Mechanism Analysis And Experimental Study Of Non-stationary Oscillation Induced By Acoustic Levitation

Acoustic levitation technology is one of the key technologies in the non-containerless contact operation technology.In recent years,the non-stationary motion state of spherical particles in the acoustic field has attracted wide attention.The research on acoustic standing wave levitation has become a hot topic in the non-containerless contact physics,biochemistry and other disciplines.The existence of non-stationary oscillations is an important source which hinders the steady levitation of small balls in standing wave sound field.The levitation state of small ball mainly includes stable levitation,constant amplitude oscillation and non-stationary oscillation,and the non-stationary oscillation of small ball may further cause resonance drift of sound field.Compared with electrostatic levitation and electromagnetic levitation,acoustic levitation has no special requirements for the materials of suspended objects,so acoustic levitation technology can be widely used in the levitation control of various materials.However,for the study of the complex motion law of suspended particles in the sound field,in particular,the internal correlation between the non-stationary oscillation mechanism of the suspended spheres and the instability induced by the composite sound field has not been clarified.Therefore,the study on the stability of acoustic levitation pellets in this paper can not only deepen and improve people’s understanding of the regularity of the instability mechanism of acoustic levitation pellets,which has certain scientific significance,but also contribute to the formation of advanced ultrasonic levitation device design and control technology,which has important practical value for the stable operation of acoustic levitation technology.This paper takes suspended spheres as the research object,through theoretical modeling,simulation analysis and experimental testing methods to carry out in-depth research on the induction mechanism of non-stationary oscillation of acoustic suspended spheres.Based on the acoustic theory,the theoretical equation of acoustic radiation force was derived,the motion model of suspended ball in standing wave acoustic field was constructed,and the numerical simulation was carried out under the vibration of the amplitude horn at the emitting end.The accuracy of numerical calculation of the height of resonant cavity and acoustic radiation force was verified by experiments.Based on numerical analysis and stability model analysis,the induced mechanism of acoustic suspended spheres under acoustic field was revealed.Combined with the sound-structure coupling equation,the stability model of the suspended sphere suitable for the composite sound field was constructed.The influence of the composite sound field on the instability of the suspended sphere was studied by the dynamic mode decomposition method.When the test system and test platform of acoustic suspended spheres are established,the nonstationary oscillatory motion of suspended spheres is analyzed by experiments.The nonlinear dynamic Duffing equation of non-stationary oscillating pellets is established and verified by experimental data.The steady state of the non-stationary oscillation of the ball is related to the initial condition.When the system damping is less than zero,the non-stationary oscillation of the ball will continue in the chaotic state.When the system damping is greater than zero,the ball is in the limit cycle vibration state,that is,the oscillation amplitude becomes larger and larger until the ball falls into the acoustic field.