Effect Of Vortex Induced Resonance On The Motion Response Of Spar-type FOWT

Because of wind energy as an abundant and renewable source of energy which is also relatively easy to exploit,large-scale development of wind power is attracting the world attention.Deep sea wind power equipment commonly uses floating wind turbine foundation.So it has great significance for research on the dynamic responses of the offshore floating wind turbine system.This paper reviews the basic form of the current floating wind turbine foundation structures and introduces the present study on the dynamic response and vortex-induced motion of floating wind turbine system.In this paper,the 5MW horizontal axis wind turbine released by the National Renewable Energy Laboratory(NREL)is used as a wind turbine model.The Hywind structure proposed by OC3 project is used as the floating foundation,and the response of the offshore floating wind turbine under the combined action of wind current and wave is studiedIn this paper,the Fluent is used to simulate the experiment of flow past a cylinder,and the vortex-induced forces on the Spar are simulated directly.Based on the established rigid flexible coupled multi-body dynamics analysis model,the vortex induced motion characteristics of Spar type are studied,and the influence of locking phenomenon on vortex-induced motion is investigated.A numerical model for nonlinear coupled motion considering vortex-induced forces,wave-induced forces,aerodynamic forces and mooring system loads is established.When the vortex frequency is similar to natural frequency of Spar,namely vortex induced resonance,the responses of Spar are calculated.And the influence of vortex induced force on the motion response of Spar fan is also analyzed.Then,in view of the different working states of the offshore floating wind turbine,the coupled dynamic responses of the FOWT under rated working conditions and maximum operating conditions are analyzed.Finally,the different flow angles in the ocean environment are simulated,and the dynamic responses of the FOWT are compared and analyzed under different current directions compared to that of wind and wave.The results show that the vortex-induced force from current will have a great impact on the movement of the Spar floating wind turbine when the locking phenomenon occurs.It is mainly shown that the vortex-induced force will greatly increase the amplitude of motion of sway and yaw,and suppress the motion of surge and pitch,and the existence of vortex-induced force will also cause greater mooring tension.Under the combined effect of wind current and wave,the change of current angle will stimulate a larger motion response of surge of Spar.