Study On Dynamic Behavior Of Droplet Desorption At Solid-liquid Interface Under Ultrasonic Standing Wave

Aiming at the research of ultrasonic inner processing assisted technology,the problem of how to separate the pitting waste liquid in closed space make it particularly important to explore the internal flow tendency and interface deformation of molten waste.During ultrasonic inner processing,the trend of molten droplet movement and deformation becomes extremel y complex due to the influence of ultrasonic radiation force,viscous force,s elf-gravit y and surface tension.Different from ordinary transparent liquid,the non-transparent properties of molten metal droplets make it difficult to directl y observe the tendency of the morphology of the mol ten droplets,and the numerical simulation method is a good solution to this problem.In this paper,we mainl y stud y the droplet movement equation and morphology change law on the solid-liquid interface under the action of ultrasonic standing wave from the theoretical model deduction,numerical simulation and experimental verification.The purpose of this stud y is to establish an experimental validation numerical model to adapt to other fluid models b y changing material parameters,so as to verify the possibility of desorption molten waste in ultrasonic inner processing.The contents of the thesis are as follows:(1)First of all,the basic theory of ultrasonic standing wave is described,then the nonlinear effect of ultrasonic wave is introduced and the fundamental wave law of fluid d ynamics is deduced.The standing wave solution of ultrasonic standing wave propagating in fluid is derived.The influence of the nonlinear effect o n the amplitude of sound pressure is simulated and compared with the linear analytical solution b y the numerical simulation method.It is finall y shown that,under the nonlinear effect,the amplitude of sound pressure will change obviousl y after a certain distance of ultrasonic wave propagation,and the nonlinear effect is dominant.Secondl y,the coupling equation of the ultrasonic wave to the liquid-solid interface droplet is established,and the zero-order equation,the first-order equation and the second-order equation of the sound wave propagating in fluid are deduced.(2)Taking the specific form of droplet wetting behavior at the solid-liquid interface as the starting point,we first l y studied the influencing factors of the size of contact angle after wetting of droplets at different solid-liquid interfaces.Then the influence factors of droplet desorption and the mechanical properties of liquid droplets on the solid-liquid interface are also studied.Secondl y,the motion equation of droplet under ultrasonic standing wave is established,and the shape change and movement trend of water and low melting point allo y under ultrasonic standing wave are simulated and anal yzed b y numerical si mulation software.The change of sound pressure amplitude under different groove sizes and depths has been studied,and the sound pressure distribution of axis and surface of water drops and molten allo ys has been studied.Finall y,the influence diagram of water and low melting point allo y on the amplitude distribution of acoustic pressure is obtained,and the droplet shape change process and flow field distribution map under the action of ultrasonic standing wave are obtained.(3)Finally,the liquid drop desorption experiment of solid-liquid interface under ultrasonic standing wave is carried out.This paper mainl y introduces how to build the experiment of droplet desorption and movement on solid-liquid interface b y ultrasonic standing wave,and studies t he desorption behavior of droplet and low melting point allo y at different grooves size and depth.The morphological changes of different droplets ultrasonic desorption and separation are studied under the same groove diameter and depth,and the morphologi cal changes of droplet ultrasonic separation under different droplet diameter and depth with the same droplet size are also studied.In order to further characterize the morphological evolution of the droplets,the morphology of the droplets under the ultrasonic desorption suspension process is anal yzed,and the change trend of the ratio of the droplet a/b is studied.It is concluded that onl y when the specific frequency and groove size and depth are applied,the droplet will be desorbed and separated from the solid-liquid interface under the action of ultrasonic standing wave,and finall y will remain stable near the standing wave node or standing wave node.