Large-Eddy Simulations of Separated Flow and Heat Transfer in a Ribbed Channel

Ribbed channel flows are encountered in numerous engineering applications to promote turbulence and enhance heat transfer in various cooling passages, e.g., in turbine blades and at combustor walls. Numerical simulations have become an increasingly useful tool for studying the behavior of fluids in rib-roughened channels to provide insights into the complex turbulence structures and flow separation, which are critical to the design and optimization of these channels. This study presents numerical investigations on turbulent flow and heat transfer in generic rib-roughened channels using wall-modeled Large-Eddy Simulations (LES). The study examines mesh resolution requirements for LES to study heat transfer, and friction factor characteristics. Comparison is made with experimental data of Wang et al. (2010) for validation purposes. The LES computations in this study provide a coherent suite of monotonically behaving predictions with all aspects of the results converging toward the predictions obtained on the finest grids. Furthermore, in order to gain insight into the turbulence mechanisms involved in separation, reattachment, and subsequent redevelopment, this study presents results pertaining to mean velocity, friction coefficient, Reynolds shear stress, turbulent kinetic energy production, shear stress production, and heat transfer performance. Investigation of turbulence anisotropy at both small and large scales of motion is conducted through the utilization of anisotropic invariant maps. Notably, a significant variation in the anisotropic characteristics of the flow within the near-wall region is observed when examining different locations between consecutive ribs.