Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session L1: General Fluid Dynamics III |
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Chair: Steven Ceccio, University of Michigan Room: 3000 |
Monday, November 24, 2014 3:35PM - 3:48PM |
L1.00001: Slow gravity-driven migration and interaction of a bubble and a solid particle near a free surface Franck Pigeonneau, Marine Gu\'emas, Antoine Sellier The interaction between a bubble and a free surface occurs in many industrial processes. This is the case for the glass melting process involving a high viscous fluid. Moreover, the bubble migration towards the free surface interacts with unmelted solid particles (sand grain). With this application in mind, the axi-symmetric gravity-driven migration of interacting bubble and solid particles near a free surface is examined. The solid particle locations and the bubble and free surface shapes are numerically tracked in time by solving the steady Stokes equations written under the boundary integral formulation. The theoretical material and the relevant numerical implementation, valid for bubbles and a free surface with either equal or unequal uniform surface tensions, are briefly described. Numerical results for a nearly-neutrally buoyant solid spherical particles interacting with a bubble and a free surface are investigated. We show that the solid particles decrease the bubble drainage dynamics. The effect of bubble size is also studied by changing the Bond number, ratio of buoyancy force to surface tension force. [Preview Abstract] |
Monday, November 24, 2014 3:48PM - 4:01PM |
L1.00002: Dynamics of viscous jet under electric field Tiantian Kong, Zhou Liu, Liqiu Wang, Ho Cheung Shum In this work, we study the folding and unfolding of viscous jets under an electric field. We show that the geometry of the jet responds sensitively to electric field and changes the jet dynamics accordingly. We demonstrate that a stable viscous straight jet can be induced to fold, and the folding morphology can be precisely tuned by varying the electric field. Under a controlled electric field configuration, a folded viscous jet can also be induced to unfold. We further confirm that viscous folding occurs only when a jet is sufficiently compressed and has an aspect ratio above a critical value, often known as the critical slenderness. The precise control of folding morphology is potentially useful for fabrication of nano-scaled features. Moreover, the underlying mechanisms have important implications for applications such as 3-dimensional printing and polymer processing, in which dispensing and manipulating of flowing viscous jets are of great importance. [Preview Abstract] |
Monday, November 24, 2014 4:01PM - 4:14PM |
L1.00003: Experimental Investigation of Spatially-periodic Scalar Patterns in an Inline Mixer Ozge Baskan, Michel Speetjens, Herman Clercx Spatially persisting patterns with exponentially decaying intensities form during the downstream evolution of passive scalars in three-dimensional (3D) spatially periodic flows due to the coupled effect of the chaotic nature of the flow and the diffusivity of the material. This has been investigated in many computational and theoretical studies on 2D time-periodic and 3D spatially-periodic flow fields, however, experimental studies, to date, have mainly focused on flow visualization with streaks of dye rather than fully 3D scalar field measurements. Our study employs the-state-of-the-art experimental methods to analyze the evolution of 3D scalar fields and the correlation between the coherent flow/scalar field structures in a representative inline mixer, called Quatro static mixer. The experimental setup consists of an optically accessible test section with transparent internal elements, accommodating a pressure-driven pipe flow. The 3D scalar fields are measured by 3D Laser-Induced Fluorescence. The preliminary results are consistent with the literature and we discuss the comparative analysis between our experimental observations and the numerical simulations from the previous studies. [Preview Abstract] |
Monday, November 24, 2014 4:14PM - 4:27PM |
L1.00004: Back to a classical problem: A fresh look at the asymptotics of the moving contact line David Sibley, Andreas Nold, Serafim Kalliadasis For contact line motion where the full Stokes flow equations hold, full matched asymptotic solutions using slip models have been obtained for droplet spreading and more general geometries, e.g. in the well-known results of Hocking and Cox. These solutions to the singular perturbation problem in the slip length, however, all involve matching through an intermediate region that is taken to be separate from the outer and inner regions and on the basis that the two do not match directly. Here, we show that not only is direct matching possible but the intermediate region is in fact an overlap region representing extensions of both the outer and the inner regions. In particular, we investigate in detail how a previously seen result of the matching of the cubes of the free surface slope is justified in the lubrication setting. We also extend this two-region direct matching to the more general Stokes flow case, offering a new perspective on the asymptotics of the moving contact line problem. [Preview Abstract] |
Monday, November 24, 2014 4:27PM - 4:40PM |
L1.00005: Time-varying creeping flow in an elastic shell enveloping a slender rigid center-body Shai Elbaz, Amir Gat Flows in contact with elastic structures apply stress at the fluid-solid interface and thus create deformation fields in the solid. We study the time-varying interaction between elastic structures, subject to external forces, and an internal viscous liquid. We neglect inertia in the liquid and solid and focus on axi-symmetric annular flow enclosed by a thin-walled slender elastic shell and internally bounded by a variable cross-section rigid center-body. We employ elastic shell theory and the lubrication approximation to show that the problem is governed by the forced porous medium equation with regard to fluid pressure. We present several solutions of the flow-field and solid-deformation for various time-varying inlet pressure and external forces. The presented interaction between viscosity and elasticity may be applied to fields such as soft-robotics and micro-swimmers. [Preview Abstract] |
Monday, November 24, 2014 4:40PM - 4:53PM |
L1.00006: Drawing of microstuctured optical fibres with pressurisation of the internal channels Michael Chen, Yvonne Stokes, Peter Buchak, Darren Crowdy, Heike Ebendorff-Heidepriem Microstructured optical fibres are distinguished from solid optical fibres by the large number of internal air channels running along their length. These fibres are manufactured by heating and stretching a preform, which has some cross-sectional pattern of holes. In stretching the preform with a diameter of 1-3cm to a fibre with a diameter of the order of 100 micrometers, the cross-sectional hole pattern changes in scale but is also deformed due to surface tension. A practical way of countering this deformation is to introduce pressurisation in the internal channels. This pressure acts against surface tension and potentially provides an extra degree of control over the shape of the internal channel geometry. We generalise an existing model of fibre drawing to include channel pressurisation and present examples of pressurised fibre drawing for several cross-sectional geometries of practical importance. [Preview Abstract] |
Monday, November 24, 2014 4:53PM - 5:06PM |
L1.00007: ABSTRACT WITHDRAWN |
Monday, November 24, 2014 5:06PM - 5:19PM |
L1.00008: The inception of eddy formation in the flow around a circular cylinder Nikolaos Malamataris, Anastasia Garatidou, George Sakkos, Konstantine Matsianikas The inception of eddy formation in the flow around a circular cylinder is studied with a home made Galerkin finite element code. The results show that the eddy begins at Re=6.2 which is the lowest Reynolds number reported so far in the literature. The code is validated with well known results for this flow. In addition, it is calculated for the first time how the pressure distribution around the cylinder surface varies for Reynolds numbers lower than 6.2 where experimental results exist from 1936. Finally, a new formula is given for the variation of the drag coefficient with respect to the Reynolds numbers under creeping flow conditions which deviates significantly from the well known result that exists in the literature. [Preview Abstract] |
Monday, November 24, 2014 5:19PM - 5:32PM |
L1.00009: Entrainment effects in the long residence times of solid spheres settling in stratified fluids Clauda Falcon, Roberto Camassa, Richard McLaughlin This talk will present results of a study, by a combination of experimental, analytical and numerical tools, of the effects of sharp density variations in the dynamics of a settling sphere in viscous dominated regimes. In particular, long residence times rivaling the ones observed for porous spheres in similar configurations will be demonstrated and discussed. Asymptotic approaches and exact solutions for the sphere exterior problem of Stokes equations will be compared in a parametric study of relevance for experiments. [Preview Abstract] |
Monday, November 24, 2014 5:32PM - 5:45PM |
L1.00010: On Gyroviscous Fluids Philip J. Morrison, Manasvi Lingam Fluid models involving gyroviscous effects, whereby momentum is transported while conserving energy, are of interest for plasma, astrophysical, and condensed matter systems. Such fluids can be viewed as possessing intrinsic angular momentum. We present a systematic method for constructing such models from an action principle formalism [1,2] that allows for an unambiguous means for introducing these effects, instead of ad-hoc phenomenological prescriptions. We also apply Noether's theorem to obtain the appropriate conserved quantities for these models. \\[4pt] [1] M. Lingam and P.J. Morrison, ``The action principle for generalized fluid motion including gyroviscosity'' (to be submitted).\\[0pt] [2] P.J. Morrison, M. Lingam and R. Acevedo, Phys. Plasmas 21, 082102 (2014). [Preview Abstract] |
Monday, November 24, 2014 5:45PM - 5:58PM |
L1.00011: Experimental Characterization of Inter-channel Mixing Through a Narrow Gap Jack Buchanan, Simo Makiharju, Alexander Mychkovsky, Kevin Hogan, Kirk Lowe, Steven Ceccio Mixing trough narrow gaps that connect primary flow paths is an important flow process for many thermal-hydraulic applications, such as flow through nuclear reactor rod bundles or heat exchangers. The flow in a narrow gap can exhibit periodic flow structures due to travelling vortices. These flow structures in the gap, as well as any pressure gradient across the gap, have a significant effect on the rate of mixing between the primary flow paths. To investigate such flows in detail, and to develop validation quality data sets for comparison with CFD, we have conducted a canonical inter-channel mixing experiment between two channels, with a (127 mm)$^{2}$ cross-section. The channels were connected by a gap 914.4 mm long in the stream-wise direction and 50.8mm wide in the cross-stream direction. The gap height could be varied from 0 to 50.8 mm. The flow speed in both channels could be independently varied to have Re $=$ (40 to 100) x 10$^{3}$. The integral mixing rates were determined by injecting fluorescent dye into one of the channels well upstream of the test section and by measuring the dye concentration at the channel inlets and outlets. Additionally, the flow fields in the gap and channels were measured with LDV and PIV. [Preview Abstract] |
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