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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。
Based on the theory of percolation and the network model, a three-dimensional pore network model of BCC is established to simulate the dispersion process under different pore radius variation coefficients and different pore connectivity under periodic boundary conditions. Suppose the particles are obeying Taylor-Aris dispersion in a single tube, the time of passing through a single tube can be obtained randomly by the cumulative distribution function; the fluid is completely mixed at the tube bundle nodes, and then randomly enters a root according to the probability that the volume flow of the connecting tube bundle Tube bundle, in order to achieve the continued movement of particles. Particle tracing method was used to determine the particle position at fixed time, and the diffusion coefficient was calculated according to the moment method. The simulation results show that the diffusion coefficient increases with the decrease of pore connectivity and increases with the increase of hydraulic radius, and both follow the corresponding power exponentiation. Combined with the permeability model, the relationship between the diffusion coefficient and permeability was explored, and compared with the experimental results to verify the correctness of the model.