Verification and Validation: the Path to Predictive Scale-Resolving Simulations of Turbulence

This work investigates the importance of verification and validation (V\&V) to achieve predictive scale-resolving simulations (SRS) of turbulence, i.e., computations capable of resolving a fraction of the turbulent flow scales. Toward this end, we present a novel but simple V\&V strategy based on grid and physical resolution refinement studies that can be used even when the exact initial flow conditions are unknown, or reference data is unavailable. This is particularly relevant for transient and transitional flow problems, as well as for the improvement of turbulence models. We start by presenting a literature survey of results obtained with distinct SRS models for flows past circular cylinders. It confirms the importance of V\&V by illustrating a large variability of results, which is independent of the selected mathematical model and Reynolds number. The proposed V\&V strategy is then used on three representative problems of practical interest. The results illustrate that it is possible to conduct reliable verification and validation exercises with SRS models, and evidence the importance of V\&V to predictive SRS of turbulence. The data also confirm the advantages of the proposed V\&V strategy.