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Titel |
Characterisation of impacts on the environment of an idealised offshore wind farm foundation, under waves and the combination of waves and currents |
VerfasserIn |
Isabel García-Hermosa, Nizar Abcha, Jérôme Brossard, Anne-Claire Bennis, Alexander Ezersky, Marcus Gross, Gregorio Iglesias, Vanesa Magar, Jon Miles, Dominique Mouazé, Gaele Perret, Grégory Pinon, Aurélie Rivier, Charlie Rogan, David Simmonds |
Konferenz |
EGU General Assembly 2015
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 17 (2015) |
Datensatznummer |
250110976
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Publikation (Nr.) |
EGU/EGU2015-11037.pdf |
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Zusammenfassung |
Offshore wind technology is currently the most widespread and advanced source of marine
renewable energy. Offshore wind farms populate waters through the North Sea and the
English Channel. The UK and French governments devised deadlines to achieve percentages
of electricity from renewable sources by 2020, these deadlines and the direct translation of
land based wind farm technology to the offshore environment resulted in the rapid expansion
of the offshore wind energy. New wind farms have been designed with a larger number of
masts and are moving from shallow offshore banks to deeper waters and in order to produce
more power the diameters of monopoles masts are becoming larger to support larger
turbines.
The three-partner EU INTERREG funded project OFELIA (http://www.interreg-ofelia.eu/)
aims to establish a cross-channel (between the UK and France) research collaboration to
improve understanding of the environmental impacts of offshore wind farm foundations.
The objective of the present study is to characterise changes in the hydrodynamics
and sea bed in the vicinity of an offshore wind farm mast and in the wake area
under wave and wave-current conditions corresponding to events in the French wind
farm site of Courseulles-sur-mer (offshore of Lower Normandy, in the English
Channel).
Experiments were carried out in two laboratory facilities: a wave flume of 35Âm long, 0.9
m wide and 1.2Âm in depth with regular and irregular waves (García-Hermosa et al., 2014);
and a wave and current flume of 17 m long, 0.5 m wide and 0.4 m depth with regular waves,
currents from 180º to the waves and a mobile bed (Gunnoo et al., 2014). Flow velocity
measurements were taken with an Acoustic Dopple Velocimeter (ADV) at various points
around the cylinder and Particle Image Velocitmetry (PIV) techniques were applied to larger
areas upstream and downstream of the cylinder. During the assessment of waves
and currents’ effects on the bed evolution were assessed using a laser and camera
system photographing the bed (Marin & Ezersky, 2007, and Jarno-Druaux et al.,
2004).
Velocity fields, and flow structures around the cylinder at low KC numbers (KC~1) were
characterised and parameters such as vorticity, turbulent kinetic energy and bed shear stresses
derived where possible. During the experiments vortex structures with a horizontal axis were
observed in the vicinity of the cylinder and the bed even at low KC. The Keulegan-Carpenter
number (KC) is defined as: KC = UmT-
D, where Um is the bottom orbital velocity, T the
peak period and D the pile diameter.
As part of the project, the findings from the experiments fed into a regional numerical
modelling (Rivier et al., 2014) to improve parametrisation of the representation of the
within-cell processes (local to the mast).
References
García-Hermosa, M. I., Brossard, J., Cohen, Z., Perret, G. (2014). Experimental
characterisation of wave induced flow fields due to an offshore wind farm mast. First
International Conference on Renewable Energies Offshore (RENEW) Lisbon, Portugal.
November 2014.
Gunnoo, H., Abcha, N., Mouazé, D., Ezersky, A., García-Hermosa, M. I. (2014).
Laboratory simulation of resonance amplification of the hydrodynamic fields in the vicinity
of wind farm masts. Proceedings of the First International Conference on Renewable
Energies Offshore (RENEW) Lisbon, Portugal. November 2014.
Jarno-Druaux, A., Brossard, J., Marin, F. (2004). Dynamical evolution of ripples in a
wave channel, European Journal of Mechanics B/Fluids 23: 695–708.
Marin, F. and Ezersky, A. B. (2007). Formation dynamics of sand bedforms under
solitons and bound states of solitons in a wave flume used in resonant mode. European
Journal of Mechanics - B/Fluids, Elsevier, 2008, 27 (3), pp.251-267.
Rivier, A., Bennis, A.-C., Pinon, G., Gross, M., Magar, V. (2014). Regional numerical
modelling of offshore monopile wind turbine impacts on hydrodynamics and sediment
transport. Proceeding of the 1st International Conference on Renewable Energies Offshore
(RENEW) Lisbon, Portugal. November 2014. |
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