Yongyan Chen

To investigate the effects of turbulence intensity on wake velocity evolution in groove-flap vertical-axis wind turbines (VAWTs) during operation, this study proposes the Dynamic Mode Decomposition (DMD) method for multi-modal visualization of wake flow fields in both baseline and groove-flap VAWTs. The spatiotemporal wake characteristics were analyzed under turbulence intensities of 0.1%, 8%, and 15%, and application scenarios for both VAWT configurations were recommended. The results reveal that spatiotemporal variations in wake velocity become increasingly unstable in both axial and normal directions with rising turbulence intensity. The baseline VAWT demonstrates simpler and more stable wake structures with periodically arranged vortices, making it suitable for low-turbulence environments such as suburban areas. In contrast, the groove-flap VAWT enhances wake mixing through localized perturbations, showing superior adaptability to urban deployment scenarios including street canyons and skyscraper rooftops.

The noise generated by wind turbines is a critical issue that impacts both operational efficiency and public health, necessitating a comprehensive investigation into its sources and propagation. This study investigates the near-wake noise of an S-airfoil horizontal-axis wind turbine using statistically optimized near-field acoustic holography (SONAH) with a 60-channel rotating microphone array in an open-jet wind tunnel. The results show that the noise in the wake is predominantly caused by the rotation of the rotor. The position of the highest sound pressure level concentration is at 0.78R of the blade under different operating conditions within the rotor’s rotation plane. The sound pressure level radiates outward in a spiral pattern across eleven identified sections, progressively decreasing with distance. The most significant attenuation occurs between 0.04 m and 0.06 m from the rotating surface. This study provides foundational insights into the near-field acoustic characteristics of wind turbines, serving as a valuable reference for noise reduction strategies and environmental impact assessments in wind energy projects.

To address the low wind energy utilization efficiency of vertical axis wind turbines (VAWTs) and enhance their engineering applicability, cavity and groove-flap structures were incorporated into turbine blades. Numerical simulations were performed to optimize these configurations, followed by wind tunnel experiments investigating output power variations of three VAWT types under different wind speeds at installation angles of 0°, 2°, 4°, and 6°. The Omega criterion was employed to comparatively analyze vortex evolution patterns at the leading and trailing edges for installation angles of 0°, 3°, and 5°. Experimental results demonstrated nonlinear growth in output power with increasing wind speed and rotational velocity, with groove-flap VAWTs exhibiting superior performance. The optimal installation angle was identified within 2.5–3.5°, where appropriate angles reduced adverse pressure gradients, delayed boundary layer separation, and mitigated vortex shedding effects. Excessive angles induced vortex accumulation and wake disturbances, compromising flow field stability. This study provides critical insights for optimizing VAWT aerodynamic performance through structural modifications and installation angle adjustments.