JAXA Repository / AIREX 未来へ続く、宙(そら)への英知
SA0200030.pdf6.34 MB
titleNumerical Analysis of Dynamic Instability at Transonic Speeds
Author(jpn)寺本, 進; 藤井, 孝藏; 平木, 講儒
Author(eng)Teramoto, Susumu; Fujii, Kozo; Hiraki, Kouju
Author Affiliation(jpn)東京大学 工学部 航空宇宙工学科; 宇宙科学研究所; 宇宙科学研究所
Author Affiliation(eng)University of Tokyo, Department of Aeronautics and Astronautics; Institute of Space and Astronautical Science (ISAS); Institute of Space and Astronautical Science (ISAS)
Issue Date2003-03
Institute of Space and Astronautical Science
Publication titleThe Institute of Space and Astronautical Science report. S.P.
Aerodynamics, Thermophysics, Thermal Protection, Flight System Analysis and Design of Asteroid Sample Return Capsule
Start page275
End page300
Publication date2003-03
AbstractA flat capsule with blunt nose like Muses-C reentry capsule tends to be dynamically unstable at transonic speeds. This instability phenomena has been studied experimentally since 1960's, but its mechanism is not well understood. The flowfield around the reentry capsule is numerically simulated and discussed to reveal the mechanism of the dynamic instability. A new post-processing technique that uses frequency filters, are applied to detect the flow structure out of complicated flowfield. The results showed that the base pressure of the capsule produces pitch-down moment for the positive pitch angle, and the oscillation of the base pressure is delayed from the pitch angle when the capsule oscillates in pitch. The delay causes the hysteresis in the aerodynamic pitching moment, and the hysteresis makes the capsule dynamically unstable. The base pressure and the wake at the neck point (the foot of the recompression shock wave) oscillate with the same delay time. When the neck point moves upward, the pressure at the upper part of the base becomes higher and the base pressure produces pitch-down moment. Two oscillations coincides each other, and therefore the base pressure is correlated to the flowfield near the neck point. There is strong reverse flow behind the capsule, and the impingement of the reverse flow against the base determines the base pressure distribution. The behavior of the reverse flow is governed by the vortex structure behind the capsule. The vortex is composed of the ring vortex and the pair of longitudinal vortices, and the interaction between the longitudinal vortices and the flowfield near the neck point defines the base pressure distribution. The base pressure does not change until the disturbance of the longitudinal vortices caused by the pitching motion of the capsule reaches the neck point, and the time lag is the cause of the phase delay of the base pressure. Both the base pressure distribution and the delay of the base pressure are governed by the pair of longitudinal vortices, and therefore the dynamic stability of the capsule is closely related to the formation of the pair of longitudinal vortices.
Document TypeDepartmental Bulletin Paper
JAXA Category宇宙科学研究所

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