Studies of AOTV's Gasdynamics

“AOTV”是指气动辅助轨道转移飞行器。当航天器从较高的轨道转移到较低的轨道时，它通过空气阻力来减速。这项研究是由20名调查人员进行的。AOTV包括以下问题：(1)激波层干扰，(2)真实气体效应，(3)稀薄气体效应和(4)热保护。本文的研究结果总结如下：(1)激波层干扰：用激光诱导流流动可视化技术观测了对向喷流与超音速自由流相互作用的流场。结果表明，当射流与自由流静压比较小时，自由流激波、接触面和马赫盘沿流动方向周期性运动。(2)真实气体效应：研究了马赫数大于20时的离解、电离和辐射效应。真实气体效应减小了钝体的激波距离，激波层内的温度分布也受到真实气体效应的显著影响。(3)稀薄气体效应：通过直接蒙特卡罗模拟和数值求解Boltzmann方程，对低密度钝体绕流进行了数值模拟。为了研究低密度大气环境下的飞行，进行了弹道靶场装置的性能试验。(4)热防护：通过实验和数值模拟研究了靶场表面的换热和壁面催化剂的作用。特别是，可以看到非催化壁面降低了表面换热。

"AOTV" means Aeroassisted Orbital Transfer Vehicle. A space vehicle decelerates by aerobraking when it transfers from a higher orbit to a lower orbit. This study was conducted by 20 investigators. The AOTV includes the following problems : (1) shock layer interaction, (2) real gas effect, (3) rarefied gas effect and (4) thermal protection.The results of this study are summarized as follows :(1) Shock layer interaction : Flow field of an interaction of an opposing jet and a supersonic free stream was observed by LIF flow visualization technique. It was observed that when the jet to free stream stagnation pressure ratio is small, a free stream shock, contact surface and Mach disk periodically moves in the flow direction. This oscillation was confirmed in the numerical simulation.(2) Real gas effect : Effect of dissociation, ionization and radiation was investigated for the flows at a Mach number larger than 20. It is seen that the real gas effect decreases the shock distance of a blunt body and also that the temperature profile in the shock layer is significantly influenced by the real gas effect.(3) Rarefied gas effect : numerical simulation of low density flows over a blunt body was made by direct Monte Carlo simulation and by numerically solving Boltzmann equation. For the purpose of investigating the flight in a low density atmosphere, the performance test of a ballistic range facility was conducted.(4) Thermal protection : the surface heat transfer and the effect of the wall catalyst was investigated experimentally and numerically. In particular, it is seen that non-catalytic wall decreases surface heat transfer.