Comparison of Hybrid RANS-LES Simulations of Turbulent Flow and Heat Transfer in a Ribbed Duct

Numerical predictions of the turbulent flow and heat transfer of a stationary duct with square ribs 45° angled to the main flow direction are presented. The rib height to channel hydraulic diameter is 0.1, the rib pitch to rib height is 10. The calculations have been carried out for a bulk Reynolds number of 50,000. The flows generated by ribs are dominated by separating and reattaching shear layers with vortex shedding and secondary flows in the cross-section. The one of hybrid RANS-LES approaches, Detached Eddy Simulation (DES), is adopted to simulate such flows at a reasonable computation cost. The capability of the various versions of DES method, depending on the RANS model, such as Spalart-Allmaras model (SA), Realizable k-ε model (RKE) and Shear Stress Transport (SST) model, has been compared and evaluated against the experimental data. The significant effect of RANS model on the accuracy of the DES prediction has been shown. The DES-SST method, which was able to reproduce the reasonable physics of flow and heat transfer in a ribbed duct, showed better performance than others.