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 L22: Particle-Laden Flows: Particle-Turbulence Interactions for General Applications |
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Chair: Sanaz Abbasi, University of Missouri - Kansas City Room: 250 F |
Monday, November 25, 2024 8:00AM - 8:13AM |
L22.00001: Segregation of charged bidispersed particles and generation of intermittent electric fields in turbulence Xuan Ruan, Matt T Gorman, Rui Ni From striking lightning in the electrified clouds to tribocharged dust particles in the sandstorm, turbulent flows laden with charged particles are prevalent in a wide range of natural phenomena and industrial applications. However, the effects of electrostatic interaction on charged particle behavior in turbulence remains less understood, and the connection between the resulting electric fields and the turbulent structures is also unclear. To address this issue, we conduct experimental investigations in homogeneous isotropic turbulence seeded with bidispersed particles carrying opposite charges. Instantaneous particle locations are accurately captured using Lagrangian particle tracking (LPT) allowing us to directly measure turbulence-driven segregation of bidispersed particles with and without electric charges. Based on the datasets, the dependence of size segregation on the competition between the electrostatic forces and the particle-turbulence interactions is further characterized. Finally, by assigning a known charge to each particle, the three-dimensional electric fields are reconstructed, and their statistics are discussed providing insights into the intrinsic relationship between intermittent electric field and turbulent coherent structures. |
Monday, November 25, 2024 8:13AM - 8:26AM |
L22.00002: Abstract Withdrawn
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Monday, November 25, 2024 8:26AM - 8:39AM |
L22.00003: Integral quantification of heat transfer in a particle-laden shearless turbulent flow Hamid Reza Zandi Pour, Perry L Johnson, Michele Iovieno Understanding thermal mixing in turbulent flows laden with inertial particles is crucial for various industrial and natural applications. Recent studies have identified inertia, thermal inertia, turbulence characteristics, and mixing dynamics as key factors influencing this process. Our study aims to elucidate heat transfer between two homothermal regions, where fluid temperature is passively advected by a homogeneous and isotropic turbulent flow, seeded by heavy particles with a finite thermal capacity. Direct numerical simulations (DNS) reveal a substantial enhancement in heat flux, resulting in a thermal mixing layer evolving in a quasi-self-similar manner. |
Monday, November 25, 2024 8:39AM - 8:52AM |
L22.00004: Particle deposition in a high temperature fully developed turbulent channel flow Miguel X. X Diaz-Lopez, Bingkai Chen, Rui Ni Deposition of particles through turbulent boundary layers onto external surfaces is infamous for its catastrophic effects in spacecraft landings, jet engine deposition, and more. To reproduce a relevant environment for these extreme conditions, a high temperature 2D fully developed channel was constructed to focus on the temperature effects in particle deposition. The temperature of the facility is systematically varied between the glass-transition point ([endif]-->) and melting point ([endif]-->) of the soda-lime glass beads used for these experiments. The Lagrangian trajectories of these particles as they approach and collied with the wall were acquired using a particle tracking algorithm. The deposition pattern was measured using a Digital Image Project technique (DIP), which obtained the time-resolved evolution of the topography of deposition. The final deposition composition is provided by a micro-CT scanner, which allows us to determine the deformation of softened particles as they collide with one another. The results from this facility will provide valuable data that will lead to a better understanding of particle-turbulence interactions and how temperature changes the deposition pattern and growth by affecting the particle sticking probability. |
Monday, November 25, 2024 8:52AM - 9:05AM |
L22.00005: A Computational Study on the correlation between flow characteristics and particle deposition Sanaz Abbasi, AMIRFARHANG MEHDIZADEH The complexity of the mechanism of particle dispersion and deposition in wall-bounded turbulent flows is a fundamental issue and it is crucial to get familiar with different aspects of it. Therefore, understanding of this phenomenon could help reduce its negative economical and environmental effects. |
Monday, November 25, 2024 9:05AM - 9:18AM |
L22.00006: Transport of Inertial Droplets in a Turbulent Boundary Layer Martin Aleksandrov Erinin, Stephane Perrard, Luc Deike The horizontal transport of inertial droplets in the presence of a turbulent boundary layer is studied experimentally in a wind tunnel. Water droplets with a wide range of initial conditions (diameter, speed, and injection angle) are injected into the boundary layer at free-stream velocities ranging from U∞ = 2.4 to 6.6 m/s with a boundary layer thickness ranging from δ = 11.4 to 12.5 cm. The number, size, and speed of droplets is measured using a cinematic in-line holographic system operating at 1250 Hz and positioned 162 cm downstream of the nozzle at several wall-normal locations, approximately coverning the thickness of the boundary layer. Using the experimental data, the dominant transport mechanisms for droplets are evaluated. The dominant transport mechanism for high Stokes number droplets (Stη >> 1) is inertia, where the initial conditions of these droplets plays a key role in determining their likelihood of transport. In contrast, the dominant transport mechanism for low Stokes number droplets (Stη << 1) is found to be droplet interactions with turbulence. A ballistic transport model which includes the effects of droplet inertia and a turbulence is presented to predict the probability of droplet transport. |
Monday, November 25, 2024 9:18AM - 9:31AM |
L22.00007: Slip velocity statistics of settling inertial particles in wall bounded turbulence Andrew P Grace, Tim Berk, Andrew D Bragg, David H Richter In studies of the dispersion of large particles (such as coarse dust grains) in the atmospheric surface layer, knowledge of both the mean and fluctuating components of the turbulent drag (through the particle slip velocity) is key. In this work, we will highlight results from a series of coupled Eulerian-Lagrangian direct numerical simulations of wall bounded turbulent flows, wherein we identify the dominant mechanisms controlling the slip velocity variance. We utilize a statistical framework to derive continuum equations for the slip velocity variance of inertial settling Lagrangian particles in a turbulent boundary layer. We find that depending on the parameter regime of the particles, the slip variance is primarily controlled by local differences between the “seen" variance and the particle velocity variance, while terms appearing due to the inhomogeneity of the turbulence are sub-leading until the settling parameter becomes large. |
Monday, November 25, 2024 9:31AM - 9:44AM |
L22.00008: Abstract Withdrawn
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Monday, November 25, 2024 9:44AM - 9:57AM |
L22.00009: Flocculation and Breakup of Finite-Sized Cohesive Particles in a Turbulent Channel Flow Alexandre Dillon Leonelli, Eckart Heinz Meiburg We present a computational study of the flocculation dynamics and turbulence modulation in a channel flow laden with small, finite size, cohesive particles. We conduct a series of four-way coupled, grain-resolved direct numerical simulations, across which the strength of the cohesive force and particle inertia (density) are varied in the absence of gravity. The strength of cohesion is shown to govern the size (Ο(1-100) particle diameters) and number of aggregates. Interestingly, despite the prevalence of shear-induced migration at higher particle Stokes numbers, the maximum floc size is shown to be insensitive to the particle density. We additionally analyze floc properties such as size, shape, and lifespan as a function of the wall normal distance. The higher mean velocity gradient and turbulent activity near the wall is found to both facilitate aggregation by bringing particles together, while also prompting breakup. Enabled by the fully coupled nature of the simulations, we quantify the effect of aggregation on the turbulence by reporting classical first and second order turbulence statistics for both the fluid and particles. Finally, the role of volume fraction and turbulence intensity on the flocculation process are briefly discussed. |
Monday, November 25, 2024 9:57AM - 10:10AM |
L22.00010: Effects of gravitational settling on the collision rate of monodisperse particles in turbulence Masoud Rezaeian, Federico Pizzi, Joan Grau Barcelo, Francesco Capuano, Lluis Jofre, Mona Rahmani Numerical simulations have been widely employed to study the collision rate of particles in turbulent flows. While most studies have focused on quantifying the rate of particle collision in homogeneous, isotropic turbulence (HIT), the additional effects of gravitational settling are still not fully understood. In this study, we investigate the collision rate of settling microparticles in HIT using direct numerical simulations (DNS) and Lagrangian tracking of point particles. The properties of the fluid and particles were selected based on suspended marine microparticles in the upper ocean. The problem setup covers a range of relatively small Stokes numbers: $1\times 10^{-3}<St<4\times 10^{-3}$ and moderate settling numbers: $1<Sv<30$. To study the effects of gravity, we compare the motion and collision of particles in three different flow conditions: HIT without gravity, HIT with gravity, and gravitational settling in quiescent fluid. The results show that gravity decreases the collision rate of monodispersed particles in HIT as it significantly reduces the horizontal velocity fluctuations of the particles. By examining the relative radial and tangential velocity components between pair particles, we propose corrections to existing theoretical models and significantly improve the predictions of the rates of collisions. |
Monday, November 25, 2024 10:10AM - 10:23AM |
L22.00011: The role of relative motion between solid particles and the carrier flow on the turbulent kinetic energy transfer Lian-Ping Wang, S Balachandar, Cheng Peng In this talk, we will examine the general question how the presence of solid particles affects the production and transfer of turbulent kinetic energy. It is argued that if there is a relative motion in the mean velocity between the particulate phase and the carrier flow, then the relative motion will provide a mechanism for production of the turbulent kinetic energy. Furthermore, at a specific grid scale, the turbulent fluctuating motion of each phase can be divided into a resolved component and a subgrid component: the relative motion in the resolved component provides a mechanism to transfer energy across the grid scale, while the subgrid relative motion contributes to the added viscous dissipation near the fluid-particle interfaces. This conceptual picture provides a basis for establishing a generalized balance equation of the turbulent kinetic energy for a particle-laden turbulent flow, which could be used to quantify the turbulence modulation by solid particles. This balance equation could be applied to address the effects of flow Reynolds number, particle volume fraction, particle-to-fluid density ratio, particle size, and particle sedimentation on turbulence modulation. |
Monday, November 25, 2024 10:23AM - 10:36AM |
L22.00012: Light finite size chiral particles in turbulence Giulia Piumini, Detlef Lohse, Roberto Verzicco We present results from direct numerical simulations of light, finite-size chiral particles in a tri-periodic domain with homogeneous isotropic turbulence. We span the particle-to-fluid density ratio from 0.5 to 0.001 for different intensities of turbulent flow. |
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