飞行高度对高超声速钝锥边界层稳定性及转捩的影响

摘要

研究了飞行高度对高超声速钝锥边界层稳定性及转捩的影响.通过求解三维可压缩Navier-Stokes方程计算了来流Ma =6,半锥角为7°的钝锥在飞行高度20～40 km条件下的基本流场,利用线性稳定性理论(LST)研究了飞行高度对钝锥边界层流动稳定性的影响,最后采用eN方法进行了转捩预测.研究发现,随着飞行高度的增加,流向不稳定Ns值和横流不稳定Ncf值均减小,由横流不稳定性引起的圆锥表面大部分区域转捩逐渐转变为流向扰动引起迎风面转捩横流扰动引起背风面转捩,继而横流扰动消失,流向不稳定波引起迎风面转捩.%The effect of flight altitude on the stability and transition of a hypersonic blunt cone boundary layer is studied.The basic flow fields of a 7-degree half angle blunt cone in a free stream with Mach number 6 is calculated at the flight altitudes of 20 ～40 km by solving the three-dimensional compressible Navier-Stokes equations numerically,and the effect of the flight altitude on the stability of the hypersonic blunt cone boundary layer is analyzed based on the linear stability theory (LST).The transition locations are predicted by employing the eN method.The results show that the streamwise Ns and cross flow Ncf both decrease as the increase of flight altitude.The transition occurrs on the most area of the cone surface caused by the cross flow instability gradually transforms to the transition on windward caused by the streamwise disturbance waves and leeward caused by the cross flow unstable waves.Afterwards,the cross flow disturbance disappears and the streamwise disturbance waves lead to the transition on windward.