EVALUATION OF THE DYNAMIC-MODEL FOR SIMULATIONS OF COMPRESSIBLE DECAYING ISOTROPIC TURBULENCE

Several issues involving the use of the dynamic subgrid-scale model in large-eddy simulations of compressible turbulent flows are investigat ed. The model is employed in simulations of compressible decaying isot ropic turbulence, and its performance is compared against results from direct numerical simulations and experiments. Results from a parametr ic study suggest the model captures compressibility effects well. Use of the dynamic model in simulations of inhomogeneous flows requires fi ltering of the flowfield in physical space rather than Fourier wave sp ace. The use of spatial filters is examined by conducting simulations of isotropic turbulence. Several implicit filters are found to perform extremely well and similar to the sharp cutoff filter. One explicit f ilter performed well, but all others provided excessive dissipation at higher modes. Two formulations of the dynamic model, proposed by Moin et al. and Lilly, perform well, with Lilly's being more accurate. Res ults suggest also a great insensitivity of the model on the filter wid th ratio, A modification of the convective terms in the momentum and e nergy equations is found to reduce the effects of aliasing errors. Fin ally, different formulations of the energy equation are examined, A no nconservative form is found to be more accurate.