Abstract
The unsteady nature of wind turbine noise is a major reason for annoyance. The variation of far-field sound pressure levels is not only caused by the continuous change in wind turbine noise source levels but also by the unsteady flow field and the ground characteristics between the turbine and receiver. To take these phenomena into account, a consistent numerical technique that models the sound propagation from the source to receiver is developed. Large eddy simulation with an actuator line technique is employed for the flow modelling and the corresponding flow fields are used to simulate sound generation and propagation. The local blade relative velocity, angle of attack, and turbulence characteristics are input to the sound generation model. Time-dependent blade locations and the velocity between the noise source and receiver are considered within a quasi-3D propagation model. Long-range noise propagation of a 5 MW wind turbine is investigated. Sound pressure level time series evaluated at the source time are studied for varying wind speeds, surface roughness, and ground impedances within a 2000 m radius from the turbine.
Highlights
As a result of increasing demand for renewable energy, fewer suitable land-based sites are available for wind farms
Accurate predictions of far-field wind turbine noise require the knowledge of the source levels and a realistic representation of the medium between the turbines and the receivers in which the sound propagation takes place
A commonly used method to model the wind turbine noise source was described in Refs. 11 and 12
Summary
As a result of increasing demand for renewable energy, fewer suitable land-based sites are available for wind farms. Accurate predictions of far-field wind turbine noise require the knowledge of the source levels and a realistic representation of the medium between the turbines and the receivers in which the sound propagation takes place. This is a complex task as both phenomena depend on a wide range of parameters. The method divides the wind turbine blades into airfoil segments and sums the contribution of each segment’s noise levels calculated using semiempirical relationships This source model along with simple propagation calculations were used in Ref. 13 and the results were compared to near-field experiments. Even though these models represented the source more accurately, the propagation effects were not well studied
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