Study On The Mass Transfer Mechanism Of Dissolved Oxygen Bubble Growth Near Micro-particles

The movement of bubbles is one of the most important research directions in multiphase flow.The study of the growth mechanism of microbubbles and the interaction near the wall is the basis for further expansion of bubble industry applications.The dissolved oxygen bubble that this article focuses on is the catalytic reaction of H₂O₂on the Pt side of Pt-SiO₂Janus microparticles to generate dissolved oxygen.When the dissolved oxygen concentration exceeds its saturation concentration,oxygen bubbles are precipitated,and when a certain critical condition is reached,the bubbles collapse extinct.Bubble growth and collapse will transfer energy to nearby microparticles,so it is of great significance in the study of a variety of self-driven microparticle bubble propulsion.In the bubble-driven microparticle experiment,due to the limitations of the current experimental equipment,it is impossible to understand the critical conditions for the transition between bubble growth and collapse.In order to study the mechanism of bubble-driven particle motion,this paper uses the COMSOL Multiphysics platform to analyze the bubbles of Janus particles.The stage of bubble growth in the driving process is simulated and analyzed.First,on the basis of the Janus particle bubble driving experiment,through the numerical simulation of the reactive diffusion flow of dissolved oxygen near the Janus particle,it is concluded that there is a time scale difference between the bubble growth process and the process of the dissolved oxygen concentration field reaching stability.Secondly,by simulating the self-diffusion process of oxygen,it is found that the bubble in the bubble is a quasi-static process during the growth process.Therefore,this paper ignores the state change in the bubble and simplifies the gas-liquid interface to a virtual wall.Then,the mass transfer model of the gas-liquid interface was established through Henry’s law and the gas state equation,and the bubble growth process was simulated by combining the dynamic boundary and dynamic grid technology.The results showed that the growth rate of the bubble gradually weakened during the growth process of tens of milliseconds.The bubble radius gradually reaches a stable state,and its stable condition is that the oxygen flux at the gas-liquid interface remains constant.Different H₂O₂solution concentration will affect the bubble size after stabilization.Finally,the influence of bubble growth on nearby loaded particles was studied.Through the conservation of momentum,the motion models of Janus particles,bubbles and loaded particles are obtained.Combined with the dynamic boundary technology,the motion simulation of the Janus particles generating bubbles and pushing the loaded particles is realized.The results show that the distance between the loaded particles and the Janus particles,the radius ratio and other factors will significantly affect the displacement of the loaded particles.This paper establishes a simplified multiphase flow model of dissolved oxygen bubble growth and mass transfer process,and explores the factors affecting the growth of Janus particles by Pt-SiO₂bubbles and the influence of bubble growth on nearby loaded particles.This research lays the foundation for understanding the movement mechanism of bubble-propelled self-driving particles and the application of microbubbles in the industrial field.