A PERSPECTIVE ON COMBINING RANS AND LES FOR COMPUTING COMPLEX FLOWS AND HEAT TRANSFER(Keynote Lecture)
Kemal Hanjalić · The Proceedings of the International Conference on Jets Wakes and Separated Flows (ICJWSF) · 2005
The paper presents a perspective of combining large-eddy simulations (LES) and Reynoldsaveraged Navier-Stokes (RANS) strategies for computation of high Reynolds (Re) and Rayleigh (Ra) number turbulent flows and heat transfer. Limitations and constraints in LES are revisited and illustrated by examples of impinging jets and thermal convection. Whilst it is recognized that RANS will further play an important role, especially in industrial and environmental computations, a new niche for RANS is identified in hybrid combinations with LES. Two routes, the zonal and seamless hybrid RANS/LES are discussed with an attempt to identify advantages and shortcomings of each approach. The potential of very large eddy simulations (VLES) of flows dominated by (pseudo)-deterministic eddy structures, based on transient RANS (T-RANS) and similar approaches is also discussed and illustrated in an example of "ultra-hard" (very high Ra) thermal convection.