Physical Experiments on Scour at Offshore Wind Turbines and Sea Ice in Waves
Offshore wind turbine farms are popular due to their larger size, consistently higher wind speed environment, and lower visual impact than their onshore equivalents. One of the significant issues associated with their construction is the problem of scour of the sediment on the sea bed at its interface with the base of the monopile foundation structure. Flow modification by the monopile causes an increase in velocity and turbulence in its locality. The resulting amplification of bed shear stress can induce scour of the sediment which is manifested as a large, steep-sided hole around the monopole that can reduce the stability of the structure and consequentially affect its longevity. This particular problem is distinctly different from the well-researched issue of bridge pier scour in steady unidirectional currents due to the tidal variation of water depth, current velocity and direction. This presentation describes a series of physical experiments that examined the case of tidal scour at offshore monopiles. Through a series of rigid bed tests the hydrodynamics around a scaled test cylinder in tidal flow was measured in detail using PIV and ADV. This was followed by mobile bed tests in which time-development of the tidal scour process was analysed along with possible mitigation techniques. The results indentify the characteristics of tidal scour and compare this to unidirectional current-induced scour. The performance of the most widely used predictor equations is also assessed against the tidal scour data, and some comments are made on the consequence of scour in prototype conditions.
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Additional Details
Contact Person - Ms Norela Buang
Contact Number - 6516 4314
Organizer - NUS