Bulletin of the American Physical Society
61st Annual Meeting of the APS Division of Fluid Dynamics
Volume 53, Number 15
Sunday–Tuesday, November 23–25, 2008; San Antonio, Texas
Session PH: Surface Tension Effects II |
Hide Abstracts |
Chair: Eric Johnsen, Stanford University Room: 101B |
Tuesday, November 25, 2008 11:35AM - 11:48AM |
PH.00001: Stretching and Slipping Liquid Bridges near Cavities Shawn Dodds, Satish Kumar, Marcio S. Carvalho The dynamics of liquid bridges are relevant to a wide variety of applications including high-speed printing, extensional rheometry, and floating-zone crystallization. Although many studies assume that the contact lines of a bridge are pinned, this is not the case for printing processes such as gravure, lithography, and microcontacting. To address this issue, we use the Galerkin/Finite-Element method to study the stretching of a finite volume of Newtonian liquid confined between two flat plates, one of which is stationary and the other moving. The contact lines are allowed to slip, and we evaluate the effect of the capillary number and contact angle on the amount of liquid transferred to the moving plate. Liquid transfer to the moving plate is found to increase as the contact angle of the stationary plate increases relative to that of the moving plate. When the contact angle is fixed and the capillary number is increased, the liquid transfer improves if the stationary plate is wetting, but worsens if it is non-wetting. The presence of a cavity on the stationary plate significantly affects the contact line motion, often causing pinning at the cavity corner. In these cases, liquid transfer is controlled primarily by the cavity shape, suggesting that the effects of surface topography dominate over those of surface wettability. [Preview Abstract] |
Tuesday, November 25, 2008 11:48AM - 12:01PM |
PH.00002: Imbibition in geometries with axial variations Mathilde Reyssat, Laurent Courbin, Etienne Reyssat, Howard A. Stone When surface wetting drives liquids to invade porous media or microstructured materials with uniform channels, the penetration distance is known to increase as the square root of time. We demonstrate, experimentally and theoretically, that shape variations of the channel, in the flow direction, modify this ``diffusive'' response. At short times, the shape variations are not significant and the imbibition is still diffusive. However, at long times, different power law responses occur, and their exponents are uniquely connected to the details of the geometry. Experiments performed with conical tubes clearly show the two theoretical limits. [Preview Abstract] |
Tuesday, November 25, 2008 12:01PM - 12:14PM |
PH.00003: Interconnectivity in Surface Wicking Structures Yongkang Chen, Donald Bell, Santiago Rodriguez, Ben Semerjian, Lawrence Melvin, Mark Weislogel Surface wicking structures possessing strong interconnectivity are designed and examined. The designs aim to optimize the structure's ability to transport fluids by exploiting capillary driven flow in interior corners combined with interconnectivity and alignment. `Waffle-like' structures consisting of vertical rectangular vanes at a variety of orientations are employed as the basic repeat unit. Due to this arrangement, such surfaces possess interconnectivity that is stronger than that of other existing designs such as those composed of micro posts. This strong interconnectivity provides several advantages. For example, it is found that the transport of fluid by wicking can be controlled by a clever choice of the interconnectivity and vane alignment. As a result, the shape of the moving front during wicking can be circular, elliptical, or rectangular. The observations as well as a study of the dynamics of the wicking flow will be presented. [Preview Abstract] |
Tuesday, November 25, 2008 12:14PM - 12:27PM |
PH.00004: Influence of surfactant solubility on the deformation and breakup of a bubble or thread in a viscous fluid Michael Booty, Yuan-Nan Young, Michael Siegel, Jie Li In a previous paper (JFM 594, 307-340, 2008) we studied effects of insoluble surfactant on the pinch-off of an inviscid bubble surrounded by a viscous fluid theoretically and numerically. In the present study the surfactant solubility is included. The adsorption-desorption kinetics of surfactants is assumed to be in the diffusion-dominated regime, and equations governing the evolution of the interface and surfactant concentration in zero-Reynolds-number flow are derived using a long wavelength approximation. Results of the long wavelength model are compared against numerical simulations of the full Navier-Stokes equations, performed using an accurate arbitrary Lagrangian-Eulerian method. The presence of insoluble surfactant significantly retards pinch-off (JFM 594, 307-340, 2008): This is due to the development of a long, slender, quasi-stable cylindrical thread at the location of minimum radius, where the destabilizing influence of capillary pressure is balanced by the internal pressure. For soluble surfactant, depending on parameter values, a thin thread forms first but pinches off later due to the exchange between bulk and surface surfactants. In some cases the collapsing of bubble is completely inhibited by the soluble surfactant. [Preview Abstract] |
Tuesday, November 25, 2008 12:27PM - 12:40PM |
PH.00005: Liquid flow over a substrate structured by seeded nanoparticles and slip boundary condition Alex Lukyanov Recent experiments have demonstrated that already sparsely distributed, over a solid substrate, nanoparticles can change substantially the amount of liquid slip at the surface. Inspired by the observations, the flow past small particles seeded on a solid substrate is investigated theoretically on the basis of an interface formation model. It has been demonstrated, for the first time, that even a single seeded particle can create sufficient surface tension gradient, with the characteristic length scale independent of the particle size, to reduce significantly the (measurable) tangential component of hydrodynamic velocity at the substrate and thus to adjust the slip boundary condition. But, it has been established, that the effect from the particle is essential for the actual slippage, while the apparent slip would be only partially disturbed. This outcome of the analysis is crucial for future experiments and can be potentially used to identify exactly the mechanism of slip in particular situations. A comparison with the experiments has shown that the results of the theoretical analysis are quantitatively consistent with the experimental measurements, in particularly the maximal separation distance between the particles to observe the deterioration of slip. [Preview Abstract] |
Tuesday, November 25, 2008 12:40PM - 12:53PM |
PH.00006: Spreading of a Fluorescent Surfactant on a Glycerine Layer David Fallest, Christopher Fox, Karen Daniels We study the spreading of a fluorescent surfactant on a thin layer of glycerine. Measurements of the height profile of the capillary ridge are conducted as the surfactant travels outward from the point of deposition. We examine the dynamics of the ridge as a function of the volume of surfactant released, and find that for the largest volumes the shape and speed of the spreading ridge are influenced by the outer edge of the underlying glycerine layer. The intensity of the fluorescence is also used to visualize the position and the concentration of surfactant as it spreads. The location of the surfactant is compared to the location of the capillary ridge. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700