Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session T24: Surface Tension Effects: Interfacial Phenomena II |
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Chair: Hyoungsoo Kim, KAIST Room: 232 |
Monday, November 21, 2022 4:10PM - 4:23PM |
T24.00001: Temperature-Independent Components of Non-polar and Polar Liquid Surface Tension Jiahui Guo, Ruisong Wang, Dion S Antao Multi-phase interfacial interaction among liquids and solids involving wetting, adhesion, and adsorption is the foundation in many industrial areas, including the separations, petroleum, and pharmaceutical industries. One of the most robust predictive frameworks of surface/interfacial tension or energy is the van Oss-Chaudhury-Good (vOCG) model, which leverages interfacial tension component theory and has been successfully applied in predicting interfacial interactions between non-polar/polar liquids and solids at room temperature. However, validation outside room temperature bounds remains unproven and limited research is available for the effect of temperature on the surface tension components. To make this theory more general and validate it outside room temperature, we characterize the temperature effect on the Lifshitz-van der Waals (LW, non-polar) and Lewis acid-base (AB, polar) components within the vOCG framework using the pendant droplet method and liquid-solid contact angle measurements at various temperatures and verify our measurements by predicting miscibility (liquid-liquid) properties and wetting (liquid-solid) behavior among other multi-phase combinations at different temperatures. This research reveals the effect of temperature on the LW and AB components of surface/interfacial tension and will guide the development of a predictive model capable of estimating interfacial interaction behavior for liquid-liquid, liquid-solid, and liquid-liquid-solid multi-phase systems. |
Monday, November 21, 2022 4:23PM - 4:36PM |
T24.00002: Soft Imbibition: experiments in 2D geometries Trinh N Huynh, Brandon Lopez, Emilie Dressaire Soft gels are commonly used to emulate viscoelastic biological substrates. When a drop of liquid wets a soft gel, the contact line deforms the surface of the gel, forming a ridge. Once the contact line has moved, the recovery depends on the gel rheology and system geometry. Here, we investigate experimentally the imbibition of a wetting fluid in 2D geometries coated with a thin layer of soft gel. When the gel-coated substrate is placed in contact with a fluid reservoir, the liquid spontaneously invades the channel. During the experiment, the thickness of the gel coating is constant, away from the contact line. We measure the imbibition length and compare its time dependence with the classical ''diffusive'' response observed in uniform channels and porous media with rigid walls. We show that the imbibition dynamics depend on the fluid and gel-layer properties. The results demonstrate that soft materials modify wetting dynamics and could lead to the development of soft coating to control transport. |
Monday, November 21, 2022 4:36PM - 4:49PM |
T24.00003: Theoretical study on Rayleigh-Plateau instability with an inner boundary condition Hyejoon Jun, Hyoungsoo Kim Rayleigh-Plateau(R-P) instability of viscous liquid is widely observed in engineering problems, such as inkjet printing and optical fiber coating. R-P instability occurs in both a viscous liquid thread and a liquid film on a fiber where the capillary effect is predominant. However to date these cases have been separately studied. In particular, it has been rarely considered how the solid structure affects the R-P instability. In this study, to consider both breakup phenomena simultaneously, we derived a new theoretical model with an additional inner boundary condition at the solid-liquid interface where we assumed that axisymmetric stokes flow and long-wave ansatz to consider the perturbation. Based on this, we obtained time-marching surface profiles and dispersion relations for any fiber radii. Finally, we found that periodic breakup and satellite droplet formation were caused by viscous stress from no-slip boundary condition at the solid-liquid interface. To evaluate our model, we compared with previous experimental and numerical results. In conclusion, we confirmed that the current theoretical model well predicts the R-P instability with a better accuracy. We hope that the current model helps to move one step forward to understand R-P instability theoretically. |
Monday, November 21, 2022 4:49PM - 5:02PM Author not Attending |
T24.00004: Design/Fabrication and Experimental validation of Omni-phobic LIS for extremely low hydrate adhesion Abhishek Mund, Arindam Das, Kripa K Varanasi Clathrate hydrate is a naturally occurring ice-like solid which forms in water phase under suitable temperature and pressure conditions, in the presence of one or more hydrophobic molecules. It also forms inside the oil and gas pipes leading to higher pumping cost, flow blockage and even catastrophic accidents. Engineered surfaces with low hydrate adhesion can provide an effective solution to this problem. Liquid impregnated surfaces is one such example of engineered surfaces which has already shown tremendous potential in reducing the nucleation and adhesion of solids. Here we report the design and synthesis of liquid impregnated surfaces with extremely low hydrate adhesion under the mixed environment of oil and water. The most challenging aspect of designing these surfaces was to stabilize a lubricant layer simultaneously under the water and oil. A detailed methodology to make such lubricant stable surfaces from theoretical analysis was described and experimentally validated for lubricant stability. Experimental measurements on such surfaces showed extremely low hydrate accumulation and at least two orders of magnitude reduction in adhesion. |
Monday, November 21, 2022 5:02PM - 5:15PM |
T24.00005: Experimental Examination of Contact Line Dynamics in a Liquid Bridge Scenario Moyosore Odunsi, Jeffrey F Morris, Mark D Shattuck Liquid bridges between particles play an important role in industrial slurries and soils, but their effects are not well understood. We experimentally measure the normal and lateral forces exerted by microliter scale liquid bridges between solid spheres and simultaneously acquire detailed images of the bridge shape. We developed a model for the lateral and normal forces as a function of displacement by analyzing the bridge shape; this analysis incorporates hysteresis and elucidates the fundamental basis for the nonequilibrium contact line force in terms of the properties of the surface and their influence on the liquid-air interface. |
Monday, November 21, 2022 5:15PM - 5:28PM |
T24.00006: Propagation of Thin-Film Rupture at the Atomic Scale Muhammad Rahman, Li Shen, James P Ewen, David M Heyes, Daniele Dini, Edward R Smith The propagation of rupture in thin-films is a surface tension driven phenomenon which can be described by the Taylor-Culick law. We examine this classical theory for freely suspended films with atomic-scale thickness. Employing non-equilibrium molecular dynamics with a Lennard-Jones fluid, the growth rate of induced and spontaneously generated holes on a thin film is measured. The terminal speed or equivalently, the film retraction rate, as predicted by Taylor and Culick, is observed to be independent of the initial conditions in the long-time limit. However, at the atomic scale, the retraction rate is slower, a trend predicted in the literature for nanoscopic films. Previous observations of an exponential early time growth regime are confirmed for induced holes, but we show that interestingly this regime is absent for films that break spontaneously due to thermal effects. This indicates the potential of atomic simulation in providing fresh insight into the mechanism and dynamics of film rupture. |
Monday, November 21, 2022 5:28PM - 5:41PM |
T24.00007: Axial thinning of a liquid bridge of polymer solution between spherical surfaces Sreeram Rajesh, Alban Sauret Capillary bridges between particles are encountered in a wide range of situations in nature and the industry. The force exerted by water between grains allows us, for instance, to build sandcastles. The characterization of liquid bridges between spherical surfaces is important in describing the transport and mixing of wet granular materials. When the two particles are separated, the extensional thinning of a Newtonian liquid results in an abrupt breakup of the bridge. However, the presence of a small amount of polymers dispersed in the liquid delays this break-up. The thinning and break-up of liquid bridges of polymer solutions have been investigated on planar surfaces. In this study, we explore the role of substrate geometry on the evolution of the capillary bridge between two particles. We investigate the thinning of a liquid bridge of dilute and semi-dilute polymer solution between two spherical surfaces. We use high-speed imaging to study the evolution of the shape and the minimum diameter of the bridge. We vary the concentration and molecular weight of the polymer solutions used to characterize the influence of the surface shape on the thinning of a liquid bridge. |
Monday, November 21, 2022 5:41PM - 5:54PM |
T24.00008: Liquid Metal Droplets in Fluid Systems: Geometry, Chemistry, and Surface Energy Gaabhin Ryu, Kwangseok Park, Hyoungsoo Kim The morphology and surface energy of gallium-based liquid metal (LM) droplets are influenced by the oxygen solubility (xg) of the surrounding liquid. Using a high-speed camera, we captured the pinch-off frames of macroscopic LM droplets in various solvents. The eccentricity of droplets increased sigmoidally with the xg of the ambient liquid. Anisotropic pear-shaped LM droplets were observed in high-xg liquids, concomitantly with surface oxidation. To explore small-scale features, we additionally fabricated micro/nanoscale LM droplets via ultrasonication in organic solvent environments and subsequent evaporation of the solvent. Carbon/Oxygen and Carbon/Gallium atomic ratios of LM microdroplets increased with the solvent’s xg, indicating that oxygen and organic solvent molecules interacted sequentially with LM. The van Oss-Good model was further implemented to determine the polar and nonpolar surface energy components of LM layers with adsorbates. While the polar component made a minor contribution to the total surface energy, the nonpolar component displayed a strong logarithmic relationship with the xg of the solvent used to treat the LM layer. |
Monday, November 21, 2022 5:54PM - 6:07PM |
T24.00009: Enhancement of immersion lens stability using vapor-driven solutal Marangoni effect Junil Ryu, Gilgu Lee, Hyoungsoo Kim In the semiconductor industry, water-based immersion lithography has been adopted to achieve O(10 nm) spatial resolution. One of the difficulties remaining in immersion lithography is to avoid the formation of residual droplets after the main lens while increasing the relative speed of the silicon wafer with respect to the main lens for a high production rate. The critical condition for the lens breakdown is highly related to the design of the immersion hood. To prevent its unstable mode, it has been suggested to apply strong shear stress using the air curtain along the immersion drop surface. However, the shear flow can also make the lens unstable due to the relatively high surface tension of the immersion liquid where the working fluid is water. Therefore, the shear and capillary flow should be controlled simultaneously. To solve this problem, we propose the volatile vapor knife to use the vapor-driven solutal Marangoni effect, which requires only a little amount of vapors to effectively alter the local capillary effect. We develop a new type of immersion hood by modifying the vapor inlet and outlet instead of the air curtain system. During the talk, experimental and theoretical findings about the improvement of immersion lens stability and wafer speed will be discussed. |
Monday, November 21, 2022 6:07PM - 6:20PM |
T24.00010: Heat transfer in liquid bridges surrounded by a heater/cooler ring Manoj K Tripathi, Aadil H Saifi, Vyankatesh M Mundhada Fluid flow and heat transfer due to Marangoni convection in a liquid-bridge suspended between two solid discs and surrounded by a heating/cooling ring is investigated in this work. The capillary bridge consists of water and the surrounding fluid is taken as a 10 cSt silicone oil. The flow and heat transfer are found to attain a quasi-steady state for most of the heater/cooler positions. In addition, heat transfer to the bridge in the heater configuration is found to be the maximum when the heater ring is closer to the bottom disc, whereas, this occurs for the cooler configuration when the cooling ring is near the top disc. Moreover, the heater configuration exhibits a transition in the heat transfer and interfacial velocity when the heater is placed midway between the two discs. There exists a range of heater locations for which such a jump in the heat transfer is observed. We examine the mechanism of this jump in this study and point out the importance of accounting for the interface deformation when dealing with Marangoni flows in liquid bridges. A similar investigation is performed for the cooler configuration, and the differences and similarities between the two configurations will be discussed. |
Monday, November 21, 2022 6:20PM - 6:33PM |
T24.00011: Elastocapillary wake Nan Xue, Lawrence Wilen, Robert Style, Eric R Dufresne Partially wetting droplets naturally deform soft substrates by the action of surface tension. These deformations are usually localized to a narrow region near the contact line, forming a so-called 'Elastocapillary ridge'. Here, we show that substrate deformations delocalize when droplets slide along the surface above a certain velocity. In particular, we observe a pair of parallel ridges that slowly fade away behind the droplet. To characterize this elastocapillary wake, we perform interferometry to measure the shape of the deformed substrate in space and time. We quantify the formation and relaxation of the elastocapillary wake as a function of sliding speed. |
Monday, November 21, 2022 6:33PM - 6:46PM |
T24.00012: An experimental study of flow patterns near a moving contact line Charul Gupta, Lakshmana D Chandrala, Harish N Dixit A contact line occurs at the intersection of a solid with two immiscible fluid phases, A and B. As a contact line moves, one fluid phase displaces the other fluid phase and consequently, flow patterns evolve in both the fluid phases. A moving contact line occurs in various applications like ink-jet printing, curtain coating, spray cooling, etc. and is thus of fundamental interest. Huh & Scriven developed a theoretical model in the viscous limit and reported three distinct flow fields in the two phases as a function of viscosity ratio and dynamic contact angle. The theory of Huh & Scriven(1971,JCIS) is incomplete since it results in a singularity at the contact line. Several models, either involving a precursor film or having slip at the contact line, have been proposed to alleviate the singularity. In particular, the slip-based model Kirkinis & Davis(JFM,2014) show a completely different flow field from that predicted by Huh & Scriven. Using careful experiments with different solid/fluid/fluid combinations, we present new PIV experiments with the aim of shedding new light on the flow fields in the vicinity of a moving contact line. These experiments complement the earlier experiments of Savelski et al.(1995,JCIS) and offer new insights into the physics of moving contact line. |
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