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Suitability of wave loading models for offshore wind turbine monopiles in rough seas ; Angemessenheit von Wellenlastmodellen für Offshore-Windkraftanlagen-Monopiles in rauer See
Motivated by the ever-growing need for secure and cost-efficient renewable energy, this thesis discusses the suitability of current numerical wave loading models for monopile-supported offshore wind turbines in highly nonlinear rough seas. To discuss the distinct influences of nonlinearities in wave loading models, combinations of six increasingly nonlinear regular wave theories, three irregular wave solvers, and three hydrodynamic loading models were modelled. Wave loading was discussed on increasingly complex slender structures: fixed rigid cylinder, bottom-hinged rigid cylinder and a fully flexible monopile-supported offshore wind turbine. It was found that in deep water the hydrodynamic loading models tend to dominate, therefore solvers can be optimised by compromising on the wave kinematics. However, in intermediate water depth, where monopile-supported offshore wind turbines are commonly placed, the nonlinearities in wave kinematics become more significant. To fully capture the nonlinear phenomena in rough seas and intermediate water depth fully nonlinear wave kinematics were found to be required. Nonetheless, if unavailable or unfeasible, less computationally intensive second order wave kinematics were found to show a significant improvement from the linear wave kinematics, which continuously resulted in underestimation of wave loading. However, attention should be paid when applying the second order wave kinematics in steeper waves where it tends towards overestimation. Attention was also drawn to several fundamental issues. Wave loading across all numerical models shows monotonic growth with increasing wave steepness in every harmonic. Such behaviour is not seen in the higher harmonics of the reported experimental values, leading to an increasing overprediction at the higher wave steepness. Moreover, nonlinear fluid-structure interaction was noted to have an effect on the natural frequency of the offshore structure. If unaccounted for, this may lead to design frequencies which fall in the resonant range ...
Suitability of wave loading models for offshore wind turbine monopiles in rough seas ; Angemessenheit von Wellenlastmodellen für Offshore-Windkraftanlagen-Monopiles in rauer See
Motivated by the ever-growing need for secure and cost-efficient renewable energy, this thesis discusses the suitability of current numerical wave loading models for monopile-supported offshore wind turbines in highly nonlinear rough seas. To discuss the distinct influences of nonlinearities in wave loading models, combinations of six increasingly nonlinear regular wave theories, three irregular wave solvers, and three hydrodynamic loading models were modelled. Wave loading was discussed on increasingly complex slender structures: fixed rigid cylinder, bottom-hinged rigid cylinder and a fully flexible monopile-supported offshore wind turbine. It was found that in deep water the hydrodynamic loading models tend to dominate, therefore solvers can be optimised by compromising on the wave kinematics. However, in intermediate water depth, where monopile-supported offshore wind turbines are commonly placed, the nonlinearities in wave kinematics become more significant. To fully capture the nonlinear phenomena in rough seas and intermediate water depth fully nonlinear wave kinematics were found to be required. Nonetheless, if unavailable or unfeasible, less computationally intensive second order wave kinematics were found to show a significant improvement from the linear wave kinematics, which continuously resulted in underestimation of wave loading. However, attention should be paid when applying the second order wave kinematics in steeper waves where it tends towards overestimation. Attention was also drawn to several fundamental issues. Wave loading across all numerical models shows monotonic growth with increasing wave steepness in every harmonic. Such behaviour is not seen in the higher harmonics of the reported experimental values, leading to an increasing overprediction at the higher wave steepness. Moreover, nonlinear fluid-structure interaction was noted to have an effect on the natural frequency of the offshore structure. If unaccounted for, this may lead to design frequencies which fall in the resonant range ...
Suitability of wave loading models for offshore wind turbine monopiles in rough seas ; Angemessenheit von Wellenlastmodellen für Offshore-Windkraftanlagen-Monopiles in rauer See
Mockutė, Agota (author) / Thiele, Klaus / Borri, Claudio
2021-12-08
Theses
Electronic Resource
English
Suitability of wave loading models for offshore wind turbine monopiles in rough seas
| UB Braunschweig | 2020
Dynamic stiffness of monopiles supporting offshore wind turbine generators
| Online Contents | 2016