Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session L12: Drops: Bouncing, Impact and Dynamic Surface Interactions IDrops FSI
|
Hide Abstracts |
Chair: Jerome Neufeld, University of Cambridge Room: 505 |
Monday, November 20, 2017 4:05PM - 4:18PM |
L12.00001: Drop trampoline Pierre Chantelot, Martin Coux, Christophe Clanet, David Quere Superhydrophobic substrates inspired from the lotus leaf have the ability to reflect impacting water drops. They do so very efficiently and contact lasts typically 10 ms for millimetric droplets. Yet unlike a lotus leaf most synthetic substrates are rigid. Focusing on the interplay between substrate flexibility and liquid repellency might allow us to understand the dynamic properties of natural surfaces. We perform liquid marbles impacts at velocity $V$ onto thin ($\sim$ 0.01 mm) stretched circular PDMS membranes. We obtain contact time reductions of up to 70\%. The bouncing mechanism is drastically modified compared to that on a rigid substrate: the marble leaves the substrate while it is still spread in a disk shape as it is kicked upwards by the membrane. We show that the bouncing is controlled by an interplay between the dynamics of the drop and the membrane. [Preview Abstract] |
Monday, November 20, 2017 4:18PM - 4:31PM |
L12.00002: Kicking droplets Martin Coux, Pierre Chantelot, Lucie Domino, Antonin Eddi, Christophe Clanet, David Quere Vibrating droplets deposited on hydrophobic substrates has lead to interesting phenomena~: it has been shown to modify widely the shape of droplets, to allow the motion of a pinned contact line and to self propulsion on flat and textured surfaces. The sollicitations leading to these behaviors are periodical, and of small amplitude. Here we study water droplets laid on a non-wetting substrate undergoing a vertical burst of order 5 to 10 ms and of maximal speed of the order of 1 m/s. A part of the droplet takes off while the rest of it remains attached to the substrate, leading to beautiful and unusual shapes. [Preview Abstract] |
Monday, November 20, 2017 4:31PM - 4:44PM |
L12.00003: Shielding Surfaces with Texture Henri-Louis Girard, Dan Soto, Thomas Binder, Kripa Varanasi We show an order of magnitude reduction in the interaction of an impacting droplet on a substrate, as defined by the integral of the wetted area over time. This interaction parameter describes the chemical, thermal of mass transport than occurs as the liquid is in contact with the underlying solid. The reduction is achieved through a macrotexture imprinted on the hydrophobic solid. We establish design guidelines to optimize the texture parameters as a function of drop diameter and Weber number. Finally, we show how this texture can be replicated and shield a surface from transferring heat to impinging droplets. [Preview Abstract] |
Monday, November 20, 2017 4:44PM - 4:57PM |
L12.00004: Dynamics of yield-stress droplets: Morphology of impact craters Jerome Neufeld, David Sohr, Leo Ferrari, Stuart Dalziel Yield strength can play an important role for the dynamics of droplets impacting on surfaces, whether at the industrial or planetary scale, and can capture a zoo of impact crater morphologies, from simple parabolic craters, to more complex forms with forms with, for example, multiple rings, central peaks. Here we show that the morphology of planetary impact craters can be reproduced in the laboratory using carbopol, a transparent yield-stress fluid, as both impactor and bulk fluid. Using high-speed video photography, we characterise the universal, transient initial excavation stage of impact and show the dependence of the subsequent relaxation to final crater morphology on impactor size, impact speed and yield stress. To further interrogate our laboratory impacts, we dye our impactor to map its final distribution and use particle tracking to determine the flow fields during impact and the maximal extent of the yield surface. We characterise the flow-fields induced during impact, and the maximal extent of the yield surface, by tracking particles within the bulk fluid and map the distribution of impactor and bulk by tracing the final distribution of dyed impactor. The results of laboratory impact droplets are used to infer the properties of planetary impactors, and aid in inter [Preview Abstract] |
Monday, November 20, 2017 4:57PM - 5:10PM |
L12.00005: Discrete Dynamical Models of Walking Droplets Aminur Rahman In recent years discrete planar dynamical models of walking droplets (walkers) on a billiards table (Shirokoff, Chaos 2013) and walking in a straight-line confined geometry (Gilet, PRE 2014) have been developed. Gilet's model was then analyzed via dynamical systems theory (Rahman-Blackmore, C,S\& F 2016). From the analysis it was shown that while Gilet's walker is confined under the threshold for chaos, it does escape the boundary once the system becomes chaotic. We modify the model to trap the walker in an annulur domain. This allows for connections between the dynamics, statistics, and experimental works (Filoux et al., PRE 2015). From this connection we derive a kicked rotator-like model for a walker in an annulus. We endeavor to manipulate the dynamics of the model to produce statistics similar to that of experiments. [Preview Abstract] |
Monday, November 20, 2017 5:10PM - 5:23PM |
L12.00006: Modeling gas kinetic effects in drop collision and impact Mykyta V. Chubynsky, Kirill I. Belousov, Duncan A. Lockerby, James E. Sprittles When liquid drops collide with each other (collision) or with a solid surface (impact), the thickness of the intervening gas film (which, in particular, gives rise to bouncing off wettable surfaces [2,3]) is often comparable to the mean free path of the gas molecules and thus gas kinetic effects are significant. We study drop collision and impact computationally using an interface-tracking finite element approach. The gas film is treated in the lubrication approximation. Gas kinetic effects are taken into account by introducing factors (functions of the Knudsen number) modifying the gas flow rate and shear stress. Our results for drop collision are in excellent agreement with those of Li [1] who modeled the gas using the full Navier-Stokes equations with an effective viscosity. For impact, where Li's approach cannot be used, we obtain good agreement with drop bouncing experiments [2,3]. [1] J. Li, PRL 117 (2016) 214502; [2] J. M. Kolinski {\it et al.}, EPL 108 (2014) 24001; [3] J. de Ruiter {\it et al.}, Nature Phys. 11 (2015) 48. [Preview Abstract] |
Monday, November 20, 2017 5:23PM - 5:36PM |
L12.00007: Numerical simulation of droplet impact onto a solid sphere in mid-air Sayed Abdolhossein Banitabaei, Alidad Amirfazli Collision of a droplet and a particle in mid-air has applications in chemical, petrochemical, and pharmaceutical industries. As a result of a head-on collision between a droplet and a hydrophobic particle with a relative diameter of a thin liquid film is created in the form of a hallow truncated cone (i.e. lamella). In this work, a numerical simulation was developed based on VOF method for head-on collision of a falling droplet and a moving particle. Impact outcomes predicted by the model shows a fair agreement with the experimental images of lamellas ($V_{p}=$6.8 and $V_{d}=$0.68 m/s) . Using the simulation model, the effect of liquid viscosity and surface tension on impact outcomes were studied. As viscosity increases, the lamella thickness increases accordingly. This happens as more energy transfer is required to move the liquid layers against each other to create a longer, and therefore thinner, lamella. However, a small decrease in viscosity halts the lamella formation as the boundary layer thickness in the spreading liquid gets so small that a crown cannot be developed. Moreover, investigation of the effect of particle wettability on the impact outcomes indicates that a lamella only forms due to impact of a droplet onto a hydrophobic particle. The lamella geometry is not affected by the particle wettability after contact angle reaches a certain threshold. These results show a good agreement with the literature of drop impact on a stationary particle. [Preview Abstract] |
Monday, November 20, 2017 5:36PM - 5:49PM |
L12.00008: Spread of pathogens through rain drop impact Seungho Kim, Hope Gruszewski, Todd Gidley, David G. Schmale III, Sunghwan Jung Rain drop impact can disperse micron-sized pathogenic particles over long distances. In this study, we aim to elucidate mechanisms for disease dispersal when a rain drop impacts a particle-laden solid surface. Three different dispersal types were observed depending on whether the dispersed glass particles were dry or wet. For a dry particle dispersal, the movement of contact line made the particles initially jump off the surface with relatively high velocity. Then, air vortex was formed due to the air current entrained along with the falling drop, and advected the particles with relatively low velocity. For a wet particle dispersal, the contact line of a spreading liquid became unstable due to the presence of the particles on the substrate. This caused splashing at the contact line and ejected liquid droplets carrying the particles. Finally, we released a drop onto wheat plants infected with the rust fungus, Puccinia triticina, and found that nearly all of the satellite droplets from a single drop contained at least one rust spore. Also, we visualized such novel dispersal dynamics with a high-speed camera and characterized their features by scaling models. [Preview Abstract] |
Monday, November 20, 2017 5:49PM - 6:02PM |
L12.00009: High-speed video analysis of forward and backward spattered blood droplets Patrick Comiskey, Alexander Yarin, Daniel Attinger High-speed videos of blood spatter due to a gunshot taken by the Ames Laboratory Midwest Forensics Resource Center are analyzed. The videos used in this analysis were focused on a variety of targets hit by a bullet which caused either forward, backward, or both types of blood spatter. The analysis process utilized particle image velocimetry and particle analysis software to measure drop velocities as well as the distributions of the number of droplets and their respective side view area. This analysis revealed that forward spatter results in drops travelling twice as fast compared to backward spatter, while both types of spatter contain drops of approximately the same size. Moreover, the close-to-cone domain in which drops are issued is larger in forward spatter than in the backward one. The inclination angle of the bullet as it penetrates the target is seen to play a significant role in the directional preference of the spattered blood. Also, the aerodynamic drop-drop interaction, muzzle gases, bullet impact angle, as well as the aerodynamic wake of the bullet are seen to greatly influence the flight of the drops. The aim of this study is to provide a quantitative basis for current and future research on bloodstain pattern analysis. [Preview Abstract] |
Monday, November 20, 2017 6:02PM - 6:15PM |
L12.00010: Drop interactions on a viscous film Maxime Costalonga, Michiel Hack, Jacco Snoeijer Every morning at their breakfast, cereal eaters can see that floating objects on a liquid bath attracts to form clusters: this is the so-called \emph{Cheerios} effect. It has been shown recently that droplets on elastic substrates also interact, either attracting or repelling each other depending on the local slope of the substrate where they lie. Here we present an experiment extending these results to the interaction of droplets deposited on a thin viscous film. By measuring independently the velocity of the droplets and the surface topography of the film, we identify non-monotonic interactions that are due to waves appearing on the film. The drag force exerted onto the droplets is also investigated. We show that the thickness of the film below the drop is intrinsically selected by the velocity of the drop, by a mechanism similar to Bretherton's bubble rising in a confining tube. [Preview Abstract] |
Monday, November 20, 2017 6:15PM - 6:28PM |
L12.00011: Flow induced on a salt waterbody due to the impingement of a freshwater drop Islam Benouaguef, Edison Amah, Naga Musunuri, Denis Blackmore, Ian Fischer, Pushpendra Singh The particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) techniques are used to study the flow induced on the surface of a salt waterbody when a drop impinges on the surface. The measurements show that the impingement of a fresh water drop causes a strong axisymmetric solutocapillary flow about the vertical line passing through the center of impact. The fluid directly below the center of impact rises upward, and near the surface it moves away from the center of impact. The flow, which develops within a fraction of second after the impact, persists for several seconds and the volume of water circulated is two orders of magnitude larger than the volume circulated when a freshwater drop falls on a freshwater body. [Preview Abstract] |
Monday, November 20, 2017 6:28PM - 6:41PM |
L12.00012: Sedimentation of a sphere through a liquid-liquid interface Luuk Altenburg, Diogo Barros, Ellen Longmire The penetration of a falling solid sphere through the interface of two immiscible fluids is examined experimentally. Depending on the solid-liquid density ratio and the Bond number, the sphere may either float or sink, entraining and trapping a volume of light silicone oil into the heavier aqueous solution. To investigate in detail the floating/sinking transition, the motion of printed spheres with controlled density is quantified using high-speed imaging and the results are compared to existing models in the literature. The parameter space includes the Bond number (computed using the liquid-liquid density difference and the sphere radius) in the range of 0.2 to 1.05 and fluid-fluid viscosity ratios of 0.05-15. The ratio of solid-oil to water-oil density difference is within the range 1.6-21. The influence of inertia in the problem is also considered by releasing spheres from multiple heights to account for a variable approach Reynolds number of up to 174. Finally, the impact of irregularities in surface geometry on the floating/sinking dynamics will be presented. [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