振动激发对高超声速气动力/热影响

摘要

随着飞行马赫数的不断提高,空气的高温气体效应越来越明显,对高超声速飞行器的气动力/热特性产生重要影响.高温气体效应对气动力/热的影响机理复杂,影响参数众多,迄今为止国内外尚未完全研究清楚.发生高温气体效应时,多个非线性物理过程耦合在一起,地面试验和数值模拟无法将这些过程解耦,无法给出关键物理机理.为了解决这一问题,文章提出一种理论分析与数值模拟相结合的两步渐进新方法:先通过牛顿迭代法得到发生振动激发过程的斜激波无黏解;再将该无黏解的结果作为边界条件,求解边界层的黏性解.利用该方法研究了振动激发过程对二维斜劈的气动力/热特性的影响规律.研究结果表明,振动激发过程对斜激波后的温度、密度、马赫数、雷诺数和斜激波角影响较大,而对压力和速度影响较小.斜激波波后的无黏流动与边界层流动是耦合在一起的.发生振动激发后,斜激波波后雷诺数的增大会导致边界层厚度减小,结合多个物理量的变化,如速度增大和温度减小,共同对边界层内的摩擦阻力和气动热产生影响.对比完全气体的结果发现,振动激发使壁面摩阻升高,而使壁面热流降低.分别通过影响激波层和边界层,振动激发对摩阻的影响是弱耦合的,而对热流的影响则是强耦合的.%With the increasing of flight Mach number, the high-temperature gas effect of air has becoming remarkable, which has significant impacts on the aerodynamics and aerothermodynamic characteristics of hypersonic vehicles. Be-cause of the complex mechanism and numerous key parameters of high-temperature gas effect, it has not been fully studied at home and abroad. When the high-temperature gas effect occurs, multiple nonlinear physical processes are cou-pled together. However, ground tests and numerical simulations can not decouple these processes and can not explain the key physical mechanisms. To solve this problem, a new two-step asymptotic approximation method combining theoretic analysis and numerical simulation is proposed. In this method, the oblique shock relation with vibration excitation effect is obtained by Newton iterative method, then the results are used as the boundary conditions of the boundary layer and it is solved numerically. By using this method, the effect of vibration excitation on the aerodynamics and aerothermody-namic characteristics of a two dimensional wedge is studied. The results show that, the vibration excitation process has great effect on the shock angle, the temperature, density, Mach number, and Reynolds number behind the oblique shock, but little influence on the pressure and velocity. The inviscid flow behind the oblique shock is coupled together with the boundary layer flow. The changes of multiple physical quantities, including the increase of velocity and the decrease of the temperature behind the oblique shock, and the decrease of the boundary layer thickness due to the increase of the Reynolds number, have an effect on the friction and aerodynamic heating in the boundary layer. Comparing with perfect gas model, vibration excitation increases the wall friction and decreases the wall heat flux of the wedge. By influencing the shock layer and the boundary layer respectively, the effects of vibration excitation on heat flux are strong coupled, while they are weak coupled on friction.