摘要
离子选择性表面(如纳米通道、离子交换膜等)复杂的动力学现象为微纳流控技术的发展提供了新思路.向带有离子选择性表面的电解质溶液施加电压,通过液体的电流密度会经历复杂的非线性变化过程;当电压超过某一临界值时会引发对流现象,这种流动被称为第二类电渗或离子选择性表面的电对流,关于此类问题的数值求解引发了大量的研究.本文提出一种基于多块网格加密的格子玻尔兹曼方法(lattice Boltzmann method,LBM)的数值模型,用于模拟第二类电渗流动.结合该算法,给出了求解流动、电势和离子浓度的网格信息交换方程,较好地解决了此类问题中大浓度梯度边界对计算分辨率的要求.利用该数值模型模拟获得的电流-电压特性曲线先随着电压升高而迅速增大,随后达到饱和状态,与理论解吻合良好.此外,模拟结果还表明,当流动发生后,相对低电压下的流动倾向于形成大涡且流动呈指数趋势增强;而较大电压则会先激发多个小涡,并逐渐合并为大涡流动,且大涡流动有更高的离子输运效率.此外,除了模拟离子选择性表面的电对流现象,本文提出的数值格式还可拓展到其他电流体动力学问题的模拟.
Abundant dynamic effects on an ion-selective surface provide a new solution for the development of microfluidic technology.If an increasing bias voltage is applied to the electrolyte solution with the ion-selective surface,the passing ion current will experience a complex nonlinear evolution.A convection phenomenon will be triggered when the imposed voltage exceeds a critical threshold.This convection is called the electroconvection near the ion-selective surface or the second kind of electroosmosis.The numerical investigation of the electroconvection attracted a number of studies.In the present work,a numerical model of the lattice Boltzmann method(LBM)based on multi-block grid refinement is proposed to simulate this model problem.The grid information exchange equations of the multi-block grid refinement method for solving the flow,potential,and ion concentration are given,which overcomes the requirement of a high concentration gradient boundary for the computational resolution.The current-voltage characteristic curve obtained by the numerical model firstly increases rapidly with the increase of voltage and then reaches a saturation state.This result is in good agreement with the theoretical solution.What is more,the results also show that after the convection occurs,the flow tends to form large rolls under a relatively low voltage which is slightly higher than the stability threshold,and the flow intensity increases exponentially.While under a relatively high voltage,multiple small rolls are formed firstly,and these rolls merge into larger rolls subsequently.The ion transport efficiency is higher when the large rolls are formed.It is worth noting that our multi-block LBM method is suitable not only for the electric convection on the ion-exchange surface but also for some other numerical studies of electrohydrodynamics.
作者
张煜
李天富
罗康
吴健
易红亮
Zhang Yu;Li Tianfu;Luo Kang;Wu Jian;Yi Hongliang(MIIT Key Laboratory of Aerospace Thermophysics,School of Energy Science and Engineering,Harbin Institute of Technology,Harbin 150001,China;Ji Hua Laboratory,Foshan 528000,Guangdong,China)
出处
《力学学报》
EI
CAS
CSCD
北大核心
2022年第10期2784-2795,I0003,共13页
Chinese Journal of Theoretical and Applied Mechanics
基金
国家自然科学基金(52076055,12172110)
广东省基础与应用基础研究基金(2021A1515110273)资助项目。
关键词
电对流
第二类电渗
离子选择性表面
格子玻尔兹曼方法
多块网格
electroconvective instability
electroosmotic of the second kind
ion-selective surface
lattice Boltzmann method
multi blocks grids
