Study On Influence Of Tilt Angle On Fluid Dynamic Performance Of Floating Offshore Wind Turbine

Recent years,exploitation of offshore wind energy has contributed to rapid progress in floating offshore wind turbine(FOWT)technology.The balance of an floating offshore wind turbine(FOWT)cannot be achieved by the dynamic coupling of wind-wave condition.The dynamic excitation of the coupling wind-wave cause six degrees of freedom(6-DOF)motion of FOWT.The six-degree-of-freedom motion of the wind turbine will affect the power generation efficiency of the wind turbine.In addition,the surge and pitch motion of the FOWT will exacerbate the interaction between the blade and the tower.For fixed wind turbine,the rotating blades have a 5 degrees tilt angle in order to reduce the interference between the tower and the blades.For the FOWT,the wind turbine will not be able to maintain balance due to the coupling of wind and waves,so the 5 degree tilt angle of the fixed wind turbine may not be suitable for FOWT.This paper uses the commercial CFD calculation software STAR-CCM?to simulate the aerodynamic performance of fixed and floating wind turbine at different tilt angles.There are two types of wind turbine used in this paper,one is the DTU-10MW wind turbine scale model and the other is the NREL 5MW wind turbine.The DTU-10MW wind turbine is mainly used for mesh convergence verification,and the NREL 5MW wind turbine is mainly used for the simulation of aerodynamic performance of the wind turbine.First,different mesh densities are used to simulate the DTU-10MW wind turbine scale model,and the calculated thrust and torque are compared to the wind tunnel experimental values to determine if the mesh is converging.At the same time,the accuracy of STAR-CCM+ wave generation was also verified.Then the influence of tilt angle on the aerodynamic performance of the fixed wind turbine is studied.The thrust and power of the wind turbine under different tilt angles are compared,and how the tilt angle affects the thrust and power of the wind turbine is analyzed.The study found that the tilt angle affects the thrust and power of the wind turbine by changing the angle of attack of the blade section airfoil.In addition,an appropriate increase in the tilt angle not only reduces the fluctuation of the thrust and power of the wind turbine,but also reduces the wake vortex behind the tower.Finally,the motion of the FOWT under the waves was simulated.In this study,it is found that the increase of tilt angle will affect the hydrodynamic performance of the FOWT,so that the average value of the pitch motion amplitude of the FOWT and the average value of the tension of the anchor chain 1 will decrease relatively.At the same time,the amplitude of the tension of the anchor chain 1 also shows a significant drop.Anchor chain tension is the main influencing factor of its life,so an appropriate increase of the tilt angle can improve the hydrodynamic performance of the FOWT,while also reducing the load of the anchor chain and improving the life of the anchor chain.In addition,the increase of the tilt angle will cause the wind turbine thrust and power mean to decrease,while the fluctuations of the wind turbine thrust curve and the power curve also decrease.The fluctuation of the wind turbine thrust and power is mainly caused by the interaction of the blade with the tower when passing through the tower.The interaction between the blade and the tower 1s the cause of blade damage,so an appropriate increase in tilt angle can reduce the interaction between the blade and the tower,thereby increasing the life of the blade.