Floating offshore wind turbines (FOWTs) offer a significant opportunity for harnessing wind energy and achieving clean energy goals. This paper investigates the effects of mooring line failure in semisubmersible FOWTs under normal and extreme environmental conditions. The OC4 DeepCwind type semisubmersible with an NREL 5 MW wind turbine is considered for investigating the behavior of FOWT under intact and failed mooring lines. This study covers a wide range of environmental conditions, operational conditions of wind turbines, and mooring line failure scenarios. This paper investigates the mooring line failure effects on platform responses, mooring line fairlead tensions, and tower responses. The results show that the platform surge, heave, pitch responses, tower fore-aft displacement, base shear force in -direction, and base moment in -direction are increased for upwind side mooring line failure during the operational condition of FOWT. Subsequently, the platform sway, roll, yaw responses, tower side-to-side displacement, base shear force in -direction, and base moment in -direction are more during downwind side mooring line failure in the same environment. On the other hand, the impact of upwind side mooring line failure affects all 6 Degrees of Freedom (DOF) platform responses significantly during the parked state of FOWT. The maximum fairlead tensions observed in the remaining mooring lines remain below the mooring line breaking strength even after a mooring line failure during both operational and parked states of FOWT. It is also observed that the platform responses (excluding heave), tower responses, and fairlead tensions exhibit greater values when an extreme turbulence wind model is employed. The platform surge, heave, pitch responses, maximum fairlead tension, tower fore-aft displacement, and tower base moment in -direction show higher values under severe sea state condition.

中文翻译：

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正常和极端环境条件下系泊线失效的半潜式浮动海上风力发电机动态响应分析

浮动式海上风力涡轮机（FOWT）为利用风能和实现清洁能源目标提供了重要机会。本文研究了正常和极端环境条件下半潜式 FOWT 系泊缆绳失效的影响。配备 NREL 5 MW 风力涡轮机的 OC4 DeepCwind 型半潜式潜水器被考虑用于研究 FOWT 在完整和失效系泊线下的行为。这项研究涵盖了广泛的环境条件、风力涡轮机的运行条件和系泊线故障场景。本文研究了系泊线故障对平台响应、系泊线导缆器张力和塔架响应的影响。结果表明，在FOWT运行工况下，迎风侧系泊线失效会导致平台纵荡、升沉、纵摇响应、塔架前后位移、基础剪力和基础弯矩增大。随后，在相同环境下，顺风侧系泊线失效时，平台的摇摆、横滚、偏航响应、塔架左右位移、基础方向剪力和基础方向力矩更大。另一方面，在 FOWT 停放状态下，逆风侧系泊线故障的影响会显着影响所有 6 个自由度 (DOF) 平台的响应。即使在 FOWT 的运行和停泊状态期间系泊索发生故障后，在剩余系泊索中观察到的最大导缆器张力仍低于系泊索断裂强度。还观察到，当采用极端湍流风模型时，平台响应（不包括升沉）、塔架响应和导缆器张力表现出更大的值。在恶劣海况条件下，平台纵荡、升沉、纵摇响应、最大导缆张力、塔架前后位移和塔架基础力矩均表现出较高的值。