:632, First page:1446, Last page:1451, 1999
    A numerical study on a planar diffusion flame stabilized behind a backward-facing step is performed. Computational model is set to simulate our experimental study where a fuel gas is supplied from a porous plate behind the backward-facing step. A flame sheet model is used because the simulation is focused on the stabilized flame. The computational scheme is the SIMPLE with the QUICK for convection terms. Although the model is restricted to two-dimensional, the results show that the flame deforms due to the Kelvin-Helmholtz instability arising from the density change due to combustion. Comparison with the experiment is succesfully performed by the schlieren photography and the temperature variation.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.65.1446, ISSN:0387-5016, CiNii Articles ID:110002395377, CiNii Books ID:AN00187441
  • Diffusion flame stabilized on a porous plate in a parallel airstream               
    TA Rohmat; H Katoh; T Obara; T Yoshihashi; S Ohyagi
    AIAA JOURNAL, Volume:36, Number:11, First page:1945, Last page:1952, Nov. 1998
    Effects of an obstacle on the structure and stability of a laminar diffusion flame established on a porous plate in a parallel airstream have been investigated experimentally. The obstacle, a backward-facing step or a rectangular cylinder, is located upstream of the porous plate through which gaseous methane is injected uniformly. Structures of the flame are elucidated by the direct and schlieren photography. Flame shapes are described and stability diagrams are plotted for the freestream velocity and the fuel injection velocity, which are discussed with flow structures.
    AMER INST AERONAUT ASTRONAUT, English
    DOI:https://doi.org/10.2514/2.300
    DOI ID:10.2514/2.300, ISSN:0001-1452, Web of Science ID:WOS:000077014000001
  • Visualization of Initiation Processes of Film Detonation               
    WATANABE Shinji; OBARA Tetsuro; YOSHIHASHI Teruo; OHYAGI Shigeharu
    Transactions of the Japan Society of Mechanical Engineers. Series B., Volume:63, Number:612, First page:2700, Last page:2706, 1997
    The detonation wave caused by the combustion of a liquid fuel film coated on an inner tube wall has recently attracted considerable attention because of its possible role in explosion hazards in compressed oxygen pipelines. This type of detonation is known as "film detonation" and is classified as a heterogeneous detonation. The structure of a heterogeneous detonation wave is very complex because physical processes such as momentum, heat and mass exchanges between liquid film and the gas phase are coupled with a chemical reaction. Experiments are conducted to investigate the initiation process of film detonation using high-speed schlieren photography and direct photography. It is clearly observed that a secondary shock wave caused by the combustion of liquid fuel film plays a significant role in the transition of film detonation wave.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.63.2700, ISSN:0387-5016, CiNii Articles ID:110002396555, CiNii Books ID:AN00187441
  • High-speed Photography and Stress Gauge Studies of Jet Impact upon Surfaces               
    BOURNE N K; OBARA T; FIELD J E
    Volume:355, Number:1724, First page:607, Last page:623, 1997
    DOI:https://doi.org/10.1098/rsta.1997.0028
    DOI ID:10.1098/rsta.1997.0028, ISSN:1364-503X, CiNii Articles ID:80009525259
  • フィルムデトネーション波開始過程の可視化(流体工学, 流体機械)               
    渡辺真次; 小原哲郎; 吉橋照夫; 大八木重治
    日本機械学會論文集. B編, Volume:63, Number:612, First page:2700, Last page:2706, 1997
    The detonation wave caused by the combustion of a liquid fuel film coated on an inner tube wall has recently attracted considerable attention because of its possible role in explosion hazards in compressed oxygen pipelines. This type of detonation is known as "film detonation" and is classified as a heterogeneous detonation. The structure of a heterogeneous detonation wave is very complex because physical processes such as momentum, heat and mass exchanges between liquid film and the gas phase are coupled with a chemical reaction. Experiments are conducted to investigate the initiation process of film detonation using high-speed schlieren photography and direct photography. It is clearly observed that a secondary shock wave caused by the combustion of liquid fuel film plays a significant role in the transition of film detonation wave.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.63.2700, ISSN:0387-5016, CiNii Articles ID:110002396555, CiNii Books ID:AN00187441
  • High-speed Photography and Stress Gauge Studies of Jet Impact upon Surfaces               
    Philosophical Transaction Royal Society of London, Volume:355, Number:1724, First page:607, Last page:623, 1997
    DOI:https://doi.org/10.1098/rsta.1997.0028
    DOI ID:10.1098/rsta.1997.0028, ISSN:1364-503X, CiNii Articles ID:80009525259
  • A high-speed photographic study of the transition from deflagration to detonation wave               
    T Obara; S Yajima; T Yoshihashi; S Ohyagi
    SHOCK WAVES, Volume:6, Number:4, First page:205, Last page:210, Oct. 1996
    Experiments were conducted to investigate the DDT process of the oxyhydrogen gas in the rectangular detonation tube of 3 m long. The repeated obstacle was installed near the ignition plug and the effects of the obstacle on the DDT process were investigated. The behaviour of the combustion and detonation wave were visualized utilizing Imacon high-speed camera with the aid of Schlieren optics.
    As a result, DDT process was visualized, i.e. (i) multiple shock waves were induced by the expanding combustion wave, because the combustion flame played a role as a piston and compressed the unburned gases. (ii) The acceleration of the combustion wave was occurred and the distance between the shock wave and the combustion flame became shorter. (iii) Eventually, the local explosion was occurred and cause overdriven detonation wave to propagate at the velocity of about 3 kms(-1).
    SPRINGER, English
    DOI:https://doi.org/10.1007/s001930050038
    DOI ID:10.1007/s001930050038, ISSN:0938-1287, eISSN:1432-2153, CiNii Articles ID:10012694180, Web of Science ID:WOS:A1996VN82400003
  • The Impact and Penetration of a Water Surface by a Liquid Jet               
    BOURNE N K; OBARA T; FIELD J E
    Volume:452, Number:1949, First page:1497, Last page:1502, 1996
    DOI:https://doi.org/10.1098/rspa.1996.0077
    DOI ID:10.1098/rspa.1996.0077, ISSN:1364-5021, CiNii Articles ID:80009046297
  • The Impact and Penetration of a Water Surface by a Liquid Jet               
    Proc. Royal Society of London, Volume:452, Number:1949, First page:1497, Last page:1502, 1996
    DOI:https://doi.org/10.1098/rspa.1996.0077
    DOI ID:10.1098/rspa.1996.0077, ISSN:1364-5021, CiNii Articles ID:80009046297
  • LIQUID-JET IMPACT ON LIQUID AND SOLID-SURFACES               
    T OBARA; NK BOURNE; JE FIELD
    WEAR, Volume:186, Number:2, First page:388, Last page:394, Aug. 1995
    Experiments were conducted to investigate the mechanisms of the liquid-jet impact on liquid and solid surfaces associated with cavitation damage and rain erosion. In this work, a liquid jet of 3 mm diameter, generated using a single impact jet apparatus, was impacted at ca. 600 m s(-1) on the surface of water and polymethyl-methacrylate (PMMA) placed 15 mm below the nozzle exit. The various phenomena which occurred were photographed using an image-converter high-speed camera. These include (i) the shock wave generated at the moment of the liquid-jet impact on the surface, (ii) shock waves reflected at the liquid/air or solid/air interfaces, as release waves, (iii) the damage to the PMMA, (iv) the overlap of release waves on the central axis, causing central damage in PMMA and cavitation in liquids. The cavitation behaviour and the process of the damage is directly related to the behaviour of the compressive wave caused by the impact of the liquid jet.
    ELSEVIER SCIENCE SA LAUSANNE, English
    DOI:https://doi.org/10.1016/0043-1648(95)07187-3
    DOI ID:10.1016/0043-1648(95)07187-3, ISSN:0043-1648, Web of Science ID:WOS:A1995RW62000007
  • The Construction and Calibration of an Inexpensive PVDF Stress Gauge for Fast Pressure Measurements               
    OBARA T; BOURNE N K; MEBAR Y
    Volume:6, Number:4, First page:345, Last page:348, 1995
    DOI:https://doi.org/10.1088/0957-0233/6/4/001
    DOI ID:10.1088/0957-0233/6/4/001, ISSN:0957-0233, CiNii Articles ID:80008225034
  • A Stress Gauge for Use in Electrically Noisy Environments               
    BOURNE N K; MEBAR Y; OBARA T
    Volume:6, Number:12, First page:1659, Last page:1661, 1995
    DOI:https://doi.org/10.1088/0957-0233/6/12/002
    DOI ID:10.1088/0957-0233/6/12/002, ISSN:0957-0233, CiNii Articles ID:80008709769
  • The Construction and Calibration of an Inexpensive PVDF Stress Gauge for Fast Pressure Measurements               
    Meas. Sci. Technology, Volume:6, Number:4, First page:345, Last page:348, 1995
    DOI:https://doi.org/10.1088/0957-0233/6/4/001
    DOI ID:10.1088/0957-0233/6/4/001, ISSN:0957-0233, CiNii Articles ID:80008225034
  • A Stress Gauge for Use in Electrically Noisy Environments               
    Meas. Sci. Technology, Volume:6, Number:12, First page:1659, Last page:1661, 1995
    DOI:https://doi.org/10.1088/0957-0233/6/12/002
    DOI ID:10.1088/0957-0233/6/12/002, ISSN:0957-0233, CiNii Articles ID:80008709769
  • Cavitation phenomena in extracorporeal microexplosion lithotripsy               
    Y. Tomita; T. Obara; K. Takayama; M. Kuwahara
    Shock Waves, Volume:3, Number:3, First page:149, Last page:157, Sep. 1994
    An experimental investigation was made of cavitation phenomena induced by underwater shock wave focusing applied to the extracorporeal microexplosion lithotripsy (microexplosion ESWL). Firstly an underwater microexplosion generated by detonation of a 10 mg silver azide pellet was studied and secondly underwater shock focusing and its induced cavitation phenomena were investgated. Underwater shock wave was focused by using a semi-ellipsoidal reflector in which a shock wave generated at the first focal point of the reflector was reflected and focused at the second focal point. It is found that an explosion product gas bubble did not produce any distinct rebound shocks. Meantime cavitation appeared after shock focusing at the second focal point where expansion waves originated at the exit of the reflector were simultaneously collected. A shock/bubble interaction is found to contribute not only to urinary tract stone disintegration but also tissue damage. The cavitation effect associated with the microexplosion ESWL was weaker in comparison with a spark discharge ESWL. The microexplosion ESWL is an effective method which can minimize the number of shock exposures hence decreasing tissue damage by conducting precise positioning of urinary tract stones. © 1994 Springer-Verlag.
    Springer-Verlag, English
    DOI:https://doi.org/10.1007/BF01414709
    DOI ID:10.1007/BF01414709, ISSN:0938-1287, SCOPUS ID:0000121423
  • Transition Processes from Deflagration to Detonation Waves : Effects of Obstacles               
    OHYAGI S.; Yajima Satoshi; Obara Tetsuro; Yoshihashi Teruo
    Transactions of the Japan Society of Mechanical Engineers. Series B., Volume:59, Number:567, First page:3552, Last page:3556, 1993
    Transition processes from deflagration to detonation waves in stoichiometric oxyhydrogen mixtures diluted with nitrogen were observed using high-speed Schlieren photography as well as pressure and ionization current measurements. In this study, effects of obstacles on the transition processes were investigated. The obstacles were multigutter shaped and were installed near an ignition plug on an inner wall of a rectangular tube. Width and depth of the gutter were selected as parameters while composition of the mixture was fixed. It was revealed that there exist optimum values of these parameters for enhancing the transition to detonation.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.59.3552, ISSN:0387-5016, CiNii Articles ID:110002392297, CiNii Books ID:AN00187441
  • デフラグレーション波からデトネーション波への遷移過程 : 障害物の影響               
    大八木重治; 小原哲郎; 吉橋照夫; 矢島智
    日本機械学會論文集. B編, Volume:59, Number:567, First page:3552, Last page:3556, 1993
    Transition processes from deflagration to detonation waves in stoichiometric oxyhydrogen mixtures diluted with nitrogen were observed using high-speed Schlieren photography as well as pressure and ionization current measurements. In this study, effects of obstacles on the transition processes were investigated. The obstacles were multigutter shaped and were installed near an ignition plug on an inner wall of a rectangular tube. Width and depth of the gutter were selected as parameters while composition of the mixture was fixed. It was revealed that there exist optimum values of these parameters for enhancing the transition to detonation.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.59.3552, ISSN:0387-5016, CiNii Articles ID:110002392297, CiNii Books ID:AN00187441
  • 衝撃波フォーカシングと肝損傷-その病態と機序の検討-               
    Volume:5, Number:1, First page:11, Last page:20, 1991
    DOI:https://doi.org/10.11210/tando1987.5.1_11
    DOI ID:10.11210/tando1987.5.1_11
  • 閉じた回転楕円体容器内での水中衝撃波フォーカッシングによる超高圧生成についての研究               
    Volume:52, Number:4, First page:301, Last page:306, 1991
  • Underwater Shock Wave Focusing by Microexplosions, a Medical Application               
    TAKAYAMA Kazuyoshi; ONODERA Osamu; OBARA Tetsuro; KUWAHARA Masaaki; KITAYAMA Osamu
    Transactions of the Japan Society of Mechanical Engineers. Series B., Volume:57, Number:539, First page:2285, Last page:2292, 1991
    This is a preliminary report of an application of underwater shock wave focusing to the so-called extracorporeal shock wave lithotripsy, ESWL. Underwater spherical shock waves were initiated by microexplosions at one of two focus points of an ellipsoidal cavity. Consequently, the reflected shock waves were focused at the second focus point outside the ellipsoidal reflector, and high pressure was generated for a few microseconds. To the shock wave propagation, human tissue has a character very similar to that of water, and we can generate high pressure inside the human body by shock wave focusing sufficient to disintegrate human calculi. This paper reports an experimental and numerical approach of determining the most effective shape of ellipsoidal reflector for the lithotriptor and clarifying the mechanism of focused high-pressure generation by microexplosions. It was found that a half-ellipsoidal shape having a major and minor axis ratio of about 1.4〜1.5 was very suitable for the lithotriptor.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.57.2285, ISSN:0387-5016, CiNii Articles ID:110002389908, CiNii Books ID:AN00187441
  • 衝撃波フォーカシングと肝損傷-その病態と機序の検討-               
    胆道, Volume:5, Number:1, First page:11, Last page:20, 1991
    DOI:https://doi.org/10.11210/tando1987.5.1_11
    DOI ID:10.11210/tando1987.5.1_11
  • 閉じた回転楕円体容器内での水中衝撃波フォーカッシングによる超高圧生成についての研究               
    亀島 望
    工業火薬, Volume:52, Number:4, First page:301, Last page:306, 1991
    Japanese
    ISSN:0368-6450, CiNii Articles ID:40004627429, CiNii Books ID:AN1016662X
  • 水中微小爆発による衝撃波フォーカッシング医療応用への基礎研究               
    Kazuyoshi TAKAYAMA; Osamu ONODERA; Tetsuro OBARA; Masaaki KUWAHARA; Osamu KITAYAMA
    日本機械学會論文集. B編, Volume:57, Number:539, First page:2285, Last page:2292, 1991
    This is a preliminary report of an application of underwater shock wave focusing to the so-called extracorporeal shock wave lithotripsy, ESWL. Underwater spherical shock waves were initiated by microexplosions at one of two focus points of an ellipsoidal cavity. Consequently, the reflected shock waves were focused at the second focus point outside the ellipsoidal reflector, and high pressure was generated for a few microseconds. To the shock wave propagation, human tissue has a character very similar to that of water, and we can generate high pressure inside the human body by shock wave focusing sufficient to disintegrate human calculi. This paper reports an experimental and numerical approach of determining the most effective shape of ellipsoidal reflector for the lithotriptor and clarifying the mechanism of focused high-pressure generation by microexplosions. It was found that a half-ellipsoidal shape having a major and minor axis ratio of about 1.4〜1.5 was very suitable for the lithotriptor.
    The Japan Society of Mechanical Engineers, Japanese
    DOI ID:10.1299/kikaib.57.2285, ISSN:0387-5016, CiNii Articles ID:110002389908, CiNii Books ID:AN00187441
  • 体外衝撃波による胆石の被破砕性の検討               
    Volume:4, Number:4, First page:451, Last page:459, 1990
    DOI:https://doi.org/10.11210/tando1987.4.4_451
    DOI ID:10.11210/tando1987.4.4_451
  • Focusing of underwater shock waves and the mechanism of high pressure generation.               
    TAKAYAMA Kazuyoshi; OBARA Tetsuro; SAITO Kazuo; KAMESHIMA Nozomu
    Transactions of the Japan Society of Mechanical Engineers Series C, Volume:56, Number:526, First page:1579, Last page:1582, 1990
    Underwater spherical shock focusing can be obtained in a closed ellipsoidal-shaped cavity by the explosion of a small silver azide pellet. The present paper reports on an experimental and numerical study of the generation of high pressure and its mechanism. The shock focusing pressure was measured in a 500mmx700mm ellipsoidal cavity with a PVDF pressure transducer which has a wide frequency response. A high pressure of 3000bar was obtained for a 100mg silver azide pellet. The process of shock focusing was also studied numerically by the TVD finite difference scheme. A quantitative agreement was obtained between the experiment and the simulation. It was demonstrated that the underwater shock focusing is one of the most efficient methods to obtain a controlled high pressure in a small region.
    The Japan Society of Mechanical Engineers, Japanese
    DOI:https://doi.org/10.1299/kikaib.56.1579
    DOI ID:10.1299/kikaib.56.1579, ISSN:0387-5016, CiNii Articles ID:110002388991
  • An experiment on the interaction between a weak plane shock wave and bubbles. Behavior of liquid microjet produced by collapse of single and double bubbles.               
    OBARA Tetsuro; SUGIYAMA Hiromu; ARAI Takakage; HIRAIWA Koji
    Transactions of the Japan Society of Mechanical Engineers Series C, Volume:56, Number:526, First page:1583, Last page:1587, 1990
    This paper is concerned with the interaction between a weak-plane shock wave and bubbles. The behavior of a liquid microjet produced by the collapse of single and double bubbles was observed using a water shock tube, Ima-Con high speed camera and a PVDF pressure sensor with a high frequency response. The behavior of single collapsing bubble agrees qualitatively with previous experimental results, and it is shown that the present experimental method is effective in investigating the bubble collapse and generation of impulsive pressure. The speed of a microjet within the bubble is estimated to be about 100 m/s, or about ten times as much as that of a microjet penetrating the other side of the bubble surface. In the case of double collapsing bubbles the direction of microjet formation is different from the case of single bubble collapse.
    The Japan Society of Mechanical Engineers, Japanese
    DOI:https://doi.org/10.1299/kikaib.56.1583
    DOI ID:10.1299/kikaib.56.1583, ISSN:0387-5016, CiNii Articles ID:110002388993
  • 体外衝撃波による胆石の被破砕性の検討               
    阿部裕
    胆道, Volume:4, Number:4, First page:451, Last page:459, 1990
    DOI:https://doi.org/10.11210/tando1987.4.4_451
    DOI ID:10.11210/tando1987.4.4_451, CiNii Articles ID:10007047324
  • 水中衝撃波のフォーカッシンング現象と高圧発生のメカニズム               
    Kazuyoshi TAKAYAMA; Tetsuro OBARA; Kazuo SAITO; Nozomu KAMESHIMA
    日本機械学會論文集. B編, Volume:56, Number:526, First page:1579, Last page:1582, 1990
    Underwater spherical shock focusing can be obtained in a closed ellipsoidal-shaped cavity by the explosion of a small silver azide pellet. The present paper reports on an experimental and numerical study of the generation of high pressure and its mechanism. The shock focusing pressure was measured in a 500mmx700mm ellipsoidal cavity with a PVDF pressure transducer which has a wide frequency response. A high pressure of 3000bar was obtained for a 100mg silver azide pellet. The process of shock focusing was also studied numerically by the TVD finite difference scheme. A quantitative agreement was obtained between the experiment and the simulation. It was demonstrated that the underwater shock focusing is one of the most efficient methods to obtain a controlled high pressure in a small region.
    The Japan Society of Mechanical Engineers, Japanese
    DOI:https://doi.org/10.1299/kikaib.56.1579
    DOI ID:10.1299/kikaib.56.1579, ISSN:0387-5016, CiNii Articles ID:110002388991
  • 弱い衝撃波と気泡の干渉に関する一実験 (単一および2個の気泡の崩壊時に発生する液体マイクロジェットの挙動)               
    Tetsuro OBARA; Hiromu SUGIYAMA; Takakage ARAI; Koji HIRAIWA
    日本機械学會論文集. B編, Volume:56, Number:526, First page:1583, Last page:1587, 1990
    This paper is concerned with the interaction between a weak-plane shock wave and bubbles. The behavior of a liquid microjet produced by the collapse of single and double bubbles was observed using a water shock tube, Ima-Con high speed camera and a PVDF pressure sensor with a high frequency response. The behavior of single collapsing bubble agrees qualitatively with previous experimental results, and it is shown that the present experimental method is effective in investigating the bubble collapse and generation of impulsive pressure. The speed of a microjet within the bubble is estimated to be about 100 m/s, or about ten times as much as that of a microjet penetrating the other side of the bubble surface. In the case of double collapsing bubbles the direction of microjet formation is different from the case of single bubble collapse.
    The Japan Society of Mechanical Engineers, Japanese
    DOI:https://doi.org/10.1299/kikaib.56.1583
    DOI ID:10.1299/kikaib.56.1583, ISSN:0387-5016, CiNii Articles ID:110002388993
  • An experimental study on the collapse of multiple air bubbles by a shock wave.               
    SUGIYAMA Hiromu; TANAKA Tetsuo; OBARA Tetsuro; HOSHIBA Noriki; OKUDA Kyokai
    Transactions of the Japan Society of Mechanical Engineers Series C, Volume:53, Number:495, First page:3141, Last page:3145, 1987
    An experimental study was made on the collapse of multiple air bubbles by a shock wave using a water shock tube and a high speed camera. High speed schlieren photographs show the processes of a high pressure region formation or of shock wave formation near multiple air bubbles when they rebound. Two impulsive pressures, 0.72 and 1.75 MPa, were applied to multiple air bubbles with an initial radius of about 1.2 mm. It is shown that in the case of impulsive pressure 1.75 MPa, the multiple air bubbles produce weak shock waves around themselves when they rebound.
    The Japan Society of Mechanical Engineers, Japanese
    DOI:https://doi.org/10.1299/kikaib.53.3141
    DOI ID:10.1299/kikaib.53.3141, ISSN:0387-5016, CiNii Articles ID:110002401041
  • 衝撃波による複数空気泡の崩壊に関する一実験               
    Hiromu SUGIYAMA; Tetsuo TANAKA; Tetsuro OBARA; Noriki HOSHIBA; Kyokai OKUDA
    日本機械学會論文集. B編, Volume:53, Number:495, First page:3141, Last page:3145, 1987
    An experimental study was made on the collapse of multiple air bubbles by a shock wave using a water shock tube and a high speed camera. High speed schlieren photographs show the processes of a high pressure region formation or of shock wave formation near multiple air bubbles when they rebound. Two impulsive pressures, 0.72 and 1.75 MPa, were applied to multiple air bubbles with an initial radius of about 1.2 mm. It is shown that in the case of impulsive pressure 1.75 MPa, the multiple air bubbles produce weak shock waves around themselves when they rebound.
    The Japan Society of Mechanical Engineers, Japanese
    DOI:https://doi.org/10.1299/kikaib.53.3141
    DOI ID:10.1299/kikaib.53.3141, ISSN:0387-5016, CiNii Articles ID:110002401041
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