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 L18: Free-Surface Flows: Surface Tension |
Hide Abstracts |
Chair: Tom Marzin, Princeton University Room: 250 B |
Monday, November 25, 2024 8:00AM - 8:13AM |
L18.00001: Twisted shells: unraveling under-extrusion instabilities in 3D printing Tom Marzin, Lauren Dreier, Barath Venkateswaran, Romain David, Stephane Pienaar, Pierre-Thomas Brun In 3D printing, ensuring the precise extrusion of material is crucial for achieving the desired shape while minimizing filament usage. One strategy involves under-extrusion, where insufficient material is used to form a uniform layer. We discovered that this results in a periodic pattern of droplets and threads, highly dependent on the previous print layer and the printing properties. We developed a minimal model based on our experiments to explain the emergence and physics behind this instability. Extending our study to more complex printing paths, such as cylindrical ones, we demonstrated the creation of highly twisted shells, showcasing the potential of this method. |
Monday, November 25, 2024 8:13AM - 8:26AM |
L18.00002: ABSTRACT WITHDRAWN
|
Monday, November 25, 2024 8:26AM - 8:39AM |
L18.00003: Rotation of a superhydrophobic cylinder in a viscous liquid Ehud Yariv, Michael Siegel Motivated by recent experiments, we address the motion of a superhydrophobic particle through an otherwise quiescent liquid. In these problems the superhydrophobic effect is naturally quantified by the enhancement of the Stokes mobility. We focus upon what may be the simplest problem in that class, namely the rotation of an infinite circular cylinder whose boundary is periodically decorated by a finite number of infinite grooves, with the goal of calculating the rotational mobility. The associated two-dimensional flow problem is defined by two geometric parameters, namely the number N of grooves and the solid fraction. Using matched asymptotic expansions we analyze the large-N limit (and arbitrary solid fraction), obtaining an approximation for the hydrodynamic mobility. Making use of conformal mapping techniques we show that the preceding approximation actually holds for all N, and therefore constitutes an exact result. |
Monday, November 25, 2024 8:39AM - 8:52AM |
L18.00004: Thin film equations on curved surfaces Robert S Hutton, James Hanna We derive governing equations for viscous thin film flows on arbitrary curved surfaces, by extending Leal's pedagogical approach that does not initially prescribe the characteristic velocity scale, and employs a direct through-thickness integration of the continuity equation. We neglect inertia but include gravitational, capillary, and Marangoni effects, the latter coupling the height dynamics to free-surface transport of a dilute, non-diffusing surfactant. The resulting general expression incorporates the leading order terms of each type, as well as additional terms that become leading order for certain nongeneric, yet simple and common, geometries. This treatment collects and compares various results, and presents a simple equation useful for exploring balances between geometry, gravity, and surface tension effects. |
Monday, November 25, 2024 8:52AM - 9:05AM |
L18.00005: Marangoni Instability Subject to Electrostatic Forcing Dinesh Bhagavatula, Thomas Corbin, Ranga Narayanan We investigate the effect of electrostatic potential on a thin liquid layer heated from below, with its free surface exposed to a hydrodynamically passive gas. The liquid and gas layers are confined between two horizontal plates. In the absence of a forced electrostatic potential, the liquid layer exhibits Marangoni instability if the temperature difference across the layer exceeds a threshold, which varies with the perturbation wavenumber. This threshold has two minima, corresponding to long- and short-wave instability modes, eventually leading to dryout. However, without the Marangoni effect, an electric field imposed on the liquid and gas layers, stable under gravity, causes instability through interfacial deflections, leading to the formation of pillars. Using linear stability analysis of the full governing equations, we derive an analytical expression for the critical potential. We also show that increasing the electrostatic potential reduces the critical Marangoni threshold, eventually making it negative. A negative Marangoni threshold indicates pillar formation due to electrostatic dominance, while a positive threshold indicates dry spot formation. These phenomena are confirmed by nonlinear interface evolution calculations using the long-wave model, specifically the Weighted Residual Integral Boundary Layer approach. |
Monday, November 25, 2024 9:05AM - 9:18AM |
L18.00006: Molecular Dynamics Simulations of Retraction and Rupture of Liquid Sheets Aaditya Upendra Joshi, Osman A Basaran, David S Corti Liquid sheets are encountered in a wide variety of natural and industrial processes. Some important examples in which a fundamental understanding of the dynamics of liquid sheets is critical include processes involved in applying coatings and paints, operation of fuel injection systems, biological membranes, bubble and droplet coalescence in foams and emulsions, and crop spraying. Not surprisingly, the retraction and rupture of liquid sheets has been a topic that has been extensively studied using continuum mechanics. In a liquid sheet, which is bound by two free surfaces, the balance between inertia and surface tension and viscous forces determines the dynamics of retraction and rupture. Depending on the application, the rupture and fragmentation of liquid sheets can either be desirable, e.g. atomization, or undesirable, e.g. curtain coating. In this study, we use molecular dynamics (MD) simulations to probe the problem on length and time scales that are much smaller than those over which the continuum assumption holds. Here, we use MD to carry out a detailed study of the rate of retraction liquid sheets. Moreover, we also explore the role played by thermal fluctuations on the liquid surface(s) in driving sheet rupture and propose an order of magnitude analysis for the same. |
Monday, November 25, 2024 9:18AM - 9:31AM |
L18.00007: Nonlinear dynamics of Faraday waves at the surfactant-covered free surface of the vertically vibrated liquid layer Alexander Mikishev, Alexander A Nepomnyashchy In our previous paper (Fluid Dyn. Res., vol. 48 (2016), 061403) we studied the influence of the solutocapillary effect due to absorbed insoluble surfactant and thermocapillary effect caused by heating on the generation of Faraday waves. The problem was considered in the framework of linear theory and Floquet method for the semi-infinite liquid layer, as well as for the layer with finite depth. Within the Faraday experiment a rich variety of complex patterns are seen, some of which have a complicated spatial structure, but are time-periodic with the periodicity of the driving force, and some have both complicated spatial and temporal structure. Here we propose a weakly nonlinear analysis of the generation of Faraday waves. |
Monday, November 25, 2024 9:31AM - 9:44AM |
L18.00008: Contact line driven fingering instability of thin fluid film flows over diverging surfaces: Spherical and Conical surfaces Gaurav Tomar, Ananthan Mohan While thin fluid film flows over flat surfaces are well studied and understood little work has been done in understanding film flows over curved surfaces. In this work we explore flow of a completely wetting Newtonian fluid over a spherical and conical surface, with particular focus on contact line instabilities at the fluid front. Understanding contact line driven instability |
Monday, November 25, 2024 9:44AM - 9:57AM |
L18.00009: Electrohydrodynamics of leaky dielectric falling films coating the interior of a tubular electrode: linear stability and nonlinear interfacial dynamics Tao Wei, Poh Seng LEE We formulated an electrostatically modified Orr–Sommerfeld eigenvalue problem using the Taylor–Melcher leaky dielectric model. This eigenvalue problem has been solved with the compound matrix method based on a generalization of the Evans function. The numerical results of electrified Stokes problems predict that apart from the classic Plateau–Rayleigh instability in the long-wave (LW) range, surface wave (SW) and leaky-dielectric (LD) modes may appear. For a given outer electrode radius (α) and a relatively smaller inner electrode radius (β), LD mode could occur in two branches of dispersion curves with SW modes in two disjoint intervals of smaller and larger wavenumbers (k). Neutral curves in the β−k plane are calculated for different values of α, the relative permittivity of liquid, and an electric Weber number. Next, we derived coupled LW evolution equations for the axisymmetrically interfacial position and charge distribution. Our parametric study shows that only in a narrow window of relatively small values of permittivity ratio can traveling waves occur. It is shown that either outer- or inner-electrode finite-time touchdown (TD) is possible for leaky dielectric cases, while only inner electrode TD is found for a pair of perfect dielectric liquids. The results demonstrate that rupture behaviors can be controlled by changing electric parameters. Phase diagrams show the existence of a large stable equilibrium region whose size increases with the dimensionless conductivities. |
Monday, November 25, 2024 9:57AM - 10:10AM |
L18.00010: Instabilities of thin-film flow over a spinning disk Alexander W Wray, Omar K Matar, Stephen K Wilson, Laura Milne, Marc Pradas We study the dynamics of a thin, axisymmetric film of Newtonian fluid on a uniformly rotating disk with topography. The system is modelled via a thin-film approximation together with the Method of Weighted Residuals up to second order. The resulting model is a closed initial-value problem for the film thickness and the radial and azimuthal fluxes, including the effects of inertia, viscosity, centrifugation and capillarity. We determine simplified models in the far field to investigate the spatial and temporal stability and find that there exist three distinct regions that exhibit qualitatively different behaviours. We also study a family of substrate shapes with parameters controlling the asymmetry, smoothness, amplitude and frequency of the topography. The effect of the topography on the flow is quantified using an integral measure of the interfacial waviness amongst other measures. In particular, we find that the presence of topography can cause additional interfacial waves, increasing the surface area of the film. |
Monday, November 25, 2024 10:10AM - 10:23AM |
L18.00011: Dynamics of three-phase contact line when crossing micro-patterns Zhicheng Yuan Within the Couette flow computational system, the slip behavior of the three-phase contact line as it crosses a micro-pattern was numerically analyzed using a modified interFoam solver shipped with OpenFoam. Micro-patterns are rectangular hydrophilic, hydrophobic, pillar, and hole areas, which are located on a surface with intrinsic contact angle at 60°. The calculation results show that on the hydrophilic area decorated surface, the three-phase contact line is slowed down, and then a shooting behavior is seen when it leaves the pattern. An inverse crossing behavior is obtained on hydrophobic area masked surface. On the surfaces with a micro- pillar or hole, the breaking of the liquid tail enhances the sliding of contact line. The findings in this work will be help for designing functional slippery surfaces. |
Monday, November 25, 2024 10:23AM - 10:36AM |
L18.00012: Abstract Withdrawn |
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. |
© 2025 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