Test And Numerical Simulation Study Of Two-Phase Flow Of Water-Sand In Fracture

When the coal mining conducts under the overlying strata with thick aeolian sand,the connected fractures were formed by the failure of overlying strata.Then the accident is always caused by the unstable flow of water and sand in the fractures.Therefore,the study of two-phase flow of water and sand in the fractures becomes the basic task to prevent the disaster of water and sand inrush.In this paper,the permeability experiment system was designed based on the seepage behavior of two-phase fluids of water and sand in the fractures.The permeability parameters of the mixtures between water and sand as the permeate medium in the fractures were tested.The influences of volume concentration and particle size of sand on permeability parameters were analyzed.Based on the Euler-Lagrange method,the control equations of the water phase and the sand phase were established.And the flow of water and sand in the fissure was simulated by ANSYS Fluent software.The spatio-temporal evolution of the physical quantity of the flow field was obtained.The influences of volume concentration,particle size and mass density of sand on the flow field of two-phase fluid of water and sand in fractures were discussed.The main results as follow:(1)In order to test the flow behavior of the two-phase fluid in the fracture,a permeation instrument for studying the seepage law of water and sand in the parallel single fissure is designed.A set of permeability experiment system with the flow of water and sand in fractures is successfully developed,the experimental system also combined with the mixing system,the water and sand transport system and the console.(2)The effects of volume concentration and particle size of sand on the permeability parameters(equivalent flow and non-Darcy flow ? factor)were obtained by steady-state permeation method.The experimental results show that the equivalent flow and non-Darcy flow ? factor increase with the volume concentration of sand,the equivalent flow and non-Darcy flow ? factor decrease with the particle size of sand.(3)Based on the Euler-Lagrange method,the mechanical model of two-phase flow of water and sand in fracture is established.The water phase is by the stress model of Stress-Omega Reynolds,and the sand phase is simulated by the orbital model of particle.(4)The two-phase flow of water and sand in the smooth and rough fractures is simulated by using ANSYS Fluent software.The spatio-temporal evolutions of pressure,velocity,turbulent kinetic energy,volume fraction of sand are obtained.The numerical simulation results show that the physical quantity of in smooth fractures does not vary with time,but the physical quantity of flow field in rough fractures varies with time.The flow of water and sand in the smooth fractures is affected by gravity,which presents the asymmetry of spatial distribution in the physical quantity of flow field.The flow of water and sand in the smooth fractures is affected by constraint of wall,which presents the randomicity of spatial distribution in the physical quantity of flow field.(5)The influence of volume concentration,particle size and mass density of sand on pressure gradient,velocity distribution and turbulent kinetic energy distribution are obtained by numerical simulation.