Open Access

ARTICLE

Detailed Observations of Convective Instability on an Interfacial Salty Layer

by R. Abdeljabar¹, F. Onofri², M.J. Safi¹

1 URME, National School of Engineers of Tunis, B.P 37,1002 Belvedere, Tunisia
2 Ecole Polytechnique de mécanique énergétique, CNRS, Marseille cedex, France

Fluid Dynamics & Materials Processing 2008, 4(4), 245-254. https://doi.org/10.3970/fdmp.2008.004.245

Abstract

This paper focuses on the mechanisms of convective instability in a stable salty gradient layer (i.e. an interfacial salty layer). This layer is assumed to be initially confined between two homogeneous liquid layers: a lower layer composed of salty water of 5wt% concentration and an upper layer composed of distilled water. The mechanisms underlying the interfacial salty layer's instability are depicted experimentally using a PIV technique and via measurements of concentration and temperature. It is found that in addition to the effect of double-diffusion across the interfacial salty layer, different forms of Kelvin-Helmholtz instability occur at different locations:\newline i. At the edge of the interfacial salty layer adjacent to the upper layer;\newline ii. At the edge of the interfacial salty layer adjacent to the lower layer;\newline iii. Within the interfacial salty layer itself.\newline The first induces horizontal moving of the interfacial layer liquid that is initially at rest. The second acts by sweeping the lower edge of the interfacial layer due to convective flows. In particular, the kinetic energy of the convective flows at the lower edge of the interfacial layer combine with the effect of double diffusion (i.e. the salty gradient layer become weaker) to generate a patch of overturning flows. This phenomenon induces the mixing of the stable interfacial layer by overturning flows that gradually erode the layer. The third effect acts by tearing the interfacial layer under the action exerted by convective vortices at the adjacent boundaries.

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