Evaluation of Turbulence Models for Unsteady Separation

Unsteady separation is an undesirable phenomenon that often occurs in fluid flows. Turbulence models for the Reynolds-Averaged Navier-Stokes equations are commonly used in industry to predict such flows, but they give unsatisfactory results, even for steady separation scenarios. To assess their precision in unsteady cases, we will use high-fidelity Large-Eddy Simulation (LES) results: by employing an identical numerical scheme and boundary conditions as the LES, along with a grid that achieves convergence, we pinpoint modelling errors. All turbulence models capture the fundamental characteristics of this unsteady flow, often more accurately than in analogous steady cases. The influence of the periodic nature of the unsteadiness plays a pivotal role in this result.