有厚度平板尾缘可压缩剪切层中的涡结构数值模拟

采用一个新型Fu Ma高精度UCD5 SCD6紧致差分算法,通过直接求解二维Navier Stokes方程,成功实现了有厚度平板尾缘可压缩剪切层中涡结构的数值模拟,并考查了平板厚度对其的影响.计算对流马赫数M_c=0.3,平板厚度分别为1,2,3,4个参考长度.结果表明,增加平板厚度可促使平板尾缘可压缩剪切层中的涡提前卷起,有利于两股气流混合.

Numerical Simulation of the Vortex Structure in Compressible Shear Layers Behind Flat Plates with Different Thicknesses

A high accuracy and resolution finite difference method is first used to simulate numerically the compressible wake shear layers induced by flat plates with different thicknesses. The new method is named the Fu-Ma UCD5-SCD6 hybrid compact scheme. The fully two-dimensional compressible Navier-Stokes equations are directly solved. Based on the Steger-Warming flux-splitting technique, the convective terms are discretized by using the fifth-order upwind compact difference method, while the dissipative terms are discretized by using sixth-order symmetric compact difference method. A third-order Rung-Kutta method is selected for time marching. At convective Mach number M_c=0.3, four flat plate thicknesses and three upper incoming Mach numbers are considered. In all cases, the self-excited large scale vortex coherent structures are captured successfully, and their spatial evolution such as eddy rollup and pairing is investigated. Results show that the flat plate thickness can obviously affect the coherent structures. Increasing the flat plate thickness can accelerate the vortex rollup and enhance mixing. Moreover, for the same convective Mach number, increasing incoming Mach number can delay the vortex rollup and damp the vortex pairing. This can somehow be attributed to the well-known compressibility effect.