地外天体起飞羽流导流气动力效应仿真

探测器自地外天体采样返回过程中，发动机羽流作用于起飞平台后返流至起飞器表面，产生气动力效应及干扰力矩。针对圆锥形羽流导流结构，利用计算流体力学/直接模拟蒙特卡罗（CFD/DSMC）耦合方法，对起飞器距离起飞平台200~700 mm，偏转角度0°~5°范围内的羽流导流气动力效应进行了仿真计算。计算结果表明，随着上升距离增加和偏转角度增大，起飞器受到的力矩出现了反向增加现象，严重影响起飞稳定。研究发现，上述现象产生的主要原因为偏转角度增加时，起飞器距离起飞平台较远一侧的羽流与起飞平台作用点由圆锥导流结构逐渐偏移至平面位置，导致羽流作用于起飞平台后的流动方向由贴近起飞平台向侧面流动急剧转变为反弹至起飞器底面方向流动，从而使远离起飞平台的一侧所受力矩高于靠近起飞平台一侧，产生反向力矩。 

Simulation of plume diversion aerodynamic effect for take-off from celestial bodies outside the Earth

During the return progress of the detector from the extraterrestrial celestial body after sampling, the ascent engine plume flows back to the ascender after the reflection from the launching pad upper surface, which causes aerodynamic effect and disturbing torque effect on the ascender. Numerical simulations have been done with the computational fluid dynamics and direct simulation Monte Carlo (CFD/DSMC) coupling method to analyze the plume aerodynamic effect during the takeoff. The influences of takeoff distance of 200-700 mm and deflection angle from 0° to 5° of ascender on plume aerodynamic effects have been considered in this paper. It has been found that with the increase of takeoff distance and deflection angle, the torque of the ascendere has been changed from positive to reverse, which seriously affects the takeoff stability. The reason of this phenomenon is considered to be that, when deflection angle increases, the impact point between the plume on the further side of the ascender from the launching pad and the launching pad has moved from the cone flame deflection to the plane. This phenomenon causes plume flow direction to change suddenly from close to the launching pad and flow to the side to rebound from the launching pad and flow to the bottom of the ascender. Eventually, the side of the ascender far from the launching pad is subjected to a higher torque than the side closer to the launching pad, and a reverse torque is generated.