Improved hybrid model for transitional separated flows over a rough compressor blade

It is known that boundary layer transition and turbulent separation flow after transition can be influenced significantly by surface roughness. Since the traditional hybrid RANS/LES method cannot predict the boundary layer transition, and the RANS-based transition model cannot accurately simulate the massively separated flow, the present study sought to build an effective modeling strategy for the laminar, roughness-induced-transition and attached turbulence/massively separated flows that couples the Very-Large-Eddy-Simulation (VLES) model and a transition model considering roughness effects. Because the hybrid function between the transition model and VLES model constructed in the previous version still has some flaws, there is still a large laminar flow indication area in the turbulent flow region, which will reduce the simulation accuracy of the turbulent flow after transition. In this paper, the hybrid function is improved, which is examined in the simulation of the high-subsonic flow around the V103 compressor blade. Our analysis shows that the new hybrid model operates in the flow around the V103 compressor blade. The predictions of laminar separation bubble-induced transition, separation evolution, and reattachment are in accord with measurements and the LES results over both smooth and rough surfaces, indicating that the present transitional VLES method can achieve the simulation accuracy close to the LES method while reducing the computational cost.