the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 03 Apr 2024
Impact of a Two-Dimensional Steep Hill on Wind Turbine Noise Propagation
Abstract. Wind turbine noise propagation in a hilly terrain is studied through numerical simulation in different scenarios. The linearized Euler equations are solved in a moving frame that follows the wavefront, and wind turbine noise is modeled with an extended moving source. We employ large eddy simulations to simulate the flow around the hill and the wind turbine. The sound pressure levels (SPL) obtained for a wind turbine in front of a 2D hill and a wind turbine on a hilltop are compared to a baseline flat case. First, the source height and wind speed strongly influence sound propagation downwind. We find that topography influences the wake shape inducing changes in the sound propagation that drastically modify the SPL downwind. Placing the turbine on the hilltop increases the average sound pressure level and amplitude modulation downwind. For the wind turbine placed upstream of a hill, a strong shielding effect is observed. But, because of the refraction by the wind gradient, levels are comparable with the baseline flat case just after the hill. Thus, considering how terrain topography alters the flow and wind turbine wake is essential to accurately predict wind turbine noise propagation.
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Status: open (until 17 May 2024)
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RC1: 'Comment on wes-2024-36', Anonymous Referee #1, 28 Apr 2024
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General Comments
In the manuscript, the authors conduct an extensive systematic study of wind turbine noise in various terrain scenarios. The computational approach combines the mean velocity from LES with sound propagation using linearized Euler equations. The authors consider no terrain, a wind turbine upwind of a hill, and a wind turbine atop a hill. The analysis is extensive, the conclusions are consistent with prior work, and the authors are careful to make comparisons to similar work in the past. Overall, the authors demonstrate the utility of the linear Euler equations approach. However, there are a few issues that need to be addressed.
Specific Comments
1. The authors use the mean velocity field from LES but do conduct analysis that is inherently unsteady with the single blade sound. What is the influence of using the mean velocity on the single blade analysis? Furthermore, what is the influence of using the mean velocity altogether? Could there be any additional focusing/defocusing of sound due to the unsteady flow field?
2. To assess the influence of the wind speed, which the authors deem to be less important, the LES results are simply scaled. How accurate is this scaling on even the mean velocity profile? For such a strong conclusion, the mean velocity scaling needs to be validated.
3. Only a single hill is considered whose height is the same as the wind turbine rotor diameter and hub height. What is the role of the hill characteristics in the conclusions? Would a smaller/larger hill change the conclusions? Would a less steep hill change the conclusions? These would be very welcome additions to a revised manuscript.
Citation: https://doi.org/10.5194/wes-2024-36-RC1
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