Double-diffusive Finger Convection in a Hele–Shaw Cell: An Experiment Exploring the Evolution of Concentration Fields, Length Scales and Mass Transfer

Abstract

We present the results of an experiment conducted to explore the temporal and spatial development of double-diffusive finger convection in a Hele–Shaw cell. Two solutions each containing a different density affecting component were layered in a density stable configuration (sucrose solution over a more dense salt solution) with a nearly perturbation-free interface between. The mismatch of diffusive time scales for the two components leads to local density instabilities that generate upward and downward convecting fingers. Throughout the course of the experiment, a full-field quantitative light transmission technique was used to measure concentration fields of a dye tracer dissolved in the salt solution. Analysis of these fields yielded the temporal evolution of length scales associated with the vertical and horizontal finger structure as well as mass transfer. Distinct developmental stages are identified with strong correlation between all measures. These data provide a baseline that can be used to develop and evaluate both process-level models that simulate the full complexity of the evolving flow field and large-scale effective models that integrate over small-scale behavior.