Coupling Hydrodynamic Analysis Of Vertical Axis Dual Rotor Floating Tidal Current Generator

The world's energy source is becoming tense,while environmental pollution keep increasing.Development and utilization of renewable energy sources are effective way to ease energy shortage and reduce environmental pollution.As a clean and pollution-free green renewable energy,tidal current has the characteristics of large reserves,wide distribution,strong predictability and little environmental pollution.The use of tidal current to generate electricity has become one of the hotspots in the field of renewable energy,which has important practical significance to alleviate energy shortage and reduce environmental pollution.And Floating tidal current generator has become a hot topic in this field.At present,most researches on floating tidal current generator are aimed at vertical axis turbine,floating carrier and mooring system.However,in actual sea condition,there exists coupling effect between hydraulic turbine and floating carrier.At the present stage,there is little research on the coupled prediction and coupling mechanism of tidal current power generation units under wind and wave environment.In this paper,a 2×150kW floating vertical axis tidal current power station is taken as the research object.The hydrodynamic performance of the floating power station is studied by using three-dimensional potential flow theory and computational fluid dynamics(CFD)method respectively.And the time domain coupling motion response of the system under the complex ocean environment load is analyzed.This paper can provide theoretical guidance and technical support for the design,development and engineering application of floating tidal current power station based on vertical axis turbine.First,three-dimensional potential flow theory is used to study the hydrodynamic performance of floating tidal current power station.The hydrodynamic model of the vertical axis turbine and the floating carrier is established,and the hydrodynamic load of the hydraulic turbine is calculated by CFD method.And the hydrodynamic coefficients of the hydraulic turbine are fitted.Based on the three-dimensional frequency-domain potential flow theory,the carrier response RAO and hydrodynamic coefficients in the regular wave are obtained in the frequency domain analysis.Then the secondary development of the AQWA software is carried out.The additional mass,radiation damping and real-time exciting force of the turbine are loaded into the model.The coupling motion responses of the floating tidal current generator station under regular wave and random wave action are analyzed in time domain.The influence of hydraulic load and different sea conditions on the hydrodynamic characteristics of the system is obtained.The results show that the load of hydraulic turbine has a significant effect on the surging and pitching motion of the system,which is disadvantageous to the hydrodynamic performance of the floating power station.Finally,the CFD method is used to analyze the dynamic response of the floating tidal current generator.The three-dimensional wave numerical water tank is established by CFD method.The flow field,force and motion response of a floating tidal current energy generator under regular wave action are analyzed by taking into account the factors such as viscosity and wave nonlinearity.Compared with the results calculated by the potential flow theory,the two results are in good agreement,which verifies the accuracy of the numerical water tank in the simulation of carrier motion.It has engineering practical value and provides a method for the subsequent floating tidal current power station performance prediction.