2008-09 IAM-PIMS-MITACS Distinguished Colloquium Series - 01

Many fluid instabilities involving free surfaces are governed by interfacial forces - for instance surface tension. However, some materials have surface forces produced by active physical processes not present in the bulk fluid, such as forces due to the electric charge residing on the interface between conducting and insulating liquids. I will give an overview of these systems, and present recent experimental observations of instabilities due to such active or reactive interfaces: two Newtonian fluids which react to produce a fragile elastic material (during impact splashes or viscous fingering), and droplets of electrolyte solution in viscous nonconducting oil, for which oppositely charged drops do not always coalesce.