Assessment of SAS and PANS models in simulations of flow over a circular cylinder

Flow past a circular cylinder at Re=3900 is simulated using shear stress transport (SST) model, scale-adaptive simulation (SST-SAS) model and partially averaged Navier-Stokes (PANS) model with two various f_k methods. The SAS and PANS models as recently proposed hybrid strategies are significantly investigated. The model performance is assessed by a detailed comparison of predictions regarding the turbulence characteristics, the aerodynamic characteristics, and the distribution of eddy-viscosity. Moreover, the grid-sensitivity of different models is also investigated using two grids. From the assessment, it is confirmed that the SAS and PANS models have the abilities to calculate the small-scale motions, and both models can be employed to predict the unsteady characteristics of wake vortices advantageously. Both the two PANS models can capture complex flow structures and physics mechanism; and the SAS model using the L_vk scale with features of local-adaptive and grid-independent can predict the eddy-viscosity reasonable. Therefore, the SAS model reproduce the shear layers and recirculation zone more accurately. Both the two PANS methods appear obvious grid-dependency, and the issue of modeled-stress depletion (MSD) is evoked with the fine grid. The f_k function with DES method has a simple structure and provides a reasonable f_k distribution, while the f_k function with tanh method obtains a low level f_k distribution in the wake area, corresponding to its inadequate capabilities in adjusting the solution scales of separated flows.