Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session A37: Multiphase Flows: Particle Laden Flows |
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Chair: Anthony Wachs, UBC Room: 619 |
Saturday, November 23, 2019 3:00PM - 3:13PM |
A37.00001: Resuspension of inertial particles in a swirling flow Benjamin Laplace, Jeremy Vessaire, Mickael Bourgoin, Romain Volk We experimentally investigate the resuspension of particles much larger than the dissipative scale, moderately dense and moving in a turbulent Von Kármán flow of water generated by one disk with straight blades placed at the top of a small tank of square section 15 $cm^2$ and 22 cm high. A mean structure composed of an overall rotation and a vertical pumping is thus created. Lagrangian measurements have been performed, allowing for the reconstruction of the velocity and the acceleration fields of particles of different diameters and densities, as well as their positions distributions profiles. Surprisingly, in most cases, the particles are vertically distributed according a density profile close to an exponential-like shape as in the well-known experiment of brownian particles placed in a gravity field. This suggests an intriguing balance between gravity and the mean and fluctuating part of the flow. Nevertheless, two types of behaviors emerge depending on the particle size. Indeed, the largest particles tend to be trap close to the disk when the rotation frequency increases, meaning that their density profile is now reverse. An effect probably due to the interaction of the disk and the particles that produces an upward force force onto the particles. [Preview Abstract] |
Saturday, November 23, 2019 3:13PM - 3:26PM |
A37.00002: Microstructure-Informed Probabilistic Model for Hydrodynamic Forces in Particle-Laden Flows Arman Seyed-Ahmadi, Anthony Wachs We propose a new model for the hydrodynamic forces exerted on a spherical particle in a randomly distributed monodisperse array of spheres for a Reynolds number range of $ 2 \le Re \le 150 $ and a solid volume fraction range of $ 0.1 \le \phi \le 0.4 $. By constructing probability distribution maps extracted from direct numerical simulations, our model takes advantage of the statistical information of the arrangement of neighbors to correlate the microscale variation of the drag and lift force with the local anisotropy of each particle’s neighborhood. Given the locations of the neighboring particles as input, our results demonstrate that the present probabilistic model is capable of predicting of up to 70\% of the observed force variation. Since precise location of each particle is known in an Eulerian-Lagrangian simulation, our model would be able to estimate subgrid force fluctuations reasonably well, and thereby greatly enhance the fidelity of mesoscale simulations through improved interphase coupling. [Preview Abstract] |
Saturday, November 23, 2019 3:26PM - 3:39PM |
A37.00003: Fluidization of Geldart A particles: Experiments and Validation Avinash Vaidheeswaran, Rupendranath Panday, Mary Ann Clarke, William Rogers We will present results from fluidization experiments performed at US Department of Energy's National Energy Technology Laboratory (NETL). Glass particles classified as Geldart A are used and the experiments are conducted over a broad range of air flow rates. The relative humidity is controlled to minimize short-range inter-particle forces and to ensure reproducibility. The design of experiments includes randomization and replicates to minimize uncertainty in measurements. Besides aiding in understanding multiphase dynamics in a fluidized system, the data provides valuable benchmark for computational codes used to analyze gas-solid flows. NETL's open-source software MFiX (Multiphase Flow with Interphase Exchanges) is used for validation in our current study. The results from Two-Fluid model (Eulerian-Eulerian) and Particle-In-Cell (Eulerian-Lagrangian) approaches are compared. The applicability of MFiX Particle-In-Cell methodology for a large particle count system is highlighted, which offers considerable potential for industrial applications. [Preview Abstract] |
Saturday, November 23, 2019 3:39PM - 3:52PM |
A37.00004: Colloidal Particle Flow through Porous Media: A Multiscale Study Navid Bizmark, Joanna Schneider, Rodney Priestley, Sujit Datta Colloidal particles hold promise for improved oil recovery and groundwater aquifer remediation. These applications rely on the transport of injected particles through a subsurface three-dimensional (3D) porous medium. However, this behavior is difficult to model due to diverse processes that may arise, including particle advection through the pore space by fluid flow, adsorption and deposition onto the solid matrix, and erosion or resuspension. Moreover, these processes are particularly difficult to study experimentally due to the opacity of typical 3D media. Here, we directly visualize the transport of colloidal particles in a model 3D porous medium using confocal microscopy. For the first time, we characterize the interplay between particle adsorption and erosion at the pore scale. Analysis of these pore-scale processes allows us to determine the net particle deposition rate, which enables us to predict the macroscopic net particle deposition profile. Our work thus demonstrates how pore-scale transport dynamics of colloidal particles can be controlled to achieve desired macroscopic goals with consequences for oil recovery, aquifer remediation, and other emerging applications. [Preview Abstract] |
Saturday, November 23, 2019 3:52PM - 4:05PM |
A37.00005: On the Role of Particle Rebound in Halo Formation in Particle Impactors Shivuday Kala, J.R. Saylor Particle impactors are a critical component of particle science measurements. These impactors consist of a nozzle through which particle laden air flows and an impactor plate oriented normal to the nozzle where particles greater than a cutoff diameter are deposited. Impactors having different cutoff diameters can be organized in series to obtain particle size distributions. Ideally the particle deposition pattern on the plate is a uniform disc of particles. However, observations have been documented of "halos" formed around this disc. The cause of these halos is not clear and have been variously attributed to rebounding of the particles from the circular deposition site to the halo location, eddies in the gas flow, the Magnus effect, and turbulence. Herein the possibility that particle rebound is the cause of halos is explored by varying the relative humidity of the gas flow containing hygroscopic particles, thereby changing the "stickiness" of these particles to determine if this changes the probability of halo formation. Simulations which quantify the degree to which other effects might contribute to the formation of halos are also presented. [Preview Abstract] |
Saturday, November 23, 2019 4:05PM - 4:18PM |
A37.00006: Experimental evaluation of deposit formation during powder transport Holger Grosshans, Nuki Susanti, Miltiadis V. Papalexandris When powders are transported pneumatically they often gain an electrostatic charge and form subsequently deposit layers on component surfaces. The resulting local accumulation of electrostatic energy can lead to hazardous spark discharges which caused in the past numerous dust explosions. In order to contribute to operational safety of industrial plants we explore the deposit of particle-laden flows with our new experimental test-rig. To this end, the particle flow will be analyzed optically using a transparent pipe as measuring section. We quantify deposit formation through the characterization of the pattern and the thickness of the deposit layers depending on the flow conditions. The parameters under consideration include the flow Reynolds number, the powder loading, the particle material, the ambient conditions (temperature, humidity), and the particle size distribution. The presented experimental facility is designed with the aim to maximize consistency with our complimentary numerical simulations. [Preview Abstract] |
Saturday, November 23, 2019 4:18PM - 4:31PM |
A37.00007: Optimisation of Graphene Production via Liquid Phase Exfoliation Jason Stafford, Usmaan Farooq, Nwachukwu Uzo, Camille Petit, Omar Matar Graphite particles dispersed in a solvent can be exposed to high shear stresses in order to produce graphene in a process called liquid phase exfoliation. Shear stress is commonly understood to be the leading `parameter’, as it overcomes the van der Waals interlayer force and leads to exfoliation. By studying two exfoliation processes with different hydrodynamics, however, it has become apparent that both shear stress {\it and} particle residence time play important roles in production output. In one setup, a thin film flowing over a spinning disc, increasing the rotational speed and/or flow rate leads to an increased radial velocity, thereby directly reducing the amount of time the particles were exposed to the shear. In the second setup, based around Taylor-Couette flow, the influence of both the pump speed and rotational speed of the cylinder have a significant effect on the resultant graphene production rate. Detailed experimental and CFD studies, including DNS of the rapidly rotating thin films and LES of the Taylor-Couette flow, were performed in order to investigate the underlying mechanisms associated with exfoliation and determine the optimal operating points. [Preview Abstract] |
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