Flow structures and heat transfer over a single dimple using hybrid URANS-LES methods

Large eddy simulations (LES) and improved delayed detached eddy simulations with wall modeling capability (IDDES) are applied to analyze flow structures and heat transfer of turbulent flow over a single dimple placed at the lower wall in a narrow channel for high Reynolds and Prandtl numbers up to ReD=105000 and Pr=3 respectively. Based on the simulations of the turbulent channel flow up to Reτ=2048, the LES and IDDES methods are validated, needed mesh sizes and its application for high Reynolds numbers are determined. The heat transfer rates and the skin-friction factors of the IDDES are consistent with empirical correlations whereas LES show large differences for higher Reynolds numbers using moderate grid sizes. The mean values, high order statistics as well as vortex structures and secondary flow structures of a spherical dimple have been analyzed and compared to experimental data. IDDES reproduces mean quantities and the asymmetric flow structures with a changing orientation towards the main flow while reducing the computation time enormously with a satisfying accuracy.