多孔介质内颗粒流动特性的格子Boltzmann模拟

Lattice Boltzmann simulation of particle flow characteristics in porous media

地下岩石孔隙中小颗粒的运移和沉积会使得储层渗透性能降低,影响石油开发。为了探究悬浮颗粒在多孔介质中的流动过程,采用格子Boltzmann方法对三维多孔介质内流体和颗粒的运动过程进行了数值模拟,采用有限体积颗粒法构建多孔介质中骨架颗粒和悬浮颗粒。通过Half-Way反弹格式实现流体与颗粒间的相互作用,考虑孔隙结构、入口流速、孔隙率和颗粒直径对颗粒流动特性的影响,探究颗粒的运移和沉积规律。结果表明,入口速度对不同孔隙结构下颗粒的运动作用显著。随着入口速度增大,颗粒与颗粒、孔隙壁面以及流体之间的动量和能量交换作用增强,缩短了颗粒的运移路径,颗粒沉积率逐渐变小,颗粒拟温度增大。孔隙率的下降强化了颗粒间的碰撞,孔隙率由0.581降低至0.400,使得颗粒拟温度提升至9倍。颗粒拟温度随颗粒直径的增加而增加。但随着孔隙率增加,颗粒轴向速度增加,颗粒最高轴向速度可达入口流速的11倍,而颗粒接触力降低。

The migration and deposition of suspended particles within porous media is of great significance in many applications such as sewage treatment,pollutant purification and well drilling.Especially in the oil industry,the deposition of small particles in the reservoir may affect the recovery of crude oil.The structure of porous media is complex,making it difficult to understand the details of the flow field.Therefore,it is necessary to explore the phenomena and mechanism of suspended particle flow in porous media.The lattice Boltzmann method(LBM)is used to numerically simulate the flow characteristics of suspended particles in porous media.The skeleton particles and suspended particles are constructed by the finite size particle(FSP)method.The Half-Way bounce back format is adopted to realize the interactions between suspended particles and the fluid.By changing the inlet velocity of the liquid phase,porosity and particle diameter,the movement and deposition of suspended particles are analyzed.The simulation results show that the increase in the inlet velocity of the liquid shortens the migration trajectory of the suspended particles and improves the contact force of the particle.There are a large number of suspended particles clogging near the inlet of porous media.The particle retention time and the particle deposition rate decrease with the increase of the inlet velocity,while the granular temperature shows the opposite trend.Meanwhile,the granular temperature first increases and then decreases,and gradually tends to be stable with time passing by.The reduction of porosity strengthens the collisions between the suspended particles.The change of porosity from 0.581 to 0.400 increases the granular temperature by 9 times.As the porosity is enhanced,the particle axial velocity increases,while the particle contact force declines.The granular temperature is raised with the increase of the particle diameter,and the maximum value of the particle axial velocity can reach 11 times of the inlet velocity.