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 A23: Experimental Techniques: Multiphase / Microscale Flows |
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Chair: Akihito Kiyama, Saitama University Room: 251 A |
Sunday, November 24, 2024 8:00AM - 8:13AM |
A23.00001: Total internal reflection fluorescence microscopy for visualizing the bottom layer of an evaporating sessile droplet. Wonho Cho, Jinkee Lee Total internal reflection fluorescence (TIRF) microscopy, unlike epifluorescence (EPI) microscopy which captures fluorescence from the entire depth of a sample, selectively visualizes only a single layer of it. TIRF achieves this by the generation of a thin evanescent field near the sample-substrate interface by total internal reflection of laser light. Conventional TIRF systems are designed with a substrate placed above the sample, making the total internal reflection occur at the upper interface of the sample. However, this design of TIRF is unsuitable for imaging sessile droplet samples, where the substrate is placed beneath the droplet. To overcome this limitation, we developed a TIRF system specifically optimized for sessile droplet imaging. Our design includes a prism, slide glass, air slit, and optical trap to create the TIRF effect. We calculated the proper light path through the prism-based TIRF system and used an optical trap to eliminate uncertainties. We then conducted a comparative analysis between TIRF and EPI microscopy by imaging the bottom layer of sessile droplets with fluorescent particles during the evaporation. Our research demonstrated that TIRF provides distinct visualization of particle sedimentation sequence and resultant drying pattern at the bottom of the sessile droplet. |
Sunday, November 24, 2024 8:13AM - 8:26AM |
A23.00002: Towards quantum-enhanced flow sensing methods using nitrogen-vacancy (NV) centers in diamond Matthew K Fu, John O. Dabiri Nitrogen-vacancy (NV) centers have garnered significant interest in the past decade as a versatile nanoscale, quantum-based sensing platform. These vacancies are point defects within a diamond lattice whose electron spin-states are highly sensitive to external perturbations, including temperature, strain, and magnetic and electric fields. NV center-based sensors function by monitoring changes to the spin-states in either an individual or ensemble of NV centers to deduce information about the parameter of interest. Because the spin state can be optically manipulated and read out at room temperature, NV center-based diagnostics are becoming an increasingly accessible option for nanoscale sensing across various applications and conditions. Despite the rapid development and proliferation of NV center-based sensing protocols, the fluid mechanics community has yet to fully utilize these emerging capabilities. Here, we discuss the promising outlook for applying this technology to problems in fluid mechanics and the sensing protocols that can be used to access fluid measurements at the nanoscale. We will also present our recent progress toward demonstrating a quantum-enhanced sensing platform for decoherence-based measurements of near-wall flow. |
Sunday, November 24, 2024 8:26AM - 8:39AM |
A23.00003: Viscosity imaging by fluorescent molecular rotor for polymer-solution flow around microstructures Yoshiyasu Ichikawa, Jun-Ying Yang, Masahiro Motosuke To understand the complex behavior of polymer solution flow and biological flow, such as blood flow, it is important to quantify the shear viscosity distribution that changes with the shear rate in a flow channel. In this study, we focused on 9-(2,2-dycyanovinyl)julolidine (DCVJ), a fluorescent molecular rotor that shows the variation in the fluorescent intensity depending on the viscosity. This study aims to demonstrate the efficiency of DCVJ for imaging the shear viscosity distribution of viscoelastic fluids. |
Sunday, November 24, 2024 8:39AM - 8:52AM |
A23.00004: Quantifying dissolution and biodegradation of oil droplets in flows by microfluidics and digital holographic microscopic interferometry (DHMI) Abdessamad Talioua, Samuel Kok Suen Cheng, Maryam Jalali-Mousavi, Chen Xu, Peter Santschi, Wei Xu, Jian Sheng The degradation of crude oil droplets in aquatic ecosystems is crucial process, particularly following major oil spills. Despite extensive research, understanding the mechanisms of degradation such as dissolution and microbial consumption as well as their rates remains challenging due to methodological limitations and study inconsistencies. Our study introduces an advanced methodology using an ecology-on-a-chip (eChip) microfluidic platform combined with DHMI to precisely evaluate the oil droplet degradation. The eChip replicates real-word hydrodynamic conditions, while DHMI provides high-resolution measurements of 3D droplet volume changes over relevant time scales (>weeks) with high precision. Our technique enables real-time evaluation of volume changes at a temporal resolution of 4 frames per minute (fpm) and spatial resolution of 7.4nm. Arrays of immobilized oil droplets are printed onto a substrate and placed in the eChip, with volume quantified directly using DHMI. The results demonstrate the capability of providing detailed insights into oil droplet degradation processes in realistic hydrodynamic and microbial environments. |
Sunday, November 24, 2024 8:52AM - 9:05AM |
A23.00005: Simultaneous flow stress and strain measurement of bacteria streamer by micro-tensiometer and digital holographic microscopy Wenjun Yi, Kok Suen Cheng, Jian Sheng The formation of biofilms allows them to survive environmental insults and colonize various surfaces. Many prior studies have focused on the formation process of biofilm under various conditions, while the understanding of biofilm rheology is less known due to the lack of suitable experiment tools to allow in-situ growth of streamers and measure fluid shear around it. In this study, we present an experimental technique that integrates a micro-pillar microfluidic platform with digital holographic microscopy (DHM) to enable simultaneous measurements of instantaneous streamer strains and flow shear stresses around it. The micro-pillar microfluidic platform allows the in-situ growth of biofilm streamers under various flow conditions, while DHM records the deformation of in-situ biofilm streamers under shear stresses and simultaneously tracks thousands of particles individually in 3D to resolve stresses over deforming streamers during a creep-recovery test. Pseudomonas fluorescens is used as a model in the current experiments. Various flow rates are employed in the current study to investigate the rheology adaptation of biofilm streamers developed to distinct hydrodynamic conditions. |
Sunday, November 24, 2024 9:05AM - 9:18AM |
A23.00006: Optical Kerr Effect Gated Imaging of High Void Fraction Bubbly Flows Daniel Andrew Hunter, Philippe M Bardet, Charles Fort High void-fraction bubbly flows are highly probable in natural and man-made environments; hence, they are of critical importance in mass and energy transfer between phases. Despite this importance, physical and experimental data with high void fractions is limited, with significant scatter in data leading to a dependence on empirical models. This lack of data results from increased optical thickness and scattering, limiting the ability to measure the bubble size distribution spectra, the most critical parameter with bubbly flows. With significant scattering and occlusion, spatial and geometric information is lost, producing a white appearance readily visible in white caps. Due to the difference in refractive index, however, a measure of the speed of light, there is a time delay between the arrival of unscattered light and scattered photons. Capturing only the initial photons will recover information lost through scattering. |
Sunday, November 24, 2024 9:18AM - 9:31AM |
A23.00007: Performance Characteristics of a Limited Angle High Speed X-ray Tomography Systems for Optically Opaque Multiphase Flows Nicholas A Lucido, Harish Ganesh, Steven Louis Ceccio Obtaining direct measurements of volume fraction fields is essential for understanding complex multiphase flows and validating computational models. X-ray-based methods, including densitometry (2-D) and tomography (3-D), facilitate direct, non-intrusive volume fraction measurement irrespective of opacity. However, high-speed applications pose significant challenges and the use of standard traditional systems is not feasible. A high-speed, limited-angle Scanning Electron Beam X-ray Tomography (SEB-XT) system has been developed and tested at the University of Michigan (UM). The UM SEB-XT system has been demonstrated to be capable of measuring volume fractions fields at a rate of 600 images per second. System performance has been characterized using both static and dynamic testing targets as well as a bubble column. Key factors impacting image quality and resolution are discussed. |
Sunday, November 24, 2024 9:31AM - 9:44AM |
A23.00008: Uncertainty reduction of unsteady drag coefficient measurements for monodispersed micronsized particles Adam A Martinez, Kyle Hughes, Antonio B Martinez, Isaiah Wall, John J Charonko, Alexander M Ames, Tiffany R Desjardins The Los Alamos National Laboratory Horizontal Shock Tube (HST) studies response of shock-accelerated particles in a gas. When subjected to the highly unsteady flow of a shock, normal drag coefficients may not properly predict the motion of the particles. These experiments were done as a part of an ongoing campaign to improve drag laws in this regime and are performed in conjunction with computational efforts. Individual particle positions were obtained using a high speed eight-pulse particle tracking technique. Solid particles of several nominal diameters selected from the range of 1-10 μm were subjected to 1.2, 1.3, and 1.4 Mach number shocks in air. The nominal particle diameter was obtained from vendor specifications and physical measurement of the size distribution before injection into the shock tube. These particles had diameter standard deviations < 1 μm, as compared to previous work with distributions larger than +/- 1-2 μm. We will demonstrate how control of the particle diameter uncertainty reduce the bias in the computed drag coefficients. As a result, we see a reduction in estimated drag as compared to previous measurements with polydispersed diameter distributions. This can be attributed to reduction in uncertainty and systematic error. |
Sunday, November 24, 2024 9:44AM - 9:57AM |
A23.00009: Experimental Analysis of Reduction Bubble Size in Subsea Gas Leakage Using Mechanical Dispersion Aníbal Alexandre Campos Bonilla, Luiz Adolfo Hegele Júnior, Edvan Seiki, Ana Júlia da Silva, Max Pacheco Subsea pipelines are fundamental to the development and production systems of offshore oil and gas fields. Subsea gas leakage is a catastrophic event in the energy sector, presenting a profoundly detrimental issue with numerous environmental consequences. If the leakage is not promptly addressed, toxic chemical compounds can quickly reach the sea surface, causing extensive damage. Gas leakage can be mitigated using burning, chemical or mechanical dispersion methods. Dispersion involves applying chemicals or water jets to break gas bubbles into smaller ones, reducing their upward speed and enhancing their biodegradation, allowing the ecosystem to eventually consume them completely. This paper addresses the behavior of reduced air bubbles, described by the two-dimensional space spanned by the Weber and Ohnesorge numbers, as a function of mechanical dispersion, using a freshwater jet, characteristics like flow rate and nozzle diameter. An experimental testbed was constructed to obtain data with different water jet configurations. Meaningful relationships were identified between reduced bubble behavior and water jet characteristics, which are useful for designing effective dispersion methods to mitigate subsea gas leakage. |
Sunday, November 24, 2024 9:57AM - 10:10AM |
A23.00010: Abstract Withdrawn |
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