LES-based numerical prediction of the trailing edge noise in a small wind turbine airfoil at different angles of attack

Abstract

Abstract In this paper, the aerodynamic field around a FX 63–137 airfoil for four angles of attack and low Reynolds numbers was simulated with a Large Eddy Simulation (LES). Following, an acoustic analogy method was employed to calculate the airfoil trailing edge (TE) noise. In this second scheme step, the far-field acoustic pressure was predicted from the LES source terms using two different methods based on Lighthill's analogy: Curle's surface approach and Ffowcs-Williams and Hall's volumetric analogy (FW-Hall). Numerical results have been validated with hot-wire anemometry for the aerodynamic fields, thus verifying the accuracy of the CFD simulation for the prediction of noise propagation to the far field. Additionally, aeroacoustic results were validated with experimental measurements carried out in an anechoic wind tunnel using a frequency analyzer. The FW-Hall formulation shows a better agreement with the experiments, especially in the range of frequencies corresponding to the trailing edge, whereas Curle's analogy overpredicts airfoil sound. An exhaustive analysis of the aerodynamic flow field has been performed in order to better understand the generation mechanisms of the TE noise. The aeroacoustic calculations presented in this work contribute to develop a more reliable and efficient prediction methodology based on the Computational Aeroacoustics Approach (CAA).