Direct numerical simulation of electroconvection with thin Debye layer matching canonical experiments

Abstract

Electroconvection has the potential to be applied in electrochemical technologies such as electrodialysis and energy storage, and has thus aroused considerable research interest. This paper describes the direct numerical simulation (DNS) of the dimensionless Poisson-Nernst-Planck and Stokes equations for electroconvection to determine why the dimensionless thin Debye layer in existing simulations does not match the results of canonical experiments. Our DNS results show that the discrepancy between the simulation results and the experimental data is mainly caused by differences in the structural characteristics of the extended space charge layer. A dimensionless thin Debye layer matching those in canonical experiments enhances the driving force of the extended space charge layer, resulting in massive vortices near the permselective membranes that cause the electroconvective flow to transition from the steady state to time-dependent spatiotemporal dynamics. Our DNS results show that choosing the thickness of the dimensionless thin Debye layer to be consistent with canonical experiments is a key factor in the high-precision quantitative analysis of electroconvection characteristics such as the vortex height, dynamic evolution, and pattern formation. These results provide important guidance for the design and instability control of microfluidic chips.