| With the depletion of traditional fossil energy and the accompanied deterioration of environment,as a kind of clean and renewable energy,tidal current energy has been a research hot at home and abroad.The floating tidal power generation device has a simple structure of floating platform which can work in deep water and can be easily repaired,moved and recycled,thus it attracts more and more attentions of the experts and scholars from many countries.However,the real complicated ocean environment has different effects on the hydrodynamics,for example,the free surface,seabed,the gradient of current velocity and wave.Because of the existence of wave and permanent connection between the vehicle and turbine,there will be motion response of the floating structure,which can lead to the change of relative flow speed and the hydrodynamic characteristics of turbine.Recently,the researches on hydrodynamic performance of tidal current turbine are mostly focused on the hydrodynamic performance of the turbine in homogeneous flow and few in the complicated environment.Therefore,the theoretical and experimental research on the hydrodynamic problems and computational method of horizontal axis tidal current turbine in swaying motion are studied in this paper.The research results will supply the design theory and related data for the hydrodynamic characteristics and load of the turbine,and also have important academic significance and application value for the research on structure strength checking,design of control system and floating movement response in wave.The model test on horizontal axis tidal current turbine is carried out in the towing tank.The testing method of power efficiency and the axial load of turbine are provided;the power efficiency and axial load of turbine are tested under different immersion depths and different wave parameters.According to the test results,the power characteristics and load characteristics of turbine are analyzed,the influence of the immersion depth and the wave on the hydrodynamic performance of turbine is obtained.Experimental study will provide useful data for the validation of numerical simulation of horizontal axis tidal current turbine and huge valuable information for the design of hydrodynamics of horizontal axis tidal current turbine.The effectiveness of CFD numerical method on horizontal axis turbine is verifiedthrough comparing with the test results.A new CFD numerical simulation method for a rotary shaft sway during turbine operation is proposed,based on the second software development of CFX.The gird quality is ensured,which is helpful to improve the computing speed and precision,by adopting the way of grid movement from the combination of sliding mesh and dynamic mesh.In order to study the effect of free surface,the CFD numerical method is used to simulate hydrodynamic performance of turbine under the free surface,and the variation rule of power efficiency and axial load coefficient is obtained.By changing the immersion depths,the influence on the power efficiency and axial load coefficient under different depths is also obtained.In order to study hydrodynamic performance of turbine under single degree freedom motion,the CFD numerical simulation on the hydrodynamic performance of horizontal axis turbine under the single degree freedom oscillation of turbine's axis(surge,sway,heave,roll and yaw)is carried out by combining the structured grid and unstructured grid,and the changing rule of power efficiency and loads is obtained.The influence of oscillation frequency,oscillation amplitude and rotation speed on power coefficient and loads are study,and the effect rule of that is obtained.Flow field characteristic of turbine under single free degree motion is analyzed,and the effect of oscillation frequency,amplitude and rotation speed on flow filed of turbine is got.In order to calculate hydrodynamic coefficients of horizontal axis turbine,a new method based on the numerical fitting method and CFD method is presented.By dividing the CFD calculation result of hydrodynamic load of horizontal axis turbine with single degree freedom motion of sway into hydrodynamics with uniform flow,speed-related sway damping force and added mass force associated with sway acceleration,the hydrodynamic coefficients of horizontal axis turbine can be obtained..The hydrodynamic coefficients are compared under different oscillation frequency,oscillation amplitude and rotation speed,so that the effect rule of that are presented.To study the hydrodynamic problems of horizontal axis turbine under multi degree freedom motions(surge and yaw,pitch and roll),the hydrodynamic performance is simulated,the power efficiency and the load coefficients of horizontal axis turbine are obtained,based onthe CFD method.The influence of oscillation frequency,oscillation amplitude and rotation speed on power coefficient and loads are studied under multi free degree motions,and the effect rule of that is obtained. |
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