High Rayleigh number convection with double diffusive fingers

TL;DR

This study investigates double diffusive convection in an electrodeposition cell, revealing how weak stabilizing temperature gradients influence finger formation and flow dynamics at high Rayleigh numbers, with results aligning with prior double diffusive convection findings.

Contribution

It demonstrates the effects of a stabilizing temperature gradient on chemical buoyancy-driven convection and characterizes the resulting finger structures and flow velocities.

Findings

Double diffusive fingers form regardless of cell height.

Flow velocities and finger sizes depend on ion concentration difference and temperature gradient.

Mass transport scaling aligns with previous double diffusive convection studies.

Abstract

An electrodeposition cell is used to sustain a destabilizing concentration difference of copper ions in aqueous solution between the top and bottom boundaries of the cell. The resulting convecting motion is analogous to Rayleigh-B\'enard convection at high Prandtl numbers. In addition, a stabilizing temperature gradient is imposed across the cell. Even for thermal buoyancy two orders of magnitude smaller than chemical buoyancy, the presence of the weak stabilizing gradient has a profound effect on the convection pattern. Double diffusive fingers appear in all cases. The size of these fingers and the flow velocities are independent of the height of the cell, but they depend on the ion concentration difference between top and bottom boundaries as well as on the imposed temperature gradient. The scaling of the mass transport is compatible with previous results on double diffusive convection.