A Study of the Effects of a Winglet on the Flow Field and Aeroacoustics for Wind Turbine Blades

The purpose of this research is to investigate the effects of a winglet on the flow field and aeroacoustics of a three dimensional wing. The SIMPLE algorithm based on finite volume method was used in this numerical analysis. For simplicity, Reynolds Averaged Navier-Stokes equations combined with Realizable turbulent model are used to solve the turbulent flow. Since the aerodynamic noise of tip vortex is induced by the turbulent flow, the flow field analysis and verification are required. First, the uniform flow past a two-dimensional airfoil and a three-dimensional wing are analyzed, in order to establish the accuracy of the simulations and understand the effects of flow induced noise on the performance of the rectangular wing. Also, tracking of the tip vortex of a rectangular wing is evaluated. The agreement between the simulated results and experimental datum is good. Therefore, all of the analyses in this study are based upon this meshing model. For the sound field analysis, the flow induced noise around a rectangular wing is computed by the Broadband Noise Source (BNS) model. Proudman’s formula was used to evaluate acoustic power per unit volume of aerodynamic noise. The study focuses on the sound power of aerodynamic noise generated by tip vortex when the flow passes through a wing and a wing with winglet. In order to understand the effects of the winglet on the aerodynamic noise, the different winglet characteristics, such as taper ratio, cant angle, and winglet length are investigated and discussed. It is found that with a winglet the dynamic coefficient is improved and the generated sound power is also reduced by about 5.4 dB. It is hoped that this study will have some contributions to the wind turbine industry.