Dynamic responses of a floating tidal turbine with 6-DOF prescribed floater motions

Abstract

This study aims to reveal the dynamic response and power output characteristics of a floating tidal turbine with prescribed motions in six degrees of freedom. Floater motions were calculated in the time domain based on linear potential theory. Both wave-induced inflow fields and floater motions are considered in a modified blade element momentum theory model for rotor load simulation. Generator power production and loads on a reference tidal turbine system were investigated. The torque and thrust response spectra are found to be dominated by floater-motion-induced contributions, and two response peaks can be clearly identified. A cancellation effect occurs between direct wave effects and floater-motion-induced loads, and horizontal and vertical rotor positions can significantly affect the dynamic responses of the blade loads; the rotor should be placed close to the floater centre to avoid large floater-motion-induced velocity on the blade section. Sensitivity studies are carried out with varying significant wave heights and peak periods. These results may contribute to a general understanding of floater-induced dynamic loads on floating tidal turbines in a random sea.