SMS scnews item created by Andrew Mathas at Fri 2 Aug 2013 1558
Expiry: 9 Aug 2013
Calendar1: 9 Aug 2013 1400-1500
CalLoc1: AGR Seminar
CalTitle1: AGR Seminar: Three Films Good, Four Films Bad!
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Three Films Good, Four Films Bad!
Dr Paul Grassia (CEAS, University of Manchester, UK)
La Trobe University
Since the work of Plateau (1873) and Kelvin (1887) it has been well known that films in a static foam meet threefold (and never fourfold) along junctions, now known as Plateau borders. The fourfold state is energetically unstable -- and will lead to bubble rearrangements producing new films, such that the threefold film meeting rule is recovered. Foam rheology concerns the application of strain to a foam, a process which causes certain films to grow but others to shrink. A detailed description of foam rheology requires tracking the evolving geometry of the strained films, which can induce the `forbidden' fourfold film meeting states, from which the foam must subsequently relax. The foam's inherent relaxation rate following the fourfold state can differ substantially from the externally imposed rate of strain driving foam flow and deformation: moreover the relaxation rate can be set either by viscous dissipation effects or by departures from physicochemical equilibrium. The effects of deforming foam at different rates will be considered here. Strong viscous dissipation can delay the onset of the fourfold film state, postponing the foam's relaxation, which leads to highly elongated bubbles and possibly even produces film bursting. Slow physicochemical equilibrium might suppress the fourfold film state -- and the subsequent relaxation -- altogether. Even weak departures from physicochemical equilibrium are shown to lead to non-trivial, non-linear rheological behaviour.
Dr Yury Nikolayevsky
If you would like to attend this seminar in our access grid room then please check to see if the grid is already booked at this time and send an email to firstname.lastname@example.org to let the CSOs know that you would like to attend.