DISCRETIZATION ERROR DOMINANCE OVER SUBGRID TERMS IN LARGE-EDDY SIMULATION OF COMPRESSIBLE SHEAR LAYERS IN 2D

Second- and fourth-order-accurate spatial discretization methods give rise to discretization errors which are larger than the corresponding subgrid terms in large eddy simulation of compressible shear layers in 2D, if the ratio between the filter width and the grid spacing is clo se to one. Even if an exact representation for the subgrid-scale contr ibutions is assumed, large eddy simulation is accurate only if this ra tio is sufficiently larger than one. In that regime fourth-order metho ds are more accurate than second-order methods. An analysis of the dat a obtained from two-dimensional direct numerical simulations of compre ssible shear layers substantiates these assertions.