Assessment of Rotor Aerodynamic Performances in Hover Using an Unstructured Mixed Mesh Method

Abstract

In the present study, numerical simulations were conducted to assess rotor aerodynamic performances in hover flight conditions. To calculate the flow around the helicopter rotors in a high-order manner, an unstructured mixed mesh flow solver was developed. The proposed mixed mesh methodology involves body-fitted prismatic/tetrahedral mesh in the near-body region around the blade and adaptive Cartesian mesh in the off-body region. In the off-body region away from the blade, high-order schemes and solution-adaptive mesh refinement were adopted to enhance the accuracy of the vortex resolution in the wake region. To interpolate the flow variables between the two mesh regions, an overset mesh technique was applied. Validation of the present mixed mesh flow solver was made for a two-bladed Caradonna-Tung rotor configuration by comparing the aerodynamic loadings and the vortex trajectories with experimental data. Then, the flow solver was applied to the S-76 rotor configuration, and the aerodynamic performance, such as rotor thrust, torque and figure of merit, were compared with experimental data. The flow characteristics around the rotor, such as the tip vortex trajectory, circulation strength of the tip vortex for the wake age, were also assessed.