Sound propagation analysis of a 10 MW wind turbine: Influence of the tower, operational states, and atmospheric conditions

Accurate prediction of wind turbine noise propagation over long distances is critical to mitigate community impact but remains challenging due to complex interactions between wake and atmospheric conditions. This study investigates the sound propagation of a 10 MW wind turbine using a hybrid computational approach that combines high-fidelity flow simulations and parabolic equation (PE) modeling. Large-eddy simulations with actuator lines (for the rotating blade modeling) and immersed boundary methods (for the tower and nacelle modeling) resolve the turbulent wind turbine wake structure, including rotor, tower, and nacelle effects, under rated (11.4 m/s) and near cut-out (24 m/s) wind conditions, with constant inflow and neutral atmosphere boundary layer (ABL) inflows. Noise propagation is analyzed using a wide-angle Parabolic Equation (PE) solver, utilizing as base flow wake generated by the high fidelity large-eddy simulation solver. The methodology allows the study of the acoustic refraction of wind turbine noise under a variety of conditions. We systematically study the effects of the rotor (without tower or nacelle), the full turbine with constant inflow, and the full turbine with a neutral ABL, for rated and cut-out operating conditions. The results demonstrate that wake-induced velocity gradients significantly alter sound propagation paths, with the tower and nacelle introducing asymmetric refraction effects that amplify near-ground noise levels. Atmospheric refraction profiles strongly modulate propagation: upward refraction (e.g., nighttime conditions) create quiet zones, while downward refraction exacerbates noise levels. Under rated condition, the ISO-9613-2 method and the solver PE without wake predict lower sound pressure level (maximum 5 dB) than the PE considering wakes (both with constant inflow and neutral ABL inflow) at critical residential ranges (500–1000 m downstream of the turbine), highlighting the need for advanced models for regulatory compliance. The study underscores the importance of integrating wake and atmospheric effects in noise assessments, providing a framework for optimizing wind farm layouts and mitigating acoustic environmental impact.