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RISS 인기검색어
- 검색키워드
- 저자 : Keisuke-ASAI (검색결과 3 건)
- 무료
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Seungwon Ha,Hiroki Nagai,Keisuke Asai,Kazuyuki Nakakita,Nobuyuki Tsuboi 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-
A blunt body in hypersonic flow is subjected to severe aerodynamic heating and drag. This is one of the most critical problems of designing the hypersonic vehicles such as Reusable Launch Vehicles (RLV). It is well known that spiked-nose (aerospike) concept is effective for aerodynamic drag reduction on asymmetric blunt bodies in hypersonic flow. In this study, we investigated the heat flux distribution on a blunt-nosed body with an aerospike in hypersonic flow. The spike length and the angle of attack were changed to verify the heat reduction effect. The experiment was conducted at Mach l0in the JAXA 0.44-m Hypersonic Wind Tunnel and the temperature of body was measured by using Temperature-Sensitive Paint (TSP), which is a global temperature measurement technique based on photochemical reaction. In addition, the heat flux distribution calculated increase rate or temperature. The flow field around a blunt-nosed body is visualized by schlieren images and compared with TSP images and CFD results to discuss the heat flux distribution. It was found from the result that the heat flux amount is decreased as the length of spike longer and the heat flux distribution is changed widely with the angle of attack. In this study, moreover, the heat-flux and the flow field relation ware clarified by shock/shock interaction analysis of the flow field for different angle-of-attack.
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Flow-induced Vibration of a High-speed Train Running in a Tunnel
Takeyuki KODERA,Hiroki NAGAI,Keisuke-ASAI,Osamu Terashima 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-
In recent years, flow-induced vibration on the tail car of a high-speed train cruising in a tunnel has become a critical aerodynamic problem because it makes a ride comfort of the train poor. To further increase the train speed, it is required to identify the cause of this phenomenon and take necessary countermeasures. The objective of the present study is to clarify the effects of the tunnel wall on vibrations of a high-speed train running inside a tunnel. We conducted wind tunnel tests of a simplified train model with a flat plate simulating the effect of tunnel wall. Pressure transducers were used to measure unsteady pressure fluctuations on the tunnel wall and Pressure Sensitive Paint (PSP) was applied to measure time-averaged surface pressure distribution on the train model. In addition, we conducted Large Eddy Simulation (LES) calculation for the same model and test condition. In the experiment, pressure fluctuations with the Strouhal number similar to the actual case were observed near the tail car locations. The results of LES calculation indicated that LES could reconstruct the spectrum of pressure fluctuation that observed in the experiment. It was suggested from these results that the vibrations on the tail car were caused by the interaction of the flow separated from the tunnel side of the tail car with the tunnel wall.
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Experimental study on three-dimensional shock interference flow of a supersonic Busemann biplane
Soshi Oyama,Hiroki Nagai,Keisuke Asai 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-
In supersonic flight, an airplane generates shock waves that cause large wave drag as well as strong sonic boom. A supersonic airplane based on Busemann biplane was proposed as an innovative solution to realize supersonic transport. Shock waves are generated at the leading edge of the Busemann biplane and are cancelled by expansion waves generated from the ridgeline or the wings so that shock waves are confined inside the biplane and the drag and the sonic boom are dramatically reduced. The objective of this study is to investigate the three-dimentional shock interactions of a Busemann biplane by experiment. A supersonic biplane model with the aspect ratio of 2.5 was tested in a blow-down supersonic wind tunnel at M∞ = 1.5 to 1.7. Interacting flow around the wings was visualized by schlieren method and the pressure distribution on an inner surface of the wing was measured using pressure-sensitive paint (PSP). CFD calculations were also made to compare with experimental results. On the basis of these experimental and computational studies, the complicated three-dimensional interference phenomenon between the two wings, including shock wave/boundary layer interactions were analyzed and the three-dimensional flow effects on the start/uri start characteristics of the Busemann biplane are discussed.
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