Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 55, Number 16
Sunday–Tuesday, November 21–23, 2010; Long Beach, California
Session RF: Non-Newtonian Flows III |
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Chair: Arezoo Ardekani, University of Notre Dame Room: Long Beach Convention Center 103A |
Tuesday, November 23, 2010 3:05PM - 3:18PM |
RF.00001: Transient swelling behavior and drug delivery from a dissolving film deploying anti-HIV microbicide Savas Tasoglu, David F. Katz, Andrew J. Szeri Despite more than two decades of HIV vaccine research, there is still no efficacious HIV vaccine. Very recently, a research group has shown that a microbicide gel formulation of antiretroviral drug Tenofovir, significantly inhibits HIV transmission to women [1]. However, there is a widespread agreement that more effective and diverse drug delivery vehicles must be developed. In this setting, there is now great interest in developing different delivery vehicles such as vaginal rings, gels, and films. Here, we develop a model for transient fluid uptake and swelling behavior, and subsequent dissolution and drug deployment from a film containing anti-HIV microbicide. In the model, the polymer structural relaxation via water uptake is assumed to follow first order kinetics. In the case of a film loaded with an osmotically active solute, the kinetic equation is modified to account for the osmotic effect. The transport rate of solvent and solute within the matrix is characterized by a diffusion equation. After the matrix is relaxed to a specified concentration of solvent, lubrication theory and convective-diffusive transport are employed for flow of the liquefied matrix and drug dispersion respectively. [1] Karim, et al., Science, 2010. [Preview Abstract] |
Tuesday, November 23, 2010 3:18PM - 3:31PM |
RF.00002: Coating flow of an anti-HIV microbicide gel: boundary dilution and yield stress Andrew J. Szeri, Savas Tasoglu, Su Chan Park, David F. Katz A recent study has confirmed, for the first time, that a vaginal gel formulation of the antiretroviral drug Tenofovir, when topically applied, significantly inhibits sexual HIV transmission to women [1]. However, the gel for this drug, and anti-HIV microbicide gels in general, have not been designed using an understanding of how gel spreading govern successful drug delivery. Elastohydrodynamic lubrication theory can be applied to model spreading of microbicide gels [2]. Here, we extend our initial analysis: we incorporate a yield stress, and we model the effects of gel dilution due to contact with vaginal fluid produced at the gel-tissue interface. Our model developed in [2] is supplemented with a convective-diffusive transport equation to characterize dilution, and solved using a multi-step scheme in a moving domain. The association between local dilution of gel and rheological properties is obtained experimentally. To model the common yield stress property of gels, we proceed by scaling analysis first. This establishes the conditions for validity of lubrication theory of a shear thinning yield stress fluid. This involves further development of the model in [2], incorporating a biviscosity model.\\[4pt] [1] Karim, et al., Science, 2010.\\[0pt] [2] Szeri, et al., Phy. of Fluids, 2008. [Preview Abstract] |
Tuesday, November 23, 2010 3:31PM - 3:44PM |
RF.00003: Motion of Non-Newtonian liquid plugs in channels Parsa Zamankhan, Brian Helenbrook, Suichi Takayama, James Grotberg Some major transport phenomena in the human respiratory system such as the reopening of the occlude airways and drug delivery involve with propagation of liquid plugs, constituted from non-Newtonian fluids. In this presentation the transport of liquid plugs, constituted from the yield stress Bingham, and shear thinning power-law fluids is investigated numerically. The governing equations are solved by a mixed-discontinuous finite element formulation while the free surface is resolved by the method of spines. The constitutive equation for Bingham fluid is implemented through a regularization method. The effects of the yield stress and the power-law index on the flow feature are compared and discussed. Special attention is given to the distribution of the stresses along the wall with applications in cell injury studies. [Preview Abstract] |
Tuesday, November 23, 2010 3:44PM - 3:57PM |
RF.00004: ABSTRACT WITHDRAWN |
Tuesday, November 23, 2010 3:57PM - 4:10PM |
RF.00005: Non-Newtonian Fluids Spreading with Surface Tension Effect: 3D Numerical Analysis Using FEM and Experimental Study Bin Hu, Sarah Kieweg Gravity-driven thin film flow down an incline is studied for optimal design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. We develop a 3D FEM model using non-Newtonian mechanics to model the flow of gels in response to gravity, surface tension and shear-thinning. Constant volume setup is applied within the lubrication approximation scope. The lengthwise profiles of the 3D model agree with our previous 2D finite difference model, while the transverse contact line patterns of the 3D model are compared to the experiments. With incorporation of surface tension, capillary ridges are observed at the leading front in both 2D and 3D models. Previously published studies show that capillary ridge can amplify the fingering instabilities in transverse direction. Sensitivity studies (2D {\&} 3D) and experiments are carried out to describe the influence of surface tension and shear-thinning on capillary ridge and fingering instabilities. [Preview Abstract] |
Tuesday, November 23, 2010 4:10PM - 4:23PM |
RF.00006: Flow of wormlike micelles in confined geometry Nicolas Louvet, Chlo\'e Masselon, Annie Colin We study wormlike micelles flowing in confined geometry to study the local rheology of such fluids. Experiments show that the properties of such fluids undergoing a strong shear stress gradient can only be described by an equation including non-local terms. Then the flow of very long wormlike micelles is studied both in microfluidic channel and in Couette geometry coupling with ultrasonic velocimetry. [Preview Abstract] |
Tuesday, November 23, 2010 4:23PM - 4:36PM |
RF.00007: Modeling of irreversible flow-induced gelation in wormlike micellar solutions Neville Dubash, Joshua Cardiel, Perry Cheung, Amy Shen Wormlike micellar solutions are known to exhibit a variety of interesting phenomena, one of which is the formation of gel-like structures under simple flow conditions. Previously, these flow-induced structures were all observed to be temporary, and the gels would dissipate upon cessation of the flow. Recently, however, it has been shown that it is possible to produce a purely flow-induced irreversible transformation in certain micellar solutions. This irreversible gel formation is brought about via a mixed shearing/extensional flow in which the fluid experiences very high rates of strain and total strains. Here, we examine this gelation phenomenon and present a model which is able to capture the irreversible rheological changes observed in our experimental system. The model is based on an existing network scission model for micellar solutions that contains two species of interacting, elastically-active micellar chains. [Preview Abstract] |
Tuesday, November 23, 2010 4:36PM - 4:49PM |
RF.00008: Switching and defect dynamics in liquid crystal devices Adriano Tiribocchi, Giuseppe Gonnella, Davide Marenduzzo, Enzo Orlandini We present some numerical results about nematic cells in which an external electric field is applied. We show that it is possible to desing a simple two-domain hybdridly aligned nematic cell which is bistable and we elucidate the role of hydrodynamics by using a lattice Boltzmann approach. Moreover we report some results of electric field induced switching of devices built starting from cholesteric blue phase, showing how various disclination patterns can be predicted. Hydrodynamic effects are also observed to affect the switching dynamics. [Preview Abstract] |
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