Scale-Resolving Simulations (SRS) of flow past a sphere at sub-critical Reynolds number

Partially-averaged Navier-Stokes (PANS) two-layer turbulence scheme offers a robust near wall closure for Scale-Resolving Simulations (SRS). This technique couples a scale-resolved one-equation model near wall with a PANS k-ε model in the outer layer. In this study, we employ the PANS two-layer closure to examine flow over a sphere in the sub-critical regime (Re = 3700). This flow embodies complex characteristics including laminar separation, transition to turbulence in the shear layer and vortex shedding. Comparison with Direct Numerical Simulation (DNS) reveals the dependence of the mean and integral flow parameters on numerical (spatio-temporal) as well as physical resolution (cut-off scales). Optimal physical resolution for capturing the vortex-shedding frequency (f_vs) and Kelvin-Helmholtz instability (f_KH) is established. Furthermore, the large-scale coherent structures shed in a helical configuration at random azimuthal locations on the sphere are visualized by means of velocity gradient invariants.