Experimental Study And Simulation Of Viscous Liquid Bridge Behavior Between Spherical Particles

Gas-liquid-solid multiphase flow widely exists in chemical production,such as in the process of solid-liquid stirring with a certain liquid holding capacity,gas-solid fluidized bed,and granulation of particles.The bridging phenomenon formed by the liquid between particles is a common form in multiphase flow.Studying the critical rupture conditions of the liquid bridge and understanding the rupture laws of the liquid bridge are of great significance to the design and optimization of related processes.In this paper,water and silicone oils with different viscosities are used as liquid bridge materials.Through experiments and numerical simulations,the process of stretching the liquid bridge between equal diameter particles to rupture is studied.The relationship between the critical rupture distance of the liquid bridge and the volume of the liquid bridge,the initial distance between the particles,the stretching velocity of the liquid bridge and the viscosity of the liquid bridge are investigated.Experimental studies have found that when the liquid bridge material is water,when the dimensionless liquid bridge volume is less than 0.22,the critical rupture distance of the liquid bridge increases with the increase of the liquid bridge volume,and there is a power function relationship between them.The critical rupture distance can be described by the modified Bond number V*Bo.When V*Bo is about 0.6,the dimensionless critical rupture distance reaches a maximum of 0.94.When the liquid bridge material is water,for a small liquid bridge(V=8mm3),there is no significant relationship between the critical rupture distance and the initial distance of the particles.As the volume of the liquid bridge increases(V=10 mm3-14 mm3),the critical rupture distance increases linearly with the initial distance between particles in a certain area.If the liquid bridge stretching distance and the initial distance between particles are used for characterization,it is found that the liquid bridge stretching distance decreases approximately linearly with the increase of the distance between particles.When the liquid bridge material is water,the capillary force plays a dominant role in the stretching process of the liquid bridge.At this time,the critical rupture distance has no obvious relationship with the particle relative velocity.When the liquid bridge material is silicone oil,the viscous force of the liquid phase begins to be significant,and the critical rupture distance increases with the increase of the capillary number.For liquid bridges with greater viscosity,the experimental results show that as the capillary number of the liquid bridge increases,the effect of the relative velocity of particles on the critical rupture distance also gradually increases.And the influence of the viscosity of the liquid bridge on the critical rupture distance increases as the volume of the liquid bridge increases.The VOF method based on overset grid was used to numerically simulate the liquid bridge stretching process.By comparing the simulated value and the experimental value of the critical rupture distance,as well as the difference between the internal and external pressure difference of the liquid bridge and the theoretical equation solution,it is shown that the numerical simulation method CFD numerical simulation results used in this paper can accurately describe the process of the liquid bridge stretching to rupture.Extracting the pressure field information in the liquid bridge from the numerical simulation results can provide important data for the selection of the capillary force model.In this paper,the theoretical equation containing the correction factor Xv proposed by Pitois is used to calculate the capillary force and the viscous force,and based on this,the rupture energy of the viscous liquid bridge is calculated.Through the calculation of the rupture energy,it is found that the rupture energy of the viscous liquid bridge is mainly related to the capillary number of the liquid bridge,and the relationship between the rupture energy and capillary number can be divided into two different stages with Ca=0.01 as the turning point.Two empirical formulas for predicting the rupture energy of the viscous liquid bridge is proposed by means of regression fitting.