研究者詳細 - 平木　講儒

論文 - 平木　講儒

分割表示78 件中 21 - 40 件目／全件表示 >>

Flow visualization around a rotating body in a wind tunnel 査読有り

Hiraki K., Zaitsu D., Yanaga Y., Kleine H.

Proceedings of SPIE - The International Society for Optical Engineering 10328 2017年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2017 SPIE. The rotational behavior of capsule-shaped models is investigated in the transonic wind tunnel of JAXA. A special support is developed to allow the model to rotate around the pitch, yaw and roll axes. This 3-DOF free rotational mounting apparatus achieves the least frictional torque from the support and the instruments. Two types of capsule models are prepared, one is drag type (SPH model) and the other is lift type (HTV-R model). The developed mounting apparatus is used in the wind tunnel tests with these capsule models. In a flow of Mach 0.9, the SPH model exhibits oscillations in pitch and yaw, and it rolls half a turn during the test. Similarly, the HTV-R model exhibits pitch and yaw oscillations in a flow of Mach 0.5. Moreover, it rolls multiple times during the test. In order to investigate the flow field around the capsule, the combined technique of color schlieren and surface tufts is applied. This visualization clearly shows the flow reattachment on the back surface of a capsule, which is suspected to induce the rapid rolling motion.

DOI： 10.1117/12.2271143

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Relative dynamics and motion control of nanosatellite formation flying 査読有り

Pimnoo A., Hiraki K.

Advances in Space Research 57 ( 7 ) 1476 - 1493 2016年04月

記述言語：英語掲載種別：研究論文（学術雑誌）

Orbit selection is a necessary factor in nanosatellite formation mission design/meanwhile, to keep the formation, it is necessary to consume fuel. Therefore, the best orbit design for nanosatellite formation flying should be one that requires the minimum fuel consumption. The purpose of this paper is to analyse orbit selection with respect to the minimum fuel consumption, to provide a convenient way to estimate the fuel consumption for keeping nanosatellite formation flying and to present a simplified method of formation control. The formation structure is disturbed by J2 gravitational perturbation and other perturbing accelerations such as atmospheric drag. First, Gauss' Variation Equations (GVE) are used to estimate the essential ΔV due to the J2 perturbation and atmospheric drag. The essential ΔV presents information on which orbit is good with respect to the minimum fuel consumption. Then, the linear equations which account for J2 gravitational perturbation of Schweighart-Sedwick are presented and used to estimate the fuel consumption to maintain the formation structure. Finally, the relative dynamics motion is presented as well as a simplified motion control of formation structure by using GVE.

DOI： 10.1016/j.asr.2016.01.004

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Relative dynamics and motion control of nanosatellite formation flying 査読有り

Ammarin Pimnoo, Koju Hiraki

Advances In Space Research 57 1476 - 1493 2016年01月

Hovering test of flapping robot using circular flight device 査読有り

Hiraki K., Mie N., Yoshino K., Inoue M.

MOVIC 2014 - 12th International Conference on Motion and Vibration Control 2014年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2014 The Japan Society of Mechanical Engineers. For the purpose of simulating a flight of a flapping vehicle a test device with a circular flight has been developed. The device provides us a flight speed, the trimmed pitch angle and the generated lift force which can be derived from the angle of a vertical arm. Thanks to this device, the appropriate parameters to achieve a stable flight can be set in advance without damaging a vehicle, such as the flapping frequency, the feathering angle and the elevator angle. In the present paper the deriviation of the lift and pitching moment generated by a flapping motion is described.

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Multi degree-of-freedom technique for dynamic characteristics of atmospheric entry capsule 査読有り

Hiraki K., Yasuoka K., Kleine H.

31st AIAA Applied Aerodynamics Conference 2013年09月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The dynamic characteristics of a model of an atmospheric entry vehicle were investigated in a transonic wind tunnel. The models were allowed to rotate freely in the tunnel and two kinds of the test devices were prepared with different degrees of freedom. The 1-DOF device allowed the model to rotate only around the pitch axis, and the 3-DOF device allowed the model to rotate around the pitch, yaw and roll axes. The dynamic tests were carried out in flows of Mach 0.5 and 0.9. Both the 1-DOF and 3-DOF tests gave the similar results on the damping properties in pitch and yaw axes. The rapid rolling behavior was also recognized in the 3-DOF test which was seemingly related to the energy conversion from the pitch to yaw axis.

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Post-flight analysis of Hayabusa; asteroid sample return capsule 査読有り

Inatani Y., Ishii N., Yamada T., Hiraki K., Yamada K., Suzuki T., Fujita K.

Advances in the Astronautical Sciences 146 685 - 696 2013年04月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

HAYABUSA(MUSES-C); an asteroid explorer returned to the earth after the 7 years of lengthy and troubled voyage, and its capsule reenters into the Earth's atmosphere. It performed a safe reentry flight and recovery. For the design of the capsule, many considerations were made due to its higher entry velocity and higher aerodynamic heating than those of normal reentry from earth orbit. Taking into account the required functions throughout the orbital flight, reentry flight, and descent/recovery phase, the capsule was deigned, tested, manufactured and flight demonstrated finally. The paper presents the concept of the design and qualification approach of the small space capsule of the asteroid sample and return mission. And presented are how the reentry flight was performed and a brief overview of the post flight analysis primarily for these design validation purposes and for the better understanding of the flight results.

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Counter-rotating type tidal-stream power unit playing favorable features in various ocean circumstances 査読有り

Usui Y., Takaki K., Kanemoto T., Hiraki K.

ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) 6 B 2013年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The authors have invented the unique counter-rotating type tidal-stream power unit, which is composed of the tandem propellers and the double rotational armature type peculiar generator without the traditional stator. In the unit of the downstream type, the front and the rear propellers counter-drive the outer and the inner armatures of the peculiar generator respectively, in keeping the rotational torque counter-balanced between both propellers/armatures. This paper discusses and verifies experimentally the almighty features of the power unit. The axial force acting on the pillar increases naturally with the increase of not only the stream velocity but also the drag of the tandem propellers. Besides, the tandem propellers bring the symmetrical vertical force from side to side though the single propeller brings the force in one direction. The counter-balanced torque makes it possible to moor the power unit with only one cable/wire/rope, and the behavior of the submerged unit was confirmed experimentally. Copyright © 2013 by ASME.

DOI： 10.1115/IMECE2013-66001

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Demonstrative power generation by twin-runner darrieus turbine in Kanmon strait 査読有り

Hiraki K., Wakita R., Kanemeoto T., Yagami R., Takao M.

Proceedings of the International Offshore and Polar Engineering Conference 725 - 729 2012年09月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In order to make the electrical-power generation feasible under the lower tidal-current condition the twin-runner Darreus water-turbine was developed. The counter rotations of twin runners are expected to increase the power output. In the water-tunnel tests using a subscale model the revolution numbers were increased up to 120 percent of those at the single-runner configuration. The current-accelerating devices were also investigated. Based on the obtained results, the design of the experimental demonstrator was carried out, which can generate 1.4-kW of electric power. The power generation test is slated to start from March 2012 at Kanmon strait. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).

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Demonstrative Power Generation by Twin-Runner Darrieus Turbine in Kanmon Strait 査読有り

Koju Hiraki, Ryo Wakita, Toshiaki Kanemoto, Ryoich Yagami, Manabu Takao

Conference Proceedings: The Twenty-second (2012) International Offshore and Polar Engineering Conference 2012年06月

Thrust measurement of deployable propeller for powered paraglider in mars atmosphere 査読有り

Hiraki K., Tashima S., Namikawa M.

Proceedings of the 18th Australasian Fluid Mechanics Conference, AFMC 2012 2012年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

A preliminary design of a propeller of the powered paraglider for Mars exploration was conducted. The blade design was made with the computational method developed by Adkins and Liebeck. In order to obtain the necessary thrust of 7.88N, the propeller diameter was computed to 1.0m. Thus, the propeller should be retracted in an entry probe, and it should have self-deploying capability. A one-fourth scaled model of the propeller was fabricated to demonstrate its capability and thrust. The special thrust-measurement device was designed for a wind-tunnel test. Some disagreement was found in the comparison between the measured and predicted thrust. In order to clarify the reason of the discrepancy the aerodynamic data of the wing in low Reynolds number environment were obtained in the wind tunnel. Based on the data obtained the thrust prediction was redone. The agreement was improved and it validated the design process of the blade in this study.

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Reynolds-averaged navier-stokes computation of transonic projectiles in ground effect 査読有り

Carriage K., Young J., Kleine H., Hiraki K.

Proceedings of the 18th Australasian Fluid Mechanics Conference, AFMC 2012 2012年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

As a transonic projectile passes near a solid object, its surrounding flow field changes quite considerably: the bow shock naturally adopts a strong solution and pushes forward from its freeflight position, and the projectile's wake is pulled down towards the object. These phenomena were first captured separately by schlieren imaging techniques during live fire and wind tunnel testing. A subsequent computational study, performed in Fluent at a free stream pressure of 72 kPa and for a projectile Mach number of 1.1, demonstrated that the presence of the wall introduces aerodynamic forces whose magnitude and direction can become significant for the subsequent projectile trajectory. The lift force was found to be up to ten percent of the projectile's drag, and may be either positive or negative depending on the proximity to the ground. Similarly, the coefficient of moment may be either positive or negative with a neutral point that does not coincide with the point of zero lift. The results are pertinent to many fields including aircraft weapons release and low level operations, wing-in-ground effect vehicles, and vehicles designed to challenge the land speed record.

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Lift-force Measurement for Hovering Flight of Four-Winged Flapping Micro Aerial Vehicle 査読有り

Koju Hiraki, Kazuki Fujii

Proceedings of ASME-JSME-KSME Joint Fluids Engineering Conference 2011 2011年07月

Separated flow around a rotating gyroball 招待有り査読有り

Koju Hiraki, Kota Ishitsu, Keisuke Yamada

Journal of Visualization 14 201 - 211 2011年04月

Particle damping with granular materials for multi degree of freedom system 招待有り査読有り

Masanobu Inoue, Isao Yokomichi, Koju Hiraki

Shock and Vibration 18 ( 1-2 ) 245 - 256 2011年02月

Scientific Application and Design of Small Unmanned Aircraft Systems 査読有り

Andreas Scholtz,Thomas Krueger,Claus-Sebastian Wilkens,Koju Hiraki,Peter Voersmann

AIAC14 Fourteenth Australian International Aerospace Congress 2011年02月

Experimental study on dynamic instability of re-entry capsule-shaped body using pressure sensitive paint 査読有り

Sugimoto D., Nagai H., Asai K., Hiraki K.

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition 2010年12月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Re-entry capsule with flat body shapes tends to be dynamically unstable in the transonic speed range, and sometimes fall into self-exited pitching oscillation. In this study, the Phase Lock Method with a fast-responding Pressure-Sensitive Paint (PSP) has been employed to visualize unsteady pressure distribution on a capsule model undergoing the pitching motion. In addition, the pressure fluctuation was measured using time-series high-speed camera PSP images. Analysis of the PSP results together with pitch angle measurement has revealed that the phase delay of the base surface pressure acts as dynamically unstable moment in the low pitch angles. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

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Improvement of straight-bladed vertical-axis water turbine for tidal current power generation 査読有り

Hiraki K., Wakita R., Inoue M.

Proceedings of the 9th (2010) ISOPE Pacific/Asia Offshore Mechanics Symposium, PACOMS-2010 169 - 174 2010年12月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Considering the tidal-current power generation in a narrow strait, a water turbine of vertical axis is preferred, since the multiple-stage system is applicable in the depth direction. The straight bladed vertical axis water turbine (S-VAWT) is appropriate in such system because of its simplicity in manufacture. On purpose to improve the performance of the S-VAWT a Gurney flap was attached on the trailing edge of the rotor blades. The modified turbine was tested in both the wind and water tunnels. Consequently, the attachment of the Gurney flap on the lower surface is effective to enhance the dynamic characteristics of the S-VAWT. Copyright © 2010 by The International Society of Offshore and Polar Engineers.

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Improvement of Straight-bladed Vertical-axis Water Turbine for Tidal Current Power Generation 査読有り

Koju Hiraki,Ryo Wakita,Masanobu Inoue

The Ninth (2010) ISOPE Pacific/Asia Offshore Mechanics Symposium PACOMS-2010 2010年11月

トンボに着想を得た4枚翼型羽ばたき機の省エネルギ飛行について査読有り

平木講儒,藤井和希,緒方尚樹

可視化情報学会誌 30 ( 119 ) 16 - 21 2010年10月

Projectiles in Transonic Ground Effect 査読有り

Harald Kleine,Koju Hiraki,Benjamin Oakes,John Young,Hideaki Kusano,Yoshifumi Inatani

The 29th International Congress on High-Speed Imaging and Photonics 2010年09月

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