Numerical investigation of effect of crossflow transition on rotor blade performance in hover

Abstract

In the present study, the effect of crossflow transition on the rotor blade performance in hover was investigated numerically. The simulations were conducted for the Pressure Sensitive Paint (PSP) rotor in hover by using a Reynolds-averaged Navier-Stokes (RANS) solver based on unstructured meshes. The k−ωSST model was used for simulating the turbulent flow fields and for calculating the turbulent eddy viscosity. For predicting the laminar-turbulent onset phenomena involving crossflow-induced transition, the γ−Reθt−CF+ transition model was adopted. For the comparison of the transition locations without considering the crossflow transition effect, simulations were also carried out using the γ−Reθt transition model. The calculations were made for the PSP rotor at collective pitch angles from four to 12 degrees with an interval of two degrees. To investigate the effect of blade tip Mach number, two blade tip Mach numbers of 0.585 and 0.65 were tested. The predicted results such as the transition onset location and the rotor aerodynamic performance in terms of thrust coefficient, torque coefficient and figure of merit were compared with experimental data. It was found that proper consideration of the effect of crossflow transition is critical for the accurate prediction of the laminar-turbulent transition onset location on rotor blades. The figure of merit also compares better with the experimental data when the effect of laminar-turbulent transition is included. With the addition of the crossflow transition, the figure of merit is slightly decreased, particularly at low thrust levels.