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 QM: Free Surface Flows: Droplets and Sheets |
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Chair: Tadd Truscott, Brigham Young University Room: Long Beach Convention Center 202B |
Tuesday, November 23, 2010 12:50PM - 1:03PM |
QM.00001: Capillary retraction of liquid sheet Gilles Agbaglah, Christophe Josserand, St\'ephane Zaleski During the atomization, drops may be formed by several distinct mechanisms. A general understanding of these processes is still lacking and is at the heart of many fundamental studies on atomization. In particular, the destabilization of a liquid sheet is known to detach small droplets. In this work, retracting liquid sheet is numerically studied in 2D and 3D. We present an asymptotic expansion of the film profile in 2D and we develop the long wave approximation dynamics of a planar 3D sheets. The role played by the ambient gas and new instabilities for the retracting liquid sheet is also discussed. [Preview Abstract] |
Tuesday, November 23, 2010 1:03PM - 1:16PM |
QM.00002: Atomization patterns of liquid sheets formed by two impinging jets Dong-Jun Ma, Xiao-Dong Chen, Vigor Yang High fidelity numerical simulations have been performed to study the atomization patterns and breakup characteristics of liquid sheets formed by two impinging jets. A fully three-dimensional Volume-of-Fluid method with adaptive mesh refinement (AMR) based on octree-mesh is used to simulate the primary atomization. The start of the art visualization techniques with volume rending were also used to highlight the breakup characteristics. The oblique collision of two cylindrical laminar jets leads to the liquid owing outward from the impact point, creating a thin sheet which lies in a plane perpendicular to the plane containing the two jets and disintegrates into ligaments or droplets. The breakup of the sheet is dominant by the viscosity and surface tension effects (Reynolds and Webber number). The periodic waves from the point of impingement were apparent on the surface of the sheet. The circumferentially space drops were shed from the periphery of the sheet, as well as the ligaments were fragmented from the leading edge of the sheet and then broke into droplets following the Rayleigh mechanism. The impact waves caused early breakdown of the sheet downstream of the impingement point, whereas waves amplified by aerodynamic stresses controlled the breakdown of the rest of the sheet and the ligaments. [Preview Abstract] |
Tuesday, November 23, 2010 1:16PM - 1:29PM |
QM.00003: Vibration-Induced Gas-Liquid Interface Breakup Timothy O'Hern, John Torczynski, Ed Romero, Bion Shelden Gas-liquid interfaces can be forced to break up when subjected to vibrations within critical ranges of frequency and amplitude. This breakup mechanism was examined experimentally using deep layers of silicone oils over a range of viscosity and sinusoidal, primarily axial vibration conditions that can produce dramatic disturbances at the gas-liquid free surface. Although small-amplitude vibrations produce standing Faraday waves, large-amplitude vibrations produce liquid jets into the gas, droplets pinching off from the jets, gas cavities in the liquid from droplet impact, and bubble transport below the interface. Experiments used several different silicone oils over a range of pressures and vibration conditions. Computational simulations exhibiting similar behavior will be included in the presentation. Applications include liquid fuel rockets, inertial sensing devices, moving vehicles, mixing processes, and acoustic excitation. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Tuesday, November 23, 2010 1:29PM - 1:42PM |
QM.00004: Crumpled liquid sheet Henri Lhuissier, Emmanuel Villermaux When a liquid jet of density $\rho$ impacts a solid disk at right
angle, it expands
radially into a thin sheet with velocity $u$ and thickness $h$.
The sheet possibly bends
under the action of surface tension $\sigma$ to form a stationary
closed bell. For
particular impacting conditions and pressure in the enclosure,
spectacular stable
shapes exhibiting {\emph{sharp edges}}, sudden inflections and
{\emph{liquid points}}
are observed. Those sharp wrinkles develop when the ratio $We =
\rho u^{2}
h/\sigma$ of the flow inertia to capillary confinement approaches
a critical value
$We_{c}=2$. There, the local curvature of the sheet in the
direction of the flow
$\kappa$ diverges. However, accounting for finite thickness
effects (i.e. $\kappa
h={\cal O}(1)$), we show that two coexisting solutions for
$\kappa$ emerge,
explaining the sudden inflection of the sheet, as if it were
crumpled. The development
of regularly spaced {\emph{liquid points}} that form along the
crumpled {\emph{edge}},
breaking the initial axial symmetry is a consequence of the
centripetal acceleration
$\kappa u^{2}$ the liquid suffers as it flows past the edge. The
resulting inertial
destabilization induces thickness modulations with drapes like
shapes on the sheet,
forming an alternation of subcritical ($We |
Tuesday, November 23, 2010 1:42PM - 1:55PM |
QM.00005: A Computational Analysis of Binary Collisions of shear-thinning Droplets Christian Focke, Dieter Bothe We investigate binary droplet collisions as a prototype sub-process inside sprays and focus on shear-thinning liquids. To understand the influence of the non-Newtonian fluid rheology on the flow inside the colliding drops as well as on the collision complex dynamics, we employ direct numerical simulations based on an extended Volume of Fluid method. During collisions, extremely thin fluid lamellas appear due to the shear-thinning behavior. These have to be accounted for in a physically sound simulation and we apply a stabilizing boundary condition to be able to keep the lamella from rupturing. The results give a quantitative prediction of the resulting droplet collision complex diameter. The simulations show that in all considered cases an effective constant viscosity can be found a posteriori which leads to the same collision dynamics. But this effective viscosity is neither the mean nor the minimum viscosity. If the collision complex becomes large enough, disturbances on the rim develop during the contraction phase, which arise from the Plateau-Rayleigh instability. [Preview Abstract] |
Tuesday, November 23, 2010 1:55PM - 2:08PM |
QM.00006: Eggs in milk Tadd Truscott, Jesse Belden, Ken Langley When a hard-boiled egg spins through a pool of milk on the kitchen counter the milk rises up the sides of the egg and droplets are ejected. The phenomena can occur for many different geometries, angular velocities and viscosities, but is independent of which kitchen counter one uses. Depending on the parameters of the experiment, the ejected fluid takes on one of three distinct forms: droplets, jets, or sheets. We propose several scaling arguments for the formation of this important household phenomenon. [Preview Abstract] |
Tuesday, November 23, 2010 2:08PM - 2:21PM |
QM.00007: The Tibetan singing bowl John Bush, Denis Terwagne Tibetan singing bowls have been used for centuries for healing, meditation and shamanic journeying. The bowls are partially filled with water, then excited by either striking or rubbing the walls of the bowl with a mallet. A wealth of curious fluid mechanical phenomena arise, and will be elucidated in our combined experimental and theoretical investigation. [Preview Abstract] |
Tuesday, November 23, 2010 2:21PM - 2:34PM |
QM.00008: Inviscid Breakup of Bubbles and Drops With and Without Surface Charge Justin Burton, Peter Taborek We present boundary-integral simulations of the breakup of inviscid bubbles and droplets, with and without surface charge. In our simulations, an inner fluid volume of density $\rho_{1}$ is surrounded by an exterior fluid of infinite extent and density $\rho_{2}$. When there is no charge on the surface, we see excellent agreement with previous work, except for intermediate density ratios, where the simulations are plagued by oscillatory instabilities not observed in experiments [1]. With the addition of surface charge, initially spherical drops and bubbles are unstable to small perturbations above a critical surface charge density. For the droplet limit, the charged drop forms a ``lemon'' shape before ejecting a highly charged jet from the tips of the ``lemon,'' where the size of the jet scales with the square of the inverse surface conductivity. For the bubble limit, we find that fission always takes place by the formation of a ``peanut''-shaped bubble, where breakup takes place at the center of the bubble, regardless of surface conductivity. For intermediate densities, combinations of droplet and bubble fission are observed.\\[4pt] [1] J.C. Burton and P. Taborek, Phys. Rev. Lett. 101, 214502 (2008) [Preview Abstract] |
Tuesday, November 23, 2010 2:34PM - 2:47PM |
QM.00009: A mesoscale analysis of the Rayleigh-Plateau instability Marco Arienti, Li Xiaoyi, Marios Soteriou, Wenxiao Pan, George Karniadakis Capillary pinch-off results carried out with the Many-Body Dissipative Particle Dynamics (MDPD) method are compared with the two-phase continuum discretization of hydrodynamics. The MDPD method provides a mesoscale description of the liquid-gas interface -- molecules can be thought of as grouped in particles with modeled Brownian and dissipative effects. No liquid-gas interface is explicitly defined; surface properties, such as surface tension, result from the MDPD interaction parameters. In side-to-side comparisons, the behavior of the MDPD liquid is demonstrated to replicate the macroscale behavior (thin interface assumption) calculated by the Combined Level Set-Volume of Fluid (CLSVOF) method. For instance, in both the continuum and mesoscale discretizations the most unstable wavelength perturbation leads to pinch-off, whereas a smaller wavelength-to-diameter ratio, as expected, does not. The behavior of the virial pressure in MDPD will be discussed in relation to the hydrodynamic capillary pressure that results from the thin interface assumption. [Preview Abstract] |
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