Dynamics and Instability of Metallic Foams
Dr. Anthony Anderson (DAMTP, University of Cambridge)
Thursday 28th October, 2010 14:00-15:00 325
Metallic foams are used as inexpensive precursors to light-weight porous solids. Unlike their aqueous counterparts, there are no surfactants available to stabilize metallic foams. Consequently, they coarsen rapidly due to the coalescence of bubbles. The time scales for coarsening are controlled by thinning and rupture processes in individual lamellae (the thin liquid films separating adjacent gas bubbles), which I describe in detail using thin-film asymptotics and stability analysis. One important result of these analyses is an improved prediction for the conditions at rupture immediately proceeding a coalescence event. Another important result is that these analyses lead naturally to a macroscopic description of a coarsening foam, involving several bubbles. A network theory for two-dimensional metallic foams is developed which incorporates the microscopic description of individual lamellae coupled through conservation conditions at Plateau borders, where multiple lamellae are joined. Preliminary simulations from the network model are presented.