Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session ZC37: Particle-Laden Flows: General and Experimental Techniques |
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Chair: Ignazio Maria Viola, University of Edinburgh Room: 203AB |
Tuesday, November 21, 2023 12:50PM - 1:03PM |
ZC37.00001: Abstract Withdrawn
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Tuesday, November 21, 2023 1:03PM - 1:16PM |
ZC37.00002: Settling dynamics of vertically aligned particles in single and two-layer fluid media Soohyeon Kang, Liu Hong, Shyuan Cheng, Jim Best, Leonardo P. Chamorro Settling dynamics of vertically aligned particles was examined in single and two-layer fluid media. Water, ethanol, water-glycerin mixture, and oil were considered for the single fluid media, while the two-layer fluids were composed of ethanol and oil, with the upper layer thickness varying from 40 mm to 160 mm. Experiments were performed in a 600 mm height tank using approximately 800 spherical glass particles of 4 mm diameter and 2200 kg/m3 density, released at frequencies fp = 4, 6, and 8 Hz. The single fluid media particles exhibited two general trajectories. At high Galileo number (Ga) in water and ethanol, particles showed preferential in-plane motions, while at low Ga in water-glycerin mixture and oil, they showed nearly vertical paths. However, particles in the lower part of the two-layer fluids near the interface showed lateral dispersions depending on the upper layer thickness, even at low Ga. For all single fluid media, particles showed higher settling velocities than a single particle while experiencing reduced drag. The drag reduction was enhanced when the particle separation was close. However, particles settled slower in the lower part of the two-layer fluids due to the additional buoyancy caused by the entrained lighter fluid from the upper layer. Drag reduction due to the leading particles became less significant as the particles no longer maintained their straight path seen in the single oil medium. An analysis of the particle pair dispersion showed its dependence on Ga and initial separation. |
Tuesday, November 21, 2023 1:16PM - 1:29PM |
ZC37.00003: A Statistical Evaluation of the Various Parameters Governing the Assembly of Solution-Based Nanoparticles on Polymer Substrates Bchara Sidnawi, Liang Zhao, Siyu Chen, Bo Li, Qianhong Wu Particle assembly on soft substrates has widely encountered applications in flexible optical and electronic systems. In this study, the various factors affecting nanoparticle deposition on a flexible substrate are examined experimentally. A PDMS substrate is prepared and mounted on the free end of a crank-slider mechanism whose settings determine the substrate's speed and position history as it is periodically immersed in and withdrawn from an aqueous solution of Silicon Dioxide (SiO2) nanoparticles. Different particle sizes and solution concentrations are used. At 7 time points within the 15-minute duration for each run, 12 square regions on the substrate are scanned at a high resolution with an optical microscope. Each square is then divided into a grid of 10x10 tiles that are individually analyzed for particle coverage. The resulting coverage data is aggregated and the effects of the particle size, concentration, and substrate's local assembly time, were statistically evaluated. The goal of this data-driven study is to infer the optimal combination of parameter settings that would yield the fastest and highest coverage performance under different constraints. Physical interpretations of the results are later proposed and discussed. |
Tuesday, November 21, 2023 1:29PM - 1:42PM |
ZC37.00004: Plumes of settling and dissolving sugar grains as a model of snow-driven flows in the lab Quentin Kriaa, Benjamin Favier, Michael Le Bars We present a laboratory analog to model snow-driven flows in planetary interiors that are driven by the settling and remelting of snow flakes in a lighter ambient fluid. Our experiments consist in settling and dissolving sugar grains that are continuously sieved above water with various mass fluxes and grain sizes. Through drag and dissolution, these particles force a central plume whose inner structure is analysed in a laser sheet thanks to PIV and the use of home-made fluorescent sugar to track the negatively buoyant sugary water through LIF. The size of grains controls a wealth of behaviours, from a laminar plume that gains intensity over a long transient when forced by the rectilinear fall of large grains, to a turbulent lazy plume that emerges faster when forced by fast-dissolving small grains. This transition is determined by the enhanced forcing imposed by smaller grains, and their ability to nourish a Rayleigh-Taylor-like instability at the plume onset. The two-way interaction between settling and dilution of the buoyant material through advection controls the quasi-steady plume velocity, as well as the maximum depth of dissolution of sugar grains. |
Tuesday, November 21, 2023 1:42PM - 1:55PM |
ZC37.00005: Concentration measurements in dense ejecta clouds using millimeter-wave radar tomography. Nicolas Rasmont, Hussein Al-Rashdan, Joshua Rovey, Gregory Elliott, Laura Villafane The impingement of a high-speed jet on a granular surface leads to surface erosion and the entrainment of particles into a dense ejecta cloud. Plume surface interactions (PSI) have far-reaching implications for the safety of future manned missions to the Moon and Mars. Experimental measurements of ejecta properties are necessary to improve PSI predictive models, but are hindered by excessive attenuation at visible wavelengths. |
Tuesday, November 21, 2023 1:55PM - 2:08PM |
ZC37.00006: Settling dynamics of thermally active particles Erika MacDonald, Erika MacDonald, Nicholas Ouellette Spotting is a wildfire spread mechanism in which small pieces of burning material, known as firebrands, travel long distances and start new fires. Many factors play a role in where these firebrands travel, but the effect of the firebrand’s generated buoyancy is often overlooked. The presence of the generated buoyancy may significantly alter the dynamics of firebrand settling, leading to improper estimates of the distance they can travel before falling to the ground. To gain a fundamental understanding of how buoyancy from internal heat sources affects particle settling, we designed an experimental system to measure the behavior of settling heated particles. We report initial results from these experiments. |
Tuesday, November 21, 2023 2:08PM - 2:21PM |
ZC37.00007: Dynamics states of particle aggregates in a forced fluid in microgravity Natalie V Frank, Karl Cardin, Facundo Cabrera-Booman, Raúl Bayoán B Cal Pollen deposition, paleoecology, algae growth linked to water quality, plastic pollution, and storm transported sea salt in bodies of water are at first examples of particles in fluid-gas interfaces. After a certain time, when and if particles sediment, the dynamics change and the involved processes can become those of a fluid-saturated granular media. Of particular interest are externally vibrated particle-laden fluids that are used to segregate different particle sizes and materials, or to fluidize the granular material and thus improve its flow characteristics such as particulate transport. Drop tower experiments at Portland State University are performed to quantifying transient dynamics of particles in an interface in the absence of gravity. These experiments serve as a steppingstone for launching containers to space aboard the ISS to access longer periods of microgravity. Results have the potential to be an important step forward towards the understanding of aggregation of particles in a gas/fluid interface where times scales are relatively large and the effects are relatively small on Earth. |
Tuesday, November 21, 2023 2:21PM - 2:34PM |
ZC37.00008: A detailed understanding of small particle deposition process Sanaz Abbasi, Amirfarhang Mehdizadeh The process of dispersion and deposition of particles in wall-bounded turbulent flows is a fundamental issue in many emerging and conventional industries. However, its complexity poses a serious problem which cannot be completely addressed. Therefore, it is important to understand the mechanisms of this phenomenon to help reduce its negative economical and environmental effects. Here, we study particle dispersion and deposition in a fully developed turbulent channel flow at a friction Reynolds number of Reτ = 180 using the point particle-direct numerical simulation (PP--DNS) method, considering a dilute system. Particulary, we investigate the interplay between particle properties (diameter and density) and deposition dynamics such that different combination of settings lead to the same Stokes number. Additionally, effects of gravity and lift on the deposition process is thoroughly studied. |
Tuesday, November 21, 2023 2:34PM - 2:47PM |
ZC37.00009: Bio-inspired hydrogel-coated air filter for particulate matter removal Jeongju Kim, Sang Joon Lee The interest of humanity in particulate matter (PM) is significantly increasing. Also, PM causes various cardiovascular and respiratory diseases. For this reason, various studies have been conducted to reduce PM concentration. Among them, Tillandsia Usneoides known as one of air plants was studied for its effectiveness in reducing PM due to its surface structure (trichome). In this study, the performance of a nature-inspired filter mimicking Tillandsia was quantitatively analyzed. This mesh filter coated with alginate hydrogel was fabricated based on Landau-Levich equation for fluid coating on wires. The filter was placed in a test chamber and a wind tunnel representing indoor space considering with and without airflow. Therefore, we measured variation in PM concentration and pressure drop by the filter to observe PM removal effect of the hydrogel-coated air filter, and also investigated the effect of the wire diameter of the filter and airflow rate on PM removal efficiency through this experimentation. |
Tuesday, November 21, 2023 2:47PM - 3:00PM |
ZC37.00010: Simultaneous High-Speed PIV-PTV Study Of Gas-Solid Suspension Flow in a Horizontal Channel Abhimanyu Dubey, Prof. Manaswita Bose, Viswanathan Kumaran Pneumatic transport of solids is a vital industrial process involving the suspension of solid particles in a gas flow conveyed through conduits in a turbulent flow. Understanding the transition between two flow regimes - homogeneous suspension and settling flow - is crucial for efficient pneumatic transport. In particle-laden turbulent flows, an intricate interplay between particle dynamics, fluid turbulence, and inter-particle interactions determines the efficiency of pneumatic transport processes. Turbulence modulation plays a critical role, with large particles intensifying turbulent fluctuations and small particles attenuating turbulence. In order to examine the connection between turbulence modulation and particle dynamics, our research utilises high-speed PIV and PTV techniques to study turbulence modulation in dilute to moderately dilute gas-solid suspensions within a horizontal channel. The experimental setup features a glass channel for optical access, allowing clear visualisation of particle behaviour. Cross-validation with PIVLab and TSI Insight 4G ensures data reliability. Investigations extend to semi-dilute regimes, where the mean and root mean square velocities for the particle and gas phase are measured and compared with simulations. This is used to obtain criteria for homogeneous and settling flows and the transitions between the two. In conclusion, this comprehensive study offers valuable insights into particle-laden turbulent flows during pneumatic transport, contributing to advancing experimental fluid mechanics and practical applications in diverse industrial sectors. |
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