Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session R12: Flow of Complex Fluids |
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Sponsoring Units: DFD Chair: Weili Luo, University of Central Florida Room: 271 |
Thursday, March 16, 2017 8:00AM - 8:12AM |
R12.00001: Flow Velocity Profiles in Actively-Driven 2D Nozzle Experiments using Freely-Suspended Smectic Liquid Crystal Films Evan Dutch, Corrina Briggs, Kyle Ferguson, Adam Green, Cheol Park, Matt Glaser, Joe Maclennan, Noel Clark Freely-suspended smectic A liquid crystal films have been used to explore a large range of interesting flow phenomena. Passive microrheology experiments have confirmed previously that such films are ideal systems with which to investigate two-dimensional (2D) hydrodynamics. Here we describe an experiment that uses smectic films to study actively-driven 2D flows. Flow excited by blowing air over a film of smectic liquid crystal material containing small inclusions is captured using digital video microscopy. The flow fields are extracted using particle imaging velocimetry. We have measured the velocity field generated by flow through a thin nozzle into a large rectangular reservoir and compared this to a theoretical model based on 2D complex potential flows. The observations confirm that there is parabolic flow in straight channels, and that the theory accurately models the film velocity flow field in the reservoir. [Preview Abstract] |
Thursday, March 16, 2017 8:12AM - 8:24AM |
R12.00002: Observation of localized, anti-equilibration flow in a quasi-one-dimensional magnetic fluid in horizontal field and temperature gradients Weili Luo, Jun Huang, Tianshu Liu Heat flows from high temperature to low temperature in almost all thermal phenomena in nature as well as in our daily life. In this paper we report a counter example: heat is held “localized” in place, halting the approaching to equilibrium in the system by magnetic body force originated from both temperature and field gradients in a magnetic fluid. Using two different configurations of temperature and magnetic field gradients, we observed magnetic field-induced flows that either enhance the gravito-thermal convection when the gradients of temperature and field are parallel to each other, or suppress it when the two gradients are antiparallel, where the convection roll in zero field was replaced by two localized flows at the two ends of the sample cell. This flow structure stops the heat flow of approaching to thermal equilibrium in the system, causing the temperature difference across the sample to increase with applied fields. The drastically different effects of the magnetic force on the equilibration processes resulted from two totally different topological flow-structures for the two experimental configurations imply a profound bifurcation of solutions for the underlying physics. [Preview Abstract] |
Thursday, March 16, 2017 8:24AM - 8:36AM |
R12.00003: Field-dependent flow patterns in a quasi one dimensional magnetic fluid Jun Huang, Tianshu Liu, Darian Smally, Ian Harmon, Weili Luo In an experiment designed to study the magnetically driven convective instability in a quasi-one-dimensional magnetic fluid, multiple intrigue phenomena occurred, including field dependent heat transfer, localized flows, possible crossover from two-dimensional to three-dimensional flows, and configuration-dependent flow patterns, etc. The gravito-thermal convective and magneto-thermal convective Rayleigh numbers, as well as Q field plots indicate the crossover from buoyancy-driven to magnetically-driven convection for field larger than 300 G. The interaction between the magnetic force and the fluid flow clearly visible at the two ends of the sample cells. These results provide the underlying mechanism for earlier observations [1] of dissimilar field dependence of temperature difference across the sample, indicating that heat transfer in a fluid can be controlled by applied magnetic field through controlling the flow structures of the system. Reference: [1] Jun Huang and Weili Luo “Heat Transfer Through Convection in a Quasi-One-Dimensional Magnetic Fluid.” Journal of Thermal Analysis & Calorimetry, 113, p449 (2013). [Preview Abstract] |
Thursday, March 16, 2017 8:36AM - 8:48AM |
R12.00004: Blood Back Spatter Caused by a Blunt Bullet Gunshot: Theory and Experiments Patrick Comiskey, Alexander Yarin, Sungu Kim, Daniel Attinger A theoretical model describing the blood back spatter pattern resulting from a blunt bullet gunshot is proposed and compared to experimental data. It is shown that the blunt bullet impact results in blood accelerating towards air opposite of the bullet motion creating a situation for the Rayleigh-Taylor instability which determines droplet sizes and initial velocities. Then, drop trajectories can be predicted accounting for all forces involved: air drag and gravity forces, as well as for the collective effect of drop-drop interaction through air which diminishes the drag force on drops moving in the wake of the others. Experimental data was acquired by shooting a blunt bullet into a porous substrate impregnated with swine blood and the spatter pattern was collected on a vertical surface located between the target and the shooter. The spatter pattern was analyzed for the number of droplets, the area of blood stains, total stain area, and location. Comparisons with the theoretical results reveal satisfactory agreement. The theory also predicts the impact angle at the collection surface, the Weber number corresponding to the drop impact onto the collection surface, and the stain ellipticity. [Preview Abstract] |
Thursday, March 16, 2017 8:48AM - 9:00AM |
R12.00005: Flow pattern in the ventricle of brain with cilia beating and CSF circulation Yong Wang, Christian Westendorf, Regina Faubel, Gregor Eichele, Eberhard Bodenschatz We recently discovered that cilia of the ventral third ventricle (v3V) of mammalian brain generate a complex flow network close to the wall. However, the flow pattern in the overall three dimensional v3V, especially under physiological condition, remains to be investigated. Computational fluid dynamics is arguably the best approach for such investigations. Several v3V geometries are reconstructed from different data for comparison study. The lattice Boltzmann method and immersed boundary method are used to reproduce the experimental set-up for an opened v3V firstly. The experimentally recorded cilia induced flow network is projected on the curved v3V wall. The flow maps obtained numerically at different heights from the v3V wall agree with the experimental data qualitatively. We then consider the entire v3V with ciliary flow network along the wall for boundary condition. Moreover, we add a time dependent flow rate to represent the CSF circulation, and study flow pattern in the ventricle. We thank the Max Planck Society (MPG) for financial support. This work is conducted within the Physics and Medicine Initiative at Goettingen Campus between MPG and University Medical Center. [Preview Abstract] |
Thursday, March 16, 2017 9:00AM - 9:12AM |
R12.00006: Explicit water based quasi-continuum approach for electric double layers (EDLs). Sikandar Y. Mashayak, Narayana R. Aluru Electrostatic interactions of interfacial water molecules play a dominant role in determining the distribution of ions in EDLs. Most theories for EDLs are inaccurate because they fail to include molecular effects of water, such as dielectric permittivity variation and ion hydration. On the other hand, a detailed atomic-level study of EDLs using molecular dynamics (MD) simulations can be prohibitively expensive. To address these issues, we propose a multiscale approach to simulate EDLs based on point dipole coarse-grained (CG) water model and an empirical potential-based quasi-continuum theory (EQT), which incorporates the polarization and hydration effects of water explicitly. To reproduce hydration of ions, ion-water CG potentials are developed. We demonstrate EQT for EDL by simulating NaCl aqueous electrolyte confined in slit-like capacitor channels at various ion concentrations and surface charge densities. We show that the ion and water densities from EQT agree well with the reference MD simulations. EQT is not only as accurate as MD but also orders of magnitude faster than MD. Therefore, EQT provides a multiscale framework to accurately model EDLs, which are fundamental to technological applications such as energy storage, water desalination, and biological systems. [Preview Abstract] |
Thursday, March 16, 2017 9:12AM - 9:24AM |
R12.00007: Comprehensive study of thin film evaporation from nanoporous membranes for enhanced thermal management Kyle Wilke, Banafsheh Barabadi, Zhengmao Lu, TieJun Zhang, Evelyn Wang Performance of emerging electronics is often dictated by the ability to dissipate heat generated in the device. Thin film evaporation from nanopores promises enhanced thermal management by reducing the thermal transport resistance across the liquid film while providing capillary pumping. We present a study of the dependence of evaporation from nanopores on a variety of geometric parameters. Anodic aluminum oxide membranes were used as an experimental template. A biphilic treatment was also used to create a hydrophobic section of the pore to control meniscus location. We demonstrated different heat transfer regimes and observed more than an order of magnitude increase in dissipated heat flux by confining fluid within the nanopore. Pore diameter had little effect on evaporation performance at pore radii of this length scale due to the negligible conduction resistance from the pore wall to the evaporating interface. The dissipated heat flux scaled linearly with porosity as the evaporative area increased. Furthermore, it was demonstrated that moving the meniscus as little as 1 $\mu $m into the pore could decrease performance significantly. The results provide a better understanding of evaporation from nanopores and provide guidance in future device design. [Preview Abstract] |
Thursday, March 16, 2017 9:24AM - 9:36AM |
R12.00008: Asphaltenes adsorption on functionalized substrates Philippe Bourrianne, Henri-Louis Girard, Dayong Chen, Kripa Varanasi, Robert Cohen, Gareth McKinley Asphaltenes are aromatic heavy components of crude oil. Their presence in petroleum applications and their ability to adsorb onto various substrates can induce serious damage such as pipe clogging. We study the effect of the chemical properties of the substrate on the extent of this adsorption. Based on chemical characterizations, wetting studies and roughness estimations, we develop different tools to investigate the deposition of those molecules. Then, we quantify the adsorption based on various techniques including QCM and ellipsometry. We discuss the effect of roughness on those results and suggest a possible mechanism for this adsorption. [Preview Abstract] |
Thursday, March 16, 2017 9:36AM - 9:48AM |
R12.00009: Nanoconfined water under varying ionic and compressive conditions Shah Khan, Peter Hoffmann The nano-mechanics and dynamics of molecularly thin layers of water are not well understood. While researchers agree at some of the characteristics such as ordering of water molecules along atomically smooth surfaces, some other properties, such as the viscoelastic response of a nanoconfined water film, remain highly controversial. Using atomic force microscope, we have shown in the past (Phys. Rev. Lett. 2010) that the viscoelastic properties of nanoconfined ultrapure water film depend upon the squeeze rate, changing from a liquid-like to a solid-like, at very low compression rate (0.8 nm/s), as observed from an order of magnitude increase in the relaxation time. Recently, we have shown that the introduction of NaCl in nanoconfined water significantly increases the range of ordered layers of water as well as the Maxwell's relaxation time at even lower compression rates, 0.2 nm/s (Langmuir 2016). Here we will discuss a collective picture of nanoconfined water film based on these findings as well as our new results about CsCl in nanoconfined water resulting in bulk-like relaxation time thereby suppressing the dynamic solidification trend. [Preview Abstract] |
Thursday, March 16, 2017 9:48AM - 10:00AM |
R12.00010: Liquid ``Coffee Rings'' and the Spreading of Volatile Liquid Mixtures Clay Wood, Justin Pye, Justin Burton When a volatile liquid drop is placed on a wetting surface, it rapidly spreads and evaporates. The spreading~dynamics and drop geometry~are determined by a balance between thermal and interfacial forces, including Marangoni effects. However, this spreading behavior is drastically altered when drops contain a miniscule amount of a less-volatile miscible liquid (solute) in the bulk (solvent); contact line instabilities in the form of ``fingers'' develop. Characteristic finger size increases with increasing solute concentration and is apparent for concentrations as small as 0.1{\%} by volume.~Also, the spreading rate depends sensitively on the solute concentration, especially if the solute~preferentially wets the substrate.~At higher solute concentrations, the spreading droplet will form ``beads'' at the contact line, rather than fingers,~and are~deposited as the~solvent~recedes and evaporates, leaving behind a complex pattern of solute micro-droplets. Liquid ``coffee rings'' are often left behind after evaporation because there is a high evaporation rate of the solvent at the contact line, which increases the concentration of the solute, and the longevity of the rings depends on the solute vapor pressure. These results highlight the unusual sensitivity to contamination of volatile spreading, and the complex patterns of liquid contamination deposited following evaporation from a wetted surface. [Preview Abstract] |
Thursday, March 16, 2017 10:00AM - 10:12AM |
R12.00011: Self-Similar Apical Sharpening of a Perfecting Conducting Ideal Fluid Subject to Maxwell and Capillary Forces Chengzhe Zhou, Sandra Troian We examine the apical behavior of a perfectly conducting, incompressible, inviscid fluid in vacuum for which Maxwell, capillary and inertial forces generate a conic cusp. A potential flow model has shown the existence of a family of self-similar solutions which in the far field away from the cusp assumes the conventional static Taylor cone angle (Zubarev 2001). These solutions were obtained by matching powers of the leading order terms in the velocity and electric field potentials to the asymptotic form dictated by the stationary cone shape. We have re-examined this original analysis and uncovered a neglected leading order term in both field potentials, whose solutions also satisfy the governing interfacial and far-field conditions. This new two-parameter family of solutions reveals a non-spherically symmetric velocity field whose streamlines are at an angle to the liquid interface and generate flow focusing. We outline the boundary-element technique used (Schulkes 1994) for solving the exact similarity forms in a semi-infinite domain and discuss consequences of our findings including time reversed shapes describing conic tip recoil after fluid ejection. [Preview Abstract] |
Thursday, March 16, 2017 10:12AM - 10:24AM |
R12.00012: A two-phase theory for non-Newtonian suspensions Christos Varsakelis In this talk, a continuum and thermodynamically consistent theory for macroscopic particles immersed in a non-Newtonian fluid is presented. According to the employed methodology, each phase of the mixture is treated as a thermodynamic system, endowed with its own set of thermodynamic and kinetic variables, and is required to separately satisfy the equations for the balance of mass, momentum and energy. As both constituents of the mixture are not simple fluids, additional degrees of freedom are introduced for the proper description of their thermodynamic state. A subsequent exploitation of the entropy inequality asserts that the accommodation of the complicated rheological characteristics of both phases requires a departure from a linear current-force relationship. For this reason, a subtle nonlinear representation of the stress tensors is employed. Importantly, the inclusion of additional degrees of freedom allows us to obtain a rate equation for the evolution of the volume fraction of the particulate phase. Following a delineation of the fundamentals of the proposed theory, the talk concludes with the presentation of some limiting cases that also serve as preliminary, sanity tests. [Preview Abstract] |
Thursday, March 16, 2017 10:24AM - 10:36AM |
R12.00013: Shear-induced clustering of Brownian suspensions in associative polymers at moderate Peclet number Juntae Kim, Matthew Helgeson The tendency for Brownian particles to cluster under shear flow is widely observed in polymer-colloid mixtures. However, the mechanics driving clustering are not well understood due to the complex coupling of non-Newtonian polymer rheology with colloidal hydrodynamics and Brownian motion. To better elucidate this coupling, we have developed a novel class of thermoresponsive polymer-colloid mixtures based on nanoemulsions suspended in associative polymer solutions. These fluids form associative polymer networks whose viscoelastic relaxation time can be varied by many orders of magnitude over a small temperature window, while keeping the Brownian relaxation time of the suspension relatively fixed. Combining this model system with novel rheo-small angle neutron scattering (rheo-SANS) measurements allows us to identify the mechanisms of shear-induced clustering, and how they vary in different dynamical regimes of fluid behavior. In particular, the ability to probe the full 3D microstructure of the fluid identifies features of shear-induced clusters, both during their formation and at steady state, that were inaccessible in previous studies. These features reveal that hydrodynamic effects dominate the clustering process over a wide range of conditions, and provide guidelines for controlling shear-induced clustering in polymeric fluids. [Preview Abstract] |
Thursday, March 16, 2017 10:36AM - 10:48AM |
R12.00014: Phototaxis beyond turning: persistent accumulation and response acclimation of the microalga Chlamydomonas reinhardtii Marco Polin, Jorge Arrieta, Ana Barreira, Maurizio Chioccioli, Idan Tuval Phototaxis is an important reaction to light displayed by a wide range of motile microorganisms, from bacteria to ciliates. Flagellated eukaryotic microalgae in particular, like the model organism Chlamydomonas reinhardtii, steer either towards or away from light by a rapid and precisely timed modulation of their flagellar activity. Cell steering, however, is only the beginning of a much longer process which ultimately allows cells to determine their light exposure history. This process is not well understood. Here we present a first quantitative study of the long timescale phototactic motility of Chlamydomonas at both single cell and population levels. Our results reveal that the phototactic strategy adopted by these microorganisms leads to an efficient exposure to light, and that the phototactic response is modulated over typical timescales of tens of sec- onds. The adaptation dynamics for phototaxis and chlorophyll fluorescence show a striking quantitative agreement, suggesting that photosynthesis controls quantitatively how cells navigate a light field. [Preview Abstract] |
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