Concepts for lift improvements of a high-lift military airfoil

Abstract

Abstract : This paper describes the computational analysis of several concepts to improve the maximum lift of a military high-lift airfoil configuration. The computational results are compared with the wind-tunnel data obtained for a gap and overhang study and a Gurney flap study. In the wind tunnel experiments, optimizing the gap and over-hang and adding a Gurney flap provided the largest increases, on the order of 3-4%. These trends were duplicated in the CFD analyses. Incremental lift improvements were found using the Gurney flap and by adjusting the gap and overhand of the flap. Life improvement was also obtained by perturbing the leading edge portion of the trailing edge flap. It was found that the lift enhancements were additive, the maximum lift increased by 14% using a Gurney flap and the flap at the optimum gap and overlap. The CFD analyses used an unstructured Navier-Stokes code. The wind tunnel tests were a cooperative effort between the Navy, Boeing (St. Louis), and NASA Langley Research Center (LaRC) and were conducted in the NASA LaRC Low Turbulence Pressure Tunnel. Forces and moments and other parameters were measured on a two-dimensional airfoil model of an advanced fighter win section configured with a deflected leading edge flap, shroud and a slotted trailing edge flap.