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 M11: Drops: Wetting and Spreading IDrops FSI
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Chair: Hamed Vahabi, Colorado State University Room: 504 |
Tuesday, November 21, 2017 8:00AM - 8:13AM |
M11.00001: Drop friction on liquid-infused surfaces Armelle Gas, Ludovic Keiser, Christophe Clanet, David Quere Trapping a thin liquid film in the roughness of a textured material creates a surface that is partially solid and partially liquid, referred to as a lubricant-impregnated surface. Those surfaces have recently raised a great interest for their promising industrial applications. Indeed, they proved to drastically reduce adhesion of a broad range of liquids, leading to enhanced mobility, and strong anti-biofouling, anti-icing and anti-fogging properties. In our talk we discuss the nature of the friction generated as a drop glides on a textured material infused by another liquid. Different regimes are observed, depending on the viscosities of both liquids. While a viscous drop is simply opposed by a Stokes-type friction, the force opposing a drop moving on a viscous substrate becomes non-linear in velocity. A liquid on an infused material is surrounded by a meniscus, and this specific feature is proposed to be responsible for the special observed frictions, on both adhesive and nonadhesive substrates. [Preview Abstract] |
Tuesday, November 21, 2017 8:13AM - 8:26AM |
M11.00002: Two Liquids Competing On A Glass Substrate Marine Borocco, David Quere, Christophe Clanet, Jean-Rene Authelin, Charlotte Pellet The advancing and receding contact angles of a liquid drop on glass are well defined. But how do the contact angles evolve when air is replaced by a second liquid? Based on the liquid-gas-solid case, we would expect the dynamic liquid-liquid-solid contact angles to depend on the capillary number only. For our study, we use a glass capillary tube, initially filled with silicone oil, in which a drop of water is injected. Surprisingly, the water-oil-glass contact angles also depend on the time the substrate spent in contact with silicone oil only, before the water was added. A change in that waiting time can cause large variations of the advancing and receding contact angles. [Preview Abstract] |
Tuesday, November 21, 2017 8:26AM - 8:39AM |
M11.00003: The early stages of drop wetting when surrounded by an immiscible liquid Alexandros Oratis, Mark Menesses, James Bird When a liquid drop comes into contact with a solid, the drop will typically spread over the solid's surface. Similarly, when a rising air bubble touches an immersed solid, it will also spread under the appropriate wetting conditions. The rates at which drops and bubbles spread over partially wetting solid surfaces at early stages have been shown to exhibit dynamics that depend on the liquid properties and the wettability of the surface. However, there is a discrepancy in the dynamics between the two systems. The initial spreading rate of low viscosity drops in air is inertially dominated; whereas, the initial spreading rate of air bubbles in liquids has been shown to be viscously dominated. Motivated by this contrast in behaviors, we study whether this discrepancy still occurs when the air phase in these systems is replaced by a second liquid. In particular, we investigate the spreading dynamics of a liquid drops surrounded by another immiscible liquid for various liquid pairings. The ultimate aim of this research is to provide insight into contact line dynamics. [Preview Abstract] |
Tuesday, November 21, 2017 8:39AM - 8:52AM |
M11.00004: Wetting dynamics of graphene matrix Yanbin Wang, Shayandev Sinha, Siddhartha Das, Liangbing Hu Wetting of atomistically-thin graphene layer(s) has attracted massive attention in the past few years due to several applications involving water-graphene interactions and the unique wetting translucency property of graphene. Holey-graphene has emerged as an important variant of nanostructured graphene that has found uses in many applications necessitating larger ion-accessible graphene surface area. Here we report our Molecular Dynamic (MD) simulation study of water-holey graphene wetting interactions. The holey graphene architecture is in form of a matrix of three layers in the vertical direction, and each of the layer consists of a porous three-layer graphene. Our simulations yield highly interesting water-holey-graphene wetting states that eventually leads to a significant enhancement of the water-accessible surface area. This is a paradigm shift in the context of holey graphene, which has so far been known to provide an increase in the ion-accessible surface area. We anticipate that our discovery will be a guiding force to large-scale manufacturing of graphene-based systems for applications involving graphene-water nexus.~ [Preview Abstract] |
Tuesday, November 21, 2017 8:52AM - 9:05AM |
M11.00005: Oil-Impregnated Polyethylene Films Ranit Mukherjee, Mohammad Habibi, Ziad Rashed, Otacilio Berbert, Shawn Shi, Jonathan Boreyko Slippery liquid-infused porous surfaces (SLIPS) minimize the contact angle hysteresis of a wide range of liquids and aqueous food products. Although hydrophobic polymers are often used as the porous substrate for SLIPS, the choice of polymer has been limited to silicone-based or fluorine-based materials. Hydrocarbon-based polymers, such as polyethylene, are cost effective and widely used in food packaging applications where SLIPS would be highly desirable. However, to date there have been no reports on using polyethylene as a SLIPS substrate, as it is considered highly impermeable. Here, we show that thin films of low-density polyethylene can be stably impregnated with carbon-based oils without requiring any surface modification. Wicking tests reveal that oils with sufficient chemical compatibility follow Washburn's equation. The nanometric effective pore size of the polyethylene does result in a very low wicking speed, but by using micro-thin films and a drawdown coater, impregnation can still be completed in under one second. The oil-impregnated polyethylene films promoted ultra-slippery behavior for water, ketchup, and yogurt while remaining durable even after being submerged in ketchup for over one month. [Preview Abstract] |
Tuesday, November 21, 2017 9:05AM - 9:18AM |
M11.00006: Universal scales of droplet spreading on wettability-patterned wedge tracks Uddalok Sen, Souvick Chatterjee, Ranjan Ganguly, Constantine Megaridis Spontaneous transport of liquid droplets on open-surface microfluidic platforms is important for a wide range of applications, and can be facilitated by having a difference of wettability on different spatial domains of the substrate. Recent studies have shown that a trapezoidal or wedge-shaped superhydrophilic track on a superhydrophobic substrate can transport microvolumes of fluid from the narrower to the wider end of the track at velocities of the order of several hundreds of mm/s and without the use of a pump or any external actuation system. Application areas of such tracks include, among others, the transport of droplets of complex biofluids in point-of-care devices, which calls for the knowledge of the spreading behavior of viscous droplets on wettability-patterned surfaces. The wetting behavior of droplets of different viscosities was observed, and a universal relationship was obtained between two dimensionless variables, which accurately described the spreading characteristics of a droplet regardless of its viscosity. Three distinct droplet spreading regimes were observed - the spreading exhibiting transition initially from a Washburn-type to a Laplace-pressure driven flow, and finally to a Tanner-type regime. [Preview Abstract] |
Tuesday, November 21, 2017 9:18AM - 9:31AM |
M11.00007: Managing oils pumplessly on open surfaces Aritra Ghosh, Jared Morrissette, Joseph Mates, Constantine Megaridis Passive management of low-surface-tension liquids (e.g. oils) can be achieved by tuning curvature of liquid volumes (Laplace pressure) on juxtaposed oleophobic/oleophilic domains. Recent advancements in material chemistry in repelling low-surface-tension liquids has enabled researchers to fabricate surfaces and transport oils without the aid of gravity or using a pump. Liquid transport on such surfaces harnesses the force arising from the spatial contrast of surface energy on the substrate, providing rapid fluid actuation. In this work, we demonstrate and study the liquid transport dynamics (velocity, acceleration) in open air for several oils of interest (Jet A, hexadecane, mineral oil) with varying surface tension and viscosity. High-speed image analysis of the motion of the bulk liquid is performed using a droplet-shape tracking algorithm; dominant forces are identified and model predictions are compared with experimental data. Experimental and analytical tools offer new insight on a problem that is relevant to open-surface passive oil transport devices like propellant management devices, oil tankers and many more. [Preview Abstract] |
Tuesday, November 21, 2017 9:31AM - 9:44AM |
M11.00008: Model description of the dynamic contact angle on an accelerating advancing contact line Takahiro Ito, Yasufumi Yamamoto, Kenji Katoh, Tatsuro Wakimoto, Ryoko Otomo, Yoshiyuki Tsuji Dynamic contact angle, the angle observed for the moving contact line, has a primary contribution on the boundary condition for a liquid interface behavior enclosed by solid wall. The variation in the dynamic contact angle is, as presented by Cox(1986) or Voinov(1976), often modeled as a function of capillary number, \textit{Ca}. However, most of these models assumes the steady state condition. We have experimentally found that the advancing contact angle on an accelerating circular rod just after the initiation of the motion takes smaller value than those observed for a steady state condition. Numerical simulation indicates that such deviation should be brought by the change in the microscopic contact angle and/or the `slip length', the characteristic contact angle and length scale in the microscopic scale in the vicinity of the contact line, from the steady state ones. Then the deviation in the microscopic contact angle, also assumed to depend on \textit{Ca} number, from the steady state was modeled as a function of the acceleration of the rod. The of the model applicability was confirmed for several kinds of liquids. [Preview Abstract] |
Tuesday, November 21, 2017 9:44AM - 9:57AM |
M11.00009: Wetting dynamics with solidification on cold substrates. Remy Herbaut, Philippe Brunet, Laurent Limat, Laurent Royon We study the contact line dynamics of a continuously fed liquid drop on a substrate of temperature T colder than the freezing temperature Tf. The substrate is put on a translation state, moving at constant velocity, and the upper part of the drop is pinned on the injection pipe. Hence, the advancing contact line is coupled to a solidification front at the solid surface that advances in the same direction. Within a certain range of substrate velocity and temperature T, the solidification can induce contact-line pinning. This pinning occurs if the velocity of the substrate is slower than a certain threshold, and leads to a discontinuous stick-slip dynamics of the contact line, while at high enough velocity the contact-line motion is continuous. We study the influence of liquid wetting properties, temperature difference (Tf-T), feeding flow-rate, and injection temperature Ti on this transition. We relate the critical velocity below which the stick-slip motion appears to the solidification velocity calculated and measured on a solid surface by Glicksman and Davis, valid in particular for dendritic crystal growth. The agreement between our data and this model is quantitatively fair. [Preview Abstract] |
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