IMPROVED SUBGRID-SCALE MODELS FOR LARGE-EDDY SIMULATION.

Abstract

Models for subgrid-scale turbulence are analyzed. The analysis indicates that there is enough information in the resolved scales to allow some of the characteristics of the complete flow field to be determined. The kinetic energy of the small-scale motions can be decomposed into two parts. One is due to energy transfer from the large scales and is correlated with them; the other is uncorrelated. This leads to a two-component eddy-viscosity model. The ″production equals dissipation″ argument does not hold for the small scales in the decay of turbulence. The two-component model can be reduced to the single-component models used previously, but it shows some of the flaws in arguments made earlier. The exchange between the large and small scales takes place mainly between the smallest scales of the former and the largest scales of the latter. This argument is the basis of a new model which preliminary tests show to be superior to the J. Smagorinsky model. Refs.