The Study Of The Vortices Distribution In The Wake Of Vertical Axis Hydroturbine

The fossil energy crisis and environment pollution has been gradually realized and focused for sustainable development of human society,the development of green renewable energy is the only way,tidal energy is one of them.The tidal current with periodic changes can be widely exploited by the characteristics of strong predictability and high energy density.As the core device of power flow energy,vertical axis water turbine has become a hot research topic for scientific research scholars because of its simple structure and high energy efficiency.Now consider a single vertical axis turbine numerical calculation method of viscous effects,although can accurately forecast the load and performance of impeller,but the large amount of calculation,slow speed,limited to the level of computer hardware,in the future design of large scale array layout engineering does not apply.Studying the wake distribution characteristics of vertical axis turbine and establishing an empirical model of tail vortex structure is a way to solve the problem of flow field and array layout design of tidal turbines,which is the scientific problem that this article concerns.First,the basic principle of the vertical axis hydroturbine and the analysis of the force of the blade are introduced,and the basic equations of fluid mechanics and the theory of vortex motion are explained.Then,the CFD simulation method of hydraulic turbine is introduced,and a two-dimensional numerical simulation scheme for vertical axis turbine is given.The reliability of the numerical simulation scheme is verified by comparison of numerical and experimental results.Then focuses on research of flow around a single blade,systematic analysis of the impact of various factors on the flow around the blade vortex frequency,for a fixed angle of attack of the situation,given the diarrhea frequency of vortex and wing length,flow speed relationship;research of rotating blade wake vortex distribution on the basis of discussion,velocity effect of speed ratio on concentrated vortex distribution characteristics,the blade vertical axis turbine wake vortex trajectory approximation formula.And then study the characteristics of two vertical axis turbine blades in the wake of the vorticity distribution,found that the wake characteristic obviously depends on the speed at rated speed ratio;for example,establish the relationship between the turbine power coefficient and vortex circulation;and calculating the velocity distribution of wake vortex equivalent method,the calculated results are in good agreement with the CFD simulation.The results of this paper lay a foundation for further study of the wake distribution characteristics of a vertical axis hydroturbine.