多孔介质中气泡尺寸对流动阻力的影响

Influence of bubble size on fluid resistance in porous media

多孔介质中的泡沫能够封堵某些孔道,降低气体流动性。由于直接观察多孔介质中的泡沫流动比较困难,所以关于泡沫流动性与气泡尺寸之间的关系研究较少。利用Navier-Stokes方程与守恒的水平集方法耦合模拟孔隙介质中气泡尺寸对流动阻力的影响,结果证实,气泡尺寸是影响流体阻力的重要因素。当气泡半径小于孔喉半径时,气泡不受孔道约束,气泡流动过程中流动阻力较稳定,此时含气泡流体流动阻力与纯液态流体流动阻力相等,所以小于孔喉尺寸的气泡对孔道无封堵作用。当气泡半径大于孔喉半径时,孔道影响气泡变形,其流动阻力存在波动性,最大流动阻力随气泡体积变大呈线性增加。当气泡体积增加到使最大流动阻力达极大值时,继续增大气泡体积,最大流动阻力随气泡体积增大而线性降低。最大流动阻力随气泡体积增大而线性增大与减小变化具有周期性,周期为单位孔体体积。

Foam in porous media can plug some pore channels and reduce gas mobility.Direct observation of foam flow patterns in porous media is difficult and therefore research on relationships between gas mobility and bubble size is scarce.The influence of bubble size on fluid resistance in porous media is simulated using the Navier-Stokes equation combined with the conservative level set method.The computational results reveal that the effect of bubble size on flow resistance is pronounced.The pore wall cannot constrain bubble deformation when size of the bubble is smaller than that of the pore throat.In that case,the flow resistance is steady in the flow and is the same as resistance of the single-phase liquid flow.Therefore,small bubbles cannot plug pore channels.The pore channel constrains bubble deformation when size of the bubble is larger than that of the pore throat;and the flow resistance is fluctuant in the flow.The maximum resistance increases linearly with the increase of bubble volume.When the flow resistance reaches the maximum,it decreases linearly with the increase of bubble volume.Alternation of the increase and decrease of the maximum resistance is periodic;and the period is unit pore-body volume.