Experimental study on the flow control mechanism of blowing flap

Abstract

Blowing flap flow control can significantly enhance airfoil lift, meeting the requirements for short takeoff and landing as well as high-lift performance in aircraft. However, the flow control mechanisms in hybrid wing models with blowing flaps are complex. To investigate the flow control principles and internal mechanisms of blowing flaps, this study conducted wind tunnel tests under a Reynolds number of 4.321 × 10⁵ to assess joint control effects. First, based on force measurement test results, this paper analyzed the flow control patterns under various flap deflection angles, blowing coefficients, and their combined effects. The research results indicate that under typical operating conditions, the impact of jet reaction force on the drag coefficient is 5.2%, making its effect on the force balance measurements negligible. With the application of blowing control, the effective deflection angle increases from 30° to 40°. Additionally, blowing flap control significantly improved the lift-to-drag ratio of the model at low angles of attack. When the flap deflection angles were set to 30° and 40°, the maximum lift-to-drag ratio increases reached 181.36% and 208.91%, respectively. Subsequently, particle image velocimetry (PIV) was used to visualize the high-lift gain flow field, revealing the internal flow control mechanisms of lift enhancement with large flap deflection angles under blowing control. The PIV results indicate that a large flap deflection angle causes significant flow separation on the flap. With the application of blowing control, this flow separation is substantially suppressed, which effectively increases the camber of the model and thereby significantly enhances its lift.