中文摘要：

为研究海上多腿浮式结构在收放桩腿的过程中水动力特性的变化规律，对某风电安装船结构进行了合理简化，使用有限元方法建立了多腿支撑结构的水动力模型，按水下桩腿长度的不同对结构划分了5种工况，探讨了船身、桩腿、桩靴的湿面单元划分，以所建模型为基础数值分析了水下桩腿长度对结构所受波浪激励力的影响，给出了结构所受波浪激励力（矩）与波浪频率的关系。结果表明：水下桩腿长度对受力、力矩的影响体现在波浪处于中频段；桩腿对引起垂荡的波浪激励力和引起纵的波浪激励力矩的影响不大，引起横的波浪激励力矩影响较大。

英文摘要：

To analyze hydrodynamic characteristics of the floating structure with legs lifting up and down, the structure of a certain type of wind farm installation vessel is simplified and a hydrodynamic model is constructed by utilizing the FEA method. According to the length of the legs underwater, 5 cases are set up and the meshes of the wetted surface on hull, pile legs and pile shoes are discussed. Based on these, the effects of the length of the legs underwater on the wave excitation forces/moments borne by structure are calculated by utilizing the potential flow theory. The relations between the wave excitation forces/moments and wave frequencies are presented, the results show that the effects of the legs underwater on the forces/moments primarily concentrate on the intermediate frequency range of the waves. There are little effects of the legs on the heave and pitch forces/moments, but there is a remarkable effect on the roll moment.