Wake-induced variations in noise levels and amplitude modulation for two interacting wind turbines

TL;DR

This study uses numerical simulations to analyze how different turbine arrangements affect sound levels and amplitude modulation caused by turbine interactions, with implications for environmental impact.

Contribution

It introduces a combined simulation framework to quantify wake effects on sound propagation and amplitude modulation in various turbine configurations.

Findings

Wake-induced flow focusing increases SPL and AM downstream.

Side-by-side and staggered setups show limited SPL increase and reduced AM.

Rotor speed differences cause beating effects and intermittent AM.

Abstract

The influence of turbine-turbine interactions on sound propagation is investigated using numerical simulations. Three configurations are examined: turbines aligned downstream of each other, placed side by side, and arranged in a staggered pattern. The simulation framework combines large-eddy simulations for aerodynamic interactions, an aeroacoustic source model to simulate turbine sound emission, and parabolic equation methods for sound propagation. When a second turbine is positioned directly downstream, wake-induced flow focusing enhances sound pressure levels (SPL) and amplitude modulation (AM) by several decibels downwind. In side-by-side and staggered configurations, SPL increases are limited (<2 dBA), and AM is generally reduced due to spatial averaging. Distinct AM patterns emerge in regions where acoustic contributions from both turbines are comparable. For identical rotor speeds, AM is strongly affected by the angular offset between rotors. When rotor speeds differ slightly, beating effects occur, resulting in intermittent AM. These findings highlight the sensitivity of AM to rotor dynamics, a key factor influencing sound perception, with implications for environmental impact and turbine siting.