The Mechanisms And Characterization Of The Micro Non-linear Interaction Between Particles And Plates In Solid-liquid Two-phase Systems

Solid-liquid two-phase flow widely appears in chemical,petroleum and other industrials and natural fields.The frequent interactions of particles-particles and particles-walls significantly affect the two-phase flow,and the presence of liquid phases further intensify the complexity of the interaction between solids phases.Although the spring-dashpot model has been widely used to characterize solid-solid interactions,its accuracy in solid-liquid two-phase systems is poor due to enhanced nonlinear and non-contact characteristics of solid-solid interactions in liquid environments.Therefore,in order to improve the understanding of solid-liquid two-phase flow,it is of great significance to clarify the mechanisms of solid-solid interactions in liquid phase environments,and a solid-solid interaction force model considering the influence of interstitial fluid is necessary to improve numerical simulations of solid-liquid two-phase flow.In this paper,an experimental platform was designed and built to measure particle-plate collision force in liquid phase environments.The particle-plate microscopic interaction force was measured by a dynamic force sensor,while particle migration trajectory was recorded using a high-speed camera.The hydrodynamic behaviors of settling particles near the wall were mainly investigated,and the influences of fluid properties,plate roughness and particle size on the interaction between particles and plates were evaluated.A non-contact interaction height of particles and plates was proposed,and quantitative characterization was carried out to represent the interaction height and particle-plate interaction force.In addition,the hydrodynamic behaviors of particles near the wall in liquid phase environments were studied by numerical simulations,and the evolution of the flow fields around settling particles was estimated,then the non-contact mechanisms between particles and plates in liquid phase environments were clarified.Apparently.when settling particles approach a plate in liquid phase environments,the fluid around the particles is influenced,and a moving front was formed.When the moving front contacts with the plate,the non-contact interaction between the particles and plate occurs,and the gap between them was defined as interaction height.Since rough plates are inclined to induce“braking effect”,the non-contact interactions between particles and rough plates are more prominent,resulting in the increase in interaction height with the increase in surface roughness.In addition,rough surfaces enhance local turbulence of flow fields,causing the hydrodynamic behaviors near plates to be more complicated,so when settling particles interact with rough plates,non-contact interaction force peaks occur before collision.Simulations were carried out to investigate the evolution of flow fields,and it was found that the migration of front fluid of settling particles and interstitial fluid between particles and plates results in particle-plate non-contact interaction,and the interactions between the central fluid layer and wall surfaces in a short time are the main reason for the formation of non-contact force peaks.Moreover,the hydrodynamics of settling particles depend on the changes in flow fields induced by fluid properties,although non-contact force peaks were all observed in Newtonian and non-Newtonian fluids,single force peaks are more common in Newtonian fluids while dual-peaks frequently occur in non-Newtonian fluids.Finally,the interaction height of the non-contact force,collision force and the force peaks of the non-contact force were quantitatively characterized by taking particle size,liquid viscosity and surface roughness into consideration,and correlations between dimensionless action height(H/d),dimensionless force(F/ρv~2d~2)and Reynolds number(Re),relative roughnessΔ/d were given.