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 Q31: Drops: Sessile and Static Surface Interactions |
Hide Abstracts |
Chair: Stuart Williams, University of Louisville Room: 239 |
Monday, November 21, 2022 1:25PM - 1:38PM |
Q31.00001: Patterned monolayer collapse from constrained sessile droplets using virtual wells and pedestals Kristopher Luck, Tonoy Mondal, Stuart J Williams A web-like pattern is created when a rigid monolayer forms at the interface of a sessile droplet and subsequently buckles during evaporation. Prior work investigated diluted bourbon whiskey droplets on coverslips (1 microliter drops, 25% alcohol-by-volume or ABV), but such investigations were limited to relatively hydrophobic liquids. In order to apply this technique to more hydrophilic samples, the sessile droplet will need to be physically pinned to increase the droplet's surface area. This can be accomplished through the use of virtual wells (i.e. patterned hydrophobic surfaces) or microfabricated pedestals. For this work we compared commercially available 2 mm diameter Teflon wells with similarly-sized SU-8 pedestals (0.12 mm height). This work demonstrates that web-like patterns were created with both methods, though pedestals produced more consistent patterns (through digital image analysis). This approach enabled the investigation of patterns created by more hydrophilic liquids (i.e. > 25% ABV), larger volumes (> 1 microliters), and explore the impact of pedestal curvature on monolayer collapse. |
Monday, November 21, 2022 1:38PM - 1:51PM |
Q31.00002: 3D holographic imaging of the evolution of internal flow and particle transport in an evaporating droplet Jiaqi Li, Jiarong Hong The internal flow motion in an evaporating droplet serves as one of the key driving mechanisms that lead to the variety of particle deposition patterns in applications such as inkjet printing, forensic analysis of blood stains, and surface patterning. Using digital inline holography (DIH), we examine the 3D internal flow for different types of droplets and the evolution of such flow fields, and corresponding particle transport throughout the entire evaporation process. Our results reveal the presence of different regimes during internal flow evolution associated with variation in the relative significance of evaporation-driven flow effect, Marangoni effect, and boundary movement and some unique 3D flow features such as the change of the extent of Marangoni flow in the 3D space and vertical fluid motions. By tracking the movement of numerous particles from beginning to deposition, our study suggests the shift of dominance of the three effects has direct impact on final particle deposition pattern. Based on our experiment results, an analytical model incorporating the effects of evaporation-driven flow, Marangoni stresses, and boundary movement is developed and can provide a reasonable prediction of internal flow and particle deposition patterns for a variety of Newtonian droplets. |
Monday, November 21, 2022 1:51PM - 2:04PM |
Q31.00003: Mesoscopic simulations of a molten sand droplet spreading on thermal barrier coatings under non-isothermal conditions Rahul Babu Koneru, Zhen Li, Alison Flatau, Luis Bravo, Muthuvel Murugan, Anindya Ghoshal, George E Karniadakis The deposition, infiltration and the ensuing solidification of molten sand on the thermal barrier coating (TBC) of gas turbine engine components alters the thermal properties of the TBC causing severe damage. The mesoscopic dynamics of a highly-viscous molten sand droplet spreading on a smooth TBC surface are investigated under non-isothermal conditions using the energy-conserving dissipative particle dynamics (eDPD) framework in conjunction with the many-body interactions to model the multiphase effects. Following the experiments conducted at the Army Research Laboratory, the droplet is subjected to a linear ramp-up of temperature from 1140 degrees Celsius to 1260 degrees Celsius where it is held constant till the end of the simulation. The contact angle obtained from the experiments is used to calibrate the contact angle in the eDPD simulations. The eDPD system is carefully parameterized to model the temperature-dependent non-linear viscosity of the molten sand droplet by setting the exponent of the weighting function as a function of temperature. The temporal evolution of the spreading radius and the corresponding scaling laws are evaluated for different drop sizes and final equilibrium contact angles and compared to previously obtained results from isothermal spreading on a smooth surface. |
Monday, November 21, 2022 2:04PM - 2:17PM |
Q31.00004: Wetting Regimes and Wetting to non-Wetting Transitions via Ambient Exposure Daniel Orejon, Junho Oh, Xiao Yan, Khaloud M Al Balushi, Soumyadip Sett, Yasuyuki Takata, Khellil Sefiane, Nenad Miljkovic The interactions between liquid droplets and solids are paramount to applications including coatings, materials processing, spray cooling, and medical diagnostics. Although interactions can be controlled by altering the material and structure, the wettability of pristine smooth materials such as metals and rare earth oxides transitions from wetting to non-wetting as they are exposed to the ambient environment. In addition, micro- and/or nano-structures can empower wettability transitions from complete wetting (superhydrophilic) to non-wetting (superhydrophobic state). Other intermediate states are also observed on micro- and nano-structured surfaces function of the pristine material, which will be introduced and described. Transitions are explained in terms of volatile organic compounds VOCs (ever present in the ambient as a consequence of manmade practices) adsorption, which are hydrophobic in nature. The wetting to non-wetting transition dynamics are dependent on both material and surface structure, which are elucidated and introduced too. Finally, superhydrophobicity of copper oxide surfaces exposed to VOCs empowering dropwise condensation phase-change are shown. Findings should be carefully considered during materials processing, surface characterization, coating deposition, and spray cooling applications. |
Monday, November 21, 2022 2:17PM - 2:30PM |
Q31.00005: Out-of-Plane Formation of Crystal Deposits on Heated Hydrophobic Surfaces Pranjal Agrawal, Virkeshwar Kumar, Susmita Dash Inorganic fouling, also termed as scaling, is pervasive in several applications ranging from heat exchangers, cooling towers, desalination membranes to household plumbing. Current methods to remove scaling are not environmentally safe and cause a significant downtime of the equipment. Evaporation of a saline droplet on substrates of different surface wettability offers a simple platform to investigate the effect of the underlying substrate on the nature of scaling. Here, we report on the out-of-plane growth of crystal deposits on hydrophobic substrates during the evaporation of saline droplets comprising of salts with high solubility. The crystals are loosely adhered to the substrate, which results in a self-cleaning behavior irrespective of the crystal morphology (cubic, needle-type, and dendritic) and the initial volume of the saline droplet. We present a generalized mechanism for the out-of-plane growth of the crystal deposit based on the relative wettability of the substrate and the salt crystals. |
Monday, November 21, 2022 2:30PM - 2:43PM |
Q31.00006: An experimental methodology for determining solid/liquid interfacial energy for wettable surfaces Sreya Sarkar, Mohamad J Gukeh, Tamal Roy, Constantine M Megaridis The solid/liquid interfacial energy is needed to predict the outcome of interactions between liquids and solids. Although several investigations have been carried out to determine this important quantity, no direct experimental method exists to achieve this goal. We perform contact angle experiments on different hydrophilic substrates with different degrees of roughness, a primary factor affecting the wettability of a surface. As the contact line of a sessile droplet advances, a resisting force acts in a direction opposite to that of the contact-line advancement. This resisting force increases linearly with surface roughness, and the slope of the corresponding curve is equal to the solid/liquid interfacial energy. The resisting force (similar to solid-solid frictional force) finds its origin in the roughness of the surfaces, and is obtained by performing simple sessile-droplet experiments. The present method demonstrates a new and simple approach to predict the solid/liquid surface energy for hydrophilic surfaces. The experimental findings are elucidated using well-known arguments from wetting theory and contact angle hysteresis. |
Monday, November 21, 2022 2:43PM - 2:56PM |
Q31.00007: Overdamped dynamics of liquid drop contact lines Chloe W Lindeman, Sidney R Nagel The dynamics of how drops move across solid surfaces are not well understood. We measure the macroscopic shape — contact angle and drop width — of drops of pure solute as they are aspirated from carefully prepared surfaces. The dynamics depend on both the speed at which the drops are removed and on the length of time that they sit on the surface before aspiration. Inspired by solid-solid friction, we simulate contact line motion with overdamped dynamics and show that fitting for just two parameters, the damping coefficient and the equilibrium contact angle, allows us to capture the behavior observed in experiments. We explore the physical picture suggested by the parameters of the simulations. |
Monday, November 21, 2022 2:56PM - 3:09PM |
Q31.00008: Contribution of droplet dynamics on contact line depinning in shearing gas flow Sung Yong Jung, Mehdi Mortazavi The depinning of sessile drop contact line with a solid substrate is a complex phenomenon that involves a complex balance of forces at the three-phase contact line. When a droplet is exposed to shearing gas flow, the drag force from the core gas flow tries to deform the droplet and depin its contact line. This external force, however, is competed against by contact angle hysteresis which describes the maximum deformation of the droplet without being dislodged from the surface. The adhesion force that pins the droplet to the solid surface is a function of the droplet surface tension, size, and its upstream and downstream contact angles. In this study, dynamics of droplets exposed to shearing gas flow are investigated by high speed imaging. We observed that droplets undergo an oscillatory pattern before contact line depinning. This oscillatory pattern induces inertia force within the droplet. When the droplet accelerates in streamwise direction, the inertia force adds to the drag force and the combined effect compete against the adhesion force. Our results indicate that droplet inertia force can reach up to half of the adhesion force. |
Monday, November 21, 2022 3:09PM - 3:22PM |
Q31.00009: De-icing by ultrasounds Pierre-Brice Bintein, Arnaud Grados, Sébastien Jammes, Jordan Bonté, Laurent Royon, Philippe Brunet
|
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