基于逾渗网络模型的弥散系数与渗透率关系研究

该文基于逾渗理论和网络模型,建立体中心网格(BCC)的三维孔隙网络模型,在周期性边界条件下模拟不同孔隙半径变异系数及不同孔隙连通性下的弥散过程。假设微粒在单管中服从Taylor-Aris弥散,其通过单管的时间可由累积分布函数随机获得;流体在管束节点处发生完全混合,随后按照节点连接管束的体积流量比对应的概率随机进入一根管束,以此实现微粒的不断运移。利用粒子追踪法确定固定时间下的微粒位置,并根据矩量法计算弥散系数。模拟结果表明弥散系数随孔隙连通性的降低而增大,随水力半径的增加而增加,且均遵循相应的乘幂关系。结合渗透率模型,探索了弥散系数与渗透率间的关系,并与实验结果进行对比,验证了模型的正确性。

Study of the relationship between dispersion coefficients and permeability by percolation network model

Based on percolation theory and network model,3D pore networkmodels with body-centered cubic (BCC) were established to simulated dispersion with different variation coefficients of pipe radius and different levels of connectivity under periodic boundary conditions.In order to simulate dispersion,it is assumed that the particles obeyed Taylor-Aris dispersion in a single pipe and fluid mixed completely in the pipe junction.The time of particles passing through the pipe was randomly obtained by cumulative distribution function.When exiting a pipe,the particle randomly entered one of pipes connected to the exit pipe in accordance with probabilities proportional to the volumetric flow of each pipe.Following above steps,the positions of the particles at different fixed time were recorded by particle tracking method,and the method of moments was used to calculate the dispersion coefficients.It is indicated that dispersion coefficients increased with the decrease of pore connectivity and increased with the increase of hydraulic radius,and the trends of evolution followed the power laws.Combined with permeability model,the relationships between dispersion coefficients and permeability in line with experiential results were established.