Interactions between steady and oscillatory convection in mushy layers

Lead Research Organisation: University of Cambridge
Department Name: Applied Maths and Theoretical Physics

Abstract

One of the challenges in predicting the solidification of multicomponentmaterials such as metallic castings is to describe the evolution of mushy layers: partially solidifiedregions in which solid and liquid phases coexist. Such systems exhibitunusual properties not seen in single-phase systems. One example is thealteration of the crystalline structure by convection of heat and solute making theflow problem nonlinear and leading to the formation of solid-free dissolution channels,or 'chimneys', in the solid matrix. A strikingly complex pattern ofchimney convection has been observed in recent laboratory experiments: a new'breathing mode' of convection has been found, in which chimneys allperiodically appeared and disappeared in phase. This project aims at anunderstanding of the observed behaviour using mathematical techniques. In particular, the nonlinear interactions between steady andstanding-wave oscillatory convection modes will be elucidated, and stableflow regimes and their parametric sensitivity quantified. Further laboratory experiments will also be conducted to provide more detailed information about this newly discovered phenomenon.

Publications


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Description The project examined modes of convection (buoyancy-driven flow) in reactive porous media, called mushy layers, that form during the solidification of alloys. The main outcome was a quantification of the conditions under which either steady or oscillatory motions occur.



The research is published in the Journal of Fluid Mechanics (2010), vol 645, pp 411-434.
Exploitation Route Convection in mushy layers is relevant to casting of metallic alloys, the evolution of the Earth's core, segregation of minerals in igneous rocks and brine drainage from sea ice. This study exposes some fundamental aspects of these systems in which phase change interacts with fluid flow.
Sectors Environment,Manufacturing/ including Industrial Biotechology