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 J09: Drops: Interaction with Elastic Surfaces, Particles and Fibers |
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Chair: Hernan Barrio Zhang, University of Edinburgh Room: Ballroom I |
Sunday, November 24, 2024 5:50PM - 6:03PM |
J09.00001: Capillary-Induced Solvent Transport in Hydrogels with Large Swelling Boxue Zheng, Tak Shing Chan, Harald Brummelen, Jacco H Snoeijer Capillary forces induced by droplets can deform a soft substrate. When the soft substrate is made of poroelastic materials such as hydrogels which consist of polymer networks that can be swollen by solvent, the deformation is coupled with the transportation of the solvent. We implement a large deformation model to investigate this coupled dynamic process. We formulate the total free energy of the system including the stretching of the polymer network and the mixing of the network with small molecules. The dissipation caused by the viscoelasticity of the gel is also included. Our work sheds light on some recent experiments. |
Sunday, November 24, 2024 6:03PM - 6:16PM |
J09.00002: Resonance and Damping in Drop-Cantilever Interactions Crystal Rain Fowler, Rehan Marshall, Sunghwan Jung The interactions of a drop and a cantilever beam represent an elaborate mechanism that is applicable to many industrial fields and natural phenomena. Previous studies have focused on the positive correlation between the length and damping ratio of an elastic cantilever; however, we observed that around the resonance beam length in which the droplet frequency matches with the beam's natural frequency, this trend is not valid. To investigate this, we tested thin polycarbonate beams of nine varying lengths with a water droplet impact and used high-speed cameras to record the vibrational responses. The damping ratio of the cantilever increases with cantilever lengths shorter than resonance due to the droplet and cantilever being out of phase. For longer cantilevers, the phase of the droplet and cantilever are aligned in momentum and is significantly less than the damping rates for shorter lengths. These beam-droplet interactions can be helpful for future developments in energy-conversion techniques by understanding how droplets interact with elastic surfaces. |
Sunday, November 24, 2024 6:16PM - 6:29PM |
J09.00003: Capsule damaged by an enclosed microswimmer Zhihan Huang, Toshihiro Omori, Takuji Ishikawa Capsules, a thin deformable membrane confining liquid inside, are relevant for applications such as microfabrication, bioengineering and targeted drug delivery. With a capsule, certain substance can be released in a controlled manner and such release need a capsule to be broken. However, breaking of a capsule from the inside is rarely studied, so we focus on the breaking of a capsule by a microswimmer trapped inside in a numerical way. Due to small size of a capsule and microswimmer, we assume that the flow field is governed by the Stokes equation, which is solved by a boundary element method. We also assume the capsule membrane to be a 2-dimensional hyper-elastic material, which is calculated by a finite element method. Damage of capsule membrane is considered as quasi-brittle damage corresponding to membrane deformation. We find out the connection among damage of capsule, capillary number, and swimming mode of microswimmer. |
Sunday, November 24, 2024 6:29PM - 6:42PM |
J09.00004: Capturing airborne microparticles through the motions of liquid droplets. HYUNGJUN JUNG, Seungho Kim We present a novel liquid droplet-based microparticle filter inspired by the scavenging of dust particles by raindrops. Porous filters have been widely used to remove microparticles, but these filters are vulnerable to clogging with microparticles, leading to increased pressure loss and requiring frequent replacement. To overcome these limitations, the motions of liquid droplets are utilized to remove airborne microparticles. This method eliminates the clogging issue since the liquid droplet-based filter is free of solid porous structures. We found that the relative distance between the liquid droplet and the particle is a crucial factor. For small relative distances, microparticles are captured by liquid droplets, while for large relative distances, microparticles are deflected from their initial path by air currents induced by the motion of the liquid droplet, causing the microparticles to move far away from the droplets and thus leading to the failure of particle capture. These characteristics depend on the speed and shape of both the liquid droplets and particles. We visualize these interfacial dynamics using a high-speed camera and characterize their salient features by combining theory and experiments. |
Sunday, November 24, 2024 6:42PM - 6:55PM |
J09.00005: Bio-inspired hairy wires for fog collection Leyun Feng, Wonjae Choi, Kyoo-Chul Kenneth Park Water collection from fog in the atmosphere can be a promising solution to water scarcity in many regions around the world. Commercial fog harvesters using mesh structures composed of cylindrical wires with a certain permeability, have a limited fog collection efficiency due to the following trade-off problem. Specifically, micrometric airborne fog droplets pass through a permeable mesh with less deposition on the wire surfaces as the wire diameter increases, resulting in low deposition efficiency. Conversely, meshes with thinner cylinders tend to clog, exhibiting lower drainage efficiency. To overcome this trade-off, we propose a bio-inspired hierarchical structure that includes a vertical core surrounded by multiple thin hairs protruding radially, which can greatly enhance both deposition and drainage efficiencies. The thin hairs allow fog droplets to make contact with the structure and deposit on the hair surfaces efficiently, while the vertical core wires facilitate the rapid drainage of deposited droplets through a wicking mechanism. The hierarchical hairy wires can achieve a steady-state water collection rate up to three times as high as that of cylindrical wires of the same outer diameter, and their excellent performance does not degrade, a common issue with conventional meshes composed of thin wires. We envision that this study offers a new way to design fog collectors with improved water collection efficiency, contributing to solving the global water crisis. |
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