LES/RANS方法混合函数特性研究

将两方程k-ω SST湍流模型和Sagaut的混合尺度亚格子模型通过一个混合函数相结合, 构造出一种混合大涡/雷诺平均N-S方程模拟方法(hybird large eddy simulation/reynolds-averaged navier-stokes, Hybrid LES/RANS), 采用这种混合模拟方法结合5阶WENO格式对Ma=2.8平板湍流边界层进行了数值模拟, 并在计算区域上游入口处采用“回收/调节”方法生成湍流脉动边界条件, 通过考查RANS区域向LES区域的过渡参数及网格分辨率对这种混合模拟方法进行了评价. 计算结果表明: 该文采用的混合模拟方法可以捕捉到湍流边界层中的大尺度结构且入口边界层平均参数不会发生漂移, 混合函数应当将RANS区域和LES区域的过渡点设置在对数律层和尾迹律层的交界处, 而过渡应当迅速以获得正确的雷诺剪切应力分布, 在该文采用的模型及数值方法的条件下, 流向及展向的网格小至与Escudier混合长相当时, 能够获得可以接受的脉动速度的单点-二阶统计值.

PARAMETRIC STUDY ON THE BLENDING FUNCTION IN TRANSITION ZONE OF THE LES/RANS METHOD

Two-equationκ-ωSST turbulence model was combined with Sagaut’s mixed-length subgrid-scale model with a blending function to construct a hybrid large-eddy/Reynolds-averaged Navier-Stokes method.The method was used to compute a plate turbulent boundary layer at Mach number 2.8 with fifth-order WENO scheme.A recycling/rescaling method was used to generate and sustain turbulent fluctuations at the inlet.The RANS to LES transition parameters and mesh resolution were considered in order to assess the method.The results showed that the hybrid method could capture the large-scale structure in the turbulent boundary-layer and no shift of the inlet mean parameters was observed.The blending function should be designed to transition to LES toward the outer part of the logarithmic region and the transition should be sharp to obtain the correct Reynolds shear stress.Single point-second order velocity fluctuations statistics might be obtained and accepted on streamwise and spanwise meshes scaled by Escudier mixing length.