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Analysis of long distance wakes of Horns Rev I using actuator disc approach
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
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2014 (English)In: Science of Making Torque from Wind 2012, 2014Conference paper (Refereed)
Abstract [en]

The wake recovery behind the Horns Rev wind farm is analysed to investigate the applicability of Large Eddy Simulations (LES) in combination with an actuator disc method (ACD) for farm to farm interaction studies. Periodic boundary conditions on the lateral boundaries are used to model the wind farm (as infinitely wide), using only two columns of turbines. The meteorological conditions of the site are taken into account by introducing wind shear and pre-generated synthetic turbulence to the simulation domain using body forces. Simulations are carried out to study the power production and the velocity deficit in the farm wake. The results are compared to the actual power production as well as to wind measurements at 2 km and 6 km behind the wind farm. The simulated power production inside the farm shows an overall good correlation with the real production, but is slightly overpredicted in the most downstream rows. The simulations overpredict the wake recovery, namely the wind velocity, at long distances behind the farm. Further studies are needed before the presented method can be applied for the simulation of long distance wakes. Suggested parameters to be studied are the development of the turbulence downstream in the domain and the impact of the grid resolution.

Place, publisher, year, edition, pages
, Journal of Physics Conference Series, ISSN 1742-6588 ; 555
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-246873DOI: 10.1088/1742-6596/555/1/012032ISI: 000347871200032OAI: diva2:794375
4th Scientific Conference on Science of Making Torque from Wind, OCT 09-11, 2012, Oldenburg, GERMANY
Available from: 2015-03-11 Created: 2015-03-11 Last updated: 2015-08-31Bibliographically approved
In thesis
1. Numerical Computations of Wakes Behind Wind Farms
Open this publication in new window or tab >>Numerical Computations of Wakes Behind Wind Farms
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

More and larger wind farms are planned offshore. As the most suitable build sites are limited wind farms will be constructed near to each other in so called wind farm clusters. Behind the wind turbines in these farms there is a disrupted flow of air called a wake that is characterized by reduced wind speed and increased turbulence. These individual turbine wakes combine to form a farm wake that can travel a long distance. In wind farm clusters farm to farm interaction will occur, i.e. the long distance wake from one wind farm will impact the wind conditions for other farms in the surrounding area.

The thesis contains numerical studies of these long distance wakes. In this study Large Eddy Simulations (LES) using an Actuator Disc method (ACD) are used. A prescribed boundary layer is used where the wind shear is introduced using body forces. The turbulence, based on the Mann model, is introduced as fluctuating body forces upstream of the farm. A neutral atmosphere is assumed. The applied method has earlier been used for studies of wake effects inside farms but not for the longer distances needed for farm to farm interaction.

Numerical studies are performed to get better knowledge about the use of this model for long distance wakes. The first study compares the simulation results with measurements behind an existing farm. Three parameter studies are thereafter setup to analyze how to best use the model. The first parameter study examines numerical and physical parameters in the model. The second one looks at the extension of the domain and turbulence as well as the characteristics of the flow far downstream. The third one gathers information on the downstream development of turbulence with different combinations of wind shear and turbulence level. The impact of placing the turbines at different distances from the turbulence plane is also studied. Finally a second study of an existing wind farm is performed and compared with a mesoscale model. The model is shown to be relevant also for studies of long distance wakes. Combining LES with a mesoscale model can be of interest.

Place, publisher, year, edition, pages
Uppsala: Institutionen för geovetenskaper, 2015. 57 p.
, Department of Earth Sciences Licentiate Thesis
Wind turbine, Wind power, Wind farm, Wakes, Long distance wakes, Farm-Farm, Farm to farm interaction, Wind farm cluster, Large Eddy simulations, LES, Actuator disc method, ACD, CFD, Ellipsys3D
National Category
Meteorology and Atmospheric Sciences
urn:nbn:se:uu:diva-255859 (URN)
, Visby (English)
Available from: 2015-08-31 Created: 2015-06-18 Last updated: 2016-02-12Bibliographically approved

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Eriksson, OlaNilsson, KarlIvanell, Stefan
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