Transition to finger convection in double-diffusive convection

TL;DR

This paper investigates the transition from finger convection to ordinary convection in a double-diffusive system with copper ions and temperature gradients, highlighting the conditions that influence the convection pattern and ion transport efficiency.

Contribution

It provides experimental insights into the conditions under which finger convection transitions to ordinary convection in a double-diffusive system, emphasizing the role of thermal and compositional buoyancy forces.

Findings

Finger convection occurs despite an overall unstable density stratification.

Transition to ordinary convection occurs when thermal buoyancy is less than 1/30 of compositional buoyancy.

Ion transport is enhanced at the transition point.

Abstract

Finger convection is observed experimentally in an electrodeposition cell in which a destabilizing gradient of copper ions is maintained against a stabilizing temperature gradient. This double-diffusive system shows finger convection even if the total density stratification is unstable. Finger convection is replaced by an ordinary convection roll if convection is fast enough to prevent sufficient heat diffusion between neighboring fingers, or if the thermal buoyancy force is less than 1/30 of the compositional buoyancy force. At the transition, the ion transport is larger than without an opposing temperature gradient.