Numerical Study Of Dynamic Stall Control Via Wavy Leading-edge Modification

The stall is very common during aircraft flight, which is tremendously dangerous. However, the mechanical performance can be enhanced via the dynamic stall. It is reported that the wavy leading-edge modification is conducive to delaying stall, while the gurney flap contributes to the improvement of lift during prestall region. It is a prospective study to explore the dynamic stall control of the wavy leading-edge modification and the combination of the wavy leading-edge and the gurney flap.Numerical simulations based on the open source code of OpenFOAM were performed to investigate the differences of mechanical performance and flow characters between the wavy leading-edge wing and conventional smoothing leading edge wing. The study is executed by solving the Reynolds-averaged Navier-Stokes equations and the implement of the k-ω SST turbulent model. The shape parameters of leading-edge and the kinematic parameters were discussed. The mechanical performance and flow property of the combination of wavy leading-edge and wavy trailing edge, as well as the combination of wavy leading-edge and gurney flap, were also analyzed to obtain the more effective ways to control dynamic stall.The results indicated that the interaction between stronger normal-wise and span-wise, weaker flow-wise vortices triggered by the wavy leading edge leads to complex vortices attaching on the upper surface of the wing during deep stall, especially in the range of high angles of attack. Hence the performance is enhanced by the wavy leading edge. The leading-edge wave amplitude has slight effect on the mean lift coefficient, while moving rotating axis forward or a larger flapping amplitude can lead to higher mean values of lift coefficient. In light stall, the wavy leading-edge modification is not effective in dynamic stall. Changing the leading-edge wavenumber, wavelength and the wavy stern modification have a little effect on the mechanic performance. However, deploying the gurney flap at the stern of wavy leading-edge wing can more greatly improve the lift coefficient, since the existence of gurney flap results in higher positive pressure region on the lower surface and stronger flow-wise and normal-wise vortices that keep the vortices more stable, which brings about higher lift coefficient.