Flow Past A Circular Cylinder - A Comparison Between RANS And Hybrid Turbulence Models For A Low Reynolds Number

Several offshore applications deal with highly unsteady and detached flows, dominated by three dimensional effects. On such conditions, the usage of scale-resolving simulation (SRS) turbulence models has increased due to the well-known limitations of common RANS models. However, some of these offshore applications, such as flows past cylinders or raisers, present highly complex non-turbulent phenomena which, if not properly resolved, may pollute the outcome of any turbulence model. Therefore, it is crucial to mimic the flow conditions of the problem, the physical settings, and fulfil the numerical requirements of such problems to obtain reliable and accurate predictions. This paper assesses RANS and hybrid turbulence models, focusing on the dependence of the numerical predictions on the physical settings. To this end, the flow past a circular cylinder at a Reynolds number of 3900 is simulated using RANS, DDES and XLES models. The obtained results reveal a large dependence on the grid spatial resolution and physical settings, in particular on the computational domain width and boundary conditions. A substantial improvement of RANS predictions is found when a 3D computational domain is used. As expected, the hybrid models, DDES and XLES, lead to a better agreement with the experiments.