探月返回器稀薄气体热化学非平衡特性数值模拟

Numerical Simulation of Rarefied Gas Thermochemical Nonequilibrium when Lunar Exploration Vehicle Re-entering into Atmosphere

通过发展直角/非结构混合网格下,适于复杂返回器含内能激发的五组元热化学非平衡稀薄气体直接模拟蒙特卡洛(DSMC)方法,数值模拟了钝体返回器稀薄流区7.5 km/s和10.6km/s再入速度下的非平衡流场特性和对物面气动力/热分布的影响。计算结果表明在月球返回速度下稀薄过渡流区存在着强烈的热化学非平衡,近连续滑移区仅在激波层区域存在着较大的平动、转动和振动非平衡度,而在高稀薄流区,热力学非平衡遍布绕流物体四周,包括整个压缩区和尾迹区。高温真实气体效应对表面热环境影响显著,对表面压力和摩擦力的影响相对较弱。计算结果显示探月返回器再入绕流过程100 km飞行高度仍需要考虑热化学非平衡的影响。

The Direct Simulation Monte Carlo（DSMC） method was developed to simulate rarefied gas flows around complex bodies with internal energy excitation and thermochemical nonequilibrium effect of five air species,using a hybrid grid technique of Cartesian coordinate meshes and surface unstructured triangular cells.The nonequilibrium flowfield characteristics and their effects on surface parameters distribution around blunt re-entry capsule in rarefied flow regime were numerically simulated under the re-entering velocities of 7.5km/s and 10.6km/s,respectively.The computational results showed that intensive thermochemical nonequilibrium occurred in the rarefied transitional region under lunar return velocity.In near continuum slip flow regime,the great degrees of translational,rotational and vibrational nonequilibrium only exited in the shock wave layer.While thermodynamic nonequilibrium distributed in the whole compress and wake regions at high rarefied flow regime.The high temperature real gas effect affected the surface thermal environment significantly and impacted relatively weak on the surface pressure and friction.It is indicated that the effect of thermochemical nonequilibrium must be considered up to 100 km during the re-entering into the atmosphere of the lunar exploration vehicle.