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Particle Dynamics Studied by Diffusing Wave Spectroscopy in a Ferrofluid Emulsion  

Microsoft Academic Search

A ferrofluid emulsion is used to study the effect of a dipole-dipole interaction on particle dynamics in high concentrations. The dipole moment in each emulsion particle is induced by an external magnetic field. The magnetic dipole-dipole interaction causes the particles to form chains, columns or labyrinthine structures which changes the particle dynamics. In the concentrated regime, diffusing wave spectroscopy is

Sadayoshi Okumoto



Hydrodynamics of ocean wave-energy utilization  

Microsoft Academic Search

This book presents papers on wave energy converters. Topics considered include hydrodynamics, resonance, air turbines, buoys, physical and mathematical modeling, nonlinear damping, China's research on wave power, wave climate, site selection, wave forces, ship propulsion, wave energy absorption, phase control, optimal control, oscillating water columns, air flow, pneumatics, wave propagation, the survival of surface-piercing wave energy devices in extreme waves,

D. V. Evans; A. F. de O. Falcao



Smooth Particle Hydrodynamics for Surf Zone Waves.  

National Technical Information Service (NTIS)

The objectives of this project are to improve the Smooth Particle Hydrodynamics (SPH) model for use in examining the physics of breaking waves, including the description of the wave-induced turbulence and sediment transport within the surf zone. Improveme...

R. A. Dalrymple



Detonation waves in relativistic hydrodynamics  

SciTech Connect

This paper is concerned with an algebraic study of the equations of detonation waves in relativistic hydrodynamics taking into account the pressure and the energy of thermal radiation. A new approach to shock and detonation wavefronts is outlined. The fluid under consideration is assumed to be perfect (nonviscous and nonconducting) and to obey the following equation of state: {ital p}=({gamma}{minus}1){rho} where {ital p}, {rho}, and {gamma} are the pressure, the total energy density, and the adiabatic index, respectively. The solutions of the equations of detonation waves are reduced to the problem of finding physically acceptable roots of a quadratic polynomial {Pi}({ital X}) where {ital X} is the ratio {tau}/{tau}{sub 0} of dynamical volumes behind and ahead of the detonation wave. The existence and the locations of zeros of this polynomial allow it to be shown that if the equation of state of the burnt fluid is known then the variables characterizing the unburnt fluid obey well-defined physical relations.

Cissoko, M. (Universite Pierre et Marie Curie, Paris VI, Laboratoire de Gravitation et de Cosmologie Relativistes, Institut Henri Poincare, 11 Rue Pierre et Marie Curie, 7500 Paris (France))



Ferrofluid Film Bearing for enhancement of rotary scanner performance  

NASA Astrophysics Data System (ADS)

Hydrodynamic bearings utilizing ferrofluids are a new class of high performance bearings. These bearings are self-contained with ferrofluid acting both as a hydrodynamic pressure film and a sealant. Although relatively unknown in the laser scanner industry, ferrofluids have been widely used over the last two decades for applications in the semiconductor, computer and audio marketplaces. In this paper, performance features of Ferrofluid Film Bearings are also discussed, and experimental data such as power consumption, rotational accuracy and audible noise are presented to show that Ferrofluid Film Bearings enhance the performance of high resolution scanners and in this application are superior to ball bearing and gas bearing performance.

Cheever, Charles; Li, Zhixin; Raj, Kuldip



PREFACE: Ferrofluids  

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



Surface Instabilities of Ferrofluids  

Microsoft Academic Search

We report on recent progress in understanding the formation of surface protuberances on a planar layer of ferrofluid in a\\u000a magnetic field oriented normally to the surface. This normal field or Rosensweig instability can be tackled by a linear and\\u000a a nonlinear description. In the linear regime of small amplitudes we focus on the wave number of maximal growth, its

R. Richter; A. Lange


Hydrodynamic interaction between two vertical cylinders in water waves  

Microsoft Academic Search

The hydrodynamic interaction between two vertical cylinders in water waves is investigated based on the linearized potential flow theory. One of the two cylinders is fixed at the bottom while the other is articulated at the bottom and oscillates with small amplitudes in the direction of the incident wave. Both the diffracted wave and the rediation wave are studied in

Zhou Xianchu; Wang Dongjiao; Allen T. Chwang



Hydrodynamic principles of wave power extraction.  


The hydrodynamic principles common to many wave power converters are reviewed via two representative systems. The first involves one or more floating bodies, and the second water oscillating in a fixed enclosure. It is shown that the prevailing basis is impedance matching and resonance, for which the typical analysis can be illustrated for a single buoy and for an oscillating water column. We then examine the mechanics of a more recent design involving a compact array of small buoys that are not resonated. Its theoretical potential is compared with that of a large buoy of equal volume. A simple theory is also given for a two-dimensional array of small buoys in well-separated rows parallel to a coast. The effects of coastline on a land-based oscillating water column are examined analytically. Possible benefits of moderate to large column sizes are explored. Strategies for broadening the frequency bandwidth of high efficiency by controlling the power-takeoff system are discussed. PMID:22184659

Mei, Chiang C



Electron magneto-hydrodynamic waves bounded by magnetic bubble  

NASA Astrophysics Data System (ADS)

The propagation of electron magneto-hydrodynamic (EMHD) waves is studied experimentally in a 3-dimensional region of low magnetic field surrounded by stronger magnetic field at its boundaries. We report observations where bounded left hand polarized Helicon like EMHD waves are excited, localized in the region of low magnetic field due to the boundary effects generated by growing strengths of the ambient magnetic field rather than a conducting or dielectric material boundary. An analytical model is developed to include the effects of radially nonuniform magnetic field in the wave propagation. The bounded solutions are compared with the experimentally obtained radial wave magnetic field profiles explaining the observed localized propagation of waves.

Anitha, V. P.; Sharma, D.; Banerjee, S. P.; Mattoo, S. K.



Electron magneto-hydrodynamic waves bounded by magnetic bubble  

SciTech Connect

The propagation of electron magneto-hydrodynamic (EMHD) waves is studied experimentally in a 3-dimensional region of low magnetic field surrounded by stronger magnetic field at its boundaries. We report observations where bounded left hand polarized Helicon like EMHD waves are excited, localized in the region of low magnetic field due to the boundary effects generated by growing strengths of the ambient magnetic field rather than a conducting or dielectric material boundary. An analytical model is developed to include the effects of radially nonuniform magnetic field in the wave propagation. The bounded solutions are compared with the experimentally obtained radial wave magnetic field profiles explaining the observed localized propagation of waves.

Anitha, V. P.; Sharma, D.; Banerjee, S. P.; Mattoo, S. K. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)



Advances in ferrofluid technology  

NASA Astrophysics Data System (ADS)

Traditional ferrofluid products such as multistage rotary seals, exclusion seals, inertia dampers and loudspeakers are now a well established industry. Additionally, in the last few years a number of new applications have emerged such as ferrofluid steppers, gauges and sensors. The purpose of this paper is to review recent advances in ferrofluid technology both in the conventional and in new market areas.

Raj, K.; Moskowitz, B.; Casciari, R.



Nonlinear Generalized Hydrodynamic Wave Equations in Strongly Coupled Dusty Plasmas  

SciTech Connect

A set of nonlinear equations for the study of low frequency waves in a strongly coupled dusty plasma medium is derived using the phenomenological generalized hydrodynamic (GH) model and is used to study the modulational stability of dust acoustic waves to parallel perturbations. Dust compressibility contributions arising from strong Coulomb coupling effects are found to introduce significant modifications in the threshold and range of the instability domain.

Veeresha, B. M.; Sen, A.; Kaw, P. K. [Institute for Plasma Research, Bhat, Gandhinagar-382428 (India)



Sound damping in ferrofluids: magnetically enhanced compressional viscosity.  


The damping of sound waves in magnetized ferrofluids is investigated and shown to be considerably higher than in the nonmagnetized case. This fact may be interpreted as a field-enhanced, effective compressional viscosity-in analogy to the ubiquitous field-enhanced shear viscosity that is known to be the reason for many unusual behaviors of ferrofluids under shear. PMID:12689056

Müller, Hanns Walter; Jiang, Yimin; Liu, Mario



Existence of Electromagnetic-Hydrodynamic Waves  

Microsoft Academic Search

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



Ferrofluidic adaptive mirrors  

NASA Astrophysics Data System (ADS)

A magnetic liquid mirror based on ferrofluids was demonstrated. Magnetic liquid mirrors represent a major departure from solid mirror technology. They present both advantages and disadvantages with respect to established technologies. Stroke (from a fraction of a wave to several hundreds of micrometers), cost (a few dollars per actuator), and scalability (hundreds of thousands of actuators) are the main advantages. Very large mirrors having diameters of the order of a meter should be feasible. There are a few disadvantages. The most important disadvantage is the time response, which is of the order of a few milliseconds. Although this time response could be further decreased with additional technical developments, it is unlikely to match the speed of solid mirrors. The technology is still in its infancy, and considerable work must still be done. However, the advantages are such that the technology is worth pursuing.

Laird, P.; Caron, N.; Rioux, M.; Borra, E. F.; Ritcey, A.




SciTech Connect

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)



Ferrofluid and cellulolytic fungi  

NASA Astrophysics Data System (ADS)

The study of petroleum ferrofluid influence upon the biology of the cellulolytic fungus Chaetomium globosum, with implications in cellulose biotechnology, was carried out. Taking into account previous results revealing the ferrofluid effects on the cellulose enzyme complex as well as on the dehydrogenases, the results of the investigation of catalase and peroxidase behavior are presented in this paper. The intensification of catalase biosynthesis in response to the increase of hydrogen peroxide after fungus cell interference with the petroleum ferrofluid was the main issue of the experiments.

Manoliu, Al.; Oprica, Lacramioara; Creanga, Dorina-Emilia



Contribution to hydrodynamic equations from interaction of oblique magnetosonic waves with plasmaspheric thermal electrons  

Microsoft Academic Search

The contribution to hydrodynamic equations from thermal electron interactions on Cerenkov resonance with magnetosonic (MS) waves propagating at ``large'' angles to the Earth's magnetic field. The Grad 13-moment approximation is used to calculate the moments of quasilinear collision integrals. The moments describe the variations of the macroscopic parameters of electron components in the respective hydrodynamic equations due to resonance interaction.

Yu. v. Konikov



Contribution to hydrodynamic equations from interaction of oblique magnetosonic waves with plasmaspheric thermal electrons  

Microsoft Academic Search

The quasi-linear approximation is presently used to calculate the contribution made to hydrodynamic equations by the interactions of plasmaspheric thermal electrons with magnetosonic (MS) waves in the Cerenkov resonance. Attention is given to waves propagating at large angles to the earth's magnetic field, with a view to modeling the thermal electron component in the outer plasmasphere, outside the wave generation

Iu. V. Konikov



Hydrodynamic theory of electromagnetic fields in continuous media  

Microsoft Academic Search

The hydrodynamic Maxwell equations of continuous media, valid for large amplitudes and small frequencies, are derived. As any hydrodynamic theory, these equations are universal, nonlinear, and irreversible. Consequences for dielectric liquids, ferrofluids, superconductors, and nematic liquid crystals are briefly outlined.

Mario Liu



A volume-based hydrodynamic approach to sound wave propagation in a monatomic gas  

NASA Astrophysics Data System (ADS)

We investigate sound wave propagation in a monatomic gas using a volume-based hydrodynamic model. In Dadzie et al. [Physica A 387, 6079 (2008)], a microscopic volume-based kinetic approach was proposed by analyzing molecular spatial distributions; this led to a set of hydrodynamic equations incorporating a mass-density diffusion component. Here we find that these new mass-density diffusive flux and volume terms mean that our hydrodynamic model, uniquely, reproduces sound wave phase speed and damping measurements with excellent agreement over the full range of Knudsen number. In the high Knudsen number (high frequency) regime, our volume-based model predictions agree with the plane standing waves observed in the experiments, which existing kinetic and continuum models have great difficulty in capturing. In that regime, our results indicate that the ``sound waves'' presumed in the experiments may be better thought of as ``mass-density waves,'' rather than pressure waves.

Dadzie, S. Kokou; Reese, Jason M.



Magnetorheology of ferrofluid composites  

Microsoft Academic Search

Composites consisting of nonmagnetic particles with sizes in the micron range suspended in a ferrofluid constitute an inverse magnetorheological fluid. Structuring occurs in an applied magnetic field and can result in the solidification of the composite. Above a critical level of applied stress the material further transforms to a liquid state. Data confirming the existence of a solidified state are

R. E. Rosensweig; J. Popplewell; J. K. Siller



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.

Taylor, Amy R.; Broadwell, Bethany P.; Jones, M. G.; Falvo, Michael R.



Ferrofluid flow for TOUGH2  

Microsoft Academic Search

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

Curtis Oldenburg; George Moridis




Microsoft Academic Search

This reissue of the classic 1932 edition of Lamb's Hydrodynamics is an indication of the lasting value of the work. Constantly in use since its first publication in 1892, this book is the definitive reference work for all fluid dynamicists. The new foreword by Professor R. Caflisch highlights the prominence of this treatise in the field and outlines the development

Horace Lamb



Simulating Wave-Driven Circulation in Tidal Inlets With Tide and River Forcing Using a Coupled Hydrodynamic-Wave Model  

NASA Astrophysics Data System (ADS)

Tidal inlets are important areas with respect to bio-diversity, sediment transport, and fresh water river outflow. This study examines the 2-D depth-averaged circulation of inlets that are driven by waves, tides, and fresh water river inflow using a coupled hydrodynamic-wave model. The circulation patterns of an ideal embayment and Bay St. Louis, located in the northeastern Gulf of Mexico, are compared under the range of forcing conditions. Wave-current interaction is simulated by iteratively coupling the depth-integrated ADCIRC-2DDI hydrodynamic model to the phase-averaged spectral wave model SWAN. Radiation stress gradients are determined from the wave predictions of SWAN and used to force the circulation model. ADCIRC-2DDI is a fully developed, 2-dimensional, finite element, barotropic hydrodynamic model capable of including wind, wave, and tidal forcing as well as river flux into the domain. The circulation within each inlet is examined during the flood, slack, and ebb phases of the tidal cycles with and without river inflow under different wave conditions. The effects of including/excluding advection and varying the strength of the lateral mixing are examined as well. The influence of the various forcings on bay/inlet circulation is further investigated by the introduction of Lagrangian tracers. Lagrangian tracers are a reasonable indicator of how circulation patterns affect the motion of sediment particles or passive biological organisms such as fish larvae. Lastly, influence of the wave model itself in the hydrodynamic coupling, and in particular the effect of wave diffraction on the wave-induced circulation, is comparatively examined within the ideal inlet by separately coupling the REF/DIF1 and REF/DIFS wave models to ADCIRC-2DDI; REF/DIF1 is a monochromatic phase-resolving wave model capable of simulating wave diffraction and refraction and REF/DIF-S is a multi-spectral version of REF/DIF1.

Cobb, M.; Blain, C. A.



Dispersion of ferrofluid aggregates in steady flows  

NASA Astrophysics Data System (ADS)

Using focused shadowgraphs, we investigate steady flows of a magnetically non-susceptible fluid interacting with ferrofluid aggregates comprised of superparamagnetic nanoparticles. The ferrofluid aggregate is retained at a specific site within the flow channel using two different applied magnetic fields. The bulk flow induces shear stresses on the aggregate, which give rise to the development of interfacial disturbances, leading to Kelvin-Helmholtz (K-H) instabilities and shedding of ferrofluid structures. Herein, the effects of bulk Reynolds number, ranging from 100 to 1000, and maximum applied magnetic fields of 1.2 × 105 and 2.4 × 105 A/m are investigated in the context of their impact on dispersion or removal of material from the core aggregate. The aggregate interaction with steady bulk flow reveals three regimes of aggregate dynamics over the span of Reynolds numbers studied: stable, transitional, and shedding. The first regime is characterized by slight aggregate stretching for low Reynolds numbers, with full aggregate retention. As the Reynolds number increases, the aggregate is in-transition between stable and shedding states. This second regime is characterized by significant initial stretching that gives way to small amplitude Kelvin-Helmholtz waves. Higher Reynolds numbers result in ferrofluid shedding, with Strouhal numbers initially between 0.2 and 0.3, wherein large vortical structures are shed from the main aggregate accompanied by precipitous decay of the accumulated ferrofluid aggregate. These behaviors are apparent for both magnetic field strengths, although the transitional Reynolds numbers are different between the cases, as are the characteristic shedding frequencies relative to the same Reynolds number. In the final step of this study, relevant parameters were extracted from the time series dispersion data to comprehensively quantify aggregate mechanics. The aggregate half-life is found to decrease as a function of the Reynolds number following a power law curve and can be scaled for different magnetic fields using the magnetic induction at the inner wall of the vessel. In addition, the decay rate of the ferrofluid is shown to be proportional to the wall shear rate. Finally, a dimensionless parameter, which scales the inertia-driven flow pressures, relative to the applied magnetic pressures, reveals a power law decay relationship with respect to the incident bulk flow.

Williams, Alicia M.; Vlachos, Pavlos P.



Full wave solution for hydrodynamic behaviors of pile breakwater  

NASA Astrophysics Data System (ADS)

Rayleigh expansion is used to study the water-wave interaction with a row of pile breakwater in finite water depth. Evanescent waves, the wave energy dissipated on the fluid resistance and the thickness of the breakwater are totally included in the model. The formulae of wave reflection and transmission coefficients are obtained. The accuracy of the present model is verified by a comparison with existing results. It is found that the predicted wave reflection and transmission coefficients for the zero order are all highly consistent with the experimental data (Hagiwara, 1984; Isaacson et al., 1998) and plane wave solutions (Zhu, 2011). The losses of the wave energy for the fluid passing through slits play an important role, which removes the phenomena of enhanced wave transmission.

Zhu, Da-tong



Ferrofluid flow for TOUGH2  

SciTech Connect

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



Simulating Wave-Driven Circulation in Tidal Inlets With Tide and River Forcing Using a Coupled Hydrodynamic-Wave Model  

Microsoft Academic Search

Tidal inlets are important areas with respect to bio-diversity, sediment transport, and fresh water river outflow. This study examines the 2-D depth-averaged circulation of inlets that are driven by waves, tides, and fresh water river inflow using a coupled hydrodynamic-wave model. The circulation patterns of an ideal embayment and Bay St. Louis, located in the northeastern Gulf of Mexico, are

M. Cobb; C. A. Blain



Hydrodynamic Wave Loading on Offshore Structures Simulated by a Two-Phase Flow Model  

Microsoft Academic Search

The numerical simulation of hydrodynamic wave loading on different types of offshore structures is important to predict forces on and water motion around these structures. This paper presents a numerical study of the effects of two-phase flow on an offshore structure subject to breaking waves.\\u000aThe details of the numerical model, an improved Volume Of Fluid (iVOF) method, are presented

Rik Wemmenhove; Erwin Loots; Arthur E. P. Veldman



Multi-body Systems in Waves - Impact of Hydrodynamic Coupling on Motions  

Microsoft Academic Search

Offshore installation procedures frequently require the operation of two or more structures in close proximity. Due to radiated and diffracted waves these multi-body systems are hydrodynamically coupled. As a consequence significant additional motions are observed. In case of lifting operations limitations are given by significant or maximum allowable relative motions which follow from the rigid body motions of each structure.

F. Clauss; Katja Jacobsen


Wake II model for hydrodynamic forces on marine pipelines including waves and currents  

Microsoft Academic Search

The Wake II model for the determination of the hydrodynamic forces on marine pipelines is extended to include currents and waves. There are two main differences between the Wake II and the traditional model. First, in the Wake II model the velocity is modified to include the pipe's encounter with the wake flow when the velocity reverses. Second, the model

Said R Sabag; Billy L Edge; Iwan Soedigdo




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...



Technology Transfer Automated Retrieval System (TEKTRAN)

Longissimus lumborum samples were removed 24 h postmortem from six U.S. Utility carcasses to be utilized in determining the effects of tenderness enhancement methods and aging time on quality attributes of beef. Within each sample, sections were randomly assigned to hydrodynamic shock waves (HSW), b...


Physics in Action: Ferrofluid Fun  

NSDL National Science Digital Library

This article describes ferrofluids, which are man-made liquid magnets. The site tells how these liquid magnets are made, what their current uses are, as well as possible future applications. There are also links to research efforts.

Central, Physics



Microelectromagnetic ferrofluid-based actuator  

NASA Astrophysics Data System (ADS)

Computer simulations were used to investigate the performance of a microscale ferrofluid-based magnetic actuator developed for liquid dispensing in microfluidic channels. The actuation was based on the movement of a ferrofluid plug in a magnetic field gradient generated by on-chip effectively infinite parallel conductors. The movement, positioning, and retaining of ferrofluid plugs with different lengths at various locations along a microfluidic channel were investigated for two cases. In case (a), the magnetic field gradient was generated by a single conductor; when the ferrofluid reached its equilibrium position, the current was switched off and the nearest neighbor conductor was energized. A similar, consecutive on/off current switching was performed for case (b), where a set of conductors was energized simultaneously.

Melikhov, Y.; Lee, S. J.; Jiles, D. C.; Schmidt, D. H.; Porter, M. D.; Shinar, R.



X-ray pulsar hydrodynamics: Collisionless shock waves and steady state infall hydrodynamics  

Microsoft Academic Search

X-ray pulsar emission is caused by mass infalling onto the magnetic polar regions of neutron stars. The collision stopping length caused by nuclear and coulomb collisions is too large for a standing shock to form above a neutron star surface. We show that collisionless excitation of plasma waves can probably produce a stopping length sufficiently small for such a shock

William K. Rose



Ferrofluid-Impregnated Paper Actuators  

Microsoft Academic Search

In this paper, we report on an inexpensive method of fabricating miniature magnetic actuators using ferrofluid- impregnated paper. Different types of papers (including soft tissue paper, cleanroom paper, Whatman-1 filter paper, printer paper, and newspaper) were loaded with oil-based ferrofluid, microma- chined by a CO2 laser and coated with a thin layer of parylene-C. The soaking capability of the different

Zhenwen Ding; Pinghung Wei; Girish Chitnis; Babak Ziaie



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



Calculation of Chemical Detonation Waves With Hydrodynamics and Thermochemical Equation of State  

SciTech Connect

We model detonation waves for solid explosives, using 2-D Arbitrary Lagrange Eulerian (ALE) hydrodynamics, with an equation of state (EOS) based on thermochemical equilibrium, coupled with simple kinetic rate laws for a few reactants. The EOS for the product species is based on either a BKWC EOS or on an exponential-6 potential model, whose parameters are fitted to a wide range of shock Hugoniot and static compression data. We show some results for the non ideal explosive, urea nitrate. Such a model is a powerful tool for studying such processes as initiation, detonation wave propagation and detonation wave propagation as a function of cylindrical radius.

Howard, W M; Fried, L E; Souers, P C; Vitello, P A



A Dynamic Analysis of Hydrodynamic Wave Journal Bearings  

Microsoft Academic Search

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

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



Three-dimensional hydrodynamic hot-spot model. [HMX, nitroguanidine; interactions of shock waves and voids  

SciTech Connect

The interaction of a shock wave with a single air hole and a matrix of air holes in PETN, HMX, and TATB has been numerically modeled. The hot-spot formation, interaction, and the resulting buildup toward detonation were computed using three-dimensional numerical Eulerian hydrodynamics with Arrhenius chemical reaction and accurate equations of state according to the hydrodynamic hot-spot model. The basic differences between shock sensitive explosives (PETN, HMX) and shock insensitive explosives (TATB, NQ) may be described using the hydrodynamic hot-spot model. The reactive hydrodynamics of desensitization of heterogeneous explosives by a weak preshock has been numerically modeled. The preshock desensitizes the heterogeneous explosive by closing the air holes and making it more homogeneous. A higher pressure second shock has a lower temperature in the multiple shocked explosive than in single shocked explosives. The multiple shock temperature may be low enough to cause a detonation wave to fail to propagate through the preshocked explosive. 10 refs., 12 figs.

Mader, C.L.; Kershner, J.D.



Second-Order Hydrodynamic Interactions in an Array of Vertical Cylinders in Bichromatic Waves  

Microsoft Academic Search

A complete second-order solution is presented for the hydrodynamic forces on an array of bottom-mounted, surface-piercing, vertical cylinders of arbitrary cross-section in bichromatic waves. Exploiting the constant structural cross-sections, the vertical dependency of the linearized potentials is expressed in terms of eigenfunction expansions. A two-dimensional Green's function approach may then be utilized to solve the first-order problem. Green's second identity

W. I. Moubayed; A. N. Williams



Calculation of Chemical Detonation Waves with Hydrodynamics and a Thermochemical Equation of State  

NASA Astrophysics Data System (ADS)

We model detonation waves for solid explosives, using 2-D Arbitrary Lagrange Eulerian (ALE) hydrodynamics, with an equation of state (EOS) based on thermochemical equilibrium, coupled with simple kinetic rate laws for a few reactants. The EOS for the product species is based on an exponential-6 potential model, whose parameters are fitted to a wide range of shock Hugoniot and static compression data. We show some results for the non-ideal explosive, urea nitrate. Such a model is a powerful tool for studying such processes as initiation, and detonation wave propagation as a function of cylindrical radius.

Howard, W. M.; Fried, L. E.; Souers, P. C.; Vitello, P. A.



Hydrodynamic forcing on salt-marsh development: Distinguishing the relative importance of waves and tidal flows  

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.



Super-rogue waves in simulations based on weakly nonlinear and fully nonlinear hydrodynamic equations.  


The rogue wave solutions (rational multibreathers) of the nonlinear Schrödinger equation (NLS) are tested in numerical simulations of weakly nonlinear and fully nonlinear hydrodynamic equations. Only the lowest order solutions from 1 to 5 are considered. A higher accuracy of wave propagation in space is reached using the modified NLS equation, also known as the Dysthe equation. This numerical modeling allowed us to directly compare simulations with recent results of laboratory measurements in Chabchoub et al. [Phys. Rev. E 86, 056601 (2012)]. In order to achieve even higher physical accuracy, we employed fully nonlinear simulations of potential Euler equations. These simulations provided us with basic characteristics of long time evolution of rational solutions of the NLS equation in the case of near-breaking conditions. The analytic NLS solutions are found to describe the actual wave dynamics of steep waves reasonably well. PMID:23944540

Slunyaev, A; Pelinovsky, E; Sergeeva, A; Chabchoub, A; Hoffmann, N; Onorato, M; Akhmediev, N



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.



Hydrodynamic Synchronization and Metachronal Waves on the Surface of the Colonial Alga Volvox carteri  

NASA Astrophysics Data System (ADS)

From unicellular ciliates to the respiratory epithelium, carpets of cilia display metachronal waves, long-wavelength phase modulations of the beating cycles, which theory suggests may arise from hydrodynamic coupling. Experiments have been limited by a lack of organisms suitable for systematic study of flagella and the flows they create. Using time-resolved particle image velocimetry, we report the discovery of metachronal waves on the surface of the colonial alga Volvox carteri, whose large size and ease of visualization make it an ideal model organism for these studies. An elastohydrodynamic model of weakly coupled compliant oscillators, recast as interacting phase oscillators, reveals that orbit compliance can produce fast, robust synchronization in a manner essentially independent of boundary conditions, and offers an intuitive understanding of a possible mechanism leading to the emergence of metachronal waves.

Brumley, Douglas R.; Polin, Marco; Pedley, Timothy J.; Goldstein, Raymond E.



Dispersion Relation in a Ferrofluid Layer of Any Thickness and Viscosity in a Normal Magnetic Field; Asymptotic Regimes  

NASA Astrophysics Data System (ADS)

We have calculated the general dispersion relationship for surface waves on a ferrofluid layer of any thickness and viscosity, under the influence of a uniform vertical magnetic field. The amplification of these waves can induce an instability called peaks instability (Rosensweig instability). The expression of the dispersion relationship requires that the critical magnetic field and the critical wavenumber of the instability depend on the thickness of the ferrofluid layer. The dispersion relationship has been simplified into four asymptotic regimes: thick or thin layer and viscous or inertial behaviour. The corresponding critical values are presented. We show that a typical parameter of the ferrofluid enables one to know in which regime, viscous or inertial, the ferrofluid will be near the onset of instability. Nous avons calculé la relation de dispersion des ondes de surface dans une couche de ferrofluide d'épaisseur et de viscosité quelconques, soumise à un champ magnétique normal à sa surface (instabilité de pics de Rosensweig). Cette relation montre que le champ magnétique critique et le vecteur d'onde critique de l'instabilité dépendent de l'épaisseur de la couche de fluide. La relation de dispersion a été simplifiée pour quatre régimes asymptotiques: couche épaisse ou mince et comportement visqueux ou inertiel. Nous avons calculé les valeurs critiques de l'instabilité dans ces quatre cas. Nous montrons qu'un paramètre typique du ferrofluide permet de savoir dans quel régime, visqueux ou inertiel, se situe le ferrofluide près du seuil de l'instabilité.

Abou, B.; Néron de Surgy, G.; Wesfreid, J. E.



Hydrodynamic equations, taking into account the interaction of oblique ion-cyclotron waves with plasmaspheric thermal electrons  

Microsoft Academic Search

The interaction between thermal electrons at Cerenkov resonance with ion-cyclotron (IC) waves propagating at 'large' angles to the geomagnetic field is included in the appropriate hydrodynamic equations. It is shown that IC waves determine the transport of particles and energy from the interaction region, thereby having a considerable effect on the spatial distribution of the plasma parameters. One of the

Iu. V. Konikov



Effects of cyclone waves on massive coral assemblages on the Great Barrier Reef: meteorology, hydrodynamics and demography  

Microsoft Academic Search

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



A new experiment for the study of hydrodynamic waves and turbulence  

NASA Astrophysics Data System (ADS)

As a complement to the existing Princeton MRI Experiment, which is used for studies of MHD waves in a rotating liquid metal, a new device is being constructed by modifying the existing Couette water experiment for the study of purely hydrodynamic waves and turbulence. A primary objective of this new device is the study of Rossby waves, which will be excited by forcing a potential vorticity gradient through surfaces which are inclined relative to the azimuthal plane. A modular design allows for change of these fluid interfaces to study of Rossby waves under different forcing conditions. The experiment will be equipped with a two dimensional laser Doppler velocimetry (LDV) system, which can measure correlated fluctuations of radial and azimuthal velocities to form a measure of the Reynolds stress. The additional use of an ultrasonic Doppler velocimetry (UDV) system will allow for instantaneous measurement of the azimuthal and radial velocity profile at multiple locations to identify bulk flow characteristics and low-order wave structures. These measurement techniques allow for detailed study of the interplay between large scale waves, turbulence and angular momentum transport.

Edlund, E.; Humanik, P.; Roach, A.; Schartman, E.; Sloboda, P.; Spence, E.; Ji, H.



A volume-based hydrodynamic approach to sound wave propagation in a monatomic gas  

Microsoft Academic Search

We investigate sound wave propagation in a monatomic gas using a volume-based\\u000ahydrodynamic model. In Physica A vol 387(24) (2008) pp6079-6094, a microscopic\\u000avolume-based kinetic approach was proposed by analyzing molecular spatial\\u000adistributions; this led to a set of hydrodynamic equations incorporating a\\u000amass-density diffusion component. Here we find that these new mass-density\\u000adiffusive flux and volume terms mean that

S. Kokou Dadzie; Jason M. Reese



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



Some biomedical applications of ferrofluids  

NASA Astrophysics Data System (ADS)

Ferrofluids are colloidal solutions of iron oxide magnetic nanoparticles in either a polar or no polar liquid. We present here two biological applications using maghemite (? Fe_{2O3}) ferrofluids: magnetic cell sorting and magnetocytolysis. The first application employs magnetic particles binding a biological effector, which is capable to recognize the target cells specifically. These cells become magnetic and can be sorted in a gradient of magnetic field. We describe first the various steps of the synthesis of a biocompatible ferrofluid and the grafting an effector protein onto the particles. We then describe the use of particles carrying annexin V in the separation and quantification of damaged erythrocytes in blood samples. This very sensitive technique can be used to follow the erythrocytes ageing of normal blood samples during their storage under blood bank conditions or to detect the membrane modifications that are associated with some pathologies such as malaria or Alzheimer's disease. The dependence of the magnetic susceptibility versus the frequency is a way to transform magnetic energy into thermal energy. Magnetocytolysis is the destruction of cells, carrying magnetic particles, through the action of an alternating magnetic field (about 1 MHz). We present here preliminary experiments with macrophages, which demonstrate the method's feasibility and the formation of the non-specific interactions between the cells and the magnetic particles.

Roger, J.; Pons, J. N.; Massart, R.; Halbreich, A.; Bacri, J. C.



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



Influence of wind–waves energy transfer on the impulsive hydrodynamic loads acting on offshore wind turbines  

Microsoft Academic Search

This paper draws some preliminary considerations about the direct wind effects on the kinematics and dynamics of steep extreme waves propagating near offshore wind turbines. Most of the hydrodynamic load models currently employed in designing offshore wind turbines take into account only indirectly the role of the wind. In fact, once the sea severity upon a certain wind speed is

Enzo Marino; Claudio Borri; Claudio Lugni



Synthesis of high intrinsic loss power aqueous ferrofluids of iron oxide nanoparticles by citric acid-assisted hydrothermal-reduction route  

NASA Astrophysics Data System (ADS)

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 nHm2/kg. So this clean and cheap route is an efficient way to synthesize high ILP aqueous ferrofluids applicable in magnetic hyperthermia.

Behdadfar, Behshid; Kermanpur, Ahmad; Sadeghi-Aliabadi, Hojjat; Morales, Maria Del Puerto; Mozaffari, Morteza



Anisotropic Light Scattering from Ferrofluids  

NASA Astrophysics Data System (ADS)

We have investigated the light scattering in DC magnetic fields from aqueous suspensions of Fe3O4 nanoparticles coated with tetra methyl ammonium hydroxide and ?-Fe2O3 nanoparticles embedded in alginate hydrogel. For Fe3O4 ferrofluid, anomalous light scattering behavior was observed when light propagated both parallel and perpendicular to the magnetic fields. This behavior is attributed to the alignment and aggregation of the nanoparticles in chain-like structures. A very different light scattering behavior was observed for ?-Fe2O3 alginate sample where, under the similar conditions, the application of the magnetic field produced no structured change in scattering. We attribute this difference to the absence of chain-like structures and constrained mobility of iron nanoparticles in the alginate sample. The observation is in agreement with our relaxation and dissipative heating results^1 where both samples exhibited Neel relaxation but only the Fe3O4 ferrofluid showed Brownian relaxation. The results suggest that Brownian relaxation and nanoparticle mobility are important for producing non-linear light scattering in such systems. ^1P.P. Vaishnava, R. Tackett, A. Dixit, C. Sudakar, R. Naik, and G. Lawes, J. Appl. Phys. 102, 063914 (2007).

Rablau, Corneliu; Vaishnava, Prem; Naik, Ratna; Lawes, Gavin; Tackett, Ron; Sudakar, C.



Integrated Catadioptric Pickup with Ferrofluidic Cooling Structure  

NASA Astrophysics Data System (ADS)

We have developed a novel integrated catadioptric pickup with a ferrofluidic cooling structure for digital versatile discs (DVDs). To miniaturize the optical system, we made the catadioptric system on a moving head. The catadioptric system consists of a holographic catadioptric lens (HCL), a reflective mirror, a laser diode (LD), and a photodiode IC (PDIC). The HCL has a holographic surface, an aspherical mirror and two aspherical surfaces. This system realized the integration of all optical components into the moving head. The height of the optical system was 8.6 mm including the working distance. To realize efficient heat transfer without sacrificing the motion of the moving head, we developed a cooling structure in which gaps between magnets and coils are filled with ferrofluid. The thermal characteristics were as good as those of conventional optical pickups, proving that the ferrofluidic cooling structure has superior cooling performance. The ferrofluid did not sacrifice the motion of the moving head because of its fluidity.

Onozawa, Kazutoshi; Yamanaka, Kazuhiko; Okuda, Takuya; Tojo, Tomoaki; Iijima, Shinichi; Ueda, Daisuke; Kubo, Junichi; Kitagawa, Seiichro



Optical Negative Refraction in Ferrofluids with Magnetocontrollability.  

National Technical Information Service (NTIS)

We numerically demonstrate optical negative refraction in ferrofluids containing isotropic Fe3O4 nanoparticles, each having an isotropic Ag shell, in the presence of an external dc magnetic field H. The all-angle broadband optical negative refraction with...

J. P. Huang K. W. Yu L. Gao Y. Gao Y. M. Liu



The design of a ferrofluid magnetic pipette  

Microsoft Academic Search

An electromagnetic pipette using a ferrofluid was designed to sample liquid volumes smaller than 0.2 ?l. Submicroliter sample sizes are desirable for reducing the amount of costly reagents and reducing sample requirement for large-scale analysis. The pipette consists of four electromagnets arranged such that air-gaps are aligned to accommodate a tube. A light-hydrocarbon-based ferrofluid is contained in the tube and

Nancy E. Greivell; Blake Hannaford



The Design of a Ferrofluid Magnetic Pipette  

Microsoft Academic Search

An electromagnetic pipette using a ferrofluid was designed to sample liquid volumes smallerthan 0.2 microliter. Submicroliter sample sizes are desirable for reducing the amount of costlyreagents and reducing sample requirement for large-scale analysis. The pipette consists of fourelectromagnets arranged such that air-gaps are aligned to accommodate a tube. A light-hydrocarbon-based ferrofluid is contained in the tube and acts as a

Nancy Greivell; Blake Hannaford



Magnetic detection of ferrofluid injection zones  

SciTech Connect

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.



Excitation of convective motions and surface hydrodynamic soliton-type waves in liquid crystals by a Gaussian laser beam  

SciTech Connect

The possibility of exciting convective motions with a toroidal symmetry in a disordered liquid-crystal cell with an open surface, which is locally heated by a Gaussian laser beam, is demonstrated experimentally. A perturbation of the free surface of the liquid crystal and a convective hydrodynamic motion are determined by temperature gradients. It is shown that a radial distribution of the director of a nematic liquid crystal appears in the convection region. Under certain experimental conditions, soliton-type hydrodynamic orientation waves are observed at the free surface of a nematic liquid crystal. It is found experimentally that the velocity of these waves is determined solely by the liquid-crystal parameters and is independent of the incident laser-radiation power. (interaction of laser radiation with matter. laser plasma)

Akopyan, R S; Alaverdyan, R B; Arakelyan, A G; Nersisyan, S Ts; Chilingaryan, Yu S [Department of Physics, Yerevan State University, Yerevan (Armenia)



Hydrodynamics of color M-mode Doppler flow wave propagation velocity V(p): a computer study.  


This study was designed to show the hydrodynamic mechanism of left ventricular (LV) flow wave propagation and to relate this propagated velocity to 2-dimensional (2D) color and color M-mode Doppler echocardiograms. A computer model is developed describing 3-dimensional axisymmetrical LV filling flow. The unsteady Navier-Stokes flow equations are solved in an LV truncated ellipsoid geometry with moving LV walls, including relaxation and compliance of the wall. The computed results confirm both intraventricular flow and pressure patterns during filling. Vortices are formed during the acceleration phases of the early and atrial filling waves. During the deceleration phases, the vortices are amplified and convected into the ventricle. The vortices are recognized on the derived 2D color echocardiograms as in vivo. The propagation of this vortex determines the propagation of the maximum velocity observed in the color M-mode Doppler echocardiogram. For pseudonormal filling of the left ventricle, the LV flow wave propagation velocity decreases. PMID:11875384

Vierendeels, Jan A; Dick, Erik; Verdonck, Pascal R



Hydrodynamic supercontinuum.  


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



Hydrodynamics of a bathymetrically complex fringing coral reef embayment: Wave climate, in situ observations, and wave prediction  

Microsoft Academic Search

Wave climate drives episodic circulation at many islandsCurrent magnitude exhibits dependence on wave energy flux in such casesPhase-averaged wave models may acceptably be applied to fringing coral reefs

Ron Hoeke; Curt Storlazzi; Peter Ridd



A consistent derivation of the wave-energy equation from basic hydrodynamic principles  

Microsoft Academic Search

Based on a decomposition of the velocity into mean flow, turbulent and wave components, momentum and hereafter a wave-energy equation is derived. It contains a turbulent energy dissipation term which is closed by applying a wave-related mixing length model and linear wave theory solutions. This closure produces a non-linear turbulent wave-energy dissipation including the wave energy in a 5\\/2 power

Andreas Malcherek



Shock-wave heating model for chondrule formation: Hydrodynamic simulation of molten droplets exposed to gas flows  

NASA Astrophysics Data System (ADS)

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 Sekyia et al. [Sekyia, M., Uesugi, M., Nakamoto, T., 2003. Prog. Theor. Phys. 109, 717-728]. We found that the non-linear terms in the hydrodynamical equations neglected by Sekiya et al. [Sekiya, M., Uesugi, M., Nakamoto, T., 2003. Prog. Theor. Phys. 109, 717-728] 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.

Miura, Hitoshi; Nakamoto, Taishi



Strongly nonlinear vortices in magnetized ferrofluids  

Microsoft Academic Search

Nonlinear convective roll cells that develop in thin layers of magnetized ferrofluids heated from above are examined in the limit as the wavenumber of the cells becomes large. Weakly nonlinear solutions of the governing equations are extended to solutions that are valid at larger distances above the curves of marginal stability. In this region, a vortex flow develops where the

Craig L. Russell; P. J. Blennerhassett; P. J. Stiles



Wave-induced cyclic pore-pressure perturbation effects in hydrodynamic uplift force acting on submarine pipeline buried in seabed sediments  

Microsoft Academic Search

Among all environmental loads usually considered in the design procedure, the most critical problem in determining a vertical stability of a submarine pipeline buried in permeable soils under progressive surface-water-wave loading is the prediction of the wave-induced cyclic pore-pressure response of a seabed in the vicinity of a submarine pipeline. A study of the hydrodynamic (i.e., wave-induced) uplift force acting

W. Magda



Hydrodynamics of shock waves with reflected particles. I. Rankine-Hugoniot relations and stationary solutions  

Microsoft Academic Search

In this work we investigate how reflected particles modify the Rankine-Hugoniot (RH) relations in a simple hydrodynamical framework. It is assumed that the ions are specularly reflected by the cross-shock potential. For simplicity, an exactly perpendicular shock is assumed, thus other reflection mechanisms, such as magnetic mirroring, can be neglected. Momentum and energy terms are introduced to model reflected particles

B. Dasgupta; R. Burrows; G. P. Zank; G. M. Webb



Relation between the Hydrodynamic and Elastic Parameters in Surface Wave Diffraction on a Floating Plate  

Microsoft Academic Search

The problem of surface wave diffraction on a floating elastic plate is considered. The relation between the parameters of the elastic vibrations of the plate and the transmitted and reflected wave amplitudes is investigated. It is shown that the maximum amplitudes of the plate stresses and deflections depend nonmonotonically on the incident wave frequency and are reached simultaneously with the

T. I. Khabakhpasheva



Wave propagation in laminates using the nonhomogenized dynamic method of cells: An alternative to standard finite-difference hydrodynamic approaches  

SciTech Connect

The nonhomogenized dynamic method of cells (NHDMOC) uses a truncated expansion for the particle displacement field; the expansion parameter is the local cell position vector. In the NHDMOC, specifying the cell structure is similar to specifying the spatial grid used in a finite-difference hydrodynamic calculation. The expansion coefficients for the particle displacement field are determined by the equation of motion, any relevant constitutive relations, plus continuity of traction and displacement at all cell boundaries. The authors derive and numerically solve the NHDMOC equations for the first, second, and third-order expansions, appropriate for modeling a plate-impact experiment. The performance of the NHDMOC is tested, at each order, for its ability to resolve a shock-wave front as it propagates through homogeneous and laminated targets. They find for both cases that the displacement field expansion converges rapidly: given the same cell widths, the first-order theory gives only a qualitative description of the propagating stress wave; the second-order theory performs much better; and the third-order theory gives small refinements over the second-order theory. The performance of the third-order NHDMOC is then compared to that of a standard finite-difference hydrodynamic calculation. The two methods differ in that the former uses a finite-difference solution to update the time dependence of the equations, whereas the hydrodynamic calculation uses finite-difference solutions for both the temporal and spatial variables. Both theories are used to model shock-wave propagation in stainless steel arising from high-velocity planar impact. To achieve the same high-quality resolution of the stress and particle velocity profiles, the NHDMOC consistently requires less fine spatial and temporal grids, and substantially less artificial viscosity to control unphysical high-frequency oscillations in the numerical solutions. Finally, the third-order NHDMOC theory is used to calculate the particle velocity for a shock-wave experiment involving an epoxy-graphite laminate. Constitutive relations suitable for the various materials are used. This includes linear and nonlinear elasticity, and when appropriate, viscoelasticity. The results agree well with the corresponding plate-impact experiment, and are compared to the second-order theory of Clements, Johnson, and Hixson.

Clements, B.E.; Johnson, J.N.



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

Microsoft Academic Search

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



Infrared wave analysis after hydrodynamic and acoustic cavitation as effective method of confirming sewage sludge destruction.  


The efficiency of disintegration of sewage sludge cells microorganisms were characterized using biochemical parameters such as COD, phosphate, ammonium nitrogen and proteins. The investigated process was additionally assessed using the coefficient DD (Degree of Disintegration). It has been demonstrated that a 30-min of hydrodynamic and ultrasonic disintegration causes the soluble COD value increased about 300 mg /L and 190 mg /L (average), while the degree of disintegration reached 24% and 21%, respectively. The efficiency of sewage sludge hydrodynamic and ultrasonic disintegration was confirmed by increased release of phosphate (V) (from 4 to 54 mg PO(3-) 4/L and to 50 mg PO(3-) 4/L, respectively), ammonium nitrogen (from 1.5 to 4 mg N-NH(+) 4/L and to 3.5 mg N-NH(+) 4/L, respectively) and proteins (from 5 to 70 mg/L and to 60 mg/L, respectively). The effectiveness of surplus activated sludge disintegration was tested in the infrared spectrum. Changes in absorbance at the specified wavelength attest to a release of i.e., amines, amino acids, amide groups (proteins), phosphates, ammonium salts of carboxylic acid, etc. during disintegration time. Revealing these chemical groups in over-sludge liquids attests to a destructive influence of hydrodynamic and ultrasonic cavitation on activated sludge microorganisms and effective cells lysis. PMID:24117089

Gr?bel, Klaudiusz; Machnicka, Alicja



Microstructural investigation of some biocompatible ferrofluids  

NASA Astrophysics Data System (ADS)

Two batches of aqueous ferrofluids based on iron oxide particles as solid nanomagnetic phase have been prepared by applying the chemical precipitation method. Tetramethylammonium hydroxide (N(CH3)4OH) and citric acid (C6H8O7) were used to functionalize magnetic cores. Physical tests have been performed in order to reveal the microstructural and magnetic features, both needed for biomedical utilization. The particle size was investigated using transmission electron microscopy (TEM), magnetization measurements and X-ray diffraction (for composition and phase information). The dimensional distribution of the ferrophase physical diameter was comparatively discussed using the box-plot statistical method revealing the fulfilling of the main requirements for ferrofluid stability.

R?cuciu, M.; Creang?, D. E.; B?descu, V.; Sulitanu, N.



Ferrofluid deformable mirrors: recent advances and results  

NASA Astrophysics Data System (ADS)

Many technical improvements have been made since we first introduced deformable mirrors that use magnetic liquids (ferrofluids) whose surface are shaped by arrays of small electric coils. We present recent advances and experimental results of a 91-actuator magnetic liquid deformable mirror that uses a novel technique that linearizes their response by placing the array of actuators inside a strong and uniform magnetic field. We show that this improved ferrofluid deformable mirror (FDM) can produce inter-actuator strokes of over 10 ?m, is capable of generating wavefront having peak-to-valley amplitudes of over 60 ?m, and predict that amplitudes greater than 100 ?m are achievable. We also present experimental results showing that these improved FDMs are good candidates for astronomical, vision science, and optical testing applications.

Brousseau, D.; Borra, E. F.



Muon spectroscopy of a frozen ferrofluid  

Microsoft Academic Search

The behavior of the muons stopped in a magnetite D_2O-based ferrofluid in the temperature range of 114-300 K, both in zero field and in a transversal field applied to the muon-spin direction, was investigated. A considerable relaxation of the muon polarization was observed in both cases. Some irregularities of the behaviour of the polarization amplitude and the relaxation rate were

M. Balasoiu; V. L. Aksenov; D. Bica; V. N. Duginov; K. I. Gritsaj; T. Mamedov; V. Tripadus; L. Vekas; V. A. Zhukov



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



Electrical dissipation effects on propagation of magneto-hydrodynamic waves in anisotropic media  

Microsoft Academic Search

The Hall effect is considered in relation to the modification of MHD wave propagation by electrical dissipation. A generalized system using Maxwell's equations and Ohm's law is developed to obtain a dispersion relation with emphasis on ion cyclotron motion. As in cases of electrical dissipation or the Hall effect, three waves are observed, the slowest of which is found to

M. Numano



Quasi-static analysis of a ferrofluid blob in a capillary tube  

NASA Astrophysics Data System (ADS)

Ferrofluids have promising application potentials for biological, medical, subsurface, and many other industrial purposes. To bring the potentials to reality, it is of utmost importance to characterize the behavior of ferrofluids under different conditions, especially in the presence of more than one phase. In this study, the quasi-static behavior of a non-wetting incompressible and inviscid ferrofluid blob surrounded by a wetting non-magnetic fluid confined in a capillary tube is theoretically and computationally investigated when a uniform magnetic field is applied, assuming isothermal conditions. The effect of geometrical, hydrodynamic, and magnetic properties of the blob on its deformations when subject to a magnetic field is explained. Moreover, the effect of nonlinear magnetization on the ferrofluid blob evolution in the capillary tube is investigated in detail. In the case of a tube with constant circular cross-section, the behavior of the blob before the critical state of detachment is determined numerically, while the post-critical behavior is resolved analytically. To characterize the pre-critical blob deformations, the magnetic field distribution inside the blob for given external magnetic fields is calculated using a commercial finite element software and is employed to calculate the interfacial configuration from balances among magnetic, capillary, and hydrostatic forces. We show that increasing magnetic field intensity above a critical value causes the blob to detach from the tube wall under certain conditions and quantitatively characterize the critical magnetic field as well as blob configurations before and after detachment. Results show that there is a maximum blob length beyond which detachment does not occur, due to the nonlinear magnetization of the ferrofluid blob. This length depends on the relative magnitude of magnetic and capillary forces and also on the geometry of the confining capillary tube. Even if detachment occurs, the nonlinear magnetization prevents the blob from evolving infinitely after detachment. The conditions under which detachment may occur are analytically determined. The simulations confirm that, for sufficiently small magnetic fields, the linear approximate magnetization yields satisfactory results. However, with increasing magnetic field intensity, the deviation between the results with nonlinear magnetization and those with linear approximate magnetization increases significantly. In addition, this deviation is more pronounced for longer blobs. These findings emphasize the importance of incorporating the nonlinear magnetization for relatively large magnetic field intensities. Finally, in order to relax the simple confining geometry assumption, we show preliminary simulations using the level set method in complex solid geometries. The method was previously developed for capillarity and used for realistic rock geometries and now accounts for the magnetic pressures as well.

Reza Rahmani, Amir; Prodanovi?, Maša; Bryant, Steven L.; Huh, Chun



Hydrodynamic forces on multitube production risers exposed to currents and waves  

SciTech Connect

This paper presents the experimental results of a joint industry riser test program. Over a five-year period, an extensive experimental investigation of hydrodynamic loads acting on various production risers was carried out. The program included the laboratory testing of many multitube riser configurations as well as a single cylinder. Several major oil companies sponsored the project. The tests were made with rather large-scale models which were: 1) held stationary in steady current, 2) moved at constant speed or constant acceleration through a quiescent fluid or through a moving fluid, and 3) held stationary in oscillating flow or in steady current superimposed on oscillating flow.

Demirbilek, Z.; Halvorsen, T.



Inertial-Fusion-Related Hydrodynamic Instabilities in a Spherical Gas Bubble Accelerated by a Planar Shock Wave  

SciTech Connect

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)



Penetration of surface-inoculated bacteria as a result of hydrodynamic shock wave treatment of beef steaks.  


The top surface of the raw eye of round steaks was inoculated with either green fluorescent protein (GFP)-labeled Escherichia coli (E. coli-GFP) or rifampin-resistant E. coli (E. coli-rif). Cryostat sampling in concert with laser scanning confocal microscopy (LSCM) or plating onto antibiotic selective agar was used to determine if hydrodynamic shock wave (HSW) treatment resulted in the movement of the inoculated bacteria from the outer inoculated surface to the interior of intact beef steaks. HSW treatment induced the movement of both marker bacteria into the steaks to a maximum depth of 300 microm (0.3 mm). Because popular steak-cooking techniques involve the application of heat from the exterior surface of the steak to achieve internal temperatures ranging from 55 to 82 degrees C, the extent of bacterial penetration observed in HSW-treated steaks does not appear to pose a safety hazard to consumers. PMID:11952209

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



Induced Magnetic Anisotropy of Ferrofluid Frozen in Magnetic Fields  

Microsoft Academic Search

The magnetization process of a ferrofluid whose carrier fluid is paraffin was investigated in the temperature range from 77 K to 300 K, as a function of the cooling field intensity and freezing rate. Phase transitions between the liquid and solid states can be simulated by using the ferrofluids as a magnetic probe. A uniaxial magnetic anisotropy was induced by

N. Inaba; H. Miyajima; S. Taketomi; S. Chikazumi



Condensation and ordering of colloidal spheres dispersed in a ferrofluid  

Microsoft Academic Search

Polystyrene microspheres of the same size dispersed in ferrofluid produce voids which have been denoted magnetic holes. The magnetic moment of one sphere (hole) is equal to the magnetic moment of the ferrofluid displaced by the sphere.The system may essentially be made two-dimensional by confining the dispersion between two glass plates with separation slightly larger than the sphere diameter. It

Arne T. Skjeltorp



Hydrodynamical equations for thermal electrons taking into account their scattering on ion-cyclotron waves in the outer plasmasphere of the earth  

Microsoft Academic Search

Using Grad's method, a system of hydrodynamical equations for thermal electrons taking into account their interaction on Cherenkov resonance with ion-cyclotron waves generated in the outer plasmasphere of the earth, is obtained. Moments of a quasi-linear integral describing wave-induced scattering of electrons are calculated. These moments determine the variations of macroparameters of the electron component in relevant equations as a

Iu. V. Konikov; O. A. Gorbachev; G. V. Khazanov; A. A. Chernov



A ferrofluidic seal specially designed for rotary blood pumps.  


One of the key technologies required for rotary blood pumps is sealing of the motor shaft. A ferrofluidic seal was developed for an axial flow pump. The seal body was composed of a plastic magnet and two pole pieces. This seal was formed by injecting ferrofluid into the gap between the pole pieces and the motor shaft. To contain the ferrofluid in the seal and to minimize the possibility of ferrofluid making contact with blood, a shield with a small cavity was provided on the pole piece. Sealing pressure of the seal was measured. The sealing pressure was maintained at more than 23.3 kPa (175 mm Hg) for a motor speed up to 11,000 rpm. The specially designed ferrofluidic seal for sealing out liquids is useful for axial flow blood pumps. PMID:8817946

Mitamura, Y; Fujiyoshi, M; Yoshida, T; Yozu, R; Okamoto, E; Tanaka, T; Kawada, S



On the Behaviour of Hydrodynamic Processes due to the Presence of Submarine Sand Waves  

Microsoft Academic Search

Radar signatures of the sea bed in coastal waters show that submarine sand waves superimposed on sandbanks or tidal current ridges change their orientation and character abruptly at the crest of the ridge. These observations were made when studying air- and spaceborne radar images of the southern North Sea (McLeish et al., 1981). Similar phenomena were already reported by analysing



Hydrodynamics of shock waves with reflected particles. I. Rankine-Hugoniot relations and stationary solutions  

SciTech Connect

In this work we investigate how reflected particles modify the Rankine-Hugoniot (RH) relations in a simple hydrodynamical framework. It is assumed that the ions are specularly reflected by the cross-shock potential. For simplicity, an exactly perpendicular shock is assumed, thus other reflection mechanisms, such as magnetic mirroring, can be neglected. Momentum and energy terms are introduced to model reflected particles at the shock and the RH conditions are examined using a geometrical entropy condition to distinguish the physically relevant states. Although such shocks have some common features with combustion shocks within a narrow range of reflection parameters, for a wide range of reflection parameters, particularly for highly oblique shocks, Chapman-Jouguet solutions do not exist. It is conjectured that these shocks comprise a distinct class. Decelerated solutions of the RH conditions are shown to exist only under specific conditions for shocks with reflected particles. Velocity flows both parallel and oblique to the perpendicular shock (with respect to an upstream magnetic field) are considered and found to be strongly sheared.

Dasgupta, B.; Burrows, R.; Zank, G. P.; Webb, G. M. [Institute of Geophysics and Planetary Physics, University of California at Riverside, California 92521 (United States)



Magnetic properties of electroplated wires coated by ferrofluid  

Microsoft Academic Search

Low-frequency magnetic properties of ferromagnetic composite wires were studied with and without coating by ferrofluid. Non-magnetic CuBe wires of 0.1mm diameter were electroplated with FeCoNi layer of 1?m thickness. Magnetization curves were measured in the frequency range of 10Hz–3kHz. The composite CuBe\\/FeCoNi\\/ferrofluid material shows a hysteretic behaviour in a small field. The hysteresis loop of ferrofluid covered electroplated wire is

H. García-Miquel; G. V. Kurlyandskaya; V. I. Levit



Diagnoses to unravel secular hydrodynamical processes in rotating main sequence stars. II. The actions of internal gravity waves  

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.



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



Magnetic field effects on viscous fingering of a ferrofluid in an anisotropic Hele-Shaw cell  

NASA Astrophysics Data System (ADS)

When a viscous fluid is pushed into a more viscous one in a Hele-Shaw cell, the interface between the two fluids may become unstable, leading to fingering and ramified patterns. Anisotropy can be introduced by engraving a grid in one plate of the cell, allowing one to obtain dendritic patterns. The use of a ferrofluid as one of the viscous fluid is a way to introduce magnetism in the problem, especially the magnetic field as a control parameter. Magnetic field effects on viscous fingering of ferrofluids have already been studied: in a rectangular Hele-Shaw cell, a magnetic field applied in the cell plane is stabilizing when parallel to the interface between the two fluids and destabilizing when normal to the interface. A magnetic field perpendicular to the plane of a radial Hele-Shaw cell has the same destabilizing effect as the pressure. We have studied the effect of a magnetic field, normal to and in the plane of anisotropic radial Hele-Shaw cells te{5}, to characterize the competing effects of hydrodynamics, magnetic field and dipolar energy, and anisotropy. Here we study more precisely the effect of a magnetic field normal to a radial anisotropic Hele-Shaw cell. Figs 8, Refs 9.

Ballou, R.; Molho, P.



INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Excitation of convective motions and surface hydrodynamic soliton-type waves in liquid crystals by a Gaussian laser beam  

NASA Astrophysics Data System (ADS)

The possibility of exciting convective motions with a toroidal symmetry in a disordered liquid-crystal cell with an open surface, which is locally heated by a Gaussian laser beam, is demonstrated experimentally. A perturbation of the free surface of the liquid crystal and a convective hydrodynamic motion are determined by temperature gradients. It is shown that a radial distribution of the director of a nematic liquid crystal appears in the convection region. Under certain experimental conditions, soliton-type hydrodynamic orientation waves are observed at the free surface of a nematic liquid crystal. It is found experimentally that the velocity of these waves is determined solely by the liquid-crystal parameters and is independent of the incident laser-radiation power.

Akopyan, R. S.; Alaverdyan, R. B.; Arakelyan, A. G.; Nersisyan, S. Ts; Chilingaryan, Yu S.



Preparation and magnetisation of a silica-magnetite inverse ferrofluid  

NASA Astrophysics Data System (ADS)

We introduce an `inverse ferrofluid' comprising sterically stabilized, colloidal silica spheres and oleic acid stabilized magnetite particles. The preparation is described as well as magnetisation measurements which turns out to be a linear function of the silica volume fraction.

de Gans, B. J.; Blom, C.; Mellema, J.; Philipse, A. P.



Modified Burgers' equation resulting from a hydrodynamic model of shock waves with reflected particles  

NASA Astrophysics Data System (ADS)

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.



Tracking, sensing and predicting flood wave propagation using nomadic satellite communication systems and hydrodynamic models  

NASA Astrophysics Data System (ADS)

The main objective of this study is to contribute to the development and the improvement of flood forecasting systems. Since hydrometric stations are often poorly distributed for monitoring the propagation of extreme flood waves, the study aims at evaluating the hydrometric value of the Global Navigation Satellite System (GNSS). Integrated with satellite telecommunication systems, drifting or anchored floaters equipped with navigation systems such as GPS and Galileo, enable the quasi-continuous measurement and near real-time transmission of water level and flow velocity data, from virtually any point in the world. The presented study investigates the effect of assimilating GNSS-derived water level and flow velocity measurements into hydraulic models in order to reduce the associated predictive uncertainty.

Hostache, R.; Matgen, P.; Giustarini, L.; Tailliez, C.; Iffly, J.-F.



Modified Burgers' equation resulting from a hydrodynamic model of shock waves with reflected particles  

SciTech Connect

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)




Microsoft Academic Search

Stable colloidal suspensions of magnetic nanoparticles called ferrofluids have attracted a lot of attention in recent years, since they can be used in numerous technological and medical applications (1-3). For biomedical applications aqueous-based ferrofluids are being tested. Besides the requirements concerning their non-toxicity and biocompatibility, their behaviour in a magnetic filed is also of great importance. Under the influence of

Alenka Mertelj; Darko Makovec



Experimental investigation of magnetically driven flow of ferrofluids in porous media  

SciTech Connect

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.



Magneto-optical and rheological behaviors of oil-based ferrofluids and magnetorheological fluids  

NASA Astrophysics Data System (ADS)

The magneto-optical and rheological behaviors of magnetic fluids and magnetorheological (MR) fluids have been investigated. A magneto-optical apparatus was constructed which enabled us to investigate the birefringence and dichroism of ferrofluids at various levels of applied magnetic field. Specifically, the effects of the film thickness of oil-based ferrofluids and the concentration of surfactant in the oil-based ferrofluids on their magneto-optical behavior were investigated. A commercial magneto-rheological instrument (Physica MCR 301, Anton Paar) equipped with a cone-and-plate fixture was employed to investigate the transient and steady-state shear flow of both ferrofluids and MR fluids as a function of shear rate at various levels of applied magnetic fields. The rheological investigation has enabled us to determine the effect of applied magnetic field on the shear viscosity and yield stress of ferrofluids and MR fluids. A special ferrofluid was prepared by filtering out nearly all of the surfactant and small particles in an oil-based ferrofluid. We then compared its magneto-optical and rheological behaviors with those of an unfiltered ferrofluid. Further, we have found that the ferrofluid with a lower concentration of surfactant gave rise to larger birefringence and yield stress, and stronger shear thinning behavior than the ferrofluid containing a higher concentration of surfactant. This observation has lead us to conclude that an increase in unbound surfactant in a ferrofluid hindered chain formation of magnetic particles, leading to a decrease in the optical and rheological behaviors of the ferrofluid. Optical microscopy confirmed no visible chain formation of magnetic particles in the ferrofluid having a high concentration of surfactant owing to weak yield stress, birefringence, and shear thinning. On the other hand, we observed from optical microscopy that the filtered ferrofluid gave rise to larger yield stress, birefringence, and stronger shear thinning behavior. Thus, using optical microscopy we were able to explain the magneto-optical and rheological behaviors of the ferrofluids and magnetorheological fluids investigated.

Getzie, Travis


Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications  

NASA Astrophysics Data System (ADS)

The high-energy-density research facilities of today can accelerate small but macroscopic amounts of material to velocities above 100 km/s, can heat such material to temperatures above 100 eV, and can produce pressures far above a million atmospheres (10^12 dynes/cm^2 or 0.1 TPascal). Many of these facilities were built to pursue inertial confinement fusion. Their emergence as versatile experimental tools has created new opportunities in basic research with astrophysical applications. In the areas of hydrodynamics and radiation hydrodynamics, one can produce dynamic processes such as instabilities that occur in astrophysical systems but cannot be directly observed. One can do this in experimental systems that are well scaled to their astrophysical counterparts, either completely or in terms of relevant dimensionless parameters. This talk will provide examples from current research in the areas of hydrodynamic instabilities at interfaces shocked by blast waves and from radiatively collapsing jets and shocks. Hydrodynamic experiments have produced blast waves that shock and then decelerate unstable interfaces to produce high-velocity spikes of dense material at very high Reynolds number. Radiation-hydrodynamic experiments have produced jets that collapse radially and shocks that collapse axially through radiation losses. The results of such experiments and the issues that arise in connecting them to astrophysics will be discussed.

Drake, R. Paul



Three-dimensional diamagnetic particle deflection in ferrofluid microchannel flows  

PubMed Central

Magnetic field-induced particle manipulation is a promising technique for biomicrofluidics applications. It is simple, cheap, and also free of fluid heating issues that accompany other common electric, acoustic, and optical methods. This work presents a fundamental study of diamagnetic particle motion in ferrofluid flows through a rectangular microchannel with a nearby permanent magnet. Due to their negligible magnetization relative to the ferrofluid, diamagnetic particles experience negative magnetophoresis and are repelled away from the magnet. The result is a three-dimensionally focused particle stream flowing near the bottom outer corner of the microchannel that is the farthest to the center of the magnet and hence has the smallest magnetic field. The effects of the particle’s relative position to the magnet, particle size, ferrofluid flow rate, and concentration on this three-dimensional diamagnetic particle deflection are systematically studied. The obtained experimental results agree quantitatively with the predictions of a three-dimensional analytical model.

Liang, Litao; Zhu, Junjie; Xuan, Xiangchun



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



Ground state microstructure of a ferrofluid thin layer  

SciTech Connect

Using a fine weave of theoretical analysis and computer simulations, we found various aggregates of magnetic single-domain nanoparticles, which can form in a quasi-two-dimensional (q2D) ferrofluid layer at low temperatures. Our theoretical investigation allowed us to obtain exact expressions and their asymptotes for the energies of each configuration. Thus, for ferrofluid q2D layers it proved possible to identify the ground states as a function of the particle number, size, and other system parameters. Our suggested approach can be used for the investigation of ground state structures in systems with more complex interparticle interactions.

Prokopieva, T. A.; Danilov, V. A.; Kantorovich, S. S., E-mail: [Ural State University (Russian Federation)



Magnetically tunable terahertz magnetoplasmons in ferrofluid-filled photonic crystals  

NASA Astrophysics Data System (ADS)

We investigated terahertz (THz) magneto-optical properties of a ferrofluid and a ferrofluid-filled photonic crystal (FFPC) by using the THz time-domain spectroscopy. A magnetoplasmon resonance splitting and an induced THz transparency phenomenon were demonstrated in the FFPC. The further investigation reveals that the induced transparency originates from the interference between magnetoplasmon modes in the hybrid magneto-optical system of FFPC, and the THz modulation with a 40% intensity modulation depth can be realized in this induced transparency frequency band. This device structure and its tunabilty scheme will have great potential applications in THz filtering, modulation and sensing.

Fan, Fei; Chen, Sai; Lin, Wei; Miao, Yin-Ping; Chang, Sheng-Jiang; Liu, Bo; Wang, Xiang-Hui; Lin, Lie



Structure and hydrodynamics of colloidal systems  

SciTech Connect

Colloidal phases (for example, micellar solutions, latex suspensions, ferrofluids and microemulsions) provide excellent model systems with which to test structural and hydrodynamic theories of the liquid state. Interparticle potentials may be attractive or repulsive, and the experimentalist is often free to control the strength, range and symmetry of the interactions. Small-angle neutron scattering (SANS) and small-angle neutron spin-echo (SANSE) provide excellent complementary tools for studying the structure and time-dependence of these systems, where correlation lengths typically vary from about one to several tens of nm. Correlation times are usually in the nsec to range, but may be of order minutes in certain systems. This paper will review some of the current theories and their recent experimental tests, using colloidal systems in which the direct interaction potentials may have spherical, dipolar or cylindrical symmetry and the hydrodynamic interactions may be weak or strong.

Hayter, J.B.



Instability of a flat horizontal interface between a thin layer of a ferrofluid and a thin layer of a nonmagnetic liquid in the presence of a vertical magnetic field  

NASA Astrophysics Data System (ADS)

An asymptotic analysis of the equations and boundary conditions of fluid dynamics is performed, and a nonlinear model is constructed for the onset of the development of Rosensweig instability in a thin horizontal ferrofluid layer at rest covered with a thin layer of a lighter nonmagnetic liquid. The surface of a nonmagnetized slab is the lower boundary of the ferrofluid, and the interface with a gas is the upper boundary of the nonmagnetic liquid. The pressure in the gas is constant. The instability being considered arises upon the application of a rather strong uniform vertical magnetic field. The proposed model involves five dimensionless parameters. The critical magnetization of the initial ferrofluid layer with a flat upper boundary and the threshold wave number are found. The effect of the governing parameters on the instability region and on the wavelength of the fastest growing mode is studied in the linear formulation of the problem.

Korovin, V. M.



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.



Reciprocity of Faraday effect in ferrofluid: Comparison with magneto-optical glass  

Microsoft Academic Search

The transmission light intensity method is carried out on a classical platform to study the reciprocity of Faraday effect in water-based Fe3O4 ferrofluid and its diluents. Setting the polarization direction of the analyzer at an angle of 45° to that of the polarizer, the switchable DC magnetic field and the alternating magnetic field are imposed to ferrofluid. The ferrofluid film

Shibin Wang; Caixin Sun; Lin Du; Chenguo Yao; Yong Yang


Hydrodynamic interaction of two spherical particles caused by sound wave propagating along center-to-center line  

Microsoft Academic Search

Forces in a two particle system in a fluid with an acoustic field are calculated, specifically for two identical spherical particles some distance apart in a boundless ideal fluid with a plane sound wave propagating along the center to center line. One problem here is diffraction of sound by the downstream particle, formulated as the corresponding wave equation in the

A. P. Zhuk



Compound chondrule formation in the shock-wave heating model: Three-dimensional hydrodynamics simulation of the disruption of a partially-molten dust particle  

NASA Astrophysics Data System (ADS)

We carried out three-dimensional hydrodynamics simulations of the disruption of a partially-molten dust particle exposed to high-speed gas flow to examine the compound chondrule formation due to mutual collisions between the fragments (fragment-collision model; [Miura, H., Yasuda, S., Nakamoto, T., 2008a. Icarus194, 811-821]). In the shock-wave heating model, which is one of the most plausible models for chondrule formation, the gas friction heats and melts the surface of the cm-sized dust particle (parent particle) and then the strong gas ram pressure causes the disruption of the molten surface layer. The hydrodynamics simulation shows details of the disruptive motion of the molten surface, production of many fragments and their trajectories parting from the parent particle, and mutual collisions among them. In our simulation, we identified 32 isolated fragments extracted from the parent particle. The size distribution of the fragments was similar to that obtained from the aerodynamic experiment in which a liquid layer was attached to a solid core and it was exposed to a gas flow. We detected 12 collisions between the fragments, which may result in the compound chondrule formation. We also analyzed the paths of all the fragments in detail and found the importance of the shadow effect in which a fragment extracted later blocks the gas flow toward a fragment extracted earlier. We examined the collision velocity and impact parameter of each collision and found that 11 collisions should result in coalescence. It means that the ratio of coalescent bodies to single bodies formed in this disruption of a parent particle is R=11/(32-11)=0.52. We concluded that compound chondrule formation can occur just after the disruption of a cm-sized molten dust particle in shock-wave heating.

Yasuda, Seiji; Miura, Hitoshi; Nakamoto, Taishi



Theory of Hydrodynamic Fragmentation of Drops of Liquids in Fluidous Media by Shock Waves with Application on the Systems Hg/H sub 2 O, Fe/H sub 2 O, Steel/Na, UO sub 2 /Na.  

National Technical Information Service (NTIS)

A theory is developed for the hydrodynamic description of the behaviour of a single fluid drop in an unlimited liquid medium under the influence of a stationary shock wave. Based on this models for five different decay mechanisms are worked out: direct sh...

J. Schriewer



Hydrodynamic mass  

SciTech Connect

Many structural components contain, or are submerged in, a fluid. The fluid moving with a vibrating structure has an important effect on the dynamics of the structure, particularly on its natural frequencies. The effect of the fluid on natural frequencies can be accounted for using the hydrodynamic mass associated with the structure. This paper provides formulas, graphs, and computer programs for calculating hydrodynamic mass.

Chung, H.; Chen, S.S.



Basic hydrodynamics  

Microsoft Academic Search

Basic hydrodynamic studies in turbomachinery and hydrodynamic drag reduction have been conducted. In the turbomachinery thrust area, the overall objective is to develop an improved understanding of the complex three-dimensional flows typical of incompressible rotor and stator flows; this effort has been primarily computational in nature. The second thrust area is axisymmetric turbulent flow drag reduction through microbubble injections. The

G. C. Lauchle



Discovery of a Nonpropagating Hydrodynamic Soliton.  

National Technical Information Service (NTIS)

A new type water-surface-wave soliton, nonpropagating hydrodynamic soliton, has been discovered. This is a self-trapped, highly localized and stationary transverse water-surface-wave excitation which appears in a rectangular cross section resonator contin...

J. R. Wu



Tritium test of a ferro-fluidic rotary seal  

SciTech Connect

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)



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



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



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



Accelerated thermal aging of petroleum-based ferrofluids  

NASA Astrophysics Data System (ADS)

The effect of elevated temperature on the physical and insulating properties of ferrofluid specifically developed for use as a liquid dielectric (D-fluid) for power transformers has been investigated. The D-fluid was produced as a colloidal mix of a specifically synthesized ferrofluid with a conventional mineral oil, and it was subjected to thermal aging conditions modeled after a typical power transformer where the insulation fluid is expected to retain its dielectric performance for about 40 years of continuous service in a sealed tank. The well-known Arrhenius relationship was employed to model ``life in service'' for up to 40 years at 105 degC which corresponded to holding the samples in sealed jars for 10 weeks at 185 degC. Another set of small ampules (5 ml) was prepared to test the main physical properties after even longer aging. D-fluid tested after a period of 34 and 50 weeks at 185 degC showed no degradation of thermal or colloid stability. The dielectric colloid was also subjected to a 21 day-long test at 110 degC in a sealed jar in the presence of typical transformer materials: copper, cellulose, and silicon steel (so-called ``bomb'' test). Finally, the ferrofluid went through an oxidation stability test (ASTM D2440). Test results show that the newly developed dielectric colloid satisfies the long-term service requirements the transformer users typically apply to conventional mineral oils.

Segal, V.; Nattrass, D.; Raj, K.; Leonard, D.



Dielectric behavior of some ferrofluids in low-frequency fields.  


The dielectric behavior of a ferrofluid with magnetite particles dispersed in kerosene was analyzed taking into account the Schwarz model, concerning the low-frequency dielectric behavior in systems consisting of colloidal particles suspended in electrolytes. For this reason, the complex dielectric permittivity and dielectric loss factor, in the frequency range of 10 Hz-500 kHz, at different temperatures between 20 degrees C and 100 degrees C were measured. Based on these experimental results, the experimental dependencies on both temperature of the relaxation time and activation energy of the relaxation process were analyzed. The obtained results show that the Schwarz model can be applied, in order to explain the low-frequency dielectric behavior of a ferrofluid with magnetite particles in kerosene, if the change of counterion concentration at the surface of colloidal particles is taken into account. Consequently, it is shown that the dielectric spectroscopy can be used in order to analyze the presence of particle agglomerations within ferrofluids. PMID:16290703

Malaescu, I; Marin, C N



Origin of magnetic anomalies and relaxation mechanisms in ferrofluids  

NASA Astrophysics Data System (ADS)

From a fundamental physics perspective, it is proposed that blocking of magnetic nanoparticles and freezing of a carrier fluid would affect the magnetization and relaxation processes in ferrofluids. To verify this hypothesis, we have conducted systematic DC magnetization and AC susceptibility studies in different ferrofluids composed of Fe3O4 and CoFe2O4 nanoparticles suspended in hexane and dodecane, which respectively have freezing temperatures below (178K) and above (264K) the blocking temperature of magnetic nanoparticles (˜200K). Experimental results reveal that the particle blocking and carrier fluid freezing effects play key roles in the formation of glass-like relaxation peaks in ferrofluids, which remained largely unexplained in previous studies. It is also shown that the nature of these peaks is strongly affected by varying particle size and carrier fluid medium. Quantitative fits of the frequency dependent AC susceptibility to the Vogel-Fulcher model, ?=?oexp[Ea/k(T-To)], clearly indicate that the blocking of magnetic nanoparticles in the frozen state significantly affects the interparticle dipole-dipole interaction, causing characteristic spin-glass-like dynamics. A clear correlation between the blocking and freezing temperatures emerges from our studies for the first time.

Morales, M. B.; Phan, M. H.; Frey, N. A.; Pal, S.; Srikanth, H.



Surf and Swash Zone Hydrodynamics.  

National Technical Information Service (NTIS)

Improve understanding of the hydrodynamics of the near-shore motions on beaches, with particular reference to the zone where the incident waves break, form surf, and run-up on the beach to give a fluctuating shoreline. This includes the waves and currents...

D. H. Peregrine I. A. Svendsen



Direct observation of dipolar chains in ferrofluids in zero field using cryogenic electron microscopy  

Microsoft Academic Search

The particle structure of ferrofluids is studied in situ, by cryogenic electron microscopy, on vitrified films of iron and magnetite dispersions. By means of synthesis of iron colloids with controlled particle size and different types of surfactant, dipolar particle interactions can be varied over a broad range, which significantly influences the ferrofluid particle structure. Our experiments on iron dispersions (in

K. Butter; P. H. Bomans; P. M. Frederik; G. J. Vroege; A. P. Philipse



Process for guidance, containment, treatment, and imaging in a subsurface environment utilizing ferro-fluids  


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)



Study of some magnetic properties of ferrofluids filtered in magnetic field gradient  

Microsoft Academic Search

The magnetic properties of some ferrofluids obtained by a new technique, in which the stabilization of particles was done by hydrofobization in the absence of the dispersion medium, and the filtration was done in the presence of a magnetic field gradient, are studied. Measurements were performed on three samples originated from the same ferrofluid with magnetite particles dispersed in kerosene.

I. Malaescu; L. Gabor; F. Claici; N. Stefu



Bbc Hydrodynamics.  

National Technical Information Service (NTIS)

Calculations of two-dimensional multifluid Eulerian hydrodynamics in BBC are discussed; hydro routines in the FORTRAN code BBC make extensive use of vectors. Calculations are performed with either cylindrical- or slab-type symmetry. The problem grid is bo...

W. G. Sutcliffe



Incorporation of Random Wave Effects into a Quasi-3D Nearshore Circulation Model (Preprint).  

National Technical Information Service (NTIS)

A coupled wave-hydrodynamic modeling system, comprised of a random wave model driving a quasi-3D nearshore hydrodynamic model, is described. Random wave formulations for several inputs to the hydrodynamic model are developed. An alternate wave dissipation...

F. Shi I. A. Svendsen J. M. Kaihatu J. T. Kirby



Surviving hydrodynamic forces in a wave-swept environment: Consequences of morphology in the feather boa kelp, Egregia menziesii (Turner)  

Microsoft Academic Search

Organisms on wave-swept intertidal shores often must withstand water velocities of 10 to 20 m\\/s and accompanying accelerations of 400 m\\/s2. Because drag and accelerational forces increase with area and volume respectively, the bigger an individual is, the larger the forces on it become. This size-force relationship suggests that large intertidal algae must be particularly well designed if they are

Michelle T. Friedland; Mark W. Denny



Energy take-out from a wave energy device. A theoretical study of the hydrodynamics of a two-body problem consisting of a buoy and a submerged plate  

NASA Astrophysics Data System (ADS)

A method for calculating the energy take-out from a single wave energy converter is presented. The converter consists of a buoy connected via a hose pump to a submerged plate. The equations of motion of the buoy and plate are solved linearly in the frequency domain, which shows that frequency dependent hydrodynamic properties can be used. The emphasis in the report is placed on the calculation of the frequency dependent hydrodynamic properties, such as the wave excited forces and the hydrodynamic coefficients. The structure is considered to be large in comparison with the wave length and, therefore, the diffraction theory was used. A method of calculating the forces that act on the bodies is presented, as well as the interaction between the bodies. The two-body problem is solved analytically. The present solution is compared with a numerical one and an analytical one, the latter, however, treats simply a single buoy riding in the waves. The calculated energy take-out of the present model is compared with a time domain dependent model, and reasonable agreement was found.

Berggren, L.



Versatile transmission ellipsometry to study linear ferrofluid magneto-optics.  


Linear birefringence and dichroism of magnetite ferrofluids are studied simultaneously using spectroscopic ellipsometry in transmission mode. It is shown that this versatile technique enables highly accurate characterisation of magneto-optical phenomena. Magnetic field-dependent linear birefringence and dichroism as well as the spectral dependence are shown to be in line with previous results. Despite the qualitative agreement with established models for magneto-optical phenomena, these fail to provide an accurate, quantitative description of our experimental results using the bulk dielectric function of magnetite. We discuss the results in relation to these models, and indicate how the modified dielectric function of the magnetite nanoparticles can be obtained. PMID:16997315

Kooij, E S; Gâlc?, A C; Poelsema, B



Two-Dimensional Melting of a Crystal of Ferrofluid Spikes  

NASA Astrophysics Data System (ADS)

We report the observation of the transition from an ordered solidlike phase to a disordered liquidlike phase of a lattice of spikes on a ferrofluid surface submitted to horizontal sinusoidal vibrations. The melting transition occurs for a critical spike displacement which is experimentally found to follow the Lindemann criterion, for two different lattice topologies (hexagonal and square) and over a wide range of lattice wavelengths. An intermediate hexaticlike phase between the solid and isotropic liquid phases is also observed and characterized by standard correlation functions. This dissipative out-of-equilibrium system exhibits strong similarities with 2D melting in solid-state physics.

Boyer, François; Falcon, Eric



Ship Hydrodynamics  

ERIC Educational Resources Information Center

|Explores in a non-mathematical treatment some of the hydrodynamical phenomena and forces that affect the operation of ships, especially at high speeds. Discusses the major components of ship resistance such as the different types of drags and ways to reduce them and how to apply those principles for the hovercraft. (GA)|

Lafrance, Pierre



Ship Hydrodynamics  

ERIC Educational Resources Information Center

Explores in a non-mathematical treatment some of the hydrodynamical phenomena and forces that affect the operation of ships, especially at high speeds. Discusses the major components of ship resistance such as the different types of drags and ways to reduce them and how to apply those principles for the hovercraft. (GA)

Lafrance, Pierre



The influence of the petroleum ferrofluids upon the cellulosolytic fungi Chaetomium globosum Kunze:Fr  

NASA Astrophysics Data System (ADS)

We present a study on the development of the cellulosolytic fungi Chaetomium globosum Kunze:Fr. under the influence of a petroleum ferrofluid, added at various concentrations to the culture medium. A positive influence of the ferrofluid was revealed at the level of the growth rate during the first week of the experiment. Further, the biomass accumulation rate was diminished in the sample in comparison to the control without the addition of ferrofluid. The ubiquitous capacity of the fungi for iron internalization under the form of complex combinations known as siderophores, is probably related to the observed behavior of Chaetomium globosum Kunze:Fr.

Manoliu, Al.; Antohe, Lacramioara; Creanga, Dorina E.; Cotae, C.



Enhanced separation of magnetic and diamagnetic particles in a dilute ferrofluid  

NASA Astrophysics Data System (ADS)

Traditional magnetic field-induced particle separations take place in water-based diamagnetic solutions, where magnetic particles are captured while diamagnetic particles flow through without being affected by the magnetic field. We demonstrate that replacing the diamagnetic aqueous medium with a dilute ferrofluid can significantly increase the throughput of magnetic and diamagnetic particle separation. This enhancement is attributed to the simultaneous positive and negative magnetophoresis of magnetic and diamagnetic particles, respectively, in a ferrofluid. The particle transport behaviors in both ferrofluid- and water-based separations are predicted using an analytical model.

Liang, Litao; Zhang, Cheng; Xuan, Xiangchun



A rheometer for the investigation of structure formation in ferrofluids under magnetic field and shear flow  

NASA Astrophysics Data System (ADS)

Due to the possibility to change their physical properties, especially their viscosity, under magnetic fields, ferrofluids are a challenging subject for engineering, fundamental research and medicine. Experimental and theoretical studies have shown that modifications of the microstructure of ferrofluids in the presence of a magnetic field have significant influence on the magnetoviscous properties. To obtain information on the structure formation, a rheometer for Small Angle Neutron Scattering (SANS) investigations of the behaviour of ferrofluids under the shear flow and the influence of a magnetic field strength was designed. Figs 6, Refs 7.

Pop, L.; Hilljegerdes, J.; Odenbach, S.



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 ?l/min is obtained given a channel width of 1000 ?m 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 ?m.

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



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



Nanoflow hydrodynamics  

NASA Astrophysics Data System (ADS)

We show by nonequilibrium molecular dynamics simulations that the Navier-Stokes equation does not correctly describe water flow in a nanoscale geometry. It is argued that this failure reflects the fact that the coupling between the intrinsic rotational and translational degrees of freedom becomes important for nanoflows. The coupling is correctly accounted for by the extended Navier-Stokes equations that include the intrinsic angular momentum as an independent hydrodynamic degree of freedom.

Hansen, J. S.; Dyre, Jeppe C.; Daivis, Peter J.; Todd, B. D.; Bruus, Henrik



Surface Waves and Rosensweig Instability in Isotropic Ferrogels  

Microsoft Academic Search

We derive the dispersion relation of surface waves for isotropic magnetic gels in the presence of an external magnetic field normal to the free surface. Above a critical field strength surface waves become linearly unstable with respect to a sta- tionary pattern of surface protuberances. This linear stability criterion generalizes that of the Rosensweig instability for ferrofluids by taking into

Stefan Bohlius; Helmut R. Brand; Harald Pleiner



The Cotton-Mouton effect in ferrofluids containing rod-like magnetite particles  

NASA Astrophysics Data System (ADS)

Ferrofluids with rod-like nano-sized magnetite particles were prepared by precipitation from aqueous solutions of ferrous hydroxide and aging them in the presence of a magnetic field. We studied the Couton-Mouton effect measuring the azimuthally distribution of the transmitted light intensity and obtained that its magnetic field dependence differs considerably for ferrofluids containing rod-like and spherical magnetic nanoparticles, respectively. After switching off the magnetizing field, the relaxation of the birefringence was observed, measured and analysed.

Badescu, V.; Udrea, L. E.; Rotariu, O.; Badescu, R.; Apreotesei, G.



Magnetic Behaviour and Heating Effect of Fe3O4 Ferrofluids Composed of Monodisperse Nanoparticles  

Microsoft Academic Search

Fe3O4 ferrofluids containing monodisperse Fe3O4 nanoparticles with different diameters of 8, 12, 16 and 18 nm are prepared by using high-temperature solution phase reaction. The particles have single crystal structures with narrow size distributions. At room temperature, the 8-nm ferrofluid shows superparamagnetic behaviour, whereas the others display hysteresis properties and the coercivity increases with the increasing particle size. The spin

Li-Ying Zhang; Yong-Hua Dou; Ling Zhang; Hong-Chen Gu



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



Magnetic Behaviour and Heating Effect of Fe3O4 Ferrofluids Composed of Monodisperse Nanoparticles  

NASA Astrophysics Data System (ADS)

Fe3O4 ferrofluids containing monodisperse Fe3O4 nanoparticles with different diameters of 8, 12, 16 and 18 nm are prepared by using high-temperature solution phase reaction. The particles have single crystal structures with narrow size distributions. At room temperature, the 8-nm ferrofluid shows superparamagnetic behaviour, whereas the others display hysteresis properties and the coercivity increases with the increasing particle size. The spin glass-like behaviour and cusps near 190 K are observed on all ferrofluids according to the temperature variation of field-cooled (FC) and zero-field-cooled (ZFC) magnetization measurements. The cusps are found to be associated with the freezing point of the solvent. As a comparison, the ferrofluids are dried and the FC and ZFC magnetization curves of powdery samples are also investigated. It is found that the blocking temperatures for the powdery samples are higher than those for their corresponding ferrofluids. Moreover, the size dependent heating effect of the ferrofluids is also investigated in ac magnetic field with a frequency of 55 kHz and amplitude of 200 Oe.

Zhang, Li-Ying; Dou, Yong-Hua; Zhang, Ling; Gu, Hong-Chen



Coupling of blocking and melting in cobalt ferrofluids  

NASA Astrophysics Data System (ADS)

Zero-field-cooling and field-cooling (FC) measurements were performed on ferrofluids of cobalt magnetic nanoparticles (MNPs) in various organic solvent. Two peaks, one broad peak corresponding to the blocking transition (TB), and one sharp peak corresponding to the melting of the solvent (TM), were observed. Furthermore, for a given MNP size, when the blocking and melting transitions were superposed by choosing an appropriate solvent, the strongest intensity of the sharp peak at the melting point of the organic solvent was obtained. This observation is explained by applying the M spectrum theory. Additionally, a first order, melting-induced magnetic phase transformation was observed at the melting point of the solvent. Associated with the first order phase transition and the supercooling effect, a thermal hysteresis loop in the FC curve was observed.

Wen, Tianlong; Liang, Wenkel; Krishnan, Kannan M.



Hartmann-Shack measurements of ferrofluidic mirror dynamics  

NASA Astrophysics Data System (ADS)

Ferrofluid mirrors have the potential to be an inexpensive adaptive optical element which can be used to improve images of structures at the rear of the eye. Their low cost could allow adaptive optics technology to find widespread use in clinical settings. As discussed elsewhere1, their stroke and speed are suitable for correcting the aberrations of the human eye. We present work on the static and dynamic responses of these mirrors using a Hartmann-Shack wavefront reconstruction technique. The displacement of the mirror versus the current in the magnetic field actuators has been measured, as well as actuator influence functions (including non-linearities). In addition, the real-time dynamics of the mirror have been characterized.

Seaman, A.; Macpherson, J. B.; Borra, E. F.; Ritcey, A. M.; Asselin, D.; Jerominek, H.; Thibault, S.; Campbell, M. C. W.



Ferrofluid drop rolling on the surface of a liquid  

NASA Astrophysics Data System (ADS)

We report on the theoretical analysis of an experiment where a ferrofluid drop swimming on top of a non-magnetic fluid layer is propelled forward by means of a rotating magnetic field. The drop is modelled first as a solid sphere with a Navier slip boundary condition, then as a liquid (half-)sphere with its own inner flow field. In both cases an analytical expression for the drop speed in terms of the experimentally accessible parameters is obtained. While the solution of the Navier slip model contains an unknown parameter, the slip length, the result of the liquid half-sphere model is completely free of fitting parameters and is shown to represent the experimentally measured dependencies very well.

Sterr, V.; Morozov, K. I.; Engel, A.



Supernova hydrodynamics  

SciTech Connect

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.



Thermodiffusion of magnetite nanoparticles in ferrofluid-doped micellar systems and in ferrofluids investigated by using the single-beam Z-scan technique  

NASA Astrophysics Data System (ADS)

The Z-scan experimental technique is used to measure the concentration-dependent Soret coefficient of surfacted magnetic nanoparticles in water [pure ferrofluid (FF)] and in a micellar lyotropic mixture [lyotropic doped with ferrofluid (FL)]. In both cases, the magnetic-particle contribution to the Soret coefficient is shown to be proportional to its concentration. In the case of the ferrofluid-doped lyotropic system, it was possible to evaluate the Soret coefficient associated with the micelles under a temperature gradient. The thermal diffusion coefficients keep the relation DFLT ? 0.4 ×D FFT. The Soret effective mobilities evaluated are ?FFs ˜ 6×1011 s kg-1 and ?FLs ˜ 2 × 1011 s kg-1 for the pure ferrofluid and micellar media, respectively. From a nanoscopic point of view, the smaller value of ?FLs when compared to ?FFs could be pictured as an additional resistance of the micellar medium to the particle's flow imposed by the temperature gradient. This procedure gives a new way of determining the Soret coefficient of a weakly absorbing medium.

Alves, Sarah; Sant'anna Cuppo, Fabio Luiz; Bourdon, Alain; Martins Figueiredo Neto, Antonio



Optical fibre long period grating spectral actuators utilizing ferrofluids as outclading overlayers  

NASA Astrophysics Data System (ADS)

Results are presented on the spectral tuning of optical fibre long period gratings utilizing water and oil based ferrofluids as outclading overlayers, under static magnetic field stimulus. Two approaches are adopted for modifying the ambient refractive index at the position of the long period grating. In the first approach, a water based ferrofluid is controllably translated along the length of the grating via a magnetic field. Changes as high as 7.5nm and 6.5dB are monitored in the wavelength and strength, respectively, of the attenuation bands of the grating. The repeatable performance of this device for repetitive forward and backward translation verifies that no ferrofluidic residue is left on the fibre, due to silanization cladding functionalisation. In the second approach, the refractive index of an oil based ferrofluidic overlayer is modified through the magneto-optical effect. For an applied static magnetic field in the order of 400 Gauss the strength of the attenuation band of the grating is modified by more than 10% while its spectral position remains unaffected. Accordingly for the implementation of the last approach, the magnetically induced refractive index changes of ferrofluids of different solution concentrations are studied by employing diffraction efficiency measurements.

Konstantaki, M.; Candiani, A.; Pissadakis, S.



Phase behavior of ferrofluid and colloidal spheres and rods in a magnetic field  

NASA Astrophysics Data System (ADS)

We have studied theoretically and experimentally different phases formed by aqueous ferrofluid only, or by mixtures of this ferrofluid with colloidal latex spheres and rods. The ferrofluid is an aqueous suspension of magnetite Fe3O4 particles, of average diameter 20nm. The latex spheres are PMMA particles of diameter 42nm. The rods are fd-virus. In the presence of a magnetic field applied perpendicular to a thin sample layer, a pure ferrofluid forms disordered columns. When latex spheres or rods are added, the mixture shows a transition from a disordered phase of columns to an hexagonal phase of columns. The columns merge into sheets of ferrofluid at higher magnetic field. Theoretically, we regard this phenomenon as a kind of liquid-solid phase transition, and we study the formation and the stability of these phases by a simple mean field theory. We gratefully acknowledge support from NSF (DMR99-71226), MRSEC (DMR00-79909) and a grant from the French Ministry of Foreign Affairs.

Islam, M. F.; Lacoste, D.; Lubensky, T. C.; Yodh, A. G.



Field-induced structures in miscible ferrofluid suspensions with and without latex spheres  

NASA Astrophysics Data System (ADS)

We explore magnetic-field-induced ordering and microphase separation of aqueous ferrofluid and of aqueous mixtures of ferrofluid with nonmagnetic latex spheres. The ferrofluid is a surfactant stabilized aqueous suspension of magnetite (Fe3O4) particles with average diameter 20 nm (including the ˜2.5-nm thick surfactant layer); the nonmagnetic latex spheres are charge stabilized polymethylmethacrylate (PMMA) particles with diameters of 42 nm, 108 nm, and 220 nm. In the presence of a uniform magnetic field, needlelike ferrofluid droplets formed that eventually grew to sample-traversing columns at fields of ˜600 G; the two-dimensional structure of these columns was, however, glassy rather than hexagonal. In higher fields, ˜1000 G, the columns stretched and coalesced into sheetlike striped liquids, but a true lamellar phase was not observed. The addition of nonmagnetic latex spheres to the ferrofluid suspension lowered substantially the critical field for the formation of columns, and induced lamellar (stripe) phases at relatively low applied fields. Image analysis was used to determine the spatial correlation functions, the average needle or column spacing, and the average lamellae spacing of these samples as a function of latex sphere size and concentration.

Islam, M. F.; Lin, K. H.; Lacoste, D.; Lubensky, T. C.; Yodh, A. G.



Perspectives in coral reef hydrodynamics  

NASA Astrophysics Data System (ADS)

Some developments in coral reef hydrodynamics over the last decade are reviewed with an overview of papers in this special issue. Advances in hydrodynamics based on improved understanding of topographic complexity are illustrated for the reef at Kilo Nalu Observatory and Kaneohe Bay (both in Hawaii). Models of the roughness layer are discussed as a background to numerical models of reef hydrodynamics for Molokai and Guam. Topographic complexity produces spatial temperature variability over reefs creating thermal microclimates which are reported in this issue for the Red Sea. Uptake of ocean nutrients by reefs is controlled by hydrodynamics, and papers in this issue show its critical role in the ecology of a fringing reef at La Réunion Island; nutrient uptake rates are discussed here using new data for Hearn Roughness and Decadal Rugosity. The role of upwelled water by large amplitude internal waves on reefs is reported for the Similan Islands, providing major new evidence for the role of hydrodynamics in the ecology of reefs and its importance to climate change. The review suggests some important areas for new research including simulated corals used in flumes and the field. Major new modeling based on measured roughness maps combined with small scale lattice Boltzmann simulations should be possible in the next decade.

Hearn, Clifford J.



Negative refractive index in hydrodynamical systems  

NASA Astrophysics Data System (ADS)

We discuss the presence of exotic electromagnetic phenomena in systems with finite charge density which are described by hydrodynamics. We show that such systems generically have negative refractive index for low frequencies electromagnetic waves, i.e. the energy flux and the phase velocity of the wave propagate in opposite directions. We comment on possible phenomenological applications, focusing on the Quark Gluon Plasma.

Amariti, Antonio; Forcella, Davide; Mariotti, Alberto



Integrable hydrodynamic chains  

Microsoft Academic Search

A new approach for derivation of Benney-type moment chains and integrable hydrodynamic type systems is presented. New integrable hydrodynamic chains are constructed; all their hydrodynamical reductions are described and integrated. New (2+1) integrable hydrodynamic type systems are found.

Maxim V. Pavlov



Experimental and numerical determination of the static critical pressure in ferrofluid seals  

NASA Astrophysics Data System (ADS)

Ferrofluids have various engineering applications; one of them are magnetic fluid seals for rotating shafts. There are various constructions of this type of seals, but the main difference is the number of sealing stages. The development of this construction is a complex process which requires knowledge of ferrofluid physical and rheological properties and the magnetic field distribution inside the sealing gap. One of the most important parameters of ferrofluid seals is the critical (burst) pressure. It is the pressure value at which a leak will occur. This study presents results of numerical simulation of magnetic field distribution inside the seal gap and calculations of the critical pressure value. The obtained pressure values were verified by experiments.

Horak, W.; Szcz?ch, M.



Stress-induced birefringence in elastomers doped with ferrofluid magnetic particles: Mechanical and optical investigation  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles from magnetic colloidal suspensions were incorporated in the urethane/urea elastomer (PU/PBDO) by adding to the prepolymers solution in toluene diverse amounts of magnetite grains. It is shown that ferrofluid grains can be efficiently incorporated into the elastomer according to this procedure. Mechanical and optical experiments performed show that the elastomer preparation procedure (casting) introduces a structural anisotropy on the optically isotropic sample. This fact is put in evidence by the measurements of the Young's moduli and orientation of the sample's optical axis under stress. The dependence of the phase shift of both the pure and ferrofluid-doped elastomer samples under strain is linear, and the strain-optic coefficient is show to be linear with the ferrofluid concentration.

Sena, C.; Bailey, C.; Godinho, M. H.; Figueirinhas, J. L.; Palffy-Muhoray, P.; Figueiredo Neto, A. M.



Elastic stability of silicone ferrofluid internal tamponade (SFIT) in retinal detachment surgery  

NASA Astrophysics Data System (ADS)

It has been argued that silicone ferrofluid internal tamponade (SFIT) can provide (360°) tamponade of the retina in retinal detachment surgery. Provided that the produced SFIT is biocompatible, exact knowledge is needed of its elastic stability in the magnetic field produced by the semi-solid magnetic silicon band (MSB) used as a scleral buckle. We propose a quantitative, phenomenological model to estimate the critical magnetic field produced by the MSB that `closes' retinal tears and results in the reattachment of the retina. The magnetic `deformation' of SFIT is modeled in accordance with the deformation of a ferrofluid droplet in an external magnetic field.

Voltairas, P. A.; Fotiadis, D. I.; Massalas, C. V.



Anomalous Decay in Short Time Response of Ternary Mixtures with Ferrofluid  

NASA Astrophysics Data System (ADS)

We study the optical transmittance of ternary mixtures of water, glycerin and ferrofluids. These mixtures are subject to pulsed magnetic field and placed between crossed polarizers. After the magnetic field is switched off, the decay process is compared with q-exponential, stretched exponential, Mittag-Leffler, and one-sided Lévy stable functions. For short time, the experimental results are interpreted in terms of stretched exponentials. The parameters of this non-exponential relaxation are investigated as functions of temperature and the water, glycerin and ferrofluid concentrations.

Laczkowski, I. M.; Mukai, H.; Fernandes, P. R. G.; Mendes, R. S.; Evangelista, Luiz Roberto



Comparison between theory and simulations for the magnetization and the susceptibility of polydisperse ferrofluids.  


The influence of polydispersity on the magnetization of ferrofluids is studied based on a previously published magnetization equation of state (Szalai and Dietrich, 2011 J. Phys.: Condens. Matter 23 326004) and computer simulations. 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. PMID:24153397

Szalai, I; Nagy, S; Dietrich, S



Structure factor of ferrofluids with chain aggregates: Theory and computer simulations  

NASA Astrophysics Data System (ADS)

In this paper we present theoretical and simulation results on the structure factor of mono- and bidisperse ferrofluids with chain aggregates, both with and without an applied external magnetic field. Chain distribution is obtained by the density functional theory (DFT). The radial distribution function (RDF) is calculated directly on the basis of the chain distribution and Fourier transformed to calculate the structure factor. An extensive comparison of the theoretical predictions to the results of the molecular dynamics computer simulations is provided. The proposed combined approach allows to elucidate the connection between experimentally observed small angle neutron scattering (SANS) images and the ferrofluid microstructure.

Pyanzina, Elena; Kantorovich, Sofia; Cerdà, Juan J.; Holm, Christian



Theoretical and experimental investigations of ferrofluids for guiding and detecting liquids in the subsurface. FY 1997 annual report  

SciTech Connect

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.



Bovine Serum Albumin Binding and Drug Delivery Studies with PVA-Ferrofluid  

Microsoft Academic Search

This paper describes a single-step method for the biomimetic synthesis of stably suspended magnetite nanoparticles in poly(vinyl alcohol) termed ferrofluids. The challenge is to synthesize water based stable magnetic colloids with a control over the particle size and morphology for biomedical applications. The polymer possibly plays a dual role of a surfactant and a functionalizing agent. Transmission electron microscopy, infrared

Suprabha Nayar; Aparna Mir; Aarti Ashok; Avijit Guha; Vikas Sharma



Direct observation of dipolar chains in iron ferrofluids by cryogenic electron microscopy  

Microsoft Academic Search

A key issue in research on ferrofluids (dispersions of magnetic colloids) is the effect of dipolar interactions on their structure and phase behaviour, which is not only important for practical applications but gives fundamental insight in dipolar fluids in general. In 1970, de Gennes and Pincus predicted a Van der Waals-like phase diagram and the presence of linear chains of

K. Butter; P. H. H. Bomans; P. M. Frederik; G. J. Vroege; A. P. Philipse



A bio-inspired device to detect equilibrium variations using IPMCs and ferrofluids  

Microsoft Academic Search

This work describes a device designed and built to detect the inclination of a body, based on two emerging smart materials: ionic polymer–metal composites (IPMCs) and ferrofluids. The system is bio-inspired and simulates the behavior of the vestibular labyrinth, a biological component of living beings, situated in the inner ear and devoted to perception of the angular acceleration the head

B. Andò; C. Bonomo; L. Fortuna; P. Giannone; S. Graziani; L. Sparti; S. Strazzeri



Optical properties of magnetic and non-magnetic composites of ferrofluids  

Microsoft Academic Search

Composites consisting of magnetic and non-magnetic micronsize particles suspended in a ferrofluid (FF) constitute magnetorheological (MR) fluid. Structuring occurs in an applied magnetic field and can results in the solidification of the composites. A novel magneto-optical effect of extremum and inversion in sign with increasing applied magnetic field strength in this composite is observed. The field strengths at which the

Rajesh Patel; R. V. Upadhyay; R. V. Mehta



A vectorial magnetometer utilising a microstructured optical fibre Bragg grating infiltrated by a ferrofluid  

Microsoft Academic Search

,+---« , ...... +; ? .... ? ? ? ? ? .§ (a) Schematic of the ferrofluid infiltrated MOF-Bragg grating magnetometer. (b) Reflection spectra of the defected Bragg grating with (dashed line) and without (solid line) magnetic field perturbation. The position of the spectral defect indicates that the Bragg grating is slightly chirped. (c) Parasitic notch visibility versus magnetic field

A. Candianil; C. Sterner; M. KonstantakiI; P. ChildsI; S. Pissadakis



Genetic Algorithm Combined with Finite Element Method for Optimum Design of Ferrofluid Actuator  

Microsoft Academic Search

This paper presents a case study concerning the optimization of a DC ferrofluid actuator designed to transmit small pressures, using genetic algorithms. The optimization problem consists in finding the values of some mechanical parameters of the actuator as well as those of the magnetic permeabilities of the device components, that render a maximum equivalent force. The magnetic field inside the

Camelia Petrescu; Lavinia Ferariu; R. Olaru



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.



Oscillatory shear response of dilute ferrofluids: predictions from rotational Brownian dynamics simulations and ferrohydrodynamics modeling.  


Ferrofluids are colloidal suspensions of magnetic nanoparticles that exhibit normal liquid behavior in the absence of magnetic fields but respond to imposed magnetic fields by changing their viscosity without loss of fluidity. The response of ferrofluids to constant shear and magnetic fields has received a lot of attention, but the response of ferrofluids to oscillatory shear remains largely unexplored. In the present work we used rotational Brownian dynamics to study the dynamic properties of ferrofluids with thermally blocked nanoparticles under oscillatory shear and constant magnetic fields. Comparisons between simulations and modeling using the ferrohydrodynamics equations were also made. Simulation results show that, for small rotational Péclet number, the in-phase and out-of-phase components of the complex viscosity depend on the magnitude of the magnetic field and frequency of the shear, following a Maxwell-like model with field-dependent viscosity and characteristic time equal to the field-dependent transverse magnetic relaxation time of the nanoparticles. Comparison between simulations and the numerical solution of the ferrohydrodynamic equations shows that the oscillatory rotational magnetoviscosity for an oscillating shear field obtained using the kinetic magnetization relaxation equation quantitatively agrees with simulations for a wide range of Péclet number and Langevin parameter but has quantitative deviations from the simulations at high values of the Langevin parameter. These predictions indicate an apparent elastic character to the rheology of these suspensions, even though we are considering the infinitely dilute limit in which there are negligible particle-particle interactions and, as such, chains do not form. Additionally, an asymptotic analytical solution of the ferrohydrodynamics equations, valid for Pe<2, was used to demonstrate that the Cox-Merz rule applies for dilute ferrofluids under conditions of small shear rates. At higher shear rates the Cox-Merz rule ceases to apply. PMID:22181497

Soto-Aquino, D; Rosso, D; Rinaldi, C



Oscillatory shear response of dilute ferrofluids: Predictions from rotational Brownian dynamics simulations and ferrohydrodynamics modeling  

NASA Astrophysics Data System (ADS)

Ferrofluids are colloidal suspensions of magnetic nanoparticles that exhibit normal liquid behavior in the absence of magnetic fields but respond to imposed magnetic fields by changing their viscosity without loss of fluidity. The response of ferrofluids to constant shear and magnetic fields has received a lot of attention, but the response of ferrofluids to oscillatory shear remains largely unexplored. In the present work we used rotational Brownian dynamics to study the dynamic properties of ferrofluids with thermally blocked nanoparticles under oscillatory shear and constant magnetic fields. Comparisons between simulations and modeling using the ferrohydrodynamics equations were also made. Simulation results show that, for small rotational Péclet number, the in-phase and out-of-phase components of the complex viscosity depend on the magnitude of the magnetic field and frequency of the shear, following a Maxwell-like model with field-dependent viscosity and characteristic time equal to the field-dependent transverse magnetic relaxation time of the nanoparticles. Comparison between simulations and the numerical solution of the ferrohydrodynamic equations shows that the oscillatory rotational magnetoviscosity for an oscillating shear field obtained using the kinetic magnetization relaxation equation quantitatively agrees with simulations for a wide range of Péclet number and Langevin parameter but has quantitative deviations from the simulations at high values of the Langevin parameter. These predictions indicate an apparent elastic character to the rheology of these suspensions, even though we are considering the infinitely dilute limit in which there are negligible particle-particle interactions and, as such, chains do not form. Additionally, an asymptotic analytical solution of the ferrohydrodynamics equations, valid for Pe?2, was used to demonstrate that the Cox-Merz rule applies for dilute ferrofluids under conditions of small shear rates. At higher shear rates the Cox-Merz rule ceases to apply.

Soto-Aquino, D.; Rosso, D.; Rinaldi, C.



Algorithm refinement for fluctuating hydrodynamics  

SciTech Connect

This paper introduces an adaptive mesh and algorithmrefinement method for fluctuating hydrodynamics. This particle-continuumhybrid simulates the dynamics of a compressible fluid with thermalfluctuations. The particle algorithm is direct simulation Monte Carlo(DSMC), a molecular-level scheme based on the Boltzmann equation. Thecontinuum algorithm is based on the Landau-Lifshitz Navier-Stokes (LLNS)equations, which incorporate thermal fluctuations into macroscopichydrodynamics by using stochastic fluxes. It uses a recently-developedsolver for LLNS, based on third-order Runge-Kutta. We present numericaltests of systems in and out of equilibrium, including time-dependentsystems, and demonstrate dynamic adaptive refinement by the computationof a moving shock wave. Mean system behavior and second moment statisticsof our simulations match theoretical values and benchmarks well. We findthat particular attention should be paid to the spectrum of the flux atthe interface between the particle and continuum methods, specificallyfor the non-hydrodynamic (kinetic) time scales.

Williams, Sarah A.; Bell, John B.; Garcia, Alejandro L.



Magnetic guidance of ferrofluidic nanoparticles in an in vitro model of intraocular retinal repair  

NASA Astrophysics Data System (ADS)

Agarose gel at a concentration of 0.6% was used to simulate the vitreous body of the eye during the infusion of a ferrofluid and the subsequent magnetic concentration of it onto a surrogate retinal surface. The 10 nm Fe3O4 particles in the ferrofluid served to mimic the cobalt particles in a silicone magnetic fluid that is being developed for use as a tamponading agent in magnetic fluid therapies designed to alleviate retinal detachments and other types of retinopathy. Magnetically guided interstitial diffusion of the nanoparticles through up to 20 mm of the gel over periods of 72 h was shown to be possible, thus demonstrating that essentially all points on the retinal surface are reachable from elsewhere in the ocular interior. The nanodynamics of the magnetic and viscous forces at work on the particles during movement through the gel are discussed; in particular the diffusion speeds of the particles are estimated and compared with observations.

Holligan, D. L.; Gillies, G. T.; Dailey, J. P.



Thermal conductivity measurements on ferrofluids with special reference to measuring arrangement  

NASA Astrophysics Data System (ADS)

Material properties like viscosity and sound propagation in colloidal suspensions of magnetic nanoparticles, so-called ferrofluids, are known to depend on external magnetic fields due to structure formation of the magnetic particles. In this experimental study we investigate the effect of magnetically driven structure formation on heat flux in ferrofluids on the basis of thermal conductivity measurements in variation of an external magnetic field. Therefore an improved measuring device based on the plane heat source instead of the standard hot wire method is used to enable both parallel and perpendicular orientation of magnetic field and heat flux. Thermal conductivity measurements are carried out in variation of strength and direction of an external magnetic field relative to heat flux. Unlike former experimental investigations for the first time the results show qualitative consistency with theoretical predictions for both orientations.

Krichler, M.; Odenbach, S.



Magnetic-field tunable transmittance in a ferrofluid-filled silicon nitride photonic crystal slab  

NASA Astrophysics Data System (ADS)

A numerical simulation was performed to demonstrate the active manipulation of the transmittance spectra in a ferrofluid-filled silicon nitride (SiN) photonic crystal slab (PCS) with magnetic field applied perpendicularly to the plane. Many sharp transmittance resonances were found to be correlated with the modes extracted from band structure calculations, where they show red-shift and mutual approach as the external magnetic field increases. By changing the angle of the incident light, we found strong coupling modes because of their asymmetric electric field distributions. This in situ control of transmittance properties of ferrofluid-filled SiN PCS should open up new applications for designing filters, mirrors and displacement sensors in compact optical devices.

Lee, H. M.; Horng, L.; Wu, J. C.



Study of magnetic and structural properties of ferrofluids based on cobalt-zinc ferrite nanoparticles  

Microsoft Academic Search

Ferrofluids are colloidal systems composed of a single domain of magnetic nanoparticles with a mean diameter around 30 nm, dispersed in a liquid carrier. Magnetic Co(1-x)ZnxFe2O4 (x=0.25, 0.50, 0.75) ferrite nanoparticles were prepared via co-precipitation method from aqueous salt solutions in an alkaline medium. The composition and structure of the samples were characterized through Energy Dispersive X-ray Spectroscopy and X-ray

J. López; L. F. González-Bahamón; J. Prado; J. C. Caicedo; G. Zambrano; M. E. Gómez; J. Esteve; P. Prieto



Magnetic resonance of nanoparticles in a ferrofluid: evidence of thermofluctuational effects  

Microsoft Academic Search

Ferromagnetic resonance (FMR) experiments on non-interacting maghemite (?-Fe2O3) nanoparticles in ferrofluids, are performed in X- and Q-bands as a function of the particle diameter (4.8–10nm) and the temperature (3.5–300K). The colloidal stability and grain size are controlled through a chemical synthesis, the polydispersity being reduced by a phase separation method. The dependencies of spectral characteristics with temperature T, particle volume

F. Gazeau; V. Shilov; J. C. Bacri; E. Dubois; F. Gendron; R. Perzynski; Yu. L. Raikher; V. I. Stepanov



Entrainment by a rotating magnetic field of a ferrofluid contained in a sphere.  


Entrainment of a ferrofluid contained in a sphere by a rotating uniform magnetic field is studied on the basis of spin-diffusion theory. The equations for flow velocity and spin velocity, coupled to Maxwell's equations of magnetostatics, are solved analytically to second order in the applied magnetic field. A similar derivation holds in electrohydrodynamics for a polar liquid contained in a sphere and subject to a rotating electrical field. PMID:22181267

Felderhof, B U



Rapid amplification of genetically modified organisms using a circular ferrofluid-driven PCR microchip  

Microsoft Academic Search

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



Magnetic Thermal Ablation Using Ferrofluids: Influence of Administration Mode on Biological Effect in Different Porcine Tissues  

SciTech Connect

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:; Hodenius, Michael, E-mail:; Baumann, Martin, E-mail:; 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:; Mahnken, Andreas H., E-mail: mahnken@rad.rwth-aachen.d [Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University, Applied Medical Engineering (Germany)



Mo¨ssbauer effect and magnetism of single domain Fe3O4 particles in ferrofluids  

Microsoft Academic Search

Three ferrofluids, consisting of suspensions of Fe3O4 particles of &bartil;100–200 A? diameter in diester, hydrocarbon, and water have been investigated at temperatures 4.2–300 K by means of Mo¨ssbauer effect and magnetic measurements. The magnetic data displays almost all the features observed in the spin glasses. The Ne´el model is used to explain the behavior of the fluids. From the temperature

A. Tari; J. Popplewell; S. W. Charles; D. St. P. Bunbury; K. M. B. Alves



Direct observation of dipolar chains in iron ferrofluids by cryogenic electron microscopy.  


A key issue in research on ferrofluids (dispersions of magnetic colloids) is the effect of dipolar interactions on their structure and phase behaviour, which is not only important for practical applications but gives fundamental insight in dipolar fluids in general. In 1970, de Gennes and Pincus predicted a Van der Waals-like phase diagram and the presence of linear chains of particles in ferrofluids in zero magnetic field. Despite many experimental studies, no direct evidence of the existence of linear chains of dipoles has been reported in the absence of magnetic field, although simulations clearly show the presence of chain-like structures. Here, we show in situ linear dipolar structures in ferrofluids in zero field, visualized on the particle level by electron cryo-microscopy on thin, vitrified films of organic dispersions of monodisperse metallic iron particles. On systematically increasing the particle size, we find an abrupt transition from separate particles to randomly oriented linear aggregates and branched chains or networks. When vitrified in a permanent magnetic field, these chains align and form thick elongated structures, indicating lateral attraction between parallel dipole chains. These findings show that the experimental model used is well suited to study the structural properties of dipolar particle systems. PMID:12612691

Butter, K; Bomans, P H H; Frederik, P M; Vroege, G J; Philipse, A P



Investigation of the effect of magnetic field on ferrofluid in microelectromechanical devices (MEMS)  

NASA Astrophysics Data System (ADS)

Considerable efforts have been spent in the development of magnetic nanoparticles (MNPs) in the last decade to understand their behaviour, and the improvement of their applicability in many different areas. Precise control over the synthesis conditions and surface functionalization of MNPs is crucial because it governs their physical properties and their colloidal stability. The magnetic platforms possess very small size and narrow size distribution together with high magnetization values. These nanoparticles (NPs) must combine high magnetic susceptibility for an optimum magnetic enrichment and loss of magnetization after removal of the magnetic field. Computational Fluid Dynamics (CFD) approach has been used to investigate the impact of a magnetic field in ferrofluid flow through a T-microchannel. The microchannel consists of one 400?m wide main branch and two 200?m wide sidebranches. Available experimental data is used to validate the Eulerian-Eulerian approach in simulating the nanoparticles in flow flow under the influence of magnetic field. In general, magnetic nanoparticles are deflected across the suspending ferrofluid by negative magnetophoresis and confined by a water flow to the center of the micro-channel. The effect of ferrofluid flow rate on the particle focusing performance has been examined. It is found that the particle focusing effectiveness increases with decreasing flow rate.

Lee, Ann; Yeoh, Guan H.; Lim, Shen H.; Prusty, B. Gangadhara



Targeted Tumor Therapy with "Magnetic Drug Targeting": Therapeutic Efficacy of Ferrofluid Bound Mitoxantrone  

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.


Optical and rheological study of gamma irradiated rare-earth nanoparticle based ferrofluids  

NASA Astrophysics Data System (ADS)

The present work reports on the optical and rheological properties of unexposed and gamma irradiated rare-earth (RE) oxide nanoparticle-based ferrofluids (FF). The ferrofluids were prepared by dispersing surfactant coated gadolinium oxide (Gd2O3) nanoparticles in ethanol medium and later on subjected to energetic gamma irradiation (1.25 MeV) at select doses. As predicted from transmission electron microscopy and X-ray diffraction (XRD) studies, the synthesized nanoparticles are of ˜7 nm size which crystallize into cubic crystal structure. The photoluminescence response reveals creation of defect states on nanoparticle surfaces when FFs are subjected to gamma irradiation. Whereas, rheology measurements showed unusual shear thinning behavior of the ferrofluids. The flow behavior of all the samples can be correlated to the bi-exponential decay curve fitting which reveals that decay phenomenon is governed by two independent mechanism: fast and slow events. The variation of the decay parameter with irradiation dose is attributed to the creation of point defects and weakening of inter nanoparticle bonding.

Paul, Nibedita; Mohanta, Dambarudhar; Saha, Abhijit



An investigation on the optimum conditions of synthesizing a magnetite based ferrofluid as MRI contrast agent using Taguchi method  

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



FROM THE CURRENT LITERATURE: Hydrodynamic cumulative processes in plasma physics  

NASA Astrophysics Data System (ADS)

This review is devoted to cumulative hydrodynamic processes in a plasma and to the possibility of using them for controlled thermonuclear fusion. The cumulation of convergent shock waves and the mechanisms of their limitation are discussed in greatest detail. Results are presented of study of non-one-dimensional cumulative shock waves, which had practically not yielded to analysis until recently.

Sokolov, Ivan V.



Field-induced motion of ferrofluids through immiscible viscous media: Testbed for restorative treatment of retinal detachment  

NASA Astrophysics Data System (ADS)

Biocompatible, hydrophobic ferrofluids comprised of magnetite nanoparticles dispersed in polydimethylsiloxane show promise as materials for the treatment of retinal detachment. This paper focuses on the motion of hydrophobic ferrofluid droplets traveling through viscous aqueous media, whereby the movement is induced by gradients in external fields generated by small permanent magnets. A numerical method was utilized to predict the force on a spherical droplet, and then the calculated force was used to estimate the time required for the droplet to reach the permanent magnet. The calculated forces and travel times were verified experimentally.

Mefford, Olin T.; Woodward, Robert C.; Goff, Jonathan D.; Vadala, T. P.; St. Pierre, Tim G.; Dailey, James P.; Riffle, Judy S.



Numerical Wave Force Simulation.  

National Technical Information Service (NTIS)

The general objectives of this project were to improve the understanding of hydrodynamic loading on offshore structures and to improve tchniques for computing loads on offshore structures. The loads are primarily due to waves and currents. The project inc...

J. K. Vandiver



Biological colloid engineering: Self-assembly of dipolar ferromagnetic chains in a functionalized biogenic ferrofluid  

PubMed Central

We have studied the dynamic behavior of nanoparticles in ferrofluids consisting of single-domain, biogenic magnetite (Fe3O4) 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.

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



Flow of a ferrofluid down a tube in an oscillating magnetic field  

NASA Astrophysics Data System (ADS)

The magnetoviscosity of a ferrofluid flowing down a circular tube in the presence of a magnetic field oscillating in the direction of the axis is studied on the basis of ferrohydrodynamics, Maxwell's equations of magnetostatics, and a relaxation equation for the magnetization. Three different relaxation equations, proposed in the literature, are considered. For large amplitude of the oscillating field the three equations lead to different values of the magnetoviscosity. For large magnetic permeability the self-consistent magnetic field generated by the magnetization has significant effect.

Felderhof, B. U.



Molecular quantum wakes in the hydrodynamic plasma waveguide in air  

SciTech Connect

We demonstrate a modulated plasma guiding effect from the molecular alignment wakes in the hydrodynamic plasma waveguide. A properly time-delayed laser pulse can be spatially confined by the hydrodynamic expansion induced plasma waveguide of an advancing femtosecond laser pulse. The spatial confinement can be further strengthened or weakened by following the quantum wakes of the impulsively excited rotational wave packets of the molecules in the plasma waveguide.

Wu Jian; Cai Hua; Zeng Heping [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China); Milchberg, H. M. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)



Hydrodynamics on the Scales of Biological Processes  

NASA Astrophysics Data System (ADS)

Aquatic organisms exchange mass and momentum with the water moving around them. To understand how organisms function in the ocean, we must study the hydrodynamics of both the environment and the organisms on the spatial and temporal scales at which water movement affects defined biological processes. I will illustrate this point using examples from my ongoing research on how dissolved chemical cues can affect the settlement of microscopic larvae onto coral reefs in turbulent, wave-driven flow, on how benthic crustaceans capture and track odors, and on how seaweeds survive on wave-swept shores

Koehl, M.



Hydrodynamics of Semiconvection in Massive Stars  

NASA Astrophysics Data System (ADS)

Semiconvection significantly affects the evolution of massive stars, but as yet there is no consensus on how to treat this instability in stellar models. An improved understanding of the nonlinear hydrodynamics of semiconvection clearly is desirable. At its onset, semiconvection consists of self-excited internal gravity waves. In massive stars, the the fastest-growing disturbances have wavelengths of order 10(3) km. Numerous finite-amplitude outcomes can be envisaged, including wave breaking by overturning or shear instability, the cascading of wave energy to smaller scales via resonant couplings to higher wave numbers, and the formation of overturning layers separated by thin diffusive interfaces. Each possibility leads to a different recipe for describing the transport of heat and chemical species in stellar models, some of which coincide with prescriptions that have previously been suggested in the literature (e.g., Spruit 1992, A&A, 253, 131, Langer, et al. 1985, A&A, 145, 179.) The present study aims to evaluate which (if any) of these prescriptions are correct by computing the nonlinear evolution of semiconvective oscillations in a 30Msun main-sequence star. Two-dimensional hydrodynamical simulations are employed to examine the growth and destruction of individual waves, the stability of overturning layers, and the adjustments occurring in the structure of the semiconvective zone as a whole. This work is supported by an International Fellowship from the Natural Sciences and Engineering Research Council of Canada.

Merryfield, W. J.



Optical Transmittance and Dynamic Properties of Ferrofluids (Fe$_{3}$ O$_{4}$ ) Under DC-Biased Magnetic Fields  

Microsoft Academic Search

The dynamic property of ferrofluids under a dc-biased magnetic field was understood by the measurement of optical transmittance. The results show that immediately after the application of a magnetic field, the transmitted optical intensity decreases to a minimum and, then, increases until it becomes stable. From the microscopic images, they indicate that this effect is due to longitudinal aggregation of

Min-Feng Chung; Chao-Ming Fu



Ferromagnetization of Target Tissues by Interstitial Injection of Ferrofluid: Formulation and Evidence of Efficacy for Magnetic Retraction  

Microsoft Academic Search

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

Zhigang Wang; Lijun Wang; Stuart I. Brown; Tim G. Frank



Determination of the minimum concentrations of ferrofluid of CoFe2O4 required to orient liquid crystals  

NASA Astrophysics Data System (ADS)

A lyotropic liquid crystal doped with CoFe2O4 ionic ferrofluid with magnetic grains of different sizes is studied by means of optical techniques. The minimum concentrations of grains required to orient liquid crystals are determined. Brochard's and de Gennes' theory of magnetic suspensions is extended to include ellipsoidal grains.

Matuo, C. Y.; Tourinho, F. A.; Neto, A. M. Figueiredo



Particle blocking and carrier fluid freezing effects on the magnetic properties of Fe3O4-based ferrofluids  

Microsoft Academic Search

We report the systematic dc and ac susceptibility studies on the particle blocking and carrier fluid freezing effects on the magnetization and relaxation processes in two different ferrofluids composed of Fe3O4 nanoparticles (mean size of ?14 nm) suspended in hexane and dodecane, which respectively have freezing temperatures below (178 K) and above (264 K) the blocking temperature of magnetic nanoparticles

M. B. Morales; M. H. Phan; S. Pal; N. A. Frey; H. Srikanth



Particle blocking and carrier fluid freezing effects on the magnetic properties of Fe3O4-based ferrofluids  

Microsoft Academic Search

We report the systematic dc and ac susceptibility studies on the particle blocking and carrier fluid freezing effects on the magnetization and relaxation processes in two different ferrofluids composed of Fe3O4 nanoparticles (mean size of ~14 nm) suspended in hexane and dodecane, which respectively have freezing temperatures below (178 K) and above (264 K) the blocking temperature of magnetic nanoparticles

M. B. Morales; M. H. Phan; S. Pal; N. A. Frey; H. Srikanth



Closed-Loop Temperature Control of Cobalt Ferrite Ferrofluids Using Continuous Modes Controllers  

NASA Astrophysics Data System (ADS)

Precise temperature control of a cobalt ferrite ferrofluid (2.5% w/w in heptane) was achieved using continuous mode controllers and a custom-made, variable frequency, magnetic field generator. Proportional-Integral (PI) and Proportional-Integral-Derivative (PID) controllers were implemented using LabVIEW and used to control the amplitude of the magnetic field applied to the ferrofluid. A fluoro-optic thermometer (Luxtron) was used to record temperature. The applied magnetic field had a maximum value of 7 kA/m (100% controller output), and a frequency of 507 kHz. The temperature (process variable) range was 0-100° C (0-100%). When properly tuned, the proportional-integral (PI) controller yielded excellent results, achieving 1.1 percent overshoot (%OS), a settling time (Ts) of 50 s, and a steady-state error of 0.10° C, for a setpoint of 40° C. The implementation of accurate and fast temperature controllers allows for the consideration of transient responses in fields of study in which magnetic nanoparticles are employed as heat sources.

Juan, Eduardo J.; Visbal-Onufrak, Michelle



Three-dimensional magnetic focusing of particles and cells in ferrofluid flow through a straight microchannel  

NASA Astrophysics Data System (ADS)

Focusing particles and cells into a tight stream is often required in order for continuous flow detection, counting and sorting. So far a variety of particle focusing methods have been developed in microfluidic devices, among which magnetic focusing is still relatively new. We develop in this work an approach to embedding symmetrically two repulsive permanent magnets about a straight rectangular microchannel in a PDMS-based microfluidic device. The closest distance between the magnets is limited only by the sizes of the embedded and holder magnets involved in the fabrication process. The developed device is used to implement and investigate the three-dimensional magnetic focusing of polystyrene particles in ferrofluid microflow with both the top- and side-view visualizations. The effects of flow speed and particle size on the particle focusing effectiveness are studied. The developed device is also applied to magnetically focus yeast cells in ferrofluid, which proves to be biocompatible as verified by a cell viability test. In addition, an analytical model is developed and found to be able to predict the experimentally observed particle and cell focusing behaviors with reasonable agreement.

Zeng, Jian; Chen, Chen; Vedantam, Pallavi; Brown, Vincent; Tzeng, Tzuen-Rong J.; Xuan, Xiangchun



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?gL(-1), and the enrichment factor (EF) 267 was obtained. Detection limit was 1.51?gL(-1) (n=7), and the relative standard deviation of 5.6% at 50ngmL(-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



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

NASA Astrophysics Data System (ADS)

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 move and rotate to minimize the total energy of the system. Once equilibrated in energy for a given input- output magnetic field pattern pair, the particles are fully or partially immobilized by cooling the carrier liquid. Thus produced particle distributions control the memory states, which are read out magnetically using spin-valve sensors incorporated into the output pads. The actual memory consists of spin distributions that are dynamic in nature, realized only in response to the input patterns that the system has been trained for. Two training algorithms for storing multiple patterns are investigated. Using Monte Carlo simulations of the physical system, we demonstrate that the device is capable of storing and recalling two sets of images, each with an accuracy approaching 100%.

Palm, R.; Korenivski, V.



Hydrodynamics of spin-polarized transport and spin pendulum  

SciTech Connect

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:; Kalinenko, A. N.; Kopeliovich, A. I.; Pyshkin, P. V.; Yanovsky, A. V. [Verkin Institute for Low-Temperature Physics and Engineering (Ukraine)



Hydrodynamics with Triangle Anomalies  

SciTech Connect

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)



Hydrodynamics and universality in cold atomic gases  

NASA Astrophysics Data System (ADS)

Recent flurry of experiments on out-of-equilibrium dynamics in cold gases (Bosonic and Fermionic) has raised great interest in understanding collective behaviour of interacting particles. Although the dynamics of interacting gases depends on many details of the system, a great insight can be obtained in a rather universal limit of weak non-linearity, dispersion and dissipation. In this limit, using a reductive perturbation method we map many hydrodynamic models relevant to cold atoms to well known chiral one-dimensional equations such as Korteweg-de Vries (KdV), Burgers, KdV-Burgers, and Benjamin-Ono equations. This mapping [1] of rather complicated hydrodynamic equations to known chiral one-dimensional equations is of great experimental and theoretical interest. For instance, this mapping gives a simple way to make estimates for original hydrodynamic equations and to study phenomena such as shock waves, solitons and the interplay between nonlinearity, dissipation and dispersion. All these phenomena have been observed in experiments and are the hallmarks of nonlinear hydrodynamics.[4pt] [1] M. Kulkarni, A. G. Abanov, Phys. Rev. A 86, 033614 (2012)

Abanov, Alexander; Kulkarni, Manas



Synthesis and characterization of Mn0.5Zn0.5Fe2O4 and Fe3O4 nanoparticle ferrofluids for thermo-electric conversion  

NASA Astrophysics Data System (ADS)

Ferrofluids containing nanoparticles of Mn0.5Zn0.5Fe2O4 (MZ5) and Fe3O4 (magnetite) have been examined as potential thermal transport media and energy harvesting materials. The ferrofluids were synthesized by chemical co-precipitation and characterized by EDX to determine composition and by TEM to determine particle size and agglomeration. A range of particle coatings and carrier fluids were used to complete the fluid preparation. Commercially available ferrofluids were tested in custom built rigs to demonstrate both thermal pumping (for waste heat removal applications) and power induction (for power conversion and energy harvesting applications). The results indicate that simple ferrofluids possess the necessary properties to remove waste heat, either into thermal storage or for conversion to electrical power.

Sansom, C. L.; Jones, P.; Dorey, R. A.; Beck, C.; Stanhope-Bosumpim, A.; Peterson, J.



A numerical study of the breaking of modulated waves generated at a wave maker  

Microsoft Academic Search

This paper is concerned with breaking criteria for generated waves. An input in the form of a time signal is prescribed to a wave maker located at one end of a wave tank as used in hydrodynamic laboratories. The motion of this wave maker produces waves propagating into initially still water in the tank. The spatial evolution of the wave

W. M. Kusumawinahyu; E. van Groesen



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)



Hydrodynamic aspects of ejectors  

Microsoft Academic Search

The use of ejectors as a gas–liquid contacting device has been reported to give higher mass transfer rates than conventional contactors. Computational fluid dynamics (CFD) modeling studies were undertaken to understand the hydrodynamic characteristics with reference to the ejector geometry. The CFD model also provides a basis for quantifying the effects of operating conditions on the ejector performance. CFD studies

M. T. Kandakure; V. G. Gaikar; A. W. Patwardhan



Smoothed particle hydrodynamics  

Microsoft Academic Search

In this review the theory and application of Smoothed particle hydrodynamics (SPH) since its inception in 1977 are discussed. Emphasis is placed on the strengths and weaknesses, the analogy with particle dynamics and the numerous areas where SPH has been successfully applied.

J. J. Monaghan



Smoothed particle hydrodynamics  

Microsoft Academic Search

The fundamentals of the smoothed particle hydrodynamics (SPH) method and its applications in astrophysics are reviewed. The discussion covers equations of motion, viscosity amd thermal conduction, spatially varying resolution, kernels, magnetic fields, special relativity, and implementation. Applications of the SPH method are discussed with reference to gas dynamics, binary stars and stellar collisions, formation of the moon and impact problems,

J. J. Monaghan



Hydrodynamic Ram Simulator.  

National Technical Information Service (NTIS)

The objective of this work was to develop a low-cost method of evaluating hydrodynamic ram and blast effects on aircraft materials that is effective for both joint and flat plate testing and able to assess failure properties of both types of structures. T...

A. Moussa G. Zhang R. Hinrichsen S. Stratton



Hydrodynamic and sediment transport modeling with emphasis on shallow-water, vegetated areas (lakes, reservoirs, estuaries and lagoons)  

Microsoft Academic Search

Modeling capabilities for shallow, vegetated, systems are reviewed to assess hydrodynamic, wind and wave, submersed plant friction, and sediment transport aspects. Typically, ecosystems with submersed aquatic vegetation are relatively shallow, physically stable and of moderate hydrodynamic energy. Wind-waves are often important to sediment resuspension. These are open systems that receive flows of material and energy to various degrees around their

Allen M. Teeter; Billy H. Johnson; Charlie Berger; Guus Stelling; Norman W. Scheffner; Marcelo H. Garcia; T. M. Parchure



The Radiation Transport Conundrum in Radiation Hydrodynamics  

SciTech Connect

The summary of this paper is: (1) The conundrum in the title is whether to treat radiation in the lab frame or the comoving frame in a radiation-hydrodynamic problem; (2) Several of the difficulties are associated with combining a somewhat relativistic treatment of radiation with a non-relativistic treatment of hydrodynamics; (3) The principal problem is a tradeoff between easily obtaining the correct diffusion limit and describing free-streaming radiation with the correct wave speed; (4) The computational problems of the comoving-frame formulation in more than one dimension, and the difficulty of obtaining both exact conservation and full u/c accuracy argue against this method; (5) As the interest in multi-D increases, as well as the power of computers, the lab-frame method is becoming more attractive; and (6) The Monte Carlo method combines the advantages of both lab-frame and comoving-frame approaches, its only disadvantage being cost.

Castor, J I



Temporal and spatial dependence of hydrodynamic correlations: Simulation and experiment  

SciTech Connect

Time-dependent hydrodynamic interactions in a colloidal suspension of hard spheres are studied, both experimentally and through computer simulation. The focus is on the behavior at small wave vectors, which directly probes the temporal evolution of hydrodynamic interactions between nearby particles. The computer simulations show that the time-dependent diffusion coefficient has the same functional form for all wave vectors, with a single characteristic scaling time for each length scale and for each volume fraction. Wave-vector-averaged effective diffusion coefficients, measured experimentally using diffusing wave spectroscopy, also scale to the same functional form. In this case, the scaling time is dependent on both volume fraction and particle size; it decreases sharply with decreasing particle radius, reflecting the greater contribution from smaller wave vectors that is contained in the scattering from the smaller particles. For a direct comparison of simulation and experiment, we simulate the experimentally observed correlation functions, by averaging the wave-vector-dependent computer-simulation data with the weighting appropriate to the experimental technique. Although the overall scaling is similar, there are quantitative differences in the simulated and measured relaxation times. We suggest these differences are due to the compressibility of the suspension, and that the resultant pressure waves make an unexpectedly significant contribution to the hydrodynamic interactions. (c) 1995 The American Physical Society

Ladd, A.J.C. [Department of Theoretical and Applied Mechanics, Cornell University, Ithaca, New York 14853 (United States); Gang, H. [Exxon Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801 (United States); Zhu, J.X. [Department of Chemical Engineering, Princeton University, Princeton, New Jersey 07954 (United States); Weitz, D.A. [Exxon Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801 (United States)



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...


Hydrodynamically coupled rigid bodies  

NASA Astrophysics Data System (ADS)

This paper considers a finite number of rigid bodies moving in potential flow. The dynamics of the solid--fluid system is described in terms of the solid variables only using Kirchhoff potentials. The equations of motion are first derived for the problem of two submerged bodies where one is forced into periodic oscillations. The hydrodynamic coupling causes the free body to drift away from or towards the oscillating body. The method of multiple scales is used to separate the slow drift from the fast response. Interestingly, the free body, when attracted towards the forced one, starts to drift away after it reaches certain separation distance. This suggests that the hydrodynamic coupling helps in preventing collisions. The fluid's role in collision avoidance and motion coordination is examined further through examples. In particular, we show that a free body can coordinate its motion with that of its neighbours, which may be relevant to understanding the coordinated motion in fish schooling.

Nair, Sujit; Kanso, Eva


Characterization of a Water-based Surfactant Stabilized Ferrofluid by Different Scattering Techniques  

NASA Astrophysics Data System (ADS)

Different scattering techniques dynamic light scattering (DLS), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) have been used to characterize a water-based surfactant stabilized ferrofluid having ferrite (Fe3O4) particles coated with oleic acid. DLS gives the overall size of the particle along with the thickness of the surfactant (oleic acid) coating and water of hydration attached to the particle. SAXS only measures the size of the ferrite particle due to poor contrast of surfactant coating for X-rays. SANS with the possibility to vary the contrast provides both the size of the ferrite particle and the thickness of the surfactant coating on the particle.

Aswal, V. K.; Chodankar, S. N.; Sastry, P. U.; Hassan, P. A.; Upadhyay, R. V.



Drug delivery observation of hydrophobe ferrofluid and magnetite nanoparticals by SPring-8 synchrotron radiation.  


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



Volume fraction dependent magnetic behaviour of ferrofluids for rotating seal applications  

NASA Astrophysics Data System (ADS)

Ferrofluid samples consisting of magnetite nanoparticles (NPs) coated with oleic acid and dispersed in a non-polar organic solvent have been synthesized by chemical routes. Different volume fractions, ?, of magnetic NPs were considered. The overall structural characterization of NPs has been performed by x-ray diffractometry, with lattice parameters and average coherence lengths evaluated via Rietveld refinements. The magnetic properties of different samples have been analysed by SQUID magnetometry and temperature-dependent Mössbauer spectroscopy and finally explained by adequate magnetic relaxation mechanisms. Zero field cooling-field cooling protocols provided useful information about specific volume fraction dependent magnetic relaxation and de-freezing processes, the lack of the Verwey transition and stronger dipolar interactions at higher volume fractions. Anisotropy energies as obtained by both temperature dependent Mössbauer spectroscopy and magnetometry data are compared and a new procedure for a quantitative characterization of the dipolar interactions is proposed.

Schinteie, G.; Palade, P.; Vekas, L.; Iacob, N.; Bartha, C.; Kuncser, V.



Disorders of CSF hydrodynamics  

Microsoft Academic Search

This article reviews the range of hydrodynamic disorders affecting the CSF circulation. Initially consideration is given to\\u000a questions of definition and classification. A scheme for the practical, clinical analysis for the diagnosis of such disorders\\u000a is then presented. The physiology and pathophysiology of the CSF circulation is reviewed, with particular emphasis on issues\\u000a that remain unresolved. This provides a background

Ian Johnston; Charles Teo



Hydrodynamic blade guide  


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)



Structural and magnetic study of zinc-doped magnetite nanoparticles and ferrofluids for hyperthermia applications  

NASA Astrophysics Data System (ADS)

Cubic-like shaped ZnxFe3-xO4 particles with crystallite mean sizes D between 15 and 117 nm were obtained by co-precipitation. Particle size effects and preferential occupation of spinel tetrahedral site by Zn2+ ions led to noticeable changes of physical properties. D ? 30 nm particles displayed nearly bulk properties, which were dominated by Zn concentration. For D ? 30 nm, dominant magnetic relaxation effects were observed by Mössbauer spectroscopy, with the mean blocking size DB ˜ 13 to 15 nm. Saturation magnetization increased with x up to x ˜ 0.1-0.3 and decreased for larger x. Power absorbed by water and chitosan-based ferrofluids from a 260 kHz radio frequency field was measured as a function of x, field amplitude H0 and ferrofluid concentration. For H0 = 41 kA m-1 the maximum specific absorption rate was 367 W g-1 for D = 16 nm and x = 0.1. Absorption results are interpreted within the framework of the linear response theory for H0 ? 41 kA m-1. A departure towards a saturation regime was observed for higher fields. Simulations based on a two-level description of nanoparticle magnetic moment relaxation qualitatively agree with these observations. The frequency factor of the susceptibility dissipative component, derived from experimental results, showed a sharp maximum at D ˜ 16 nm. This behaviour was satisfactorily described by simulations based on moment relaxation processes, which furthermore indicated a crossover from Néel to Brown mechanisms at D ˜ 18 nm. Hints for further improvement of magnetite particles as nanocalefactors for magnetic hyperthermia are discussed.

Mendoza Zélis, P.; Pasquevich, G. A.; Stewart, S. J.; Fernández van Raap, M. B.; Aphesteguy, J.; Bruvera, I. J.; Laborde, C.; Pianciola, B.; Jacobo, S.; Sánchez, F. H.



Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field  

SciTech Connect

Field-induced structure formation in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment was studied with small-angle neutron scattering (SANS) as a function of the magnetic interactions. The interactions were tuned by adjusting the size of the well-defined, single-magnetic-domain magnetite (Fe{sub 3}O{sub 4}) particles and by applying an external magnetic field. For decreasing particle dipole moments, the data show a progressive distortion of the hexagonal symmetry, resulting from the formation of magnetic sheets. The SANS data show qualitative agreement with recent cryogenic transmission electron microscopy results obtained in 2D [Klokkenburg et al., Phys. Rev. Lett. 97, 185702 (2006)] on the same ferrofluids.

Klokkenburg, M.; Erne, B. H.; Petukhov, A. V.; Philipse, A. P. [Van 't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht (Netherlands); Wiedenmann, A. [Hahn-Meitner-Institut Berlin, Department SF3, Glienickerstrasse 100, D-14109 Berlin (Germany)



Particle blocking and carrier fluid freezing effects on the magnetic properties of Fe3O4-based ferrofluids  

NASA Astrophysics Data System (ADS)

We report the systematic dc and ac susceptibility studies on the particle blocking and carrier fluid freezing effects on the magnetization and relaxation processes in two different ferrofluids composed of Fe3O4 nanoparticles (mean size of ~14 nm) suspended in hexane and dodecane, which respectively have freezing temperatures below (178 K) and above (264 K) the blocking temperature of magnetic nanoparticles (~200 K). Experimental results reveal that these effects play a key role in the formation of glasslike peaks and magnetic anomalies in ferrofluids. Quantitative fits of the frequency dependent ac susceptibility to the Vogel-Fulcher model ?=?o exp[Ea/k(T-To)] clearly indicate that the blocking of magnetic nanoparticles in the frozen state significantly affects the interparticle dipole-dipole interaction, causing characteristic spin-glass-like dynamics.

Morales, M. B.; Phan, M. H.; Pal, S.; Frey, N. A.; Srikanth, H.



Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system  

Microsoft Academic Search

Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system are investigated using numerical models. The ocean forcing including tidal and wave actions and sediment transport is simulated using Delft3D model. Fluvial processes in Delft3D are taken into account as results from SOBEK RURAL model. Analysis of the numerical simulation results allows enhancing insight the mechanisms behind the behaviours of

Nghiem Tien Lam; Marcel J. F. Stive; Zheng Bing Wang; Henk Jan Verhagen; V. T. T. Thuy



Fast Lattice Boltzmann Solver for Relativistic Hydrodynamics  

SciTech Connect

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)



Smoothed Particle Hydrodynamics  

NASA Astrophysics Data System (ADS)

Smoothed Particle Hydrodynamics (SPH) is a unique numerical method widely used for astrophysical problems since it involves no spatial grid. Rather, fluid quantities are carried by a set of Lagrangian `particles' which move with the flow, meaning that complicated dynamics and asymmetric phenomena are treated with ease. Since adaptivity is a built-in feature of the method there is no need to resort to complicated additional mesh refinement procedures. In this chapter we have undertaken a thorough review of the SPH method in order to develop a sufficiently accurate method which can be applied to MHD problems (Chapters 4-5). The review contains several results which have not been published elsewhere.

Price, Daniel



Hydrodynamics of confined membranes  

NASA Astrophysics Data System (ADS)

We calculate the hydrodynamic interaction ?(k) (Oseen interaction kernel) and relaxation frequency ?(k) for the fluctuations of a membrane that is harmonically bounded to a permeable or impermeable wall. We show that due to the confining wall there is an increase in the effective viscosity of the fluid surrounding the membrane. This has been observed in experiments on confined membranes, such as lamellar phases and the red-blood cell membrane. Our results allow a quantitative analysis of these experiments, in terms of the strength of the membrane confining potential and dislocations.

Gov, N.; Zilman, A. G.; Safran, S.



Hydrodynamic interactions between flagella  

NASA Astrophysics Data System (ADS)

Many bacteria, such as E. coli, use several rotating flagella to propel themselves at low-Reynolds numbers. If the flagella are all rotating counter-clockwise, they bundle up, and the cell moves at great speed. However, if one flagellum starts to rotate clockwise, it disentangles from the bundle, and the cell starts to rotate randomly. After a while, the rotation of all flagella becomes counter-clockwise again, and the cell starts moving again, now in a different direction. The bundling and disentangling is poorly understood from a fluid mechanics point of view. We investigate the hydrodynamic interactions between flagella that may lead to the bundling. Flagella are modeled as series of spheres connected through hinges with bending and twisting resistance. Hydrodynamic interaction between the spheres is incorporated through standard expressions. The cell body is described with a boundary-integral method. Synchronization between the flagella is shown, and we investigate the effect of stiffness, pitch and length of the flagella, and of the hook connecting the flagellum to the cell. Furthermore, we show the effect on the orientation, rotation and speed of the cell body under the influence of multiple flagella.

Janssen, Pieter; Graham, Michael



Hydrodynamic escape from planetary atmospheres  

Microsoft Academic Search

Hydrodynamic escape is an important process in the formation and evolution of planetary atmospheres. Due to the existence of a singularity point near the transonic point, it is difficult to find transonic steady state solutions by solving the time-independent hydrodynamic equations. In addition to that, most previous works assume that all energy driving the escape flow is deposited in one

Feng Tian



QGP Hydrodynamics for RHIC Energies  

Microsoft Academic Search

The relativistic hydrodynamic approach in this field became one of the best established theoretical and experimental methods [1]. The applicability of this method is vital, so we have to discuss the initial and final stages of heavy ion reactions in great detail, in addition to the middle stages of the reaction where the relativistic hydrodynamic description provides an adequate and

L. P. Csernai; C. Anderlik; A. Keranen



Hydrodynamics of stochastic cellular automata  

Microsoft Academic Search

We investigate a stochastic version of cellular automata used for simulating hydrodynamical flows, e.g. the HPP and FHP models. The extra stochasticity consists of “random exchanges” between neighboring cells which conserve momentum. We prove that, in suitable limits, these models satisfy the appropriate continuous Boltzmann and hydrodynamic equations, the same as those conjectured for the original models (except that there

A. Demasi; R. Esposito; J. L. Lebowitz; E. Presutti



Study of magnetic and structural properties of ferrofluids based on cobalt-zinc ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

Ferrofluids are colloidal systems composed of a single domain of magnetic nanoparticles with a mean diameter around 30 nm, dispersed in a liquid carrier. Magnetic Co(1-x)ZnxFe2O4 (x=0.25, 0.50, 0.75) ferrite nanoparticles were prepared via co-precipitation method from aqueous salt solutions in an alkaline medium. The composition and structure of the samples were characterized through Energy Dispersive X-ray Spectroscopy and X-ray diffraction, respectively. Transmission Electron Microscopy (TEM) studies permitted determining nanoparticle size; grain size of nanoparticle conglomerates was established via Atomic Force Microscopy. The magnetic behavior of ferrofluids was characterized by Vibrating Sample Magnetometer (VSM); and finally, a magnetic force microscope was used to visualize the magnetic domains of Co(1-x)ZnxFe2O4 nanoparticles. X-ray diffraction patterns of Co(1-x)ZnxFe2O4 show the presence of the most intense peak corresponding to the (311) crystallographic orientation of the spinel phase of CoFe2O4. Fourier Transform Infrared Spectroscopy confirmed the presence of the bonds associated to the spinel structures; particularly for ferrites. The mean size of the crystallite of nanoparticles determined from the full-width at half maximum of the strongest reflection of the (311) peak by using the Scherrer approximation diminished from (9.5±0.3) nm to (5.4±0.2) nm when the Zn concentration increases from 0.21 to 0.75. The size of the Co-Zn ferrite nanoparticles obtained by TEM is in good agreement with the crystallite size calculated from X-ray diffraction patterns, using Scherer's formula. The magnetic properties investigated with the aid of a VSM at room temperature presented super-paramagnetic behavior, determined by the shape of the hysteresis loop. In this study, we established that the coercive field of Co(1-x)ZnxFe2O4 magnetic nanoparticles, the crystal and nanoparticle sizes determined by X-ray Diffraction and TEM, respectively, decrease with the increase of the Zn at%. Finally, our magnetic nanoparticles are not very hard magnetic materials given that the hysteresis loop is small and for this reason Co(1-x)ZnxFe2O4 nanoparticles are considered as soft magnetic material.

López, J.; González-Bahamón, L. F.; Prado, J.; Caicedo, J. C.; Zambrano, G.; Gómez, M. E.; Esteve, J.; Prieto, P.



Smoothed Particle Hydrodynamics  

NASA Astrophysics Data System (ADS)

I present a review of Smoothed Particle Hydrodynamics (SPH), with the aim of providing a mathematically rigorous, clear derivation of the algorithms from first principles. The method of discretising a continuous field into particles using a smoothing kernel is considered, and also the errors associated with this approach. A fully conservative form of SPH is then derived from the Lagrangian, demonstrating the explicit conservation of mass, linear and angular momenta and energy/entropy. The method is then extended to self-consistently include spatially varying smoothing lengths, (self) gravity and various forms of artificial viscosity, required for the correct treatment of shocks. Finally two common methods of time integration are discussed, the Runge-Kutta-Fehlberg and leapfrog integrators, along with an overview of time-stepping criteria.

Cossins, Peter J.



Synchronization and hydrodynamic interactions  

NASA Astrophysics Data System (ADS)

Cilia and flagella commonly beat in a coordinated manner. Examples include the flagella that Volvox colonies use to move, the cilia that sweep foreign particles up out of the human airway, and the nodal cilia that set up the flow that determines the left-right axis in developing vertebrate embryos. In this talk we present an experimental study of how hydrodynamic interactions can lead to coordination in a simple idealized system: two nearby paddles driven with fixed torques in a highly viscous fluid. The paddles attain a synchronized state in which they rotate together with a phase difference of 90 degrees. We discuss how synchronization depends on system parameters and present numerical calculations using the method of regularized stokeslets.

Powers, Thomas; Qian, Bian; Breuer, Kenneth



Electric field distribution around the chain of composite nanoparticles in ferrofluids  

NASA Astrophysics Data System (ADS)

Composite nanoparticles (NPs) have the ability of combining materials with different properties together, thus receiving extensive attention in many fields. Here we theoretically investigate the electric field distribution around core/shell NPs (a type of composite NPs) in ferrofluids under the influence of an external magnetic field. The NPs are made of cobalt (ferromagnetic) coated with gold (metallic). Under the influence of the external magnetic field, these NPs will align along the direction of this field, thus forming a chain of NPs. According to Laplace's equations, we obtain electric fields inside and outside the NPs as a function of the incident wavelength by taking into account the mutual interaction between the polarized NPs. Our calculation results show that the electric field distribution is closely related to the resonant incident wavelength, the metallic shell thickness, and the inter-particle distance. These analytical calculations agree well with our numerical simulation results. This kind of field-induced anisotropic soft-matter systems offers the possibility of obtaining an enhanced Raman scattering substrate due to enhanced electric fields.

Fan, Chun-Zhen; Wang, Jun-Qiao; Cheng, Yong-Guang; Ding, Pei; Liang, Er-Jun; Huang, Ji-Ping



Magnetic field synthesis of Fe3O4 nanoparticles used as a precursor of ferrofluids  

NASA Astrophysics Data System (ADS)

Methods to synthesize magnetic Fe3O4 nanoparticles and to modify the nanoparticle surface are presented in this paper. In these methods, Fe3O4 nanoparticles were prepared by co-precipitation, and the aging of nanoparticles was improved by applied magnetic field. The obtained nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and vibrating sample magnetometer (VSM). Thereafter, to enhance the compatibility between nanoparticles and water, an effective surface modification method was developed by grafting acrylic acid onto the nanoparticle surface. FT-IR, XRD, transmission electron microscopy (TEM), and thermogravimetry (TG) were used to characterize the resultant sample. The testing results indicated that the polyacrylic acid chains have been covalently bonded to the surface of magnetic Fe3O4 nanoparticles. The effects of initiator dosage, monomer concentration, and reaction temperature on the characteristics of surface-modified Fe3O4 nanoparticles were investigated. Moreover, the Fe3O4-g-PAA hybrid nanoparticles were dispersed in water to form ferrofluids (FFs). The obtained FFs were characterized by UV vis spectrophotometer, Gouy magnetic balance and laser particle-size analyzer. The testing results showed that the high-concentration FF had excellent stability, with high susceptibility and high saturation magnetization. The rheological properties of the FFs were also investigated using a rotating rheometer.

Hong, R. Y.; Pan, T. T.; Han, Y. P.; Li, H. Z.; Ding, J.; Han, Sijin



Orienting rigid and flexible biological assemblies in ferrofluids for small-angle neutron scattering studies  

PubMed Central

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

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



Triple- Diffusive Convection in a Micropolar Ferrofluid in the Presence of Rotation  

NASA Astrophysics Data System (ADS)

This paper deals with the theoretical investigation of the triple-diffusive convection in a micropolar ferrofluid layer heated and soluted below subjected to a transverse uniform magnetic field in the presence of uniform vertical rotation. For a flat fluid layer contained between two free boundaries, an exact solution is obtained. A linear stability analysis theory and normal mode analysis method have been employed to study the onset convection. The influence of various parameters like rotation, solute gradients, and micropolar parameters (i.e., the coupling parameter, spin diffusion parameter and micropolar heat conduction parameter) on the onset of stationary convection has been analyzed. The critical magnetic thermal Rayleigh number for the onset of instability is also determined numerically for sufficiently large value of the buoyancy magnetization parameter M1 (ratio of the magnetic to gravitational forces). The principle of exchange of stabilities is found to hold true for the micropolar fluid heated from below in the absence of micropolar viscous effect, microinertia, solute gradient and rotation. The oscillatory modes are introduced due to the presence of the micropolar viscous effect, microinertia , solute gradient and rotation, which were non-existent in their absence. In this paper, an attempt is also made to obtain the sufficient conditions for the non-existence of overstability.

Chand, S.



Constraining relativistic viscous hydrodynamical evolution  

SciTech Connect

We show that by requiring positivity of the longitudinal pressure it is possible to constrain the initial conditions one can use in second-order viscous hydrodynamical simulations of ultrarelativistic heavy-ion collisions. We demonstrate this explicitly for (0+1)-dimensional viscous hydrodynamics and discuss how the constraint extends to higher dimensions. Additionally, we present an analytic approximation to the solution of (0+1)-dimensional second-order viscous hydrodynamical evolution equations appropriate to describe the evolution of matter in an ultrarelativistic heavy-ion collision.

Martinez, Mauricio [Helmholtz Research School and Otto Stern School, Goethe-Universitaet Frankfurt am Main Ruth-Moufang-Strasse 1, D-60438 Frankfurt am Main (Germany); Strickland, Michael [Physics Department, Gettysburg College Gettysburg, Pennsylvania 17325 (United States)



On the anomalous superfluid hydrodynamics  

NASA Astrophysics Data System (ADS)

It has been shown by Son and Surówka that the presence of anomaly in hydrodynamics with global U(1) symmetry can induce vortical and magnetic currents. The induced current is uniquely determined by anomaly from the existence of an entropy current with non-negative divergence. In this work, we extended the analysis to hydrodynamics with U(1) symmetry spontaneously broken, i.e. U(1) superfluid hydrodynamics. We found that all possible first order gradient corrections are determined up to one arbitrary function. Furthermore, the stress tensor does not receive correction from anomaly and the corrections to "Josephson" equation are fully determined by anomaly.

Lin, Shu



Estimation of Internal Wave Currents from Sar and Infrared Scatterometer Imagery.  

National Technical Information Service (NTIS)

Models for estimating internal-wave surface currents from SAR and infrared scatterometer images of the ocean surface are presented. Selected SAR images were analyzed using linear hydrodynamic interaction theory and first-order hydrodynamic interaction the...

S. J. Hughes B. A. Hughes



Hydrodynamics of micropipette aspiration.  

PubMed Central

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.

Drury, J L; Dembo, M



Astrophysical smooth particle hydrodynamics  

NASA Astrophysics Data System (ADS)

The paper presents a detailed review of the smooth particle hydrodynamics (SPH) method with particular focus on its astrophysical applications. We start by introducing the basic ideas and concepts and thereby outline all ingredients that are necessary for a practical implementation of the method in a working SPH code. Much of SPH’s success relies on its excellent conservation properties and therefore the numerical conservation of physical invariants receives much attention throughout this review. The self-consistent derivation of the SPH equations from the Lagrangian of an ideal fluid is the common theme of the remainder of the text. We derive a modern, Newtonian SPH formulation from the Lagrangian of an ideal fluid. It accounts for changes of the local resolution lengths which result in corrective, so-called “grad-h-terms”. We extend this strategy to special relativity for which we derive the corresponding grad-h equation set. The variational approach is further applied to a general-relativistic fluid evolving in a fixed, curved background space-time. Particular care is taken to explicitly derive all relevant equations in a coherent way.

Rosswog, Stephan



Hydrodynamic response of viscous fluids under seismic excitation  

SciTech Connect

Hydrodynamic response of liquid-tank systems, such as reactor vessels, spent-fuel pools and liquid storage tanks have been studied extensively in the last decade (Chang et al. 1988; Ma et al. 1991). However, most of the studies are conducted with the assumption of an inviscid fluid. In recent years, the hydrodynamic response of viscous fluids has received increasing attention in high level waste storage tanks containing viscous waste material. This paper presents a numerical study on the hydrodynamic response of viscous fluids in a large 2-D fluid-tank system under seismic excitation. Hydrodynamic responses (i.e. sloshing wave height, fluid pressures, shear stress, etc.) are calculated for a fluid with various viscosities. Four fluid viscosities are considered. They are 1 cp, 120 cp, 1,000 cp and 12,000 cp (1 cp = 1.45 {times} 10{sup {minus}7} lb-sec/in{sup 2}). Note that the liquid sodium of the Liquid-Metal Reactor (LMR) reactor has a viscosity of 1.38 {times} 10{sup {minus}5} lb-sec/in{sup 2} (about 95 cp) at an operational temperature of 900{degree}F. Section 2 describes the pertinent features of the mathematical model. In Section 3, the fundamental sloshing phenomena of viscous fluid are examined. Sloshing wave height and shear stress for fluid with different viscosities are compared. The conclusions are given in Section 4.

Ma, D.C.



Relativistic hydrodynamics on graphic cards  

NASA Astrophysics Data System (ADS)

We show how to accelerate relativistic hydrodynamics simulations using graphic cards (graphic processing units, GPUs). These improvements are of highest relevance e.g. to the field of high-energetic nucleus-nucleus collisions at RHIC and LHC where (ideal and dissipative) relativistic hydrodynamics is used to calculate the evolution of hot and dense QCD matter. The results reported here are based on the Sharp And Smooth Transport Algorithm (SHASTA), which is employed in many hydrodynamical models and hybrid simulation packages, e.g. the Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). We have redesigned the SHASTA using the OpenCL computing framework to work on accelerators like graphic processing units (GPUs) as well as on multi-core processors. With the redesign of the algorithm the hydrodynamic calculations have been accelerated by a factor 160 allowing for event-by-event calculations and better statistics in hybrid calculations.

Gerhard, Jochen; Lindenstruth, Volker; Bleicher, Marcus



Boltzmann equation and hydrodynamic fluctuations.  


We apply the method of invariant manifolds to derive equations of generalized hydrodynamics from the linearized Boltzmann equation and determine exact transport coefficients, obeying Green-Kubo formulas. Numerical calculations are performed in the special case of Maxwell molecules. We investigate, through the comparison with experimental data and former approaches, the spectrum of density fluctuations and address the regime of finite Knudsen numbers and finite frequencies hydrodynamics. PMID:20364972

Colangeli, Matteo; Kröger, Martin; Ottinger, Hans Christian



A New Relativistic Hydrodynamic Code  

Microsoft Academic Search

Relativistic temperature of gas raises the issue of equation of state (EoS) in relativistic hydrodynamics. We present a code for relativistic hydrodynamics with an EoS that is simple but approximates very closely the EoS of single- component perfect gas in the relativistic regime. Tests with a code based on the TVD scheme are presented to highlight dierences induced by dieren

Dongsu Ryu; Indranil Chattopadhyay; Eunwoo Choi


Polarized seismic and solitary waves run-up at the sea bed  

SciTech Connect

The polarization effects in hydrodynamics are studied. Hydrodynamic equation for the nonlinear wave is used along with the polarized solitary waves and seismic waves act as initial waves. The model is then solved by Fourier spectral and Runge-Kutta 4 methods, and the surface plot is drawn. The output demonstrates the inundation behaviors. Consequently, the polarized seismic waves along with the polarized solitary waves tend to generate dissimilar inundation which is more disastrous.

Dennis, L. C.C.; Zainal, A. A.; Faisal, S. Y. [Universiti Teknologi PETRONAS, 31750 Tronoh, Perak (Malaysia); Universiti Teknologi Malaysia, 81310 Johor Bahru (Malaysia)



Divergence-type nonlinear conformal hydrodynamics  

SciTech Connect

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)



Conservative regularization of ideal hydrodynamics and magnetohydrodynamics  

NASA Astrophysics Data System (ADS)

Inviscid, incompressible hydrodynamics and incompressible ideal magnetohydrodynamics (MHD) share many properties such as time-reversal invariance of equations, conservation laws, and certain topological features. In three dimensions, these systems may lead to singular solutions (involving vortex and current sheets). While dissipative (viscoresistive) effects can regularize the equations leading to bounded solutions to the initial-boundary value (Cauchy) problem which presumably exist uniquely, the time-reversal symmetry and associated conservation properties are certainly destroyed. The present work is analogous to (and suggested by) the Korteweg-de Vries regularization of the one-dimensional, nonlinear kinematic wave equation. Thus the regularizations applied to the original equations of hydrodynamics and ideal MHD retain conservation properties and the symmetries of the original equations. Integral invariants which generalize those known for the original systems are shown to imply bounded enstrophy. The regularization developed can also be applied to the corresponding dissipative models (such as the Navier-Stokes equations and the viscoresistive MHD equations) and may imply interesting regularity properties for the solutions of the latter as well. The models developed thus have intrinsic mathematical interest as well as possible applications to large-scale numerical simulations in systems where dissipative effects are extremely small or even absent.

Thyagaraja, A.



Conservative regularization of ideal hydrodynamics and magnetohydrodynamics  

SciTech Connect

Inviscid, incompressible hydrodynamics and incompressible ideal magnetohydrodynamics (MHD) share many properties such as time-reversal invariance of equations, conservation laws, and certain topological features. In three dimensions, these systems may lead to singular solutions (involving vortex and current sheets). While dissipative (viscoresistive) effects can regularize the equations leading to bounded solutions to the initial-boundary value (Cauchy) problem which presumably exist uniquely, the time-reversal symmetry and associated conservation properties are certainly destroyed. The present work is analogous to (and suggested by) the Korteweg-de Vries regularization of the one-dimensional, nonlinear kinematic wave equation. Thus the regularizations applied to the original equations of hydrodynamics and ideal MHD retain conservation properties and the symmetries of the original equations. Integral invariants which generalize those known for the original systems are shown to imply bounded enstrophy. The regularization developed can also be applied to the corresponding dissipative models (such as the Navier-Stokes equations and the viscoresistive MHD equations) and may imply interesting regularity properties for the solutions of the latter as well. The models developed thus have intrinsic mathematical interest as well as possible applications to large-scale numerical simulations in systems where dissipative effects are extremely small or even absent.

Thyagaraja, A. [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)



Diffraction–radiation of multiple floating structures in directional waves  

Microsoft Academic Search

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



Hydrodynamic escape from planetary atmospheres  

NASA Astrophysics Data System (ADS)

Hydrodynamic escape is an important process in the formation and evolution of planetary atmospheres. Due to the existence of a singularity point near the transonic point, it is difficult to find transonic steady state solutions by solving the time-independent hydrodynamic equations. In addition to that, most previous works assume that all energy driving the escape flow is deposited in one narrow layer. This assumption not only results in less accurate solutions to the hydrodynamic escape problem, but also makes it difficult to include other chemical and physical processes in the hydrodynamic escape models. In this work, a numerical model describing the transonic hydrodynamic escape from planetary atmospheres is developed. A robust solution technique is used to solve the time dependent hydrodynamic equations. The method has been validated in an isothermal atmosphere where an analytical solution is available. The hydrodynamic model is applied to 3 cases: hydrogen escape from small orbit extrasolar planets, hydrogen escape from a hydrogen rich early Earth's atmosphere, and nitrogen/methane escape from Pluto's atmosphere. Results of simulations on extrasolar planets are in good agreement with the observations of the transiting extrasolar planet HD209458b. Hydrodynamic escape of hydrogen from other hypothetical close-in extrasolar planets are simulated and the influence of hydrogen escape on the long-term evolution of these extrasolar planets are discussed. Simulations on early Earth suggest that hydrodynamic escape of hydrogen from a hydrogen rich early Earth's atmosphere is about two orders magnitude slower than the diffusion limited escape rate. A hydrogen rich early Earth's atmosphere could have been maintained by the balance between the hydrogen escape and the supply of hydrogen into the atmosphere by volcanic outgassing. Origin of life may have occurred in the organic soup ocean created by the efficient formation of prebiotic molecules in the hydrogen rich early Earth's atmosphere. Simulations show that hydrodynamic escape of nitrogen from Pluto is able to remove a ~3 km layer of ice over the age of the solar system. The escape flux of neutral nitrogen may interact with the solar wind at Pluto's orbit and may be detected by the New Horizon mission.

Tian, Feng


Hydrodynamic equation of a spinor dipolar Bose-Einstein condensate  

SciTech Connect

We introduce equations of motion for spin dynamics in a ferromagnetic Bose-Einstein condensate with magnetic dipole-dipole interaction, written using a vector expressing the superfluid velocity and a complex scalar describing the magnetization. This simple hydrodynamical description extracts the dynamics of spin wave and affords a straightforward approach by which to investigate the spin dynamics of the condensate. To demonstrate the advantages of the description, we illustrate dynamical instability and magnetic fluctuation preference, which are expressed in analytical forms.

Kudo, Kazue [Division of Advanced Sciences, Ochadai Academic Production, Ochanomizu University, 2-1-1 Ohtsuka, Bunkyo-ku, Tokyo 112-8610 (Japan); Kawaguchi, Yuki [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)



Formulating viscous hydrodynamics for large velocity gradients  

SciTech Connect

Viscous corrections to relativistic hydrodynamics, which are usually formulated for small velocity gradients, have recently been extended from Navier-Stokes formulations to a class of treatments based on Israel-Stewart equations. Israel-Stewart treatments, which treat the spatial components of the stress-energy tensor {tau}{sub ij} as dynamical objects, introduce new parameters, such as the relaxation times describing nonequilibrium behavior of the elements {tau}{sub ij}. By considering linear response theory and entropy constraints, we show how the additional parameters are related to fluctuations of {tau}{sub ij}. Furthermore, the Israel-Stewart parameters are analyzed for their ability to provide stable and physical solutions for sound waves. Finally, it is shown how these parameters, which are naturally described by correlation functions in real time, might be constrained by lattice calculations, which are based on path-integral formulations in imaginary time.

Pratt, Scott [Department of Physics and Astronomy, Michigan State University East Lansing, Michigan 48824-1321 (United States)



Preheat Measurements for Supernova Hydrodynamics Experiments  

NASA Astrophysics Data System (ADS)

The use of multi-kilojoule, ns lasers to launch shock waves has become a standard method for initiating hydrodynamic experiments in the field of Laboratory Astrophysics. However, the intense laser ablation that creates moving plasma also leads to the production of unwanted energetic x-rays and suprathermal electrons, both of which can be sources of material preheating. In principle, this preheat can alter the conditions of the experimental setup prior to the desired experiment actually taking place. At the University of Michigan, ongoing Rayleigh-Taylor instability experiments are defined by precise initial conditions, and potential deformation due to preheat could greatly affect their accuracy. An experiment devised and executed in an attempt to assess the preheat in this specific case will be presented, along with the quantitative analysis of the data obtained.

Krauland, Christine; Kuranz, Carolyn; Drake, Paul; Grosskopf, Mike; Campbell, Duncan



Polariton superfluids reveal quantum hydrodynamic solitons.  


A quantum fluid passing an obstacle behaves differently from a classical one. When the flow is slow enough, the quantum gas enters a superfluid regime, and neither whirlpools nor waves form around the obstacle. For higher flow velocities, it has been predicted that the perturbation induced by the defect gives rise to the turbulent emission of quantized vortices and to the nucleation of solitons. Using an interacting Bose gas of exciton-polaritons in a semiconductor microcavity, we report the transition from superfluidity to the hydrodynamic formation of oblique dark solitons and vortex streets in the wake of a potential barrier. The direct observation of these topological excitations provides key information on the mechanisms of superflow and shows the potential of polariton condensates for quantum turbulence studies. PMID:21636766

Amo, A; Pigeon, S; Sanvitto, D; Sala, V G; Hivet, R; Carusotto, I; Pisanello, F; Leménager, G; Houdré, R; Giacobino, E; Ciuti, C; Bramati, A



A Self-Organized Vortex Array of Hydrodynamically Entrained Sperm Cells  

NASA Astrophysics Data System (ADS)

Many patterns in biological systems depend on the exchange of chemical signals between cells. We report a spatiotemporal pattern mediated by hydrodynamic interactions. At planar surfaces, spermatozoa self-organized into dynamic vortices resembling quantized rotating waves. These vortices formed an array with local hexagonal order. Introducing an order parameter that quantifies cooperativity, we found that the array appeared only above a critical sperm density. Using a model, we estimated the hydrodynamic interaction force between spermatozoa to be ~0.03 piconewtons. Thus, large-scale coordination of cells can be regulated hydrodynamically, and chemical signals are not required.

Riedel, Ingmar H.; Kruse, Karsten; Howard, Jonathon



Granular hydrodynamics and pattern formation in vertically oscillated granular disk layers  

NASA Astrophysics Data System (ADS)

The goal of this study is to demonstrate numerically that certain hydrodynamic systems, derived from inelastic kinetic theory, give fairly good descriptions of rapid granular flows even if they are way beyond their supposed validity limits. A numerical hydrodynamic solver is presented for a vibrated granular bed in two dimensions. It is based on a highly accurate shock capturing state-of-the-art numerical scheme applied to a compressible Navier-Stokes system for granular flow. The hydrodynamic simulation of granular flows is challenging, particularly in systems where dilute and dense regions occur at the same time and interact with each other. As a benchmark experiment, we investigate the formation of Faraday waves in a two-dimensional thin layer exposed to vertical vibration in the presence of gravity. The results of the hydrodynamic simulations are compared with those of event-driven molecular dynamics and the overall quantitative agreement is good at the level of the formation and structure of periodic patterns. The accurate numerical scheme for the hydrodynamic description improves the reproduction of the primary onset of patterns compared to previous literature. To our knowledge, these are the first hydrodynamic results for Faraday waves in two-dimensional granular beds that accurately predict the wavelengths of the two-dimensional standing waves as a function of the perturbation's amplitude. Movies are available with the online version of the paper.

Carrillo, Jos? A.; P?Schel, Thorsten; Salue?A, Clara


Nonlinear response of membranes to ocean waves using boundary and finite elements  

Microsoft Academic Search

The behavior of a highly deformable membrane to ocean waves was studied by coupling a nonlinear boundary element model of the fluid domain to a nonlinear finite element model of the membrane. The hydrodynamic loadings induced by water waves are computed assuming large body hydrodynamics and ideal fluid flow and then solving the transient diffraction\\/radiation problem. Either linear waves or

L. L. Broderick; J. W. Leonard



Dispersive shock waves with nonlocal nonlinearity  

Microsoft Academic Search

We consider dispersive optical shock waves in nonlocal nonlinear media. Experiments are performed using spatial beams in a thermal liquid cell, and results agree with a hydrodynamic theory of propagation.

Christopher Barsi; Wenjie Wan; Can Sun; Jason W. Fleischer



Microscopic theory of relaxation processes in systems of particles interacting with the hydrodynamic medium  

SciTech Connect

Our work considers spatially nonuniform states of particles, weakly interacting with a hydrodynamic medium. We developed a microscopic theory, describing such systems involving Bogolubov's reduced description method. It was shown that such systems have both kinetic and hydrodynamic stages of evolution. At the kinetic stage of evolution the one-particle distribution function is a reduced description parameter for particles, and, therefore, a medium is described by five hydrodynamic parameters (density, temperature, and velocity). The coupled system of equations of motion describing the system on the kinetic stage of evolution was obtained on the basis of Bogolubov's reduced description method. The transition from the kinetic to hydrodynamic stage of evolution for particles interacting with the medium was also studied within the reduced description method. It was shown that on the hydrodynamic stage the only description parameter of particles is their density, although the medium is still described by five hydrodynamic variables. Consequently, a coupled system of equations, which completely describe the evolution of the system under consideration on the hydrodynamic stage, including dissipation processes, was obtained. These equations were used to study the propagation of acoustic waves in our system. Also the influence of particles on relaxation processes was discussed. The obtained equations, for example, may be used to describe the neutrons propagating in a hydrodynamic medium without multiplication and capture.

Nikolayenko, S. O.; Slyusarenko, Yu. V. [Akhiezer Institute for Theoretical Physics, NSC KIPT, 1 Akademicheskaya str., 61108 Kharkiv (Ukraine)



Isogeometric analysis of Lagrangian hydrodynamics  

NASA Astrophysics Data System (ADS)

Isogeometric analysis of Lagrangian shock hydrodynamics is proposed. The Euler equations of compressible hydrodynamics in the weak form are discretized using Non-Uniform Rational B-Splines (NURBS) in space. The discretization has all the advantages of a higher-order method, with the additional benefits of exact symmetry preservation and better per-degree-of-freedom accuracy. An explicit, second-order accurate time integration procedure, which conserves total energy, is developed and employed to advance the equations in time. The performance of the method is examined on a set of standard 2D and 3D benchmark examples, where good quality of the computational results is attained.

Bazilevs, Y.; Akkerman, I.; Benson, D. J.; Scovazzi, G.; Shashkov, M. J.



Black brane entropy and hydrodynamics  

SciTech Connect

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)



Hydrodynamics of fractal continuum flow.  


A model of fractal continuum flow employing local fractional differential operators is suggested. The generalizations of the Green-Gauss divergence and Reynolds transport theorems for a fractal continuum are suggested. The fundamental conservation laws and hydrodynamic equations for an anisotropic fractal continuum flow are derived. Some physical implications of the long-range correlations in the fractal continuum flow are briefly discussed. It is noteworthy to point out that the fractal (quasi)metric defined in this paper implies that the flow of an isotropic fractal continuum obeying the Mandelbrot rule of thumb for intersection is governed by conventional hydrodynamic equations. PMID:22463270

Balankin, Alexander S; Elizarraraz, Benjamin Espinoza



Hydrodynamic model experiment of the collision of supernova 1987A with its circumstellar ring using high-power laser  

NASA Astrophysics Data System (ADS)

Laboratory simulation of the ejecta-ring collision of Supernova 1987A has been performed by using a high power laser syste. Pure hydrodynamic modeling was applied using the invariance of the Euler equations and the experiment was designed with 1D hydrodynamic simulations. Three laser beams of (lambda) equals 0.53 micrometers , at the intensity I equals 2 X 1014 W/cm2 irradiated a CH foil to generate a strong shock wave and subsequent dense plasma flow in a low density CHO foam including a solid sphere at its center. Shock wave propagation and ma sam flow with vortex ring-like structures were observed with gated x-ray radiography. Overall hydrodynamic behaviors are consistent with 1D and 2D hydrodynamic simulations. The collision dynamics is dominated by a complicated interplay of reflected shock, diffracted shock, transmitted shock waves, and plasma flow behind the main shock passage.

Kang, Young-Gwang; Nishimura, Hiroaki; Takabe, Hideaki; Azechi, Hiroshi; Norimatsu, Takayoshi; Nakai, Mitsuo; Nagatomo, Hideo; Sunahara, J.; Fujita, Katsumasa; Nakatsuka, Masahiro; Mima, Kunioki; Kim, H. G.; Kong, Hong-Jin



Supersymmetric version of a hydrodynamic system in Riemann invariants and its solutions  

SciTech Connect

In this paper, a supersymmetric extension of a system of hydrodynamic-type equations involving Riemann invariants is formulated in terms of a superspace and superfield formalism. The symmetry properties of both the classical and supersymmetric versions of this hydrodynamical model are analyzed through the use of group-theoretical methods applied to partial differential equations involving both bosonic and fermionic variables. More specifically, we compute the Lie superalgebras of both models and perform classifications of their respective subalgebras. A systematic use of the subalgebra structures allows us to construct several classes of invariant solutions, including traveling waves, centered waves, and solutions involving monomials, exponentials, and radicals.

Grundland, A. M. [Centre de Recherches Mathematiques, Universite de Montreal, C.P. 6128, Succ. Centre-ville, Montreal, Quebec H3C 3J7 (Canada); Universite du Quebec, Trois-Rivieres, C.P. 500, Quebec G9A 5H7 (Canada); Hariton, A. J. [Centre de Recherches Mathematiques, Universite de Montreal, C.P. 6128, Succ. Centre-ville, Montreal, Quebec H3C 3J7 (Canada)



Softened Lagrangian hydrodynamics for cosmology  

NASA Astrophysics Data System (ADS)

A new approach to cosmological hydrodynamics is discussed that is based on a moving, quasi-Lagrangian mesh. The softened Lagrangian hydrodynamics (SLH) method utilizes a high-resolution Lagrangian hydrodynamic code combined with a low-resolution Eulerian solver to deal with severe mesh distortions. Most of the volume of a simulation is treated with the Lagrangian code and only in sites where the Lagrangian approach fails, due to mesh distortions, does the Eulerian part of the code step in. This approach utilizes a high-resolution gravity solver without use of TREE or P3M methods; Poisson's equation is solved on the moving baryonic mesh using a simple relaxation technique. The dark matter is included by means of the cloud-in-cell method on the Lagrangian mesh. All three components of the cosmological code--gravity, dark matter, and baryons--are thus treated selft-consistently with exactly the same resolution. The computer code based on the SLH approach is described in detail, and comparison with existing Eulerian and smooth particle hydrodynamics (SPH) codes is presented. For most purposes the SLH approach turns out to be the intermediate between Eulerian and SPH codes, but it outperforms both of these approaches in resolving caustics. Thus, it may turn out to be a valuable tool to study galaxy formation.

Gnedin, Nickolay Y.



Hydrodynamic instabilities in inertial fusion  

SciTech Connect

This report discusses topics on hydrodynamics instabilities in inertial confinement: linear analysis of Rayleigh-Taylor instability; ablation-surface instability; bubble rise in late-stage Rayleigh-Taylor instability; and saturation and multimode interactions in intermediate-stage Rayleigh-Taylor instability.

Hoffman, N.M.



The Gulf of Lions' hydrodynamics  

Microsoft Academic Search

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



Smoothed Particle Hydrodynamics Stability Analysis  

Microsoft Academic Search

SPH (smoothed particle hydrodynamics) is a gridless Lagrangian technique which is appealing as a possible alternative to numerical techniques currently used to analyze large deformation events. Recent tests of the standard SPH method using the cubic B-spline kernel indicated the possibility of an instability in the tensile regime, even though no such difficulties were observed in compression. A von Neumann

J. W. Swegle; D. L. Hicks; S. W. Attaway



Hydrodynamic Aspects of AUV Design  

Microsoft Academic Search

The design of a concrete AUV for oceanographic research in the Mediterranean revealed the lack of general design guidelines for AUVs. During a cooperation phase between AUV designers and naval architectural hydrodynamicists some design guidelines for AUVs were compiled. This compilation exemplifies the design approach, combining empirical estimates where available with advanced hydrodynamic simulations. Some general guidelines for hull shape

Volker Bertram


Anisotropic hydrodynamics for rapidly expanding systems  

NASA Astrophysics Data System (ADS)

We exactly solve the relaxation-time approximation Boltzmann equation for a system which is transversely homogeneous and undergoing boost-invariant longitudinal expansion. We compare the resulting exact numerical solution with approximate solutions available in the anisotropic hydrodynamics and second order viscous hydrodynamics frameworks. In all cases studied, we find that the anisotropic hydrodynamics framework is a better approximation to the exact solution than traditional viscous hydrodynamical approaches.

Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael




Microsoft Academic Search

ABS>A new type of hydrodynamic-wave heating is proposed for the solar ; corona. It is shown that internal gravity waves are preferentially generated by ; the convection zone and are easily transmitted to the corona. Acoustic waves ; with frequency characteristic of the photospheric granules cannot be transmitted ; through the reversing layer. The gravity waves are shown to dissipate

William A. Whitaker



The quantum hydrodynamic model for semiconductor devices  

Microsoft Academic Search

The classical hydrodynamic equations can be extended to include quantum effects by incorporating the first quantum corrections. The full three-dimensional quantum hydrodynamic (QHD) model is derived for the first time by a moment expansion of the Wigner-Boltzmann equations. The QHD conservation laws have the same form as the classical hydrodynamic equations, but the energy density and stress tensor have additional

Carl L. Gardner



Lectures on hydrodynamic fluctuations in relativistic theories  

NASA Astrophysics Data System (ADS)

These are pedagogical lecture notes on hydrodynamic fluctuations in normal relativistic fluids. The lectures discuss correlation functions of conserved densities in thermal equilibrium, interactions of the hydrodynamic modes, an effective action for viscous fluids and the breakdown of the derivative expansion in hydrodynamics.

Kovtun, Pavel



Hydrodynamic damping in trapped Bose gases  

Microsoft Academic Search

Griffin, Wu and Stringari have derived the hydrodynamic equations of a trapped dilute Bose gas above the Bose-Einstein transition temperature. We give the extension which includes hydrodynamic damping, following the classic work of Uehling and Uhlenbeck based on the Chapman-Enskog procedure. Our final result is a closed equation for the velocity fluctuations $\\\\delta v$ which includes the hydrodynamic damping due

T. Nikuni; A. Griffin



Hydrodynamic Damping in Trapped Bose Gases  

Microsoft Academic Search

Griffin, Wu and Stringari have derived the hydrodynamic equations of a trapped dilute Bose gas above the Bose-Einstein transition temperature. We give the extension which includes hydrodynamic damping, following the classic work of Uehling and Uhlenbeck based on the Chapman-Enskog procedure. Our final result is a closed equation for the velocity fluctuations dvwhich includes the hydrodynamic damping due to the

T. Nikuni; A. Griffin



Influence of homogeneous magnetic fields on the flow of a ferrofluid in the Taylor-Couette system.  


We investigate numerically the influence of a homogeneous magnetic field on a ferrofluid in the gap between two concentric, independently rotating cylinders. The full Navier-Stokes equations are solved with a combination of a finite difference method and a Galerkin method. Structure, dynamics, symmetry properties, bifurcation, and stability behavior of different vortex structures are investigated for axial and transversal magnetic fields, as well as combinations of them. We show that a transversal magnetic field modulates the Taylor vortex flow and the spiral vortex flow. Thus, a transversal magnetic field induces wavy structures: wavy Taylor vortex flow (wTVF) and wavy spiral vortex flow. In contrast to the classic wTVF, which is a secondarily bifurcating structure, these magnetically generated wavy Taylor vortices are pinned by the magnetic field, i.e., they are stationary and they appear via a primary forward bifurcation out of the basic state of circular Couette flow. PMID:20866739

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



Magnetic separation of particles and cells in ferrofluid flow through a straight microchannel using two offset magnets  

NASA Astrophysics Data System (ADS)

The separation of particles and cells is critical in many chemical and biological applications. This work presents a simple idea for utilizing a pair of permanent magnets to continuously separate diamagnetic particles and cells in ferrofluid flow through a straight microchannel. The first magnet is placed close to the microchannel for focusing the particle mixture to a single stream without the use of a sheath flow. The second magnet, which is offset from the first magnet and placed farther from the channel, is to displace the aligned particles to dissimilar flow paths for a continuous sorting. This idea is first demonstrated through the separation of 3 ?m- and 10 ?m-diameter polystyrene particles, where the effects of flow speed and magnet distance are both examined. The experimental data are found to fit well with the predictions of an analytical model. Furthermore, a continuous separation of live yeast cells from 10 ?m polystyrene particles is implemented in the same device.

Zeng, Jian; Deng, Yanxiang; Vedantam, Pallavi; Tzeng, Tzuen-Rong; Xuan, Xiangchun



Axially symmetric pseudo-Newtonian hydrodynamics code  

NASA Astrophysics Data System (ADS)

We develop a numerical hydrodynamics code using a pseudo-Newtonian formulation that uses the weak-field approximation for the geometry, and a generalized source term for the Poisson equation that takes into account relativistic effects. The code was designed to treat moderately relativistic systems such as rapidly rotating neutron stars. The hydrodynamic equations are solved using a finite volume method with high-resolution shock-capturing techniques. We implement several different slope limiters for second-order reconstruction schemes and also investigate higher order reconstructions such as the piecewise parabolic method, essentially non-oscillatory method (ENO) and weighted ENO. We use the method of lines to convert the mixed spatial-time partial differential equations into ordinary differential equations (ODEs) that depend only on time. These ODEs are solved using second- and third-order Runge-Kutta methods. The Poisson equation for the gravitational potential is solved with a multigrid method, and to simplify the boundary condition, we use compactified coordinates which map spatial infinity to a finite computational coordinate using a tangent function. In order to confirm the validity of our code, we carry out four different tests including one- and two-dimensional shock tube tests, stationary star tests of both non-rotating and rotating models, and radial oscillation mode tests for spherical stars. In the shock tube tests, the code shows good agreement with analytic solutions which include shocks, rarefaction waves and contact discontinuities. The code is found to be stable and accurate: for example, when solving a stationary stellar model the fractional changes in the maximum density, total mass, and total angular momentum per dynamical time are found to be 3 × 10-6, 5 × 10-7 and 2 × 10-6, respectively. We also find that the frequencies of the radial modes obtained by the numerical simulation of the steady-state star agree very well with those obtained by linear analysis.

Kim, Jinho; Kim, Hee Il; Choptuik, Matthew William; Lee, Hyung Mok



Theory of macroscopic fluctuations in systems of particles, interacting with hydrodynamic and gaslike media  

SciTech Connect

Our work offers a stochastic approach for description of long wave fluctuations in systems of particles interacting with hydrodynamic media. The approach is based on the averaging of nonlinear dynamic equations over random initial conditions for these equations. Random character of the initial conditions for motion equations causes the development of long wave fluctuations of description parameters in the system. Within the framework of our approach we derived evolution equations of long wale fluctuations in the system for both fluctuation-kinetic and fluctuation-hydrodynamic stages of evolution. We also found the class of description parameter transformations which does not change the dynamic equation structure. Dynamics of pair correlations has been studied. The 'long hydrodynamic tails' theory for system of particles interacting with the hydrodynamic medium has been built. The system considered can be a model of neutron transport in hydrodynamic media without their multiplication and capture. The possibility of usage of our results for experimental evidence of long hydrodynamic tails in neutron scattering experiments is discussed.

Nikolayenko, S. O.; Slyusarenko, Yu. V. [Akhiezer Institute for Theoretical Physics, NSC KIPT, 1, Akademicheskaya str., 61108 Kharkiv (Ukraine)



Hydrodynamic synchronization of nonlinear oscillators at low Reynolds number  

NASA Astrophysics Data System (ADS)

We introduce a generic model of a weakly nonlinear self-sustained oscillator as a simplified tool to study synchronization in a fluid at low Reynolds number. By averaging over the fast degrees of freedom, we examine the effect of hydrodynamic interactions on the slow dynamics of two oscillators and show that they can lead to synchronization. Furthermore, we find that synchronization is strongly enhanced when the oscillators are nonisochronous, which on the limit cycle means the oscillations have an amplitude-dependent frequency. Nonisochronity is determined by a nonlinear coupling ? being nonzero. We find that its (?) sign determines if they synchronize in phase or antiphase. We then study an infinite array of oscillators in the long-wavelength limit, in the presence of noise. For ?>0, hydrodynamic interactions can lead to a homogeneous synchronized state. Numerical simulations for a finite number of oscillators confirm this and, when ?<0, show the propagation of waves, reminiscent of metachronal coordination.

Leoni, M.; Liverpool, T. B.



Hydrodynamic Fluctuations in Confined Particle-Laden Fluids  

NASA Astrophysics Data System (ADS)

We address the collective dynamics of non-Brownian particles cruising in a confined microfluidic geometry and 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 kinetic theory which quantitatively accounts for our experimental findings, demonstrating that the fluctuation spectrum of this nonequilibrium system is shaped by the combination of truly long-range hydrodynamic interactions and local collisions. We also demonstrate that the free propagation of density waves is a generic phenomenon which should be observed in a much broader range of hydrodynamic systems.

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



Anomalous hydrodynamics of fractional quantum Hall states  

NASA Astrophysics Data System (ADS)

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.



Hydrodynamics of cold atomic gases in the limit of weak nonlinearity, dispersion, and dissipation  

NASA Astrophysics Data System (ADS)

Dynamics of interacting cold atomic gases have recently become a focus of both experimental and theoretical studies. Often cold-atom systems show hydrodynamic behavior and support the propagation of nonlinear dispersive waves. Although this propagation depends on many details of the system, great insight can be obtained in the rather universal limit of weak nonlinearity, dispersion, and dissipation. In this limit, using a reductive perturbation method we map some of the hydrodynamic models relevant to cold atoms to well-known chiral one-dimensional equations such as the Korteweg-de Vries (KdV), Burgers, KdV-Burgers, and Benjamin-Ono equations. These equations have been thoroughly studied in the literature. The mapping gives us a simple way to make estimates for the original hydrodynamic equations and to study the interplay between nonlinearity, dissipation, and dispersion which are the hallmarks of nonlinear hydrodynamics.

Kulkarni, Manas; Abanov, Alexander G.



Extent of validity of the hydrodynamic description of ions in dense plasmas  

SciTech Connect

We show that the hydrodynamic description can be applied to modeling the ionic response in dense plasmas for a wide range of length scales that are experimentally accessible. Using numerical simulations for the Yukawa model, we find that the maximum wave number k{sub max} at which the hydrodynamic description applies is independent of the coupling strength, given by k{sub max}{lambda}s{approx_equal}0.43, where {lambda}{sub s} is the ionic screening length. Our results show that the hydrodynamic description can be used for interpreting x-ray scattering data from fourth generation light sources and high power lasers. In addition, our investigation sheds new light on how the domain of validity of the hydrodynamic description depends on both the microscopic properties and the thermodynamic state of fluids in general.

Mithen, James P.; Gregori, Gianluca [Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Daligault, Jerome [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)



Dispersion of linear waves in quantum plasmas  

SciTech Connect

The dispersion of linear waves in a uniform cold quantum plasma is derived using the quantum hydrodynamic equations with the magnetic field of the Wigner-Poisson system. The dispersion of the Langmuir wave becomes whistler-like due to quantum effects and, therefore, the Langmuir wave can propagate in a cold plasma. It is also found that quantum effects do not affect the dispersion of the left-handed, right-handed, and ordinary waves00.

Ren Haijun; Wu Zhengwei; Chu, Paul K. [CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefts 230026 (China); CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefts 230026 (China) and Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)



Hydrodynamic simulations with the Godunov smoothed particle hydrodynamics  

NASA Astrophysics Data System (ADS)

We present results based on an implementation of the Godunov smoothed particle hydrodynamics (GSPH), originally developed by Inutsuka, in the GADGET-3 hydrodynamic code. We first review the derivation of the GSPH discretization of the equations of moment and energy conservation, starting from the convolution of these equations with the interpolating kernel. The two most important aspects of the numerical implementation of these equations are (a) the appearance of fluid velocity and pressure obtained from the solution of the Riemann problem between each pair of particles, and (b) the absence of an artificial viscosity term. We carry out three different controlled hydrodynamical three-dimensional tests, namely the Sod shock tube, the development of Kelvin-Helmholtz instabilities in a shear-flow test and the 'blob' test describing the evolution of a cold cloud moving against a hot wind. The results of our tests confirm and extend in a number of aspects those recently obtained by Cha, Inutsuka & Nayakshin: (i) GSPH provides a much improved description of contact discontinuities, with respect to smoothed particle hydrodynamics (SPH), thus avoiding the appearance of spurious pressure forces; (ii) GSPH is able to follow the development of gas-dynamical instabilities, such as the Kevin-Helmholtz and the Rayleigh-Taylor ones; (iii) as a result, GSPH describes the development of curl structures in the shear-flow test and the dissolution of the cold cloud in the 'blob' test. Besides comparing the results of GSPH with those from standard SPH implementations, we also discuss in detail the effect on the performances of GSPH of changing different aspects of its implementation: choice of the number of neighbours, accuracy of the interpolation procedure to locate the interface between two fluid elements (particles) for the solution of the Riemann problem, order of the reconstruction for the assignment of variables at the interface, choice of the limiter to prevent oscillations of interpolated quantities in the solution of the Riemann Problem. The results of our tests demonstrate that GSPH is in fact a highly promising hydrodynamic scheme, also to be coupled to an N-body solver, for astrophysical and cosmological applications.

Murante, G.; Borgani, S.; Brunino, R.; Cha, S.-H.



Generic Conditions for Hydrodynamic Synchronization  

NASA Astrophysics Data System (ADS)

Synchronization of actively oscillating organelles such as cilia and flagella facilitates self-propulsion of cells and pumping fluid in low Reynolds number environments. To understand the key mechanism behind synchronization induced by hydrodynamic interaction, we study a model of rigid-body rotors making fixed trajectories of arbitrary shape under driving forces that are arbitrary functions of the phase. For a wide class of geometries, we obtain the necessary and sufficient conditions for synchronization of a pair of rotors. We also find a novel synchronized pattern with an oscillating phase shift. Our results shed light on the role of hydrodynamic interactions in biological systems, and could help in developing efficient mixing and transport strategies in microfluidic devices.

Uchida, Nariya; Golestanian, Ramin



Hydrodynamics of cold holographic matter  

NASA Astrophysics Data System (ADS)

We show that at any temperature, the low-energy (with respect to the chemical potential) collective excitations of the transverse components of the energy-momentum tensor and the global U(1) current in the field theory dual to the planar RN-AdS4 black hole are simply those of hydrodynamics. That is, hydrodynamics is applicable even at energy scales much greater than the temperature. It is applicable even at zero temperature. Specifically, we find that there is always a diffusion mode with diffusion constant proportional to the ratio of entropy density to energy density. At low temperatures, the leading order momentum and temperature dependences of the dispersion relation of this mode are controlled by the dimension of an operator in the thermal CFT1 dual to the near-horizon Schwarzschild-AdS2 geometry.

Davison, Richard A.; Parnachev, Andrei



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



Membrane Paradigm and Holographic Hydrodynamics  

NASA Astrophysics Data System (ADS)

We discuss recent work showing that in certain cases the membrane paradigm equations governing the dynamics of black hole horizons can be recast as relativistic conservation law equations. In the context of gauge/gravity dualities, these equations are interpreted as defining the viscous hydrodynamics of a holographically dual relativistic field theory. Using this approach, one can derive the viscous transport coefficients and the form of the entropy current for field theories dual to gravity plus matter fields.

Eling, Christopher; Neiman, Yasha; Oz, Yaron



Concepts of Shock Waves  

NASA Astrophysics Data System (ADS)

Shock Waves Definition and Formation Properties of Sonic Waves Formation of a Shock Wave Rankine-Hugoniot Equations (Conservation Laws) Conservation of Mass, Momentum and Energy in the Laboratory Frame The Same in the Shock Front Frame The Same in Special Relativity Hugoniot Curve and Its Representation in the (P, up) Plane Comments on Conservation Laws and Relative Position of Hugoniot and - Isentropic Curves in the (P, V) Plane Comments on Conservation Laws Position of Hugoniot Curve (H) Relatively to Isentropic Curves - in the (P,V) Plane Experimental Results Some Experimental Results on Simple Metals Relation Between Us (Shock Wave Velocity) and up (Particular - Velocity) Some Results on Geogical Materials Numerical Compendiums Hydrodynamic Attenuation Hydrodynamic Decay of Pressure Pulses Shock Transmissions Between Two Media Reflected Shock Waves Reflected Release Waves Equilibrium State at the Interface Approximation on Curves H'1 and S_{1^-} Planar Impact of Projectile on Semi-infinite and Massice Target at - Rest Chronology of Events Theory Numerical Examples Equation of State and Temperature Evaluation Mie-Gruneisen Equation of State Temperature Behind a Shock Front. Low Pressure Temperature Behind a Shock Front. High Pressure Numerical Applications Release from the Shocked State Residual Temperature Isentropic Curve from the Initial State Comments Reference

Miigault, A.



Microsoft Academic Search

Bridge structures along the coasts are often subjected to hydrodynamics loads of various forms and intensities. The most dramatic loads are those due to tsunamis and storm surges as vividly demonstrated by images of the Dec. 2004 Indian Ocean Tsunami and the Sept. 2005 Katrina Hurricane in the Gulf of Mexico. Other loads include wave impact, current induced scour, and

Solomon C. Yim


The Effect of Viscosity on Hydrodynamic Stability of a Plane Flame Front  

Microsoft Academic Search

This paper presents a linear analysis of the hydrodynamic stablity of the plane flame front of a premixed laminar flame. The technique of outer and inner asymptotic expansions is used to calculate the next approximation to the classical long-wave Landau limit. The resulting correction turns out to be independent of the Prandtl number. This implies that, although diffusivity, conductivity and




Hydrodynamic Simulation of Ultrashort Pulse High-Intensity Laser-Plasma Interaction  

Microsoft Academic Search

Interaction of ultrashort laser pulses with dense plasmas is important to ultrafast x-ray sources, ICF, atomic physics and astrophysics. We studied numerically the interaction of various pulses with solid targets by a 1D hydrodynamic code including wave solver, nonlinear absorption, nonlocal heat transport and modified heat conductivity. The simulated ionization and emission from high density plasma is strongly dependent on

G. Ma; M. Nantel; S. Gu; D. Umstadter



Hydrodynamic approximation with self-diffusion for collision-free beams  

SciTech Connect

A transition from the generalized kinetic equation for kinetic, hydrodynamic and diffusion processes in charged particle beams to equations of gas dynamics has been accomplished. A nonlinear Schr{umlt o}dinger-like equation has been derived and the stability of its stationary wave solution has been analysed. {copyright} {ital 1997 American Institute of Physics.}

Tzenov, S.I. [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Mostra dOltremare PAD. 20, I-80125 Napoli (Italy)]|[Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, boul. Tzarigradsko shausse 72, 1784 Sofia (Bulgaria)



A comparison of hydrodynamic impacts prediction methods with two dimensional drop test data  

Microsoft Academic Search

The effect of hydrodynamic impacts on a ship's bow structure is an important design consideration. In addition, to possible failure to local structure, such impacts can generate slam-induced whipping loads, the magnitude of which when combined with ordinary wave induced loads, could lead to first passage failure of a ship's hull girder. This paper presents the results of a recent

Allen Engle; Richard Lewis



Hydrodynamic forces on a marine riser: a velocity-potential method  

SciTech Connect

A linear equation is mathematically derived for hydrodynamic forces on a marine riser under effects of free surface and floating-vessel motion using a velocity-potential method. It accounts for inertia and wave damping forces, including the force caused by riser motion, and empirically includes the drag force caused by viscosity. 8 refs.

Chung, J.S.



Three-dimensional nonlinear hydrodynamic pressures by earthquakes on dam faces with arbitrary reservoir shapes  

Microsoft Academic Search

A complete three-dimensional finite difference scheme has been developed to analyze the earthquake-induced nonlinear hydrodynamic pressures on inclined dam faces with arbitrary reservoir shapes. Both the free surface waves and the nonlinear convective acceleration were included in the analysis. Numerical experiments have been made to determine the desirable mesh arrangements and time increments. The computational accuracy were assured by checking

Bang-Fuh Chen; Yin-Shen Yuan; Jaw-Fan Lee



Interaction between hydrodynamics and salt marsh dynamics: An example from Jiangsu coast  

Microsoft Academic Search

Salt marshes are distributed along more than 400 km of the Jiangsu coast in Eastern China, which are regarded as important habitats and serve as coastal protection as well. Previous research has proven that salt-marsh vegetation can reduce current velocity and dampen waves by its stems and leaves. Reversely, hydrodynamic forces also have a significant influence on the growth of

Z. Hu; M. J. F. Stive; T. J. Zitman; Q. H. Ye; Z. B. Wang; A. Luijendijk; Z. Gong; T. Suzuki



Shock waves in disordered media.  


We experimentally investigate the interplay between spatial shock waves and the degree of disorder during nonlinear optical propagation in a thermal defocusing medium. We characterize the way the shock point is affected by the amount of disorder and scales with wave amplitude. Evidence for the existence of a phase diagram in terms of nonlinearity and amount of randomness is reported. The results are in quantitative agreement with a theoretical approach based on the hydrodynamic approximation. PMID:23368319

Ghofraniha, N; Gentilini, S; Folli, V; Delre, E; Conti, C



Flow estimation for the Persian Gulf using a Kelvin wave expansion  

Microsoft Academic Search

Hydrodynamic simulations of tidal currents in the Persian Gulf are presented. Water surface level and velocity have been determined by a Kelvin wave expansion as a new hydrodynamic calibration tool for estimating the dynamical field and flow patterns. In the procedure, leading to the Kelvin wave expansion, data of tidal constituents from co-tidal charts play a role. Results of the

M. A. Badri; P. Wilders; A. R. Azimian



A hydrodynamic sensory antenna used by killifish for nocturnal hunting.  


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



Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications  

SciTech Connect

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



Freak waves. Theory and experiments  

Microsoft Academic Search

We present numerical simulation of several problem related to free surface hydro- dynamics: a) when nonlinear Shredinger approximation breaks, b) nonlinear stage of modulation instability - freak wave formation, c) stability analysis of the free surface hydrodynamics. Simulation is done using two-dimensional code, based on conformal mapping of the uid to the lower half-plane.

V. E. Zakharov; A. I. Dyachenko; A. O. Prokoev



Direct Measurement of Wave-Induced Bottom Shear Stress Under Irregular Waves  

Microsoft Academic Search

\\u000a Wave-induced bottom shear stress is one of most important parameters in modelling of wave hydrodynamics and coastal sediment\\u000a transport, but has not been accurately estimated so far. A new type of shear plate is developed to measure instantaneous wave\\u000a bottom shear stress under both regular and irregular waves. The shear plate directly measures instantaneous horizontal force\\u000a by applying the Wheatstone

Zaijin You; Baoshu Yin; Guang Huo


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



Disruptive Innovation in Numerical Hydrodynamics  

SciTech Connect

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



Problems in astrophysical radiation hydrodynamics  

SciTech Connect

The basic equations of radiation hydrodynamics are discussed in the regime that the radiation is dynamically as well as thermally important. Particular attention is paid to the question of what constitutes an acceptable approximate non-relativistic system of dynamical equations for matter and radiation in this regime. Further discussion is devoted to two classes of application of these ideas. The first class consists of problems dominated by line radiation, which is sensitive to the velocity field through the Doppler effect. The second class is of problems in which the advection of radiation by moving matter dominates radiation diffusion.

Castor, J.I.



Hydrodynamics of post CHF region  

SciTech Connect

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.



Nonsteady hydrodynamics of biopolymer motions  

NASA Astrophysics Data System (ADS)

Many biopolymers undergo conformational fluctuations in which large subunits move relative to each other under the influence of significant mechanical restoring forces. It is shown that nonsteady hydrodynamic effects may be important in the solvent response to such macromolecular motions. This result is in marked contrast to the familiar case of conformational fluctuations of random coil polymers, which move under the influence of weak entropic forces. The nonsteady solvent response is shown to affect the details of the biopolymer motion and to produce special qualitative features in the Raman light scattering spectrum of such macromolecules.

McCammon, J. A.; Wolynes, Peter G.



Modeling shallow-water hydrodynamics: Rotations, rips, and rivers  

NASA Astrophysics Data System (ADS)

Hydrodynamic models are used as a diagnostic tool to understand the temporal variability of shallow-water processes that are difficult to completely resolve with traditional field measurements. For all simulations, modeled quantities are qualitatively or quantitatively compared with available measurements to gain confidence in conclusions derived from the modeled results. In this work we consider both vorticity motions and rip currents, which arise from alongshore inhomogeneities in the wave momentum flux but occur at much different time scales (O(min) vs. O(hours-weeks)). They each have an effect on sediment transport processes and dispersion of sediments or pollutants in the surf zone, which makes understanding their structure and persistence essential. The vorticity motions of interest here are associated with spatial and temporal wave height variations caused by wave grouping and can exist with either normally or obliquely incident wave conditions. We find that these flows persist for O(1000s) but their lifespan is controlled by the sequence of wave forcing rather than bottom friction as previously hypothesized. These motions can also be observed in combination with either stable or unstable alongshore currents. Our results suggest that, at times, these alongshore propagating wave group forced vortices are misinterpreted as instabilities of the alongshore current. Alternately, the rip currents considered in this research are controlled by strong wave height gradients in the surf zone generated by the refraction of incident waves over variable offshore depth contours. Thus, this type of circulation is governed by timescales associated with changing offshore wave conditions (O(hours - days)). We consider a four- week time period when variable offshore wave spectra were observed during a large-scale field experiment. The model and data are in good agreement for all wave conditions during the month and estimated model errors are similar to those found previously for alongshore uniform beaches. Through comparisons with remote sensing observations, the model proves it is capable of predicting rip currents when they are observed. Analysis suggests that the direction of the offshore wave spectra will dictate when and where rip currents will appear. We also find that for bi-modal offshore spectra, the relative amount of energy in each spectral mode is a better predictor of rip current development than the peak spectral characteristics. Finally, some preliminary work to estimate water depths from the combination of hydrodynamic models and available data is also presented. We focus this work in a river meander for our initial tests. A simple analytical model shows skill in predicting the water depth at only one of the two river meanders considered. This discrepancy appears to be related to river curvature and as curvature weakens, the model accuracy decreases. This is hypothesized to be the result of dispersive mixing which is not accounted for in this simple model but confirmation is still required. At the same time, we perform simulations within a river meander to determine the efficacy of using coastal hydrodynamic models in riverine environments where the principles governing the flow are the same. Our initial tests of the Regional Ocean Modeling System (ROMS) suggests that it is able to reproduce the flow through a river meander which opens the door to developing one model that can simulate conditions from upland rivers out to the continental shelf.

Long, Joseph W.


The hydrodynamics of lamprey locomotion  

NASA Astrophysics Data System (ADS)

The lamprey, an anguilliform swimmer, propels itself by undulating most of its body. This type of swimming produces flow patterns that are highly three-dimensional in nature and not very well understood. However, substantial previous work has been done to understand two-dimensional unsteady propulsion, the possible wake structures and thrust performance. Limited studies of three-dimensional propulsors with simple geometries have displayed the importance of the third dimension in designing unsteady swimmers. Some of the results of those studies, primarily the ways in which vorticity is organized in the wake region, are seen in lamprey swimming as well. In the current work, the third dimension is not the only important factor, but complex geometry and body undulations also contribute to the hydrodynamics. Through dye flow visualization, particle induced velocimetry and pressure measurements, the hydrodynamics of anguilliform swimming are studied using a custom built robotic lamprey. These studies all indicate that the undulations of the body are not producing thrust. Instead, it is the tail which acts to propel the animal. This conclusion led to further investigation of the tail, specifically the role of varying tail flexibility on hydrodymnamics. It is found that by making the tail more flexible, one decreases the coherence of the vorticity in the lamprey's wake. Additional flexibility also yields less thrust.

Leftwich, Megan C.


Web-based hydrodynamics computing  

NASA Astrophysics Data System (ADS)

Proteins are long chains of amino acids that have a definite 3-d conformation and the shape of each protein is vital to its function. Since proteins are normally in solution, hydrodynamics (describes the movement of solvent around a protein as a function of shape and size of the molecule) can be used to probe the size and shape of proteins compared to those derived from X-ray crystallography. The computation chain needed for these hydrodynamics calculations consists of several separate programs by different authors on various platforms and often requires 3D visualizations of intermediate results. Due to the complexity, tools developed by a particular research group are not readily available for use by other groups, nor even by the non-experts within the same research group. To alleviate this situation, and to foment the easy and wide distribution of computational tools worldwide, we developed a web based interactive computational environment (WICE) including interactive 3D visualization that can be used with any web browser. Java based technologies were used to provide a platform neutral, user-friendly solution. Java Server Pages (JSP), Java Servlets, Java Beans, JOGL (Java bindings for OpenGL), and Java Web Start were used to create a solution that simplifies the computing chain for the user allowing the user to focus on their scientific research. WICE hides complexity from the user and provides robust and sophisticated visualization through a web browser.

Shimoide, Alan; Lin, Luping; Hong, Tracie-Lynne; Yoon, Ilmi; Aragon, Sergio R.



Hydrocodes support visualization of shock-wave phenomena  

Microsoft Academic Search

The response of objects to impact or explosive loading is greatly elucidated by the presence of shock waves in solids; wave-propagation codes are accordingly invaluable in the study of wave interactions occurring in multidimensional bodies. Computer animation renders the understanding-through visualization of these complex motions possible. The present consideration of the cases of hydrodynamic ramming and meteoroid impact on space

J. A. Zukas; S. B. Segletes; J. R. Furlong



Probabilistic analysis for wave?induced submarine landslides  

Microsoft Academic Search

When waves propagate over the ocean floor, they induce a change of hydrodynamic pressure, positive under the crest and negative under the trough. These pressure changes may cause shear failure in soft sediments and lead to submarine landslides. This paper presents a general analytical procedure for evaluating the probability of wave?induced failure in offshore clay sediments. Both the wave and

M. S. Rahman; F. M. Layas



Propagation of ionizing electron shock waves in electrical breakdown  

Microsoft Academic Search

A numerical solution of a hydrodynamic second-order model shows that the propagation of the first ionizing wave arises from an overgrowth of hot electrons in the wave front in a zone of a greatly disturbed electric field. This gives rise, in the electron shock zone ahead of the wave, to a precursor phenomenon, whose effect is to accelerate the channel

P. Bayle; B. Cornebois



Wave journal bearing. Part 2: Experimental pressure measurements and fractional frequency whirl threshold for wave and plain journal bearings  

Microsoft Academic Search

A new hydrodynamic bearing concept, the wave journal bearing, is being developed because it has better stability characteristics than plain journal bearings while maintaining similar load capacity. An analysis code to predict the steady state and dynamic performance of the wave journal bearing is also part of the development. To verify numerical predictions and contrast the wave journal bearing's stability

James F. Walker; Florin Dimofte; Harold E. Addy Jr.



On the low-frequency hydrodynamic damping forces acting on offshore moored vessels  

SciTech Connect

Moored floating structures for drilling, production-storage-offloading or other purposes are being installed in ever increasing water depths and in areas where the environmental conditions are also more severe. Such structures, moored permanently in high seas, have to survive safely the most severe weather conditions. Therefore it is of importance to understand the mechanisms which govern the motions and the mooring forces of these facilities. In deep water the mooring systems inevitably have soft elasticity characteristics. With the increase in the elasticity of the mooring, the low frequency horizontal motions induced by low frequency second order wave drift forces also become larger. The low frequency resonant motion components completely dominate the horizontal motions and, consequently, also the mooring forces. In order to predict the amplitudes of the low frequency resonant motions the magnitude of the second order wave drift forces and the values of the low frequency hydrodynamic damping must be known. The low frequency hydrodynamic potential damping due to the radiated waves is negligibly small. In general the low frequency damping is determined by viscous effects and a damping caused by the presence of waves. The last mentioned damping is called the wave damping. Dependent on the wave spectra the wave damping can significantly dominate the viscous damping contributions. In this paper results are given of a study of the origin of the wave damping. For this purpose the second order wave drift forces acting on the moored vessel in head waves have been expanded to the low frequency surge displacement and surge velocity. The wave damping can be defined by taking into account the dependence on velocity of the second order wave drift forces. To verify the results, model experiments were carried out in which the velocity dependent second order wave drift forces were determined.

Wichers, J.E.W.; Huijsmans, R.M.H.



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

SciTech Connect

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



On the Phenomenology of Hydrodynamic Shear Turbulence  

Microsoft Academic Search

The question of a purely hydrodynamic origin of turbulence in accretion disks is reexamined, on the basis of a large body of experimental and numerical evidence on various subcritical (i.e., linearly stable) hydrodynamic flows. One of the main points of this paper is that the length scale and velocity fluctuation amplitude that are characteristic of turbulent transport in these flows

Pierre-Yves Longaretti



Hydrodynamic fluctuations near the convection instability  

Microsoft Academic Search

Hydrodynamic fluctuations of a horizontal liquid layer heated from below are considered in the vicinity of the point where convection sets in because of buoyancy. It is assumed that convection occurs in the form of nearly two-dimensional rolls. Close to the instability, the hydrodynamics (described in the Boussinesq approximation) is simplified considerably by the appearance of a slow mode which

Robert Graham



Hydrodynamical Models of Lyalpha Forest Clouds  

Microsoft Academic Search

~ }} <}}} The hydrodynamical evolution of spherical perturbations consisting of dark matter and a hydrogen\\/helium baryonic component is computed to model the evolution of Lyalpha forest systems. If the IGM is photoionized for z≲6, the baryons in perturbations with circular velocities less than the sound speed will expand into the IGM driven by their thermal pressure. The hydrodynamical motion

A. Meiksin



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



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…

Ollitrault, Jean-Yves



Hydrodynamic description for ballistic annihilation systems  

SciTech Connect

The problem of the validity of a hydrodynamic description for a system in which there are no collisional invariants is addressed. Hydrodynamic equations have been derived and successfully tested against simulation data for a system where particles annihilate with a probability p, or collide elastically otherwise. The response of the system to a linear perturbation is analyzed as well.

Garcia de Soria, Maria Isabel; Trizac, Emmanuel [LPTMS (CNRS UMR 8626), Universite Paris-Sud, Orsay Cedex, F-91405 (France); Maynar, Pablo [LPT - CNRS UMR 8627, Universite Paris-Sud, Orsay Cedex, F-91405 (France) and Fisica Teorica, Universidad de Sevilla, Apartado de Correos 1065, E-41080, Sevilla (Spain); Schehr, Gregory; Barrat, Alain [LPT - CNRS UMR 8627, Universite Paris-Sud, Orsay Cedex, F-91405 (France)



Experimental Determination of the Soret Coefficient of Ionic Ferrofluids: Influence of the Volume Fraction and Ionic Strength  

NASA Astrophysics Data System (ADS)

Forced Rayleigh scattering (FRS) is a powerful technique for investigating heat and mass transfers in colloids. In the present work, we determine the Soret coefficient S T and the thermal diffusion coefficient D T of magnetic colloids (ferrofluids). It has been theoretically predicted that the thermal diffusion coefficient D T of colloids depends both on the particle-solvent interfacial interaction and on the interactions between the colloidal particles. In order to understand the microscopic behavior of the Soret effect in these ionic magnetic colloids, experiments are performed on aqueous samples of various volume fractions ? and ionic strengths. The dominant effect on the Soret coefficient comes from the particle-solvent interaction and determines its sign. Interparticle interactions have an influence on S T in the moderate concentration range where virial-like expansions are possible. In this range (? ? 0.10) and within the experimental error bars, the thermal diffusion does not depend on the ionic strength of the dispersion, and the ?-dependence of the friction coefficient is comparable to that of hard spheres. At larger concentrations, the thermal diffusion drastically decreases as the colloid approaches its dynamical glass transition.

Mériguet, Guillaume; Demouchy, Gilles; Dubois, Emmanuelle; Perzynski, Régine; Bourdon, Alain



Gaseous laser targets and optical diagnostics for studying compressible hydrodynamic instabilities  

SciTech Connect

Explore the combination of optical diagnostics and gaseous targets to obtain important information about compressible turbulent flows that cannot be derived from traditional laser experiments for the purposes of V and V of hydrodynamics models and understanding scaling. First year objectives: Develop and characterize blast wave-gas jet test bed; Perform single pulse shadowgraphy of blast wave interaction with turbulent gas jet as a function of blast wave Mach number; Explore double pulse shadowgraphy and image correlation for extracting velocity spectra in the shock-turbulent flow interaction; and Explore the use/adaptation of advanced diagnostics.

Edwards, J M; Robey, H; Mackinnon, A



The spontaneous emission of waves by a fast shock wave in a longitudinal magnetic field  

NASA Astrophysics Data System (ADS)

The stability of a fast longitudinal shock wave relative to small disturbances in the discontinuity surface is considered from the standpoint of ideal magnetic hydrodynamics. It is shown that the region of spontaneous wave emission caused by a discontinuity in a plasma with an arbitrary equation of state is determined by the magnetic field and that it expands in relation to the case in ordinary hydrodynamics. It is noted that in a sufficiently strong magnetic field spontaneous wave emission by a discontinuity can occur in an ideal gas whose heat capacity is a constant.

Pimenov, S. F.



Comparative Hydrodynamics of Bacterial Polymorphism  

NASA Astrophysics Data System (ADS)

Most bacteria swim through fluids by rotating helical flagella which can take one of 12 distinct polymorphic shapes, the most common of which is the normal form used during forward swimming runs. To shed light on the prevalence of the normal form in locomotion, we gather all available experimental measurements of the various polymorphic forms and compute their intrinsic hydrodynamic efficiencies. The normal helical form is found to be the most efficient of the 12 polymorphic forms by a significant margin—a conclusion valid for both the peritrichous and polar flagellar families, and robust to a change in the effective flagellum diameter or length. Hence, although energetic costs of locomotion are small for bacteria, fluid mechanical forces may have played a significant role in the evolution of the flagellum.

Spagnolie, Saverio E.; Lauga, Eric



Hydrodynamics of vibrated granular monolayer.  

SciTech Connect

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.)



The hydrodynamics of dolphin drafting  

PubMed Central

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.

Weihs, Daniel



Waves, Hydrodynamics and Sediment Transport Modeling at Grays Harbor, WA.  

National Technical Information Service (NTIS)

This numerical modeling study was performed for the purpose of addressing short- and mid-term dredge material management issues for the Federal Navigation Project at Grays Harbor (GH), Washington. Seattle District (NWS) is also currently evaluating GH nav...

E. Hayter E. Smith J. Smith L. Lin Z. Demirbilek



An overview of seismic-induced hydrodynamic phenomena in LMR reactor tanks  

SciTech Connect

Liquid metal reactors (LMTs) usually contain a huge volume of liquid sodium as reactor coolant. Since most reactor components are submerged in the sodium coolant, the seismic-induced hydrodynamic effects are of great importance in the design of LMR reactor components. Because LMRs operate at low pressures, the reactor components are made of thin-walled structures. Of interest in reactor design, in particular, are the hydrodynamic pressures imposed on various components, such as the reactor vessel wall, thermal liner, and components projecting down into the liquid sodium. The sloshing wave height and impact forces on the reactor cover are also important in assessing the safety of the reactor system. This paper presents an overview of the seismic-induced hydrodynamic phenomena in the LMR reactor tanks. 10 refs., 14 figs., 2 tabs.

Ma, D.C.; Chang, Y.W.; Seidensticker, R.W.



Cycloidal Wave Energy Converter  

SciTech Connect

This program allowed further advancing the development of a novel type of wave energy converter, a Cycloidal Wave Energy Converter or CycWEC. A CycWEC consists of one or more hydrofoils rotating around a central shaft, and operates fully submerged beneath the water surface. It operates under feedback control sensing the incoming waves, and converts wave power to shaft power directly without any intermediate power take off system. Previous research consisting of numerical simulations and two dimensional small 1:300 scale wave flume experiments had indicated wave cancellation efficiencies beyond 95%. The present work was centered on construction and testing of a 1:10 scale model and conducting two testing campaigns in a three dimensional wave basin. These experiments allowed for the first time for direct measurement of electrical power generated as well as the interaction of the CycWEC in a three dimensional environment. The Atargis team successfully conducted two testing campaigns at the Texas A&M Offshore Technology Research Center and was able to demonstrate electricity generation. In addition, three dimensional wave diffraction results show the ability to achieve wave focusing, thus increasing the amount of wave power that can be extracted beyond what was expected from earlier two dimensional investigations. Numerical results showed wave cancellation efficiencies for irregular waves to be on par with results for regular waves over a wide range of wave lengths. Using the results from previous simulations and experiments a full scale prototype was designed and its performance in a North Atlantic wave climate of average 30kW/m of wave crest was estimated. A full scale WEC with a blade span of 150m will deliver a design power of 5MW at an estimated levelized cost of energy (LCOE) in the range of 10-17 US cents per kWh. Based on the new results achieved in the 1:10 scale experiments these estimates appear conservative and the likely performance at full scale will exceed this initial performance estimates. In advancing the Technology Readiness Level (TRL) of this type of wave energy converter from 3 to 4, we find the CycWEC to exceed our initial estimates in terms of hydrodynamic performance. Once fully developed and optimized, it has the potential to not just outperform all other WEC technologies, but to also deliver power at a lower LCOE than competing conventional renewables like wind and solar. Given the large wave power resource both domestically and internationally, this technology has the potential to lead to a large improvement in our ability to produce clean electricity at affordable cost.

Stefan G. Siegel, Ph.D.



Dileptons from transport and hydrodynamical models  

SciTech Connect

Transport and hydrodynamical models used to describe the expansion stage of a heavy-ion collision at the CERN SPS give different dilepton spectrum even if they are tuned to reproduce the observed hadron spectra. To understand the origin of this difference we compare the dilepton emission from transport and hydrodynamical models using similar initial states in both models. We find that the requirement of pion number conservation in a hydrodynamical model does not change the dilepton emission. Also the mass distribution from the transport model indicates faster cooling and longer lifetime of the fireball.

Huovinen, P.; Koch, V.



The South Carolina Coastal Erosion Study: Nearshore Hydrodynamics Field Experiment  

NASA Astrophysics Data System (ADS)

As part of the South Carolina Coastal Erosion Study (SCCES) a nearshore field experiment was carried out for five days in December 2003 just north of Myrtle Beach, South Carolina, providing measurements of the waves, currents and morphological evolution. This experiment occurred concurrently with an extensive field campaign several kilometers offshore which included measurements of the waves and currents on and near a significant sand shoal. The purpose of the nearshore experiment was to aid in the identification of the effect of the offshore shoal on the nearshore processes. The resulting dataset will be used for verification of numerical models being used to investigate the hydrodynamics of the region. The experiment was carried out from December 10 to December 15 and consisted of measurements of the waves and currents, extensive surveys of the bathymetry every day, grab samples of the sediments, and video imagery. The hydrodynamics were measured using two Sontek Triton downward-looking Acoustic Doppler Velocimeters and two Nortek AquaDopp profilers arranged in a cross-shore line from inside the swash to several surf zone widths past the breakers. The bathymetric surveying was accomplished using both a differential GPS system and a total station. Surveying was performed each day in order to capture the morphological changes. On the last day, seven sediment samples were taken along a single cross-section to determine the sediment characteristics across the beach. Additionally, a video camera was located on a balcony of the top floor of a nearby hotel providing an excellent field of view of the entire experimental area. Digital video was captured directly onto a computer during all daylight hours and many control points were surveyed in each day to facilitate rectification of the imagery. A variety of conditions were encountered during the experiment, including two storm fronts which passed through, generating wind speeds up to 15 m/s. The first storm generated waves from the south driving a longshore current towards the north. After several relatively calm days with nearly normal incident waves the second front passed through the area with strong wind and waves approaching the shore with a large angle of incidence from the north. This drove an extremely strong longshore current in excess of 1.4 m/s and caused significant morphological changes.

Haas, K. A.; Voulgaris, G.; Demir, H.; Work, P. A.; Hanes, D. M.



Detonation-wave interactions. [PBX-9404  

SciTech Connect

The interaction of laterally colliding, diverging, cylindrical detonation waves in PBX-9404 has been studied using the radiographic machine PHERMEX and the two-dimensional, reactive Lagrangian hydrodynamic code 2DL. The experimentally observed flow could be numerically reproduced using the Forest Fire heterogeneous shock initiation burn model which permits realistic numerical simulation of the burning region of regular and diverging detonation waves, and the interacting detonation waves undergoing regular and Mach reflection. The interaction of two, three, and five colliding, diverging spherical detonation waves in PBX-9404 has been numerically modeled using the three-dimensional, reactive Eulerian hydrodynamic code 3DE. The size and magnitude of the high pressure double, triple, quadruple, and quintuple interactions depends significantly upon the number and relative locations of initiators. The initiation of propagating detonation in the insensitive explosive PBX-9502 by triple shock-wave interaction resulting from three initiators has been studied using the 3DE code with Forest Fire kinetics.

Mader, C.L.



Theoretical investigation of hydrodynamic surface mode in a lined duct with sheared flow and comparison with experiment  

NASA Astrophysics Data System (ADS)

A spectral collocation method is used to solve the linearized Euler equations in a duct with shear flow and lined walls in order to identify a possible hydrodynamic instability observed in published experiments. This method is first checked against a reference test case in a cylindrical duct. Then a theoretical test case in a plane bi-dimensional duct with no-slip flow is considered: the Briggs-Bers stability criterion is proved to be valid and it shows that the hydrodynamic instability does correspond to a right-running amplified wave. Eigenmode analyses are then performed on the experimental configuration. An unstable hydrodynamic surface mode is found, with an axial wavenumber and velocity eigenfunctions which are in good agreement with the experimental ones. Acoustic energy calculations show that the hydrodynamic instability paradoxically carries noticeable levels of acoustic energy in the upstream direction. Finally, the influence of Mach number and frequency is investigated.

Boyer, Germain; Piot, Estelle; Brazier, Jean-Philippe



Hydrodynamic constraints to the seaward development of Posidonia oceanica meadows  

NASA Astrophysics Data System (ADS)

Posidonia oceanica, the most important and abundant seagrass in the Mediterranean Sea, forms large meadows from the sea surface down to 40 m. The depth of the lower limit of the meadows marks the boundary between the infralittoral and the circalittoral zone, and is said to be normally set by light attenuation underwater, while the role of water movement has been little explored. In this paper, the position (i.e. distance from the shoreline and depth) of P. oceanica meadow lower limits along the whole Ligurian coastline (about 350 km) was related to the annual storm wave base. This depth represents the limit of interaction between waves and seafloor and corresponds to L0/2, where L0 is the annual offshore wave length. In all meadows, the lower limit has never been found deeper than the annual storm wave base, and its depth (Zc) showed related to L0 according to the equation Zc = 0.32•L0 + 5.62. In the coastal tracts affected by the least intense waves, the reduction of water movement with depth represents the most important constraint to the seaward development of the meadow, whereas light availability plays a major role in meadows affected by the most intense waves. The present study represents the first attempt at understanding the role of hydrodynamic factors in setting the depth limit of seagrass meadows. If corroborated by future research at other sites, this will have important implications for both basic and applied science, as it would imply rethinking about the relative importance of water movement and light in seagrass depth distribution, and could allow for a better estimate of the extent of meadow regression in anthropized areas.

Vacchi, Matteo; Montefalcone, Monica; Bianchi, Carlo N.; Morri, Carla; Ferrari, Marco



Hydrodynamic limits of the vlasov equation  

Microsoft Academic Search

We study the Vlasov equation for repulsive forces in the hydrodynamic regime. For initial distributions at zero temperature the limit equations turn out to be the compressible and incompressible Euler equations under suitable space-time scalings.

S. Caprino; R. Esposito; R. Marra; M. Pulvirenti



Hydrodynamic Gradient Expansion in Gauge Theory Plasmas  

NASA Astrophysics Data System (ADS)

We utilize the fluid-gravity duality to investigate the large order behavior of hydrodynamic gradient expansion of the dynamics of a gauge theory plasma system. This corresponds to the inclusion of dissipative terms and transport coefficients of very high order. Using the dual gravity description, we calculate numerically the form of the stress tensor for a boost-invariant flow in a hydrodynamic expansion up to terms with 240 derivatives. We observe a factorial growth of gradient contributions at large orders, which indicates a zero radius of convergence of the hydrodynamic series. Furthermore, we identify the leading singularity in the Borel transform of the hydrodynamic energy density with the lowest nonhydrodynamic excitation corresponding to a ‘nonhydrodynamic’ quasinormal mode on the gravity side.

Heller, Michal P.; Janik, Romuald A.; Witaszczyk, Przemys?aw



Hydrodynamics-Dispersion Studies in Storm Sewers.  

National Technical Information Service (NTIS)

The objective of this report was to simulate through mathematical modeling and laboratory experimentation, the hydrodynamics of diffusion-dispersion processes in partially-full pipe flows descriptive of sewer flows. Equations of motion and species balance...

A. M. Oguntuase E. L. Bourodimos



Self-Acting and Hydrodynamic Shaft Seals.  

National Technical Information Service (NTIS)

Self-acting and hydrodynamic seals are described. The analytical procedures are outlined for obtaining a seal force balance and the operating film thickness. Particular attention is given to primary ring response (seal vibration) to rotating seat face run...

L. P. Ludwig



Flagellar Synchronization Independent of Hydrodynamic Interactions  

NASA Astrophysics Data System (ADS)

Inspired by the coordinated beating of the flagellar pair of the green algae Chlamydomonas, we study theoretically a simple, mirror-symmetric swimmer, which propels itself at low Reynolds number by a revolving motion of a pair of spheres. We show that perfect synchronization between these two driven spheres can occur due to the motion of the swimmer and local hydrodynamic friction forces. Hydrodynamic interactions, though crucial for net propulsion, contribute little to synchronization for this free-moving swimmer.

Friedrich, Benjamin M.; Jülicher, Frank



Hydrodynamic Cavitation for Food and Water Processing  

Microsoft Academic Search

Hydrodynamic cavitation, which was and is still looked upon as an unavoidable nuisance in the flow systems, can be a serious\\u000a contender as an alternative to acoustic cavitation for intensification of different physical and chemical processing applications.\\u000a Hydrodynamic cavitation results in the generation of hot spots, highly reactive free radicals and turbulence associated with\\u000a liquid circulation currents, which can result

Parag R. Gogate



Spiral magneto-electron waves in interstellar gas dynamics  

Microsoft Academic Search

We discuss possible observational consequences resulting from the propagation of transverse magneto-electron waves in the\\u000a interstellar medium. We briefly describe a magnetohydrodynamic model for the cyclotron waves with emphasis on their analogy\\u000a with hydrodynamic inertial waves. It is shown that the cyclotron waves are heavily damped in the interstellar medium and,\\u000a therefore, cannot affect the gas dynamics of star-forming molecular

S. I. Bastrukov; J. Yang; D. V. Podgainy



Quantum hydrodynamics of electron gases.  


Electron gases in metals are described as quantum charged Newtonian viscous fluids experiencing Ohmic Darcy friction on the solid lattice ions as well. The dispersion relation of the electron acoustic waves is derived, which shows the existence of new quantum diffusion processes. The electric double layer near a metal surface is studied, which exhibits a new quantum oscillatory-decaying behavior different from the Friedel oscillations. PMID:20192305

Slavchov, Radomir; Tsekov, Roumen



Self-organization of hydrodynamically entrained sperm cells into an array of vortices  

NASA Astrophysics Data System (ADS)

The emergence of spatiotemporal patterns is of great interest in many scientific disciplines. Here we report a new dynamically self-organized pattern formed by hydrodynamically entrained sperm cells at planar surfaces. The sperm cells form vortices resembling quantized rotating waves. These vortices form an array with local hexagonal order. Using a novel order parameter, we show that the array is only formed above a critical sperm density. Supported by numerical simulation we suggest a mechanism for the appearance of the array and we estimate the strength of the hydrodynamic coupling between the cells. The vortex array represents a new chiral active gel and may serve as an experimentally accessible model for the metachronal wave of ciliated epithelia and other non-equilibrium phenomena in general. Finally we discuss the biological implications of our work.

Riedel, Ingmar; Kruse, Karsten; Howard, Jonathon



Hydrodynamic trail following in a California sea lion ( Zalophus californianus )  

Microsoft Academic Search

The mystacial vibrissae of pinnipeds constitute a sensory system for active touch and detection of hydrodynamic events. Harbour\\u000a seals (Phoca vitulina) and California sea lions (Zalophus californianus) can both detect hydrodynamic stimuli caused by a small sphere vibrating in the water (hydrodynamic dipole stimuli). Hydrodynamic\\u000a trail following has only been shown in harbour seals. Hydrodynamical and biomechanical studies of single

Nele Gläser; Sven Wieskotten; Christian Otter; Guido Dehnhardt; Wolf Hanke



Effects of hydrodynamics on phosphorus concentrations in water of Lake Taihu, a large, shallow, eutrophic lake of China  

Microsoft Academic Search

To understand the effect of hydrodynamical process on water phosphorus concentration, wind, wave, and several water quality\\u000a indices were observed in Meiliang Bay, a shallow and eutrophic bay locates in north of Lake Taihu. During the 7 day observation\\u000a period, wind speed and significant wave height were recorded more than 3 h per day, and water samples were collected in

Guangwei Zhu; Boqiang Qin; Guang Gao; Lu Zhang; Liancong Luo; Yunlin Zhang


Effects of hydrodynamics on phosphorus concentrations in water of Lake Taihu, a large, shallow, eutrophic lake of China  

Microsoft Academic Search

To understand the effect of hydrodynamical process on water phosphorus concentration, wind, wave, and several water quality\\u000a indices were observed in Meiliang Bay, a shallow and eutrophic bay locates in north of Lake Taihu. During the 7 day observation\\u000a period, wind speed and significant wave height were recorded more than 3 h per day, and water samples were collected in five\\u000a water-depth

Guangwei Zhu; Boqiang Qin; Guang Gao; Lu Zhang; Liancong Luo; Yunlin Zhang



Verification for ALEGRA using magnetized shock hydrodynamics problems.  

SciTech Connect

Two classical verification problems from shock hydrodynamics are adapted for verification in the context of ideal magnetohydrodynamics (MHD) by introducing strong transverse magnetic fields, and simulated using the finite element Lagrange-remap MHD code ALEGRA for purposes of rigorous code verification. The concern in these verification tests is that inconsistencies related to energy advection are inherent in Lagrange-remap formulations for MHD, such that conservation of the kinetic and magnetic components of the energy may not be maintained. Hence, total energy conservation may also not be maintained. MHD shock propagation may therefore not be treated consistently in Lagrange-remap schemes, as errors in energy conservation are known to result in unphysical shock wave speeds and post-shock states. That kinetic energy is not conserved in Lagrange-remap schemes is well known, and the correction of DeBar has been shown to eliminate the resulting errors. Here, the consequences of the failure to conserve magnetic energy are revealed using order verification in the two magnetized shock-hydrodynamics problems. Further, a magnetic analog to the DeBar correction is proposed and its accuracy evaluated using this verification testbed. Results indicate that only when the total energy is conserved, by implementing both the kinetic and magnetic components of the DeBar correction, can simulations in Lagrange-remap formulation capture MHD shock propagation accurately. Additional insight is provided by the verification results, regarding the implementation of the DeBar correction and the advection scheme.

Rider, William J.; Niederhaus, John H.; Robinson, Allen Conrad; Gardiner, Thomas Anthony



Kinematics and hydrodynamics of linear acceleration in eels, Anguilla rostrata.  


The kinematics and hydrodynamics of routine linear accelerations were studied in American eels, Anguilla rostrata, using high-speed video and particle image velocimetry. Eels were examined both during steady swimming at speeds from 0.6 to 1.9 body lengths (L) per second and during accelerations from -1.4 to 1.3 L s(-2). Multiple regression of the acceleration and steady swimming speed on the body kinematics suggests that eels primarily change their tail-tip velocity during acceleration. By contrast, the best predictor of steady swimming speed is body wave speed, keeping tail-tip velocity an approximately constant fraction of the swimming velocity. Thus, during steady swimming, Strouhal number does not vary with speed, remaining close to 0.32, but during acceleration, it deviates from the steady value. The kinematic changes during acceleration are indicated hydrodynamically by axial fluid momentum in the wake. During steady swimming, the wake consists of lateral jets of fluid and has minimal net axial momentum, which reflects a balance between thrust and drag. During acceleration, those jets rotate to point downstream, adding axial momentum to the fluid. The amount of added momentum correlates with the acceleration, but is greater than the necessary inertial force by 2.8+/-0.6 times, indicating a substantial acceleration reaction. PMID:15615678

Tytell, Eric D



Partial determinacy of wave fields  

NASA Astrophysics Data System (ADS)

The paper is concerned with the relation between the stochastic and the deterministic in complex wave fields with a complex interference structure, such as interference structures in multimode acoustic and optic waveguides, speckle-inhomogeneous light fields, fields in multimode lasers, and hydrodynamic wave processes on the surface of a liquid. An approach to this problem is proposed which is based of the concept of partially deterministic wave fields. The theory of partially deterministic wave fields can be developed in a manner similar to that of the theory of partially deterministic processes (Ilkova et al. 1985) and is based on a quantitative parameter, the degree of determinacy, which describes the predictability of a wave field by a model.

Kravtsov, Iu. A.; Petnikov, V. G.


The Earthquake Hydrodynamic Pressure Effects Analysis of the Large Bridge Group Piles Foundation Based on ABAQUS Software  

Microsoft Academic Search

Computed on the ABAQUS finite element software, took the large group piles foundation of the Changjiang river road bridge as the research project, based on the Morison equation, using the added water mass method to consider the effects of hydrodynamic pressure, selecting three earthquake wave with different spectrum, considering dynamic nonlinear characteristics of soils and concrete, building the finite element

Li Fu-rong; Chen Guo-xing; Wang Zhi-hua



A field investigation into the effects of a kelp forest (Macrocystis pyrifera) on coastal hydrodynamics and transport  

Microsoft Academic Search

Macrocystis pyrifera (Giant Kelp) forests form important habitats in temperate coastal regions. Hydrodynamics control the transport of nutrients, food particles, larvae and spores at scales ranging from boundary layers around individual blades to entire kelp forests. Our measurements include vertical profiles of current and temperature, and concurrent wave measurements, at a number of different locations in and around a kelp

Johanna H. Rosman; Jeffrey R. Koseff; Stephen G. Monismith; Jamie Grover



Effect of the damping and excitation on the identification of the hydrodynamic parameters for an underwater robotic vehicle  

Microsoft Academic Search

The main objective of this work is to investigate the effects of the damping level as well as different excitation forms on the overall prediction of the hydrodynamic parameters in the equations describing the coupled heave and pitch motions for an Underwater Robotic Vehicle (URV) sailing near the sea surface in random waves. The response of an underwater vehicle heaving

Ayman B. Mahfouz; Mahmoud R. Haddara



Constraining GPR data inversion using hydrodynamic laws for noninvasive soil hydraulic and electric property determination  

Microsoft Academic Search

We constrain full-wave inversion of time-lapse radar data using hydrodynamic modeling to simultaneously identify the shallow subsurface hydraulic properties and continuous vertical electric profiles. Radar data are acquired in the frequency domain using a vector network analyzer combined with an off-ground monostatic antenna. This permits to accurately filter antenna effects and to derive Green functions from which the inversion is

S. Lambot; S. Guillasot; H. Vereeckent; E. Slob



Stabilized Shock Hydrodynamics: V. Von Neumann Stability Analysis of a Predictor\\/Multi-corrector Lagrangian Method  

Microsoft Academic Search

The typical structure of the linearized equations of Lagran gian shock-hydrodynamics is given by the first-order system form of the wave equation with dissipative effects. This article presents the complete von Neumann stability and dispersion analysis for a predictor\\/multi-corrector time integrator applied to a stabilized va riational multiscale finite element formulation of such sys tem of equations. Bounds for stable

G. Scovazzi; W. J. Rider; J. N. Shadidb Love


On the analogy of stability of tangential discontinuities in hydrodynamics and in nonisothermal collisionless plasma  

SciTech Connect

Analogy between stability of tangential discontinuities in an ideal liquid in conventional hydrodynamics and in collisionless nonisothermal plasma with T{sub e} >> T{sub i} is shown. The difference is due to specific features of dispersion of ion sound waves in nonisothermal plasma in the short-wavelength range, in which the lasma quasineutrality is violated and the dispersion curve tends to the ion Langmuir frequency.

Kirtshaliya, V. G.; Minaev, I. M.; Rukhadze, A. A.; Chogovadze, M. V. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation)



The Nature of the Radiative Hydrodynamic Instabilities in Radiatively Supported Thomson Atmospheres  

Microsoft Academic Search

Atmospheres having a significant radiative support are shown to be\\u000aintrinsically unstable at luminosities above a critical fraction Gamma_crit ~\\u000a0.5-0.85 of the Eddington limit, with the exact value depending on the boundary\\u000aconditions. Two different types of absolute radiation-hydrodynamic\\u000ainstabilities of acoustic waves are found to take place even in the electron\\u000ascattering dominated limit. Both instabilities grow over

Nir J. Shaviv



Hydrodynamic simulations of a combined hydrogen, helium thermonuclear runaway on a 10-km neutron star  

SciTech Connect

We have used a Lagrangian, hydrodynamic stellar-evolution computer code to evolve a thermonuclear runaway in the accreted hydrogen rich envelope of a 1.0M, 10-km neutron star. Our simulation produced an outburst which lasted about 2000 sec and peak effective temperature was 3 keV. The peak luminosity exceeded 2 x 10/sup 5/ L. A shock wave caused a precursor in the light curve which lasted 10/sup -5/ sec.

Starrfield, S.; Kenyon, S.; Truran, J.W.; Sparks, W.M.



Surface tension and viscosity with Lagrangian hydrodynamics on a triangular mesh. Memorandum report  

SciTech Connect

Numerical algorithms for surface tension and viscosity are presented in the context of a Lagrangian treatment of incompressible hydrodynamics with a dynamically restructuring grid. New algorithms are given which update previous Lagrangian approaches in the code SPLISH. Test problems involving internal gravity and capillary waves, an oscillating droplet and a viscous shear layer are described. An example is given of a flow calculated in and around a viscous droplet with surface tension in a shear flow.

Fyfe, D.E.; Oran, E.S.; Fritts, M.J.



Seismically induced, non-stationary hydrodynamic pressure in a dam-reservoir system  

Microsoft Academic Search

Stochastic seismic analysis of hydrodynamic pressure in a dam-reservoir system is presented in this paper. The analysis is conducted assuming infinite reservoir compressible fluid and modeling seismic acceleration as a normal zero-mean stochastic process obtained by Penzien filter. The non-homogeneous boundary conditions associated to the problem have been incorporated into the equation of pressure wave scattering in the form of

Massimiliano Zingales



Renormalization and universality of blowup in hydrodynamic flows.  


We consider self-similar solutions describing intermittent bursts in shell models of turbulence and study their relationship with blowup phenomena in continuous hydrodynamic models. First, we show that these solutions are very close to self-similar solution for the Fourier transformed inviscid Burgers equation corresponding to shock formation from smooth initial data. Then, the result is generalized to hyperbolic conservation laws in one space dimension describing compressible flows. It is shown that the renormalized wave profile tends to a universal function, which is independent both of initial conditions and of a specific form of the conservation law. This phenomenon can be viewed as a new manifestation of the renormalization group theory. Finally, we discuss possibilities for application of the developed theory for detecting and describing a blowup in incompressible flows. PMID:23005216

Mailybaev, Alexei A



Hydrodynamics and aerodynamics - Cross fertilisation in research and design  

NASA Astrophysics Data System (ADS)

Areas of intersection between theory and applications in hydrodynamics and aerodynamics are investigated. Fluid mechanics principles involve the minimization of drag and considers the energy exchange between a craft and its wake, which leads to boundary layer examinations. The effects of surface roughness and of turbulent boundary layers are applicable to both seagoing and airborne craft, as are flow separation and vortical flows. Boundary layer control and reenergizing of the boundary layer with redirected vortex energy are discussed. Vortex interaction studies are prominent in the design of offshore oil rig platforms, where orbital wave motion is equivalent to vortex occurrence, and interaction is modelled as flow over a cylinder. Descriptions are given of the design of foil-like shapes, wind-propelled commercial ships, and other applications are presented.

Pearcey, H. H.



Hydrodynamic view of electrodynamics: energy rays and electromagnetic effective stress  

NASA Astrophysics Data System (ADS)

Energy rays ('photon trajectories') based upon the hydrodynamic formulation of electrodynamics are presented for time-dependent electromagnetic wave propagation. We derive Cauchy's equation of motion for the electromagnetic effective force governing the dynamics of energy rays. The effective force generated by the electromagnetic effective stress provides a surface force acting on the energy fluid element. For the head-on collision of two electromagnetic Gaussian pulses, the electromagnetic effective force, analogous to the role played by the quantum force in Bohmian mechanics, guides these non-crossing energy rays. For an electromagnetic pulse traveling from free space to a dielectric medium, the energy rays guided by the electromagnetic effective stress display reflection and refraction at the interface.

Chou, Chia-Chun; Wyatt, Robert E.



No-slip hydrodynamic boundary condition for hydrophilic particles.  


We describe measurement and interpretation of the force acting on a smooth hydrophilic glass particle during rapid (1-100 microm s(-1) approach to, and separation from, a hydrophilic glass plate in viscous concentrated aqueous sucrose solutions (0.001 Pa shydrodynamic forces on small particles, we reduce the uncertainty in the absolute particle-plate separation by using an evanescent-wave measurement of the separation. PMID:17358657

Honig, Christopher D F; Ducker, William A



``Oenodynamic'': hydrodynamic of wine swirling  

NASA Astrophysics Data System (ADS)

A crucial step in wine tasting is the so called ``swirling,'' necessary to release the bouquet of the wine: a gentle circular movement of the glass generates a wave propagating along the glass walls, enhancing oxygenation and mixing. Although being used in a large variety of other applications (e.g. cells cultures in orbital shaken bioreactors) this motion is not yet well understood. Using a simplified model we experimentally investigated the shape of the free surface and the mixing, and we identified a group of dimensionless parameters governing the flow.

Reclari, Martino; Dreyer, Matthieu; Tissot, Stephanie; Obreschkow, Danail; Wurm, Florian; Farhat, Mohamed



Hydrodynamic loads acting on an oscillating cylinder submerged in a stratified fluid with ice cover  

NASA Astrophysics Data System (ADS)

The two-dimensional problem of steady oscillations of a horizontal cylinder submerged in a linearly stratified fluid layer whose upper boundary is ice cover is considered in a linear treatment using the Boussinesq approximation. The method of mass sources distributed along the body contour is used for the internal wave generation regime, and the integral equation for the disturbed pressure in the fluid is used for the regime of no internal waves. The hydrodynamic load acting on the body was calculated as a function of the oscillation frequency for the case of a continuous ice cover and for special cases (broken ice, free surface, and rigid lid).

Sturova, I. V.



Seismic Waves  

NSDL National Science Digital Library

In this activity, students learn about the different types of seismic waves in an environment they can control. Using an interactive, online wave generator, they will study P waves, S waves, Love waves, and Rayleigh waves, and examine a combination of P and S waves that crudely simulates the wave motion experienced during an earthquake. A tutorial is provided to show how the wave generator is used.


Fluctuating hydrodynamics and direct simulation Monte Carlo  

NASA Astrophysics Data System (ADS)

Thermodynamic fluctuations are significant at microscopic scales even when hydrodynamic transport models (i.e., Navier-Stokes equations) are still accurate; a well-known example is Rayleigh scattering, which makes the sky blue. Interesting phenomena also appear in non-equilibrium systems, such as the enhancement of diffusion during mixing due to the correlation of velocity and concentration fluctuations. Direct Simulation Monte Carlo (DSMC) simulations are useful in the study of hydrodynamic fluctuations due to their computational efficiency and ability to model molecular detail, such as internal energy and chemical reactions. More recently, finite volume schemes based on the fluctuating hydrodynamic equations of Landau and Lifshitz have been formulated and validated by comparisons with DSMC simulations. This paper discusses some of the relevant numerical issues and physical effects investigated using DSMC and stochastic Navier-Stokes simulations. This paper also presents the multi-component fluctuating hydrodynamic equations, including chemical reactions, and illustrates their numerical solutions in the study of Turing patterns. We find that behind a propagating reaction front, labyrinth patterns are produced due to the coupling of reactions and species diffusion. In general, fluctuations accelerate the propagation speed of the leading front but differences are observed in the Turing patterns depending on the origin of the fluctuations (stochastic hydrodynamic fluxes versus Langevin chemistry).

Balakrishnan, Kaushik; Bell, John B.; Donev, Aleksandar; Garcia, Alejandro L.



On the definition of discrete hydrodynamic variables.  


The Green-Kubo formula for discrete hydrodynamic variables involves information about not only the fluid transport coefficients but also about discrete versions of the differential operators that govern the evolution of the discrete variables. This gives an intimate connection between discretization procedures in fluid dynamics and coarse-graining procedures used to obtain hydrodynamic behavior of molecular fluids. We observed that a natural definition of discrete hydrodynamic variables in terms of Voronoi cells leads to a Green-Kubo formula which is divergent, rendering the full coarse-graining strategy useless. In order to understand this subtle issue, in the present paper we consider the coarse graining of noninteracting Brownian particles. The discrete hydrodynamic variable for this problem is the number of particles within Voronoi cells. Thanks to the simplicity of the model we spot the origin of the singular behavior of the correlation functions. We offer an alternative definition, based on the concept of a Delaunay cell that behaves properly, suggesting the use of the Delaunay construction for the coarse graining of molecular fluids at the discrete hydrodynamic level. PMID:19894926

Español, Pep; Zúñiga, Ignacio



Three-dimensional hydrodynamic instabilities in stellar core collapses  

NASA Astrophysics Data System (ADS)

A spherically symmetric hydrodynamic stellar core collapse process under gravity is time-dependent and may become unstable once disturbed. Subsequent non-linear evolutions of such growth of hydrodynamic instabilities may lead to various physical consequences. Specifically for a homologous collapse of a stellar core characterized by a polytropic exponent ?= 4/3, we examine oscillations and/or instabilities of three-dimensional (3D) general polytropic perturbations. Being incompressible, the radial component of vorticity perturbation always grows unstably during the same homologous core collapse. For compressible 3D perturbations, the polytropic index ? of perturbations can differ from ?= 4/3 of the general polytropic hydrodynamic background flow, where the background specific entropy is conserved along streamlines and can vary in radius and time. Our model formulation here is more general than previous ones. The Brunt-Väisälä buoyancy frequency ? does not vanish, allowing for the existence of internal gravity g- modes and/or g+ modes, depending on the sign of ? respectively. Eigenvalues and eigenfunctions of various oscillatory and unstable perturbation modes are computed, given asymptotic boundary conditions. As studied in several specialized cases of Goldreich & Weber and of Lou & Cao and Cao & Lou, we further confirm that acoustic p modes and surface f modes remain stable in the current more general situations. In comparison, g- modes and sufficiently high radial order g+ modes are unstable, leading to inevitable convective motions within the collapsing stellar interior; meanwhile, sufficiently low radial order g+ modes remain stably trapped in the collapsing core. Unstable growths of 3D g-mode disturbances are governed dominantly by the angular momentum conservation and modified by the gas pressure restoring force. We note in particular that unstable temporal growths of 3D vortical perturbations exist even when the specific entropy distribution becomes uniform and ?=?= 4/3. Conceptually, unstable g modes might bear conceivable physical consequences on supernova explosions, the initial kicks of nascent proto-neutron stars of as high as ? up to ? and breakups of the collapsing core, while unstable growths of vortical perturbations can lead to fast spins of compact objects, 3D vortical convections inside the collapsing core for possible magnetohydrodynamic dynamo actions on seed magnetic fields, and the generation of Rossby waves further stimulated by gravitational wave emissions.

Lou, Yu-Qing; Lian, Biao



An integrated coastal model for aeolian and hydrodynamic sediment transport  

NASA Astrophysics Data System (ADS)

Dunes are formed by aeolian and hydrodynamic processes. Over the last decades numerical models were developed that capture our knowledge of the hydrodynamic transport of sediment near the coast. At the same time others have worked on creating numerical models for aeolian-based transport. Here we show a coastal model that integrates three existing numerical models into one online-coupled system. The XBeach model simulates storm-induced erosion (Roelvink et al., 2009). The Delft3D model (Lesser et al., 2004) is used for long term morphology and the Dune model (Durán et al., 2010) is used to simulate the aeolian transport. These three models were adapted to be able to exchange bed updates in real time. The updated models were integrated using the ESMF framework (Hill et al., 2004), a system for composing coupled modeling systems. The goal of this integrated model is to capture the relevant coastal processes at different time and spatial scales. Aeolian transport can be relevant during storms when the strong winds are generating new dunes, but also under relative mild conditions when the dunes are strengthened by transporting sand from the intertidal area to the dunes. Hydrodynamic transport is also relevant during storms, when high water in combination with waves can cause dunes to avalanche and erode. While under normal conditions the hydrodynamic transport can result in an onshore transport of sediment up to the intertidal area. The exchange of sediment in the intertidal area is a dynamic interaction between the hydrodynamic transport and the aeolian transport. This dynamic interaction is particularly important for simulating dune evolution at timescales longer than individual storm events. The main contribution of the integrated model is that it simulates the dynamic exchange of sediment between aeolian and hydrodynamic models in the intertidal area. By integrating the numerical models, we hope to develop a model that has a broader scope and applicability than existing models and is capable of simulating both the growth and destruction of coastal dunes. The integrated version of XBeach and Dune is currently being applied for a test case in Assateague Island in the United States. The integrated version of XBeach, Dune and Delft3D is applied to the Sand Engine in the Netherlands. In the presentation we show the current status of the development, experiences with the first test cases and our plans for future developments. [Durán et al., 2010] Durán, O., Parteli, E. J., and Herrmann, H. J. (2010). A continuous model for sand dunes: Review, new developments and application to barchan dunes and barchan dune fields. Earth Surface Processes and Landforms, 35(13):1591-1600. [Hill et al., 2004] Hill, C., DeLuca, C., Balaji, Suarez, M., and Da Silva, A. (2004). The architecture of the earth system modeling framework. Computing in Science Engineering, 6(1):18 - 28. [Lesser et al., 2004] Lesser, G. R., Roelvink, J. A., van Kester, J. A. T. M., and Stelling, G. S. (2004). Development and validation of a three-dimensional morphological model. Coastal Engineering, 51(8-9):883-915. Coastal Morphodynamic Modeling. [Roelvink et al., 2009] Roelvink, D., Reniers, A., van Dongeren, A., de Vries, J. v. T., McCall, R., and Lescinski, J. (2009). Modelling storm impacts on beaches, dunes and barrier islands. Coastal Engineering, 56(11-12):1133-1152.

Baart, F.; den Bieman, J.; van Koningsveld, M.; Luijendijk, A. P.; Parteli, E. J. R.; Plant, N. G.; Roelvink, J. A.; Storms, J. E. A.; de Vries, S.; van Thiel de Vries, J. S. M.; Ye, Q.



Intensity wave and polarization waves  

NASA Astrophysics Data System (ADS)

Extending the idea of the intensity waves, a new term, that of polarization waves is introduced. Unlike the light waves, the intensity waves and the polarization waves belong to the class of observable phenomena. The formalism of intensity waves and of polarization waves is presented for some simple fundamental cases.

Tudor, Tiberiu S.



Hydrodynamical comparison test of solar models  

NASA Astrophysics Data System (ADS)

We present three dimensional radiation-hydrodynamical (RHD) simulations for solar surface convection based on three most recent solar mixtures: Grevesse & Sauval (1998), Asplund, Grevesse & Sauval (2005), and Asplund, Grevesse, Sauval & Scott (2009). The outer convection zone of the Sun is an extremely turbulent region composed of partly ionized compressible gases at high temperature. The super-adiabatic layer (SAL) is the transition region where the transport of energy changes drastically from convection to radiation. In order to describe physical processes accurately, a realistic treatment of radiation should be considered as well as convection. However, newly updated solar mixtures that are established from radiation-hydrodynamics do not generate properly internal structures estimated by helioseismology. In order to address this fundamental problem, solar models are constructed consistently based on each mixture and used as initial configurations for radiation-hydrodynamical simulations. From our simulations, we find that the turbulent flows in each model are statistically similar in the SAL.

Bach, K.; Kim, Y.-C.



The RAGE radiation-hydrodynamic code  

NASA Astrophysics Data System (ADS)

We describe RAGE, the 'radiation adaptive grid Eulerian' radiation-hydrodynamics code, including its data structures, its parallelization strategy and performance, its hydrodynamic algorithm(s), its (gray) radiation diffusion algorithm, and some of the considerable amount of verification and validation efforts. The hydrodynamics is a basic Godunov solver, to which we have made significant improvements to increase the advection algorithm's robustness and to converge stiffnesses in the equation of state. Similarly, the radiation transport is a basic gray diffusion, but our treatment of the radiation-material coupling, wherein we converge nonlinearities in a novel manner to allow larger timesteps and more robust behavior, can be applied to any multi-group transport algorithm.

Gittings, Michael; Weaver, Robert; Clover, Michael; Betlach, Thomas; Byrne, Nelson; Coker, Robert; Dendy, Edward; Hueckstaedt, Robert; New, Kim; Oakes, W. Rob; Ranta, Dale; Stefan, Ryan



Toward a Fully Consistent Radiation Hydrodynamics  

SciTech Connect

Dimitri Mihalas set the standard for all work in radiation hydrodynamics since 1984. The present contribution builds on 'Foundations of Radiation Hydrodynamics' to explore the relativistic effects that have prevented having a consistent non-relativistic theory. Much of what I have to say is in FRH, but the 3-D development is new. Results are presented for the relativistic radiation transport equation in the frame obtained by a Lorentz boost with the fluid velocity, and the exact momentum-integrated moment equations. The special-relativistic hydrodynamic equations are summarized, including the radiation contributions, and it is shown that exact conservation is obtained, and certain puzzles in the non-relativistic radhydro equations are explained.

Castor, J I



Synchronization of rotating helices by hydrodynamic interactions.  


Some types of bacteria use rotating helical flagella to swim. The motion of such organisms takes place in the regime of low Reynolds numbers where viscous effects dominate and where the dynamics is governed by hydrodynamic interactions. Typically, rotating flagella form bundles, which means that their rotation is synchronized. The aim of this study is to investigate whether hydrodynamic interactions can be at the origin of such a bundling and synchronization. We consider two stiff helices that are modelled by rigidly connected beads, neglecting any elastic deformations. They are driven by constant and equal torques, and they are fixed in space by anchoring their terminal beads in harmonic traps. We observe that, for finite trap strength, hydrodynamic interactions do indeed synchronize the helix rotations. The speed of phase synchronization decreases with increasing trap stiffness. In the limit of infinite trap stiffness, the speed is zero and the helices do not synchronize. PMID:16096696

Reichert, M; Stark, H



Twisted electrostatic ion-cyclotron waves in dusty plasmas.  


We show the existence of a twisted electrostatic ion-cyclotron (ESIC) wave carrying orbital angular momentum (OAM) in a magnetized dusty plasma. For our purposes, we derive a 3D wave equation for the coupled ESIC and dust ion-acoustic (DIA) waves from the hydrodynamic equations that are composed of the continuity and momentum equations, together with Poisson's equation. The 3D wave equation reveals the formation of a braided or twisted ESIC wave structure carrying OAM. The braided or twisted ESIC wave structure can trap and transport plasma particles in magnetoplasmas, such as those in Saturn's F-ring and in the forthcoming magnetized dusty plasma experiments. PMID:23410477

Shukla, P K



Twisted electrostatic ion-cyclotron waves in dusty plasmas  

NASA Astrophysics Data System (ADS)

We show the existence of a twisted electrostatic ion-cyclotron (ESIC) wave carrying orbital angular momentum (OAM) in a magnetized dusty plasma. For our purposes, we derive a 3D wave equation for the coupled ESIC and dust ion-acoustic (DIA) waves from the hydrodynamic equations that are composed of the continuity and momentum equations, together with Poisson's equation. The 3D wave equation reveals the formation of a braided or twisted ESIC wave structure carrying OAM. The braided or twisted ESIC wave structure can trap and transport plasma particles in magnetoplasmas, such as those in Saturn's F-ring and in the forthcoming magnetized dusty plasma experiments.

Shukla, P. K.



Wave energy desalinization  

SciTech Connect

A device for producing fresh water from salt sea water by utilizing the hydrodynamic energy of waves, comprising a buoyant platform; means for mooring the platform; a pump connected to the mooring means; a reservoir for pressurized sea water; a desalination system for extracting fresh water from the sea water; hydraulic flow control means for causing the pump to pump sea water into the sea water reservoir, as motion of the buoyant platform is produced due to the passing of waves beneath it; measuring means for measuring parameters of the sea adjacent the buoyant platform; and a control device connected to control the pressure in the sea water reservoir and the flow of sea water from the reservoir through the desalination system in response to the parameters of the sea.

Hopfe, H.H.



Supernova hydrodynamics experiments using the Nova laser  

SciTech Connect

We are developing experiments using the Nova laser to investigate two areas of physics relevant to core-collapse supernovae (SN): (1) compressible nonlinear hydrodynamic mixing and (2) radiative shock hydrodynamics. In the former, we are examining the differences between the 2D and 3D evolution of the Rayleigh-Taylor instability, an issue critical to the observables emerging from SN in the first year after exploding. In the latter, we are investigating the evolution of a colliding plasma system relevant to the ejecta-stellar wind interactions of the early stages of SN remnant formation. The experiments and astrophysical implications are discussed.

Remington, B.A.; Glendinning, S.G.; Estabrook, K.; Wallace, R.J.; Rubenchik, A. [Lawrence Livermore National Lab., CA (United States); Kane, J.; Arnett, D. [Arizona Univ., Tucson, AZ (United States). Stewart Observatory; Drake, R.P. [Michigan Univ., Ann Arbor, MI (United States); McCray, R. [Colorado Univ., Boulder, CO (United States)



Development of a hydrodynamic code: MINNIE  

NASA Astrophysics Data System (ADS)

The development of hydrodynamic two dimensional Lagrangian code (Minnie) adapted to the study of plasmas created by laser-material interaction is outlined. The geometry of the plasma and the mesh are described and the steps for the simulation are explained. The code is principally intended for the study of the radiative transfer of an X-ray using hydrodynamic results obtained at different times. Steps to position at one point in space, and study, in a certain direction and for a given angular aperture, the luminous spectrum coming from the plasma, are given.

Marcerou, Pascal; Dinguirard, Jean-Pierre



Hydrodynamic Simulations with the Godunov SPH  

NASA Astrophysics Data System (ADS)

We present results based on an implementation of the Godunov Smoothed Particle Hydrodynamics (GSPH). We carry out controlled hydrodynamical three-dimensional tests, namely the Sod shock tube and the development of Kelvin-Helmholtz instabilities in a shear flow test. The results of our tests demonstrate GSPH provides a much improved description of contact discontinuities, with respect to SPH, and is able to follow the development of gas-dynamical instabilities, such as the Kevin-Helmholtz and the Rayleigh-Taylor ones.

Borgani, S.; Murante, G.; Brunino, R.; Cha, S.-H.



Exact hydrodynamic solution for the elliptic flow  

SciTech Connect

Looking for the underlying hydrodynamic mechanisms determining the elliptic flow we show that for an expanding relativistic perfect fluid the transverse flow may derive from a solvable hydrodynamic potential, if the entropy is transversally conserved and the corresponding expansion is ''quasi-stationary,'' that is, mainly governed by the temperature cooling. Exact solutions for the velocity flow coefficients v{sub 2} and the temperature dependence of the spatial and momentum anisotropy are obtained and shown to be in agreement with the elliptic flow features of heavy-ion collisions.

Peschanski, Robi [Institut de Physique Theorique, CEA, IPhT, and Centre National de la Recherche Scientifique (CNRS), URA 2306, F-91191 Gif-sur-Yvette (France); Saridakis, Emmanuel N. [Department of Physics, University of Athens, GR-15771 Athens (Greece)



Second order hydrodynamic coefficients from kinetic theory  

SciTech Connect

In a relativistic setting, hydrodynamic calculations which include shear viscosity (which is first order in an expansion in gradients of the flow velocity) are unstable and acausal unless they also include terms to second order in gradients. To date such terms have only been computed in supersymmetric N=4 super-Yang-Mills theory at infinite coupling. Here we compute these second-order hydrodynamic coefficients in weakly coupled QCD, perturbatively to leading order in the QCD coupling, using kinetic theory. We also compute them in QED and scalar {lambda}{phi}{sup 4} theory.

York, Mark Abraao; Moore, Guy D. [McGill University, Department of Physics, 3600 rue University, Montreal QC H3A 2T8 (Canada)



Wave Properties  

NSDL National Science Digital Library

In this lesson plan students will learn the components of a wave, then discuss the effects of wave height, wavelength, and wave period in determining the overall size of a wave. They will use the National Geographic Wave Simulator to experiment with creating different kinds of waves. Discussion will then focus on the effects of geography on wave size as well as additional forces on boats trying to navigate waves.


Anti-dark solitary waves for a derivative nonlinear Schrodinger system  

Microsoft Academic Search

The propagation of wavepackets in hydrodynamic free surface waves is governed by the nonlinear Schrodinger (NLS) equation to leading order. Higher (fourth) order perturbation theory typically leads to derivative NLS (DNLS) systems. `Dark' solitary waves, or wave trains with a local minimum in intensity relative to the far field, are computed for a special DNLS system. In contrast to the

Kwok W. Chow; Derek W. C. Lai



Running in the surf: hydrodynamics of the shore crab Grapsus tenuicrustatus.  


When locomoting in water, animals experience hydrodynamic forces due to ambient water motion and their own motion through the water. Because an aquatic pedestrian must maintain contact with the substratum to locomote, hydrodynamic forces which can dislodge an animal have the capacity to constrain the postures, gaits and speeds an animal can use. This study measured hydrodynamic forces on the amphibious shore crab Grapsus tenuicrustatus in aquatic and terrestrial postures. The crabs' locomotory speeds and ambient water velocities in their habitat were considered in predicting the conditions under which a crab is likely to overturn or wash away. A non-moving crab can withstand 200% faster flow in the aquatic posture than in the terrestrial posture. A crab using the terrestrial posture while locomoting through still water experiences 132% greater drag and 17% greater acceleration reaction forces than it does in the aquatic posture. Due to the lower hydrodynamic forces in the aquatic posture, a crab could locomote up to 50% more quickly or through a faster water flow environment than it could in the terrestrial posture. In faster flow environments like wave-swept rocky shores, a crab in either posture would have to actively grasp the substratum to keep from being dislodged, preventing it from using a punting gait. In slower flow environments, animals can locomote faster and take advantage of different gaits that are not available to them in faster flow environments. PMID:11551997

Martinez, M M



Influence of cavity shape on hydrodynamic noise by a hybrid LES-FW-H method  

NASA Astrophysics Data System (ADS)

The flow past various mechanical cavity, which is a common structure on the surface of the underwater vehicle, and generating hydrodynamic noise has attracted considerable attention in recent years. In this paper, a hybrid method is presented to investigate the hydrodynamic noise induced by mechanical cavities with various shapes. With this method, the noise sources in the near wall turbulences or in the wake are computed by the large eddy simulation (LES) and the generation and propagation of the acoustic waves are solved by the Ffowcs Williams-Hawkings (FW-H) acoustic analogy method with acoustic source terms extracted from the time-dependent solutions of the unsteady flow. The feasibility and reliability of the current method was verified by comparing with experimental data (Wang, 2009). The 2D cavity models with different cross-section shapes and 3D cavity models with different cavity mouth shapes (rectangular and circular) are developed to study the influence of cavity shape on the hydrodynamic noise. By comparing the flow mechanisms, wall pressure fluctuations, near-field and far-field sound propagation distributions, it is found that the quadrangular cavity with equal depths of leading-edge and trailing-edge is preferred for its inducing lower hydrodynamic noise than the cylindrical cavity does.

Wang, Yu; Wang, Shu-Xin; Liu, Yu-Hong; Chen, Chao-Ying




Microsoft Academic Search

Strange attractors are fractal limit sets describing the evolution of chaotic systems in phase space. Recent progress in measuring the properties of strange attractors for weakly turbulent hydrodynamic flows is reviewed. We then describe some of the difficulties and open questions suggested by these developments.




Determining blood cell size using microfluidic hydrodynamics  

Microsoft Academic Search

Microfluidic flow cytometers currently analyze far fewer parameters than conventional flow cytometry or fluorescence activated cell sorting (FACS) in order to minimize cost and complexity. There is a need for microfluidic devices that analyze more and or new cell parameters with compact and minimal means. Here we show a new and explicitly microfluidic parameter, “hydrodynamic” cell size, and compare it

David W. Inglis; John A. Davis; Thomas J. Zieziulewicz; David A. Lawrence; Robert H. Austin; James C. Sturm



UV polymerization of hydrodynamically shaped fibers.  


Most natural and man-made fibers have circular cross-sections; thus the properties of materials composed of non-circular fibers are largely unexplored. We demonstrate the technology for fabricating fibers with predetermined cross-sectional shape. Passive hydrodynamic focusing and UV polymerization of a shaped acrylate stream produced metre-long fibers for structural and mechanical characterization. PMID:21246152

Thangawng, Abel L; Howell, Peter B; Spillmann, Christopher M; Naciri, Jawad; Ligler, Frances S



Hydrodynamic analysis of feeding in sand dollars  

Microsoft Academic Search

Subtidal sand dollars, Dendraster excentricus, assume an inclined posture under conditions of moderate water flow (10 cm s-1 to 2 m s-1). In this posture, when the test is in the usual position parallel to the water flow, the test acts as a lifting body. Analysis of the hydrodynamic characteristics of the sand dollar test was accomplished by slender body

Patricia L. O'Neill



On the hydrodynamics of soap films  

Microsoft Academic Search

Several experiments aiming at the exploration of the hydrodynamical properties of soap films are presented. Their interpretation takes into account the very specific equation of state of these films. It is shown that on short time scales each element of the film moves as a whole so that the film can be considered as a two-dimensional fluid with a local

Y. Couder; J. M. Chomaz; M. Rabaud




Microsoft Academic Search

This paper summarizes briefly the main features of some hydrodynamic ; problems in the design of reactors for containcnent against internal explosions. ; The pertinent conclusions which summarize this experience are as follows and ; apply to explosions in various solid and liquid media: the Rankine-Hugoniot ; equations are of general applicability to both shocks and strong pressure pulses; ;




Hydrodynamic implications for submarine launched underwater gliders  

Microsoft Academic Search

Underwater gliders are a type of long range unmanned vehicle that use bouyancy control and lifting surfaces to travel in a sawtooth trajectory through the water column. These vehicles are typically employed by oceanographers for environmental monitoring and also show promise as a sensor platform in military applications. This paper presents investigations of vehicle hydrodynamics relating to the deployment of

Joshua D. Rodgers; John M. Wharington



Hydrodynamics of maneuvering bodies: LDRD Final Report  

Microsoft Academic Search

The objective of the 'Hydrodynamics of Maneuvering Bodies' LDRD project was to develop a Lagrangian, vorticity-based numerical simulation of the fluid dynamics associated with a maneuvering submarine. Three major tasks were completed. First, a vortex model to simulate the wake behind a maneuvering submarine was completed, assuming the flow to be inviscid and of constant density. Several simulations were performed

S. N. Kempka; J. H. Strickland



A Hydrodynamic Theory of Turbidity Currents  

Microsoft Academic Search

A theory of steady-state turbidity currents along sloping and horizontal ocean or lake bottoms is developed on the basis of hydrodynamic boundary-layer assumptions. The theory is applied to the Grand Banks turbidity current of 1929; reasonable values of current thickness and sediment content are obtained, as well as satisfactory agreement between observed and calculated velocities. Introduction. A turbidity current occurs

John E. Plapp; James P. Mitchell



Microflow Cytometers with Integrated Hydrodynamic Focusing  

PubMed Central

This study demonstrates the suitability of microfluidic structures for high throughput blood cell analysis. The microfluidic chips exploit fully integrated hydrodynamic focusing based on two different concepts: Two-stage cascade focusing and spin focusing (vortex) principle. The sample—A suspension of micro particles or blood cells—is injected into a sheath fluid streaming at a substantially higher flow rate, which assures positioning of the particles in the center of the flow channel. Particle velocities of a few m/s are achieved as required for high throughput blood cell analysis. The stability of hydrodynamic particle positioning was evaluated by measuring the pulse heights distributions of fluorescence signals from calibration beads. Quantitative assessment based on coefficient of variation for the fluorescence intensity distributions resulted in a value of about 3% determined for the micro-device exploiting cascade hydrodynamic focusing. For the spin focusing approach similar values were achieved for sample flow rates being 1.5 times lower. Our results indicate that the performances of both variants of hydrodynamic focusing suit for blood cell differentiation and counting. The potential of the micro flow cytometer is demonstrated by detecting immunologically labeled CD3 positive and CD4 positive T-lymphocytes in blood.

Frankowski, Marcin; Theisen, Janko; Kummrow, Andreas; Simon, Peter; Ragusch, Hulya; Bock, Nicole; Schmidt, Martin; Neukammer, Jorg



Vlasov hydrodynamics of a quantum mechanical model  

Microsoft Academic Search

We derive the Vlasov hydrodynamics from the microscopic equations of a quantum mechanical model, which simulates that of an assembly of gravitating particles. In addition we show that the local microscopic dynamics of the model corresponds, on a suitable time-scale, to that of an ideal Fermi gas.

Heide Narnhofer; Geoffrey L. Sewell



Improved FCT Algorithm for Shock Hydrodynamics  

Microsoft Academic Search

The new YDFCT algorithm is presented for the numerical solution of hydrodynamic flow problems with steep gradients. This algorithm is an explicit finite-difference scheme based on the flux-corrected transport technique and it is an improvement of the ETBFCT and the XDFCT algorithms. The erosion of sharp edges, the phase distortion of curved profiles and the terracing effect and velocity oscillations

Dus Odstrcil



Hydrodynamic fluctuations at the convective instability  

Microsoft Academic Search

The effects of thermal fluctuations on the convective instability are considered. It is shown that the Langevin equations for hydrodynamic fluctuations are equivalent, near the instability, to a model for the crystallization of a fluid in equilibrium. Unlike the usual models, however, the free energy of the present system does not possess terms cubic in the order parameter, and therefore

J. B. Swift; P. C. Hohenberg



Stabilizing geometry for hydrodynamic rotary seals  


A hydrodynamic sealing assembly including a first component having first and second walls and a peripheral wall defining a seal groove, a second component having a rotatable surface relative to said first component, and a hydrodynamic seal comprising a seal body of generally ring-shaped configuration having a circumference. The seal body includes hydrodynamic and static sealing lips each having a cross-sectional area that substantially vary in time with each other about the circumference. In an uninstalled condition, the seal body has a length defined between first and second seal body ends which varies in time with the hydrodynamic sealing lip cross-sectional area. The first and second ends generally face the first and second walls, respectively. In the uninstalled condition, the first end is angulated relative to the first wall and the second end is angulated relative to the second wall. The seal body has a twist-limiting surface adjacent the static sealing lip. In the uninstalled condition, the twist-limiting surface is angulated relative to the peripheral wall and varies along the circumference. A seal body discontinuity and a first component discontinuity mate to prevent rotation of the seal body relative to the first component.

Dietle, Lannie L. (Houston, TX); Schroeder, John E. (Richmond, TX)



Laboratory and Astrophysical Radiation Hydrodynamics: An Introduction  

NASA Astrophysics Data System (ADS)

The radiation received from stars provides the diagnostic tool to infer temperatures, densities, hydrodynamic motions, and chemical compositions in their atmospheres. For most stars it appears to be an adequate first approximation to assume that there are no large-scale hydrodynamic motions. However, in the most luminous stars the intense radiation field deposits sufficient photon momentum in the outermost layers to drive them off in a supersonic hydrodynamic flow. Likewise, in exploding stars such as novae and supernovae, the dominant form of energy and momentum content and transfer may reside not in the material flow, but in the radiation field. Further, pulsating stars are driven by an internal ``radiation engine'' in which the variation of the opacity of the material with temperature and density acts as a thermodynamic valve. In all these objects, and adequate analysis of the physics of the atmosphere requires application of the discipline of Radiation Hydrodynamics, where one considers the dynamics of a two-component (at least!) radiating fluid. This talk will illustrate some aspects of the radiation-material interaction that produce large-scale motions in stellar atmospheres and envelopes, and make some connections between stellar and laboratory radiation-driven phenomena.

Mihalas, D.



Laboratory and Astrophysical Radiation Hydrodynamics : An Introduction  

SciTech Connect

In this talk, the author discusses some aspects of radiation-material interactions that can produce radiation from a violently moving fluid, or, reciprocally, can result in macroscopic motion in fluids which are subject to intense radiation fields. The author also outlines some similarities and contrasts between 'laboratory' and astrophysical phenomena in which radiation hydrodynamics plays an important role.

Mihalas, Dimitri,



Geometrical Methods for Equations of Hydrodynamical Type  

NASA Astrophysics Data System (ADS)

We describe some recent results for a class of nonlinear hydrodynamical approximation models where the geometric approach gives insight into a variety of aspects. The main contribution concerns analytical results for Euler equations on the diffeomorphism group of the circle for which the inertia operator is a nonlocal operator.

Escher, Joachim; Kolev, Boris



First order and stable relativistic dissipative hydrodynamics  

NASA Astrophysics Data System (ADS)

Relativistic thermodynamics is derived from kinetic equilibrium in a general frame. Based on a novel interpretation of Lagrange multipliers in the equilibrium state we obtain a generic stable but first order relativistic dissipative hydrodynamics. Although this was believed to be impossible, we circumvent this difficulty by a specific handling of the heat flow.

Ván, P.; Biró, T. S.



Smoothed Particle Hydrodynamics: Applications within DSTO  

Microsoft Academic Search

Smoothed Particle Hydrodynamics (SPH) is a computational technique for the numerical simulation of the equations of fluid dynamics without the use of an underlying numerical mesh. Although originally developed for use in astrophysical gas dynamics, SPH has recently been applied to many other areas of numerical fluid dynamics and materials modelling, several of which have particular relevance to defence problems

D. A. Jones; D. Belton


Hydrodynamically Driven Colloidal Assembly in Dip Coating  

NASA Astrophysics Data System (ADS)

We study the hydrodynamics of dip coating from a suspension and report a mechanism for colloidal assembly and pattern formation on smooth substrates. Below a critical withdrawal speed where the coating film is thinner than the particle diameter, capillary forces induced by deformation of the free surface prevent the convective transport of single particles through the meniscus beneath the film. Capillary-induced forces are balanced by hydrodynamic drag only after a minimum number of particles assemble within the meniscus. The particle assembly can thus enter the thin film where it moves at nearly the withdrawal speed and rapidly separates from the next assembly. The interplay between hydrodynamic and capillary forces produces periodic and regular structures below a critical ratio Ca2/3/Bo<0.7, where Ca and Bo are the capillary and Bond numbers, respectively. An analytical model and numerical simulations are presented for the case of two-dimensional flow with circular particles in suspension. The hydrodynamically driven assembly documented here is consistent with stripe pattern formations observed experimentally in dip coating.

Colosqui, Carlos E.; Morris, Jeffrey F.; Stone, Howard A.



Hydrodynamically driven colloidal assembly in dip coating.  


We study the hydrodynamics of dip coating from a suspension and report a mechanism for colloidal assembly and pattern formation on smooth substrates. Below a critical withdrawal speed where the coating film is thinner than the particle diameter, capillary forces induced by deformation of the free surface prevent the convective transport of single particles through the meniscus beneath the film. Capillary-induced forces are balanced by hydrodynamic drag only after a minimum number of particles assemble within the meniscus. The particle assembly can thus enter the thin film where it moves at nearly the withdrawal speed and rapidly separates from the next assembly. The interplay between hydrodynamic and capillary forces produces periodic and regular structures below a critical ratio Ca(2/3)/sqrt[Bo] < 0.7, where Ca and Bo are the capillary and Bond numbers, respectively. An analytical model and numerical simulations are presented for the case of two-dimensional flow with circular particles in suspension. The hydrodynamically driven assembly documented here is consistent with stripe pattern formations observed experimentally in dip coating. PMID:23683248

Colosqui, Carlos E; Morris, Jeffrey F; Stone, Howard A



Hydrodynamic construction of the electromagnetic field  

Microsoft Academic Search

We present an alternative Eulerian hydrodynamic model for the electromagnetic field in which the discrete vector indices in Maxwell's equations are replaced by continuous angular freedoms, and develop the corresponding Lagrangian picture in which the fluid particles have rotational and translational freedoms. This enables us to extend to the electromagnetic field the exact method of state construction proposed previously for

Peter Holland



Hydrodynamics of tubes of varying cross section  

Microsoft Academic Search

A method is suggested of reducing the hydrodynamic resistance by replacing circular cylindrical tubes (CT) by socalled asymmetrical wavy tubes of varying cross section with long exist cone and short nozzle portions. Mathematical simulation of laminar motion of an incompressible fluid (the Navier-Stokes equations) has shown that a change in geometric parameters can change the resistance substantially, making it larger

I. L. Povkh; N. V. Finoshin



Chiral Magnetic Effect in Hydrodynamic Approximation  

NASA Astrophysics Data System (ADS)

We review derivations of the chiral magnetic effect (ChME) in hydrodynamic approximation. The reader is assumed to be familiar with the basics of the effect. The main challenge now is to account for the strong interactions between the constituents of the fluid. The main result is that the ChME is not renormalized: in the hydrodynamic approximation it remains the same as for non-interacting chiral fermions moving in an external magnetic field. The key ingredients in the proof are general laws of thermodynamics and the Adler-Bardeen theorem for the chiral anomaly in external electromagnetic fields. The chiral magnetic effect in hydrodynamics represents a macroscopic manifestation of a quantum phenomenon (chiral anomaly). Moreover, one can argue that the current induced by the magnetic field is dissipation free and talk about a kind of "chiral superconductivity". More precise description is a quantum ballistic transport along magnetic field taking place in equilibrium and in absence of a driving force. The basic limitation is the exact chiral limit while temperature—excitingly enough—does not seemingly matter. What is still lacking, is a detailed quantum microscopic picture for the ChME in hydrodynamics. Probably, the chiral currents propagate through lower-dimensional defects, like vortices in superfluid. In case of superfluid, the prediction for the chiral magnetic effect remains unmodified although the emerging dynamical picture differs from the standard one.

Zakharov, Valentin I.


Observation of Shock Waves in a Strongly Interacting Fermi Gas  

SciTech Connect

We study collisions between two strongly interacting atomic Fermi gas clouds. We observe exotic nonlinear hydrodynamic behavior, distinguished by the formation of a very sharp and stable density peak as the clouds collide and subsequent evolution into a boxlike shape. We model the nonlinear dynamics of these collisions by using quasi-1D hydrodynamic equations. Our simulations of the time-dependent density profiles agree very well with the data and provide clear evidence of shock wave formation in this universal quantum hydrodynamic system.

Joseph, J. A.; Thomas, J. E. [Department of Physics, Duke University, Durham, North Carolina 27708 (United States); Kulkarni, M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800 (United States); Department of Condensed Matter Physics and Material Science, Brookhaven National Laboratory, Upton, New York 11973 (United States); Abanov, A. G. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800 (United States)



On pulsating and cellular forms of hydrodynamic instability in liquid-propellant combustion  

SciTech Connect

An extended Landau/Levich model of liquid-propellant combustion, one that allows for a local dependence of the burning rate on the (gas) pressure at the liquid/gas interface, exhibits not only the classical hydrodynamic cellular instability attributed to Landau, but also a pulsating hydrodynamic instability associated with sufficiently negative pressure sensitivities. Exploiting the realistic limit of small values of the gas-to-liquid density ratio {rho}, analytical formulas for both neutral stability boundaries may be obtained by expanding all quantities in appropriate powers of {rho} in each of three distinguished wavenumber regimes. In particular, composite analytical expressions are derived for the neutral stability boundaries A{sub p}(k), where A{sub p} is the pressure sensitivity of the burning rate and k is the wavenumber of the disturbance. For the cellular boundary, the results demonstrate explicitly the stabilizing effect of gravity on long-wave disturbances, the stabilizing effect of viscosity and surface tension on short-wave perturbations, and the instability associated with intermediate wavenumbers for negative values of A{sub p}, which is characteristic of many hydroxylammonium nitrate-based liquid propellants over certain pressure ranges. In contrast, the pulsating hydrodynamic stability boundary is insensitive to gravitational and surface-tension effects, but is more sensitive to the effects of liquid viscosity since, for typical nonzero values of the latter, the pulsating boundary decreases to larger negative values of A{sub p} as k increases through O(1) values.

Margolis, S.B. [Sandia National Labs., Livermore, CA (United States). Combustion Research Facility



Adaptive smoothed particle hydrodynamics for high strain hydrodynamics with material strength  

Microsoft Academic Search

This paper presents the implementation of an adaptive smoothed particle hydrodynamics (ASPH) method for high strain Lagrangian\\u000a hydrodynamics with material strength. In ASPH, the isotropic kernel in the standard SPH is replaced with an anisotropic kernel\\u000a whose axes evolve automatically to follow the mean particle spacing as it varies in time, space, and direction around each\\u000a particle. Except for the

M. B. Liu; G. R. Liu; K. Y. Lam



Is hydrodynamic escape from Titan possible?  

NASA Astrophysics Data System (ADS)

When examining thermal atmospheric escape, usually either Jeans escape or hydrodynamic escape is considered. Jeans escape, where particles with velocities higher than the escape velocity can escape a planetary atmosphere, is usually considered, when particles in a collision-free region are examined. Hydrodynamic escape, on the other hand, presumes that the outflowing gas can be considered as a continuous, homogeneous medium where neither light, nor heavy particles can be discriminated from each other. Recently, Strobel (2009) applied a so-called 'slow hydrodynamic escape model', which describes cases intermediate between Jeans escape and hydrodynamic escape, for the nitrogen and methane molecules in Titan's upper atmosphere. This model requires an extended quasi-collisional region above the exobase where efficient energy transfer can presumably occur. In this study, we examine the collision probability of nitrogen and methane molecules with ambient atmospheric particles within Titan's exosphere using a modified Monte Carlo code introduced by Wurz and Lammer (2003), to analyze if the 'slow hydrodynamic escape model' is applicable to Titan's exosphere or not. Our results show that the collision probability of nitrogen and methane within Titan's exosphere decreases quickly with height above the exobase. Also, the probability of a nitrogen or a methane molecule to collide with another heavy molecule is far larger than the probability of a collision with a light particle, since in the region where nitrogen and methane are mainly present, the heavy molecules dominate the light molecules by a factor of 10-100. The results of our particle simulation do not confirm the existence of an extended quasi-collisional region above the exobase, where heavy, slow molecules can gain the escape velocity through collisions with light, fast particles.

Schaufelberger, A.; Wurz, P.; Lammer, H.; Kulikov, Yu. N.



Frontiers of Ergometry and Hydrodynamics in Aquatic Sports  

Microsoft Academic Search

DAL MONTE A., MIRRI G. and SARDELLA F. Frontiers of Ergometry and Hydrodynamics in Aquatic Sports. Kinesiology, Vol. 2, No. 1, pp. 69-74, 1997. The practice of swimming has existed for milleniums, but man has not developed an hydrodynamic form. For this reason many studies have been carried out to improve hydrodynamics of swimmers. These studies have underlined the positive



Wave Climatology in Coastal Maine for Aquaculture and Other Applications  

Microsoft Academic Search

Wind waves represent a significant hydrodynamic factor affecting many oceanographic studies such as sediment transport, design\\u000a of structures, etc. In coastal Maine, wave information is needed, among other applications, for aquaculture-related activities.\\u000a As few data sources exist, a question that confronts scientists pertains to the magnitudes of typical and extreme wave conditions\\u000a at various times. To address this, numerical modeling

Vijay G. Panchang; Chankwon Jeong; Dongcheng Li



Faraday waves in elongated superfluid fermionic clouds  

NASA Astrophysics Data System (ADS)

We use hydrodynamic equations to study the formation of Faraday waves in a superfluid Fermi gas at zero temperature confined in a strongly elongated cigar-shaped trap. First, we treat the role of the radial density profile in the limit of an infinite cylindrical geometry and analytically evaluate the wavelength of the Faraday pattern. The effect of the axial confinement is fully taken into account in the numerical solution of hydrodynamic equations, and shows that the infinite cylinder geometry provides a very good description of the phenomena.

Capuzzi, P.; Vignolo, P.



Modeling of hydrodynamic cavitation reactors based on orifice plates considering hydrodynamics and chemical reactions occurring in bubble  

Microsoft Academic Search

In the present work, a model has been developed for predicting the cavitational intensity in a hydrodynamic cavitation reactor based on the use of orifice plates considering the hydrodynamic conditions and the different chemical reactions taking place inside the cavity. The model is based on a set of ordinary differential equations and considers the bubble hydrodynamics and heat exchange including

Amit Sharma; Parag R. Gogate; Amit Mahulkar; Aniruddha B. Pandit



Effects of jet quenching on the hydrodynamical evolution of quark-gluon plasma.  


We study the effects of jet quenching on the hydrodynamical evolution of the quark-gluon plasma (QGP) fluid created in a heavy-ion collision. In jet quenching, a hard QCD parton, before fragmenting into a jet of hadrons, deposits a fraction of its energy in the medium, leading to suppressed production of high-pT hadrons. Assuming that the deposited energy quickly thermalizes, we simulate the subsequent hydrodynamic evolution of the QGP fluid. For partons moving at supersonic speed, vp>cs, and sufficiently large energy loss, a shock wave forms leading to conical flow. The PHENIX Collaboration recently suggested that observed structures in the azimuthal angle distribution might be caused by conical flow. We show here that, for phenomenologically acceptable values of parton energy loss, conical flow effects are too weak to explain these structures. PMID:17026164

Chaudhuri, A K; Heinz, Ulrich



Effects of Jet Quenching on the Hydrodynamical Evolution of Quark-Gluon Plasma  

SciTech Connect

We study the effects of jet quenching on the hydrodynamical evolution of the quark-gluon plasma (QGP) fluid created in a heavy-ion collision. In jet quenching, a hard QCD parton, before fragmenting into a jet of hadrons, deposits a fraction of its energy in the medium, leading to suppressed production of high-p{sub T} hadrons. Assuming that the deposited energy quickly thermalizes, we simulate the subsequent hydrodynamic evolution of the QGP fluid. For partons moving at supersonic speed, v{sub p}>c{sub s}, and sufficiently large energy loss, a shock wave forms leading to conical flow. The PHENIX Collaboration recently suggested that observed structures in the azimuthal angle distribution might be caused by conical flow. We show here that, for phenomenologically acceptable values of parton energy loss, conical flow effects are too weak to explain these structures.

Chaudhuri, A. K. [Variable Energy Cyclotron Centre, 1-AF, Bidhan Nagar, Kolkata-700 064 (India); Heinz, Ulrich [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)



Aeroacoustic power generated by multiple compact axisymmetric cavities: Effect of hydrodynamic interference on the sound production  

NASA Astrophysics Data System (ADS)

Aeroacoustic sound generation due to self-sustained oscillations by a series of compact axisymmetric cavities exposed to a grazing flow is studied both experimentally and numerically. The driving feedback is produced by the velocity fluctuations resulting from a coupling of vortex sheddings at the upstream cavity edges with acoustic standing waves in the coaxial pipe. When the cavities are separated sufficiently from each other, the whistling behavior of the complete system can be determined from the individual contribution of each cavity. When the cavities are placed close to each other there is a strong hydrodynamic interference between the cavities which affects both the peak amplitude attained during whistling and the corresponding Strouhal number. This hydrodynamic interference is captured successfully by the proposed numerical method.

Nakibo?lu, G.; Hirschberg, A.



Analysis of hydrodynamic phenomena in simulant experiments investigating cavity interactions following postulated vessel meltthrough  

SciTech Connect

An analysis of hydrodynamic phenomena in simulant experiments examining aspects of ex-vessel material interactions in a PWR reactor cavity following postulated core meltdown and localized breaching of the reactor vessel has been carried out. While previous analyses of the tests examined thresholds for the onset of sweepout of fluid from the cavity, the present analysis considers the progression of specific hydrodynamic phenomena involved in the dispersal process: crater formation due to gas jet impingement, radial wave motion and growth, entrainment and transport of liquid droplets, liquid layer formation due to droplet recombination, fluidization of liquid remaining in the cavity, removal of fluidized liquid droplets from the cavity, and the ultimate removal of the remaining liquid layer within the tunnel passageway. Phenomenological models which may be used to predict the phenomena are presented.

Sienicki, J.J.; Spencer, B.W.



Spin hydrodynamics in the S=(1)/(2) anisotropic Heisenberg chain  

NASA Astrophysics Data System (ADS)

We study the finite-temperature dynamical spin susceptibility of the one-dimensional (generalized) anisotropic Heisenberg model within the hydrodynamic regime of small wave vectors and frequencies. Numerical results are analyzed using the memory-function formalism with the central quantity being the spin-current decay rate ?(q,?). It is shown that in a generic nonintegrable model the decay rate is finite in the hydrodynamic limit, consistent with normal spin-diffusion modes. On the other hand, in the gapless integrable model within the XY regime of anisotropy ?<1 the behavior is anomalous with vanishing ?(q,?=0)?|q|, in agreement with dissipationless uniform transport. Furthermore, in the integrable system the finite-temperature q=0 dynamical conductivity ?(q=0,?) reveals besides the dissipationless component a regular part with vanishing ?reg(q=0,??0)?0.

Herbrych, J.; Steinigeweg, R.; Prelovšek, P.



Ion acoustic shock waves in degenerate plasmas  

SciTech Connect

Korteweg de Vries Burgers equation for negative ion degenerate dissipative plasma has been derived using reductive perturbation technique. The quantum hydrodynamic model is used to study the quantum ion acoustic shock waves. The effects of different parameters on quantum ion acoustic shock waves are studied. It is found that quantum parameter, electrons Fermi temperature, temperature of positive and negative ions, mass ratio of positive to negative ions, viscosity, and density ratio have significant impact on the shock wave structure in negative ion degenerate plasma.

Akhtar, N. [Theoretical Plasma Physics Division, PINSTECH, Nilore, Islamabad 44000 Pakistan (Pakistan); Hussain, S. [Theoretical Plasma Physics Division, PINSTECH, Nilore, Islamabad 44000 Pakistan (Pakistan); Department of Physics and Applied Mathematics, PIEAS, Nilore, Islamabad 44000 Pakistan (Pakistan)



Experiments on hydrodynamic transport in ultra-cold bose gasses  

NASA Astrophysics Data System (ADS)

At temperatures near the absolut zero, a gas, here atomic sodium vapour, with high enough density cannot be described as tiny balls moving around as in classical physics. Since the temperature is low, the atoms are so slow that the matterwave of each atom starts to extend over the size of the atom and even over the interatomic distance. Therefore, they start to interfere like waves. Quantum mechanics start to dominate the physics in this regime. Further, depending on the sort of atoms (bosons or fermions) the atoms prefer to be in the same state or avoid to be in the same state. In the case of bosons as in the thesis, if the temperature is lowered to sub micro Kelvin temperature, a new state of matter appears after a phase transition - a macroscopic, standing wave, the Bose-Einstein condensate. This leads to a new phenomena: superfluidity - frictionless flow, second sound, vorticity and coherent scattering effects to name a few. The atoms are trapped in a elongated trap as in most of the experiments in ultra cold gasses. Usually experiments are done in a regime where the atoms seldomly collide with each other while travelling from one end to the other end of the cloud. In this experiment, however, the atoms collide many times with each other when they oscillate in the trap. This means that the cloud is hydrodynamic and leads to a very different behaviour. Two different sound waves (first and second sound), heat conduction, and collisional dominated transport can be observed in this case. The fact that the gas is weakly interacting allows comparison with current theory. At very low temperatures as in the experiments described in the thesis, the Bose character strongly alters the collisions of the atoms. The outcome of the collision does not only depend on the colliding atoms, but also on the atoms near by in phase space. The experiments outlined in this thesis cover some aspects of physics involved. Vortices have been created and observed in the Bose-Einstein condensate that rested in a weak trap. Both sound modes first and second sound have been observed with slight local heating. In the regime considered, first sound, that has not been observed in a dilute Bose-Einstein condensate before, is mainly a modulation in local temperature and not density. In another experiment a particular effect is observed when the cloud is only axially hydrodynamic. When the trap is suddenly axially relaxed, the cloud creats a strip pattern that is in the radial direction and moving outward. The analysis of this experiment suggests that this is only the case when the cloud is indeed only axially hydrodynamic. The last chapter describs a spin drag experiment. In this experiment two spin species of atoms are prepared and on one of them a force is applied. Through collisions, the other species is dragged along. This effect is Bose enhanced at temperatures approaching the transition temperature to a Bose-Einstein condensate which is observed and matches recent theory.

Koller, S. B.



Hydrodynamic Object Recognition: When Multipoles Count  

NASA Astrophysics Data System (ADS)

The lateral-line system is a unique mechanosensory facility of aquatic animals that enables them not only to localize prey, predator, obstacles, and conspecifics, but also to recognize hydrodynamic objects. Here we present an explicit model explaining how aquatic animals such as fish can distinguish differently shaped submerged moving objects. Our model is based on the hydrodynamic multipole expansion and uses the unambiguous set of multipole components to identify the corresponding object. Furthermore, we show that within the natural range of one fish length the velocity field contains far more information than that due to a dipole. Finally, the model we present is easy to implement both neuronally and technically, and agrees well with available neuronal, physiological, and behavioral data on the lateral-line system.

Sichert, Andreas B.; Bamler, Robert; van Hemmen, J. Leo



Hydrodynamic Instability Test Problems in CRASH  

NASA Astrophysics Data System (ADS)

We present the results of hydrodynamic instability simulations using the current version of the CRASH code. In particular, we concentrate on the early-time behavior of Rayleigh-Taylor and Richtmyer-Meshkov instabilities as a necessary validation and verification step before exploring the behavior of Rayleigh-Taylor instabilities in laser experiments relevant to supernovae. We compare the quantitative growth rates calculated based on the extracted features of the test runs with the analytical and semi-analytical solutions, as well as with previous results with other hydrodynamic simulation packages. In addition to test runs replicating the parameters used in previous studies, we also conducted systematic surveys of slices of the parameter space where analytical solutions are available using different simulation resolutions where computational resources permitted. We will discuss any systematic errors discovered in the CRASH test runs and their plausible causes.

Chou, Chuan-Chih; Fryxell, Bruce; Myra, Eric; Drake, Paul



A hydrodynamically modified, abyssal isopod fauna  

NASA Astrophysics Data System (ADS)

At the High Energy Benthic Boundary Layer Experiment (HEBBLE) site (4820 m depth in the western North Atlantic) periods of strong currents and sediment erosion alternate with periods of weak flow and massive deposition. We investigated the impact of this atypical hydrodynamic environment on the isopod fauna by testing for a difference in composition between the HEBBLE site and a tranquil location, the Deep Ocean Mining Environmental Study (DOMES) site A ( ca. 5000 m) in the equatorial Pacific. Epifaunal isopods were significantly less abundant at the HEBBLE site than at the comparison site despite significantly greater total isopod numbers at the HEBBLE site. We suggest that the hydrodynamic regime puts epifaunal isopods at risk, making them rare at the HEBBLE site.

Thistle, David; Wilson, George D. F.



Stochastic Hydrodynamic Synchronization in Rotating Energy Landscapes  

NASA Astrophysics Data System (ADS)

Hydrodynamic synchronization provides a general mechanism for the spontaneous emergence of coherent beating states in independently driven mesoscopic oscillators. A complete physical picture of those phenomena is of definite importance to the understanding of biological cooperative motions of cilia and flagella. Moreover, it can potentially suggest novel routes to exploit synchronization in technological applications of soft matter. We demonstrate that driving colloidal particles in rotating energy landscapes results in a strong tendency towards synchronization, favoring states where all beads rotate in phase. The resulting dynamics can be described in terms of activated jumps with transition rates that are strongly affected by hydrodynamics leading to an increased probability and lifetime of the synchronous states. Using holographic optical tweezers we quantitatively verify our predictions in a variety of spatial configurations of rotors.

Koumakis, N.; Di Leonardo, R.



Stochastic hydrodynamic synchronization in rotating energy landscapes.  


Hydrodynamic synchronization provides a general mechanism for the spontaneous emergence of coherent beating states in independently driven mesoscopic oscillators. A complete physical picture of those phenomena is of definite importance to the understanding of biological cooperative motions of cilia and flagella. Moreover, it can potentially suggest novel routes to exploit synchronization in technological applications of soft matter. We demonstrate that driving colloidal particles in rotating energy landscapes results in a strong tendency towards synchronization, favoring states where all beads rotate in phase. The resulting dynamics can be described in terms of activated jumps with transition rates that are strongly affected by hydrodynamics leading to an increased probability and lifetime of the synchronous states. Using holographic optical tweezers we quantitatively verify our predictions in a variety of spatial configurations of rotors. PMID:23679732

Koumakis, N; Di Leonardo, R



Hydrodynamics of fluidized beds using image analysis  

NASA Astrophysics Data System (ADS)

Fluidized beds, originally developed in the 1920s, have become the reactors of choice in several industrial processes. For example, coal combustion within fluidized bed systems has improved efficiency over other combustion technologies. There are however, several issues related to this technology that remain to be resolved. Three of the more significant issues are the dynamics of equal-density particle segregation and the influence of horizontal tube banks on both bubble hydrodynamics and solids mixing. These topics were investigated through the use of video image analysis of thin transparent fluidized beds. Experimental data, obtained from bubbling beds with and without simulated horizontal heat exchanger tubes, were used to evaluate existing hydrodynamic models and derive new semi-empirical models.

Hull, Ashley Samuel


Hydrodynamic Interactions between Two Swimming Bacteria  

PubMed Central

This article evaluates the hydrodynamic interactions between two swimming bacteria precisely. We assume that each bacterium is force free and torque free, with a Stokes flow field around it. The geometry of each bacterium is modeled as a spherical or spheroidal body with a single helical flagellum. The movements of two interacting bacteria in an infinite fluid otherwise at rest are computed using a boundary element method, and the trajectories of the two interacting bacteria and the stresslet are investigated. The results show that as the two bacteria approach each other, they change their orientations considerably in the near field. The bacteria always avoided each other; no stable pairwise swimming motion was observed in this study. The effects of the hydrodynamic interactions between two bacteria on the rheology and diffusivity of a semidilute bacterial suspension are discussed.

Ishikawa, T.; Sekiya, G.; Imai, Y.; Yamaguchi, T.



MTBE degradation by hydrodynamic induced cavitation.  


Hydrodynamic induced cavitation generates imploding cavitation bubbles which can lead to degradation or even mineralisation of water constituents without addition of any chemicals. This technology overcomes the problems of ultrasound irradiation by the local production of a cavitation cloud close to the sonotrodes. Hydrodynamic cavitation can be stabilised downstream of the nozzle depending on the ambient pressure conditions. If the pressure is kept low, the imploding cavitation bubbles generate new cavities, analogous to a chain reaction, and elevate the radical synthesis inside the apparatus. During the pilot tests MTBE and ETBE were degraded and complete mineralisation started at a time delay of app. 30 min. The specific energy demand for MTBE degradation lies in the range of app. 200 Wh/ppm in the investigated concentration range of about 30 ppm. PMID:20453332

Schmid, A



Davidson Laboratory: Marine Hydrodynamics & Coastal Engineering  

NSDL National Science Digital Library

Davidson Laboratory, a hydrodynamic and ocean engineering research center, is part of the Civil, Environmental and Ocean Engineering department at the Stevens Institute of Technology. This laboratory is focused on marine craft and testing as well as coastal engineering, marine environmental engineering, and underwater acoustics. Ongoing research projects in areas such as marine hydrodynamics, coastal engineering, acoustics, turbulence, and computational fluid dynamics are explained in greater detail in the Departments section. A highlight of the Davidson Laboratory site is the Coastal Monitoring Network section, where users have the opportunity to view and read about the coastal conditions (atmosphere pressure, air temperature, wind speed, wind direction, and wind gust) at locations such as Avalon, New Jersey. The image and data on this page are updated on a regular basis. Although some parts of this site are under construction, the currently available information makes it worth a visit.


Hydrodynamics and relativistic heavy-ion collisions  

SciTech Connect

The hydrodynamic model as applied to heavy-ion collisions is introduced. The Euler equations are derived for both relativistic and non-relativistic domains. The effects of imposing relativistic invariance are discussed. Concepts proposed to analyze 4..pi.. exclusive reactions are introduced. Selected theoretical results are presented for reactions in which the projectile has a laboratory energy of 400 MeV per nucleon to 100 GeV per nucleon.

Strottman, D.



Holography and hydrodynamics: diffusion on stretched horizons  

Microsoft Academic Search

We show that long-time, long-distance fluctuations of plane-symmetric horizons exhibit universal hydrodynamic behavior. By considering classical fluctuations around black-brane backgrounds, we find both diffusive and shear modes. The diffusion constant and the shear viscosity are given by simple formulas, in terms of metric components. For a given metric, the answers can be interpreted as corresponding kinetic coefficients in the holographically

Pavel Kovtun; Dam T. Son; Andrei O. Starinets



5-dimensional special relativistic hydrodynamics and cosmology  

Microsoft Academic Search

5-dimensional special relativity can be considered as the 5-dimensional extension of Carmeli's cosmological special relativity, as well as the flat specialization of 5-d brane world theory. To this framework we add a 5-dimensional perfect fluid stress-energy tensor, and unify the equations of perfect hydrodynamics in a single 5-dimensional tensor conservation law. This picture permits to interpret particle production phenomena as

Gianluca Gemelli; L. S. B. Pascal; V. P. Nenni



Compatible Poisson brackets of hydrodynamic type  

NASA Astrophysics Data System (ADS)

Some general properties of compatible Poisson brackets of hydrodynamic type are discussed, in particular: (a) an invariant differential-geometric criterion of the compatibility based on the Nijenhuis tensor which is slightly different from those existing in the literature; (b) the Lax pair with a spectral parameter governing compatible Poisson brackets in the diagonalizable case; (c) the connection of this problem with the class of surfaces in Euclidean space which possess non-trivial deformations preserving the Weingarten operator.

Ferapontov, E. V.



Experimental investigation of orbitally shaken bioreactor hydrodynamics  

NASA Astrophysics Data System (ADS)

The growing interest in the use of orbitally shaken bioreactors for mammalian cells cultivation raises challenging hydrodynamic issues. Optimizations of mixing and oxygenation, as well as similarity relations between different culture scales are still lacking. In the present study, we investigated the relation between the shape of the free surface, the mixing process and the velocity fields, using specific image processing of high speed visualization and Laser Doppler velocimetry. Moreover, similarity parameters were identified for scale-up purposes.

Reclari, Martino; Dreyer, Matthieu; Farhat, Mohamed



Flow hydrodynamics in tidal marsh canopies  

Microsoft Academic Search

The transport of particulate and dissolved matter on the surface of coastal marshes is controlled by the hydrodynamic characteristics of over-marsh flows. High-frequency (5 Hz) in situ measurements of flow speed were collected in Spartina alternijlora, Juncus roemerianus, and Di:-tichlis spicata canopies using hot-film anemometry sensor arrays. These data indicate that mean flow speed, turbulence intensity, and the shape of




Wave Motion  

NSDL National Science Digital Library

This site from Carl Nave at Georgia State University presents a discussion of wave motion. The site explains the velocity of idealized ocean waves and details the measurement of large waves aboard the USS Ramapo.

Carl R. (Rod) Nave; University, Georgia S.