5 MW 半潛式浮式風機極端海況上浪效應數值模擬

Abstract

本研究採用高解析度計算流體力學模型，同時耦合集中質量式繫泊模型 MoorDyn，探討部署於 70 m 水深，承受臺灣海峽極端海況之 5 MW 浮式離岸風 力機的上浪負荷、運動響應及上浪響應機制。本研究採用的五十年回歸週期海氣象 條件係根據新竹浮標的量測資料，對應風速為 57 m/s、示性波高為 12.7 m、波浪 週期為 11.8s。本研究求解非定常雷諾平均納維–斯托克斯方程式以及SSTk-ω 紊 流模型，並使用流體體積法捕捉自由液面變化與上浪衝擊現象，同時採用重疊網格 技術解析浮式風機之六個自由度運動。流場求解器透過雙向耦合程序與繫泊模型 連結，於每一時間步交換平台運動狀態與繫泊回復力，以確保水動力載荷、平台運 動與繫泊響應在各求解器間具有一致性。本研究針對平台運動、速度、加速度及上 浪效應進行完整分析，並比較駁船式與半潛式平台於頂浪、側浪與順浪等不同波浪 入射方向下之動態響應行為。計算結果顯示，駁船式平台於順浪下之最大上浪力達 52.69MN，半潛式平台則於頂浪下達 29.93MN;此外，駁船式平台於側浪下之繫 泊張力最為嚴峻，達最大斷裂強度之 72%，顯示平台構型不僅主導上浪發生方向 與機制，亦顯著影響繫泊系統之受力表現。 關鍵字:上浪效應、極端海況、臺灣海峽、運動響應、回復、壓力負荷

This study employs a high-resolution computational fluid dynamics model coupled with the lumped-mass mooring model MoorDyn to investigate green water loads, motion responses, and the associated response mechanisms of a 5 MW floating offshore wind turbine deployed in 70 m water depth under an extreme condition in the Taiwan Strait. The employed 50-year return period metocean conditions are based on measurements from the Hsinchu buoy, corresponding to a wind speed of 57 m/s, a significant wave height of 12.7 m, and a wave period of 11.8 s. The unsteady Reynolds-averaged Navier– Stokes equations are solved along with the SST k–ω turbulence model, while the volume of fluid method is adopted to capture free-surface evolution and green water impact. Overset mesh techniques are employed to accurately resolve the six-degrees-of-freedom motions of the floating wind turbine. The flow solver is two-way coupled with MoorDyn at each time step, ensuring consistency among hydrodynamic loads, platform motions, and mooring responses. A comprehensive analysis of platform motions, velocities, accelerations, and green water effects is performed for barge and semi-submersible platforms under head sea, beam sea, and following sea conditions. Numerical results show that peak green water forces of 52.69 MN for the barge platform in following seas and 29.93 MN for the semi-submersible platform in head seas. For the barge platform, the mooring line tension under beam sea condition is the most severe, reaching 72% of the maximum breaking load, indicating that platform configuration not only governs the direction and mechanism of green water occurrence, but also significantly affects the load response of the mooring system. Keywords: Green water, Extreme condition, Taiwan Strait, Motion response, Restoring, Impulse pressure