TURBULENCE MODELING FOR TIME-DEPENDENT RANS AND VLES - A REVIEW

Reynolds stress models and traditional large-eddy simulations are reex amined with a view toward developing a combined methodology for the co mputation of complex turbulent flows. More specifically, an entirely n ew approach to time-dependent Reynolds-averaged Navier-Stokes (RANS) c omputations and very large-eddy simulations (VLES) is presented in whi ch subgrid scale models are proposed that allow a direct numerical sim ulation (DNS) to go continuously to a RANS computation in the coarse m esh/infinite Reynolds number limit, In between these two limits, we ha ve a large eddy simulation (LES) or VLES, depending on the level of re solution. The Reynolds stress model that is ultimately recovered in th e coarse mesh/infinite Reynolds number limit has built in nonequilibri um features that make it suitable for time-dependent RANS. The fundame ntal technical issues associated with this new approach, which has the capability of bridging the gap between DNS, LES and RANS, are discuss ed in detail. Illustrative calculations are presented along with a dis cussion of the future implications of these results for the simulation of the turbulent flows of technological importance.