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1

Nonlinear traveling waves in confined ferrofluids.

We study the development of nonlinear traveling waves on the interface separating two viscous fluids flowing in parallel in a vertical Hele-Shaw cell. One of the fluids is a ferrofluid and a uniform magnetic field is applied in the plane of the cell, making an angle with the initially undisturbed interface. We employ a mode-coupling theory that predicts the possibility of controlling the speed of the waves by purely magnetic means. The influence of the tilted magnetic field on the waves shape profile and the establishment of stationary traveling wave structures are investigated. PMID:23214870

Lira, Sérgio A; Miranda, José A

2012-11-01

2

NASA Astrophysics Data System (ADS)

Yves Couder, Emmanuel Fort, and coworkers recently discovered that a millimetric droplet sustained on the surface of a vibrating fluid bath may self-propel through a resonant interaction with its own wave field. This article reviews experimental evidence indicating that the walking droplets exhibit certain features previously thought to be exclusive to the microscopic, quantum realm. It then reviews theoretical descriptions of this hydrodynamic pilot-wave system that yield insight into the origins of its quantum-like behavior. Quantization arises from the dynamic constraint imposed on the droplet by its pilot-wave field, and multimodal statistics appear to be a feature of chaotic pilot-wave dynamics. I attempt to assess the potential and limitations of this hydrodynamic system as a quantum analog. This fluid system is compared to quantum pilot-wave theories, shown to be markedly different from Bohmian mechanics and more closely related to de Broglie's original conception of quantum dynamics, his double-solution theory, and its relatively recent extensions through researchers in stochastic electrodynamics.

Bush, John W. M.

2015-01-01

3

Hydrodynamics of chains in ferrofluid-based magnetorheological fluids under rotating magnetic field.

Ferrofluid-based magnetorheological (MR) fluid is prepared by dispersing micron-size magnetic spheres in a ferrofluid. We report here the mechanism of chain formation in ferrofluid based MR fluid, which is quite different from conventional MR fluid. Some of the nanomagnetic particles of ferrofluid filled inside the microcavities are formed due to association of large particles, and some of them are attached at the end of large particles. Under rotating magnetic field, fragmentation of a single chain into three parts is observed. Two of them are chains of micron-size magnetic particles which are suspended in a ferrofluid, and the third one is the chain of nanomagnetic particles of ferrofluid, which may be the connecting bridge between the two chains of larger magnetic particles. The rupture of a single chain provides evidence for the presence of nanomagnetic particles within the magnetic field-induced chainlike structure in this bidispersed MR fluid. PMID:19658750

Patel, Rajesh; Chudasama, Bhupendra

2009-07-01

4

Yves Couder, Emmanuel Fort, and coworkers recently discovered that a millimetric droplet sustained on the surface of a vibrating fluid bath may self-propel through a resonant interaction with its own wave field. This article ...

Bush, John W. M.

5

Generalized hydrodynamics and heat waves

By using the evolution equations of generalized hydrodynamics we investigate heat-pulse propagation in a Lennard-Jones liquid contained in the annulus between two concentric cylinders at different temperatures. It is found that the heat pulse propagates as a wave of a finite speed when a composite fluid dynamic number N(R) that depends on the thermal conductivity and wall temperature ratio is

R. E. Khayat; Byung C. Eu

1992-01-01

6

Surface waves on ferrofluids exposed to a dc magnetic field exhibit a nonmonotonic dispersion relation. The effect of a parametric driving on such waves is studied within suitable coupled Ginzburg-Landau equations. Due to the nonmonotonicity the neutral curve for the excitation of standing waves can have up to three minima. The stability of the waves with respect to long-wave perturbations is determined via a phase-diffusion equation. It shows that the band of stable wave numbers can split up into two or three subbands. The resulting competition between the wave numbers corresponding to the respective subbands leads quite naturally to patterns consisting of multiple domains of standing waves which differ in their wave number. The coarsening dynamics of such domain structures is addressed. {copyright} {ital 1997} {ital The American Physical Society}

Raitt, D. [SCRI, Florida State University B-186, 400 Dirac Science Center Library, Tallahassee, Florida 32306 (United States)] [SCRI, Florida State University B-186, 400 Dirac Science Center Library, Tallahassee, Florida 32306 (United States); Riecke, H. [Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois 60208 (United States)] [Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois 60208 (United States)

1997-05-01

7

Nonlinear waves in second order conformal hydrodynamics

NASA Astrophysics Data System (ADS)

In this work we study wave propagation in dissipative relativistic fluids described by a simplified set of the 2nd order viscous conformal hydrodynamic equations corresponding to Israel-Stewart theory. Small amplitude waves are studied within the linearization approximation while waves with large amplitude are investigated using the reductive perturbation method, which is generalized to the case of 2nd order relativistic hydrodynamics. Our results indicate the presence of a 'soliton-like' wave solution in Israel-Stewart hydrodynamics despite the presence of dissipation and relaxation effects.

Fogaça, D. A.; Marrochio, H.; Navarra, F. S.; Noronha, J.

2015-02-01

8

NASA Technical Reports Server (NTRS)

A new Ferrofluidics exclusion seal promises improvement in controlling "fugitive emissions" -vapors that escape into the atmosphere from petroleum refining and chemical processing facilities. These are primarily volatile organic compounds, and their emissions are highly regulated by the EPA. The ferrofluid system consists of a primary mechanical seal working in tandem with a secondary seal. Ferrofluids are magnetic liquids - fluids in which microscopic metal particles have been suspended, allowing the liquid to be controlled by a magnetic force. The concept was developed in the early years of the Space program, but never used. Two Avco scientists, however, saw commercial potential in ferrofluids and formed a company. Among exclusion seal commercial applications are rotary feedthrough seals, hydrodynamic bearings and fluids for home and automotive loudspeakers. Ferrofluidics has subsidiaries throughout the world.

1993-01-01

9

Propagation of waves in hydrodynamic shear flows

A range of phenomena connected with the propagation of waves in hydrodynamic shear flows is studied. The problem of calculating the energy and momentum of a wave packet in a moving medium is discussed in detail. It is shown that in many cases the momentum of a body moving in a liquid can be correctly calculated only if the compressibility

Yu A Stepanyants; A L Fabrikant

1989-01-01

10

Based on the momentum and continuity equations for ferrofluid under an applied magnetic field, a modified Reynolds equation has been obtained. Assuming linear behavior for the magnetic material of the ferrofluid, the magnetic force was calculated. The magnetic pressure resulting from the magnetic force was incorporated into the Reynolds equation and it was not separately treated. The derived Reynolds equation

T. A. Osman; G. S. Nada; Z. S. Safar

2001-01-01

11

The superreflection of waves in hydrodynamic flows

NASA Astrophysics Data System (ADS)

A mechanism for the amplification of different types of waves in hydrodynamics upon reflection from plane and cylindrical tangential discontinuities is analyzed. Consideration is given to the problem of the momentum and energy of the waves in the medium. The amplification is associated with the presence of negative-energy waves. The discussion of superreflection covers the Miles-Ribner problem, the resonances of supersonic flow, the superreflection of internal gravity waves, and Rossby waves at a tangential discontinuity. The related question of vortex oscillations is also considered.

Fabrikant, A. L.

12

Simple Waves in Ideal Radiation Hydrodynamics

In the dynamic diffusion limit of radiation hydrodynamics, advection dominates diffusion; the latter primarily affects small scales and has negligible impact on the large scale flow. The radiation can thus be accurately regarded as an ideal fluid, i.e., radiative diffusion can be neglected along with other forms of dissipation. This viewpoint is applied here to an analysis of simple waves in an ideal radiating fluid. It is shown that much of the hydrodynamic analysis carries over by simply replacing the material sound speed, pressure and index with the values appropriate for a radiating fluid. A complete analysis is performed for a centered rarefaction wave, and expressions are provided for the Riemann invariants and characteristic curves of the one-dimensional system of equations. The analytical solution is checked for consistency against a finite difference numerical integration, and the validity of neglecting the diffusion operator is demonstrated. An interesting physical result is that for a material component with a large number of internal degrees of freedom and an internal energy greater than that of the radiation, the sound speed increases as the fluid is rarefied. These solutions are an excellent test for radiation hydrodynamic codes operating in the dynamic diffusion regime. The general approach may be useful in the development of Godunov numerical schemes for radiation hydrodynamics.

Johnson, B M

2008-09-03

13

Optical hydrodynamics: A shock wave perspective

NASA Astrophysics Data System (ADS)

This dissertation presents experimental and theoretical studies of spatial dispersive shock waves. Inspired by the fluid analogy of wave dynamics, we made the first demonstration of a dispersive shock wave in spatial nonlinear optics. Richer phenomena are revealed with such dispersive waves' interactions and dynamics under various initial configurations. The phenomenological observations here will enable a novel way of all-optical modeling of fluid-like experiments in optics. Implied applications can be extended into many fields, including novel optical broadband sources, signal processing, optoelectronic devices, imaging and microscopy. Dispersive shock waves arise from nonlinear wave breaking and mode dispersion, and are a fundamental type of fluid behavior in systems with no or near-zero viscosity, such as inertia-dominated hydraulic bores, cold plasmas, and superfluids. At first, we experimentally exploit the well-known relation between superfluids and nonlinear optics to study the photonic equivalence of dispersive, dissipationless shock waves in the spatial regime. Basic interactions between them indicate a nonlinear version of Huygens' Principle. Although viscosity is absent in our physical systems, we investigate other means to suppress the dispersive shock wave through non-locality and spatial incoherence of light. This spatially incoherent light enables us to experimentally demonstrate a new type shock wave with effective "negative pressure" under a nonlinear Fresnel diffraction configuration. Also, we study the associated problem of the wave nonlinearly scattered by a barrier potential. Our observations suggest nonlinear wave tunneling, dispersive shock wave formation and optical hydrodynamic flow. Finally, we develop a novel method to probe the wave evolution dynamics along the nonlinear distorted medium. This new holographic approach may eventually lead to a new type of super-resolution microscopy in the near future.

Wan, Wenjie

14

Symposium: Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas

nonlinear phenomena ranging from optical communications and Bose con- densation to ocean waves. SolutionsSymposium: Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas Ildar R. Gabitov in a better scientific under- standing of nonlinear waves in various fields of nonlinear optics, hydrodynamics

Lushnikov, Pavel

15

Hydrodynamic Performance of a Wave Energy Converter

NASA Astrophysics Data System (ADS)

To harvest energy from ocean waves, a new wave energy converter (WEC) was proposed and tested in a wave tank. The WEC freely floats on the water surface and rides waves. It utilizes its wave-driven angular oscillation to convert the mechanical energy of waves into electricity. To gain the maximum possible angular oscillation of the WEC under specified wave conditions, both floatation of the WEC and wave interaction with the WEC play critical roles in a joint fashion. During the experiments, the submersion condition of the WEC and wave condition were varied. The results were analyzed in terms of the oscillation amplitude, stability, auto-orientation capability, and wave frequency dependency.

Yang, Yingchen

2010-11-01

16

Symposium: Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas

Progress in the development of new tools for modem apphed mathematics resulted in a better scientific under standing of nonlinear waves in various fields of nonlinear optics, hydrodynamics, and plasmas. The universahty of the equations describing wave processes is one of the most important components of this success. Nonlinear Schrodinger equation (NLS) and Korteweg de Vries equation are among best

Ildar R. Gabitov; Pavel M. Lushnikov

2009-01-01

17

NASA Astrophysics Data System (ADS)

This issue of Journal of Physics: Condensed Matter is dedicated to results in the field of ferrofluid research. Ferrofluids—suspensions of magnetic nanoparticles—exhibit as a specific feature the magnetic control of their physical parameters and of flows appearing in such fluids. This magnetic control can be achieved by means of moderate magnetic fields with a strength of the order of 10 mT. This sort of magnetic control also enables the design of a wide variety of technical applications such as the use of the magnetic forces for basic research in fluid dynamics. The overall field of ferrofluid research is already about 40 years old. Starting with the first patent on the synthesis of magnetic nanoparticle suspensions by S Papell in 1964, a vivid field of research activities has been established. Looking at the long time in which ferrofluids have been the focus of scientific interest, one can ask the question, what kind of recent developments justify a special issue of a scientific journal? New developments in a field, which depends strongly on a certain material class and which opens research possibilities in different scientific fields will nowadays usually require an interdisciplinary approach. This kind of approach starting from the synthesis of magnetic suspensions, including research concerning their basic properties and flow behaviour and focusing on new applications has been the core of a special research programme funded by the Deutsche Forschungsgemeinschaft (DFG) over the past 6 years. Within this programme—entitled `Colloidal Magnetic Fluids: Basics, Synthesis and Applications of New Ferrofluids'—more than 30 different research groups have been coordinated to achieve new results in various fields related to ferrofluid research. The basic approach of the program has been the assumption that new applications well beyond the typical ferrofluid techniques, for example loud speaker cooling or sealing of rotary shafts, will require tailored magnetic suspensions with properties clearly focused towards the need of the application. While such tailoring of fluids to certain well defined properties sounds like a straightforward approach one has to face the fact that it requires a clear definition of the required properties. This definition itself has to be based on a fundamental physical knowledge of the processes determining certain magnetically controlled phenomena in ferrofluids. To make this point concrete one can look into the detailed aims of the mentioned research program. The application areas identified for the future development of research and application of suspensions of magnetic nanoparticles have been on the one hand the biomedical application—especially with respect to cancer treatment—and on the other hand the use of magnetically controlled rheological properties of ferrofluids for new active technical devices. Both directions require, as mentioned, as a basis for success the synthesis of new ferrofluids with dedicated properties. While the medical applications have to rely on biocompatibility as well as on stability of the suspensions in a biomedical environment, the use of ferrofluids in technical devices employing their magnetically controlled rheological properties will depend on an enhancement of the changes of the fluid's viscous properties in the presence of moderate magnetic fields. For both requirements ferrofluids with a make up clearly different from the usual magnetite based fluids have to be synthesized. The question of how the detailed microscopic make up of the fluids would have to look has to be answered on the basis of basic research results defining the physics background of the respective phenomena. Taking these aspects together it becomes obvious that the aforementioned research program had goals aiming far beyond the state of the art of classical ferrofluid research. These goals as well as the basic strategy to achieve them is in a way reflected by the structure of this issue of Journal of Physics: Condensed Matter. The issue contains results emerging from the research pr

Odenbach, Professor Stefan

2006-09-01

18

Wave attenuation by vegetation is a highly dynamic process and its quantification is important for accurately understanding and predicting coastal hydrodynamics. However, the influence of vegetation on wave dissipation is not yet fully established...

Anderson, Mary Elizabeth

2011-10-21

19

Existence of Electromagnetic-Hydrodynamic Waves

IF a conducting liquid is placed in a constant magnetic field, every motion of the liquid gives rise to an E.M.F. which produces electric currents. Owing to the magnetic field, these currents give mechanical forces which change the state of motion of the liquid. Thus a kind of combined electromagnetic-hydro-dynamic wave is produced which, so far as I know, has

H. Alfvén

1942-01-01

20

Nonlinear hydrodynamic Langmuir waves in fully degenerate relativistic plasma

NASA Astrophysics Data System (ADS)

The combined effect of special relativity and electron degeneracy on Langmuir waves is analyzed by utilizing a rigorous fully relativistic hydrodynamic model. Assuming a traveling wave solution form, a set of conservation laws is identified, together with a pseudo-potential function depending on the relativistic parameter pF/(m c) (where pF is the Fermi momentum, m is the mass of the charge carriers and c the speed of light), as well as on the amplitude of the electrostatic energy perturbation.

Haas, F.; Kourakis, I.

2015-04-01

21

Comparison of methods for computing hydrodynamic characteristics of arrays of wave power devices

A comparison of methods for the calculation of the hydrodynamic characteristics of arrays of wave power devices is presented. In particular, the plane-wave approximation and an exact multiple scattering formulation have been used to compute exciting wave forces, hydrodynamic coefficients and q factors for arrays of interacting wave power devices. The results obtained are compared with each other, and accuracy

S. A. Mavrakos; P. McIver

1997-01-01

22

The velocities and accelerations accompanying ocean waves can impose large hydrodynamic forces no guarantee, however, that these plants will not be broken. Indeed, wave forces imposed during storms tear (Koehl and Wainwright, 1977; Seymour et al. 1989). Despite the recognition of wave-induced hydrodynamic

Denny, Mark

23

Hydrodynamic Modes of a holographic $p-$ wave superfluid

In this work we analyze the hydrodynamics of a $p-$ wave superfluid on its strongly coupled regime by considering its holographic description. We obtain the poles of the retarded Green function through the computation of the quasi-normal modes of the dual AdS black hole background finding diffusive, pseudo-diffusive and sound modes. For the sound modes we compute the speed of sound and its attenuation as function of the temperature. For the diffusive and pseudo-diffusive modes we find that they acquire a non-zero real part at certain finite momentum.

Raul E. Arias; Ignacio Salazar Landea

2014-11-04

24

Hydrodynamic modes of a holographic p-wave superfluid

NASA Astrophysics Data System (ADS)

In this work we analyze the hydrodynamics of a p- wave superfluid on its strongly coupled regime by considering its holographic description. We obtain the poles of the retarded Green function through the computation of the quasi-normal modes of the dual AdS black hole background finding diffusive, pseudo-diffusive and sound modes. For the sound modes we compute the speed of sound and its attenuation as function of the temperature. For the diffusive and pseudo-diffusive modes we find that they acquire a non-zero real part at certain finite momentum.

Arias, Raúl E.; Landea, Ignacio Salazar

2014-11-01

25

RADIATIVE HYDRODYNAMIC SIMULATIONS OF ACOUSTIC WAVES IN SUNSPOTS

We investigate the formation and evolution of the Ca II H line in a sunspot. The aim of our study is to establish the mechanisms underlying the formation of the frequently observed brightenings of small regions of sunspot umbrae known as 'umbral flashes'. We perform fully consistent NLTE radiation hydrodynamic simulations of the propagation of acoustic waves in sunspot umbrae and conclude that umbral flashes result from increased emission of the local solar material during the passage of acoustic waves originating in the photosphere and steepening to shock in the chromosphere. To quantify the significance of possible physical mechanisms that contribute to the formation of umbral flashes, we perform a set of simulations on a grid formed by different wave power spectra, different inbound coronal radiation, and different parameterized chromospheric heating. Our simulations show that the waves with frequencies in the range 4.5-7.0 mHz are critical to the formation of the observed blueshifts of umbral flashes while waves with frequencies below 4.5 mHz do not play a role despite their dominance in the photosphere. The observed emission in the Ca II H core between flashes only occurs in the simulations that include significant inbound coronal radiation and/or extra non-radiative chromospheric heating in addition to shock dissipation.

Bard, S. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); Carlsson, M. [Also at Center of Mathematics for Applications, University of Oslo, P.O. Box 1053, Blindern, N-0316 Oslo, Norway. (Norway)

2010-10-10

26

Hydrodynamic view of wave-packet interference: quantum caves.

Wave-packet interference is investigated within the complex quantum Hamilton-Jacobi formalism using a hydrodynamic description. Quantum interference leads to the formation of the topological structure of quantum caves in space-time Argand plots. These caves consist of the vortical and stagnation tubes originating from the isosurfaces of the amplitude of the wave function and its first derivative. Complex quantum trajectories display counterclockwise helical wrapping around the stagnation tubes and hyperbolic deflection near the vortical tubes. The string of alternating stagnation and vortical tubes is sufficient to generate divergent trajectories. Moreover, the average wrapping time for trajectories and the rotational rate of the nodal line in the complex plane can be used to define the lifetime for interference features. PMID:19659057

Chou, Chia-Chun; Sanz, Angel S; Miret-Artés, Salvador; Wyatt, Robert E

2009-06-26

27

Ferrofluids: Thermophysical properties and formation of microstructures

NASA Astrophysics Data System (ADS)

This work is a combined effort of experimental and theoretical studies toward better understanding the structural and physical properties of aqueous ferrofluids containing nano-sized magnetite (iron oxide magnetic particles) of about 10nm. Ferrofluids have attracted remarkable attention mainly because their properties can be controlled by means of an externally applied magnetic field. The dispersion of nano-sized magnets in a carrier liquid exhibits superparamagnetic behaviour while retaining its fluid properties. The interplay between hydrodynamic and magnetic phenomena has made ferrofluids an extremely promising and useful tool in wide spectra of applications, from technical applications to biomedical ones. In the presence of a magnetic field, magnetic moments of the nanomagnets suspended in the host liquid are aligned toward the field direction and begin to form microstructures such as short chains, strands and long stripes. As this process advances the microstructures may collapse into bundles and thick chains and form macrostructures. Upon the removal of the magnetic field, nanoparticles will be homogeneously redistributed throughout the sample due to thermal agitation. Zero-field structures, and especially the field-induced assembly of magnetic nanoparticles, are primarily responsible for the change in physical properties of ferrofluids, including thermophysical, optical, rheological, and magnetization properties. Because of the field-induced assembly of magnetic nanoparticles in the field direction, ferrofluids become strongly anisotropic and as a result, ferrofluids can significantly enhance directional heat transfer in a thermal system. Thermophysical properties of a ferrofluid are important in studying heat transfer processes in any thermal application, making the study of their behavior a necessity. Taking into account the influence of the formation and growth of microstructures on change in properties of ferrofluids, one can find the significance of identifying and studying the parameters by which ferrofluids' properties can be tailored for a specific need. In Chapter 2 of this dissertation, the influences of magnetic field strength and concentration of ferrofluids on the formation and growth of the chains are observed by employing cryogenic transmission electron microscopy technique. The samples are aqueous magnetite dispersions with concentrations of 0.15%, 0.48% and 0.59% (w/v%). Magnetic field strengths varies from a relatively weak strength of 51.5 mT to the strong field of 0.42 T. Cryo-TEM imaging technique is employed as it allows us to observe the near-native state of the hydrated samples. The cryo-TEM images draw a qualitative comparison basis on the relative significance of magnetic field and concentration on chaining processes. They also provide better understanding of the chains, columns and their internal structures. From a theoretical perspective, an energy equation employing an Eulerian formalism is derived in Chapter 3. Introducing the definition for isotropy and anisotropy of the medium, the equation of heat conduction can be simplified to govern each of the regimes. The equation has taken into account contributions from the important parameters (1) Brownian motion of nanoparticles, (2) magnetic field, (3) temperature, (4) particle size, and (5) volume fraction of particles. In chapter 4, change in effective heat capacity of ferrofluids is addressed and studied with the help of the derivation of the energy equation. The relative significance of the various aforementioned parameters that may have influence on heat capacity of a given medium is quantitatively studied. Lastly, a theoretical model to predict thermal conductivity of a ferrofluid is developed in Chapter 5. From the study on the micrographs, the ferrofluid that becomes anisotropic in the presence of the field is treated as a heterogeneous medium. A structural model, taken into account the anisotropy of the ferrofluid, is introduced in order to develop a theoretical model for effective thermal conductivity of ferrofluids. In order fo

Mousavi Khoeini, NargesSadat Susan

28

Hydrodynamic Synchronization and Metachronal Waves on the Surface of the Colonial Alga Volvox of the colonial alga Volvox carteri, whose large size and ease of visualization make it an ideal model organism

Goldstein, Raymond E.

29

Hydrodynamics of the double-wave structure of insect spermatozoa flagella

In addition to conventional planar and helical flagellar waves, insect sperm flagella have also been observed to display a double-wave structure characterized by the presence of two superimposed helical waves. In this paper, we present a hydrodynamic investigation of the locomotion of insect spermatozoa exhibiting the double-wave structure, idealized here as superhelical waves. Resolving the hydrodynamic interactions with a non-local slender body theory, we predict the swimming kinematics of these superhelical swimmers based on experimentally collected geometric and kinematic data. Our consideration provides insight into the relative contributions of the major and minor helical waves to swimming; namely, propulsion is owing primarily to the minor wave, with negligible contribution from the major wave. We also explore the dependence of the propulsion speed on geometric and kinematic parameters, revealing counterintuitive results, particularly for the case when the minor and major helical structures are of opposite chirality. PMID:22298815

Pak, On Shun; Spagnolie, Saverio E.; Lauga, Eric

2012-01-01

30

REVIEWS OF TOPICAL PROBLEMS: Propagation of waves in hydrodynamic shear flows

A range of phenomena connected with the propagation of waves in hydrodynamic shear flows is studied. The problem of calculating the energy and momentum of a wave packet in a moving medium is discussed in detail. It is shown that in many cases the momentum of a body moving in a liquid can be correctly calculated only if the compressibility

Yu A. Stepanyants; A. L. Fabrikant

1989-01-01

31

REVIEWS OF TOPICAL PROBLEMS: Propagation of waves in hydrodynamic shear flows

NASA Astrophysics Data System (ADS)

A range of phenomena connected with the propagation of waves in hydrodynamic shear flows is studied. The problem of calculating the energy and momentum of a wave packet in a moving medium is discussed in detail. It is shown that in many cases the momentum of a body moving in a liquid can be correctly calculated only if the compressibility of the medium is taken into account. The phenomenon of super-reflection of waves from the interface between moving media—the fact that the amplitude of the reflected wave can be much greater than the amplitude of the incident wave—is described. An interpretation of this phenomenon is given based on the concept of waves with negative energy. It is also shown that the reflected wave can be amplified when the sign of the dissipation in the moving medium changes. The behavior of different types of waves on a tangential discontinuity of the velocity is described (surface and internal waves as well as Rossby waves are studied). A separate section is devoted to resonant interaction between waves and the flow. Here the plasma-hydrodynamic analogy and its generalization to the case of stratified media are discussed. Resonance amplification in shear flows is studied for sound waves, surface waves on water, and internal gravity waves. The interaction of waves with vortices is discussed briefly. An algebraic method for solving problems is described for cylindrical vortices. Different mechanisms of amplification of sound by vortices are examined.

Stepanyants, Yu A.; Fabrikant, A. L.

1989-09-01

32

Wave Turbulence on the Surface of a Ferrofluid in a Magnetic Field Francois Boyer and Eric Falcon*

normal magnetic field. We show that magnetic surface waves arise only above a critical field. The power spectrum of their amplitudes displays a frequency-power law leading to the observation of a magnetic wave of wave turbulence is the random state of ocean surface waves, but it appears in various systems

Falcon, Eric

33

normal magnetic field. We show that magnetic surface waves arise only above a critical field. The power spectrum of their amplitudes displays a frequency-power law leading to the observation of a magnetic wave is the random state of ocean surface waves, but it appears in various systems: capillary waves [1, 2], plasma

Paris-Sud XI, UniversitÃ© de

34

Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas

in nature. Mature ocean waves and ripples on the surface of the tea in a pot, for example, can be described in experimental wave tanks as well as in the ocean. Nonlinear Schrödinger equation (NLS) is among best ranging from optical communications and Bose condensation to ocean waves. Solutions of nonlinear equations

Lushnikov, Pavel

35

Optical Negative Refraction in Ferrofluids with Magnetocontrollability J. P. Huang,1,* Y. M. Liu,3

in ferrofluids containing isotropic Fe3O4 nanoparticles, each having an isotropic Ag shell, in the presence refraction of optical waves or microwaves in different systems, includ- ing metamaterials [2,3], photonic for designing tunable, active metamaterials. In general, ferrofluids are colloidal suspensions com- posed

Huang, Ji-Ping

36

Chain-like structures in polydisperse ferrofluids

NASA Astrophysics Data System (ADS)

An influence of polydispersity of ferrofluids on structure of internal chain-like aggregates is studied theoretically. For maximal simplification of analysis we consider a bidisperse model of ferrofluid consisting of relatively big and small particles. In accordance with the composition of many real ferrofluids, we suppose that the energy of magnetic interaction between big particles strongly exceeds thermal energy kT of the system; the energy of interaction between big and small particles is about kT; between two small particles it is significantly smaller than kT. This gives us ground to consider the model of chains, consisting of only big particles, surrounded by the gas of small ones. Both magnetic and steric interactions of the chains with this gas are taken into account. The analysis shows that the magnetic interaction decreases the length of the chains, whereas steric interaction increases it. The final influence of the gas of small particles on the chain is a result of competition of these interactions. Our estimates show that under the increase of hydrodynamical volume concentration of the small particles from zero till 30% the chains can vary several-fold in mean size.

Zubarev, A. Yu.; Iskakova, L. Yu.

2004-04-01

37

Ferrofluid mediated nanocytometry.

We present a low-cost, flow-through nanocytometer that utilizes a colloidal suspension of non-functionalized magnetic nanoparticles for label-free manipulation and separation of microparticles. Our size-based separation is mediated by angular momentum transfer from magnetically excited ferrofluid particles to microparticles. The nanocytometer is capable of rapidly sorting and focusing two or more species, with up to 99% separation efficiency and a throughput of 3 × 10(4) particles/s per mm(2) of channel cross-section. The device is readily scalable and applicable to live cell sorting with biocompatible ferrofluids, offering competitive cytometer performance in a simple and inexpensive package. PMID:22076536

Kose, Ayse Rezzan; Koser, Hur

2012-01-01

38

COUPLING OF HYDRODYNAMIC AND WAVE MODELS FOR STORM TIDE SIMULATIONS: A CASE STUDY FOR HURRICANE for the simulation of storm tides. The hydrodynamic model employed for calculating tides and surges is ADCIRC-2DDI) astronomical tides, 2) inflows from tributaries, 3) meteorological effects (winds and pressure), and 4) waves

Central Florida, University of

39

Hydrodynamic responses of a thin floating disk to regular waves

Laboratory wave basin measurements of the surge, heave and pitch of a floating plastic disk caused by regular incident waves are presented. The measurements are used to validate two theoretical models: one based on slope-sliding theory and the other on combined potential-flow and thin-plate theories.

Yiew, Lucas; Meylan, Michael; French, Ben; Thomas, Giles

2015-01-01

40

Vortex density waves and high-frequency second sound in superfluid turbulence hydrodynamics

In this Letter we show that a recent hydrodynamical model of superfluid turbulence describes vortex density waves and their effects on the speed of high-frequency second sound. In this frequency regime, the vortex dynamics is not purely diffusive, as for low frequencies, but exhibits ondulatory features, whose influence on the second sound is here explored.

David Jou; M. Sciacca

2007-01-01

41

NO EFFECT OF HYDRODYNAMIC SHOCK WAVE ON PROTEIN FUNCTIONALITY OF BEEF MUSCLE

Technology Transfer Automated Retrieval System (TEKTRAN)

The protein functionality of meat proteins after treatment with hydrodynamic shock wave was determined. Frankfurters (cooked to 71 deg C) were evaluated for cooking yield, CIE L*a*b*, nitrosylhemochrome, Texture Profile Analysis (hardness, cohesiveness), and stress and strain (torsion testing). Comp...

42

Plasma-Hydrodynamic Analogy for Waves and Vortices in Shear Flows

NASA Astrophysics Data System (ADS)

A physical analogy between resonant wave-particle interactions in plasma and in fluid mechanics is considered in details. Numerous examples show that the plasma-hydrodynamical analogy is a powerful tool for classification of known phenomena, clarifying their physical nature, discovering new unexpected effects and inventing new devices. The analogy shows up both in plane parallel and in circular shear flows.

Fabrikant, Anatoly

43

Small viscosity method and criteria for shock wave existence in relativistic magnetic hydrodynamics

We obtain criteria for shock wave (SW)existence in relativistic magnetic hydrodynamics with no suppositions about convexity of the equation of state. Method of derivation involves consideration of a continuous SW profile in presence of Landau-Lifshitz relativistic viscosity tensor with both non-zero viscosity coefficients.

V. I. Zhdanov; M. S. Borshch

2005-08-22

44

Nanomagnets: Fun with Ferrofluid

NSDL National Science Digital Library

Ferrofluid provides an easy opportunity to introduce students to the fascinating properties of the nanoscale. It is essentially a liquid magnet made of nanosized magnetic particles suspended in water or oil. Not only does it demonstrate the strange and beautiful properties of the nanoscale, but it also illustrates a case where nanoparticles and their associated properties provide interesting opportunities for technological applications.

Amy R. Taylor

2007-01-01

45

Exploring Materials: Ferrofluid

NSDL National Science Digital Library

In this activity, learners discover that a material can act differently when it's nanometer-sized. Learners investigate the properties of ferrofluid and magnetic black sand and learn that the surprising difference in the behavior of these two materials is due to size. Use this activity to talk about the differences in nanoscale materials.

Nanoscale Informal Science Education Network

2010-01-01

46

A Dynamic Analysis of Hydrodynamic Wave Journal Bearings

NASA Technical Reports Server (NTRS)

The purpose of this paper is to study the dynamic behavior of a three-wave journal bearing using a transient approach. The transient analysis permits the determination of the rotor behavior after the fractional frequency whirl appears. The journal trajectory is determined by solving a set of nonlinear equations of motion using the Runge-Katta method. The fluid film forces are computed by integrating the transient Reynolds equation at each time step location of the shaft with respect to the bearing. Because of the large values of the rotational speeds, turbulent effects were included in the computations. The influence of the temperature on the viscosity was also considered. Numerical results were compared to experimenta1 results obtained at the NASA Glenn Research Center. Comparisons of the theoretical results with experimental data were found to be in good agreement. The numerical and experimental results showed that the fluid film of a three-wave journal bearing having a diameter of 30 mm, a length of 27 mm, and a wave amplitude ratio greater than 0.15 is stable even at rotational speeds of 60,000 RPM. For lower wave amplitude ratios, the threshold speed at which the fluid film becomes unstable depends on the wave amplitude and on the supply pocket pressure. Even if the fluid film is unstable, the wave bearing maintains the whirl orbit inside the bearing clearance.

Ene, Nicoleta M.; Dimofte, Florin; Keith, Theo G.

2008-01-01

47

The hydrodynamics of a wave-power device in a tapered harbor

This paper considers the hydrodynamic performance of a single wave-power device placed at the end of a tapered harbor and set in a reflecting coastline. A relatively simple model, in which the harbor width is assumed to be much smaller than the incident wavelength, is used to calculate approximate values for the hydrodynamic coefficients and hence determine the energy absorbing capabilities of the device. A comparison is presented between a device in a rectangular harbor and one in a tapered harbor in order to make a preliminary assessment of the influence of the taper.

Gallachoir, B.P.O.; Thomas, G.P. [University College, Cork (Ireland). Dept. of Mathematical Physics; Sarmento, A.J.N.A. [Instituto Superior Tecnico, Lisbon (Portugal). Dept. de Engenharia Mecanica

1995-12-31

48

NASA Astrophysics Data System (ADS)

To unravel the relation between hydrodynamic forcing and the dynamics of the tidal flat-salt-marsh ecosystem, we compared hydrodynamic forcing in terms of proxies relevant to bed sediment motion for four tidal flat-salt-marsh ecosystems that were contrasting in terms of wind exposure (sheltered vs. exposed) and lateral development (shrinking vs. expanding). Wave and current field measurements on these four contrasting tidal flat and salt-marsh ecosystems indicated that the hydrodynamic forcing on the bottom sediment (bed shear stress) was strongly influenced by wind-generated waves, more so than by tidal- or wind-drive currents. The measurements further showed that the hydrodynamic forcing decreased considerably landward of the marsh cliff, highlighting a transition from vigorous (tidal flat and pioneer zone) to sluggish (mature marsh) fluid forcing. Spatial wave modeling using measured wind, revealed that the time-integrated wave forcing on the intertidal mudflat in front of the marsh (i.e., the potential bed sediment pickup) was a factor two higher for salt marshes that are laterally shrinking than for laterally expanding marshes, regardless of whether these marshes were exposed to or sheltered from the wind. The same result could not be obtained from a straightforward wind speed and fetch length approach for estimating wave forcing. This confirmed that wave force estimates required spatial modeling to be consistent with the sites trends of shrinking or expanding marshes and wind exposure is not enough to characterize the wave forcing at these sites. Seasonal changes in wave forcing identified from wind measurements potentially provide an alternative mechanism for marsh cliff formation. During the calm summer, fine sediments switches from the water column to the bed. During the following winter, fine sediment is retained within the vegetated regions while being returned to the water column from the bare tidal flats. The continuous slow upward growth of vegetated areas combined with the seasonal cyclic tidal flat elevations, could, during winter, cause a discontinuity at the bare/vegetated boundary. If this discontinuity grows large enough for plant die-off to occur, then a small cliff will form.

Callaghan, D. P.; Bouma, T. J.; Klaassen, P.; van der Wal, D.; Stive, M. J. F.; Herman, P. M. J.

2010-09-01

49

This research paper presents an incompressible smoothed particle hydrodynamics (ISPH) technique to investigate a regular wave overtopping on the coastal structure of different types. The SPH method is a mesh-free particle modeling approach that can efficiently treat the large deformation of free surface. The incompressible SPH approach employs a true hydrodynamic formulation to solve the fluid pressure that has less pressure fluctuations. The generation of flow turbulence during the wave breaking and overtopping is modeled by a subparticle scale (SPS) turbulence model. Here the ISPH model is used to investigate the wave overtopping over a coastal structure with and without the porous material. The computations disclosed the features of flow velocity, turbulence, and pressure distributions for different structure types and indicated that the existence of a layer of porous material can effectively reduce the wave impact pressure and overtopping rate. The proposed numerical model is expected to provide a promising practical tool to investigate the complicated wave-structure interactions. PMID:22919291

Pu, Jaan Hui; Shao, Songdong

2012-01-01

50

Hydrodynamic instabilities and transverse waves in propagation mechanism of gaseous detonations

NASA Astrophysics Data System (ADS)

The present study examines the role of transverse waves and hydrodynamic instabilities mainly, Richtmyer-Meshkov instability (RMI) and Kelvin-Helmholtz instability (KHI) in detonation structure using two-dimensional high-resolution numerical simulations of Euler equations. To compare the numerical results with those of experiments, Navier-Stokes simulations are also performed by utilizing the effect of diffusion in highly irregular detonations. Results for both moderate and low activation energy mixtures reveal that upon collision of two triple points a pair of forward and backward facing jets is formed. As the jets spread, they undergo Richtmyer-Meshkov instability. The drastic growth of the forward jet found to have profound role in re-acceleration of the detonation wave at the end of a detonation cell cycle. For irregular detonations, the transverse waves found to have substantial role in propagation mechanism of such detonations. In regular detonations, the lead shock ignites all the gases passing through it, hence, the transverse waves and hydrodynamic instabilities do not play crucial role in propagation mechanism of such regular detonations. In comparison with previous numerical simulations present simulation using single-step kinetics shows a distinct keystone-shaped region at the end of the detonation cell.

Mahmoudi, Y.; Mazaheri, K.; Parvar, S.

2013-10-01

51

We have developed EOS7M, a ferrofluid flow and transport module for TOUGH2. EOS7M calculates the magnetic forces on ferrofluid caused by an external magnetic field and allows simulation of flow and advective transport of ferrofluid-water mixtures through porous media. Such flow problems are strongly coupled and well suited to the TOUGH2 framework. Preliminary applications of EOS7M to some simple pressure and flow problems for which experiments were carried out in the lab show good qualitative agreement with the laboratory results.

Oldenburg, Curtis; Moridis, George

1998-03-24

52

Acoustic waves in a stratified atmosphere. IV. Three-dimensional nonlinear hydrodynamics

NASA Astrophysics Data System (ADS)

Context. The quiet solar chromosphere in the interior of supergranulation cells is believed to be heated by the dissipation of acoustic waves that originate with a typical period of 3 min in the photosphere. Aims: We investigate how the horizontal expansion with height of acoustic waves traveling upward into an isothermal, gravitationally stratified atmosphere depends on the size of the source region. Methods: We have solved the three-dimensional, nonlinear, time-dependent hydrodynamic equations for impulsively-generated, upward-propagating acoustic waves, assuming cylindrical symmetry. Results: When the diameter of the source of acoustic waves is small, the pattern of the upward-propagating waves is that of a point source, for which the energy travels upward in a vertical cone, qualitatively matching the observed pattern of bright-point expansion with height. For the largest plausible size of a source region, i.e., with granular size of 1 Mm, wave propagation in the low chromosphere is approximately that of plane waves, but in the middle and upper chromosphere it is also that of a point source. The assumption of plane-wave propagation is not a good approximation in the solar chromosphere. The upward-directed energy flux is larger than that of the solar chromosphere, at least in the middle and upper chromosphere, and probably throughout. Conclusions: Simulations of impulsively generated acoustic waves emitted from source regions with diameters that are small compared to the pressure scale height of the atmosphere qualitatively reproduce the upward expansion observed in chromospheric bright points. The emission features in the cores of the H and K lines are predicted to be blueshifted for a pulse and redshifted for the waves in its wake. The contribution of internal gravity waves to the upward energy flux is small and decreases with increasing size of the source region.

Kalkofen, W.; Rossi, P.; Bodo, G.; Massaglia, S.

2010-09-01

53

Cyclone waves directly affect the density, structure and local distribution of coral assemblages by acting as agents of mortality and colony transport. Using the meteorological record, hydrodynamic formulations and risk analysis, we predict some demographic consequences of cyclones for massive corals growing in different regions of the Great Barrier Reef. Analysis of shear, compression and tension forces generated by waves

S. R. Massel; T. J. Done

1993-01-01

54

East Frisian Wadden Sea hydrodynamics and wave effects in an unstructured-grid model

NASA Astrophysics Data System (ADS)

An unstructured-grid model (FVCOM) coupled to a surface wave model (FVCOM-SWAVE) with two different setups is used to investigate the hydrodynamic and wave energy conditions during a moderate wind and a storm situation in the southern North Sea. One setup covers the whole North Sea with moderately increased grid resolution at the coast, whereas the other is a very high-resolution Wadden Sea setup that is one-way coupled to the coarser North Sea model. The results of both model setups are validated, compared to each other and analysed with a focus on longshore currents and wave energy. The numerical results show that during storm conditions, strong wave-induced longshore currents occur in front of the East Frisian Wadden Sea islands with current speeds up to 1 m/s. The model setup with the higher resolution around the islands shows even stronger currents than the coarser setup. The wave-current interaction also influences the surface elevation by raising the water level in the tidal basins. The calculated wave energies show large differences between moderate wind and storm conditions with time-averaged values up to 200 kW/m.

Grashorn, Sebastian; Lettmann, Karsten A.; Wolff, Jörg-Olaf; Badewien, Thomas H.; Stanev, Emil V.

2015-02-01

55

East Frisian Wadden Sea hydrodynamics and wave effects in an unstructured-grid model

NASA Astrophysics Data System (ADS)

An unstructured-grid model (FVCOM) coupled to a surface wave model (FVCOM-SWAVE) with two different setups is used to investigate the hydrodynamic and wave energy conditions during a moderate wind and a storm situation in the southern North Sea. One setup covers the whole North Sea with moderately increased grid resolution at the coast, whereas the other is a very high-resolution Wadden Sea setup that is one-way coupled to the coarser North Sea model. The results of both model setups are validated, compared to each other and analysed with a focus on longshore currents and wave energy. The numerical results show that during storm conditions, strong wave-induced longshore currents occur in front of the East Frisian Wadden Sea islands with current speeds up to 1 m/s. The model setup with the higher resolution around the islands shows even stronger currents than the coarser setup. The wave-current interaction also influences the surface elevation by raising the water level in the tidal basins. The calculated wave energies show large differences between moderate wind and storm conditions with time-averaged values up to 200 kW/m.

Grashorn, Sebastian; Lettmann, Karsten A.; Wolff, Jörg-Olaf; Badewien, Thomas H.; Stanev, Emil V.

2015-03-01

56

Smoothed-particle-hydrodynamics modeling of dissipation mechanisms in gravity waves.

The smoothed-particle-hydrodynamics (SPH) method has been used to study the evolution of free-surface Newtonian viscous flows specifically focusing on dissipation mechanisms in gravity waves. The numerical results have been compared with an analytical solution of the linearized Navier-Stokes equations for Reynolds numbers in the range 50-5000. We found that a correct choice of the number of neighboring particles is of fundamental importance in order to obtain convergence towards the analytical solution. This number has to increase with higher Reynolds numbers in order to prevent the onset of spurious vorticity inside the bulk of the fluid, leading to an unphysical overdamping of the wave amplitude. This generation of spurious vorticity strongly depends on the specific kernel function used in the SPH model. PMID:23496634

Colagrossi, Andrea; Souto-Iglesias, Antonio; Antuono, Matteo; Marrone, Salvatore

2013-02-01

57

Hydrodynamics of the Oscillating Wave Surge Converter in the open ocean

A potential flow model is derived for a large flap-type oscillating wave energy converter in the open ocean. Application of the Green's integral theorem in the fluid domain yields a hypersingular integral equation for the jump in potential across the flap. Solution is found via a series expansion in terms of the Chebyshev polynomials of the second kind and even order. Several relationships are then derived between the hydrodynamic parameters of the system. Comparison is made between the behaviour of the converter in the open ocean and in a channel. The degree of accuracy of wave tank experiments aiming at reproducing the performance of the device in the open ocean is quantified. Parametric analysis of the system is then undertaken. It is shown that increasing the flap width has the beneficial effect of broadening the bandwidth of the capture factor curve. This phenomenon can be exploited in random seas to achieve high levels of efficiency.

Renzi, E

2012-01-01

58

Ferrofluid Photonic Dipole Contours

NASA Astrophysics Data System (ADS)

Understanding magnetic fields is important to facilitate magnetic applications in diverse fields in industry, commerce, and space exploration to name a few. Large electromagnets can move heavy loads of metal. Magnetic materials attached to credit cards allow for fast, accurate business transactions. And the Earth's magnetic field gives us the colorful auroras observed near the north and south poles. Magnetic fields are not visible, and therefore often hard to understand or characterize. This investigation describes and demonstrates a novel technique for the visualization of magnetic fields. Two ferrofluid Hele-Shaw cells have been constructed to facilitate the imaging of magnetic field lines [1,2,3,4]. We deduce that magnetically induced photonic band gap arrays similar to electrostatic liquid crystal operation are responsible for the photographed images and seek to mathematically prove the images are of exact dipole nature. We also note by comparison that our photographs are very similar to solar magnetic Heliosphere photographs.

Snyder, Michael; Frederick, Jonathan

2008-03-01

59

Synthesis of Aqueous Ferrofluid

NSDL National Science Digital Library

This video lab manual, by the Interdisciplinary Education Group of the University of Wisconsin â?? Madison Materials Research Science and Engineering Center (MRSEC), walks students through the process synthesizing aqueous ferrofluids, which "respond to an external magnetic field enabling the solution's location to be controlled through the application of a magnetic field." Each step of the procedure is detailed and accompanied with a video showing it as it is performed. A brief background of the procedure and the necessary safety and laboratory materials are also given. This detailed resource helps students to explore nanotechnology and advanced materials science through hands-on laboratory activities. A printer-friendly version with an example image for each step is also available, perfect for an in-class handout.

Breitzer, Jonathan

60

Two-temperature hydrodynamics of laser-generated ultrashort shock waves in elasto-plastic solids

NASA Astrophysics Data System (ADS)

Shock-wave generation by ultrashort laser pulses opens new doors for study of hidden processes in materials happened at an atomic-scale spatiotemporal scales. The poorly explored mechanism of shock generation is started from a short-living two-temperature (2T) state of solid in a thin surface layer where laser energy is deposited. Such 2T state represents a highly non-equilibrium warm dense matter having cold ions and hot electrons with temperatures of 1-2 orders of magnitude higher than the melting point. Here for the first time we present results obtained by our new hybrid hydrodynamics code combining detailed description of 2T states with a model of elasticity together with a wide-range equation of state of solid. New hydro-code has higher accuracy in the 2T stage than molecular dynamics method, because it includes electron related phenomena including thermal conduction, electron-ion collisions and energy transfer, and electron pressure. From the other hand the new code significantly improves our previous version of 2T hydrodynamics model, because now it is capable of reproducing the elastic compression waves, which may have an imprint of supersonic melting like as in MD simulations. With help of the new code we have solved a difficult problem of thermal and dynamic coupling of a molten layer with an uniaxially compressed elastic solid. This approach allows us to describe the recent femtosecond laser experiments.

Ilnitsky, Denis K.; Khokhlov, Viktor A.; Inogamov, Nail A.; Zhakhovsky, Vasily V.; Petrov, Yurii V.; Khishchenko, Konstantin V.; Migdal, Kirill P.; Anisimov, Sergey I.

2014-05-01

61

Tunable optical and magneto-optical properties of ferrofluid in the terahertz regime.

The dielectric property and magneto-optical effects of ferrofluids have been investigated in the terahertz (THz) regime by using THz time-domain spectroscopy. The experiment results show that the refractive index and absorption coefficient of ferrofluid for THz waves rise up with the increase of nanoparticle concentration in the ferrofluid. Moreover, two different THz magneto-optical effects have been found with different external magnetic fields, of which mechanisms have been theoretically explained well by microscopic structure induced refractive index change in the magnetization process and the transverse magneto-optical effect after the saturation magnetization, respectively. This work suggests that ferrofluid is a promising magneto-optical material in the THz regime which has widely potential applications in THz functional devices for THz sensing, modulation, phase retardation, and polarization control. PMID:24663979

Chen, Sai; Fan, Fei; Chang, Shengjiang; Miao, Yinping; Chen, Meng; Li, Jining; Wang, Xianghui; Lin, Lie

2014-03-24

62

Numerical modeling on hydrodynamic performance of a bottom-hinged flap wave energy converter

NASA Astrophysics Data System (ADS)

The hydrodynamic performance of a bottom-hinged flap wave energy converter (WEC) is investigated through a frequency domain numerical model. The numerical model is verified through a two-dimensional analytic solution, as well as the qualitative analysis on the dynamic response of avibrating system. The concept of "optimum density" of the bottom-hinged flap is proposed, and its analytic expression is derived as well. The frequency interval in which the optimum density exists is also obtained. The analytic expression of the optimum linear damping coefficient is obtained by a bottom-hinged WEC. Some basic dynamic properties involving natural period, excitation moment, pitch amplitude, and optimum damping coefficient are analyzed and discussed in detail. In addition, this paper highlights the analysis of effects on the conversion performance of the device exerted by some important parameters. The results indicate that "the optimum linear damping period of 5.0 s" is the most ideal option in the short wave sea states with the wave period below 6.0 s. Shallow water depth, large flap thickness and low flap density are advised in the practical design of the device in short wave sea states in order to maximize power capture. In the sea state with water depth of 5.0 m and wave period of 5.0 s, the results of parametric optimization suggest a flap with the width of 8.0 m, thickness of 1.6 m, and with the density as little as possible when the optimum power take-off (PTO) damping coefficient is adopted.

Zhao, Hai-tao; Sun, Zhi-lin; Hao, Chun-ling; Shen, Jia-fa

2013-03-01

63

From AdS/CFT correspondence to hydrodynamics. II. Sound waves

As a non-trivial check of the non-supersymmetric gauge/gravity duality, we use a near-extremal black brane background to compute the retarded Green's functions of the stress-energy tensor in N=4 super-Yang-Mills (SYM) theory at finite temperature. For the long-distance, low-frequency modes of the diagonal components of the stress-energy tensor, hydrodynamics predicts the existence of a pole in the correlators corresponding to propagation of sound waves in the N=4 SYM plasma. The retarded Green's functions obtained from gravity do indeed exhibit this pole, with the correct values for the sound speed and the rate of attenuation.

G. Policastro; D. T. Son; A. O. Starinets

2005-07-26

64

Development of novel ferrofluidic pumps.

The development and realization of micropipettes and micropumps has captured the interest of people working in both biomedical and chemical areas for the capability of managing very low quantity of liquid (drug, biological liquid or expensive reagent) as well as everyone interested in controlling small flows for dedicated applications. In this paper a novel ferrofluidic pump adopting an electromagnetic actuation is proposed. The pump is realized by injecting three drops of ferrofluids into the pipe (two valves and a plunger are required) in the position where the pump must operate and by exploiting the forces produced onto each ferrofluid drop by some coils externally placed with respect to the pipe. The absence of any mechanical moving parts, the possibility to realize a volumetric pump in a section of an existing pipe without interruptions and deformation are the main advantages of the architecture proposed as compared to existing prototypes. A detailed description of the strategy proposed is presented along with a preliminary characterization of the prototype developed. PMID:17945743

Andò, Bruno; Ascia, Alberto; Baglio, Salvatore; Pitrone, Nicola

2006-01-01

65

Ferrofluid separator for nonferrous scrap separation

NASA Technical Reports Server (NTRS)

Behavior of nonmagnetic objects within separator is essentially function of density, and independent of size or shape of objects. Results show close agreement between density of object and apparent density of ferrofluid required to float it. Results also demonstrate that very high separation rates are achievable by ferrofluid sink-float separation.

Kaiser, R.; Mir, L.

1974-01-01

66

NASA Astrophysics Data System (ADS)

The complex dynamics of the Adriatic Sea are the result of geographical position, orography and bathymetry, as well as rivers discharge and meteorological conditions that influence, more strongly, the shallow northern part. Such complexity requires a constant monitoring of marine conditions in order to support several activities (marine resources management, naval operations, emergency management, shipping, tourism, as well as scientific ones). Platforms, buoys and mooring located in Adriatic Sea supply almost continuously real time punctual information, which can be spatially extended, with some limitations, by drifters and remote sensing. Operational forecasting systems represent valid tools to provide a complete tridimensional coverage of the area, with a high spatial and temporal resolution. The Hydro-Meteo-Clima Service of the Emilia-Romagna Environmental Agency (ARPA-SIMC, Bologna, Italy) and the Dept. of Life and Environmental Sciences of Università Politecnica delle Marche (DISVA-UNIVPM, Ancona, Italy), in collaboration with the Institute of Marine Science of the National Research Council (ISMAR-CNR, Italy) operationally run several wave and hydrodynamic models on the Adriatic Sea. The main implementations are based on the Regional Ocean Modeling System (ROMS), the wave model Simulating WAves Nearshore (SWAN), and the coupling of the former two models in the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) system. Horizontal resolutions of the different systems range from the 2 km of AdriaROMS to the 0.5 km of the recently implemented northern Adriatic COAWST. Forecasts are produced every day for the subsequent 72 hour with hourly resolution. All the systems compute the fluxes exchanged through the interface with the atmosphere from the numerical weather prediction system named COSMO-I7, an implementation for Italy of the Consortium for Small-scale Modeling (COSMO) model, at 7 km horizontal resolution. Considering the several operational implementations currently running, there is the need to: assess their forecast skill; quantitatively evaluate if the new, coupled systems provide better performances than the uncoupled ones; individuate weaknesses and eventual time trends in the forecasts quality, their causes, and actions to improve the systems. This work presents a first effort aimed to satisfy such need. We employ in situ and remote sensing data collected starting from November 2011, in particular: temperature and salinity data collected during several oceanographic cruises, sea surface temperature derived from satellite measurements, waves, sea level and currents measurements from oceanographic buoys and platforms; specific observational activities funded by the Italian Flagship project RITMARE allowed to collect new measurements in NA coastal areas. Data-model comparison is firstly performed with exploratory qualitative comparisons in order to highlight discrepancies between observed and forecasted data, then a quantitative comparison is performed through the computation of standard statistical scores (root mean square error, mean error, mean bias, standard deviation, cross-correlation). Results are plotted in Taylor diagrams for a rapid evaluation of the overall performances.

Busca, Claudia; Coluccelli, Alessandro; Valentini, Andrea; Benetazzo, Alvise; Bonaldo, Davide; Bortoluzzi, Giovanni; Carniel, Sandro; Falcieri, Francesco; Paccagnella, Tiziana; Ravaioli, Mariangela; Riminucci, Francesco; Sclavo, Mauro; Russo, Aniello

2014-05-01

67

Monodispersed aqueous ferrofluids of iron oxide nanoparticle were synthesized by hydrothermal-reduction route. They were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy and dynamic light scattering. The results showed that certain concentrations of citric acid (CA) are required to obtain only magnetic iron oxides with mean particle sizes around 8 nm. CA acts as a modulator and reducing agent in iron oxide formation which controls nanoparticle size. The XRD, magnetic and heating measurements showed that the temperature and time of hydrothermal reaction can affect the magnetic properties of obtained ferrofluids. The synthesized ferrofluids were stable at pH 7. Their mean hydrodynamic size was around 80 nm with polydispersity index (PDI) of 0.158. The calculated intrinsic loss power (ILP) was 9.4 nHm{sup 2}/kg. So this clean and cheap route is an efficient way to synthesize high ILP aqueous ferrofluids applicable in magnetic hyperthermia. - Graphical abstract: Monodispersed aqueous ferrofluids of iron oxide nanoparticles were synthesized by hydrothermal-reduction method with citric acid as reductant which is an efficient way to synthesize aqueous ferrofluids applicable in magnetic hyperthermia. Highlights: Black-Right-Pointing-Pointer Aqueous iron oxide ferrofluids were synthesized by hydrothermal-reduction route. Black-Right-Pointing-Pointer Citric acid acted as reducing agent and surfactant in the route. Black-Right-Pointing-Pointer This is a facile, low energy and environmental friendly route. Black-Right-Pointing-Pointer The aqueous iron oxide ferrofluids were monodispersed and stable at pH of 7. Black-Right-Pointing-Pointer The calculated intrinsic loss power of the synthesized ferrofluids was very high.

Behdadfar, Behshid, E-mail: bbehdadfar@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Kermanpur, Ahmad [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Sadeghi-Aliabadi, Hojjat [School of Pharmacy, Isfahan Pharmaceutical Research Center, Isfahan University of Medical Sciences, Isfahan (Iran, Islamic Republic of); Morales, Maria del Puerto [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco 28049, Madrid (Spain); Mozaffari, Morteza [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of)

2012-03-15

68

Hydrodynamic roughness is a critical parameter for characterizing bottom drag in boundary layers, and it varies both spatially and temporally due to variation in grain size, bedforms, and saltating sediment. In this paper we investigate temporal variability in hydrodynamic roughness using velocity profiles in the bottom boundary layer measured with a high-resolution acoustic Doppler profiler (PCADP). The data were collected on the ebb-tidal delta off Grays Harbor, Washington, in a mean water depth of 9 m. Significant wave height ranged from 0.5 to 3 m. Bottom roughness has rarely been determined from hydrodynamic measurements under conditions such as these, where energetic waves and medium-to-fine sand produce small bedforms. Friction velocity due to current u*c and apparent bottom roughness z0a were determined from the PCADP burst mean velocity profiles using the law of the wall. Bottom roughness kB was estimated by applying the Grant-Madsen model for wave-current interaction iteratively until the model u*c converged with values determined from the data. The resulting kB values ranged over 3 orders of magnitude (10-1 to 10-4 m) and varied inversely with wave orbital diameter. This range of kB influences predicted bottom shear stress considerably, suggesting that the use of time-varying bottom roughness could significantly improve the accuracy of sediment transport models. Bedform height was estimated from kB and is consistent with both ripple heights predicted by empirical models and bedforms in sonar images collected during the experiment. Copyright 2005 by the American Geophysical Union.

Lacy, J.R.; Sherwood, C.R.; Wilson, D.J.; Chisholm, T.A.; Gelfenbaum, G.R.

2005-01-01

69

NASA Astrophysics Data System (ADS)

We show that the exact partition function of U( N) six-dimensional gauge theory with eight supercharges on ?2 × S 2 provides the quantization of the integrable system of hydrodynamic type known as gl( N) periodic Intermediate Long Wave (ILW). We characterize this system as the hydrodynamic limit of elliptic Calogero-Moser integrable system. We compute the Bethe equations from the effective gauged linear sigma model on S 2 with target space the ADHM instanton moduli space, whose mirror computes the Yang-Yang function of gl( N) ILW. The quantum Hamiltonians are given by the local chiral ring observables of the six-dimensional gauge theory. As particular cases, these provide the gl( N) Benjamin-Ono and Korteweg-de Vries quantum Hamiltonians. In the four dimensional limit, we identify the local chiral ring observables with the conserved charges of Heisenberg plus W N algebrae, thus providing a gauge theoretical proof of AGT correspondence.

Bonelli, Giulio; Sciarappa, Antonio; Tanzini, Alessandro; Vasko, Petr

2014-07-01

70

We report the experimental observation of multi-bound-soliton solutions of the nonlinear Schrödinger equation (NLS) in the context of hydrodynamic surface gravity waves. Higher-order N-soliton solutions with N=2, 3 are studied in detail and shown to be associated with self-focusing in the wave group dynamics and the generation of a steep localized carrier wave underneath the group envelope. We also show that for larger input soliton numbers, the wave group experiences irreversible spectral broadening, which we refer to as a hydrodynamic supercontinuum by analogy with optics. This process is shown to be associated with the fission of the initial multisoliton into individual fundamental solitons due to higher-order nonlinear perturbations to the NLS. Numerical simulations using an extended NLS model described by the modified nonlinear Schrödinger equation, show excellent agreement with experiment and highlight the universal role that higher-order nonlinear perturbations to the NLS play in supercontinuum generation. PMID:23952405

Chabchoub, A; Hoffmann, N; Onorato, M; Genty, G; Dudley, J M; Akhmediev, N

2013-08-01

71

Controlling ferrofluid permeability across the blood–brain barrier model.

In the present study, an in vitro blood–brain barrier model was developed using murine brain endothelioma cells (b.End3 cells). Confirmation of the blood–brain barrier model was completed by examining the permeability of FITCDextran at increasing exposure times up to 96 h in serum-free medium and comparing such values with values from the literature. After such confirmation, the permeability of five novel ferrofluid (FF) nanoparticle samples, GGB (ferrofluids synthesized using glycine, glutamic acid and BSA), GGC (glycine, glutamic acid and collagen), GGP (glycine, glutamic acid and PVA), BPC (BSA, PEG and collagen) and CPB (collagen, PVA and BSA), was determined using this blood–brain barrier model. All of the five FF samples were characterized by zeta potential to determine their charge as well as TEM and dynamic light scattering for determining their hydrodynamic diameter. Results showed that FF coated with collagen passed more easily through the blood–brain barrier than FF coated with glycine and glutamic acid based on an increase of 4.5% in permeability. Through such experiments, diverse magnetic nanomaterials (such as FF) were identified for: (1) MRI use since they were less permeable to penetrate the blood–brain barrier to avoid neural tissue toxicity (e.g. GGB) or (2) brain drug delivery since they were more permeable to the blood–brain barrier (e.g. CPB). PMID:24457539

Shi, Di; Sun, Linlin; Mi, Gujie; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

2014-02-21

72

Controlling ferrofluid permeability across the blood-brain barrier model

NASA Astrophysics Data System (ADS)

In the present study, an in vitro blood-brain barrier model was developed using murine brain endothelioma cells (b.End3 cells). Confirmation of the blood-brain barrier model was completed by examining the permeability of FITC-Dextran at increasing exposure times up to 96 h in serum-free medium and comparing such values with values from the literature. After such confirmation, the permeability of five novel ferrofluid (FF) nanoparticle samples, GGB (ferrofluids synthesized using glycine, glutamic acid and BSA), GGC (glycine, glutamic acid and collagen), GGP (glycine, glutamic acid and PVA), BPC (BSA, PEG and collagen) and CPB (collagen, PVA and BSA), was determined using this blood-brain barrier model. All of the five FF samples were characterized by zeta potential to determine their charge as well as TEM and dynamic light scattering for determining their hydrodynamic diameter. Results showed that FF coated with collagen passed more easily through the blood-brain barrier than FF coated with glycine and glutamic acid based on an increase of 4.5% in permeability. Through such experiments, diverse magnetic nanomaterials (such as FF) were identified for: (1) MRI use since they were less permeable to penetrate the blood-brain barrier to avoid neural tissue toxicity (e.g. GGB) or (2) brain drug delivery since they were more permeable to the blood-brain barrier (e.g. CPB).

Shi, Di; Sun, Linlin; Mi, Gujie; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J.

2014-02-01

73

Millimeter-sized, spherical silicate grains abundant in chondritic meteorites, which are called as chondrules, are considered to be a strong evidence of the melting event of the dust particles in the protoplanetary disk. One of the most plausible scenarios is that the chondrule precursor dust particles are heated and melt in the high-velocity gas flow (shock-wave heating model). We developed the non-linear, time-dependent, and three-dimensional hydrodynamic simulation code for analyzing the dynamics of molten droplets exposed to the gas flow. We confirmed that our simulation results showed a good agreement in a linear regime with the linear solution analytically derived by Sekiya et al. (2003). We found that the non-linear terms in the hydrodynamical equations neglected by Sekiya et al. (2003) can cause the cavitation by producing negative pressure in the droplets. We discussed that the fragmentation through the cavitation is a new mechanism to determine the upper limit of chondrule sizes. We also succeeded to reproduce the fragmentation of droplets when the gas ram pressure is stronger than the effect of the surface tension. Finally, we compared the deformation of droplets in the shock-wave heating with the measured data of chondrules and suggested the importance of other effects to deform droplets, for example, the rotation of droplets. We believe that our new code is a very powerful tool to investigate the hydrodynamics of molten droplets in the framework of the shock-wave heating model and has many potentials to be applied to various problems.

Hitoshi Miura; Taishi Nakamoto

2006-11-09

74

Some results of the hydrodynamic theory of finite-amplitude waves

NASA Technical Reports Server (NTRS)

Standing waves can be interpreted as free waves between two vertical walls; for a standing wave in an unlimited container there is no transport of liquid mass in the horizontal direction. Standing waves of finite amplitude also possess the following properties not possessed by the waves of the linear theory: (1) there are no motionless points, (2) the points of maximum amplitude (crests and troughs) are fixed, and coincide with the antinodes of the original linear wave, (3) the ordinates of the wave crests are greater in absolute magnitude than the ordinates of the troughs; the wave is similar to a trochoid curve; (4) the wave profile never becomes straight; and (5) the frequency of the oscillations depends not only on the wave length but also on the amplitude.

Sekerzh-Zenkovich, Y. I.

1975-01-01

75

Correlation of hydrodynamic features with LGA radar backscatter from breaking waves

Backscatter characteristics of 1-4-m-long, mechanically generated breaking waves have been investigated with a C-band frequency modulated continuous wave (FMCW) radar (up to 3.77-cm range resolution) in the large wind-wave tank at the Ocean Engineering Laboratory, University of California, Santa Barbara. The grazing angle was 6°. Wave breaking was caused to occur in the test section due to wave group selfmodulation,

J. Fuchs; D. Regas; T. Waseda; S. Welch; M. P. Tulin

1999-01-01

76

NASA Astrophysics Data System (ADS)

In this paper, we explicate a method of quantum hydrodynamics (QHD) for the study of the quantum evolution of a system of polarized particles. Although we focused primarily on the two-dimensional (2D) physical systems, the method is valid for three-dimensional (3D) and one-dimensional (1D) systems too. The presented method is based upon the Schrödinger equation. Fundamental QHD equations for charged and neutral particles were derived from the many-particle microscopic Schrödinger equation. The fact that particles possess the electric dipole moment (EDM) was taken into account. The explicated QHD approach was used to study dispersion characteristics of various physical systems. We analyzed dispersion of waves in a two-dimensional ion and hole gas placed into an external electric field, which is orthogonal to the gas plane. Elementary excitations in a system of neutral polarized particles were studied for 1D, 2D, and 3D cases. The polarization dynamics in systems of both neutral and charged particles is shown to cause formation of a new type of waves as well as changes in the dispersion characteristics of already known waves. We also analyzed wave dispersion in 2D exciton systems, in 2D electron-ion plasma, and in 2D electron-hole plasma. Generation of waves in 3D-system neutral particles with EDM by means of the beam of electrons and neutral polarized particles is investigated.

Andreev, P. A.; Kuzmenkov, L. S.; Trukhanova, M. I.

2011-12-01

77

In this paper, we explicate a method of quantum hydrodynamics (QHD) for the study of the quantum evolution of a system of polarized particles. Although we focused primarily on the two-dimensional (2D) physical systems, the method is valid for three-dimensional (3D) and one-dimensional (1D) systems too. The presented method is based upon the Schroedinger equation. Fundamental QHD equations for charged and neutral particles were derived from the many-particle microscopic Schroedinger equation. The fact that particles possess the electric dipole moment (EDM) was taken into account. The explicated QHD approach was used to study dispersion characteristics of various physical systems. We analyzed dispersion of waves in a two-dimensional ion and hole gas placed into an external electric field, which is orthogonal to the gas plane. Elementary excitations in a system of neutral polarized particles were studied for 1D, 2D, and 3D cases. The polarization dynamics in systems of both neutral and charged particles is shown to cause formation of a new type of waves as well as changes in the dispersion characteristics of already known waves. We also analyzed wave dispersion in 2D exciton systems, in 2D electron-ion plasma, and in 2D electron-hole plasma. Generation of waves in 3D-system neutral particles with EDM by means of the beam of electrons and neutral polarized particles is investigated.

Andreev, P. A.; Kuzmenkov, L. S.; Trukhanova, M. I. [Department of General Physics, Physics Faculty, Moscow State University, Moscow (Russian Federation); Dpartment of Theoretical Physics, Physics Faculty, Moscow State University, Moscow (Russian Federation)

2011-12-15

78

Magnetic detection of ferrofluid injection zones

Ferrofluids are stable colloidal suspensions of magnetic particles that can be stabilized in various carrier liquids. In this study the authors investigate the potential of ferrofluids to trace the movement and position of liquids injected in the subsurface using geophysical methods. An ability to track and monitor the movement and position of injected liquids is essential in assessing the effectiveness of the delivery system and the success of the process. Ferrofluids can also provide a significant detection and verification tool in containment technologies, where they can be injected with the barrier liquids to provide a strong signature allowing determination of the barrier geometry, extent, continuity and integrity. Finally, ferrofluids may have unique properties as tracers for detecting preferential flow features (such as fractures) in the subsurface, and thus allow the design of more effective remediation systems. In this report the authors review the results of the investigation of the potential of ferrofluids to trace the movement and position of liquids injected in the subsurface using geophysical methods. They demonstrate the feasibility of using conventional magnetometry for detecting subsurface zones of injected ferrofluids used to trace liquids injected for remediation or barrier formation. The geometrical shapes considered were a sphere, a thin disk, a rectangular horizontal slab, and a cylinder. Simple calculations based on the principles of magnetometry are made to determine the detection depths of FTs. Experiments involving spherical, cylindrical and horizontal slabs show a very good agreement between predictions and measurements.

Borglin, S.; Moridis, G.; Becker, A.

1998-03-01

79

Investigation into loss in ferrofluid magnetization

NASA Astrophysics Data System (ADS)

Ferrofluids containing ?-Fe2O3/Ni2O3 nanoparticles (not chemically treated) were synthesized using water and mixed water-glycerol as carrier liquid and the ferrofluid viscosity was modified by varying the glycerol content in the carrier liquid. The apparent magnetization of the ferrofluids decreased with increasing glycerol content. The loss in magnetization is described by the ratio of effective magnetic volume fraction to physical volume fraction of nanoparticles in the ferrofluids as a characteristic parameter. We ascribe the loss to the formation of "dead aggregates" having a ring-like structure of closed magnetic flux rather than to any chemical reaction. Such dead aggregates exist in zero magnetic field and do not contribute to the magnetization in the low or high field regime, so that the effective magnetic volume fraction in the ferrofluids decrease. An increase in carrier liquid viscosity is similar to a weakening of the thermal effect, so the number of dead aggregates increases and the magnetization decreases in inverse proportion to the viscosity. This relationship between the apparent magnetization and ferrofluid carrier liquid viscosity can be termed the "viscomagnetic effect".

Li, J.; Gong, X. M.; Lin, Y. Q.; Liu, X. D.; Chen, L. L.; Li, J. M.; Mao, H.; Li, D. C.

2014-07-01

80

The principles of restricted superposition of circularly polarized arbitrary-amplitude waves for several hydrodynamic type models are illustrated systematically with helical representation in a unified sense. It is shown that the only general modes satisfying arbitrary-amplitude superposition to kill the generic nonlinearity are the mono-wavelength homochiral Beltrami mode and the one-dimensional-two-component stratified vorticity mode, which we call the XYz flow/wave; while, there are other special superposition principles for some specific cases. We try to remark on the possible connections with the geo- and/or astro-physical fluid and magnetohydrodynamic turbulence issues, such as the rotating turbulence, dynamo and solar atmosphere turbulence, especially with the introduction of disorder locally frozen in some (randomly distributed) space-time regions. Recent disagreements about exact solutions of Hall and fully two-fluid magnetohydrodynamics are also settled down by such a treatment. This work complement...

Zhu, Jian-Zhou

2014-01-01

81

Viscoelastic properties of ferrofluids D. N. Chirikov,1

magnetic field. The first theories of the magnetorheological effects in ferrofluids 3,4 deal with very. 614 . Both of them can induce strong magnetorheological effects in ferrofluids 8 . Unfortunately

Fedotov, Sergei

82

NASA Astrophysics Data System (ADS)

We report studies of the structural, magnetic, magneto-thermal and magneto-optic properties of dextran, oleic acid, lauric acid and myristic acid surfacted Fe3O4 nanoparticles of hydrodynamic sizes ranging from 32 nm to 92 nm. All the samples showed saturation magnetization of ˜50 emu/g, significantly smaller than the bulk value for Fe3O4, together with superparamagnetic behavior. The ac magnetization measurements on the dextran coated nanoparticles showed frequency dependent blocking temperature, consistent with superparamgnetic blocking. The ferrofluid heating rates in a 250 Gauss, 100 kHz ac magnetic field varied with the chain lengths of the surfactants, with higher heating rates for longer chains. DC-magnetic-field-induced light scattering patterns produced by two orthogonal He-Ne laser beams passing through the ferrofluid sample revealed different optical signatures for different surfactants.

Rablau, Corneliu; Vaishnava, Prem; Regmi, Rajesh; Sudakar, Chandran; Black, Correy; Lawes, Gavin; Naik, Ratna; Lavoie, Melissa; Kahn, David

2009-03-01

83

NASA Astrophysics Data System (ADS)

The investigations carried out between 2002 and 2004 during six field experiments within the Operational Radar and Optical Mapping in monitoring hydrodynamic, morphodynamic and environmental parameters for coastal management (OROMA) project aimed to improve the effectiveness of new remote sensing monitoring technologies such as shipborne imaging radars in coastal waters. The coastal monitoring radar of the GKSS Research Center, Geesthacht, Germany, is based on a Kelvin Hughes RSR 1000 X band (9.42 GHz) vertical (VV) polarized river radar and was mounted on board the research vessel Ludwig Prandtl during the experiments in the Lister Tief, a tidal inlet of the German Bight in the North Sea. The important progress realized in this investigation is the availability of calibrated X band radar data. Another central point of the study is to demonstrate the applicability of the quasi-specular scattering theory in combination with the weak hydrodynamic interaction theory for the radar imaging mechanism of the seabed. Radar data have been taken at very low grazing angles ?2.6° of flood and ebb tide-oriented sand wave signatures at the sea surface during ebb tidal current phases. Current speeds perpendicular to the sand wave crest ?0.6 m s-1 have been measured at wind speeds ?4.5 m s-1 and water depths ?25 m. The difference between the maximum measured and simulated normalized radar cross section (NRCS) modulation of the ebb tide-oriented sand wave is 27%. For the flood tide-oriented sand wave, a difference of 21% has been calculated. The difference between the minimum measured and simulated NRCS modulation of the ebb tide-oriented sand wave is 10%, and for the flood tide-oriented sand wave, a value of 43% has been derived. Phases of measured and simulated NRCS modulations correspond to asymmetric sand wave slopes. The results of the simulated NRCS modulation show the qualitative trend but do not always quantitatively match the measured NRCS modulation profiles because the quasi-specular scattering theory at very low grazing angle is a first-order theory.

Hennings, Ingo; Herbers, Dagmar

2006-10-01

84

Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles

Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles W. Brullot a in revised form 20 December 2011 Available online 3 February 2012 Keywords: Ferrofluid Polyethylene glycol Magneto-optics Magnetite Rheology a b s t r a c t Versatile ferrofluids based on polyethylene glycol

85

From AdS\\/CFT correspondence to hydrodynamics. II. Sound waves

As a non-trivial check of the non-supersymmetric gauge\\/gravity duality, we use a near-extremal black brane background to compute the retarded Green's functions of the stress-energy tensor in = 4 super-Yang-Mills (SYM) theory at finite temperature. For the long-distance, low-frequency modes of the diagonal components of the stress-energy tensor, hydrodynamics predicts the existence of a pole in the correlators corresponding to

Giuseppe Policastro; Dam T. Son; Andrei O. Starinets

2002-01-01

86

Characteristics of the Cerenkov radiation of drift waves in hydrodynamics and in plasma

NASA Astrophysics Data System (ADS)

Calculations are made of radiation forces acting on point sources (monopoles and dipoles) during their uniform motion in a rotating liquid or inhomogeneous plasma. These forces are due to the radiation of Rossby waves (in liquids) or drift waves (in plasma) associated with the Cerenkov mechanism. It is shown that, as a result of the anisotropic nature of both types of waves, a force normal to the source velocity exists in addition to the wave drag force directed against the direction of motion velocity. The results obtained are used to interpret the Larichev-Reznik solution which describes stationary dipole vortices capable of moving without radiation losses over a certain velocity range.

Stepaniants, Iu. A.; Fabrikant, A. L.

1992-11-01

87

A contribution about ferrofluid based flow manipulation and locomotion systems

NASA Astrophysics Data System (ADS)

With the background of developing apedal bionic inspired locomotion systems for future application fields like autonomous (swarm) robots, medical engineering and inspection systems, this article presents a selection of locomotion systems with bifluidic flow control using ferrofluid. By controlling the change of shape, position and pressure of the ferrofluid in a secondary low viscous fluid by magnetic fields locomotion of objects or the ferrofluid itself can be realised. The locomotion of an object is caused in the first example by a ferrofluid generated flow of the secondary fluid and in the second and third case by the direct alteration of the ferrofluid position.

Zimmermann, K.; Zeidis, I.; Bohm, V.; Popp, J.

2009-02-01

88

This paper examines the relationship between offshore wave climate and nearshore waves and currents at Hanalei Bay, Hawaii, an exposed bay fringed with coral reefs. Analysis of both offshore in situ data and numerical hindcasts identify the predominance of two wave conditions: a mode associated with local trade winds and an episodic pattern associated with distant source long-period swells. Analysis of 10 months of in situ data within the bay show that current velocities are up to an order of magnitude greater during long-period swell episodes than during trade wind conditions; overall circulation patterns are also fundamentally different. The current velocities are highly correlated with incident wave heights during the swell episodes, while they are not during the modal trade wind conditions. A phase-averaged wave model was implemented with the dual purpose of evaluating application to bathymetrically complex fringing reefs and to examine the propagation of waves into the nearshore in an effort to better explain the large difference in observed circulation during the two offshore wave conditions. The prediction quality of this model was poorer for the episodic condition than for the lower-energy mode, however, it illustrated how longer-period swells are preferentially refracted into the bay and make available far more nearshore wave energy to drive currents compared to waves during modal conditions. The highly episodic circulation, the nature of which is dependent on complex refraction patterns of episodic, long-period swell has implications for flushing and sediment dynamics for incised fringing reef-lined bays that characterize many high islands at low latitudes around the world.

Hoeke, R.; Storlazzi, C.; Ridd, P.

2011-01-01

89

Experiments studying the compression and unstable growth of a dense spherical bubble in a gaseous medium subjected to a strong planar shock wave (2.8 < M < 3.4) are performed in a vertical shock tube. The test gas is initially contained in a free-falling spherical soap-film bubble, and the shocked bubble is imaged using planar laser diagnostics. Concurrently, simulations are carried out using a compressible hydrodynamics code in r-z axisymmetric geometry.Experiments and computations indicate the formation of characteristic vortical structures in the post-shock flow, due to Richtmyer-Meshkov and Kelvin-Helmholtz instabilities, and smaller-scale vortices due to secondary effects. Inconsistencies between experimental and computational results are examined, and the usefulness of the current axisymmetric approach is evaluated.

Niederhaus, John [University of Wisconsin-Madison (United States); Ranjan, Devesh [University of Wisconsin-Madison (United States); Anderson, Mark [University of Wisconsin-Madison (United States); Oakley, Jason [University of Wisconsin-Madison (United States); Bonazza, Riccardo [University of Wisconsin-Madison (United States); Greenough, Jeff [Lawrence Livermore National Laboratory (United States)

2005-05-15

90

Magnetoviscous effect in a maghemite ferrofluid.

An iron oxide ferrofluid with mean particle size of 10.6 nm was synthesized by co-precipitation. The nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, electron energy loss spectroscopy, and dynamic light scattering. The magnetorheological properties of ferrofluid were investigated using a rotating rheometer. The effect of magnetic field on the aggregation of magnetic nanoparticles and rheological behavior were investigated. Moreover the effects of concentration and particle size on the magnetoviscousity of ferrofluid were studied. The results showed that the maghemite is the major magnetic phase. The magnetoviscous effect leads to phase separation at high magnetic fields which is dependent to the concentration. It was shown that the smaller particle sizes which are not contributed in magnetoviscous effect can contribute at higher magnetic fields. PMID:21770177

Ghasemi, E; Mirhabibi, A; Edrissi, M

2011-06-01

91

Use of ferrofluids in machining of metals

NASA Astrophysics Data System (ADS)

Ferrofluids controlled by an external magnetic field are suitable as lubricants for moving metal machining parts. Empirical relations of the form M sub c = kDt sub bs sup av sup c were established for the unit cutting torque M sub c as function of the drill diameter, the depth of hole t, the feed rate s, and the cutting rate v when holes in Al3V aluminum alloy, TsAM10-5 zinc alloy, VT1 titanium alloy, or 12Cr18Ni10Ti stainless are cut with a drill of R6M5 high-speed steel using a fixture made of nonmagnetic stainless and a ferrofluid based on MVP mineral tool oil as lubricant. Values of the coefficient and the exponents were determined by the Student significance test and Fisher adequacy test. It is found that ferrofluid as lubricant is more effective in machining of nonmagnetic materials.

Podgorkov, V. V.

1985-03-01

92

Hydrodynamic Models of Bipolar Semiconductors Best Asymptotic Profiles

Hydrodynamic Models of Bipolar Semiconductors Best Asymptotic Profiles Convergence to Stationary Waves Asymptotic Profiles for Bipolar Hydrodynamic System of Semiconductors Ming Mei Champlain College for Bipolar Hydrodynamic System of Semicon #12;Hydrodynamic Models of Bipolar Semiconductors Best Asymptotic

93

A landslide block perched on the northern wall of Tidal Inlet, Glacier Bay National Park (Figure 1), has the potential to generate large waves in Tidal Inlet and the western arm of Glacier Bay if it were to fail catastrophically. Landslide-generated waves are a particular concern for cruise ships transiting through Glacier Bay on a daily basis during the summer months. The objective of this study is to estimate the range of wave amplitudes and periods in the western arm of Glacier Bay from a catastrophic landslide in Tidal Inlet. This study draws upon preliminary findings of a field survey by Wieczorek et al. (2003), and evaluates the effects of variations in landslide source parameters on the wave characteristics.

Geist, Eric L.; Jakob, Matthias; Wieczoreck, Gerald F.; Dartnell, Peter

2003-01-01

94

Magnetization and susceptibility of polydisperse ferrofluids

On the basis of the mean spherical approximation of multicomponent dipolar hard sphere mixtures an analytical expression is proposed for the magnetic field dependence of the magnetization of size polydisperse ferrofluids. The polydispersity of the particle diameter is described by the gamma distribution function. Canonical ensemble Monte Carlo simulations have been performed in order to test these theoretical results for the initial susceptibility and the magnetization. The results for the magnetic properties of the polydisperse systems turn out to be in quantitative agreement with our present simulation data. In addition, we find good agreement between our theory and experimental data for magnetite-based ferrofluids.

I. Szalai; S. Nagy; S. Dietrich

2013-07-17

95

Quantum hydrodynamic (QHD) model of charged spin-1/2 particles contains physical quantities defined for all particles of a species including particles with spin-up and with spin-down. Different population of states with different spin direction is included in the spin density (magnetization). In this paper we derive a QHD model, which separately describes spin-up electrons and spin-down electrons. Hence we consider electrons with different projection of spin on the preferable direction as two different species of particles. We show that numbers of particles with different spin direction do not conserve. Hence the continuity equations contain sources of particles. These sources are caused by the interactions of spins with magnetic field. Terms of similar nature arise in the Euler equation. We have that z-projection of the spin density is no longer an independent variable. It is proportional to difference between concentrations of electrons with spin-up and electrons with spin-down. In terms of new model we consider propagation of waves in magnetized plasmas of degenerate electrons and motionless ions. We show that new form of QHD equations gives all solutions obtained from traditional form of QHD equations with no distinguish of spin-up and spin-down states. But it also reveals a sound-like solution we call the spin-electron acoustic wave. Coincidence of most solutions is expected since we started derivation with the same basic equation.

Pavel A. Andreev

2014-05-04

96

NASA Astrophysics Data System (ADS)

The gas response to the underlying stellar spirals is explored for M81 using unmagnetized hydrodynamic simulations. Constrained within the uncertainty of observations, 18 simulations are carried out to study the effects of self-gravity and to cover the parameter space comprising three different sound speeds and three different arm strengths. The results are confronted with the data observed at wavelengths of 8 ?m and 21 cm. In the outer disk, the ring-like structure observed in the 8 ?m image is consistent with the response of cold neutral medium with an effective sound speed 7 km s–1. For the inner disk, the presence of spiral shocks can be understood as a result of 4:1 resonances associated with the warm neutral medium with an effective sound speed 19 km s–1. Simulations with a single effective sound speed alone cannot simultaneously explain the structures in the outer and inner disks. Instead this justifies the coexistence of cold and warm neutral media in M81. The anomalously high streaming motions observed in the northeast arm and the outward shifted turning points in the iso-velocity contours seen along the southwest arm are interpreted as signatures of interactions with companion galaxies. The level of simulated streaming motions narrows down the uncertainty of the observed arm strength toward larger amplitudes.

Wang, Hsiang-Hsu; Lee, Wing-Kit; Taam, Ronald E.; Feng, Chien-Chang; Lin, Lien-Hsuan

2015-02-01

97

NASA Astrophysics Data System (ADS)

The impact of a deformable object with a body of water, such as with tsunamigenic, subaerial landslides, can lead to a complex near-field wave structure that can involve the generation of a substantial air cavity. The structure of the initiation and collapse of this cavity depends on the impact angle, velocity and geometry of the impacting landslide and is a likely source of the significant variations in the efficiency of energy transfer from landslide motion to the resulting wave energy. The severe deformation of the interfaces between landslide material, water and air can be problematic to simulate with many numerical methods. Eulerian grid- based methods are disadvantaged by their inherent difficulty tracking interfaces between phases. While Lagrangian grid-based methods naturally track material interfaces, they generally have difficulties with the significant deformation during the impact. Combination grid-based methods, such as the Arbitrary Lagrangian-Eulerian method, have been constructed to both allow for large deformation and track Lagrangian motion, and have been applied to modeling tsunamigenic landslides. In contrast to these grid- based methods, Lagrangian particle methods, such as Smoothed Particle Hydrodynamics (SPH), do not rely on an underlying mesh and both allow for large deformations and the tracking of Lagrangian motion. We have implemented an SPH model to study this impact process, cavity generation, and energy transfer. We treat the landslide as an incompressible, viscous fluid and the water as an incompressible, inviscid fluid. We present numerical experiments showing the dependence of the predicted solitary wave motion on the velocity and impact angle of the landslide, as well as the geometry of the impacting front of the landslide.

Schwaiger, H. F.

2008-12-01

98

Mechanical Properties of Ferrofluids in Loudspeakers.

1 Mechanical Properties of Ferrofluids in Loudspeakers. Guy Lemarquand, Romain Ravaud, Valerie in ironless electrodynamic loudspeak- ers. The motor is constituted of several outer stacked ring permanent between the loudspeaker faces. Second, they act as bearings and center the moving part. Finally

Paris-Sud XI, UniversitÃ© de

99

Ferrofluid Would Seal Linear-Motion Valve

NASA Technical Reports Server (NTRS)

Proposed valve employs ferrofluid to make tight seal. Seal requires no precisely machined parts, and hand lapping of valve seats are unnecessary. Magnetic fluid fills gap between shaft and annular pole piece in chamber wall. Precise shaft fit is not necessary.

Chandler, J. A.

1983-01-01

100

Passive Magnetic Bearing With Ferrofluid Stabilization

NASA Technical Reports Server (NTRS)

A new class of magnetic bearings is shown to exist analytically and is demonstrated experimentally. The class of magnetic bearings utilize a ferrofluid/solid magnet interaction to stabilize the axial degree of freedom of a permanent magnet radial bearing. Twenty six permanent magnet bearing designs and twenty two ferrofluid stabilizer designs are evaluated. Two types of radial bearing designs are tested to determine their force and stiffness utilizing two methods. The first method is based on the use of frequency measurements to determine stiffness by utilizing an analytical model. The second method consisted of loading the system and measuring displacement in order to measure stiffness. Two ferrofluid stabilizers are tested and force displacement curves are measured. Two experimental test fixtures are designed and constructed in order to conduct the stiffness testing. Polynomial models of the data are generated and used to design the bearing prototype. The prototype was constructed and tested and shown to be stable. Further testing shows the possibility of using this technology for vibration isolation. The project successfully demonstrated the viability of the passive magnetic bearing with ferrofluid stabilization both experimentally and analytically.

Jansen, Ralph; DiRusso, Eliseo

1996-01-01

101

NASA Astrophysics Data System (ADS)

Context. With the progress of observational constraints on stellar rotation and on the angular velocity profile in stars, it is necessary to understand how angular momentum is transported in stellar interiors during their whole evolution. In this context, more highly refined dynamical stellar evolution models have been built that take into account transport mechanisms. Aims: Internal gravity waves (IGWs) excited by convective regions constitute an efficient transport mechanism over long distances in stellar radiation zones. They are one of the mechanisms that are suspected of being responsible for the quasi-flat rotation profile of the solar radiative region up to 0.2 R?. Therefore, we include them in our detailed analysis started in Paper I of the main physical processes responsible for the transport of angular momentum and chemical species in stellar radiation zones. Here, we focus on the complete interaction between differential rotation, meridional circulation, shear-induced turbulence, and IGWs during the main sequence. Methods: We improved the diagnosis tools designed in Paper I to unravel angular momentum transport and chemical mixing in rotating stars by taking into account IGWs. The star's secular hydrodynamics is treated using projection on axisymmetric spherical harmonics and appropriate horizontal averages that allow the problem to be reduced to one dimension while preserving the non-diffusive character of angular momentum transport by the meridional circulation and IGWs. Wave excitation by convective zones is computed at each time-step of the evolution track. We choose here to analyse the evolution of a 1.1 M?, Z? star in which IGWs are known to be efficient. Results: We quantify the relative importance of the physical mechanisms that sustain meridional currents and that drive the transport of angular momentum, heat, and chemicals when IGWs are taken into account. First, angular momentum extraction, Reynolds stresses caused by IGWs, and viscous stresses sustain a large-scale multi-cellular meridional circulation. This circulation in turn advects entropy, which generates temperature fluctuations and a new rotation profile because of thermal wind. Conclusions: We have refined our diagnosis of secular transport processes in stellar interiors. We confirm that meridional circulation is sustained by applied torques, internal stresses, and structural readjustments, rather than by thermal imbalance, and we detail the impact of IGWs. These large-scale flows then modify the thermal structure of stars, their internal rotation profile, and their chemical stratification. The tools we developed in Paper I and generalised for the present analysis will be used in the near future to study secular hydrodynamics of rotating stars taking into account IGWs in the whole Hertzsprung-Russell diagram.

Mathis, S.; Decressin, T.; Eggenberger, P.; Charbonnel, C.

2013-10-01

102

Anomalous attenuation of ultrasound in ferrofluids under the influence of a magnetic field

NASA Technical Reports Server (NTRS)

Ultrasonic wave propagation has been studied in a water-base ferrofluid by pulse-echo methods. A commercial box-car integrator was used to measure the change in attenuation due to an external magnetic field applied at various angles relative to the ultrasonic propagation vector. Anomalous results were obtained when the attenuation was plotted as a function of the magnetic field strength. As the field increased, the attenuation reached a maximum and then decreased to a flat minimum before it approached saturation at a field of 2 KG. This variation of attenuation with magnetic field cannot be explained from the simple picture derivable from the work of McTague on the viscosity of ferrofluids. In no case was the viscosity seen to decrease with field, nor was the oscillatory behavior observed. The results of this study were compared with the theory developed by Parsons.

Isler, W. E.; Chung, D. Y.

1978-01-01

103

Resistive magneto-hydrodynamical cut-off of Alfvén wave in fully ionized plasmas

The term cut-off in the theory of the Alfvén wave is used to describe several different phenomena. In this work, the cut-off due to magnetohydrodynamic resistive damping in fully ionized plasmas is revisited. This cut-off requires short enough wavelengths, it is routinely discussed in numerous works, and graphs depicting it are available even in textbooks. We show that this cut-off is hardly ever possible in real plasmas. This is due to the fact that some essential criteria and conditions become strongly violated in order to achieve the cut-off.

Vranjes, J., E-mail: jvranjes@yahoo.com [Institute of Physics Belgrade, Pregrevica 118, 11080 Zemun (Serbia); Kono, M., E-mail: kono@fps.chuo-u.ac.jp [Faculty of Policy Studies, Chuo University, Tokyo (Japan)

2014-01-15

104

NASA Astrophysics Data System (ADS)

Quantum hydrodynamics in superfluid helium and atomic Bose-Einstein condensates (BECs) has been recently one of the most important topics in low temperature physics. In these systems, a macroscopic wave function (order parameter) appears because of Bose-Einstein condensation, which creates quantized vortices. Turbulence consisting of quantized vortices is called quantum turbulence (QT). The study of quantized vortices and QT has increased in intensity for two reasons. The first is that recent studies of QT are considerably advanced over older studies, which were chiefly limited to thermal counterflow in 4He, which has no analog with classical traditional turbulence, whereas new studies on QT are focused on a comparison between QT and classical turbulence. The second reason is the realization of atomic BECs in 1995, for which modern optical techniques enable the direct control and visualization of the condensate and can even change the interaction; such direct control is impossible in other quantum condensates like superfluid helium and superconductors. Our group has made many important theoretical and numerical contributions to the field of quantum hydrodynamics of both superfluid helium and atomic BECs. In this article, we review some of the important topics in detail. The topics of quantum hydrodynamics are diverse, so we have not attempted to cover all these topics in this article. We also ensure that the scope of this article does not overlap with our recent review article (arXiv:1004.5458), “Quantized vortices in superfluid helium and atomic Bose-Einstein condensates”, and other review articles.

Tsubota, Makoto; Kobayashi, Michikazu; Takeuchi, Hiromitsu

2013-01-01

105

Colloids on the frontier of ferrofluids. Rheological properties.

This paper is devoted to the steady-state rheological properties of two new kinds of ferrofluids. One of these was constituted by CoNi nanospheres of 24 nm in diameter, whereas the other by CoNi nanofibers of 56 nm in length and 6.6 nm in width. These ferrofluids were subjected to shear rate ramps under the presence of magnetic fields of different intensity, and the corresponding shear stress values were measured. From the obtained rheograms (shear stress vs shear rate curves) the values of both the static and the dynamic yield stresses were obtained as a function of the magnetic field. The magnetoviscous effect was also obtained as a function of both the shear rate and the magnetic field. The experimental results demonstrate that upon magnetic field application these new ferrofluids develop yield stresses and magnetoviscous effects much greater than those of conventional ferrofluids, based on nanospheres of approximately 10 nm in diameter. Besides some expected differences, such as the stronger magnetorheological effect in the case of ferrofluids based on nanofibers, some intriguing differences are found between the rheological behaviors of nanofiber ferrofluids and nanosphere ferrofluid. First, upon field application the rheograms of nanofiber ferrofluids present N-shaped dependence of the shear stress on the shear rate. The decreasing part of the rheograms takes place at low shear rate. These regions of negative differential viscosity, and therefore, unstable flow is not observed in the case of nanosphere ferrofluids. The second intriguing difference concerns the curvature of the yield stress vs magnetic field curves. This curvature is negative in the case of nanosphere ferrofluid, giving rise to saturation of the yield stress at medium field, as expected. However, in the case of nanofiber ferrofluid this curvature is positive, which means a faster increase of the yield stress with the magnetic field the higher the magnitude of the latter. These interesting differences may be due to the existence of strong interparticle solid friction in the case of nanofiber ferrofluids. Finally, theoretical models for the static yield stress of the ferrofluids were developed. These models consider that upon field application the ferrofluid nanoparticles are condensed in drops of dense phase. These drops tend to be aligned along the field direction, opposing the flow of the ferrofluids and being responsible for the static quasielastic deformation and the yield-stress phenomena. By considering the existence of interparticle dry friction only in the case of nanofiber ferrofluids, the developed models predicted quite well not only the magnitude of the static yield stress but also the differences in curvature of the yield stress vs magnetic field curves. PMID:22432510

López-López, Modesto T; Gómez-Ramírez, Ana; Rodríguez-Arco, Laura; Durán, Juan D G; Iskakova, Larisa; Zubarev, Andrey

2012-04-17

106

Ion reflection at perpendicular, collisionless shock waves is treated in a simple gas dynamical context. The effect of pickup ions reflected by the cross-shock potential and their subsequent energization in the motional electric field is included through the introduction of source terms in the basic inviscid fluid equations. From a weak source description, a Burgers' equation is derived modified by the addition of a quadratically nonlinear term. The construction of Burgers' equation demonstrates explicitly that particle reflection is a dissipation mechanism for collisionless shocks. Numerical solutions for the modified Burgers' equation (MBE) are presented. From these solutions it is implied that the dissipative term of the MBE is associated with the length scale of the shock foot, while the additional term is associated with the shock ramp. The general physical model is discussed in terms of the reflection and energization of pickup ions at outer heliospheric perpendicular shocks.

Burrows, R. H.; Zank, G. P.; Dasgupta, B.; Webb, G. M. [Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville (United States)

2010-12-30

107

Fine-Scale Density Wave Structure of Saturn's Main Rings: A Hydrodynamic Theory

NASA Astrophysics Data System (ADS)

The theoretical studies of Maxwell (1859) have showed that the rings around Saturn could not be solid or liquid, but rather a swarm of millions of individual particles rotating in separate concentric orbits at different speeds. A modern very popular model of the particles in Saturn's rings is a smooth ice sphere, whose restitution coefficient is quite high (exceeding 0.63) and decreases as the collision velocity increases. In this work, the linear stability of the Saturnian ring disk of mutually gravitating and physically colliding particles is examined with special emphasis on its fine-scale of the order of 100 m density wave structure, that is, almost regularly spaced, aligned cylindric density enhancements and optically-thin zones with the width and the spacing between them of roughly several tens particle diameters. Jeans' instabilities of small-amplitude gravity perturbations (e.g., those produced by a spontaneous disturbance) are analyzed analytically through the use of Navier-Stokes dynamical equations of a compressible fluid. An essential feature of this study is that the theory is not restricted by any assumptions regarding the thickness of the system. The simple model of the system is considered: the ring disk is considered to be thin, a weakly spatially inhomogeneous, and its structure is considered in a horizontally local short-wave approximation. We show that the disk is probably unstable and gravity perturbations grow effectively within a few orbital periods; self-gravitation plays a key role in the formation of the fine-scale structure while particle collisions play a secondary role. The predictions of the theory are compared with recent observations of Saturn's rings by the Cassini spacecraft and are found to be in good agreement. Particulary, it appears very likely that some of the microstructures observed in Saturn's A and B rings -both axisymmetric and nonaxisymmetric ones -are manifestations of these effects produced by Jeans' gravitational instability. We argue that the quasi-periodic density enhancements revealed by Cassini obser-vations are flattened structures, with height/width ratio of about 0.3 or even less. A separate investigation based on high-resolution of the order of 10 m observations of Saturn's A and B rings (and probably C ring as well) should be done to confirm this prediction. It is also shown that the gravitational instability might be proposed as potential clusters-forming mechanism leading to formation of porous 100-meter-diameter moonlets ("clumpy moons") embedded in the mid and outer A ring, and this has also yet to be directly measured. This work was supported in part by the Israel Science Foundation.

Griv, Evgeny; Gedalin, Michael

108

Fine-Scale ~ 100 m Density Wave Structure of the Saturnian Ring Disk: A Hydrodynamic Theory

NASA Astrophysics Data System (ADS)

The linear stability of the Saturnian ring disk of mutually gravitating and physically colliding particles is examined with special emphasis on its fine-scale of the order of 100 m or even less density wave structure (almost regularly spaced, aligned cylindric density enhancements and optically-thin zones with the width and the spacing between them of roughly several tens particle diameters). Jeans instabilities of gravity perturbations (e.g., those produced by a spontaneous disturbance) are analyzed analytically through the use of Navier-Stokes equations of a compressible fluid. An essential feature of this study is that the theory is not restricted by any assumptions regarding the thickness of the system. The simple model of the system is considered: the ring disk is considered to be thin and its structure is considered in a horizontally local Wenzel-Kramer-Brillouin (or short-wavelength) approximation. A plasma physics method is given for the solution of the self-consistent system of the gasdynamical equations and the Poisson equation describing the stability of Saturn's A, B, and C rings when the system is perturbed in an arbitrary manner. That is, when a gravity perturbation does not distort the rings' plane (modes of even symmetry with respect to the equatorial plane, or even Jeans-type perturbations) and when does distort the rings' plane (odd bending-type perturbations). This approach is introduced here for the first time in an astrophysical context. We show that the disk is probably unstable and gravity perturbations grow effectively within a few orbital periods; self-gravitation plays a key role in the formation of the fine-scale structure while particle collisions play a secondary role. It appears very likely that some of the microstructures in Saturn's rings recently revealed by the CASSINI spacecraft high-resolution observations is a manifestation of these density wave effects. The predictions of the theory are compared with observations of Saturn's rings by the CASSINI and are found to be in good agreement. Particulary, we show that the quasi-periodic density enhancements are flattened structures, with height/width ratio of about 0.3. This work was supported in part by the Israel Science Foundation and the Binational US-Israel Science Foundation.

Griv, E.; Gedalin, M.

2009-04-01

109

NASA Astrophysics Data System (ADS)

The quantum hydrodynamic (QHD) model of charged spin-1/2 particles contains physical quantities defined for all particles of a species including particles with spin-up and with spin-down. Different populations of states with different spin directions are included in the spin density (the magnetization). In this paper I derive a QHD model, which separately describes spin-up electrons and spin-down electrons. Hence electrons with different projections of spins on the preferable direction are considered as two different species of particles. It is shown that the numbers of particles with different spin directions do not conserve. Hence the continuity equations contain sources of particles. These sources are caused by the interactions of the spins with the magnetic field. Terms of similar nature arise in the Euler equation. The z projection of the spin density is no longer an independent variable. It is proportional to the difference between the concentrations of the electrons with spin-up and the electrons with spin-down. The propagation of waves in the magnetized plasmas of degenerate electrons is considered. Two regimes for the ion dynamics, the motionless ions and the motion of the degenerate ions as the single species with no account of the spin dynamics, are considered. It is shown that this form of the QHD equations gives all solutions obtained from the traditional form of QHD equations with no distinction of spin-up and spin-down states. But it also reveals a soundlike solution called the spin-electron acoustic wave. Coincidence of most solutions is expected since this derivation was started with the same basic equation: the Pauli equation. Solutions arise due to the different Fermi pressures for the spin-up electrons and the spin-down electrons in the magnetic field. The results are applied to degenerate electron gas of paramagnetic and ferromagnetic metals in the external magnetic field. The dispersion of the spin-electron acoustic waves in the partially spin-polarized degenerate neutron matter are also considered.

Andreev, Pavel A.

2015-03-01

110

NASA Astrophysics Data System (ADS)

Axially symmetric flows with converging shock waves in conical solid targets of steel or lead filled by porous aluminum, graphite, or polytetrafluoroethylene under impact of an aluminum plate with the velocity from 2.5 to 9 km/s have been simulated numerically in the framework of the model of the hypoelastic ideal-plastic solid. Equations of state for all materials in question are used to describe thermodynamic properties of the impactor and target over a wide range of pressures and temperatures, taking into account phase transitions. The graphite-to-diamond transformation is taken into consideration based on a kinetic model. Three different convergent cone configurations of the targets either with a closed cavity or with an outlet hole are analyzed. An appreciable increase of the pressure and temperature within the target cavity as well as of the ejected material velocity on decreasing the initial density of a sample is demonstrated in the simulations. Numerical results that can be compared with possible further experiments for verification of the predictions are presented and discussed.

Khishchenko, K. V.; Charakhch'yan, A. A.; Fortov, V. E.; Frolova, A. A.; Milyavskiy, V. V.; Shurshalov, L. V.

2011-09-01

111

Ferrofluid based micro-electrical energy harvesting

NASA Astrophysics Data System (ADS)

Innovations in energy harvesting have seen a quantum leap in the last decade. With the introduction of low energy devices in the market, micro energy harvesting units are being explored with much vigor. One of the recent areas of micro energy scavenging is the exploitation of existing vibrational energy and the use of various mechanical motions for the same, useful for low power consumption devices. Ferrofluids are liquids containing magnetic materials having nano-scale permanent magnetic dipoles. The present work explores the possibility of the use of this property for generation of electricity. Since the power generation is through a liquid material, it can take any shape as well as response to small acceleration levels. In this work, an electromagnet-based micropower generator is proposed to utilize the sloshing of the ferrofluid within a controlled chamber which moves to different low frequencies. As compared to permanent magnet units researched previously, ferrofluids can be placed in the smallest of containers of different shapes, thereby giving an output in response to the slightest change in motion. Mechanical motion from 1- 20 Hz was able to give an output voltage in mV's. In this paper, the efficiency and feasibility of such a system is demonstrated.

Purohit, Viswas; Mazumder, Baishakhi; Jena, Grishma; Mishra, Madhusha

2013-03-01

112

Aqueous ferrofluids based on manganese and cobalt ferrites

Synthesis of two new aqueous ferrofluids is performed chemically according to Massart's procedure. Manganese and cobalt ferrite magnetic particles are precipitated and treated in order to obtain colloidal sols by creating a charge density on their surface. Such “ionic” ferrofluids can be prepared in an acidic (after a treatment by ferric nitrate) or in an alkaline medium at a concentration

Francisco Augusto Tourinho; Raymonde Franck; René Massart

1990-01-01

113

Electrospray from an Ionic Liquid Ferrofluid utilizing the Rosensweig Instability

Electrospray from an Ionic Liquid Ferrofluid utilizing the Rosensweig Instability Edmond J. Meyer Technological University. This thruster utilized an ionic liquid ferrofluid that was synthesized by suspending magnetic nanoparticles in an ionic liquid carrier solution so that the resulting fluid is superparamagnetic

King, Lyon B.

114

Numerical Modeling of Ferrofluid Droplets in Magnetic Fields

into the vitreous cavity of the eye and guided by a permanent magnet inserted outside the scleral wall of the eye of a ferrofluid liquid and an immiscible viscous medium. The magnetic force competes with the interfacial tension the magnetic forces at the interface between a ferrofluid and an immiscible surrounding liquid in the context

Renardy, Yuriko

115

Waves in Radial Gravity Using Magnetic Fluid

NASA Technical Reports Server (NTRS)

We are beginning laboratory experiments using magnetically active ferrofluids to study surface waves in novel geometries. Terrestrial gravity is eliminated from the dynamics, and the magnetic body force felt by ferrofluid in the presence of a magnetic field gradient is used to create a geopotential field which is a section of or an entire sphere or cylinder. New optical, electromagnetic and ultrasonic diagnostic techniques are under development to initially study capillary-gravity wave propagation and interaction in such geometries.

Ohlsen, Daniel R.; Hart, John E.; Weidman, Patrick D.

1996-01-01

116

Traumatic brain injury (TBI) caused by an explosive blast (blast-TBI) is postulated to result, in part, from transvascular transmission to the brain of a hydrodynamic pulse (a.k.a., volumetric blood surge, ballistic pressure wave, hydrostatic shock, or hydraulic shock) induced in major intrathoracic blood vessels. This mechanism of blast-TBI has not been demonstrated directly. We tested the hypothesis that a blast wave impacting the thorax would induce a hydrodynamic pulse that would cause pathological changes in the brain. We constructed a Thorax-Only Blast Injury Apparatus (TOBIA) and a Jugular-Only Blast Injury Apparatus (JOBIA). TOBIA delivered a collimated blast wave to the right lateral thorax of a rat, precluding direct impact on the cranium. JOBIA delivered a blast wave to the fluid-filled port of an extracorporeal intravenous infusion device whose catheter was inserted retrograde into the jugular vein, precluding lung injury. Long Evans rats were subjected to sublethal injury by TOBIA or JOBIA. Blast injury induced by TOBIA was characterized by apnea and diffuse bilateral hemorrhagic injury to the lungs associated with a transient reduction in pulse oximetry signals. Immunolabeling 24 h after injury by TOBIA showed up-regulation of tumor necrosis factor alpha, ED-1, sulfonylurea receptor 1 (Sur1), and glial fibrillary acidic protein in veins or perivenular tissues and microvessels throughout the brain. The perivenular inflammatory effects induced by TOBIA were prevented by ligating the jugular vein and were reproduced using JOBIA. We conclude that blast injury to the thorax leads to perivenular inflammation, Sur1 up-regulation, and reactive astrocytosis resulting from the induction of a hydrodynamic pulse in the vasculature. PMID:24673157

Simard, J Marc; Pampori, Adam; Keledjian, Kaspar; Tosun, Cigdem; Schwartzbauer, Gary; Ivanova, Svetlana; Gerzanich, Volodymyr

2014-07-15

117

We discuss complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider contribution of the annihilation interaction in the quantum hydrodynamic equations and in spectrum of waves in magnetized electron-positron plasmas. We consider propagation of waves parallel and perpendicular to an external magnetic field. We also consider oblique propagation of longitudinal waves. We derive set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory for the linear wave behavior in absence of external fields. We calculate contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for electron-positron plasmas including the Darwin and annihilation interactions. Existence of conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that annihilation interaction plays an important role in quantum electron-positron plasmas giving contribution of the same magnitude as the spin-spin interaction.

Pavel A. Andreev

2014-04-18

118

Elongational flow effects on the vortex growth out of Couette flow in ferrofluids.

The growth behavior of stationary axisymmetric vortices and of oscillatory, nonaxisymmetric spiral vortices in Taylor-Couette flow of a ferrofluid in between differentially rotating cylinders is analyzed using a numerical linear stability analysis. The investigation is done as a function of the inner and outer cylinder's rotation rates, the axial wave number of the vortex flows, and the magnitude of an applied homogeneous axial magnetic field. In particular, the consequences of incorporating elongational flow effects in the magnetization balance equation on the marginal control parameters that separate growth from decay behavior are determined. That is done for several values of the transport coefficient that measures the strength of these effects. PMID:23767623

Altmeyer, S; Leschhorn, A; Hoffmann, Ch; Lücke, M

2013-05-01

119

Drops deformation and magnetic permeability of a ferrofluid emulsion

In the paper the novel soft magnetic composite system is investigated. A ferrofluid emulsion studied demonstrates the strong magnetic properties which are atypical for commonly known emulsions. Interaction of ferrofluid emulsions with a magnetic field is considered. Structural transformations in these media, such as deformation of emulsion microdroplets and emulsion inversion, are studied. The changes in the relative permeability of emulsion associated with structural transformations are investigated. The theory of the observed phenomena is developed, and the feasibility of effectively controlling the magnetic properties of ferrofluid emulsions by applying a magnetic field is demonstrated.

Arthur Zakinyan; Yury Dikansky

2011-04-17

120

Damping induced by ferrofluid seals in ironless loudspeaker

NASA Astrophysics Data System (ADS)

Damping induced by ferrofluid seals in ironless loudspeakers is investigated in this paper. The magnetic field is steady but not spatially constant. A model to determine the viscous damping coefficient induced by the ferrofluid seal is derived. It is a function of geometrical parameters and local viscosity of the ferrofluid in which dependence from magnetic field, shear rate and frequency is accounted for. Comparison with experimental results shows a good agreement for the thinner seals. An overestimation of the damping is observed for higher volumes. This discrepancy comes from geometric irregularities of the magnet assembly made out of several tiles.

Pinho, M.; Génevaux, J. M.; Dauchez, N.; Brouard, B.; Collas, P.; Mézière, H.

2014-04-01

121

Hydrodynamics is the appropriate "effective theory" for describing any fluid medium at sufficiently long length scales. This paper treats the vacuum as such a medium and derives the corresponding hydrodynamic equations. Unlike a normal medium the vacuum has no linear sound-wave regime; disturbances always "propagate" nonlinearly. For an "empty vacuum" the hydrodynamic equations are familiar ones (shallow water-wave equations) and they describe an experimentally observed phenomenon -- the spreading of a clump of zero-temperature atoms into empty space. The "Higgs vacuum" case is much stranger; pressure and energy density, and hence time and space, exchange roles. The speed of sound is formally infinite, rather than zero as in the empty vacuum. Higher-derivative corrections to the vacuum hydrodynamic equations are also considered. In the empty-vacuum case the corrections are of quantum origin and the post-hydrodynamic description corresponds to the Gross-Pitaevskii equation. I conjecture the form of the post-hydrodynamic corrections in the Higgs case. In the 1+1-dimensional case the equations possess remarkable `soliton' solutions and appear to constitute a new exactly integrable system.

P. M. Stevenson

2005-07-30

122

Ferrohydrodynamic evaluation of rotational viscosity and relaxation in certain ferrofluids.

A significant effect of aggregation dynamics for aqueous ferrofluid (AF) and kerosene based ferrofluid (KF) using magnetic field dependent capillary viscosity and magneto-optical relaxation measurements is studied. For better comparison parameters of AF and KF are kept similar. Ferrohydrodynamic equations of chain forming ferrofluids, dilute ferrofluids, and Brownian dynamic simulations are compared. It is observed that the rotational viscosity of AF is larger than that of KF due to field induced aggregates in it and strong dipolar interactions. It is also observed that at ?? ~ 0.04 both AF and KF viscosity becomes almost similar, suggesting similar behavior at that shear rate. The magneto-optical relaxation in AF exhibits nonexponential behavior when relaxed from higher magnetic field and follows irreversible thermodynamics, whereas for KF the relaxation is exponential and follows the effective field method. This discrepancy is explained based on aggregation dynamics of magnetic particles. Results are well described by the corresponding theoretical models. PMID:23005542

Patel, Rajesh

2012-07-01

123

Ferrofluid surface and volume flows in uniform rotating magnetic fields

Ferrofluid surface and volume effects in uniform dc and rotating magnetic fields are studied. Theory and corroborating measurements are presented for meniscus shapes and resulting surface driven flows, spin-up flows, and ...

Elborai, Shihab M. (Shihab Mahmoud), 1977-

2006-01-01

124

NASA Astrophysics Data System (ADS)

The effect of magnetic fields on flows of ferrofluids enters the basic hydrodynamic equations by an expression for the relaxation of magnetization of the fluid. Despite intense investigations of ferrohydrodynamics, the question of the appropriate approach to describe the magnetization outside equilibrium is still open. By a comparison of experimental and theoretical data of a Taylor-Couette system as a model system, this question is highlighted in this paper. The fluid cell of the Taylor-Couette system is subject to a homogeneous axial magnetic field and the flow profiles are measured by ultrasound-Doppler velocimetry. In this paper, experimental results concerning the transition from circular Couette flow to Taylor vortex flow at different axial magnetic field strengths are measured, compared to theory and discussed.

Reindl, M.; Leschhorn, A.; Lücke, M.; Odenbach, S.

125

Characterizing ferrofluid spin-up flow in rotating uniform magnetic fields

A ferrofluid is a collection of nanoscale ferromagnetic particles with a stabilizing surfactant in a liquid to form a colloid. The dynamic behavior of ferrofluids in the presence of magnetic fields has long been an area ...

Dozier, Kahlil A

2014-01-01

126

Ferrofluid spin-up flows from uniform and non-uniform rotating magnetic fields

When ferrofluid in a cylindrical container is subjected to a rotating azimuthally directed magnetic field, the fluid "spins up" into an almost rigid-body rotation where ferrofluid nanoparticles have both a linear and an ...

Khushrushahi, Shahriar Rohinton

2010-01-01

127

Experimental investigation of magnetically driven flow of ferrofluids in porous media

This report presents experimental results of the flow of ferrofluids in porous media to investigate the potential for precisely controlling fluid emplacement in porous media using magnetic fields. Ferrofluids are colloidal suspensions of magnetic particles stabilized in various carrier liquids. In the presence of an external magnetic field, the ferrofluid becomes magnetized as the particles align with the magnetic field. Potential applications of ferrofluids to subsurface contamination problems include magnetic guidance of reactants to contaminated target zones in the subsurface for in situ treatment or emplacement of containment barriers. Laboratory experiments of magnetically induced ferrofluid flow in porous media in this report demonstrate the potential for mobilizing ferrofluid and controlling fluid emplacement through control of the external magnetic field. The pressures measured in ferrofluid due to the attraction of ferrofluid to a permanent magnet agree well with calculated values. The results show that a predictable pressure gradient is produced in the fluid which is strong near the magnet and drops off quickly with distance. This pressure gradient drives the fluid through sand without significant loss of ferrofluid strength due to filtration or dilution. Flow visualization experiments of ferrofluid in water-filled horizontal Hele-Shaw cells demonstrate that ferrofluid obtains a consistent final arc-shaped configuration around the magnet regardless of initial configuration or flow path toward the magnet. Analogous experiments in actual porous media showed similar features and confirm the ability of ferrofluid to move through porous media by magnetic forces.

Borglin, S.E.; Moridis, G.J.; Oldenburg, C.M.

1998-08-01

128

This paper presents an analytical method based on the coulombian model of a magnet for studying a ferrofluid seal in ironless electrodynamic loudspeakers. Such an approach differs from the ones generally used for studying such geometries because the ferrofluid used is submitted to a magnetic field greater than 1 T which saturates the ferrofluid. Consequently, its shape and its mechanical

Romain Ravaud; Guy Lemarquand

2009-01-01

129

Viscoelasticity of mono- and polydisperse inverse ferrofluids.

We report on measurements of a magnetorheological model fluid created by dispersing nonmagnetic microparticles of polystyrene in a commercial ferrofluid. The linear viscoelastic properties as a function of magnetic field strength, particle size, and particle size distribution are studied by oscillatory measurements. We compare the results with a magnetostatic theory proposed by De Gans et al. [Phys. Rev. E 60, 4518 (1999)] for the case of gap spanning chains of particles. We observe these chain structures via a long distance microscope. For monodisperse particles we find good agreement of the measured storage modulus with theory, even for an extended range, where the linear magnetization law is no longer strictly valid. Moreover we compare for the first time results for mono- and polydisperse particles. For the latter, we observe an enhanced storage modulus in the linear regime of the magnetization. PMID:16965057

Saldivar-Guerrero, Ruben; Richter, Reinhard; Rehberg, Ingo; Aksel, Nuri; Heymann, Lutz; Rodriguez-Fernández, Oliverio S

2006-08-28

130

Thermodiffusion in ferrofluids regarding thermomagnetic convection

NASA Astrophysics Data System (ADS)

Magnetic fluids, also called ferrofluids, are binary liquids consisting of magnetic nanoparticles being dispersed in a carrier liquid. They show very strong thermodiffusive behaviour with a Soret coefficient (ST) of approximately 0.16 K without a magnetic field. The dependence of the Soret coefficient on a magnetic field can lead to even higher values, and to a change in the coefficient's sign. This change in the direction of movement of the nanoparticles strongly affects the onset of thermomagnetic convection. A linear stability analysis reveals that thermodiffusion with a positive sign of the Soret coefficient enhances the onset of convection, whereas negative coefficients starting at about -0.001 K suppress convection at all.

Sprenger, Lisa; Lange, Adrian; Odenbach, Stefan

2013-04-01

131

The extrinsic hysteresis behavior of dilute binary ferrofluids.

We report on the magnetization behavior of dilute binary ferrofluids based on ?-Fe(2)O(3)/Ni(2)O(3) composite nanoparticles (A particles), with diameter about 11 nm, and ferrihydrite (Fe(5)O(7)(OH) ?4H2O) nanoparticles (B particles), with diameter about 6 nm. The results show that for the binary ferrofluids with A-particle volume fraction ?(A) = 0.2% and B-particle volume fractions ?(B) = 0.1% and ?(B) = 0.6%, the magnetization curves exhibit quasi-magnetic hysteresis behavior. The demagnetizing curves coincide with the magnetizing curves at high fields. However, for single ?-Fe(2)O(3)/Ni(2)O(3) ferrofluids with ?(A) = 0.2% and binary ferrofluids with ?(A) = 0.2% and ?(B) = 1.0%, the magnetization curves do not behave in this way. Additionally, at high field (750 kA/m), the binary ferrofluid with ?(B) = 1.0% has the smallest magnetization. From the model-of-chain theory, the extrinsic hysteresis behavior of these samples is attributed to the field-induced effects of pre-existing A particle chains, which involve both Brownian rotation of the chains'moments and a Néel rotation of the particles' moments in the chains. The loss of magnetization for the ferrofluids with ?(B) = 1.0% is attributed to pre-existing ring-like A-particle aggregates. These magnetization behaviors of the dilute binary ferrofluids not only depend on features of the strongly magnetic A-particle system, but also modifications of the weaker magnetic B-particle system. PMID:25365919

Lin, Lihua; Li, Jian; Lin, Yueqiang; Liu, Xiaodong; Chen, Longlong; Li, Junming; Li, Decai

2014-10-01

132

We show that the exact partition function of U(N) six-dimensional gauge theory with eight supercharges on C^2 x S^2 provides the quantization of the integrable system of hydrodynamic type known as gl(N) periodic Intermediate Long Wave (ILW). We characterize this system as the hydrodynamic limit of elliptic Calogero-Moser integrable system. We compute the Bethe equations from the effective gauged linear sigma model on S^2 with target space the ADHM instanton moduli space, whose mirror computes the Yang-Yang function of gl(N) ILW. The quantum Hamiltonians are given by the local chiral ring observables of the six-dimensional gauge theory. As particular cases, these provide the gl(N) Benjamin-Ono and Korteweg-de Vries quantum Hamiltonians. In the four dimensional limit, we identify the local chiral ring observables with the conserved charges of Heisenberg plus W_N algebrae, thus providing a gauge theoretical proof of AGT correspondence.

Giulio Bonelli; Antonio Sciarappa; Alessandro Tanzini; Petr Vasko

2014-05-07

133

NASA Astrophysics Data System (ADS)

Observations in all electromagnetic bands show that many supernova remnants (SNRs) have a very aspherical shape. This can be the result of asymmetries in the supernova explosion or a clumpy circumstellar medium. We study the generation of inhomogeneities and the mixing of elements arising from these two sources in multidimensional hydrodynamic simulations of the propagation of a supernova blast wave into a cloudy environment. We model a specific SNR, Vela Jr (RX J0852.0-4622). By comparing our results with recent observations, we can constrain the properties of the explosion. We find that a very energetic explosion of several 1051 erg occurring roughly about 800 years ago is consistent with the shape and emission of the SNR, as well as a supernova with an energy closer to the canonical value of 1051 erg a few thousand years ago.

Obergaulinger, M.; Iyudin, A. F.; Müller, E.; Smoot, G. F.

2014-01-01

134

The top surface of boneless skinless chicken breasts was inoculated with either green fluorescent protein (GFP)-labeled Escherichia coli (E. coli-GFP) or rifampicin-resistant E. coli (E. coli-Rif) and subjected to electrically generated hydrodynamic shock wave treatment (HVADH). Cryostat sampling in concert with laser scanning confocal microscopy or plating onto antibiotic selective agar was used to determine if HVADH treatment resulted in the movement of the inoculated bacteria from the outer inoculated surface to the interior of intact boneless skinless chicken breasts. In HVADH-treated boneless skinless chicken breasts, marker bacteria were detected within the first 200 microm below the inoculated surface, 50 to 100 microm beyond the depth of untreated surface inoculated boneless skinless chicken breasts. The exact depth at which the marker bacteria were found was dependent on the cryostat sampling distance used. These results suggest that HVADH treatments affect the movement of surface bacteria. PMID:12872981

Lorca, T A; Claus, J R; Eifert, J D; Marcy, J E; Sumner, S S

2003-07-01

135

Sink-float ferrofluid separator applicable to full scale nonferrous scrap separation

NASA Technical Reports Server (NTRS)

Design and performance of a ferrofluid levitation separator for recovering nonferrous metals from shredded automobiles are reported. The scrap separator uses an electromagnet to generate a region of constant density within a pool of ferrofluid held between the magnetic poles; a saturated kerosene base ferrofluid as able to float all common industrial metals of interest. Conveyors move the scrap into the ferrofluid for separation according to density. Results of scrap mixture separation studies establish the technical feasibility of relatively pure aluminum alloy and zinc alloy fractions from shredded automobile scrap by this ferrofluid levitation process. Economic projections indicate profitable operation for shredders handling more than 300 cars per day.

1973-01-01

136

Study on the magnetorheological properties of maghemite-kerosene ferrofluid.

As the ferrofluids are synthesized in a controlled atmosphere to Prevent oxidation of the magnetite phase; most reports of rheological properties have been derived from magnetite based ferrofluids. In this paper a ferrofluid based on iron oxide was synthesized by co-precipitation with air. Lauric acid was used to coat magnetic nanoparticles in the kerosene. The microstructural features of the ferrofluid and the variation with time and temperature of its rheologic and magnetic properties were investigated. The results indicated that the magnetic particles had an average size of 10.6 nm consisting of maghemite as the major phase. Viscosity of ferrofluid showed considerable variation with time and temperature. It was specified that the time dependency of the magnetoviscousity is related to particle size and rearrangement of nanoparticles of product is independent from the magnetic field. Moreover at low shear rates (< 0.1 s(-1)) the interaction of nanoparticles is related to the van der waals forces which cause the increase of the viscosity with time. The temperature effect showed that the magnetoviscosity decreases considerably above 45 degrees C. PMID:19916442

Ghasemi, E; Mirhabibi, A; Edrissi, M; Aghababazadeh, R; Brydson, R M

2009-07-01

137

Stress relaxation in a ferrofluid with clustered nanoparticles

NASA Astrophysics Data System (ADS)

The formation of structures in a ferrofluid by an applied magnetic field causes various changes in the rheological behaviour of the ferrofluid. A ferrofluid based on clustered iron nanoparticles was investigated. We experimentally and theoretically consider stress relaxation in the ferrofluid under the influence of a magnetic field, when the flow is suddenly interrupted. It is shown that the residual stress observed in the fluid after the relaxation is correlated with the measured and theoretically predicted magnetic field-induced yield stress. Furthermore, we have shown that the total macroscopic stress in the ferrofluid after the flow is interrupted is defined by the presence of both linear chains and dense, drop-like bulk aggregates. The proposed theoretical approach is consistent with the experimentally observed behaviour, despite a number of simplifications which have been made in the formulation of the model. Thus, the obtained results contribute a lot to the understanding of the complex, magnetic field-induced rheological properties of magnetic colloids near the yield stress point.

Borin, Dmitry Yu; Zubarev, Andrey Yu; Chirikov, Dmitry N.; Odenbach, Stefan

2014-10-01

138

Stress relaxation in a ferrofluid with clustered nanoparticles.

The formation of structures in a ferrofluid by an applied magnetic field causes various changes in the rheological behaviour of the ferrofluid. A ferrofluid based on clustered iron nanoparticles was investigated. We experimentally and theoretically consider stress relaxation in the ferrofluid under the influence of a magnetic field, when the flow is suddenly interrupted. It is shown that the residual stress observed in the fluid after the relaxation is correlated with the measured and theoretically predicted magnetic field-induced yield stress. Furthermore, we have shown that the total macroscopic stress in the ferrofluid after the flow is interrupted is defined by the presence of both linear chains and dense, drop-like bulk aggregates. The proposed theoretical approach is consistent with the experimentally observed behaviour, despite a number of simplifications which have been made in the formulation of the model. Thus, the obtained results contribute a lot to the understanding of the complex, magnetic field-induced rheological properties of magnetic colloids near the yield stress point. PMID:25229878

Borin, Dmitry Yu; Zubarev, Andrey Yu; Chirikov, Dmitry N; Odenbach, Stefan

2014-10-01

139

Experimental demonstration of metamaterial "multiverse" in a ferrofluid.

Extraordinary light rays propagating inside a hyperbolic metamaterial look similar to particle world lines in a 2 + 1 dimensional Minkowski spacetime. Magnetic nanoparticles in a ferrofluid are known to form nanocolumns aligned along the magnetic field, so that a hyperbolic metamaterial may be formed at large enough nanoparticle concentration nH. Here we investigate optical properties of such a metamaterial just below nH. While on average such a metamaterial is elliptical, thermal fluctuations of nanoparticle concentration lead to transient formation of hyperbolic regions (3D Minkowski spacetimes) inside this metamaterial. Thus, thermal fluctuations in a ferrofluid look similar to creation and disappearance of individual Minkowski spacetimes (universes) in the cosmological multiverse. This theoretical picture is supported by experimental measurements of polarization-dependent optical transmission of a cobalt based ferrofluid at 1500 nm. PMID:23787680

Smolyaninov, Igor I; Yost, Bradley; Bates, Evan; Smolyaninova, Vera N

2013-06-17

140

Ferrofluid nucleus phase transitions in an external uniform magnetic field

Phase transition between massive dense phase and diluted superparamagnetic phase is studied by means of direct molecular dynamics simulation. Equilibrium structures of ferrofluid aggregate nucleus are obtained for different values of temperature and external magnetic field magnitude. For the ferrofluid phase diagram (coordinates "field-temperature"): approximate match of experiment and simulation is shown. Obtained phase coexistence curve has opposite trend compare to some of known theoretical results. This contradiction is related to postulating and comparing of the free energy of only simplest ferrofluid structures: diluted superparamagnetic phase, linear chains of the particles, and dense globes. The present results provide more fine structure of transition from "linear chains" to "dense globes" phase, e.g. through the ring assembly structure.

B. M. Tanygin; S. I. Shulyma; V. F. Kovalenko; M. V. Petrychuk

2015-02-18

141

Hydrodynamics of insect spermatozoa

NASA Astrophysics Data System (ADS)

Microorganism motility plays important roles in many biological processes including reproduction. Many microorganisms propel themselves by propagating traveling waves along their flagella. Depending on the species, propagation of planar waves (e.g. Ceratium) and helical waves (e.g. Trichomonas) were observed in eukaryotic flagellar motion, and hydrodynamic models for both were proposed in the past. However, the motility of insect spermatozoa remains largely unexplored. An interesting morphological feature of such cells, first observed in Tenebrio molitor and Bacillus rossius, is the double helical deformation pattern along the flagella, which is characterized by the presence of two superimposed helical flagellar waves (one with a large amplitude and low frequency, and the other with a small amplitude and high frequency). Here we present the first hydrodynamic investigation of the locomotion of insect spermatozoa. The swimming kinematics, trajectories and hydrodynamic efficiency of the swimmer are computed based on the prescribed double helical deformation pattern. We then compare our theoretical predictions with experimental measurements, and explore the dependence of the swimming performance on the geometric and dynamical parameters.

Pak, On Shun; Lauga, Eric

2010-11-01

142

In this paper, we develop a formalism in order to incorporate the contribution of internal gravity waves to the transport of angular momentum and chemicals over long time-scales in stars. We show that the development of a double peaked shear layer acts as a filter for waves, and how the asymmetry of this filter produces momentum extraction from the core when it is rotating faster than the surface. Using only this filtered flux, it is possible to follow the contribution of internal waves over long (evolutionary) time-scales. We then present the evolution of the internal rotation profile using this formalism for stars which are spun down via magnetic torquing. We show that waves tend to slow down the core, creating a "slow" front that may then propagate from the core to the surface. Further spin down of the surface leads to the formation of a new front. Finally we show how this momentum transport reduces rotational mixing in a 1.2Msun, Z=0.02 model, leading to a surface lithium abundance in agreement with observations in the Hyades.

S. Talon; C. Charbonnel

2005-05-11

143

Azimuthal field instability in a confined ferrofluid

NASA Astrophysics Data System (ADS)

We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes.

Dias, Eduardo O.; Miranda, José A.

2015-02-01

144

Hydrodynamic forces due to waves and a current induced on a pipeline placed in an open trench

waves and a co-existing current condition through model tests. A. The Initiative of the Research Marine pipelines, tankers and barges are employed to transport recovered petroleum and natural gas from offshore wells to onshore sites. Over 95 percent... of oil and gas production in the Gulf of Mexico is delivered to shore by marine pipelines (15). Plants use pipelines to extract cool ocean water and to discharge hot water circulated from power generators. Ocean outfalls are also used in the ocean...

Lee, Jaeyoung

1991-01-01

145

A three-dimensional (3D) numerical model of fixed Oscillating Water Column system (OWC) is presented and validated. The steady-state potential flow boundary value problem due to regular wave interaction with the OWC is solved by a first order mixed distribution panel method. Ocean response predictions are derived using a deterministic statistical model based on a spectral analysis method. The model validation

Y. M. C. Delauré; A. Lewis

2003-01-01

146

\\u000a The problem ofplane shock waves indilute gases is considered. Its importance relies upon the fact that is an example in which\\u000a theNavier–Stokes equations have been shown to be susceptible of improvement. Several alternatives to these equations are briefly\\u000a mentioned in order to give an idea of the importance that the problem of extending the Navier–Stokes equations has these days.\\u000a We

Francisco J. Uribe

147

A rheological and microscopical characterization of biocompatible ferrofluids

NASA Astrophysics Data System (ADS)

There is an increasing interest in suspensions of magnetic nanoparticles in the biomedical area. Those ferrofluids are e.g. used for magnetic resonance imaging and emerging research focuses on employing the fluids for magnetic drug targeting or magnetic particle heating as a potential treatment for cancer. For these applications the knowledge of the suspensions' thermophysical properties is of major interest to guarantee a safe and effective application. Therefore the flow behavior cannot be neglected as it might significantly influence the execution of the aforementioned applications. In this experimental study two biocompatible ferrofluids were investigated. Rheological measurements were carried out using rotational rheometry. To allow an interpretation of the fluids' behavior the microscopic make-up was investigated using dynamic light scattering and transmission electron microscopy. Measurements of diluted ferrofluids were carried out as a first step to simulate the rheological behavior reflecting the concentration of magnetic nanoparticles found in blood flow for most biomedical applications of such fluids. The detected strong effects show the potential to significantly influence application and handling of the biocompatible ferrofluids in the medical area and should therefore be taken into account for further research as well as for the application of such fluids.

Nowak, J.; Wolf, D.; Odenbach, S.

2014-03-01

148

Magnetic sensing with ferrofluid and fiber optic connectors.

A simple, cost effective and sensitive fiber optic magnetic sensor fabricated with ferrofluid and commercially available fiber optic components is described in this paper. The system uses a ferrofluid infiltrated extrinsic Fabry-Perot interferometer (EFPI) interrogated with an infrared wavelength spectrometer to measure magnetic flux density. The entire sensing system was developed with commercially available components so it can be easily and economically reproduced in large quantities. The device was tested with two different ferrofluid types over a range of magnetic flux densities to verify performance. The sensors readily detected magnetic flux densities in the range of 0.5 mT to 12.0 mT with measurement sensitivities in the range of 0.3 to 2.3 nm/mT depending on ferrofluid type. Assuming a conservative wavelength resolution of 0.1 nm for state of the art EFPI detection abilities, the estimated achievable measurement resolution is on the order 0.04 mT. The inherent small size and basic structure complimented with the fabrication ease make it well-suited for a wide array of research, industrial, educational and military applications. PMID:24573312

Homa, Daniel; Pickrell, Gary

2014-01-01

149

Magnetic Sensing with Ferrofluid and Fiber Optic Connectors

A simple, cost effective and sensitive fiber optic magnetic sensor fabricated with ferrofluid and commercially available fiber optic components is described in this paper. The system uses a ferrofluid infiltrated extrinsic Fabry-Perot interferometer (EFPI) interrogated with an infrared wavelength spectrometer to measure magnetic flux density. The entire sensing system was developed with commercially available components so it can be easily and economically reproduced in large quantities. The device was tested with two different ferrofluid types over a range of magnetic flux densities to verify performance. The sensors readily detected magnetic flux densities in the range of 0.5 mT to 12.0 mT with measurement sensitivities in the range of 0.3 to 2.3 nm/mT depending on ferrofluid type. Assuming a conservative wavelength resolution of 0.1 nm for state of the art EFPI detection abilities, the estimated achievable measurement resolution is on the order 0.04 mT. The inherent small size and basic structure complimented with the fabrication ease make it well-suited for a wide array of research, industrial, educational and military applications. PMID:24573312

Homa, Daniel; Pickrell, Gary

2014-01-01

150

The effects of polydispersity on the initial susceptibilities of ferrofluids.

The effects of particle-size polydispersity on the initial susceptibilities of concentrated ferrofluids are analyzed using a combination of theory and computer simulation. The study is focused on a model ferrofluid with a prescribed magnetic-core diameter distribution, a fixed non-magnetic surface layer (corresponding to a demagnetized layer and adsorbed surfactant) and a combination of dipolar and hard-core interactions. The non-trivial effects of polydispersity are identified by comparing the initial susceptibilities of monodisperse and polydisperse ferrofluids with the same Langevin susceptibility. The theory is based on a correction to the second-order modified mean-field theory arising from a formal Mayer-type cluster expansion; this correction is dependent on a parameter similar to the normal dipolar coupling constant, except that it contains a complicated double average over the particle-size distribution, which means that the initial susceptibility should depend significantly on polydispersity. Specifically, the theory predicts that the initial susceptibility is enhanced significantly by polydispersity. This prediction is tested rigorously against results from Monte Carlo simulations and is found to be robust. The qualitative agreement between theory and simulation is already satisfactory, but the quantitative agreement could be improved by a systematic extension of the cluster expansion. The overall conclusion is that polydispersity should be accounted for carefully in magnetogranulometric analyses of real ferrofluids. PMID:25327692

Camp, Philip J; Elfimova, Ekaterina A; Ivanov, Alexey O

2014-11-12

151

Shear Stress Analysis in a Ferrofluidic Magnetic Micropump

The article presents analytical and numerical computational fluid dynamics (CFD) simulations of the flow performance in a newly introduced ferrofluidic magnetic micropump, with the purpose of estimating the stress distribution in its flow field. Analytical expressions were developed for the shear stress generated at the upper and lower walls of the pump's channel in terms of dimensionless parameters by solving

M. I. Kilani; A. T. Al Halhouli; S. Büttgenbach

2011-01-01

152

Optical properties in the soft photonic crystals based on ferrofluids

NASA Astrophysics Data System (ADS)

We theoretically investigate the properties of optical propagation in one-dimensional soft photonic crystals based on ferrofluids using the transfer matrix method. The proposed structure is composed of an alternating ferrofluid layer and a dielectric layer. Ferrofluids are composed of suspended ferromagnetic nanoparticles coated with silver, which has a frequency-dependent dielectric function. Core-shell nanocomposites incorporating an optical signature with magnetic response are particularly useful. The calculated results of dispersion relation show that tunable band gaps can be realized by varying the local magnetic field factor ?, the shell thickness parameter t, or the filling fraction ? of the ferrofluid layer. An additional band gap appears in the lower frequency region due to the absorption. These band gaps blue shift when the external magnetic field is enhanced, and red shift when either t or ? is increased. We also extend our analysis to the variation of band width. To meet the requirements of optical devices, such a tunable structure can be used to design optical filters, modulators and waveguides.

Fan, C. Z.; Liang, E. J.; Huang, J. P.

2011-08-01

153

Light scattering from a magnetically tunable dense random medium with weak dissipation : ferrofluid

We present a semi-phenomenological treatment of light transmission through and its reflection from a ferrofluid, which we regard as a magnetically tunable system of dense random dielectric scatterers with weak dissipation. Partial spatial ordering is introduced by the application of a transverse magnetic field that superimposes a periodic modulation on the dielectric randomess. This introduces Bragg scattering which effectively enhances the scattering due to disorder alone, and thus reduces the elastic mean free path towards Anderson localization. Our theoretical treatment, based on invariant imbedding, gives a simultaneous decrease of transmission and reflection without change of incident linear polarisation as the spatial order is tuned magnetically to the Bragg condition, namely the light wave vector being equal to half the Bragg vector (Q). Our experimental observations are in qualitative agreement with these results. We have also given expressions for the transit (sojourn) time of light and for the light...

Shalini, M; Sharma, Divya; Mathur, Deepak; Ramachandran, Hema; Kumar, N

2011-01-01

154

Dynamics of Single Chains of Suspended Ferrofluid Particles

NASA Technical Reports Server (NTRS)

We present an experimental study of the dynamics of isolated chains made of super-paramagnetic particles under the influence of a magnetic field. The motivation of this work is to understand if the chain fluctuations exist and, if it does, how does the fluctuation affect chain aggregation. We find that single chains strongly fluctuate and that the characteristic frequency of their fluctuations is inversely proportional to the magnetic field strength. The higher the field the lower the characteristic frequency of the chain fluctuations. In the high magnetic field limit, chains behave like rigid rods without any internal motions. In this work, we used ferrofluid particles suspended in water. These particles do not have any intrinsic magnetization. Once a magnetic field is applied, a dipole moment is induced in each particle, proportional to the magnetic field. A dipolar magnetic interaction then occurs between particles. If dipole-dipole magnetic energy is higher than the thermal energy, the result is a structure change inside the dipolar fluid. The ratio of these two energies is expressed by a coupling constant lambda as: lambda = (pi(a(exp 3))(chi(exp 2))(mu(sub 0))(H(sub 0))(exp 2))/18kT Where a is the particle radius, mu(sub 0) is the vacuum magnetic permeability, H(sub 0) the applied magnetic field, k the Boltzmann constant and T the absolute temperature. If lambda > 1, magnetic particles form chains along the field direction. The lateral coalescence of several chains may form bigger aggregates especially if the particle volume fraction is high. While many studies and applications deal with the rheological properties and the structural changes of these dipolar fluids, this work focuses on the understanding of the chain dynamics. In order to probe the chain dynamics, we used dynamic light scattering (DLS) in self-beating mode as our experimental technique. The experimental geometry is such that the scattering plane is perpendicular to the magnetic field. Therefore, only motions in this plane are probed. A very dilute sample of a ferrofluid emulsion with a particle volume fraction of 10(exp -5) is used in this experiment. We chose such a low volume fraction to avoid multiple light scattering as well as lateral chain-chain aggregation. DLS measures the dynamic structure factor S(q,t) of the sample (q is the scattering wave vector, t is the time). In the absence of the magnetic field, identical particles of ferrofluid droplets are randomly distributed and S(q,t) reduces to exp(-q(exp 2)2D(sub 0)t). D(sub 0)=(kT/(6(pi)(eta)(a)) is the diffusion coefficient of Brownian particles (where Xi = (6(pi)(eta)(a)) is the Stokes frictional coefficient of a spherical particle in a fluid of viscosity eta). If interactions or polydispersity can not be ignored, an effective diffusion coefficient is introduced. Formally, D(sub eff) is defined as: D(sub eff) = - q(exp -2) partial derivative of (ln(S(q,t)) with respect to time, as t goes to 0. D(sub eff) reduces to D(sub 0) if no interactions and only a few particles size are present. Therefore, we can use DLS to measure particle size. The particle radius was found to be a=0.23 mu m with 7% of polydispersity. In this case, if we vary the scattering angle theta (and so q) we do not have any change in the measured diffusion coefficient: it is q-independent. When a magnetic field is applied, particles aggregate into chains if lambda > 1. We first studied the kinetics of the chain formation when lambda = 406. At a fixed scattering angle, we measured diffusion coefficient D(sub eff) as a function of time. Experimentally, we find that D(sub eff) decreases monotonously with time. Physically, this means that chains are becoming longer and longer. Since we are only sensitive to motions in the scattering plane and since chains have their main axis perpendicular to this plane, the measured diffusion coefficient is the trans-verse diffusion coefficient. We can relate D(sub eff) to the mean number of particles per chain N(t) at a given time and to the diffusion coefficient of an isolated particle

Cutillas, S.; Liu, J.

1999-01-01

155

We present a low-cost, reconfigurable, parallel optofluidic switch that exploits the optical and magnetic properties of water-based ferrofluid. Each switch is composed of an integrated waveguide orthogonally crossing a microfluidic channel containing high-index oil and a ferrofluid plug. The switch is turned ON or OFF by movement of the ferrofluid plug. In contrast to conventional integrated switches, ferrofluid plugs act as switching mechanisms that are portable and reconfigurable. Switches are demonstrated in parallel geometries for single and multimode waveguides. Possible applications include optofluidic memory, multiplexed sensing for lab-on-chip, or frequency-encoded laser excitation. PMID:24514168

Gu, Yu; Valentino, Gianna; Mongeau, Eric

2014-02-01

156

A hybrid Godunov method for radiation hydrodynamics

From a mathematical perspective, radiation hydrodynamics can be thought of as a system of hyperbolic balance laws with dual multiscale behavior (multiscale behavior associated with the hyperbolic wave speeds as well as multiscale behavior associated with source term relaxation). With this outlook in mind, this paper presents a hybrid Godunov method for one-dimensional radiation hydrodynamics that is uniformly well behaved

Michael D. Sekora; James M. Stone

2010-01-01

157

We present a detailed theoretical analysis of the gravitational wave (GW) signal of the post-bounce evolution of core-collapse supernovae (SNe), employing for the first time relativistic, two-dimensional explosion models with multi-group, three-flavor neutrino transport based on the ray-by-ray-plus approximation. The waveforms reflect the accelerated mass motions associated with the characteristic evolutionary stages that were also identified in previous works: a quasi-periodic modulation by prompt post-shock convection is followed by a phase of relative quiescence before growing amplitudes signal violent hydrodynamical activity due to convection and the standing accretion shock instability during the accretion period of the stalled shock. Finally, a high-frequency, low-amplitude variation from proto-neutron star (PNS) convection below the neutrinosphere appears superimposed on the low-frequency trend associated with the aspherical expansion of the SN shock after the onset of the explosion. Relativistic effects in combination with detailed neutrino transport are shown to be essential for quantitative predictions of the GW frequency evolution and energy spectrum, because they determine the structure of the PNS surface layer and its characteristic g-mode frequency. Burst-like high-frequency activity phases, correlated with sudden luminosity increase and spectral hardening of electron (anti-)neutrino emission for some 10 ms, are discovered as new features after the onset of the explosion. They correspond to intermittent episodes of anisotropic accretion by the PNS in the case of fallback SNe. We find stronger signals for more massive progenitors with large accretion rates. The typical frequencies are higher for massive PNSs, though the time-integrated spectrum also strongly depends on the model dynamics.

Mueller, Bernhard; Janka, Hans-Thomas; Marek, Andreas, E-mail: bjmuellr@mpa-garching.mpg.de, E-mail: thj@mpa-garching.mpg.de, E-mail: amarek@mpa-garching.mpg.de [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany)] [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany)

2013-03-20

158

Tritium test of a ferro-fluidic rotary seal

The ferro-fluidic seal is being investigated as an internal rotary seal for tritium compatible mechanical roots type vacuum pumps. After its successful testing with helium and integration into a small (250 m{sup 3}/h) test roots pump, the seal, made as a cartridge, has been integrated into a special test unit and is currently being tested with tritium in order to define the leak rates and the possible degradation of the ferro-fluid under long term exposure to tritium radiation. The tritium pressure from one side of the seal is 0.125 MPa, the nitrogen pressure from the other side is 0.075 MPa, the rotation speed is maintained at 1500 rpm. The tritium leak through the cartridge contributes to the tritium concentration in the nitrogen, which is continuously measured by an ionisation chamber; the pressure in both chambers is continuously registered by precise pressure gauges. The experimental program is discussed. (authors)

Antipenkov, A.; Day, C.; Adami, H. D. [Forschungszentrum Karlsruhe, Inst. for Technical Physics, Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, 76344 (Germany)

2008-07-15

159

Domain Structure and MR Effect of Ferrofluid Emulsion

NASA Astrophysics Data System (ADS)

Blends of immiscible liquids with different dielectric constants and viscosities were known to show the ER effect due to the change of the domain structure by the electric field. In this paper, we report on our attempt to explore the possibility of the magnetic analog of these blend-type ER fluids. Water-based ferrofluid was blended with silicone oil with higher viscosity than the ferrofluid, in order to see whether the negative MR effect can be induced. The domain structure and the viscosity under the magnetic field and shear flow were studied. Growth of the droplet due to coalescence was observed under the field, which resulted in the gradual decrease of the shear viscosity.

Ogawa, Chikara; Masubuchi, Yuichi; Takimoto, Jun-Ichi; Koyama, Kiyohito

160

On the theory of the magnetoviscous effect in ferrofluids

The microscopic origin of viscoelastic effects in ferrofluids is studied theoretically. The growth kinetics of chain aggregates formed by magnetic ferroparticles under the action of the dipole-dipole interaction between them is analyzed. It is shown that the evolution rate for an ensemble of chains determines the rate of variation in the macroscopic stress of the medium upon a change in the applied external field and/or in the shear flow velocity. Consequently, the viscoelastic properties of magnetic fluids can be explained by the chain formation-destruction processes. The proposed microscopic model of a ferrofluid makes it possible (apparently, for the first time) to estimate the characteristic time of viscoelasticity corresponding to experimental results.

Zubarev, A. Yu., E-mail: andrey.zubarev@usu.ru; Chirikov, D. N. [Ural State University (Russian Federation)

2010-06-15

161

Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles were obtained by a facile protocol and thoroughly characterized. Superparamagnetic iron oxide nanoparticles synthesized using a modified forced hydrolysis method were functionalized with polyethylene glycol silane (PEG silane), precipitated and dried. These functionalized particles are dispersable in a range of solvents and concentrations depending on the desired properties. Examples of tunable properties are magnetic behavior, optical and magneto-optical response, thermal features and rheological behavior. As such, PEG silane functionalized particles represent a platform for the development of new materials that have broad applicability in e.g. biomedical, industrial or photonic environments. Magnetic, optical, magneto-optical, thermal and rheological properties of several ferrofluids based on PEG coated particles with different concentrations of particles dispersed in low molecular mass polyethylene glycol were investigated, establishing the applicability of such materials.

Brullot, W.; Reddy, N. K.; Wouters, J.; Valev, V. K.; Goderis, B.; Vermant, J.; Verbiest, T.

2012-06-01

162

Preparation of a biocompatible magnetic film from an aqueous ferrofluid

NASA Astrophysics Data System (ADS)

Very promising nanoparticles for biomedical applications or in medical drug targeting are superparamagnetic nanoparticles based on a core consisting of iron oxides (SPION) that can be targeted through external magnets. Polyvinyl alcohol (PVA) is a unique synthetic biocompatible polymer that can be chemically cross-linked to form a gel. Biotechnology applications of magnetic gels include biosensors, targeted drug delivery, artificial muscles and magnetic buckles. These gels are produced by incorporating magnetic materials in the polymer composites. In this paper we report the synthesis of an aqueous ferrofluid and the preparation of a biocompatible magnetic gel with polyvinyl alcohol and glutharaldehyde (GTA). HClO 4 was used to induce the peptization since this kind of ferrofluid does not have surfactant. The magnetic gel was dried to generate a biocompatible film.

Albornoz, Cecilia; Jacobo, Silvia E.

2006-10-01

163

Effects of fatty acid surfactants on the magnetic and magnetohydrodynamic properties of ferrofluids

NASA Astrophysics Data System (ADS)

We prepared Fe3O4 magnetic nanoparticles having diameters of approximately 12 nm by chemical coprecipitation, which were coated with three different fatty acid surfactants: oleic acid, lauric acid, and myristic acid. From x-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy measurements we confirmed that Fe3O4 is the only phase present in the samples. The zero field cooled magnetization curves for the nanoparticles exhibit broad peaks, consistent with superparamagnetic blocking for the polydisperse samples, and a saturation magnetization smaller than that for bulk Fe3O4. Although there are minimal differences in the magnetic properties of the nanoparticles having different surfactants, we find significant changes in the hydrodynamic response depending on chain length. Hyperthermia measurements show considerably larger response for oleic acid-coated samples, while magneto-optical studies indicate that these samples have slower dynamics of aggregation under the influence of a dc field. These results suggest that the magnetohydrodynamic response of ferrofluids can be controlled by judiciously selecting appropriate surfactants.

Regmi, Rajesh; Black, Correy; Sudakar, C.; Keyes, P. H.; Naik, Ratna; Lawes, G.; Vaishnava, Prem; Rablau, Cornel; Kahn, David; Lavoie, Melissa; Garg, Vijayendra K.; Oliveira, A. C.

2009-12-01

164

Small-amplitude oscillatory shear magnetorheology of inverse ferrofluids.

A comprehensive investigation is performed on highly monodisperse silica-based inverse ferrofluids under small-amplitude oscillatory shear in the presence of external magnetic fields up to 1 T. The effect of particle volume fraction and continuous medium Newtonian viscosity is thoroughly investigated. Experimental results for storage modulus are used to validate existing micromechanical magnetorheological models assuming different particle-level field-induced structures. PMID:20345105

Ramos, Jose; de Vicente, Juan; Hidalgo-Alvarez, Roque

2010-06-15

165

Magnetic-field-induced nonequilibrium structures in a ferrofluid emulsion

Using optical microscopy, we studied magnetic-field-induced structures in a confined ferrofluid emulsion where the magnetic field is applied quickly as a step function. Columnar, bent-wall-like, and labyrinthine structures in three dimensions are observed, corresponding to disks, ``worms,'' and branchlike patterns in cross-sectional area normal to the magnetic-field direction. These two-dimensional structures are characterized by both the ratio of worms to

George A. Flores; Jing Liu; M. Mohebi; N. Jamasbi

1999-01-01

166

Cluster formation in ferrofluids induced by holographic optical tweezers.

Holographic optical tweezers were used to show the interaction between a strongly focused laser beam and magnetic nanoparticles in ferrofluid. When the light intensity was high enough, magnetic nanoparticles were removed from the beam center and formed a dark ring. The same behavior was observed when focusing vortex or Bessel beams. The interactions between two or more separated rings of magnetic nanoparticles created by independent optical traps were also observed. PMID:24081086

Masajada, Jan; Bacia, Marcin; Drobczy?ski, S?awomir

2013-10-01

167

Magnetic Soret effect: Application of the ferrofluid dynamics theory

The ferrofluid dynamics theory is applied to thermodiffusive problems in magnetic fluids in the presence of magnetic fields. The analytical form for the magnetic part of the chemical potential and the most general expression of the mass flux are given. By employing these results to experiments, global Soret coefficients in agreement with measurements are determined. Also an estimate for a hitherto unknown transport coefficient is made.

Adrian Lange

2004-11-11

168

Ferrofluid-based dispersive solid phase extraction of palladium.

A new mode of dispersive solid phase extraction based on ferrofluid has been developed. In this method, an appropriate amount of ferrofluid is injected rapidly into the aqueous sample by a syringe. Since the sorbent is highly dispersed in the aqueous phase, extraction can be achieved within a few seconds. The ferrofluid can be attracted by a magnet and no centrifugation step is needed for phase separation. Palladium was used as a model compound in the development and evaluation of the extraction procedure in combination with flame atomic absorption spectrometry. The experimental parameters (pH, DDTC concentration, type and concentration of eluent, the amount of adsorbent, extraction time, and the effect of interfering ions) were investigated in detail. Under the optimized conditions, the calibration graph was linear over the range of 1-100 ?g L(-1) and relative standard deviation of 3.3% at 0.1 ?g mL(-1) was obtained (n=7). The limit of detection and enrichment factor (EF) was obtained to be 0.35 ?g L(-1) and 267, respectively. The maximum adsorption capacity of the adsorbent at optimum conditions was found to be 24.6 mg g(-1) for Pd(II). The method was validated using certified reference material, and has been applied for the determination of trace Pd(II) in actual samples with satisfactory results. PMID:23618148

Farahani, Malihe Davudabadi; Shemirani, Farzaneh; Gharehbaghi, Maysam

2013-05-15

169

Self-suspended permanent magnetic FePt ferrofluids.

We present the synthesis and characterization of a new class of self-suspended ferrofluids that exhibit remanent magnetization at room temperature. Our system relies on the chemisorption of a thiol-terminated ionic liquid with very low melting point on the surface of L10 FePt nanoparticles. In contrast, all types of ferrofluids previously reported employ either volatile solvents as the suspending media or superparamagnetic iron oxide nanoparticles (that lacks permanent magnetization) as the inorganic component. The ferrofluids do not show any sign of flocculation or phase separation, despite the strong interactions between the magnetic nanoparticles due to the strong chemisorption of the ionic liquid as evidenced by Raman spectroscopy and thermal analysis. Composites with high FePt loading (40 and 70 wt%) exhibit a pseudo solid-like rheological behavior and high remanent magnetization values (10.1 and 12.8 emu/g respectively). At lower FePt loading (12 wt%) a liquid like behavior is observed and the remanent and saturation magnetization values are 3.5 and 6.2 emu/g, respectively. The magnetic and flow properties of the materials can be easily fine tuned by controlling the type and amount of FePt nanoparticles used. PMID:23859815

Dallas, Panagiotis; Kelarakis, Antonios; Sahore, Ritu; DiSalvo, Francis J; Livi, Sebastien; Giannelis, Emmanuel P

2013-10-01

170

Disclosed are processes for monitoring and control of underground contamination, which involve the application of ferrofluids. Two broad uses of ferrofluids are described: (1) to control liquid movement by the application of strong external magnetic fields; and (2) to image liquids by standard geophysical methods.

Moridis, George J. (Oakland, CA); Oldenburg, Curtis M. (Mill Valley, CA)

2001-01-01

171

A ferrofluid-based neural network: design of an analogue associative memory

We analyse an associative memory based on a ferrofluid, consisting of a system of magnetic nano-particles suspended in a carrier fluid of variable viscosity subject to patterns of magnetic fields from an array of input and output magnetic pads. The association relies on forming patterns in the ferrofluid during a training phase, in which the magnetic dipoles are free to

R. Palm; V. Korenivski

2009-01-01

172

NSDL National Science Digital Library

We will review some basic properties of waves and then further explore sound and light. For a quick overview of some properties of all waves, click on this first site. Make sure you fill out your hand out as you work! Waves and Wave Motion : Describing Waves Practice what you've already learned about waves with this site: Waves This site will let you play around some more with transverse waves: Wave on a String Sound waves are mechanical waves, ...

Mrs. Petersen

2014-05-27

173

We give a pedagogical review of relativistic hydrodynamics relevant to relativistic heavy ion collisions. Topics discussed include linear response theory derivation of 2nd order viscous hydrodynamics including the Kubo formulas, kinetic theory derivation of 2nd order viscous hydrodynamics, anisotropic hydrodynamics and a brief review of numerical algorithms. Emphasis is given to the theory of hydrodynamics rather than phenomenology.

Jeon, Sangyong

2015-01-01

174

The effect of suspended Fe3O4 nanoparticle size on magneto-optical properties of ferrofluids

NASA Astrophysics Data System (ADS)

We investigate the effect of hydrodynamic particle size on the magnetic field induced light transmission and transmitted speckle pattern in water based ferrofluids containing functionalized Fe3O4 nanoparticles of size ranging from 15 to 46 nm. Three water-based magnetic nanofluids, containing Fe3O4 nanoparticles functionalized with poly-acrylic acid (PAA), tetra-methyl ammonium hydroxide (TMAOH) and phosphate, are used in the present study. In all three cases, the transmitted light intensity starts decreasing above a certain magnetic field (called first critical field) and becomes a minimum at another field (second critical field). These two critical fields signify the onset of linear aggregation process and zippering transitions between fully grown chains, respectively. Both these critical fields shift towards a lower magnetic field with increasing hydrodynamic diameter, due to stronger magnetic dipolar interactions. The first and the second critical fields showed a power law dependence on the hydrodynamic diameters. The dipolar resonances occurring at certain values of the scatterer size, leads to the field induced extinction of light. Both the onset of chaining and zippering transitions were clearly evident in the time dependent transmitted light intensity. Above the first critical field, the lobe part of the transmitted intensity and the lobe speckle contrast values increase with increasing external magnetic field due to reduced Brownian motion of the field induced aggregates. The speckle contrast was highest for nanoparticle with the largest hydrodynamic diameter, due to reduced Brownian motion. These results provide better insight into field dependent light control in magnetic colloids, which may find interesting applications in magneto-optical devices.

Brojabasi, Surajit; Muthukumaran, T.; Laskar, J. M.; Philip, John

2015-02-01

175

The explosion of a star supernova occurs at the end of its evolution when the nuclear fuel in its core is almost, or completely, consumed. The star may explode due to a small residual thermonuclear detonation, type I SN or it may collapse, type I and type II SN leaving a neutron star remnant. The type I progenitor should be thought to be an old accreting white dwarf, 1.4 M/sub theta/, with a close companion star. A type II SN is thought to be a massive young star 6 to 10 M/sub theta/. The mechanism of explosion is still a challenge to our ability to model the most extreme conditions of matter and hydrodynamics that occur presently and excessively in the universe. 39 references.

Colgate, S.A.

1981-01-01

176

Field-Induced Labyrinthine Patterns in Ferrofluid Emulsions

NASA Astrophysics Data System (ADS)

A ferrofluid emulsion goes through gas — solid phase transition when an external magnetic field is applied. The solid structures are observed as either column, bent-wall, or labyrinthine patterns. The appearance of these different patterns depend upon the rate of the field applied, thickness of the sample cell along the field direction, and the volume fraction of the emulsion droplets used. Using optical microscopy, formed patterns are recorded and analyzed in which a “phase” diagram of the structural transition from column to bent-wall is measured.

Flores, George A.; Ivey, Mark L.; Liu, Jing; Mohebi, M.; Jamasbi, N.

177

Diffraction patterns in ferrofluids: Effect of magnetic field and gravity

NASA Astrophysics Data System (ADS)

In this paper, we report the experimental observation of diffraction patterns in a ferrofluid comprising of Fe3O4 nanoparticles in hexane by a 10 mW He-Ne laser beam. An external dc magnetic field (0-2 kG) was applied perpendicular to the beam. The diffraction pattern showed a variation at different depths of the sample in both zero and applied magnetic field. The patterns also exhibit a change in shape and size as the external field is varied. This effect arises due to thermally induced self-diffraction under the influence of gravity and external magnetic field.

Radha, S.; Mohan, Shalini; Pai, Chintamani

2014-09-01

178

A Ferrofluidic Magnetic Micropump for Variable-Flow-Rate Applications

NASA Astrophysics Data System (ADS)

A novel micropump is proposed comprising two ferrofluidic plugs contained within a circular poly(methyl methacrylate) (PMMA) microchannel and a permanent magnet positioned beneath one of the plugs and driven by a rotating stepping motor. The ferrofluidic plugs are immiscible with the sample fluid. Thus, as the stepping motor rotates, the sample trapped between the two plugs is driven through the circular microchannel and exits the pump via the outlet diffuser. Meanwhile, more sample fluid is drawn into the microchannel on the inlet side. As a result, a continuous pumping effect is achieved. It is shown that the flow rate in the proposed device can be easily controlled by adjusting the rotational velocity of the stepping motor. In addition, for a constant motor velocity, the flow rate can be improved by increasing the circular channel width. The experimental results show that a maximum flow rate of 93 µl/min is obtained given a channel width of 1000 µm and a rotational velocity of 8 rpm. In addition, it is shown that the pump is capable of developing a maximum pressure head of 75 mm water (0.66 kPa) with channel width of 500 µm.

Lee, Chia-Yen; Leong, Jik-Chang; Wang, Yao-Nan; Fu, Lung-Ming; Chen, Sih-Jia

2012-04-01

179

A comparative study of different ferrofluid constitutive equations.

NASA Astrophysics Data System (ADS)

Ferrofluids are stable colloidal suspensions of fine ferromagnetic monodomain nanoparticles in a non-conducting carrier fluid.The particles are coated with a surfacant to avoid agglomeration and coagulation.Brownian motion keeps the nanoparticles from settling under gravity.In recent years these fluids have found several applications including in liquid seals in rotary shafts for vacuum system and in hard disk drives of personal computers,in cooling and damping of loud speakers, in shock absorbers and in biomedical applications. A continuum description of ferrofluids was initiated by Neuringer and Rosensweig [1] but the theory had some limitations. In subsequent years,several authors have proposed generalization of the above theory.Some of these are based upon the internal particle rotation concept, some are phemonological,some are based upon a thermodynamic framework,some employ statistical approach and some have used the dynamic mean field approach.The results based upon these theories ane in early stages and inconclusive. Our purpose is, first, to critically examine the basic foundations of these equations and then study the pedictions obtained in all the theories related to an experimental as well as a theoretical study. [1]J.L.Neuringer and R.E. Rosensweig, Physics Fluids,7.1727 (1964)..

Kaloni, Purna

2011-11-01

180

Design and manufacture of a modular cylindrical apparatus for ferrofluid experimentation

Ferrofluids, colloidal suspensions of coated magnetic nanoparticles inside a carrier fluid, respond to externally applied magnetic fields. This thesis addresses the behavior of these fluids when subjected to an azimuthally ...

Schoen, Katrina Leigh

2011-01-01

181

The mechanisms that lead to bulk flow within a ferrofluid-filled container subjected to a rotating uniform magnetic field are experimentally studied. There are two prevailing theories: spin diffusion theory and flow due ...

Snively, Michael John

2011-01-01

182

Hydrodynamical simulations using a fully threaded tree

NASA Astrophysics Data System (ADS)

We developed a 3D code of Adaptive Mesh Refinement (AMR) hydrodynamical simulations that is useful for propagations of an interplanetary shock wave. In this code, we adopted the Fully Threaded Tree (FTT; Khokhlov 1998) for AMR part, the 3rd order MUSCL of the Roe method for hydrodynamical part, and the two step method for the 2nd order time development. In this article, we explain our 3D AMR code and the FTT, and report some results of test calculation.

Ogawa, Tomoya; Yamashita, Kazuyuki; Ohta, Takuma; Matsumoto, Ryoji; Den, Mitsue

183

Hydrodynamic compressibility of high-strength ceramics

In this study we have developed the techniques to investigate the hydrodynamic response of high-strength ceramics by mixing these powders with copper powder, preparing compacts, and performing shock compression tests on these mixtures. Hydrodynamics properties of silicon carbide, titanium diboride, and boron carbide to 30 GPa were examined by this method, and hydrodynamic compression data for these ceramics have been determined. We have concluded, however, that the measurement method is sensitive to sample preparation and uncertainties in shock wave measurements. Application of the experimental technique is difficult and further efforts are needed.

Grady, D.E.

1993-08-01

184

Hydrodynamic loading of tensegrity structures

NASA Astrophysics Data System (ADS)

This paper introduces hydrodynamic loads for tensegrity structures, to examine their behavior in marine environments. Wave compliant structures are of general interest when considering large marine structures, and we are motivated by the aquaculture industry where new concepts are investigated in order to make offshore installations for seafood production. This paper adds to the existing models and software simulations of tensegrity structures exposed to environmental loading from waves and current. A number of simulations are run to show behavior of the structure as a function of pretension level and string stiffness for a given loading condition.

Wroldsen, Anders S.; Johansen, Vegar; Skelton, Robert E.; Sørensen, Asgeir J.

2006-03-01

185

Three-dimensional x-ray imaging of macro-clusters in ferrofluids

NASA Astrophysics Data System (ADS)

Ferrofluids are a class of magnetic fluids where nano-sized (˜ 10 nm) magnetic particles are dispersed in a carrier fluid. Ferrofluids have long been used for vacuum seals, but lately, has been proposed for a multitude of new applications including heat transfer and biomedicine. It has been known for some time that the magnetic particles tend to align with an applied magnetic field and that the individual chains can coalesce and form thick and long macro-sized structures whose shapes depend on the properties of the ferrofluid and the applied field. However, due to their opacity to visible light, ferrofluid experiments have been mainly limited to very thin films (˜ 10s of microns). Since the macro-structures can be in the 10-100 micron range, thin film measurements are susceptible to wall effects. TEM and resin techniques have been used to study the structure of these clusters. However, it is doubtful if these frozen or dried structures reflect the natural fluid state. Here, we present x-ray microtomography measurements on a mm-sized tube of ferrofluid under an applied magnetic field. We show the three-dimensional nature of the columns and labyrinth structures. The measurements also allow us to provide estimates on the local magnetic particle concentration within the ferrofluid.

Lee, Wah-Keat

2009-11-01

186

Motion of a droplet on a planar surface has applications in droplet-based lab on a chip technology. This paper reports the experimental results of the shape, contact angles, and motion of ferrofluid droplets driven by a permanent magnet on a planar homogeneous surface. The water-based ferrofluid in use is a colloidal suspension of single-domain magnetic nanoparticles. The effect of the magnetic field on the apparent contact angle of the ferrofluid droplet was first investigated. The results show that an increasing magnetic flux decreases the apparent contact angle of a sessile ferrofluid droplet. Next, the dynamic contact angle was investigated by observing the shape and the motion of a sessile ferrofluid droplet. The advancing and receding contact angles of the moving ferrofluid were measured at different moving speeds and magnetic field strengths. The measured contact angles were used to estimate the magnitude of the forces involved in the sliding motion. Scaling analysis was carried out to derive the critical velocity, beyond which the droplet is not able to catch up with the moving magnet. PMID:20608704

Nguyen, Nam-Trung; Zhu, Guiping; Chua, Yong-Chin; Phan, Vinh-Nguyen; Tan, Say-Hwa

2010-08-01

187

Hydrodynamic Simulations of Planetary Rings

NASA Astrophysics Data System (ADS)

Simulations of rings have traditionally been done using N-body methods, granting insight into the interactions of individual ring particles on varying scales. However, due to the scale of a typical ring system and the sheer number of particles involved, a global N-body simulation is too computationally expensive, unless particle collisions are replaced by stochastic forces (Bromley & Kenyon, 2013). Rings are extraordinarily flat systems and therefore are well-suited to existing geophysical shallow-water hydrodynamics models with well-established non-linear advection methods. By adopting a general relationship between pressure and surface density such as a polytropic equation of state, we can modify the shallow-water formula to treat a thin, compressible, self-gravitating, shearing fluid. Previous hydrodynamic simulations of planetary rings have been restricted to axisymmetric flows and therefore have not treated the response to nonaxisymmetric perturbations by moons (Schmidt & Tscharnuter 1999, Latter & Ogilvie 2010). We seek to expand on existing hydrodynamic methods and, by comparing our work with complementary N-body simulations and Cassini observations, confirm the veracity of our results at small scales before eventually moving to a global domain size. We will use non-Newtonian, dynamically variable viscosity to model the viscous transport caused by unresolved self-gravity wakes. Self-gravity will be added to model the dynamics of large-scale structures, such as density waves and edge waves. Support from NASA Outer Planets and Planetary Geology and Geophysics programs is gratefully acknowledged.

Miller, Jacob; Stewart, G. R.; Esposito, L. W.

2013-10-01

188

The gap between two concentric rotating cylinders is filled with a ferrofluid. A homogeneous magnetic field is applied parallel to the cylinder axis. The stability of the circular Couette flow is analyzed with different models that take into account the polydispersity of the ferrofluid to a varying degree. Their results are compared and their merits are discussed. PMID:19392050

Leschhorn, A; Lücke, M; Hoffmann, C; Altmeyer, S

2009-03-01

189

Ferrofluids based on magnetic Co{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} ferrite nanoparticles were prepared by co-precipitation method from aqueous salt solutions of Co (II), ZnSO{sub 4}, and Fe (III) in an alkaline medium. Ferrofluids placed in an external magnetic field show properties that make them interesting as magneto-controllable soft photonic crystals. Morphological and structural characterizations of the samples were obtained from Scanning Electron Microscopy and Transmission Electron Microscopy studies. Magnetic properties were investigated with the aid of a vibrating sample magnetometer at room temperature. Herein, the Co{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} samples showed superparamagnetic behavior, according to hysteresis loop results. Taking in mind that the Co-Zn ferrite hysteresis loop is very small, our magnetic nanoparticles can be considered soft magnetic material with interesting technological applications. In addition, by using the plane-wave expansion method, we studied the photonic band structure of 2D photonic crystals made of ferrofluids with the same nanoparticles. Previous experimental results show that a magnetic field applied perpendicular to the ferrofluid plane agglomerates the magnetic nanoparticles in parallel rods to form a hexagonal 2D photonic crystal. We calculated the photonic band structure of photonic crystals by means of the effective refractive index of the magnetic fluid, basing the study on the Maxwell-Garnett theory, finding that the photonic band structure does not present any band gaps under the action of applied magnetic field strengths used in our experimental conditions.

López, J., E-mail: javier.lopez@correounivalle.edu.co; González, Luz E.; Quiñonez, M. F.; Gómez, M. E.; Porras-Montenegro, N.; Zambrano, G. [Departamento de Física, Universidad del Valle, A.A. 25360, Cali (Colombia)

2014-05-21

190

Any single permanent or electro magnet will always attract a magnetic fluid. For this reason it is difficult to precisely position and manipulate ferrofluid at a distance from magnets. We develop and experimentally demonstrate optimal (minimum electrical power) 2-dimensional manipulation of a single droplet of ferrofluid by feedback control of 4 external electromagnets. The control algorithm we have developed takes into account, and is explicitly designed for, the nonlinear (fast decay in space, quadratic in magnet strength) nature of how the magnets actuate the ferrofluid, and it also corrects for electro-magnet charging time delays. With this control, we show that dynamic actuation of electro-magnets held outside a domain can be used to position a droplet of ferrofluid to any desired location and steer it along any desired path within that domain – an example of precision control of a ferrofluid by magnets acting at a distance. PMID:21218157

Probst, R.; Lin, J.; Komaee, A.; Nacev, A.; Cummins, Z.

2010-01-01

191

Interfacial stress balances in structured continua and free surface flows in ferrofluids

Interfacial linear and internal angular momentum balances are obtained for a structured continuum and for the special case of a ferrofluid, a suspension of magnetic nanoparticles in a Newtonian fluid. The interfacial balance equations account for the effects of surface tension and surface tension gradient, magnetic surface excess forces, antisymmetric stresses, and couple stresses in driving interfacial flows in ferrofluids. Application of the interfacial balance equations is illustrated by obtaining analytical expressions for the translational and spin velocity profiles in a thin film of ferrofluid on an infinite flat plate when a rotating magnetic field is applied with axis of rotation parallel to the ferrofluid/air interface. The cases of zero and non-zero spin viscosity are considered for small applied magnetic field amplitude. Expressions for the maximum translational velocity, slope of the translational velocity profile at the ferrofluid/air interface, and volumetric flow rate are obtained and their use to test the relevance of spin viscosity and couple stresses in the flow situation under consideration is discussed.

Chaves, Arlex [School of Chemical Engineering, Universidad Industrial de Santander, Calle 9 Cra. 27, Edificio 24, Bucaramanga, Santander (Colombia)] [School of Chemical Engineering, Universidad Industrial de Santander, Calle 9 Cra. 27, Edificio 24, Bucaramanga, Santander (Colombia); Rinaldi, Carlos, E-mail: carlos.rinaldi@bme.ufl.edu [J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611, USA and Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611, USA and Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2014-04-15

192

Waves in Radial Gravity Using Magnetic Fluid

NASA Technical Reports Server (NTRS)

Terrestrial laboratory experiments studying various fluid dynamical processes are constrained, by being in an Earth laboratory, to have a gravitational body force which is uniform and unidirectional. Therefore fluid free-surfaces are horizontal and flat. Such free surfaces must have a vertical solid boundary to keep the fluid from spreading horizontally along a gravitational potential surface. In atmospheric, oceanic, or stellar fluid flows that have a horizontal scale of about one-tenth the body radius or larger, sphericity is important in the dynamics. Further, fluids in spherical geometry can cover an entire domain without any sidewall effects, i.e. have truly periodic boundary conditions. We describe spherical body-force laboratory experiments using ferrofluid. Ferrofluids are dilute suspensions of magnetic dipoles, for example magnetite particles of order 10 nm diameter, suspended in a carrier fluid. Ferrofluids are subject to an additional body force in the presence of an applied magnetic field gradient. We use this body force to conduct laboratory experiments in spherical geometry. The present study is a laboratory technique improvement. The apparatus is cylindrically axisymmetric. A cylindrical ceramic magnet is embedded in a smooth, solid, spherical PVC ball. The geopotential field and its gradient, the body force, were made nearly spherical by careful choice of magnet height-to-diameter ratio and magnet size relative to the PVC ball size. Terrestrial gravity is eliminated from the dynamics by immersing the "planet" and its ferrofluid "ocean" in an immiscible silicone oil/freon mixture of the same density. Thus the earth gravity is removed from the dynamics of the ferrofluid/oil interface and the only dynamically active force there is the radial magnetic gravity. The entire apparatus can rotate, and waves are forced on the ferrofluid surface by exterior magnets. The biggest improvement in technique is in the wave visualization. Fluorescing dye is added to the oil/freon mixture and an argon ion laser generates a horizontal light that can be scanned vertically. Viewed from above, the experiment is a black circle with wave deformations surrounded by a light background. A contour of the image intensity at any light sheet position gives the surface of the ferrofluid "ocean" at that "latitude". Radial displacements of the waves as a function of longitude are obtained by subtracting the contour line positions from a no-motion contour at that laser sheet latitude. The experiments are run by traversing the forcing magnet with the laser sheet height fixed and images are frame grabbed to obtain a time-series at one latitude. The experiment is then re-run with another laser-sheet height to generate a full picture of the three-dimensional wave structure in the upper hemisphere of the ball as a function of time. We concentrate here on results of laboratory studies of waves that are important in Earth's atmosphere and especially the ocean. To get oceanic scaling in the laboratory, the experiment must rotate rapidly (4-second rotation period) so that the wave speed is slow compared to the planetary rotation speed as in the ocean. In the Pacific Ocean, eastward propagating Kelvin waves eventually run into the South American coast. Theory predicts that some of the wave energy should scatter into coastal-trapped Kelvin waves that propagate north and south along the coast. Some of this coastal wave energy might then scatter into mid-latitude Rossby waves that propagate back westward. Satellite observations of the Pacific Ocean sea-surface temperature and height seem to show signatures of westward propagating mid-latitude Rossby waves, 5 to 10 years after the 1982-83 El Nino. The observational data is difficult to interpret unambiguously owing to the large range of motions that fill the ocean at shorter timescales. This series of reflections giving eastward, north- ward, and then westward traveling waves is observed cleanly in the laboratory experiments, confirming the theoretical expectations

Ohlsen, D. R.; Hart, J. E.; Weidman, P. D.

1999-01-01

193

Hydrodynamic obstruction to bubble expansion

We discuss a hydrodynamic obstruction to bubble wall acceleration during a cosmological first-order phase transition. The obstruction results from the heating of the plasma in the compression wave in front of the phase transition boundary. We provide a simple criterion for the occurrence of the obstruction at subsonic bubble wall velocity in terms of the critical temperature, the phase transition temperature, and the latent heat of the model under consideration. The criterion serves as a sufficient condition of subsonic bubble wall velocities as required by electroweak baryogenesis.

Konstandin, Thomas [CERN Physics Department, Theory Division, CH-1211 Geneva 23 (Switzerland); No, José M., E-mail: tkonstan@cern.ch, E-mail: jose-miguel.no@cea.fr [Institut de Physique Théorique, CEA/Saclay, F-91191 Gif-sur-Yvette Cédex (France)

2011-02-01

194

Ergoregion instability: The hydrodynamic vortex

Four-dimensional, asymptotically flat spacetimes with an ergoregion but no horizon have been shown to be linearly unstable against a superradiant-triggered mechanism. This result has wide implications in the search for astrophysically viable alternatives to black holes, but also in the understanding of black holes and Hawking evaporation. Here we investigate this instability in detail for a particular setup which can be realized in the laboratory: the {\\it hydrodynamic vortex}, an effective geometry for sound waves, with ergoregion and without an event horizon.

Leandro A. Oliveira; Vitor Cardoso; Luís C. B. Crispino

2014-05-16

195

Dielectric response of transformer oil based ferrofluid in low frequency range

NASA Astrophysics Data System (ADS)

In this article, our experimental study of the dynamic dielectric behaviour of transformer oil-based ferrofluid with magnetite nanoparticles is presented. Frequency-dependent dielectric permittivity and dissipation factor were measured within the frequency range from 20 Hz to 2 MHz by a capacitance method. The ferrofluid samples were placed in a liquid crystal cell, and experiments were carried out in an electromagnetically anechoic chamber. Two polarization processes and corresponding relaxations were revealed within the applied frequency range. Schwarz theory of electric double layer polarization is used to explain the low frequency relaxation maximum. Moreover, the shift of the maximum position towards higher frequencies is observed as the magnetic volume fraction in the ferrofluid increases. The related decrease in relaxation time due to higher counterion mobility is analysed. Reduced electric field intensity due to depolarization field, which is dependent on the particle concentration, is proposed as the reason for the maxima shift. This assumption is wholly supported by a complementary experiment.

Rajnak, M.; Kurimsky, J.; Dolnik, B.; Marton, K.; Tomco, L.; Taculescu, A.; Vekas, L.; Kovac, J.; Vavra, I.; Tothova, J.; Kopcansky, P.; Timko, M.

2013-07-01

196

Optical properties in one-dimensional graded soft photonic crystals with ferrofluids

NASA Astrophysics Data System (ADS)

We theoretically investigate the optical properties in one-dimensional graded soft photonic crystals (1D GSPCs). The proposed structure is constituted of the stacked ferrofluids layer and the dielectric layer. Due to the supermagnetic response of the ferromagnetic nanoparticles, they will align in a line under the influence of the initiated magnetic field, thereby modulating the refractive index of the ferrofluids layer. By resorting to the transfer matrix method, the dispersion relation, transmittance and reflectance in 1D GSPCs were calculated. Numerical results show that a broad photonic band gap appears in such systems, which can even be broadened by increasing the volume fraction of ferromagnetic nanoparticles. Moreover, perfect transmittance of our proposed structure can be realized with an increased number of ferrofluid layers. In comparison with conventional PCs materials, 1D GSPCs composed of liquid material offer a very flexible route to implementation, which can be widely used in the application of optical filters, waveguides, reflectors and so on.

Fan, Chunzhen; Wang, Junqiao; Zhu, Shuangmei; He, Jinna; Ding, Pei; Liang, Erjun

2013-05-01

197

All-optical modulator based on a ferrofluid core metal cladding waveguide chip

NASA Astrophysics Data System (ADS)

We propose a novel optical intensity modulator based on the combination of a symmetrical metal cladding optical waveguide (SMCW) and ferrofluid, where the ferrofluid is sealed in the waveguide to act as a guiding layer. The light matter interaction in the ferrofluid film leads to the formation of a regular nanoparticle pattern, which changes the phase match condition of the ultrahigh order modes in return. When two lasers are incident on the same spot of the waveguide chip, experiments illustrate all-optical modulation of one laser beam by adjusting the intensity of the other laser. A possible theoretical explanation may be due to the optical trapping and Soret effect since the phenomenon is considerable only when the control laser is effectively coupled into the waveguide.

Han, Qing-Bang; Yin, Cheng; Li, Jian; Tang, Yi-Bin; Shan, Ming-Lei; Cao, Zhuang-Qi

2013-09-01

198

Investigating the energy harvesting potential of ferro-fluids sloshing in base-excited containers

NASA Astrophysics Data System (ADS)

This paper investigates the potential of designing a vibratory energy harvester which utilizes a ferrofluid sloshing in a seismically excited tank to generate electric power. Mechanical vibrations change the orientational order of the magnetic dipoles in the ferrofluid and create a varying magnetic flux which induces an electromotive force in a coil wound around the tank, thereby generating an electric current according to Faraday's law. Several experiments are performed on a cylindrical container of volume 5x10-5 m3 carrying a ferrofluid and subjected to different base excitation levels. Initial results illustrate that the proposed device can be excited at one or multiple modal frequencies depending on the container's size, can exhibit tunable characteristics by adjusting the external magnetic field, and currently produces 28 mV of open-circuit voltage using a base excitation of 2.5 m/s2 at a frequency of 5.5 Hz.

Bibo, A.; Masana, R.; King, A.; Li, G.; Daqaq, M. F.

2012-04-01

199

Electromagnetic Vibration Energy Harvester Using Springless Proof Mass and Ferrofluid as a Lubricant

NASA Astrophysics Data System (ADS)

This paper presents an electromagnetic energy harvester using an array of rectangular permanent magnets as springless proof mass and ferrofluid as a lubricating material. Lateral motion of the multi-pole magnet array generates voltage across an array of copper windings formed under the aluminum channel in response to low frequency external vibrations such as human-body-induced motion. A proof-of-concept device has been fabricated and output voltage has been measured at various input frequencies and accelerations provided by a vibration exciter. Device with ferrofluid lubrication generated maximum open-circuit voltage of 0.47V at 3g vibration at 12Hz, which is 8% higher than that of the device without lubricant. Maximum output power of 71.26?W has been obtained at 40.8? with the device with ferrofluid lubrication.

Chae, S. H.; Ju, S.; Choi, Y.; Jun, S.; Park, S. M.; Lee, S.; Lee, H. W.; Ji, C.-H.

2013-12-01

200

The present work reports on magnetically induced optical activity (such as Faraday rotation and linear dichroism) of pristine and gamma-irradiated gadolinium oxide (Gd{sub 2}O{sub 3}) nanoparticle-based ferrofluids. The ferrofluids were produced by dispersing N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB)-coated {approx}9-nm-sized Gd{sub 2}O{sub 3} particles in a carrier fluid of ethanol. The ferrofluids were then irradiated with 1.25 MeV energetic gamma rays (dose: 868 Gy and 2.635 kGy). Irradiation-led formation of a number of point defects was revealed through high resolution electron microscopy. The interaction of light with the ionized point defects is believed to have caused substantial improvement in the magneto-optic response of irradiated magnetic fluids.

Paul, Nibedita; Devi, Manasi; Mohanta, Dambarudhar [Nanoscience and Soft Matter Laboratory, Department of Physics, Tezpur University, PO Napaam, Tezpur 784 028, Assam (India); Saha, Abhijit [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700 098 (India)

2012-02-15

201

Ferrofluids are stable colloidal suspensions of magnetic particles in various carrier liquids with high saturation magnetizations, which can be manipulated in virtually any fashion, defying gravitational or viscous forces in response to external magnetic fields. In this report, the authors review the results of their investigation of the potential of ferrofluids (1) to accurately and effectively guide reactants (for in-situ treatment) or barrier liquids (low-viscosity permeation grouts) to contaminated target zones in the subsurface using electromagnetic forces, and (2) to trace the movement and position of liquids injected in the subsurface using geophysical methods. They investigate the use of ferrofluids to enhance the efficiency of in-situ treatment and waste containment through (a) accurate guidance and delivery of reagent liquids to the desired subsurface contamination targets and/or (b) effective sweeping of the contaminated zone as ferrofluids move from the application point to an attracting magnet/collection point. They also investigate exploiting the strong magnetic signature of ferrofluids to develop a method for monitoring of liquid movement and position during injection using electromagnetic methods. The authors demonstrated the ability to induce ferrofluid movement in response to a magnetic field, and measured the corresponding magnetopressure. They demonstrated the feasibility of using conventional magnetometry for detecting subsurface zones of various shapes containing ferrofluids for tracing liquids injected for remediation or barrier formation. Experiments involving spherical, cylindrical and horizontal slabs showed a very good agreement between predictions and measurements.

Moridis, G.J.; Borglin, S.E.; Oldenburg, C.M.; Becker, A.

1998-03-01

202

Magnetic field tunability of optical microfiber taper integrated with ferrofluid.

Optical microfiber taper has unique propagation properties, which provides versatile waveguide structure to design the tunable photonic devices. In this paper, the S-tapered microfiber is fabricated by using simple fusion spicing. The spectral characteristics of microfiber taper integrated with ferrofluid under different magnetic-field intensities have been theoretically analyzed and experimentally demonstrated. The spectrum are both found to become highly magnetic-field-dependent. The results indicate the transmission and wavelength of the dips are adjustable by changing magnetic field intensity. The response of this device to the magnetic field intensity exhibits a Langvin function. Moreover, there is a linear relationship between the transmission loss and magnetic field intensity for a magnetic field intensity range of 25 to 200Oe, and the sensitivities as high as 0.13056dB/Oe and 0.056nm/Oe have been achieved, respectively. This suggests a potential application of this device as a tunable all-in-fiber photonic device, such as magneto-optic modulator, filter, and sensing element. PMID:24514542

Miao, Yinping; Wu, Jixuan; Lin, Wei; Zhang, Kailiang; Yuan, Yujie; Song, Binbin; Zhang, Hao; Liu, Bo; Yao, Jianquan

2013-12-01

203

Magnetoviscosity and thread-like agglomerations in ferrofluids

NASA Astrophysics Data System (ADS)

We report on experiments and simulations performed on small non-magnetic glass balls falling under gravity through a magnetized ferrofluid. The applied magnetic field is oriented horizontally, normal to the fall, and is uniform but its magnitude can be adjusted over a wide range. Using the Advanced Photon Source x-ray beamline at Argonne, we were able to achieve sufficient spatial and temporal resolution to track the dynamics of these 500 ?m diameter spheres simultaneously with an array of magnetic particle macro-chains -- thread-like agglomerations each several mm long and 2-10 ?m thick. The enhanced drag induced by the macro-chains is enormous: up to four times larger than for unmagnetized fluid, a value greater than is predicted by the prevailing magneto-viscosity model. We provide direct visualization of a possible mechanism by which macro-chains impede the transverse motion of spheres. Numerical simulations can reproduce the observed drag, without modeling it physically, by implementing a simple magnetization dependent anisotropic viscosity.

Yecko, Philip; Cali, A.; Lee, W.-K.; Nunez, S.; Prescod, J.; Smith, R.; Trubatch, A. D.; Vieira, M.

2011-11-01

204

Natural convection of ferrofluids in partially heated square enclosures

NASA Astrophysics Data System (ADS)

In this study, natural convection of ferrofluid in a partially heated square cavity is numerically investigated. The heater is located to the left vertical wall and the right vertical wall is kept at constant temperature lower than that of the heater. Other walls of the square enclosure are assumed to be adiabatic. Finite element method is utilized to solve the governing equations. The influence of the Rayleigh number (104?Ra?5×105), heater location (0.25H?yh?0.75H), strength of the magnetic dipole (0???2), horizontal and vertical location of the magnetic dipole (-2H?a?-0.5H, 0.2H?b?0.8H) on the fluid flow and heat transfer characteristics are investigated. It is observed that different velocity components within the square cavity are sensitive to the magnetic dipole source strength and its position. The length and size of the recirculation zones adjacent to the heater can be controlled with magnetic dipole strength. Averaged heat transfer increases with decreasing values of horizontal position of the magnetic dipole source. Averaged heat transfer value increases from middle towards both ends of the vertical wall when the vertical location of the dipole source is varied. When the heater location is changed, a symmetrical behavior in the averaged heat transfer plot is observed and the minimum value of the averaged heat transfer is attained when the heater is located at the mid of vertical wall.

Selimefendigil, Fatih; Öztop, Hakan F.; Al-Salem, Khaled

2014-12-01

205

COCHLEAR HYDRODYNAMICS DEMYSTIFIED

#12;COCHLEAR HYDRODYNAMICS DEMYSTIFIED By Richard F. Lyon Apple Computer, Inc. and California in the design of active adaptive cochlear models. c 1988, California Institute of Technology. All-- and modified--by an improved treatment of cochlear hydrodynamics as an adaptive linear system. We present

Allen, Jont

206

Skew resisting hydrodynamic seal

A novel hydrodynamically lubricated compression type rotary seal that is suitable for lubricant retention and environmental exclusion. Particularly, the seal geometry ensures constraint of a hydrodynamic seal in a manner preventing skew-induced wear and provides adequate room within the seal gland to accommodate thermal expansion. The seal accommodates large as-manufactured variations in the coefficient of thermal expansion of the sealing

William T. Conroy; Lannie L. Dietle; Jeffrey D. Gobeli; Manmohan S. Kalsi

2001-01-01

207

Ejection of ferrofluid grains using nonlinear acoustic impulses--A particle dynamical study

Photonic and Electronic Materials, State University of New York at Buffalo, Buffalo, New York 14260 with the grains suspended in water e.g., -Fe2O3 and subject the system to a strong, homogeneous magnetic field the ferrofluid grains can be suspended in water or oil and the system is subjected to a strong, homogeneous

Sen, Surajit

208

Nonmonotonic field-dependent magnetic permeability of a paramagnetic ferrofluid emulsion.

The ferrofluid emulsion, made of kerosene-based ferrofluid droplets suspended in nonmiscible aviation oil, demonstrates experimentally the nonmonotonic dependence of the effective magnetic permeability as a function of the uniform static magnetic field. In weak fields the emulsion permeability rapidly grows; it reaches its maximum at fields on the order of 1 kA/m; after that, it decays to zero. The theoretical explanation of the effect, as we show here, could be based on the following idea: In a weak magnetic field the growth of the induced droplet magnetic moment is faster than the linear one due to the droplet elongation accompanied by the reduction of the demagnetizing field. Further increase of the external magnetic field strength cannot lead to a significant decrease of the demagnetizing field, as the droplets are already highly elongated. On the other hand, the magnetic susceptibility of the ferrofluid reduces with the field strength. Thus, the effective magnetic permeability of the ferrofluid suspension starts decreasing. The developed theoretical model describes well the experimental observations. PMID:22680473

Ivanov, Alexey O; Kuznetsova, Olga B

2012-04-01

209

American Institute of Aeronautics and Astronautics 1 Ferroelectrohydrodynamics of ionic liquid, the ionic liquid ferrofluid described by Meyer and King is the first liquid to simultaneously respond superparamagnetic liquid. 6,7 When this fluid is subjected to simultaneous magnetic and electric fields a self

King, Lyon B.

210

Applications of ferrofluids in Micro Electro Mechanical Systems (MEMS) and micropumps

NASA Astrophysics Data System (ADS)

The micro-pump is one of the most promising micro-flow devices. At micro-level electronically controlled pumping of any fluid by a mechanical pump is not so easy and reliable. In the realm of nano-tech materials, ferrofluids have unique properties in both liquids and solids and have potential applications for MEMS/NEMS devices. This paper presents two new types of concepts, a micro-flowmeter based on a micro-turbine made using MEMS technology and the other is a micro-pump based on ferrofluidic actuation. In our first device an optical photovoltaic sensor has also been integrated with this device, and the micro-turbine rotates with a speed of 50000 rpm. We have fabricated a ferrofluid-based glass micro-pump of size 20 × 20 × 10 mm^{3}, in which micro actuation is electrically controlled by NdFeB (N50) permanent magnets (diameter 5 × 3 mm, B_{r} = 1400 mT, coercive field H_c=840 ,kA/m) with a ferrofluid bearing. The device is able to pump the fluid at the rate of 10 ? L/actuation. Figs 3, Refs 19.

Jain, V. K.; Pant, R. P.; Vinod Kumar, .

2008-12-01

211

Effects of surfactant friction on Brownian magnetic relaxation in nanoparticle ferrofluids

Effects of surfactant friction on Brownian magnetic relaxation in nanoparticle ferrofluids-fluids of surfactant-coated Co nanoparticles, 20 nm in diameter, in dichlorobenzene in a wide concentration range with oleic acid. It is shown that at a close distance between particles surfactant friction leads

Krishnan, Kannan M.

212

A 3-D time domain method is developed to investigate the gap influence on the wave forces for 3-D multiple floating structures. Special hydrodynamic resonance due to small gaps between multiple floating structures on wave forces is examined. Strong and complicate hydrodynamic interactions between the floating bodies are observed and the numerical computations have proved the existence of the sharp peak

Hai-rong ZHU; Ren-chuan ZHU; Guo-ping MIAO

2008-01-01

213

1. Department, course number, title ORE 609 Hydrodynamics of Fluid-Body Interaction

of Fluid-Body Interaction. (3) Hydrodynamics of ships, coastal and offshore structures. Wave forces with prescribed body motion, fixed and freely floating bodies. 4. Prerequisites Water-Wave Theories (ORE 607 on Offshore Structures 2. Newman: Marine Hydrodynamics 3. Currie: Fundamental Mechanics of Fluids 4. Ippen

Frandsen, Jannette B.

214

Magnetic-field-induced nonequilibrium structures in a ferrofluid emulsion

NASA Astrophysics Data System (ADS)

Using optical microscopy, we studied magnetic-field-induced structures in a confined ferrofluid emulsion where the magnetic field is applied quickly as a step function. Columnar, bent-wall-like, and labyrinthine structures in three dimensions are observed, corresponding to disks, ``worms,'' and branchlike patterns in cross-sectional area normal to the magnetic-field direction. These two-dimensional structures are characterized by both the ratio of worms to total aggregates and the average complexity

Flores, George A.; Liu, Jing; Mohebi, M.; Jamasbi, N.

1999-01-01

215

Direct observations of field-induced assemblies in magnetite ferrofluids

NASA Astrophysics Data System (ADS)

Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ? 10 nm) is studied with an emphasis on examining the effects of particle concentration (?) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ? = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05-0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.

Mousavi, N. S. Susan; Khapli, Sachin D.; Kumar, Sunil

2015-03-01

216

An analytical theoretical model for the influence of the magnetically induced nanoparticle chaining on the linear dichroism in ferrofluids was developed. The model is based on a statistical theory for magnetic nanoparticle chaining in ferrofluids. Together with appropriate experimental approach and data processing strategy, the model grounds a magneto-optical granulometry method able to determine the magnetic field dependence of the statistics of magnetically induced particle chains in concentrated ferrofluids.

V. Socoliuc; L. B. Popescu

2014-10-09

217

Hydrodynamics of vegetated channels

This paper highlights some recent trends in vegetation hydrodynamics, focusing on conditions within channels and spanning spatial scales from individual blades, to canopies or vegetation patches, to the channel reach. At ...

Nepf, Heidi

218

For many technological applications of ferrofluids, the magnetorheological properties require being precisely controlled. We study the effect of hydrophilic silica on the magnetorheology of an oil-based ferrofluid containing Fe3O4 nanoparticles of size ?10 nm. We observe that the presence of silica nanoparticles lowers the yield stresses, viscoelastic moduli, and shear thinning behavior of the ferrofluid because of the weakening of dipolar interactions, which was evident from the observed lower yield stresses exponent (<2). The ferrofluid containing silica exhibits a dominant elastic behavior, a reduced hysteresis during the forward and reverse magnetic field sweeps, and a longer linear viscoelastic regime under nonlinear deformation. The Mason number plots at low shear rates and magnetic fields show deviations from the master curve in the presence of silica. The magnetic field induced microstructures, visualized using opto-magnetorheometer, showed columnar aggregate structures along the field directions, which are reoriented along the shear flow direction at high shear rates. The image analysis shows that the average thickness of the columnar aggregates in pure ferrofluid is much larger than that of the mixed system, which suggests that the intervening silica matrix hampers the zippering transition of columns at higher magnetic field and shear rates. Our results suggest that optimization of rheological properties of ferrofluids is possible by carefully adding suitable silica nanoparticles, which may find practical applications such as dynamic seals, heat transfer, sensors, and opto-fluidic devices, etc. PMID:25734232

Felicia, Leona J; Philip, John

2015-03-24

219

Geometries and flows in optical hydrodynamics

NASA Astrophysics Data System (ADS)

The nature of light propagation suggests its correspondence to many universal problems in wave physics. Considering the complexity in many wave systems and taking advantage of optical systems which allow easy control of the input and direct imaging of the output, we treat nonlinear optics within the broader context in connection with general wave dynamic problems. This thesis presents experimental and theoretical work probing physics into the crossover between nonlinear optics and fluid dynamics. The main theme of the thesis concerns three aspects. First, we develop the fundamental model of optical hydrodynamics and use the model to demonstrate all-optical dispersive shockwaves, hydrodynamic instabilities, as well as spatial supercontinuum generation. Second, we control 'light flow' propagation by adding it into optically induced structures. This leads to the observation of nonlinear wave propagations in periodic, rotating and fractal potentials. Wave dynamics and energy transfer are dramatically different from those in homogeneous media. Finally, we shape the 'light flow' itself to observe the interactions between wave evolution and nonlinearity. The realization of diffraction-free Airy beam in nonlinear material provides potential applications to novel photonic imaging devices.

Jia, Shu

220

Hydrodynamical evolution of coalescing binary neutron stars

NASA Technical Reports Server (NTRS)

The hydrodynamics of the final merging of two neutron stars and the corresponding gravitational wave emission is studied in detail. Various test calculations are presented, including the compressible Roche and Darwin problems and the head-on collision of two polytropes. A complete coalescence calculation is presented for the simplest case of two identical neutron stars, represented by Gamma = 2 polytropes, in a circular orbit, with their spins aligned and synchronized with the orbital rotation.

Rasio, Frederic A.; Shapiro, Stuart L.

1992-01-01

221

Lattice hydrodynamic model with bidirectional pedestrian flow

The two-dimensional lattice hydrodynamic model of traffic is extended to the two-dimensional bidirectional pedestrian flow via taking four types of pedestrians into account. The stability condition and the mKdV equation to describe the density wave of pedestrian congestion are obtained by linear stability and nonlinear analysis, respectively. In addition, there exist three phase transitions among the freely moving phase, the

Huan-Huan Tian; Hong-Di He; Yan-Fang Wei; Xue Yu; Wei-Zhen Lu

2009-01-01

222

Ion holes in the hydrodynamic regime in ultracold neutral plasmas

We describe the creation of localized density perturbations, or ion holes, in an ultracold neutral plasma in the hydrodynamic regime, and show that the holes propagate at the local ion acoustic wave speed. We also observe the process of hole splitting, which results from the formation of a density depletion initially at rest in the plasma. One-dimensional, two-fluid hydrodynamic simulations describe the results well. Measurements of the ion velocity distribution also show the effects of the ion hole and confirm the hydrodynamic conditions in the plasma.

McQuillen, P.; Castro, J.; Strickler, T.; Bradshaw, S. J.; Killian, T. C. [Department of Physics and Astronomy, Rice University, Houston, Texas 77005 (United States)

2013-04-15

223

The hydrodynamic behaviour of long floating structures in directional seas

The diffraction\\/radiation boundary value problem arising from the interaction of oblique waves with freely floating long structures is studied using finite-element techniques. Further, the hydrodynamic behaviour of two-dimensional horizontal floating structures under the action of multi-directional waves has been studied. The linear transfer function approach is used to determine the wave exciting forces and motion responses of a structure of

S. A. Sannasiraj; V. Sundar; R. Sundaravadivelu

1995-01-01

224

A note on the hydrodynamical description of cosmic ray propagation

NASA Astrophysics Data System (ADS)

The set of hydrodynamic equations governing a system of cosmic rays, waves and background plasma, is derived. The cosmic rays interact with the background plasma via hydromagnetic waves (e.g., Alfven waves) which in turn are produced by the cosmic ray streaming instability. The convection, diffusion and second order Fermi effect of the cosmic rays are taken into account. A simple example emphasizing the second order Fermi effect is given.

Ko, C.-M.

1992-06-01

225

Ejection of ferrofluid grains using nonlinear acoustic impulses[emdash] A particle dynamical study

We consider a model dilute ferrofluid with the grains suspended in water (e.g.,[gamma]-Fe[sub 2]O[sub 3]) and subject the system to a strong, homogeneous magnetic field directed perpendicular to the surface such that there is chain formation along the field direction. We show that an appropriate impulse initiated at the base of the container might travel as a nondispersive soliton pulse with sufficient energy to overcome surface tension and eject the ferrofluid grain nearest to the liquid[endash]air interface. The proposed mechanism, if successfully realized in the laboratory, could help design a nozzle-free, ink-jet printer of unparalleled resolution. [copyright] [ital 1999 American Institute of Physics.

Sen, S.; Manciu, M.; Manciu, F.S. (Department of Physics and Center for Advanced Photonic and Electronic Materials, State University of New York at Buffalo, Buffalo, New York 14260 (United States))

1999-09-01

226

A study of modified Fe 3O 4 nanoparticles for the synthesis of ionic ferrofluids

NASA Astrophysics Data System (ADS)

XRD and XPS analyses revealed that a Fe(NO 3) 3·9H 2O layer formed outside ?-Fe 2O 3 particles when Fe 3O 4 nanoparticles were treated with ferric nitrate. The particle density differed for untreated and treated particles and was not uniform for the latter. The specific saturation magnetization of both treated and untreated particles was used to estimate the thickness of the Fe(NO 3) 3·9H 2O layer and the average density of the treated particles. The density of the treated particles was used to calculate the density of ferrofluids of different particle volume fractions. These values are in agreement with measured results. Therefore, the particle volume fraction can be designed to synthesize acid ionic ferrofluids based on Fe 3O 4 nanoparticles using Massart's method.

Li, Jian; Qiu, Xiaoyan; Lin, Yueqiang; Liu, Xiaodong; Gao, Rongli; Wang, Anrong

2010-09-01

227

The magnetic assembly of polymer colloids in a ferrofluid and its display applications.

Nonmagnetic polymer colloids have been assembled into colloidal photonic crystals in a ferrofluid by applying an external magnetic field based on the dipole-dipole interactions of "magnetic holes". The photonic crystal disassembles immediately when the magnetic field is removed. The mechanism of assembly can be explained by two simultaneous processes: phase separation and colloidal assembly. In this work, increasing the size of the building blocks still produces colorful photonic crystals due to their 2nd order diffraction. With a larger building block, the magnetic response between the polymer colloids is greatly enhanced so that an instant and reversible assembly/disassembly can be realized in a much weaker magnetic field and lower ferrofluid concentration. Based on these investigations, a magnetically controlled photonic display unit has been fabricated, which works in a weak magnetic field, has stable reflection signals and possesses fast and reversible on/off switching of reflections. PMID:22297654

Liu, Jing; Mao, Yiwu; Ge, Jianping

2012-03-01

228

Active surfaces: Ferrofluid-impregnated surfaces for active manipulation of droplets

NASA Astrophysics Data System (ADS)

Droplet manipulation and mobility on non-wetting surfaces is of practical importance for diverse applications ranging from micro-fluidic devices, anti-icing, dropwise condensation, and biomedical devices. The use of active external fields has been explored via electric, acoustic, and vibrational, yet moving highly conductive and viscous fluids remains a challenge. Magnetic fields have been used for droplet manipulation; however, usually, the fluid is functionalized to be magnetic, and requires enormous fields of superconducting magnets when transitioning to diamagnetic materials such as water. Here we present a class of active surfaces by stably impregnating active fluids such as ferrofluids into a textured surface. Droplets on such ferrofluid-impregnated surfaces have extremely low hysteresis and high mobility such that they can be propelled by applying relatively low magnetic fields. Our surface is able to manipulate a variety of materials including diamagnetic, conductive and highly viscous fluids, and additionally solid particles.

Khalil, Karim S.; Mahmoudi, Seyed Reza; Abu-dheir, Numan; Varanasi, Kripa K.

2014-07-01

229

Rheological investigations on the theoretical predicted “Poisoning” effect in bidisperse ferrofluids

NASA Astrophysics Data System (ADS)

Interparticle interactions in ferrofluids especially the influence of small particles on the agglomeration behaviour of large particles were the topic of numerous theoretical predictions and simulations as well as of experimental investigations. In this context the "Poisoning" effect describes the decrease of the magnetoviscous effect in the presence of small particles in a bidisperse model fluid. In order to examine this effect rheological experiments have been carried out by means of a specially designed rheometer, which allows measurements under the influence of an applied magnetic field. We were able to synthesize ferrofluids with a narrow particle size distribution containing only small or large cobalt ferrite nanoparticles, which were mixed to receive various bidisperse fluid samples. With these fluids changes of the viscous behaviour in a magnetic field have been measured and compared according to their individual compositions.

Siebert, E.; Dupuis, V.; Neveu, S.; Odenbach, S.

2015-01-01

230

Hydrodynamics of spin-polarized transport and spin pendulum

The dynamics of a nonequilibrium spin system dominated by collisions preserving the total quasimomentum of the interacting electrons and quasiparticles is considered. An analysis of the derived hydrodynamic equations shows that weakly attenuated spin-polarization waves associated with an oscillating drift current can exist in a magnetically inhomogeneous conducting ring. Spin-polarized transport in a ballistic regime of wave propagation through a conductor is also considered, and a simple method is proposed for distinguishing these waves from spin and current oscillations that develop in the hydrodynamic regime. It is shown that a potential difference arises between the leads of an open nonuniformly spin-polarized conductor as a manifestation of spin polarization of electron density. This spin-mediated electrical phenomenon occurs in both hydrodynamic and diffusive limits.

Gurzhi, R. N., E-mail: gurzhi@ilt.kharkov.ua; Kalinenko, A. N.; Kopeliovich, A. I.; Pyshkin, P. V.; Yanovsky, A. V. [Verkin Institute for Low-Temperature Physics and Engineering (Ukraine)

2007-07-15

231

Study of polydiethylsiloxane-based ferrofluid with excellent frost resistance property

The polydiethylsiloxane-based ferrofluid was prepared by dispersing finely divided magnetic Fe3O4 particles which are modified with oleoyl sarcosine and lauroyl sarcosine. The optimized experiment parameters including molar ratio of surfactant to Fe3O4 (1:5), temperature (80°C), stirring rate (300RPM), the surfactant content of lauroyl sarcosine (0 to 33mol%) and the modification time (25min) were obtained by the orthogonal test. The magnetic

Y. X. Zhao; L. Zhuang; H. Shen; W. Zhang; Z. J. Shao

2009-01-01

232

Low-field DC-magnetization study of Ho 3+-doped Mn–Zn ferrite ferrofluid

The physical and magnetic properties of magnetic nanoparticles are crucial for their effectiveness and reliability in biomedical applications. In this article, we report the synthesis of a stable Ho-substituted Mn–Zn ferrite ferrofluid and its physical and magnetic properties. Substitution by rare earth metal plays an important role in determining the magneto-crystalline anisotropy in 4f-3d inter-metallic compounds. Ho3+ substitution not only

Ramesh V. Upadhyay; Kinnari Parekh; Lybua Belova; K. V. Rao

2007-01-01

233

A process is reported to obtain a nanoparticle sol from co-precipitated iron oxide particles without using any surfactant. The sol - a true ferrofluid - is not only stable over a wide range of pH but also in physiological solutions. This is a decisive step towards biomedical applications where nanoparticle agglomeration could so far only be prevented by using unwanted surfactants. PMID:25580829

Mandel, K; Straßer, M; Granath, T; Dembski, S; Sextl, G

2015-02-18

234

The purpose of this study was to compare the effects of magnetic thermal ablation in different porcine tissues using either a singular injection or a continuous infusion of superparamagnetic iron oxide nanoparticles. In the first setting samples of three ferrofluids containing different amounts of iron (1:171, 2:192, and 3:214 mg/ml) were singularly interstitially injected into specimens of porcine liver, kidney, and muscle (n = 5). Then the specimens were exposed to an alternating magnetic field (2.86 kA/m, 190 kHz) generated by a circular coil for 5 min. In the second experimental setup ferrofluid samples were continuously interstitially infused into the tissue specimens during the exposure to the magnetic field. To measure the temperature increase two fiber-optic temperature probes with a fixed distance of 0.5 cm were inserted into the specimens along the puncture tract of the injection needle and the temperature was measured every 15 s. Finally, the specimens were dissected, the diameters of the created thermal lesions were measured, and the volumes were calculated and compared. Compared to continuous infusion, a single injection of ferrofluids resulted in smaller coagulation volumes in all tissues. Significant differences regarding coagulation volume were found in kidney and muscle specimens. The continuous infusion technique led to more elliptically shaped coagulation volumes due to larger diameters along the puncture tract. Our data show the feasibility of magnetic thermal ablation using either a single interstitial injection or continuous infusion for therapy of lesions in muscle, kidney, and liver. Continuous infusion of ferrofluids results in larger zones of necrosis compared to a single injection technique.

Bruners, Philipp, E-mail: bruners@hia.rwth-aachen.de; Hodenius, Michael, E-mail: hodenius@hia.rwth-aachen.de; Baumann, Martin, E-mail: baumann@hia.rwth-aachen.de; Oversohl, Jessica, E-mail: jessy@oversohl.d [Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University, Applied Medical Engineering (Germany); Guenther, Rolf W., E-mail: guenther@rad.rwth-aachen.d [RWTH Aachen University, Department of Diagnostic Radiology (Germany); Schmitz-Rode, Thomas, E-mail: smiro@hia.rwth-aachen.de; Mahnken, Andreas H., E-mail: mahnken@rad.rwth-aachen.d [Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University, Applied Medical Engineering (Germany)

2008-11-15

235

Ferrofluidity in a Two-Component Dipolar Bose-Einstein Condensate

It is shown that the interface in a two-component Bose-Einstein condensate (BEC) with a dipole-dipole interaction spontaneously develops patterns similar to those formed in a ferrofluid. Hexagonal, labyrinthine, solitonlike structures, and hysteretic behavior are numerically demonstrated. Superflow is found to circulate around the hexagonal pattern at rest, offering evidence of supersolidity. The system sustains persistent current with a vortex line pinned by the hexagonal pattern. These phenomena may be realized using a {sup 52}Cr BEC.

Saito, Hiroki [Department of Applied Physics and Chemistry, University of Electro-Communications, Tokyo 182-8585 (Japan); Kawaguchi, Yuki [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Ueda, Masahito [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); ERATO Macroscopic Quantum Project, JST, Tokyo 113-8656 (Japan)

2009-06-12

236

Synthesis and characterization of size-controlled cobalt-ferrite-based ionic ferrofluids

Size-controlled synthesis of cobalt-ferrite nanoparticles, their passivation and peptization as stable ferrofluids are reported. Transmission electron microscopy and Mössbauer spectroscopy were used as characterization techniques. Particles with little change in size distribution, in the 10–15nm diameter ranges, were obtained using stirring speeds between 2700 and 8100rpm. The anomalous diffusion has been used to explain the nanoparticle size-control mechanism.

P. C. Morais; V. K. Garg; A. C. Oliveira; L. P. Silva; R. B. Azevedo; A. M. L. Silva; E. C. D. Lima

2001-01-01

237

Taylor-Couette flow of ferrofluid: Spin field and spin boundary condition effects

NASA Astrophysics Data System (ADS)

We solve for the steady flow solutions of a ferrofluid between concentric cylinders (the Taylor-Couette problem) and consider the effects of the spin field and the spin boundary conditions on the flow. In particular, our model includes the full spin equations. We analyze families of solutions for a range of realistic flow parameters and radial magnetic fields. Particular attention is paid to regimes in which different spin boundary conditions lead to significantly different flow profiles.

Mukherjee, Arup; Childress, William; Yecko, Philip

238

The use of genetically modified organisms (GMOs) as food and in food products is becoming more and more widespread. Polymerase\\u000a chain reaction (PCR) technology is extensively used for the detection of GMOs in food products in order to verify compliance\\u000a with labeling requirements. In this paper, we present a novel close-loop ferrofluid-driven PCR microchip for rapid amplification\\u000a of GMOs. The

Yi Sun; Yien-Chian Kwok; Peter Foo-Peng Lee; Nam-Trung Nguyen

2009-01-01

239

Hydrodynamics with Triangle Anomalies

We consider the hydrodynamic regime of theories with quantum anomalies for global currents. We show that a hitherto discarded term in the conserve current is not only allowed by symmetries, but is in fact required by triangle anomalies and the second law of thermodynamics. This term leads to a number of new effects, one of which is chiral separation in a rotating fluid at nonzero chemical potential. The new kinetic coefficients can be expressed, in a unique fashion, through the anomalies coefficients and the equation of state. We briefly discuss the relevance of this new hydrodynamic term for physical situations, including heavy ion collisions.

Dam T. Son; Piotr Surowka

2009-07-13

240

Hydrodynamics with Triangle Anomalies

We consider the hydrodynamic regime of theories with quantum anomalies for global currents. We show that a hitherto discarded term in the conserved current is not only allowed by symmetries, but is in fact required by triangle anomalies and the second law of thermodynamics. This term leads to a number of new effects, one of which is chiral separation in a rotating fluid at nonzero chemical potential. The new kinetic coefficients can be expressed, in a unique fashion, through the anomaly coefficients and the equation of state. We briefly discuss the relevance of this new hydrodynamic term for physical situations, including heavy-ion collisions.

Son, Dam T. [Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550 (United States); Surowka, Piotr [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)

2009-11-06

241

Theory and simulation of anisotropic pair correlations in ferrofluids in magnetic fields.

Anisotropic pair correlations in ferrofluids exposed to magnetic fields are studied using a combination of statistical-mechanical theory and computer simulations. A simple dipolar hard-sphere model of the magnetic colloidal particles is studied in detail. A virial-expansion theory is constructed for the pair distribution function (PDF) which depends not only on the length of the pair separation vector, but also on its orientation with respect to the field. A detailed comparison is made between the theoretical predictions and accurate simulation data, and it is found that the theory works well for realistic values of the dipolar coupling constant (? = 1), volume fraction (? ? 0.1), and magnetic field strength. The structure factor is computed for wavevectors either parallel or perpendicular to the field. The comparison between theory and simulation is generally very good with realistic ferrofluid parameters. For both the PDF and the structure factor, there are some deviations between theory and simulation at uncommonly high dipolar coupling constants, and with very strong magnetic fields. In particular, the theory is less successful at predicting the behavior of the structure factors at very low wavevectors, and perpendicular Gaussian density fluctuations arising from strongly correlated pairs of magnetic particles. Overall, though, the theory provides reliable predictions for the nature and degree of pair correlations in ferrofluids in magnetic fields, and hence should be of use in the design of functional magnetic materials. PMID:22612098

Elfimova, Ekaterina A; Ivanov, Alexey O; Camp, Philip J

2012-05-21

242

Deformation of ferrofluid marbles in the presence of a permanent magnet.

This paper investigates the deformation of ferrofluid marbles in the presence of a permanent magnet. Ferrofluid marbles are formed using a water-based ferrofluid and 1 ?m hydrophobic polytetrafluoride particles. A marble placed on a Teflon coated glass plate deforms under gravity. In the presence of a permanent magnet, the marble is further deformed with a larger contact area. The geometric parameters are normalized by the radius of an undistorted spherical marble. The paper first discusses a scaling relationship between the dimensionless radius of the contact area as well as the dimensionless height and the magnetic Bond number. The dimensionless contact radius is proportional to the fourth root of the magnetic bond number. The dimensionless height scales with the inverse square root of the magnetic Bond number. In the case of a moving marble dragged by a permanent magnet, the deformation is evaluated as the difference between advancing and receding curvatures of the top view. The dimensionless height and the contact diameter of the marble do not significantly depend on the speed or the capillary number. The scaling analysis and experimental data show that the deformation is proportional to the capillary number. PMID:24164113

Nguyen, Nam-Trung

2013-11-12

243

Convective Instability of Magnetized Ferrofluids: Influence of Magnetophoresis and Soret Effect

Convective instability in a ferrofluid layer heated from below or from above in the presence of a uniform vertical magnetic field is investigated theoretically. Convection is caused by a magnetic mechanism based on the temperature and concentration dependence of magnetization. An imposed temperature gradient establishes (by the Soret effect) a concentration gradient of magnetic particles of which the ferrofluid is composed. Both these gradients cause a spatial variation in magnetization, which induces a gradient of magnetic field intensity within the fluid layer. The field gradient induces in its turn an additional redistribution of magnetic grains due to magnetophoresis. Resulting self-consistent magnetic force tries to mix the fluid. A linear stability analysis predicts oscillatory instability in a certain region of the magnetic field strength and the fluid parameters. The instability owes magneto- and thermophoresis its origin: were the particle diffusion not operative, then only stationary instability would occur. A discovery of predicted convective oscillations is expected in ferrofluid layers about 1 mm thick, where the buoyancy mechanism is negligible and the characteristic diffusion time is not too long.

Mark I. Shliomis

2001-06-20

244

NASA Astrophysics Data System (ADS)

The difference between success or failure of chemotherapy depends not only on the drug itself but also on how it is delivered to its target. Biocompatible ferrofluids (FF) are paramagnetic nanoparticles, that may be used as a delivery system for anticancer agents in locoregional tumor therapy, called "magnetic drug targeting". Bound to medical drugs, such magnetic nanoparticles can be enriched in a desired body compartment (tumor) using an external magnetic field, which is focused on the area of the tumor. Through this form of target directed drug application, one attempts to concentrate a pharmacological agent at its site of action in order to minimize unwanted side effects in the organism and to increase its locoregional effectiveness. Tumor bearing rabbits (VX2 squamous cell carcinoma) in the area of the hind limb, were treated by a single intra-arterial injection (A. femoralis) of mitoxantrone bound ferrofluids (FF-MTX), while focusing an external magnetic field (1.7 Tesla) onto the tumor for 60 minutes. Complete tumor remissions could be achieved in these animals in a dose related manner (20% and 50% of the systemic dose of mitoxantrone), without any negative side effects, like e.g. leucocytopenia, alopecia or gastrointestinal disorders. The strong and specific therapeutic efficacy in tumor treatment with mitoxantrone bound ferrofluids may indicate that this system could be used as a delivery system for anticancer agents, like radionuclids, cancer-specific antibodies, anti-angiogenetic factors, genes etc.

Alexiou, Ch.; Schmid, R.; Jurgons, R.; et al.

245

Low-temperature magnetic susceptibility of concentrated ferrofluids: The influence of polydispersity

NASA Astrophysics Data System (ADS)

In this paper we address the question of theoretical explanation of extremely high low-temperature initial magnetic susceptibility of concentrated ferrofluids. These laboratory synthesized samples [A.F. Pshenichnikov, A.V. Lebedev, J. Chem. Phys. 121(11) (2004) 5455; Colloid J. 67(2) (2005) 189] demonstrated the record-breaking values ? ~ 120 - 150 at temperatures ~ 230-240 K. The existing models predict such high susceptibility only under the assumption of unreasonably large dipolar coupling constant, which is out of the range of applicability. Here we calculate the second virial contribution to susceptibility for polydisperse ferrofluid, modeled by the dipolar hard sphere fluid. In the resulting expression there exists the parameter, which plays a part of dipolar coupling constant and which is defined in a form of double averaging of high powers of particle sizes over the granulometric distribution. For real particle size distribution this effective parameter at least twice exceeds the commonly defined polydisperse dipolar coupling constant. We show that the low-temperature magnetic susceptibility of the record-breaking ferrofluids could be explained theoretically on the basis of the first terms of the polydisperse second virial contribution in combination with the second-order modified mean field model.

Ivanov, Alexey O.; Elfimova, Ekaterina A.

2015-01-01

246

Skew resisting hydrodynamic seal

A novel hydrodynamically lubricated compression type rotary seal that is suitable for lubricant retention and environmental exclusion. Particularly, the seal geometry ensures constraint of a hydrodynamic seal in a manner preventing skew-induced wear and provides adequate room within the seal gland to accommodate thermal expansion. The seal accommodates large as-manufactured variations in the coefficient of thermal expansion of the sealing material, provides a relatively stiff integral spring effect to minimize pressure-induced shuttling of the seal within the gland, and also maintains interfacial contact pressure within the dynamic sealing interface in an optimum range for efficient hydrodynamic lubrication and environment exclusion. The seal geometry also provides for complete support about the circumference of the seal to receive environmental pressure, as compared the interrupted character of seal support set forth in U.S. Pat. Nos. 5,873,576 and 6,036,192 and provides a hydrodynamic seal which is suitable for use with non-Newtonian lubricants.

Conroy, William T. (Pearland, TX); Dietle, Lannie L. (Sugar Land, TX); Gobeli, Jeffrey D. (Houston, TX); Kalsi, Manmohan S. (Houston, TX)

2001-01-01

247

The influence of a magnetic field on the dynamics of the flow of a ferrofluid in the gap between two concentric, independently rotating cylinders is investigated numerically. The Navier-Stokes equations are solved using a hybrid finite difference and Galerkin method. We show that the frequently used assumption that the internal magnetic field within a ferrofluid is equal to the external applied field is only a leading-order approximation. By accounting for the ferrofluid's magnetic susceptibility, we show that a uniform externally imposed magnetic field is modified by the presence of the ferrofluid within the annulus. The modification to the magnetic field has an r(-2) radial dependence and a magnitude that scales with the susceptibility. For ferrofluids typically used in laboratory experiments of the type simulated in this paper, the modification to the imposed magnetic field can be substantial. This has significant consequences on the structure and stability of the basic states, as well as on the bifurcating solutions. PMID:23005213

Altmeyer, S; Do, Younghae; Lopez, J M

2012-06-01

248

Astron. Nachr./AN 32X (200X) X, XXX--XXX 3D hydrodynamic simulations of the solar chromosphere

Astron. Nachr./AN 32X (200X) X, XXX--XXX 3ÂD hydrodynamic simulations of the solar chromosphere S chromosphere, comÂ puted with the radiation hydrodynamics code CO 5 BOLD. Acoustic waves which are excited at the top of the convection zone propagate upwards into the chromosphere where the waves steepen into shocks

249

Hyperbolic metamaterial lens with hydrodynamic nonlocal response.

We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we propose to measure the near-field distribution of a hyperbolic metamaterial lens. PMID:23787690

Yan, Wei; Mortensen, N Asger; Wubs, Martijn

2013-06-17

250

A Hybrid Godunov Method for Radiation Hydrodynamics

From a mathematical perspective, radiation hydrodynamics can be thought of as a system of hyperbolic balance laws with dual multiscale behavior (multiscale behavior associated with the hyperbolic wave speeds as well as multiscale behavior associated with source term relaxation). With this outlook in mind, this paper presents a hybrid Godunov method for one-dimensional radiation hydrodynamics that is uniformly well behaved from the photon free streaming (hyperbolic) limit through the weak equilibrium diffusion (parabolic) limit and to the strong equilibrium diffusion (hyperbolic) limit. Moreover, one finds that the technique preserves certain asymptotic limits. The method incorporates a backward Euler upwinding scheme for the radiation energy density and flux as well as a modified Godunov scheme for the material density, momentum density, and energy density. The backward Euler upwinding scheme is first-order accurate and uses an implicit HLLE flux function to temporally advance the radiation components accordi...

Sekora, Michael D

2010-01-01

251

NASA Astrophysics Data System (ADS)

In this study, some stabilized magnetite based ferrofluids were synthesized using Dextran as a stabilizing agent. In order to achieve optimum experimental conditions for synthesizing ferrofluids as MRI contrast agents, the Taguchi method was used. This approach was employed to design and minimize the number of required experiments. By using the Taguchi orthogonal (L16) array, four parameters including solution temperature and alkalinity, reaction temperature and stirring rate were selected at four predetermined levels for 16 experiments. Synthesizing processes established based on this set of experimental conditions were carried out and the obtained ferrofluids were characterized using PCS, VSM, TEM and FT-IR techniques. The obtained results were used and analyzed through the Qualitek-4 software and the proposed optimum experimental conditions were used for synthesizing the desired sample. Finally, this sample was used as a potential MRI contrast agent for imaging lymph nodes.

Ahmadi, Reza; Hosseini, Hamid Reza Madaah

2013-04-01

252

Predictions of undirectional irregular wave kinematics and evolution

components. A Hybrid Wave Model is developed to describe these nonlinear interactions between the wave components. In this study, the formulations of the Hybrid Wave Model are derived and examined to satisfy the basic hydrodynamic principles up to second...

Ye, Mao

1994-01-01

253

Hydrodynamics of polarizable liquids

The complete hydrodynamic theory of polarizable and magnetizable isotropic liquids is presented. This is a century-old problem that the authors claim to have solved. Starting from an extensive discussion of the results and controversies of the past 90 years, and of the present literature, the obvious difficulties are first presented and then cleansed of their notational content. Using only input of universal acceptance, the Lorentz transformation, the macroscopic Maxwell equations, and the thermodynamics, a set of hydrodynamic equations of motion is derived rigorously, without any ad-hoc assumptions or residual ambiguities. Definite expressions are especially provided for the total momentum density, its stress tensor, and the acceleration of a polarized body. Other controversial concepts, such as the field momentum density, the pressure, and the force density in the polarized body, are shown to be arbitrary, the extent of which, however, is clarified. 31 refs.

Henjes, K.; Liu, M. (Universitat Hannover (Germany))

1993-05-01

254

Landau hydrodynamics reexamined

NASA Astrophysics Data System (ADS)

We review the formulation of Landau hydrodynamics and find that the rapidity distribution of produced particles in the center-of-mass system should be more appropriately modified as dN/dy?exp{yb2-y2}, where yb=ln{sNN/mp} is the beam nucleon rapidity, instead of Landau's original distribution, dN/dy(Landau)?exp{L2-y2}, where L=ln{sNN/2mp}. The modified distribution agrees better with experimental dN/dy data than the original Landau distribution and can be represented well by the Gaussian distribution, dN/dy(Gaussian)?exp{-y2/2L}. Past successes of the Gaussian distribution in explaining experimental rapidity data can be understood, not because it is an approximation of the original Landau distribution, but because it is in fact a close representation of the modified distribution. Predictions for pp and AA collisions at LHC energies in Landau hydrodynamics are presented.

Wong, Cheuk-Yin

2008-11-01

255

Hydrodynamic modeling of tsunamis from the Currituck landslide Eric L. Geist a,

Hydrodynamic modeling of tsunamis from the Currituck landslide Eric L. Geist a, , Patrick J. Lynett: Accepted 24 September 2008 Keywords: tsunami landslide hydrodynamic runup numerical model sensitivity analysis Tsunami generation from the Currituck landslide offshore North Carolina and propagation of waves

Lynett, Patrick

256

Modeling of textural changes in beef loins subjected to hydrodynamic pressure

Technology Transfer Automated Retrieval System (TEKTRAN)

High hydrodynamic pressure has been considered as a new novel food processing technique to impart favorable textural changes in meat. It is believed that a hydrodynamic pressure wave could be used to tenderize otherwise unacceptably tough cuts of beef, and allow them to be used in more valuable prod...

257

Relativistic cosmological hydrodynamics

We investigate the relativistic cosmological hydrodynamic perturbations. We present the general large scale solutions of the perturbation variables valid for the general sign of three space curvature, the cosmological constant, and generally evolving background equation of state. The large scale evolution is characterized by a conserved gauge invariant quantity which is the same as a perturbed potential (or three-space curvature) in the comoving gauge.

J. Hwang; H. Noh

1997-11-29

258

NSDL National Science Digital Library

Hydrodynamics and viscosity: This site contains a complete description of fluid properties and fluid mechanics by defining the nature of a fluid, show where fluid mechanics concepts are common with those of solid mechanics and indicate some fundamental areas of difference, introduce viscosity and show what are Newtonian and non-Newtonian fluids and define the appropriate physical properties and show how these allow differentiation between solids and fluids as well as between liquids and gases.

259

Hydrodynamics of fossil fishes

From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms. PMID:24943377

Fletcher, Thomas; Altringham, John; Peakall, Jeffrey; Wignall, Paul; Dorrell, Robert

2014-01-01

260

A saw having a self-pumped hydrodynamic blade guide or bearing for retaining the saw blade in a centered position in the saw kerf (width of cut made by the saw). The hydrodynamic blade guide or bearing utilizes pockets or grooves incorporated into the sides of the blade. The saw kerf in the workpiece provides the guide or bearing stator surface. Both sides of the blade entrain cutting fluid as the blade enters the kerf in the workpiece, and the trapped fluid provides pressure between the blade and the workpiece as an inverse function of the gap between the blade surface and the workpiece surface. If the blade wanders from the center of the kerf, then one gap will increase and one gap will decrease and the consequent pressure difference between the two sides of the blade will cause the blade to re-center itself in the kerf. Saws using the hydrodynamic blade guide or bearing have particular application in slicing slabs from boules of single crystal materials, for example, as well as for cutting other difficult to saw materials such as ceramics, glass, and brittle composite materials.

Blaedel, Kenneth L. (Dublin, CA); Davis, Pete J. (Pleasanton, CA); Landram, Charles S. (Livermore, CA)

2000-01-01

261

From Field Theory to the Hydrodynamics of Relativistic Superfluids

The hydrodynamic description of a superfluid is usually based on a two-fluid picture. In this thesis, basic properties of such a relativistic two-fluid system are derived from the underlying microscopic physics of a complex scalar quantum field theory. To obtain analytic results of all non-dissipative hydrodynamic quantities in terms of field theoretic variables, calculations are first carried out in a low-temperature and weak-coupling approximation. In a second step, the 2-particle-irreducible formalism is applied: This formalism allows for a numerical evaluation of the hydrodynamic parameters for all temperatures below the critical temperature. In addition, a system of two coupled superfluids is studied. As an application, the velocities of first and second sound in the presence of a superflow are calculated. The results show that first (second) sound evolves from a density (temperature) wave at low temperatures to a temperature (density) wave at high temperatures. This role reversal is investigated for ult...

Stetina, Stephan

2015-01-01

262

The stability of a planar hydrodynamic shock is investigated. The fluid ; on each side of the shock is taken to be an ideal fluid satisfying the adiabatic ; equation of state with a ratio of specific heats greater than unity. The ; standard non-relativistic shock conditions are used. In the unperturbed fluid ; state a frame of reference moving

Kruskal

1962-01-01

263

Operational oceanographic system for coastal hydrodynamics in Korea

NASA Astrophysics Data System (ADS)

We have developed an operational oceanographic system for the coastal waters of Korea using ROMS. The operational oceanographic modeling system consists of atmospheric and hydrodynamic models coupled with three-dimensional hydrodynamics, wave, sediment transport and water quality modules. We forecast the results two times a day in the 72 hours base including sea surface elevation, currents, temperature, salinity, and wave information etc. for the coastal waters of Korea. The predicted results are exported to the web-GIS based coastal information system for the application of various coastal activities and problems and the real-time dissemination to the public. The modeling system for the coastal waters of Korea uses operational ocean model ROMS coupled with wave model SWAN for the hydrodynamics and waves, meteorological model WRF for the atmospheric surface forcing, regional tide model NAO.99jb for the tides, and eutrophication model CE-QUAL-ICM for the water quality. The predicted results of WRF and ROMS for the Yellow Sae are nested for the boundary condition of the model. The model ROMS was calibrated with tidal surface data, then the model was verified with current data observed near the coastal waters of Korea with bottom mounted ADCP and AWAC. To validate the operational model we use real-time monitoring data obtained by Buoy, HF-Radar, stationary Satellite, and observatory tower system installed by KORDI and KHOA funded by Korean government for the observation of hydrodynamics in Korea. In this study, we have developed an operational oceanographic system for the coastal hydrodynamics in Korea. The operational model ROMS predicts the information of coastal waters of Korea twice a day for 72 hours. The predicted result is visualized effectively through the web-GIS system to provide predicted coastal hydrodynamics in Korea to the public. This high-resolution coastal operational oceanographic system will be used as a part of the development of Korea Operational Oceanographic System (KOOS) with other operational oceanographic system.

Lim, H.; Kim, C. S.; Park, K.

2011-12-01

264

Generalized hydrodynamic transport in lattice-gas automata

NASA Technical Reports Server (NTRS)

The generalized hydrodynamics of two-dimensional lattice-gas automata is solved analytically in the linearized Boltzmann approximation. The dependence of the transport coefficients (kinematic viscosity, bulk viscosity, and sound speed) upon wave number k is obtained analytically. Anisotropy of these coefficients due to the lattice symmetry is studied for the entire range of wave number, k. Boundary effects due to a finite mean free path (Knudsen layer) are analyzed, and accurate comparisons are made with lattice-gas simulations.

Luo, Li-Shi; Chen, Hudong; Chen, Shiyi; Doolen, Gary D.; Lee, Yee-Chun

1991-01-01

265

Hydrodynamic simulations of bubble collapse and picosecond sonoluminescence

Numerical hydrodynamic simulations of the growth and collapse of a 10-[mu]m air bubble in water were performed. Both the air and the water are treated as compressible fluids. The calculations show that the collapse is nearly isentropic until the final 10 ns, after which a strong spherically converging shock wave evolves and creates enormous temperatures and pressures in the inner

William C. Moss; D. B. Clarke; J. W. White; D. A. Young

1994-01-01

266

Inactivation and injury of pathogenic bacteria by hydrodynamic pressure treatment

Technology Transfer Automated Retrieval System (TEKTRAN)

Hydrodynamic pressure processing (HDP) is an innovative non-thermal technology developed for improving meat tenderness. The shock waves generated in the HDP process cause significant disruption of myofibrillar proteins in muscle tissue resulting in improved tenderness of various beef cuts. The same ...

267

A new shock-capturing numerical scheme for ideal hydrodynamics

We present a new algorithm for solving ideal relativistic hydrodynamics based on Godunov method with an exact solution of Riemann problem for an arbitrary equation of state. Standard numerical tests are executed, such as the sound wave propagation and the shock tube problem. Low numerical viscosity and high precision are attained with proper discretization.

Zuzana Feckova; Boris Tomasik

2015-01-07

268

A new shock-capturing numerical scheme for ideal hydrodynamics

We present a new algorithm for solving ideal relativistic hydrodynamics based on Godunov method with an exact solution of Riemann problem for an arbitrary equation of state. Standard numerical tests are executed, such as the sound wave propagation and the shock tube problem. Low numerical viscosity and high precision are attained with proper discretization.

Feckova, Zuzana

2015-01-01

269

Effect of hydrodynamic pressure processing on chevon quality characteristics

Technology Transfer Automated Retrieval System (TEKTRAN)

Hydrodynamic pressure processing (HDP) technology, which involves exposure of packaged meat to a supersonic shock wave under water created by a small amount of explosive, has been shown to improve meat tenderness, but its effect on chevon tenderness has not been studied so far. The objective of this...

270

Postexplosion hydrodynamics of supernovae in red supergiants

NASA Technical Reports Server (NTRS)

Shock propagation, mixing, and clumping are studied in the explosion of red supergiants as Type II supernovae using a two-dimensional smooth particle hydrodynamic (SPH) code. We show that extensive Rayleigh-Talor instabilities develop in the ejecta in the wake of the reverse shock wave. In all cases, the shell structure of the progenitor is obliterated to leave a clumpy, well-mixed supernova remnant. However, the occurrence of mass loss during the lifetime of the progenitor can significantly reduce the amount of mixing. These results are independent of the Type II supernova explosion mechanism.

Herant, Marc; Woosley, S. E.

1994-01-01

271

Fast lattice Boltzmann solver for relativistic hydrodynamics.

A lattice Boltzmann formulation for relativistic fluids is presented and numerically validated through quantitative comparison with recent hydrodynamic simulations of relativistic fluids. In order to illustrate its capability to handle complex geometries, the scheme is also applied to the case of a three-dimensional relativistic shock wave, generated by a supernova explosion, impacting on a massive interstellar cloud. This formulation opens up the possibility of exporting the proven advantages of lattice Boltzmann methods, namely, computational efficiency and easy handling of complex geometries, to the context of (mildly) relativistic fluid dynamics at large, from quark-gluon plasmas up to supernovae with relativistic outflows. PMID:20867451

Mendoza, M; Boghosian, B M; Herrmann, H J; Succi, S

2010-07-01

272

Fast Lattice Boltzmann Solver for Relativistic Hydrodynamics

NASA Astrophysics Data System (ADS)

A lattice Boltzmann formulation for relativistic fluids is presented and numerically validated through quantitative comparison with recent hydrodynamic simulations of relativistic fluids. In order to illustrate its capability to handle complex geometries, the scheme is also applied to the case of a three-dimensional relativistic shock wave, generated by a supernova explosion, impacting on a massive interstellar cloud. This formulation opens up the possibility of exporting the proven advantages of lattice Boltzmann methods, namely, computational efficiency and easy handling of complex geometries, to the context of (mildly) relativistic fluid dynamics at large, from quark-gluon plasmas up to supernovae with relativistic outflows.

Mendoza, M.; Boghosian, B. M.; Herrmann, H. J.; Succi, S.

2010-07-01

273

Newtonian hydrodynamics with general relativistic pressure

We present the general relativistic pressure correction terms in Newtonian hydrodynamic equations to the nonlinear order: these are equations (1.1)–(1.3). The derivation is made in the zero-shear gauge based on the fully nonlinear formulation of cosmological perturbation in Einstein's gravity. The correction terms differ from many of the previously suggested forms in the literature based on hand-waving manners. We confirm our results by comparing with (i) the nonlinear perturbation theory, (ii) the first order post-Newtonian approximation, and (iii) the special relativistic limit, and by checking (iv) the consistency with full Einstein's equation.

Hwang, Jai-chan [Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Noh, Hyerim, E-mail: jchan@knu.ac.kr, E-mail: hr@kasi.re.kr [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)

2013-10-01

274

Fast Lattice Boltzmann Solver for Relativistic Hydrodynamics

A lattice Boltzmann formulation for relativistic fluids is presented and numerically validated through quantitative comparison with recent hydrodynamic simulations of relativistic fluids. In order to illustrate its capability to handle complex geometries, the scheme is also applied to the case of a three-dimensional relativistic shock wave, generated by a supernova explosion, impacting on a massive interstellar cloud. This formulation opens up the possibility of exporting the proven advantages of lattice Boltzmann methods, namely, computational efficiency and easy handling of complex geometries, to the context of (mildly) relativistic fluid dynamics at large, from quark-gluon plasmas up to supernovae with relativistic outflows.

Mendoza, M.; Herrmann, H. J. [ETH Zuerich, Computational Physics for Engineering Materials, Institute for Building Materials, Schafmattstrasse 6, HIF, CH-8093 Zuerich (Switzerland); Boghosian, B. M. [Department of Mathematics, Tufts University, Bromfield-Pearson, Medford, Massachusetts 02155 (United States); Succi, S. [Istituto per le Applicazioni del Calcolo C.N.R., Via dei Taurini, 19 00185, Rome (Italy) and Freiburg Institute for Advanced Studies, Albertstrasse, 19, D-79104, Freiburg (Germany)

2010-07-02

275

Extinction of polarized light in ferrofluids with different magnetic particle concentrations

NASA Astrophysics Data System (ADS)

The magnetic field intensity and nanoparticle concentration dependence of the polarized light extinction in a ferrofluid made of magnetite particles stabilized with technical grade oleic acid dispersed in transformer oil was experimentally investigated. The magnetically induced optical anisotropy, i.e. the dichroism divided by concentration, was found to decrease with increasing sample concentration from 2% to 8%. The magnetically induced change in the optical extinction of light polarized at 54.74° with respect to the magnetic field direction was found to be positive for the less concentrated sample (2%) and negative for the samples with 4% and 8% magnetic nanoparticle concentrations, the more negative the higher the concentration and field intensity. Based on the theoretically proven fact [11] that the particle orientation mechanism has no effect on the extinction of light polarized at 54.74° with respect to the field direction, we analyzed the experimental findings in the frames of the agglomeration and long-range pair correlations theories for the magnetically induced optical anisotropy in ferrofluids. We developed a theoretical model in the approximation of single scattering for the optical extinction coefficient of a ferrofluid with magnetically induced particle agglomeration. The model predicts the existence of a polarization independent component of the optical extinction coefficient that is experimentally measurable at 54.74° polarization angle. The change in the optical extinction of light polarized at 54.74° is positive if only the formation of straight n-particle chains is considered and may become negative in the hypothesis that the longer chains degenerate to more isotropic structures (polymer-like coils, globules or bundles of chains). The model for the influence on the light absorption of the long-range pair correlations, published elsewhere, predicts that the change in the optical extinction of light polarized at 54.74° is always negative, the more negative the higher the magnetic field intensity and particle concentration.

Socoliuc, V.; Popescu, L. B.

2012-01-01

276

Hydrodynamic Simulations of Giant Impacts

NASA Astrophysics Data System (ADS)

We studied the basic numerical aspects of giant impacts using Smoothed Particles Hydrodynamics (SPH), which has been used in most of the prior studies conducted in this area (e.g., Benz, Canup). Our main goal was to modify the massive parallel, multi-stepping code GASOLINE widely used in cosmological simulations so that it can properly simulate the behavior of condensed materials such as granite or iron using the Tillotson equation of state. GASOLINE has been used to simulate hundreds of millions of particles for ideal gas physics so that using several millions of particles in condensed material simulations seems possible. In order to focus our attention of the numerical aspects of the problem we neglected the internal structure of the protoplanets and modelled them as homogenous (isothermal) granite spheres. For the energy balance we only considered PdV work and shock heating of the material during the impact (neglected cooling of the material). Starting at a low resolution of 2048 particles for the target and the impactor we run several simulations for different impact parameters and impact velocities and successfully reproduced the main features of the pioneering work of Benz from 1986. The impact sends a shock wave through both bodies heating the target and disrupting the remaining impactor. As in prior simulations material is ejected from the collision. How much, and whether it leaves the system or survives in an orbit for a longer time, depends on the initial conditions but also on resolution. Increasing the resolution (to 1.2x10? particles) results in both a much clearer shock wave and deformation of the bodies during the impact and a more compact and detailed "arm" like structure of the ejected material. Currently we are investigating some numerical issues we encountered and are implementing differentiated models, making one step closer to more realistic protoplanets in such giant impact simulations.

Reinhardt, Christian; Stadel, Joachim

2013-07-01

277

Field-Induced Columnar and Bent-Wall-Like Patterns in a Ferrofluid Emulsion

NASA Astrophysics Data System (ADS)

Using optical microscopy, we studied magnetic-field-induced structures in a confined ferrofluid emulsion. Disks, "worms" and branch-like patterns are observed in 2-D, reflecting columnar, bent-wall-like and labyrinthine structures in 3-D. These structures are controlled by varying either the thickness of the cell used to confine the sample, the particle concentration, or the rate of the magnetic field application. The induced structures are characterized by both the ratio of "worms" vs. total aggregates and the average complexity of the aggregates. "Phase" diagrams are obtained between these tuning parameters to characterize columnar to bent-wall structural transitions.

Flores, G. A.; Liu, J.; Mohebi, M.; Jamasbi, N.

278

Ag nanoplates and Fe(3)O(4) nanoparticle-based ferrofluids were utilized to fabricate a magnetic field controlled optic switch. The changing of light transmittance (LT) is caused by the rotation of Ag nanoplates, whose long axis always follows the orientation of external magnetic field to minimize the potential energy. The sensitivity of switching was optimized by choosing Ag nanoplates with appropriate size and concentration. The switching of transmission is proved to be fast and fully reversible. This phenomenon not only indicates an effective method to adjust the propagation of optical signals, but also reveals the possibility and great potential to develop magnetic controlled functional devices. PMID:22873949

Mao, Yiwu; Liu, Jing; Ge, Jianping

2012-09-11

279

EUNHA: a New Cosmological Hydrodynamic Simulation Code

NASA Astrophysics Data System (ADS)

We develop a parallel cosmological hydrodynamic simulation code designed for the study of formation and evolution of cosmological structures. The gravitational force is calculated using the TreePM method and the hydrodynamics is implemented based on the smoothed particle hydrodynamics. The initial displacement and velocity of simulation particles are calculated according to second-order Lagrangian perturbation theory using the power spectra of dark matter and baryonic matter. The initial background temperature is given by Recfast and the temperature fluctuations at the initial particle position are assigned according to the adiabatic model. We use a time-limiter scheme over the individual time steps to capture shock-fronts and to ease the time-step tension between the shock and preshock particles. We also include the astrophysical gas processes of radiative heating/cooling, star formation, metal enrichment, and supernova feedback. We test the code in several standard cases such as one-dimensional Riemann problems, Kelvin-Helmholtz, and Sedov blast wave instability. Star formation on the galactic disk is investigated to check whether the Schmidt-Kennicutt relation is properly recovered. We also study global star formation history at different simulation resolutions and compare them with observations.

Shin, Jihye; Kim, Juhan; Kim, Sungsoo S.; Park, Changbom

2014-06-01

280

Modeling multiphase flow using fluctuating hydrodynamics.

Fluctuating hydrodynamics provides a model for fluids at mesoscopic scales where thermal fluctuations can have a significant impact on the behavior of the system. Here we investigate a model for fluctuating hydrodynamics of a single-component, multiphase flow in the neighborhood of the critical point. The system is modeled using a compressible flow formulation with a van der Waals equation of state, incorporating a Korteweg stress term to treat interfacial tension. We present a numerical algorithm for modeling this system based on an extension of algorithms developed for fluctuating hydrodynamics for ideal fluids. The scheme is validated by comparison of measured structure factors and capillary wave spectra with equilibrium theory. We also present several nonequilibrium examples to illustrate the capability of the algorithm to model multiphase fluid phenomena in a neighborhood of the critical point. These examples include a study of the impact of fluctuations on the spinodal decomposition following a rapid quench, as well as the piston effect in a cavity with supercooled walls. The conclusion in both cases is that thermal fluctuations affect the size and growth of the domains in off-critical quenches. PMID:25314536

Chaudhri, Anuj; Bell, John B; Garcia, Alejandro L; Donev, Aleksandar

2014-09-01

281

Modeling multiphase flow using fluctuating hydrodynamics

NASA Astrophysics Data System (ADS)

Fluctuating hydrodynamics provides a model for fluids at mesoscopic scales where thermal fluctuations can have a significant impact on the behavior of the system. Here we investigate a model for fluctuating hydrodynamics of a single-component, multiphase flow in the neighborhood of the critical point. The system is modeled using a compressible flow formulation with a van der Waals equation of state, incorporating a Korteweg stress term to treat interfacial tension. We present a numerical algorithm for modeling this system based on an extension of algorithms developed for fluctuating hydrodynamics for ideal fluids. The scheme is validated by comparison of measured structure factors and capillary wave spectra with equilibrium theory. We also present several nonequilibrium examples to illustrate the capability of the algorithm to model multiphase fluid phenomena in a neighborhood of the critical point. These examples include a study of the impact of fluctuations on the spinodal decomposition following a rapid quench, as well as the piston effect in a cavity with supercooled walls. The conclusion in both cases is that thermal fluctuations affect the size and growth of the domains in off-critical quenches.

Chaudhri, Anuj; Bell, John B.; Garcia, Alejandro L.; Donev, Aleksandar

2014-09-01

282

Incompressible smoothed particle hydrodynamics

We present a smoothed particle hydrodynamic model for incompressible fluids. As opposed to solving a pressure Poisson equation in order to get a divergence-free velocity field, here incompressibility is achieved by requiring as a kinematic constraint that the volume of the fluid particles is constant. We use Lagrangian multipliers to enforce this restriction. These Lagrange multipliers play the role of non-thermodynamic pressures whose actual values are fixed through the kinematic restriction. We use the SHAKE methodology familiar in constrained molecular dynamics as an efficient method for finding the non-thermodynamic pressure satisfying the constraints. The model is tested for several flow configurations.

Ellero, Marco [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Lehrstuhl fuer Aerodynamik, Technische Universitaet Muenchen, 85748 Garching (Germany)], E-mail: marco.ellero@aer.mw.tum.de; Serrano, Mar; Espanol, Pep [Departamento de Fisica Fundamental, UNED, Apartado 60141, 28080 Madrid (Spain)

2007-10-01

283

Generalized Burnett Hydrodynamics

NASA Astrophysics Data System (ADS)

Equations of hydrodynamics (derived from the Boltzmann equation) beyond the Navier-Stokes level are studied by a method proposed earlier by the author. The main question we consider is the following: What is the most natural replacement for classical (ill-posed) Burnett equations? It is shown that, in some sense, it is a two-parameter set of Generalized Burnett Equations (GBEs) derived in this paper. Some equations of this class are even simpler than original Burnett equations. The region of stability in the space of parameters and other properties of GBEs are discussed.

Bobylev, A. V.

2008-08-01

284

Radiation Hydrodynamics in Supernovae

NASA Astrophysics Data System (ADS)

We discuss the current status of our hydrodynamical radiation (HYDRA) code for rapidly expanding, low-density envelopes commonly found in core collapse and thermonuclear supernovae. In supernovae, one of the main issues is the coupling between a radiation field and properties of the matter. Due to the low densities, nonthermal excitation by high-energy photons from radioactive decays and the time dependence of the problem, significant departures from local thermodynamical equilibrium (LTE) are common throughout the envelope even at large optical depths. This effect must be taken into account to simulate the evolution of spectra and light curves which are the basic tools to link between explosion physics and observations.

Höflich, Peter

2005-07-01

285

A simple and low-cost colorimetric assay utilizing ferrofluidic nanoparticulate probes (FNPs) and a ligase for single-nucleotide polymorphism genotyping is described. Excellent sensitivity and selectivity were accomplished through the engagement of the FNPs and a ligase chain reaction. PMID:23923128

Shen, Wei; Lim, Cai Le; Gao, Zhiqiang

2013-09-21

286

A horizontal ferrofluid layer is submitted to a lateral heating and to a strong oblique magnetic field. The problem, combining the momentum and heat balance equations with the Maxwell equations, introduces two Rayleigh numbers, Ra the gravitational one and Ram the magnetic one, to represent the buoyancy and the Kelvin forces, which induce motion, versus the momentum viscous diffusion and

M. Hennenberg; B. Weyssow; S. Slavtchev; Th. Desaive; B. Scheid

2006-01-01

287

permanent magnet or electromagnet will always attract a magnetic fluid. For this reason it is difficult the magnets actuate the ferrofluid, and it also corrects for electromagnet charging time delays of four electromagnets at a distance R. Probst, J. Lin, A. Komaee, A. Nacev, Z. Cummins, B. Shapiro n

Shapiro, Benjamin

288

Ferrofluid flow in cylindrical and annular geometries under the influence of a uniform rotating magnetic field was studied experimentally using aqueous ferrofluids consisting of low concentrations (<0.01 v/v) of cobalt ferrite nanoparticles with Brownian relaxation to test the ferrohydrodynamic equations, elucidate the existence of couple stresses, and determine the value of the spin viscosity in these fluids. An ultrasound technique was used to measure bulk velocity profiles in the spin-up (cylindrical) and annular geometries, varying the intensity and frequency of the rotating magnetic field generated by a two pole stator winding. Additionally, torque measurements in the cylindrical geometry were made. Results show rigid-body like velocity profiles in the bulk, and no dependence on the axial direction. Experimental velocity profiles were in quantitative agreement with the predictions of the spin diffusion theory, with a value of the spin viscosity of ?10{sup ?8} kg m/s, two orders of magnitude larger than the value estimated earlier for iron oxide based ferrofluids, and 12 orders of magnitude larger than estimated using dimensional arguments valid in the infinite dilution limit. These results provide further evidence of the existence of couple stresses in ferrofluids and their role in driving the spin-up flow phenomenon.

Torres-Diaz, I.; Cortes, A.; Rinaldi, C., E-mail: carlos.rinaldi@bme.ufl.edu [Department of Chemical Engineering, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9000 (United States); Cedeño-Mattei, Y. [Department of Chemistry, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9019 (United States)] [Department of Chemistry, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9019 (United States); Perales-Perez, O. [Department of Engineering Science and Materials, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9044 (United States)] [Department of Engineering Science and Materials, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9044 (United States)

2014-01-15

289

Load responsive hydrodynamic bearing

A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.

Kalsi, Manmohan S. (Houston, TX); Somogyi, Dezso (Sugar Land, TX); Dietle, Lannie L. (Stafford, TX)

2002-01-01

290

Landau hydrodynamics reexamined

We review the formulation of Landau hydrodynamics and find that the rapidity distribution of produced particles in the center-of-mass system should be more appropriately modified as dN/dy{proportional_to}exp({radical}(y{sub b}{sup 2}-y{sup 2})), where y{sub b}=ln({radical}(s{sub NN})/m{sub p}) is the beam nucleon rapidity, instead of Landau's original distribution, dN/dy(Landau){proportional_to}exp({radical}(L{sup 2}-y{sup 2})), where L=ln({radical}(s{sub NN})/2m{sub p}). The modified distribution agrees better with experimental dN/dy data than the original Landau distribution and can be represented well by the Gaussian distribution, dN/dy(Gaussian){proportional_to}exp(-y{sup 2}/2L). Past successes of the Gaussian distribution in explaining experimental rapidity data can be understood, not because it is an approximation of the original Landau distribution, but because it is in fact a close representation of the modified distribution. Predictions for pp and AA collisions at LHC energies in Landau hydrodynamics are presented.

Wong, Cheuk-Yin [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

2008-11-15

291

In the present study, the permeability of 11 different iron oxide nanoparticle (IONP) samples (eight fluids and three powders) was determined using an in vitro blood–brain barrier model. Importantly, the results showed that the ferrofluid formulations were statistically more permeable than the IONP powder formulations at the blood–brain barrier, suggesting a role for the presently studied in situ synthesized ferrofluid formulations using poly(vinyl) alcohol, bovine serum albumin, collagen, glutamic acid, graphene, and their combinations as materials which can cross the blood–brain barrier to deliver drugs or have other neurological therapeutic efficacy. Conversely, the results showed the least permeability across the blood–brain barrier for the IONP with collagen formulation, suggesting a role as a magnetic resonance imaging contrast agent but limiting IONP passage across the blood–brain barrier. Further analysis of the data yielded several trends of note, with little correlation between permeability and fluid zeta potential, but a larger correlation between permeability and fluid particle size (with the smaller particle sizes having larger permeability). Such results lay the foundation for simple modification of iron oxide nanoparticle formulations to either promote or inhibit passage across the blood–brain barrier, and deserve further investigation for a wide range of applications. PMID:23426527

Hoff, Dan; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

2013-01-01

292

In the present study, the permeability of 11 different iron oxide nanoparticle (IONP) samples (eight fluids and three powders) was determined using an in vitro blood-brain barrier model. Importantly, the results showed that the ferrofluid formulations were statistically more permeable than the IONP powder formulations at the blood-brain barrier, suggesting a role for the presently studied in situ synthesized ferrofluid formulations using poly(vinyl) alcohol, bovine serum albumin, collagen, glutamic acid, graphene, and their combinations as materials which can cross the blood-brain barrier to deliver drugs or have other neurological therapeutic efficacy. Conversely, the results showed the least permeability across the blood-brain barrier for the IONP with collagen formulation, suggesting a role as a magnetic resonance imaging contrast agent but limiting IONP passage across the blood-brain barrier. Further analysis of the data yielded several trends of note, with little correlation between permeability and fluid zeta potential, but a larger correlation between permeability and fluid particle size (with the smaller particle sizes having larger permeability). Such results lay the foundation for simple modification of iron oxide nanoparticle formulations to either promote or inhibit passage across the blood-brain barrier, and deserve further investigation for a wide range of applications. PMID:23426527

Hoff, Dan; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

2013-01-01

293

Protein-polymer functionalized aqueous ferrofluids showing high T2 relaxivity.

Controlled size, shape and dispersibility of superparamagnetic iron oxide nanoparticles (SPIONs), has been achieved in a protein-polymer colloidal dispersion. Stable ferrofluid (FF) is synthesized in an aqueous medium of collagen, bovine serum albumin and poly(vinyl) alcohol that equilibrates with time, at ambient conditions, into an organized matrix with iron oxide particles sterically caged at defined sites. It mimics a biomineralization system; hence the process is termed biomimetics. Though the exact mechanism is not understood at this stage, we have established, with serial dilution of the protein-polymer solution that the SPIONs are formed inside the self-contained clusters of the two proteins and the polymer, which show a tendency to self assemble. More than the interparticle dipolar attractions of magnetic particles, electrostatic interactions play a role in cluster formation and collagen is responsible for the overall stability, supported by systematic dynamic light scattering data. The basic aim of this study was to increase magnetization of a previously synthesized ferrofluid without hampering stability, by reducing the total macromolecular concentration. Thrice the magnetization was achieved and in addition, the synthesized FFs exhibited very high transverse relaxivity and showed good contrast in mice liver, in the in vivo studies. PMID:24734534

Bhattacharya, S; Sheikh, L; Tiwari, V; Ghosh, M; Patel, J N; Patel, A B; Nayar, S

2014-05-01

294

We review the use of Monte Carlo simulations in the description of magnetic nanoparticles dispersed in a liquid carrier. Our main focus is the use of theory and simulation as tools for the description of the properties of ferrofluids. In particular, we report on the influence of polydispersity and short-range interaction on the self-organization of nanoparticles. Such contributions are shown to be extremely important for systems characterized by particles with diameters smaller than 10nm. A new 3D polydisperse Monte Carlo implementation for biocompatible magnetic colloids is proposed. As an example, theoretical and simulation results for an ionic-surfacted ferrofluid dispersed in a NaCl solution are directly compared to experimental data (transmission electron microscopy - TEM, magneto-transmissivity, and electron magnetic resonance - EMR). Our combined theoretical and experimental results suggest that during the aging process two possible mechanisms are likely to be observed: the nanoparticle's grafting decreases due to aggregate formation and the Hamaker constant increases due to oxidation. In addition, we also briefly discuss theoretical agglomerate formation models and compare them to experimental data. PMID:23360743

Bakuzis, Andris Figueiroa; Branquinho, Luis César; e Castro, Leonardo Luiz; e Eloi, Marcos Tiago de Amaral; Miotto, Ronei

2013-05-01

295

Probing of field-induced structures and their dynamics in ferrofluids using oscillatory rheology.

We probe field-induced structures and their dynamics in ferrofluids using oscillatory rheology. The magnetic field dependence of the relaxation time and crossover modulus showed two distinct regions, indicating the different microstructures in those regions. The observed relaxation at various magnetic field strengths indicates that side chains are attached to the pinned single-sphere-width chains between the rheometer plates. Our results suggest that the ferrofluid under a magnetic field exhibits a soft solidlike behavior whose relaxation is governed by the imposed strain rate and the magnetic field. Using the scaling factors obtained from the frequency and modulus at the crossover point in the oscillatory rheological measurements, the constant strain-rate frequency sweep data is superimposed onto a single master curve. The frequency scaling factor increases with the strain rate as a power law with an exponent close to unity, whereas the amplitude scaling factor is almost strain-rate-independent at high magnetic field strengths. These findings are useful for a better understanding of field-induced ordering of nanoparticles in fluids and their optimization for practical applications. PMID:25268053

Felicia, Leona J; Philip, John

2014-10-21

296

Ferrofluid based dispersive-solid phase extraction for spectrophotometric determination of dyes.

For the first time, ferrofluid based dispersive-solid phase extraction (D-SPE) has been applied for determination of trace levels of dyes in aqueous and fish samples. The contaminant used as a model compound was crystal violet (CV), a cationic dye, and was preconcentrated without any derivatization or ion-pair formation. The method is based on rapid injection of ferrofluid into the aqueous sample by a syringe. The sample preparation time is decreased by the fact that the sorbent dispersed in the bulk solution and extraction can be achieved very fast. In this way, the separation of sorbent from the aqueous bulk was achieved by a magnet, and no centrifugation is required. These significant features which obtained with this method are of key interest for routine trace laboratory analysis. The influence of different variables on D-SPE was investigated. Under optimum conditions, the calibration graph was linear over the range of 3.3-90 ?g L(-1), and the enrichment factor (EF) 267 was obtained. Detection limit was 1.51 ?g L(-1) (n=7), and the relative standard deviation of 5.6% at 50 ng mL(-1) was obtained (n=7). The proposed method was successfully applied for the determination of crystal violet in various samples. PMID:23849184

Davudabadi Farahani, Malihe; Shemirani, Farzaneh

2013-10-01

297

Hydrodynamic effects in the atmosphere of variable stars

NASA Technical Reports Server (NTRS)

Numerical models of variable stars are established, using a nonlinear radiative transfer coupled hydrodynamics code. The variable Eddington method of radiative transfer is used. Comparisons are for models of W Virginis, beta Doradus, and eta Aquilae. From these models it appears that shocks are formed in the atmospheres of classical Cepheids as well as W Virginis stars. In classical Cepheids, with periods from 7 to 10 days, the bumps occurring in the light and velocity curves appear as the result of a compression wave that reflects from the star's center. At the head of the outward going compression wave, shocks form in the atmosphere. Comparisons between the hydrodynamic motions in W Virginis and classical Cepheids are made. The strong shocks in W Virginis do not penetrate into the interior as do the compression waves formed in classical Cepheids. The shocks formed in W Virginis stars cause emission lines, while in classical Cepheids the shocks are weaker.

Davis, C. G., Jr.; Bunker, S. S.

1975-01-01

298

Active Carbon and Oxygen Shell Burning Hydrodynamics

We have simulated 2.5$\\times10^3$ s of the late evolution of a $23 \\rm M_\\odot$ star with full hydrodynamic behavior. We present the first simulations of a multiple-shell burning epoch, including the concurrent evolution and interaction of an oxygen and carbon burning shell. In addition, we have evolved a 3D model of the oxygen burning shell to sufficiently long times (300 s) to begin to assess the adequacy of the 2D approximation. We summarize striking new results: (1) strong interactions occur between active carbon and oxygen burning shells, (2) hydrodynamic wave motions in nonconvective regions, generated at the convective-radiative boundaries, are energetically important in both 2D and 3D with important consequences for compositional mixing, and (3) a spectrum of mixed p- and g-modes are unambiguously identified with corresponding adiabatic waves in these computational domains. We find that 2D convective motions are exaggerated relative to 3D because of vortex instability in 3D. We discuss the implications for supernova progenitor evolution and symmetry breaking in core collapse.

Casey Meakin; David Arnett

2006-01-16

299

Analytical solutions of Landau (1+1)-dimensional hydrodynamics

NASA Astrophysics Data System (ADS)

To help guide our intuition, summarize important features, and point out essential elements, we review the analytical solutions of Landau (1+1)-dimensional hydrodynamics and discuss the full evolution of the dynamics from the very beginning. Special emphasis is placed on the matching and the interplay between the Khalatnikov solution and the Riemann simple wave solution, at the earliest times and in the edge regions at later times. These analytical solutions collected and developed here serve well as a useful guide and cross-check in the development of complicated numerically intensive relativistic hydrodynamical Monte Carlo simulations.

Wong, Cheuk-Yin; Sen, Abhisek; Gerhard, Jochen; Torrieri, Giorgio; Read, Kenneth

2014-12-01

300

Central Amazon Floodplain Hydrodynamics

NASA Astrophysics Data System (ADS)

Amazon floodplain wetlands contain high biological diversity for which the flow regime, particularly the flood-pulse, provides the driving force. Surface water flow is recognized as the key factor in the establishment and maintenance of wetland ecosystems and their functioning, exerting a strong control on channel formation and determining the spatial and temporal complexity of wetland habitats. However, the hydrodynamics of seasonally flooded wetlands in the Amazon basin remains poorly quantified through ground observations, satellite observations or modelling. In this research, fieldwork was conducted between March and August 2012 for 850 km^{2} of várzea floodplain to the south of a 75 km reach of the Rio Solimões, downstream (east) of the confluence with the Rio Purus. The primary aim of this was to collect ground-based measurements of surface water flows from mid-rising, through high-water to mid-falling flood conditions to allow a detailed picture of floodplain hydrodynamics to be constructed. Four 10-day periods of fieldwork were completed, during which measurements were taken at 42 locations along the floodplain channel network and in floodplain lakes, together with main channel measurements on the Solimões and Purus. Measurements were obtained of: (i) flow rates along floodplain channels, using an Acoustic Current Doppler Profiler (ADCP); (ii) runoff from terra firma via measurement of flows out of ria lakes at the southern edge of the floodplain; (iii) water conductivity; and (iv) suspended sediment concentrations. Overbank flow rates from the Rio Solimões and Rio Purus into the floodplain forest were also obtained using a current meter at several locations during high water. In addition, floodplain channel and lake depths were obtained using continuous recording of sonar connected to a Global Positioning System, enabling the estimation of bathymetry. Using these measurements, detailed hydrodynamic maps of the floodplain were produced from mid-rising to mid-falling flood stages. Initial results show that floodplain channels play an important role in floodplain hydrodynamics, carrying the bulk of flood water into the floodplain during rising water. Once main-channel water levels are above-bankfull, overbank flow directly into the floodplain forest becomes significant. At high-water, the flow rate out of the Purus along the major floodplain channel was 2,200 m^{3}s^{-1}, representing around 10% of the total Purus channel flow ( 23,000 m^{3}s^{-1} at Beruri). In addition, an estimated 2,000 - 4,000 m^{3}s^{-1} of overbank flow occurred from the lower Purus into the floodplain. Floodplain channel flow from the Solimões was less significant than from the Purus at less than 1,000 m^{3}s^{-1}, under 1% of Solimões channel flow ( 116,000 m^{3}s^{-1} upstream of the Purus); however overbank flow into the floodplain forest may have been as much as 10,000 m^{3}s^{-1} along the study reach. Terra firma runoff, measured at the outflows of ria lakes, contributed an insignificant amount of flow during the measurement periods. The first-order estimate of flow through the floodplain area during high water was 15,000 to 17,000 m^{3}s^{-1} (an average of 17.6 to 20.0 m^{3}s^{-1} per km^{2}), with 30-40% of the flow contributed by the Purus.

Wilson, M. D.; Vega, M. C.; Forsberg, B. R.

2012-12-01

301

Hydrodynamics of periodic breathers.

We report the first experimental observation of periodic breathers in water waves. One of them is Kuznetsov-Ma soliton and another one is Akhmediev breather. Each of them is a localized solution of the nonlinear Schrödinger equation (NLS) on a constant background. The difference is in localization which is either in time or in space. The experiments conducted in a water wave flume show results that are in good agreement with the NLS theory. Basic features of the breathers that include the maximal amplitudes and spectra are consistent with the theoretical predictions. PMID:25246673

Chabchoub, A; Kibler, B; Dudley, J M; Akhmediev, N

2014-10-28

302

Anisotropic hydrodynamics: Motivation and methodology

NASA Astrophysics Data System (ADS)

In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can be made around an anisotropic background, and the resulting dynamical framework has been dubbed “anisotropic hydrodynamics”. I also discuss expectations for the degree of momentum-space anisotropy of the quark-gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches.

Strickland, Michael

2014-06-01

303

NASA Astrophysics Data System (ADS)

Microfluidic networks and microporous materials have long been of interest in areas such as hydrology, petroleum engineering, chemical and electrochemical engineering, medicine and biochemical engineering. With the emergence of new processes in gas separation, cell sorting, ultrafiltration, and advanced materials synthesis, the importance of building a better qualitative and quantitative understanding of these key technologies has become apparent. However, microfluidic measurement and theory is still relatively underdeveloped, presenting a significant obstacle to the systematic design of microfluidic devices and materials. Theoretical challenges arise from the breakdown of classical viscous flow models as the flow dimensions approach the mean free path of individual molecules. Experimental challenges arise from the lack of flow profilometry techniques at sub-micron length scales. Here we present an extension of scanning probe microscopy techniques, which we have termed Hydrodynamic Force Microscopy (HFM). HFM exploits fluid drag to profile microflows and to map the permeability of microporous materials. In this technique, an atomic force microscope (AFM) cantilever is scanned close to a microporous sample surface. The hydrodynamic interactions arising from a pressure-driven flow through the sample are then detected by mapping the deflection of an AFM cantilever. For gas flows at atmospheric pressure, HFM has been shown to achieve a velocity sensitivity of 1 cm/s with a spatial resolution of ˜ 10 nm. This compares very favorably to established techniques such as hot-wire and laser Doppler anemometry, whose spatial resolutions typically exceed 1 mum and which may rely on the use of tracer particles or flow markers1. We demonstrate that HFM can successfully profile Poiseuille flows inside pores as small as 100 nm and can distinguish Poiseuille flow from uniform flow for short entry lengths. HFM detection of fluid jets escaping from porous samples can also reveal a "permeability map" of a sample's pore structure, allowing us to distinguish between clear and blocked pores, even in cases where the subsurface fouling is undetectable by conventional AFM. The experimental data is discussed in context with theoretical aspects of HFM microflow measurement and practical limits of this technique. Finally, we conclude with variations of standard HFM techniques that show some promise for investigation of smaller nanometer-scale flows of gases and liquids.

Ulrich, Elaine Schmid

304

Advanced in Macrostatistical Hydrodynamics

An overview is presented of research that focuses on slow flows of suspensions in which colloidal and inertial effects are negligibly small (Macrostatistical Hydrodynamics). First, we describe nuclear magnetic resonance imaging experiments to quantitatively measure particle migration occurring in concentrated suspensions undergoing a flow with a nonuniform shear rate. These experiments address the issue of how the flow field affects the microstructure of suspensions. In order to understand the local viscosity in a suspension with such a flow-induced, spatially varying concentration, one must know how the viscosity of a homogeneous suspension depends on such variables as solids concentration and particle orientation. We suggest the technique of falling ball viscometry, using small balls, as a method to determine the effective viscosity of a suspension without affecting the original microstructure significantly. We also describe data from experiments in which the detailed fluctuations of a falling ball`s velocity indicate the noncontinuum nature of the suspension and may lead to more insights into the effects of suspension microstructure on macroscopic properties. Finally, we briefly describe other experiments that can be performed in quiescent suspensions (in contrast to the use of conventional shear rotational viscometers) in order to learn more about the microstructure and boundary effects in concentrated suspensions.

Graham, A.L.; Tetlow, N.; Abbott, J.R. [Los Alamos National Lab., NM (United States); Mondy, L.S. [Sandia National Labs., Albuquerque, NM (United States); Brenner, H. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemical Engineering

1993-08-01

305

Hydrodynamics of Holographic Superconductors

We study the poles of the retarded Green functions of a holographic superconductor. The model shows a second order phase transition where a charged scalar operator condenses and a U(1) symmetry is spontaneously broken. The poles of the holographic Green functions are the quasinormal modes in an AdS black hole background. We study the spectrum of quasinormal frequencies in the broken phase, where we establish the appearance of a massless or hydrodynamic mode at the critical temperature as expected for a second order phase transition. In the broken phase we find the pole representing second sound. We compute the speed of second sound and its attenuation length as function of the temperature. In addition we find a pseudo diffusion mode, whose frequencies are purely imaginary but with a non-zero gap at zero momentum. This gap goes to zero at the critical temperature. As a technical side result we explain how to calculate holographic Green functions and their quasinormal modes for a set of operators that mix under the RG flow.

Irene Amado; Matthias Kaminski; Karl Landsteiner

2009-06-17

306

Hydrodynamics of Holographic Superconductors

We study the poles of the retarded Green functions of a holographic superconductor. The model shows a second order phase transition where a charged scalar operator condenses and a U(1) symmetry is spontaneously broken. The poles of the holographic Green functions are the quasinormal modes in an AdS black hole background. We study the spectrum of quasinormal frequencies in the broken phase, where we establish the appearance of a massless or hydrodynamic mode at the critical temperature as expected for a second order phase transition. In the broken phase we find the pole representing second sound. We compute the speed of second sound and its attenuation length as function of the temperature. In addition we find a pseudo diffusion mode, whose frequencies are purely imaginary but with a non-zero gap at zero momentum. This gap goes to zero at the critical temperature. As a technical side result we explain how to calculate holographic Green functions and their quasinormal modes for a set of operators that mix under...

Amado, Irene; Landsteiner, Karl

2009-01-01

307

Hydrodynamics of micropipette aspiration.

The dynamics of human neutrophils during micropipette aspiration are frequently analyzed by approximating these cells as simple slippery droplets of viscous fluid. Here, we present computations that reveal the detailed predictions of the simplest and most idealized case of such a scheme; namely, the case where the fluid of the droplet is homogeneous and Newtonian, and the surface tension of the droplet is constant. We have investigated the behavior of this model as a function of surface tension, droplet radius, viscosity, aspiration pressure, and pipette radius. In addition, we have tabulated a dimensionless factor, M, which can be utilized to calculate the apparent viscosity of the slippery droplet. Computations were carried out using a low Reynolds number hydrodynamics transport code based on the finite-element method. Although idealized and simplistic, we find that the slippery droplet model predicts many observed features of neutrophil aspiration. However, there are certain features that are not observed in neutrophils. In particular, the model predicts dilation of the membrane past the point of being continuous, as well as a reentrant jet at high aspiration pressures. PMID:9876128

Drury, J L; Dembo, M

1999-01-01

308

Onset of superradiant instabilities in the hydrodynamic vortex model

The hydrodynamic vortex, an effective spacetime geometry for propagating sound waves, is studied analytically. In contrast with the familiar Kerr black-hole spacetime, the hydrodynamic vortex model is described by an effective acoustic geometry which has no horizons. However, this acoustic spacetime possesses an ergoregion, a property which it shares with the rotating Kerr spacetime. It has recently been shown numerically that this physical system is linearly unstable due to the superradiant scattering of sound waves in the ergoregion of the effective spacetime. In the present study we use analytical tools in order to explore the onset of these superradiant instabilities which characterize the effective spacetime geometry. In particular, we derive a simple analytical formula which describes the physical properties of the hydrodynamic vortex system in its critical (marginally-stable) state, the state which marks the boundary between stable and unstable fluid configurations. The analytically derived formula is shown to agree with the recently published numerical data for the hydrodynamic vortex system.

Shahar Hod

2014-07-30

309

Effect of dimerization on the field-induced birefringence in ferrofluids.

The magnetic-field-induced birefringence in a ferrofluid composed of spherical cobalt nanoparticles has been studied both experimentally and theoretically. The considerable induced birefringence determined experimentally has been attributed to the formation of chains of nanoparticles. The birefringence has been measured as a function of the external magnetic field and the volume fraction (f) of nanoparticles. It is quadratic in f as opposed to the Faraday effect, which is linear in f. Experimental results agree well with the theoretical model based on a simple density functional approach. For dilute solutions the experimental results can be explained by assuming that only dimers of nanoparticles are formed while the concentration of longer chains is negligible. PMID:23848690

Szczytko, Jacek; Vaupoti?, Nataša; Osipov, Mihail A; Madrak, Karolina; Górecka, Ewa

2013-06-01

310

Properties of ferrofluid bilayer (modeled as a system of two planar layers separated by a distance h and each layer carrying a soft sphere dipolar liquid) are calculated in the framework of inhomogeneous Ornstein-Zernike equations with reference hypernetted chain closure (RHNC). The bridge functions are taken from a soft sphere (1/r(12)) reference system in the pressure-consistent closure approximation. In order to make the RHNC problem tractable, the angular dependence of the correlation functions is expanded into special orthogonal polynomials according to Lado. The resulting equations are solved using the Newton-GRMES algorithm as implemented in the public-domain solver NITSOL. Orientational densities and pair distribution functions of dipoles are compared with Monte Carlo simulation results. A numerical algorithm for the Fourier-Hankel transform of any positive integer order on a uniform grid is presented. PMID:25173007

Polyakov, Evgeny A; Vorontsov-Velyaminov, Pavel N

2014-08-28

311

We have studied the dynamic behavior of nanoparticles in ferrofluids consisting of single-domain, biogenic magnetite (Fe(3)O(4)) isolated from Magnetospirillum magnetotacticum (MS-1). Although dipolar chains form in magnetic colloids in zero applied field, when dried upon substrates, the solvent front disorders nanoparticle aggregation. Using avidin-biotin functionalization of the particles and substrate, we generated self-assembled, linear chain motifs that resist solvent front disruption in zero-field. The engineered self-assembly process we describe here provides an approach for the creation of ordered magnetic structures that could impact fields ranging from micro-electro-mechanical systems development to magnetic imaging of biological structures. PMID:22952408

Ruder, Warren C; Hsu, Chia-Pei D; Edelman, Brent D; Schwartz, Russell; Leduc, Philip R

2012-08-01

312

In this study, the composite magnetic nanoparticles of coated SiO nano film with about 8 nm size and high saturation magnetization value, were synthesized by liquid phase precipitation method. The magnetic nanoparticles can be dispersed in various liquid media, widely known as magnetic fluids or ferrofluids with both magnetic and liquid properties. The materials been collected great interests and more and more attentions to focus into Drug Delivery System (DDS) as a new technology in this paper. We use the composite nanoparticles to disperse H2O and inject the solutions into rat's in-vivo organs. And, in the experiments by using a strong photon beam of SPring-8 Synchrotron Radiation facility, the distribution stat and the effects of magnetic field as well as drug delivery behaviour of nanoparticles in the rat' kidney are verified by the in-vivo observations. PMID:22400252

Ju, D Y; Bian, P; Kumazawa, T; Nakano, M; Matsuura, H; Umetani, K; Komdo, T; Uozumi, Y; Makino, K; Noda, N; Koide, K; Akutsu, M; Masuyama, K

2011-10-01

313

Non-isothermal separation of ferrofluid particles through grids: Abnormal magnetic Soret effect

NASA Astrophysics Data System (ADS)

Nanoparticle transport through thin non-isothermal ferrofluid layer between permeable walls is investigated. The transient mass flux is determined from measurements of particle concentration changes in two fluid chambers of different temperatures which are attached on both sides of the layer. Experiments are performed employing fluid samples of small ordinary magnetic Soret effect, which is detected by thermal grating technique. The separation measurements say that a magnetic field, aligned along a temperature gradient, causes a remarkable increase in the mass diffusion coefficient and a simultaneous decrease in particle thermodiffusion mobility. It is proposed that the observed effects may be evoked by specific microconvective mass transfer induced by nonmagnetic grid elements of the permeable walls.

Blums, Elmars; Sints, Viesturs; Kronkalns, Gunars; Mezulis, Ansis

2013-04-01

314

Drag enhancement due to macro-chains in uniformly magnetized ferrofluids

NASA Astrophysics Data System (ADS)

We report on experiments and simulations performed on small non-magnetic glass balls and nearly spherical gas bubbles moving through a uniformly magnetized ferrofluid. Use of the Advanced Photon Source X-ray beamline at Argonne National Laboratory permitted sufficient spatial and temporal resolution to accurately track the dynamics of these 500 ?m diameter spheres simultaneously with an array of magnetic particle macro-chains —agglomerations each of several mm long and 4-20 ?m thick. The enhanced drag induced by the macro-chains is substantial: we infer viscosity coefficients up to four times larger than for unmagnetized fluid. We provide direct visualization of a possible mechanism by which macro-chains mechanically impede the transverse motion of spheres, enhancing the drag and effecting an anisotropic viscosity. Direct numerical simulations of spheres falling through magnetic fluid can reproduce the observed dynamics by means of a phenomenological magnetization-dependent viscosity model with one free parameter.

Yecko, Philip; Lee, Wah-Keat; David Trubatch, A.; Vieira, Matthew

2011-05-01

315

X-ray microtomography of field-induced macro-structures in a ferrofluid.

X-ray microtomography is used to visualize, in-situ, the three-dimensional nature of the magnetic field induced macro-structures (>1 ?m) inside a bulk (not, vert, similar1 mm diameter) magnetite-particle-mineral oil ferrofluid sample. Columnar structures of not, vert, similar10 ?m diameter were seen under a 0.35 kG applied magnetic field, while labyrinth type structures not, vert, similar4 ?m in width were seen at 0.55 kG. The structures have height/width aspect ratios >100. The results show that the magnetite volume fraction is not constant within the structures and on average is considerably less than a random sphere packing model.

Lee, W.; X-Ray Science Division

2010-09-01

316

The anisotropy of the magnetoviscous effect of a ferrofluid has been studied in a specially designed slit die viscometer, which allows three distinct orientations of the magnetic field with respect to the fluid flow. The corresponding Miesowicz viscosity coefficients were determined in dependence of the shear rate and the magnetic field intensity to gain a comprehensive magnetorheological characterization of the fluid. The particles in the fluid have a mean diameter of 13 nm corresponding to an interaction parameter of ? ? 1.3 for magnetite. Thus, the fluid can be expected to show a transition from non-interacting individual particles to microstructures with chain-like associated particles when the magnetic field intensity is increased and the shear rate is decreased. The observed field and shear dependent anisotropy of the magnetoviscous effect is explained coherently in terms of these microstructural changes in the fluid. PMID:25837303

Linke, J M; Odenbach, S

2015-05-01

317

Low frequency swash motion induced by wave grouping

This paper concerns the low frequency motion of swash directly induced by wave grouping on a steep beach. A new experimental investigation is presented which considers the hydrodynamics of the inner surf zone and swash zone using vertical wave gauges and a run-up wire. Results for regular waves, wave groups and random waves are discussed, with particular reference to low

T. E. Baldock; P. Holmes; D. P. Horn

1997-01-01

318

Triangle Anomalies, Thermodynamics, and Hydrodynamics

We consider 3+1-dimensional fluids with U(1)^3 anomalies. We use Ward identities to constrain low-momentum Euclidean correlation functions and obtain differential equations that relate two and three-point functions. The solution to those equations yields, among other things, the chiral magnetic conductivity. We then compute zero-frequency functions in hydrodynamics and show that the consistency of the hydrodynamic theory also fixes the anomaly-induced conductivities.

Kristan Jensen

2012-04-11

319

A hybrid Godunov method for radiation hydrodynamics

NASA Astrophysics Data System (ADS)

From a mathematical perspective, radiation hydrodynamics can be thought of as a system of hyperbolic balance laws with dual multiscale behavior (multiscale behavior associated with the hyperbolic wave speeds as well as multiscale behavior associated with source term relaxation). With this outlook in mind, this paper presents a hybrid Godunov method for one-dimensional radiation hydrodynamics that is uniformly well behaved from the photon free streaming (hyperbolic) limit through the weak equilibrium diffusion (parabolic) limit and to the strong equilibrium diffusion (hyperbolic) limit. Moreover, one finds that the technique preserves certain asymptotic limits. The method incorporates a backward Euler upwinding scheme for the radiation energy density Er and flux Fr as well as a modified Godunov scheme for the material density ?, momentum density m, and energy density E. The backward Euler upwinding scheme is first-order accurate and uses an implicit HLLE flux function to temporally advance the radiation components according to the material flow scale. The modified Godunov scheme is second-order accurate and directly couples stiff source term effects to the hyperbolic structure of the system of balance laws. This Godunov technique is composed of a predictor step that is based on Duhamel's principle and a corrector step that is based on Picard iteration. The Godunov scheme is explicit on the material flow scale but is unsplit and fully couples matter and radiation without invoking a diffusion-type approximation for radiation hydrodynamics. This technique derives from earlier work by Miniati and Colella (2007) [41]. Numerical tests demonstrate that the method is stable, robust, and accurate across various parameter regimes.

Sekora, Michael D.; Stone, James M.

2010-09-01

320

A hybrid Godunov method for radiation hydrodynamics

From a mathematical perspective, radiation hydrodynamics can be thought of as a system of hyperbolic balance laws with dual multiscale behavior (multiscale behavior associated with the hyperbolic wave speeds as well as multiscale behavior associated with source term relaxation). With this outlook in mind, this paper presents a hybrid Godunov method for one-dimensional radiation hydrodynamics that is uniformly well behaved from the photon free streaming (hyperbolic) limit through the weak equilibrium diffusion (parabolic) limit and to the strong equilibrium diffusion (hyperbolic) limit. Moreover, one finds that the technique preserves certain asymptotic limits. The method incorporates a backward Euler upwinding scheme for the radiation energy density E{sub r} and flux F{sub r} as well as a modified Godunov scheme for the material density {rho}, momentum density m, and energy density E. The backward Euler upwinding scheme is first-order accurate and uses an implicit HLLE flux function to temporally advance the radiation components according to the material flow scale. The modified Godunov scheme is second-order accurate and directly couples stiff source term effects to the hyperbolic structure of the system of balance laws. This Godunov technique is composed of a predictor step that is based on Duhamel's principle and a corrector step that is based on Picard iteration. The Godunov scheme is explicit on the material flow scale but is unsplit and fully couples matter and radiation without invoking a diffusion-type approximation for radiation hydrodynamics. This technique derives from earlier work by Miniati and Colella (2007) . Numerical tests demonstrate that the method is stable, robust, and accurate across various parameter regimes.

Sekora, Michael D., E-mail: sekora@math.princeton.ed [Program in Applied and Computational Mathematics, Princeton University, Princeton, NJ 08544 (United States); Stone, James M. [Program in Applied and Computational Mathematics, Princeton University, Princeton, NJ 08544 (United States); Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2010-09-20

321

A grating-less in-fibre magnetometer realised in a polymer-MOF infiltrated using ferrofluid

NASA Astrophysics Data System (ADS)

We report a grating-less, in-fibre magnetometer realised in a polymethylmethacrylate (PMMA) microstructured optical fibre that has been infiltrated using a hydrocarbon oil based ferrofluid. The lossy magnetic fluid has been infiltrated by capillarity action into the microcapillaries of the fiber cladding, resulting in a generation of a short cut-off band located in the vicinity of 600nm. When the magnetic field is applied perpendicular to the fiber axis, the ferrofluid undergoes refractive index and scattering loss changes, modulating the transmission properties of the infiltrated microstructured fibre. Spectral measurements of the transmitted signal are reported for magnetic field changes up to 1300Gauss, revealing a strong decrease of the signal near its bandgap edge proportionally with the increase of the magnetic field. Instead, when the magnetic field is applied with respect to the rotational symmetry the fibre axis, the sensor exhibits high polarisation sensitivity for a specific wavelength band, providing the possibility of directional measurements.

Candiani, A.; Argyros, A.; Lwin, R.; Leon-Saval, S. G.; Zito, G.; Selleri, S.; Pissadakis, S.

2012-04-01

322

Quantum hydrodynamics: capturing a reactive scattering resonance.

The hydrodynamic equations of motion associated with the de Broglie-Bohm formulation of quantum mechanics are solved using a meshless method based upon a moving least-squares approach. An arbitrary Lagrangian-Eulerian frame of reference and a regridding algorithm which adds and deletes computational points are used to maintain a uniform and nearly constant interparticle spacing. The methodology also uses averaged fields to maintain unitary time evolution. The numerical instabilities associated with the formation of nodes in the reflected portion of the wave packet are avoided by adding artificial viscosity to the equations of motion. A new and more robust artificial viscosity algorithm is presented which gives accurate scattering results and is capable of capturing quantum resonances. The methodology is applied to a one-dimensional model chemical reaction that is known to exhibit a quantum resonance. The correlation function approach is used to compute the reactive scattering matrix, reaction probability, and time delay as a function of energy. Excellent agreement is obtained between the scattering results based upon the quantum hydrodynamic approach and those based upon standard quantum mechanics. This is the first clear demonstration of the ability of moving grid approaches to accurately and robustly reproduce resonance structures in a scattering system. PMID:16108631

Derrickson, Sean W; Bittner, Eric R; Kendrick, Brian K

2005-08-01

323

Divergence-type nonlinear conformal hydrodynamics

Within the theoretical framework of divergence-type theories (DTTs), we set up a consistent nonlinear hydrodynamical description of a conformal fluid in flat space-time. DTTs go beyond second-order (in velocity gradients) theories, and are closed in the sense that they do not rely on adiabatic expansions. We show that the stress-energy tensor constructed from second-order conformal invariants is obtained from the DTT by a consistent adiabatic expansion. The DTT satisfies the second law, and is causal in a set of fluid states near equilibrium. Finally, we compare, analytically and numerically, the equations of motion of the DTT and its truncation to second-order terms for the case of boost invariant flow. Our numerical results indicate that the relaxation towards ideal hydrodynamics is significantly faster in the DTT than in the second-order theory. Not relying on a gradient expansion, our findings may be useful in the study of early-time dynamics and in the evolution of shock waves in heavy-ion collisions.

Peralta-Ramos, J.; Calzetta, E. [CONICET and Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires-Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina)

2009-12-15

324

Multiscale temporal integrators for fluctuating hydrodynamics.

Following on our previous work [S. Delong, B. E. Griffith, E. Vanden-Eijnden, and A. Donev, Phys. Rev. E 87, 033302 (2013)], we develop temporal integrators for solving Langevin stochastic differential equations that arise in fluctuating hydrodynamics. Our simple predictor-corrector schemes add fluctuations to standard second-order deterministic solvers in a way that maintains second-order weak accuracy for linearized fluctuating hydrodynamics. We construct a general class of schemes and recommend two specific schemes: an explicit midpoint method and an implicit trapezoidal method. We also construct predictor-corrector methods for integrating the overdamped limit of systems of equations with a fast and slow variable in the limit of infinite separation of the fast and slow time scales. We propose using random finite differences to approximate some of the stochastic drift terms that arise because of the kinetic multiplicative noise in the limiting dynamics. We illustrate our integrators on two applications involving the development of giant nonequilibrium concentration fluctuations in diffusively mixing fluids. We first study the development of giant fluctuations in recent experiments performed in microgravity using an overdamped integrator. We then include the effects of gravity and find that we also need to include the effects of fluid inertia, which affects the dynamics of the concentration fluctuations greatly at small wave numbers. PMID:25615227

Delong, Steven; Sun, Yifei; Griffith, Boyce E; Vanden-Eijnden, Eric; Donev, Aleksandar

2014-12-01

325

Multiscale temporal integrators for fluctuating hydrodynamics

NASA Astrophysics Data System (ADS)

Following on our previous work [S. Delong, B. E. Griffith, E. Vanden-Eijnden, and A. Donev, Phys. Rev. E 87, 033302 (2013), 10.1103/PhysRevE.87.033302], we develop temporal integrators for solving Langevin stochastic differential equations that arise in fluctuating hydrodynamics. Our simple predictor-corrector schemes add fluctuations to standard second-order deterministic solvers in a way that maintains second-order weak accuracy for linearized fluctuating hydrodynamics. We construct a general class of schemes and recommend two specific schemes: an explicit midpoint method and an implicit trapezoidal method. We also construct predictor-corrector methods for integrating the overdamped limit of systems of equations with a fast and slow variable in the limit of infinite separation of the fast and slow time scales. We propose using random finite differences to approximate some of the stochastic drift terms that arise because of the kinetic multiplicative noise in the limiting dynamics. We illustrate our integrators on two applications involving the development of giant nonequilibrium concentration fluctuations in diffusively mixing fluids. We first study the development of giant fluctuations in recent experiments performed in microgravity using an overdamped integrator. We then include the effects of gravity and find that we also need to include the effects of fluid inertia, which affects the dynamics of the concentration fluctuations greatly at small wave numbers.

Delong, Steven; Sun, Yifei; Griffith, Boyce E.; Vanden-Eijnden, Eric; Donev, Aleksandar

2014-12-01

326

Slurry bubble column hydrodynamics

NASA Astrophysics Data System (ADS)

Slurry bubble column reactors are presently used for a wide range of reactions in both chemical and biochemical industry. The successful design and scale up of slurry bubble column reactors require a complete understanding of multiphase fluid dynamics, i.e. phase mixing, heat and mass transport characteristics. The primary objective of this thesis is to improve presently limited understanding of the gas-liquid-solid slurry bubble column hydrodynamics. The effect of superficial gas velocity (8 to 45 cm/s), pressure (0.1 to 1.0 MPa) and solids loading (20 and 35 wt.%) on the time-averaged solids velocity and turbulent parameter profiles has been studied using Computer Automated Radioactive Particle Tracking (CARPT). To accomplish this, CARPT technique has been significantly improved for the measurements in highly attenuating systems, such as high pressure, high solids loading stainless steel slurry bubble column. At a similar set of operational conditions time-averaged gas and solids holdup profiles have been evaluated using the developed Computed Tomography (CT)/Overall gas holdup procedure. This procedure is based on the combination of the CT scans and the overall gas holdup measurements. The procedure assumes constant solids loading in the radial direction and axially invariant cross-sectionally averaged gas holdup. The obtained experimental holdup, velocity and turbulent parameters data are correlated and compared with the existing low superficial gas velocities and atmospheric pressure CARPT/CT gas-liquid and gas-liquid-solid slurry data. The obtained solids axial velocity radial profiles are compared with the predictions of the one dimensional (1-D) liquid/slurry recirculation phenomenological model. The obtained solids loading axial profiles are compared with the predictions of the Sedimentation and Dispersion Model (SDM). The overall gas holdup values, gas holdup radial profiles, solids loading axial profiles, solids axial velocity radial profiles and solids shear stress radial profiles are correlated using several widely used empirical correlations that are modified and improved to better represent present data.

Rados, Novica

327

Hydrodynamic modelling of small upland lakes under strong wind forcing

NASA Astrophysics Data System (ADS)

Small lakes (Area < 1 km2) represent 46.3% of the total lake surface globally and constitute an important source of water supply. Lakes also provide an important sedimentary archive of environmental and climate changes and ecosystem function. Hydrodynamic controls on the transport and distribution of lake sediments, and also seasonal variations in thermal structure due to solar radiation, precipitation, evaporation and mixing and the complex vertical and horizontal circulation patterns induced by the action of wind are not very well understood. The work presented here analyses hydrodynamic motions present in small upland lakes due to circulation and internal scale waves, and their linkages with the distribution of bottom sediment accumulation in the lake. For purpose, a 3D hydrodynamic is calibrated and implemented for Llyn Conwy, a small oligotrophic upland lake in North Wales, UK. The model, based around the FVCOM open source community model code, resolves the Navier-Stokes equations using a 3D unstructured mesh and a finite volume scheme. The model is forced by meteorological boundary conditions. Improvements made to the FVCOM code include a new graphical user interface to pre- and post process the model input and results respectively, and a JONSWAT wave model to include the effects of wind-wave induced bottom stresses on lake sediment dynamics. Modelled internal scale waves are validated against summer temperature measurements acquired from a thermistor chain deployed at the deepest part of the lake. Seiche motions were validated using data recorded by high-frequency level sensors around the lake margins, and the velocity field and the circulation patterns were validated using the data recorded by an ADCP and GPS drifters. The model is shown to reproduce the lake hydrodynamics and reveals well-developed seiches at different frequencies superimposed on wind-driven circulation patterns that appear to control the distribution of bottom sediments in this small upland lake.

Morales, L.; French, J.; Burningham, H.

2012-04-01

328

Diffraction–radiation of multiple floating structures in directional waves

The dynamics of multiple floating structures have been studied using the finite element method. The emphasis is on the hydrodynamic behaviour of multiple bodies under a multi-directional wave field. A two-dimensional numerical model has been adopted to evaluate hydrodynamic coefficients and forces in an oblique wave field. The responses in sway, heave and roll modes are reported. The linear filter

S. A. Sannasiraj; R. Sundaravadivelu; V. Sundar

2001-01-01

329

The hydrodynamics of water strider locomotion

NASA Astrophysics Data System (ADS)

Water striders Gerridae are insects of characteristic length 1cm and weight 10 dynes that reside on the surface of ponds, rivers, and the open ocean. Their weight is supported by the surface tension force generated by curvature of the free surface, and they propel themselves by driving their central pair of hydrophobic legs in a sculling motion. Previous investigators have assumed that the hydrodynamic propulsion of the water strider relies on momentum transfer by surface waves. This assumption leads to Denny's paradox: infant water striders, whose legs are too slow to generate waves, should be incapable of propelling themselves along the surface. We here resolve this paradox through reporting the results of high-speed video and particle-tracking studies. Experiments reveal that the strider transfers momentum to the underlying fluid not primarily through capillary waves, but rather through hemispherical vortices shed by its driving legs. This insight guided us in constructing a self-contained mechanical water strider whose means of propulsion is analogous to that of its natural counterpart.

Hu, David L.; Chan, Brian; Bush, John W. M.

2003-08-01

330

Hamiltonian Hydrodynamics and Irrotational Binary Inspiral

Gravitational waves from neutron-star and black-hole binaries carry valuable information on their physical properties and probe physics inaccessible to the laboratory. Although development of black-hole gravitational-wave templates in the past decade has been revolutionary, the corresponding work for double neutron-star systems has lagged. Neutron stars can be well-modelled as simple barotropic fluids during the part of binary inspiral most relevant to gravitational wave astronomy, but the crucial geometric and mathematical consequences of this simplification have remained computationally unexploited. In particular, Carter and Lichnerowicz have described barotropic fluid motion via classical variational principles as conformally geodesic. Moreover, Kelvin's circulation theorem implies that initially irrotational flows remain irrotational. Applied to numerical relativity, these concepts lead to novel Hamiltonian or Hamilton-Jacobi schemes for evolving relativistic fluid flows. Hamiltonian methods can conserve not only flux, but also circulation and symplecticity, and moreover do not require addition of an artificial atmosphere typically required by standard conservative methods. These properties can allow production of high-precision gravitational waveforms at low computational cost. This canonical hydrodynamics approach is applicable to a wide class of problems involving theoretical or computational fluid dynamics.

Charalampos M. Markakis

2014-10-28

331

Toward a hydrodynamic theory of sonoluminescence

For small Mach numbers the Rayleigh--Plesset equations (modified to include acoustic radiation damping) provide the hydrodynamic description of a bubble's breathing motion. Measurements are presented for the bubble radius as a function of time. They indicate that in the presence of sonoluminescence the ratio of maximum to minimum bubble radius is about 100. Scaling laws for the maximum bubble radius and the temperature and duration of the collapse are derived in this limit. Inclusion of mass diffusion enables one to calculate the ambient radius. For audible sound fields these equations yield picosecond hot spots, such as are observed experimentally. However, the analysis indicates that a detailed description of sonoluminescence requires the use of parameters for which the resulting motion reaches large Mach numbers. Therefore the next step toward explaining sonoluminescence will require the extension of bubble dynamics to include nonlinear effects such as shock waves.

Loefstedt, R.; Barber, B.P.; Putterman, S.J. (Department of Physics, University of California, Los Angeles, California 90024 (United States))

1993-11-01

332

Phonon hydrodynamics in two-dimensional materials.

The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane. PMID:25744932

Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola

2015-01-01

333

Phonon hydrodynamics in two-dimensional materials

NASA Astrophysics Data System (ADS)

The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane.

Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola

2015-03-01

334

A new hydrodynamic analysis of double layers

NASA Technical Reports Server (NTRS)

A genuine two-fluid model of plasmas with collisions permits the calculation of dynamic (not necessarily static) electric fields and double layers inside of plasmas including oscillations and damping. For the first time a macroscopic model for coupling of electromagnetic and Langmuir waves was achieved with realistic damping. Starting points were laser-produced plasmas showing very high dynamic electric fields in nonlinear force-produced cavitous and inverted double layers in agreement with experiments. Applications for any inhomogeneous plasma as in laboratory or in astrophysical plasmas can then be followed up by a transparent hydrodynamic description. Results are the rotation of plasmas in magnetic fields and a new second harmonic resonance, explanation of the measured inverted double layers, explanation of the observed density-independent, second harmonics emission from laser-produced plasmas, and a laser acceleration scheme by the very high fields of the double layers.

Hora, Heinrich

1987-01-01

335

During curative cancer surgery, magnetic retraction could offer advantages over retraction by graspers because of reduced tissue trauma and with the potential for noncontact retraction. To realize magnetic retraction, magnetic fluid was injected into harvested porcine stomachs and an external permanent magnet was used to retract the ferromagnetized tissue. The magnetic forces of four ferrofluids were measured. The results of these experiments showed that iron-oxide-nanoparticle-based ferrofluids do not provide the required retraction force. However, sufficient retraction force is obtained by ferromagnetic microparticles fluids (stainless steel 410, denoted MP-SS410) by virtue of their high magnetization and saturation. In ex vivo surgical retraction experiments, MP-SS410 powder was dispersed in phosphate-buffered saline and other fluids. These ferrofluids were injected into the submucosal layer of harvested porcine stomachs at different concentrations and volumes. The inoculum generated a magnetic retraction force linearly proportional to the concentration and injected volume. Ex vivo surgical retraction, and dissection and resection were possible with a simple magnetic probe. The results of this study indicate that ferromagnetization of tissue can be used to facilitate localized tissue retraction and resection. PMID:19272870

Wang, Zhigang; Wang, Lijun; Brown, Stuart I; Frank, Tim G; Cuschieri, Alfred

2009-09-01

336

Hydrodynamics of coalescing binary neutron stars: Ellipsoidal treatment

NASA Technical Reports Server (NTRS)

We employ an approximate treatment of dissipative hydrodynamics in three dimensions to study the coalescence of binary neutron stars driven by the emission of gravitational waves. The stars are modeled as compressible ellipsoids obeying a polytropic equation of state; all internal fluid velocities are assumed to be linear functions of the coordinates. The hydrodynamics equations then reduce to a set of coupled ordinary differential equations for the evolution of the principal axes of the ellipsoids, the internal velocity parameters, and the binary orbital parameters. Gravitational radiation reaction and viscous dissipation are both incorporated. We set up exact initial binary equilibrium configurations and follow the transition from the quasi-static, secular decay of the orbit at large separation to the rapid dynamical evolution of the configurations just prior to contact. A hydrodynamical instability resulting from tidal interactions significantly accelerates the coalescence at small separation, leading to appreciable radial infall velocity and tidal lag angles near contact. This behavior is reflected in the gravitational waveforms and may be observable by gravitational wave detectors under construction. In cases where the neutron stars have spins which are not aligned with the orbital angular momentum, the spin-induced quadrupole moment can lead to precession of the orbital plane and therefore modulation of the gravitational wave amplitude even at large orbital radius. However, the amplitude of the modulation is small for typical neutron star binaries with spins much smaller than the orbital angular momentum.

Lai, Dong; Shapiro, Stuart L.

1995-01-01

337

Effect of Second-Order Hydrodynamics on a Floating Offshore Wind Turbine

The design of offshore floating wind turbines uses design codes that can simulate the entire coupled system behavior. At the present, most codes include only first-order hydrodynamics, which induce forces and motions varying with the same frequency as the incident waves. Effects due to second- and higher-order hydrodynamics are often ignored in the offshore industry, because the forces induced typically are smaller than the first-order forces. In this report, first- and second-order hydrodynamic analysis used in the offshore oil and gas industry is applied to two different wind turbine concepts--a spar and a tension leg platform.

Roald, L.; Jonkman, J.; Robertson, A.

2014-05-01

338

Hydrodynamic interactions in protein folding

NASA Astrophysics Data System (ADS)

We incorporate hydrodynamic interactions (HIs) in a coarse-grained and structure-based model of proteins by employing the Rotne-Prager hydrodynamic tensor. We study several small proteins and demonstrate that HIs facilitate folding. We also study HIV-1 protease and show that HIs make the flap closing dynamics faster. The HIs are found to affect time correlation functions in the vicinity of the native state even though they have no impact on same time characteristics of the structure fluctuations around the native state.

Cieplak, Marek; Niewieczerza?, Szymon

2009-03-01

339

Black brane entropy and hydrodynamics

Recent advances in holography have led to the formulation of fluid-gravity duality, a remarkable connection between the hydrodynamics of certain strongly coupled media and dynamics of higher dimensional black holes. This paper introduces a correspondence between phenomenologically defined entropy currents in relativistic hydrodynamics and 'generalized horizons' of near-equilibrium black objects in a dual gravitational description. A general formula is given, expressing the divergence of the entropy current in terms of geometric objects which appear naturally in the gravity dual geometry. The proposed definition is explicitly covariant with respect to boundary diffeomorphisms and reproduces known results when evaluated for the event horizon.

Booth, Ivan; Heller, Michal P.; Spalinski, Michal [Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, A1C 5S7 (Canada); Instituut voor Theoretische Fysica, Universiteit van Amsterdam, Science Park 904, 1090 GL Amsterdam (Netherlands); Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw (Poland) and Physics Department, University of Bialystok, 15-424 Bialystok (Poland)

2011-03-15

340

Abnormal pressures as hydrodynamic phenomena

So-called abnormal pressures, subsurface fluid pressures significantly higher or lower than hydrostatic, have excited speculation about their origin since subsurface exploration first encountered them. Two distinct conceptual models for abnormal pressures have gained currency among earth scientists. The static model sees abnormal pressures generally as relict features preserved by a virtual absence of fluid flow over geologic time. The hydrodynamic model instead envisions abnormal pressures as phenomena in which flow usually plays an important role. This paper develops the theoretical framework for abnormal pressures as hydrodynamic phenomena, shows that it explains the manifold occurrences of abnormal pressures, and examines the implications of this approach. -from Author

Neuzil, C.E.

1995-01-01

341

Evaluation of using ferrofluid as an interface material for a field-reversible thermal connector

NASA Astrophysics Data System (ADS)

The electrical functionality of an avionics chassis is limited due to heat dissipation limits. The limits arise due to the fact that components in an avionic computer boxes are packed very compactly, with the components mounted onto plug-in cards, and the harsh environment experienced by the chassis limits how heat can be dissipated from the cards. Convective and radiative heat transfer to the ambient are generally not possible. Therefore it is necessary to have heat transferred from the components conducted to the edge of the plug-in cards. The heat then needs to conduct from the card edge to a cold block that not only holds the card in place, but also removes the generated heat by some heat transfer fluid that is circulated through the cold block. The interface between the plug-in card and the cold block typically has a high thermal resistance since it is necessary for the card to have the capability to be re-workable, meaning that the card can be removed and then returned to the chassis. Reducing the thermal resistance of the interface is the objective of the current study and the topic of this thesis. The current design uses a pressure interface between the card and cold block. The contact pressure is increased through the addition of a wedgelock, which is a field-reversible mechanical connector. To use a wedgelock, the cold block has channels milled on the surface with widths that are larger than the thickness of the plug-in card and the un-expanded wedgelock. The card edge is placed in the channel and placed against one of the channel walls. A wedgelock is then placed between the card and the other channel wall. The wedgelock is then expanded by using either a screw or a lever. As the wedgelock expands it fills in the remaining channel gap and bears against the other face of the plug-in card. The majority of heat generated by the components on the plug-in card is forced to conduct from the card into the wall of the cold block, effectively a single sided, dry conduction heat transfer path. Having started as a student design competition named RevCon Challenge, work was performed to evaluate the use of new field-reversible thermal connectors. The new design proposed by the University of Missouri utilized oil based iron nanoparticles, commonly known as a ferrofluid, as a thermal interface material. By using a liquid type of interface material the channel gap can be reduced to a few micrometers, within machining tolerances, and heat can be dissipated off both sides of the card. The addition of nanoparticles improves the effective thermal conductivity of base fluid. The use of iron nanoparticles allows magnets to be used to hold the fluid in place, so the electronic cards may be easily inserted and removed while keeping the ferrofluid in the cold block channel. The ferrofluid-based design which was investigated has shown lower thermal resistance than the current wedgelock design. These results open the door for further development of electronic cards by using higher heat emitting components without compromising the simplicity of attaching/detaching cards from cooling plates.

Yousif, Ahmed S.

342

1.138J / 2.062J Wave Propagation, Fall 2000

Linearized theory of wave phenomena in applied mechanics. Examples are chosen from elasticity, acoustics, geophysics, hydrodynamics and other subjects. Basic concepts. One dimensional examples. Characteristics, dispersion ...

Mei, Chiang C.

343

Ferrofluids consist of magnetic nanoparticles dispersed in a carrier liquid. Their strong thermodiffusive behaviour, characterised by the Soret coefficient, coupled with the dependency of the fluid's parameters on magnetic fields is dealt with in this work. It is known from former experimental investigations on the one hand that the Soret coefficient itself is magnetic field dependent and on the other hand that the accuracy of the coefficient's experimental determination highly depends on the volume concentration of the fluid. The thermally driven separation of particles and carrier liquid is carried out with a concentrated ferrofluid (? = 0.087) in a horizontal thermodiffusion cell and is compared to equally detected former measurement data. The temperature gradient (1 K/mm) is applied perpendicular to the separation layer. The magnetic field is either applied parallel or perpendicular to the temperature difference. For three different magnetic field strengths (40 kA/m, 100 kA/m, 320 kA/m) the diffusive separation is detected. It reveals a sign change of the Soret coefficient with rising field strength for both field directions which stands for a change in the direction of motion of the particles. This behaviour contradicts former experimental results with a dilute magnetic fluid, in which a change in the coefficient's sign could only be detected for the parallel setup. An anisotropic behaviour in the current data is measured referring to the intensity of the separation being more intense in the perpendicular position of the magnetic field: S{sub T?} = ?0.152 K{sup ?1} and S{sub T?} = ?0.257 K{sup ?1} at H = 320 kA/m. The ferrofluiddynamics-theory (FFD-theory) describes the thermodiffusive processes thermodynamically and a numerical simulation of the fluid's separation depending on the two transport parameters ?{sub ?} and ?{sub ?} used within the FFD-theory can be implemented. In the case of a parallel aligned magnetic field, the parameter can be determined to ?{sub ?} = (2.8;?9.1;?11.2)?×?10{sup ?11}?·?D{sub ?} kg/(A{sup 2}m) for the different field strengths and in dependence on the magnetic diffusion coefficient D{sub ?}. An adequate fit in the perpendicular case is not possible, by ?{sub ?} = 1?×?10{sup ?17} kg/(Am{sup 2}) a rather good agreement between numerical and experimental data can be found for a field strength of 40 kA/m, a change in the coefficient's sign in the perpendicular setup is not numerically determinable via this theory. The FFD-theory is only partly applicable to calculate the concentration profile in concentrated magnetic fluids established due to a temperature gradient and magnetic field applied.

Sprenger, Lisa, E-mail: Lisa.Sprenger@tu-dresden.de; Lange, Adrian; Odenbach, Stefan [Institute of Fluid Mechanics, Chair of Magnetofluiddynamics, Measuring and Automation Technology, TU Dresden, 01062 Dresden (Germany)] [Institute of Fluid Mechanics, Chair of Magnetofluiddynamics, Measuring and Automation Technology, TU Dresden, 01062 Dresden (Germany)

2014-02-15

344

NASA Astrophysics Data System (ADS)

Ferrofluids consist of magnetic nanoparticles dispersed in a carrier liquid. Their strong thermodiffusive behaviour, characterised by the Soret coefficient, coupled with the dependency of the fluid's parameters on magnetic fields is dealt with in this work. It is known from former experimental investigations on the one hand that the Soret coefficient itself is magnetic field dependent and on the other hand that the accuracy of the coefficient's experimental determination highly depends on the volume concentration of the fluid. The thermally driven separation of particles and carrier liquid is carried out with a concentrated ferrofluid (? = 0.087) in a horizontal thermodiffusion cell and is compared to equally detected former measurement data. The temperature gradient (1 K/mm) is applied perpendicular to the separation layer. The magnetic field is either applied parallel or perpendicular to the temperature difference. For three different magnetic field strengths (40 kA/m, 100 kA/m, 320 kA/m) the diffusive separation is detected. It reveals a sign change of the Soret coefficient with rising field strength for both field directions which stands for a change in the direction of motion of the particles. This behaviour contradicts former experimental results with a dilute magnetic fluid, in which a change in the coefficient's sign could only be detected for the parallel setup. An anisotropic behaviour in the current data is measured referring to the intensity of the separation being more intense in the perpendicular position of the magnetic field: ST? = -0.152 K-1 and ST? = -0.257 K-1 at H = 320 kA/m. The ferrofluiddynamics-theory (FFD-theory) describes the thermodiffusive processes thermodynamically and a numerical simulation of the fluid's separation depending on the two transport parameters ?? and ?? used within the FFD-theory can be implemented. In the case of a parallel aligned magnetic field, the parameter can be determined to ?? = {2.8; 9.1; 11.2} × 10-11 . D? kg/(A2m) for the different field strengths and in dependence on the magnetic diffusion coefficient D?. An adequate fit in the perpendicular case is not possible, by ?? = 1 × 10-17 kg/(Am2) a rather good agreement between numerical and experimental data can be found for a field strength of 40 kA/m, a change in the coefficient's sign in the perpendicular setup is not numerically determinable via this theory. The FFD-theory is only partly applicable to calculate the concentration profile in concentrated magnetic fluids established due to a temperature gradient and magnetic field applied.

Sprenger, Lisa; Lange, Adrian; Odenbach, Stefan

2014-02-01

345

POSITIVE HYDRODYNAMIC INTERACTION BETWEEN SWIMMING

for interaction effects. A positive hydrodynamic interaction could be demonstrated, the mean velocity with the time of storage (r = + o.9g6), but partial correlation analysis showed that this is not a real effect mammals have a nearly flat profile, the shape of the boundary curve in normal specimens conforming closely

Boyer, Edmond

346

Hydrodynamic focusing – a versatile tool

The control of hydrodynamic focusing in a microchannel has inspired new approaches for microfluidic mixing, separations, sensors, cell analysis and microfabrication. Achieving a flat interface between the focusing and focused fluids is dependent on Reynolds number and device geometry, and many hydrodynamic focusing systems can benefit from this understanding. For applications where a specific cross-sectional shape is desired for the focused flow, advection generated by grooved structures in the channel walls can be used to define the shape of the focused flow. Relative flow rates of the focused flow and focusing streams can be manipulated to control the crosssectional area of the focused flows. This manuscript discusses the principles for defining the shape of the interface between the focused and focusing fluids and provides examples from our lab that use hydrodynamic focusing for impedance-based sensors, flow cytometry, and microfabrication to illustrate the breadth of opportunities for introducing new capabilities into microfluidic systems. We evaluate each example for the advantages and limitations integral to utilization of hydrodynamic focusing for that particular application. PMID:21952728

Golden, Joel P.; Justin, Gusphyl A.; Nasir, Mansoor; Ligler, Frances S.

2011-01-01

347

Acid dissolution hydrodynamic force analysis

The purpose of this calculation is to analyze the hydrodynamic forces associated with the in-tank piping feeding the tank fluid agitation eductor (sparger), as well as eductor induced forces. These forces will be used as input to the structural analysis of the support structure used for the acid dissolution assembly, and the acid dissolution assembly itself.

2003-01-01

348

Acid dissolution hydrodynamic force analysis

The purpose of this calculation is to analyze the hydrodynamic forces associated with the in-tank piping feeding the tank fluid agitation eductor (sparger), as well as eductor induced forces. These forces will be used as input to the structural analysis of the support structure used for the acid dissolution assembly, and the acid dissolution assembly itself.

WHITE, M.A.

2003-05-21

349

The Gulf of Lions' hydrodynamics

From an hydrodynamical point of view, the Gulf of Lions can be considered as a very complex region, because several intense and highly variable phenomena compete simultaneously. These processes include the powerful general circulation along the continental slope, the formation of dense water both on the shelf and offshore, a seasonal variation of stratification and the extreme energies associated with

Claude Millot

1990-01-01

350

From Field Theory to the Hydrodynamics of Relativistic Superfluids

The hydrodynamic description of a superfluid is usually based on a two-fluid picture. In this thesis, basic properties of such a relativistic two-fluid system are derived from the underlying microscopic physics of a complex scalar quantum field theory. To obtain analytic results of all non-dissipative hydrodynamic quantities in terms of field theoretic variables, calculations are first carried out in a low-temperature and weak-coupling approximation. In a second step, the 2-particle-irreducible formalism is applied: This formalism allows for a numerical evaluation of the hydrodynamic parameters for all temperatures below the critical temperature. In addition, a system of two coupled superfluids is studied. As an application, the velocities of first and second sound in the presence of a superflow are calculated. The results show that first (second) sound evolves from a density (temperature) wave at low temperatures to a temperature (density) wave at high temperatures. This role reversal is investigated for ultra-relativistic and near-nonrelativistic systems for zero and nonzero superflow. The studies carried out in this thesis are of a very general nature as one does not have to specify the system for which the microscopic field theory is an effective description. As a particular example, superfluidity in dense quark and nuclear matter in compact stars are discussed.

Stephan Stetina

2015-01-31

351

NASA Astrophysics Data System (ADS)

We report on the observation of all-optically tunable Goos-Hänchen (GH) shift in a symmetrical metal-cladding waveguide, whose guiding layer is filled with the water-based ferrofluid. The strong dependence of the GH shift and its switching time on the control beam power is suggested to be arising from the light-induced periodic-like microstructure transitions of ferrofluid in virtue of the competition between the optical trapping effect and the Soret effect. The indirect evidence of our qualitative hypothesis is given. The presented tunability of GH shift may have potential applications in optical switching and sensing.

Wang, Xianping; Yin, Cheng; Sun, Jingjing; Li, Honggen; Sang, Minghuang; Yuan, Wen; Cao, Zhuangqi; Huang, Meizhen

2013-10-01

352

NASA Astrophysics Data System (ADS)

An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field.

Rajnak, Michal; Kurimsky, Juraj; Dolnik, Bystrik; Kopcansky, Peter; Tomasovicova, Natalia; Taculescu-Moaca, Elena Alina; Timko, Milan

2014-09-01

353

An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field. PMID:25314449

Rajnak, Michal; Kurimsky, Juraj; Dolnik, Bystrik; Kopcansky, Peter; Tomasovicova, Natalia; Taculescu-Moaca, Elena Alina; Timko, Milan

2014-09-01

354

The formation of spherical superparamagnetic colloidal aggregates of magnetite nanoparticles by emulsification of a ferrofluid and subsequent solvent evaporation has been systematically studied. The colloidal aggregates occur as a dense sphere with magnetite nanoparticles randomly packed and preserved particle-particle separation due to chemisorbed oleic acid. The voids between nanoparticles are filled with solvent and free oleic acid. The latter was found to influence the formation of colloidal aggregates and their surface properties. The choice of surfactant, whether low molecular weight or polymeric, was shown to lead to the colloidal aggregates having tailored interfacial behavior. Magnetization measurements at ambient temperature revealed that the magnetite colloidal aggregates preserve the superparamagnetic properties of the starting nanoparticle units and show high saturation magnetization values up to 57 emu/g. The size distribution of magnetite nanoparticle colloidal aggregates produced by such an approach was found to be a function of emulsion droplet breakup-coalescence and stabilization kinetics and therefore is influenced by the emulsification process conditions and concentrations of the emulsion compounds. PMID:22365838

Lobaz, Volodymyr; Klupp Taylor, Robin N; Peukert, Wolfgang

2012-05-15

355

Analytical centrifugation is used for the first time to measure sedimentation equilibrium concentration profiles of a ferrofluid, a concentrated colloidal dispersion of strongly absorbing magnetic nanoparticles. To keep the optical absorbance from becoming too strong, the optical path length is restricted to 50 ?m by placing the dispersion in a flat glass capillary. The concentration profile is kept from becoming too steep, despite the relatively high buoyant mass of the nanoparticles, by making novel use of a low-velocity analytical centrifuge that was not designed to measure equilibrium profiles. The experimental approach is validated by comparison with profiles obtained using an analytical ultracentrifuge. At concentrations of a few hundred grams per liter, the osmotic pressures calculated from the equilibrium profiles are lower than expected for hard spheres or non-interacting particles, due to magnetic dipolar interactions. By following the presented experimental approach, it will now also be possible to characterize the interparticle interactions of other strongly absorbing colloidal particles not studied before by analytical centrifugation. PMID:22617483

Luigjes, Bob; Thies-Weesie, Dominique M E; Philipse, Albert P; Erné, Ben H

2012-06-20

356

Field-dependent anisotropic microrheological and microstructural properties of dilute ferrofluids.

We have measured microrheological and microstructural properties of a superparamagnetic ferrofluid made of Mn0.75Zn0.25Fe2O4 (MZF) nanoparticles, using passive microrheology in a home-built inverted microscope. Thermal motion of a probe microsphere was measured for different values of an applied external magnetic field and analysed. The analysis shows anisotropy in magneto-viscous effect. Additional microrheological properties, such as storage modulus and loss modulus and their transition are also seen. We have also obtained microstructural properties such as elongational flow coefficient [Formula: see text] , relaxation time constant [Formula: see text] , coefficient of dissipative magnetization [Formula: see text] , etc., using the analysis given in Oliver Muller et al., J. Phys.: Condens. Matter 18, S2623, (2006) and Stefan Mahle et al., Phys. Rev. E 77, 016305 (2008) over our measured viscosity data. Our values for the above parameters are in agreement with earlier theoretical calculations and macro-rheological experimental measurements. These theoretical calculations consider an ideal situation of zero-shear limit, which is best approximated only in the passive microrheology technique described here and a first time measurement of all these parameters with passive microrheology. PMID:25117500

Yendeti, Balaji; Thirupathi, G; Vudaygiri, Ashok; Singh, R

2014-08-01

357

The Use of Ferrofluids to Model Materials Processing (MSFC Center Director's Discretionary Fund)

NASA Technical Reports Server (NTRS)

Many crystals grown in space have structural flaws believed to result from convective motions during the growth phase. The character of these instabilities is not well understood but is associated with thermal and solutal density variations near the solidification interface in the presence of residual gravity and g-jitter. To study these instabilities in a separate, controlled space experiment, a concentration gradient would first have to be artificially established in a timely manner as an initial condition. This is generally difficult to accomplish in a microgravity environment because the momentum of the fluid injected into a test cell tends to swirl around and mix in the absence of a restoring force. The use of magnetic fields to control the motion and position of liquids has received recent, growing interest. The possibility of using the force exerted by a non-uniform magnetic field on a ferrofluid to not only achieve fluid manipulation but also to actively control fluid motion makes it an attractive candidate for space applications. This paper describes a technique for quickly establishing a linear or exponential fluid concentration gradient using a magnetic field in place of gravity to stabilize the deployment. Also discussed is a photometric technique for measuring the concentration profile using light attenuation. Although any range of concentrations can be realized, photometric constraints impose some limitations on measurements. Results of the ground-based experiments indicate that the species distribution is within 3 percent of the predicted value.

Leslie, F.; Ramachandran, N.

2000-01-01

358

Ferrofluid pipe flow under the influence of the magnetic field of a cylindrical coil

NASA Astrophysics Data System (ADS)

Ferrofluid pipe flow under the effect of a co-linear, finite length cylindrical coil is examined numerically. The specific flow configuration is chosen as it is encountered in engineering and bioengineering applications such as magnetic drug targeting systems. The objective of the paper is twofold: first, to investigate the accuracy of an analytical solution for the magnetization equation and assess its validity when used for non-uniform magnetic fields. It is found that it can be very helpful as a means of estimating the magnetization, especially for strong magnetic fields with low gradients; second, to examine the effects of the magnetic field on the flow and study the relevant importance of the magnetic terms of the momentum equation. The parameters that we examine are the strength of the magnetic field and of its gradients, the volumetric concentration of the magnetic particles, and the dimensions (length and diameter) of the coil. It is revealed that the axial pressure drop depends linearly on the volumetric concentration and that the magnetoviscosity effect is negligible in cases of non-uniform magnetic fields.

Papadopoulos, P. K.; Vafeas, P.; Hatzikonstantinou, P. M.

2012-12-01

359

Small-angle scattering from macromolecules in solution is widely used to study their structures, but the information content is limited because the molecules are generally randomly oriented and hence the data are spherically averaged. The use of oriented rodlike structures for scattering, as in fiber diffraction, greatly increases the amount of structural detail that can be obtained. A new technique using a ferromagnetic fluid has been developed to align elongated structures independent of their intrinsic magnetic properties. This technique is ideal for small-angle neutron scattering because the scattering from the ferrofluid particles can be reduced significantly by matching the neutron scattering length density of the particles to a D2O solvent (“contrast matching”). The net result is scattering primarily from the ordered biological assembly in a solution environment that can be adjusted to physiological pH and ionic strength. Scattering results from ordered tobacco mosaic virus, tobacco rattle virus, and chromain fibers are presented. ImagesFIGURE 4FIGURE 4 PMID:19431809

Sosnick, T.; Charles, S.; Stubbs, G.; Yau, P.; Bradbury, E. M.; Timmins, P.; Trewhella, J.

1991-01-01

360

NASA Astrophysics Data System (ADS)

Using light transmission experiments and optical microscope observations with a longitudinal gradient magnetic field configuration, the relationship between the behavior of the transmitted light relaxation and the microstructure evolution of ionic ferrofluids in the central region of an axisymmetric field is investigated. Under a low-gradient magnetic field, there are two types of relaxation process. When a field is applied, the transmitted light intensity decreases to a minimum within a time on the order of 101-102 s. It is then gradually restored, approaching its initial value within a time on the order of 102 s. This is type I relaxation, which corresponds to the formation of magnetic columns. After the transmission reaches this value, it either increases or decreases slowly, stabilizing within a time on the order of 103 s, according to the direction of the field gradient. This is a type II relaxation, which results from the shadowing effect, corresponding to the motion of the magnetic columns under the application of a gradient force. Under a magnetic field with a centripetal high-gradient (magnetic materials subjected to a force pointing toward the center of the axisymmetric field), the transmitted light intensity decreases monotonously and more slowly than that under a low-gradient field. Magnetic transport and separation resulted from magnetophoresis under high-gradient fields, changing the formation dynamics of the local columns and influencing the final state of the column system.

Huang, Yan; Li, Decai; Li, Feng; Zhu, Quanshui; Xie, Yu

2015-03-01

361

Formation Interuniversitaire de Physique Hydrodynamics

" . . . . . . . . . . . . . . . . . . . . 16 3.2 Rotating Frames . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.3 Manipulating Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4.2.1 Hydraulic Jumps

Balbus, Steven

362

Lattice-Boltzmann modeling of phonon hydrodynamics

NASA Astrophysics Data System (ADS)

Based on the phonon Boltzmann equation, a lattice-Boltzmann model for phonon hydrodynamics is developed. Both transverse and longitudinal polarized phonons that interact through normal and umklapp processes are considered in the model. The collision term is approximated by the relaxation time model where normal and umklapp processes tend to relax distributions of phonons to their corresponding equilibrium distribution functions—the displaced Planck distribution and the Planck distribution, respectively. A macroscopic phonon thermal wave equation (PTWE), valid for the second-sound mode, is derived through the technique of Chapman-Enskog expansion. Compared to the dual-phase-lag (DPL) -based thermal wave equation, the PTWE has an additional fourth-ordered spatial derivative term. The fundamental difference between the two models is discussed through examining a propagating thermal pulse in a single-phased medium and the transient and steady-state transport phenomena on a two-layered structure subjected to different temperatures at boundaries. Results show that transport phenomena are significantly different between the two models. The behavior exhibited by the DPL model, as thermal wave behavior goes over to diffusive behavior, ?T??q is incompatible with any microscopic phonon propagating mode. Unlike the DPL model, in which ?T only has an effect on the transient phenomena, in the PTWE model ?T shows effects on phenomena at both transient and steady state. With the intrinsic compatibility to the microscopic state, discontinuous quantities, such as a jump of temperature at a boundary or at an interface, can be calculated naturally and straightforwardly with the present lattice-Boltzmann method.

Jiaung, Wen-Shu; Ho, Jeng-Rong

2008-06-01

363

Lattice-Boltzmann modeling of phonon hydrodynamics.

Based on the phonon Boltzmann equation, a lattice-Boltzmann model for phonon hydrodynamics is developed. Both transverse and longitudinal polarized phonons that interact through normal and umklapp processes are considered in the model. The collision term is approximated by the relaxation time model where normal and umklapp processes tend to relax distributions of phonons to their corresponding equilibrium distribution functions-the displaced Planck distribution and the Planck distribution, respectively. A macroscopic phonon thermal wave equation (PTWE), valid for the second-sound mode, is derived through the technique of Chapman-Enskog expansion. Compared to the dual-phase-lag (DPL) -based thermal wave equation, the PTWE has an additional fourth-ordered spatial derivative term. The fundamental difference between the two models is discussed through examining a propagating thermal pulse in a single-phased medium and the transient and steady-state transport phenomena on a two-layered structure subjected to different temperatures at boundaries. Results show that transport phenomena are significantly different between the two models. The behavior exhibited by the DPL model, as thermal wave behavior goes over to diffusive behavior, tau_{T}-->tau_{q} is incompatible with any microscopic phonon propagating mode. Unlike the DPL model, in which tau_{T} only has an effect on the transient phenomena, in the PTWE model tau_{T} shows effects on phenomena at both transient and steady state. With the intrinsic compatibility to the microscopic state, discontinuous quantities, such as a jump of temperature at a boundary or at an interface, can be calculated naturally and straightforwardly with the present lattice-Boltzmann method. PMID:18643400

Jiaung, Wen-Shu; Ho, Jeng-Rong

2008-06-01

364

Enhanced Heat Flow in the Hydrodynamic Collisionless Regime

We study the heat conduction of a cold, thermal cloud in a highly asymmetric trap. The cloud is axially hydrodynamic, but due to the asymmetric trap radially collisionless. By locally heating the cloud we excite a thermal dipole mode and measure its oscillation frequency and damping rate. We find an unexpectedly large heat conduction compared to the homogeneous case. The enhanced heat conduction in this regime is partially caused by atoms with a high angular momentum spiraling in trajectories around the core of the cloud. Since atoms in these trajectories are almost collisionless they strongly contribute to the heat transfer. We observe a second, oscillating hydrodynamic mode, which we identify as a standing wave sound mode.

Meppelink, R.; Rooij, R. van; Vogels, J. M.; Straten, P. van der [Atom Optics and Ultrafast Dynamics, Utrecht University, P.O. Box 80000, 3508 TA Utrecht (Netherlands)

2009-08-28

365

Anomalous hydrodynamics of fractional quantum Hall states

We propose a comprehensive framework for quantum hydrodynamics of the fractional quantum Hall (FQH) states. We suggest that the electronic fluid in the FQH regime can be phenomenologically described by the quantized hydrodynamics of vortices in an incompressible rotating liquid. We demonstrate that such hydrodynamics captures all major features of FQH states, including the subtle effect of the Lorentz shear stress. We present a consistent quantization of the hydrodynamics of an incompressible fluid, providing a powerful framework to study the FQH effect and superfluids. We obtain the quantum hydrodynamics of the vortex flow by quantizing the Kirchhoff equations for vortex dynamics.

Wiegmann, P., E-mail: wiegmann@uchicago.edu [University of Chicago, Department of Physics (United States)

2013-09-15

366

NASA Astrophysics Data System (ADS)

Ferrofluids are colloidal suspensions consisting of magnetic nanoparticles dispersed in a carrier liquid. Their thermodiffusive behaviour is rather strong compared to molecular binary mixtures, leading to a Soret coefficient (ST) of 0.16 K-1. Former experiments with dilute magnetic fluids have been done with thermogravitational columns or horizontal thermodiffusion cells by different research groups. Considering the horizontal thermodiffusion cell, a former analytical approach has been used to solve the phenomenological diffusion equation in one dimension assuming a constant concentration gradient over the cell's height. The current experimental work is based on the horizontal separation cell and emphasises the comparison of the concentration development in different concentrated magnetic fluids and at different temperature gradients. The ferrofluid investigated is the kerosene-based EMG905 (Ferrotec) to be compared with the APG513A (Ferrotec), both containing magnetite nanoparticles. The experiments prove that the separation process linearly depends on the temperature gradient and that a constant concentration gradient develops in the setup due to the separation. Analytical one dimensional and numerical three dimensional approaches to solve the diffusion equation are derived to be compared with the solution used so far for dilute fluids to see if formerly made assumptions also hold for higher concentrated fluids. Both, the analytical and numerical solutions, either in a phenomenological or a thermodynamic description, are able to reproduce the separation signal gained from the experiments. The Soret coefficient can then be determined to 0.184 K-1 in the analytical case and 0.29 K-1 in the numerical case. Former theoretical approaches for dilute magnetic fluids underestimate the strength of the separation in the case of a concentrated ferrofluid.

Sprenger, Lisa; Lange, Adrian; Odenbach, Stefan

2013-12-01

367

Ferrofluids are colloidal suspensions consisting of magnetic nanoparticles dispersed in a carrier liquid. Their thermodiffusive behaviour is rather strong compared to molecular binary mixtures, leading to a Soret coefficient (S{sub T}) of 0.16?K{sup ?1}. Former experiments with dilute magnetic fluids have been done with thermogravitational columns or horizontal thermodiffusion cells by different research groups. Considering the horizontal thermodiffusion cell, a former analytical approach has been used to solve the phenomenological diffusion equation in one dimension assuming a constant concentration gradient over the cell's height. The current experimental work is based on the horizontal separation cell and emphasises the comparison of the concentration development in different concentrated magnetic fluids and at different temperature gradients. The ferrofluid investigated is the kerosene-based EMG905 (Ferrotec) to be compared with the APG513A (Ferrotec), both containing magnetite nanoparticles. The experiments prove that the separation process linearly depends on the temperature gradient and that a constant concentration gradient develops in the setup due to the separation. Analytical one dimensional and numerical three dimensional approaches to solve the diffusion equation are derived to be compared with the solution used so far for dilute fluids to see if formerly made assumptions also hold for higher concentrated fluids. Both, the analytical and numerical solutions, either in a phenomenological or a thermodynamic description, are able to reproduce the separation signal gained from the experiments. The Soret coefficient can then be determined to 0.184?K{sup ?1} in the analytical case and 0.29?K{sup ?1} in the numerical case. Former theoretical approaches for dilute magnetic fluids underestimate the strength of the separation in the case of a concentrated ferrofluid.

Sprenger, Lisa, E-mail: Lisa.Sprenger@tu-dresden.de; Lange, Adrian; Odenbach, Stefan [Institute of Fluid Mechanics, Chair of Magnetofluiddynamics, Measuring and Automation Technology, TU Dresden, 01062 Dresden (Germany)

2013-12-15

368

The magneto-induced stress and relative microstructure in a colloidal suspension of paramagnetic and superparamagnetic particles dispersed in a ferrofluid medium is studied using particle-level dynamics simulation. It shows that the stress perpendicular to the direction of an external uniaxial magnetic field can be strongly enhanced by increasing the ratio of paramagnetic particles to approaching that of superparamagnetic particles. The magnetic field-induced net-like or embedded chain-like microstructures formed by paramagnetic and superparamagnetic particles contribute to this stress enhancing effect. PMID:24837318

Liu, Taixiang; Gong, Xinglong; Xu, Yangguang; Xuan, Shouhu

2014-02-14

369

NASA Astrophysics Data System (ADS)

A study is conducted on the influence of magnetic fields on the flow behavior of two ferrofluids with different levels of interparticle interaction, determined by prior rheological measurements. A Taylor-Couette system is used as a model for the investigations. A homogeneous magnetic field is applied in axial and transverse direction relative to the rotational axis of the system. The results presented comprise changes in the flow structure of the Taylor-vortex flow and the stabilization of the circular Couette flow due to magnetic fields.

Reindl, M.; Odenbach, S.

2011-09-01

370

Hydrodynamics of Confined Active Fluids

NASA Astrophysics Data System (ADS)

We theoretically describe the dynamics of swimmer populations in rigidly confined thin liquid films. We first demonstrate that hydrodynamic interactions between confined swimmers depend solely on their shape and are independent of their specific swimming mechanism. We also show that, due to friction with the nearby rigid walls, confined swimmers do not just reorient in flow gradients but also in uniform flows. We then quantify the consequences of these microscopic interaction rules on the large-scale hydrodynamics of isotropic populations. We investigate in detail their stability and the resulting phase behavior, highlighting the differences with conventional active, three-dimensional suspensions. Two classes of polar swimmers are distinguished depending on their geometrical polarity. The first class gives rise to coherent directed motion at all scales, whereas for the second class we predict the spontaneous formation of coherent clusters (swarms).

Brotto, Tommaso; Caussin, Jean-Baptiste; Lauga, Eric; Bartolo, Denis

2013-01-01

371

Post-Newtonian smoothed particle hydrodynamics calculations of binary neutron star coalescence. II particle hydrodynamics code, we study the final coales- cence and merging of neutron star NS binaries. We the coalescence of NS binaries with an irrotational initial condition, and find that the gravity wave signal

Rasio, Frederic A.

372

Hydrodynamic simulations of the solar chromosphere Sven Wedemeyer 1 , Bernd Freytag 2 , Matthias model at a height of 1000 km (middle chromosphere): Hot wave fronts and cool regions. Fig.2: Snapshot and low/middle chromosphere with propaÂ gating shock waves. 500 1000 1500 Height z [km] 2000 4000 6000

373

Hydrodynamic stability and stellar oscillations

Chandrasekhar’s monograph on Hydrodynamic and hydromagnetic stability, published in 1961, is a standard reference on linear stability theory. It gives a detailed account of stability of fluid\\u000a flow in a variety of circumstances, including convection, stability of Couette flow, Rayleigh–Taylor instability, Kelvin–Helmholtz\\u000a instability as well as the Jean’s instability for star formation. In most cases he has extended these studies

H M ANTIA

374

Hydrodynamics of catheter biofilm formation

A hydrodynamic model is proposed to describe one of the most critical problems in intensive medical care units: the formation of biofilms inside central venous catheters. The incorporation of approximate solutions for the flow-limited diffusion equation leads to the conclusion that biofilms grow on the internal catheter wall due to the counter-stream diffusion of blood through a very thin layer close to the wall. This biological deposition is the first necessary step for the subsequent bacteria colonization.

Sotolongo-Costa, Oscar; Rodriguez-Perez, Daniel; Martinez-Escobar, Sergio; Fernandez-Barbero, Antonio

2009-01-01

375

Numerical hydrodynamics in special relativity

This review is concerned with a discussion of numerical methods for the\\u000asolution of the equations of special relativistic hydrodynamics (SRHD).\\u000aParticular emphasis is put on a comprehensive review of the application of\\u000ahigh-resolution shock-capturing methods in SRHD. Results obtained with\\u000adifferent numerical SRHD methods are compared, and two astrophysical\\u000aapplications of SRHD flows are discussed. An evaluation of the

Jose M. Marti; E. Muller

1999-01-01

376

Some open questions in hydrodynamics

When speaking of unsolved problems in physics, this is surprising at first glance to discuss the case of fluid mechanics. However, there are many deep open questions that come with the theory of fluid mechanics. In this paper, we discuss some of them that we classify in two categories, the long term behavior of solutions of equations of hydrodynamics and the definition of initial (boundary) conditions. The first set of questions come with the non-relativistic theory based on the Navier-Stokes equations. Starting from smooth initial conditions, the purpose is to understand if solutions of Navier-Stokes equations remain smooth with the time evolution. Existence for just a finite time would imply the evolution of finite time singularities, which would have a major influence on the development of turbulent phenomena. The second set of questions come with the relativistic theory of hydrodynamics. There is an accumulating evidence that this theory may be relevant for the description of the medium created in high energy heavy-ion collisions. However, this is not clear that the fundamental hypotheses of hydrodynamics are valid in this context. Also, the determination of initial conditions remains questionable. The purpose of this paper is to explore some ideas related to these questions, both in the non-relativistic and relativistic limits of fluid mechanics. We believe that these ideas do not concern only the theory side but can also be useful for interpreting results from experimental measurements.

Mateusz Dyndal; Laurent Schoeffel

2014-12-16

377

Aeroelastic simulation tools are routinely used to design and analyze onshore wind turbines, in order to obtain cost effective machines that achieve favorable performance while maintaining structural integrity. These tools employ sophisticated models of wind-inflow; aerodynamic, gravitational, and inertial loading of the rotor, nacelle, and tower; elastic effects within and between components; and mechanical actuation and electrical responses of the generator and of control and protection systems. For offshore wind turbines, additional models of the hydrodynamic loading in regular and irregular seas, the dynamic coupling between the support platform motions and wind turbine motions, and the dynamic characterization of mooring systems for compliant floating platforms are also important. Hydrodynamic loading includes contributions from hydrostatics, wave radiation, and wave scattering, including free surface memory effects. The integration of all of these models into comprehensive simulation tools, capable of modeling the fully coupled aeroelastic and hydrodynamic responses of floating offshore wind turbines, is presented.

Jonkman, J. M.; Sclavounos, P. D.

2006-01-01

378

It is shown that the hydrodynamic interpretation of a charged quantum particle leads to a different theoretical prediction for low energy bremsstrahlung than does quantum electrodynamics (QED). In the calculations, the electromagnetic fields are treated classically in the hydrodynamic case, but are quantized in QED. Calculations show the hydrodynamic model to have a different and more sensitive dependence on the size and shape of the radiating particle's wave packet then does QED. In particular it is shown that bremsstrahlung is sometimes greatly reduced when the force acting on the particle is localized to a volume small compared to the particle's wave packet. QED exhibits no such reduction. Therefore it is possible to test this effect experimentally. An experiment is proposed. It involves an electron microscope with a Wien filter for producing monochromatic beam electrons and an accurate energy measurement of the particle after passing through a local force field.

Mark P. Davidson

2006-03-30

379

Coping with the node problem in quantum hydrodynamics: The covering function method

A conceptually simple approach, the covering function method (CFM), is developed to cope with the node problem in the hydrodynamic formulation of quantum mechanics. As nodes begin to form in a scattering wave packet (detected by a monitor function), a nodeless covering wave function is added to it yielding a total function that is also nodeless. Both local and global choices for the covering function are described. The total and covering functions are then propagated separately in the hydrodynamic picture. At a later time, the actual wave function is recovered from the two propagated functions. The results obtained for Eckart barrier scattering in one dimension are in excellent agreement with exact results, even for very long propagation times t=1.2 ps. The capability of the CFM is also demonstrated for multidimensional propagation of a vibrationally excited wave packet.

Babyuk, Dmytro; Wyatt, Robert E. [Institute for Theoretical Chemistry and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712-1167 (United States)

2004-11-15

380

Topics in Fluctuating Nonlinear Hydrodynamics.

NASA Astrophysics Data System (ADS)

Models of fluctuating nonlinear hydrodynamics have enjoyed much success in explaining the effects of long-wavelength fluctuations in diverse hydrodynamic systems. This thesis explores two such problems; in both, the body of hydrodynamic assumptions powerfully constrains the predictions of a well-posed theory. We first examine the effects of layer fluctuations in smectic-A liquid crystals. The static theory (introduced by Grinstein and Pelcovits) is reviewed. Ward identities, resulting from the arbitrariness of the layering direction, are derived and exploited. The static results motivate an examination of dynamic fluctuation effects. We review a series of increasingly drastic predictions (made by Mazenko, Ramaswamy, and Toner) of divergent corrections to viscosities. The first prediction, that smectic-A bulk viscosities diverge as 1/(omega), explains the anomalous acoustic attenuation observed in the materials. Later, MRT predicted a divergent shear viscosity, which gives results radically different from classical hydrodynamics: (1) a minimum applied yield stress as in plastic flow, and (2) an effective shear modulus without long-range order. We refute these two predictions by showing the results are inconsistent with the static limit. We prove that the shear viscosity (eta)(,2) is finite to all orders, and check the result with a one-loop calculation. The perturbative corrections are summed within the RG framework, which properly contains the GP theory. Sound -damping experiments are reviewed and prospects for observing RG corrections are examined. A new sound-damping experiment is proposed which would probe singular dependence of viscosities on applied stress. We then analyze a theory of Procaccia and Gitterman that reaction rates of chemically reacting binary mixtures are drastically reduced near their thermodynamic critical points. We apply hydrodynamic arguments and Van Hove theory, and conclude that the PG idea is untenable--spatially uniform composition fluctuations are not drastically slowed, and spatially varying composition fluctuations are at best slowed down over a narrow range of wavenumbers. RG corrections to Van Hove theory are considered. At small and large wavenumbers, the modes most affected near the critical point are thermal and particle diffusion respectively.

Milner, Scott Thomas

381

For the first time, a selective ionic liquid ferrofluid has been used in dispersive solid phase extraction (IL-FF-D-SPE) for simultaneous preconcentration and separation of lead and cadmium in milk and biological samples combined with flame atomic absorption spectrometry. To improve the selectivity of the ionic liquid ferrofluid, the surface of TiO2 nanoparticles with a magnetic core as sorbent was modified by loading 1-(2-pyridylazo)-2-naphtol. Due to the rapid injection of an appropriate amount of ionic liquid ferrofluid into the aqueous sample by a syringe, extraction can be achieved within a few seconds. In addition, based on the attraction of the ionic liquid ferrofluid to a magnet, no centrifugation step is needed for phase separation. The experimental parameters of IL-FF-D-SPE were optimized using a Box-Behnken design (BBD) after a Plackett-Burman screening design. Under the optimum conditions, the relative standard deviations of 2.2% and 2.4% were obtained for lead and cadmium, respectively (n=7). The limit of detections were 1.21 µg L(-1) for Pb(II) and 0.21 µg L(-1) for Cd(II). The preconcentration factors were 250 for lead and 200 for cadmium and the maximum adsorption capacities of the sorbent were 11.18 and 9.34 mg g(-1) for lead and cadmium, respectively. PMID:25281121

Fasih Ramandi, Negin; Shemirani, Farzaneh

2015-01-01

382

. In higher fields, 1000 G, the columns stretched and coalesced into sheetlike striped liquids, but a true is water, and both the magnetic and nonmagnetic particles are stabilized in water. More commonly, the ferrofluid is composed of magnetic par- ticles suspended in one solvent e.g., oil that is then mixed

Lacoste, David

383

or an asymmetric configuration. A pair of symmetric counter-rotating circulations of concentrated particles and progress up the flow. In contrast, the single asymmetric circulation of concentrated particles formedExploiting magnetic asymmetry to concentrate diamagnetic particles in ferrofluid microflows James J

Xuan, Xiangchun "Schwann"

384

A method for studying the evolution of discontinuities in radiating spherically symmetric distributions of matter has been extended to model hydrodynamic phase transitions in a composite radiant sphere. In the present scenario, the matter configuration is divided into two regions by a shock wave front, with each side of the interface having a different anisotropic phase. The resultant models are shown to be strongly dependent on the anisotropic jump across the interface and on the luminosity (opacity) of the shock wave. 44 refs.

Herrera, L.; Nunez, L.

1989-04-01

385

On the estimation method of hydrodynamic forces acting on a very large floating structure

The floating structures that may be used for such purposes as an international airport or an offshore city are expected to be as large as several kilometers long and wide. For the estimation of hydrodynamic forces due to waves or motions that will act on such huge structures, a direct application of conventional numerical methods is practically prohibitive, because the

Hiroshi Kagemoto; Masataka Fujino; Tingyao Zhu

1997-01-01

386

difficult to disentangle the effects of materials properties on seaweed performance because size, shape the largest source of mortality for seaweeds in high wave energy environments, tissues with material properties of 16 species of foliose red macroalgae were determined, and their effects on hydrodynamic

Martone, Patrick T.

387

Ocean Engineering 34 (2007) 22312239 Hydrodynamic shape optimization of thin floating plates

is consistent with this. That included only wave effects and the prediction for the free decay of the motionOcean Engineering 34 (2007) 2231Â2239 Hydrodynamic shape optimization of thin floating plates Abstract In this work, the problem of optimizing the shape of a thin floating plate (sometimes called

Damaren, Christopher J.

388

3212 Langmuir 1993,9,3212-3218 Hydrodynamic Modes of Viscoelastic Soap Films

3212 Langmuir 1993,9,3212-3218 Hydrodynamic Modes of Viscoelastic Soap Films P. Sens,C. Marques of a soap f i i containing a viscoelastic Maxwellfluidmodelingawater solublepolymer. Twotypesof modesexist,bendingmodesand squeezing modes. In addition to the modes existing for a usual viscous soap f i i , we find Rayleigh waves

Sens, Pierre

389

Hydrodynamics StÂ´ephan T. Grilli University of Rhode Island, Depart. of Ocean Engng., Narragansett, RI 02882 to as Numerical Wave Tank (NWT), a term coined some 20 years ago [52], at a time when NWTs were only the dream

Grilli, StÃ©phan T.

390

PSEUDO-SPECTRUM OF THE RESISTIVE MAGNETO-HYDRODYNAMICS OPERATOR: RESOLVING THE RESISTIVE ALFV

PSEUDO-SPECTRUM OF THE RESISTIVE MAGNETO-HYDRODYNAMICS OPERATOR: RESOLVING THE RESISTIVE ALFV #19, pseudospectrum, non-normal op- erators, continuous spectrum, Alfv#19;en waves, magnetohydrodynamic stability to the ideal spectrum in the limit of asymptotically small resistiv- ity. As the resistivity, #17;, decreases

391

PSEUDO-SPECTRUM OF THE RESISTIVE MAGNETO-HYDRODYNAMICS OPERATOR: RESOLVING THE RESISTIVE ALFV, continuous spectrum, Alfv´en waves, magnetohydrodynamic stability. PACS 03.40.Kf, 47.65.+a, 52.30.Jb, 52 would converge to the ideal spectrum in the limit of asymptotically small resistiv- ity

392

and buoyancy in the tropical alga Turbinaria ornata Hannah L. Stewart* Department of Integrative Biology of buoyancy and flexural stiffness (EI) affect hydrodynamic forces on, and flow velocity relative by side on the reef at a site exposed to moderate wave action. To examine the effect of buoyancy alone

Stewart, Hannah Louise

393

Computations of fully nonlinear three-dimensional wave-body interactions

Nonlinear effects in hydrodynamics of wave-body interaction problems become critically important when large-amplitude body motions and/or extreme surface waves are involved. Accurate prediction and understanding of these ...

Yan, Hongmei

2010-01-01

394

Advances in the hydrodynamics solver of CO5BOLD

NASA Astrophysics Data System (ADS)

Many features of the Roe solver used in the hydrodynamics module of CO5BOLD have recently been added or overhauled, including the reconstruction methods (by adding the new second-order ``Frankenstein's method''), the treatment of transversal velocities, energy-flux averaging and entropy-wave treatment at small Mach numbers, the CTU scheme to combine the one-dimensional fluxes, and additional safety measures. All this results in a significantly better behavior at low Mach number flows, and an improved stability at larger Mach numbers requiring less (or no) additional tensor viscosity, which then leads to a noticeable increase in effective resolution.

Freytag, Bernd

395

An exact Riemann Solver for multidimensional special relativistic hydrodynamics

We have generalised the exact solution of the Riemann problem in special relativistic hydrodynamics for arbitrary tangential flow velocities. The solution is obtained by solving the jump conditions across shocks plus an ordinary differential equation arising from the self-similarity condition along rarefaction waves, in a similar way as in purely normal flow. The dependence of the solution on the tangential velocities is analysed. This solution has been used to build up an exact Riemann solver implemented in a multidimensional relativistic (Godunov-type) hydro-code.

J. Pons; J. Ma. Marti; E. Muller

1999-10-26

396

NASA Astrophysics Data System (ADS)

Rate of heat generated by magnetic nanoparticles in a ferrofluid is affected by their magnetic properties, temperature, and viscosity of the carrier liquid. We have investigated temperature dependent magnetic hyperthermia in ferrofluids, consisting of dextran coated superparamagnetic Fe3O4 nanoparticles, subjected to external magnetic fields of various frequencies (188-375 kHz) and amplitudes (140-235 Oe). Transmission electron microscopy measurements show that the nanoparticles are polydispersed with a mean diameter of 13.8 ± 3.1 nm. The fitting of experimental dc magnetization data to a standard Langevin function incorporating particle size distribution yields a mean diameter of 10.6 ± 1.2 nm, and a reduced saturation magnetization (˜65 emu/g) compared to the bulk value of Fe3O4 (˜95 emu/g). This is due to the presence of a finite surface layer (˜1 nm thickness) of non-aligned spins surrounding the ferromagnetically aligned Fe3O4 core. We found the specific absorption rate, measured as power absorbed per gram of iron oxide nanoparticles, decreases monotonically with increasing temperature for all values of magnetic field and frequency. Using the size distribution of magnetic nanoparticles estimated from the magnetization measurements, we have fitted the specific absorption rate versus temperature data using a linear response theory and relaxation dissipation mechanisms to determine the value of magnetic anisotropy constant (28 ± 2 kJ/m3) of Fe3O4 nanoparticles.

Nemala, H.; Thakur, J. S.; Naik, V. M.; Vaishnava, P. P.; Lawes, G.; Naik, R.

2014-07-01

397

The optical magnetic chaining technique (MCT) developed by Leal-Calderon, Bibette and co-workers in the 1990 s allows precise measurements of force profiles between droplets in monodisperse ferrofluid emulsions. However, the method lacks an in-situ determination of droplet size and therefore requires the combination of separately acquired measurements of droplet chain periodicity versus an applied magnetic field from optical Bragg scattering and droplet diameter inferred from dynamic light scattering (DLS) to recover surface force-distance profiles between the colloidal particles. Compound refractive lens (CRL) focussed small-angle scattering (SANS) MCT should result in more consistent measurements of droplet size (form factor measurements in the absence of field) and droplet chaining period (from structure factor peaks when the magnetic field is applied); and, with access to shorter length scales, extend force measurements to closer approaches than possible by optical measurements. We report on CRL-SANS measurements of monodisperse ferrofluid emulsion droplets aligned in straight chains by an applied field perpendicular to the incident beam direction. Analysis of the scattering from the closely spaced droplets required algorithms that carefully treated resolution and its effect on mean scattering vector magnitudes in order to determine droplet size and chain periods to sufficient accuracy. At lower applied fields scattering patterns indicate structural correlations transverse to the magnetic field direction due to the formation of intermediate structures in early chain growth.

Jain, Dr Nirmesh [University of Sydney, Australia] [University of Sydney, Australia; Liu, Dr C K [Institute of Materials research and Engineering, A-STAR, Singapore] [Institute of Materials research and Engineering, A-STAR, Singapore; Hawkett, Dr B. S. [University of Sydney, Australia] [University of Sydney, Australia; Warr, G. G. [University of Sydney, Australia] [University of Sydney, Australia; Hamilton, William A [ORNL] [ORNL

2014-01-01

398

\\u000a The wave equation in an ideal fluid can be derived from hydrodynamics and the adiabatic relation between pressure and density.\\u000a The equation for conservation of mass, Euler’s equation (Newton’s second law), and the adiabatic equation of state are respectively\\u000a \\u000a \\u000a \\u000a \\u000a \\u000a ${rcl} & \\\\frac{\\\\partial \\\\rho } {\\\\partial t} = -\\\\mathbf{\\\

Finn B. Jensen; William A. Kuperman; Michael B. Porter; Henrik Schmidt

399

Hydrodynamic instability in eccentric astrophysical discs

NASA Astrophysics Data System (ADS)

Eccentric Keplerian discs are believed to be unstable to three-dimensional hydrodynamical instabilities driven by the time-dependence of fluid properties around an orbit. These instabilities could lead to small-scale turbulence, and ultimately modify the global disc properties. We use a local model of an eccentric disc, derived in a companion paper, to compute the non-linear vertical (`breathing mode') oscillations of the disc. We then analyse their linear stability to locally axisymmetric disturbances for any disc eccentricity and eccentricity gradient using a numerical Floquet method. In the limit of small departures from a circular reference orbit, the instability of an isothermal disc is explained analytically. We also study analytically the small-scale instability of an eccentric neutrally stratified polytropic disc with any polytropic index using a Wentzel-Kramers-Brillouin (WKB) approximation. We find that eccentric discs are generically unstable to the parametric excitation of small-scale inertial waves. The non-linear evolution of these instabilities should be studied in numerical simulations, where we expect them to lead to a decay of the disc eccentricity and eccentricity gradient as well as to induce additional transport and mixing. Our results highlight that it is essential to consider the three-dimensional structure of eccentric discs, and their resulting vertical oscillatory flows, in order to correctly capture their evolution.

Barker, A. J.; Ogilvie, G. I.

2014-12-01

400

Lattice hydrodynamic model with bidirectional pedestrian flow

NASA Astrophysics Data System (ADS)

The two-dimensional lattice hydrodynamic model of traffic is extended to the two-dimensional bidirectional pedestrian flow via taking four types of pedestrians into account. The stability condition and the mKdV equation to describe the density wave of pedestrian congestion are obtained by linear stability and nonlinear analysis, respectively. In addition, there exist three phase transitions among the freely moving phase, the coexisting phase and the uniformly congested phase in the phase diagram. It can also be found that the critical point ac refers to not only the fraction c1 of the eastbound and westbound pedestrians, but also the fraction c2 of the northbound and southbound pedestrians. However, the critical point ac could not appear in the phase diagram and congested crowd at any time when two fractions are equal to same value of 0.5 ( c1=c2=0.5). Furthermore, numerical simulation is carried out to examine the performance of such a model and the results show coincidence with the theory analysis results.

Tian, Huan-huan; He, Hong-di; Wei, Yan-fang; Yu, Xue; Lu, Wei-zhen

2009-07-01

401

Hydrodynamic modeling of tsunamis from the Currituck landslide

Tsunami generation from the Currituck landslide offshore North Carolina and propagation of waves toward the U.S. coastline are modeled based on recent geotechnical analysis of slide movement. A long and intermediate wave modeling package (COULWAVE) based on the non-linear Boussinesq equations are used to simulate the tsunami. This model includes procedures to incorporate bottom friction, wave breaking, and overland flow during runup. Potential tsunamis generated from the Currituck landslide are analyzed using four approaches: (1) tsunami wave history is calculated from several different scenarios indicated by geotechnical stability and mobility analyses; (2) a sensitivity analysis is conducted to determine the effects of both landslide failure duration during generation and bottom friction along the continental shelf during propagation; (3) wave history is calculated over a regional area to determine the propagation of energy oblique to the slide axis; and (4) a high-resolution 1D model is developed to accurately model wave breaking and the combined influence of nonlinearity and dispersion during nearshore propagation and runup. The primary source parameter that affects tsunami severity for this case study is landslide volume, with failure duration having a secondary influence. Bottom friction during propagation across the continental shelf has a strong influence on the attenuation of the tsunami during propagation. The high-resolution 1D model also indicates that the tsunami undergoes nonlinear fission prior to wave breaking, generating independent, short-period waves. Wave breaking occurs approximately 40-50??km offshore where a tsunami bore is formed that persists during runup. These analyses illustrate the complex nature of landslide tsunamis, necessitating the use of detailed landslide stability/mobility models and higher-order hydrodynamic models to determine their hazard.

Geist, E.L.; Lynett, P.J.; Chaytor, J.D.

2009-01-01

402

Hydrodynamic pressure processing (HDP), a novel non-thermal technology that uses a small amount of explosive (100 g) to generate a supersonic–hydrodynamic shock wave in a water filled steel container (54 L) was evaluated for inactivation of Escherichia coli O157:H7 (EHEC) in ground beef. The ground beef was inoculated with a six strain cocktail of E. coli O157:H7 at three different concentrations (103,

R. Podolak; M. B. Solomon; J. R. Patel; M. N. Liu

2006-01-01

403

Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications

We report the ongoing work of our group in hydrodynamics and radiative hydrodynamics with astrophysical applications. During the period of the existing grant, we have carried out two types of experiments at the Omega laser. One set of experiments has studied radiatively collapsing shocks, obtaining high-quality scaling data using a backlit pinhole and obtaining the first (ever, anywhere) Thomson-scattering data from a radiative shock. Other experiments have studied the deeply nonlinear development of the Rayleigh-Taylor (RT) instability from complex initial conditions, obtaining the first (ever, anywhere) dual-axis radiographic data using backlit pinholes and ungated detectors. All these experiments have applications to astrophysics, discussed in the corresponding papers either in print or in preparation. We also have obtained preliminary radiographs of experimental targets using our x-ray source. The targets for the experiments have been assembled at Michigan, where we also prepare many of the simple components. The above activities, in addition to a variety of data analysis and design projects, provide good experience for graduate and undergraduates students. In the process of doing this research we have built a research group that uses such work to train junior scientists.

R. Paul Drake

2005-12-01

404

A hydrodynamic sensory antenna used by killifish for nocturnal hunting

SUMMARY The perception of sensory stimuli by an animal requires several steps, commencing with the capture of stimulus energy by an antenna that, as the interface between the physical world and the nervous system, modifies the stimulus in ways that enhance the animal's perception. The mammalian external ear, for example, collects sound and spectrally alters it to increase sensitivity and improve the detection of directionality. In view of the morphological diversity of the lateral-line system across species and its accessibility to observation and experimental intervention, we sought to investigate the role of antennal structures on the response characteristics of the lateral line. The surface-feeding killifish Aplocheilus lineatus is able to hunt in darkness by detecting surface capillary waves with the lateral-line system atop its head. This cephalic lateral line consists of a stereotyped array of 18 mechanosensitive neuromasts bordered by fleshy ridges. By recording microphonic potentials, we found that each neuromast has a unique receptive field defined by its sensitivity to stimulation of the water's surface. The ridges help determine these receptive fields by altering the flow of water over each neuromast. Modification of the hydrodynamic environment by the addition of a supplemental ridge changes the pattern of water movement, perturbs the receptive fields of adjacent neuromasts and impairs the fish's localization ability. On the basis of electrophysiological, hydrodynamic and behavioral evidence, we propose that the ridges constitute a hydrodynamic antenna for the cephalic lateral line. PMID:21562172

Schwarz, Jason S.; Reichenbach, Tobias; Hudspeth, A. J.

2011-01-01

405

Balance equations in semi-relativistic quantum hydrodynamics

NASA Astrophysics Data System (ADS)

Method of the quantum hydrodynamics has been applied in quantum plasmas studies. As the first step in our consideration, derivation of classical semi-relativistic (i.e., described by the Darwin Lagrangian on microscopic level) hydrodynamical equations is given after a brief review of method development. It provides better distinguishing between classic and quantum semi-relativistic effects. Derivation of the classical equations is interesting since it is made by a natural, but not very widespread method. This derivation contains explicit averaging of the microscopic dynamics. Derivation of corresponding quantum hydrodynamic equations is presented further. Equations are obtained in the five-momentum approximation including the continuity equation, Euler and energy balance equations. It is shown that relativistic corrections lead to presence of new quantum terms in expressions for a force field, a work field etc. The semi-relativistic generalization of the quantum Bohm potential is obtained. Quantum part of the energy current, which is an analog of the quantum Bohm potential for the energy evolution equation, is derived. The Langmuir wave dispersion in semi-relativistic quantum plasmas, corresponding to the Darwin Lagrangian, is also considered to demonstrate contribution of semi-relativistic effects on basic plasma phenomenon.

Ivanov, A. Yu.; Andreev, P. A.; Kuz'menkov, L. S.

2014-05-01

406

Foundation of Hydrodynamics of Strongly Interacting Systems

Hydrodynamics and quantum mechanics have many elements in common, as the density field and velocity fields are common variables that can be constructed in both descriptions. Starting with the Schroedinger equation and the Klein-Gordon for a single particle in hydrodynamical form, we examine the basic assumptions under which a quantum system of particles interacting through their mean fields can be described by hydrodynamics.

Wong, Cheuk-Yin [ORNL] [ORNL

2014-01-01

407

Foundation of Hydrodynamics of Strongly Interacting Systems

Hydrodynamics and quantum mechanics have many elements in common, as the density field and velocity fields are common variables that can be constructed in both descriptions. Starting with the Schroedinger equation and the Klein-Gordon for a single particle in hydrodynamical form, we examine the basic assumptions under which a quantum system of particles interacting through their mean fields can be described by hydrodynamics.

Cheuk-Yin Wong

2014-04-03

408

Microscale hydrodynamics near moving contact lines

NASA Technical Reports Server (NTRS)

The hydrodynamics governing the fluid motions on a microscopic scale near moving contact lines are different from those governing motion far from the contact line. We explore these unique hydrodynamics by detailed measurement of the shape of a fluid meniscus very close to a moving contact line. The validity of present models of the hydrodynamics near moving contact lines as well as the dynamic wetting characteristics of a family of polymer liquids are discussed.

Garoff, Stephen; Chen, Q.; Rame, Enrique; Willson, K. R.

1994-01-01

409

Cluster Dynamics of Planetary Waves

The dynamics of nonlinear atmospheric planetary waves is determined by a small number of independent wave clusters consisting of a few connected resonant triads. We classified the different types of connections between neighboring triads that determine the general dynamics of a cluster. Each connection type corresponds to substantially different scenarios of energy flux among the modes. The general approach can be applied directly to various mesoscopic systems with 3-mode interactions, encountered in hydrodynamics, astronomy, plasma physics, chemistry, medicine, etc.

Elena Kartashova; Victor S. L'vov

2008-11-05

410

Progress in smooth particle hydrodynamics

Smooth Particle Hydrodynamics (SPH) is a meshless, Lagrangian numerical method for hydrodynamics calculations where calculational elements are fuzzy particles which move according to the hydrodynamic equations of motion. Each particle carries local values of density, temperature, pressure and other hydrodynamic parameters. A major advantage of SPH is that it is meshless, thus large deformation calculations can be easily done with no connectivity complications. Interface positions are known and there are no problems with advecting quantities through a mesh that typical Eulerian codes have. These underlying SPH features make fracture physics easy and natural and in fact, much of the applications work revolves around simulating fracture. Debris particles from impacts can be easily transported across large voids with SPH. While SPH has considerable promise, there are some problems inherent in the technique that have so far limited its usefulness. The most serious problem is the well known instability in tension leading to particle clumping and numerical fracture. Another problem is that the SPH interpolation is only correct when particles are uniformly spaced a half particle apart leading to incorrect strain rates, accelerations and other quantities for general particle distributions. SPH calculations are also sensitive to particle locations. The standard artificial viscosity treatment in SPH leads to spurious viscosity in shear flows. This paper will demonstrate solutions for these problems that they and others have been developing. The most promising is to replace the SPH interpolant with the moving least squares (MLS) interpolant invented by Lancaster and Salkauskas in 1981. SPH and MLS are closely related with MLS being essentially SPH with corrected particle volumes. When formulated correctly, JLS is conservative, stable in both compression and tension, does not have the SPH boundary problems and is not sensitive to particle placement. The other approach to solving SPH problems, pioneered by Randles and Libersky, is to use a different SPH equation and to renormalize the kernel gradient sums. Finally the authors present results using the SPH statistical fracture model (SPHSFM). It has been applied to a series of ball on plate impacts performed by Grady and Kipp. A description of the model and comparison with the experiments will be given.

Wingate, C.A.; Dilts, G.A.; Mandell, D.A.; Crotzer, L.A.; Knapp, C.E.

1998-07-01

411

Hydrodynamic Simulations of Galaxy Formation

We have developed an accurate, one-dimensional, spherically symmetric, Lagrangian hydrodynamics/gravity code, designed to study the effects of radiative cooling and photo-ionization on the formation of protogalaxies. We examine the ability of collapsing perturbations to cool within the age of the universe. In contrast to some studies based on order-of-magnitude estimates, we find that cooling arguments alone cannot explain the sharp upper cutoff observed in the galaxy luminosity function. We also look at the effect of a photoionizing background on the formation of low-mass galaxies.

A. A. Thoul

1994-12-09

412

Hydrodynamic characteristics of UASB bioreactors.

The hydrodynamic characteristics of UASB bioreactors operated under different organic loading and hydraulic loading rates were studied, using three laboratory scale models treating concocted sucrose wastewater. Residence time distribution (RTD) analysis using dispersion model and tanks-in-series model was directed towards the characterization of the fluid flow pattern in the reactors and correlation of the hydraulic regime with the biomass content and biogas production. Empty bed reactors followed a plug flow pattern and the flow pattern changed to a large dispersion mixing with biomass and gas production. Effect of increase in gas production on the overall hydraulics was insignificant. PMID:23505813

John, Siby; Tare, Vinod

2011-10-01

413

Disruptive Innovation in Numerical Hydrodynamics

We propose the research and development of a high-fidelity hydrodynamic algorithm for tetrahedral meshes that will lead to a disruptive innovation in the numerical modeling of Laboratory problems. Our proposed innovation has the potential to reduce turnaround time by orders of magnitude relative to Advanced Simulation and Computing (ASC) codes; reduce simulation setup costs by millions of dollars per year; and effectively leverage Graphics Processing Unit (GPU) and future Exascale computing hardware. If successful, this work will lead to a dramatic leap forward in the Laboratory's quest for a predictive simulation capability.

Waltz, Jacob I. [Los Alamos National Laboratory

2012-09-06

414

Hydrodynamics of post CHF region

Among various two-phase flow regimes, the inverted flow in the post-dryout region is relatively less well understood due to its special heat transfer conditions. The review of existing data indicates further research is needed in the areas of basic hydrodynamics related to liquid core disintegration mechanisms, slug and droplet formations, entrainment, and droplet size distributions. In view of this, the inverted flow is studied in detail both analytically and experimentally. Criteria for initial flow regimes in the post-dryout region are given. Preliminary models for subsequent flow regime transition criteria are derived together with correlations for a mean droplet diameter based on the adiabatic simulation data.

Ishii, M.; De Jarlais, G.

1984-04-01

415

Thermal Transport in a Noncommutative Hydrodynamics

We find the hydrodynamic equations of a system of particles constrained to be in the lowest Landau level. We interpret the hydrodynamic theory as a Hamiltonian system with the Poisson brackets between the hydrodynamic variables determined from the noncommutativity of space. We argue that the most general hydrodynamic theory can be obtained from this Hamiltonian system by allowing the Righi-Leduc coefficient to be an arbitrary function of thermodynamic variables. We compute the Righi-Leduc coefficients at high temperatures and show that it satisfies the requirements of particle-hole symmetry, which we outline.

Michael Geracie; Dam Thanh Son

2015-02-24

416

Hydrodynamics of internal solitons and a comparison of SIR-A and SIR-B data with ocean measurements

NASA Technical Reports Server (NTRS)

Large internal solitary waves have been observed by Shuttle SIR-A and SIR-B at locations in the Andaman Sea and the New York Bight. Satellite imagery and oceanographic measurements are used in conjunction with hydrodynamic interaction and electromagnetic scattering models to estimate the expected SAR image intensity modulations associated with the internal waves. There is reasonable agreement between the predicted and observed internal wave signatures.

Apel, J. R.; Gasparovic, R. F.; Thompson, D. R.

1986-01-01

417

Hydrodynamics on non-commutative space --A step toward hydrodynamics of granular materials--

Hydrodynamics on non-commutative space is studied based on a formulation of hydrodynamics by Y. Nambu in terms of Poisson and Nambu brackets. Replacing these brackets by Moyal brackets with a parameter $\\theta$, a new hydrodynamics on non-commutative space is derived. It may be a step toward to find the hydrodynamics of granular materials whose minimum volume is given by $\\theta$. To clarify this minimum volume, path integral quantization and uncertainty relation of Nambu dynamics are examined.

Mayumi Saitou; Kazuharu Bamba; Akio Sugamoto

2014-09-16

418

Pulsed power hydrodynamics : a new application of high magnetic fields.

Pulsed Power Hydrodynamics is a new application of high magnetic fields recently developed to explore advanced hydrodynamics, instabilities, fluid turbulences, and material properties in a highly precise, controllable environment at the extremes of pressure and material velocity. The Atlas facility at Los Alamos is the world's first and only laboratory pulsed power system designed specifically to explore this relatively new family of megagauss magnetic field applications. Constructed in 2000 and commissioned in August 2001, Atlas is a 24-MJ high-performance capacitor bank delivering up to 30 MA with a current risetime of 5-6 {micro}sec. The high-precision, cylindrical, imploding liner is the tool most frequently used to convert electrical energy into the hydrodynamic (particle kinetic) energy needed to drive the experiments. For typical liner parameters including initial radius of 5 cm, the peak current of 30 MA delivered by Atlas results in magnetic fields just over 1 MG outside the liner prior to implosion. During the 5 to 10-{micro}sec implosion, the field outside the liner rises to several MG in typical situations. At these fields the rear surface of the liner is melted and it is subject to a variety of complex behaviors including: diffusion dominated andor melt wave field penetration and heating, magneto Raleigh-Taylor sausage mode behavior at the liner/field interface, and azimuthal asymmetry due to perturbations in current drive. The first Atlas liner implosion experiments were conducted in September 2000 and 10-15 experiments are planned in the: first year of operation. Immediate applications of the new pulsed power hydrodynamics techniques include material property topics including: exploration of material strength at high rates of strain, material failure including fracture and spall, and interfacial dynamics at high relative velocities and high interfacial pressures. A variety of complex hydrodynamic geometries will be explored and experiments will be designed to explore uristable perturbation growth and transition to turbulence. This paper will provide an overview of the range of problems to which pulsed power hydrodynamics can be applied and the issues associated with these techniques. Other papers at this Conference will present specifics of individual experiments and elaborate on the liner physics issues.

Reinovsky, R. E. (Robert E.); Anderson, W. E. (Wallace E.); Atchison, W. L. (Walter L.); Faehl, R. J. (Rickey J.); Keinigs, R. K. (Rhonald K.); Lindemuth, I. R.; Scudder, D. W. (David W.); Shlachter, Jack S.; Taylor, Antoinette J.,

2002-01-01

419

The effects of second-order hydrodynamics on a semisubmersible floating offshore wind turbine

NASA Astrophysics Data System (ADS)

The objective of this paper is to assess the second-order hydrodynamic effects on a semisubmersible floating offshore wind turbine. Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of a floating system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure. Observations of supposed second-order responses in wave-tank tests performed by the DeepCwind consortium at the Maritime Research Institute Netherlands (MARIN) offshore basin suggest that these effects might be more important than originally expected. These observations inspired interest in investigating how second-order excitation affects floating offshore wind turbines and whether second-order hydrodynamics should be included in offshore wind simulation tools like FAST. In this work, the effects of second-order hydrodynamics on a floating semisubmersible offshore wind turbine are investigated. Because FAST is currently unable to account for second-order effects, a method to assess these effects was applied in which linearized properties of the floating wind system derived from FAST (including the 6x6 mass and stiffness matrices) are used by WAMIT to solve the first- and second-order hydrodynamics problems in the frequency domain. The method was applied to the Offshore Code Comparison Collaboration Continuation OC4-DeepCwind semisubmersible platform, supporting the National Renewable Energy Laboratory's 5-MW baseline wind turbine. In this paper, the loads and response of the system caused by the second-order hydrodynamics are analysed and compared to the first-order hydrodynamic loads and induced motions in the frequency domain. Further, the second-order loads and induced response data are compared to the loads and motions induced by aerodynamic loading as solved by FAST.

Bayati, I.; Jonkman, J.; Robertson, A.; Platt, A.

2014-06-01

420

Effects of Second-Order Hydrodynamics on a Semisubmersible Floating Offshore Wind Turbine: Preprint

The objective of this paper is to assess the second-order hydrodynamic effects on a semisubmersible floating offshore wind turbine. Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of the system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure. Observations of supposed second-order responses in wave-tank tests performed by the DeepCwind consortium at the MARIN offshore basin suggest that these effects might be more important than originally expected. These observations inspired interest in investigating how second-order excitation affects floating offshore wind turbines and whether second-order hydrodynamics should be included in offshore wind simulation tools like FAST in the future. In this work, the effects of second-order hydrodynamics on a floating semisubmersible offshore wind turbine are investigated. Because FAST is currently unable to account for second-order effects, a method to assess these effects was applied in which linearized properties of the floating wind system derived from FAST (including the 6x6 mass and stiffness matrices) are used by WAMIT to solve the first- and second-order hydrodynamics problems in the frequency domain. The method has been applied to the OC4-DeepCwind semisubmersible platform, supporting the NREL 5-MW baseline wind turbine. The loads and response of the system due to the second-order hydrodynamics are analysed and compared to first-order hydrodynamic loads and induced motions in the frequency domain. Further, the second-order loads and induced response data are compared to the loads and motions induced by aerodynamic loading as solved by FAST.

Bayati, I.; Jonkman, J.; Robertson, A.; Platt, A.

2014-07-01

421

Hydrodynamic fluctuations in confined emulsions

When an ensemble of particles interact hydrodynamically, they generically display large-scale transient structures such as swirls in sedimenting particles [1], or colloidal strings in sheared suspensions [2]. Understanding these nonequilibrium fluctuations is a very difficult problem, yet they are of great importance for a wide range of processes including pigment deposition in cosmetic or paint films, the transport of microfluidic droplets, ... All these samples concern rigidly confined fluids, which we consider in this paper. We address the collective dynamics of non-Brownian droplets cruising in a shallow microchannel. We provide a comprehensive characterization of their spatiotemporal density fluctuations. We show that density excitations freely propagate at all scales, and in all directions even though the particles are neither affected by potential forces nor by inertia. We introduce a theory which quantitatively accounts for our experimental findings. By doing so we demonstrate that the fluctuation spectrum of this nonequilibrium system is shaped by the combination of truly long-range hydrodynamic interactions and local collisions.

Nicolas Desreumaux; Jean-Baptiste Caussin; Raphael Jeanneret; Eric Lauga; Denis Bartolo

2013-01-23

422

Inducer Hydrodynamic Load Measurement Devices

NASA Technical Reports Server (NTRS)

Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six-component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This rotating balance was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher-frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.

Skelley, Stephen E.; Zoladz, Thomas F.; Turner, Jim (Technical Monitor)

2002-01-01

423

Hydrodynamic Jet Experiments at LLE

NASA Astrophysics Data System (ADS)

Observed jet and jet-like morphologies range from highly collimated flows associated with young stellar objects and active galactic nuclei to less-collimated flows associated with planetary nebulae. A technique, where seven beams from the OMEGA laser are incident onto a mid-Z plug embedded in a tungsten washer and two beams are used to generate x rays for radiography, is used to study jet outflows. An adiabatic model^1 best describes jet propagation. Episodic flows are created using double-pulse laser irradiation and show a different jet structure with more material along the jet stem. Episodic experiments have been designed for the OMEGA EP Laser System where the time between outflows can be made comparable to the hydrodynamic evolution time. 2-D Eulerian hydrodynamic simulations both model OMEGA and design OMEGA EP experiments. ^1E. C. Ostriker et al., ApJ 557, 443 (2001). This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.

Knauer, J. P.; Sublett, S.; Craxton, R. S.; Collins, T. J. B.; Igumenshchev, I. V.; Meyerhofer, D. D.; Frank, A.; Drake, R. P.

2008-04-01

424

Inducer Hydrodynamic Load Measurement Devices

NASA Technical Reports Server (NTRS)

Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This "rotating balance" was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.

Skelley, Stephen E.; Zoladz, Thomas F.

2002-01-01

425

Langmuir wave linear evolution in inhomogeneous nonstationary anisotropic plasma

Langmuir wave linear evolution in inhomogeneous nonstationary anisotropic plasma I. Y. Dodin, V. I A hydrodynamic equation describing the linear evolution of a nondissipative Langmuir wave in inhomogeneous, focused, and or deposited where necessary. In the case of Langmuir, or plasma waves,8 there may

426

Ocean waves, nearshore ecology, and natural selection Mark W. Denny*

-1 Ocean waves, nearshore ecology, and natural selection Mark W. Denny* Stanford University and Helmuth 2002). At high tide, ocean waves break on the shore, imposing large hydrodynamic forces, Intertidal communities, Lift, Wave theory Abstract Although they are subjected to one of the most stressful

Denny, Mark

427

Wave-swept shores are among the most stressful flow environments on earth. Near the shore, ocean waves are accompanied by velocities that may exceed 20 ms-1 and accelerations in excess of 500 ms-2 hydrodynamic forces on exposed plants and animals, and wave-induced damage is characteristic of intertidal

Denny, Mark

428

Hydrodynamics of an ultra-relativistic fluid in the flat anisotropic cosmological model

Motion of an ultra-relativistic perfect fluid in space-time with the Kasner metrics is investigated by the Hamiltonian method. It is found that in the limit of small times a tendency takes place to formation of strong inhomogeneities in matter distribution. In the case of slow flows the effect of non-stationary anisotropy on dynamics of sound waves and behaviour of frozen-in vortices is considered. It is shown that hydrodynamics of slow vortices on the static homogeneous background is equivalent to the usual Eulerian incompressible hydrodynamics, but in the presence of an external non-stationary strain velocity field.

V. P. Ruban; D. I. Podolsky

2001-02-20

429

NASA Astrophysics Data System (ADS)

We report the results of FLASH hydrodynamic simulations of the experiments conducted by the University of Oxford High Energy Density Laboratory Astrophysics group and its collaborators at the Laboratoire pour l'Utilisation de Lasers Intenses (LULI). In these experiments, a long-pulse laser illuminates a target in a chamber filled with Argon gas, producing shock waves that generate magnetic fields via the Biermann battery mechanism. The simulations show that the result of the laser illuminating the target is a series of complex hydrodynamic phenomena.

Scopatz, A.; Fatenejad, M.; Flocke, N.; Gregori, G.; Koenig, M.; Lamb, D. Q.; Lee, D.; Meinecke, J.; Ravasio, A.; Tzeferacos, P.; Weide, K.; Yurchak, R.

2013-03-01

430

Reliable estimation of shock position in shock-capturing compressible hydrodynamics codes

The displacement method for estimating shock position in a shock-capturing compressible hydrodynamics code is introduced. Common estimates use simulation data within the captured shock, but the displacement method uses data behind the shock, making the estimate consistent with and as reliable as estimates of material parameters obtained from averages or fits behind the shock. The displacement method is described in the context of a steady shock in a one-dimensional lagrangian hydrodynamics code, and demonstrated on a piston problem and a spherical blast wave.The displacement method's estimates of shock position are much better than common estimates in such applications.

Nelson, Eric M [Los Alamos National Laboratory

2008-01-01

431

Quantum-relativistic hydrodynamic model for a spin-polarized electron gas interacting with light.

We develop a semirelativistic quantum fluid theory based on the expansion of the Dirac Hamiltonian to second order in 1/c. By making use of the Madelung representation of the wave function, we derive a set of hydrodynamic equations that comprises a continuity equation, an Euler equation for the mean velocity, and an evolution equation for the electron spin density. This hydrodynamic model is then applied to study the dynamics of a dense and weakly relativistic electron plasma. In particular, we investigate the impact of the quantum-relativistic spin effects on the Faraday rotation in a one-dimensional plasma slab irradiated by an x-ray laser source. PMID:25122397

Morandi, Omar; Zamanian, Jens; Manfredi, Giovanni; Hervieux, Paul-Antoine

2014-07-01

432

Hydrodynamics of prey capture in sharks: effects

REPORT Hydrodynamics of prey capture in sharks: effects of substrate Sandra Nauwelaerts1,*, Cheryl predictions regarding the effects of substrate proximity on the feeding hydrodynamics of a benthic shark. An oblique circular cylinder and a shark head model were used. To test the models, we used digital particle

Nauwelaerts, Sandra

433

Hydrodynamic Modeling and the QGP Shear Viscosity

In this article, we will briefly review the recent progress on hydrodynamic modeling and the extraction of the quark-gluon plasma (QGP) specific shear viscosity with an emphasis on results obtained from the hybrid model VISHNU that couples viscous hydrodynamics for the macroscopic expansion of the QGP to the hadron cascade model for the microscopic evolution of the late hadronic stage.

Huichao Song

2012-07-10

434

Hydrodynamic investigation of the AUV PICASSO

JAMSTEC developed the AUV PICASSO for study of the deep-sea plankton and marine snow. To obtain adequate cruising performance such as propulsive performance and maneuverability, investigation of hydrodynamic performance is of necessity. The authors conducted the investigations of hydrodynamic performance of the AUV PICASSO such as a water resistance of hull with the numerical analysis - CFD and the experiments

Tomoya Inoue; Hiroyoshi Suzuki; Atsushi Yamamichi; Risa Kitamoto; Yoshitaka Watanabe; Hiroshi Yoshida

2011-01-01

435

Hydrodynamic flow from RHIC to LHC

The hydrodynamic model for the expansion of the fireball in relativistic heavy-ion collisions is presented. Calculations using relativistic hydrodynamics of a fluid with small viscosity yield a satisfactory description of the experimental data on the particle spectra, the elliptic flow or the interferometry radii.

Piotr Bozek

2011-11-18

436

Relativistic Hydrodynamics for Heavy-Ion Collisions

ERIC Educational Resources Information Center

Relativistic hydrodynamics is essential to our current understanding of nucleus-nucleus collisions at ultrarelativistic energies (current experiments at the Relativistic Heavy Ion Collider, forthcoming experiments at the CERN Large Hadron Collider). This is an introduction to relativistic hydrodynamics for graduate students. It includes a detailed…

Ollitrault, Jean-Yves

2008-01-01

437

Hydrodynamic models of a Cepheid atmosphere

NASA Technical Reports Server (NTRS)

Instead of computing a large number of coarsely zoned hydrodynamic models covering the entire atmospheric instability strip, the author computed a single model as well as computer limitations allow. The implicit hydrodynamic code of Kutter and Sparks was modified to include radiative transfer effects in optically thin zones.

Karp, A. H.

1975-01-01

438

The hydrodynamic theory of detonation

NASA Technical Reports Server (NTRS)

This report derives equations containing only directly measurable constants for the quantities involved in the hydrodynamic theory of detonation. The stable detonation speed, D, is revealed as having the lowest possible value in the case of positive material velocity, by finding the minimum of the Du curve (u denotes the speed of the gases of combustion). A study of the conditions of energy and impulse in freely suspended detonating systems leads to the disclosure of a rarefaction front traveling at a lower speed behind the detonation front; its velocity is computed. The latent energy of the explosive passes into the steadily growing detonation zone - the region between the detonation front and the rarefaction front. The conclusions lead to a new definition of the concept of shattering power. The calculations are based on the behavior of trinitrotoluene.

Langweiler, Heinz

1939-01-01

439

Hydrodynamics of vibrated granular monolayer.

We investigate the long-standing puzzle of phase separation in a granular monolayer vibrated from below. Although this system is three dimensional, an interesting dynamics occurs mostly in the horizontal plane, perpendicular to the direction of vibration. Experiments [Olafsen and Urbach, Phys. Rev. Lett. 81 4369 (1998)] demonstrated that for a high amplitude of vibration the system is in the gaslike phase, but when the amplitude becomes smaller than a certain threshold, a phase separation occurs: A solidlike dense condensate of particles forms in the center of the system, surrounded by particles in the gaslike phase. We explain theoretically the experimentally observed coexistence of dilute and dense phases, employing Navier-Stokes granular hydrodynamics. We show that the phase separation is associated with a negative compressibility of granular gas.

Khain, E.; Aranson, I. S. (Materials Science Division); (Oakland Univ.)

2011-01-01

440

Hydrodynamics and phases of flocks

We review the past decade's theoretical and experimental studies of flocking: the collective, coherent motion of large numbers of self-propelled 'particles' (usually, but not always, living organisms). Like equilibrium condensed matter systems, flocks exhibit distinct 'phases' which can be classified by their symmetries. Indeed, the phases that have been theoretically studied to date each have exactly the same symmetry as some equilibrium phase (e.g., ferromagnets, liquid crystals). This analogy with equilibrium phases of matter continues in that all flocks in the same phase, regardless of their constituents, have the same 'hydrodynamic'-that is, long-length scale and long-time behavior, just as, e.g., all equilibrium fluids are described by the Navier-Stokes equations. Flocks are nonetheless very different from equilibrium systems, due to the intrinsically nonequilibrium self-propulsion of the constituent 'organisms'. This difference between flocks and equilibrium systems is most dramatically manifested in the ability of the simplest phase of a flock, in which all the organisms are, on average moving in the same direction (we call this a 'ferromagnetic' flock; we also use the terms 'vector-ordered' and 'polar-ordered' for this situation) to exist even in two dimensions (i.e., creatures moving on a plane), in defiance of the well-known Mermin-Wagner theorem of equilibrium statistical mechanics, which states that a continuous symmetry (in this case, rotation invariance, or the ability of the flock to fly in any direction) can not be spontaneously broken in a two-dimensional system with only short-ranged interactions. The 'nematic' phase of flocks, in which all the creatures move preferentially, or are simply oriented preferentially, along the same axis, but with equal probability of moving in either direction, also differs dramatically from its equilibrium counterpart (in this case, nematic liquid crystals). Specifically, it shows enormous number fluctuations, which actually grow with the number of organisms faster than the N 'law of large numbers' obeyed by virtually all other known systems. As for equilibrium systems, the hydrodynamic behavior of any phase of flocks is radically modified by additional conservation laws. One such law is conservation of momentum of the background fluid through which many flocks move, which gives rise to the 'hydrodynamic backflow' induced by the motion of a large flock through a fluid. We review the theoretical work on the effect of such background hydrodynamics on three phases of flocks-the ferromagnetic and nematic phases described above, and the disordered phase in which there is no order in the motion of the organisms. The most surprising prediction in this case is that 'ferromagnetic' motion is always unstable for low Reynolds-number suspensions. Experiments appear to have seen this instability, but a quantitative comparison is awaited. We conclude by suggesting further theoretical and experimental work to be done.

Toner, John [Institute of Theoretical Science, Department of Physics, University of Oregon, Eugene, OR 97403-5203 (United States); Tu Yuhai [IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States)]. E-mail: yuhai@us.ibm.com; Ramaswamy, Sriram [Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012 (India)

2005-07-01

441

Hydrodynamic Coarsening of Binary Fluids

NASA Astrophysics Data System (ADS)

By suitable interpretation of results from the linear analysis of interface dynamics, it is found that the hydrodynamic growth of the size L of domains that follow spinodal decomposition in fluid mixtures scales with time as L~t?, with ? = 4/7 in the inertial regime. The previously proposed exponent ? = 2/3 is shown to indicate only the scaling of the oscillatory frequency ?-2/3~L of the largest structures of the system. The viscous dissipation in the system occurs within a layer of thickness Ld that also follows a power law of the form Ld~L3/4 in the inertial regime. In the viscous regime the growth is linear in time L~t and the dissipative region remains constant Ld~L0.

Solis, Francisco J.; Olvera de La Cruz, Monica

2000-04-01

442

Hydrodynamic coarsening of binary fluids

By suitable interpretation of results from the linear analysis of interface dynamics, it is found that the hydrodynamic growth of the size L of domains that follow spinodal decomposition in fluid mixtures scales with time as L approximately t(alpha), with alpha = 4/7 in the inertial regime. The previously proposed exponent alpha = 2/3 is shown to indicate only the scaling of the oscillatory frequency omega(-2/3) approximately L of the largest structures of the system. The viscous dissipation in the system occurs within a layer of thickness L(d) that also follows a power law of the form L(d) approximately L3/4 in the inertial regime. In the viscous regime the growth is linear in time L approximately t and the dissipative region remains constant L(d) approximately L0. PMID:11019087

Solis; Olvera De La Cruz M

2000-04-10

443

Hydrodynamic Limit for Interacting Neurons

NASA Astrophysics Data System (ADS)

This paper studies the hydrodynamic limit of a stochastic process describing the time evolution of a system with N neurons with mean-field interactions produced both by chemical and by electrical synapses. This system can be informally described as follows. Each neuron spikes randomly following a point process with rate depending on its membrane potential. At its spiking time, the membrane potential of the spiking neuron is reset to the value 0 and, simultaneously, the membrane potentials of the other neurons are increased by an amount of potential . This mimics the effect of chemical synapses. Additionally, the effect of electrical synapses is represented by a deterministic drift of all the membrane potentials towards the average value of the system. We show that, as the system size N diverges, the distribution of membrane potentials becomes deterministic and is described by a limit density which obeys a non linear PDE which is a conservation law of hyperbolic type.

De Masi, A.; Galves, A.; Löcherbach, E.; Presutti, E.

2015-02-01

444

The hydrodynamics of dolphin drafting

Background Drafting in cetaceans is defined as the transfer of forces between individuals without actual physical contact between them. This behavior has long been surmised to explain how young dolphin calves keep up with their rapidly moving mothers. It has recently been observed that a significant number of calves become permanently separated from their mothers during chases by tuna vessels. A study of the hydrodynamics of drafting, initiated in the hope of understanding the mechanisms causing the separation of mothers and calves during fishing-related activities, is reported here. Results Quantitative results are shown for the forces and moments around a pair of unequally sized dolphin-like slender bodies. These include two major effects. First, the so-called Bernoulli suction, which stems from the fact that the local pressure drops in areas of high speed, results in an attractive force between mother and calf. Second is the displacement effect, in which the motion of the mother causes the water in front to move forwards and radially outwards, and water behind the body to move forwards to replace the animal's mass. Thus, the calf can gain a 'free ride' in the forward-moving areas. Utilizing these effects, the neonate can gain up to 90% of the thrust needed to move alongside the mother at speeds of up to 2.4 m/sec. A comparison with observations of eastern spinner dolphins (Stenella longirostris) is presented, showing savings of up to 60% in the thrust that calves require if they are to keep up with their mothers. Conclusions A theoretical analysis, backed by observations of free-swimming dolphin schools, indicates that hydrodynamic interactions with mothers play an important role in enabling dolphin calves to keep up with rapidly moving adult school members. PMID:15132740

Weihs, Daniel

2004-01-01

445

Exchange interaction effects on waves in magnetized quantum plasmas

NASA Astrophysics Data System (ADS)

We have applied the many-particle quantum hydrodynamics that includes the Coulomb exchange interaction to magnetized quantum plasmas. We considered a number of wave phenomena that are affected by the Coulomb exchange interaction. Since the Coulomb exchange interaction affects the longitudinal and transverse-longitudinal waves, we focused our attention on the Langmuir waves, the Trivelpiece-Gould waves, the ion-acoustic waves in non-isothermal magnetized plasmas, the dispersion of the longitudinal low-frequency ion-acoustic waves, and low-frequency electromagnetic waves at Te ? Ti. We have studied the dispersion of these waves and present the numeric simulation of their dispersion properties.

Trukhanova, Mariya, Iv.; Andreev, Pavel A.

2015-02-01

446

Analogies and distinctions between hydrodynamic and optical nonlinear waves

NASA Astrophysics Data System (ADS)

We present the algorithm based on the Lax pair generalization to reveal some properties of nonautonomous KdV solitons. Starting from the general method of solution for the nonisospectral IST problem, we demonstrate how the varying-coefficient KdV equation can arise in nonuniformed and inhomogeneous media. We write down the one- and two-soliton solution of the nonautonomous varying-coefficient KdV with the time-dependent spectral parameter and consider some special cases of the isospectral solutions of the KdV equation with varying dispersion, nonlinearity, and gain. Finally, we compare these solutions with the nonautonomous solitons of the NLSE emphasizing their common features.

Mena-Contla, A.; Peña-Moreno, R.; Morales-Lara, L.; Serkin, V. N.; Belyaeva, T. L.

2015-01-01

447

Pilot-wave hydrodynamics in a rotating frame: Exotic orbits

We present the results of a numerical investigation of droplets walking on a rotating vibrating fluid bath. The drop's trajectory is described by an integro-differential equation, which is simulated numerically in various parameter regimes. As the forcing acceleration is progressively increased, stable circular orbits give way to wobbling orbits, which are succeeded in turn by instabilities of the orbital center characterized by steady drifting then discrete leaping. In the limit of large vibrational forcing, the walker's trajectory becomes chaotic, but its statistical behavior reflects the influence of the unstable orbital solutions. The study results in a complete regime diagram that summarizes the dependence of the walker's behavior on the system parameters. Our predictions compare favorably to the experimental observations of Harris and Bush [“Droplets walking in a rotating frame: from quantized orbits to multimodal statistics,” J. Fluid Mech. 739, 444–464 (2014)].

Oza, Anand U.; Harris, Daniel M.; Rosales, Rodolfo R.; Bush, John W. M., E-mail: bush@math.mit.edu [Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Wind-Willassen, Øistein [Department of Applied Mathematics and Computer Science, Technical University of Denmark, 2800 Kongens Lyngby (Denmark)

2014-08-15

448

Hydrodynamic Analysis of Some Wave-Energy Conversion Systems

A general formulation of the hydromechanic problem of floating as well as bottom-mounted structures with oscillating water column devices is given here. Three types of first-order boundary-value problems are investigated, the volume flow through the OWC device is considered including the turbine characteristics. The boundary-value problems are solved using the macroelement technique for both arbitrary cross-sections and for vertical bodies

K. Kokkinowrachos; I. Thanos; H. G. Zibell

1987-01-01