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ISSN Print: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Dynamics of laterally heated double-diffusive intrusions

Get access DOI: 10.1615/IHTC12.2630
6 pages

Abstract

A fluid that is stably stratified by a solute gradient and heated laterally with a constant wall heat flux develops a double-diffusive instability with characteristic intrusions growing from wall to core. Here we provide a simple model describing the dynamics of such a complex flow for large heat fluxes, i.e. far from the onset of the instability. The basic idea is to estimate the velocity and heat transfer at the wall for a shallow enclosure represented by the double-diffusive intrusion with variable thickness η and length l. From this simple theoretical description of the constant heat-flux condition, we show that the lateral stability number Π can be interpreted as a Nusselt number; that, contrary to the constant-temperature condition, the instability always develops with a time scale inversely proportional to the cube of the heat flux; and finally that the Reynolds number based on the front propagation velocity is effectively proportional to Π. For validation, several measurements were carried out in a cartesian enclosure and in a large cylindrical geometry of 0.5m diameter. Several Π values were tested from the "critical" value, 0.7, to very large values up to 80 (which have not been obtained in the laboratory). Comparisons exhibit good agreement with the model for large Π values. For smaller values, however, convective motions are weaker and less organised and thus the model must be modified for this low Π regime.
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