Large-eddy simulation of a spatially-evolving supersonic turbulent boundary layer at M∞= 2

Abstract

The ability of large-eddy simulation (LES) to resolve the most energetic coherent structures of a spatially-evolving supersonic turbulent boundary layer over a flat plate at M∞ =2 and Reθ ≈ 6000 is analyzed using three types of local subgrid scale models. Aditionally, an Implicit LES (ILES), which relies on the intrinsic numerical dissipation to act as a subgrid model, is investigated to assess the consistency and the accuracy of the method. Direct comparison with data from high resolution DNS calculations [S. Pirozzoli and M. Bernardini, Turbulence in supersonic boundary layers at moderate Reynolds number, J. Fluid Mech, 68, 120-168, 2011] provides validation of the different modeling approaches. Turbulence statistics up to the fourth-order are reported, which helps emphasizing some salient features related to near-wall asymptotic behavior, mesh resolution and models prediction. Detailed analysis of the nearwall asymptotic behavior of all relevant quantities shows that the models are able to correctly reproduce the near-wall tendencies. The thermodynamic fluctuations, Trms and ρrms, show a lack of independence from SGS modeling and grid refinement in contrast to the velocity fluctuating field. The pressure fluctuations, which are assumed to be associated with the acoustic mode, are not significantly affected by the modeling and the mesh resolution. Furthermore, the comparison of different contributions to the viscous dissipation reveals that the solenoidal dissipation plays the most dominant role regardless of the model. Finally, it is found that the ILES is more likely to produce consistent results even though a small amount of numerical viscosity is introduced through a sixth-order skew-symmetric split-centered scheme to emulate the effects of unresolved scales.