旋成体大迎角分离流的Euler方程数值模拟

Numerical Simulation of Separation Flow on Bodies of Revolution at High Angle of Attack Using Euler Equations

用三维Euler方程计算旋成体的大迎角绕流,我们发现:亚声速自由流时,计算得到的是无分离流动,与实际的分离流不相符合,因而计算的法向力大大小于有分离的实验值;而当自由流为超声速,且横向自由流M数较高时,由于背风表面出现激波,无粘Euler方程的数值计算能自动捕捉到背风面上的分离涡,计算法向力与实验值接近。为了对亚声速自由流用Euler方程数值模拟大迎角旋成体背风面上分离涡,根据问题的物理图像,在假设的分离线上,提出强加Kutta条件的方法,成功地计算出有分离流动,使计算的法向力与实验值接近。

Using our developed 3-D Euler code EU3V0L to compute compressible flow over bodies of revolution at high angle of attack, no separation we found when the free stream is subsonic. This fact is in opposition to what happened in practice. Thus, the normal force computed on the body is much more less than that by experiment because we did not consider the vortex lift due to the separation. On the other hand when the free stream is supersonic and the cross-flow Mach number is high enough, the computation with Euler equations can easily capture the separation vortex due to the shock induced separation on leeward side of the body. In such a case, the value of the computed normal force on the body is close to that by experiment. To capture the separation vortex with Euler equations for subsonic free-stream,it is suggested in this paper that a forced Kutta condition is applied on one or two lines near the assumed separation line on the body surface. The computation by the proposed method with Euler equations shows that we capture successfully the separation vortex and get good prediction of the normal force on the body with inviscid computation.