Research On Energy-capturing Characteristics Of Vortex Induced Vibration Of Tandem Double Cylinders

Green renewable energy is the key research and development direction of countries today.Among many renewable energy sources,ocean current energy has become the focus of research in coastal countries due to its rich reserves and wide distribution.The low-velocity ocean current energy power generation technology based on the principle of vortex-induced vibration is a relatively new power generation technology.This technology uses the vortex-induced vibration of the cylinder to obtain the water flow energy of the surrounding water area,and then converts it into electrical energy or other forms of available energy,which has attracted wide attention.In order to develop and utilize ocean current energy on a large scale in practical applications,vortex-induced vibration power generation devices must consist of double cylinders or multiple cylinders.To this end,this paper takes tandem double cylinders as the research object,and carries out the study of the vortex-induced vibration characteristics of the double cylinders,and on this basis,explores the influence of different parameters on the energy capture characteristics of the double cylinders.The main work content and conclusion of this article are as follows:First,the research progress in the numerical simulation,experimental research,and energy conversion of vortex-induced vibration of double cylinders is introduced.The principle of wake vortex shedding,the main dimensionless parameters that affect the vortex-induced vibration of the cylinder,and the control equations and numerical simulation methods involved in the numerical simulation process are described.The mathematical model of the energy conversion of the cylinder is derived,and the key parameters that affect the energy capture characteristics of the cylinder are obtained.A three-dimensional numerical verification model of a single cylinder with elastic support and single-degree-of-freedom motion was established,and the grid and time step were independently verified.In addition,the verification model was numerically simulated at Re= 3900,and the numerical results were compared with the literature results to verify the effectiveness of the numerical model and numerical calculation method in this paper.Secondly,a three-dimensional numerical model of double-cylinders with equal diameters and unequal diameters with elastic support and single-degree-of-freedom movement was established and numerically simulated.The numerical simulation results are analyzed in detail from three aspects: vibration response characteristics,hydrodynamic characteristics,and wake vortex morphology.The results show that the vibration response of the two cylinders interferes with each other and is mainly affected by the spacing.The interference effect gradually weakens as the spacing increases;the hydrodynamic characteristics are mainly affected by the spacing ratio G/D,reduced velocity Ur,and diameter ratio d/D influences.The size of the spacing affects the degree of hydrodynamic fluctuations.The reduction speed affects the hydrodynamic amplitude.The diameter ratio affects the range of hydrodynamic changes;the wake vortex shape is mainly affected by the spacing,reduction speed,and diameter ratio.The size of the gap affects the distribution form of the wake vortex,the reduction speed affects the strength of the wake vortex,and the diameter ratio affects the shedding pattern of the wake vortex.Finally,the energy harvesting power and energy conversion efficiency of the double cylinders are compared and analyzed in detail.The results show that the energy harvesting power of the double cylinders with unequal diameter is much higher than that under the same working conditions.After a comparative analysis,a double cylinder with a diameter ratio d/D = 0.6 and a spacing ratio G/D = 2?4 is selected.The vortex-induced vibration energy acquisition device can obtain more water flow energy;Energy conversion efficiency is mainly affected by the spacing ratio,Diameter ratio and reduction speed.The energy harvesting efficiency of the double-cylinders with different diameters at each pitch is higher than that under the same working conditions.Considering comprehensively,in order to obtain a higher energy harvesting efficiency,when G/D<3,the vortex-induced vibration energy acquisition device can select a double cylinder with d/D=0.4 and Ur?(4,7).When G/D>3,the double-cylinder with d/D=0.8 and Ur?(4,6)can be selected for the vortex-induced vibration energy acquisition device.In this paper,the numerical simulation analysis of vortex-induced vibration of double-cylinders with equal diameters and unequal diameters is used to verify the feasibility of the device.It provides a reference and theory for the optimal design of the double-cylinder vortex-induced vibration ocean current energy power generation device.basis.