Bulletin of the American Physical Society
60th Annual Meeting of the Divison of Fluid Dynamics
Volume 52, Number 12
Sunday–Tuesday, November 18–20, 2007; Salt Lake City, Utah
Session JK: Viscous Flows |
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Chair: John Elsnab, University of Utah Room: Salt Palace Convention Center 250 E |
Monday, November 19, 2007 3:35PM - 3:48PM |
JK.00001: Stirring fluid with a `taffy pulling' device J. Alec Calhoun, Mark Stremler The four-pronged taffy pulling machine is a classic candy-making device. Two intersecting U-shaped pieces stretch and fold the taffy as they rotate. We demonstrate that this mechanism is an effective tool for stirring viscous fluid. The rods `braid' the fluid in a way that guarantees exponential stretching of non-trivial material lines. We analyze this stirring experimentally and using methods from topology and dynamical systems theory. [Preview Abstract] |
Monday, November 19, 2007 3:48PM - 4:01PM |
JK.00002: Flight times for Stokes and potential flows past symmetric bodies Ashwin Vaidya, Roberto Camassa, Richard McLaughlin, Nick Moore We consider, by a combination of asymptotic, computational, and experimental techniques, the flight time for passive fluid particles flowing past fixed obstacles under the assumptions of potential, stokes, and slightly inertial flow. We observe some intriguing differences between the three cases. [Preview Abstract] |
Monday, November 19, 2007 4:01PM - 4:14PM |
JK.00003: Bending at the base of a dragged-out viscous thread Maurice Blount, John Lister We consider steady flow of a slender viscous thread falling from a nozzle onto a moving horizontal belt. We analyse the asymptotic limit of a very slender thread, and show that it has a boundary-layer structure in which bending stresses only become important near the belt, where they support a vertical stress and allow the velocity and rolling conditions to be satisfied. The outer solution is analogous to a viscous catenary, with velocity fixed at the belt and at the nozzle. There are three asymptotic regimes, with distinct structures, corresponding to the cases that the belt speed is larger than, smaller than, or close to the velocity of a freely falling thread. The implications for the onset and amplitude of meanders in the `fluid-mechanical sewing machine' are explored. [Preview Abstract] |
Monday, November 19, 2007 4:14PM - 4:27PM |
JK.00004: Complex three particle dynamics in a viscous liquid filled rotating drum. James Davidheiser, Phil Segre We will describe experiments on the motions of three heavy spheres moving within a viscous liquid filled rotating cylindrical drum. Numerous works, in other geometries, have demonstrated that assemblies of non-brownian particles in viscous liquids have the potential to exhibit chaotic motion. We find that at the lowest drum rotation rates $\omega$, the beads first undergo a transformation from fixed-point to periodic motion as $\omega$ is increased. At the highest rotation rates, the motion is also periodic. At intermediate rates $\omega$, however, the particles exhibit very complex and apparently chaotic trajectories. Our results, which will be presented in the form of particle trajectories in time obtained using digital particle tracking software, demonstrate how these complex trajectories vary with $\omega$. [Preview Abstract] |
Monday, November 19, 2007 4:27PM - 4:40PM |
JK.00005: ABSTRACT WITHDRAWN |
Monday, November 19, 2007 4:40PM - 4:53PM |
JK.00006: Dewetting of a fluid between parallel plane surface with nonconstant forcing Parousia Rockstroh, Thomas Ward We examine the effect of applying a nonconstant force to the radial squeezing and de-wetting of a thin film of viscous Newtonian fluid between parallel plane walls. We explore the problem theoretically for gap spacings much smaller than the typical capillary length for air-liquid systems ($<$ O(1) $mm$). In our model, we parameterize force using a single variable $F$ which is proportional to a constant force $F_0$ and the height of the gap spacing $h$ to some integer power $n \in \mathcal{Z}^+.$ Since there is no known analytic solution for $n>0$, we analyze the solution of the dewetting problem numerically. Analysis reveals the formation of a singularity, leading to capillary adhesion, as the gap spacing approaches a critical value that depends on $F_0$, $n$ and a variable $C$ that is analogous to a spring constant. [Preview Abstract] |
Monday, November 19, 2007 4:53PM - 5:06PM |
JK.00007: ABSTRACT WITHDRAWN |
Monday, November 19, 2007 5:06PM - 5:19PM |
JK.00008: Scaling laws for drag of a compliant body in an incompressible viscous flow Luoding Zhu Motivated by an important discovery on the drag scaling law (the four-thirds power law) of a flexible fiber in a flowing soap film by Alben, Shelley and Zhang ({\it Nature} {\bf 420}, 479 (2002)) at high Reynolds numbers $(2,000 < Re < 40,000)$, we investigate drag scaling laws at moderate $Re$ for a compliant fiber tethered at the midpoint submerged in an incompressible viscous flow using the Immersed Boundary (IB) method. Our work shows that the scalings of drag with respective to oncoming flow speed vary with $Re$ and the range of a dimensionless parameter $\eta$ that measures the relative importance of fluid kinetic energy and body elastic potential energy. In particular, the exponents of the power laws gradually decrease from approximately two to approximately four-thirds as $Re$ decreases from $10$ to $800$ for $\eta$ in a certain range. [Preview Abstract] |
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