Numerical investigation of Gurney flap influences on aerodynamic performance of a pitching airfoil in low Reynolds number flow

Abstract

The main purpose of present work is to investigate the aerodynamic performance of a pitching NACA 0012 airfoil equipped with a Gurney flap in flow with low Reynolds number. The aerodynamic influences of flap location, mounting angle, and height are numerically studied. In this regard, a Lagrangian–Eulerian pressure-based numerical algorithm is developed on hybrid grids attached to a pitching solid boundary. A finite volume-based finite element method is used to discretize the governing equations. As reported in previously related studies, this unified algorithm could be used to solve the unsteady incompressible flow in domains with moving mesh and/or moving boundary with sufficient robustness and accuracy. The other advantage of this algorithm is that it does not need any type of dissipation term and/or damping function. Using this unified algorithm, the numerical experiments indicate that the Gurney flap increases the lift and drag coefficients and enhances the aerodynamic efficiency. The best aerodynamic performance is predicted for the case in which the flap is located at trailing edge with the mounting angle of 90°. The flap height is predicted to have different and most impacts on aerodynamic efficiency during upstroke and downstroke. The numerical results show that the airfoils equipped by flaps with height between 6% and 12% of the airfoil chord are the most aerodynamically efficient airfoils. Changing of lift and drag coefficients are due to increase of effective camber and thickness in all cases.