XY-SAS模型中不同网格尺度限制器的影响分析

XY-SAS(Xu & Yan Scale Adaptive Simulation)模型通过在SA(Spalart-Allmaras)模型耗散项的湍流尺度中引入基于平均涡量的冯卡门长度尺度,在不稳定流动区域具有类似LES(Large Eddy Simulation)的计算性能,且不存在DES(Detached Eddy Simulation)方法中RANS(Reynolds Averaged Navier-Stokes)与LES的交界面问题.由于SAS类模型预测的湍流能谱存在高波数衰减不足的缺陷,需要进一步在湍流尺度中引入网格尺度作为限制器.采用不同形式的网格尺度限制器构造了3种XY-SAS模型,对Re=3 900的圆柱绕流进行数值模拟,并与DES及实验数据进行比较.结果表明网格尺度限制器对XY-SAS模型的计算性能有较大影响,以最小网格间距作为高波数衰减限制器是较为合理的选择,此时模型对于大分离流动能够达到DES的模拟能力.

Influence analysis on grid scale limiter of XY-SAS model

The Xu & Yan scale adaptive simulation (XY-SAS) model is based on the introduction of the von Karman length scale into the destruction term of spalart-allmaras (SA) turbulence model, which results in a large eddy simulation (LES)-like behavior in unsteady regions of the flowfield without explicit grid dependence. Because the SAS models could not provide sufficient damping of the smallest scales, the grid spacing was introduced as the high wave number damping limitation. Three different XY-SAS models were constructed by using various grid limiters and were tested by the numerical example of circular cylinder at Re=3 900. The numerical results were compared with detached eddy simulation (DES) and experimental data. It is concluded that, the grid limiter has a strong influence on the performance of the model and the minimum grid spacing is a good limitation, under which the XY-SAS model performs as well as DES method.