基于DES类混合方法模拟后台阶分离流动

摘要

DES类混合方法结合了大涡模拟和传统RANS方法各自的优势,在一定程度上达到了计算精度和计算效率的统一.采用基于两方程SST模型的DDES、IDDES方法,结合高精度的空间离散格式,对雷诺数为36000的后台阶流动进行了数值模拟研究.计算结果表明:IDDES方法和2种DDES方法都能够捕捉到后台阶分离涡结构的发展过程;在台阶下游分离区域,相对于DDES方法,IDDES能够捕捉到更加丰富的湍流涡结构;IDDES方法预测的下游流动再附位置与实验结果一致,而URANS得到分离区域较小,预测的再附位置更靠近上游;几种DES方法得到的速度剖面和雷诺应力分布没有明显差异,URANS结果与实验值差异较大.%The detached?eddy?simulation ( DES ) method combines the strong points of large?eddy?simulation (LES) and Reynolds?averaged numerical simulation (RANS), which takes into the computational accuracy and computational efficiency. The delayed detached?eddy?simulation ( DDES) method and improved delayed detached?eddy?simulation ( IDDES) method based on the k?ωshear stress transport ( SST) model with the improved fifth?or?der WENO scheme are applied to simulated the unsteady flow over back facing step with the Reynolds number of 36000. The numerical results are compared with available experimental data. The computational results show both the DDES and IDDES method can simulate the unsteady vortex?shedding. The IDDES method can capture more vor?tex structures than the two DDES methods in the downstream separated region, the predicted reattachment location by the IDDES method agrees well with the measurement. The DDES and IDDES methods make no significant differ?ences in the averaged streamwise velocity and RMS fluctuations at different streamwise locations, but the numerical result by unsteady RANS deviate from the measurements.