A COMPUTATIONAL STUDY ON BLADE-VORTEX INTERACTION FOR COAXIAL ROTORS IN HOVER USING A NOVEL HIGH-ORDER SCHEME

Accurate prediction of tip vortices is crucial for mechanism study on the blade-vortex interaction(BVI) for coaxial rotors. A new high-order scheme (WENO-K) proposed by our research group is employed to minimize numerical dissipation and extended to numerical simulation of unsteady flows dominated by tip vortices around hovering coaxial rotors. WENO-K is referred to as an adaptively optimized WENO scheme with Gauss-Kriging reconstruction, and its advantage is to reduce dissipation in smooth regions of flow while preserving high-resolution around discontinuities. Here WENO-K scheme is adopted to reconstruct left and right state values within the Roe Riemann solver updating the inviscid fluxes on a structured dynamic overset grid. To minimize the accuracy loss for high-order reconstruction on artificial boundaries of overset grid, a method of multilayer fringes is proposed to carry out interpolation between background grid and blade grid. A conservative method is developed for the flow variable interpolation in the overset grid interface. High-accurate numerical simulation of vortex wake structure over a coaxial rotor was carried out. The results indicates that the tip vortex structure and its unsteady generation, development and evolution process can be completely simulated and preserved by WENO-K scheme, and the pressure impulses on the blade caused by BVI can also be well captured.