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Title: Experimental studies of extreme waves and wave-induced loads on wind turbine support structures in intermediate depth water
Author: Luxmoore, James Francis
ISNI:       0000 0004 7229 9689
Awarding Body: Lancaster University
Current Institution: Lancaster University
Date of Award: 2014
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Current plans to build large numbers of wind turbines in far offshore locations around the UK require an improved understanding of the risks associated with deeper water and more exposed sites. There is little published research on the forces resulting from wave action on monopile or jacket type wind turbine support structures in the water depths proposed. The wave environment is also far from being fully described; questions remain about the development of bi-modal short-crested seas, in particular with regards to rogue wave occurrence which may be of critical importance to wind turbine support structures. The four main contributions of this thesis are as follows. The force spectrum on a monopile support follows the wave height spectrum closely, but for a jacket structure there is a significant peak enhancement, so rogue and extreme waves will have a larger effect on a jacket structure than would be extrapolated from smaller waves. Jacket structures are also sensitive to wave direction, experiencing up to 50% dif­ference in peak forces depending on the wave direction. Nonetheless, the overall wave-induced forces and wave run-up heights on a jacket type wind turbine support structure are considerably lower than those on an equivalent monopile. In bi-modal short-crested seas the kurtosis is well predicted by an empirical relation­ship including bound mode effects based on the properties of the whole wave spectrum. The kurtosis has been previously shown to be related to rogue wave activity. For broad spread bi-modal short-crested seas the four wave resonant interactions are sufficient to explain the observed spectral development. At crossing angles less than 20° or when the individual components both have narrow directional spreading the modulation instabilities become increasingly important.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available