A DYNAMIC SUBGRID-SCALE MODEL FOR LOW-REYNOLDS-NUMBER CHANNEL FLOW

Several issues related to applications of the dynamic subgrid-scale (S GS) model in large-eddy simulation (LES) at low Reynolds number are in vestigated. A modified formulation of the dynamic model is constructed and its performance in low-Reynolds-number LES of channel flow is ass essed through a comparison of length scales computed respectively by t his modified model, the German-Lilly dynamic SGS model and two empiric al wall damping functions with optimum model coefficients, which have been successfully used in many simulations of channel flows. Two value s of the ratio of filter widths are set for each of the dynamic models . The results have confirmed that the modified dynamic SGS model gives the correct behaviour of the subgrid eddy viscosity in the region of a plane wall to an accuracy that exceeds the best-tuned wall damping f unction, and almost collapses with the theoretical behaviour of the le ngth scale near the wall without any tuning and adjustment. In additio n, the impact of the choice of the ratio of filter widths on the modif ied dynamic SGS model is found to be much less than with the Germane-L illy model.