一种改进的类DES湍流模拟方法

Improved DES-like method for simulation of turbulent flows

构造了一种基于一方程S-A(Spalart-Allmaras)模型和一方程Yoshizawa亚格子模型的混合RANS/LES(Reynolds-averaged Navier-Stokes/large eddy simulation)湍流模拟方法.在涡黏假设的基础上,将Yoshizawa亚格子湍动能方程转化为等效的亚格子湍流涡黏性输运方程,并采用混合函数将其与S-A模型方程进行混合,从而改进了DES(detached eddy simulation)模型的亚格子行为,同时克服了其依靠网格控制模型转换的缺点.模拟了超声速的带斜坡凹腔流动,并与相同网格下的LES及DES结果进行了比较,结果表明该混合RANS/LES方法在远离壁面的自由剪切流区域与LES行为一致,而在附着边界层区域表现优于LES和DES方法.

A hybrid RANS/LES（Reynolds-averaged Navier-Stokes/large eddy simulation） approach based on one-equation S-A（Spalart-Allmaras） RANS model and one-equation Yoshizawa SGS（sub-grid scale） model was developed.The turbulent kinetic energy transport equation of the SGS model was transformed to an equivalent eddy viscosity transport equation,and then blended with the S-A model equation to generate a hybrid eddy viscosity transport equation,wherein both the SGS behavior and the grid-depending RANS-LES transition of DES were improved.The hybrid RANS/LES approach was then applied to simulate a supersonic,ramped cavity flow,where LES and DES were also implemented on the same mesh for comparison.It shows that the hybrid RANS/LES acts like LES in the free shear flow far away from the wall and outperforms LES and DES in the attached boundary layer.