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Bulk electroconvective instability at high Péclet numbers
Brian D Storey1, Boris Zaltzman, Isaak Rubinstein
1Franklin W. Olin College of Engineering, Needham, Massachusetts 02492, USA.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|November 13, 2007
Summary
Bulk electroconvection instability in electrolytes is re-examined. New findings show instability occurs at high Péclet numbers, influenced by ion diffusivity ratios, challenging previous claims.
Area of Science:
- Electrochemistry
- Fluid Dynamics
- Physical Chemistry
Background:
- Bulk electroconvection is flow driven by electric fields in electrolytes.
- Stability of electric conduction in electrolytes into charge-selective solids has been debated.
- Prior studies suggested instability is unlikely at order-unity Péclet numbers.
Purpose of the Study:
- To investigate bulk electroconvection stability in electrolytes under varying conditions.
- To analyze the transition from bulk electroconvection to the leaky dielectric model.
- To determine the influence of ion diffusivity and Péclet number on electroconvective instability.
Main Methods:
- Mathematical modeling of bulk electroconvection.
- Analysis of the system in the limit of infinite Péclet number (leaky dielectric model).
- Investigation of stability with respect to cation and anion diffusivity ratios.
Main Results:
- Bulk electroconvection becomes unstable at sufficiently large Péclet numbers.
- Instability is sensitive to the ratio of cation to anion diffusivity.
- A bifurcation point exists at equal ionic diffusivities for infinite Péclet number.
- An unreported instability occurs at finite Péclet numbers with high anion diffusivity.
- Instability transitions from monotonic to oscillatory as diffusivity ratio changes.
Conclusions:
- Contrary to recent claims, bulk electroconvective instability is possible at high Péclet numbers.
- The stability of electric conduction depends critically on ion transport properties and flow conditions.
- This work clarifies the conditions under which electroconvective instabilities arise in electrolytes.
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