Tuesday, June 26, 2012 - 11:00am - 11:50am
Felix Otto (Max-Planck-Institut für Mathematik in den Naturwissenschaften)
Thursday, October 15, 2009 - 9:45am - 10:25am
Andrew Kraynik (Sandia National Laboratories)
Soap froth—the quintessential foam—is composed of polyhedral gas bubbles separated by thin liquid films. Why do foams have a shear modulus and yield stress, which we usually associate with solids? How are the bubbles shaped and how are they packed? These and other questions have been explored through simulations with the Surface Evolver, a computer program developed by Brakke. The calculations are in excellent agreement with seminal experiments by Matzke (1946) on the foam structure and shear modulus measurements by Princen and Kiss (1986).
Wednesday, September 16, 2009 - 9:00am - 9:45am
Georges Debrégeas (École Normale Supérieure)
Aqueous foams, like other macroscopically divided materials, display
intriguing rheological properties. The bubble-scale structure allows for
the existence of frozen stresses within the material which can not
spontaneously relax by thermal activation. Upon shearing, the system
undergoes a series of plastic events which irreversibly modify this
internal stress pattern. Reversely, the internal state of the material
controls to a large extent its mechanical response to shear.
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