Numerical Investigation of the Effects of Gurney Flap on the Aerodynamic Characteristics of A821201 Airfoil

Two-dimensional steady Navier-Stokes equations with Spalart-Allmaras turbulence model were solved to explore the effects of Gurney flap on the aerodynamic behavior of an A821201 airfoil. This airfoil was designed specifically for use on the V-22 tiltrotor aircraft. Firstly, Gurney flaps with the heights ranging from 0.5 to 4% of the chord are investigated. The computational results show that Gurney flap can significantly augment the airfoil lift, and the Gurney flap with a height of 1% chord length provides the highest lift-to-drag ratio among the investigated configurations. In comparison with the clean A821201 airfoil, the maximum lift coefficient is increased by 17.3, 26.2, 38.3 and 53.7% for the 0.5, 1, 2 and 4% chord length height Gurney flaps, respectively. In addition, the airfoil drag and nose-down pitching moment are also increased with Gurney flap height. Secondly, the impacts of Gurney flap location are numerically studied. The distance between the mounting location and the trailing edge of the airfoil is s=0, 5 and 10% chord length, respectively. It is demonstrated that the best aerodynamic performance can be achieved when the Gurney flap is installed at the trailing edge (s=0). Furthermore, the surface pressure distribution, boundary layer velocity profile, and flowfield structure are illustrated, which are useful to understand the mechanisms of Gurney flap on the aerodynamic characteristics of tiltrotor airfoil. © 2022 The Aeronautical and Astronautical Society of the Republic of China. All rights reserved.