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 A19: Microscale and Nanoscale Flows: Particles, Drops, Bubbles I |
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Chair: Steven Wereley, Purdue University Room: 250 C |
Sunday, November 24, 2024 8:00AM - 8:13AM |
A19.00001: Effect of temperature on nanoscale wettability: an atomistic study Harvey A Zambrano, Gonzalo Cepeda, Jens H Walther Understanding line tension effects on wettability in nanofluidics is crucial for nanoscale thermal management, nanofabrication, and interfacial fluid control. Wettability is characterized by the contact angle (CA) between the liquid-vapor interface and the solid surface described by Young's equation (YE). In nanodroplets, CA deviates significantly from predicted values using YE. It has been attributed to line tension effects which magnify as the droplet size decreases. A modified YE has been proposed (Boruvka and Newmann J. Chem. Phys.1977) including line tension effects however the fundamental relation between nanoscale wettability, line tension and CA remains an open question. It is not clear how local temperature and surface characteristics impact line tension magnitude and nanoscale CA. Here, we study how temperature in a sessile nanodroplet affects CA and line tension. To this end, we employ all-atom Molecular Dynamics simulations consisting of water droplets on a copper substrate. Species are described using the TIP4P/2005 water model, and a copper model that robustly reproduces thermal lattice vibrations, surface roughness and thermal transport. Different size Semi-spherical and semi-cylindrical nanodroplets are considered, the latter directly reproducing the macroscopic CA. Our results show the importance of considering equilibrium temperature in the modified YE to predict water CA. |
Sunday, November 24, 2024 8:13AM - 8:26AM |
A19.00002: Navigation of smart artificial microswimmers in confined flow via reinforcement learning Priyam Chakraborty, Rahul Roy, Shubhadeep Mandal Artificial microswimmers propel like natural micro-organisms by breaking symmetry and employing unique physico-chemical mechanisms in real environments to perform complex tasks. Recent studies with 'smart' microswimmers have expanded the scope with respect to their responses to external/tactic stimuli, hydrodynamic traps and multiple functions such as aggregated swimming. However, the rapid and precise regulation of these smart swimmers mediated by imposed flow conditions remains elusive. Here, we model them as active Brownian particles which satisfy a system of overdamped stochastic Langevin equations of motion that determine their position and orientation in a pressure-driven confined flow. To attain precise navigation from random position to pre-defined target, we intermittently guide these particles via reinforcement learning wherein the numerical rewards depend on their choice of actions that is derived from a discrete set of possible orientations. Further, to mitigate the reliance on domain knowledge, we automate the reward policy based on a desired sequence of actions which has the potential to eventually bring these smart microswimmers closer to nature. |
Sunday, November 24, 2024 8:26AM - 8:39AM |
A19.00003: ABSTRACT WITHDRAWN
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Sunday, November 24, 2024 8:39AM - 8:52AM |
A19.00004: Deterministic Lateral Displacement: Are contact interactions necessary? Partha Kumar Das, Xuchen Liu, Sascha Hilgenfeldt One of the simplest microfluidic separation techniques, Deterministic Lateral Displacement (DLD), involves flowing particles of different size across a grid of cylindrical obstacles. Particles of different sizes follow different paths, even at very small Reynolds number, a fact traditionally explained by invoking contact interactions with the obstacles that force particles off streamlines. However, in true Stokes flow of force-free particles, contact in finite time is impossible. We investigate here whether hydrodynamic interactions alone can explain permanent particle deflections at vanishing Re. Using recent analytical results for corrections of tangential and normal particle velocity near a wall, we model displacement of a neutrally buoyant spherical particle encountering a single obstacle in a uniform flow. By changing the obstacle and flow geometry in order to break both the fore-aft symmetry and the cross-flow symmetry, we find permanent displacement without invoking contact or other short-range forces. While the magnitude of the effect is small, it is predictable and can be enhanced for different particle shapes or by using multiple obstacles, as in DLD. For a range of initial conditions, hydrodynamic effects force the particle to approach the interface so closely as to engage short-range interaction (e.g. sticking) in realistic scenarios. These results serve as fundamental building blocks for the understanding of hydrodynamic particle manipulation at zero Reynolds number. |
Sunday, November 24, 2024 8:52AM - 9:05AM |
A19.00005: Microflow behavior of solvent-rich droplets in coaxial channels Thomas Cubaud, Thai Dinh We experimentally study the microfluidic behavior of ternary fluid systems made of two immiscible fluids and a miscible solvent. We examine, in particular, the multiphase flow situation where the solvent is mixed in the dispersed phase and we investigate the two complementary configurations of water-in-oil and oil-in-water dispersions at short time scales. Flow maps are delineated over a wide range of flow rates and solvent concentrations and we show a variety of intriguing interfacial flow phenomena, such as typical dripping, jetting, and core-annular flows at low solvent concentration and unique regimes, such as dynamic wetting, spontaneous emulsification, and tip streaming at high concentration. Methods based on flow pattern analysis are developed to elucidate the relationship between complex flow morphology and fluid properties of multiphase materials in confined microsystems. |
Sunday, November 24, 2024 9:05AM - 9:18AM |
A19.00006: libMobility: a fast Stokesian dynamics library Ryker Fish, Brennan Sprinkle, Raúl Pérez Peláez, Aleksandar Donev We'll introduce a fast and modular GPU library, libMobility, that solves the hydrodynamic mobility problem for Stokesian particle suspensions in open, periodic, and confined geometries. In particular, we've implemented fast routines to apply mobility matrices and their principle square root, ensuring that the library is immediately available for use in Brownian dynamics applications. In addition to being a high-performance library, libMobility is designed to have a streamlined installation and be easy to integrate into existing codes. We present examples with fluctuating membranes, slender filaments, and active particles that demonstrates both the flexibility and the computational advantage of the library. |
Sunday, November 24, 2024 9:18AM - 9:31AM |
A19.00007: Orientation Dynamics of Elongated Particles in Viscous Converging-Diverging Flows Francisco J Goio Castro, Anke Lindner, Olivia Du Roure, Andrea de la Sen, Anuran Kar Gupta, Andreas Zoettl Neutrally buoyant, ellipsoidal particles in unidirectional flows at zero Reynolds number follow streamlines and perform tumbling motions. In more complex geometries, such as converging-diverging channels, rigid elongated particles exhibit a markedly different behavior: they align parallel to the flow before the constriction and reorient perpendicular to the flow direction after the constriction. |
Sunday, November 24, 2024 9:31AM - 9:44AM |
A19.00008: Algorithmic Spherical Mode Decomposition and Rheological Analysis of Nonlinear Interactions in Variable Density Deformable Particle Domains Amin Isazadeh, Davide Ziviani, David E Claridge This study investigates nonlinear interactions from pressure waves emitted during particle deformation in domains with variable particle density distributions. We propose a novel algorithm to generate irregular 3D shapes by combining spherical harmonic modes and decomposing them into dominant modes. The domain includes particles ranging from nanometers to millimeters. We examine the impact of centroid distance, initial shape, and material properties on interaction dynamics. Geometry and mesh generation are performed using GMSH, creating a structured quad mesh with smaller cell sizes near the particles to avoid mass diffusion. CFD modeling is conducted using the compressibleInterDyMFoam solver in OpenFOAM. The study includes rheological analysis via analytically derived equations and explores the use of physics-informed neural networks (PINNs) to predict dynamics of nonspherical deformable particles. |
Sunday, November 24, 2024 9:44AM - 9:57AM |
A19.00009: Abstract Withdrawn
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Sunday, November 24, 2024 9:57AM - 10:10AM |
A19.00010: Bionanoparticle Characterization Using an Integrated Acoustofluidic Device with Raman Spectroscopy for Vaccine Development Taehong Kim, Ehsan Esmaili, Shreya Milind Athalye, Tiago Matos, Mahdi Hosseini, Mohit S. Verma, Arezoo M Ardekani The impact of pandemics and viral outbreaks depends heavily on the speed of the vaccine development. Traditional vaccine production methods involve multiple stages and require manual human intervention, resulting in a long lead time. Developing reliable sensors and measurement methods for automated, real-time monitoring could significantly accelerate this process. Raman spectroscopy is a potential real-time measurement technique for determining the physical characteristics of samples. When dealing with bionanoparticles ranging from 50 nm to 400 nm in diameter, higher concentrations (more than 1E+9 particles/mL) are required. In this presentation, we will develop optimized acoustofluidics, demonstrating the practical application of the acoustofluidic device by successfully measuring Raman spectra from low-concentration Ebola vaccine. Our work offers an approach of real-time bionanoparticle monitoring through microfluidics, enabling the real-time quantification of vaccines. |
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