Analysis of the Relationships Between Scale-Adaptive and Large-Eddy Simulation

The relationships between scale-adaptive simulation (SAS) and large-eddy simulation (LES) have been investigated systematically using theoretical analysis and numerical simulation techniques. In the theoretical analysis, some key factors were compared, including the definitions of ensemble average and filter, resolving approaches of the turbulent viscosity coefficient in the Spalart-Allmaras (SA) turbulence model and dynamic subgrid-scale model. Theoretical results show that ensemble average is equivalent to the box filter, and governing equations of SAS is corresponding to that of LES. Extra turbulent dissipation exists in the SAS method, which results from the diffusion term of SA turbulence model. In the numerical simulation, compressible turbulent flow past a circular cylinder at free-stream Mach number 0.55 and Reynolds number 2×10⁵ was chosen as the comparative case. Computational results show that the time-averaged flow-field predicted by SAS is nearly same as that obtained by LES. However, turbulent fluctuations predicted by SAS is evidently less than that calculated by LES. Compared to LES, SAS displays more turbulent dissipation in the near wake of circular cylinder. Fortunately, SAS is equivalent to LES in the slightly farther wake of circular cylinder.