Abstract: In order to simulate the flow field and calculate the aerodynamic performance of advanced helicopter rotor in hover with high accuracy, a hybrid CFD method based on the Navier-Stokes/Euler equations has been developed. The flow solver has two modules: 1) a compressible Navier-Stokes analysis near the viscous region of the blade for modeling the viscous flow and near wake; 2) an Euler flow analysis for modeling the inviscid flow regions far away from the rotor. For the solution of Naiver-Stokes/Euler equations, the combination of the third-order upwind scheme (MUSCL) and flux-difference splitting scheme without adding artificial viscosity has been employed, which can reduce the false dissipation of the rotor wake vorticity effectively. The methodology of embedded grids is also adopted to solve the flow field separately and implement the periodic boundary conditions, and a method aimed at passing information among rotor grids and background grids has been given. With the developed method, the flow fields of a 2D airfoil and the 3D M6 wing are firstly simulated and the calculated results are compared with available experimental data for the purpose of validation. Secondly, the flow fields of a four-bladed HELISHAPE 7A rotor and a four-bladed UH-60A rotor with advanced aerodynamic shapes are emphatically calculated. The calculated results including pressure distributions, sectional thrust loading of the rotors, details of the flow field on blade surface and the aerodynamic performance, etc. are compared with available experimental data, which further demonstrate the validity of this method.

Key words: helicopter, rotor, aerodynamic performance, Navier-Stokes equations, embedded grids