Numerical Investigation of Powered High-Lift Model with Externally Blown Flap

The externally blown flap is an approach of powered-lift technology utilizing conventional pod-mounted engines to blow exhaust over the flap surfaces. Based upon multiblock structured grid techniques and three-dimensional Reynolds-averaged Navier-Stokes computational methods, a powered high-lift principle model with externally blown flap is constructed for analysis. Different influencing factors, including engine position, engine-exhaust condition, flap deflection, and flap gap, are investigated in detail to improve powered high-lift effects. Then, flow-control techniques, such as the cove tab and downward deflection of the spoiler, are studied. The cove tab can be helpful for longitude-trim and stability problems, whereas the spoiler downward deflection can help increase lift-to-drag ratios. Both the cove tab and spoiler downward deflection can contribute to the augmentation of the lift coefficients and the elimination of the flow separation over the flap, as well as the reduction of jet-flow spanwise spreading on the leading edge of the lower flap.