R.Makarewicz, R.Gołębiewski, The Influence of a low level jet on the thumps generated by a wind turbine, Renewable and Sustainable Energy Reviews, 104 (2019), p. 337–342 (DOI: 10.1016/j.rser.2019.01.022)
ABSTRACT
Annoyance caused by wind turbine noise is assessed in terms of the A-weighted time average sound level. The amplitude modulation of a wind turbine, defined as the fluctuations in the noise level, increases the annoyance caused. There are two types of modulation: normal (in close proximity to the turbine) and abnormal (at a distance from the turbine). The latter is perceived as very annoying thumps. To determine the noise level of thumps, the standard simulations divide the noise source (turbine blades) into hundreds of segments. Then, taking refraction and other wave phenomena into account, the segment contributions to the sound level at the receiver are estimated. These steps are repeated for all the blade segments at each angular position of the blade. In the present study, a simple phenomenological model of noise generation and propagation is proposed. It is based on the finding that the blade tips are the major contributors to the sound power of a wind turbine. Since the abnormal modulation of wind turbine noise is heard at a long distance, refraction is taken into account for a special case of a low level jet. To apply the proposed model, two in situ noise measurements are required: within the fully insonified zone and within the partly insonified zone.
https://www.sciencedirect.com/
