基于涡方法生成大涡模拟进口条件的数值计算

探索改进涡方法来生成大涡模拟的非定常进口条件.改进方法中,为了避免局部漩涡数量过多或者过少,采用密度分布方式放置漩涡场.并用Langevin方程控制漩涡运动,模拟实验方法中的蜂窝器,使改进后的涡方法生成的脉动速度场更加符合湍流的特征.在已知雷诺平均的流场结果下,利用涡方法产生漩涡场,进而生成能满足大涡模拟所需要的非定常进口流场.为了检验改进后的涡方法在生成脉动速度过程中的效果,在槽道中进行了对比数值试验,并借助于直接数值模拟数据做对比,对比分析槽道进出口的平均速度、涡量以及雷诺应力统计,证明改进后的涡方法在生成大涡模拟进口条件下是非常有效的.

Generation of unsteady inflow conditions for compressible LES with a modified vortex method

This article is to explore and modify vortex method to generate large eddy simulation (LES) inlet condition. In the modification, a density distribution of vortex which can avoid unreasonable vortex quantity in local place was used. The movement of vortex was controlled by Langevin equation, which mimics the active grid turbulence so as to generate an unsteady flow field which is more like the real turbulence. Knowing the results of Reynolds-averaged Navier-Stokes equations (RANS) and reconstructing the turbulence by vortex method (VM), the method was tested in the experimental channel. The statistical results of both inlet and outlet of the channel were given, which include the mean velocity, the vorticity and the Reynolds stress. By analyzing the generated field with the reference of direct numerical simulation (DNS) results and comparing with the results of original method, during the development of turbulence in the channel, it shows that the modified vortex method is viable and cost-effective for generating unsteady inflow condition for LES.