Bulletin of the American Physical Society
78th Annual Meeting of the Southeastern Section of the APS
Volume 56, Number 9
Wednesday–Saturday, October 19–22, 2011; Roanoke, Virginia
Session DA: Complex Fluids |
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Chair: Beate Schmittman, Virginia Polytechnic Institute and State University Room: Crystal Ballroom A |
Thursday, October 20, 2011 1:30PM - 2:00PM |
DA.00001: Chaotic Advection in Multi-component Melts for the Manufacture of Composite Materials Invited Speaker: Several forces arise when different liquids are placed into contact. The relative importance of these forces depends on the sizes and shapes of liquid domains and also on molecular characteristics of the liquids. When the liquids are agitated and in the absence of interdiffusion, a composite structure results that is defined by the spatial extent and size of each liquid domain in the presence of the other. Shaking a bottle with about equal parts of water and oil gives a structure that resembles a household sponge, for example. If the oil volume is much smaller than the water volume, oil droplets result instead. In polymer blends and composites, the structure can have feature sizes at the micron scale or smaller. Little has been known about the variety of structural types that can be formed because current information is based on mixing machinery that intrinsically restricts structural outcomes. This shortcoming has important consequences because physical properties of composite materials obtained by solidifying the structured liquids depend appreciably on structure characteristics. A recent approach to overcome this shortcoming makes use of \textit{chaotic advection} to establish conditions that organize liquid domains into numerous thin layers. A multi-layer construction undergoes morphological changes in situ. P\textit{rogressive structure development }arises, whereby a specific structure leads in sequence to a morphologically different structure. A new manufacturing technology has resulted which allows control of the internal structure in extruded plastic materials. Micro- and nanostructured materials have been obtained. On-line process control allows rapid optimization of physical properties. In this presentation, the underlying physics will be described, examples of novel materials and their applications will be shown, and research opportunities will be highlighted. [Preview Abstract] |
Thursday, October 20, 2011 2:00PM - 2:30PM |
DA.00002: How animals drink and swim in fluids Invited Speaker: Fluids are essential for most living organisms to maintain a healthy body and also serve as a medium in which they locomote. The fluid bulk or interfaces actively interact with biological structures, which produces highly nonlinear, interesting, and complicated dynamical problems. We studied the lapping of cats and the swimming of Paramecia in various fluidic environments. The problem of the cat drinking can be simplified as the competition between inertia and gravity whereas the problem of Paramecium swimming in viscous fluids results from the competition between viscous drag and thrust. The underlying mechanisms are discussed and understood through laboratory experiments utilizing high-speed photography. [Preview Abstract] |
Thursday, October 20, 2011 2:30PM - 3:00PM |
DA.00003: Jamming and Fluidization in Granular Flows Invited Speaker: Granular materials exist all around us, from avalanches in nature to the mixing of pharmaceuticals, yet the behavior of these ``fluids'' is poorly understood. While the interaction of individual particles is simply through friction and inelastic collisions, the non-linear forces and large number of particles leads to an unpredictable, complex system. Flow can be characterized by the continuous forming and breaking of a strong force network resisting flow, leading to jamming, avalanching and shear banding. I'll present recent work on quasi-static shear and free-surface granular flows under the influence of external vibrations as well as related experiments on particle-fluid suspensions. By using photoelastic grains, we are able to measure both particle trajectories and the local force network in 2D flows. We find through particle tracking that dense granular flow is composed of comparable contributions from the mean flow, elastic deformations, and permanent, plastic deformations. Vibration typically weakens granular materials and removes hysteresis, though small vibrations can lead to strengthening of a pile. Flows of particle-fluid suspensions allow another avenue to probe failure of granular piles and additional control parameters, such as the surface chemistry of the particles. [Preview Abstract] |
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