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 EC: Drops and Bubbles IV |
Hide Abstracts |
Chair: Joseph Katz, Johns Hopkins University Room: Salt Palace Convention Center 150 G |
Sunday, November 18, 2007 4:10PM - 4:23PM |
EC.00001: High order quadratures to compute evolution of axis-symmetric interfacial Stokes flows Monika Nitsche, Hector Ceniceros, Aino Karniala Boundary integral methods have been used widely for the simulation of interfacial Stokes flows. These methods reduce the dimensionality of the problem by one since the fluid velocity reduces to an integral over the interface. In the case of axisymmetric interfaces it is difficult to approximate these integrals accurately. The integrands have singular behaviour at the symmetry axis and as a result, existing quadrature rules are, at best, of a limited second order accuracy. Furthermore, cancellation of large terms introduces large roundoff errors. In this work, we propose a new numerical approach to overcome these difficulties. The approach is based on analytic error corrections constructed from an asymptotic analysis of the integrands. We present quadratures that achieve a uniform accuracy of order five, apply them to compute the evolution of a drop, and demonstrate numerically their superior accuracy and efficiency. [Preview Abstract] |
Sunday, November 18, 2007 4:23PM - 4:36PM |
EC.00002: Atomistic water droplet simulation John Thomas, Madhur Paharia, Eric Landry, Gary Lee, Alan McGaughey A water droplet in equilibrium with its own vapor is modeled using molecular dynamics simulations. The density, velocity distribution, orientation, and energetics of~liquid and vapor~molecules near the droplet surface are examined.~ Deviations from Maxwellian statistics are predicted in both phases. Hydrogen bonding and molecular orientation also vary with distance from the droplet center.~ We~predict~the force landscape near the interface over a range of temperatures and explore~the~mechanisms responsible for evaporation.~ [Preview Abstract] |
Sunday, November 18, 2007 4:36PM - 4:49PM |
EC.00003: FEM calculations of drop breakup beyond the first singularity Ronald Suryo, Osman Basaran Computational analysis of drop breakup, which is of common occurrence in nature and technology, is important for advancing understanding of pinch-off singularities and developing new technologies. During drop formation from a tube, as more liquid flows from the tube into the drop, the drop elongates and thins. At the incipience of breakup, a spherical mass -- the precursor of the primary drop -- is connected to the liquid in the tube by a thin thread -- the precursor of one or more satellites. Numerical algorithms for analyzing this phenomenon at finite Reynolds number have been of two types: ones based on finite element methods (FEMs) and others based on various diffuse interface (DI) techniques. Numerical solutions must agree with scaling solutions of interface pinch-off, which are exact solutions of the nonlinear Navier-Stokes equations, and experiments. To date, the DI approach, despite its coarseness, has been more popular because it is simple and can predict the formation of several drops in sequence. Predictions made with FEM algorithms have been shown to be in excellent agreement with scaling theories and measurements but only until the instant of first breakup. Here we describe new FEM computations of unparalleled accuracy to predict the dynamics of continuous drop formation and support them with high-speed visualization experiments. [Preview Abstract] |
Sunday, November 18, 2007 4:49PM - 5:02PM |
EC.00004: A numeric investigation of co-flowing liquid streams using the Lattice Boltzmann Method Andy Somogyi, Randall Tagg We present a numerical investigation of co-flowing immiscible liquid streams using the Lattice Boltzmann Method (LBM) for multi component, dissimilar viscosity, immiscible fluid flow. When a liquid is injected into another immiscible liquid, the flow will eventually transition from jetting to dripping due to interfacial tension. Our implementation of LBM models the interfacial tension through a variety of techniques. Parallelization is also straightforward for both single and multi component models as only near local interaction is required. We compare the results of our numerical investigation using LBM to several recent physical experiments. [Preview Abstract] |
Sunday, November 18, 2007 5:02PM - 5:15PM |
EC.00005: Flow Focused steady liquid jetting by gas: numerical and experimental studies on the minimum flow rate Miguel A. Herrada, Antonio Ojeda-Monge, Bluth Benjamin, Alfonso M. Ganan-Calvo A direct axisymmetric VOF numerical simulation on flow-focused liquid jetting by gas, and a collection of detailed experiments are presented in this work. The minimum liquid flow rate for which steady jetting is possible is analyzed both from the numerical and the experimental sides. In particular, a strong recirculation is observed in the numerical simulations to take place inside the conical meniscus and is found to play an important role on the global stability of the system. Close to the minimum liquid flow rate for steady jetting, the recirculation cell penetrates deep into the feed tube. Besides, the jet size reported agrees very well with a simple theoretical prediction (Ganan-Calvo 1998, Phys. Rev. Lett. 80, 285). In addition, the transition from jetting to dripping is numerically analyzed in detail in some illustrative cases, showing a remarkable agreement with experiments. [Preview Abstract] |
Sunday, November 18, 2007 5:15PM - 5:28PM |
EC.00006: Numerical study of the motion of microscopic oil droplets under high turbulence. Murray Snyder, Omar Knio, Joseph Katz, Olivier Le Ma\^Itre The rise of small oil droplets in water undergoing isotropic turbulence is analyzed computationally to explain the observations of Friedman and Katz (2002), where the rise velocity of droplets smaller than 800 $\mu$m diameter is enhanced by turbulence whereas rise of larger droplets is retarded. The study explores whether these effects can be explained using a one-way coupling model combining DNS of the field with Lagrangian tracking of droplets using a dynamical equation with buoyancy, virtual mass, pressure, drag, lift and history forces. Results indicate that using empirically-determined drag and lift coefficients, the observed droplet behavior is not reproduced. Lift and history forces are shown to not to account for the observed mean droplet rise. From correlations for settling of heavy particles under intense turbulence, suppression of drag and virtual mass for droplet diameters near ten times the Kolmogorov lengthscale was postulated. Analysis indicate that the model then recovers observed small droplet rise enhancement and large droplet rise retardation. Results underscore difficulties in modeling the motion of small particles under high turbulence, especially when the particle size is near the turbulence microscale. [Preview Abstract] |
Sunday, November 18, 2007 5:28PM - 5:41PM |
EC.00007: Computation of the rolling motion of a viscous drop Xinli Wang We consider the gravity induced rolling motion of a nonwetting viscous droplet on a flat or tilted solid surface, which is a moving contact line problem with a free surface. One of main difficulties in this problem is the infinite stress singularity at the contact line when we assume an incompressible viscous Newtonian fluid with a no-slip boundary condition on the solid. A 180 degree contact angle is considered as a special case in which the stress singularity is absent. The boundary element method is applied to implement a time-dependent solution of a drop rolling on solid surface with a 180 degree contact angle. An asymptotic solution is enforced at the contact line for which the stress singularity is absent. For small drops, we find the velocity of rolling is proportional 1/R where R is the radius of the drop; for large drops, the velocity of rolling does not depend on the radius of drops. These results are in agreement with a recent theory of Mahadevan and Pomeau. [Preview Abstract] |
Sunday, November 18, 2007 5:41PM - 5:54PM |
EC.00008: Two-way Interaction of Lagrangian Bubble Dynamics and Eulerian Mixture Flow Field Jin-Keun Choi, Chao-Tsung Hsiao, Georges Chahine Although under simple flow conditions a well dispersed bubble cloud in a liquid can be modeled with an Eulerian continuum model, the fine scale interactions between the two phases, the potential non-uniformities and high bubble concentrations in stiff gradient regions of complex flows can only be represented by more detailed numerical models such as Lagrangian tracking of individual bubbles. To meet both needs of describing individual bubbles and of including the collective effects in the two-phase continuum, we have developed a method coupling in a two-way fashion the two approaches. The bubble dynamics and tracking scheme is based on extensive studies on bubble dynamics and interactions at \textsc{Dynaflow} and is based on a Surface Averaged Pressure spherical model using a modified incompressible Rayleigh-Plesset equation or a modified compressible Gilmore equation. The bubbles presence in the Eulerian flow field is considered through a variable medium density formulation resulting from the instantaneous bubble population distribution in the field. The developed method is applicable to many practical flows in pipes, jets, pumps, propellers, ships, and the ocean. We present the method and its application to waterjet thrust augmentation by bubble injection. [Preview Abstract] |
Sunday, November 18, 2007 5:54PM - 6:07PM |
EC.00009: Effect of Inertia on the Hydrodynamic Interaction between Two Liquid Capsules in Shear Flow Sai Doddi, Prosenjit Bagchi Three-dimensional numerical simulations using front-tracking method are performed to study the hydrodynamic interaction between two liquid capsules suspended in simple shear flow in presence of inertia. Capsules are modeled as liquid drops surrounded by elastic membranes. In the limit of zero inertia, it is known that the hydrodynamic interaction between two deformable particles (drops/capsules) in shear flow results in an irreversible shift in the trajectories of the particles leading to shear-induced diffusion. Here we show that the presence of inertia can significantly alter capsule trajectories. When inertia is small but finite, capsules do undergo shear-induced diffusion, but the lateral separation between them first decreases before they roll over each other. For moderate to high inertia, capsules reverse their directions of motion before coming close to each other. The reversal of motion occurs progressively earlier in time with increasing inertia. The long-time behavior of the capsule-capsule interaction at finite inertia shows that the capsules engage in spiraling motions. The reversal of motion, and the spiraling trajectories at finite inertia have no analogy in the limit of zero inertia. Such motions are explained by analyzing the flow field around a deformed capsule which shows reverse flow regions and off-surface stagnation points, similar to those previously reported in case of rigid spheres and cylinders under torque-free condition. [Preview Abstract] |
Sunday, November 18, 2007 6:07PM - 6:20PM |
EC.00010: Hydraulic oscillator Luc Lebon, Christophe Pirat, Jean-Sebastien Roche, Laurent Limat When a liquid jet impacts an horizontal surface, it induces a radial flow in a thin film with formation of an hydraulic jump. Drops can levitate on this jump, separated from the liquid film by a thin layer of air. If we incline slightly the surface, and therefore the hydraulic jump, we can observe that a drop trapped on the jump does not stay static, but oscillates along the inner side of the jump. This oscillation appears to be self-sustained ; we investigated its caracteristics as a fonction of the liquid properties, the inclination and the jet flow rate. [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