Research On The Settlement Characteristics Of Two Side By Side Particles Of Different Densities

The phenomenon of particle sedimentation has widely existed in nature and engineering fields,and most of the fluids often exist in the form of non-Newtonian fluid.Manipulation of a settling particle in liquids is a topic of intense interest to those involved in the engineered processes recently such as composite materials,pharmaceutical manufacture,chemistry and petroleum industry.In this paper,the particle release device utilizes an ejector to generate vacuum negative pressure and suck particles,which can accurately release particles;and two high-speed cameras were used to capture the settling motion of the particles by the shadow method.To study the effect of the initial distance L and particle density ratio on the settlement behavior of the two side-by-side particles with different density in quiescent water and polyacrylamide solution PAAm(viscoelastic fluid),and two particles dynamics were compared with the free settling of a single particle.When the initial distance is small(L?3d),the light particles obviously affected by the wake of the heavy particle,and significant lateral migration will appear.In quiescent water,when Reynolds number at high subcritical(7000<Re<15000),the heavy particle wake has an obvious drag-and-drop effect on the light particle when the initial distance is small,leading to the light particles will follow the wake of the heavy particle;the coupling of light and heavy particle wake has little impact on the settlement velocity of particles,the lateral velocity appears "inverse phase" symmetry at initial settlement,then the "in-phase" similarity will appear.But in viscoelastic fluid(PAAm),the light particle will be strongly dragged by the wake of the heavy particle,and approaching,following and rebounding out the trajectory of the heavy particle(L=1.2d).The greater difference of density,the larger the lateral offset distance of light particle,and there will be a significant fluctuation in the settling velocity of light particle,but this phenomenon will disappear quickly with the distance increasing(L?2d).Moreover,due to the difference of settling velocity caused by inertia difference,the light particles have little effect on the heavy particles.after the existence of initial distance(5d?L?7d)is observed in both fluids,there is almost no interaction between particles.