二阶波浪力下超大型半潜浮式风力机动态响应分析

针对DTU(Technical University of Denmark)10 MW风力机，使用FAST软件对典型海况下不同水动力分量作用下的半潜浮式风力机系统进行全耦合分析，包括仅一阶波浪力作用、一阶波浪力和采用Newman近似计算的二阶差频波浪力作用、一阶波浪力和全域二次传递函数（quadratic transfer functions,QTFs）计算的二阶差频波浪力作用、一阶波浪力和全域QTFs计算的二阶和频波浪力作用以及一阶波浪力和全域QTFs计算的完整二阶波浪力作用，以对比分析二阶差频、和频波浪力对超大型半潜浮式风力机动态响应的影响；基于风力机结构疲劳计算理论，分析二阶差频和频波浪力对风力机结构疲劳破坏的影响。研究发现：在极端海况下，二阶差频波浪力对平台运动响应，二阶差频及和频波浪力对半潜浮式风力机结构荷载和疲劳破坏均产生显著影响。此外，Newman近似方法明显低估二阶差频波浪力对半潜浮式风力机动态响应的影响。

DYNAMIC RESPONSE ANALYSIS OF AN ULTRA-LARGE SEMI-SUBMERSIBLE FLOATING WIND TURBINE UNDER SECOND-ORDER WAVE FORCES

For DTU （Technical University of Denmark, DTU） 10 MW wind turbines, the fully coupled analysis for the semi-submersible floating offshore wind turbine （FOWT） system was conducted by using FAST software under the typical sea states with different hydrodynamic components to compare and analyze the effect of second-order difference- and sum-frequency wave forces on the dynamic responses of the ultra-large semi-submersible FOWT, including only first-order wave force, first- and second-order difference-frequency wave forces calculated by Newman’s approximation and full-field quadratic transfer functions （QTFs）,respectively, first- and second-order sum-frequency wave forces calculated by full-field QTFs, and first- and complete second-order wave forces calculated by full-field QTFs. Based on the fatigue calculation theory of the wind turbine structure, the effect of second-order difference- and sum-frequency wave forces on the fatigue failure of the wind turbine structure is analyzed. The study found that under extreme sea states,second-order difference-frequency wave force has a significant effect on the platform motions, and the second-order difference- and sum-frequency wave forces has a significant effect on the structural loads and fatigue failure of the semi-submersible FOWT. In addition, the Newman’s approximation method obviously underestimates the effect of second-order difference-frequency wave forces on the dynamic response of the semi-submersible FOWT.