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 H12: Drops: Splashing, Stability and Breakup II |
Hide Abstracts |
Chair: Jose Manuel Gordillo, Universidad de Sevilla Room: 3018 |
Monday, November 24, 2014 10:30AM - 10:43AM |
H12.00001: Fragmentation dynamics in the droplet bag breakup regime Varun Kulkarni, Paul Sojka The closing stages of a droplet bag breakup event is marked by the appearance of several topological changes in the drop shape, followed by its fragmentation owing to hydrodynamics instabilities. In the present work we examine this breakup event, which occurs when a drop enters a continuous jet air stream. The deformed drop before eventual fragmentation is comprised of two main features: a bag and a bounding rim. Our investigation discusses the mechanism of rim/ bag breakup and the ensuing drop size distribution. The role of two possible instabilities, Plateau$-$Rayleigh and Rayleigh$-$Taylor, in rim breakup is examined and the dominant role of the Plateau$-$Rayleigh instability is revealed. In contrast, the Rayleigh$-$Taylor instability is seen to explain the disintegration of the bag well. The effects of viscosity and air jet velocity are also investigated. The formation of secondary features, such as nodes on the rim and holes on the bag, are also discussed. To conclude, a simple scaling argument based on the characteristic time scales of these instabilities is presented to explain the commonly observed early bursting of the bag, vis-\`{a}-vis the rim. [Preview Abstract] |
Monday, November 24, 2014 10:43AM - 10:56AM |
H12.00002: Faraday instability of a spherical drop A. Ebo Adou, Laurette Tuckerman, Seungwon Shin, Jalel Chergui, Damir Juric A liquid drop subjected to an oscillatory radial force comprises a spherical version of the Faraday instability, with a subharmonic response which is half of the forcing frequency. The time-dependent shape of the drop and the velocity field in and around it are calculated using BLUE, a code based on a hybrid Front Tracking/Level-set algorithm for Lagrangian tracking of arbitrarily deformable phase interfaces. We compare this shape with the spherical harmonic selected at onset, calculated by adapting the Floquet stability analysis of Kumar and Tuckerman to a spherical geometry. We interpret the shape in light of theoretical results by Busse, Matthews and others concerning pattern formation in the presence of O(3) symmetry. [Preview Abstract] |
Monday, November 24, 2014 10:56AM - 11:09AM |
H12.00003: Drop deformation and breakup in a partially filled horizontal rotating cylinder Andrew White, Caroline Pereira, Hyaquino Hyacinthe, Thomas Ward Drop deformation and breakup due to shear flow has been studied extensively in Couette devices as well as in gravity-driven flows. In these cases shear is generated either by the moving wall or the drop's motion. For such flows the drop shape remains unperturbed at low capillary number ($Ca$), deforms at moderate $Ca$, and can experience breakup as $Ca\to1$ and larger. Here single drops of NaOH$_{(aq)}$ will be placed in a horizontal cylindrical rotating tank partially filled with vegetable oil resulting in $10^{-2} |
Monday, November 24, 2014 11:09AM - 11:22AM |
H12.00004: Moving and deforming a liquid drop by pulsed laser irradiation Alexander L. Klein, Claas Willem Visser, Henri Lhuissier, Emmanuel Villermaux, Chao Sun, Detlef Lohse, Hanneke Gelderblom The impact of a focused laser pulse onto a liquid drop can be so violent that the drop strongly deforms and eventually explodes. We studied the drop dynamics that results from this laser impact experimentally, in order to understand the time evolution of the drop and find the underlying driving mechanism. The high reproducibility of the dynamics allowed us to use stroboscopic illumination with short, ns exposure times. Combining this technique with high-speed imaging we captured key details of the laser impact and drop deformation. The laser impact ablates the front the drop while the remainder of the drop acquires a velocity of several m/s. The drop expands radially into a disk-like shape with a velocity of the same order of magnitude, before instabilities develop and the drop fragments. A parameter study of the time-resolved drop shape and velocity as a function of the laser energy is presented. [Preview Abstract] |
Monday, November 24, 2014 11:22AM - 11:35AM |
H12.00005: How a laser pulse deforms a liquid drop Hanneke Gelderblom, Wilco Bouwhuis, Alexander L. Klein, Detlef Lohse, Emmanuel Villermaux, Henri Lhuissier, Jacco H. Snoeijer When a liquid drop is hit by a ns laser pulse it experiences a strong pressure kick. As a consequence, the drop is propelled forward and deforms into a thin sheet that eventually becomes unstable and fragments. We aim to understand how the drop motion, deformation and fragmentation depend on the laser-pulse properties and drop characteristics. On the time scale of the laser pulse, where the drop dynamics is purely inertial, an analytical expression for the internal velocity field is obtained. The output of this inertial model is then used as input for a later-stage model that describes the surface-tension limited expansion of the liquid sheet. In the intermediate regime, where the drop is not a sheet yet, its shape evolution is investigated with a boundary integral method. The drop deformation dynamics described by these models is the starting point to study the subsequent drop fragmentation. [Preview Abstract] |
Monday, November 24, 2014 11:35AM - 11:48AM |
H12.00006: Yield stress fluid droplet impact on coated horizontal surfaces Randy Ewoldt, Brendan Blackwell, Marc Deetjen Yield stress fluids, including gels and pastes, are effectively fluid at high stress and solid at low stress. Droplet impacts on a solid surface can create localized lumps and craters, or extended splash events featuring long lifetime ejection sheets. Here we experimentally study liquid-solid impact of yield stress fluids on pre-coated horizontal surfaces. Under critical splash conditions sheet breakup occurs, and ejected droplets can be nonspherical and threadlike due to the inability of capillary stresses to deform material above a certain lengthscale. The presence of a yield stress also allows complex contours forming on the surface to be stable at long times. Droplet size, impact velocity, surface coating thickness, and rheological material properties are varied. We identify regime maps of the stick/splash transition and quantify behavior with measures such as crater diameter, deposition thickness, impact event timescale, and radial extent of material deposition. The results are characterized as a function of appropriate dimensionless parameters in a manner that supports rheological fluid design for specific applications. [Preview Abstract] |
Monday, November 24, 2014 11:48AM - 12:01PM |
H12.00007: Multi-Scale Simulation of Atomization with small drops represented by Lagrangian Point-Particle Model Yue Ling, St\'ephane Zaleski Numerical simulation is conducted to investigate the drop formation and evolution in gas-assisted atomization. The atomizer consists of two parallel planar jets: the fast gas jet and the slow liquid jet. Due to the shear between gas and liquid streams, the liquid-gas interface is unstable, and this eventually leads to full atomization. A fundamental challenge in atomization simulations is the existence of multiple length scales involved. In order to accurately capture both the gas-liquid interface instability and the drop dynamics, a multi-scale multiphase flow simulation strategy is proposed. In the present model, the gas-liquid interface is resolved by the Volume-of-Fluid (VOF) method, while the small drops are represented by Lagrangian point-particle (LPP) models. Particular attention is paid on validating the coupling and conversion between LPP and VOF. The present model is validated by comparing with direct numerical simulation (DNS) results and also experimental data. The simulation results show complex coupling between the interface instability and the turbulent gas jet, which in turn influence the formation and evolution of the drops formed in atomization. [Preview Abstract] |
Monday, November 24, 2014 12:01PM - 12:14PM |
H12.00008: Investigation on Liquid Atomization Mechanism in Sparkling Fireworks Chihiro Inoue The physics behind the beauty of sparkling fireworks is a mystery over 300 years. There are two types of liquid atomization phenomena; the ejection of streaks of light from a mother fireball, and the spreading streaks burst downstream to produce pine needle-like streaks of light. In the present study, the mechanism of the atomization process in sparkling fireworks is investigated by using a high-speed video camera. It is clarified that bursting bubbles on the mother fireball is essential for the ejection of droplets, which will be streaks of light. The secondary bursting of the light streaks is due to the sudden expansion and catastrophic bursting of spreading droplets. The results of temperature variance of spreading droplets and those of the TG-DTA-MS are also discussed. [Preview Abstract] |
Monday, November 24, 2014 12:14PM - 12:27PM |
H12.00009: Instability of a large Leidenfrost drop under confinement Pascal Raux, Guillaume Dupeux, Christophe Clanet, David Quere A Leidenfrost drop confined between two hot plates is unstable, when large enough. After a short delay necessary to build a vapor pocket at its center, it forms a ring which rapidly expands and eventually bursts. We analyze this instability, and show that the ring size increases in a non-linear manner, as a function of time, in agreement with the experiments. [Preview Abstract] |
Monday, November 24, 2014 12:27PM - 12:40PM |
H12.00010: Break-up of droplets in a concentrated emulsion flowing through a narrow constriction Minkyu Kim, Liat Rosenfeld, Sindy Tang Droplet microfluidics has enabled a wide range of high throughput screening applications. Compared with other technologies such as robotic screening technology, droplet microfluidics has 1000 times higher throughput, which makes the technology one of the most promising platforms for the ultrahigh throughput screening applications. Few studies have considered the throughput of the droplet interrogation process, however. In this research, we show that the probability of break-up increases with increasing flow rate, entrance angle to the constriction, and size of the drops. Since single drops do not break at the highest flow rate used in the system, break-ups occur primarily from the interactions between highly packed droplets close to each other. Moreover, the probabilistic nature of the break-up process arises from the stochastic variations in the packing configuration. Our results can be used to calculate the maximum throughput of the serial interrogation process. For 40 pL-drops, the highest throughput with less than 1{\%} droplet break-up was measured to be approximately 7,000 drops per second. In addition, the results are useful for understanding the behavior of concentrated emulsions in applications such as mobility control in enhanced oil recovery. [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