Large eddy simulation of complex flow fields

The large eddy simulation (LES) technique can provide detailed information about time-dependent and three-dimensional turbulent flow fields at high Reynolds number. The application of LES to practical problems and in the basic study of turbulence require investigation. More studies are needed on the boundary conditions and on the subgrid-scale (SGS) model in order to make LES practical. In this paper, the laws of the wall (two-layer model or Spalding's law) are applied as a special approach to the solid boundary in LES. This wall boundary condition is adapted to plane channel flow and the suitability of this method is tested. Further, improvements of the SGS model in which the Smagorinsky model coefficient C_S is not constant are attempted. Recently, Yoshizawa [Phys. Fluids A1(7), 1293 (1989)] derived the form of the variable C_S from a statistical analysis. Here, we optimize this new model in both the decay of isotropic turbulence and plane channel flow simultaneously.