Detached-Eddy Simulation of flow around a 1:5 rectangular cylinder

This paper deals with the numerical simulation of the unsteady flow field around a 1:5 rectangular cylinder at zero flow incidence, low Mach number and high Reynolds number. The three-dimensional Detached-Eddy Simulation technique associated with the one-equation turbulence model of Spalart and Allmaras (SA-DES) is employed. This is a hybrid method which combines the RANS approach near the walls and the LES approach away from the walls. It is particularly useful in case high-Reynolds-number turbulent boundary layers have to be computed. 2-D and 3-D unsteady RANS simulations using the Spalart-Allmaras (SAE) and an Explicit Algebraic Reynolds Stress Model (LEA k - ω) are also proposed. Comparison with experiments shows that, while the URANS-SAE equations are not able to capture the unsteadiness of the flow, the 2-D URANS-LEA computation gives reasonable results, although the frequency of vortex shedding is slightly underestimated and the lift mean fluctuation is overestimated. No improvement is obtained by applying the URANS-LEA approach on the much more expensive 3-D mesh, since nearly two-dimensional flow field is obtained. In contrast, the accuracy of the result can be enhanced by performing a 3-D SA-DES simulation, which allows to resolve much finer and three-dimensional vortical structures. The conclusions of this work confirm the interest for this hybrid non-zonal technique and encourage to apply it for even more challenging test case.