Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session F29: Flow of Complex Fluids, Polymers, and Particles |
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Sponsoring Units: DFD GSOFT GSNP Chair: Marco G. Mazza, Max Planck Institute for Dynamics and Self-Organization Room: BCEC 162A |
Tuesday, March 5, 2019 11:15AM - 11:27AM |
F29.00001: Probing multiphase flows with x-ray near-field speckles Jin Wang, Qing Zhang, Ya Ga, Qingteng Zhang, Miaoqi Chu Multiphase flows of simple and complex fluids are of great fundamental and practical interests due to their multitude of applications. However, multiphase flows are also often difficult to study optically because of intense multiple light scattering from the phase boundaries in the flow, such as liquid/gas interfaces. X-rays are highly penetrable in a multiphase flow because of the weak interaction between x-rays and materials. X-ray near-field speckles can be generated readily when x-rays pass through the flow. The x-rays do not need to be completely coherent. A partial or local coherence is sufficient to produce significant intensity fluctuation in the transmitted beam that can used to probe both morphology and dynamics. Combined with ultrafast imaging, x-ray near-field speckles and their spatiotemporal correlations have been proven powerful to interrogate multiphase flows highly transient and far from equilibrium. |
Tuesday, March 5, 2019 11:27AM - 11:39AM |
F29.00002: Effects of passive hydrodynamics force on harmonic and chaotic oscillations in nonlinear chemical dynamics Jean Bio Chabi Orou
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Tuesday, March 5, 2019 11:39AM - 11:51AM |
F29.00003: HYDRODYNAMIC RESISTANCE DUE TO POLYMER-INDUCED ELASTIC TURBULENCE IN MICROFLUIDIC SERPENTINE FLOWS Siddhartha Gupta, Raju Neelamegam, Siva A Vanapalli It has been shown that viscoelastic curvilinear flows transition to turbulence in the limit of diminishing Reynolds numbers (Re → 0) with the onset determined by a critical Weissenberg number (Wic). Serpentine microfluidic geometries have been used to characterize such flows, however, the pressure drop-flow rate dynamics during elastic turbulence is still unexplored. To quantify the hydrodynamic resistance due to elastic turbulence, we map the pressure drop versus flow rate relationship due to elastic turbulence using the iCapillary technique. The instability was investigated for high molecular weight poly ethylene oxide in aqueous-glycerol solvents and a scaling relationship with a saturation plateau was observed for different solvent viscosities based on normalized solution driving pressure with respect to the solvent (ΔP/ ΔPsol) and plotting against the Weissenberg number. Additionally, Lagrangian representation of the flow was done with digital holography microscopy and CFD simulations were used to analyze deviations from simple shear thinning flows. Thus, we report the first known characterization of flow resistance due to elastic turbulence. The flow resistance relations may provide new insights for structural characterization of polymeric and biofluids. |
Tuesday, March 5, 2019 11:51AM - 12:03PM |
F29.00004: Heat Transfer Enhancement in Helically Micro-Coiled Tubes Using Nanoparticle-Viscoelastic Fluids by Elastic Turbulence Haie Yang, Guice Yao, Haichuan Jin, Dongsheng Wen In recent years, the application of micro-systems has received more and more attention. However, the microsystem scale is small, which greatly limits the flow Reynolds number. It’s difficult for the flow of Newtonian fluid to be turbulent flow at low Reynolds number, limiting the mixing and heat transfer in micro-systems. Nanoparticle-viscoelastic fluids (henceforth referred to as NPVE fluid) were utilized as the experimental group and water as the comparison group. Heat transfer performance of these two groups of fluids under different Reynolds numbers was tested, respectively. Heat transfer efficiency is approximately 35% stronger than water under the same conditions after using a viscoelastic suspension of nanoparticles. |
Tuesday, March 5, 2019 12:03PM - 12:15PM |
F29.00005: Turbulent Submerged Jets of Dilute Polymer Solutions Sami Yamanidouzisorkhabi, Gareth McKinley, Irmgard Bischofberger Dilute synthetic polymer solutions have been shown to reduce turbulent drag in pipelines and around marine vehicles. Water-soluble biopolymers such as flax seed mucilage extracts have the potential to serve as cheap and environmentally friendly alternatives to synthetic polymers. In this work, we employ Schlieren imaging to unveil the mixing dynamics and recirculating regions that develop in turbulent jets of dilute aqueous polymer solutions submerged in quiescent water. At the interface of the viscoelastic jet and water, a free shear boundary layer develops leading to momentum transfer between the two fluids. We demonstrate the impact of viscoelasticity on this momentum transfer and evaluate the performance of both synthetic polymers and biopolymers in damping turbulent vortical structures. |
Tuesday, March 5, 2019 12:15PM - 12:27PM |
F29.00006: Hydrodynamics around aggregating charged grains Chamkor Singh, Marco G. Mazza The growth of protoplanetary dust from sub-millimeter sized particles to much larger scales is not well understood. There is considerable debate about the role of electrostatic charging of grains in the aggregation process. Additional complexity arises due to the presence of complex hydrodynamic flow that couples to the aggregating grains. We study this growth process using massively parallel molecular dynamics simulations for the granular particles in combination with the smoothed-particle hydrodynamics for the interstitial flow. The results from a detailed cluster analysis are presented. Finally we propose an effective kinetic model for the charged grain aggregation inside interstitial flow. |
Tuesday, March 5, 2019 12:27PM - 12:39PM |
F29.00007: Gravity-Driven Flow and Clogging in the Presence of an Obstacle Anna Belle Harada, Kerstin Nordstrom We present experimental results of 2D gravity-driven flows of >10,000 monodisperse hard spheres (diameter = D) through an aperture (width = W). We introduce into the system a fixed obstacle of varying size (diameter = D0) and distance above the aperture (L). We use a force sensor to measure the bulk flow rate, and high-speed, high-resolution video to track individual grains. We observe that obstacles tend to decrease the flow rate, but also decrease the clogging probability, and specifically measure the flow rate and clogging probability as a function of D0 and L for different aperture widths. As our packing is crystalline, we can correlate these features with structural measurements in the material such as dislocations and the bond order parameter. We also present dynamical measurements such as nonaffine rearrangements and cooperative motion. |
Tuesday, March 5, 2019 12:39PM - 12:51PM |
F29.00008: Large-scale flow out of spatiotemporal chaos in electroconvection of cholesteric liquid crystal Yohsuke Fukai, Masaki Sano Convection in a thin layer of liquid crystal driven by an electric field has long been studied as a model system to investigate pattern formation in out-of-equilibrium systems. In particular, it has been known that the flow typically shows spatiotemporal chaotic patterns called dynamic scattering mode with high voltage. In this presentation, we report our observation that this chaotic pattern organizes itself into a large-scale flow perpendicular to the electric field in the case where cholesteric liquid crystal with the negative dielectric constant difference is used. The typical scale of this flow pattern is more than 100 times larger than the distance between the electrodes, the characteristic length scale of the convection. We will discuss the effect of the anchoring and boundary conditions, and possible interpretation toward understanding the mechanism. |
Tuesday, March 5, 2019 12:51PM - 1:03PM |
F29.00009: Chemical and hydrodynamic instabilities produced by enzymatic surface reactions Oleg Shklyaev, Victor V Yashin, Anna Christina Balazs Chemical oscillations are ubiquitous in nature and have a variety of promising applications. Here, we examine a linear stability of a multicomponent reactive fluid that contains two species, X and Y, which undergo transformations catalyzed by enzymes immobilized at two infinite horizontal plates confining the fluid. The surface reactions with the enzymes provide a negative feedback in the system. The first enzyme, localized on the first plate, promotes production of chemical X, while the second enzyme, immobilized on the second plate, promotes production of chemical Y, which inhibits the production of chemical X. Depending on the reaction rates and densities of the reactants, the monotonic and oscillatory instabilities could occur in the system. The first instability (similar to Rayleigh-Benard case) leads to roll-like convective structures that are periodically distributed along the layer. The second instability produces horizontally uniform temporal oscillations of concentrations of the chemicals X and Y. The findings provide guidance for designing micro-scale chemical reactors with improved functionalities. |
Tuesday, March 5, 2019 1:03PM - 1:15PM |
F29.00010: RMD2Kin: an automated, self-consistent, first-principles based approach to extract kinetic data from reactive molecular dynamics simulations Daniil Ilyin, William Goddard, Julius Oppenheim, Tao Cheng, Sergey Zybin, Robert Nielsen Capturing intricate details of the chemistry of important technological processes such as combustion and chemical vapor deposition is a challenge in large-scale simulations. Conventionally, necessary kinetic data are obtained either empirically or from experiments in dilute conditions, and these data may not fully describe interactions that occur in realistic systems. We present here an automated, self-consistent, first-principles based approach to extract kinetic data and reaction mechanisms from reactive molecular dynamics simulations. This approach provides a detailed analytic description of the evolution of a complex chemical system from reactants through various intermediates to products, which can then be used to incorporate the correct reaction chemistry into computational fluid dynamics and/or continuum chemical dynamics simulations. This approach is self-consistent and does not require previous knowledge of the specific chemistry of the system. We refer to this approach as RMD2Kin. |
Tuesday, March 5, 2019 1:15PM - 1:27PM |
F29.00011: Distribution of tracer particles around a catalytic Janus particle William Uspal, Jaideep Katuri, Mihail N. Popescu, Samuel Sanchez Active Janus particles self-propel by catalyzing the decomposition of molecular “fuel” available in the surrounding solution. The resulting self-generated chemical gradients drive phoretic flow in an interfacial layer surrounding the particle, as well as chemi-osmotic interfacial flows along nearby container walls. Through experiments and theory, we consider the distribution of small tracer particles around a Janus particle in the vicinity of a planar wall. The Janus particle is either free to move or stuck to the wall, and its axis of symmetry is oriented in the plane of the wall. Experimentally, we observe that, under certain conditions, the catalytic cap of a particle is surrounded by a tracer-free exclusion zone. To understand this finding, we model the motion of tracer particles. In our model, the tracers are advected by fluid flows driven in the bulk solution by phoretic and/or chemi-osmotic interfacial flows. Additionally, the tracers can respond to chemical gradients through phoresis, providing a third contribution to tracer velocity. We find that these three ingredients can combine to create an exclusion zone. In particular, we highlight the essential role of chemi-osmotic flow, which is often neglected in modeling and interpretation of experiments. |
Tuesday, March 5, 2019 1:27PM - 1:39PM |
F29.00012: Reducing Blood Viscosity and Suppressing Turbulence with Magnetic Field to Prevent Heart Attack and Stroke Rongjia Tao Heart attacks and strokes are the leading causes of death. High blood viscosity and turbulence in blood circulation are the keys to trigger these diseases, as they place much heavier workload on the heart, develop atherosclerotic plaque and may rapture blood vessels. Reducing blood viscosity and suppressing turbulence is thus the key to prevent cardiovascular diseases. Unfortunately, these two tasks conflict each other. Presently, the only method to reduce blood viscosity is to take medicine, but this method makes the turbulence worse because the Reynolds number goes up with viscosity reduction. Here we report our discovery with magnetorheology (MR): applying a strong magnetic field to blood along its flow direction, red blood cells are polarized and aggregated into short chains. The blood viscosity becomes anisotropic: it is significantly reduced along the flow direction, but is considerably increased in the directions perpendicular to the flow. The blood flow thus becomes laminar and turbulence is suppressed. Our lab and animal tests show that this technology can successfully prevent plaque development. The clinical trials further confirm that this MR technology can effectively cure hypertension and help people to prevent heart attack and stroke. |
Tuesday, March 5, 2019 1:39PM - 1:51PM |
F29.00013: Exploiting magnetocapillary interactions for swimming along liquid interfaces Nicolas Vandewalle, Galien Grosjean When soft ferromagnetic particles are suspended at air-water interfaces in the presence of a vertical magnetic field, dipole-dipole repulsion competes with capillary attraction such that 2d structures self-assemble. The complex arrangements of such floating bodies are emphasized. The equilibrium distance between particles exhibits hysteresis when the applied magnetic field is modified. Irreversible processes are evidenced. By adding a horizontal and oscillating magnetic field, periodic deformations of the assembly are induced. We show herein that collective particle motions induce locomotion at low Reynolds number. The physical mechanisms and geometrical ingredients behind this cooperative locomotion are identified. These physical mechanisms can be exploited to much smaller scales, offering the possibility to create artificial and versatile microscopic swimmers. Moreover, we show that it is possible to generate complex structures that are able to capture particles, perform cargo transport, fluid mixing, etc... |
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