高亚临界雷诺数圆柱绕流的尺度自适应模拟

SCALE ADAPTIVE SIMULATION OF FLOWS AROUND A CIRCULAR CYLINDER AT HIGH SUB-CRITICAL REYNOLDS NUMBER

借助γ--Reθ转捩模型,实现了高亚临界雷诺数(Re=1.4×105)下圆柱层流分离流动的尺度自适应模拟.统计平均结果表明数值计算和实验测量较为接近,尤其在圆柱后半段的分离区中,压力系数和实验符合得很好,误差主要源于分离点预测的不准确.瞬态流动则显示,层流分离的剪切层中出现了展向不稳定,且在向下游的输运过程中不断增强,最后转捩为完全湍流.在湍流分离模拟中,由于缺乏剪切层失稳的非定常性,SST-SAS模型的尺度分辨能力变弱,因此在分离区以及下游尾迹中求解出的湍流尺度要明显较层流分离时大.

Combining with γ--Reθtransition model, scale adaptive simulation(SAS) is successfully applied on the laminar separation flow past a circular cylinder at high sub-critical Reynolds number(Re = 1.4 × 105). Numerical results are statistically closed to experimental data, and especially the agreement of pressure recovery in separation zone is fairly well. The major error comes from the inaccurate prediction of the separation position. Transient flows indicate that there are spanwise instabilities in the shear layer of laminar separation flow, and they will grow to be fully turbulence when transporting downstream. Comparing to laminar separation, because of the lack of the unsteadiness related to the shear layer instability, the scale resolving capability of SST-SAS is weaker for turbulent separation flow. Therefore, the scale of turbulent structures resolved by SAS in the wake of turbulent separation is much larger than the laminar separation.