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 D25: Microscale Flows: Particles |
Hide Abstracts |
Chair: Sascha Hilgenfeldt, University of Illinois at Urbana-Champaign Room: E145 |
Sunday, November 20, 2016 2:57PM - 3:10PM |
D25.00001: Attractive and Repulsive Forces on Particles in Oscillatory Flow Siddhansh Agarwal, Bhargav Rallabandi, David Raju, Raqeeb Thameem, Sascha Hilgenfeldt A large class of oscillating flows gives rise to rectified streaming motion of the fluid. It has recently been shown that particle transport in such flows, excited by bubbles oscillating at ultrasound frequencies, leads to differential displacement and efficient sorting of microparticles by size. We derive a general expression for the instantaneous radial force experienced by a small spherical particle in the vicinity of an oscillating interface, and generalize the radial projection of the Maxey-Riley equation to include this effect. Varying relevant system parameters, we show that the net effect on the particle can be either an attraction to or a repulsion from the bubble surface, depending in particular on the particle size and the particle/fluid density contrast. We demonstrate that these predictions are in agreement with a variety of experiments. [Preview Abstract] |
Sunday, November 20, 2016 3:10PM - 3:23PM |
D25.00002: Rectified Motion of Microparticles: Generalizing Streaming and Radiation Forces David Raju, Siddhansh Agarwal, Bhargav Rallabandi, Sascha Hilgenfeldt It is well known that a wide variety of oscillating flows gives rise to steady streaming, i.e., rectified motion of fluid elements. Small spherical particles introduced into such a flow have been shown to experience an additional lift force that ultimately leads to particle trajectories that differ systematically from the fluid element pathlines. We demonstrate a systematic derivation of this differential particle motion on the steady streaming time scale, so that time-averaged particle trajectories can be directly predicted without computation on the fast, oscillatory time scale. The resulting dynamics can be interpreted as a generalization of streaming flow, while the closed-form lift force provides a generalization of the secondary radiation force, to which it reduces in appropriate limiting cases. These very general results are validated by comparison with experiments in the context of bubble streaming, but apply to a large class of other flows as well. [Preview Abstract] |
Sunday, November 20, 2016 3:23PM - 3:36PM |
D25.00003: 3D deterministic lateral displacement separation systems Siqi Du, German Drazer We present a simple modification to enhance the separation ability of deterministic lateral displacement (DLD) systems by expanding the two-dimensional nature of these devices and driving the particles into size-dependent, fully three-dimensional trajectories. Specifically, we drive the particles through an array of long cylindrical posts, such that they not only move parallel to the basal plane of the posts as in traditional two-dimensional DLD systems ({\it in-plane motion}), but also along the axial direction of the solid posts ({\it out-of-plane motion}). We show that the (projected) in-plane motion of the particles is completely analogous to that observed in 2D-DLD systems and the observed trajectories can be predicted based on a model developed in the 2D case. More importantly, we analyze the particles out-of-plane motion and observe significant differences in the net displacement depending on particle size. Therefore, taking advantage of both the in-plane and out-of-plane motion of the particles, it is possible to achieve the simultaneous fractionation of a polydisperse suspension into multiple streams. We also discuss other modifications to the obstacle array and driving forces that could enhance separation in microfluidic devices. [Preview Abstract] |
Sunday, November 20, 2016 3:36PM - 3:49PM |
D25.00004: Inertial Particle Migration in the Presence of a Permeate Flow Mike Garcia, Amanda Singelton, Sumita Pennathur Tangential Flow Filtration (TFF) is a rapid and efficient method for the filtration and separation of suspensions of particles such as viruses, bacteria or cellular material. Enhancing the efficacy of TFF not only requires a detailed understanding of particle transport mechanisms, but also the interactions between these mechanisms and a porous wall. In this work, we numerically and experimentally explore the mechanisms of inertial particle migration in the presence of a permeate flow through the porous walls of a microchannel. Numerically, we develop a force balance model to understand the competition between permeate and inertial forces and the resultant consequences on the particle equilibrium location. Experimentally, we fabricated MEMS TFF devices to study the migration of 5, 10 and 15 \textmu m fluorescent polystyrene beads in straight channels with perpendicular permeate flow rates up to 90{\%} of the inlet flow rate. We find that the permeate flow directly influences the inertial focusing position of the particles, both as a function of downstream channel position and ratio of inlet to outlet flow rate. Comparing experiments to our model, we can identify inertial, viscous and a co-dominant regimes. [Preview Abstract] |
Sunday, November 20, 2016 3:49PM - 4:02PM |
D25.00005: Two-dimensional confocal laser scanning microscopy image correlation for nanoparticle flow velocimetry Brian Jun, Matthew Giarra, Brian Golz, Russell Main, Pavlos Vlachos We present a methodology to mitigate the major sources of error associated with two-dimensional confocal laser scanning microscopy (CLSM) images of nanoparticles flowing through a microfluidic channel. The correlation-based velocity measurements from CLSM images are subject to random error due to the Brownian motion of nanometer-sized tracer particles, and a bias error due to the formation of images by raster scanning. Here, we develop a novel ensemble phase correlation with dynamic optimal filter that maximizes the correlation strength, which diminishes the random error. In addition, we introduce an analytical model of CLSM measurement bias error correction due to two-dimensional image scanning of tracer particles. We tested our technique using both synthetic and experimental images of nanoparticles flowing through a microfluidic channel. We observed that our technique reduced the error by up to a factor of ten compared to ensemble standard cross correlation (SCC) for the images tested in the present work. Subsequently, we will assess our framework further, by interrogating nanoscale flow in the cell culture environment (transport within the lacunar-canalicular system) to demonstrate our ability to accurately resolve flow measurements in a biological system. [Preview Abstract] |
Sunday, November 20, 2016 4:02PM - 4:15PM |
D25.00006: Extension of Kirkwood-Riseman Theory across the Entire Range of Knudsen Numbers James Corson, Michael Zachariah, George Mulholland, Howard Baum Aggregates of small, spherical particles form in many high temperature processes (e.g. soot formation). We consider the drag force on a fractal aggregate using Kirkwood-Riseman (KR) theory, in which the force exerted on each particle in the aggregate can be obtained from the hydrodynamic interaction tensor \textbf{T} and the friction coefficient $f$ for flow around an isolated sphere. The force on the aggregate is the vector sum of the force on each particle. Meakin and Deutch (1987) demonstrated that this approach yields a reasonable estimate of the drag force for an aggregate in continuum flow, where \textbf{T} is the modified Oseen tensor of Rotne and Prager. We have extended this approach across the entire Knudsen range by calculating \textbf{T} and $f$ using the BGK model in the linearized Boltzmann equation. Our results for $f$ agree with Millikan's data for the entire Knudsen range, and the free molecular drag force on the aggregate calculated with our extended KR theory is within a few percent of the drag computed using Monte Carlo methods. These results suggest that we can obtain a reasonable estimate of the drag in the transition regime in seconds once we have obtained \textbf{T} and $f$ for a given Knudsen number. [Preview Abstract] |
Sunday, November 20, 2016 4:15PM - 4:28PM |
D25.00007: Sheath-Free Elasto-Inertia Separation of Particles Based on Shape in Straight Rectangular Microchannels. Xiangchun Xuan, Xinyu Lu We demonstrate the use of straight rectangular microchannels to obtain a shape-based separation of equal-volumed spherical and peanut-shaped particles in viscoelastic fluids. This continuous sheath-free separation arises from the shape-dependent equilibrium particle positions as a result of the flow-induced elasto-inertial lift. A continuous transition from single to dual and to triple equilibrium positions is observed for both types of particles with the increase of flow rate. However, the flow rate at which the transition occurs differs with the particle shape, which is thought to correlate the rotational effects of non-spherical particles. [Preview Abstract] |
Sunday, November 20, 2016 4:28PM - 4:41PM |
D25.00008: Dynamical Density Functional Theory and Hydrodynamic Interactions in Confined Systems Benjamin Goddard, Andreas Nold, Serafim Kalliadasis Colloidal systems consist of nano- to micrometer-sized particles suspended in a bath of many more, much smaller and much lighter particles. Motion of the colloidal particles through the bath, e.g. when driven by external forces such as gravity, induces flows in the bath. These flows in turn impart forces on the colloid particles. These bath-mediated forces, known as Hydrodynamic Interactions (HIs) strongly influence the dynamics of the colloid particles. This is particularly true in confined systems, in which the presence of walls substantially modifies the HIs compared to unbounded geometries. For many-particle systems, the many of degrees of freedom prohibit a direct solution of the underlying stochastic equations and a reduced model is necessary. We employ elements from the statistical mechanics of classical fluids, namely Dynamical Density Functional Theory (DDFT) [1,2], the computational complexity of which is independent of the number of particles to include both inter-particle and particle-wall HI and demonstrate the physical importance of using the correct description of HIs in confined systems. In addition, DDFT allows us to isolate and investigate different components of HIs.\\{} [1] Phys. Rev. Lett. 109, 120603 (2012)\\{} [2] J. Phys.: Condens. Matter 25, 035101 (2013) [Preview Abstract] |
Sunday, November 20, 2016 4:41PM - 4:54PM |
D25.00009: Three-dimensional particle migration in a bubble-driven acoustic streaming flow Andreas Volk, Massimiliano Rossi, Bhargav Rallabandi, Sascha Hilgenfeldt, Christian J. Kaehler, Alvaro Marin Oscillations of hemicylindrical bubbles in microchannels generate streaming flows with characteristic toroidal structures. Over long times, a passive tracer in such a flow typically explores a large fluid volume extending several bubble radii away from the bubble center and covering the whole height of the microchannel parallel to the bubble axis. In contrast, finite-sized particles are observed to migrate to specific confined locations along the axial direction while being confined to orbits of much smaller radial extent. The size of the orbits and the axial location not only depend on the particle size, but also on the relative particle density with the surrounding fluid. In this work we will show three-dimensional measurements that reveal the size- and density-sensitive migration of the particles. A simple way to emulate the migration is to solve numerically the trajectory of a particle including only steric interactions with the bubble and the walls due to its finite size (no penetration). By comparing the experimental results with this simplistic numerical model, we will show that additional forces are necessary to explain the particle dynamics. Finally, we will discuss the effect of hydrodynamic and acoustic forces experienced by the particle in the vicinity of the bubble. [Preview Abstract] |
Sunday, November 20, 2016 4:54PM - 5:07PM |
D25.00010: Experimental analysis on viscoelasticity-induced migration of RBCs using digital holographic microscopy Taesik Go, Hyeokjun Byeon, Sang Joon Lee Migration of particles in viscoelastic fluids has recently received large attention, because the generated elastic forces in viscoelastic fluids give rise to a simple focusing pattern over a wide range of flow rates. In this study, the vertical focusing and alignment of rigid spherical particles, normal and hardened RBCs in a viscoelastic fluid were experimentally investigated by employing a digital in-line holographic microscopy (DIHM). By the elastic forces, the three different particles are pushed away from the walls and concentrated in the midplane of the rectangular microchannel. Furthermore, most of both RBCs maintain face-on orientation in the microchannel. The effects of deformability of RBC on the viscoelasticity-induced migration and orientation in the channel were also examined. In contrary to non-deformable particles, normal RBCs are dispersed as flow rate increases. In the region near side wall of the microchannel, normal RBCs have edge-on orientation with a large angle of inclination, compared to hardened RBCs. These findings have a strong potential in the design of microfluidic devices for deformability-based separation of cells in viscoelastic fluid flows and label-free diagnoses of certain hematological diseases. [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