Studies of AOTV's Gasdynamics

“AOTV”是指航空辅助轨道转移飞行器。当太空飞行器从较高的轨道转到较低的轨道时，它通过空气制动来减速。这项研究是由20名调查人员进行的。AOTV包括以下几个问题：(1)激波层相互作用；(2)真实气体效应；(3)稀薄气体效应；(4)热防护。本文的研究结果总结如下：(1)激波层相互作用：利用LIF流动显示技术观察了对向射流与超声速自由流相互作用的流场。观察到，当射流与自由流的滞止压力比较小时，自由流激波、接触面和马赫盘在流动方向上周期性运动。数值模拟证实了这种振荡。(2)真实气体效应：研究了马赫数大于20时的分离、电离和辐射效应。可以看出，真实气体效应减小了钝体的激波距离，并且真实气体效应对激波层的温度分布有显著的影响。(3)稀薄气体效应：采用直接蒙特卡罗模拟和数值求解玻尔兹曼方程的方法对钝体低密度流动进行了数值模拟。为了研究在低密度大气中的飞行，对弹道靶场设施进行了性能试验。(4)热防护：通过实验和数值模拟研究了壁面催化剂的表面传热和作用。特别地，非催化壁降低了表面传热。

"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.