Stall control on the wind turbine airfoil via the single and dual-channel of combining bowing and suction technique

Abstract

Based on the single-channel jet control strategy with a suction slot on the upper surface and injection slots near the trailing edge on the lower surface, proposed in this work is a novel flow control technique, known as the dual-channel jet, which amalgamates the beneficial aspects of leading-edge suction and a suction slot positioned downstream of the airfoil's maximum thickness position. To demonstrate the superior aerodynamic characteristics of the dual-channel over the single-channel, comprehensive comparisons of three distinct control strategies are made with two jet momentum coefficients employed on the S809 airfoils. Simulations using Reynolds-averaged Navier-Stokes with a transitional SST turbulence model are performed, showing that the position of a suction slot in the single-channel significantly impacts its ability to inhibit separation, while the dual-channel jet facilitates a fuller boundary layer velocity profile and a posterior shift in the stagnation point, outperforming the single-channel approach in removing low-momentum fluid and increasing the airfoil virtual camber. In the case with a jet strength of 0.004 and pitching oscillation, compared to the clean airfoil, the dual-channel achieves a remarkable 84.21 % increase in the lift coefficient at 18.1°, and the control efficiency can further be enhanced with the momentum coefficient increased.