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 × 106. The numerical results showed that, for positive angles of attack, highest values of the lift-to-drag ratio CL/CD are obtained with GF lengths between 0.25% c and 0.75% c. Particularly, an increase of 21.57 in CL/CD 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 CL/CD ratio enhancement. Additionally, an ANN has been developed to predict the aerodynamic efficiency of the airfoil in terms of CL/CD ratio. This tool allows to obtain an accurate prediction model of the aerodynamic behavior of the airfoil with GFs.
Highlights
The wind power capacity installed in the last years has been showing an increase and, the requirement for bigger rotor wind turbines is becoming increasingly more necessary
Due to their low cost, simplicity and reliable performance, Gurney flaps (GFs) are being taken into consideration within passive flow control devices, showing promising results to extend the lifetime of future wind turbines [7]
The current work presents a parametric study to evaluate the influence of different GF lengths in
Summary
The wind power capacity installed in the last years has been showing an increase and, the requirement for bigger rotor wind turbines is becoming increasingly more necessary. Fernandez-Gamiz et al [5,6] performed numerical simulations to study the characteristics of the primary vortex downstream of a rectangular VG along with a prediction model Due to their low cost, simplicity and reliable performance, GFs are being taken into consideration within passive flow control devices, showing promising results to extend the lifetime of future wind turbines [7]. Liebeck [8] discussed first this application and, subsequently, several experiments were carried out by Jeffrey et al [9] on a NACA 0012 airfoil to investigate the effects of GFs and how they provide a lift improvement and a drag reduction once properly sized They have been more widely researched for lift enhancement in aeronautics, where their advantages and applications were extensively studied by Wang et al [10] Pastrikakis et al [11] compared the performance of a helicopter rotor with GFs at low and high forward flight speeds.
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