Research On Simulation Of Particle Sedimentation And Particle Motion In Shear Flow

The particles sedimentation and suspended particles' motion in the shear flow widely exists in industrial production,environmental protection and other related field.The research has been a classical problem of fluid field.In this paper,the lattice Boltzmann method are used to simulate the particle sedimentation and particle motion in shear flow.The main work and results as follows:(1)The lattice Boltzmann-direct forcing/fictitious method has been used to simulate the sedimentation of two particles in a channel for the Reynolds number of50?Re?200.It has been shown that the two particles eventually sedimenting at 1/4and 3/4 of channel width,respectively,irrespective of initial particle distance,Reynolds numbers and channel width.Secondly,the lateral forces(perpendicular to gravity)experienced by the particles sedimenting are examined in detail.It has been found that the frequency of the lateral forces increases quadratically with increased Reynolds number.Furthermore,the frequency of single-particle system is always smaller than that of two-particle system.The significant power-law relationship between the frequency and the channel width has also been found through numerical simulations.The power-law exponent depends on the Reynolds number.(2)The settling of three particles in a two-dimensional channel is simulated by the lattice Boltzmann-Direct Forcing/Fictitious Domain(LB-DF/FD)method.The effects of the wall and Reynolds number are studied.It has been found that for low Reynolds number the left particle tends to sediment at a certain position(0.175 of channel in width)irrespective of its initial potions.Moreover,numerical results have shown that the lateral particles lead for very low Reynolds number,while the center particle leads for large Reynolds number.Finally it has been found that all the particles are sedimenting at a similar velocity when the Reynolds number is below110.(3)The lattice Boltzmann-moment exchange method has been used to simulate the sedimentation of elliptical particle in a shear flow for the Re within the range of0-170 in this paper.First,the effect of Re has been studied,and the results show thatif the Re is less than 29,there is a power function relationship between the rotation period of the elliptical particle and Re.The larger the Re is,the larger the rotation period is.When the Re is greater than 29,the elliptical particle will finally be in stationary state at the rotation angle ?=?,and the rotation angle of the particle is in a power function with Re.The larger the Re is,the larger the rotation angle is.The effect of ?--the length to short axis ratio of the elliptical particle is also studied.It shows that there is a power function relationship between the rotation period of the elliptical particle and ?.The larger the ? is,the smaller the rotation period is.When? is over the critical value,the rotation period will approach infinity and finally the elliptical particle will reach the stationary state at certain rotation angle ?,which is in in a power function with ?.