Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session ZC31: General Fluid Dynamics: Viscous Flow |
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Chair: Junshi Wang, Princeton University Room: 156 |
Tuesday, November 21, 2023 12:50PM - 1:03PM |
ZC31.00001: Blister dynamics beneath thick elastic layers Adam J Butler, Jerome A Neufeld Many geophysical systems involve a coupling between fluid flow and solid deformation, such as drainage of supraglacial lakes, geological carbon sequestration, and the inflation of magmatic bodies. Measurements of surface deformation offer one of the few ways to interrogate these systems. |
Tuesday, November 21, 2023 1:03PM - 1:16PM |
ZC31.00002: Mixing liquids of different viscosity Ilaria Castaldi, Henri Lhuissier, Bloen Metzger We experimentally characterize the deformation of a blob of viscosity η' subjected to a simple shear in a fully miscible bath of viscosity η. We show that increasing the viscosity ratio η'/η results in a sharp stretching-to-rolling transition, with dramatic consequences on the blob mixing timescale. For low viscosity ratios (0 < η'/ η ≤ 2), the blob elongates continuously and linearly into a thin lamella. In contrast, for large viscosity ratios (η'/η > 4), the blob essentially rotates, following periodic orbits with a small elongation. For intermediate ratios, η'/η ∼ 4, the blob follows a continuous sub-stretching regime and, eventually, destabilizes by folding. From these qualitatively different kinematic regimes — in good agreement with analytical predictions based on Eshelby's theory of elastic deformation — we will discuss how, and to which extent, the viscosity ratio affects the mixing of the blob. |
Tuesday, November 21, 2023 1:16PM - 1:29PM |
ZC31.00003: Verifying the validity of nonlinear slip for water under shear using molecular dynamics simulations. Hafizul Islam, Joseph John Thalakkottor To model fluid flows, certain assumptions about how the fluid moves past a surface (boundary condition) at the solid-fluid interface are necessary. A commonly used boundary condition is known as the "no-slip condition", which states that fluid elements adjacent to a surface adopt its velocity. While this condition has been successful in replicating the characteristics of many flow types, it can lead to unusual or singular behavior when applied to scenarios like spreading fluid on solid substrates or corner flow. |
Tuesday, November 21, 2023 1:29PM - 1:42PM |
ZC31.00004: Blowing away a sticky particule Amandine Lechantre, Pierre-Brice Bintein, Bérengère Abou, José Bico Adhesive surfaces tend to trap particles. However, when submitted to wind, the particles may be blown away. We present a model experiment where spherical beads deposited on a horizontal surface coated with a layer of viscous liquid is placed in a wind tunnel. Interestingly, the wind-induced motion of this sphere involves a combination of rolling and sliding. We will present how the steady velocity of the sphere depends on materials parameters and wind velocity. Different regimes are observed depending on the relative importance of capillary and gravitational forces. The experimental data are compared with a previous study of a sphere rolling down an incline [1] and we propose an empirical law compatible with both configurations. |
Tuesday, November 21, 2023 1:42PM - 1:55PM |
ZC31.00005: The effect of a temperature-dependent viscosity on pressure drop in narrow, converging channel flows Marcel M Louis, Evgeniy Boyko, Howard A Stone We investigate theoretically the influence of a temperature-dependent viscosity on the pressure drop in channels with converged heated walls, for cases where the Reynolds number is small. We anticipate this to be particularly applicable wherever there are highly viscous flows through heated nozzles such as in 3D printing. We employ the Lorentz reciprocal theorem to derive an expression for pressure drop across an arbitrary geometry for a viscosity field that depends on temperature. Assuming the fractional change in viscosity with temperature is small, we linearize the viscosity field using perturbation techniques. Also, for both the momentum and energy equations we apply the lubrication approximation, which we expect to be typically appropriate for flows where the maximum channel radius is much less than the channel length. We consider linear, quadratic, and hyperbolic converging channels at different contraction ratios to elucidate how the wall shape coupled with the wall heating influence the reduction in the pressure drop. We use numerical and similarity solution methods to solve for the temperature distribution under constant temperature and constant heat flux boundary conditions for each respective geometry. We report the results as a function of the effective Peclet number for each geometry and compare the numerical results with analytical predictions in the low and high Peclet number limits. |
Tuesday, November 21, 2023 1:55PM - 2:08PM |
ZC31.00006: Influence of porous flow on dip coating of a rough surface Lebo Molefe, Giuseppe A Zampogna, John M Kolinski, François Gallaire Surface roughness significantly modifies the liquid film thickness when dip coating a solid surface at low velocity. To investigate the relative importance of slip atop the roughness compared to flow through the textured layer, we experimentally measure film thicknesses deposited on surfaces with roughness resembling disconnected pores in comparison with porous surfaces that allow flow through the textures. Here, the film thickness is calculated by modeling the flow with a homogenized boundary condition at an equivalent flat surface between the porous region and outer film, which accounts for both flow through the porous layer and slip at the equivalent surface. The model is found to be in good agreement with experimental data and requires no fitting parameters. Furthermore, our model may be applied to arbitrary periodic roughness patterns, facilitating characterization of surfaces found in natural and industrial coating processes. |
Tuesday, November 21, 2023 2:08PM - 2:21PM |
ZC31.00007: Viscous friction acting on a solid disk falling in confined fluid: lessons for the scaling analysis Nana Tanaka, Ko Okumura We fill a viscous liquid in a vertically stood cell of millimeter thickness, called the Hele-Shaw cell, and insert a disk in the liquid whose thickness is smaller than the cell thickness. The disk starts falling in the liquid due to gravity with opposed by viscous friction. We focus on the case in which lubricating films formed in the gap between the cell surface and the disk surface are thinner than the disk thickness. As a result, we find an apparent scaling regime for the falling velocity of a disk, in which the thickness of the lubricating film characterizes the dynamics. We further show that the apparent scaling regime is explained simply as a result of competition of two scaling regimes, elucidating physics of the viscous friction to make the present study relevant to fundamental issues and applications in various fields such as microfluidics, bioconvection, and active matter. The simple scenario for explaining an apparent scaling law demonstrated in the present study would be useful in diverse fields. |
Tuesday, November 21, 2023 2:21PM - 2:34PM |
ZC31.00008: Coalescence of elastic blisters filled with a viscous fluid Torstein Saeter, Christian Pedersen, Jacco H Snoeijer, Thomas Salez, Andreas Carlson Pockets of a viscous fluid that coalesce underneath a soft elastic plate is a situation encountered in a myriad of natural phenomena and engineering processes, across scales. We study such an elastohydrodynamic coalescence problem by combining experiments, lubrication theory and numerical simulations. As the pockets coalesce, a bridge is formed and further exhibits an exponential growth with time, which corresponds to a self-similar solution of the bending-driven thin-film equation governing the spatio-temporal evolution of the thickness profile. We address this exotic self-similarity, and rationalize in details the observed experimental dynamics, from the numerical simulations and scaling analysis. |
Tuesday, November 21, 2023 2:34PM - 2:47PM |
ZC31.00009: Effects of slip on highly viscous thin-film flows inside a vertical tube Mark Schwitzerlett, Harold R Ogrosky, Ihsan Topaloglu Viscous liquid film flows in a tube arise in numerous industrial and biological applications, including the transport of mucus in human airways. Previous modeling studies have typically used no-slip boundary conditions, but in some applications the effects of slip at the boundary may not be negligible. We derive a long-wave model based on lubrication theory which allows for slippage along the boundary. Linear stability analysis verifies the impact of slip-length on the speed, growth rate, and wavelength of the most unstable mode. Nonlinear simulations demonstrate the impact of slip-length on plug formation and wave dynamics. These simulations are conducted for flows driven by gravity, core flow, or a combination of the two. We derive a second long-wave model to explore the effect of slip on fluid flow in a constricted tube. The results of simulations in such a tube will be discussed. |
Tuesday, November 21, 2023 2:47PM - 3:00PM |
ZC31.00010: Microhydrodynamics of an autophoretic particle Günther Turk, Rajesh Singh, Ronojoy Adhikari We study the autophoretic motion of an active particle interacting chemically and hydrodynamically with its thermally fluctuating environment. For a spherical active particle in an unbounded domain, we have shown that the boundary integral formulation of Stokes equation can be solved exactly in a basis of tensor spherical harmonics [1]. Here, by simultaneously solving the boundary integral equations of Laplace and Stokes, we extend this to the full chemo-hydrodynamics of an autophoretic swimmer. In an unbounded domain, we again find an exact solution. While in more complex environments the rigid body motion of a passive particle in a fluctuating fluid can be defined in terms of mobilities alone, activity gives rise to extra contributions from so-called propulsion tensors. Using an iterative method, we can obtain these tensors to arbitrary accuracy numerically. To leading order, we provide ready solutions for various experimentally relevant settings. Similarly, we obtain analytical expressions for an autophoretic particle’s elastance and linear response to a background concentration field. We then apply this to the dynamics of a bottom-heavy Brownian Janus swimmer near a plane interface characterised by an arbitrary ratio of viscosities and diffusivities. The resulting dynamical system, containing both the chemical and fluctuating hydrodynamic interactions between the particle and the interface, is explored in numerical simulations. |
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