The coupling effects of the matrix thickness and Peclet number on the late time transport tailing in the fracture-matrix systems
The coupling effects of the matrix thickness and Peclet number on the late time transport tailing in the fracture-matrix systems
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DOI：
10.1016/j.jhydrol.2022.128829
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发表时间：
2022-11
影响因子：
6.4
通讯作者：
Junnan Wang;Lichun Wang;Junyi Dai
中科院分区：
文献类型：
--
作者：
Junnan Wang;Lichun Wang;Junyi Dai
裂隙岩体中溶质运移过程是许多工程应用的核心问题。然而，基质扩散如何影响非Fickian传输行为，这是典型的特征在于在突破曲线和停留时间分布的后期时间拖尾，仍然未充分探索，特别是考虑到有限的基质厚度（h）和传输制度量化的佩克莱数（Pe）的耦合效应。在考虑基质扩散的二维网格-基质系统中，通过直接求解Navier-Stokes方程和对流扩散方程来模拟流体流动和溶质运移。共进行了80个考虑手Pe变化的情况，以研究手Pe对以幂律函数中的指数（n）表征的晚期溶质拖尾的影响。数值结果表明，n随pE的增大而减小，最终减小到无限矩阵区域的理论值1.5.此外，通过多项式函数建立了k（h，Pe）之间的关系，并通过三维非均匀矩阵系统进一步验证了这一关系.在已知可测手Pe的情况下，新建立的函数可用于准确评估幂律拖尾过程。
Solute transport process in fractured rocks is central to many engineering applications. However, how matrix diffusion affects non-Fickian transport behavior, which is typically characterized by the late time tailing in breakthrough curves and residence time distributions, remains underexplored, especially considering the coupling effects of the finite matrix thickness (h) and transport regimes quantified by Peclet number (Pe). In this work, the fluid flow and solute transport were simulated by directly solving the Navier-Stokes equations and advection-diffusion equation in a two-dimensional fracture-matrix system considering matrix diffusion. In total, eighty cases considering variations ofhandPewere conducted to investigate the impacts ofhandPeon the late time solute tailing characterized by the exponent (n) in the power law function. Numerical results demonstrate thatndecreases with an increase ofhandPe, whereneventually reduces to 1.5 that is a theoretical value for an infinite matrix domain. Moreover, the relationship betweennand (h,Pe) is established via a polynomial function, which is further validated by the three-dimensional heterogeneous fracture-matrix system. The newly-established function can be used to accurately assess the power law tailing process given the knowledge of measurablehandPe.