Interface Conditions for Hybrid RANS/LES Simulations of Complex and Compressible Flows

摘要

We have demonstrated the applicability of synthetic turbulence coupled with the controlled-forcing method to generate eddies at the interface between RANS and LES in hybrid calculations. We obtained shorter transition regions and improved model accuracy. Realistic turbulence can be generated within 5 boundary-layer thicknesses of the RANS/LES interface even in cases in which the data supplied by the RANS is inaccurate, or the assumptions on which the forcing is based are invalid. We applied this technique in a variety of turbulent flows with uniformly good results. A single-block hybrid calculation was performed in a geometry that, although simple, presented several difficulties. We demonstrated that unless turbulent eddies are artificially generated at the RANS/LES interface, very significant errors appear in the flow statistics even at low order (skin-friction coefficient, mean velocity profile). Establishing realistic turbulent eddies capable to transport momentum, energy and mass, appears to be a critical factor for the accurate prediction of shallow separation by hybrid RANS/LES methods.