Hydroelastic Responses Of Pontoon-type Very Large Floating Structures In Random Water Waves And In Nearshore Regions

This thesis is concerned with the linear hydroelastic response of pontoon-type very large floating structures (VLFS) in random water waves and in nearshore regions. Based on the assumption that both the structural motion and the fluid motion are linear, the fluid-structure interaction problem of VLFS in waves is divided into two parts, i.e., the structural motion part and the fluid motion part. VLFS is modeled as a Mindlin plate, and the three-dimensional linear potential theory in frequency domain is used to build the model of the fluid motion. Then the hybrid finite element method and the boundary element method (FEM-BEM), and the mode superposition method are adopted to solve the fluid-structure dynamic equations for VLFS. Hydroelastic responses of VLFS are investigates in two cases in this thesis, i.e., the case that VLFS are subjected to stochastic waves in the fluid domain of constant water depth, and regular waves in the fluid domain of variable water depth. In the first case, a calculation method is proposed by combining the hybrid FEM-BEM with the pseudo excitation method, which can give a fast evaluation of the stationary stochastic response of VLFS in the fluid domain of constant water depth. The accuracy and high efficiency of this method is verified by comparing the computational results with some test results and the computational results obtained in the traditional method. In the second case, firstly the higher order boundary element method is adopted to calculate the propagation of linear regular waves in nearshore regions; secondly the radiation boundary condition of the linear potential theory in nearshore regions is built using the theory of the perfectly matched layer; finally a method to the hydroelastic analysis of VLFS in nearshore region is given by combining the hybrid FEM-BEM and the radiation boundary condition. Then the accuracy and stability of this method are studied using three numerical examples, which confirm that this method is applicable to the hydroelastic analysis of VLFS subjected to linear regular waves in nearshore regions.