Study On Hydrodynamic Performance Of Horizontal Axis Tidal Current Turbine In Different Conditions

With the gradual depletion of traditional fossil energy and the aggravation of environmental pollution,development and utilization of renewable energy is the only way for sustainable development of human society.The tidal current energy has become the research focus in the world by the characteristics of strong predictability and high energy density.However the real ocean environment is very different and complicated,and has different effects on the hydrodynamic characteristics of turbine and floating platform,for example,the shear flow,the wave and free surface.At the present stage,the researches on the hydrodynamic performance of tidal horizontal axis turbine mostly focus on the ideal condition of uniform flow,without considering the influence of shear flow.The researches on the motion response of floating platform take few consider of the coupling between the turbine and the floating platform.In this paper,CFD method is used to analyze the hydrodynamic performance and flow field of tidal horizontal axis turbine in uniform flow and shear flow.And the coupling motion response in three degrees of freedom(surge,pitching and heaving)and hydrodynamic performance of the turbine and the floating platform affected by wave are studied.This paper will provide technical support for the design and construction of horizontal axis turbine tidal current power generation devices.First,this paper introduces the basic theory of CFD numerical simulation method of horizontal axis turbine.And then the energy utilization coefficient and axial load coefficient of horizontal axis turbine in uniform flow are calculated by STAR-CCM+software.The reliability of CFD numerical simulation method is proved by comparing with the experimental results.Secondly,the hydrodynamic performance and flow field characteristics of horizontal axis turbine under different speed ratios in uniform flow are calculated and analyzed.It is found that the speed ratio has obvious influence on the hydrodynamic performance and flow field of horizontal axis turbine.Then the lift and drag coefficients of blades at different span positions are studied and compared with the two-dimensional theoretical results.Thirdly,the hydrodynamic performance and flow field characteristics of horizontal axis turbine in shear flow are calculated and analyzed,and the reasult reveals the influence of shear flow on them.At the same time,the variation curves of lift drag coefficient and angle of attack at different span positions are given.Finally,CFD method is used to simulate the coupled motion among turbine,floating platform and mooring system.The effects of different wavelength,wave amplitude and turbine speed on the motion response of the floating platform and turbine,mooring pull force and energy utilization efficiency are revealed Then the flow field and wave surface are analyzed,and it is found that the wake field of the turbine in waves is obviously shortened.