Detailed investigation of subgrid scale models in large-eddy simulation using high aspect-ratio grid spacing

In large eddy simulation (LES), we generally use information of the grid width in representing a filter (Δ) to evaluate subgrid scale (SGS) model. practical applications, however, widths are largely different streamwise and cross-streamwise directions, resulting cells having high aspect ratios. such case, often adopt cube root grid-cell volume for width; i.e., Δ=(ΔxΔyΔz)1/3 Cartesian system. Although this has been regarded as standard way determine width, its superiority over other strategies, using maximum all directions (i.e., Δ=max(Δx,Δy,Δz)), not always made clear. paper, investigate effect definition on prediction accuracy an SGS model, report priori tests several models highly resolved LES data backward-facing step flow. We focus particularly model performance shear layer downstream step, where there exists strong velocity gradient ratio cell is despite region being far from wall surfaces. This investigation enables us distinguish that near-wall damping. make important finding appropriate width. To properly, one direction much smaller than must be excluded determining