Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session T09: Drops: Sessile and Static Surface Interactions |
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Chair: Vladimir Ajaev, Southern Methodist University Room: Ballroom I |
Monday, November 25, 2024 4:45PM - 4:58PM |
T09.00001: Droplets and rivulets on substrates with complex topography: evaporation and viscous flows in the vicinity of a contact line Nikolai Kubochkin, Tatiana Gambaryan-Roisman, Vladimir S Ajaev Understanding of wetting and evaporation of liquid films and drops on porous, rough, fractured or textured surfaces is crucial for many industrial processes such as development of inks, adhesives and coatings and manufacturing of microelectronic devices. In the present work, we consider volatile drops and rivulets on substrates with complex topography. We develop an analytical model and obtain local solutions for the viscous flows in the liquid as well as in the gas phase in the vicinity of the contact line, assumed to be pinned to a wedge-shaped non-uniformity of a substrate. We take Stefan flow into account and show how it can affect the flow in the liquid phase. We also determine the impact of the wedge opening angles on the flow topology and existence of critical angles, at which the dominant flow contribution changes. |
Monday, November 25, 2024 4:58PM - 5:11PM |
T09.00002: Siliconization to create liquid-like coatings for medically-relevant surfaces Hernan Barrio Zhang, Glen McHale, Jinju Chen, Gary George Wells, Rodrigo Ledesma Aguilar Liquid-like surfaces have garnered significant attention due to their exceptional repellency to liquids and enhanced droplet mobility. These surfaces are created by grafting polymer chains onto a hydroxyl-rich substrate through acid-catalyzed covalent bonds. The flexibility of these polymer chains allows liquids to flow with minimal resistance, providing a unique platform for studying the fundamental interactions between liquids and solids. Recent breakthroughs have shown that liquid-like surfaces can effectively prevent biofilm formation in both static and dynamic conditions, attributed to their ultra-low in-plane static and dynamic friction. Furthermore, recent advancements have shown that it is possible to adjust the kinetic friction of liquids on these surfaces by methylation of the polymer chains. In this study, we demonstrate that simple modifications to the coating process can stably graft a liquid-like layer onto substrates such as glass, polydimethylsiloxane, polyurethane, and stainless steel using a chlorinated organopolysiloxane in heptane (Sigmacote), characterized by ultra-low contact angle hysteresis (<3°). Additionally, we show that methylating this liquid-like coating enhances droplet mobility on the surface. This research holds potential implications in medicine and the study of droplet dynamics. |
Monday, November 25, 2024 5:11PM - 5:24PM |
T09.00003: Shape Deformation of Liquid Droplets Falling in a Liquid Media Aimen Laalam, Parisa Bazazi We experimentally investigate the hydrodynamics of initially spherical liquid droplets as they fall through a stationary continuous liquid phase under the action of gravity. Our study focuses on understanding the influence of droplet size, interfacial tension, particle concentration in droplets, and surfactant concentration in the continuous phase on droplet deformation and oscillation using an automated dosing system. Results reveal that increasing particle and surfactant concentrations led to greater droplet deformation but reduced oscillation. A viscoelastic emulsion interfacial layer is generated at the droplet interface at the high particle (above 4 wt.%) and surfactant (above 1 wt.%) concentrations and contribute to the stability of droplets, effectively minimizing their oscillation. Additionally, the oscillations decay over time where the droplets keep their flattened pancake shape due to the low interfacial tension, which cannot counteract the gravitational force. Interestingly, we observed that droplet deformation was independent of the Reynolds number, while the correlation with the Weber number varied with surfactant concentration. These findings have potential applications in various fields including microfluidics, emulsion formation, and industrial processes involving liquid-liquid interactions. |
Monday, November 25, 2024 5:24PM - 5:37PM |
T09.00004: Free-foaming: harnessing the free surface of expanding polyurethane foams Lauren Dreier, Tom Marzin, Julien Le Dreff, Abigail Plummer, PT Brun Expanding polyurethane foams are used widely in industry as lightweight, cost-effective fillers with exceptional insulation properties. Despite their appearance in everyday products such as building insulation, sporting equipment, and furniture, they are typically hidden from view – often sandwiched between sheathing layers and intended to take the shape of their container. Contrarily, our study examines the rich potential for harnessing this material's free surface. We probe the behavior of puddles, droplets, and droplet collisions to build a predictive understanding of the material through the lens of familiar physical laws applicable to simpler fluids. Our findings enable us to sculpt the foam's free surface into target shapes by controlling the reservoir geometry from which it grows, presenting a novel manufacturing technique for self-forming 3D structures. |
Monday, November 25, 2024 5:37PM - 5:50PM |
T09.00005: Effect of Needle and Dosing Parameters on Contact Angle Hysteresis Measurements Janice C To, Khellil Sefiane, Rodrigo Ledesma Aguilar, Daniel Orejon Contact Angle Hysteresis (CAH), a fundamental metric for characterising surface wettability, provides insight into intimate solid-liquid interactions. The widely used optical needle method inflates and deflates a droplet to measure the resulting CAH. Multiple factors can influence CAH results, but a standard has yet to be established to ensure consistent and accurate results between studies. |
Monday, November 25, 2024 5:50PM - 6:03PM |
T09.00006: Spreading of viscoelastic drop on curved substrates Peyman Rostami, Thomas C Sykes, Alfonso A Castrejón-Pita, Günter K Auernhammer The spreading behavior of drops of polymer solutions plays a critical role in various technologies such as 3D and inkjet printing, paint spraying, or coating. Recently, it has been shown that on flat surfaces the early phase of spreading follows a power law, where the exponent and pre-factor depend on the ratio between the internal relaxation time scale of the polymer solution and the spreading (elastocapillary) time scale. |
Monday, November 25, 2024 6:03PM - 6:16PM |
T09.00007: Abstract Withdrawn |
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