SST-DES在小分离流动数值模拟中的改进

在基于剪切应力运输（SST，Shear Stress Transport）分离涡模拟（DES，Detached Eddy Simulation）应对小分离流动的数值模拟中，上游雷诺平均方法（RANS，Reynolds Averaged Navier Stokes）区域内较大的涡黏性通过对流扩散方程传递到下游大涡模拟方法（LES，Large Eddy Simulation）区域，导致自由剪切层解析湍流解迟迟得不到发展，剪切层失稳延后，出现强烈的灰区效应。为此将SST-DES中体现LES求解的类亚格子模式重新构造成标准k方程亚格子模式，防止多变量在RANS和LES交界面处对湍流黏性系数的混合影响，最终得到了一种改进的SST-DES方法。采用该方法对AS239翼型小分离数值模拟并与DES和延迟分离涡模拟（DDES，Delayed Detached Eddy Simulation）结果进行对比，可以看出该方法在壁面边界层保留了SST-DDES特性的同时，在尾迹区大大提高了LES的可解能力，显著降低了灰区的影响。

Improved SST-DES in numerical simulation of mild separation

In the numerical simulation of mild separation by detached eddy simulation (DES) based on shear stress transport (SST) turbulence model, too large turbulent viscosity may translate from the upstream Reynolds averaged navier stokes (RANS) zone to the downstream large eddy simulation (LES) zone by convection, which could restrain the development of resolved turbulence, delay the instability of shear layer and is known as the grey area. Starting from the standard k-equation sub-grid scale model, an improved SST-DES was put forward by preventing the influence of the mixed dependent variables to turbulent viscosity as a result of the original k-equation-like sub-grid model. The numerical study of flow over AS239 airfoil shows that the improved SST-DES keeps the characteristics of delayed detached eddy simulation (DDES) in the boundary layer and increases the accuracy of resolution in the regions far away from the wall at the same time and gets closer results to the experiment compared with SST-DES and SST-DDES.