Study On The Flow-induced Vibration Of Piezoelectric Energy Harvesting With Different Cross-section Shapes

Many kinds of energy in the environment are objects in the study of energy harvesting,such as light,heat,mean flow and mechanical vibration.The mean flow energy is a kind of energy with huge reserves and wide distribution.The energy harvesting of mean flow which is based on piezoelectric technology is a widely favored form of energy harvesting.The flow of water around the ship will produce a certain velocity of flow,which contains huge energy.How to harvest and use this part of the energy,such as supplying power for small electronic devices,has important research value.First of all,a distributed parameter model and a lumped parameter model for cantilever piezoelectric energy harvester are established.Then,four kinds of piezoelectric energy harvester which are based on flow induced vibration are designed with different profile shape columns.Using the wake oscillator model and the lift drag model which combine with the finite element method,the four kinds of piezoelectric energy harvester with different profile shapes are numerically modeled.The results of numerical calculation show that the cylinder shows good vortex induced vibration characteristics.When the flow velocity is 0.24m/s,the maximum amplitude and output voltage of the cylinder are obtained,0.032 m and 7.7V respectively.The amplitude and output voltage of square 1 and triangle increase with the increase of flow velocity,showing obvious galloping characteristics.The amplitude and voltage of square 2 fluctuate at 0.045 m and 3.5V after the incoming velocity is 0.177m/s.the four kinds of piezoelectric energy harvester have good energy output efficiency.A small circulating water tunnel is designed and built for experiment which is flow induced vibration of the piezoelectric energy harvester.Flow induced vibration experimental scheme is established for different profile shapes column piezoelectric energy harvester.The experimental study on the flow induced vibration of four kinds of piezoelectric energy harvester with the same feature size but different profile shape,cylinder,square 1,square 2,triangle,is carried out.Some laws of flow induced vibration and output electric energy which are different from simple cylinders are obtained.The energy harvesting effect of different profiles shape is evaluated.The influence of profile shape on the flow induced vibration characteristics of columns is discussed.It is found that for a cylinder,under the experimental velocity range,the cylinder can exhibit excellent vortex induced vibration characteristics.In the vortex induced vibration frequency locking stage,the harvester output voltage characteristic of piezoelectric energy harvesting shows well performance.The maximum output voltage can reach 7.5V,and the output power reaches 0.053 mw,and the density of power is 0.118w/m2.For two square with different attack angles,the square 2 is more prominent than the square 1 under the same flow condition.The square 2 has a sharp edge on the inlet,which shows more obvious flow induced vibration characteristics than the square 1.The output voltage of square 2 is stable at 3.5V after 0.167m/s.In the low velocity range,the dominant frequency of the triangular is near the first natural frequency of the triangular,which shows that the triangular has a higher energy conversion efficiency than the other three Columns in the low velocity range.The experimental results of the amplitude and output voltage of the four harvester are in agreement with the numerical results.The experimental results of the amplitude and output voltages of the four harvesters are in good agreement with the numerical results.It is feasible to use the wake oscillator model and the lift drag empirical model to simulate the energy harvest process of the piezoelectric energy harvester of this type by combining the finite element method.A built-in cantilever beam piezoelectric energy harvester is proposed,which has the advantages of corrosion protection and insulation.The results of the flow induced vibration experiment show that the energy harvester has an optimum matching resistance.When the flow velocity is 0.816m/s,the best matched resistance is 680kΩ and the maximum output power is 6.44μW.