Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session X41: Micro/Nano scale Flows: Interfaces II |
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Chair: Gerald Wang, Carnegie Mellon Univ Room: 206 |
Tuesday, November 21, 2023 8:00AM - 8:13AM |
X41.00001: Diffusion of aqueous LiCl electrolytes in 3D-nanoporous graphene structures LIU Biyuan, Le Zhou, Yixiang Wang, Shaobin Zhuo, Yanguang ZHOU, Jinglei YANG, Zhigang LI Diffusion of electrolytes in 3D nanoporous structures is of great importance in various areas, especially in energy storage fields. Our study employs molecular dynamics simulations to investigate the diffusion of LiCl electrolytes within 3D nanoporous graphene structures (3D-NGSs). We calculate the diffusion coefficients (D) of water, Li+, and Cl- in 3D-NGSs with different porosities and surface charge densities at various temperatures. Our findings reveal that the diffusion coefficients conform to the Arrhenius Equation and power laws that describe their dependence on temperature and porosity, respectively. The surface charge density has a negligible effect on the diffusion coefficients. We determine that these relationships are governed by the potential energy distribution within the 3D-NGSs. Furthermore, we propose general scaling laws to describe the diffusion coefficients of water, Li+, and Cl-. Our results provide valuable insights for the development of electrodes and other energy systems. |
Tuesday, November 21, 2023 8:13AM - 8:26AM |
X41.00002: Computational design of nanostructures and nanofluidic Systems Daniela A Damasceno, Alexsandro Kirch, Rene Q Rodriguez, Renato P Sanches, Julio R Meneghini, Caetano R Miranda, Emilio C Nelli The rational design of nanostructures and nanofluidic systems with enhanced mechanical and physical properties is an emerging area. Nanofluidics, which involves the study of fluid transport at the nanoscale, has opened up exciting possibilities for various applications, including innovative microreactors and membrane technologies. To gain a deeper understanding of fluid dynamics and molecular interactions, researchers have turned to molecular dynamics (MD) simulations. These simulations track the movement of atoms, providing detailed insights into system behavior and fundamental properties. However, to unlock the full potential of nanofluidic systems, it is crucial to go beyond traditional structures and explore new designs through optimization strategies. Topology optimization (TO), a powerful computational method used in engineering, allows researchers to find an optimal distribution of materials within a given space. In this pioneering study, we present the first application of combined MD and TO approaches for the design of nanostructures and nanofluidic systems. By leveraging the strengths of both methods, we aim to unlock new possibilities and advance the development of highly efficient nanoscale devices. |
Tuesday, November 21, 2023 8:26AM - 8:39AM |
X41.00003: In-situ optical spectroscopy on nanoporous silicon thin films and photonic crystals for high spatial resolution in imbibition experiments Guido Dittrich, Luisa G Cencha, Claudio L Berli, Raul Urteaga, Patrick Huber Nanoporous silicon is investigated for sensing applications in a variety of fields. Combinations of layered structures and porosity modulations are among others used to improve the sensing performance. In view of the fluidics inside nanopores a combination of a thin film interference layer followed by a photonic crystal unlocks much more than that. [1] In-situ optical spectroscopy of capillary imbibition into this structure allows the observation of fluid front broadening, the liquid meniscus and ultra-thin precursor films at micro-second resolution. The method compares local and collective filling dynamics by differentiating in between optical features. Overall, we introduce an exceptionally precise technique for fluid and in particular polymer characterization inside nanopores on a chip. |
Tuesday, November 21, 2023 8:39AM - 8:52AM Author not Attending |
X41.00004: Abstract Withdrawn
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Tuesday, November 21, 2023 8:52AM - 9:05AM |
X41.00005: Control and Manipulation of Surface Flows Using Photo Marangoni Effect Yaofa Li, Mahedi Hassan, Damien Baigl Marangoni flows are pervasive in numerous natural and engineering processes and often play a defining role in micro- and nanoscale systems. With “tears of wine” being one famous manifestation of the Marangoni effect, other notable applications included painting, printing, and wicking in heat pipes for thermal management, among others. Typically, Marangoni effect (i.e., the surface tension gradient) can be created in two ways: by a temperature and/or concentration gradient, termed thermocapillarity and/or solutocapillarity, respectively. In both cases, however, the capillary forces are inevitably coupled with other forces, such as buoyancy, which hinders our ability to study capillary forces and their role in other processes like capillary instabilities. In this study, we aim to control, manipulate, and characterize surface tension drive flows using so called photo Marangoni effect. This approach is based on the unique property of a surfactant called azobenzene trimethylammonium bromide (AzoTAB), whose tension increases subject to UV light and decreases subject to blue light. Employing this effect, an isothermal surface flow can be produced by pure surface tension effect, allowing us to investigate the behavior of capillarity with other effects effectively decoupled. Particle image velocimetry will be used to characterize the flow. Additionally, droplet manipulation in microfluidic porous media is possible with this technique. |
Tuesday, November 21, 2023 9:05AM - 9:18AM |
X41.00006: Stretching and entrainment in jet-assisted wet spinning (JAWS) Zehao Pan, Janine K Nunes, Barath Venkateswaran, Xana Keating, Howard A Stone A submerged fluid jet can entrain and accelerate surrounding fluid to a speed comparable to the jet velocity. Recently, we have used a submerged liquid jet in jet-assisted wet spinning (JAWS) to stretch a nearby pre-fiber (liquid) jet to make hydrogel fibers thinner than the diameter of the spinneret. In this work, we systematically investigated the diameter of the pre-fiber jet as a function of its flow rate and placement distance to the main submerged liquid jet. We find that the pre-fiber jet diameter scales as the square root of its flow rate when the flow rate ratio between the pre-fiber jet and main jet is small, hinting (because of mass conservation) at constant pre-fiber jet velocity after being entrained by the main jet. Deviation from the square root scaling at high pre-fiber jet flow rates is found to be related to the high flow rate ratio between the pre-fiber jet and main jet that delays entrainment by the main jet. A model based on the Landau-Squire solution to describe the main jet is used to model the different entrainment behaviors. |
Tuesday, November 21, 2023 9:18AM - 9:31AM |
X41.00007: A role for hydrophobic nanostructures in optimizing microchannel heat sinks. Lekwetje Maureen M Ramaube, Marcel M Louis, Howard A Stone, Sonya T Smith Liquid cooling integrated in microchannel heat sinks (MCHSs) is a technology that can be used for high heat flux dissipation in electronic components. The pressure drop experienced within microchannels continues to present a limitation on their application. This study investigates the impact on performance of adding hydrophobic nanostructures within MCHSs. The model used is based on a single-phase flow in a rectangular channel with a given aspect ratio. The results, employing an evaluation matrix of the microchannel performance, will be a comparison of test cases at different Reynolds numbers, with and without the nanostructures. The study will further evaluate the influence of the flow development accounting for viscosity variations when there are temperature variations. The findings of this study hold great significance as they offer insights into the design optimization and performance of microchannel-based cooling systems. |
Tuesday, November 21, 2023 9:31AM - 9:44AM |
X41.00008: Ion and Hydrodynamic Translucency in 1D van der Waals Heterostructured BN-SWCNTs Semih Cetindag, Sei Jin Park, Steven F Buchsbaum, Yongjia Zheng, Ming Liu, Shuhui Wang, Rong Xiang, Shigeo Maruyama, Francesco Fornasiero, Jerry W Shan An unresolved challenge in nanofluidics is tuning ion selectivity and hydrodynamic transport for pores with diameters larger than a nanometer. In contrast to conventional strategies that focus on changing surface functionalization or confinement degree by varying the radial dimension of the pores, we explore a new approach for manipulating ion selectivity and hydrodynamic flow enhancement by externally coating single-wall carbon nanotubes (SWCNTs) with a few layers of hexagonal boron nitride (h-BN). For the van der Waals heterostructured BN-SWCNT, we observed a 50% increase in cation selectivity for K+ versus Cl- compared to pristine SWCNTs of the same diameter, while hydrodynamic slip lengths decreased by more than an order of magnitude. These results suggest that the single-layer-graphene inner surface may be translucent to charge-regulation and hydrodynamic-slip effects arising from h-BN on the outside of the SWCNT. As a consequence, the choice of the matrix material may significantly influence the transport properties of SWCNT membranes. Such 1D heterostructured nanotubes could serve as synthetic platforms with tunable properties for exploring novel nanofluidic phenomena and their potential applications for separations, power generation, and water filtration or desalination. |
Tuesday, November 21, 2023 9:44AM - 9:57AM |
X41.00009: Evaporating meniscus in a nanochannel: comparison of continuum models and nonequilibrium molecular dynamics simulations Vladimir S Ajaev, Mustafa Ozsipahi, Ali Beskok
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Tuesday, November 21, 2023 9:57AM - 10:10AM |
X41.00010: A differentiable representation of solvent-solute interface Zhenyu Wei, Yunfei Chen The success of an implicit solvent model hinges on the accurate representation of the solvent-solute interface. However, current models primarily depend on specific geometric criteria, making the calculation of interface derivatives an arduous task. |
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