Skip to main content Skip to navigation

Theory Group Lunchtime Seminars

Scheduled seminars are listed below.

Announcements and reminders will be posted to the physics_theory_group_seminar list. Click here to subscribe.

[If you are a member of the group, you will receive postings to this list via physics-theory or physics-theory-staff. You do NOT need to subscribe to the above mailing list.]


 
 
Thu 14 Nov, '19
-
Theory Seminar: Shreyas Mandre (Warwick), Surfactants driven out of equilibrium by a flow
PS1.28

A surfactant is a chemical compound that adsorbs onto a fluid-fluid interface and reduces its surface tension. A non-uniform distribution of such compounds at the interface causes a Marangoni stress that drives a flow, which in turn transports the surfactant. Estimating in situ the degree to which the adsorbed surfactant is out of equilibrium with the dissolved state is critical but challenging, especially because of the multiple length- and time-scales the surfactant and fluid dynamics span. In this presentation, I show that combining asymptotic analysis of the governing mathematical model with experimental flow visualization and velocimetry can furnish a near-complete description of the dynamics.
An epitome of such a system is the axisymmetric flow driven by a steady point source of surfactant on the surface of a deep liquid pool. In this case, the state of the surfactant is difficult to gauge, without which even simple order-of-magnitude scaling theories remain incomplete. I show that by examining three invariant characteristics of the flow, and without knowledge of the surfactant physicochemical parameters, the nature of the surfactant dynamics can be deduced.