超声速空气介质自由扩散混合流涡的演化

在不同谐波扰动促发方式下,观察二维超声速空气/空气自由扩散混合流中涡的形成及演化.考虑含空气组分扩散效应的可压缩Navier-Stokes方程,对流项采用3阶迎风紧致格式离散,输运项采用6阶对称紧致格式离散,非定常时间推进采用3阶紧致存储显式Runge-Kutta方法.在无相差情形下,获得了大尺度基频涡结构的饱和、一次对并、二次对并、三涡对并等现象.在Mac=0.3低对流Mach数下,基频涡较饱满,但流向尺度较小.受空气真实气体特性影响,在Mac=0.8高对流Mach数下未发现涡/小激波结构.

Vortex evolution in supersonic air free diffused mixing layers

The vortex formation and evolution in a supersonic air / air free diffused plane mixing layer are investigated numerically through forcing four different harmonic disturbances without phase differences. The two-dimensional compressible Navier-Stokes equations including the diffusion effect of air components are solved by using a high accuracy finite difference method. The convective terms and the transport terms are discretized by a third-order upwind compact scheme and a sixth-order symmetric compact scheme, respectively. The unsteady time marching method is a third-order compact storage explicit Runge-Kutta algorithm. Some phenomena of large scale primary vortex growing and interacting are revealed, such as saturating, paring once and twice, and triple-vortex pairing. For low convective Mach number of Mc = 0.3, primary vortices are fatter, but their streamwise lengths are shorter. Under the influence of air real-gas characteristics, the vortex-shocklet structure is not discovered for the case of high convective Mach number of Mc = 0.8.