Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session L12: Multiphase Flows: Particle-Particle and Particle-Shock Interactions |
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Chair: Heather Zunino, Arizona State University Room: C123 |
Monday, November 21, 2016 4:30PM - 4:43PM |
L12.00001: Taylor-Couette flows with radial fluid injection during co- and counter- rotation, for controlled mixing applications. Nikolas Wilkinson, Cari Dutcher Flow between rotating concentric cylinders, called Taylor-Couette (TC) flow, offers high control over hydrodynamics, making TC flow ideal to study mixing. However, traditional TC cell design limits the ability to study the initial solution mixing dynamics while the cell is operating, due to geometric confinement and complexity when both cylinders are rotating. Here, we present a new TC cell design that allows for radial injection of fluids into the annulus while both cylinders are rotating. This Taylor-Couette cell has radius ratio of Ri/Ro $=$ 0.89, an aspect ratio of L/d $=$ 60 with 16 injection ports, and allows for both cylinders to rotate simultaneously and independently. With this geometry, we discuss how the injection port modification effects flow instabilities, as well as how radial injection during cylinder rotation modifies the flow. In our current work, we are studying flocculation of micron clay particles with polyelectrolyte solutions and how the hydrodynamics effects assembly and structure of these materials during the flocculation process. [Preview Abstract] |
Monday, November 21, 2016 4:43PM - 4:56PM |
L12.00002: Flow induced streamer formation in particle laden complex flows Nandini Debnath, Mahtab Hassanpourfard, Ranajay Ghosh, Japan Trivedi, Thomas Thundat, Aloke Kumar We study the combined flow of a polyacrylamide (PAM)solution with polystyrene (PS) nanoparticles, through a microfluidic device containing an array of micropillars. The flow is characterized by a very low Reynolds number (\textit{Re\textless \textless 1}). We find that for exceeding a critical Weissenberg number (\textit{Wi}$\ge $ 20), PS nanoparticles localize near pillar walls to form thin slender string-like structures, which we call `streamers' due to their morphology. Post-formation, these streamers show significant viscous behavior for short observational time-scales, and at longer observational time scales elastic response dominates. Our abiotic streamers could provide a framework for understanding similar structures that often form in biological systems. [Preview Abstract] |
Monday, November 21, 2016 4:56PM - 5:09PM |
L12.00003: Shear flows of dense suspensions: flow modification by particle clustering and mixing Bernhard Vowinckel, Meital Carmi, Edward Biegert, Eckart Meiburg We investigate numerically the behavior of sheared, dense suspensions of neutrally buoyant particles, for finite Reynolds number values. This type of problem is of particular interest for multiple applications in environmental, mechanical as well as process engineering such as debris flows, slurries, and pneumatic conveying in pipelines. Controlling channel flows laden with dense suspensions is very important as it can result in jamming of the channel, hence, lowering the efficiency of a hydraulic facility. It was observed that there exists a regime for which a small increase in shear force can cause a drastic, discontinuous increase of the effective viscosity of the mixture. This abrupt transition is commonly referred to as discontinuous shear thickening. We carry out phase-resolved numerical simulations to understand the modification of the flow on the grain scale in full detail allowing for improved definitions of threshold conditions. As the properties of the carrier fluid remain unchanged during the simulation, the thickening must be caused by the disperse phase, for example, by effects of changes in spatial particle distribution, clustering, and mixing. We provide a detailed statistical analysis to answer this question. [Preview Abstract] |
Monday, November 21, 2016 5:09PM - 5:22PM |
L12.00004: Preferential Concentration of Inertial Sub-Kolmogorov Particles.The roles of mass loading of particles, $St$ and $Re_{\lambda}$ numbers} Sholpan Sumbekova, Alberto Aliseda, Alain Cartellier, Mickael Bourgoin Turbulent flows laden with inertial particles present multiple open questions and are a subject of great interest in current research. Due to their higher density compared to the carrier fluid, inertial particles tend to form high concentration regions, i.e. clusters, and low concentration regions, i.e. voids, due to the interaction with the turbulence. In this work, we present an experimental investigation of the clustering phenomenon of heavy sub-Kolmogorov particles in homogeneous isotropic turbulent flows. Three control parameters have been varied over significant ranges: $Re_{\lambda} \in [170 - 450]$, $St\in [0.1 - 5]$ and volume fraction $\phi_v\in [2\times 10^{-6} - 2\times 10^{-5}]$. The scaling of clustering characteristics, such as the distribution of Vorono\"i areas and the dimensions of cluster and void regions, with the three parameters are discussed. In particular, for the polydispersed size distributions considered here, clustering is found to be enhanced strongly (quasi-linearly) by $Re_{\lambda}$ and noticeably (with a square-root dependency) with $\phi_v$, while characteristic cluster and void lengths are driven primarily by $Re_{\lambda}$. Weak dependence on St supports "sweep-stick" mechanism of clustering. [Preview Abstract] |
Monday, November 21, 2016 5:22PM - 5:35PM |
L12.00005: ABSTRACT WITHDRAWN |
Monday, November 21, 2016 5:35PM - 5:48PM |
L12.00006: Erosion of a grooved surface caused by impact of particle-laden flow Sohyun Jung, Eunjin Yang, Ho-Young Kim Solid erosion can be a life-limiting process for mechanical elements in erosive environments, thus it is of practical importance in many industries such as construction, mining, and coal conversion. Erosion caused by particle-laden flow occurs through diverse mechanisms, such as cutting, plastic deformation, brittle fracture, fatigue and melting, depending on particle velocity, total particle mass and impingement angle. Among a variety of attempts to lessen erosion, here we investigate the effectiveness of millimeter-sized grooves on the surface. By experimentally measuring the erosion rates of smooth and triangular-grooved surfaces under various impingement angles, we find that erosion can be significantly reduced within a finite range of impingement angles. We show that such erosion resistance is attributed to the swirls of air within grooves and the differences in erosive strength of normal and slanted impact. In particular, erosion is mitigated when we increase the effective area under normal impact causing plastic deformation and fracture while decreasing the area under slanted impact that cuts the surface to a large degree. Our quantitative model for the erosion rate of grooved surfaces considering the foregoing effects agrees with the measurement results. [Preview Abstract] |
Monday, November 21, 2016 5:48PM - 6:01PM |
L12.00007: Experimental measurement of unsteady drag on shock accelerated micro-particles Ankur Bordoloi, Adam Martinez, Katherine Prestridge The unsteady drag history of shock accelerated micro-particles in air is investigated in the Horizontal Shock Tube (HST) facility at Los Alamos National laboratory. Drag forces are estimated based on particle size, particle density, and instantaneous velocity and acceleration measured on hundreds of post-shock particle tracks. We use previously implemented 8-frame Particle Tracking Velocimetry/Anemometry (PTVA) diagnostics to analyze particles in high spatiotemporal resolution from individual particle trajectories. We use a simultaneous LED based shadowgraph to register shock location with respect to a moving particle in each frame. To measure particle size accurately, we implement a Phase Doppler Particle Analyzer (PDPA) in synchronization with the PTVA. In this presentation, we will corroborate with more accuracy our earlier observation that post-shock unsteady drag coefficients (C$_{\mathrm{D}}$(t)) are manifold times higher than those predicted by theoretical models. Our results will also show that all C$_{\mathrm{D}}$(t) measurements collapse on a master-curve for a range of particle size, density, Mach number and Reynolds number when time is normalized by a shear velocity based time scale, t* $=$ d/(u$_{\mathrm{f}}$-u$_{\mathrm{p}})$, where d is particle diameter, and u$_{\mathrm{f}}$ and u$_{\mathrm{p}}$ are post-shock fluid and particle velocities. [Preview Abstract] |
Monday, November 21, 2016 6:01PM - 6:14PM |
L12.00008: Early motion in a rapidly decompressed particle bed Heather Zunino, Ronald Adrian, Amanda Clarke Rapid expansion of dense, pressurized beds of fine particles subjected to rapid reduction of the external pressure is studied in a vertical shock tube. Located at bottom of a high pressure chamber below the shock tube diaphragm, a particle bed expands when the diaphragm bursts, releasing a near-sonic expansion wave that impinges on the particle bed-gas interface. The expansion wave presents a very rapid unloading to the particle bed. A high-speed video camera and pressure sensors capture events occurring during bed expansion. Interesting structures during the first few milliseconds include two-dimensional instabilities of the particle bed's surface and roughly spatially periodic regions void of particles within the bed. One-dimensional and two-dimensional Fourier analyses are used to measure their frequencies in space-time. It is found that the frequencies and patterns exhibit a clear dependence on particle diameter in which cell frequency decreases and cell size increases with increasing particle size. This work is supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science and Academic Alliance Program, under Contract No. DE-NA0002378. [Preview Abstract] |
Monday, November 21, 2016 6:14PM - 6:27PM |
L12.00009: Eulerian-Lagrangian Simulation of an Explosive Dispersal of Particles Bertrand Rollin, Frederick Ouellet, Rahul Koneru, Subramanian Annamalai Explosive dispersal of solid particles can be observed in a wide variety of contexts, notably in natural phenomenon such as volcanic eruptions or in engineering applications such as detonation of multiphase explosives. As the initial blast wave crosses the surrounding layer of particles, compaction occurs shortly before particles disperse radially outward at high speed. During the dispersion phase, complex multiphase interactions occurs between particles and detonation products of the explosive. Using a Eulerian-Lagrangian approach, namely point particle simulations, we study the case of a bed of particles of cylindrical shape surrounding an explosive chord. Our interest lies in predicting the behavior of particles after detonation. In particular, capturing and describing the mechanisms responsible for late-time formation of stable particle jets is sought. Therefore, detonation of the explosive material is not simulated. Instead an equivalent energy source is used to initiate the simulation. We present a detailed description of our approach to solving this problem, and our most recent progress in the analysis of particles explosive dispersal. [Preview Abstract] |
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