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An experimental study of shear-enhanced convection in a mushy layer

Published online by Cambridge University Press:  10 October 2008

JEROME A. NEUFELD  and
J. S. WETTLAUFER
JEROME A. NEUFELD
Affiliation:
Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA
J. S. WETTLAUFER
Affiliation:
Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA Department of Physics, Yale University, New Haven, CT 06520, USA
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Abstract

The influence of an external shear flow on the evolution of a solidifying array of dendritic crystals, termed a mushy layer, is investigated through controlled cooling of an aqueous ammonium chloride solution in a laboratory flume. The controlled cooling produces a mushy layer that grows at a constant rate from the base of the flume over which a laminar shear flow is applied. We find a critical flow speed above which a spatiotemporal variation of the solid fraction of the layer appears with a planform transverse to the flow direction. The presence of this distinctive pattern of spanwise crevasses is compared with a simplified stability analysis in which the motion of the external fluid over the corrugated mush–liquid interface produces a pressure perturbation that drives flow and phase change within the mushy layer. This flow leads to a pattern of solidification and dissolution that is compared to the experimental results. The physical mechanism underlying the pattern formation is confirmed by the agreement between the theoretical predictions and experimental results. Finally, the comparison between theory and experiment provides a value for the mushy layer permeability, the evolution of which is of relevance to a host of geophysical, biological and engineering systems.

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Type
Papers
Information
Journal of Fluid Mechanics , Volume 612 , 10 October 2008 , pp. 363 - 385
Copyright
Copyright © Cambridge University Press 2008

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