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 T22: Particle-Laden Flows: Clustering |
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Chair: Sarah Beetham, Oakland University Room: 250 F |
Monday, November 25, 2024 4:45PM - 4:58PM |
T22.00001: Euler-Lagrange simulations of dust resuspension by impinging laminar and turbulent jets shuai shuai, Morrison Z Rickard, M. Houssem H Kasbaoui We conduct 3D Eulerian-Lagrangian simulations to explore the mechanisms of inertial particle resuspension and dust cloud formation caused by impinging downward laminar and turbulent jets on cohesion-less particle bed. The particle-to-fluid density ratio is to simulate a dust-air scenario, and the Galileo numbers is 3.2. We vary the Reynolds number from 3,500 (laminar) to 10,000 (turbulent) by varying the jet velocity. To capture the effects of flow intrusion within the bed with accuracy, we consider a thick particle bed tall by about 30 particle diameters. The impinging jet induces particle resuspension, creating a crater. These dynamics accelerate with increasing Reynolds number. We analyze the clustering patterns of the resuspended dust cloud, the formation mechanism of the crater, and their interaction with primary downward vortices and secondary upwash vortices. Our findings show a linear growth of the crater depth and radius, which we characterize as a function of time. |
Monday, November 25, 2024 4:58PM - 5:11PM |
T22.00002: On the settling and clustering behavior of polydisperse gas-solid flows with application to pyroclastic density currents Emily S Foster, Eric Breard, Ph.D., Sarah Beetham Sedimenting flows occur in a wide range of industrial and natural systems, such as circulating fluidized bed reactors and pyroclastic density currents (PDCs). In systems with sufficiently high mass loading, momentum coupling between the phases gives rise to mesoscale behavior, such as clustering. These structures have been demonstrated to generate and sustain turbulence in the carrier phase and directly impact large-scale quantities of interest, such as settling time. As an added complexity, all real-world flows consist of a polydisperse particulate phase, in which parameters, such as particle diameter, vary widely across the ensemble. In this study, we characterize the sedimentation behavior of a range of polydisperse gas-solid flows, sampled from a parameter space typically associated with PDCs. Highly resolved data for two polydisperse distributions of particles at two volume fractions is collected using an Euler-Lagrange framework and compared with analogous monodisperse configurations. We propose a new metric for predicting the degree of clustering, termed 'surface loading' and quantify the effect of polydispersity and volume fraction on both clustering and settling behavior. |
Monday, November 25, 2024 5:11PM - 5:24PM |
T22.00003: Changes in aggregation and fragmentation dynamics of marine aggregates throughout the course of a phytoplankton bloom David Fierli, Ashley Kraekel, Matthew J Rau Cohesive organic particulate matter in the ocean readily clusters and aggregates into large (>0.5 mm) marine snow particles. These relatively large aggregates have higher settling velocities than their microscopic component particles, which facilitates the transport of this organic material out of the surface and to the deep ocean. This process is particularly prevalent during blooms of phytoplankton, where high concentrations of particles and sticky extracellular biopolymers facilitate particle-particle contacts and cohesion. Here, we perform aggregation and disaggregation experiments on field-sampled phytoplankton during a spring bloom in the California Current. Samples of phytoplankton were collected, then aggregated in a cylindrical rolling tank prior to disaggregation through exposure to controlled laminar shear. We found that the type of phytoplankton, the bloom stage, and biopolymer concentrations all influenced the aggregation and fragmentation rates of the marine snow particles when exposed to these hydrodynamic environments relevant to the surface ocean. These results enhance our ability to predict the formation of large, fast-settling particles in the ocean and ultimately our ability to understand processes contributing to carbon sequestration in the marine environment. |
Monday, November 25, 2024 5:24PM - 5:37PM |
T22.00004: Time-resolved measurements of clustered particles in channel flow turbulence Tuhin Bandopadhyay, Laura Villafane Small heavy particles in turbulent flows preferentially concentrate forming clusters, regions of high local concentration. The temporal persistence of these clusters and the dynamics of clustered and non-clustered particles are experimentally investigated in the core region of a vertical turbulent channel flow for different particle to flow time scales ratios (Stη) by independently varying particle and flow parameters. The Stokes number is varied in the range 0.6 to 54 while keeping particle sizes smaller than the dissipative scales in all cases, and particle volume loadings at about 4.8x10-5 to minimize global flow modification by particles. Synchronous high-speed imaging from two cameras with different but overlapping fields of view is used to measure particle trajectories and velocity statistics, and cluster dynamics. We focus on the kinematics of clustered particles conditioned on local concentration and explore their correlation with cluster size and lifetime. This research aims to develop phenomenological models for particle cluster evolution and to advance our understanding of particle preferential concentration in turbulence. |
Monday, November 25, 2024 5:37PM - 5:50PM |
T22.00005: Sedimentation of Flexible Inertial Particles with Different Aspect Ratios Akshay Anand, Vahid Tavanashad, Kourosh Shoele This study investigates the sedimentation of flexible suspensions with different aspect ratios in quiescent fluid environments, focusing on the complex interplay between particle properties, hydrodynamics, and cluster formation. We employ numerical simulations to solve the Navier-Stokes equations for the fluid phase, while an incompressible hyperelastic Mooney-Rivlin material description represents the flexible particles. Our results reveal that for large aspect ratios, such as flexible fibers, denser clusters are formed compared to rigid fibers, significantly influencing overall sedimentation behavior. The cluster lifespan and morphology evolution will be discussed, with aggregation and disaggregation phases identified and correlated. We will show how the aspect ratio modifies the observed behavior and discuss how the aspect ratio and flexibility can be leveraged in applications to regulate the sedimentation dynamics of dense clusters. |
Monday, November 25, 2024 5:50PM - 6:03PM |
T22.00006: Interactions and collective dynamics of inertial particles in oscillatory flow Xiaokang Zhang, Bhargav Rallabandi Suspensions of particles exposed to oscillatory flows are known to exhibit complex collective behaviors. We develop a theoretical framework to study the dynamics of interacting particles in uniform oscillatory flow, focusing on time-averaged motion due to the interplay between viscous and inertial forces. Starting with a pair of particles, we utilize a dual multipole expansion to obtain the oscillatory disturbance flow created by each particle. We then use the Lorentz reciprocal theorem to evaluate time-averaged hydrodynamic interaction forces between the particles. The theory is in excellent agreement with previous numerical computations. It reveals regions of attraction and repulsion depending on the distance between the particles, the orientation between the particle line-of-centers and the imposed flow, and the oscillation frequency. We then demonstrate how the theory can be adapted to multiple interacting particles, and use it to explore collective motion and pattern formation in oscillating suspensions. |
Monday, November 25, 2024 6:03PM - 6:16PM |
T22.00007: Motion of large non-spherical particles in 2D flow Helena Schreder, Michelle Heather DiBenedetto Large non-spherical floating objects, such as logs, ice, and debris, are common in environmental flows. Their relatively large sizes and irregular shapes can cause them to exhibit complex responses to the underlying flow; however, it is not clear how the effects of both finite size and anisotropic shape together affect the behavior of these objects in the flow. Particle shape changes how finite-sized particles respond to velocity gradients, which can affect their transport and distribution. To investigate how size and shape affect how these objects sample the flow, we simulate inertialess non-spherical particles in a 2D flow, idealized as ellipses and rods. We find that, even in the inertialess limit, these particles display patterns of preferential concentration solely due to their geometry. For example, highly anisotropic objects tend to concentrate in regions of higher vorticity. We also find that object behavior can be categorized into distinct regimes; for example, in a cellular flow, we observe steady, periodic, and chaotic motion depending on object size and shape. |
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