A micro-layer model is proposed to account for the lubrication effect of liquid layer near collisions of immersed particles at moderate particle Reynolds number.This new model is to allow determination of the pressure...A micro-layer model is proposed to account for the lubrication effect of liquid layer near collisions of immersed particles at moderate particle Reynolds number.This new model is to allow determination of the pressure profile within the micro-layer including the fluid inertia and viscosity.Then a correction based on the micro-layer model is applied to unsteady 3-D direct simulation of a particle approaching another one.The simulation is based on a modified immersed boundary method with direct force scheme.The quantitative agreement between numerical and experimental results validates the model presented in the study.The simulation results show that the fluid is squeezed prior to contact.When a particle approaches a flat wall or another particle,the lubrication force,obtained by integrating the pressure profile over the particle surface,is increased and prevents the particle from approaching.The model predicts that the velocity of approaching particle starts to decrease when separation distance of particles is less than 0.1dp,where dp is the particle diameter.展开更多
To explore the microscopic responses of granular materials to wetting,the inter-particle lubrication effect and particle breakage in an odometer were simulated using a two-dimensional discrete element method.The lubri...To explore the microscopic responses of granular materials to wetting,the inter-particle lubrication effect and particle breakage in an odometer were simulated using a two-dimensional discrete element method.The lubrication effect was modeled by reduction of the inter-particle friction coefficient and particle breakage was initiated by decreasing the particle strength.Once the strength of the particles decreased to a threshold value,the particles began to break so that new contacts could be established to transfer the external loads.Numerical simulations successfully reproduced the additional compaction of the material and the intensification of the horizontal stress in addition to the microscopic responses of the granular assemblies.The microscopic interpretation of the earth pressure coefficient at rest and the evolution of the grain number distribution during particle breaking were also investigated.展开更多
文摘A micro-layer model is proposed to account for the lubrication effect of liquid layer near collisions of immersed particles at moderate particle Reynolds number.This new model is to allow determination of the pressure profile within the micro-layer including the fluid inertia and viscosity.Then a correction based on the micro-layer model is applied to unsteady 3-D direct simulation of a particle approaching another one.The simulation is based on a modified immersed boundary method with direct force scheme.The quantitative agreement between numerical and experimental results validates the model presented in the study.The simulation results show that the fluid is squeezed prior to contact.When a particle approaches a flat wall or another particle,the lubrication force,obtained by integrating the pressure profile over the particle surface,is increased and prevents the particle from approaching.The model predicts that the velocity of approaching particle starts to decrease when separation distance of particles is less than 0.1dp,where dp is the particle diameter.
基金supported by the National Natural Science Foundation of China (51179059)the Innovation Plan for Postgraduate Students Sponsored by the Education Department of Jiangsu Province, China (CX08B_107Z)
文摘To explore the microscopic responses of granular materials to wetting,the inter-particle lubrication effect and particle breakage in an odometer were simulated using a two-dimensional discrete element method.The lubrication effect was modeled by reduction of the inter-particle friction coefficient and particle breakage was initiated by decreasing the particle strength.Once the strength of the particles decreased to a threshold value,the particles began to break so that new contacts could be established to transfer the external loads.Numerical simulations successfully reproduced the additional compaction of the material and the intensification of the horizontal stress in addition to the microscopic responses of the granular assemblies.The microscopic interpretation of the earth pressure coefficient at rest and the evolution of the grain number distribution during particle breaking were also investigated.
