Influence of Mooring Tension on Dynamic Performance of Semi-submersible Wind Turbine under Typhoon Condition

Abstract

A numerical model of a 5 MW semi-submersible wind turbine is established based on the reference wind turbine of American national renewable energy laboratory (NREL). The nominal diameter of the mooring chains was determined after the static wind load and wave load of the turbine under the action of typhoon being calculated by CFD method and Morison method. Finally, the dynamic responses of the turbine and the internal forces of the chains are obtained by the dynamic finite element analysis for three cases. The results show that when pretension chains are used, the turbine motion frequency is consistent with wave frequency, the surge is small, the pitch is reciprocally symmetrical, and the peak internal force of the chains is quite high. When mooring chains without pretension are adopted, the motion of the turbine consists of low-frequency drift and forced motion in sync with the wave frequency, the pitch is asymmetrical, and the internal tension force of the chains is relatively low.