Aerodynamics simulation of a rotorcraft main-rotor blade in a hovering condition

Abstract

Aerodynamic simulations of rotorcraft main rotor blades under hovering conditions were performed. The compressible Navier-Stokes solver CFL3D was applied in hover to a UH-60A model rotor blade to validate its ability for hover performance prediction. This analysis utilizes the second-order Roe scheme for convective fluxes and the second-order central differencing for the viscous fluxes. The elastic twist and coning angle measured in experiments were included in the blade geometry. Comparisons with experimental thrust, torque, and figure of merit were made, and the flow field was examined in detail. The comparison with the experimental thrust coefficient and tip vortex position was considered to be acceptable for the current study using meshes with 15 million cells. However, there are discrepancies with experimental data. These are believed to be due to fully-turbulent boundary condition at the blade surface, resulting in poor predictions of torque coefficient. Manually tripped cases that assume a specific area as a laminar condition showed better torque coefficient and figure of merit prediction than the fully-turbulent case. Therefore, it is possible to simulate a more practical flow by considering the transition effect.