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Location of aerodynamic noise sources from a 200 kW vertical-axis wind turbine
Ottermo, Fredric, Möllerström, Erik, Nordborg, Anders, Hylander, Jonny, Bernhoff, Hans
Article in journal (Refereegranskat)
Noise levels emitted from a 200 kW H-rotor vertical-axis wind turbine have been measured using a microphone array at four different positions, each at a hub-height distance from the tower. The microphone array, comprising 48 microphones in a spiral pattern, allows for directional mapping of the noise sources in the range of 500 Hz to 4 kHz. The produced images indicate that most of the noise is generated in a narrow azimuth-angle range, compatible with the location where increased turbulence is known to be present in the flow, as a result of the previous passage of a blade and its support arms. It is also shown that a semi-empirical model for inflow-turbulence noise seems to produce noise levels of the correct order of magnitude, based on the amount of turbulence that could be expected from power extraction considerations.
Key words: Vertical-axis wind turbine; H-rotor; Noise; Microphone array; Beamforming