Parameter analysis of dual synthetic jets control for rotor airfoil dynamic stall under unsteady freestream

To suppress the dynamic stall phenomenon of helicopter rotors, a numerical simulation study was conducted on the unsteady aerodynamic characteristics of dual synthetic jets (DSJ) control under unsteady freestream. A moving-embedded grid method was employed to simulate the variation in freestream velocity and airfoil pitch by translating and rotating the airfoil. A multi-parameter joint analysis was carried out to examine the effects of jet angle(θjet), momentum coefficient(Cμ), excitation frequency(F+), and jet location on dynamic stall control for the NACA (National Advisory Committee for Aeronautics) 0015 airfoil. The results showed that jets located at the leading edge of the airfoil produced a more significant lift increase as the momentum coefficient increased at jet angles of 30° and 60°. However, excessively high or low momentum coefficients were found to reduce the effectiveness of control over drag and moment. When the jet angle was 90°, the DSJ exhibited less effective control over deep dynamic stall. Jets located at the midsection of the airfoil, with jet angles of 60° and 90°, were effective in suppressing rear separation, while jets with a 30° jet angle showed poorer control performance. Based on these findings, further numerical simulations were carried out on jet array control with different jet angles. The results indicated that a well-designed array with optimal jet angle combinations significantly enhanced control over varying inflow dynamic stall, achieving a maximum increase in lift coefficient of 64.98% and a maximum reduction in drag coefficient of 65.26% on average over the cycle.