Experimental Study On The Characteristics Of Energy Conversion Of Bluff Body With Piezoelectric Plate The Finite Channel

Blunt body is a kind of non-streamlined structure which can be seen everywhere in daily life.The flow past bluff body is a kind of physical phenomenon prevalent in nature.This seemingly simple physical phenomenon actually contains extremely complicated flow mechanism.When the blunt body is fixed for elastic support or deformation occurs,the vortex shedding from the both sides of the bluff body caused by the pulsating force will make the blunt body produce periodic vibration,the vibration of the cylinder further changes the vortex formation and vortex shedding patterns,the interaction between the fluid and the blunt body is called flow-induced motion(FIM).In the field of engineering,the sustained oscillation caused by FIM may lead to structural fatigue damage;this also shows that FIM has a lot of energy can be used.Due to the vortex shedding in FIM and flow past bluff body will occur in the low-speed flow conditions,if the vortex shedding caused by vibration can be used to generate electricity,compared to traditional power generation technology,there will be no rotating parts,sliding or rolling friction in this type of device,which is more suitable for miniaturization of devices.In this paper,the wind tunnel experiment is carried out by analyzing the output voltage,the output voltage frequency and the average peak voltage curve,and the cross-sectional shape and the length of the piezoelectric plate are studied by using the blunt body-piezoelectric system with different cross-sectional shape blunt body and different piezoelectric plate parameters on the energy output characteristics of the bluff body-piezoelectric system,and provide a theoretical basis for the energy collection using the bluff body-piezoelectric plate system.The main conclusions of this paper are as follows:Firstly,the wind tunnel test was carried out on the square-piezoelectric plate system of the piezoelectric plates with different lengths.The effect of the length of piezoelectric plates on the energy collection characteristics of the square-piezoelectric system was studied.It is found that the flow velocity has a direct effect on the output voltage of the square-piezoelectric plate system.As the flow velocity increases,the amplitude of the free end of the piezoelectric plate increases and the vibration frequency decreases.When the length of the piezoelectric plate is short,the vibration frequency will be resonant when the frequency is close to or equal to vortex shedding frequency of square cylinder,the output voltage will rise sharply.With the increase of wind speed,there will be an output voltage stable transition zone after the resonance point.When the part of the piezoelectric piece near the fixed end began to participate in vibration,it marks the end of the transition phase,the wind speed reach to the critical wind speed,the output voltage has a rapid growth again.Then,the wind tunnel experiment is carried out on the blunt body-piezoelectric system with the different front blunt body as the triangular cylinder,the trapezoid cylinder and the reverse trapezoid cylinder.The influence of the shape of the front blunt body on the output voltage of the system is studied.The results show that the blunt body shape is an important influencing factor to the output voltage of the bluff body-piezoelectric plate system.When the shape of the bluff body changes,the separation of the flow boundary layer around the bluff body and the position of the vortex shedding are different.The boundary layer of the triangular cylinder and the trapezoid cylinder is separated from the edge of the leeward side,and the shedding vortex is no longer directly affected by the blunt body.The flow boundary layer of the reverse trapezoid cylinder and the square cylinder is separated at the cover of the windward.And the width of the reverse trapezoidal piezoelectric system,which is perpendicular to the front of the windward,is decreasing,the effect of the boundary layer on the edge of the windward edge is reduced,which reduces the hindrance to the formation and shedding of the vortex,and its voltage output is stronger than that of the square-piezoelectric plate system.In this paper,the performance of the reverse trapezoids-piezoelectric system voltage system is better in all operating conditions,especially at high peak speed is particularly prominent,the maximum average peak voltage Vpeak = 1.829 V,this When the output power is P = 1.67?W.