Numerical Simulation Of Particle Sedimentation And Particle-bubble Collision Behavior With Different Shapes

Particle settling phenomenon and particle-bubble collision in the liquid phase can be found in nature and industry such as the free settling process of suspended particles and the collision process between particles and blown bubble in water treatment process.The particle sedimentation and particle-bubble collision behavior has been studied extensively.But there are still many problems have not been solved such as the non-circular particle settling behavior under different channel width,effect of particle aspect ratio on settlement behavior of rectangular particles with the constant mass.Moreover,during the bubble-particle collision process,the bubble was set as rest state without considering the bubble movement.Based on the above problems,the numerical simulation has been employed to study the sedimentation behavior of different shape particles under different channel width and the particle-bubble collision and attachment behavior with different shape particles.The main conclusions are as follows:(I)Particle sedimentation behavior(1)There are four kinds of sedimentation behavior of particle under different Reynolds numbers:stable sedimentation,weak oscillation sedimentation,strong oscillation sedimentation and irregular oscillation sedimentation.(2)When the channel width is less than 10mm,the channel width has a great impact on the particle settling behavior,whereas the channel width is more than 10mm,the channel width has no effect on the particle settling behavior(3)The average drag coefficient increases with the increasing aspect ratio under the same particle mass.(4)The average drag coefficient of circular particle is smaller than that of square and elliptical particles under the same Reynolds number.For elliptical and square particles,the average drag coefficient of the square particle is less than elliptical particle when the Reynolds number is less than 110,whereas the average drag coefficient of the square particle is more than that of the elliptical particle when the Reynolds number is greater than 110.(II)Particle-bubble collision behavior(1)The advance contact angle is more larger and the collision time of particle collides with bubble is more shorter.(2)There are two kinds of collision and attachment modes for circular particle,moreover there are two kinds of attachment modes for square particle,while there is one kind of collision mode.(3)When the bubble diameter is less than 0.8mm,the collision and the critical attachment time of the circular particle increases with the increasing bubble diameter.However,the trend of the collision and the critical attachment time for the square particle are opposite.(4)When the bubble diameter is larger than 0.4mm,the collision and attachment time of the square particle are smaller than that of circular particles.