Experimental and numerical investigation of blade–tower interaction noise

Abstract

This paper describes the generation of blade-tower interaction (BTI) noise from upwind turbines and pylon-mounted fans using a combination of experimental and numerical means. An experimental rotor-rig was used in an anechoic chamber to obtain BTI acoustic data under controlled conditions. A computational model, based on the solution of the unsteady Reynolds Averaged Navier Stokes (URANS) equations and Curle's acoustic analogy, was used to describe the generation of fan and simplistic model of wind turbine BTI noise by the rotor-rig. For both the fan and model wind turbine case, the tower was found to be a more significant source of BTI noise than rotor blades. The acoustic waveforms for both turbine and fan are similar; however, in the case of the turbine, the blade contribution reinforces that from the tower, while in the case of a fan, there is some cancellation between the tower source and the blade source. This behavior can be explained by the unsteady aerodynamics occurring during BTI.

Influence of atmospheric conditions on measured infrasound from wind turbines

“…This local velocity deficit produces a change in the angle of attack of the passing blade, thus a periodical change in its aerodynamic loading, resulting in a discrete pressure level at the BPF [7]. Recently, Yauwenas et al [8] and Zajamsek et al [9] hypothesized that the blade-tower interaction noise could be attributed to the aerodynamic disturbances generated by the blades and impacting on the tower. Through numerical simulations, they could identify the tower as the dominant pressure generation point of BPF noise.…”

Investigations on Low Frequency Noises of On-Shore Wind Turbines

“…One of the reasons for this development are slow approval processes often caused by local resistance in terms of environmental aspects (e.g., animal protection, deforestation) and expected visual or acoustic disturbances caused by the planned wind turbines (WT) [2]. In many cases, it is argued that low frequency and infrasonic (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) acoustic emissions in combination with low frequency vibrations lead to the perceptibility of wind turbines even at large distances.…”

“…In fact it is physically indisputable that the elastic rotor blades cause air pressure changes with every passage of the tower, which are spread as acoustic waves in the atmosphere [9][10][11]. Moreover, other rotating parts of a WT (e.g., power train, generator) also cause acoustic emissions [12][13][14].…”

Recent Advances in Wind Turbine Noise Research

“…Recent work [30] has suggested that impulsive aerodynamic loading caused by the blades interacting with the wind speed deficit in the vicinity of the support tower (due to the blocking effect of the tower) can result in low-frequency aerodynamic noise generation. It was shown that this contribution was twice that of the noise caused by blades passing through the air.…”