Parametric study of a Gurney flap implementation in a DU91W(2)250 airfoil

Abstract

The growth in size and weight of wind turbines over the last years has led to the development of flow control devices, such as Gurney flaps (GFs). In the current work, a parametric study is presented to find the optimal GF length to improve the airfoil aerodynamic performance. Therefore, the influence of GF lengths from 0.25% to 3% of the airfoil chord c on a widely used DU91W(2)250 airfoil has been investigated by means of RANS based numerical simulations at Re = 2 × 10 6 . The numerical results showed that, for positive angles of attack, highest values of the lift-to-drag ratio C L /C D are obtained with GF lengths between 0.25% c and 0.75% c. Particularly, an increase of 21.57 in C L /C D ratio has been obtained with a GF length of 0.5% c at 2 ◦ of angle of attack AoA. The influence of GFs decreased at AoAs larger than 5 ◦ , where only a GF length of 0.25% c provides a slight improvement in terms of C L /C D ratio enhancement. Additionally, an ANN has been developed to predict the aerodynamic efficiency of the airfoil in terms of C L /C D ratio. This tool allows to obtain an accurate prediction model of the aerodynamic behavior of the airfoil with GFs.