Three-Dimensional Effects on Dynamic Stall of Rotor Airfoil

In order to research the three-dimensional effects on the dynamic stall of rotor blade, the unsteady flowfields of finite-wing and rotor are simulated under dynamic stall conditions respectively. The unsteady RANS equations coupling with third -order Roe-MUSCL spatial discretizat ion scheme are chosen as the governing equations to predict the three dimensional flowfields of finite-wing and rotor, and the Spalart -Allmaras turbulence model is employed to calculate the viscidity of unsteady flowfields. From the simulat ion results of finite-wing, it is illustrated that the aerodynamic loads of wing would be reduced due to the effect of wing-tip vortex. As a result, the dynamic stall vortex of wing would be weakened near the wing-tip. Therefore, the peaks of lift coefficient, drag coefficient, and pitching moment coefficient are decreased near wing-tip. The spanwise flow on finite-wing would cause accumulat ion of dynamic stall vortex. As a result, the dynamic stall is restricted near the wing-root, and aggravated near wing-tip. By simulating the flowfield of a rotor in forward flight, it is illustrated that the centrifugal force would lead to generate spanwise flow. As a result, the dynamic stall characteristics of rotor would be restricted due to the Coriolis force. What is more, the decrease of angle of attack of rotor blade induced by downwash flow would inhibit the dynamic stall characteristics further.