A filtered-wall formulation for large-eddy simulation of wall-bounded turbulence

Simulating high Reynolds number wall-bounded turbulence using large-eddy simulation (LES) requires modeling the subgrid force in the bulk of the flow and instantaneous viscous and pressure stresses at the wall. Here, LES of turbulent channel flow is conducted at Re(tau)=590 using a filtered-wall formulation, in which a buffer region with u=0 is attached adjacent to the wall, and the underlying velocity field defined over the extended domain is filtered using a nonlocal filter (in this case, a Fourier cutoff filter) in all directions. The instantaneous wall stress is computed by first prescribing a target velocity field for the filtered velocity inside the buffer and then minimizing the error between the actual and target velocity at every time step. The optimal LES (OLES) approach is used to model the subgrid force in terms of the resolved velocity field via linear stochastic estimation. The correlations required to carry out this stochastic estimation are computed from direct numerical simulation (DNS). Results of the LES simulation show reasonable agreement with filtered DNS statistics. Also, simulations performed after introducing modifications to the linear OLES kernel show that the positive eigenvalues in the kernel and the skew-symmetric part of the kernel play important roles in LES of wall-bounded turbulence. (c) 2008 American Institute of Physics.