Investigation On The Dynamics Of Toroidal Droplets In Liquid Phase

Toroidal droplet is a ring-shaped structure with a circular cross-section.This structure has a wide range of application prospects in the preparation of biological organs.Using 3D printing technology to prepare topographic structures with annular free interfaces is currently the most commonly used method in the fields of materials engineering and biomedical engineering,and can be used for the formation of hydrogels and the reconstruction of biological tissues and organs.This subject is based on the key scientific issues faced by fluids with free surfaces in 3D printing.The main research object is the annular droplet suspended in a viscous liquid and the dynamic characteristics of the annular droplet in the liquid-liquid phase.As the main research goal,systematic experimental research and numerical research have been carried out to reveal the toroidal-forming mechanism,fracture mechanism,and dynamic characteristics of toroidal droplet.And combined with light-curing 3D printing technology to explore the application prospects of toroidal droplets in practical engineering.In terms of numerical research,considering the liquid-liquid interaction,a two-dimensional mathematical and physical model of the ring droplet is established based on the Level-Set method,the fracture process of the ring droplet in the viscous liquid is simulated,and the different interfacial tensions and viscosities are analyzed.Impact on the rupture of annular droplets.Numerical results show that the breakage of toroidal droplet is determined by the initial aspect ratio.As the aspect ratio increases,the number of toroidal droplets broken into small droplets increases.In terms of experimental research,through the establishment of a toroidal droplets experimental device,the evolution of toroidal droplet was observed,and the dynamic characteristics and nonlinear evolution law of toroidal droplet were revealed.First,the toroidal-forming mechanism of toroidal droplet is studied,and the results show that whether the toroidal droplets can be formed is affected by factors such as rotation speed and interfacial tension.Secondly,the characteristics of the toroidal droplets are studied.It is found that the toroidal droplets shrink slowly to the center in the liquid environment,and then the toroidal droplet breaks into multiple droplets due to Rayleigh-Plateau instability,and the number of toroidal droplets broken increases with the aspect ratio linearly.In the end,we studied the dynamic characteristics of toroidal droplets,and explored the influence of interfacial tension and viscosity on the dynamic characteristics of toroidal droplets suspended in viscous oil.The results show that the interfacial tension determines the morphology of the initial equilibrium state of the toroidal droplet.As the interfacial tension decreases,toroidal droplet is less likely to shrink and deform,the fission is slower,and the time for the same number of small droplets to fission is longer.Viscous stress helps stabilize the interface and suppress the rupture of the toroidal droplet caused by interfacial tension.In terms of application,toroidal droplet preparation and photo-curing technology are combined.The dynamic characteristics of toroidal droplet can be used to precisely control the size of solid ring.And by controlling the deformation time to obtain ring structures with different morphologies.The preparation technology of the solid ring provides help for the subsequent application of toroidal droplets in engineering.