Numerical Prediction of the Aerodynamics and Aeroacoustics of a 25 kW Horizontal Axis Wind Turbine

Abstract

In this study, low-frequency-based numerical methods were used to predict the noise radiating from rotating horizontal axis wind turbine (HAWT) blades. The flow parameters in the vicinity of blade surfaces, which are required for the Ffowcs Williams–Hawkings (FW–H) equation, were calculated using ANSYS FLUENT. The numerical model was verified against the experimental re-sults from the National Renewable Energy Laboratory Phase VI wind turbine blades. The coupling analysis was integrated with four Reynolds-averaged Navier–Stokes turbulence models and FW–H equation under various boundary conditions. The standard k-ε, SST k-ω, and V2f turbulence models produced results in agreement with the available experimental pressure coefficient and relative velocity distribution data in the flow fields. Under the verification of aeroacoustic results, the SST k-ω turbulence model were more consistent with the LES data. An Institute of Nuclear Energy Research (INER) 25-kW HAWT was employed to predict noise frequency distribution at nine points on the tower on the windward and leeward sides under different operating conditions. Noise frequency distributions on the windward and leeward sides exhibited slight differences, whereas those on the left and right sides of the tower were different because of wind-shear influence. Under operating conditions, the decibels of the low-frequency noise at 0–200 Hz were ∼25–40 dB, and the noise frequency distributions on the windward and leeward sides were similar. With increasing distance, the decibel number of the monitoring point ∼25 m away dropped to 0 dB. For the noise prediction in Case 2 (wind speed = 12 m/s, pitches = 18°), the decibel number at 50 m was ∼25 dB and was ∼15 dB at 70 m. In Case 3 (wind speed = 18 m/s, pitches = 33°), the decibel number at 50 m was ∼30 dB and was ∼20 dB at 70 m. The peak amplitude of the noise was inversely proportional to the increasing distance from the tower but proportional to the wind and rotational speeds.