DeepCwind半潛式浮動式離岸風機，在不規則海況下繫纜耗損之風浪荷載研究

The Investigation of The Wind and Wave Loadings on A DeepCwind Semisubmersible Floating Offshore Wind Turbine with Mooring Lines Losses in An Irregular Sea Condition

本研究基於NPD風譜與JONSWAP波譜，在考慮二階波浪激盪力與動態繫泊模型的基礎上，分析OC4 DeepCwind半潛式浮式風機在不規則風浪條件下的動態響應。此外，在分析浮台運動中考慮了風力作為一個影響參數。在流體動力的計算上，本研究使用三維小板法求解線性化勢流繞射與輻射問題。為了引入非線性黏性阻力的影響，本研究採用二次阻尼矩陣取代莫里森公式。在模擬非線性運動響應下，本研究使用二次轉換函數(QTF)計算慢漂移力，並藉由團塊質量法研究纜繩對運動響應的影響。最後，本研究採用同時考慮風-波浪-繫泊的模擬下，對OC4 DeepCwind半潛式浮式風機繫纜斷裂時的性能進行分析。本研究在不同斷纜情況下，針對風機漂移的軌跡進行計算，而分析結果可作為浮式風機在初步設計階段下的參考依據。

"This study aims to analyze the motion response of the OC4 DeepCwind semisubmersible floating platform in irregular wind-wave conditions based on Norwegian Petroleum Directorate (NPD) wind spectrum and the Joint North Sea Wave Project (JONSWAP) spectrum by considering the second-order wave exciting force as well as the dynamic mooring model. In addition, the wind force is considered as an influential parameter in the analysis of platform motion. Both of linearized potential-flow diffraction and radiation problems of hydrodynamic forces in the frequency domain are solved using the three-dimensional panel method. To supplement the nonlinear viscous drag, this study adopts the quadratic damping matrix instead of Morison’s element. Besides, the slow-drift force is calculated using quadratic transfer function (QTF) matrices to simulate nonlinear motion responses. The study also investigates the mooring effect on motion responses by using the lump-mass method. Finally, this study applies an wind–wave-mooring simulation for the analysis of the OC4 DeepCwind semisubmersible floating offshore wind turbine (FOWT) when the mooring line is broken. For different conditions of broken mooring lines, the trajectories are approximately estimated. The analyzed results can be thought of as a reference of the FOWT in the initial design stage."