Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session H3: Soft Interfaces |
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Sponsoring Units: DCMP Chair: Thomas Powers, Brown University Room: Baltimore Convention Center Ballroom I |
Tuesday, March 14, 2006 11:15AM - 11:51AM |
H3.00001: A few Landau-Levich films Invited Speaker: We describe a few situations which produce a Landau-Levich films, such as the withdrawal of a solid plate out of a bath of wetting liquid~or the air withdrawal by a jet plunging in a bath of liquid. We show why such antagonist situations can be described by similar arguments. We also discuss the shape and the stability of the film, and the way it bursts, in particular when it is surrounded by a viscous environment. Other contributors to this work : Etienne Reyssat, Jens Eggers and Elise Lorenceau [Preview Abstract] |
Tuesday, March 14, 2006 11:51AM - 12:27PM |
H3.00002: Humps, Spouts {\&} Tendrils: Topological Transition Driven by Viscous Flow Invited Speaker: Viscous flows with large-scale spatial gradients can create small-scale structure on a steady-state interface separating two liquids. Here we focus on how an axisymmetric large-scale withdrawal flow in one liquid can break the interface between two liquids and thereby entrain a second liquid. Above the entrainment transition, thin spouts or tendrils of entrained liquid that persist over time form. Below the entrainment transition, the interface is deflected upwards by the flow and can form a hump with a strongly curved tip. To understand what mechanism allows a large-scale withdrawal flow to create small-scale feature on an initially flat interface, we analyze two simple scenarios. First, we consider the hump formed on an interface separating immiscible liquids. As the entrainment transition is approached from below, the minimum radius of curvature at the hump tip is determined by the maximum interface deflection height. Second, we consider the steady-state tendril formed on an interface between two miscible liquids. Again, the tendril radius is determined by the zero-entrainment deflection height of the interface. [Preview Abstract] |
Tuesday, March 14, 2006 12:27PM - 1:03PM |
H3.00003: Surfactant mass transfer effects on drop detachment Invited Speaker: When a buoyant viscous drop is injected into a viscous fluid, it evolves to form a distended shape that detaches via the rapid formation and pinching of a neck. The effects of surfactants in altering this process are studied numerically. In the absence of surfactants, surface contraction is fastest in the vicinity of the neck. When surfactants are present, they accumulate there and alter the ensuing dynamics by reducing the surface tension that drives the contraction. When surfactant adsorption-desorption is very slow, interfaces dilute significantly during drop expansion, and drops form necks which are only slightly perturbed in their dynamics from the surfactant-free case. When adsorption-desorption dynamics are comparable to rate of expansion, a family of drop necks are predicted. Drops break at the primary neck at low surfactant coverage, at both the primary and secondary necks at moderate coverages, only at the secondary neck at higher coverages, or fail to neck at elevated coverages. When adsorption-desorption kinetics are rapid, the surface remains in equilibrium with the surrounding solution, and drops break like surfactant-free drops with a uniform surface tension. A map of neck/no-neck thresholds is constructed as a function of surfactant coverage and sorption dynamics, suggesting that drop detachment can be used as a means of characterizing surfactant dynamics. Co-authors: Mr. Fang Jin, Prof. Nivedita Gupta. [Preview Abstract] |
Tuesday, March 14, 2006 1:03PM - 1:39PM |
H3.00004: Bubble microstreaming: Force focusing on lipid membranes Invited Speaker: Ultrasound-driven oscillating microbubbles at container walls excite steady streaming flows of surprising speed that can be directed and controlled by patterning of the substrate. This new kind of microfluidics is simple to set up and does not need microchannels to guide flow transport. Hydrodynamic forces are locally focused around the oscillating bubbles and can be used to deform and rupture soft objects, such as the lipid membranes of vesicles and cells. We demonstrate these processes in experiment and quantify the stress exerted onto soft objects in the flow, investigating small and large deformations. We point out applications in bio-MEMS and biomedical studies of cellular response to hydrodynamic stimuli. [Preview Abstract] |
Tuesday, March 14, 2006 1:39PM - 2:15PM |
H3.00005: Topographies and Instabilities in Surfactant Monolayers Invited Speaker: |
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