Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session L32: Electrokinetic Transport II |
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Chair: Michael Booty, New Jersey Institute of Technology Room: 158AB |
Monday, November 20, 2023 8:00AM - 8:13AM |
L32.00001: Electrokinetic Flow for a Drop Michael R Booty, Manman Ma, Michael Siegel A general, time-dependent model is described for the induced charge electrokinetic flow in and near an electrolyte drop that is suspended in an external electrolyte solution. The model assumes a sharp interface that separates a pair of thin Debye layers with evolution on the timescale for charge-up of the layers by an impulsively applied electric field. The dynamics and behavior with respect to the influence of various effects and parameters are explored, with an emphasis on analytical results under conditions of small applied field strength. |
Monday, November 20, 2023 8:13AM - 8:26AM |
L32.00002: Effect of finite Debye layer in electromigration Taylor-Aris dispersion of charged species in a thin channel Anirban Chatterjee, Ameeya K Nayak
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Monday, November 20, 2023 8:26AM - 8:39AM |
L32.00003: Application of Physics Informed Neural Networks (PINNs) on combined electroosmotic-pressure driven flow Arshia Merdasi, Saman Ebrahimi Multi-physics involved in micro-electro-mechanical systems (MEMS) is of great importance to analyze the fluid motion in biomedical and biotechnological applications, chemical synthesis, mixing and various other applications. We have implemented different architectures of physics-informed neural networks (PINNs) to investigate the mixed electroosmotic pressure driven (EOF/PD) flow in microchannels with non-uniform zeta-potential distribution on the walls. Through performing a detailed numerical simulation and PINN solutions based on Poisson-Boltzmann, Laplace, Navier-Stokes, concentration, and energy equations, we have predicted the non-uniformly distributed zeta-potential on the fluid dynamic, and heat transfer characteristics. It is found that there is a good agreement between the Finite Volume Method (FVM) and segregated PINN approach. From the grid point distribution effect on PINNs, we also demonstrate that using boundary layer collocation points can drastically improve the training efficiency and reduce the total loss for EOF/PD flow. Furthermore, comparing the PINN results with the numerical simulation for mixing index and Nusselt number variation, we present that applying a single PINN leads to higher training loss when compared to the multi-structured PINN, where a PINN is separately trained for each governing equation. Specifically, the normalized mean absolute percentage errors in the velocity prediction of the single and segregated PINNs are 20.17% and 9.2% respectively. |
Monday, November 20, 2023 8:39AM - 8:52AM |
L32.00004: Viscoelectric effect analysis in an electroosmotic flow with microchannel wall slip Edgar Ramos, Ian Guillermo Monsivais Montoliu, Federico Mendez, Jose Lizardi In the present work, we developed a numerical analysis for an electroosmotic flow circulating in a rectangular microchannel considering electrolyte viscosity as a function of the induced electric field; which is also reflected in the slip condition imposed on the system walls, since the slip length is a function of the fluid viscosity. It should be clarified this is an entirely hydrodynamic problem, and for this reason there are no induced pressure gradients, because we are in the presence of a purely electroosmotic flow, where the fluid motion is due only to electrokinetic forces. Based on these comments, the problem is centered on high induced potentials, enabling viscoelectric effect analysis in the electroosmotic flow, which leads to significant increases in velocity and volumetric flow profiles compared to the case where the viscosity is a constant and there is no slip condition. Due to analytical analysis limitations, we implemented a dimensionless equation scheme defined by the continuity equation, the momentum equations in the x and y direction, the Poisson-Boltzmann equation, and the charge conservation equation to obtain the velocity and volumetric flow rate profiles mentioned above. This model is described in its variational form in order to implement the finite element technique using free software, FreeFem++. The results obtained show how the viscoelectric effect is relevant when working with high induced potentials; that is, for values of ζ>1, when the dimensionless viscoelectric parameter f increases, there is a significant decrease in the velocity profiles u, a situation that is not observed when ζ≤1, where there are low induced potentials, and for this reason, as the dimensionless parameter f increases, the velocity profiles remain constant. This condition is preserved for different values of the slip length δ. |
Monday, November 20, 2023 8:52AM - 9:05AM |
L32.00005: A new Lattice Boltzmann application to plasma wakefield acceleration Daniele Simeoni, Gianmarco Parise, Fabio Guglietta, Mauro Sbragaglia, Alessandro Cianchi, Andrea Renato Rossi Plasma wakefiled consitutes a new technique in the field of particle acceleration, that promises same (or superior) energy gains w.r.t. conventional modern-day methods, while being operated in more compact and less expensive physical structures. In this talk we present the first application of the Lattice Boltzmann (LB) method to the problem of plasma wakefield acceleration, where the relevant macroscopic equations can be re-casted as advection equations. |
Monday, November 20, 2023 9:05AM - 9:18AM |
L32.00006: Optimization of Multi-Electrode Dielectric Barrier Discharge Arrays for Active Flow Control Anthony Tang, Benjamin Price, Nicholas Kirschbaum, Alexander Mamishev, Igor Novosselov Dielectric barrier discharge (DBD) plasma actuators for active flow control offer several advantages over conventional flow control techniques, including no moving parts, instantaneous response, and quiet operations. However, DBD actuators are limited to low-speed applications and require further optimization. The addition of DBD in series electrodes can improve the thrust of and increase the area averaged the density of the overall system. Optimization of a multi-DBD array requires adjusting AC phase shift and streamwise spacing over a range of applied voltages and frequencies. Direct thrust and fluid velocity measurements as a function of electrical parameters are presented for two- and three-stage arrays. A multi-DBD array with out-of-phase AC electrodes provides significantly more thrust than previously reported multi-DBD systems. It is found to scale well for geometric constraints. This optimization allows DBD plasma actuators to increase the trust density and modify a fluid system more effectively. |
Monday, November 20, 2023 9:18AM - 9:31AM |
L32.00007: Convection Influences the Charging Dynamics of Porous Electrodes Alexander J Wagner, Aaron D Ratschow, Mathijs A Janssen, Steffen Hardt Electrolyte-immersed porous electrodes are essential for various electrochemical technologies and subject to ongoing research. Most theories for porous electrode charging consider only diffusion and electromigration as ionic charge transport mechanisms. However, the charging process can induce a fluid flow causing additional convective charge transport, whose influence on the charging dynamics of porous electrodes is unknown so far. Here, we simulate the charging using the fully coupled modified Poisson-Nernst-Planck and Navier-Stokes equations for a single cylindrical pore next to a reservoir. The simulations show that convection caused by an induced fluid flow can substantially speed up the charging of porous electrodes. Furthermore, we present a semi-heuristic analytical model describing the induced fluid velocity and the electric current arising from convection. We demonstrate the model’s applicability for moderate applied potentials and that, in this regime, convection speeds up charging most for pore radii roughly ten times larger than the Debye length. Our results show that neglecting convective effects when studying the charging dynamics of porous electrodes is often not realistic, which opens a direction for future research. |
Monday, November 20, 2023 9:31AM - 9:44AM |
L32.00008: Enhancing Conductivity of PEDOT:PSS by Blending PEO in Films and Jets: A Combined Ab Initio Modeling and Experimental Study Vitaliy Yurkiv, Xinnian Wang, Yong Kim, Farzad Mashayek, yayue pan, Alexander L Yarin The rapid advancement of innovative organic-based technologies has led to significant development of various electronic devices. Conducting polymers in blends with non-conducting polymers acquire viscoelasticity sufficient for direct ink writing (DIW) of conducting circuits on knitted and nonwoven materials. In this regard, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) in blends with poly(ethylene oxide) (PEO) posses beneficial properties, excellent thermal stability and processability. In this study, a combination of ab initio modeling and experimental analysis is presented to investigate the electronic conductivity of composed PEDOT:PSS/PEO films. Ab initio DFT calculations are performed based on experimental data to unveil the band structure and density of states of the composite materials. Various polymer compositions with varying PEDOT, PSS, and PEO ratios are examined, revealing unexpected electronic properties of these polymer blends. Notably, the addition of PEO results in a significant change in the band gap, particularly near the maximum PEO content of 52 weight-%. These findings are consistent with our own measurements of film conductivity. This combined modeling and experimental approach provides a mechanistic interpretation of the underlying reasons behind the variations in polymer blends conductivity and opens way for synthesizing highly-conducting polymers for extrusion-based manufacturing techniques such as DIW . |
Monday, November 20, 2023 9:44AM - 9:57AM |
L32.00009: Microstructure and dynamic characteristics of electric double layer at montmorillonite-NaCl aqueous interface Yixuan Feng, Hongwei Fang, Yitian Gao, Jiale Han The microscopic structure of solid-liquid interface is of widespread interest across the physical science, with electric double layer (EDL) playing a pivotal role in enhancing our understanding of macroscopic properties of liquid flow. In this study, we employ molecular dynamics simulations to analyze the structure and dynamic properties of liquids in montmorillonite-NaCl aqueous systems. Our focus lies on measuring the distributions of ions and hierarchical water clusters within the hydrogen bond network, providing a comprehensive overview of the liquid structure. |
Monday, November 20, 2023 9:57AM - 10:10AM |
L32.00010: Interplay between metal deposition and electroconvection on a charge selective electrode Sungyeong Choi, Jeonghwan Kim, Minsang Kang, Rhokyun Kwak We investigate an unknown coupling effect between dendrite growth and electroconvective instability (EC), which arises from electrokinetic instability at the electrolyte-electrode interface. To achieve this, we design an in situ Operando microscopy platform that visualizes ion concentration, fluid flow, and dendrite growth at the electrode-electrolyte (Zn-ZnSO4) interface. Based on the order of occurrence between EC and dendrite formations, we identified five distinct dynamic regimes: (i) inert regime where neither EC nor dendrites occur, (ii) EC regime exhibiting only EC, (iii) EC-dendrite regime where dendrites form at current hotspots induced by EC, (iv) EC/dendrite regime where the both EC and dendrites simultaneously occur, and (v) dendrite regime where only dendrite forms. By incorporating the Damkohler number (ion reduction reaction vs. self-diffusion on the electrode), electric Rayleigh number, and the second Damkohler number (ion diffusion from the electrolyte vs. ion reduction reaction on the electrode), we diversify the five dynamic regimes. Our study sheds light on the interplay between EC and dendrite formation, providing valuable insights for devising novel strategies to control dendrite growth. |
Monday, November 20, 2023 10:10AM - 10:23AM |
L32.00011: Biomimetic membranes in electric fields: capacitive charging and stability Petia M Vlahovska, Shuozhen Zhao, Michael J Miksis Cells and cellular organelles are encapsulated by nanometrically thin membranes whose main component is a lipid bilayer. In the presence of electric fields, the ion-impermeable lipid bilayer acts as a capacitor and supports a potential difference across the membrane. We analyze the dynamics of a planar membrane separating bulk solutions with different electrolyte concentrations in an applied uniform DC electric field. The membrane is modeled as a zero-thickness capacitive interface. The evolution of the evolution potential and ions distributions are solved for using the Poisson-Nernst-Planck equations. Asymptotic solutions are derived in the limit of thin Debye layers and weak fields (compared to the thermal electric potential). The effect of the field on the thermal fluctuations of a membrane is also considered. |
Monday, November 20, 2023 10:23AM - 10:36AM |
L32.00012: Vortical structures of electroconvection on ion-selective surfaces during the steady-to-chaotic transition Gwiyeol Kim, Rhokyun Kwak When an electric field is applied to an ion-selective membrane, exclusive transport of positive or negative ions induces hydrodynamic instability, initiating electrokinetic flows known as electroconvection(EC). In this study, we directly observe convective states of EC during the steady-to-chaotic transition for the first time. By conducting a tomography scan with 3D confocal microscopy, we classify two hitherto-unknown states between two well-known initial and final states: i) single-layer steady EC, ii) double-layer EC with steady primary and secondary vortices. iii) double-layer EC with steady primary and chaotic secondary vortices, and iv) fully chaotic EC. First, as described in previous studies, single-layer primary EC occurs on the membrane at the threshold voltage. Secondly, with increased voltage, smaller vortices arise between the larger primary vortices. These primary vortices lead to current hotspots between them, in which the influx of vortices presents towards the membrane. Consequently, in these hotspots, the ion flux and electric field become concentrated, inducing EC once again. Initially, this secondary EC is stable while keeping the balance with the primary EC. In the third state, however, the secondary EC becomes chaotic, spreading to the beneath primary EC and causing the current fluctuations of a finite value. Finally, when voltage is far beyond the threshold, both primary and secondary EC become chaotic. |
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