Hydrodynamic Analysis of a Semi-Submersible FOWT by Hybrid Panel-Stick Models

摘要

A diffraction-radiation analysis is usually required when thehydrodynamic interactions between structural members occur in shortwaves. For bracings or small cylinder members, which play importantroles in the vicinity of the natural frequency of a floating platform,special care should be taken into account for the effect of viscousdamping. Two hybrid panel-stick models are therefore developed,through the combination of the standard diffraction-radiation methodand the Morison’s formulae, while considering the effect of smallmembers differently. The fluid velocity is obtained directly by thepanel model. The viscous fluid force is calculated for individualmembers by the stick model. A semi-submersible type platform with anumber of fine cylindrical structures, which is designed as a floatingfoundation for multiple wind turbines, is analysed as a numericalexample. The results show that viscous force has large influence on thebehaviour of the floating body and can successfully be considered bythe proposed hybrid models.