Electroconvective instability near an ion-selective surface: A mesoscopic lattice Boltzmann study

Area of Science:

• Physics
• Physical Chemistry
• Fluid Dynamics

Background:

• Electrohydrodynamics (EHD) describes the interplay between electric fields and fluid motion.
• Ion-selective surfaces are critical in electrochemical systems, influencing transport phenomena.
• Understanding electroconvection is key to predicting system behavior under various electrical conditions.

Purpose of the Study:

• To investigate electroconvection instability near ion-selective surfaces.
• To analyze the impact of electroconvection on current-voltage characteristics.
• To explore the transition from steady flow to chaotic behavior in EHD systems.

Main Methods:

• Direct numerical simulations using the lattice Boltzmann method (LBM).
• Solving Poisson-Nernst-Planck and Navier-Stokes equations for electric and flow fields.
• Analysis of Ohmic, limiting, and overlimiting current regimes.

Main Results:

• Simulations align well with analytical solutions for current-voltage relationships.
• Electroconvection is identified as a significant ion transport mechanism, comparable to others.
• Flow within the extended space charge layer is primarily driven by electroconvection.

Conclusions:

• Electroconvection plays a vital role in EHD flow and current-voltage behavior near ion-selective surfaces.
• The electrohydrodynamic coupling constant is a key parameter for convective instability.
• The study details flow patterns, ion distribution, and transitions to complex dynamics like chaos.