Modeling And Characteristics Of The Vortex-induced Vibration Pizeoelectric Energy Harvesting Based On The Aero-electromechanical Multi-physics Field Coupling

With the rapid development of technologies of mirco power,MEMS and wirelesssensor networks(WSNS), using piezoelectric vibrational energy harvesting equipment toharvest power from fluid flow has become the research focus in recent years. As aneffective technology for harvesting energy from the ambient environment, piezoelectricvibrational energy harvesting(PEH) has caught the attention of the researchers. It hasbeen employed mainly in the health monitoring, WSNS system and mirco-sizedelectromechanical coupling devices. Thus, it has broad prospect of research andpractical value to carry on researches of PEH. The phenomenon of vortex-inducedvibration(VIV) converts the flow energy into the vibrational energy. The effect of“lock-in” in VIV enhances the vibration intensity, and improves the efficiency of energycollection. However, there are a few researches focusing on PEH, especially onesfocusing on modeling and solving the flow-vibration-electrical circuit multiphycicalcoupling. Thus, the studies in this paper have significant meanings on the modeling andsolving the flow-vibration-electrical circuit multiphycical coupling energy harvesting.Firstly, to solve the existing problems of fluid-structure interaction in VIV, themathematical model of FSI is developed and implemented. Secondly, the researches onhow to couple VIV and PEH in multiphysical fields are carried on. Then, basing on thetechnology of vortex-induced vibration piezoelectric energy harvesting(VIVPEH), thevibration response, flow field characteristics and energy harvest behaviors aresystematically investigated with the smooth, PTC circular cylinder, square columns withattack angles, triangular columns at different apex angles.①A numerical method for solving the FSI problems of VIV has been proposed.The method can solve the continuity and N-S equations simultaneously. To verify themodel, a method of static flowing is examined the accuracy of the calculation ofexternal flow field. Then, the comparisons are conducted between the experimental dataand simulation results at different free stream velocities to validate the accuracy of theFSI solving method.②Based on the lumped parameter model of PEH, a mathematical model forsolving the aero-electromechanical coupling VIVPEH has been established for the firsttime considering of the interaction between the vibrational of bluff body, flowing of theflow field outside and the piezoelectric loop, and then the method of solving the model has been given. In order to solve the problems of the piezoelectric energy harvestingVIV conversion of electromechanical coupling, the second order linear equations of thespring-linear oscillator form and Gauss’s law equation are solved using the matrixcoefficient method.The relationship between the negative feedback effects of thevibration system and the external load resistor is obtained when the electromechanicalcoupling occurs through the analysis of the eigenvalues of the coefficient matrix. As aresult, the voltage term has been eliminated, and dimensional reduction is realized. Thus,the vibrational response and flow characteristics have been obtained. The Gauss’s law issolved using the theoretical model of the quasi-steady aero-electromechanical couplingsystem amplitude to obtain the quasi-steady-state form of the voltage output.Finally, thevibraitonal response and flow features can be obtained by substituting the vibrationamplitude of the calculation results into the expressions of the output voltage and thepower output.③By using the numerical models and solving methods of multi physical fieldscoupling VIVPEH, the vibrational response and energy harvesting characteristics ofsmooth and PTC cylinder has been obtained for the first time under the negativefeedback caused by aero-elcctromechanical coupling effects. The elcctromechanicalcoupling damping increases and then decreases with the increasing of the loadresistance, and the elcctromechanical coupling frequency increases and reaches a steadystate. Three different branches of vibration have been captured. The maximumvibrational amplitudes of smooth and PTC cylinder are quite close and the lock-inregion is decayed. The maximum voltage and power output of smooth and PTC cylinderare also quite close.④The energy harvesting features of square column with different attack angle andtriangle columns at various apex angles were investigated. It shows that the energyharvesting features of square column is better than that of circular cylinder,while theenergy harvesting features of triangle column is better than that of square column. Theattack angle has significant influence on the maximum value of vibrational amplitude ofsquare column and the lock-in region. The maximum amplitue,voltage and poweroutput appear when the attack angle is45°. It is obviously that the energy harvestingability of triangle column VIVPEH is better than that of the circular cylinder and squarecolumn. At the same time,the lock-in region, voltage and power output are improved.⑤The energy harvesting ability of60°triangular column is stronger than that ofthe cylinder with other cross-sections, which is the most beneficial to the energy harvesting. The maximum voltage of60°triangular column is increased by176.23%than that of PTC circular cylinder, while the maximum power is increased by661.8%.