Research On Eccentric Elliptic Cylinder Flow Around The Movement And Flow

With the continuous rise of energy demand,the contradiction between environment and fossil energy consumption is becoming more and more prominent.The development of renewable energy is a hot research topic at present.A single renewable energy source cannot meet the world's energy needs.As a clean and renewable energy source,ocean current energy density is proportional to the cube of velocity.However,the current technology can not use the ocean current energy on a large scale and efficiently,especially the low velocity ocean current energy.In this paper,a device for extracting ocean current energy by elliptic cylinder swing around flow is proposed,and the research on fluid-solid coupling characteristics and energy conversion is carried out through experiments and numerical simulation,which provides scientific theoretical guidance for the development and utilization of ocean current energy and low head water energy resources.The motion of elliptic cylinder under the action of incoming flow can be considered as the fixed-axis auto-rotation.The motion process continuously converts the flow energy into mechanical energy of the auto-rotation elliptic cylinder,to realize the purpose of capturing the incoming flow energy.In order to explore the influence of geometric parameters,motion parameters and viscous parameters of the flow on the hydrodynamic and energy capture performance of the auto-rotation elliptic cylinder,the following research work has been done:The effects of Reynolds number,eccentric distance ratios and axis rations on the oscillation angle and oscillation frequency of elliptic cylinder were studied by physical model test.The experimental results show that Reynolds number has insignificant influence on the oscillation angle of elliptic cylinder,but Reynolds number has a good line increasing relationship with the oscillation frequency of elliptic cylinder.The swing angle of elliptic cylinder increases with the increase of eccentric distance ratios and axis rations.The eccentric distance ratios has no relation with the oscillation frequency of elliptic cylinder.This paper studies two way Fluid-Structure Interaction of the fixed-axis auto-rotation of rigid elliptic cylinder using a coupled Computational Fluid Dynamics(CFD)– Rigid Body Dynamics(RBD)model.Based on Solving two-dimensional unsteady incompressible N-S equations and SST k-? turbulent governing equations,wake flow features and motion characteristics of elliptic cylinder were investigated in different axis rations,eccentricdistance ratios and Reynolds number conditions.Wake evolution behind the cylinder and variations of instantaneous pressure coefficients are analyzed in order to reveal mechanism of swing motion of elliptic cylinder.The harvesting energy efficiency of auto-rotation elliptic cylinder is studied,and the basic principle of generating device for harvesting ocean current energy is revealed.From the point of view of energy,the harvesting energy efficiency of elliptic cylinder and the energy contained in flow field are calculated theoretically,and the formula of harvesting energy efficiency is established.The harvesting energy efficiency of elliptic cylinder system are discussed in different Reynolds number,eccentric distance ratios and axis rations.The results show that the harvesting energy efficiency of elliptical cylinder system increases with Reynolds number,eccentric distance ratios and axis rations.The harvesting energy efficiency of cylinder system is greater than elliptical cylinder system.The study provides a theoretical guidance for obtaining low velocity ocean current energy and low head water energy by auto-rotation.