Numerical investigation of an active Gurney flap performance in a new flow control strategy to reduce dynamic stall effects of helicopter blade section in forward flight condition

A new flow control strategy is proposed to mitigate the dynamic stall effects on a helicopter blade section during forward flight condition. This approach involves modification of the blade section pitch angle on the retreating side. However, to compensate for the resulting loss of lift due to the reduction in angle of attack, an active Gurney flap (AGF) is incorporated into the blade section. The AGF is positioned on the lower surface of the SSC-A09 airfoil at 95% chord from the leading edge. The flow field around the pitching blade section equipped with the AGF is simulated using two-dimensional compressible unsteady Reynolds-averaged Navier–Stokes equations with the k-w SST turbulence model. Forward flight conditions, including variable Mach number flow and the pitching motion of the blade, are modeled using the zone motion method, while the deployment and retraction of the AGF are implemented using the overset grid method. The investigation focuses on numerically evaluating the performance of the AGF under various combinations of deployment and retraction azimuth angles. Results demonstrate that the proposed strategy reduces drag force by up to 37% compared to the base blade section while maintaining the same lift force and balance. Notably, reducing the pitch angle on the retreating side decreases the maximum magnitude of negative aerodynamic damping of the blade section equipped with the AGF by up to 39%, compared to the base blade section. This reduction enhances blade stability and mitigates stall flutter divergence.