Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session R18: Particle Laden Flows VII: |
Hide Abstracts |
Chair: Joe Barranco, San Francisco State University Room: 28D |
Tuesday, November 20, 2012 1:00PM - 1:13PM |
R18.00001: Dust Settling in Protoplanetary Disks with a Terminal Velocity Approach Joseph Barranco, Diana Madera It is a remarkable fact that planets start out as microscopic grains within protoplanetary disks of gas and dust in orbit around newly-formed protostars, somehow growing by a factor of $10^{40}$ in mass in a period no more than $10^7$ years. In the early stages of the planet formation, small dust grains settle into the midplane of the disk in a few thousand years. As the dust layer gets thinner, a vertical shear develops between the dust-rich layer at the midplane and the dust-poor gas above and below. Of great interest is whether such a layer will be unstable to Kelvin-Helmholtz instability (KHI), which will remix the dust with the gas, thwarting the formation of planets. In our previous work, we worked in the single-fluid limit in which the local dust-to gas ratio was an advectively conserved quantity (valid when the dust-gas friction time is very short). Here, we present new simulation in which this assumption is relaxed with a terminal velocity approach that allows dust to slowly drift apart from the gas. We investigate under what conditions dust may settle into dense layers at the midplane or get concentrated inside coherent vortices. Can dust concentrate enough to trigger a gravitational instability and clump up to form planetesimals, the building blocks of planets? [Preview Abstract] |
Tuesday, November 20, 2012 1:13PM - 1:26PM |
R18.00002: ABSTRACT WITHDRAWN |
Tuesday, November 20, 2012 1:26PM - 1:39PM |
R18.00003: ABSTRACT WITHDRAWN |
Tuesday, November 20, 2012 1:39PM - 1:52PM |
R18.00004: Modeling Particle-Laden Compressible Flows Using Lattice-Boltzmann Simulation Orlando Ayala, John Thomas, Lian-Ping Wang Combing the three-dimensional compressible Lattice-Boltzmann model with a fluid-particle interaction model, a robust computational framework for predicting fluid/solid momentum transfer within a particle-laden compressible flow field is developed.~ This tool is used to examine the effects of a moving shock front on the time-evolution of the displacement, velocity, and acceleration vectors of a single spherical particle initially at rest.~ These results are compared to analytical solutions obtained from the Navier-Stokes equations for compressible flows and a relationship between Mach number and drag coefficient is developed.~ Next, momentum transport through a system of particles is examined and the effects of particle-particle interactions on shock front propagation/attenuation are discussed.~ These results are used to understand fluid/solid momentum transfer within detonation shock waves.~ [Preview Abstract] |
Tuesday, November 20, 2012 1:52PM - 2:05PM |
R18.00005: Equation of Motion for a Drop or Bubble in Viscous Compressible Flows M. Parmar, S. Balachandar, A. Haselbacher Here we theoretically analyze the unsteady motion of a bubble/drop with the inclusion of compressibility effects,but in the limit of vanishing Mach and Reynolds numbers. Linearized viscous compressible Navier-Stokes equations are solved inside and outside of the spherical bubble/drop and an expression of the transient force is first obtained in the Laplace domain and then transformed to the time domain. The total force is separated into the quasi-steady, the inviscid-unsteady, and the viscous-unsteady contributions. The quasi-steady and inviscid unsteady forces are the same as those given in the literature for an incompressible drop in an incompressible flow and for a particle in a compressible flow, respectively. For large times, the viscous unsteady force on a drop is the same as that in an incompressible flow. For acoustically short times, the viscous unsteady force is modified due to compressibility effects. Contrary to the finding in incompressible flow, where the viscous unsteady force on a bubble becomes non-singular for short times, the compressibility re-introduces an inverse-square-root decay rate. The present theoretical results are valid only in the limit of zero Mach- and Reynolds-numbers, using DNS we extend the results to finite Reynolds- and Mach-numbers. [Preview Abstract] |
Tuesday, November 20, 2012 2:05PM - 2:18PM |
R18.00006: ABSTRACT MOVED TO M1.00010 |
Tuesday, November 20, 2012 2:18PM - 2:31PM |
R18.00007: Particle-laden flow in a spiral separator Sungyon Lee, Yvonne Stokes, Andrea Bertozzi Spiral concentrators are used in the mining industry to separate particles of different size or density. The existing modeling literature considers the flow as a background fluid carrying non-neutrally buoyant particles. However recent work on modeling of slurries on inclines shows that at relatively modest volume fractions of particles, the presence of the particles affects the flow and, moreover, interparticle interactions such as hindered settling and shear-induced migration can quantitatively explain the dynamics of the separation of particle mixtures under gravity. We incorporate this physics into a model for particle segregation in a spiral concentrator. [Preview Abstract] |
Tuesday, November 20, 2012 2:31PM - 2:44PM |
R18.00008: Bi-disperse particle-laden flows in the Stokes regime Gilberto Urdaneta, Saro Meguerdijian, Kali Allison, Thomas Crawford, Wylie Rosenthal, Sungyon Lee, Aliki Mavromoustaki, Andrea Bertozzi We present an experimental study which investigates the motion of bi-disperse suspensions consisting of ceramic (heavy) and glass (light) beads in PDMS oil flowing down an inclined plane under the action of gravity. Both types of beads are denser than the oil. We perform a parametric study in which we vary the inclination angle of the plane, the total particle volume fraction and the relative ratio of glass to ceramic beads. Mono-disperse suspensions of negatively buoyant particles give rise to three regimes: a ``settled'' regime in which particles settle to the substrate, a ``ridged'' regime in which particles settle to the front, and a transient, ``well-mixed'' regime in which settling does not occur. A similar trend is observed in the current study; lower inclination angles and higher concentrations of the ceramic beads favor the settled regime. Further, the addition of a second particle species induces a striking effect in which the heavier ceramic beads migrate on top of the lighter beads; this phenomenon is thought to be the result of competing forces in the direction normal to the flow arising from gravitational settling and shear-induced migration. We discuss the effect of experimental parameters on the location of the front versus time and changes in the fingering instability. [Preview Abstract] |
Tuesday, November 20, 2012 2:44PM - 2:57PM |
R18.00009: Characterization of Oscillatory Boundary Layer Over a Closely Packed Bed of Sediment Particles Joseph Skitka, Sourabh Apte Lack of accurate criteria for onset of incipient motion and sediment pickup function remain two of the biggest hurdles in developing better predictive models for sediment transport. To study pickup and transport of sediment, it is necessary to have a detailed knowledge of the small amplitude oscillatory flow over the sediment layer near the sea bed. Fully resolved direct numerical simulations are performed using fictitious domain approach (Apte et al., JCP 2009) to investigate the effect of a sinusoidally oscillating flow field over a rough wall made of regular hexagonal pack of spherical particles. The flow arrangement is similar to the experimental data of Keiller \& Sleath (JFM 1976). Transitional and turbulent flows at $Re_{\delta} = 50,100,150,200$ (based on the Stokes layer thickness, $delta$) are explored over a range of non-dimensional sphere sizes. The coherent vortex structures, turbulent cross-correlations and lift forces on the roughness elements are characterized for these flow conditions and compared against available data of Keiller \& Sleath (JFM 1976) and Sleath (JFM 1986). The dynamics of the oscillatory flow over the sediment bed is used to understand the mechanism of sediment pick-up. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700