Direction-adaptive Flow Velocity Sensing And Energy Harvesting Design Under Vortex Induced Vibration

Environmental problems are significant and affect the living conditions of human beings.The oceans,which occupy more than 70% of the Earth’s surface,regulate global temperature and absorb and process pollution worldwide.To closely monitor changes in marine environments,many ocean monitors and sensors placed in deep-ocean areas are required to gather information on velocity,temperature,and other quantities.Energy is essential to run these monitors and sensors.However,traditional batteries easily leak in the ocean’s high electrolyte environment,causing further pollution and the failure and eventual disposal of equipment.Since the power consumption of ocean monitors and sensors is relatively low,permitting the use of marine energy harvesters.Marine environments provide a rich source of fluid flow mechanical energy,solar energy,chemical energy,and osmotic power,among other energy types.The use of marine energy harvesting technology reduces the risk of further pollution,lower recall costs caused by frequent equipment recycling,and conceivably prolong equipment life.Among the types of marine energy,fluid flow mechanical energy has important research value due to its extensive distribution and continuous availability.Based on the micro marine kinetic energy harvester,here puts forward a research on underwater flow adaptive ocean current sensing.In the research,the basic cantilever beam structure is used.According to the variability of ocean current flow direction,two series of flow direction adaptive structural forms are designed and their advantages and disadvantages are analyzed.Based on the characteristics of cantilever torsion and pendulum,the principle and analysis method of velocity sensing are analyzed,and its velocity sensing function is preliminarily realized.This paper focuses on the theoretical research and preliminary implementation of ocean current flow direction and velocity sensing based on piezoelectric energy harvester.Firstly,aiming at the flow direction adaptation,the L-shaped elastomer structure based on traditional transverse vibration with guide wing and the arc(C/S-shaped)elastomer beam structure based on torsional vibration are proposed.The structural analysis and theoretical research of two forms of flow direction adaptation systems are carried out.Based on the traditional cantilever model,the design of L-shaped elastomer transverse vibration system applies theoretical mechanics and hydrodynamics to analyze the three motion states of rotation,transverse vibration and lodging in the process of flow direction adaptation.A mechanical model is used to analyze its starting conditions.The vibration balance angle as the critical value of rotation and transverse vibration is analyzed based on the principle of minimum action and the rotation stall angle as the critical value of rotation and lodging is got by Kc number.Totally,the direction adaptive angle is comprehensively analyzed.Design and analysis of curved(C/S)elastomer torsional vibration system is based on the progress of solid trajectory study of vortex induced vibration,combined with the boundary layer theory and vibration theory in hydrodynamics.The structural coupling superposition of torsional vibration is analyzed.The mathematical model of flow direction adaptation is established and analyzed through the first-order rigid body model.Secondly,according to the velocity sensing principle,the frequency-velocity equation is established for the L-shaped elastomer system.A two degree of freedom mechanical model of torsional vibration for C/S-shaped system is established.Through the relationship between torsional amplitude and vortex shedding frequency,the relationship between size parameters and velocity sensing resolution and the relationship between velocity and frequency are analyzed.Thirdly,based on the realization of velocity sensing and flow direction adaptation,the modeling and analysis of the two systems combined with piezoelectric material for vibration energy harvesting are further carried out.In the research of Lshaped elastomer system,the position parameters are simulated and the energy capture experiment is prepared.The three degree of freedom mechanical model of C/S-shaped elastomer system is established,and the influence of important parameters on energy harvesting effect is analyzed,including the structural parameters of cylinder bluff and the arc elastic beam,bearing friction coefficient and so on.Finally,the flow direction adaptation,flow sensing and energy harvesting are verified and analyzed by experiments.The effects of important parameters on the performance of three functions are further verified,and the data linearity of velocity sensing is studied.By comparing the experimental data and mathematical model,the flow direction adaptation model,velocity sensing model,and energy harvesting model are verified.