Two-layer approximate boundary conditions for large-eddy simulations

A new method to model the effect of the solid boundaries on the rest of the flowfield in large-eddy simulations is proposed. The filtered Navier-Stokes equations are solved up to the first computational point. From there to the wall, a simplified set of equations is solved, and an estimate of the instantaneous wall shear stress required to impose boundary conditions is obtained. Computations performed for the plane channel, square duct, and the rotating channel flow cases gave improved results compared with existing models. The additional computing time required by the model is on the order of 10-15% of the overall computing time. The mean flow quantities and low-order statistics, which are of primary interest in engineering calculations, are in very good agreement with the reference data available in the literature.