论文标题

在孔网络中建模带电物种的传输:溶液的溶液与流体流量和电荷保护方程式结合

Modeling transport of charged species in pore networks: solution of the Nernst-Planck equations coupled with fluid flow and charge conservation equations

论文作者

Agnaou, Mehrez, Sadeghi, Mohammad Amin, Tranter, Thomas George, Gostick, Jeff

论文摘要

提出了用于在多孔介质中模拟带电物种(例如离子)传输的孔网络建模(PNM)框架。它包括电解溶液中每个带电物种的Nernst-Planck(NP)方程,除了将物种浓度彼此相关的电荷保护方程。此外,采用了动量和质量保护方程,并在那里解决方案可以计算对NP方程中运输的对流贡献。 提出的框架是通过首先得出基于几个不同的时间和空间离散化方案对应于部分微分方程(PDE)的数值模型方程(NME)来开发的,这些方程将进行比较,以评估解决方案的准确性。该派生还考虑了各种收费保护方案,这些方案在速度和准确性方面也具有利弊。使用PNM和有限元方法(FEM)求解器考虑并解决了任意孔网络中的离子传输问题。比较在离子浓度方面,PNM和FEM低于$ 5 \%$之间的平均偏差,而PNM模拟超过$ {10}^{4} $倍的$次,$ tem $ term yest的介质(包括$ {10}}^{4} $毛孔的媒介。通过利用CFD文献采用的对流和移民术语的更准确的离散化方案,可以实现提高的精度。 NME是在开源软件包OpenPNM中实现的,基于迭代的Gummel算法,并放松。 这项工作提出了一种全面的方法,用于建模带电物种的运输,适用于从电化学设备到地下中纳米颗粒运动的广泛应用。

A pore network modeling (PNM) framework for the simulation of transport of charged species, such as ions, in porous media is presented. It includes the Nernst-Planck (NP) equations for each charged species in the electrolytic solution in addition to a charge conservation equation which relates the species concentration to each other. Moreover, momentum and mass conservation equations are adopted and there solution allows for the calculation of the advective contribution to the transport in the NP equations. The proposed framework is developed by first deriving the numerical model equations (NMEs) corresponding to the partial differential equations (PDEs) based on several different time and space discretization schemes, which are compared to assess solutions accuracy. The derivation also considers various charge conservation scenarios, which also have pros and cons in terms of speed and accuracy. Ion transport problems in arbitrary pore networks were considered and solved using both PNM and finite element method (FEM) solvers. Comparisons showed an average deviation, in terms of ions concentration, between PNM and FEM below $5\%$ with the PNM simulations being over ${10}^{4}$ times faster than the FEM ones for a medium including about ${10}^{4}$ pores. The improved accuracy is achieved by utilizing more accurate discretization schemes for both the advective and migrative terms, adopted from the CFD literature. The NMEs were implemented within the open-source package OpenPNM based on the iterative Gummel algorithm with relaxation. This work presents a comprehensive approach to modeling charged species transport suitable for a wide range of applications from electrochemical devices to nanoparticle movement in the subsurface.

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