Computational Acoustic Beamforming of Noise Source on Wind Turbine Airfoil

Abstract

A new method, Computational Acoustic Beamforming, is proposed in this thesis. This novel numerical sound source localization methodology combines the advantages of the Computational Fluid Dynamics (CFD) simulation and experimental acoustic beamforming, which enable this method to take directivity of sound source emission into account while maintaining a relatively low cost. This method can also aid the optimization of beamforming algorithm and microphone array design. In addition, it makes sound source prediction of large structures in the low frequency range possible. Three modules, CFD, Computational Aeroacoustics (CAA) and acoustic beamforming, are incorporated in this proposed method. This thesis adopts an open source commercial software OpenFOAM for the flow field simulation with the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model. The CAA calculation is conducted by an in-house code using impermeable Ffowcs-Williams and Hawkings (FW-H) equation for static sound source. The acoustic beamforming is performed by an in-house Delay and Sum (DAS) beamformer code with several different microphone array designs. Each module has been validated with currently available experimental data and numerical results. A flow over NACA 0012 airfoil case was chosen as a demonstration case for the new method. The aerodynamics and aeroacoustics results are shown and compared with the experimental measurements. A relatively good agreement has been achieved which gives the confidence of using this newly proposed method in sound source localization applications.