Lattice Boltzmann Simulation And Experiment Study Of Rising Bubble Collides With Oil Droplet

Air flotation is a widely used wastewater treatment technology.It is usually used to dispose oily wastewater and suspended solids that is close to the density of water.The key step of oil removal using air flotation is the collision of oil droplets and bubbles.Therefore,it is useful and scientific that conducting researches to investigate the collision process of oil droplets and bubbles and its influence factors.Experiments using high-speed camera with a microscopic lens have been conducted to record and analyze the process of collision.Furthermore,lattice Boltzmann method(LBM)is adopted to simulate this process and to investigate effects of different factors from the aspect of simulation.First,many improved approaches such as the adjustment method of surface tension,multi-relaxation-time format and amendment of inconsistency of thermodynamics have been integrated into original multiphase pseudo-potential model.Based on the improved LBM model,a multi-component multiphase program has been accomplished.Through the simulation of static droplet and rising bubble,the consistency with Maxwell structure has been guaranteed and the capability to simulate large density ratio multiphase fluid has been proved.It shows the program is reliable.Subsequently,influences of different oil-gas ratios,such as collision angles,oil-gas phase force and the kinematic viscosity of oil have been investigated.It is clear from the simulation results that under the head-on collision situation,when oil-gas diameter ratio is larger than 1.22,bubble will lift the oil droplet and rise up.It shows great stability.With the decrease of oil-gas diameter ratio,when it less than0.821,the form of packaging changed from lifting to wrapping.Collision angle affects the efficiency of momentum transfer.The smaller the collision angle is,the larger acceleration speed the droplet will have.In addition,it is obviously that large collision angles damage the adhesion of oil droplet and bubble.Oil-gas force mainly controls the contact angle and stability of collision.With the increase of oil-gas force,the contact angle will increase and the adhesion will become more unstable.However,the kinematic viscosity of oil shows little influence towards the collision at the range of a half to three times of the experiment kinematic viscosity of oil(2.158×10~-66 m~2/s).