| Bubble migration near the wall exists widely in the fields of energy power,environment and chemical industry.Characteristic parameters such as bubble diameter,motion trajectory,shape,and speed are important parameters that affect the flow behavior of gas and liquid in two phases,which have a direct impact on heat transfer and mass transfer and chemical reaction rate in industrial processes.Therefore,systematically studying the migration behavior of near-wall bubbles has important theoretical guiding significance for rationally regulating the flow of gas and liquid in the near-wall surface.Based on high-speed photography technology,this paper conducts experimental research on the migration behavior of bubbles under different wall conditions and liquid phase properties,in order to reveal the migration behavior of bubbles near the wall surface under different wall conditions and liquid phase properties.The main work and conclusions are as follows:（1）A set of experimental test platform for visual gas-liquid two-phase flow was built,and a set of automated processing procedures were written based on digital image processing algorithms to achieve batch and accurate extraction of bubble characteristic parameters.（2）In pure water,the different initial distances of bubbles and the wall show different effects on the lateral migration of single bubble,the smaller the initial distance from the wall,the stronger the attraction effect of the wall facing the bubble,and the shorter the bubble straight up stage.The larger the bubble diameter,the more pronounced the wall repulsion effect.The wall has a stabilizing effect on changes in the shape of bubbles.PTFE hydrophobic walls show a stronger attraction effect.When the bubble is very small from the wall,the bubble adsorbs on the wall and slips,and the bubble trajectory oscillation period and amplitude are smaller than the glass wall under hydrophobic wall conditions.When the bubble collides with the wall surface periodically,there is a conversion between the bubble kinetic energy Ek and the surface energy Es,and between the kinetic energy Ekx and Eky,and the energy dissipates during the collision,and the kinetic energy peak gradually decreases.（3）In 1-pentanol solution,the influence of the wall on the aspect ratio and velocity of the bubbles is weakened.The bubble trajectory is more stable,and the trajectory amplitude and period are reduced.1-pentanol inhibits bubble deformation,reducing bubble detachment diameter and terminal velocity.（4）In pure water,Fan’s E-Ta correlation formula can better predict the aspect ratio of 1.96～2.97mm diameter bubbles,and Liu’s E-We correlation formula can better predict the aspect ratio of 4.12～5.49mm diameter bubbles.Fan’s terminal velocity prediction model can predict the terminal velocity of bubbles with a diameter of 1.96mm to 5.42mm.In n-pentanol solution,Wellek’s E-Eo correlation formula can predict the aspect ratio of2.4 mm to 5.1 mm diameter bubbles very well,and the terminal velocity prediction model proposed by Tomiyama can predict the terminal velocity of 2.4 mm to 5.1 mm diameter bubbles.Compared with the existing classical drag coefficient prediction model,Li Chen’s prediction model is the most accurate in predicting the bubble drag coefficient in n-amyl alcohol solution and pure water.（5）The coefficient of drag force of bubbles in 1-pentanol solution is greater than that of pure water,and the coefficient of drag force increases with the increase of bubble diameter.Based on the experimental data,the prediction model of the wall-force coefficient is revised,and the error between the prediction value of the revised model and the experimental value is within±15%.Figure 72,Table 4,References 78... |
