Convection-induced bridging during alloy solidification

Kumar, V and Sakalkale, K and Karagadde, S (2022) Convection-induced bridging during alloy solidification. In: Physics of Fluids, 34 (5).

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Abstract

In this work, the effect of solute expansion coefficient on the natural convection and freezing front propagation is investigated by performing three-side cooled solidification experiments. Four different aqueous salt solutions, and different compositions thereof, were employed for experimentation. The mixtures were solidified to analyze the effect of solute expansion coefficients on the convection currents and the composition distribution in the bulk. The initial compositions were chosen such that all cases have the same primary solid fraction at eutectic temperature, for obtaining similar compositional changes in the bulk liquid at various stages. Similar cooling conditions were also maintained to ensure that the variation in convection strength is primarily caused by different solute expansion coefficients. A distinct observation of the free surface freezing before the bulk, termed bridging, is reported in certain cases. Further analysis revealed that the bridging could be attributed to a difference in solute convection caused by the solute expansion coefficient. Numerical simulations were performed to further ascertain the plausible initiation mechanisms for bridging. The predicted compositional and solid fraction distribution revealed lesser solute accumulation near the surface, for the lower solute expansion cases, and the resulting increase in the tendency of freezing at the top. An upper limit for the ratio of solutal to thermal Rayleigh numbers in the experimental conditions has been identified for the occurrence of bridging in high Prandtl number fluids. © 2022 Author(s).

Item Type:	Journal Article
Publication:	Physics of Fluids
Publisher:	American Institute of Physics Inc.
Additional Information:	The copyright for this article belongs to the American Institute of Physics Inc.
Keywords:	Expansion; Prandtl number; Solidification, Alloy solidification; Aqueous salt solution; Compositions distributions; Convection currents; Effect of solutes; Eutectic temperature; Expansion coefficients; Front propagation; Initial composition; Solids fraction, Freezing
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	05 Jun 2022 09:23
Last Modified:	05 Jun 2022 09:23
URI:	https://eprints.iisc.ac.in/id/eprint/73113

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