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 X22: Particle-Laden Flows: Numerical and Experimental Techniques |
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Chair: Manhar Dhanak, Florida Atlantic University Room: 250 F |
Tuesday, November 26, 2024 8:00AM - 8:13AM |
X22.00001: Spatially Resolved Measurement of Triboelectric Charging in Turbulent Particle-Laden Flows Wenchao Xu, Holger Grosshans Triboelectrification in pneumatic conveyors leads to particle charging, which can alter flow patterns, influence particle trajectories, and potentially cause hazards like spark discharges. Existing charge measurement methods lack the ability to provide detailed charge distribution information necessary for a comprehensive understanding of triboelectric charging in turbulent flows and for validating numerical simulations. |
Tuesday, November 26, 2024 8:13AM - 8:26AM |
X22.00002: Early Simulations of a Reacting Metal Ejecta Particle in Still Gas Ryan Jozef Myers, Frederick Ouellet, Jonathan D Regele, Jacob A McFarland Metal ejecta particles are an important part of studying shocked materials. Ejecta particles are created when a shock travels through a perturbed material interface, creating molten metal drops which are released from the surface as a limiting case of the Richtmyer-Meshkov instability. For our study, we focus on metal ejecta transporting in a chemically reactive fluid. The physical consequences of this process, such as mass transfer, energy release, and particle deformation, are still being accounted for and are an active area of research. To study these phenomena, we have simplified the case to focus on a single ejecta particle interacting with a reactive ambient gas. Using a reaction mechanism made for a Lagrangian multi-physics hydrocode, we analyze how the reaction affects the ejecta particle. The varying effects of the gas diffusion rate, exothermic heat release and possible material deformation are analyzed using 2D simulations. We also consider the stress development in the shell and how it aligns with the analytic solution for a thin shell sphere. Future work on placing the particle in a dynamic flow field, and important considerations for the particle's life span, will be discussed. |
Tuesday, November 26, 2024 8:26AM - 8:39AM |
X22.00003: Investigation of Particle Dynamics in a Low-Pressure Cold Spray Additive Manufacturing Process Bikash Mahato, Jay Yoder, Gloyd Simmons, Nathan Huft, Isaac Nault, Peter Lucon Cold spray (CS) additive manufacturing is a solid-state deposition process for repairing and fabricating components in aerospace, medical, and other critical fields. It uses converging-diverging (CD) nozzles to accelerate particles to high velocities, depositing them onto a substrate. This study investigates the particle dynamics in a low-pressure CS system. Lower particle velocity in low-pressure CS systems generally leads to poor quality deposits. Reduced drag on the particles within the boundary layer results in non-uniform and slower particle velocities, thereby lowering the deposition quality. Proper mixing of the particles, facilitated by turbulence inside the nozzle, can address this challenge. A large-eddy simulation model combined with a discrete phase model (DPM) is used to perform the flow and particle simulations. An improved particle drag model has been developed and is used to track the dynamics of irregularly shaped particles in the flow stream. Simultaneously, measurements are conducted in an in-house developed cold spray research facility. Results show that flow turbulence significantly increases particle dispersion for this particular system. |
Tuesday, November 26, 2024 8:39AM - 8:52AM |
X22.00004: Colloidal Assembly of Electrosprayed Particles at a Static Water-Air Interface Joseph Mario Prisaznuk, Xin Yong, Peter Huang, Paul Chiarot In electrospray deposition, materials dispersed in a solvent are delivered to a substrate, driven by an electric potential. The high voltage source imparts a net electric charge on suspended colloids, which dissipates over long time scales for insulative materials. Particles delivered to a water-air interface via electrospray repel each other due to the charge, and self-assemble depending on the properties of the substrate. Here, we show that the assembly of electrosprayed colloidal materials at a static interface is governed by two parameters: the dissipation of electric charge over time, and the conductivity of the fluid phase. To observe the assembly over an arbitrary length of time, we use a 3D printed fluidic device with integrated water channels to continuously compensate for evaporation. The conductivity of the water was modulated by adding salt to achieve concentrations of ~0, 1, and 5 mM NaCl. We found that the lowest conductivity case exhibited a "frozen" assembly, where relative motion between particles was very limited. However, for the 5 mM salt experiment particles reorganized into a near-hexagonal structure to minimize their interaction energy. We attribute these findings to the capacity of the water-air interface to maintain a static charge for the low conductivity case, which screens electrostatic repulsion between the particles. This result highlights the significance of surface charge in the electrospray deposition process. |
Tuesday, November 26, 2024 8:52AM - 9:05AM |
X22.00005: Influence of the particle trajectory patterns on the heat transfer efficiency in the finite-size particle-laden thermal convection Jie Shen, Kairzhan Karzhaubayev, Lian-Ping Wang Particle-laden thermal convection exists in a variety of natural phenomena and engineering applications. Compared to the single-phase thermal convection flows, particle-laden thermal convection flow involves more governing parameters, and the alteration of thermal transport by the presence of solid particles is still not well understood. In this work, three-dimensional Rayleigh-Bénard convection in a half cubic cell laden with finite-size solid particles is simulated. Two-way momentum and thermal couplings between the particulate phase and the carrier fluid are considered in the simulations. The flow Rayleigh number is fixed at 107, and the particle volume fraction is varied from 1% to 9%. For small to moderate particle volume fraction, the increase of particle volume fraction is found to augment the heat transfer efficiency of the system, due to the enhanced heat transport carried by the solid particles. The simulation results reveal four typical particle transport modes: the large-scale circulation, vertical/horizontal spiral motion, small-scale circulation, and the trapped motion. The enhanced heat transport by solid particles is found to be mainly associated with the larger-scale circulation and vertical spiral motion of the particles. |
Tuesday, November 26, 2024 9:05AM - 9:18AM |
X22.00006: Experimental methodology and uncertainty quantification on full-body rotation measurements of micro-sized curved fibers in turbulence Giuseppe Caridi, Vlad Giurgiu, Marco De Paoli, Alfredo Soldati This work details the principles of a novel technique for measuring full-body rotation coupled with Lagrangian tracking of anisotropic micro-sized fibers. This method leverages the fiber's geometric anisotropy: its tapered shape enables the measurement of tumbling, while its curvature allows for the quantification of spinning. Existing literature provides comprehensive insights into Lagrangian tracking for estimating point-wise variables such as velocities and acceleration. However, there is a noticeable gap in guidelines pertaining to gyro-tracking, specifically the tumbling and spinning along fiber trajectories. |
Tuesday, November 26, 2024 9:18AM - 9:31AM |
X22.00007: Volume fraction gradient effects in compressible particle-laden flow Magnus Vartdal, Andreas N Osnes, Suhas Jain The effect of volume fraction gradients in compressible particle-laden flow is investigated using data from particle-resolved simulations of flows through random beds of fixed particles. Accurate prediction of particle forces is essential for simulations of engineering systems such as pneumatic conveying, fluidized beds and more. The results of the present study shows that the forces on the particles can be predicted reasonably well by a drag law developed for homogeneous flow conditions; however, a systematic underprediction with steepening volume fraction gradient is observed. This indicates that particle gradient effects should be accounted for in the drag law to obtain more accurate results. Sharper volume fraction gradients also result in increasing pseudo turbulent stress contributions in the momentum balances. Nevertheless, the overall direct contribution of the pseudo turbulence remains small for the cases considered here. |
Tuesday, November 26, 2024 9:31AM - 9:44AM |
X22.00008: Erosion dynamics of particle laden thin film flows over a granular block Claudia Falcon, Isaias Bahena, Jacob Riley Kathman, Lane Ellisor, Penelope Jiang, Joyce Lin The processes of erosion, deposition, and transportation of particles in a viscous shear flow are crucial for understanding landslides, oil spills in coastal areas, coral reef health, and wastewater treatment. This work presents an experimental study of particle-laden flows over granular blocks. We gathered spatial-temporal data under varying physical parameters to measure erosion rates, speeds, and particle concentrations.We describe a technique combining image processing template matching and particle image velocimetry to determine particle concentration. The results provide insights into a bifurcation of erosion rates affected by critial initial particle volume fractions. Finally, we compared our experimental findings with theoretical predictions using a lubrication model for gravity-driven thin-film flow of viscous fluid and suspended particles. |
Tuesday, November 26, 2024 9:44AM - 9:57AM |
X22.00009: Pseudo-turbulence in steady state flows through random particle suspensions at finite Mach number. Andreas Nygård Osnes, Magnus Vartdal Pseudo-turbulent fluctuations are an inherent part of flow through particle clouds. Meso-scale models, both Eulerian-Eulerian and Eulerian-Lagrangian formulations, require modeling of the pseudo-turbulence. Pseudo-turbulence is also linked to the variation in drag and lift forces in particle suspensions. Therefore, advanced modeling of particle forces can benefit greatly from a better understanding of the pseudo-turbulence. In this work, we analyze the pseudo-turbulence in steady state flows through particle clouds at finite Mach numbers, based on data obtained from particle resolved simulations. We examine the pseudo-turbulent kinetic energy, its anisotropy, and the various unresolved terms in the volume-averaged compressible Navier-Stokes equations. We compare the data to existing models for pseudo-turbulence in incompressible flows and propose extensions to account for the effects of compressibilty. |
Tuesday, November 26, 2024 9:57AM - 10:10AM |
X22.00010: Abstract Withdrawn
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Tuesday, November 26, 2024 10:10AM - 10:23AM |
X22.00011: Modeling contaminant spread in the wake of moving notional geometries Autumn N Weber, Michael J Hargather Particles are released and deposited behind moving objects as they move through an environment due to their trailing wake. These deposited particles create contamination fields in an environment. For human exploration of pristine environments, mapping this contamination spread provides a way to understand and characterize human impact. This work aims to create an experiment-informed, scalable model that maps the particle setting from these trailing wakes, characterizing the contamination spread in various environments and atmospheric conditions. Preliminary small-scale testing utilized an airbrush as a notional contamination source to emit paint droplets, which settled onto the surface below in a characteristic pattern. Moving source experiments were conducted to determine the effect of complex wake profiles on the deposition pattern in comparison to stationary source experiments. Image process techniques determined the paint deposition pattern under different experimental conditions, creating paint concentration graphs. These graphs were nondimensionalized using key known nondimensional numbers identified with Buckingham Pi Theorem. |
Tuesday, November 26, 2024 10:23AM - 10:36AM |
X22.00012: Testing Efficacies of Facial Masks in Mitigating Transmission of Aerosolized Droplets Emitted During a Cough Manhar R Dhanak, John Frankenfield, Siddhartha Verma, Lee Portnoff
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