Chaired by: J. Sørensen, S. Ivanell
16:30
Wind Turbine Noise Propagation Modelling: An Unsteady Approach
Emre Barlas | DTU | Denmark
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Authors:
Emre Barlas | DTU | Denmark
Wei Jun Zhu | Denmark
Wen Zhong Shen | Denmark
Søren Juhl Andersen | Denmark
Wind turbine sound generation and propagation phenomena are inherently time dependent, hence tools that incorporate the dynamic nature of these two issues are needed for accurate modelling. In this paper, we investigate the sound propagation from a wind turbine by considering the effects of unsteady flow around it and time dependent source characteristics. For the acoustics modelling we employ the Parabolic Equation (PE) method while Large Eddy Simulation (LES) as well as synthetically generated turbulence fields are used to generate the medium flow upon which sound propagates. Unsteady acoustic simulations are carried out for three incoming wind shear and various turbulence intensities, using a moving source approach to mimic the rotating turbine blades. The focus of the present paper is to study the near and far field amplitude modulation characteristics and time evolution of Sound Pressure Level (SPL).
16:50
Maturing of Serration Design Methodology for Wind Turbine Noise Reduction
Jesper Madsen | LM Wind Power | India
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Authors:
Ashish Singh | LM Wind Power | India
Jesper Madsen | LM Wind Power | India
Carlos Arce | India
Trailing edge serrations are today an established method to reduce the aeroacoustic noise from wind turbine blades. In this paper, a brief introduction to the aerodynamic and acoustic design procedure used at LM Wind Power is given. Early field tests on serrations, retrofitted to the turbine blades, gave preliminary indication of their noise reduction potential. However, a multitude of challenges stand in the way of any proof of concept and a viable commercial product. LM undertook a methodical test and validation procedure to understand the impact of design parameters on serration performance, and quantify the uncertainties associated with the proposed designs. Aerodynamic and acoustic validation tests were carried out in number of wind tunnel facilities. LM serration designs have evolved over the period of time to address constraints imposed by aero performance, structural reliability, manufacturing and installation. The latest LM serration offering 1.5 dB+ noise reduction in field.
17:10
Ice accretion prediction on wind turbines and consequent power losses
Ismail Hakki Tuncer | Turkey
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Authors:
Ozcan Yirtici | METU | Turkey
Ismail Hakki Tuncer | Turkey
Serkan Ozgen | Turkey
Ice accretion on wind turbine blades modifies the sectional profiles and causes alteration in the aerodynamic characteristic of the blades. The objective of this study is to determine performance losses on wind turbines due to the formation of ice in cold climate regions and mountainous areas where wind energy resources are found. In this study, the Blade Element Momentum method is employed together with an ice accretion prediction tool in order to estimate the ice build-up on wind turbine blades and the energy production for iced and clean blades. The predicted ice shapes of the various airfoil profiles are validated with the experimental data and it is shown that the tool developed is promising to be used in the prediction of power production losses of wind turbines.
17:30
Rotor experiments in controlled conditions continued: New Mexico
Dr. Koen Boorsma | ECN | Netherlands
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Authors:
Dr. Koen Boorsma | ECN | Netherlands
Gerard Schepers | Netherlands
To validate and reduce the large uncertainty associated with rotor aerodynamic and acoustic models, there is a need for detailed force, noise and surrounding flow velocity measurements on wind turbines under controlled conditions. However, high quality wind tunnel campaigns on horizontal axis wind turbine models are scarce due to the large wind tunnel size needed and consequently high associated costs. To serve this purpose an experiment using the Mexico turbine was set-up in the large low speed facility of the DNW wind tunnel. An overview of the experiments is given including a selection of results. A comparison of calculations to measurements for design conditions shows a satisfactory agreement. In summary, after years of preparation, ECN and partners have performed very successful aerodynamic experiments in the largest wind tunnel in Europe. The comprehensive high quality database that has been obtained will be used in the international Mexnext consortium to further develop wind energy aerodynamic and acoustic modeling.
17:50
Design of advanced airfoil for stall-regulated wind turbines
Dr. Francesco Grasso | Aerodynamix - University of Naples Federico II | Italy
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Authors:
Dr. Francesco Grasso | Aerodynamix - University of Naples Federico II | Italy
Domenico Coiro | Italy
Nadia Bizzarini | Italy
G Calise | Italy
Nowadays, all the modern MW-class wind turbines make use of pitch control to optimize the rotor performance and control the turbine. However, for kW-range machines, stall-regulated solutions are still attractive and largely used for their simplicity and robustness. On the design phase, the aerodynamics plays a crucial role, especially concerning the selection/design of the necessary airfoils. This is because the airfoil performance should guarantee high wind turbine performance, but also the needed machine control capabilities. In the present work, the design of a new airfoil dedicated for stall machines is discussed. The design strategy makes use of numerical optimization scheme where a gradient-based algorithm is coupled with XFOIL code and an original Bezier-curves-based parameterization to describe the airfoil shape. The performances of the new airfoil are compared in free and fixed transition conditions. In addition, the performance of the rotor is analysed comparing the impact of the new geometry with alternative candidates. The results show that the new airfoil offers better performance and control than existing candidates do.