火星进入器小攻角飞行的静不稳定性

Static Instability of Mars Entry Vehicles Flying at Small Angle of Attack

针对火星探路者号进入段飞行过程,求解三维流体力学Navier-Stokes方程,采用高温真实气体模型和等效比热比完全气体模型,对气动力特性进行预测和分析,对发现的小攻角静不稳定现象开展机理分析.比较海盗号数值计算结果、文献数据和飞行试验数据,结果符合很好,验证了物理化学模型及数值方法;探路者号的升阻特性和配平特性预测数据表明,真实气体模型和LAURA数据符合很好,等效比热比模型可以较准确地计算升力和阻力系数;2°攻角飞行时,进入器沿轨道出现静不稳定,完全气体模型无法模拟,分析认为迎风区声速线在肩部的移动和背风区亚声速区的分布变化以及亚声速区泡的出现,导致激波层压力下降和肩部膨胀区的压力下降向上游的传递过程发生变化,造成表面压力分布改变,最终诱发静不稳定.

Three-dimensional Navier-Stokes equations in high temperature real gas model and perfect gas model are solved for hypersonic entry process. Good agreement is achieved between numerical results,reference values and flight data of Viking,which validates physical-chemical models and numerical methods. Aerodynamic prediction of Mars Pathfinder proves that results of real gas model are close to LAURA. Perfect gas model with effective specific heat ratio is capable of computing lift and drag coefficients. At 2°angle of attack,MPF exhibits static instability along trajectory,which perfect gas model failed to catch on. It is considered that main reasons of static instability are sonic line shifting around shoulder in windward,subsonic area varying and subsonic bubble occurring in leeward. They result in different pressure change in shock layer and in transportation process from expansion zone to upstream.