Speaker: David Loper
Title: Mush-Chimney Convection.
Affiliation: The Florida State University
Date: Friday, September 17.
Place and Time: Room 101 - Love Building, 3:30-4:30 pm.
Refreshments: Room 204 - Love Building, 3:00 pm.

Abstract. A mush is a region of mixed solid and liquid which commonly forms during the solidification of a molten alloy. If the solid phase is dense, the residual liquid is buoyant and prone to convective instability. The convection alters the structure of the mush and the fully non-linear convective state involves upward motion within chimneys - free of solid - that form spontaneously within the mush. Fluid flow and structure in a convecting mush are governed by a complicated set of coupled non-linear PDEs (containing nine dimensionless parameters) and solution of this problem requires the location of several free boundaries. This problem is generally believed to be analytically intractable. I will describe a remarkable analytic solution of this problem which has been found by Paul Roberts (Mathematics, UCLA) and me. My presentation will be preceded by a brief movie of mush chimney convection, and followed by an experimental illustration. Immediately after my talk, members of the audience will have a chance to come forward and have a closer look at a mush with active chimneys.