In the rotating coordinate system

Reynolds-averaged Navier-Stokes (RANS) equations and Spalart-Allmaras (S-A) equation model were coupled as a new strongly coupled RANS equation

then a strongly coupled RANS algorithm based on overlap grids was proposed and applied to simulate helicopter rotors viscous flow in hover. In order to improve efficiency

a new implementation method of multigrid algorithm based on overset grids was proposed for solving the difficulty of implementation in chimera grids system. The effectiveness of strongly coupled RANS method and the proposal of multigrid algorithm based on chimera grids was verified using Caradonna-Tung (C-T) and ONERA 7A hover test cases. The results show that the proposal of multigrid algorithm based on overlap grids has much higher efficiency

and the speed up ratio of three-level multigrid is about 7.7; the accuracy of strongly coupled RANS algorithm is super higher than loosely coupled RANS algorithm

especially in the prediction of performance parameters relevant to drag force.