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 A18: Microscale and Nanoscale Flows: Mixing, Separation, and Non-Newtonian |
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Chair: Myung-Suk Chun, Korea Institute of Science and Technology Room: 250 B |
Sunday, November 24, 2024 8:00AM - 8:13AM |
A18.00001: Advective species separation in combined steady and unsteady flows: Taylor dispersion analysis Oles Dubrovski, Steffen Hardt, Benno Liebchen Counter flow mass transfer provides viable routes for species separation in microchannels by effectively imposing different mass transfer resistances on different species, e.g. counter flow electromigration. Here, we propose a separation technique that exploits the competition between unsteady advective flows and diffusive mass transfer. We show that this method discriminates between species having different diffusion coefficients at high Peclet number flows. A Taylor dispersion approximation reveals that two Peclet numbers appear: one based on the overall length of the channel and the other on its radius. Increasing the radial Peclet number enhances the diffusive mass transfer in the duct, which reduces selectivity, while increasing the longitudinal Peclet number enhances selectivity through advective counterflow effects. Both Peclet numbers are species-dependent, and even a modest difference in Peclet numbers introduces a significant selectivity for species separation. We perform parametric studies to identify parameter space regions that maximize species separation. |
Sunday, November 24, 2024 8:13AM - 8:26AM |
A18.00002: Microfluidic Mixing Mediated by Acoustic Streaming around Microscale Obstacles Md. Abdul Karim Miah, Md. Mohaimeen Ul-Islam, Richa Ghosh, Chandra S Tangudu, Michael Gary Olsen, Jaime J Juarez Microscale mixing is an important chemical process that facilitates reactions for biomedical diagnostics and drug development. In this work, we present the application of a microfluidic platform that utilizes acoustic streaming as a mechanism for fluid mixing. The platform features a Y-channel configuration with circular obstacles embedded within the channel. A piezoelectric transducer, driven at a frequency of 5.6 kHz and varying voltage levels (15 V – 70 V), is used to generate streaming about the circular obstacles that induce mixing within the channel. Fluorescent polystyrene particles are used to visualize the mixing process and evaluate the local flow field via microscopic particle image velocimetry (uPIV). The polystyrene particles are also used to assess the quality of the mixing process for flow rates ranging from 100 uL/hr to 400 uL/hr. The mixing process mediated by the acoustic streaming about the circular obstacles is compared to the case where the obstacles are triangular in structure. Although the triangular obstacles generate stronger vortices in comparison to the circular obstacles, we find that the circular obstacles are more efficient at mixing the fluid due to localized trapping at the triangle corners. Lastly, we introduced a polymer solution consisting of Methoxy poly(ethylene glycol)-block-poly(ε-caprolactone), a block polymer to test if the mixing process will result in flash precipitation. When an organic stream of block polymer is mixed with water under acoustic conditions, ~200 nm diameter polymer nanoparticles are created. Thus, ultimately demonstrating the applicability of this platform as a microfluidic reactor. |
Sunday, November 24, 2024 8:26AM - 8:39AM |
A18.00003: Mixing toplogy of microchannel plug flow with an Ionic Liquid, experimental and computation investigations. CHARLOTTE PHEASEY, Loïc Chagot, Omar K. Matar, Lyes Kahouadji, Panagiota Angeli Small channel contactors alongside alternative solvents such as Ionic Liquids (IL) offer a novel double process intensification for mass transfer applications. The superior mass transfer in part due to intensified mixing in a plug flow regime (Angeli & Gavriilidis, 2008). However, the comparatively high viscosities of IL are observed to alter flow hydrodynamics with potential mixing limitations (Balestra et al., 2018). Here we investigate experimentally with Bright field Particle Image Velocimetry (PIV) and three-dimensional solver that uses a high-fidelity hybrid Front-Tracking/Level-Set for treating the interface the mixing topology of an IL in small channels with increased mixture velocity. |
Sunday, November 24, 2024 8:39AM - 8:52AM |
A18.00004: Coarse Grained Modeling for Diffusion of Macromolecules in Biphasic Systems Marco T Portella, Thao X Nguyen, Dimitrios V Papavassiliou Bicontinuous Interfacially Jammed Emulsion Gels (Bijels) are biphasic structures with potential applications in catalysis, separation processes, and tissue engineering.1 Here we use Dissipative Particle Dynamics (DPD) simulations via the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS)2,3 to explore macromolecule transport within Bijel structures. Our system consists of two immiscible fluid phases, water and diethyl phthalate, stabilized by neutrally wetting nanoparticles. To validate our results, we model macromolecules by incorporating intra-bead interaction potentials, focusing on conformational characteristics like the radius of gyration. Machine learning regression models are employed to predict the final conformation based on the DPD model parameters. Dynamic phenomena, including macromolecule diffusivity in both water and oil phases, are investigated. A protocol is developed to enhance the reliability and consistency of DPD computations. The dependence of diffusivity on viscous effects is examined using the Stokes-Einstein analogy, validating our studies. Ultimately, our model investigates the migratory behavior of hydrophilic compounds from the oil phase to the water phase, providing insights essential for optimizing Bijel-based processes. |
Sunday, November 24, 2024 8:52AM - 9:05AM |
A18.00005: Thermally Driven Flows for Species Separation in a Microcavity Ali Lotfian, Ehsan Roohi
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Sunday, November 24, 2024 9:05AM - 9:18AM |
A18.00006: Adapting Taylor Dispersion to Measure the Enhanced Diffusion Coefficient of Multispecies Electrolyte Solutions at the Microfluidic Scale James M Teague, Lingyun Ding, Francesca Bernardi Microfluidics applications in fields like biomedical engineering and chemistry have become increasingly prominent as they allow for rapid and precise studies, such as synthesizing compounds and separating mixtures. We developed an accessible and repeatable experimental method that adapts the Taylor Dispersion experiment to the microscale and used it to quantify the enhanced diffusivity of a passive single-species solute undergoing shear flow. Our protocol accurately measures the enhanced diffusivity and leverages it to compute the diffusion coefficient of single-species passive tracers while changing experimental parameters. We have since extended our experimental procedure to characterize the influence of multispecies electrolyte solutions on the enhanced diffusivity of the system. In these solutions, the electric current is carried by the dissolved ions. The electric field exerts significant body forces on the ions, affecting their fluxes and enhancing the diffusion coefficient. These interactions and consequent separation of ion species and their effects on each ion's enhanced diffusivity are observed and compared to theoretical predictions. Current challenges and potential future directions will be discussed. |
Sunday, November 24, 2024 9:18AM - 9:31AM |
A18.00007: ABSTRACT WITHDRAWN
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Sunday, November 24, 2024 9:31AM - 9:44AM |
A18.00008: ABSTRACT WITHDRAWN
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