Trailing Edge Noise Source Characteristics for Wind Turbine Airfoils

This paper deals with the topic of upper surface blowing noise. Using a model-scale rectangular nozzle of an aspect ratio of 10 and a sharp trailing edge, detailed noise contours were acquired with and without a subsonic jet blowing over a flat surface to determine the noise source location as a function of frequency. Additionally, velocity scaling of the upper surface blowing noise was carried out. It was found that the upper surface blowing increases the noise significantly. This is a result of both the trailing edge noise and turbulence downstream of the trailing edge, referred to as wake noise in the paper. It was found that low-frequency noise with a peak Strouhal number of 0.02 originates from the trailing edge whereas the high-frequency noise with the peak in the vicinity of Strouhal number of 0.2 originates near the nozzle exit. Low frequency (low Strouhal number) follows a velocity scaling corresponding to a dipole source where as the high Strouhal numbers as quadrupole sources. The culmination of these two effects is a cardioid-shaped directivity pattern. On the shielded side, the most dominant noise sources were at the trailing edge and in the near wake. The trailing edge mounting geometry also created anomalous acoustic diffraction indicating that not only is the geometry of the edge itself important, but also all geometry near the trailing edge.

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The Effect of Airfoil Shape on Trailing Edge Noise

Journal of Theoretical and Computational Acoustics ◽

10.1142/s2591728518500202 ◽

2019 ◽

Vol 27 (02) ◽

pp. 1850020 ◽

Cited By ~ 1

Author(s):

Seongkyu Lee

Keyword(s):

Boundary Layer ◽

Noise Source ◽

Source Region ◽

Low Frequency ◽

Suction Side ◽

Frequency Noise ◽

Pressure Side ◽

Trailing Edge ◽

Trailing Edge Noise ◽

Naca0012 Airfoil

This paper investigates the effect of airfoil shape on trailing edge noise. The boundary layer profiles are obtained by XFOIL and the trailing edge noise is predicted by a TNO semi-empirical model. In order to investigate the noise source characteristics, the wall pressure spectrum is decomposed into three components. This decomposition helps in finding the dominant source region and the peak noise frequency for each airfoil. The method is validated for a NACA0012 airfoil, and then five additional wind turbine airfoils are examined: NACA0018, DU96-w-180, S809, S822 and S831. It is found that the dominant source region is around 40% of the boundary layer thickness for both the suction and pressure sides for a NACA0012 airfoil. As airfoil thickness and camber increase, the maximum source region moves slightly upward on the suction side. However, the effect of the airfoil shape on the maximum source region on the pressure side is negligible, except for the S831 airfoil, which exhibits an extension of the noise source region near the wall at high frequencies. As airfoil thickness and camber increase, low frequency noise is increased. However, a higher camber reduces low frequency noise on the pressure side. The maximum camber position is also found to be important and its rear position increases noise levels on the suction side.

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Comparison of inflow-turbulence and trailing-edge noise models with measurements of a 200-kW vertical axis wind turbine

Journal of Physics Conference Series ◽

10.1088/1742-6596/1222/1/012028 ◽

2019 ◽

Vol 1222 ◽

pp. 012028 ◽

Cited By ~ 1

Author(s):

E. Möllerström ◽

F. Ottermo

Keyword(s):

Wind Turbine ◽

Vertical Axis ◽

Vertical Axis Wind Turbine ◽

Trailing Edge ◽

Trailing Edge Noise ◽

Inflow Turbulence ◽

Noise Models

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Computational Acoustic Beamforming for Noise Source Identification for Small Wind Turbines

International Scholarly Research Notices ◽

10.1155/2017/7061391 ◽

2017 ◽

Vol 2017 ◽

pp. 1-24

Author(s):

Ping Ma ◽

Fue-Sang Lien ◽

Eugene Yee

Keyword(s):

Wind Turbine ◽

Noise Source ◽

Sound Generation ◽

Noise Sources ◽

Wind Turbine Noise ◽

Trailing Edge Noise ◽

Small Wind Turbine ◽

Small Wind Turbines ◽

Noise Source Identification ◽

Naca 0012

This paper develops a computational acoustic beamforming (CAB) methodology for identification of sources of small wind turbine noise. This methodology is validated using the case of the NACA 0012 airfoil trailing edge noise. For this validation case, the predicted acoustic maps were in excellent conformance with the results of the measurements obtained from the acoustic beamforming experiment. Following this validation study, the CAB methodology was applied to the identification of noise sources generated by a commercial small wind turbine. The simulated acoustic maps revealed that the blade tower interaction and the wind turbine nacelle were the two primary mechanisms for sound generation for this small wind turbine at frequencies between 100 and 630 Hz.

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