A Wall-modeled hybrid RANS/LES model for flow around a circular cylinder with coherent structures in subcritical Reynolds number regions

In present paper, a hybrid RANS/LES model with the wall-modelled LES capability (called as WM-HRL model) is developed to perform the high-fidelity CFD simulation investigation for complex flow phenomena around a bluff body with coherent structures in subcritical Reynolds number regions. The proposed method can achieve a fast and seamless transition from RANS to LES through a filter parameter r_k which is only related to the space resolution capability of the local grid system for various turbulent scales. Furthermore, the boundary positions of the transition region from RANS to LES, as well as the resolving capabilities for the turbulent kinetic energies in the three regions including RANS, LES and transition ones can be preset by two guide index parameters nr_k1-Q and nr_k2-Q. Through a series of numerical simulations of the flow around a circular cylinder at Reynolds number Re=3900, the combination conditions are obtained for such two guide index parameters nr_k1-Q and nr_k2-Q with the capability of high-fidelity resolving and capturing temporally/spatially-developing coherent structures for such complex three- dimensional flows around such a circular cylinder. Results demonstrate that the new WM-HRL model is capable of accurately resolving and capturing the fine spectral structures of the small-scale K-H instability in the shear layer for flow around such a circular cylinder. Furthermore, the fine structures for the recirculation zones with two different lengths and the U-shape to V-shape profiles for the mean stream-wise velocity in the near wake region of the circular cylinder can also be obtained under a consistent grid system through different combinations for such two guide index parameters r_k1 and r_k2.