Abstract
The generation and radiation of tip vortex noise from wind turbine blades have been investigated. The aim was to derive concepts for design of silent rotor tips by analytical approach. The primary noise source is identified as the tip vortex passing the trailing edge. By applying an acoustic analogy it is possible to distinguish between the aerodynamic generation and the aeroacoustic radiation of noise. Amplification of the acoustic field at the trailing edge was treated by Amiets model. The tip vortex flow is 3-dimensional. Mainly semi-empirical prediction models are presented. The aerodynamic modelling covers only simple tip shapes. It is assessed that a detailed description of the tip flow when depending on an arbitrary tip geometry hardly can be gained from semi-empirical methods. Numerical modelling could be applied for this purpose. A prediction code was implemented, following a model by George, and this part of the code was found to be valid. Distinction between individual noise sources presented problems. The prediction code was applied for an investigation of the influence on the noise radiation of tip parameter variations. The investigation showed a significant influence on the noise radiation from variations of the tip speed, the tip chord and the tip
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Nielsen, O W
[1]
- DEFU, Lyngby (Denmark)
Citation Formats
Nielsen, O W.
Rotor noise from wind turbines. Tip vortex noise.
Denmark: N. p.,
1993.
Web.
Nielsen, O W.
Rotor noise from wind turbines. Tip vortex noise.
Denmark.
Nielsen, O W.
1993.
"Rotor noise from wind turbines. Tip vortex noise."
Denmark.
@misc{etde_10122928,
title = {Rotor noise from wind turbines. Tip vortex noise}
author = {Nielsen, O W}
abstractNote = {The generation and radiation of tip vortex noise from wind turbine blades have been investigated. The aim was to derive concepts for design of silent rotor tips by analytical approach. The primary noise source is identified as the tip vortex passing the trailing edge. By applying an acoustic analogy it is possible to distinguish between the aerodynamic generation and the aeroacoustic radiation of noise. Amplification of the acoustic field at the trailing edge was treated by Amiets model. The tip vortex flow is 3-dimensional. Mainly semi-empirical prediction models are presented. The aerodynamic modelling covers only simple tip shapes. It is assessed that a detailed description of the tip flow when depending on an arbitrary tip geometry hardly can be gained from semi-empirical methods. Numerical modelling could be applied for this purpose. A prediction code was implemented, following a model by George, and this part of the code was found to be valid. Distinction between individual noise sources presented problems. The prediction code was applied for an investigation of the influence on the noise radiation of tip parameter variations. The investigation showed a significant influence on the noise radiation from variations of the tip speed, the tip chord and the tip angle of attack. Comparison was made between full-scale measured noise signatures for a wind turbine equipped with different tip shapes and predicted noise levels. The aerodynamic input to the prediction code was based on Lifting Line calculations. The Lifting Line calculation and the noise prediction supported the result from the full-scale measurements that an Ogee tip radiates less noise than the Standard tip. The ``I`` tip did not radiate more noise than the Standard tip. It is estimated that the prediction code can be applied in the design stage of silent wind turbine tips for simple modelling. (AB) (42 refs.)}
place = {Denmark}
year = {1993}
month = {Sep}
}
title = {Rotor noise from wind turbines. Tip vortex noise}
author = {Nielsen, O W}
abstractNote = {The generation and radiation of tip vortex noise from wind turbine blades have been investigated. The aim was to derive concepts for design of silent rotor tips by analytical approach. The primary noise source is identified as the tip vortex passing the trailing edge. By applying an acoustic analogy it is possible to distinguish between the aerodynamic generation and the aeroacoustic radiation of noise. Amplification of the acoustic field at the trailing edge was treated by Amiets model. The tip vortex flow is 3-dimensional. Mainly semi-empirical prediction models are presented. The aerodynamic modelling covers only simple tip shapes. It is assessed that a detailed description of the tip flow when depending on an arbitrary tip geometry hardly can be gained from semi-empirical methods. Numerical modelling could be applied for this purpose. A prediction code was implemented, following a model by George, and this part of the code was found to be valid. Distinction between individual noise sources presented problems. The prediction code was applied for an investigation of the influence on the noise radiation of tip parameter variations. The investigation showed a significant influence on the noise radiation from variations of the tip speed, the tip chord and the tip angle of attack. Comparison was made between full-scale measured noise signatures for a wind turbine equipped with different tip shapes and predicted noise levels. The aerodynamic input to the prediction code was based on Lifting Line calculations. The Lifting Line calculation and the noise prediction supported the result from the full-scale measurements that an Ogee tip radiates less noise than the Standard tip. The ``I`` tip did not radiate more noise than the Standard tip. It is estimated that the prediction code can be applied in the design stage of silent wind turbine tips for simple modelling. (AB) (42 refs.)}
place = {Denmark}
year = {1993}
month = {Sep}
}