Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session AA04: V: Fluids I |
Hide Abstracts |
Sponsoring Units: DFD Chair: Simon Huynh, Brandeis University Room: Virtual Room 4 |
Monday, March 20, 2023 5:00AM - 5:12AM |
AA04.00001: Dynamical Motion of Surface Active Flow Driven Droplets Zheng Yang Active droplets which can autonomously locomote are of both fundamental interest and of practical importance. Due to the action of the active agents in the droplet, hydrodynamic flows may arise on its interface, and can drive the droplet to propel. However, our current understanding of how surface active flows determine the dynamical modes of the droplet remains elusive to date. To address this question, here we consider the dynamical motion of a droplet driven by microswimmers self-propelling on its interface. Specifically, we use rigid multiblob method to simulate the dynamic trajectory of a single spherical droplet near a no-slip wall mobilized by active point-like particles on its interface. Interestingly, we find that the simulated trajectories exhibit rich dynamical modes consisting of circular, helical, or petal-like circular motions. These modes can be controlled by the initial pitch angle and swimmer configurations. The dynamical behaviors are further quantitatively analyzed and explained. Our work sheds light on understanding the surface flow mediated autonomous motion of active droplets. |
Monday, March 20, 2023 5:12AM - 5:24AM |
AA04.00002: The role of drop shape in impact and splash Lei Xu, Zhipeng Jin, Jiangtao Zhao, Gang Chen, Guo Chen, Zhenlin Luo The impact and splash of liquid drops on solid substrates are ubiquitous in many important fields. However, previous studies have mainly focused on spherical drops while the non-spherical situations, such as raindrops, charged drops, oscillating drops, and drops affected by electromagnetic field, remain largely unexplored. Using ferrofluid, we realize various drop shapes and illustrate the fundamental role of shape in impact and splash. Experiments show that different drop shapes produce large variations in spreading dynamics, splash onset, and splash amount. However, underlying all these variations we discover universal mechanisms across various drop shapes: the impact dynamics is governed by the superellipse model, the splash onset is triggered by the Kelvin-Helmholtz instability, and the amount of splash is determined by the energy dissipation before liquid taking off. Our study generalizes the drop impact research beyond the spherical geometry, and reveals the potential of using drop shape to control impact and splash [1, 2]. |
Monday, March 20, 2023 5:24AM - 5:36AM |
AA04.00003: Forces on objects immersed in active fluids Ashreya Jayaram Depending on their shape, objects immersed in active fluids may be subjected to a net force or net torque. We show that in a finite, periodic system, the force/torque on such an object is determined by the vorticity of the polarization of the surrounding active fluid which in turn is localized to regions close to the object where its curvature changes. We find that the system size L has a colossal influence on the magnitude of the force which grows as L2 before saturating to a constant. We relate this force to the current away from the body and substantiate our theoretical results with numerical simulations of active Brownian particles. |
Monday, March 20, 2023 5:36AM - 5:48AM |
AA04.00004: Refractive microswimmers with a symmetry-broken refractive index profile Julian Jeggle, Matthias Rüschenbaum, Cornelia Denz, Raphael Wittkowski We present a novel type of active matter system consisting of a suspension of microparticles fabricated from a transparent polymer with a symmetry-broken refractive index profile. Under illumination these particles are subject to a driving force due to the momentum transfer associated with light refraction. Using the refractive index profile instead of the particle shape to break particle symmetry allows a decoupling of the propulsion mechanism from the hydrodynamic properties of the particles, which distinguishes this archetype of active particles from, e.g., acoustically driven particles. With structured light, a high degree of both spatial and temporal control of particle propulsion can be achieved. In contrast to optothermally driven particles, refractive microswimmers possess sensitivity also to the phase component of the light field giving a richer space of control parameters. Additionally, we find that particles can interact on much larger distances via mediation by the light field compared to simple steric repulsion. Combining this with external feedback mechanisms allows for high complexity particle networks, thus making this kind of active particle a promising candidate for novel, adaptive materials. |
Monday, March 20, 2023 5:48AM - 6:00AM |
AA04.00005: Contact angle hysteresis for wetting of hydrophobic, anisotropically curved surfaces Mingzhu Cui, Nadav Benhamou Goldfajn, Joseph Amendolare, Anthony D Dinsmore Our study is focused on the influence of solid surface geometry on contact angle hysteresis, specifically on the values of the advancing contact angle θA and receding contact angle θR. Recent studies show that when mm-sized spheres coated with polydimethylsiloxane (PDMS) were partially immersed in an air–water interface, θR decreased monotonically with increasing deviatoric curvature D, defined as half the difference between the two principal curvatures. θA remained unchanged. Here we report on experiments with two different geometries. First, we focused on pendant water droplets on PDMS-coated flat glass plates and cylindrical glass rods with mm-scale diameters. We find that the quasi-static θR increases monotonically from about 85° to about 94° and the quasi-static θA remains unchanged as the dimensionless product of deviatoric curvature and contact-line diameter increases from 0 to 0.9. To further explore the effect of anisotropic interface curvature, next we studied a PDMS coated glass rod partially immersed into an initially flat water-air interface. With the rod held at an angle from the vertical, we inserted it and withdrew it and measured θA and θR on the left and right sides. These angles change when the rod tilt angle varies between 0 and 60°. We will present all of these curvature-dependent advancing and receding angle data and discuss possible mechanisms. This work may provide new insights into the origin of contact angle hysteresis. |
Monday, March 20, 2023 6:00AM - 6:12AM |
AA04.00006: Applications of the image method in low-Reynolds-number hydrodynamics and linear elasticity to right-angled edges and corners Lukas Fischer, Tyler Lutz, Andreas M Menzel The image method is useful for solving boundary problems, known from e.g. electrostatics. Here, we present a general overview of when and how this method can be applied to the linear equations in classical continuum mechanics, the Stokes and Navier-Cauchy equations. In the two cases, our aim is to calculate the fluid velocity or displacement field in the whole domain under consideration, respectively. A Green's function method that characterizes the response to a point force is utilized. |
Monday, March 20, 2023 6:12AM - 6:24AM |
AA04.00007: Hysteretic wetting and dewetting of a thin sheet peeling off a liquid interface Nuoya Zhou We peel a thin polymeric sheet on and off an air-water interface with controlled velocity. |
Monday, March 20, 2023 6:24AM - 6:36AM |
AA04.00008: Manipulating droplet jumping on hot substrates with surface topography: from vibration to explosion Jiangtao Cheng Liquid droplet rapid and facile detachment from a substrate surface has received increasing attention due to its broad applications in a variety of fields such as anti-icing, surface self-cleaning, and thermal management. During the past several decades, many research efforts have been made for rapid droplet detachment by designing various functional substrates with complex macro/micro/nanostructures or resorting to costly external stimuli such as electrical, photothermal or magnetic fields. But our understating of the inherent and intricate droplet-substrate interactions still remains elusive, impeding simple designs of engineered surfaces for agile droplet manipulations. Here we introduce a simple but effective method to manipulate droplet jumping behaviors on micro-pillared superhydrophobic substrates at moderate superheat of about 30 °C by controlling the vapor bubble growth thereon. We find that the vapor bubble growth at the droplet base can be transferred from the heat-transfer-controlled slow growth mode to the inertia-controlled rapid growth mode by simply increasing the substrate micropillar height from 20 um to 80 um. As opposed to the relatively slow vibration jumping in seconds, the change of vapor bubble growth to the inertia-controlled mode at the droplet base leads to the prompt droplet out-of-plane explosion jumping in milliseconds. The rapid sessile droplet detachment stems from the vapor bubble explosion at the droplet base on the hot substrate, during which the vapor bubble expanding velocity can reach as high as ~4 m/s. Our observations in this study unveil the mechanism of droplet rapid detachment from a hot micro-structured surface and shed lights on engineered surface design avoiding the damage of vapor explosion. |
Monday, March 20, 2023 6:36AM - 6:48AM |
AA04.00009: Magnetic resonance imaging of bubbles injected into liquid suspensions Alireza Bordbar, Wasif Zia, Javad Omidi, Janine Birnbaum, Einat Lev, Christopher M Boyce Magnetic resonance imaging is used to reveal the dynamics of consecutive bubble injection into opaque liquid suspensions. A 3D cylindrical system and a custom-built magnetic resonance imaging (MRI) coil are employed. The base fluid is 5000 cst Silicone oil and sesame seeds are dispersed into the fluid at varying levels of volume fraction to investigate the effect on bubble dynamics. Such experiments can be analogs of air bubbles or air slugs ascending in magma. In some conditions, regular coalescence was observed at certain heights in the suspension. |
Monday, March 20, 2023 6:48AM - 7:00AM |
AA04.00010: Influence of Cement Concentration on Gas Migration in a Cement Slurry Arthur Ndri A Konan Gas invasion into a freshly cemented wellbore annulus from the surrounding geological formation can cause loss of isolation, leaking, or other environmental issues. Cement slurries behave as complex nonlinear fluids that may exhibit viscoelasticity, thixotropy, yield stress, shear-thinning effects, etc... In this work, laboratory scale room temperature experiments, representative of the flow of gas invading wellbore cement are simulated. A column of cement slurry undergoes continuous air injection from the bottom. The flow of the slurry and the air bubbles are modeled relying upon the volume of fluid (VOF) approach, in which the interfacial interactions between the immiscible gas and the cement slurry is described through the surface force technique to account for the net tensile force acting on the interface. The cement slurry is considered as a suspension and the spatio-temporal distribution of the cement particles is described by using a convection-diffusion equation for the particle transport flux due to mechanisms such as the compactness and collision of the grains, the gravity, and the change in the viscosity. The effective viscosity of the slurry is based on the Herschel-Bulkley fluid model, modified by the volume fraction of the cement particles by using a polynomial expression or a function depending on the maximum packing fraction. We also look at the dependence of the yield stress on the volume fraction of the cement particles and the water-to-cement ratio. These equations are implemented as customized non-Newtonian viscosity libraries and are solved in OpenFOAM. The results of the air bubble property distributions along with their average rising velocities are discussed with respect to the baseline slurry (Herschel-Bulkley fluid) and the viscosity dependence on the cement volume fraction, over a range of gas injection flow rate. |
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