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 A28: Multiphase Flows: General |
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Room: 610 |
Saturday, November 23, 2019 3:00PM - 3:13PM |
A28.00001: Interaction Between Fibers and Viscous Flow Evaluated by Simplified Bead-Chain Model and Generalized SPH Yoshiaki Abe, Tomonaga Okabe This study investigates the motion of short fibers in melted resin for a three-dimensional (3D) printing process. We developed a numerical model for fiber and viscous-flow interaction problems based on the generalized smoothed particle hydrodynamics (generalized SPH) and the simplified bead-chain model (SBCM) for short fibers. The generalized SPH allocates particles inhomogeneously in a physical space and arranges them via mapping in a generalized coordinate system where the particles are aligned at a uniform spacing, which allows efficient simulation compared with conventional Cartesian SPH approaches. The SBCM models each fiber as a chain of spheres given by a single equation of translational motion. The effects of bending and hydrodynamic torques are converted to equivalent translational forces, which significantly simplifies the governing equations and results in a more cost-effective simulation than conventional models such as the BCM or classical microstructure-based fiber suspension model. This study proposes the SBCM-SPH model for predicting a fiber-flow interaction and investigates the motion of short fibers in the fused decomposition modeling process of 3D printer. [Preview Abstract] |
Saturday, November 23, 2019 3:13PM - 3:26PM |
A28.00002: The Quest For Enhanced Pulsed Slurry Atomization Via Modulation Wayne Strasser Our non-Newtonian airblast atomization flowfield violently pulses (axially and radially) by self- generating and self-sustaining interfacial instability mechanisms. Recent work demonstrated that exothermic chemical reactions enhance this moderate Mach number atomization. Explored herein is the potential to further enhance reaction-assisted disintegration by superimposing forced mass flow variations onto otherwise constant gas feed streams. Two nozzle geometries (high and low prefilming distance) and multiple superimposed feed frequencies are considered for each gas stream. Results indicate that superimposed frequencies have potential to enhance chaotic atomization in a statistically significant manner. Ironically, the most efficient atomization did not coincide with the highest levels of gas resonance. A detailed study of reactor start-up flow reveals new mechanisms which explain performance differences. The prefilming design facilitates an isolated mixing region where secondary ignition occurs nearly immediately after startup and augments reaction product conversion. [Preview Abstract] |
Saturday, November 23, 2019 3:26PM - 3:39PM |
A28.00003: A novel selective lithium separation using amorphous pMOF/alginate interfaces Sung Ho Park, Sang Joon Lee Anomalous opposite ion behaviors of Li$^{\mathrm{+}}$ and Mg$^{\mathrm{2+}}$ ions are experimentally observed from amorphous interfaces of phosphonate metal$-$organic framework (pMOF)/alginate composites. The amorphous structures of pMOF/alginate composites are significantly varied according to reaction temperature and intertwinement degree of alginate networks. As a proof-of-concept application, Li$^{\mathrm{+}}$ and Mg$^{\mathrm{2+}}$ ions are separated using pMOF/alginate composite depending on the degree of pMOF growth. Initially, lots of Li$^{\mathrm{+}}$ ions are effectively attracted compared to Mg$^{\mathrm{2+}}$ ions due to the strong repulsion force of Al$^{\mathrm{3+}}$ ions in amorphous alginate interfaces on multi valent metal ions. However, amorphous pMOF/alginate interfaces induce effective rejection of Li$^{\mathrm{+}}$ ions with low hydration energy through dehydration due to the significant interaction with water molecules, while Mg$^{\mathrm{2+}}$ ions with high hydration energy are significantly attracted by negatively charged phosphonate groups. The present results of amorphous MOF/alginate interfaces would provide a variety of benefiting separation opportunities with unique property in seawater desalination and rare metal recovery. [Preview Abstract] |
Saturday, November 23, 2019 3:39PM - 3:52PM |
A28.00004: The impact of monovalent and divalent ions on the viscosity of a solution with silica nanoparticles Saheed Olawale Olayiwola, Morteza Dejam Nanoparticles (NPs) are injected into the reservoirs for enhanced oil recovery. Several mechanisms like wettability alteration, reduction in the interfacial tension, and change in the rheological properties of the fluid are involved in this process. The rheological properties of the fluid depend on the interaction between the ionic components of the brine and the injected silica NPs. As a result, the flow is affected by the interaction of NPs and salt ions. The viscosity of fluid reduces with an increase in the temperature but the impact of the ionic components of brine on the viscosity of nanofluid is rarely investigated. Therefore, this study focuses on the effect of ionic components of brine (Na$^{\mathrm{+}}$, K$^{\mathrm{+}}$, Ca$^{\mathrm{2+}}$, Mg$^{\mathrm{2+}}$, Cl$^{\mathrm{-}}$, and SO$_{\mathrm{4}}^{\mathrm{2-}})$ at different concentrations of silica NPs (0.01-1 wt{\%}) on the viscosity of fluid. It was observed from the experimental data that the viscosity of fluid is increased by the divalent anions while it is reduced by the divalent cations. The interaction between the ions of NPs and the salt ions, which causes the variation in the viscosity of fluid, is further investigated by measuring the zeta potential and the particle size distributions. [Preview Abstract] |
Saturday, November 23, 2019 3:52PM - 4:05PM |
A28.00005: Unsteady fragmentation upon drop impact: Sheet dynamics Y. Wang, L. Bourouiba Prior work, Wang \& Bourouiba 2018b, showed that upon drop impact on a finite surface, continuous secondary droplet shedding occurs, and that both size and speed distributions of the droplets ejected are governed by the unsteadiness of the sheet expansion. In turn, this continuous shedding influences the sheet expansion. Incorporating continuous droplet shedding, we show how the sheet is governed by a non-Galilean expansion law from which we predict the time evolution of all key physical quantities from the sheet radius to the fluid shed by the rim, all in agreement with experimental measurements. We also discuss a peculiar property of the governing equation which imposes a time-to-maximum-radius independent of the impact energy. This property results in a temporal evolution of the partition of mass, momentum, and energy in the sub-parts of the fragmentating system that is independent of the impact conditions. We discuss the robustness of the results to changes of fluid properties. [Preview Abstract] |
Saturday, November 23, 2019 4:05PM - 4:18PM |
A28.00006: Unsteady fragmentation upon drop impact: prediction of droplet size and speed distributions L. Bourouiba, Y. Wang Upon impact on a finite surface, a drop first expands into a sheet in the air, surrounded by a rim that destabilizes into ligaments that, in turn, shed secondary droplets. Wang \& Bourouiba 2018b and Wang et al. 2018 showed that both size and speed distributions of the secondary droplets ejected during fragmentation are shaped by the unsteadiness of the sheet and rim. In this combined experimental and theoretical study, we derive and validate the analytic expression governing both size and speed distributions of secondary droplets ejected during such unsteady fragmentation, including time-evolution of the mean quantities associated with the distributions. We discuss the implications for various applications including contamination dispersal. [Preview Abstract] |
Saturday, November 23, 2019 4:18PM - 4:31PM |
A28.00007: Drop impacts close to edges of complex geometry: Sheet dynamics S. El Mousadik, Y. Wang, L. Bourouiba Drop impacts close to surface edges of complex geometry lead to secondary spray droplets that are important for rain-induced foliar pathogen transmission and cleaning of contaminated surfaces. Despite the ubiquitous nature of impacts close to edges, little is known on the role of complex edges in shaping fragmentation or retention of the impacting fluid drop. Upon impact, a drop is transformed into a liquid sheet expanding partially on the surface and partially in the air, bounded by a rim which can eventually destabilize into ejected secondary droplets of varying sizes and speeds. Predicting the secondary droplet sizes and speeds emitted or the portion of fluid remaining on, or in the vicinity of, the impacted surface starts by elucidating the physics of the sheet created upon drop impact. In this combined experimental and theoretical study, we incorporate the history of the fluid parcels on the surface, into the evolution of the liquid sheet in the air. This is done via both modelling and direct measurement of the properties of the boundary layer on the surfaces. Our analysis enables the prediction of the time-varying evolution of the asymmetric liquid sheet dynamics. [Preview Abstract] |
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