Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session S23: Bubbles: Collapse II |
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Chair: Hector Gomez, Purdue University Room: 605 |
Tuesday, November 26, 2019 10:31AM - 10:44AM |
S23.00001: Dynamic buckling of collapsing viscous bubbles Alexandros Oratis, John Bush, Howard Stone, James Bird When air bubbles rise to the surface of a liquid, they create a thin-film dome that eventually ruptures. In liquids with relatively low viscosity, film rupture is followed by rapid film retraction dominated by surface tension and inertia, and typically occurs over a period of milliseconds. In liquids with relatively high viscosity, viscous dissipation slows the film retraction sufficiently that the bubble collapses. As it does so, radial wrinkles appear on its surface. Previous investigations have concluded that gravity is responsible for both the bubble collapse and the wrinkling instability. We here demonstrate that experiments yield the same radial wrinkle pattern independent of the bubble orientation relative to gravity. We develop an alternative model for the wrinkles in which surface tension initiates a dynamic buckling instability. [Preview Abstract] |
Tuesday, November 26, 2019 10:44AM - 10:57AM |
S23.00002: Flow and mixing dynamics of phase-transforming multicomponent fluids Hector Gomez, Saikat Mukherjee We develop a continuum model for two-component flow, where one of the components is an non-condensable gas and the other one is a fluid that undergoes liquid-vapor phase transformations accompanied by changes in its miscibility with the gas. We derive the model from a Gibbs free energy that includes gradients of the fluid density and gas concentration, leading to a generalization of the classical equations of multiphase flow hydrodynamics. High-fidelity numerical simulations of the model show a very complex interplay between flow, mixing and phase transformations. The model predicts quantitatively the saturation vapor pressure of water for a given mixture of air and water vapor at different temperatures. When applied to the problem of collapse of cavitation bubbles, the model shows that even very small amounts of gas dissolved in the liquid phase can have a significant impact on the dynamics of the collapsing bubble. [Preview Abstract] |
Tuesday, November 26, 2019 10:57AM - 11:10AM |
S23.00003: Bursting Bubbles and The Formation of Gas Jets and Vortex Rings Ali Al Dasouqi, David Murphy Bursting bubbles play an important role in ocean-atmosphere and industrial processes (e.g. marine aerosol formation, froth flotation for metal concentration) and food science (e.g. beer). Earlier work focused on the fluid dynamics of droplet formation (film and jet drops) and film cap retraction, but the ejection of pressurized gas from inside a bursting bubble, which may affect the spatial distribution of generated droplets, is much less studied. Here we examine the gas flow emerging from the bursting of smoke-filled bubbles floating at an air-water interface using two synchronized orthogonal high-speed cameras filming at 5-10 kHz. We describe the bubble bursting and subsequent formation of vortex rings for bubbles ranging in size from 400 microns to 4 cm. No vortex rings are formed for bubbles less than 1 mm diameter. The number of initially formed vortices increases from one for a 1.4 mm bubble up to six for a 39 mm bubble. Using stereophotogrammetric tracking, the initial speed of the gas jet released from the bursting bubble also is quantified and can reach up to 9.6 m/s for a 39 mm bubble. Jet speed is found to be a function of film retraction speed, bubble diameter, and bubble submergence. Successful vortex ring formation also is found to rely on film retraction behavior. [Preview Abstract] |
Tuesday, November 26, 2019 11:10AM - 11:23AM |
S23.00004: Collective Effects in Bursting Bubbles Aerosol Production Baptiste Neel, Luc Deike The bursting of surface bubbles, understood as a production mechanism of sea spray aerosols, is a key feature of gas and mass transfers between ocean and atmosphere. While the case of a single bursting bubble has been extensively studied recently, little is known about collective effects in this context. Our experimental study characterizes the dynamical and statistical properties of an ensemble of initially mono-disperse air bubbles at the water surface, and the resulting spray droplets being produced. After rising in a still bath, the bubbles stand at the free surface, where they coalesce and move around before they eventually burst. The addition of surface active agents, because they prevent bubbles coalescence above a certain concentration, modify the features of the surface bubbles population (coalescence and lifetime), whose consequences on the spray production are discussed. [Preview Abstract] |
Tuesday, November 26, 2019 11:23AM - 11:36AM |
S23.00005: Jet drops produced by bursting bubbles: number, size, velocity and resulting mass transfer Alexis Berny, Thomas Seon, Luc Deike, Stephane Popinet When a bubble bursts at a liquid-air interface, it produces a jet that may break up and eject drops called jet drops. Numerous studies focused on this phenomenon motivated by the wide range of application, from the bubble in a glass of champagne to spray generation at the surface of the ocean. Here, we solve the two-phase Navier-Stokes equations in axi-symmetrical coordinates with the free software basilisk. We first compare the size and velocity of the first drop in our simulations with the recent experimental, numerical and theoretical results from the literature, before characterizing the number, size and velocity of all ejected droplets. This approach is done for a wide range of controlling parameters, defined as the Laplace and Bond numbers. The resulting total vertical momentum and mass transfer is then discussed. [Preview Abstract] |
Tuesday, November 26, 2019 11:36AM - 11:49AM |
S23.00006: The physics of bubble bursting followed by jet ejection Jose M. Lopez-Herrera, Alfonso M. Ganan-Calvo Under the light of recent research on this phenomenon, and performing exhaustive simulations, dimensional and similarity analysis, the collapse of a superficial bubble and the subsequent ejection of a microjet are studied here in great detail. The different models proposed, their description of the physics involved, their degree of innovation and their predictive abilities comparing with experiments are put into perspective. In particular, the conditions under which the phenomenon can be described around an elusive temporal singularity, and the resulting self-similar flow configuration are carefully analyzed. Using high resolution numerical simulation techniques of free-surface flows, this study demonstrates the existence of said singularity and the value of the critical parameter for which it appears, showing the natural change in the time scaling law of the self-similar flow sufficiently close to the singularity. This self-similar flow shows a rich topology that is discussed in this work. [Preview Abstract] |
Tuesday, November 26, 2019 11:49AM - 12:02PM |
S23.00007: Compressibility Effects for Spherical Bubble Collapse in Water Roy Baty, Scott Ramsey, Cory Ahrens, Jason Albright This presentation outlines the derivation and solution of a potential flow equation used to model the effect of compressibility on bubble collapse in water. An unsteady potential flow equation is developed by adding a perturbation term to a classical incompressible flow solution describing the radial motion of a spherical bubble as a function of time. The flow is assumed to be one-dimensional and inviscid. Both linear and nonlinear forms of the compressible potential equation are presented assuming a general isentropic equation of state for water. The linear compressible potential flow equation is obtained by linearizing the perturbation term about the incompressible collapsing flow field. The linear and nonlinear compressible potential flow equations are integrated numerically for an analytical equation of state approximating water in the kilobar pressure range. [Preview Abstract] |
Tuesday, November 26, 2019 12:02PM - 12:15PM |
S23.00008: Lie Symmetries of a Potential Flow Equation Modeling Compressibility Effects of Spherical Bubble Collapse in Water Scott Ramsey, Roy Baty, Eric Albright, Cory Ahrens This work applies analytical methods for differential equations to derive Lie symmetries associated with a potential flow equation used to model the effect of compressibility on bubble collapse in water. The compressible potential equation describes the unsteady radial motion of a one-dimensional, inviscid, spherical bubble. The potential equation is obtained by linearizing a perturbation term about an incompressible flow field modeling the collapse of a spherical cavity in water. The symmetry analysis is performed for an arbitrary isentropic equation of state for water over the pressure and density range observed for cavitation. The resulting symmetry groups obtained from the Lie analysis are then related to a general form of the method of characteristics developed to integrate second order hyperbolic equations. [Preview Abstract] |
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