Frontiers in Energy Research (Sep 2024)
Experimental study of tower noise on the basis of blade-tower interaction
Abstract
This paper investigates the relationship between unsteady flow and radiated noise in the near wake of a wind turbine tower due to the blade tower interaction (BTI) in Wind tunnel experiments. The two-dimensional hot-wire probe is used to collect the instantaneous velocity field in the BTI region, and the microphone sensor is used to collect sound field information. The effects of Reynolds stress and turbulent kinetic energy on BTI noise are further analyzed based on the instantaneous velocity field. The results show that the blade’s passing effect causes irregular velocity distribution and vortex migration and mixing in the near wake of the tower, resulting in the most significant difference in Reynolds shear stress at the 0.71R position of the blade during the blade’s transition from an azimuthal angle of 180°–210°(upward). Furthermore, a strong correlation is identified between the peak turbulent kinetic energy and the peak acoustic pressure value measured during the rotational cycle when the blade ran up to 210° azimuth angle. It is deduced that the aerodynamic noise at the rear of the tower is attributed to the increase in momentum exchange caused by fluid doping and bursting, which are driven by Reynolds shear stress. Momentum exchange induces an increase in turbulent kinetic energy, which results in fluid velocity pulsations, pressure pulsations, and, thus, noise. The reduction in fluid mixing and the reduction in pressure pulsation subsequently lead to a reduction in the noise generated by the tower. Therefore, a viable approach to reducing BTI noise involves minimizing momentum exchange.
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