Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session H25: Particle-laden Flows III |
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Chair: Alberto Aliseda, University of Washington Room: 328 |
Monday, November 21, 2011 10:30AM - 10:43AM |
H25.00001: Particle Impaction for Trace Contaminant Detection in a Very-High-Volume Airstream Matthew Fulghum, Michael Hargather, Gary Settles An impactor with automated thermal desorption has been designed and tested for airborne trace contaminant detection in a very- high-volume airstream, up to one cubic meter per second. This airflow is scanned for contaminants using an ion mobility spectrometer, which is flow rate-limited to $\sim10\frac{cc}{s} $. As the chemicals of interest, once impacted, are capable of being thermally desorbed and interrogated as a vapor, a novel method of collecting these particles was devised. A 0.3m long linear-slot impactor is used to concentrate particles upon a periodically-heated notch of equal length in a rotating rod. After impaction, this rod is rotated into the interrogation position and is heated to thermally desorb the impacted particles into the carrier-gas flow as a vapor. This flow is several orders of magnitude smaller than the primary airstream being sampled and carries a heavy concentration of the desorbed vapor from the impacted particles to subsequent chemical analysis by the IMS, improving contaminant detection without overwhelming its flow rate capabilities. [Preview Abstract] |
Monday, November 21, 2011 10:43AM - 10:56AM |
H25.00002: Significance of Neglected Hydrodynamic Forces on the Motion of Submerged Particles Acted on by External Body Forces Daniel Cooper, John Charonko, Pavlos Vlachos Recently, the manipulation of submerged particles using electromagnetic body forces has drawn increasing interest from a variety of fields, particularly medicine, where electrophoretic manipulation in lab-on-a-chip applications and magnetic drug targeting have become important areas of interest. As a direct result of this increasing interest a large number of simulations have been performed investigating the performance of devices and systems whose operation is based upon these physics. In the vast majority of cases, these simulations are based upon a force balance of the applicable body force and Stokes drag. Such simulations neglect additional hydrodynamic forces, including the added mass, Basset, Saffman, and Magnus forces. In the current study, the full equations of motion containing all of the aforementioned terms are nondimensionalized leading to a set of nondimensional parameters governing the behavior of the particle. A parametric investigation is then performed by calculating particle trajectories for both Poiseuille and Womersley flows. This analysis reveals that in many cases, the forces neglected in previous simulations are significant and should not be neglected in future studies. [Preview Abstract] |
Monday, November 21, 2011 10:56AM - 11:09AM |
H25.00003: Migration of suspended particles and topological defects within a nematic liquid crystal in anisotropic microfluidic devices Nicholas Flower, Raghavendra Devendra, Joel Rovner, Robert Leheny, German Drazer Devendra et al. (2010) have explored the mobility of particles in periodic anisotropic arrays of obstacles. They observed that the particles migrate away from the applied force at angles that depend on the size of the particle, suggesting a method for microfluidic separation. Rovner et al. (2010) have shown that a lift force redirects particles in a nematic liquid crystal at an angle to the applied force that depends on the anchoring of the nematic director at the surface of the particle. Combining these approaches for separation of particles, we have investigated the behavior of the nematic 4-cyano-4'-pentylbiphenyl (5CB), both with and without suspended particles, flowing inside microfluidic devices containing arrays of obstacles. We report a certain degree of control over generation of topological defects in the nematic order, which we image using polarized microscopy, and control of the flow direction of these defects and suspended particles. The results suggest new ways to conduct microfluidic separation, as well as a new, controlled method for investigating the behavior of liquid crystal defects in flow. [Preview Abstract] |
Monday, November 21, 2011 11:09AM - 11:22AM |
H25.00004: Modeling Coupled Particle/Fluid/Thermal/Charge/Ion Transport with a Hybrid Lattice Boltzmann and Immersed Boundary Method Miao Wang, Ying Sun A hybrid model based on lattice Boltzmann method and immersed boundary method is developed to simulate complex transport processes in semi-solid flow batteries, where electrode slurries are composite of both electrolyte and electrode particles flowing through an electrochemical reaction zone. In such a case, the coupled charge and ion transport need to be solved in a moving frame of reference, accounting for the motion of electrode particles. The model is first validated by studying the sedimentation of non-isothermal particles in a fluid domain, where the hydrodynamic forces are determined by the lattice Boltzmann equation and the immersed boundary method is used to solve for heat transfer. The hybrid model is then applied to solving for the species and ion transport in both the electrolyte and electrode particles inside semi-solid electrode slurries. The charge/ion transport properties as a function of particle volume fraction and particle size of the electrode material are presented. [Preview Abstract] |
Monday, November 21, 2011 11:22AM - 11:35AM |
H25.00005: 3D description of particle detachment from a smooth surface Alex Liberzon, Hadar Traugott This study explores the necessary turbulent flow conditions for initial entrainment of particles from smooth beds into zero-mean-shear flow in an oscillating grid chamber as compared to the bounded shear flow created in a lid-driven cavity. The experiments are not designed to fully mimic the real problem of sediment transport but rather identify key mechanisms, utilizing direct observation and quantification of particle motion at the beginning, during and after lift-off. In both turbulent flows, particle image velocimetry (PIV) and three-dimensional particle tracking velocimetry (3D-PTV) are used to determine the properties of turbulent flows and to track the movement of individual particles through the various phases of the resuspension. The combination of the experimental methods allow to correlate in a quantitative manner the flow conditions responsible for rolling, pick-up, detachment and re-entrainment of particles. [Preview Abstract] |
Monday, November 21, 2011 11:35AM - 11:48AM |
H25.00006: ABSTRACT WITHDRAWN |
Monday, November 21, 2011 11:48AM - 12:01PM |
H25.00007: Capillary breakup of discontinuously shear thickening suspensions Pawel Zimoch, Gareth McKinley, Anette Hosoi Extensional rheology of discontinuously shear thickening suspensions is not well understood, in part due to unresolved experimental challenges. Such suspensions tend to sag, drain or fracture when tested using traditional tools such as filament-stretching or capillary breakup extensional rheometers. We present an alternative method of conducting capillary breakup experiments with thickening suspensions by placing them between two layers of immiscible oil. In experiments conducted with silica and cornstarch particles we observe the formation of bead-on-a-string morphologies with multiple satellite and sub-satellite bead generations, similar to the morphologies observed in breakup of viscoelastic fluids. Using a one dimensional numerical model, we show that formation of beads is a consequence of the discontinuous nature of thickening in the suspensions. Finally, we delineate the parameter regimes where formation of beads occurs, and where it is suppressed. [Preview Abstract] |
Monday, November 21, 2011 12:01PM - 12:14PM |
H25.00008: An experimental study of gravity-driven thin-film flow with buoyant particles Wylie Rosenthal, Paul Latterman, Spencer Hill, Paul David, Matthew Mata, Aliki Mavromoustaki, Andrea Bertozzi Our experimental study involves silicone oil with buoyant foamed glass spheres, flowing under the action of gravity. We perform an extensive parametric study varying the angle of inclination, particle size, density and concentration. In the case of heavy particles, three regimes arise involving settling of particles to the substrate versus settling to the front of the flow. In contrast, only one regime is observed with buoyant particles, however the dynamics depart significantly from that of a clear fluid. We discuss results for front position versus time as well as changes in the fingering instability as a function of experimental parameters. [Preview Abstract] |
Monday, November 21, 2011 12:14PM - 12:27PM |
H25.00009: Theoretical challenges in modeling gravity-driven thin-film flow with buoyant particles Paul David, Spencer Hill, Paul Latterman, Wylie Rosenthal, Aliki Mavromoustaki, Matthew Mata, Andrea Bertozzi We discuss the role of shear-induced migration in particle-laden thin-film flow. For heavy particles, recent experimental results show that this effect explains separation of behavior into three different regimes. In contrast only one regime is present in the case of buoyant particles although the behavior can depart significantly from that of a clear fluid. We discuss current modeling challenges for buoyant particle-laden flow including stability and dynamics of the front in the context of several available models for this problem. [Preview Abstract] |
Monday, November 21, 2011 12:27PM - 12:40PM |
H25.00010: Bridging the Rheology of Dense Granular Flows in Three Regimes Sebastian Chialvo, Jin Sun, Sankaran Sundaresan Using the discrete element method, simulations of simple shear flow of dense assemblies of soft, frictional particles have been carried out over a range of shear rates and volume fractions in order to characterize the rheology of granular flows in three regimes. In agreement with previous results for frictionless spheres [1], the pressure in each regime is found to obey an asymptotic power law relation with shear rate. These relations are then used to construct a blended pressure model. Additionally, we constitute the shear stress ratio in terms of two dimensionless groups: the inertia number [2], which governs the rheology of hard particles, and the ratio of shear time to the particle binary collision time, which characterizes the departure from hard-sphere behavior. The pressure and shear stress ratio relations form a rheological model that, in the hard-sphere limit, can be written as a modified kinetic theory for dense granular flows [3].\\[4pt] [1] T. Hatano, et al., J. Phys. Soc. Japan 76, 023001 (2007).\\[0pt] [2] da Cruz, F. et al., Phys. Rev. E 72, 021309 (2005).\\[0pt] [3] J. Jenkins, and D. Berzi, Granular Matter 12, 151 (2010). [Preview Abstract] |
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