Abstract The platform pitch motion of a Floating Wind Turbine (FWT) introduces additional relative wind speed to the rotor. This additional relative wind speed distributes linearly along the vertical altitude, which is similar to the linear wind shear, thus it is addressed as the platform-pitch-induced (PPI) wind shear effect. In this paper, the PPI wind shear is investigated numerically with the Free Vortex Method (FVM). Firstly, the typical wind shear and the PPI wind shear are separately analyzed and then compared with each other. The wind profile of the typical wind shear is stationary. However, the wind profile of the PPI wind shear is time-varying, which complicates the aerodynamics of the FWT. Subsequently, the influencing factors of the PPI wind shear are thoroughly discussed. Results show that the PPI wind shear is related to the FWTstructures, and it is increased with the increases of the platform pitch amplitude, frequency and the tip speed ratio. The PPI wind shear introduces significant fluctuations to the aerodynamic loads, which smear the power quality and result in potential fatigue damages to the FWT structures. To mitigate the adverse effects of the PPI wind shear, advanced control strategies and optimized structure designs should be developed.

中文翻译：

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Spar型浮动风力机平台俯仰运动引起的风切变效应

摘要 浮动式风力涡轮机 (FWT) 的平台俯仰运动向转子引入了额外的相对风速。这种额外的相对风速沿垂直高度呈线性分布，类似于线性风切变，因此被称为平台俯仰诱发 (PPI) 风切变效应。在本文中，PPI 风切变采用自由涡流法 (FVM) 进行数值研究。首先分别对典型风切变和PPI风切变进行分析和比较。典型风切变的风廓线是静止的。然而，PPI 风切变的风廓线是随时间变化的，这使得 FWT 的空气动力学复杂化。随后，深入讨论了PPI风切变的影响因素。结果表明，PPI风切变与FWT结构有关，并且随着平台俯仰幅度、频率和叶尖速比的增加而增加。PPI 风切变给气动载荷带来了显着的波动，这会影响电能质量并导致 FWT 结构的潜在疲劳损坏。为了减轻 PPI 风切变的不利影响，应开发先进的控制策略和优化的结构设计。