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 R26: Suspensions: Confined Flows |
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Chair: Amanda Howard, Brown University Room: E146 |
Tuesday, November 22, 2016 1:30PM - 1:43PM |
R26.00001: Development of wall layering in non-homogenous suspension shear flows Amanda Howard, Martin Maxey Fully developed homogeneous suspensions of particles in a pressure driven flow show a net increase in particle volume fraction in the center of the channel, representing a densely packed core region, as well as particle layering along the channel walls. Using numerical simulations, we examine the early development of the wall layers in a suspension of neutrally buoyant, non-Brownian particles in steady and unsteady low Reynolds number flows. Because of the no-slip boundary condition, the particles have no tangential velocity at the wall, but can roll in the streamwise direction. When the particle roughness is monodispersed the particles form a layer a uniform distance from the channel wall. Using a bidispersed particle roughness breaks up the coherence of the wall layer resulting in a greater exchange of particles between the wall and the core region. We will report on a series of simulations varying the particle roughness and sizes to examine the development of the wall layer and near-wall particle fluxes. [Preview Abstract] |
Tuesday, November 22, 2016 1:43PM - 1:56PM |
R26.00002: ABSTRACT WITHDRAWN |
Tuesday, November 22, 2016 1:56PM - 2:09PM |
R26.00003: Are hydrodynamic interactions screened in spherically confined micro-compartments? Christian Aponte-Rivera, Roseanna Zia We study diffusion of hydrodynamically interacting particles confined by a spherical cavity via dynamic simulation, as a model for intracellular transport. Previous models of 3D confined transport typically assume that hydrodynamic interactions are screened and thus can be neglected, but such assumptions lead to qualitative errors in predictive models. Recent studies show that crowding does not screen hydrodynamic entrainment of freely diffusing particles in unbound suspensions, and that diffusing near a planar wall can weaken (but does not screen) hydrodynamic entrainment. Biophysical and other confined suspensions are crowded, watery compartments, suggesting a role of both crowding and confinement in hydrodynamic entrainment. In the present work, we utilize our new computational framework to study the effect of 3D micro-confinement on particle entrainment, and whether such entrainment is algebraically screened. We measure the hydrodynamic entrainment of one particle in the flow induced by another, in suspensions of arbitrary concentration. We find that the strength of entrainment varies spatially in the cavity, changes qualitatively with the size of the confined particles relative to the enclosure, but varies only quantitatively with the concentration of particles. [Preview Abstract] |
Tuesday, November 22, 2016 2:09PM - 2:22PM |
R26.00004: Stokesian Dynamics Simulation for Particulate Suspensions Flowing through Y-Shaped Bifurcating Channel Mallikarjuna Mallela, Pankaj Tiwari, Anugrah Singh Suspension of particles dispersed in a fluid medium are encountered in various situations. Many methods, both analytical and numerical, have been developed for understanding and predicting the macroscopic equilibrium and transport properties of these multiphase systems. Stokesian dynamics(Brady and Bossis, 1988) is also one such simulation method which has been fairly successful towards this end. Many interesting phenomena that are often observed in the suspension flow, such as shear induced migration, size segregation, wall slip, etc. are not encountered in simple Newtonian homogeneous liquids. The shear-induced migration phenomena exhibited by concentrated suspensions lead to many interesting observations such as inhomogeneous distribution of the particles and blunting of velocity profiles. Moreover, this phenomenon causes the fractionation of fluid and particle when the suspension flows through the specially designed bifurcating geometries and have been attracting wide attention. In the present work, we are studying the distribution of the particles in the 2D Y-shaped geometry. We have also carried out simulations with varying relative flow rate in daughter branches by varying the width of the daughter branches to study the partitioning of the particlesin the daughter branche [Preview Abstract] |
Tuesday, November 22, 2016 2:22PM - 2:35PM |
R26.00005: Stokes-flow simulations of a rising particle suspension in a horizontal rotating cylinder Sudarshan Konidena, Ankireddy Katha, Anugrah Singh Experiments performed by Makrand et al. [1] with a suspension of rising particles in a horizontal rotating cylinder exhibit a wide spectrum of non-equilibrium patterns. The axial banding patterns also show a tendency to travel along the rotational axis. We performed Stokes-flow simulations to investigate the aforementioned axial banding along with providing a mechanism for the traveling bands. An order parameter is established basing on either the centrifugal velocity or rising velocity of an isolated particle and the average angular velocity of all the particles. Basing on the rotational frequency, the low and high frequency bands could be characterized into either gravitationally dominant or centrifugally dominant phases with respect to the order parameter. This analysis could aid in providing with a unifying mechanism for axial banding in horizontal rotating cylinders. [Preview Abstract] |
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