Study On Energy Harvesting And Hydrodynamic Characteristics Of A Power Convertor Using Rod-controlled VIV

How to obtain clean energy efficiently from the ocean has become a hot research topic in the field of marine engineering,and it is also an important direction of the future energy strategy.Based on this engineering background,the optimization of energy extraction from vortex induced vibration of a single cylinder is realized by adding two small control cylinders.Through the adjustment of related parameters,the influence of different parameters on optimization is studied.The variable structure and geometric parameters selected in this paper are as follows:the reduced velocity Ur,the damping ratio(?harness),the dimensionless rotation speed of the control cylinders ?,the control angle ?,the diameter ratio d/D and the gap ratio g/D.On the basis of single factor analysis,the parameters(reduced velocity Ur,gap ratio g/D and diameter ratio d/D)are selected for the simple rule of the energy utilization efficiency and the clear mechanism.With these parameters,the energy harness efficiency and the hydrodynamic characteristics of the vortex induced vibration system in the multi parameter space including the damping ratio ?harness,the dimensionless rotation speed?and the control angle?,are comprehensively analyzed.The main results are as follows:The influence of fixed parameters on energy efficiency is analyzed.(1)The net energy harness efficiency increases with the reduced velocity,and reaches the maximum at the rate of 6.0.(2)With the increase of gap ratio g/D,the efficiency of net energy harness decreased.(3)When the damping ratio is 0.1 and 0.2,the net energy harness efficiency increases first and then decreases with the increase of the diameter ratio.When the damping ratio is 0.3 and 0.4,the net energy harness efficiency decreases with the increase of the diameter ratio.And the harness efficiency of net energy is the highest when the diameter ratio is 0.25.Considering the feasibility and the adaptability of power convertor,the selected parameters are determined as:Ur=6,g/D=0.125,d/D=0.A25.It is found that the optimal net energy harness efficiency is 0.195 in the parameter space,and the corresponding parameter combination includes:zero rotation speed,the control angle ?=65° and the damping ratio ?harness=0.2.With the increase of damping ratio,rotation speed and control angle,the harness efficiency of net energy shows a tendency to increase initially and decreases afterwards.The effects of structural and geometric parameters on the hydrodynamic characteristics of a power generation unit are discussed.The distribution of the lift and drag coefficient,the amplitude,the vortex shedding frequency and the phase difference between the lift and the displacement in the parameter space are analyzed.A combined parameter ?/? is presented.The formula of the relationship between energy efficiency/hydrodynamic parameters and combined parameters is obtained by fitting.It shows that the combined parameters are in good parabola relation with energy coefficient,amplitude and the phase difference between lift and the displacement while there is a linear relationship between the combined parameters and drag/lift coefficient.