基于LBM-DEM耦合研究多孔介质中生物膜对悬浮粒子运移的影响

生物膜是多孔介质中普遍存在的细菌群落,会与悬浮粒子相互作用并影响粒子的迁移沉积。采用格子玻尔兹曼-离散单元耦合方法(LBM-DEM)研究了悬浮粒子在覆盖生物膜多孔介质中的运移。发现生物膜的存在会降低孔喉尺寸和DLVO排斥势垒,这有助于增强悬浮粒子的沉积。进出口压差是影响粒子滞留率的主要因素,低进出口压差下粒子无法突破排斥能垒,高压差下流体力通过改变粒子的沉积位置可提高渗透率。溶液离子强度变化主要影响排斥屏障。高离子强度的溶液中,粒子滞留率对压差变化响应较小;低离子强度溶液中,粒子滞留率受进出口压差的影响较大。此外,从介观角度观察入流速度对悬浮粒子黏附与滚动的影响,发现粒子的初始沉积点与来流方向的角度随着粒子速度的增加而减小。

EFFECT OF BIOFILM ON SUSPENDED PARTICLES TRANSPORT IN POROUS MEDIA BASED ON LBM-DEM COUPLING

Biofilm is a common bacterial community in porous media,which can interact with suspended particles and affect the migration and deposition of particles.The Lattice Boltzmann-discrete element coupling method (LBM-DEM) was used to study the migration of suspended particles in porous media covered with biofilm.The presence of biofilms reduced the pore-throat size and the DLVO repulsive barrier,which helped enhance the deposition of suspended particles.The pressure difference between inlet and outlet was the main factor affecting the retention rate of particles.Under low-pressure difference between inlet and outlet,particles couldn't break through the exclusion barrier,and the flow force of high-pressure difference could increase the permeability by changing the deposition position of the particles.The change of ion concentration in the solution mainly affected the exclusion barrier.In the solution with high ion concentration,the particle retention rate had little response to the change of pressure difference.In the solution with low ion concentration,the particle retention was greatly affected by the inlet and outlet pressure difference.In addition,the effects of inflow velocity on the adhesion and rolling of suspended particles were also observed from a mesoscopic perspective.The angle between the initial deposition points of particles and the incoming flow direction decreased with the increase of particle velocity.