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Three-dimensional coherent structures of electrokinetic instability
E A Demekhin1, N V Nikitin2, V S Shelistov3
1Department of Computation Mathematics and Computer Science, Kuban State University, Krasnodar, 350040, Russian Federation and Laboratory of General Aeromechanics, Institute of Mechanics, Moscow State University, Moscow, 117192, Russian Federation.
Summary
Direct numerical simulations reveal three electrokinetic instability patterns near charged surfaces, including rolls, hexagonal structures, and spatiotemporal chaos, crucial for understanding overlimiting currents in microfluidic devices.
Area of Science:
- Electrokinetics
- Computational Fluid Dynamics
- Surface Science
Background:
- Electrokinetic phenomena are crucial in micro- and nanofluidic devices.
- Understanding instabilities near charge-selective surfaces is key for controlling ion transport and overlimiting currents.
- Previous studies often focused on 2D models or specific geometries.
Purpose of the Study:
- To perform direct numerical simulations of three-dimensional electrokinetic instability.
- To analyze the characteristic patterns of overlimiting currents near charge-selective surfaces.
- To investigate the transition mechanisms between different instability regimes.
Main Methods:
- Direct numerical simulation (DNS) using a finite-difference method for spatial discretization.
- Semi-implicit 31/3-step Runge-Kutta scheme for temporal integration.
- Utilized parallel computing for complex 3D calculations.
Main Results:
- Observed three distinct patterns corresponding to overlimiting currents: 2D electroconvective rolls, 3D regular hexagonal structures, and 3D spatiotemporal chaos.
- The spatiotemporal chaos regime is characterized by a combination of unsteady hexagons, quadrangles, and triangles.
- The transition from hexagonal structures to chaos involves the generation of interacting 2D solitary pulses.
Conclusions:
- The study provides a comprehensive 3D numerical analysis of electrokinetic instabilities.
- Identified distinct patterns and transition dynamics leading to overlimiting currents.
- Results offer insights into complex fluid behavior in micro/nanochannels with charged surfaces.
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