Coupled aerodynamic and aeroacoustic effects of trailing-edge serrations in a low-Reynolds-number vertical-axis wind turbine (VAWT)

Abstract

Rotating machinery operating at low-to-moderate Reynolds numbers is governed by complex transport phenomena that strongly influence aerodynamic loading, noise emission, and structural fatigue. In vertical-axis wind turbines (VAWTs), cyclic variations in angle of attack and Reynolds number make trailing-edge flow physics a critical factor in both performance and durability. This study experimentally investigates the impact of trailing-edge serrations (TES) on the coupled aerodynamic and aeroacoustic behaviour of a representative VAWT airfoil. Aerodynamic forces and pitching moments are measured to assess load redistribution, while anechoic measurements quantify broadband noise generated by turbulent boundary-layer trailing-edge interactions. Results indicate that TES modify boundary-layer coherence and turbulence convection mechanisms without significant degradation of aerodynamic efficiency. However, a systematic increase in pitching moment is observed, suggesting a non-negligible contribution to cyclic loading. All serrated configurations achieve broadband noise reduction, with sound pressure level decreases of up to 4 dB. A clear trade-off between aerodynamic loading and noise mitigation is identified, with intermediate serration geometries providing the most favourable compromise. These findings offer valuable insights for the design of low-Reynolds-number rotating machinery, including wind turbines and compact turbomachinery systems.