Nowak, J; Wiekhorst, F; Trahms, L; Odenbach, S
2014-04-30
Suspensions of magnetic nanoparticles have received increasing interest in the biomedical field. While these ferrofluids are already used for magnetic resonance imaging, emerging research on cancer treatment focuses, for example, on employing the particles as drug carriers, or using them in magnetic hyperthermia to destroy diseased cells by heating of the particles. To enable safe and effective applications, an understanding of the flow behaviour of the ferrofluids is essential. Regarding the applications mentioned above, in which flow phenomena play an important role, viscosity under the influence of an external magnetic field is of special interest. In this respect, the magnetoviscous effect (MVE) leading to an increasing viscosity if an external magnetic field of a certain strength is applied, is well-known for singlecore ferrofluids used in the engineering context. In the biomedical context, multicore ferrofluids are preferred in order to avoid remanence magnetization and to enable a deposition of the particles by the organism without complications. This study focuses on a comparison of the MVE for three ferrofluids whose composition is identical except in relation to their hydrodynamic diameter and core composition-one of the fluids contains singlecore particles, while the other two feature multicore particles. This enables confident conclusions about the influence of those parameters on flow behaviour under the influence of a magnetic field. The strong effects found for two of the fluids should be taken into account, both in future investigations and in the potential use of such ferrofluids, as well as in manufacturing, in relation to the optimization of flow behaviour. PMID:24721897
NASA Astrophysics Data System (ADS)
Bush, John W. M.
2015-01-01
Yves Couder, Emmanuel Fort, and coworkers recently discovered that a millimetric droplet sustained on the surface of a vibrating fluid bath may self-propel through a resonant interaction with its own wave field. This article reviews experimental evidence indicating that the walking droplets exhibit certain features previously thought to be exclusive to the microscopic, quantum realm. It then reviews theoretical descriptions of this hydrodynamic pilot-wave system that yield insight into the origins of its quantum-like behavior. Quantization arises from the dynamic constraint imposed on the droplet by its pilot-wave field, and multimodal statistics appear to be a feature of chaotic pilot-wave dynamics. I attempt to assess the potential and limitations of this hydrodynamic system as a quantum analog. This fluid system is compared to quantum pilot-wave theories, shown to be markedly different from Bohmian mechanics and more closely related to de Broglie's original conception of quantum dynamics, his double-solution theory, and its relatively recent extensions through researchers in stochastic electrodynamics.
Falcon, Eric
are observed on the ferrofluid surface. A ferrofluid is a stable suspension of nanometric magnetic particles magnetic fluid layer surrounding a current-carrying metallic tube. According to the ratio between the magnetic and capillary forces, both elevation and depression solitary waves are observed with profiles
Hydrodynamics of chains in ferrofluid-based magnetorheological fluids under rotating magnetic field.
Patel, Rajesh; Chudasama, Bhupendra
2009-07-01
Ferrofluid-based magnetorheological (MR) fluid is prepared by dispersing micron-size magnetic spheres in a ferrofluid. We report here the mechanism of chain formation in ferrofluid based MR fluid, which is quite different from conventional MR fluid. Some of the nanomagnetic particles of ferrofluid filled inside the microcavities are formed due to association of large particles, and some of them are attached at the end of large particles. Under rotating magnetic field, fragmentation of a single chain into three parts is observed. Two of them are chains of micron-size magnetic particles which are suspended in a ferrofluid, and the third one is the chain of nanomagnetic particles of ferrofluid, which may be the connecting bridge between the two chains of larger magnetic particles. The rupture of a single chain provides evidence for the presence of nanomagnetic particles within the magnetic field-induced chainlike structure in this bidispersed MR fluid. PMID:19658750
NASA Technical Reports Server (NTRS)
1993-01-01
A new Ferrofluidics exclusion seal promises improvement in controlling "fugitive emissions" -vapors that escape into the atmosphere from petroleum refining and chemical processing facilities. These are primarily volatile organic compounds, and their emissions are highly regulated by the EPA. The ferrofluid system consists of a primary mechanical seal working in tandem with a secondary seal. Ferrofluids are magnetic liquids - fluids in which microscopic metal particles have been suspended, allowing the liquid to be controlled by a magnetic force. The concept was developed in the early years of the Space program, but never used. Two Avco scientists, however, saw commercial potential in ferrofluids and formed a company. Among exclusion seal commercial applications are rotary feedthrough seals, hydrodynamic bearings and fluids for home and automotive loudspeakers. Ferrofluidics has subsidiaries throughout the world.
Bush, John W. M.
Yves Couder, Emmanuel Fort, and coworkers recently discovered that a millimetric droplet sustained on the surface of a vibrating fluid bath may self-propel through a resonant interaction with its own wave field. This article ...
Wave Turbulence on the Surface of a Ferrofluid in a Magnetic Field Francois Boyer and Eric Falcon*
Falcon, Eric
instability [10], the labyrinthine instabil- ity, magnetic levitation [11]. In contrast with usual liquidsWave Turbulence on the Surface of a Ferrofluid in a Magnetic Field Franc¸ois Boyer and Eric Falcon normal magnetic field. We show that magnetic surface waves arise only above a critical field. The power
Chiral Alfvén Wave in Anomalous Hydrodynamics.
Yamamoto, Naoki
2015-10-01
We study the hydrodynamic regime of chiral plasmas at high temperature. We find a new type of gapless collective excitation induced by chiral effects in an external magnetic field. This is a transverse wave, and it is present even in incompressible fluids, unlike the chiral magnetic and chiral vortical waves. The velocity is proportional to the coefficient of the gravitational anomaly. We briefly discuss the possible relevance of this "chiral Alfvén wave" in physical systems. PMID:26551804
Chiral Alfvén Wave in Anomalous Hydrodynamics
NASA Astrophysics Data System (ADS)
Yamamoto, Naoki
2015-10-01
We study the hydrodynamic regime of chiral plasmas at high temperature. We find a new type of gapless collective excitation induced by chiral effects in an external magnetic field. This is a transverse wave, and it is present even in incompressible fluids, unlike the chiral magnetic and chiral vortical waves. The velocity is proportional to the coefficient of the gravitational anomaly. We briefly discuss the possible relevance of this "chiral Alfvén wave" in physical systems.
NASA Astrophysics Data System (ADS)
Odenbach, Professor Stefan
2006-09-01
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
Anderson, Mary Elizabeth
2011-10-21
Wave attenuation by vegetation is a highly dynamic process and its quantification is important for accurately understanding and predicting coastal hydrodynamics. However, the influence of vegetation on wave dissipation is not yet fully established...
Nonlinear Generalized Hydrodynamic Wave Equations in Strongly Coupled Dusty Plasmas
Veeresha, B. M.; Sen, A.; Kaw, P. K.
2008-09-07
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.
Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas
Lushnikov, Pavel
of modern optical fiber communication systems. A key technological tool for development of ultrafast highNonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas Alexander O. Korotkevich and Pavel M. Lushnikov Department of Mathematics and Statistics, University of New Mexico, Albuquerque, NM
Symposium: Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas
Lushnikov, Pavel
) is a basis for the description of modem optical fiber communication systems. A key technological tool-managed optical fiber is described by NLS with periodic variation of dispersion along an optical line whichSymposium: Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas Ildar R. Gabitov
Hydrodynamic Waves in an Anomalous Charged Fluid
Navid Abbasi; Ali Davody; Zahra Rezaei
2015-10-11
We study the collective excitations in a relativistic fluid with an anomalous $U(1)$ current. In $3+1$ dimensions, in addition to ordinary sound modes we find two propagating modes in presence of an external magnetic field. The first one propagates with a velocity proportional to the coefficient of gauge-gravitational anomaly; this is in fact the Chiral Alfv\\'en wave recently found in arXiv:1505.05444. The other wave whose velocity depends on both chiral anomaly and the gauge gravitational anomaly coefficients, is actually a chiral magnetic wave (CMW). We also show that the Chiral Alfv\\'en mode is split into two chiral dissipative waves when taking into account the effect of dissipation in the fluid. In 1+1 dimensions we find only one propagating mode associated with the anomalous effects. We explicitly compute the velocity of this wave and show that in contrast to $3+1$ dimensions, no external field is needed for this mode to propagate.
Hydrodynamic Waves in an Anomalous Charged Fluid
Abbasi, Navid; Rezaei, Zahra
2015-01-01
We study the collective excitations in a relativistic fluid with an anomalous conserved charge. In $3+1$ dimensions, in addition to two ordinary sound modes we find two propagating modes in presence of an external magnetic field: one with a velocity proportional to the coefficient of gauge-gravitational anomaly coefficient and the other with a velocity which depends on both chiral anomaly and the gauge gravitational anomaly coefficients. While the former is the Chiral Alfv\\'en wave recently found in arXiv:1505.05444, the latter is a new type of collective excitations originated from the density fluctuations. We refer to these modes as the Type-M and Type-D chiral Alfv\\'en waves respectively. We show that the Type-M Chiral Alfv\\'en mode is split into two chiral Alfv\\'en modes when taking into account the effect of dissipation processes in the fluid. In 1+1 dimensions we find only one propagating mode associated with the anomalous effects. We explicitly compute the velocity of this wave and show that in contras...
Ferrofluid and cellulolytic fungi
NASA Astrophysics Data System (ADS)
Manoliu, Al.; Oprica, Lacramioara; Creanga, Dorina-Emilia
2005-03-01
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.
Propagation of elastic waves in granular solid hydrodynamics
NASA Astrophysics Data System (ADS)
Mayer, Michael; Liu, Mario
2010-10-01
The anisotropic stress-dependent velocity of elastic waves in glass beads—as observed by Khidas and Jia [Phys. Rev. E 81, 021303 (2010)]10.1103/PhysRevE.81.021303—is shown to be well accounted for by “granular solid hydrodynamics,” a broad-range macroscopic theory of granular behavior. As the theory makes no reference to fabric anisotropy, the influence of which on sound is in doubt.
Negative magnetophoresis in diluted ferrofluid flow.
Hejazian, Majid; Nguyen, Nam-Trung
2015-07-21
We report magnetic manipulation of non-magnetic particles suspended in diluted ferrofluid. Diamagnetic particles were introduced into a circular chamber to study the extent of their deflection under the effect of a non-uniform magnetic field of a permanent magnet. Since ferrofluid is a paramagnetic medium, it also experiences a bulk magnetic force that in turn induces a secondary flow opposing the main hydrodynamic flow. Sheath flow rate, particle size, and magnetic field strength were varied to examine this complex behaviour. The combined effect of negative magnetophoresis and magnetically induced secondary flow leads to various operation regimes, which can potentially find applications in separation, trapping and mixing of diamagnetic particles such as cells in a microfluidic system. PMID:26054840
Hydrodynamic modes of a holographic p-wave superfluid
NASA Astrophysics Data System (ADS)
Arias, Raúl E.; Landea, Ignacio Salazar
2014-11-01
In this work we analyze the hydrodynamics of a p- wave superfluid on its strongly coupled regime by considering its holographic description. We obtain the poles of the retarded Green function through the computation of the quasi-normal modes of the dual AdS black hole background finding diffusive, pseudo-diffusive and sound modes. For the sound modes we compute the speed of sound and its attenuation as function of the temperature. For the diffusive and pseudo-diffusive modes we find that they acquire a non-zero real part at certain finite momentum.
Hydrodynamic electron transport and nonlinear waves in graphene
NASA Astrophysics Data System (ADS)
Svintsov, D.; Vyurkov, V.; Ryzhii, V.; Otsuji, T.
2013-12-01
We derive the system of hydrodynamic equations governing the collective motion of massless fermions in graphene. The obtained equations demonstrate the lack of Galilean and Lorentz invariance and contain a variety of nonlinear terms due to the quasirelativistic nature of carriers. Using these equations, we show the possibility of soliton formation in an electron plasma of gated graphene. The quasirelativistic effects set an upper limit for soliton amplitude, which marks graphene out of conventional semiconductors. The mentioned noninvariance of the equations is revealed in spectra of plasma waves in the presence of steady flow, which no longer obey the Doppler shift. The feasibility of plasma-wave excitation by direct current in graphene channels is also discussed.
The dynamics analysis of a ferrofluid shock absorber
NASA Astrophysics Data System (ADS)
Yao, Jie; Chang, Jianjun; Li, Decai; Yang, Xiaolong
2016-03-01
The paper presents a shock absorber using three magnets as the inertial mass. Movement of the inertial mass inside a cylindrical body filled with ferrofluid will lead to a viscous dissipation of the oscillating system energy. The influence of a dumbbell-like ferrofluid structure on the energy dissipation is considered and the magnetic restoring force is investigated by experiment and theoretical calculation. A theoretical model of the hydrodynamics and energy dissipation processes is developed, which includes the geometrical characteristics of the body, the fluid viscosity, and the external magnetic field. The theory predicts the experimental results well under some condition. The shock absorber can be used in spacecraft technology.
Hydrodynamic forces and surface topography: Centimeter-scale spatial variation in wave forces
Denny, Mark
that protection from hydrodynamic forces is not a certain consequence of a rugose substratum, suggesting. On the rugose rock surfaces of wave-swept shores, interactions between substratum topography and wave
Hydrodynamical simulations of penetrative convection and generation of internal gravity waves
Stêpieñ, Kazimierz
Hydrodynamical simulations of penetrative convection and generation of internal gravity waves M investigate the generation of internal gravity waves in the stable region below a convective layer by means interiors that can be affected by internal gravity waves. Considered so far are: mixing of chemical elements
Three-dimensional wave-coupled hydrodynamics modeling in South San Francisco Bay
NASA Astrophysics Data System (ADS)
Chou, Yi-Ju; Holleman, Rusty C.; Fringer, Oliver B.; Stacey, Mark T.; Monismith, Stephen G.; Koseff, Jeffrey R.
2015-12-01
In this paper, we present a numerical model to simulate wind waves and hydrodynamics in the estuary. We employ the unstructured-grid SUNTANS model for hydrodynamics, and within this model we implement a spectral wave model which solves for transport of wave action density with the finite-volume formulation. Hydrodynamics is coupled to the wave field through the radiation stress. Based on the unstructured grid and finite-volume formulation of SUNTANS, the radiation stress is implemented in a way that directly calculates the divergence of transport of the wave-induced orbital velocity. A coupled hydrodynamics-wave simulation of San Francisco Bay is then performed. Through the input of wind forcing that is obtained from the reconstructed wind field, the model is capable of predicting wave heights that are in good agreement with the field measurements. We examine the importance of modeling sea bed dissipation in muddy shallow water environments by using a bottom friction model and a bed mud model with different mud layer thicknesses. Moreover, currents driven by wave shoaling and dissipation are investigated in the presence of abrupt bathymetric change. We find that spatially varying wave heights induced by spatially heterogeneous bottom mud dissipation produce wave-driven currents that are stronger than those induced by wave shoaling and can be of the same order as the tidal currents in shallow water.
Hydrodynamic forces on larvae affect their settlement on coral reefs in turbulent, wave-driven flow
Koehl, Mimi
Hydrodynamic forces on larvae affect their settlement on coral reefs in turbulent, wave- driven coral reefs as the system to address this question. Laser Doppler anemometry was utilized within sitting at different locations within a reef of the branching coral Porites compressa. Comparing wave
Energy harvesting via ferrofluidic induction
NASA Astrophysics Data System (ADS)
Monroe, J. G.; Vasquez, Erick S.; Aspin, Zachary S.; Fairley, John D.; Walters, Keisha B.; Berg, Matthew J.; Thompson, Scott M.
2015-05-01
A series of experiments were conducted to investigate and characterize the concept of ferrofluidic induction - a process for generating electrical power via cyclic oscillation of ferrofluid (iron-based nanofluid) through a solenoid. Experimental parameters include: number of bias magnets, magnet spacing, solenoid core, fluid pulse frequency and ferrofluid-particle diameter. A peristaltic pump was used to cyclically drive two aqueous ferrofluids, consisting of 7-10 nm iron-oxide particles and commercially-available hydroxyl-coated magnetic beads (~800 nm), respectively. The solutions were pulsated at 3, 6, and 10 Hz through 3.2 mm internal diameter Tygon tubing. A 1000 turn copper-wire solenoid was placed around the tube 45 cm away from the pump. The experimental results indicate that the ferrofluid is capable of inducing a maximum electric potential of approximately +/- 20 ?V across the solenoid during its cyclic passage. As the frequency of the pulsating flow increased, the ferro-nanoparticle diameter increased, or the bias magnet separation decreased, the induced voltage increased. The type of solenoid core material (copper or plastic) did not have a discernible effect on induction. These results demonstrate the feasibility of ferrofluidic induction and provide insight into its dependence on fluid/flow parameters. Such fluidic/magneto-coupling can be exploited for energy harvesting and/or conversion system design for a variety of applications.
Morphology and hydrodynamics of wave-cut gullies
NASA Astrophysics Data System (ADS)
Priestas, A. M.
2010-12-01
Wave-cut gullies are triangular incisions formed by the concentration of wave energy on a vegetated marsh scarp. Wave gullies are usually equispaced and incise the marsh and enlarge in time both in length and width. Here we provide a high resolution survey of ten wave gullies formed along the chenier plain of the Rockefeller Wildlife Refuge, Louisiana, USA. Our measurements capture the morphologic character, evolution, and erosion rates of wave-cut gullies over a two month period. We further relate changes in morphology to geometric factors and shoreline retreat. Finally, we present the first analysis of wave data measured by acoustic doppler velocity profilers to show how propagating waves are transformed inside a wave-cut gully in order to describe the processes leading to their formation. Results show that waves of intermediate period (4-6 sec) yield very strong swash currents that hit the gully head detaching marsh substrate and triggering headward erosion. A conceptual model of wave gully evolution is finally presented as an explanation for this non-uniform, episodic shoreline erosion. Snapshots of a wave propagating in wave gully. The convergent geometry of wave gullies concentrates wave energy and incites rapid headward erosion.
NASA Astrophysics Data System (ADS)
Rezzolla, Luciano; Zanotti, Olindo
2013-09-01
1. A brief review of general relativity; 2. A kinetic-theory description of fluids; 3. Relativistic perfect fluids; 4. Linear and nonlinear hydrodynamic waves; 5. Reaction fronts: detonations and deflagrations; 6. Relativistic non-perfect fluids; 7. Formulation of the Einstein-Euler equations; 8. Numerical relativistic hydrodynamics: finite difference methods; 9. Numerical relativistic hydrodynamics: HRSC methods; 10. Numerical relativistic hydrodynamics: high order methods; 11. Relativistic hydrodynamics of non-selfgravitating fluids; 12. Relativistic hydrodynamics of selfgravitating fluids.
Hydrodynamic analysis of elastic floating collars in random waves
NASA Astrophysics Data System (ADS)
Bai, Xiao-dong; Zhao, Yun-peng; Dong, Guo-hai; Li, Yu-cheng
2015-06-01
As the main load-bearing component of fish cages, the floating collar supports the whole cage and undergoes large deformations. In this paper, a mathematical method is developed to study the motions and elastic deformations of elastic floating collars in random waves. The irregular wave is simulated by the random phase method and the statistical approach and Fourier transfer are applied to analyze the elastic response in both time and frequency domains. The governing equations of motions are established by Newton's second law, and the governing equations of deformations are obtained based on curved beam theory and modal superposition method. In order to validate the numerical model of the floating collar attacked by random waves, a series of physical model tests are conducted. Good relationship between numerical simulation and experimental observations is obtained. The numerical results indicate that the transfer function of out-of-plane and in-plane deformations increase with the increasing of wave frequency. In the frequency range between 0.6 Hz and 1.1 Hz, a linear relationship exists between the wave elevations and the deformations. The average phase difference between the wave elevation and out-of-plane deformation is 60° with waves leading and the phase between the wave elevation and in-plane deformation is 10° with waves lagging. In addition, the effect of fish net on the elastic response is analyzed. The results suggest that the deformation of the floating collar with fish net is a little larger than that without net.
Morphology and hydrodynamics of wave-cut gullies
NASA Astrophysics Data System (ADS)
Priestas, A. M.; Fagherazzi, S.
2011-08-01
Wave-cut gullies are sub-triangular incisions common along deteriorating marsh scarps. Wave gullies may be equispaced to quasi-equispaced and enlarge in time, incising the marsh boundary. A high resolution survey is provided for ten wave gullies formed along the chenier plain of the Rockefeller Wildlife Refuge, Louisiana, USA. The measurements capture the morphologic character, evolution, and erosion rates of wave-cut gullies over a two month period. The data relate changes in morphology to geometric factors and shoreline retreat. Finally, the first analysis of wave data measured by acoustic Doppler velocity profilers is presented to show how propagating waves are transformed inside a wave-cut gully in order to describe the processes leading to their formation. Results show that waves of intermediate period (4-6 s) yield very strong swash currents that hit the gully head, detaching marsh substrate and triggering headward erosion. A conceptual model of wave gully evolution is presented as an explanation for this non-uniform, episodic shoreline erosion.
Algebraic Traveling Wave Solutions of a Non-local Hydrodynamic-type Model
NASA Astrophysics Data System (ADS)
Chen, Aiyong; Zhu, Wenjing; Qiao, Zhijun; Huang, Wentao
2014-12-01
In this paper we consider the algebraic traveling wave solutions of a non-local hydrodynamic-type model. It is shown that algebraic traveling wave solutions exist if and only if an associated first order ordinary differential system has invariant algebraic curve. The dynamical behavior of the associated ordinary differential system is analyzed. Phase portraits of the associated ordinary differential system is provided under various parameter conditions. Moreover, we classify algebraic traveling wave solutions of the model. Some explicit formulas of smooth solitary wave and cuspon solutions are obtained.
Wake II model for hydrodynamic forces on marine pipelines for the wave plus current case
Ramirez Sabag, Said
1999-01-01
The concept of the Wake II model for the determination of the hydrodynamic forces on marine pipelines is extended to include the wave plus current case. There are two main differences between the Wake II and the traditional model that uses Morison...
Goldstein, Raymond E.
and help explain the generation and regulation of flagellar motion [10], their complexity prevents a simpleHydrodynamic Synchronization and Metachronal Waves on the Surface of the Colonial Alga Volvox fast, robust synchronization in a manner essentially independent of boundary conditions, and offers
NO EFFECT OF HYDRODYNAMIC SHOCK WAVE ON PROTEIN FUNCTIONALITY OF BEEF MUSCLE
Technology Transfer Automated Retrieval System (TEKTRAN)
The protein functionality of meat proteins after treatment with hydrodynamic shock wave was determined. Frankfurters (cooked to 71 deg C) were evaluated for cooking yield, CIE L*a*b*, nitrosylhemochrome, Texture Profile Analysis (hardness, cohesiveness), and stress and strain (torsion testing). Comp...
Kinetic models for chemotaxis: Hydrodynamic limits and the back-of-the-wave problem
Arnold, Anton
Kinetic models for chemotaxis: Hydrodynamic limits and the back-of-the-wave problem Y. Dolak and C. Schmeiser June 10, 2003 Abstract We study kinetic models for amoebal chemotaxis, incorporating the ability perform numerical experiments. 1 Introduction Chemotaxis can be de#12;ned as the biased migration of cells
A Dynamic Analysis of Hydrodynamic Wave Journal Bearings
NASA Technical Reports Server (NTRS)
Ene, Nicoleta M.; Dimofte, Florin; Keith, Theo G.
2008-01-01
The purpose of this paper is to study the dynamic behavior of a three-wave journal bearing using a transient approach. The transient analysis permits the determination of the rotor behavior after the fractional frequency whirl appears. The journal trajectory is determined by solving a set of nonlinear equations of motion using the Runge-Katta method. The fluid film forces are computed by integrating the transient Reynolds equation at each time step location of the shaft with respect to the bearing. Because of the large values of the rotational speeds, turbulent effects were included in the computations. The influence of the temperature on the viscosity was also considered. Numerical results were compared to experimenta1 results obtained at the NASA Glenn Research Center. Comparisons of the theoretical results with experimental data were found to be in good agreement. The numerical and experimental results showed that the fluid film of a three-wave journal bearing having a diameter of 30 mm, a length of 27 mm, and a wave amplitude ratio greater than 0.15 is stable even at rotational speeds of 60,000 RPM. For lower wave amplitude ratios, the threshold speed at which the fluid film becomes unstable depends on the wave amplitude and on the supply pocket pressure. Even if the fluid film is unstable, the wave bearing maintains the whirl orbit inside the bearing clearance.
A review of hydrodynamic investigations into arrays of ocean wave energy converters
De Chowdhury, S; Sanchez, A Madrigal; Fleming, A; Winship, B; Illesinghe, S; Toffoli, A; Babanin, A; Penesis, I; Manasseh, R
2015-01-01
Theoretical, numerical and experimental studies on arrays of ocean wave energy converter are reviewed. The importance of extracting wave power via an array as opposed to individual wave-power machines has long been established. There is ongoing interest in implementing key technologies at commercial scale owing to the recent acceleration in demand for renewable energy. To date, several reviews have been published on the science and technology of harnessing ocean-wave power. However, there have been few reviews of the extensive literature on ocean wave-power arrays. Research into the hydrodynamic modelling of ocean wave-power arrays is analysed. Where ever possible, comparisons are drawn with physical scaled experiments. Some critical knowledge gaps have been found. Specific emphasis has been paid on understanding how the modelling and scaled experiments are likely to be complementary to each other.
Paul D. Lasky; Mark F. Bennett; Andrew Melatos
2013-02-25
Hydrodynamic turbulence driven by crust-core differential rotation imposes a fundamental noise floor on gravitational wave observations of neutron stars. The gravitational wave emission peaks at the Kolmogorov decoherence frequency which, for reasonable values of the crust-core shear, \\Delta\\Omega, occurs near the most sensitive part of the frequency band for ground-based, long-baseline interferometers. We calculate the energy density spectrum of the stochastic gravitational wave background from a cosmological population of turbulent neutron stars generalising previous calculations for individual sources. The spectrum resembles a piecewise power law, \\Omega_{gw}(\
On the consistency of the drag between air and water in meteorological, hydrodynamic and wave models
NASA Astrophysics Data System (ADS)
van Nieuwkoop, Joana; Baas, Peter; Caires, Sofia; Groeneweg, Jacco
2015-07-01
For the design, assessment and flood control of water defences, hydraulic loads in terms of water levels and wave conditions are required and often obtained from numerical models. For these hydraulic loads to be reliable, accurate atmospheric forcing is required. Waves and surges are typically forced by surface stress. However, in most cases, the input for these models consists of 10-m wind velocities that are internally converted to surface stress by applying a particular drag relation. This procedure generally leads to inconsistencies, since the hydrodynamic, wave and atmospheric models often apply different drag relations. By means of a case study, we explored the consequences of this inconsistency in the drag formulation for a North Sea storm wave and surge hindcast. This was done by forcing the hydrodynamic and wave models using both the 10-m wind velocity and the surface stress fields computed by the atmospheric model. Our study results show significant differences between the wave parameter values and water levels computed with surface stress input and 10-m wind velocity input. Our goal is not to assess different drag parameterizations but to raise awareness for this issue and to plea for the use of a consistent drag relation in meteorological and hydrodynamic/wave models. The consistent use of one drag formulation facilitates the identification of problems and the eventual improvement of the drag formulation. Furthermore, we suggest using the so-called pseudo-wind, which is a translation of the surface stress to the 10-m wind speed using a reference drag relation.
Hydrodynamic sensing and behavior by oyster larvae in turbulence and waves.
Fuchs, Heidi L; Gerbi, Gregory P; Hunter, Elias J; Christman, Adam J; Diez, F Javier
2015-05-01
Hydrodynamic signals from turbulence and waves may provide marine invertebrate larvae with behavioral cues that affect the pathways and energetic costs of larval delivery to adult habitats. Oysters (Crassostrea virginica) live in sheltered estuaries with strong turbulence and small waves, but their larvae can be transported into coastal waters with large waves. These contrasting environments have different ranges of hydrodynamic signals, because turbulence generally produces higher spatial velocity gradients, whereas waves can produce higher temporal velocity gradients. To understand how physical processes affect oyster larval behavior, transport and energetics, we exposed larvae to different combinations of turbulence and waves in flow tanks with (1) wavy turbulence, (2) a seiche and (3) rectilinear accelerations. We quantified behavioral responses of individual larvae to local instantaneous flows using two-phase, infrared particle-image velocimetry. Both high dissipation rates and high wave-generated accelerations induced most larvae to swim faster upward. High dissipation rates also induced some rapid, active dives, whereas high accelerations induced only weak active dives. In both turbulence and waves, faster swimming and active diving were achieved through an increase in propulsive force and power output that would carry a high energetic cost. Swimming costs could be offset if larvae reaching surface waters had a higher probability of being transported shoreward by Stokes drift, whereas diving costs could be offset by enhanced settlement or predator avoidance. These complex behaviors suggest that larvae integrate multiple hydrodynamic signals to manage dispersal tradeoffs, spending more energy to raise the probability of successful transport to suitable locations. PMID:25788721
Mader, C.L.; Kershner, J.D.
1985-01-01
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.
NASA Astrophysics Data System (ADS)
Degtyarev, A.; Gankevich, I.
2015-05-01
Determining the impact of external excitations on a dynamic marine object such as ship hull in a seaway is the main goal of simulations. Now such simulations is most often based on approximate mathematical models that use results of the theory of small amplitude waves. The most complicated software for marine objects behavior simulation LAMP IV (Large amplitude motion program) uses numerical solution of traditional hydrodynamic problem without often used approximations but on the basis of theory of small amplitude waves. For efficiency reasons these simulations can be based on autoregressive model to generate real wave surface. Such a surface possesses all the hydrodynamic characteristics of sea waves, preserves dispersion relation and also shows superior performance compared to other wind wave models. Naturally, the known surface can be used to compute velocity field and in turn to determine pressures in any point under sea surface. The resulting computational algorithm can be used to determine pressures without use of theory of small-amplitude waves.
Equilibrium structure of ferrofluid aggregates
Yoon, Mina; Tomanek, David
2010-01-01
We study the equilibrium structure of large but finite aggregates of magnetic dipoles, representing a colloidal suspension of magnetite particles in a ferrofluid. With increasing system size, the structural motif evolves from chains and rings to multi-chain and multi-ring assemblies. Very large systems form single- and multi-wall coils, tubes and scrolls. These structural changes result from a competition between various energy terms, which can be approximated analytically within a continuum model. We also study the effect of external parameters such as magnetic field on the relative stability of these structures. Our results may give insight into experimental data obtained during solidification of ferrofluid aggregates at temperatures where thermal fluctuations become negligible in comparison to inter-particle interactions. These data may also help to experimentally control the aggregation of magnetic particles.
Pu, Jaan Hui; Shao, Songdong
2012-01-01
This research paper presents an incompressible smoothed particle hydrodynamics (ISPH) technique to investigate a regular wave overtopping on the coastal structure of different types. The SPH method is a mesh-free particle modeling approach that can efficiently treat the large deformation of free surface. The incompressible SPH approach employs a true hydrodynamic formulation to solve the fluid pressure that has less pressure fluctuations. The generation of flow turbulence during the wave breaking and overtopping is modeled by a subparticle scale (SPS) turbulence model. Here the ISPH model is used to investigate the wave overtopping over a coastal structure with and without the porous material. The computations disclosed the features of flow velocity, turbulence, and pressure distributions for different structure types and indicated that the existence of a layer of porous material can effectively reduce the wave impact pressure and overtopping rate. The proposed numerical model is expected to provide a promising practical tool to investigate the complicated wave-structure interactions. PMID:22919291
NASA Astrophysics Data System (ADS)
Freytag, B.
2015-08-01
In the Sun, low-amplitude small-scale acoustic waves are just detectable in the photosphere and start to become dynamically relevant only in the lower chromosphere. The generation of these waves by non-stationary convective flows can be studied in detail by local 3-D radiation-hydrodynamics simulations. Using this technique for global models of AGB stars reveals roughly similar phenomena but on a larger scale and with much higher amplitude. Convection cells spanning a significant fraction of the entire surface produce strong waves that cause a network of smaller shocks in the inner photosphere and occasional global shocks, travelling outward in large arcs. Material falling back interacts with the surface convection cells. A new generation of 3-D RHD simulations of these layers with CO5BOLD is presented and analyzed with particular attention given to acoustic waves and shock fronts.
Ferrofluid separator for nonferrous scrap separation
NASA Technical Reports Server (NTRS)
Kaiser, R.; Mir, L.
1974-01-01
Behavior of nonmagnetic objects within separator is essentially function of density, and independent of size or shape of objects. Results show close agreement between density of object and apparent density of ferrofluid required to float it. Results also demonstrate that very high separation rates are achievable by ferrofluid sink-float separation.
Dispensing nano-pico droplets of ferrofluids
NASA Astrophysics Data System (ADS)
Irajizad, Peyman; Farokhnia, Nazanin; Ghasemi, Hadi
2015-11-01
Dispensing miniature volumes of a ferrofluid is of fundamental and practical importance for diverse applications ranging from biomedical devices, optics, and self-assembly of materials. Current dispensing systems are based on microfluidics flow-focusing approaches or acoustic actuation requiring complicated structures. A simple method is presented to continuously dispense the miniature droplets from a ferrofluid reservoir. Once a jet of the ferrofluid is subjected to a constrained flux through a membrane and an inhomogeneous magnetic field, the jet experiences a curvature-driven instability and transforms to a droplet. Ferrofluid droplets in the range of 0.1-1000 nl are dispensed with tunable dispensing frequencies. A model is developed that predicts the dispensed volume of the ferrofluid droplets with an excellent agreement with the measurements.
Transition to turbulence in Taylor-Couette ferrofluidic flow
Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng
2015-01-01
It is known that in classical fluids turbulence typically occurs at high Reynolds numbers. But can turbulence occur at low Reynolds numbers? Here we investigate the transition to turbulence in the classic Taylor-Couette system in which the rotating fluids are manufactured ferrofluids with magnetized nanoparticles embedded in liquid carriers. We find that, in the presence of a magnetic field transverse to the symmetry axis of the system, turbulence can occur at Reynolds numbers that are at least one order of magnitude smaller than those in conventional fluids. This is established by extensive computational ferrohydrodynamics through a detailed investigation of transitions in the flow structure, and characterization of behaviors of physical quantities such as the energy, the wave number, and the angular momentum through the bifurcations. A finding is that, as the magnetic field is increased, onset of turbulence can be determined accurately and reliably. Our results imply that experimental investigation of turbulence may be feasible by using ferrofluids. Our study of transition to and evolution of turbulence in the Taylor-Couette ferrofluidic flow system provides insights into the challenging problem of turbulence control. PMID:26065572
A Stability Analysis for a Hydrodynamic Three-Wave Journal Bearing
NASA Technical Reports Server (NTRS)
Ene, Nicoleta M.; Dimofte, Florin; Keith, Theo G., Jr.
2007-01-01
The influence of the wave amplitude and oil supply pressure on the dynamic behavior of a hydrodynamic three-wave journal bearing is presented. Both, a transient and a small perturbation technique, were used to predict the threshold to fractional frequency whirl (FFW). In addition, the behavior of the rotor after FFW appeared was determined from the transient analysis. The turbulent effects were also included in the computations. Bearings having a diameter of 30 mm, a length of 27.5 mm, and a clearance of 35 microns were analyzed. Numerical results were compared to experimental results obtained at the NASA GRC. Numerical and experimental results showed that the above-mentioned wave bearing with a wave amplitude ratio of 0.305 operates stably at rotational speeds up to 60,000 rpm, regardless of the oil supply pressure. For smaller wave amplitude ratios, a threshold of stability was found. It was observed that the threshold of stability for lower wave amplitude strongly depends on the oil supply pressure and on the wave amplitude. When the FFW occurs, the journal center maintains its trajectory inside the bearing clearance and therefore the rotor can be run safely without damaging the bearing surfaces.
Behdadfar, Behshid; Kermanpur, Ahmad; Sadeghi-Aliabadi, Hojjat; Morales, Maria del Puerto; Mozaffari, Morteza
2012-03-15
Monodispersed aqueous ferrofluids of iron oxide nanoparticle were synthesized by hydrothermal-reduction route. They were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy and dynamic light scattering. The results showed that certain concentrations of citric acid (CA) are required to obtain only magnetic iron oxides with mean particle sizes around 8 nm. CA acts as a modulator and reducing agent in iron oxide formation which controls nanoparticle size. The XRD, magnetic and heating measurements showed that the temperature and time of hydrothermal reaction can affect the magnetic properties of obtained ferrofluids. The synthesized ferrofluids were stable at pH 7. Their mean hydrodynamic size was around 80 nm with polydispersity index (PDI) of 0.158. The calculated intrinsic loss power (ILP) was 9.4 nHm{sup 2}/kg. So this clean and cheap route is an efficient way to synthesize high ILP aqueous ferrofluids applicable in magnetic hyperthermia. - Graphical abstract: Monodispersed aqueous ferrofluids of iron oxide nanoparticles were synthesized by hydrothermal-reduction method with citric acid as reductant which is an efficient way to synthesize aqueous ferrofluids applicable in magnetic hyperthermia. Highlights: Black-Right-Pointing-Pointer Aqueous iron oxide ferrofluids were synthesized by hydrothermal-reduction route. Black-Right-Pointing-Pointer Citric acid acted as reducing agent and surfactant in the route. Black-Right-Pointing-Pointer This is a facile, low energy and environmental friendly route. Black-Right-Pointing-Pointer The aqueous iron oxide ferrofluids were monodispersed and stable at pH of 7. Black-Right-Pointing-Pointer The calculated intrinsic loss power of the synthesized ferrofluids was very high.
Hydrodynamics of the Oscillating Wave Surge Converter in the open ocean
Renzi, E
2012-01-01
A potential flow model is derived for a large flap-type oscillating wave energy converter in the open ocean. Application of the Green's integral theorem in the fluid domain yields a hypersingular integral equation for the jump in potential across the flap. Solution is found via a series expansion in terms of the Chebyshev polynomials of the second kind and even order. Several relationships are then derived between the hydrodynamic parameters of the system. Comparison is made between the behaviour of the converter in the open ocean and in a channel. The degree of accuracy of wave tank experiments aiming at reproducing the performance of the device in the open ocean is quantified. Parametric analysis of the system is then undertaken. It is shown that increasing the flap width has the beneficial effect of broadening the bandwidth of the capture factor curve. This phenomenon can be exploited in random seas to achieve high levels of efficiency.
Metachronal waves in the flagellar beating of Volvox and their hydrodynamic origin.
Brumley, Douglas R; Polin, Marco; Pedley, Timothy J; Goldstein, Raymond E
2015-07-01
Groups of eukaryotic cilia and flagella are capable of coordinating their beating over large scales, routinely exhibiting collective dynamics in the form of metachronal waves. The origin of this behavior--possibly influenced by both mechanical interactions and direct biological regulation--is poorly understood, in large part due to a lack of quantitative experimental studies. Here we characterize in detail flagellar coordination on the surface of the multicellular alga Volvox carteri, an emerging model organism for flagellar dynamics. Our studies reveal for the first time that the average metachronal coordination observed is punctuated by periodic phase defects during which synchrony is partial and limited to specific groups of cells. A minimal model of hydrodynamically coupled oscillators can reproduce semi-quantitatively the characteristics of the average metachronal dynamics, and the emergence of defects. We systematically study the model's behaviour by assessing the effect of changing intrinsic rotor characteristics, including oscillator stiffness and the nature of their internal driving force, as well as their geometric properties and spatial arrangement. Our results suggest that metachronal coordination follows from deformations in the oscillators' limit cycles induced by hydrodynamic stresses, and that defects result from sufficiently steep local biases in the oscillators' intrinsic frequencies. Additionally, we find that random variations in the intrinsic rotor frequencies increase the robustness of the average properties of the emergent metachronal waves. PMID:26040592
Metachronal waves in the flagellar beating of $Volvox$ and their hydrodynamic origin
Douglas R. Brumley; Marco Polin; Timothy J. Pedley; Raymond E. Goldstein
2015-05-10
Groups of eukaryotic cilia and flagella are capable of coordinating their beating over large scales, routinely exhibiting collective dynamics in the form of metachronal waves. The origin of this behaviour -- possibly influenced by both mechanical interactions and direct biological regulation -- is poorly understood, in large part due to lack of quantitative experimental studies. Here we characterise in detail flagellar coordination on the surface of the multicellular alga $Volvox~carteri$, an emerging model organism for flagellar dynamics. Our studies reveal for the first time that the average metachronal coordination observed is punctuated by periodic phase defects during which synchrony is partial and limited to specific groups of cells. A minimal model of hydrodynamically coupled oscillators can reproduce semi-quantitatively the characteristics of the average metachronal dynamics, and the emergence of defects. We systematically study the model's behaviour by assessing the effect of changing intrinsic rotor characteristics, including oscillator stiffness and the nature of their internal driving force, as well as their geometric properties and spatial arrangement. Our results suggest that metachronal coordination follows from deformations in the oscillators' limit cycles induced by hydrodynamic stresses, and that defects result from sufficiently steep local biases in the oscillators' intrinsic frequencies. Additionally, we find that random variations in the intrinsic rotor frequencies increase the robustness of the average properties of the emergent metachronal waves.
Metachronal waves in the flagellar beating of Volvox and their hydrodynamic origin
Brumley, Douglas R.; Polin, Marco; Pedley, Timothy J.; Goldstein, Raymond E.
2015-01-01
Groups of eukaryotic cilia and flagella are capable of coordinating their beating over large scales, routinely exhibiting collective dynamics in the form of metachronal waves. The origin of this behaviour—possibly influenced by both mechanical interactions and direct biological regulation—is poorly understood, in large part due to a lack of quantitative experimental studies. Here we characterize in detail flagellar coordination on the surface of the multicellular alga Volvox carteri, an emerging model organism for flagellar dynamics. Our studies reveal for the first time that the average metachronal coordination observed is punctuated by periodic phase defects during which synchrony is partial and limited to specific groups of cells. A minimal model of hydrodynamically coupled oscillators can reproduce semi-quantitatively the characteristics of the average metachronal dynamics, and the emergence of defects. We systematically study the model's behaviour by assessing the effect of changing intrinsic rotor characteristics, including oscillator stiffness and the nature of their internal driving force, as well as their geometric properties and spatial arrangement. Our results suggest that metachronal coordination follows from deformations in the oscillators' limit cycles induced by hydrodynamic stresses, and that defects result from sufficiently steep local biases in the oscillators' intrinsic frequencies. Additionally, we find that random variations in the intrinsic rotor frequencies increase the robustness of the average properties of the emergent metachronal waves. PMID:26040592
Controlling ferrofluid permeability across the blood-brain barrier model
NASA Astrophysics Data System (ADS)
Shi, Di; Sun, Linlin; Mi, Gujie; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J.
2014-02-01
In the present study, an in vitro blood-brain barrier model was developed using murine brain endothelioma cells (b.End3 cells). Confirmation of the blood-brain barrier model was completed by examining the permeability of FITC-Dextran at increasing exposure times up to 96 h in serum-free medium and comparing such values with values from the literature. After such confirmation, the permeability of five novel ferrofluid (FF) nanoparticle samples, GGB (ferrofluids synthesized using glycine, glutamic acid and BSA), GGC (glycine, glutamic acid and collagen), GGP (glycine, glutamic acid and PVA), BPC (BSA, PEG and collagen) and CPB (collagen, PVA and BSA), was determined using this blood-brain barrier model. All of the five FF samples were characterized by zeta potential to determine their charge as well as TEM and dynamic light scattering for determining their hydrodynamic diameter. Results showed that FF coated with collagen passed more easily through the blood-brain barrier than FF coated with glycine and glutamic acid based on an increase of 4.5% in permeability. Through such experiments, diverse magnetic nanomaterials (such as FF) were identified for: (1) MRI use since they were less permeable to penetrate the blood-brain barrier to avoid neural tissue toxicity (e.g. GGB) or (2) brain drug delivery since they were more permeable to the blood-brain barrier (e.g. CPB).
Viscoelastic properties of ferrofluids D. N. Chirikov,1
Fedotov, Sergei
magnetic field. The first theories of the magnetorheological effects in ferrofluids 3,4 deal with very. 614 . Both of them can induce strong magnetorheological effects in ferrofluids 8 . Unfortunately
NASA Astrophysics Data System (ADS)
Griv, Evgeny; Wang, Hsiang-Hsu
2014-07-01
Most rapidly and differentially rotating disk galaxies, in which the sound speed (thermal velocity dispersion) is smaller than the orbital velocity, display graceful spiral patterns. Yet, over almost 240 yr after their discovery in M51 by Charles Messier, we still do not fully understand how they originate. In this first paper of a series, the dynamical behavior of a rotating galactic disk is examined numerically by a high-order Godunov hydrodynamic code. The code is implemented to simulate a two-dimensional flow driven by an internal Jeans gravitational instability in a nonresonant wave-“fluid” interaction in an infinitesimally thin disk composed of stars or gas clouds. A goal of this work is to explore the local and linear regimes of density wave formation, employed by Lin, Shu, Yuan and many others in connection with the problem of spiral pattern of rotationally supported galaxies, by means of computer-generated models and to compare those numerical results with the generalized fluid-dynamical wave theory. The focus is on a statistical analysis of time-evolution of density wave structures seen in the simulations. The leading role of collective processes in the formation of both the circular and spiral density waves (“heavy sound”) is emphasized. The main new result is that the disk evolution in the initial, quasilinear stage of the instability in our global simulations is fairly well described using the local approximation of the generalized wave theory. Certain applications of the simulation to actual gas-rich spiral galaxies are also explored.
NASA Astrophysics Data System (ADS)
Lasky, Paul D.; Bennett, Mark F.; Melatos, Andrew
2013-03-01
Hydrodynamic turbulence driven by crust-core differential rotation imposes a fundamental noise floor on gravitational wave observations of neutron stars. The gravitational wave emission peaks at the Kolmogorov decoherence frequency which, for reasonable values of the crust-core shear, ??, occurs near the most sensitive part of the frequency band for ground-based, long-baseline interferometers. We calculate the energy density spectrum of the stochastic gravitational wave background from a cosmological population of turbulent neutron stars generalizing previous calculations for individual sources. The spectrum resembles a piecewise power law, ?gw(?)=????, with ?=-1 and 7 above and below the decoherence frequency respectively, and its normalization scales as ???(??)7. Nondetection of a stochastic signal by Initial LIGO implies an upper limit on ?? and hence by implication on the internal relaxation time scale for the crust and core to come into corotation, ?d=??/??, where ?? is the observed electromagnetic spin-down rate, with ?d?107yr for accreting millisecond pulsars and ?d?105yr for radio-loud pulsars. Target limits on ?d are also estimated for future detectors, namely Advanced LIGO and the Einstein Telescope, and are found to be astrophysically interesting.
NASA Astrophysics Data System (ADS)
Marques, Wilson, Jr.; Jacinta Soares, Ana; Pandolfi Bianchi, Miriam; Kremer, Gilberto M.
2015-06-01
A shock wave structure problem, like the one which can be formulated for the planar detonation wave, is analyzed here for a binary mixture of ideal gases undergoing the symmetric reaction {{A}1}+{{A}1}\\rightleftharpoons {{A}2}+{{A}2}. The problem is studied at the hydrodynamic Euler limit of a kinetic model of the reactive Boltzmann equation. The chemical rate law is deduced in this frame with a second-order reaction rate, in a chemical regime such that the gas flow is not far away from the chemical equilibrium. The caloric and the thermal equations of state for the specific internal energy and temperature are employed to close the system of balance laws. With respect to other approaches known in the kinetic literature for detonation problems with a reversible reaction, this paper aims to improve some aspects of the wave solution. Within the mathematical analysis of the detonation model, the equation of the equilibrium Hugoniot curve of the final states is explicitly derived for the first time and used to define the correct location of the equilibrium Chapman-Jouguet point in the Hugoniot diagram. The parametric space is widened to investigate the response of the detonation solution to the activation energy of the chemical reaction. Finally, the mathematical formulation of the linear stability problem is given for the wave detonation structure via a normal-mode approach, when bidimensional disturbances perturb the steady solution. The stability equations with their boundary conditions and the radiation condition of the considered model are explicitly derived for small transversal deviations of the shock wave location. The paper shows how a second-order chemical kinetics description, derived at the microscopic level, and an analytic deduction of the equilibrium Hugoniot curve, lead to an accurate picture of the steady detonation with reversible reaction, as well as to a proper bidimensional linear stability analysis.
From AdS/CFT correspondence to hydrodynamics. II. Sound waves
G. Policastro; D. T. Son; A. O. Starinets
2005-07-26
As a non-trivial check of the non-supersymmetric gauge/gravity duality, we use a near-extremal black brane background to compute the retarded Green's functions of the stress-energy tensor in N=4 super-Yang-Mills (SYM) theory at finite temperature. For the long-distance, low-frequency modes of the diagonal components of the stress-energy tensor, hydrodynamics predicts the existence of a pole in the correlators corresponding to propagation of sound waves in the N=4 SYM plasma. The retarded Green's functions obtained from gravity do indeed exhibit this pole, with the correct values for the sound speed and the rate of attenuation.
Wave-driven Hydrodynamics for Different Reef Geometries and Roughness Scenarios
NASA Astrophysics Data System (ADS)
Franklin, G. L.; Marino-Tapia, I.; Torres-Freyermuth, A.
2013-05-01
In fringing reef systems where a shallow lagoon is present behind the reef crest, wave breaking appears to dominate circulation, controlling numerous key processes such as the transport and dispersion of larvae, nutrients and sediments. Despite their importance, there is a need for more detailed knowledge on the hydrodynamic processes that take place within the surf zone of these systems and the effects different combinations of geometries and roughness have on them. The present study focuses on the use of two-dimensional (2DV) numerical model simulations and data obtained during a field campaign in Puerto Morelos, Quintana Roo, Mexico to better understand the detailed surf zone processes that occur over a fringing reef. The model used is Cornell Breaking Wave and Structures (COBRAS), which solves Reynolds-Averaged Navier-Stokes (RANS) equations. Reef geometries implemented in the model include a reef flat and two different reef crests. The effect of roughness on wave setup, radiation stress, mean flows, and cross-shore spectral evolution for the model results was studied using different roughness coefficients (Nikuradse) and a bathymetric profile obtained in the field using the bottom track option of an Acoustic Doppler Current Profiler. Field data were also analysed for the configuration and roughness of Puerto Morelos. Model results reveal that for all profiles wave setup increased significantly (~22%) with increasing bed roughness, in agreement with previous findings for sandy beaches.For all wave heights and periods studied, increasing roughness also affected spectral wave evolution across the reef, with a significant reduction in energy, particularly at infragravity frequencies. The presence of a reef crest in the profile resulted in differences in behaviour at infragravity frequencies. For example, preliminary results suggest that there is a shift towards higher frequencies as waves progress into the lagoon when a crest is present, something that does not appear to occur over the reef flat. Time-averaged velocities exhibited a dominant onshore flow due to waves at the surface, as is generally reported for coral reefs. Model results also suggest the presence of offshore velocities, which were slightly greater over the reef flat compared to the reef crest. Maximum offshore velocities appear to be more localised in the case of the reef flat whereas they extended over a larger area in the case of the reef crest. In all cases, increased roughness resulted in reduced velocities. These results are important since they concern processes that affect the circulation within the lagoon, which has implications in terms of the lagoon's residence time and hence heat dispersion and exposure to pollutants.
Use of ferrofluids in machining of metals
NASA Astrophysics Data System (ADS)
Podgorkov, V. V.
1985-03-01
Ferrofluids controlled by an external magnetic field are suitable as lubricants for moving metal machining parts. Empirical relations of the form M sub c = kDt sub bs sup av sup c were established for the unit cutting torque M sub c as function of the drill diameter, the depth of hole t, the feed rate s, and the cutting rate v when holes in Al3V aluminum alloy, TsAM10-5 zinc alloy, VT1 titanium alloy, or 12Cr18Ni10Ti stainless are cut with a drill of R6M5 high-speed steel using a fixture made of nonmagnetic stainless and a ferrofluid based on MVP mineral tool oil as lubricant. Values of the coefficient and the exponents were determined by the Student significance test and Fisher adequacy test. It is found that ferrofluid as lubricant is more effective in machining of nonmagnetic materials.
Magnetoviscous effect in a maghemite ferrofluid.
Ghasemi, E; Mirhabibi, A; Edrissi, M
2011-06-01
An iron oxide ferrofluid with mean particle size of 10.6 nm was synthesized by co-precipitation. The nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, electron energy loss spectroscopy, and dynamic light scattering. The magnetorheological properties of ferrofluid were investigated using a rotating rheometer. The effect of magnetic field on the aggregation of magnetic nanoparticles and rheological behavior were investigated. Moreover the effects of concentration and particle size on the magnetoviscousity of ferrofluid were studied. The results showed that the maghemite is the major magnetic phase. The magnetoviscous effect leads to phase separation at high magnetic fields which is dependent to the concentration. It was shown that the smaller particle sizes which are not contributed in magnetoviscous effect can contribute at higher magnetic fields. PMID:21770177
Smolyaninov, Igor I; Smolyaninov, Alexei I
2014-01-01
Cobalt nanoparticle-based ferrofluid in the presence of external magnetic field forms a self-assembled hyperbolic metamaterial. Wave equation describing propagation of extraordinary light inside the ferrofluid exhibits 2+1 dimensional Lorentz symmetry. The role of time in the corresponding effective 3D Minkowski spacetime is played by the spatial coordinate directed along the periodic nanoparticle chains aligned by the magnetic field. Here we present a microscopic study of point, linear and volume defects of the nanoparticle chain structure and demonstrate that they may exhibit strong similarities with such Minkowski spacetime defects as magnetic monopoles, cosmic strings and the recently proposed spacetime cloaks. Experimental observations of such defects are described.
Dynamics of Ferrofluidic Drops Impacting Superhydrophobic Surfaces
Bolleddula, D A; Alliseda, A; Bhosale, P; Berg, J C
2010-01-01
This is a fluid dynamics video illustrating the impact of ferrofluidic droplets on surfaces of variable wettability. Surfaces studied include mica, teflon, and superhydrophobic. A magnet is placed beneath each surface, which modifies the behavior of the ferrofluid by applying additional downward force apart from gravity resulting in reduced droplet size and increased droplet velocity. For the superhydrophobic droplet a jetting phenomena is shown which only occurs in a limited range of impact speeds, higher than observed before, followed by amplified oscillation due to magnetic field as the drop stabilizes on the surface.
Magnetization and susceptibility of polydisperse ferrofluids
I. Szalai; S. Nagy; S. Dietrich
2013-07-17
On the basis of the mean spherical approximation of multicomponent dipolar hard sphere mixtures an analytical expression is proposed for the magnetic field dependence of the magnetization of size polydisperse ferrofluids. The polydispersity of the particle diameter is described by the gamma distribution function. Canonical ensemble Monte Carlo simulations have been performed in order to test these theoretical results for the initial susceptibility and the magnetization. The results for the magnetic properties of the polydisperse systems turn out to be in quantitative agreement with our present simulation data. In addition, we find good agreement between our theory and experimental data for magnetite-based ferrofluids.
NASA Astrophysics Data System (ADS)
Chen, Jia-Lin; Hsu, Tian-Jian; Shi, Fengyan; Raubenheimer, Britt; Elgar, Steve
2015-06-01
The interactions between waves, tidal currents, and bathymetry near New River Inlet, NC, USA are investigated to understand the effects on the resulting hydrodynamics and sediment transport. A quasi-3-D nearshore community model, NearCoM-TVD, is used in this integrated observational and modeling study. The model is validated with observations of waves and currents at 30 locations, including in a recently dredged navigation channel and a shallower channel, and on the ebb tidal delta, for a range of flow and offshore wave conditions during May 2012. In the channels, model skills for flow velocity and wave height are high. Near the ebb tidal delta, the model reproduces the observed rapid onshore (offshore) decay of wave heights (current velocities). Model results reveal that this sharp transition coincides with the location of the breaker zone over the ebb tidal delta, which is modulated by semidiurnal tides and by wave intensity. The modulation of wave heights is primarily owing to depth changes rather than direct wave-current interaction. The modeled tidally averaged residual flow patterns show that waves play an important role in generating vortices and landward-directed currents near the inlet entrance. Numerical experiments suggest that these flow patterns are associated with the channel-shoal bathymetry near the inlet, similar to the generation of rip currents. Consistent with other inlet studies, model results suggest that tidal currents drive sediment fluxes in the channels, but that sediment fluxes on the ebb tidal delta are driven primarily by waves.
Passive Magnetic Bearing With Ferrofluid Stabilization
NASA Technical Reports Server (NTRS)
Jansen, Ralph; DiRusso, Eliseo
1996-01-01
A new class of magnetic bearings is shown to exist analytically and is demonstrated experimentally. The class of magnetic bearings utilize a ferrofluid/solid magnet interaction to stabilize the axial degree of freedom of a permanent magnet radial bearing. Twenty six permanent magnet bearing designs and twenty two ferrofluid stabilizer designs are evaluated. Two types of radial bearing designs are tested to determine their force and stiffness utilizing two methods. The first method is based on the use of frequency measurements to determine stiffness by utilizing an analytical model. The second method consisted of loading the system and measuring displacement in order to measure stiffness. Two ferrofluid stabilizers are tested and force displacement curves are measured. Two experimental test fixtures are designed and constructed in order to conduct the stiffness testing. Polynomial models of the data are generated and used to design the bearing prototype. The prototype was constructed and tested and shown to be stable. Further testing shows the possibility of using this technology for vibration isolation. The project successfully demonstrated the viability of the passive magnetic bearing with ferrofluid stabilization both experimentally and analytically.
NASA Astrophysics Data System (ADS)
Zablotsky, Dmitry; Blums, Elmars
2011-08-01
In this paper, we consider a concentration grating of magnetic nanoparticles optically induced by thermodiffusion in a layer of ferrofluid in the presence of the external homogeneous magnetic field. The applied field is directed along the concentration gradient and leads to the appearance of the internal nonhomogeneous demagnetizing fields. When the system reaches equilibrium, the optical pumping is switched off, and the grating is allowed to relax. We carry out a stability analysis using the Galerkin approach and numerical simulations of the full system of equations to determine the growth rates and the mode amplitudes of the hydrodynamic and concentration perturbations during the relaxation stage.
Floating and flying ferrofluid bridges induced by external magnetic fields
NASA Astrophysics Data System (ADS)
Ma, Rongchao; Zhou, Yixin; Liu, Jing
2015-04-01
A ferrofluid is a mixture that exhibits both magnetism and fluidity. This merit enables the ferrofluid to be used in a wide variety of areas. Here we show that a floating ferrofluid bridge can be induced between two separated boards under a balanced external magnetic field generated by two magnets, while a flying ferrofluid bridge can be induced under an unbalanced external magnetic field generated by only one magnet. The mechanisms of the ferrofluid bridges were discussed and the corresponding mathematical equations were also established to describe the interacting magnetic force between the ferro particles inside the ferrofluid. This work answered a basic question that, except for the well-known floating water bridges that are related to electricity, one can also build up a liquid bridge that is related to magnetism.
A Novel Implantable Glaucoma Valve Using Ferrofluid
Paschalis, Eleftherios I.; Chodosh, James; Sperling, Ralph A.; Salvador-Culla, Borja; Dohlman, Claes
2013-01-01
Purpose To present a novel design of an implantable glaucoma valve based on ferrofluidic nanoparticles and to compare it with a well-established FDA approved valve. Setting Massachusetts Eye & Ear Infirmary, Boston, USA. Methods A glaucoma valve was designed using soft lithography techniques utilizing a water-immiscible magnetic fluid (ferrofluid) as a pressure-sensitive barrier to aqueous flow. Two rare earth micro magnets were used to calibrate the opening and closing pressure. In-vitro flow measurements were performed to characterize the valve and to compare it to Ahmed™ glaucoma valve. The reliability and predictability of the new valve was verified by pressure/flow measurements over a period of three months and X-ray diffraction (XRD) analysis over a period of eight weeks. In vivo assessment was performed in three rabbits. Results In the in vitro experiments, the opening and closing pressures of the valve were 10 and 7 mmHg, respectively. The measured flow/pressure response was linearly proportional and reproducible over a period of three months (1.8 µl/min at 12 mmHg; 4.3 µl/min at 16 mmHg; 7.6 µl/min at 21 mmHg). X-ray diffraction analysis did not show oxidization of the ferrofluid when exposed to water or air. Preliminary in vivo results suggest that the valve is biocompatible and can control the intraocular pressure in rabbits. Conclusions The proposed valve utilizes ferrofluid as passive, tunable constriction element to provide highly predictable opening and closing pressures while maintaining ocular tone. The ferrofluid maintained its magnetic properties in the aqueous environment and provided linear flow to pressure response. Our in-vitro tests showed reliable and reproducible results over a study period of three months. Preliminary in-vivo results were very promising and currently more thorough investigation of this device is underway. PMID:23840691
Colloids on the frontier of ferrofluids. Rheological properties.
López-López, Modesto T; Gómez-Ramírez, Ana; Rodríguez-Arco, Laura; Durán, Juan D G; Iskakova, Larisa; Zubarev, Andrey
2012-04-17
This paper is devoted to the steady-state rheological properties of two new kinds of ferrofluids. One of these was constituted by CoNi nanospheres of 24 nm in diameter, whereas the other by CoNi nanofibers of 56 nm in length and 6.6 nm in width. These ferrofluids were subjected to shear rate ramps under the presence of magnetic fields of different intensity, and the corresponding shear stress values were measured. From the obtained rheograms (shear stress vs shear rate curves) the values of both the static and the dynamic yield stresses were obtained as a function of the magnetic field. The magnetoviscous effect was also obtained as a function of both the shear rate and the magnetic field. The experimental results demonstrate that upon magnetic field application these new ferrofluids develop yield stresses and magnetoviscous effects much greater than those of conventional ferrofluids, based on nanospheres of approximately 10 nm in diameter. Besides some expected differences, such as the stronger magnetorheological effect in the case of ferrofluids based on nanofibers, some intriguing differences are found between the rheological behaviors of nanofiber ferrofluids and nanosphere ferrofluid. First, upon field application the rheograms of nanofiber ferrofluids present N-shaped dependence of the shear stress on the shear rate. The decreasing part of the rheograms takes place at low shear rate. These regions of negative differential viscosity, and therefore, unstable flow is not observed in the case of nanosphere ferrofluids. The second intriguing difference concerns the curvature of the yield stress vs magnetic field curves. This curvature is negative in the case of nanosphere ferrofluid, giving rise to saturation of the yield stress at medium field, as expected. However, in the case of nanofiber ferrofluid this curvature is positive, which means a faster increase of the yield stress with the magnetic field the higher the magnitude of the latter. These interesting differences may be due to the existence of strong interparticle solid friction in the case of nanofiber ferrofluids. Finally, theoretical models for the static yield stress of the ferrofluids were developed. These models consider that upon field application the ferrofluid nanoparticles are condensed in drops of dense phase. These drops tend to be aligned along the field direction, opposing the flow of the ferrofluids and being responsible for the static quasielastic deformation and the yield-stress phenomena. By considering the existence of interparticle dry friction only in the case of nanofiber ferrofluids, the developed models predicted quite well not only the magnitude of the static yield stress but also the differences in curvature of the yield stress vs magnetic field curves. PMID:22432510
NASA Astrophysics Data System (ADS)
Busca, Claudia; Coluccelli, Alessandro; Valentini, Andrea; Benetazzo, Alvise; Bonaldo, Davide; Bortoluzzi, Giovanni; Carniel, Sandro; Falcieri, Francesco; Paccagnella, Tiziana; Ravaioli, Mariangela; Riminucci, Francesco; Sclavo, Mauro; Russo, Aniello
2014-05-01
The complex dynamics of the Adriatic Sea are the result of geographical position, orography and bathymetry, as well as rivers discharge and meteorological conditions that influence, more strongly, the shallow northern part. Such complexity requires a constant monitoring of marine conditions in order to support several activities (marine resources management, naval operations, emergency management, shipping, tourism, as well as scientific ones). Platforms, buoys and mooring located in Adriatic Sea supply almost continuously real time punctual information, which can be spatially extended, with some limitations, by drifters and remote sensing. Operational forecasting systems represent valid tools to provide a complete tridimensional coverage of the area, with a high spatial and temporal resolution. The Hydro-Meteo-Clima Service of the Emilia-Romagna Environmental Agency (ARPA-SIMC, Bologna, Italy) and the Dept. of Life and Environmental Sciences of Università Politecnica delle Marche (DISVA-UNIVPM, Ancona, Italy), in collaboration with the Institute of Marine Science of the National Research Council (ISMAR-CNR, Italy) operationally run several wave and hydrodynamic models on the Adriatic Sea. The main implementations are based on the Regional Ocean Modeling System (ROMS), the wave model Simulating WAves Nearshore (SWAN), and the coupling of the former two models in the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) system. Horizontal resolutions of the different systems range from the 2 km of AdriaROMS to the 0.5 km of the recently implemented northern Adriatic COAWST. Forecasts are produced every day for the subsequent 72 hour with hourly resolution. All the systems compute the fluxes exchanged through the interface with the atmosphere from the numerical weather prediction system named COSMO-I7, an implementation for Italy of the Consortium for Small-scale Modeling (COSMO) model, at 7 km horizontal resolution. Considering the several operational implementations currently running, there is the need to: assess their forecast skill; quantitatively evaluate if the new, coupled systems provide better performances than the uncoupled ones; individuate weaknesses and eventual time trends in the forecasts quality, their causes, and actions to improve the systems. This work presents a first effort aimed to satisfy such need. We employ in situ and remote sensing data collected starting from November 2011, in particular: temperature and salinity data collected during several oceanographic cruises, sea surface temperature derived from satellite measurements, waves, sea level and currents measurements from oceanographic buoys and platforms; specific observational activities funded by the Italian Flagship project RITMARE allowed to collect new measurements in NA coastal areas. Data-model comparison is firstly performed with exploratory qualitative comparisons in order to highlight discrepancies between observed and forecasted data, then a quantitative comparison is performed through the computation of standard statistical scores (root mean square error, mean error, mean bias, standard deviation, cross-correlation). Results are plotted in Taylor diagrams for a rapid evaluation of the overall performances.
Anomalous attenuation of ultrasound in ferrofluids under the influence of a magnetic field
NASA Technical Reports Server (NTRS)
Isler, W. E.; Chung, D. Y.
1978-01-01
Ultrasonic wave propagation has been studied in a water-base ferrofluid by pulse-echo methods. A commercial box-car integrator was used to measure the change in attenuation due to an external magnetic field applied at various angles relative to the ultrasonic propagation vector. Anomalous results were obtained when the attenuation was plotted as a function of the magnetic field strength. As the field increased, the attenuation reached a maximum and then decreased to a flat minimum before it approached saturation at a field of 2 KG. This variation of attenuation with magnetic field cannot be explained from the simple picture derivable from the work of McTague on the viscosity of ferrofluids. In no case was the viscosity seen to decrease with field, nor was the oscillatory behavior observed. The results of this study were compared with the theory developed by Parsons.
Lacy, J.R.; Sherwood, C.R.; Wilson, D.J.; Chisholm, T.A.; Gelfenbaum, G.R.
2005-01-01
Hydrodynamic roughness is a critical parameter for characterizing bottom drag in boundary layers, and it varies both spatially and temporally due to variation in grain size, bedforms, and saltating sediment. In this paper we investigate temporal variability in hydrodynamic roughness using velocity profiles in the bottom boundary layer measured with a high-resolution acoustic Doppler profiler (PCADP). The data were collected on the ebb-tidal delta off Grays Harbor, Washington, in a mean water depth of 9 m. Significant wave height ranged from 0.5 to 3 m. Bottom roughness has rarely been determined from hydrodynamic measurements under conditions such as these, where energetic waves and medium-to-fine sand produce small bedforms. Friction velocity due to current u*c and apparent bottom roughness z0a were determined from the PCADP burst mean velocity profiles using the law of the wall. Bottom roughness kB was estimated by applying the Grant-Madsen model for wave-current interaction iteratively until the model u*c converged with values determined from the data. The resulting kB values ranged over 3 orders of magnitude (10-1 to 10-4 m) and varied inversely with wave orbital diameter. This range of kB influences predicted bottom shear stress considerably, suggesting that the use of time-varying bottom roughness could significantly improve the accuracy of sediment transport models. Bedform height was estimated from kB and is consistent with both ripple heights predicted by empirical models and bedforms in sonar images collected during the experiment. Copyright 2005 by the American Geophysical Union.
Brownian magnetic relaxation of water-based cobalt nanoparticle ferrofluids
Krishnan, Kannan M.
Brownian magnetic relaxation of water-based cobalt nanoparticle ferrofluids Y. Bao, A. B. Pakhomov of monodispersed 20 nm cobalt nanoparticles via a thermal decomposition method we have successfully transferred of water-based cobalt nanoparticle ferrofluids was measured at room temperature in the frequency range of 0
Chabchoub, A; Hoffmann, N; Onorato, M; Genty, G; Dudley, J M; Akhmediev, N
2013-08-01
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
Hitoshi Miura; Taishi Nakamoto
2006-11-09
Millimeter-sized, spherical silicate grains abundant in chondritic meteorites, which are called as chondrules, are considered to be a strong evidence of the melting event of the dust particles in the protoplanetary disk. One of the most plausible scenarios is that the chondrule precursor dust particles are heated and melt in the high-velocity gas flow (shock-wave heating model). We developed the non-linear, time-dependent, and three-dimensional hydrodynamic simulation code for analyzing the dynamics of molten droplets exposed to the gas flow. We confirmed that our simulation results showed a good agreement in a linear regime with the linear solution analytically derived by Sekiya et al. (2003). We found that the non-linear terms in the hydrodynamical equations neglected by Sekiya et al. (2003) can cause the cavitation by producing negative pressure in the droplets. We discussed that the fragmentation through the cavitation is a new mechanism to determine the upper limit of chondrule sizes. We also succeeded to reproduce the fragmentation of droplets when the gas ram pressure is stronger than the effect of the surface tension. Finally, we compared the deformation of droplets in the shock-wave heating with the measured data of chondrules and suggested the importance of other effects to deform droplets, for example, the rotation of droplets. We believe that our new code is a very powerful tool to investigate the hydrodynamics of molten droplets in the framework of the shock-wave heating model and has many potentials to be applied to various problems.
NASA Astrophysics Data System (ADS)
Miura, Hitoshi; Nakamoto, Taishi
2007-05-01
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.
Hydrodynamics of the double-wave structure of insect spermatozoa flagella
Lauga, Eric
helical structures are of opposite chirality. Keywords: swimming micro-organisms; flagellar hydrodynamics into the fluid opposite to the direction of locomotion. Micro-organisms mean- while inhabit in a world of low stringent constraints on a micro-organism's locomotive capabilities. Many micro-organisms propel themselves
Magneto-optical extinction inversion in ferrofluid
S. I. Shulyma; B. M. Tanygin; V. F. Kovalenko; M. V. Petrychuk
2015-11-25
An influence of a pulse magnetic field on an optical transmission of thin ferrofluid layers has been experimentally investigated. It is shown that under an impact of an external uniform magnetic field pulse applied in the sample surface normal direction, reduction of the optical transmission occurs with further returning of the optical transmission to its original state even before the end of the field pulse. The dependencies of the observed effect on the magnetic pulse magnitude for the samples with different thickness have been investigated. The experimental results are explained by the ferrofluid rod-shaped aggregates growth and fusion under an influence of a magnetic field leading to a light scattering type Rayleigh-to-Mie transition (cylindrical particle types). Further evolution of this process comes to a geometrical optics scale and respective macroscopic observable opaque ferrofluid rod-shaped aggregates emergence. These changes of an optical transmission is non-monotonic during the magnetic field pulse duration with minimal value in case of Mie scattering which is known as a magneto-optical extinction inversion. The residual magneto-optical inversion was detected after the external magnetic field pulse falling edge. The molecular dynamics simulation provides a qualitative match and an asymptotic quantitative match to the experiment. It was shown that a homogeneous external magnetic field is enough for the rod-shaped aggregates formation and their fusion. This result supplements the known Li theory (Jian Li et al., 2004, 2007) which implies an inhomogeneous field as a required prerequisite of the magneto-optical extinction inversion phenomenon.
Nonlinear dynamics of a ferrofluid pendulum.
Shliomis, Mark I; Zaks, Michael A
2004-07-23
A ferrofluid torsion pendulum in an oscillating magnetic field exhibits a rich variety of nonlinear self-oscillatory regimes. The dynamics is governed by the system of coupled differential equations for the in- and off-axis components of the fluid magnetization and the pendulum angular deflection. In the limiting case of high driving frequency, the system reduces to the sole Rayleigh-type equation. Much more complicated temporal patterns arise when the field frequency and the pendulum eigen frequency are of the same order. PMID:15323788
Drops deformation and magnetic permeability of a ferrofluid emulsion
Arthur Zakinyan; Yury Dikansky
2011-04-17
In the paper the novel soft magnetic composite system is investigated. A ferrofluid emulsion studied demonstrates the strong magnetic properties which are atypical for commonly known emulsions. Interaction of ferrofluid emulsions with a magnetic field is considered. Structural transformations in these media, such as deformation of emulsion microdroplets and emulsion inversion, are studied. The changes in the relative permeability of emulsion associated with structural transformations are investigated. The theory of the observed phenomena is developed, and the feasibility of effectively controlling the magnetic properties of ferrofluid emulsions by applying a magnetic field is demonstrated.
Electromagnetic induction by ferrofluid in an oscillating heat pipe
NASA Astrophysics Data System (ADS)
Monroe, J. G.; Vasquez, E. S.; Aspin, Z. S.; Walters, K. B.; Berg, M. J.; Thompson, S. M.
2015-06-01
Thermal-to-electrical energy conversion was demonstrated using an oscillating heat pipe (OHP) filled with ferrofluid and equipped with an annular-type solenoid. The OHP was subjected to a 100 °C axial temperature difference allowing the ferrofluid to passively oscillate through the solenoid, thus accomplishing electromagnetic induction. The measured solenoid voltage consisted of aperiodic pulses with dominant frequencies between 2 and 5 Hz and peak-to-peak amplitudes approaching 1 mV. Despite exposure to the thermal and phase change cycling within the OHP, nanoparticle morphologies and magnetic properties of the ferrofluid remained intact. This energy harvesting method allows for combined thermal management and in-situ power generation.
Hoeke, R.; Storlazzi, C.; Ridd, P.
2011-01-01
This paper examines the relationship between offshore wave climate and nearshore waves and currents at Hanalei Bay, Hawaii, an exposed bay fringed with coral reefs. Analysis of both offshore in situ data and numerical hindcasts identify the predominance of two wave conditions: a mode associated with local trade winds and an episodic pattern associated with distant source long-period swells. Analysis of 10 months of in situ data within the bay show that current velocities are up to an order of magnitude greater during long-period swell episodes than during trade wind conditions; overall circulation patterns are also fundamentally different. The current velocities are highly correlated with incident wave heights during the swell episodes, while they are not during the modal trade wind conditions. A phase-averaged wave model was implemented with the dual purpose of evaluating application to bathymetrically complex fringing reefs and to examine the propagation of waves into the nearshore in an effort to better explain the large difference in observed circulation during the two offshore wave conditions. The prediction quality of this model was poorer for the episodic condition than for the lower-energy mode, however, it illustrated how longer-period swells are preferentially refracted into the bay and make available far more nearshore wave energy to drive currents compared to waves during modal conditions. The highly episodic circulation, the nature of which is dependent on complex refraction patterns of episodic, long-period swell has implications for flushing and sediment dynamics for incised fringing reef-lined bays that characterize many high islands at low latitudes around the world.
NASA Astrophysics Data System (ADS)
Derbenev, Ilya; Dremov, Vladimir; Karavaev, Alexey; Sapozhnikov, Filipp; Soulard, Laurent
2009-06-01
Here we present results of investigations of the process of detonation wave refraction on the border with inert material. The effects of broad reaction zone in TATB-like HE and high sound speed in Be were of particular interest. Molecular Dynamics (MD) was chosen as an instrument of the investigation. An atomistic approach to the contrast of HydroDynamics (HD) does not use any phenomenological models for physical processes but intreatomic potentials. Therefore MD allows for the direct and explicit simulation of such phenomena as detonation kinetics, elastic-plastic transition mechanism and shear stress relaxation kinetics from the microscopic point of view. Nevertheless it was very interesting and important to compare results of MD and HD approaches to the same problem. To make possible hydrodynamics modeling the parameters of the models used in HD were determined from MD simulations. In the course, we used MD results to choose parameters for Be and TATB-like HE equations of state and to evaluate parameters of elastic- plastic transition models for these materials. HD and MD results have been compared and analyzed.
Ferrofluid surface and volume flows in uniform rotating magnetic fields
Elborai, Shihab M. (Shihab Mahmoud), 1977-
2006-01-01
Ferrofluid surface and volume effects in uniform dc and rotating magnetic fields are studied. Theory and corroborating measurements are presented for meniscus shapes and resulting surface driven flows, spin-up flows, and ...
Artificial viscosity in simulation of shock waves by smoothed particle hydrodynamics
M. Nejad-Asghar; A. R. Khesali; J. Soltani
2007-11-10
The artificial viscosity is reconsidered in smoothed particle hydrodynamics to prevent inter-particle penetration, unwanted heating, and unphysical solutions. The coefficients in the Monaghan's standard artificial viscosity are considered as time variable, and a restriction on them is proposed such that avoiding the undesired effects in the subsonic regions. The shock formation in adiabatic and isothermal cases are used to study the ability of this modified artificial viscosity recipe. The computer experiments show that the proposal appears to work and the accuracy of this restriction is acceptable.
NASA Astrophysics Data System (ADS)
Dyer, Ashton; Blondin, J. M.; Reynolds, S. P.
2014-01-01
High resolution imaging of two young Type Ia supernova remnants (SNRs), Tycho and SN 1006, has revealed several morphological features which have resisted explanation with numerical simulations. One such feature is the presence of shocked ejecta blobs protruding beyond the mean forward shock radius. Two current theories explain the presence of such ejecta: highly dense ejecta shrapnel produced in the explosion penetrating the forward shock, or plumes generated by hydrodynamic instabilities long after the initial explosion. We investigate the shrapnel theory through hydrodynamic simulations in 2D and 3D of the evolution of dense ejecta clumps embedded in an exponential density profile, appropriate for Type Ia supernovae. We use high-resolution 2D simulations to identify relevant clump parameters which we investigate further in 3D. In contradiction to some former work, we find that sufficiently resolved clumps in 2D models shatter upon collision with the forward shock, yielding new protrusion features. In both 2D and 3D, shrapnel is capable of penetrating the forward shock, but the resultant protrusions in 3D simulations vary significantly from those in similar 2D runs, implying 2D simulations may not be an accurate method of investigating the shrapnel theory. We compare the our simulations with Chandra observations of projections seen in Tycho and SN 1006. This work was performed as part of NC State University's Undergraduate Research in Computational Astrophysics (URCA) program, an REU program supported by the National Science Foundation through award AST-1032736.
Thin viscous ferrofluid film in a magnetic field
NASA Astrophysics Data System (ADS)
Conroy, Devin T.; Matar, Omar K.
2015-09-01
We consider a thin, ferrofluidic film flowing down an inclined substrate, under the action of a magnetic field, bounded above by an inviscid gas. Its dynamics are governed by a coupled system of the steady Maxwell's, the Navier-Stokes, and the continuity equations. The magnetization of the film is a function of the magnetic field and may be prescribed by a Langevin function. We make use of a long-wave reduction in order to solve for the dynamics of the pressure and velocity fields inside the film. In addition, we investigate the problem in the limit of a large magnetic permeability. Imposition of appropriate interfacial conditions allows for the construction of an evolution equation for the interfacial shape via use of the kinematic condition. The resultant one-dimensional equations are solved numerically using spectral methods. The magnetic effects give rise to a non-local contribution. We conduct a parametric study of both the linear and nonlinear stabilities of the system in order to evaluate the effects of the magnetic field. Through a linear stability analysis, we verify that the Maxwell's pressure generated from a normally applied magnetic field is destabilizing and can be used to control the size and shape of lobes and collars on the free surface. We also find that in the case of a falling drop, the magnetic field causes an increase in the velocity and capillary ridge of the drop.
Ferrofluid spin-up flows from uniform and non-uniform rotating magnetic fields
Khushrushahi, Shahriar Rohinton
2010-01-01
When ferrofluid in a cylindrical container is subjected to a rotating azimuthally directed magnetic field, the fluid "spins up" into an almost rigid-body rotation where ferrofluid nanoparticles have both a linear and an ...
Characterizing ferrofluid spin-up flow in rotating uniform magnetic fields
Dozier, Kahlil A
2014-01-01
A ferrofluid is a collection of nanoscale ferromagnetic particles with a stabilizing surfactant in a liquid to form a colloid. The dynamic behavior of ferrofluids in the presence of magnetic fields has long been an area ...
Igor I. Smolyaninov; Vera N. Smolyaninova; Alexei I. Smolyaninov
2014-11-12
Cobalt nanoparticle-based ferrofluid in the presence of external magnetic field forms a self-assembled hyperbolic metamaterial. Wave equation describing propagation of extraordinary light inside the ferrofluid exhibits 2+1 dimensional Lorentz symmetry. The role of time in the corresponding effective 3D Minkowski spacetime is played by the spatial coordinate directed along the periodic nanoparticle chains aligned by the magnetic field. Here we present a microscopic study of point, linear, planar and volume defects of the nanoparticle chain structure and demonstrate that they may exhibit strong similarities with such Minkowski spacetime defects as magnetic monopoles, cosmic strings and the recently proposed spacetime cloaks. Experimental observations of such defects are described.
Dynamic analysis of hydrodynamic behavior of a flatfish cage system under wave conditions
NASA Astrophysics Data System (ADS)
Cui, Yong; Guan, Chang-tao; Wan, Rong; Huang, Bin; Li, Jiao
2014-04-01
This paper presents a simulation model based on the finite element method. The method is used to analyze the motion response and mooring line tension of the flatfish cage system in waves. The cage system consists of top frames, netting, mooring lines, bottom frames, and floats. A series of scaled physical model tests in regular waves are conducted to verify the numerical model. The comparison results show that the simulated and the experimental results agree well under the wave conditions, and the maximum pitch of the bottom frame with two orientations is about 12°. The motion process of the whole cage system in the wave can be described with the computer visualized technology. Then, the mooring line tensions and the motion of the bottom frame with three kinds of weight are calculated under different wave conditions. According to the numerical results, the differences in mooring line tensions of flatfish cages with three weight modes are indistinct. The maximum pitch of the bottom frame decreases with the increase of the bottom weight.
NASA Astrophysics Data System (ADS)
Suwa, T.; Imamura, F.; Sugawara, D.; Ogasawara, K.; Watanabe, M.; Hirahara, T.
2014-12-01
A tsunami simulator integrating a 3-D fluid simulation technology that runs on large-scale parallel computers using smoothed-particle hydrodynamics (SPH) method has been developed together with a 2-D tsunami propagation simulation technique using a nonlinear shallow water wave model. We use the 2-D simulation to calculate tsunami propagation of scale of about 1000km from epicenter to near shore. The 3-D SPH method can be used to calculate the water surface and hydraulic force that a tsunami can exert on a building, and to simulate flooding patterns at urban area of at most km scale. With our simulator we can also see three dimensional fluid feature such as complex changes a tsunami undergoes as it interacts with coastal topography or structures. As a result it is hoped that, e.g. , effect of the structures to dissipate waves energy passing over it can be elucidated. The authors utilize the simulator in the third of five fields of the Strategic Programs for Innovative Research, "Advanced Prediction Researches for Natural Disaster Prevention and Reduction," or the theme "Improvement of the tsunami forecasting system on the HPCI computer." The results of tsunami simulation using the K computer will be reported. We are going to apply it to a real problem of the disaster prevention in future.
NASA Astrophysics Data System (ADS)
Wang, Hsiang-Hsu; Lee, Wing-Kit; Taam, Ronald E.; Feng, Chien-Chang; Lin, Lien-Hsuan
2015-02-01
The gas response to the underlying stellar spirals is explored for M81 using unmagnetized hydrodynamic simulations. Constrained within the uncertainty of observations, 18 simulations are carried out to study the effects of self-gravity and to cover the parameter space comprising three different sound speeds and three different arm strengths. The results are confronted with the data observed at wavelengths of 8 ?m and 21 cm. In the outer disk, the ring-like structure observed in the 8 ?m image is consistent with the response of cold neutral medium with an effective sound speed 7 km s-1. For the inner disk, the presence of spiral shocks can be understood as a result of 4:1 resonances associated with the warm neutral medium with an effective sound speed 19 km s-1. Simulations with a single effective sound speed alone cannot simultaneously explain the structures in the outer and inner disks. Instead this justifies the coexistence of cold and warm neutral media in M81. The anomalously high streaming motions observed in the northeast arm and the outward shifted turning points in the iso-velocity contours seen along the southwest arm are interpreted as signatures of interactions with companion galaxies. The level of simulated streaming motions narrows down the uncertainty of the observed arm strength toward larger amplitudes.
The evolution of field-induced structure of confined ferrofluid emulsions
Mou, T.; Flores, G.A.; Liu, J. . Dept. of Physics and Astronomy); Bibette, J. ); Richard, J. )
1994-09-01
The authors report a real-time study of the evolution of the structure of confined ferrofluid emulsions during the ''liquid-solid'' phase transition. A monodisperse oil-in-water ferrofluid emulsion is used. The structure evolution of the emulsion after rapidly applying a magnetic field is probed by the static light scattering. The scattering pattern exhibits pronounced rings reflecting the formation of chains and their coalescence to columns or even ''worm'' structures. The scattering ring is found to decrease in size and brighten in intensity with time. To monitor the structure evolution in time, both the ring peak position in scattering wave vector, q[sub max], and the peak intensity, I[sub max], are measured as a function of time. Both q[sub max] and I[sub max] saturate in less than 0.5 seconds after applying a magnetic field. At a constant cell thickness of 25 [mu]m, the evolution of structure is essentially independent of volume fraction ranging from 0.015 to 0.13. In addition, a very good scaling is found in the scattered light intensity as a function of the scattering wave vector.
Sink-float ferrofluid separator applicable to full scale nonferrous scrap separation
NASA Technical Reports Server (NTRS)
1973-01-01
Design and performance of a ferrofluid levitation separator for recovering nonferrous metals from shredded automobiles are reported. The scrap separator uses an electromagnet to generate a region of constant density within a pool of ferrofluid held between the magnetic poles; a saturated kerosene base ferrofluid as able to float all common industrial metals of interest. Conveyors move the scrap into the ferrofluid for separation according to density. Results of scrap mixture separation studies establish the technical feasibility of relatively pure aluminum alloy and zinc alloy fractions from shredded automobile scrap by this ferrofluid levitation process. Economic projections indicate profitable operation for shredders handling more than 300 cars per day.
An adaptive liquid microlens driven by a ferrofluidic transducer
NASA Astrophysics Data System (ADS)
Xiao, Wenjia; Hardt, Steffen
2010-05-01
Ferrofluids behave superparamagnetically and can be manipulated by external magnetic fields, providing numerous applications in microfluidic systems. In this paper, an adaptive liquid microlens driven by a ferrofluidic actuator is presented. The microlens consists of a cylindrical well filled with a lens liquid connected to a microchannel containing a ferrofluid plug. When the ferrofluid plug is moved back and forth by an external magnetic field, the lens liquid is displaced, forming a liquid lens with an adaptive focus in the cylindrical well. The focal length of the lens can be changed from infinity to the scale of the radius of the cylindrical well, leading to a high optical power compared to conventional liquid lenses utilizing liquid crystals or electrowetting. The lens curvature is reversibly tunable without hysteresis when the ferrofluid plug moves with a speed below a specific threshold value. The lens can be acted on by a magnetic field of about 100 mT which can be generated by microcoils requiring much lower voltages than the electrowetting principle.
Study on the magnetorheological properties of maghemite-kerosene ferrofluid.
Ghasemi, E; Mirhabibi, A; Edrissi, M; Aghababazadeh, R; Brydson, R M
2009-07-01
As the ferrofluids are synthesized in a controlled atmosphere to Prevent oxidation of the magnetite phase; most reports of rheological properties have been derived from magnetite based ferrofluids. In this paper a ferrofluid based on iron oxide was synthesized by co-precipitation with air. Lauric acid was used to coat magnetic nanoparticles in the kerosene. The microstructural features of the ferrofluid and the variation with time and temperature of its rheologic and magnetic properties were investigated. The results indicated that the magnetic particles had an average size of 10.6 nm consisting of maghemite as the major phase. Viscosity of ferrofluid showed considerable variation with time and temperature. It was specified that the time dependency of the magnetoviscousity is related to particle size and rearrangement of nanoparticles of product is independent from the magnetic field. Moreover at low shear rates (< 0.1 s(-1)) the interaction of nanoparticles is related to the van der waals forces which cause the increase of the viscosity with time. The temperature effect showed that the magnetoviscosity decreases considerably above 45 degrees C. PMID:19916442
Resistive magneto-hydrodynamical cut-off of Alfvén wave in fully ionized plasmas
NASA Astrophysics Data System (ADS)
Vranjes, J.; Kono, M.
2014-01-01
The term cut-off in the theory of the Alfvén wave is used to describe several different phenomena. In this work, the cut-off due to magnetohydrodynamic resistive damping in fully ionized plasmas is revisited. This cut-off requires short enough wavelengths, it is routinely discussed in numerous works, and graphs depicting it are available even in textbooks. We show that this cut-off is hardly ever possible in real plasmas. This is due to the fact that some essential criteria and conditions become strongly violated in order to achieve the cut-off.
Resistive magneto-hydrodynamical cut-off of Alfvén wave in fully ionized plasmas
Vranjes, J.; Kono, M.
2014-01-15
The term cut-off in the theory of the Alfvén wave is used to describe several different phenomena. In this work, the cut-off due to magnetohydrodynamic resistive damping in fully ionized plasmas is revisited. This cut-off requires short enough wavelengths, it is routinely discussed in numerous works, and graphs depicting it are available even in textbooks. We show that this cut-off is hardly ever possible in real plasmas. This is due to the fact that some essential criteria and conditions become strongly violated in order to achieve the cut-off.
Ferrofluid nucleus phase transitions in an external uniform magnetic field
NASA Astrophysics Data System (ADS)
M. Tanygin, B.; I. Shulyma, S.; F. Kovalenko, V.; V. Petrychuk, M.
2015-10-01
The phase transition between a massive dense phase and a diluted superparamagnetic phase has been studied by means of a direct molecular dynamics simulation. The equilibrium structures of the ferrofluid aggregate nucleus are obtained for different values of a temperature and an external magnetic field magnitude. An approximate match of experiment and simulation has been shown for the ferrofluid phase diagram coordinates “field-temperature”. The provided phase coexistence curve has an opposite trend comparing to some of known theoretical results. This contradiction has been discussed. For given experimental parameters, it has been concluded that the present results describe more precisely the transition from linear chains to a dense globes phase. The theoretical concepts which provide the opposite binodal curve dependency trend match other experimental conditions: a diluted ferrofluid, a high particle coating rate, a high temperature, and/or a less particles coupling constant value.
Ferrofluid nucleus phase transitions in an external uniform magnetic field
B. M. Tanygin; S. I. Shulyma; V. F. Kovalenko; M. V. Petrychuk
2015-02-18
Phase transition between massive dense phase and diluted superparamagnetic phase is studied by means of direct molecular dynamics simulation. Equilibrium structures of ferrofluid aggregate nucleus are obtained for different values of temperature and external magnetic field magnitude. For the ferrofluid phase diagram (coordinates "field-temperature"): approximate match of experiment and simulation is shown. Obtained phase coexistence curve has opposite trend compare to some of known theoretical results. This contradiction is related to postulating and comparing of the free energy of only simplest ferrofluid structures: diluted superparamagnetic phase, linear chains of the particles, and dense globes. The present results provide more fine structure of transition from "linear chains" to "dense globes" phase, e.g. through the ring assembly structure.
Experimental demonstration of metamaterial ``multiverse'' in a ferrofluid
NASA Astrophysics Data System (ADS)
Smolyaninov, Igor I.; Yost, Bradley; Bates, Evan; Smolyaninova, Vera N.
2013-06-01
Extraordinary light rays propagating inside a hyperbolic metamaterial look similar to particle world lines in a 2+1 dimensional Minkowski spacetime [1]. 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.
Experimental demonstration of metamaterial "multiverse" in a ferrofluid.
Smolyaninov, Igor I; Yost, Bradley; Bates, Evan; Smolyaninova, Vera N
2013-06-17
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
Experimental demonstration of metamaterial multiverse in a ferrofluid
Igor I. Smolyaninov; Bradley Yost; Evan Bates; Vera N. Smolyaninova
2013-04-15
Extraordinary light rays propagating inside a hyperbolic metamaterial look similar to particle world lines in a 2+1 dimensional Minkowski spacetime [1]. 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.
Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system.
Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng
2015-01-01
We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices. PMID:26687638
Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system
Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng
2015-01-01
We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices. PMID:26687638
Printing microstructures in a polymer matrix using a ferrofluid droplet
NASA Astrophysics Data System (ADS)
Abdel Fattah, Abdel Rahman; Ghosh, Suvojit; Puri, Ishwar K.
2016-03-01
We print complex curvilinear microstructures in an elastomer matrix using a ferrofluid droplet as the print head. A magnetic field moves the droplet along a prescribed path in liquid polydimethylsiloxane (PDMS). The droplet sheds magnetic nanoparticle (MNP) clusters in its wake, forming printed features. The PDMS is subsequently heated so that it crosslinks, which preserves the printed features in the elastomer matrix. The competition between magnetic and drag forces experienced by the ferrofluid droplet and its trailing MNPs highlight design criteria for successful printing, which are experimentally confirmed. The method promises new applications, such as flexible 3D circuitry.
NASA Astrophysics Data System (ADS)
Larmat, C. S.; Rougier, E.; Knight, E.; Yang, X.; Patton, H. J.
2013-12-01
A goal of the Source Physics Experiments (SPE) is to develop explosion source models expanding monitoring capabilities beyond empirical methods. The SPE project combines field experimentation with numerical modelling. The models take into account non-linear processes occurring from the first moment of the explosion as well as complex linear propagation effects of signals reaching far-field recording stations. The hydrodynamic code CASH is used for modelling high-strain rate, non-linear response occurring in the material near the source. Our development efforts focused on incorporating in-situ stress and fracture processes. CASH simulates the material response from the near-source, strong shock zone out to the small-strain and ultimately the elastic regime where a linear code can take over. We developed an interface with the Spectral Element Method code, SPECFEM3D, that is an efficient implementation on parallel computers of a high-order finite element method. SPECFEM3D allows accurate modelling of wave propagation to remote monitoring distance at low cost. We will present CASH-SPECFEM3D results for SPE1, which was a chemical detonation of about 85 kg of TNT at 55 m depth in a granitic geologic unit. Spallation was observed for SPE1. Keeping yield fixed we vary the depth of the source systematically and compute synthetic seismograms to distances where the P and Rg waves are separated, so that analysis can be performed without concern about interference effects due to overlapping energy. We study the time and frequency characteristics of P and Rg waves and analyse them in regard to the impact of free-surface interactions and rock damage resulting from those interactions. We also perform traditional CMT inversions as well as advanced CMT inversions, developed at LANL to take into account the damage. This will allow us to assess the effect of spallation on CMT solutions as well as to validate our inversion procedure. Further work will aim to validate the developed models with the data recorded on SPEs. This long-term goal requires taking into account the 3D structure and thus a comprehensive characterization of the site.
Nonlinear hydrodynamic effects induced by Rayleigh surface acoustic wave in sessile droplets.
Alghane, M; Chen, B X; Fu, Y Q; Li, Y; Desmulliez, M P Y; Mohammed, M I; Walton, A J
2012-11-01
We report an experimental and numerical characterization of three-dimensional acoustic streaming behavior in small droplets of volumes (1-30 ?l) induced by surface acoustic wave (SAW). We provide a quantitative evidence of the existence of strong nonlinear nature of the flow inertia in this SAW-driven flow over a range of the newly defined acoustic parameter F{NA}=F?/(?/R_{d})?0.01, which is a measure of the strength of the acoustic force to surface tension, where F is the acoustic body force, ? is the SAW wavelength, ? is the surface tension, and R{d} is the droplet radius. In contrast to the widely used Stokes model of acoustic streaming, which generally ignores such a nonlinearity, we identify that the full Navier-Stokes equation must be applied to avoid errors up to 93% between the computed streaming velocities and those from experiments as in the nonlinear case. We suggest that the Stokes model is valid only for very small acoustic power of ?1 ?W (F{NA}<0.002). Furthermore, we demonstrate that the increase of F{NA} above 0.45 induces not only internal streaming, but also the deformation of droplets. PMID:23214873
Azimuthal field instability in a confined ferrofluid
NASA Astrophysics Data System (ADS)
Dias, Eduardo O.; Miranda, José A.
2015-02-01
We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes.
Linear and nonlinear magnetic properties of ferrofluids.
Szalai, I; Nagy, S; Dietrich, S
2015-10-01
Within a high-magnetic-field approximation, employing Ruelle's algebraic perturbation theory, a field-dependent free-energy expression is proposed which allows one to determine the magnetic properties of ferrofluids modeled as dipolar hard-sphere systems. We compare the ensuing magnetization curves, following from this free energy, with those obtained by Ivanov and Kuznetsova [Phys. Rev. E 64, 041405 (2001)10.1103/PhysRevE.64.041405] as well as with new corresponding Monte Carlo simulation data. Based on the power-series expansion of the magnetization, a closed expression for the magnetization is also proposed, which is a high-density extension of the corresponding equation of Ivanov and Kuznetsova. From both magnetization equations the zero-field susceptibility expression due to Tani et al. [Mol. Phys. 48, 863 (1983)MOPHAM0026-897610.1080/00268978300100621] can be obtained, which is in good agreement with our MC simulation results. From the closed expression for the magnetization the second-order nonlinear magnetic susceptibility is also derived, which shows fair agreement with the corresponding MC simulation data. PMID:26565247
Linear and nonlinear magnetic properties of ferrofluids
NASA Astrophysics Data System (ADS)
Szalai, I.; Nagy, S.; Dietrich, S.
2015-10-01
Within a high-magnetic-field approximation, employing Ruelle's algebraic perturbation theory, a field-dependent free-energy expression is proposed which allows one to determine the magnetic properties of ferrofluids modeled as dipolar hard-sphere systems. We compare the ensuing magnetization curves, following from this free energy, with those obtained by Ivanov and Kuznetsova [Phys. Rev. E 64, 041405 (2001), 10.1103/PhysRevE.64.041405] as well as with new corresponding Monte Carlo simulation data. Based on the power-series expansion of the magnetization, a closed expression for the magnetization is also proposed, which is a high-density extension of the corresponding equation of Ivanov and Kuznetsova. From both magnetization equations the zero-field susceptibility expression due to Tani et al. [Mol. Phys. 48, 863 (1983), 10.1080/00268978300100621] can be obtained, which is in good agreement with our MC simulation results. From the closed expression for the magnetization the second-order nonlinear magnetic susceptibility is also derived, which shows fair agreement with the corresponding MC simulation data.
Aqueous Ferrofluid of Magnetite Nanoparticles: Fluorescence Labeling and Magnetophoretic Control
Swihart, Mark T.
of nanometers making them smaller than or comparable in size to important biological entities such as cells (10Aqueous Ferrofluid of Magnetite Nanoparticles: Fluorescence Labeling and Magnetophoretic Control, and Paras N. Prasad*, Department of Chemistry, Department of Chemical and Biological Engineering, Institute
Magnetic Sensing with Ferrofluid and Fiber Optic Connectors
Homa, Daniel; Pickrell, Gary
2014-01-01
A simple, cost effective and sensitive fiber optic magnetic sensor fabricated with ferrofluid and commercially available fiber optic components is described in this paper. The system uses a ferrofluid infiltrated extrinsic Fabry-Perot interferometer (EFPI) interrogated with an infrared wavelength spectrometer to measure magnetic flux density. The entire sensing system was developed with commercially available components so it can be easily and economically reproduced in large quantities. The device was tested with two different ferrofluid types over a range of magnetic flux densities to verify performance. The sensors readily detected magnetic flux densities in the range of 0.5 mT to 12.0 mT with measurement sensitivities in the range of 0.3 to 2.3 nm/mT depending on ferrofluid type. Assuming a conservative wavelength resolution of 0.1 nm for state of the art EFPI detection abilities, the estimated achievable measurement resolution is on the order 0.04 mT. The inherent small size and basic structure complimented with the fabrication ease make it well-suited for a wide array of research, industrial, educational and military applications. PMID:24573312
Global weak solutions to a ferrofluid flow model Youcef Amirat
Hamdache, Kamel
of a colloidal suspension of magnetized nanoparticles in a nonconducting liquid, under the action of an external to an external magnetic field. Ferrofluids (also called magnetic fluids) are suspensions of ferromagnetic magnetic field. The system is a combination of the Navier-Stokes equations, the magnetization equation
Pampori, Adam; Keledjian, Kaspar; Tosun, Cigdem; Schwartzbauer, Gary; Ivanova, Svetlana; Gerzanich, Volodymyr
2014-01-01
Abstract Traumatic brain injury (TBI) caused by an explosive blast (blast-TBI) is postulated to result, in part, from transvascular transmission to the brain of a hydrodynamic pulse (a.k.a., volumetric blood surge, ballistic pressure wave, hydrostatic shock, or hydraulic shock) induced in major intrathoracic blood vessels. This mechanism of blast-TBI has not been demonstrated directly. We tested the hypothesis that a blast wave impacting the thorax would induce a hydrodynamic pulse that would cause pathological changes in the brain. We constructed a Thorax-Only Blast Injury Apparatus (TOBIA) and a Jugular-Only Blast Injury Apparatus (JOBIA). TOBIA delivered a collimated blast wave to the right lateral thorax of a rat, precluding direct impact on the cranium. JOBIA delivered a blast wave to the fluid-filled port of an extracorporeal intravenous infusion device whose catheter was inserted retrograde into the jugular vein, precluding lung injury. Long Evans rats were subjected to sublethal injury by TOBIA or JOBIA. Blast injury induced by TOBIA was characterized by apnea and diffuse bilateral hemorrhagic injury to the lungs associated with a transient reduction in pulse oximetry signals. Immunolabeling 24?h after injury by TOBIA showed up-regulation of tumor necrosis factor alpha, ED-1, sulfonylurea receptor 1 (Sur1), and glial fibrillary acidic protein in veins or perivenular tissues and microvessels throughout the brain. The perivenular inflammatory effects induced by TOBIA were prevented by ligating the jugular vein and were reproduced using JOBIA. We conclude that blast injury to the thorax leads to perivenular inflammation, Sur1 up-regulation, and reactive astrocytosis resulting from the induction of a hydrodynamic pulse in the vasculature. PMID:24673157
Stone, G.W.; Pepper, D.A.; Xu, Jie; Zhang, X.
2004-01-01
Ship Shoal, a transgressive sand body located at the 10 m isobath off south-central Louisiana, is deemed a potential sand source for restoration along the rapidly eroding Isles Dernieres barrier chain and possibly other sites in Louisiana. Through numerical wave modeling we evaluate the potential response of mining Ship Shoal on the wave field. During severe and strong storms, waves break seaward of the western flank of Ship Shoal. Therefore, removal of Ship Shoal (approximately 1.1 billion m3) causes a maximum increase of the significant wave height by 90%-100% and 40%-50% over the shoal and directly adjacent to the lee of the complex for two strong storm scenarios. During weak storms and fair weather conditions, waves do not break over Ship Shoal. The degree of increase in significant wave height due to shoal removal is considerably smaller, only 10%-20% on the west part of the shoal. Within the context of increasing nearshore wave energy levels, removal of the shoal is not significant enough to cause increased erosion along the Isles Dernieres. Wave approach direction exerts significant control on the wave climate leeward of Ship Shoal for stronger storms, but not weak storms or fairweather. Instrumentation deployed at the shoal allowed comparison of measured wave heights with numerically derived wave heights using STWAVE. Correlation coefficients are high in virtually all comparisons indicating the capability of the model to simulate wave behavior satisfactorily at the shoal. Directional waves, currents and sediment transport were measured during winter storms associated with frontal passages using three bottom-mounted arrays deployed on the seaward and landward sides of Ship Shoal (November, 1998-January, 1999). Episodic increases in wave height, mean and oscillatory current speed, shear velocity, and sediment transport rates, associated with recurrent cold front passages, were measured. Dissipation mechanisms included both breaking and bottom friction due to variable depths across the shoal crest and variable wave amplitudes during storms and fair-weather. Arctic surge fronts were associated with southerly storm waves, and southwesterly to westerly currents and sediment transport. Migrating cyclonic fronts generated northerly swell that transformed into southerly sea, and currents and sediment transport that were southeasterly overall. Waves were 36% higher and 9% longer on the seaward side of the shoal, whereas mean currents were 10% stronger landward, where they were directed onshore, in contrast to the offshore site, where seaward currents predominated. Sediment transport initiated by cold fronts was generally directed southeasterly to southwesterly at the offshore site, and southerly to westerly at the nearshore site. The data suggest that both cold fronts and the shoal, exert significant influences on regional hydrodynamics and sediment transport.
Rheological characterization of a magnetorheological ferrofluid using iron nitride nanoparticles
NASA Astrophysics Data System (ADS)
Armijo, Leisha M.; Ahuré-Powell, Louise A.; Wereley, Norman M.
2015-05-01
Magnetorheology of a magnetorheological ferrofluid (MRFF) was investigated to study the role of a ferromagnetic nanoparticle (NP) additive in magnetorheological fluids (MRFs). Iron nitride (Fe16N2) NPs, nominally within the diameter range of ˜16-45 nm (spherical NPs) and ˜30-66 nm (cubic NPs), were coated with carboxy-polyethylene glycol (carboxy-PEG) and dispersed in silicone oil in order to produce a magnetic carrier fluid or ferrofluid for two solids loadings: 2 vol. % and 5 vol. %. Conventional spherical carbonyl iron (CI) particles, varying in diameter from 6 to 10 ?m, were suspended in the ferrofluid at 25 vol. % solids loading. Rheological properties of the MRFF synthesized with the carboxy-PEG-based ferromagnetic carrier fluid were compared to the MRF synthesized with silicone oil to determine how ferrofluid can influence dynamic viscosity and yield stress. Rheological measurements of both MRF and MRFF samples were carried out using a Paar Physica 300 rheometer to estimate the field-off viscosity and to measure flow curves (i.e., shear stress vs. shear rate) as a function of magnetic field. A Bingham-plastic model was used to characterize the flow curves, and results show that there is an increase in the dynamic viscosity of the MRFF over the MRF. The ferromagnetic carrier fluid greatly increases yield stress as only 2 vol. % of added carboxy-PEG NPs improves the yield stress performance by almost 5%. A second MRFF sample synthesized with 5 vol. % of added carboxy-PEG NPs contained in the ferrofluid significantly enhanced the yield stress performance by 13% over the MRF at the same CI solids loading (25 vol. %).
Dynamics of Single Chains of Suspended Ferrofluid Particles
NASA Technical Reports Server (NTRS)
Cutillas, S.; Liu, J.
1999-01-01
We present an experimental study of the dynamics of isolated chains made of super-paramagnetic particles under the influence of a magnetic field. The motivation of this work is to understand if the chain fluctuations exist and, if it does, how does the fluctuation affect chain aggregation. We find that single chains strongly fluctuate and that the characteristic frequency of their fluctuations is inversely proportional to the magnetic field strength. The higher the field the lower the characteristic frequency of the chain fluctuations. In the high magnetic field limit, chains behave like rigid rods without any internal motions. In this work, we used ferrofluid particles suspended in water. These particles do not have any intrinsic magnetization. Once a magnetic field is applied, a dipole moment is induced in each particle, proportional to the magnetic field. A dipolar magnetic interaction then occurs between particles. If dipole-dipole magnetic energy is higher than the thermal energy, the result is a structure change inside the dipolar fluid. The ratio of these two energies is expressed by a coupling constant lambda as: lambda = (pi(a(exp 3))(chi(exp 2))(mu(sub 0))(H(sub 0))(exp 2))/18kT Where a is the particle radius, mu(sub 0) is the vacuum magnetic permeability, H(sub 0) the applied magnetic field, k the Boltzmann constant and T the absolute temperature. If lambda > 1, magnetic particles form chains along the field direction. The lateral coalescence of several chains may form bigger aggregates especially if the particle volume fraction is high. While many studies and applications deal with the rheological properties and the structural changes of these dipolar fluids, this work focuses on the understanding of the chain dynamics. In order to probe the chain dynamics, we used dynamic light scattering (DLS) in self-beating mode as our experimental technique. The experimental geometry is such that the scattering plane is perpendicular to the magnetic field. Therefore, only motions in this plane are probed. A very dilute sample of a ferrofluid emulsion with a particle volume fraction of 10(exp -5) is used in this experiment. We chose such a low volume fraction to avoid multiple light scattering as well as lateral chain-chain aggregation. DLS measures the dynamic structure factor S(q,t) of the sample (q is the scattering wave vector, t is the time). In the absence of the magnetic field, identical particles of ferrofluid droplets are randomly distributed and S(q,t) reduces to exp(-q(exp 2)2D(sub 0)t). D(sub 0)=(kT/(6(pi)(eta)(a)) is the diffusion coefficient of Brownian particles (where Xi = (6(pi)(eta)(a)) is the Stokes frictional coefficient of a spherical particle in a fluid of viscosity eta). If interactions or polydispersity can not be ignored, an effective diffusion coefficient is introduced. Formally, D(sub eff) is defined as: D(sub eff) = - q(exp -2) partial derivative of (ln(S(q,t)) with respect to time, as t goes to 0. D(sub eff) reduces to D(sub 0) if no interactions and only a few particles size are present. Therefore, we can use DLS to measure particle size. The particle radius was found to be a=0.23 mu m with 7% of polydispersity. In this case, if we vary the scattering angle theta (and so q) we do not have any change in the measured diffusion coefficient: it is q-independent. When a magnetic field is applied, particles aggregate into chains if lambda > 1. We first studied the kinetics of the chain formation when lambda = 406. At a fixed scattering angle, we measured diffusion coefficient D(sub eff) as a function of time. Experimentally, we find that D(sub eff) decreases monotonously with time. Physically, this means that chains are becoming longer and longer. Since we are only sensitive to motions in the scattering plane and since chains have their main axis perpendicular to this plane, the measured diffusion coefficient is the trans-verse diffusion coefficient. We can relate D(sub eff) to the mean number of particles per chain N(t) at a given time and to the diffusion coefficient of an isolated particle
Combined Langevin dynamics/Monte-Carlo simulations of the non-equilibrium ferrofluid remagnetization
NASA Astrophysics Data System (ADS)
Berkov, D. V.; Gorn, N.; Stock, D.
2004-05-01
We present a powerful method for simulations of fast remagnetization processes in ferrofluids which combines the stochastic (Langevin) dynamics and Monte-Carlo method. Our Langevin equations for the description of ferrofluid dynamics include both the mechanical (translational and rotational particle motion) and magnetic (rotation of the magnetic moment with respect to the particle) degrees of freedom. As an application example we present new physical results concerning the dependence of the magnetization relaxation in ferrofluids after switching off the external field.
An Approach to Measurment of Permeability/Permittivity Tensor of Ferrofluids
NASA Astrophysics Data System (ADS)
Mayer, Daniel
2015-09-01
The magnetic field acting on the ferrofluids causes microstructural conversions that result in a change of their permeability. For this physical phenomenon is referred to as field induced magnetism (FIMA). An experimental method is described for ferrofluids in this state to examine their permeability tensor. Also an analogous phenomenon is described also when there is a change of the ferrofluids permittivity. We call it field induced dielectric anisotropy (FIDA). The contribution describes the method of measuring of the permittivity tensor. It can be expected that the FIMA and FIDA of ferrofluids will find interesting applications in designing of various sensors, in measurement technology, in mechatronic and in other areas of practice.
Smolyaninov, Igor I; Smolyaninova, Vera N; Smolyaninov, Alexei I
2015-08-28
In the presence of an external magnetic field, cobalt nanoparticle-based ferrofluid forms a self-assembled hyperbolic metamaterial. The wave equation, which describes propagation of extraordinary light inside the ferrofluid, exhibits 2+1 dimensional Lorentz symmetry. The role of time in the corresponding effective three-dimensional Minkowski space-time is played by the spatial coordinate directed along the periodic nanoparticle chains aligned by the magnetic field. Here, we present a microscopic study of point, linear, planar and volume defects of the nanoparticle chain structure and demonstrate that they may exhibit strong similarities with such Minkowski space-time defects as magnetic monopoles, cosmic strings and the recently proposed space-time cloaks. Experimental observations of such defects are described. PMID:26217055
Karpitschka, Stefan; Riegler, Hans
2012-08-10
Capillarity always favors drop fusion. Nevertheless, sessile drops from different but completely miscible liquids often do not fuse instantaneously upon contact. Rather, intermediate noncoalescence is observed. Two separate drop bodies, connected by a thin liquid neck, move over the substrate. Supported by new experimental data, a thin film hydrodynamic analysis of this state is presented. Presumably advective and diffusive volume fluxes in the neck region establish a localized and temporarily stable surface tension gradient. This induces a local surface (Marangoni) flow that stabilizes a traveling wave, i.e., the observed moving twin drop configuration. The theoretical predictions are in excellent agreement with the experimental findings. PMID:23006285
Karpitschka, Stefan
2015-01-01
Capillarity always favors drop fusion. Nevertheless sessile drops from different but completely miscible liquids often do not fuse instantaneously upon contact. Rather, intermediate non-coalescence is observed. Two separate drop bodies, connected by a thin liquid neck move over the substrate. Supported by new experimental data a thin film hydrodynamic analysis of this state is presented. Presumably advective and diffusive volume fluxes in the neck region establish a localized and temporarily stable surface tension gradient. This induces a local surface (Marangoni) flow that stabilizes a traveling wave i.e., the observed moving twin drop configuration. The theoretical predictions are in excellent agreement with the experimental findings.
NASA Astrophysics Data System (ADS)
Karpitschka, Stefan; Riegler, Hans
2012-08-01
Capillarity always favors drop fusion. Nevertheless, sessile drops from different but completely miscible liquids often do not fuse instantaneously upon contact. Rather, intermediate noncoalescence is observed. Two separate drop bodies, connected by a thin liquid neck, move over the substrate. Supported by new experimental data, a thin film hydrodynamic analysis of this state is presented. Presumably advective and diffusive volume fluxes in the neck region establish a localized and temporarily stable surface tension gradient. This induces a local surface (Marangoni) flow that stabilizes a traveling wave, i.e., the observed moving twin drop configuration. The theoretical predictions are in excellent agreement with the experimental findings.
Tritium test of a ferro-fluidic rotary seal
Antipenkov, A.; Day, C.; Adami, H. D.
2008-07-15
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)
Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles
NASA Astrophysics Data System (ADS)
Brullot, W.; Reddy, N. K.; Wouters, J.; Valev, V. K.; Goderis, B.; Vermant, J.; Verbiest, T.
2012-06-01
Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles were obtained by a facile protocol and thoroughly characterized. Superparamagnetic iron oxide nanoparticles synthesized using a modified forced hydrolysis method were functionalized with polyethylene glycol silane (PEG silane), precipitated and dried. These functionalized particles are dispersable in a range of solvents and concentrations depending on the desired properties. Examples of tunable properties are magnetic behavior, optical and magneto-optical response, thermal features and rheological behavior. As such, PEG silane functionalized particles represent a platform for the development of new materials that have broad applicability in e.g. biomedical, industrial or photonic environments. Magnetic, optical, magneto-optical, thermal and rheological properties of several ferrofluids based on PEG coated particles with different concentrations of particles dispersed in low molecular mass polyethylene glycol were investigated, establishing the applicability of such materials.
Domain Structure and MR Effect of Ferrofluid Emulsion
NASA Astrophysics Data System (ADS)
Ogawa, Chikara; Masubuchi, Yuichi; Takimoto, Jun-Ichi; Koyama, Kiyohito
Blends of immiscible liquids with different dielectric constants and viscosities were known to show the ER effect due to the change of the domain structure by the electric field. In this paper, we report on our attempt to explore the possibility of the magnetic analog of these blend-type ER fluids. Water-based ferrofluid was blended with silicone oil with higher viscosity than the ferrofluid, in order to see whether the negative MR effect can be induced. The domain structure and the viscosity under the magnetic field and shear flow were studied. Growth of the droplet due to coalescence was observed under the field, which resulted in the gradual decrease of the shear viscosity.
Effect of interparticle interaction on magnetic hyperthermia in ferrofluids
NASA Astrophysics Data System (ADS)
Zubarev, A. Yu.; Iskakova, L.; Abu-Bakr, A. F.
2015-11-01
The work deals with the theoretical study of effect of magnetic interaction between single-domain ferromagnetic particles on the hyperthermia effect produced by these particles under the action of oscillating magnetic field. We consider a homogeneous (without heterogeneous aggregates) ferrofluid consisting of identical spherical Brownian particles. Effects of the particles diameter and their magnetic properties on the intensity of the heat production are studied.
Size dependence of magnetorheological properties of cobalt ferrite ferrofluid
NASA Astrophysics Data System (ADS)
Radhika, B.; Sahoo, Rasmita; Srinath, S.
2015-06-01
Cobalt Ferrite nanoparticles were synthesized using co-precipitation method at reaction temperatures of 40°C and 80°C. X-Ray diffraction studies confirm cubic phase formation. The average crystallite sizes were found to be ˜30nm and ˜48nm for 40°C sample and 80°C sample respectively. Magnetic properties measured using vibrating sample magnetometer show higher coercivety and magnetization for sample prepared at 80°C. Magnetorheological properties of CoFe2O4 ferrofluids were measured and studied.
Small-amplitude oscillatory shear magnetorheology of inverse ferrofluids.
Ramos, Jose; de Vicente, Juan; Hidalgo-Alvarez, Roque
2010-06-15
A comprehensive investigation is performed on highly monodisperse silica-based inverse ferrofluids under small-amplitude oscillatory shear in the presence of external magnetic fields up to 1 T. The effect of particle volume fraction and continuous medium Newtonian viscosity is thoroughly investigated. Experimental results for storage modulus are used to validate existing micromechanical magnetorheological models assuming different particle-level field-induced structures. PMID:20345105
Coupling of blocking and melting in cobalt ferrofluids Tianlong Wen,1,a
Krishnan, Kannan M.
Coupling of blocking and melting in cobalt ferrofluids Tianlong Wen,1,a Wenkel Liang,2 and Kannan M performed on ferrofluids of cobalt magnetic nanoparticles MNPs in various organic solvent. Two peaks, one Brownian relaxation of cobalt MNPs when TB TM by in- specting the M spectrum8 of the FFs. Cobalt MNPs were
Moridis, George J. (Oakland, CA); Oldenburg, Curtis M. (Mill Valley, CA)
2001-01-01
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.
Interaction model for magnetic holes in a ferrofluid layer Renaud Toussaint*
Toussaint, Renaud
of the magnetic particles 0.01 m in suspension. The ferrofluid appears then as homogeneous at the scaleInteraction model for magnetic holes in a ferrofluid layer Renaud Toussaint* Department of Physics layer magnetic holes present dipolar interactions when an external magnetic field is exerted
Preparation of a novel ferrofluidic photoresist for two-photon photopolymerization technique
NASA Astrophysics Data System (ADS)
Tian, Ye; Lu, Dongxiao; Jiang, Haobo; Lin, Xiaomei
2012-10-01
We present a novel route for the preparation of ferrofluidic photoresist compatible with two-photon photopolymerization (TPP). To get a homogeneous ferrofluidic photoresit, the compatibility of photoresist and magnetic materials has been improved. Monodispersed Fe3O4 nanoparticles synthesized via thermal decomposition of iron precursor were stabilized by 6-(methacryloyloxy) hexanoic acid (a kind of acrylate-based monomer). A ferrofluidic photoresist was prepared by doping the modified Fe3O4 nanoparticles in acrylate-based resin. In this way, the dispersibility of nanoparticles in photoresist was enhanced significantly. As a representative example, a precise magnetic micron-sized spring was created. In the test of the magnetic response, the sensitivity of magnetic microspring was improved remarkably due to the optimization of the ferrofluidic photoresist. When the intensity of external magnetic field reached a value of 1500 Gs, the deformation rate of the microspring would get to 2.25, indicating the compatibility of the ferrofluidic photoresist in microfabrication.
NASA Astrophysics Data System (ADS)
Manoliu, Al.; Antohe, Lacramioara; Creanga, Dorina E.; Cotae, C.
1999-07-01
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.
The effect of suspended Fe3O4 nanoparticle size on magneto-optical properties of ferrofluids
NASA Astrophysics Data System (ADS)
Brojabasi, Surajit; Muthukumaran, T.; Laskar, J. M.; Philip, John
2015-02-01
We investigate the effect of hydrodynamic particle size on the magnetic field induced light transmission and transmitted speckle pattern in water based ferrofluids containing functionalized Fe3O4 nanoparticles of size ranging from 15 to 46 nm. Three water-based magnetic nanofluids, containing Fe3O4 nanoparticles functionalized with poly-acrylic acid (PAA), tetra-methyl ammonium hydroxide (TMAOH) and phosphate, are used in the present study. In all three cases, the transmitted light intensity starts decreasing above a certain magnetic field (called first critical field) and becomes a minimum at another field (second critical field). These two critical fields signify the onset of linear aggregation process and zippering transitions between fully grown chains, respectively. Both these critical fields shift towards a lower magnetic field with increasing hydrodynamic diameter, due to stronger magnetic dipolar interactions. The first and the second critical fields showed a power law dependence on the hydrodynamic diameters. The dipolar resonances occurring at certain values of the scatterer size, leads to the field induced extinction of light. Both the onset of chaining and zippering transitions were clearly evident in the time dependent transmitted light intensity. Above the first critical field, the lobe part of the transmitted intensity and the lobe speckle contrast values increase with increasing external magnetic field due to reduced Brownian motion of the field induced aggregates. The speckle contrast was highest for nanoparticle with the largest hydrodynamic diameter, due to reduced Brownian motion. These results provide better insight into field dependent light control in magnetic colloids, which may find interesting applications in magneto-optical devices.
Anisotropy of magnetoviscous effect in structure-forming ferrofluids.
Sreekumari, Aparna; Ilg, Patrick
2015-07-01
The magnetoviscous effect, change in viscosity with change in magnetic field strength, and the anisotropy of the magnetoviscous effect, change in viscosity with orientation of magnetic field, have been a focus of interest for four decades. A satisfactory understanding of the microscopic origin of anisotropy of the magnetoviscous effect in magnetic fluids is still a matter of debate and a field of intense research. Here, we present an extensive simulation study to understand the relation between the anisotropy of the magnetoviscous effect and the underlying change in microstructures of ferrofluids. Our results indicate that field-induced chainlike structures respond very differently depending on their orientation relative to the direction of an externally applied shear flow, which leads to a pronounced anisotropy of viscosity. In this work, we focus on three exemplary values of dipolar interaction strengths which correspond to weak, intermediate, and strong interactions between dipolar colloidal particles. We compare our simulation results with an experimental study on cobalt-based ferrofluids as well as with an existing theoretical model called the chain model. A nonmonotonic behavior in the anisotropy of the magnetoviscous effect is observed with increasing dipolar interaction strength and is explained in terms of microstructure formation. PMID:26274161
Anisotropy of magnetoviscous effect in structure-forming ferrofluids
NASA Astrophysics Data System (ADS)
Sreekumari, Aparna; Ilg, Patrick
2015-07-01
The magnetoviscous effect, change in viscosity with change in magnetic field strength, and the anisotropy of the magnetoviscous effect, change in viscosity with orientation of magnetic field, have been a focus of interest for four decades. A satisfactory understanding of the microscopic origin of anisotropy of the magnetoviscous effect in magnetic fluids is still a matter of debate and a field of intense research. Here, we present an extensive simulation study to understand the relation between the anisotropy of the magnetoviscous effect and the underlying change in microstructures of ferrofluids. Our results indicate that field-induced chainlike structures respond very differently depending on their orientation relative to the direction of an externally applied shear flow, which leads to a pronounced anisotropy of viscosity. In this work, we focus on three exemplary values of dipolar interaction strengths which correspond to weak, intermediate, and strong interactions between dipolar colloidal particles. We compare our simulation results with an experimental study on cobalt-based ferrofluids as well as with an existing theoretical model called the chain model. A nonmonotonic behavior in the anisotropy of the magnetoviscous effect is observed with increasing dipolar interaction strength and is explained in terms of microstructure formation.
A comparative study of different ferrofluid constitutive equations.
NASA Astrophysics Data System (ADS)
Kaloni, Purna
2011-11-01
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 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.
Nonlinear deformation of a ferrofluid droplet in a uniform magnetic field.
Zhu, Gui-Ping; Nguyen, Nam-Trung; Ramanujan, R V; Huang, Xiao-Yang
2011-12-20
This paper reports experimental and numerical results of the deformation of a ferrofluid droplet on a superhydrophobic surface under the effect of a uniform magnetic field. A water-based ferrofluid droplet surrounded by immiscible mineral oil was stretched by a magnetic field parallel to the substrate surface. The results show that an increasing flux density increases the droplet width and decreases the droplet height. A numerical model was established to study the equilibrium shape of the ferrofluid droplet. The governing equations for physical fields, including the magnetic field, are solved by the finite volume method. The interface between the two immiscible liquids was tracked by the level-set method. Nonlinear magnetization was implemented in the model. Comparison between experimental and numerical results shows that the numerical model can predict well the nonlinear deformation of a ferrofluid droplet in a uniform magnetic field. PMID:22044246
Design and manufacture of a modular cylindrical apparatus for ferrofluid experimentation
Schoen, Katrina Leigh
2011-01-01
Ferrofluids, colloidal suspensions of coated magnetic nanoparticles inside a carrier fluid, respond to externally applied magnetic fields. This thesis addresses the behavior of these fluids when subjected to an azimuthally ...
Snively, Michael John
2011-01-01
The mechanisms that lead to bulk flow within a ferrofluid-filled container subjected to a rotating uniform magnetic field are experimentally studied. There are two prevailing theories: spin diffusion theory and flow due ...
Three-dimensional x-ray imaging of macro-clusters in ferrofluids
NASA Astrophysics Data System (ADS)
Lee, Wah-Keat
2009-11-01
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.
Hydrodynamics of Turning Flocks.
Yang, Xingbo; Marchetti, M Cristina
2015-12-18
We present a hydrodynamic model of flocking that generalizes the familiar Toner-Tu equations to incorporate turning inertia of well-polarized flocks. The continuum equations controlled by only two dimensionless parameters, orientational inertia and alignment strength, are derived by coarse-graining the inertial spin model recently proposed by Cavagna et al. The interplay between orientational inertia and bend elasticity of the flock yields anisotropic spin waves that mediate the propagation of turning information throughout the flock. The coupling between spin-current density to the local vorticity field through a nonlinear friction gives rise to a hydrodynamic mode with angular-dependent propagation speed at long wavelengths. This mode becomes unstable as a result of the growth of bend and splay deformations augmented by the spin wave, signaling the transition to complex spatiotemporal patterns of continuously turning and swirling flocks. PMID:26722945
Finite element model of magnetoconvection of a ferrofluid
NASA Astrophysics Data System (ADS)
Snyder, Suzanne M.; Cader, Tahir; Finlayson, Bruce A.
2003-06-01
Combined natural and magnetic convective heat transfer through a ferrofluid in a cubic enclosure is simulated numerically. The momentum equation includes a magnetic term that arises when a magnetic fluid is in the presence of a magnetic field gradient and a temperature gradient. In order to validate the theory, the wall temperature isotherms and Nusselt numbers are compared to experimental work of Sawada et al. (Int. J. Appl. Electromagn. Mater. 4 (1994) 329). Results are obtained using standard computational fluid dynamics codes, with modifications to account for the Langevin factor when needed. The CFD code FIDAP uses the finite element method, sometimes with a user-defined subroutine. The CFD code FEMLAB uses the finite element method with a user-supplied body force.
Photonic Dipole Contours of Ferrofluid Hele-Shaw Cell
Michael Snyder; Jonathan Frederick
2009-03-31
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. 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 dipole nature. A simple way of explaining this work is to think of the old magnetic iron filling experiments; but now each iron filling is a molecule floating in a liquid. Each molecule has the freedom to act as an independent lens that can be aligned by an external magnetic field. Because each lens directs light, the external field can be analyzed by following the light paths captured in the photographs.
Falcon, Eric
magnetic and gravitational energies. The ferrofluid used is an ionic aqueous suspension synthesized with 12Instability of the Origami of a Ferrofluid Drop in a Magnetic Field Timothe´e Jamin, Charlotte Py capillary and elastic forces. Here, we use a drop of magnetic fluid whose shape is known to strongly depend
Lacoste, David
perpendicular to a thin sample layer, a suspension of magnetic colloidal particles ferrofluid can form spatially of these suspensions in which particle concentration and magnetization, determined by the degree of alignmentPhase transitions in a ferrofluid at magnetic-field-induced microphase separation D. Lacoste and T
Probst, R.; Lin, J.; Komaee, A.; Nacev, A.; Cummins, Z.
2010-01-01
Any single permanent or electro magnet will always attract a magnetic fluid. For this reason it is difficult to precisely position and manipulate ferrofluid at a distance from magnets. We develop and experimentally demonstrate optimal (minimum electrical power) 2-dimensional manipulation of a single droplet of ferrofluid by feedback control of 4 external electromagnets. The control algorithm we have developed takes into account, and is explicitly designed for, the nonlinear (fast decay in space, quadratic in magnet strength) nature of how the magnets actuate the ferrofluid, and it also corrects for electro-magnet charging time delays. With this control, we show that dynamic actuation of electro-magnets held outside a domain can be used to position a droplet of ferrofluid to any desired location and steer it along any desired path within that domain – an example of precision control of a ferrofluid by magnets acting at a distance. PMID:21218157
Probst, R; Lin, J; Komaee, A; Nacev, A; Cummins, Z; Shapiro, B
2011-04-01
Any single permanent or electro magnet will always attract a magnetic fluid. For this reason it is difficult to precisely position and manipulate ferrofluid at a distance from magnets. We develop and experimentally demonstrate optimal (minimum electrical power) 2-dimensional manipulation of a single droplet of ferrofluid by feedback control of 4 external electromagnets. The control algorithm we have developed takes into account, and is explicitly designed for, the nonlinear (fast decay in space, quadratic in magnet strength) nature of how the magnets actuate the ferrofluid, and it also corrects for electro-magnet charging time delays. With this control, we show that dynamic actuation of electro-magnets held outside a domain can be used to position a droplet of ferrofluid to any desired location and steer it along any desired path within that domain - an example of precision control of a ferrofluid by magnets acting at a distance. PMID:21218157
Supersonic flow past bodies in dispersive hydrodynamics
Gurevich, A.V.; Krylov, A.L.; Khodorovskii, V.V.
1995-07-01
The problem of steady two-dimensional supersonic flow about slender pointed bodies is studied in dispersive hydrodynamics. The equivalence of this problem to the Gurevich-Pitaevskii evolutionary problem of dissipationless shock waves in Korteweg-de Vries hydrodynamics is shown. The Whitham technique is used to derive a number of exact solutions describing different cases of flow around objects in dispersive hydrodynamics. 22 refs., 7 figs.
ERIC Educational Resources Information Center
Lafrance, Pierre
1978-01-01
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)
Interfacial stress balances in structured continua and free surface flows in ferrofluids
Chaves, Arlex; Rinaldi, Carlos
2014-04-15
Interfacial linear and internal angular momentum balances are obtained for a structured continuum and for the special case of a ferrofluid, a suspension of magnetic nanoparticles in a Newtonian fluid. The interfacial balance equations account for the effects of surface tension and surface tension gradient, magnetic surface excess forces, antisymmetric stresses, and couple stresses in driving interfacial flows in ferrofluids. Application of the interfacial balance equations is illustrated by obtaining analytical expressions for the translational and spin velocity profiles in a thin film of ferrofluid on an infinite flat plate when a rotating magnetic field is applied with axis of rotation parallel to the ferrofluid/air interface. The cases of zero and non-zero spin viscosity are considered for small applied magnetic field amplitude. Expressions for the maximum translational velocity, slope of the translational velocity profile at the ferrofluid/air interface, and volumetric flow rate are obtained and their use to test the relevance of spin viscosity and couple stresses in the flow situation under consideration is discussed.
NASA Astrophysics Data System (ADS)
López, J.; González, Luz E.; Quiñonez, M. F.; Gómez, M. E.; Porras-Montenegro, N.; Zambrano, G.
2014-05-01
Ferrofluids based on magnetic Co0.25Zn0.75Fe2O4 ferrite nanoparticles were prepared by co-precipitation method from aqueous salt solutions of Co (II), ZnSO4, and Fe (III) in an alkaline medium. Ferrofluids placed in an external magnetic field show properties that make them interesting as magneto-controllable soft photonic crystals. Morphological and structural characterizations of the samples were obtained from Scanning Electron Microscopy and Transmission Electron Microscopy studies. Magnetic properties were investigated with the aid of a vibrating sample magnetometer at room temperature. Herein, the Co0.25Zn0.75Fe2O4 samples showed superparamagnetic behavior, according to hysteresis loop results. Taking in mind that the Co-Zn ferrite hysteresis loop is very small, our magnetic nanoparticles can be considered soft magnetic material with interesting technological applications. In addition, by using the plane-wave expansion method, we studied the photonic band structure of 2D photonic crystals made of ferrofluids with the same nanoparticles. Previous experimental results show that a magnetic field applied perpendicular to the ferrofluid plane agglomerates the magnetic nanoparticles in parallel rods to form a hexagonal 2D photonic crystal. We calculated the photonic band structure of photonic crystals by means of the effective refractive index of the magnetic fluid, basing the study on the Maxwell-Garnett theory, finding that the photonic band structure does not present any band gaps under the action of applied magnetic field strengths used in our experimental conditions.
López, J. González, Luz E.; Quiñonez, M. F.; Gómez, M. E.; Porras-Montenegro, N.; Zambrano, G.
2014-05-21
Ferrofluids based on magnetic Co{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} ferrite nanoparticles were prepared by co-precipitation method from aqueous salt solutions of Co (II), ZnSO{sub 4}, and Fe (III) in an alkaline medium. Ferrofluids placed in an external magnetic field show properties that make them interesting as magneto-controllable soft photonic crystals. Morphological and structural characterizations of the samples were obtained from Scanning Electron Microscopy and Transmission Electron Microscopy studies. Magnetic properties were investigated with the aid of a vibrating sample magnetometer at room temperature. Herein, the Co{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} samples showed superparamagnetic behavior, according to hysteresis loop results. Taking in mind that the Co-Zn ferrite hysteresis loop is very small, our magnetic nanoparticles can be considered soft magnetic material with interesting technological applications. In addition, by using the plane-wave expansion method, we studied the photonic band structure of 2D photonic crystals made of ferrofluids with the same nanoparticles. Previous experimental results show that a magnetic field applied perpendicular to the ferrofluid plane agglomerates the magnetic nanoparticles in parallel rods to form a hexagonal 2D photonic crystal. We calculated the photonic band structure of photonic crystals by means of the effective refractive index of the magnetic fluid, basing the study on the Maxwell-Garnett theory, finding that the photonic band structure does not present any band gaps under the action of applied magnetic field strengths used in our experimental conditions.
Mueller, Bernhard; Janka, Hans-Thomas; Marek, Andreas E-mail: thj@mpa-garching.mpg.de
2013-03-20
We present a detailed theoretical analysis of the gravitational wave (GW) signal of the post-bounce evolution of core-collapse supernovae (SNe), employing for the first time relativistic, two-dimensional explosion models with multi-group, three-flavor neutrino transport based on the ray-by-ray-plus approximation. The waveforms reflect the accelerated mass motions associated with the characteristic evolutionary stages that were also identified in previous works: a quasi-periodic modulation by prompt post-shock convection is followed by a phase of relative quiescence before growing amplitudes signal violent hydrodynamical activity due to convection and the standing accretion shock instability during the accretion period of the stalled shock. Finally, a high-frequency, low-amplitude variation from proto-neutron star (PNS) convection below the neutrinosphere appears superimposed on the low-frequency trend associated with the aspherical expansion of the SN shock after the onset of the explosion. Relativistic effects in combination with detailed neutrino transport are shown to be essential for quantitative predictions of the GW frequency evolution and energy spectrum, because they determine the structure of the PNS surface layer and its characteristic g-mode frequency. Burst-like high-frequency activity phases, correlated with sudden luminosity increase and spectral hardening of electron (anti-)neutrino emission for some 10 ms, are discovered as new features after the onset of the explosion. They correspond to intermittent episodes of anisotropic accretion by the PNS in the case of fallback SNe. We find stronger signals for more massive progenitors with large accretion rates. The typical frequencies are higher for massive PNSs, though the time-integrated spectrum also strongly depends on the model dynamics.
A new method to prepare water based Fe3O4 ferrofluid with high stabilization
NASA Astrophysics Data System (ADS)
Guo, Tongxiao; Bian, Xiufang; Yang, Chuncheng
2015-11-01
A new method to prepare water based Fe3O4 ferrofluid with high stabilization has been reported in this paper. Oleic acid/ polyethylene glycol 4000 (PEG 4000)/agar/oleic acid have been used as surfactants and added to the fluid one after another. X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS) method, Fourier transform infrared (FT-IR) spectra and thermogravimetric analysis (TGA) have been used to characterize the structure, component and morphology of magnetic nanoparticles, respectively. We have observed the microstructure of chain-like (or stick-like) structure under applied magnetic field, which composes of several nanoparticles in the width direction and hundreds of nanoparticles in the length direction. Vibrating sample magnetometer (VSM) and Gouy magnetic balance (GMB) have been used to measure the magnetic properties and stability of the ferrofluid. The result shows that the magnetic nanoparticles have high saturation magnetization and the ferrofluid has high stability under magnetic and gravitational field.
Paul, Nibedita; Devi, Manasi; Mohanta, Dambarudhar; Saha, Abhijit
2012-02-15
The present work reports on magnetically induced optical activity (such as Faraday rotation and linear dichroism) of pristine and gamma-irradiated gadolinium oxide (Gd{sub 2}O{sub 3}) nanoparticle-based ferrofluids. The ferrofluids were produced by dispersing N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB)-coated {approx}9-nm-sized Gd{sub 2}O{sub 3} particles in a carrier fluid of ethanol. The ferrofluids were then irradiated with 1.25 MeV energetic gamma rays (dose: 868 Gy and 2.635 kGy). Irradiation-led formation of a number of point defects was revealed through high resolution electron microscopy. The interaction of light with the ionized point defects is believed to have caused substantial improvement in the magneto-optic response of irradiated magnetic fluids.
NASA Astrophysics Data System (ADS)
Lopez, Javier; Gonzalez, Luz Esther; Quinonez, Mario; Porras, Nelson; Zambrano, Gustavo; Gomez, Maria Elena
2014-03-01
Using a ferrfluid of cobalt-zinc ferrite nanoparticles Co(1 - x)ZnxFe2O4 coated with oleic acid and suspended in ethanol, we have fabricated a 2D photonic crystal (PC) by the application of an external magnetic field perpendicular to the plane of the ferrofluid. The 2D PC is made by rods of nanoparticles organized in a hexagonal structure. By means of the plane-wave expansion method, we study its photonic band structure (PBS) which depends on the effective permittivity and on the area ratio of the liquid phase. Additionaly, taking into account the Maxwell-Garnett theory we calculated the effective permittivity of the rods. We have found that the effective refractive index of the ferrofluid increases with its magnetization. Using these results we calculate the band structure of the photonic crystal at different applied magnetic fields, finding that the increase of the applied magnetic field shifts the band structure to lower frequencies with the appearance of more band gaps. Departamento de Física, Universidad del Valle, A.A. 25360, Cali, Colombia
Eric Lauga
2015-09-07
Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells yet they represent the bulk of the world's biomass, and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds-number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micron scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically-complex environments. Using hydrodynamics as an organizing framework, we review the biomechanics of bacterial motility and look ahead to future challenges.
Lauga, Eric
2015-01-01
Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells yet they represent the bulk of the world's biomass, and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds-number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micron scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically-complex environments. Using hydrodynamics as an organizing framework, we review the biomechanics of bacterial motility and look ahead to future challenges.
Elastic stability of silicone ferrofluid internal tamponade (SFIT) in retinal detachment surgery
NASA Astrophysics Data System (ADS)
Voltairas, P. A.; Fotiadis, D. I.; Massalas, C. V.
2001-01-01
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.
Magnetic field tunability of optical microfiber taper integrated with ferrofluid.
Miao, Yinping; Wu, Jixuan; Lin, Wei; Zhang, Kailiang; Yuan, Yujie; Song, Binbin; Zhang, Hao; Liu, Bo; Yao, Jianquan
2013-12-01
Optical microfiber taper has unique propagation properties, which provides versatile waveguide structure to design the tunable photonic devices. In this paper, the S-tapered microfiber is fabricated by using simple fusion spicing. The spectral characteristics of microfiber taper integrated with ferrofluid under different magnetic-field intensities have been theoretically analyzed and experimentally demonstrated. The spectrum are both found to become highly magnetic-field-dependent. The results indicate the transmission and wavelength of the dips are adjustable by changing magnetic field intensity. The response of this device to the magnetic field intensity exhibits a Langvin function. Moreover, there is a linear relationship between the transmission loss and magnetic field intensity for a magnetic field intensity range of 25 to 200Oe, and the sensitivities as high as 0.13056dB/Oe and 0.056nm/Oe have been achieved, respectively. This suggests a potential application of this device as a tunable all-in-fiber photonic device, such as magneto-optic modulator, filter, and sensing element. PMID:24514542
Stable ferrofluids of magnetite nanoparticles in hydrophobic ionic liquids
NASA Astrophysics Data System (ADS)
Mestrom, Luuk; Lenders, Jos J. M.; de Groot, Rick; Hooghoudt, Tonnis; Sommerdijk, Nico A. J. M.; Vilaplana Artigas, Marcel
2015-07-01
Ferrofluids (FFs) of metal oxide nanoparticles in ionic liquids (ILs) are a potentially useful class of magnetic materials for many applications because of their properties related to temperature/pressure stability, hydrophobicity, viscosity and recyclability. In this work, the screening of several designer surfactants for their stabilizing capabilities has resulted in the synthesis of stable FFs of superparamagnetic 7 ± 2 nm magnetite (Fe3O4) nanoparticles in the hydrophobic IL 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([CRMIM][NTf2]). The designed and synthesized 1-butyl-3-(10-carboxydecyl)-1H-imidazol-3-ium bromide (ILC10-COOH) surfactant that combines the same imidazole moiety as the IL with a long alkyl chain ensured compatibility with the IL and increased the steric repulsion between the magnetite nanoparticles sufficiently such that stable dispersions of up to 50 wt% magnetite were obtained according to stability tests in the presence of a magnetic field (0.5-1 Tesla). Cryo-transmission electron microscopy (cryo-TEM) of the IL-based FFs allowed direct visualization of the surfactant-stabilized nanoparticles in the ILs and the native, hardly aggregated state of their dispersion.
Structure and Dynamics of Ferrofluid Emulsion in Magnetic Field
NASA Astrophysics Data System (ADS)
Liu, Jing
1996-03-01
Ferrofluid emulsion is an oil-in-water suspension where each oil droplet contains thousands of magnetic grains. An applied magnetic field induces a magnetic dipole moment in each droplet. When the dipole-dipole interaction energy exceeds the thermal energy, a structural transition occurs as the randomly dispersed droplets form chains and chains further coalesce to form columns or other larger structures. This field-induced structures increase viscosity of the fluid dramatically and give rise to finite yield stress, leading to many potential applications such as active vibration damper. The mechanism of the chain coarsening to columns is the key in understanding the physics of this novel material and its application. I will discuss the chain dynamics studied by dynamic light scattering in a dilute system and column formation studied by optical microscopy and static light scattering in a denser system. I will then show the comparison of the experiments with theoretical models based on chain fluctuation to understand the chain dynamics and the chain coarsening mechanism.
Moridis, G.J.; Borglin, S.E.; Oldenburg, C.M.; Becker, A.
1998-03-01
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.
NASA Astrophysics Data System (ADS)
Jeon, Sangyong; Heinz, Ulrich
2015-10-01
Hydrodynamics has been successful in providing a good description of the bulk dynamics in ultra-relativistic heavy ion collisions. In this brief review, we provide basics of the theory of viscous hydrodynamics. Topics covered include derivation of the 2nd order viscous hydrodynamics from the linear response theory and kinetic theory, viscous anisotropic hydrodynamics, and numerical implementation of relativistic hydrodynamics.
King, Lyon B.
mixture that is superparamagnetic and electrically conductive. In the presence of a magnetic field and is coined the Rosensweig-Taylor instability. This combination of magnetic with electric stress on the fluid ferrofluid emission source through the use of a stepper motor. Current density vs. angle was recorded for two
Magnetic Field-Controlled Lithium Polysulfide Semiliquid Battery with Ferrofluidic Properties
Cui, Yi
,7,9,10 such as vanadium redox batteries, typically operate at low voltages (Magnetic Field-Controlled Lithium Polysulfide Semiliquid Battery with Ferrofluidic Properties that can deliver high energy density and efficiency for such storage often involve the flow of redox
Two-Dimensional Melting of a Crystal of Ferrofluid Spikes Francois Boyer1
Falcon, Eric
driven by a magnetic field gradient, magnetic levitation, labyrinthine and Rosensweig instabilities [18 thin colloidal suspensions [11,12], liquid films [13], vibrated granular monolayers [14,15], magnetic]. This latter occurs when a normal static magnetic field applied to a pool of ferrofluid exceeds a critical
NASA Astrophysics Data System (ADS)
de, Anindya
2005-11-01
Ferrofluids are colloidal suspensions of magnetic nanoparticles in carrier liquids which can be readily maneuvered from a distance using magnetic fields. When functionalized with different antibodies or medicinal compounds the ferrofluid nanoparticles can be used for various purposes, e.g., to detect bacteria or as a carrier of chemotherapeutic agents for targeted drug delivery. Localized magnetic nanoparticle agglomerates can also be remotely moved to create perturbations within a microchannel flow, thereby resulting in better mixing of various fluids. We have numerically investigated ferrofluid agglomeration and its influence on enhancing local mixing in microchannels by using the lattice Boltzmann method. Employing this method, we solve for the one-particle probability distribution function f which denotes the probability density of finding a particle at time t, at the location x, moving with velocity v when a force F is acting on it. (A Chapman-Enskog expansion recreates the continuum relation and the Navier-Stokes equation for weakly compressible flows.) We have simulated ferrofluid agglomeration near a magnetic dipole for flow through a rectangular microchannel. When a number of such magnets are placed across the channel and activated in sequence, they locally perturb the fluid flow to produce better mixing in two initially unmixed fluids.
Direct observations of field-induced assemblies in magnetite ferrofluids
NASA Astrophysics Data System (ADS)
Mousavi, N. S. Susan; Khapli, Sachin D.; Kumar, Sunil
2015-03-01
Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ? 10 nm) is studied with an emphasis on examining the effects of particle concentration (?) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ? = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05-0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.
Colgate, S.A.
1981-01-01
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.
Waves in Radial Gravity Using Magnetic Fluid
NASA Technical Reports Server (NTRS)
Ohlsen, D. R.; Hart, J. E.; Weidman, P. D.
1999-01-01
Terrestrial laboratory experiments studying various fluid dynamical processes are constrained, by being in an Earth laboratory, to have a gravitational body force which is uniform and unidirectional. Therefore fluid free-surfaces are horizontal and flat. Such free surfaces must have a vertical solid boundary to keep the fluid from spreading horizontally along a gravitational potential surface. In atmospheric, oceanic, or stellar fluid flows that have a horizontal scale of about one-tenth the body radius or larger, sphericity is important in the dynamics. Further, fluids in spherical geometry can cover an entire domain without any sidewall effects, i.e. have truly periodic boundary conditions. We describe spherical body-force laboratory experiments using ferrofluid. Ferrofluids are dilute suspensions of magnetic dipoles, for example magnetite particles of order 10 nm diameter, suspended in a carrier fluid. Ferrofluids are subject to an additional body force in the presence of an applied magnetic field gradient. We use this body force to conduct laboratory experiments in spherical geometry. The present study is a laboratory technique improvement. The apparatus is cylindrically axisymmetric. A cylindrical ceramic magnet is embedded in a smooth, solid, spherical PVC ball. The geopotential field and its gradient, the body force, were made nearly spherical by careful choice of magnet height-to-diameter ratio and magnet size relative to the PVC ball size. Terrestrial gravity is eliminated from the dynamics by immersing the "planet" and its ferrofluid "ocean" in an immiscible silicone oil/freon mixture of the same density. Thus the earth gravity is removed from the dynamics of the ferrofluid/oil interface and the only dynamically active force there is the radial magnetic gravity. The entire apparatus can rotate, and waves are forced on the ferrofluid surface by exterior magnets. The biggest improvement in technique is in the wave visualization. Fluorescing dye is added to the oil/freon mixture and an argon ion laser generates a horizontal light that can be scanned vertically. Viewed from above, the experiment is a black circle with wave deformations surrounded by a light background. A contour of the image intensity at any light sheet position gives the surface of the ferrofluid "ocean" at that "latitude". Radial displacements of the waves as a function of longitude are obtained by subtracting the contour line positions from a no-motion contour at that laser sheet latitude. The experiments are run by traversing the forcing magnet with the laser sheet height fixed and images are frame grabbed to obtain a time-series at one latitude. The experiment is then re-run with another laser-sheet height to generate a full picture of the three-dimensional wave structure in the upper hemisphere of the ball as a function of time. We concentrate here on results of laboratory studies of waves that are important in Earth's atmosphere and especially the ocean. To get oceanic scaling in the laboratory, the experiment must rotate rapidly (4-second rotation period) so that the wave speed is slow compared to the planetary rotation speed as in the ocean. In the Pacific Ocean, eastward propagating Kelvin waves eventually run into the South American coast. Theory predicts that some of the wave energy should scatter into coastal-trapped Kelvin waves that propagate north and south along the coast. Some of this coastal wave energy might then scatter into mid-latitude Rossby waves that propagate back westward. Satellite observations of the Pacific Ocean sea-surface temperature and height seem to show signatures of westward propagating mid-latitude Rossby waves, 5 to 10 years after the 1982-83 El Nino. The observational data is difficult to interpret unambiguously owing to the large range of motions that fill the ocean at shorter timescales. This series of reflections giving eastward, north- ward, and then westward traveling waves is observed cleanly in the laboratory experiments, confirming the theoretical expectations
Felicia, Leona J; Philip, John
2015-03-24
For many technological applications of ferrofluids, the magnetorheological properties require being precisely controlled. We study the effect of hydrophilic silica on the magnetorheology of an oil-based ferrofluid containing Fe3O4 nanoparticles of size ?10 nm. We observe that the presence of silica nanoparticles lowers the yield stresses, viscoelastic moduli, and shear thinning behavior of the ferrofluid because of the weakening of dipolar interactions, which was evident from the observed lower yield stresses exponent (<2). The ferrofluid containing silica exhibits a dominant elastic behavior, a reduced hysteresis during the forward and reverse magnetic field sweeps, and a longer linear viscoelastic regime under nonlinear deformation. The Mason number plots at low shear rates and magnetic fields show deviations from the master curve in the presence of silica. The magnetic field induced microstructures, visualized using opto-magnetorheometer, showed columnar aggregate structures along the field directions, which are reoriented along the shear flow direction at high shear rates. The image analysis shows that the average thickness of the columnar aggregates in pure ferrofluid is much larger than that of the mixed system, which suggests that the intervening silica matrix hampers the zippering transition of columns at higher magnetic field and shear rates. Our results suggest that optimization of rheological properties of ferrofluids is possible by carefully adding suitable silica nanoparticles, which may find practical applications such as dynamic seals, heat transfer, sensors, and opto-fluidic devices, etc. PMID:25734232
Perspectives in coral reef hydrodynamics
NASA Astrophysics Data System (ADS)
Hearn, Clifford J.
2011-06-01
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.
Hydrodynamics of Turning Flocks
NASA Astrophysics Data System (ADS)
Yang, Xingbo; Marchetti, M. Cristina
2015-03-01
We present a hydrodynamic model of flocking that generalizes the familiar Toner-Tu equations to incorporate turning inertia of well polarized flocks. The continuum equations are derived by coarse graining the inertial spin model recently proposed by Cavagna et al. The interplay between orientational inertia and bend elasticity of the flock yields spin waves that mediate the propagation of turning information throughout the flock. When the inertia is large, we find a novel instability that signals the transition to complex spatio-temporal patterns of continuously turning and swirling flocks. This work was supported by the NSF Awards DMR-1305184 and DGE-1068780 at Syracuse University and NSF Award PHY11-25915 and the Gordon and Betty Moore Foundation Grant No. 2919 at the KITP at the University of California, Santa Barbara.
Bruinsma, Robijn; Grosberg, Alexander Y.; Rabin, Yitzhak; Zidovska, Alexandra
2014-01-01
Following recent observations of large scale correlated motion of chromatin inside the nuclei of live differentiated cells, we present a hydrodynamic theory—the two-fluid model—in which the content of a nucleus is described as a chromatin solution with the nucleoplasm playing the role of the solvent and the chromatin fiber that of a solute. This system is subject to both passive thermal fluctuations and active scalar and vector events that are associated with free energy consumption, such as ATP hydrolysis. Scalar events drive the longitudinal viscoelastic modes (where the chromatin fiber moves relative to the solvent) while vector events generate the transverse modes (where the chromatin fiber moves together with the solvent). Using linear response methods, we derive explicit expressions for the response functions that connect the chromatin density and velocity correlation functions to the corresponding correlation functions of the active sources and the complex viscoelastic moduli of the chromatin solution. We then derive general expressions for the flow spectral density of the chromatin velocity field. We use the theory to analyze experimental results recently obtained by one of the present authors and her co-workers. We find that the time dependence of the experimental data for both native and ATP-depleted chromatin can be well-fitted using a simple model—the Maxwell fluid—for the complex modulus, although there is some discrepancy in terms of the wavevector dependence. Thermal fluctuations of ATP-depleted cells are predominantly longitudinal. ATP-active cells exhibit intense transverse long wavelength velocity fluctuations driven by force dipoles. Fluctuations with wavenumbers larger than a few inverse microns are dominated by concentration fluctuations with the same spectrum as thermal fluctuations but with increased intensity. PMID:24806919
NASA Astrophysics Data System (ADS)
Cherief, Wahid; Avenas, Yvan; Ferrouillat, Sébastien; Kedous-Lebouc, Afef; Jossic, Laurent; Berard, Jean; Petit, Mickael
2015-07-01
Applying a magnetic field on a ferrofluid flow induces a large increase of the convective heat transfer coefficient. In this paper, the thermal-hydraulic behaviors of two commercial ferrofluids are compared. The variations of both the pressure drop and the heat transfer coefficient due to the magnetic field are measured in the following conditions: square duct, laminar flow and uniform wall heat flux. The square section with two insulated walls allows for the characterization of the effect of the magnetic field direction. The experimental results show that the heat transfer is better enhanced when the magnetic field is perpendicular to the heat flux. In the best case, the local heat transfer coefficient increase is about 75%. On the contrary, another experimental setup shows no enhancement of thermal conductivity when the magnetic field is perpendicular to the heat flux. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2014) - Elected submissions", edited by Adel Razek
Heat Transfer in MHD Mixed Convection Flow of a Ferrofluid along a Vertical Channel
Gul, Aaiza; Khan, Ilyas; Shafie, Sharidan; Khalid, Asma; Khan, Arshad
2015-01-01
This study investigated heat transfer in magnetohydrodynamic (MHD) mixed convection flow of ferrofluid along a vertical channel. The channel with non-uniform wall temperatures was taken in a vertical direction with transverse magnetic field. Water with nanoparticles of magnetite (Fe3O4) was selected as a conventional base fluid. In addition, non-magnetic (Al2O3) aluminium oxide nanoparticles were also used. Comparison between magnetic and magnetite nanoparticles were also conducted. Fluid motion was originated due to buoyancy force together with applied pressure gradient. The problem was modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions were obtained for velocity and temperature. Graphical results were plotted and discussed. It was found that temperature and velocity of ferrofluids depend strongly on viscosity and thermal conductivity together with magnetic field. The results of the present study when compared concurred with published work. PMID:26550837
Modeling of retardance in ferrofluid with Taguchi-based multiple regression analysis
NASA Astrophysics Data System (ADS)
Lin, Jing-Fung; Wu, Jyh-Shyang; Sheu, Jer-Jia
2015-03-01
The citric acid (CA) coated Fe3O4 ferrofluids are prepared by a co-precipitation method and the magneto-optical retardance property is measured by a Stokes polarimeter. Optimization and multiple regression of retardance in ferrofluids are executed by combining Taguchi method and Excel. From the nine tests for four parameters, including pH of suspension, molar ratio of CA to Fe3O4, volume of CA, and coating temperature, influence sequence and excellent program are found. Multiple regression analysis and F-test on the significance of regression equation are performed. It is found that the model F value is much larger than Fcritical and significance level P <0.0001. So it can be concluded that the regression model has statistically significant predictive ability. Substituting excellent program into equation, retardance is obtained as 32.703°, higher than the highest value in tests by 11.4%.
Magnetic guidance of ferrofluidic nanoparticles in an in vitro model of intraocular retinal repair
NASA Astrophysics Data System (ADS)
Holligan, D. L.; Gillies, G. T.; Dailey, J. P.
2003-06-01
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.
Ejection of ferrofluid grains using nonlinear acoustic impulses[emdash] A particle dynamical study
Sen, S.; Manciu, M.; Manciu, F.S. )
1999-09-01
We consider a model dilute ferrofluid with the grains suspended in water (e.g.,[gamma]-Fe[sub 2]O[sub 3]) and subject the system to a strong, homogeneous magnetic field directed perpendicular to the surface such that there is chain formation along the field direction. We show that an appropriate impulse initiated at the base of the container might travel as a nondispersive soliton pulse with sufficient energy to overcome surface tension and eject the ferrofluid grain nearest to the liquid[endash]air interface. The proposed mechanism, if successfully realized in the laboratory, could help design a nozzle-free, ink-jet printer of unparalleled resolution. [copyright] [ital 1999 American Institute of Physics.
Heat Transfer in MHD Mixed Convection Flow of a Ferrofluid along a Vertical Channel.
Gul, Aaiza; Khan, Ilyas; Shafie, Sharidan; Khalid, Asma; Khan, Arshad
2015-01-01
This study investigated heat transfer in magnetohydrodynamic (MHD) mixed convection flow of ferrofluid along a vertical channel. The channel with non-uniform wall temperatures was taken in a vertical direction with transverse magnetic field. Water with nanoparticles of magnetite (Fe3O4) was selected as a conventional base fluid. In addition, non-magnetic (Al2O3) aluminium oxide nanoparticles were also used. Comparison between magnetic and magnetite nanoparticles were also conducted. Fluid motion was originated due to buoyancy force together with applied pressure gradient. The problem was modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions were obtained for velocity and temperature. Graphical results were plotted and discussed. It was found that temperature and velocity of ferrofluids depend strongly on viscosity and thermal conductivity together with magnetic field. The results of the present study when compared concurred with published work. PMID:26550837
Mandel, K; Straßer, M; Granath, T; Dembski, S; Sextl, G
2015-02-18
A process is reported to obtain a nanoparticle sol from co-precipitated iron oxide particles without using any surfactant. The sol - a true ferrofluid - is not only stable over a wide range of pH but also in physiological solutions. This is a decisive step towards biomedical applications where nanoparticle agglomeration could so far only be prevented by using unwanted surfactants. PMID:25580829
NASA Astrophysics Data System (ADS)
Lewis, O.; Benson, P. M.; Vinciguerra, S.; Meredith, P. G.
2005-12-01
Most crustal rocks are anisotropic. In volcanic areas, anisotropy primarily results due to preferred directions of microcracks as magma cools. This effect is, in turn, enhanced due to local stress fields during deposition. The combined effects of these processes may thus give rise to a complex anisotropic fabric. Such fabrics can play crucial roles when enhancing the formation of slip surfaces which can lead to sector collapses of volcanic edifices, as is the case of Stromboli volcano (Italy) which experienced 4 sector collapses in the past 13ka. However, the rapid analysis of anisotropic microcrack fabrics (in terms of magnitude and principal direction) remains non-trivial. Current methods range from time consuming microcrack analysis of thin sections to the preparation of oriented cores for elastic-wave velocity measurement. To further our understanding of how microcrack fabrics influence the bulk properties of volcanic basalt, we employ a novel method which rapidly evaluates the 3-D microcrack orientation using technique of Anisotropy of Magnetic Susceptibility (AMS). First, we determine the rock matrix AMS (mAMS) using standard methods (via a Agico KLY-4 Kappabridge). Samples are then saturated with a magnetic ferrofluid, filling the microcrack network with a magnetically susceptible suspension of microscopic (10nm) magnetite particles. The AMS is then re-measured, with the matrix susceptibility values subtracted from these readings to yield the average 3-D pore space shape, size and orientation (pAMS). We describe the use of this method using basalt from Stromboli and comparing to a granite (Takidani) from the Japanese Alps in order to verify the technique and to investigate the relationship between the basalt microcrack geometry and field scale observation. For Takidani granite we find the structural anisotropy formed by the void space, as measured by pAMS, is well described by elastic wave velocity measurement; exhibiting anisotropy values of 19.1% and 7.6% for P-waves and S-waves respectively. Stromboli basalt possesses a weaker anisotropy of 4.7% and 3.0% (P-wave and S-wave velocity). We relate our pore space AMS measurements to the layering observed in Stromboli basalt on the flanks of the volcanic edifice; and infer that the microcrack network is both formed by this deposition and active tectonics as well as providing a key control on its physical properties. Such data has crucial significance upon the accurate assessment of flank stability, with consequences to hazard assessment for the surrounding area.
Theory and simulation of anisotropic pair correlations in ferrofluids in magnetic fields.
Elfimova, Ekaterina A; Ivanov, Alexey O; Camp, Philip J
2012-05-21
Anisotropic pair correlations in ferrofluids exposed to magnetic fields are studied using a combination of statistical-mechanical theory and computer simulations. A simple dipolar hard-sphere model of the magnetic colloidal particles is studied in detail. A virial-expansion theory is constructed for the pair distribution function (PDF) which depends not only on the length of the pair separation vector, but also on its orientation with respect to the field. A detailed comparison is made between the theoretical predictions and accurate simulation data, and it is found that the theory works well for realistic values of the dipolar coupling constant (? = 1), volume fraction (? ? 0.1), and magnetic field strength. The structure factor is computed for wavevectors either parallel or perpendicular to the field. The comparison between theory and simulation is generally very good with realistic ferrofluid parameters. For both the PDF and the structure factor, there are some deviations between theory and simulation at uncommonly high dipolar coupling constants, and with very strong magnetic fields. In particular, the theory is less successful at predicting the behavior of the structure factors at very low wavevectors, and perpendicular Gaussian density fluctuations arising from strongly correlated pairs of magnetic particles. Overall, though, the theory provides reliable predictions for the nature and degree of pair correlations in ferrofluids in magnetic fields, and hence should be of use in the design of functional magnetic materials. PMID:22612098
NASA Astrophysics Data System (ADS)
Alexiou, Ch.; Schmid, R.; Jurgons, R.; et al.
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.
Gui, Lichuan
speed and regular head waves with the Iowa Institute of Hydraulic Research (IIHR) towing tank facilities. Stern Iowa Institute of Hydraulic Research (IIHR), The University of Iowa Iowa City, IA 52242, USA
Algorithm refinement for fluctuating hydrodynamics
Williams, Sarah A.; Bell, John B.; Garcia, Alejandro L.
2007-07-03
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.
LaCure, Mari Mae
2010-04-29
Waves is the supporting document to the Master of Fine Arts thesis exhibition of the same title. Exhibited March 7-12 2010 in the Art and Design Gallery at the University of Kansas, Waves was comprised of a series of mixed media drawings...
Existence and asymptotic behavior of multi-dimensional quantum hydrodynamic
Markowich, Peter A.
and quantum uid equation was described in view of nonlinear geometric optic (WKB){ansatz of the wave functionExistence and asymptotic behavior of multi-dimensional quantum hydrodynamic model quantum hydrodynamic equations for the electron particle density, the current density
NASA Astrophysics Data System (ADS)
van Rijssel, Jos; Kuipers, Bonny W. M.; Erné, Ben H.
2014-03-01
A numerical inversion method known from the analysis of light scattering by colloidal dispersions is now applied to magnetization curves of ferrofluids. The distribution of magnetic particle sizes or dipole moments is determined without assuming that the distribution is unimodal or of a particular shape. The inversion method enforces positive number densities via a non-negative least squares procedure. It is tested successfully on experimental and simulated data for ferrofluid samples with known multimodal size distributions. The created computer program MINORIM is made available on the web.
NASA Astrophysics Data System (ADS)
Mefford, Olin T.; Woodward, Robert C.; Goff, Jonathan D.; Vadala, T. P.; St. Pierre, Tim G.; Dailey, James P.; Riffle, Judy S.
2007-04-01
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.
Revisiting spherically symmetric relativistic hydrodynamics
Guzman, F S; Morales, M D
2012-01-01
In this paper we revise two classical examples of Relativistic Hydrodynamics in order to illustrate in detail the numerical methods commonly used in fluid dynamics, specifically those designed to deal with shocks, which are based on a finite volume approximation. The two cases we consider are the relativistic blast wave problem and the evolution of a Tolman-Oppenheimer-Volkoff star model, in spherical symmetry. In the first case we illustrate the implementation of relativistic Euler's equations on a fixed background space-time, whereas in the second case we also show how to couple the evolution of the fluid to the evolution of the space-time.
Revisiting spherically symmetric relativistic hydrodynamics
F. S. Guzman; F. D. Lora-Clavijo; M. D. Morales
2012-12-06
In this paper we revise two classical examples of Relativistic Hydrodynamics in order to illustrate in detail the numerical methods commonly used in fluid dynamics, specifically those designed to deal with shocks, which are based on a finite volume approximation. The two cases we consider are the relativistic blast wave problem and the evolution of a Tolman-Oppenheimer-Volkoff star model, in spherical symmetry. In the first case we illustrate the implementation of relativistic Euler's equations on a fixed background space-time, whereas in the second case we also show how to couple the evolution of the fluid to the evolution of the space-time.
Candiani, A.; Argyros, A.; Leon-Saval, S. G.; Lwin, R.; Selleri, S.; Pissadakis, S.
2014-03-17
We report an in-fiber magnetic field sensor based on magneto-driven optical loss effects, while being implemented in a ferrofluid infiltrated microstructured polymer optical fiber. We demonstrate that magnetic field flux changes up to 2000 gauss can be detected when the magnetic field is applied perpendicular to the fiber axis. In addition, the sensor exhibits high polarization sensitivity for the interrogated wavelengths, providing the possibility of both field flux and direction measurements. The underlying physical and guidance mechanisms of this sensing transduction are further investigated using spectrophotometric, light scattering measurements, and numerical simulations, suggesting photonic Hall effect as the dominant physical, transducing mechanism.
Torres-Diaz, I.; Cortes, A.; Rinaldi, C.; Cedeño-Mattei, Y.; Perales-Perez, O.
2014-01-15
Ferrofluid flow in cylindrical and annular geometries under the influence of a uniform rotating magnetic field was studied experimentally using aqueous ferrofluids consisting of low concentrations (<0.01 v/v) of cobalt ferrite nanoparticles with Brownian relaxation to test the ferrohydrodynamic equations, elucidate the existence of couple stresses, and determine the value of the spin viscosity in these fluids. An ultrasound technique was used to measure bulk velocity profiles in the spin-up (cylindrical) and annular geometries, varying the intensity and frequency of the rotating magnetic field generated by a two pole stator winding. Additionally, torque measurements in the cylindrical geometry were made. Results show rigid-body like velocity profiles in the bulk, and no dependence on the axial direction. Experimental velocity profiles were in quantitative agreement with the predictions of the spin diffusion theory, with a value of the spin viscosity of ?10{sup ?8} kg m/s, two orders of magnitude larger than the value estimated earlier for iron oxide based ferrofluids, and 12 orders of magnitude larger than estimated using dimensional arguments valid in the infinite dilution limit. These results provide further evidence of the existence of couple stresses in ferrofluids and their role in driving the spin-up flow phenomenon.
NASA Astrophysics Data System (ADS)
Vorobiev, A.; Gordeev, G.; Konovalov, O.; Orlova, D.
2009-03-01
We studied the internal structure of sterically stabilized water- and oil-based ferrofluids in the vicinity of the free interface with a gas by means of x-ray reflectometry and grazing-incidence x-ray diffraction. It was found that in-depth distribution of the magnetic nanoparticles in the layer close to the interface is essentially inhomogeneous. In the case of water-based ferrofluids an enhanced concentration of surfactant and subsequent reduced concentration of the particles were detected in the 100-200-Å -thick interface-adjacent layer. Scattering patterns possessing characteristic features of powder diffraction revealed partial ordering of the surfactant in a multilamellar structure. External magnetic fields applied perpendicular to the interface effectively reduced thickness of the depleted layer bringing the particles from the bulk to the surface. However no field-induced correlations between the particles were detected. In the top 500-Å -thick layer of an oil-based ferrofluid depletion of the particles density was also present; however, no special arrangement of the surfactant molecules was manifested by the experimental data. Interestingly, for all samples we observed wavy surface deformation appearing in the normal magnetic field of a strength H much smaller than the critical values Hc calculated according to the conventional theory of ferrofluid surface instability. This deformation with lateral periodicity of a few millimeters has an amplitude smoothly increasing up to a few microns at H=0.5Hc .
Frictionless dispersive hydrodynamics of Stokes flows
Maiden, Michelle D; Anderson, Dalton V; Schubert, Marika E; Hoefer, Mark A
2016-01-01
Effectively frictionless, dispersive flow characterizes superfluids, nonlinear optical diffraction, and geophysical fluid interfaces. Dispersive shock waves (DSWs) and solitons are fundamental nonlinear excitations in these media, but DSW studies to date have been severely constrained by a loss of coherence. Here we report on a novel dispersive hydrodynamics testbed: the effectively frictionless flow of interfacial waves between two high contrast, low Reynolds' number Stokes fluids. This system enables high fidelity observations of large amplitude DSWs, found to agree quantitatively with a nonlinear wave averaging theory. We then report on observations of highly coherent phenomena including DSW backflow, the refraction or absorption of solitons by DSWs, and multi-phase DSW-DSW merger. The complex, coherent, nonlinear mixing of DSWs and solitons observed here are universal features of dissipationless, dispersive hydrodynamic flows.
Hydrodynamic equations for attractive particle systems on ?
NASA Astrophysics Data System (ADS)
Andjel, Enrique Daniel; Vares, Maria Eulália
1987-04-01
Hydrodynamic properties for a class of nondiffusive particle systems are investigated. The method allows one to study local equilibria for a class of asymmetric zero-range processes, and applies as well to other models, such as asymmetric simple exclusion and "misanthropes." Attractiveness is an essential ingredient. The hydrodynamic equations present shock wave phenomena. Preservation of local equilibrium is proven to hold away from the shocks. The problem of breakdown of local ergodicity at the shocks, which was investigated by D. Wick in a particular model, remains open in this more general setup.
NASA Astrophysics Data System (ADS)
Zeng, Jian; Chen, Chen; Vedantam, Pallavi; Brown, Vincent; Tzeng, Tzuen-Rong J.; Xuan, Xiangchun
2012-10-01
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.
Anisotropy of the magnetoviscous effect in a cobalt ferrofluid with strong interparticle interaction
NASA Astrophysics Data System (ADS)
Linke, J. M.; Odenbach, S.
2015-12-01
The anisotropy of the magnetoviscous effect (MVE) of a cobalt ferrofluid has been studied in a slit die viscometer for three orientations of the applied magnetic field: in the direction of the fluid flow (??1), the velocity gradient (??2), and the vorticity (??3). The majority of the cobalt particles in the ferrofluid exhibit a strong dipole-dipole interaction, which corresponds to a weighted interaction parameter of ?w?10.6. Thus the particles form extended microstructures inside the fluid which lead to enhanced MVE ratios ??2/??1>3 and ??3/??1>0.3 even for strong shearing and weak magnetic fields compared to fluids which contain non-interacting spherical particles with ??2/??1?1 and ??3/??1=0. Furthermore, a non-monotonic increase has been observed in the shear thinning behavior of ??2 for weak magnetic fields <10 kA/m, which cannot be explained solely by the magnetization of individual particles and the formation and disintegration of linear particle chains but indicates the presence of heterophase structures.
Takahashi, Hayato; Nagao, Daisuke; Watanabe, Kanako; Ishii, Haruyuki; Konno, Mikio
2015-05-26
Monodisperse, nonmagnetic, asymmetrical composite dumbbells in a suspension of magnetic nanoparticles (ferrofluid) were aligned by application of an external magnetic field to the ferrofluid. The asymmetrical composite dumbbells were prepared by two-step soap-free emulsion polymerization consisting of the first polymerization to coat spherical silica cores with cross-linked poly(methyl methacrylate) (PMMA) shell and the second polymerization to protrude a polystyrene (PSt) lobe from the core-shell particles. A chain structure of nonmagnetic dumbbells oriented to the applied magnetic field was observed at nanoparticle content of 2.0 vol % and field strengths higher than 1.0 mT. A similar chain structure of the dumbbells was observed under application of alternating electric field at strengths higher than 50 V/mm. Parallel and orthogonally combined applications of the electric and magnetic fields were also conducted to examine independence of the electric and magnetic applications as operational factors in the dumbbell assembling. Dumbbell chains stiffer than those in a single application of external field were formed in the parallel combined application of electric and magnetic fields. The orthogonal combination of the different applied fields could form a magnetically aligned chain structure of the nonmagnetic dumbbells oriented to the electric field. The present work experimentally indicated that the employment of inverse magnetorheological effect for nonmagnetic, anisotropic particles can be a useful method for the simultaneous controls over the orientation and the positon of anisotropic particles in their assembling. PMID:25927488
Spreading of a ferrofluid core in three-stream micromixer channels
NASA Astrophysics Data System (ADS)
Wang, Zhaomeng; Varma, V. B.; Xia, Huan Ming; Wang, Z. P.; Ramanujan, R. V.
2015-05-01
Spreading of a water based ferrofluid core, cladded by a diamagnetic fluid, in three-stream micromixer channels was studied. This spreading, induced by an external magnetic field, is known as magnetofluidic spreading (MFS). MFS is useful for various novel applications where control of fluid-fluid interface is desired, such as micromixers or micro-chemical reactors. However, fundamental aspects of MFS are still unclear, and a model without correction factors is lacking. Hence, in this work, both experimental and numerical analyses were undertaken to study MFS. We show that MFS increased for higher applied magnetic fields, slower flow speed of both fluids, smaller flow rate of ferrofluid relative to cladding, and higher initial magnetic particle concentration. Spreading, mainly due to connective diffusion, was observed mostly near the channel walls. Our multi-physics model, which combines magnetic and fluidic analyses, showed, for the first time, excellent agreement between theory and experiment. These results can be useful for lab-on-a-chip devices.
Sun, Yi; Kwok, Yien-Chian; Foo-Peng Lee, Peter; Nguyen, Nam-Trung
2009-07-01
The use of genetically modified organisms (GMOs) as food and in food products is becoming more and more widespread. Polymerase chain reaction (PCR) technology is extensively used for the detection of GMOs in food products in order to verify compliance with labeling requirements. In this paper, we present a novel close-loop ferrofluid-driven PCR microchip for rapid amplification of GMOs. The microchip was fabricated in polymethyl methacrylate by CO2 laser ablation and was integrated with three temperature zones. PCR solution was contained in a circular closed microchannel and was driven by magnetic force generated by an external magnet through a small oil-based ferrofluid plug. Successful amplification of genetically modified soya and maize were achieved in less than 13 min. This PCR microchip combines advantages of cycling flexibility and quick temperature transitions associated with two existing microchip PCR techniques, and it provides a cost saving and less time-consuming way to conduct preliminary screening of GMOs. PMID:19399482
The Evolution of Field-Induced Structure of Confined Ferrofluid Emulsions
NASA Astrophysics Data System (ADS)
Mou, T.; Flores, G. A.; Liu, J.; Bibette, J.; Richard, J.
We report a real-time study of the evolution of the structure of confined ferrofluid emulsions during the "liquid-solid" phase transition. A monodisperse oil-in-water ferrofluid emulsion is used. The structure evolution of the emulsion after rapidly applying a magnetic field is probed by the static light scattering. The scattering pattern exhibits pronounced rings reflecting the formation of chains and their coalescence to columns or even "worm" structures. The scattering ring is found to decrease in size and brighten in intensity with time. To monitor the structure evolution in time, both the ring peak position in scattering wavevector, qmax, and the peak intensity, Imax, are measured as a function of time. Both qmax and Imax saturate in less than 0.5 seconds after applying a magnetic field. At a constant cell thickness of 25 µm, the evolution of structure is essentially independent of volume fraction ranging from 0.015 to 0.13. In addition, a very good scaling is found in the scattered light intensity as a function of the scattering wavevector.
Spreading of a ferrofluid core in three-stream micromixer channels
Wang, Zhaomeng; Varma, V. B.; Ramanujan, R. V.; Xia, Huan Ming; Wang, Z. P.
2015-05-15
Spreading of a water based ferrofluid core, cladded by a diamagnetic fluid, in three-stream micromixer channels was studied. This spreading, induced by an external magnetic field, is known as magnetofluidic spreading (MFS). MFS is useful for various novel applications where control of fluid-fluid interface is desired, such as micromixers or micro-chemical reactors. However, fundamental aspects of MFS are still unclear, and a model without correction factors is lacking. Hence, in this work, both experimental and numerical analyses were undertaken to study MFS. We show that MFS increased for higher applied magnetic fields, slower flow speed of both fluids, smaller flow rate of ferrofluid relative to cladding, and higher initial magnetic particle concentration. Spreading, mainly due to connective diffusion, was observed mostly near the channel walls. Our multi-physics model, which combines magnetic and fluidic analyses, showed, for the first time, excellent agreement between theory and experiment. These results can be useful for lab-on-a-chip devices.
NASA Astrophysics Data System (ADS)
Zeng, Jian
Microfluidic devices have been increasingly used in the past two decades for particle and cell manipulations in many chemical and biomedical applications. A variety of force fields have been demonstrated to control particle and cell transport in these devices including electric, magnetic, acoustic, and optical forces etc. Among these particle handling techniques, the magnetic approach provides clear advantages over others such as low cost, noninvasive, and free of fluid heating issues. However, the current knowledge of magnetic control of particle transport is still very limited, especially lacking is the handling of diamagnetic particle. This thesis is focused on the magnetic manipulation of diamagnetic particles and cells in ferrofluid flow through the use of a pair of permanent magnets. By varying the configuration of the two magnets, diverse operations of particles and cells is implemented in a straight microchannel that can potentially be integrated into lab-on-a-chip devices for various applications. First, an approach for embedding two, symmetrically positioned, repulsive permanent magnets about a straight rectangular microchannel in a PDMS-based microfluidic device is developed for particle focusing. Focusing particles and cells into a tight stream is often required in order for continuous detection, counting, and sorting. The closest distance between the magnets is limited only by the size of the magnets involved in the fabrication process. The device is used to implement and investigate the three-dimensional magnetic focusing of polystyrene particles in ferrofluid microflow with both top-view and side-view visualizations. The effects of flow speed and particle size on the particle focusing effectiveness are studied. This device is also applied to magnetically focus yeast cells in ferrofluid, which proves to be biocompatible as verified by 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. Next, a simple magnetic technique to concentrate polystyrene particles and live yeast cells in ferrofluid flow through a straight rectangular microchannel is developed. Concentrating particles to a detectable level is often necessary in many applications. The magnetic field gradient is created by two attracting permanent magnets that are placed on the top and bottom of the planar microfluidic device and held in position by their natural attractive force. The effects of flow speed and magnet-magnet distance are studied and the device was applied for use for concentrating live yeast cells. The magnet-magnet distance is mainly controlled by the thickness of the device substrate and can be made small, providing a locally strengthened magnetic field as well as allowing for the use of dilute ferrofluid in the developed magnetic concentration technique. This advantage not only enables a magnetic/fluorescent label-free handling of diamagnetic particles but also renders such handling biocompatible. Lastly, a device is presented for a size-based continuous separation of particles through a straight rectangular microchannel. Particle separation is critical in many applications involving the sorting of cells. A first magnet is used for focusing the particle mixture into a single stream due to its relative close positioning with respect to the channel, thus creating a greater magnetic field magnitude. Then, a following magnet is used to displace the aligned particles to dissimilar flow paths by placing it farther away compared the first magnet, which provides a weaker magnetic field, therefore more sensitive towards the deflection of particles based on their size. The effects of both flow speed and separator magnet position are examined. The experimental data are found to fit well with analytical model predictions. This is followed by a study replacing the particles which are closely sized to that of live yeast cells and observe the separation of the cells from larger particles. Afterwards, a test for
Hydrodynamics of the Chiral Dirac Spectrum
Liu, Yizhuang; Zahed, Ismail
2015-01-01
We derive a hydrodynamical description of the eigenvalues of the chiral Dirac spectrum in the vacuum and in the large $N$ (volume) limit. The linearized hydrodynamics supports sound waves. The stochastic relaxation of the eigenvalues is captured by a hydrodynamical instanton configuration which follows from a pertinent form of Euler equation. The relaxation from a phase of localized eigenvalues and unbroken chiral symmetry to a phase of de-localized eigenvalues and broken chiral symmetry occurs over a time set by the speed of sound. We show that the time is $\\Delta \\tau=\\pi\\rho(0)/2\\beta N$ with $\\rho(0)$ the spectral density at zero virtuality and $\\beta=1,2,4$ for the three Dyson ensembles that characterize QCD with different quark representations in the ergodic regime.
Hydrodynamics of the Chiral Dirac Spectrum
Yizhuang Liu; Piotr Warchol; Ismail Zahed
2015-06-29
We derive a hydrodynamical description of the eigenvalues of the chiral Dirac spectrum in the vacuum and in the large $N$ (volume) limit. The linearized hydrodynamics supports sound waves. The stochastic relaxation of the eigenvalues is captured by a hydrodynamical instanton configuration which follows from a pertinent form of Euler equation. The relaxation from a phase of localized eigenvalues and unbroken chiral symmetry to a phase of de-localized eigenvalues and broken chiral symmetry occurs over a time set by the speed of sound. We show that the time is $\\Delta \\tau=\\pi\\rho(0)/2\\beta N$ with $\\rho(0)$ the spectral density at zero virtuality and $\\beta=1,2,4$ for the three Dyson ensembles that characterize QCD with different quark representations in the ergodic regime.
Hydrodynamics of vegetated channels
Nepf, Heidi
This paper highlights some recent trends in vegetation hydrodynamics, focusing on conditions within channels and spanning spatial scales from individual blades, to canopies or vegetation patches, to the channel reach. At ...
Polyakov, Evgeny A; Vorontsov-Velyaminov, Pavel N
2014-08-28
Properties of ferrofluid bilayer (modeled as a system of two planar layers separated by a distance h and each layer carrying a soft sphere dipolar liquid) are calculated in the framework of inhomogeneous Ornstein-Zernike equations with reference hypernetted chain closure (RHNC). The bridge functions are taken from a soft sphere (1/r(12)) reference system in the pressure-consistent closure approximation. In order to make the RHNC problem tractable, the angular dependence of the correlation functions is expanded into special orthogonal polynomials according to Lado. The resulting equations are solved using the Newton-GRMES algorithm as implemented in the public-domain solver NITSOL. Orientational densities and pair distribution functions of dipoles are compared with Monte Carlo simulation results. A numerical algorithm for the Fourier-Hankel transform of any positive integer order on a uniform grid is presented. PMID:25173007
NASA Astrophysics Data System (ADS)
Polyakov, Evgeny A.; Vorontsov-Velyaminov, Pavel N.
2014-08-01
Properties of ferrofluid bilayer (modeled as a system of two planar layers separated by a distance h and each layer carrying a soft sphere dipolar liquid) are calculated in the framework of inhomogeneous Ornstein-Zernike equations with reference hypernetted chain closure (RHNC). The bridge functions are taken from a soft sphere (1/r12) reference system in the pressure-consistent closure approximation. In order to make the RHNC problem tractable, the angular dependence of the correlation functions is expanded into special orthogonal polynomials according to Lado. The resulting equations are solved using the Newton-GRMES algorithm as implemented in the public-domain solver NITSOL. Orientational densities and pair distribution functions of dipoles are compared with Monte Carlo simulation results. A numerical algorithm for the Fourier-Hankel transform of any positive integer order on a uniform grid is presented.
X-ray microtomography of field-induced macro-structures in a ferrofluid.
Lee, W.; X-Ray Science Division
2010-09-01
X-ray microtomography is used to visualize, in-situ, the three-dimensional nature of the magnetic field induced macro-structures (>1 ?m) inside a bulk (not, vert, similar1 mm diameter) magnetite-particle-mineral oil ferrofluid sample. Columnar structures of not, vert, similar10 ?m diameter were seen under a 0.35 kG applied magnetic field, while labyrinth type structures not, vert, similar4 ?m in width were seen at 0.55 kG. The structures have height/width aspect ratios >100. The results show that the magnetite volume fraction is not constant within the structures and on average is considerably less than a random sphere packing model.
Deng, Ming; Huang, Can; Liu, Danhui; Jin, Wei; Zhu, Tao
2015-08-10
An ultra-compact optical fiber magnetic field sensor based on a microstructured optical fiber (MOF) modal interference and ferrofluid (FF) has been proposed and experimentally demonstrated. The magnetic field sensor was fabricated by splicing a tapered germanium-doped index guided MOF with six big holes injected with FF to two conventional single-mode fibers. The transmission spectra of the proposed sensor under different magnetic field intensities have been measured and theoretically analyzed. Due to an efficient interaction between the magnetic nanoparticles in FF and the excited cladding mode, the magnetic field sensitivity reaches up to117.9pm/mT with a linear range from 0mT to 30mT. Moreover, the fabrication process of the proposed sensor is simple, easy and cost-effective. Therefore, it will be a promising candidate for military, aviation industry, and biomedical applications, especially, for the applications where the space is limited. PMID:26367919
Investigation of temperature dependent magnetic hyperthermia in Fe3O4 ferrofluids
NASA Astrophysics Data System (ADS)
Nemala, Humeshkar Bhaskar
Magnetic nanoparticles (MNPs) of Fe3O4 and gamma-Fe2O3 have been exploited in the biomedical fields for imaging, targeted drug delivery and magnetic hyperthermia. Magnetic hyperthermia (MHT), the production of heat using ferrofluids, colloidal suspensions of MNPs, in an external AC magnetic field (amplitude, 100-500 Oe and frequency 50 kHz -1MHz), has been explored by many researchers, both in vitro and in vivo, as an alternative viable option to treat cancer. The heat energy generated by Neel and Brownian relaxation processes of the internal magnetic spins could be used to elevate local tissue temperature to about 46 ?C to arrest cancerous growth. MHT, due to its local nature of heating, when combined with other forms of treatment such as chemotherapy and/or radiation therapy, it could become an effective therapy for cancer treatment. The efficiency of heat production in MHT is quantified by specific absorption rate (SAR), defined as the power output per gram of the MNPs used. In this thesis, ferrofluids consisting of Fe3O4 MNPs of three different sizes (˜ 10 - 13 nm) coated with two different biocompatible surfactants, dextran and polyethylene glycol (PEG), have been investigated. The structural and magnetic characterization of the MNPs were done using XRD, TEM, and DC magnetization measurements. While XRD revealed the crystallite size, TEM provided the information about morphology and physical size distribution of the MNPs. Magnetic measurements of M-vs-H curves for ferrofluids provided information about the saturation magnetization (Ms) and magnetic core size distribution of MNPs. Using MHT measurements, the SAR has been studied as a function of temperature, taking into account the heat loss due to non-adiabatic nature of the experimental set-up. The observed SAR values have been interpreted using the theoretical framework of linear response theory (LRT). We found the SAR values depend on particle size distribution of MNPs, Ms (65-80 emu/g) and the magnetic anisotropy energy density (K: 12-20 KJ/m3), as well as the amplitude and frequency of the applied AC field (amplitude, 150-250 Oe and frequency, 180-380 kHz). In general, Ms and magnetic core diameter of MNPs increased with the increase in particle size. However, our detailed analysis of MHT data show that although SAR increased with the particle size, the polydispersity of the particles as well as the magnetic anisotropy energy density significantly affected the SAR values. Dextran and PEG coatings essentially yielded similar SAR values ~ 100 W/g using ferrofluids of Fe3O4 MNPs with an average crystallite size of 11.6 +/- 2.1 nm, in AC field of 245 Oe and 375 KHz.
NASA Astrophysics Data System (ADS)
Linke, J. M.; Odenbach, S.
2015-05-01
The anisotropy of the magnetoviscous effect of a ferrofluid has been studied in a specially designed slit die viscometer, which allows three distinct orientations of the magnetic field with respect to the fluid flow. The corresponding Miesowicz viscosity coefficients were determined in dependence of the shear rate and the magnetic field intensity to gain a comprehensive magnetorheological characterization of the fluid. The particles in the fluid have a mean diameter of 13 nm corresponding to an interaction parameter of ? ? 1.3 for magnetite. Thus, the fluid can be expected to show a transition from non-interacting individual particles to microstructures with chain-like associated particles when the magnetic field intensity is increased and the shear rate is decreased. The observed field and shear dependent anisotropy of the magnetoviscous effect is explained coherently in terms of these microstructural changes in the fluid.
Linke, J M; Odenbach, S
2015-05-01
The anisotropy of the magnetoviscous effect of a ferrofluid has been studied in a specially designed slit die viscometer, which allows three distinct orientations of the magnetic field with respect to the fluid flow. The corresponding Miesowicz viscosity coefficients were determined in dependence of the shear rate and the magnetic field intensity to gain a comprehensive magnetorheological characterization of the fluid. The particles in the fluid have a mean diameter of 13 nm corresponding to an interaction parameter of ? ? 1.3 for magnetite. Thus, the fluid can be expected to show a transition from non-interacting individual particles to microstructures with chain-like associated particles when the magnetic field intensity is increased and the shear rate is decreased. The observed field and shear dependent anisotropy of the magnetoviscous effect is explained coherently in terms of these microstructural changes in the fluid. PMID:25837303
Nonlinear hydrodynamic theory of crystallization.
Tóth, Gyula I; Gránásy, László; Tegze, György
2014-02-01
We present an isothermal fluctuating nonlinear hydrodynamic theory of crystallization in molecular liquids. A dynamic coarse-graining technique is used to derive the velocity field, a phenomenology which allows a direct coupling between the free energy functional of the classical density functional theory and the Navier-Stokes equation. In contrast to the Ginzburg-Landau type amplitude theories, the dynamic response to elastic deformations is described by parameter-free kinetic equations. Employing our approach to the free energy functional of the phase-field crystal model, we recover the classical spectrum for the phonons and the steady-state growth fronts. The capillary wave spectrum of the equilibrium crystal-liquid interface is in good qualitative agreement with the molecular dynamics simulations. PMID:24334547
Nonlinear hydrodynamic theory of crystallization
Gyula I. Tóth; László Gránásy; György Tegze
2013-10-14
We present an isothermal fluctuating nonlinear hydrodynamic theory of crystallization in molecular liquids. A dynamic coarse-graining technique is used to derive the velocity field, a phenomenology, which allows a direct coupling between the free energy functional of the classical Density Functional Theory and the Navier-Stokes equation. Contrary to the Ginzburg-Landau type amplitude theories, the dynamic response to elastic deformations is described by parameter-free kinetic equations. Employing our approach to the free energy functional of the Phase-Field Crystal model, we recover the classical spectrum for the phonons and the steady-state growth fronts. The capillary wave spectrum of the equilibrium crystal-liquid interface is in a good qualitative agreement with the molecular dynamics simulations.
NASA Astrophysics Data System (ADS)
Wang, Siqi; Li, Decai
2015-09-01
This paper describes the design and characterization of a plane vibration-based electromagnetic generator that is capable of converting low-frequency vibration energy into electrical energy. A magnetic spring is formed by a magnetic attractive force between fixed and movable permanent magnets. The ferrofluid is employed on the bottom of the movable permanent magnet to suspend it and reduce the mechanical damping as a fluid lubricant. When the electromagnetic generator with a ferrofluid of 0.3 g was operated under a resonance condition, the output power reached 0.27 mW, and the power density of the electromagnetic generator was 5.68 µW/cm2. The electromagnetic generator was also used to harvest energy from human motion. The measured average load powers of the electromagnetic generator from human waist motion were 0.835 mW and 1.3 mW during walking and jogging, respectively.
Test problems for radiation and radiation-hydrodynamics codes
Ensman, L.
1994-03-01
A number of test problems for radiation and radiation-hydrodynamics computer codes are described. These include evolution to radiative equilibrium, cooling from radiative equilibrium, subcritical and supercritical radiating shocks, and a radiating blast wave in a power-law density distribution. For each test problem, example input parameters and plots of the results are presented. Some test problems for pure hydrodynamics are also suggested. The radiation-hydrodynamics code used to perform the example test problems and the equations it solves are described in some detail.
Klein-Gordon Equation in Hydrodynamical Form
Wong, Cheuk-Yin
2010-01-01
We follow and modify the Feshbach-Villars formalism by separating the Klein-Gordon equation into two coupled time-dependent Schroedinger equations for the particle and antiparticle wave functions with positive probability densities. We find that the equation of motion for the probability densities is in the form of relativistic hydrodynamics where various forces have their physical and classical counterparts. An additional element is the presence of the quantum stress tensor that depends on the derivatives of the amplitude of the wave function.
Hydrodynamics of spin-polarized transport and spin pendulum
Gurzhi, R. N. Kalinenko, A. N.; Kopeliovich, A. I.; Pyshkin, P. V.; Yanovsky, A. V.
2007-07-15
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.
NASA Technical Reports Server (NTRS)
Sabelman, E. E. (inventor)
1973-01-01
An electromechanical actuator for producing mechanical force and/or motion in response to electrical signals is disclosed. The actuator includes a ferromagnetic fluid and a coil which are contained within an elastomeric capsule. Energization of the coil by application of current to a pair of coil electrodes extending through the walls of the elastomeric capsule produces distortion of the capsule, i.e., radial expansion and axial contraction. This distortion is caused by the redistribution of the ferromagnetic fluid within the capsule under the influence of the magnetic field. Variation of the current input will produce corresponding variations in the degree of capsule distortion.
Purely hydrodynamic origin for swarming of swimming particles
Norihiro Oyama; John Jairo Molina; Ryoichi Yamamoto
2015-09-29
Three-dimensional simulations with fully resolved hydrodynamics are performed to study the collective motion of model swimmers in confinement. We show that certain swimming mechanisms can lead to traveling wave-like collective motion even without any direct alignment mechanism. It is also shown that by varying the swimming mechanism, this collective motion can be suppressed, contrary to the perception that hydrodynamic effects are completely screened at high volume fraction. From an analysis of bulk systems, it is shown that this traveling wave-like motion, which can be characterized as a pseudo-acoustic mode, is mainly due to the intrinsic swimming property of the particles.
Evaluation of using ferrofluid as an interface material for a field-reversible thermal connector
NASA Astrophysics Data System (ADS)
Yousif, Ahmed S.
The electrical functionality of an avionics chassis is limited due to heat dissipation limits. The limits arise due to the fact that components in an avionic computer boxes are packed very compactly, with the components mounted onto plug-in cards, and the harsh environment experienced by the chassis limits how heat can be dissipated from the cards. Convective and radiative heat transfer to the ambient are generally not possible. Therefore it is necessary to have heat transferred from the components conducted to the edge of the plug-in cards. The heat then needs to conduct from the card edge to a cold block that not only holds the card in place, but also removes the generated heat by some heat transfer fluid that is circulated through the cold block. The interface between the plug-in card and the cold block typically has a high thermal resistance since it is necessary for the card to have the capability to be re-workable, meaning that the card can be removed and then returned to the chassis. Reducing the thermal resistance of the interface is the objective of the current study and the topic of this thesis. The current design uses a pressure interface between the card and cold block. The contact pressure is increased through the addition of a wedgelock, which is a field-reversible mechanical connector. To use a wedgelock, the cold block has channels milled on the surface with widths that are larger than the thickness of the plug-in card and the un-expanded wedgelock. The card edge is placed in the channel and placed against one of the channel walls. A wedgelock is then placed between the card and the other channel wall. The wedgelock is then expanded by using either a screw or a lever. As the wedgelock expands it fills in the remaining channel gap and bears against the other face of the plug-in card. The majority of heat generated by the components on the plug-in card is forced to conduct from the card into the wall of the cold block, effectively a single sided, dry conduction heat transfer path. Having started as a student design competition named RevCon Challenge, work was performed to evaluate the use of new field-reversible thermal connectors. The new design proposed by the University of Missouri utilized oil based iron nanoparticles, commonly known as a ferrofluid, as a thermal interface material. By using a liquid type of interface material the channel gap can be reduced to a few micrometers, within machining tolerances, and heat can be dissipated off both sides of the card. The addition of nanoparticles improves the effective thermal conductivity of base fluid. The use of iron nanoparticles allows magnets to be used to hold the fluid in place, so the electronic cards may be easily inserted and removed while keeping the ferrofluid in the cold block channel. The ferrofluid-based design which was investigated has shown lower thermal resistance than the current wedgelock design. These results open the door for further development of electronic cards by using higher heat emitting components without compromising the simplicity of attaching/detaching cards from cooling plates.
Skew resisting hydrodynamic seal
Conroy, William T. (Pearland, TX); Dietle, Lannie L. (Sugar Land, TX); Gobeli, Jeffrey D. (Houston, TX); Kalsi, Manmohan S. (Houston, TX)
2001-01-01
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.
Sprenger, Lisa Lange, Adrian; Odenbach, Stefan
2014-02-15
Ferrofluids consist of magnetic nanoparticles dispersed in a carrier liquid. Their strong thermodiffusive behaviour, characterised by the Soret coefficient, coupled with the dependency of the fluid's parameters on magnetic fields is dealt with in this work. It is known from former experimental investigations on the one hand that the Soret coefficient itself is magnetic field dependent and on the other hand that the accuracy of the coefficient's experimental determination highly depends on the volume concentration of the fluid. The thermally driven separation of particles and carrier liquid is carried out with a concentrated ferrofluid (? = 0.087) in a horizontal thermodiffusion cell and is compared to equally detected former measurement data. The temperature gradient (1 K/mm) is applied perpendicular to the separation layer. The magnetic field is either applied parallel or perpendicular to the temperature difference. For three different magnetic field strengths (40 kA/m, 100 kA/m, 320 kA/m) the diffusive separation is detected. It reveals a sign change of the Soret coefficient with rising field strength for both field directions which stands for a change in the direction of motion of the particles. This behaviour contradicts former experimental results with a dilute magnetic fluid, in which a change in the coefficient's sign could only be detected for the parallel setup. An anisotropic behaviour in the current data is measured referring to the intensity of the separation being more intense in the perpendicular position of the magnetic field: S{sub T?} = ?0.152 K{sup ?1} and S{sub T?} = ?0.257 K{sup ?1} at H = 320 kA/m. The ferrofluiddynamics-theory (FFD-theory) describes the thermodiffusive processes thermodynamically and a numerical simulation of the fluid's separation depending on the two transport parameters ?{sub ?} and ?{sub ?} used within the FFD-theory can be implemented. In the case of a parallel aligned magnetic field, the parameter can be determined to ?{sub ?} = (2.8;?9.1;?11.2)?×?10{sup ?11}?·?D{sub ?} kg/(A{sup 2}m) for the different field strengths and in dependence on the magnetic diffusion coefficient D{sub ?}. An adequate fit in the perpendicular case is not possible, by ?{sub ?} = 1?×?10{sup ?17} kg/(Am{sup 2}) a rather good agreement between numerical and experimental data can be found for a field strength of 40 kA/m, a change in the coefficient's sign in the perpendicular setup is not numerically determinable via this theory. The FFD-theory is only partly applicable to calculate the concentration profile in concentrated magnetic fluids established due to a temperature gradient and magnetic field applied.
Heat capacity of liquids: A hydrodynamic approach
T. Bryk; T. Scopigno; G. Ruocco
2015-04-06
We study autocorrelation functions of energy, heat and entropy densities obtained by molecular dynamics simulations of supercritical Ar and compare them with the predictions of the hydrodynamic theory. It is shown that the predicted by the hydrodynamic theory single-exponential shape of the entropy density autocorrelation functions is perfectly reproduced for small wave numbers by the molecular dynamics simulations and permits the calculation of the wavenumber-dependent specific heat at constant pressure. The estimated wavenumber-dependent specific heats at constant volume and pressure, $C_{v}(k)$ and $C_{p}(k)$, are shown to be in the long-wavelength limit in good agreement with the macroscopic experimental values of $C_{v}$ and $C_{p}$ for the studied thermodynamic points of supercritical Ar.
Hydrodynamic modeling of tsunamis from the Currituck landslide Eric L. Geist a,
Lynett, Patrick
Hydrodynamic modeling of tsunamis from the Currituck landslide Eric L. Geist a, , Patrick J. Lynett: Accepted 24 September 2008 Keywords: tsunami landslide hydrodynamic runup numerical model sensitivity analysis Tsunami generation from the Currituck landslide offshore North Carolina and propagation of waves
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...
Active Carbon and Oxygen Shell Burning Hydrodynamics Casey A. Meakin1
Arnett, W. David
Active Carbon and Oxygen Shell Burning Hydrodynamics Casey A. Meakin1 & David Arnett1 cmeakin occur between active carbon and oxygen burning shells, (2) hydrodynamic wave motions in nonconvective. A Double Shell Model: Active Oxygen and Carbon Burning Previously we have evolved a 23M model with the one
NASA Astrophysics Data System (ADS)
Wang, Xianping; Yin, Cheng; Sun, Jingjing; Li, Honggen; Sang, Minghuang; Yuan, Wen; Cao, Zhuangqi; Huang, Meizhen
2013-10-01
We report on the observation of all-optically tunable Goos-Hänchen (GH) shift in a symmetrical metal-cladding waveguide, whose guiding layer is filled with the water-based ferrofluid. The strong dependence of the GH shift and its switching time on the control beam power is suggested to be arising from the light-induced periodic-like microstructure transitions of ferrofluid in virtue of the competition between the optical trapping effect and the Soret effect. The indirect evidence of our qualitative hypothesis is given. The presented tunability of GH shift may have potential applications in optical switching and sensing.
Probing magnetic properties of ferrofluids using temperature dependent magnetic hyperthermia studies
NASA Astrophysics Data System (ADS)
Nemala, Humeshkar; Thakur, Jagdish; Naik, Vaman; Naik, Ratna
2014-03-01
Tuning the properties of magnetic nanoparticles is essential for biomedical and technological applications. An important phenomenon displayed by these nanoparticles is the generation of heat in the presence of an external oscillating magnetic field and is known as magnetic hyperthermia (MHT). The heat dissipation by the magnetic nanoparticles occurs via Neel relaxation (the flip of the internal magnetic moment of the nanoparticles) and Brownian relaxation (the physical rotation of the nanoparticles in the suspended media). Dextran coated iron oxide (Fe3O4) nanoparticles were synthesized using the co-precipitation method and characterized using XRD, TEM and DC magnetometry measurements. Roughly spherical in shape the particles have an average size of 13nm and a saturation magnetization of 65 emu/g. The MHT properties of these nanoparticles suspended in a weakly basic solution (ferrofluid) have been investigated as a function of the frequency and amplitude of magnetic field by incorporating a complete thermodynamical analysis of the experimental set-up. The heat generation is quantified using the specific power loss (SPL) and compared with the predictions of linear response theory. This analysis sheds light on important physical and magnetic properties of the nanoparticles.
On the self-assembly of net-like nanostructures in ferrofluids
NASA Astrophysics Data System (ADS)
Elkady, Ashraf S.; Iskakova, Larisa; Zubarev, Andrey
2015-06-01
Understanding the physical forces that govern nanoparticles self-assembly is central to the ability to engineer super-nanostructures for advanced nanotechnology applications. Magnetic force represents one of such important forces that is responsible for structural transformations and condensation in ferrofluids (FF). In this work, we study internal structural transformations in FF in the absence of external magnetic field by introducing the first direct statistical model that takes into account formation of linear chains, Y-forks and net-like nanostructures. The results show that, in agreement with experiments, when the concentration of the magnetic nanoparticles and their magnetic interaction energy are small enough, majority of the particles are united in individual linear chains. But, when these parameters exceed some threshold magnitude, the main particles population switches to net-like nanostructures. These results highlight the importance of magnetic dipole interactions in the absence of external magnetic field, and their essential role in the bottom-up construction of hierarchical nano-architectures of viable fundamental and practical implications.
The Use of Ferrofluids to Model Materials Processing (MSFC Center Director's Discretionary Fund)
NASA Technical Reports Server (NTRS)
Leslie, F.; Ramachandran, N.
2000-01-01
Many crystals grown in space have structural flaws believed to result from convective motions during the growth phase. The character of these instabilities is not well understood but is associated with thermal and solutal density variations near the solidification interface in the presence of residual gravity and g-jitter. To study these instabilities in a separate, controlled space experiment, a concentration gradient would first have to be artificially established in a timely manner as an initial condition. This is generally difficult to accomplish in a microgravity environment because the momentum of the fluid injected into a test cell tends to swirl around and mix in the absence of a restoring force. The use of magnetic fields to control the motion and position of liquids has received recent, growing interest. The possibility of using the force exerted by a non-uniform magnetic field on a ferrofluid to not only achieve fluid manipulation but also to actively control fluid motion makes it an attractive candidate for space applications. This paper describes a technique for quickly establishing a linear or exponential fluid concentration gradient using a magnetic field in place of gravity to stabilize the deployment. Also discussed is a photometric technique for measuring the concentration profile using light attenuation. Although any range of concentrations can be realized, photometric constraints impose some limitations on measurements. Results of the ground-based experiments indicate that the species distribution is within 3 percent of the predicted value.
NASA Astrophysics Data System (ADS)
Huang, Yan; Li, Decai; Li, Feng; Zhu, Quanshui; Xie, Yu
2015-03-01
Using light transmission experiments and optical microscope observations with a longitudinal gradient magnetic field configuration, the relationship between the behavior of the transmitted light relaxation and the microstructure evolution of ionic ferrofluids in the central region of an axisymmetric field is investigated. Under a low-gradient magnetic field, there are two types of relaxation process. When a field is applied, the transmitted light intensity decreases to a minimum within a time on the order of 101-102 s. It is then gradually restored, approaching its initial value within a time on the order of 102 s. This is type I relaxation, which corresponds to the formation of magnetic columns. After the transmission reaches this value, it either increases or decreases slowly, stabilizing within a time on the order of 103 s, according to the direction of the field gradient. This is a type II relaxation, which results from the shadowing effect, corresponding to the motion of the magnetic columns under the application of a gradient force. Under a magnetic field with a centripetal high-gradient (magnetic materials subjected to a force pointing toward the center of the axisymmetric field), the transmitted light intensity decreases monotonously and more slowly than that under a low-gradient field. Magnetic transport and separation resulted from magnetophoresis under high-gradient fields, changing the formation dynamics of the local columns and influencing the final state of the column system.
Rajnak, Michal; Kurimsky, Juraj; Dolnik, Bystrik; Kopcansky, Peter; Tomasovicova, Natalia; Taculescu-Moaca, Elena Alina; Timko, Milan
2014-09-01
An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field. PMID:25314449
Investigation of the Magnetic Behavior in Fe3O4 Ferrofluid Functionalized by Carapa Guianensis Oil
NASA Astrophysics Data System (ADS)
López, Jorge Luis; Rodriguez, Anselmo Fortunato Ruiz; de Jesus Nascimento Pontes, Maria; de Morais, Paulo Cesar; de Azevedo, Ricardo Bentes; Pfannes, Hans Dieter; Dias Filho, José Higino
2010-12-01
A ferrofluid based on Fe3O4 has been synthesized using the condensation method by coprecipitating aqueous solutions of FeSO4 and FeCl3 mixtures in NH4OH and treated further in order to obtain colloidal sols by creating a charge density on their surface and functionalized by carapa guianensis (andiroba oil). Aqueous sample with an average particle diameter ˜7 nm were studied by Mössbauer spectroscopy and dc magnetization measurements in the range of 4.2-250 K. The saturation magnetization (Ms) at 4.2 K was determined from M vs 1/H plots by extrapolating the value of magnetizations to infinite fields, to 5.6 emu/g and coercivity to 344 Oe. The low saturation magnetization value was attributed to spin noncollinearity predominantly at the surface. From the magnetization measurements a magnetic anisotropy energy constant (K) of 1×104 J/m3 was calculated. Fe3O4 spectra at room temperature showed a singlet due to superparamagnetic relaxation and a sextet at low temperature.
Relativistic Hydrodynamics with Wavelets
DeBuhr, Jackson; Anderson, Matthew; Neilsen, David; Hirschmann, Eric W
2015-01-01
Methods to solve the relativistic hydrodynamic equations are a key computational kernel in a large number of astrophysics simulations and are crucial to understanding the electromagnetic signals that originate from the merger of astrophysical compact objects. Because of the many physical length scales present when simulating such mergers, these methods must be highly adaptive and capable of automatically resolving numerous localized features and instabilities that emerge throughout the computational domain across many temporal scales. While this has been historically accomplished with adaptive mesh refinement (AMR) based methods, alternatives based on wavelet bases and the wavelet transformation have recently achieved significant success in adaptive representation for advanced engineering applications. This work presents a new method for the integration of the relativistic hydrodynamic equations using iterated interpolating wavelets and introduces a highly adaptive implementation for multidimensional simulati...
Cylindrically asymmetric hydrodynamic equations
Mikolaj Chojnacki
2006-09-20
We show that the boost-invariant and cylindrically asymmetric hydrodynamic equations for baryon-free matter may be rewritten as only two coupled partial differential equations. In the case where the system exhibits the cross-over phase transition, the standard numerical methods may be applied to solve these equations. An example of our results describing non-central gold on gold collisions at RHIC energies is presented.
How (non-) linear is the hydrodynamics of heavy ion collisions?
Floerchinger, Stefan; Beraudo, Andrea; Del Zanna, Luca; Inghirami, Gabriele; Rolando, Valentina
2014-01-01
We provide evidence from full numerical solutions that the hydrodynamical evolution of initial density fluctuations in heavy ion collisions can be understood order-by-order in a perturbative series in deviations from a smooth and azimuthally symmetric background solution. To leading linear order, modes with different azimuthal wave numbers do not mix. Quadratic and higher order corrections are small and can be understood as overtones with corresponding wave numbers.
Sprenger, Lisa Lange, Adrian; Odenbach, Stefan
2013-12-15
Ferrofluids are colloidal suspensions consisting of magnetic nanoparticles dispersed in a carrier liquid. Their thermodiffusive behaviour is rather strong compared to molecular binary mixtures, leading to a Soret coefficient (S{sub T}) of 0.16?K{sup ?1}. Former experiments with dilute magnetic fluids have been done with thermogravitational columns or horizontal thermodiffusion cells by different research groups. Considering the horizontal thermodiffusion cell, a former analytical approach has been used to solve the phenomenological diffusion equation in one dimension assuming a constant concentration gradient over the cell's height. The current experimental work is based on the horizontal separation cell and emphasises the comparison of the concentration development in different concentrated magnetic fluids and at different temperature gradients. The ferrofluid investigated is the kerosene-based EMG905 (Ferrotec) to be compared with the APG513A (Ferrotec), both containing magnetite nanoparticles. The experiments prove that the separation process linearly depends on the temperature gradient and that a constant concentration gradient develops in the setup due to the separation. Analytical one dimensional and numerical three dimensional approaches to solve the diffusion equation are derived to be compared with the solution used so far for dilute fluids to see if formerly made assumptions also hold for higher concentrated fluids. Both, the analytical and numerical solutions, either in a phenomenological or a thermodynamic description, are able to reproduce the separation signal gained from the experiments. The Soret coefficient can then be determined to 0.184?K{sup ?1} in the analytical case and 0.29?K{sup ?1} in the numerical case. Former theoretical approaches for dilute magnetic fluids underestimate the strength of the separation in the case of a concentrated ferrofluid.
Hydrodynamics of fossil fishes
Fletcher, Thomas; Altringham, John; Peakall, Jeffrey; Wignall, Paul; Dorrell, Robert
2014-01-01
From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms. PMID:24943377
Hydrodynamics of fossil fishes.
Fletcher, Thomas; Altringham, John; Peakall, Jeffrey; Wignall, Paul; Dorrell, Robert
2014-08-01
From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms. PMID:24943377
Blaedel, Kenneth L. (Dublin, CA); Davis, Pete J. (Pleasanton, CA); Landram, Charles S. (Livermore, CA)
2000-01-01
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.
A new shock-capturing numerical scheme for ideal hydrodynamics
Zuzana Feckova; Boris Tomasik
2015-01-07
We present a new algorithm for solving ideal relativistic hydrodynamics based on Godunov method with an exact solution of Riemann problem for an arbitrary equation of state. Standard numerical tests are executed, such as the sound wave propagation and the shock tube problem. Low numerical viscosity and high precision are attained with proper discretization.
The Dramatic Impact of Hydrodynamic Mixing on Supernova Progenitors
Arnett, W. David
on the main sequence (Young, Mamajek, Arnett, & Liebert 2001; Young et al. 2005). The model with wave physicsThe Dramatic Impact of Hydrodynamic Mixing on Supernova Progenitors Patrick A. Young 1,2 , Casey, and composition. The impact of this process increases with stellar mass. Stellar models which incorporate
Inactivation and injury of pathogenic bacteria by hydrodynamic pressure treatment
Technology Transfer Automated Retrieval System (TEKTRAN)
Hydrodynamic pressure processing (HDP) is an innovative non-thermal technology developed for improving meat tenderness. The shock waves generated in the HDP process cause significant disruption of myofibrillar proteins in muscle tissue resulting in improved tenderness of various beef cuts. The same ...
Effect of hydrodynamic pressure processing on chevon quality characteristics
Technology Transfer Automated Retrieval System (TEKTRAN)
Hydrodynamic pressure processing (HDP) technology, which involves exposure of packaged meat to a supersonic shock wave under water created by a small amount of explosive, has been shown to improve meat tenderness, but its effect on chevon tenderness has not been studied so far. The objective of this...
NASA Astrophysics Data System (ADS)
Aursand, Eskil; Gjennestad, Magnus Aa.; Yngve Lervåg, Karl; Lund, Halvor
2016-03-01
A one-dimensional multi-phase flow model for thermomagnetically pumped ferrofluid with heat transfer is proposed. The thermodynamic model is a combination of a simplified particle model and thermodynamic equations of state for the base fluid. The magnetization model is based on statistical mechanics, taking into account non-uniform particle size distributions. An implementation of the proposed model is validated against experiments from the literature, and found to give good predictions for the thermomagnetic pumping performance. However, the results reveal a very large sensitivity to uncertainties in heat transfer coefficient predictions.
Atmospheric-hydrodynamic coupling in the nearshore
NASA Astrophysics Data System (ADS)
Ortega-Sánchez, M.; Bramato, S.; Quevedo, E.; Mans, C.; Losada, M. A.
2008-12-01
Natural beach shorelines commonly present morphological rhythmic or non-rhythmic features of varying geometrical characteristics. Traditionally, their formation is believed to be due to wave-induced processes, a line thoroughly investigated during the last few decades. However, these natural beach formations are frequently bounded by coastal cliffs (or capes) and are affected by intense winds, a fact not previously considered. This paper presents the results of a field survey, demonstrating the existence of atmospheric-hydrodynamic coupling in the nearshore region outside of the breaking zone at Carchuna beach (Motril, Spain), where the atmospheric conditions are influenced by a lateral geographic obstacle (Cape Sacratif).
Hydrodynamic phase-locking of swimming microorganisms
Gwynn J. Elfring; Eric Lauga
2009-07-06
Some microorganisms, such as spermatozoa, synchronize their flagella when swimming in close proximity. Using a simplified model (two infinite, parallel, two-dimensional waving sheets), we show that phase-locking arises from hydrodynamics forces alone, and has its origin in the front-back asymmetry of the geometry of their flagellar waveform. The time-evolution of the phase difference between co-swimming cells depends only on the nature of this geometrical asymmetry, and microorganisms can phase-lock into conformations which minimize or maximize energy dissipation.
Modeling multiphase flow using fluctuating hydrodynamics
NASA Astrophysics Data System (ADS)
Chaudhri, Anuj; Bell, John B.; Garcia, Alejandro L.; Donev, Aleksandar
2014-09-01
Fluctuating hydrodynamics provides a model for fluids at mesoscopic scales where thermal fluctuations can have a significant impact on the behavior of the system. Here we investigate a model for fluctuating hydrodynamics of a single-component, multiphase flow in the neighborhood of the critical point. The system is modeled using a compressible flow formulation with a van der Waals equation of state, incorporating a Korteweg stress term to treat interfacial tension. We present a numerical algorithm for modeling this system based on an extension of algorithms developed for fluctuating hydrodynamics for ideal fluids. The scheme is validated by comparison of measured structure factors and capillary wave spectra with equilibrium theory. We also present several nonequilibrium examples to illustrate the capability of the algorithm to model multiphase fluid phenomena in a neighborhood of the critical point. These examples include a study of the impact of fluctuations on the spinodal decomposition following a rapid quench, as well as the piston effect in a cavity with supercooled walls. The conclusion in both cases is that thermal fluctuations affect the size and growth of the domains in off-critical quenches.
EUNHA: a New Cosmological Hydrodynamic Simulation Code
NASA Astrophysics Data System (ADS)
Shin, Jihye; Kim, Juhan; Kim, Sungsoo S.; Park, Changbom
2014-06-01
We develop a parallel cosmological hydrodynamic simulation code designed for the study of formation and evolution of cosmological structures. The gravitational force is calculated using the TreePM method and the hydrodynamics is implemented based on the smoothed particle hydrodynamics. The initial displacement and velocity of simulation particles are calculated according to second-order Lagrangian perturbation theory using the power spectra of dark matter and baryonic matter. The initial background temperature is given by Recfast and the temperature fluctuations at the initial particle position are assigned according to the adiabatic model. We use a time-limiter scheme over the individual time steps to capture shock-fronts and to ease the time-step tension between the shock and preshock particles. We also include the astrophysical gas processes of radiative heating/cooling, star formation, metal enrichment, and supernova feedback. We test the code in several standard cases such as one-dimensional Riemann problems, Kelvin-Helmholtz, and Sedov blast wave instability. Star formation on the galactic disk is investigated to check whether the Schmidt-Kennicutt relation is properly recovered. We also study global star formation history at different simulation resolutions and compare them with observations.
Fasih Ramandi, Negin; Shemirani, Farzaneh
2015-01-01
For the first time, a selective ionic liquid ferrofluid has been used in dispersive solid phase extraction (IL-FF-D-SPE) for simultaneous preconcentration and separation of lead and cadmium in milk and biological samples combined with flame atomic absorption spectrometry. To improve the selectivity of the ionic liquid ferrofluid, the surface of TiO2 nanoparticles with a magnetic core as sorbent was modified by loading 1-(2-pyridylazo)-2-naphtol. Due to the rapid injection of an appropriate amount of ionic liquid ferrofluid into the aqueous sample by a syringe, extraction can be achieved within a few seconds. In addition, based on the attraction of the ionic liquid ferrofluid to a magnet, no centrifugation step is needed for phase separation. The experimental parameters of IL-FF-D-SPE were optimized using a Box-Behnken design (BBD) after a Plackett-Burman screening design. Under the optimum conditions, the relative standard deviations of 2.2% and 2.4% were obtained for lead and cadmium, respectively (n=7). The limit of detections were 1.21 µg L(-1) for Pb(II) and 0.21 µg L(-1) for Cd(II). The preconcentration factors were 250 for lead and 200 for cadmium and the maximum adsorption capacities of the sorbent were 11.18 and 9.34 mg g(-1) for lead and cadmium, respectively. PMID:25281121
Lacoste, David
2002; published 14 February 2003 We explore magnetic-field-induced ordering and microphase separation is water, and both the magnetic and nonmagnetic particles are stabilized in water. More commonly, the ferrofluid is composed of magnetic par- ticles suspended in one solvent e.g., oil that is then mixed
Anisotropic Flow and Viscous Hydrodynamics
Li Yan
2012-08-15
We report part of our recent work on viscous hydrodynamics with consistent phase space distribution $f(x,\\p)$ for freeze out. We develop the gradient expansion formalism based on kinetic theory, and with the constraints from the comparison between hydrodynamics and kinetic theory, viscous corrections to $f(x,\\p)$ can be consistently determined order by order. Then with the obtained $f(x,\\p)$, second order viscous hydrodynamical calculations are carried out for elliptic flow $v_2$.
Influence of large size magnetic particles on the magneto-viscous properties of ferrofluid
NASA Astrophysics Data System (ADS)
Shah, Kruti; Upadhyay, R. V.; Aswal, V. K.
2012-07-01
We compare the magneto-viscous behavior in a shear flow of three different types of magnetic suspension in the presence of a magnetic field. The first suspension contains magnetite particles of average size 10 nm dispersed in transformer oil. The second one is made of large sized magnetite particles having 30 nm particle size dispersed in transformer oil. The third suspension is a mixture of the first and second fluids in different weight proportions. The size and size distribution have been confirmed by transmission microscopy and small angle neutron scattering experiments. The rheological properties of the first two suspensions were measured for varying shear and field values. The flow behavior of the nanosized dispersed ferrofluid is described with Bingham’s yield stress model and it varied from 2.2 to 5.5 Pa on increasing the field from 0 to 1 T. The large sized particle dispersed fluid exhibits magneto-viscous behavior with increasing field. The value of Bingham’s yield stress obtained is nearly 15 times higher than that of the small size dispersion. On mixing these two fluids with different weight fractions, the Bingham yield stress value increases by a factor of three compared with that of the large sized particle dispersed fluid. The Mason number provides a good scaling of data in the steady simple flow regime. The observed yielding behavior is due to the formation of a longer chain structure in the system under the field and in-field microscopy confirms the same. The present study shows that the addition of large sized magnetic particles in magnetic fluid increases the yield stress as well as the fluid stability under a field.
Magnetic Field-Controlled Lithium Polysulfide Semiliquid Battery with Ferrofluidic Properties.
Li, Weiyang; Liang, Zheng; Lu, Zhenda; Tao, Xinyong; Liu, Kai; Yao, Hongbin; Cui, Yi
2015-11-11
Large-scale energy storage systems are of critical importance for electric grids, especially with the rapid increasing deployment of intermittent renewable energy sources such as wind and solar. New cost-effective systems that can deliver high energy density and efficiency for such storage often involve the flow of redox molecules and particles. Enhancing the mass and electron transport is critical for efficient battery operation in these systems. Herein, we report the design and characterization of a novel proof-of-concept magnetic field-controlled flow battery using lithium metal-polysulfide semiliquid battery as an example. A biphasic magnetic solution containing lithium polysulfide and magnetic nanoparticles is used as catholyte, and lithium metal is used as anode. The catholyte is composed of two phases of polysulfide with different concentrations, in which most of the polysulfide molecules and the superparamagnetic iron oxide nanoparticles can be extracted together to form a high-concentration polysulfide phase, in close contact with the current collector under the influence of applied magnetic field. This unique feature can help to maximize the utilization of the polysulfide and minimize the polysulfide shuttle effect, contributing to enhanced energy density and Coulombic efficiency. Additionally, owing to the effect of the superparamagnetic nanoparticles, the concentrated polysulfide phase shows the behavior of a ferrofluid that is flowable with the control of magnetic field, which can be used for a hybrid flow battery without the employment of any pumps. Our innovative design provides new insight for a broad range of flow battery chemistries and systems. PMID:26422674
NASA Astrophysics Data System (ADS)
Vales-Pinzón, C.; Alvarado-Gil, J. J.; Medina-Esquivel, R.; Martínez-Torres, P.
2014-11-01
Magneto-optic phenomena in ferrofluids have been shown to be related to the formation of chain structures, due to the arrangement of the ferromagnetic particles, induced by an applied magnetic field. In this work, the effects on transmission of polarized light due to anisotropic effects induced by an external magnetic field in ferrofluids with carbon nanotubes are studied. The time response of the system presents two well defined stages, in the first one, which is very short, the fluid behaves as a polarizer. In contrast in the second stage, the effects of light transmission dominate. In this stage the transmitted light intensity grows with time and after a long time reaches a constant stable value. It is shown that these phenomena depend on the carbon nanotubes concentration as well as on the strength of the applied magnetic field. Using a simple model that considers a chain-like structure formation, it is possible to determine the rate of agglomeration of the formed structures and the attenuation coefficient of the transmitted light. The formation of nanostructures leads to variation in the transmitted light, depending on the polarization of the incident light. These magnetic nanostructures can find numerous applications in nanotechnology, optical devices and medicine.
Jain, Dr Nirmesh; Liu, Dr C K; Hawkett, Dr B. S.; Warr, G. G.; Hamilton, William A
2014-01-01
The optical magnetic chaining technique (MCT) developed by Leal-Calderon, Bibette and co-workers in the 1990 s allows precise measurements of force profiles between droplets in monodisperse ferrofluid emulsions. However, the method lacks an in-situ determination of droplet size and therefore requires the combination of separately acquired measurements of droplet chain periodicity versus an applied magnetic field from optical Bragg scattering and droplet diameter inferred from dynamic light scattering (DLS) to recover surface force-distance profiles between the colloidal particles. Compound refractive lens (CRL) focussed small-angle scattering (SANS) MCT should result in more consistent measurements of droplet size (form factor measurements in the absence of field) and droplet chaining period (from structure factor peaks when the magnetic field is applied); and, with access to shorter length scales, extend force measurements to closer approaches than possible by optical measurements. We report on CRL-SANS measurements of monodisperse ferrofluid emulsion droplets aligned in straight chains by an applied field perpendicular to the incident beam direction. Analysis of the scattering from the closely spaced droplets required algorithms that carefully treated resolution and its effect on mean scattering vector magnitudes in order to determine droplet size and chain periods to sufficient accuracy. At lower applied fields scattering patterns indicate structural correlations transverse to the magnetic field direction due to the formation of intermediate structures in early chain growth.
The Quantum Hydrodynamic Description of Tunneling
Kendrick, Brian K.
2012-06-15
The quantum hydrodynamic approach is based on the de Broglie-Bohm formulation of quantum mechanics. The resulting fluid-like equations of motion describe the flow of probability and an accurate solution to these equations is equivalent to solving the time-dependent Schroedinger equation. Furthermore, the hydrodynamic approach provides new insight into the mechanisms as well as an alternative computational approach for treating tunneling phenomena. New concepts include well-defined 'quantum trajectories', 'quantum potential', and 'quantum force' all of which have classical analogues. The quantum potential and its associated force give rise to all quantum mechanical effects such as zero point energy, tunneling, and interference. A new numerical approach called the Iterative Finite Difference Method (IFDM) will be discussed. The IFDM is used to solve the set of non-linear coupled hydrodynamic equations. It is 2nd-order accurate in both space and time and exhibits exponential convergence with respect to the iteration count. The stability and computational efficiency of the IFDM is significantly improved by using a 'smart' Eulerian grid which has the same computational advantages as a Lagrangian or Arbitrary Lagrangian Eulerian (ALE) grid. The IFDM is also capable of treating anharmonic potentials. Example calculations using the IFDM will be presented which include: a one-dimensional Gaussian wave packet tunneling through an Eckart barrier, a one-dimensional bound-state Morse oscillator, and a two-dimensional (2D) model collinear reaction using an anharmonic potential energy surface. Approximate treatments of the quantum hydrodynamic equations will also be discussed which could allow scaling of the calculations to hundreds of degrees of freedom which is important for treating tunneling phenomena in condensed phase systems.
Klein-Gordon Equation in Hydrodynamical Form
Cheuk-Yin Wong
2010-12-22
We follow and modify the Feshbach-Villars formalism by separating the Klein-Gordon equation into two coupled time-dependent Schroedinger equations for particle and antiparticle wave function components with positive probability densities. We find that the equation of motion for the probability densities is in the form of relativistic hydrodynamics where various forces have their classical counterparts, with the additional element of the quantum stress tensor that depends on the derivatives of the amplitude of the wave function. We derive the equation of motion for the Wigner function and we find that its approximate classical weak-field limit coincides with the equation of motion for the distribution function in the collisionless kinetic theory.
Simulating hydrodynamics on tidal mudflats
NASA Astrophysics Data System (ADS)
Cook, S.; Lippmann, T. C.
2014-12-01
Biogeochemical cycling in estuaries is governed by fluxes from both riverine sources and through estuarine sediment deposits. Although estimates from river sources are relatively common and easily sampled, estimates of nutrient fluxes through the fluid-sediment interface are less common and limited to deeper portions of the bays away from intertidal areas. Lack of quantifiable shear stress estimates over intertidal areas limits our overall understanding of nutrient budgets in estuaries. Unfortunately, observation of intertidal hydrodynamics and nutrient fluxes over tidal flats and near the water's edge is difficult owing to the temporally varying and spatially extensive region where the tides inundate, and thus numerical modeling is often employed. In this work, the Regional Ocean Modeling System (ROMS), a three dimensional numerical hydrodynamic model was used to investigate the shear stresses over intertidal mudflats in the Great Bay, a tidally-dominated New England estuary cut by several tidal channels and with over 50% of the estuary exposed at low tide. The ROMS wetting and drying scheme was used to simulate the rising and falling tide on the flats, a successful approach adapted in other regions of the world but not always inclusive of tidal channels. Bathymetric data obtained in 2009 and 2013 was used to define the model grid. Predicted tides are forced at Adam's Pt., a natural constriction in the estuary about 20 km upstream of the mouth and at the entrance to the Great Bay. Of particular interest are fluxes of material on-to and off-of the tidal flats which contribute to water quality conditions in the estuary, and are largely governed by shear stresses that drive nutrient fluxes at the fluid-sediment interface. Basin wide estimates of near-bottom shear stresses can be used to estimate first order nutrient fluxes over a tidal cycle and hence describe general biogeochemical dynamics of the estuary. Future work will include enhanced forcing of currents by winds and wave processes at the shallow edges of the estuary. This research was supported by UNH College of Engineering and Physical Sciences fellowship and ONR.
Study of Angular Momentum Transport in Hydrodynamic and Magnetohydrodynamic Experiments
NASA Astrophysics Data System (ADS)
Ji, H.; Edlund, E.; Spence, E.; Roach, A.
2010-11-01
Rapid angular momentum transport has been observed to occur in both laboratory fusion plasmas and astrophysical plasmas, but its physical mechanisms still remain illusive. In this paper, we describe a series of laboratory fluid experiments in order to investigate a variety of the proposed mechanisms either in hydrodynamics or magnetohydrodynamics (MHD). They include (1) hydrodynamic turbulence for Keplerian flows. (2) Magnetocoriolis (MC) waves, (3) Magnetorotational Instability (MRI), (4) Rossby waves, and (5) Magneto-Rossby waves. The first three mechanisms have been or are being investigated on the ongoing Princeton MRI experiment (http://mri.pppl.gov) while the last two mechanisms will be investigated on a newly built experiment, this mini-conference and on a further modified Princeton MRI experiments. Implications of these experimental results for the astrophysical problems will be discussed.
Hydrodynamic effects in the atmosphere of variable stars
NASA Technical Reports Server (NTRS)
Davis, C. G., Jr.; Bunker, S. S.
1975-01-01
Numerical models of variable stars are established, using a nonlinear radiative transfer coupled hydrodynamics code. The variable Eddington method of radiative transfer is used. Comparisons are for models of W Virginis, beta Doradus, and eta Aquilae. From these models it appears that shocks are formed in the atmospheres of classical Cepheids as well as W Virginis stars. In classical Cepheids, with periods from 7 to 10 days, the bumps occurring in the light and velocity curves appear as the result of a compression wave that reflects from the star's center. At the head of the outward going compression wave, shocks form in the atmosphere. Comparisons between the hydrodynamic motions in W Virginis and classical Cepheids are made. The strong shocks in W Virginis do not penetrate into the interior as do the compression waves formed in classical Cepheids. The shocks formed in W Virginis stars cause emission lines, while in classical Cepheids the shocks are weaker.
Load responsive hydrodynamic bearing
Kalsi, Manmohan S. (Houston, TX); Somogyi, Dezso (Sugar Land, TX); Dietle, Lannie L. (Stafford, TX)
2002-01-01
A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.
Landau Hydrodynamics Reexamined
Cheuk-Yin Wong
2008-11-06
We review the formulation of Landau hydrodynamics and find that the rapidity distribution of produced particles in the center-of-mass system should be more appropriately modified as dN/dy \\exp[\\sqrt{y_b^2-y^2}], where y_b=\\ln[\\sqrt{s_{NN}}/m_p] is the beam nucleon rapidity, instead of Landau's original distribution, dN/dy(Landau) \\exp[\\sqrt{L^2-y^2}], where L=\\ln[\\sqrt{s_{NN}}/2m_p]. The modified distribution agrees better with experimental dN/dy data than the original Landau distribution and can be represented well by the Gaussian distribution, dN/dy(Gaussian) \\exp[-y^2/2L]. Past successes of the Gaussian distribution in explaining experimental rapidity data can be understood, not because it is an approximation of the original Landau distribution, but because it is in fact a close representation of the modified distribution. Predictions for pp and AA collisions at LHC energies in Landau hydrodynamics are presented.
Lectures on Landau Hydrodynamics
Cheuk-Yin Wong
2008-09-02
Landau hydrodynamics is a plausible description for the evolution of the dense hot matter produced in high-energy heavy-ion collisions. We review the formulation of Landau hydrodynamics to pave the way for its application in high-energy heavy-ion collisions. It is found that Landau's rapidity distribution needs to be modified to provide a better quantitative description. In particular, the rapidity distribution in the center-of-mass system should be more appropriately given as dN/dy \\exp{\\sqrt{y_b^2-y^2}}, where y_b=\\ln{\\sqrt{s_NN}/m_p} is the beam nucleon rapidity, instead of Landau's original result of dN/dy({Landau}) \\exp{\\sqrt{L^2-y^2}} where L=\\ln{\\sqrt{s_NN}/2m_p}. The modified distribution is compared with the Landau distribution and experimental data. It is found that the modified distribution agrees better with experimental $dN/dy$ data than the Landau distribution and it differs only slightly from the Landau Gaussian distribution dN/dy(Landau-Gaussian) \\exp{-y^2/2L}. Past successes of the Gaussian distribution in explaining experimental rapidity data arises, not because it is an approximation of the original Landau distribution, but because it is in fact a close representation of the modified distribution.
Generalized hydrodynamics model for strongly coupled plasmas
NASA Astrophysics Data System (ADS)
Diaw, A.; Murillo, M. S.
2015-07-01
Beginning with the exact equations of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy, we obtain the density, momentum, and stress tensor-moment equations. We close the moment equations with two closures, one that guarantees an equilibrium state given by density-functional theory and another that includes collisions in the relaxation of the stress tensor. The introduction of a density functional-theory closure ensures self-consistency in the equation-of-state properties of the plasma (ideal and excess pressure, electric fields, and correlations). The resulting generalized hydrodynamics thus includes all impacts of Coulomb coupling, viscous damping, and the high-frequency (viscoelastic) response. We compare our results with those of several known models, including generalized hydrodynamic theory and models obtained using the Singwi-Tosi-Land-Sjolander approximation and the quasilocalized charge approximation. We find that the viscoelastic response, including both the high-frequency elastic generalization and viscous wave damping, is important for correctly describing ion-acoustic waves. We illustrate this result by considering three very different systems: ultracold plasmas, dusty plasmas, and dense plasmas. The new model is validated by comparing its results with those of the current autocorrelation function obtained from molecular-dynamics simulations of Yukawa plasmas, and the agreement is excellent. Generalizations of this model to mixtures and quantum systems should be straightforward.
Active Carbon and Oxygen Shell Burning Hydrodynamics
Casey Meakin; David Arnett
2006-01-16
We have simulated 2.5$\\times10^3$ s of the late evolution of a $23 \\rm M_\\odot$ star with full hydrodynamic behavior. We present the first simulations of a multiple-shell burning epoch, including the concurrent evolution and interaction of an oxygen and carbon burning shell. In addition, we have evolved a 3D model of the oxygen burning shell to sufficiently long times (300 s) to begin to assess the adequacy of the 2D approximation. We summarize striking new results: (1) strong interactions occur between active carbon and oxygen burning shells, (2) hydrodynamic wave motions in nonconvective regions, generated at the convective-radiative boundaries, are energetically important in both 2D and 3D with important consequences for compositional mixing, and (3) a spectrum of mixed p- and g-modes are unambiguously identified with corresponding adiabatic waves in these computational domains. We find that 2D convective motions are exaggerated relative to 3D because of vortex instability in 3D. We discuss the implications for supernova progenitor evolution and symmetry breaking in core collapse.
Generalized hydrodynamics model for strongly coupled plasmas.
Diaw, A; Murillo, M S
2015-07-01
Beginning with the exact equations of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy, we obtain the density, momentum, and stress tensor-moment equations. We close the moment equations with two closures, one that guarantees an equilibrium state given by density-functional theory and another that includes collisions in the relaxation of the stress tensor. The introduction of a density functional-theory closure ensures self-consistency in the equation-of-state properties of the plasma (ideal and excess pressure, electric fields, and correlations). The resulting generalized hydrodynamics thus includes all impacts of Coulomb coupling, viscous damping, and the high-frequency (viscoelastic) response. We compare our results with those of several known models, including generalized hydrodynamic theory and models obtained using the Singwi-Tosi-Land-Sjolander approximation and the quasilocalized charge approximation. We find that the viscoelastic response, including both the high-frequency elastic generalization and viscous wave damping, is important for correctly describing ion-acoustic waves. We illustrate this result by considering three very different systems: ultracold plasmas, dusty plasmas, and dense plasmas. The new model is validated by comparing its results with those of the current autocorrelation function obtained from molecular-dynamics simulations of Yukawa plasmas, and the agreement is excellent. Generalizations of this model to mixtures and quantum systems should be straightforward. PMID:26274294
On the choice of random wave simulation in the surf zone processes
Yuan, Jing
2010-01-01
In this paper, the two common approaches to account for wave randomness, the spectral approach and the wave-by-wave approach, are compared through numerical experiments conducted with the coupling of a surf zone hydrodynamic ...
Biomechanical consequences of branching in flexible wave-swept macroalgae
Martone, Patrick T.
Biomechanical consequences of branching in flexible wave-swept macroalgae Samuel Starko1,2 *, Barry Key words: biomechanics, dislodgement, drag, evolution, hydrodynamics, intertidal, macroalgae morphology, reconfiguration. Summary Wave-swept macroalgae present an excellent system for studying
Local Polynomial Regression Hydrodynamics
NASA Astrophysics Data System (ADS)
Wallin, J. F.
2001-12-01
Smoothed Particle Hydrodynamics has been to model a wide variety of astronomical phenomena. However, the artificial viscosity in and the slow convergence of SPH can lead to numerical artifacts that appear to mimic physical phenomena. LPRH is a new particle-based method for modeling gas dynamics. It uses Godunov-based solvers instead of artificial viscosity and has a higher convergence rate than SPH. The method has been formulated on an Arbitrary Lagrangian-Eulerian framework, allowing us to draw parallels between Finite Volume codes and particle-based methods. A description of the method along with selected test cases will be presented. Parts of this work were funded through the NASA Astrophysics Theory Program
Hydrodynamic effects on coalescence.
Dimiduk, Thomas G.; Bourdon, Christopher Jay; Grillet, Anne Mary; Baer, Thomas A.; de Boer, Maarten Pieter; Loewenberg, Michael; Gorby, Allen D.; Brooks, Carlton, F.
2006-10-01
The goal of this project was to design, build and test novel diagnostics to probe the effect of hydrodynamic forces on coalescence dynamics. Our investigation focused on how a drop coalesces onto a flat surface which is analogous to two drops coalescing, but more amenable to precise experimental measurements. We designed and built a flow cell to create an axisymmetric compression flow which brings a drop onto a flat surface. A computer-controlled system manipulates the flow to steer the drop and maintain a symmetric flow. Particle image velocimetry was performed to confirm that the control system was delivering a well conditioned flow. To examine the dynamics of the coalescence, we implemented an interferometry capability to measure the drainage of the thin film between the drop and the surface during the coalescence process. A semi-automated analysis routine was developed which converts the dynamic interferogram series into drop shape evolution data.
NASA Astrophysics Data System (ADS)
Jones, S.; Benson, P.; Meredith, P.
2005-12-01
We present results from an experimental and theoretical study of pore fabric anisotropy using the method of anisotropy of magnetic susceptibility (AMS) and synthetic pore spaces of known geometry. AMS has traditionally been used to measure the magnetic anisotropy of a dry rock matrix. Here we use the technique to determine the anisotropy of the void space. We provide the voids with an artificial magnetic susceptibility by saturating them with magnetic ferrofluid. AMS measurements are made in the normal manner, and interpreted using the theoretical equivalent pore concept (EPC) proposed by Hrouda et al. (2000). This theory attempts to relate the magnetic measurements of lineation, foliation and anisotropy to the lineation, foliation and anisotropy of the real, physical pore fabric. Essentially, an average physical pore space shape and alignment is modeled that will produce the same magnetic properties as those measured on the real sample. In order to test the theory, we prepared a range of synthetic samples with known pore geometries from cylindrical polycarbonate blanks 25mm in diameter by 22mm long. Firstly, a set of "special fabrics" were machined axially into the sample blanks: (a) a set of 19 equally spaced holes, 2mm in diameter by 12mm long, (b); a row of 5 holes, 3.3mm in diameter by 16mm long; and (c) a tier of four disks, 18mm in diameter by 1.4mm thick. The total bulk susceptibility of each "special fabric" was approximately the same. Secondly, a set of seven samples were machined with quasi-ellipsoidal voids with axial to radial axis ratios of: 0.75, 0.83, 0.92, 1.0, 1.1, 1.2, and 1.3. All of the special-fabric samples showed high magnetic anisotropy, with a maximum foliation of 1.41 and lineation of 1.29. The results are as expected intuitively, with the 19 hole sample exhibiting a highly prolate fabric and the 5 hole sample exhibiting a highly oblate fabric. For the quasi-ellipsoids, the foliation decreases and the lineation increases as the axial to radial axis ratio increases from 0.75 to 1.3; i.e. as we move from an oblate to a prolate void. The measured magnetic foliations and lineations are then used to estimate the pore fabric via the EPC, for direct comparison with the known geometry. We find that the EPC method underestimates the anisotropy of the void space, especially for low ferrofluid concentration. As we increase the concentration this discrepancy decreases, but does not disappear even for the highest concentration (undiluted ferrofluid with an intrinsic susceptibility of 3.34).
Kinematics measurements of regular, irregular, and rogue waves by PIV/LDV
Choi, Hae-Jin
2007-04-25
. Giant waves often come unexpectedly from directions other than the prevailing wind and waves. Freak waves or rogue waves are known for their extraordinary height and abnormal shape. Although it is impossible to anticipate rogue waves completely..., it has been found that there is a solution to Schrödinger nonlinear hydrodynamics equations for exceptionally high freak waves. However, a solution of Schrödinger nonlinear hydrodynamics equations can not simulate fully the random nature of the sea...
Polarized seismic and solitary waves run-up at the sea bed
Dennis, L. C.C.; Zainal, A. A.; Faisal, S. Y.
2012-09-26
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.
COER HYDRODYNAMIC MODELING COMPETITION: MODELING THE DYNAMIC RESPONSE OF A FLOATING BODY USING of Maynooth in Ireland organized a hydrodynamic modeling competition in conjunction with OMAE2015. Researchers tested in a series of wave-tank tests. Specifically, COER set up a blind competition, where the device
INTRODUCTION Wave and current interactions are an important aspect of
of simulating the hydrodynamic processes due to waves, rivers, winds, and ambient currents (Chen et al. 2006; Qi In order to resolve the alongshore-current feature of the relatively small coastal area and the river leveeINTRODUCTION Wave and current interactions are an important aspect of hydrodynamics, especially
Weijgaert, Rien van de
;14/03/2014 3 Kayak Surfing on ocean gravity waves Oregon Coast Waves: sea & ocean waves #12;14/03/2014 4 Sound Waves Sound Waves: #12;14/03/2014 5 Sound Waves Linear Waves Sound Waves compression rarefaction #12 are inevitable if sound waves propagate over long distances; 4. Shocks always occur when a flow hits an obstacle
Constraining relativistic viscous hydrodynamical evolution
Martinez, Mauricio; Strickland, Michael
2009-04-15
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.
Sweetman, Bert
From Proceedings, BOSS-97: Behaviour of Offshore Structures Volume 2 (Hydrodynamics), ed. J motions of a floating spar buoy platform with the results of wave tank experiments. Results studiedKeywordsKeywordsKeywordsKeywordsKeywords Nonlinear wave diffraction; offshore structures; random vibration; spar buoys, structural reliability; wave
NASA Astrophysics Data System (ADS)
Zeng, Jian; Deng, Yanxiang; Vedantam, Pallavi; Tzeng, Tzuen-Rong; Xuan, Xiangchun
2013-11-01
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.
NASA Astrophysics Data System (ADS)
Krupka, Jerzy
2015-09-01
Few resonance cavities operating on different modes have been used for the accurate multi-frequency determination of the complex permittivity of highly concentrated aqueous NaCl solutions at a frequency range of 2.5?GHz to 24?GHz. It has been shown that the use of the perturbation method would lead to significant measurement uncertainties especially for lossy samples and should be avoided especially for TE0n1 mode cavities. At frequencies that are smaller than 15?GHz the imaginary part of the permittivity of NaCl solutions increases while at frequencies larger than 15?GHz it decreases, with the increasing conductivity of the electrolyte. In the last case the total dielectric losses for the saturated electrolyte are noticeably smaller than for pure water. The complex permittivity and complex permeability of ferrofluid, liquid that exhibits diamagnetic properties at microwave frequencies, were measured by employing two cylindrical cavities operating on complementary modes.
A hybrid Godunov method for radiation hydrodynamics
Sekora, Michael D.; Stone, James M.
2010-09-20
From a mathematical perspective, radiation hydrodynamics can be thought of as a system of hyperbolic balance laws with dual multiscale behavior (multiscale behavior associated with the hyperbolic wave speeds as well as multiscale behavior associated with source term relaxation). With this outlook in mind, this paper presents a hybrid Godunov method for one-dimensional radiation hydrodynamics that is uniformly well behaved from the photon free streaming (hyperbolic) limit through the weak equilibrium diffusion (parabolic) limit and to the strong equilibrium diffusion (hyperbolic) limit. Moreover, one finds that the technique preserves certain asymptotic limits. The method incorporates a backward Euler upwinding scheme for the radiation energy density E{sub r} and flux F{sub r} as well as a modified Godunov scheme for the material density {rho}, momentum density m, and energy density E. The backward Euler upwinding scheme is first-order accurate and uses an implicit HLLE flux function to temporally advance the radiation components according to the material flow scale. The modified Godunov scheme is second-order accurate and directly couples stiff source term effects to the hyperbolic structure of the system of balance laws. This Godunov technique is composed of a predictor step that is based on Duhamel's principle and a corrector step that is based on Picard iteration. The Godunov scheme is explicit on the material flow scale but is unsplit and fully couples matter and radiation without invoking a diffusion-type approximation for radiation hydrodynamics. This technique derives from earlier work by Miniati and Colella (2007) . Numerical tests demonstrate that the method is stable, robust, and accurate across various parameter regimes.
Relativistic Hydrodynamics on Graphic Cards
Jochen Gerhard; Volker Lindenstruth; Marcus Bleicher
2012-09-09
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.
Hydrodynamic flows in electrowetting.
Ko, Sung Hee; Lee, Horim; Kang, Kwan Hyoung
2008-02-01
Hydrodynamic flows are generated inside a droplet in electrowetting when an ac voltage is applied. To discover the characteristics and origin of the flows, we investigated the flow pattern for a sessile droplet for various needle-electrode positions, electrolyte concentrations, and applied electrical frequencies. Two distinct types of flows were observed under current experimental conditions. In the typical experimental condition, a quite fast flow appears in the low-frequency range of about 10 Hz to 15 kHz. A different type of flow is observed in the high-frequency range of about 35 to 256 kHz, but this frequency range depends significantly on the electrolyte concentration. Most typically, the flow directions are different for the two flows. A shape oscillation of a droplet was observed in the low-frequency range by a high-speed camera. The flow in the low-frequency range is insensitive to the conductivity of the solution and may be caused by the interfacial oscillation of the droplet. The flow at high frequency is very sensitive to the conductivity of the solution and electrode position, so the high-frequency flow is believed to be caused by some electrohydrodynamic effect. PMID:18177057
Hydrodynamics of Holographic Superconductors
Amado, Irene; Landsteiner, Karl
2009-01-01
We study the poles of the retarded Green functions of a holographic superconductor. The model shows a second order phase transition where a charged scalar operator condenses and a U(1) symmetry is spontaneously broken. The poles of the holographic Green functions are the quasinormal modes in an AdS black hole background. We study the spectrum of quasinormal frequencies in the broken phase, where we establish the appearance of a massless or hydrodynamic mode at the critical temperature as expected for a second order phase transition. In the broken phase we find the pole representing second sound. We compute the speed of second sound and its attenuation length as function of the temperature. In addition we find a pseudo diffusion mode, whose frequencies are purely imaginary but with a non-zero gap at zero momentum. This gap goes to zero at the critical temperature. As a technical side result we explain how to calculate holographic Green functions and their quasinormal modes for a set of operators that mix under...
Hydrodynamics of Holographic Superconductors
Irene Amado; Matthias Kaminski; Karl Landsteiner
2009-06-17
We study the poles of the retarded Green functions of a holographic superconductor. The model shows a second order phase transition where a charged scalar operator condenses and a U(1) symmetry is spontaneously broken. The poles of the holographic Green functions are the quasinormal modes in an AdS black hole background. We study the spectrum of quasinormal frequencies in the broken phase, where we establish the appearance of a massless or hydrodynamic mode at the critical temperature as expected for a second order phase transition. In the broken phase we find the pole representing second sound. We compute the speed of second sound and its attenuation length as function of the temperature. In addition we find a pseudo diffusion mode, whose frequencies are purely imaginary but with a non-zero gap at zero momentum. This gap goes to zero at the critical temperature. As a technical side result we explain how to calculate holographic Green functions and their quasinormal modes for a set of operators that mix under the RG flow.
Advanced in Macrostatistical Hydrodynamics
Graham, A.L.; Tetlow, N.; Abbott, J.R.; Mondy, L.S.; Brenner, H.
1993-08-01
An overview is presented of research that focuses on slow flows of suspensions in which colloidal and inertial effects are negligibly small (Macrostatistical Hydrodynamics). First, we describe nuclear magnetic resonance imaging experiments to quantitatively measure particle migration occurring in concentrated suspensions undergoing a flow with a nonuniform shear rate. These experiments address the issue of how the flow field affects the microstructure of suspensions. In order to understand the local viscosity in a suspension with such a flow-induced, spatially varying concentration, one must know how the viscosity of a homogeneous suspension depends on such variables as solids concentration and particle orientation. We suggest the technique of falling ball viscometry, using small balls, as a method to determine the effective viscosity of a suspension without affecting the original microstructure significantly. We also describe data from experiments in which the detailed fluctuations of a falling ball`s velocity indicate the noncontinuum nature of the suspension and may lead to more insights into the effects of suspension microstructure on macroscopic properties. Finally, we briefly describe other experiments that can be performed in quiescent suspensions (in contrast to the use of conventional shear rotational viscometers) in order to learn more about the microstructure and boundary effects in concentrated suspensions.
Simulation of astrophysical jet using the special relativistic hydrodynamics code
Orhan Donmez; Refik Kayali
2006-02-14
This paper describes a multidimensional hydrodynamic code which can be used for the studies of relativistic astrophysical flows. The code solves the special relativistic hydrodynamic equations as a hyperbolic system of conservation laws based on High Resolution Shock Capturing (HRSC) Scheme. Two standard tests, one of which is the relativistic blast wave tested in our previous paper\\cite{DO1}, and the other is the collision of two ultrarelativistic blast waves tested in here, are presented to demonstrate that the code captures correctly and gives solution in the discontinuities, accurately. The relativistic astrophysical jet is modeled for the ultrarelativistic flow case. The dynamics of jet flowing is then determined by the ambient parameters such as densities, and velocities of the jets and the momentum impulse applied to the computational surface. We obtain solutions for the jet structure, propagation of jet during the time evolution, and variation in the Mach number on the computational domain at a fixed time.
Complex quantum hydrodynamics with teleportation
R. Tsekov
2015-05-25
It is shown how the Schrodinger equation can be transformed to a complex quantum Navier-Stokes equation with imaginary dilatational viscosity. The self-diffusion in quantum gases is described by this complex quantum hydrodynamics and the quantum Marangoni effect is introduced. The density matrix operator and Wigner function equations, corresponding to quantum hydrodynamics, are described. Finally, the quantum teleportation in time is also discussed via a non-relativistic version of the Majorana equation.
NASA Astrophysics Data System (ADS)
Hennenberg, M.; Slavtchev, S.; Valchev, G.
2013-12-01
When an isothermal ferrofluid is submitted to an oscillating magnetic field, the initially motionless liquid free surface can start to oscillate. This physical phenomenon is similar to the Faraday instability for usual Newtonian liquids subjected to a mechanical oscillation. In the present paper, we consider the magnetic field as a sum of a constant part and a time periodic part. Two different cases for the constant part of the field, being vertical in the first one or horizontal in the second one are studied. Assuming both ferrofluid magnetization and magnetic field to be collinear, we develop the linear stability analysis of the motionless reference state taking into account the Kelvin magnetic forces. The Laplace law describing the free surface deformation reduces to Hill's equation, which is studied using the classical method of Ince and Erdelyi. Inside this framework, we obtain the transition conditions leading to the free surface oscillations.
Vegetation Hydrodynamics - Recent Developments and Future Challenges
NASA Astrophysics Data System (ADS)
Nepf, H. M.
2014-12-01
For over a century vegetation has been removed from channels and coastal zones to facilitate navigation and development. In recent decades, however, we have recognized the ecologic and economic benefits of aquatic vegetation. It buffers against coastal eutrophication, damps waves and coastal storm surge, provides habitat, inhibits bank erosion, and provides significant carbon storage. The management of watersheds and coastal zones has turned from vegetation removal to restoration. In the past 20 years, the study of vegetation hydrodynamics has accelerated to meet the need to understand feedbacks between vegetation, flow and sediment transport. This presentation will describe key features of vegetation hydrodynamics, first at the meadow scale and then at the scale of individual patches, examining how vegetation density and meadow (or patch) morphology impact flow, with subsequent implications for sediment fate. Finally, the talk highlights differences in turbulence generation between bare and vegetated beds that may limit the transfer of open channel sediment transport models to vegetated channels, creating the future challenge of defining sediment transport models appropriate for vegetated regions.
Phonon hydrodynamics in two-dimensional materials.
Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola
2015-01-01
The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane. PMID:25744932
Phonon hydrodynamics in two-dimensional materials
NASA Astrophysics Data System (ADS)
Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola
2015-03-01
The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane.
Effect of Second-Order Hydrodynamics on a Floating Offshore Wind Turbine
Roald, L.; Jonkman, J.; Robertson, A.
2014-05-01
The design of offshore floating wind turbines uses design codes that can simulate the entire coupled system behavior. At the present, most codes include only first-order hydrodynamics, which induce forces and motions varying with the same frequency as the incident waves. Effects due to second- and higher-order hydrodynamics are often ignored in the offshore industry, because the forces induced typically are smaller than the first-order forces. In this report, first- and second-order hydrodynamic analysis used in the offshore oil and gas industry is applied to two different wind turbine concepts--a spar and a tension leg platform.
Investigation on the hydrodynamic performance of an ultra deep turret-moored FLNG system
NASA Astrophysics Data System (ADS)
Zhao, Wen-hua; Yang, Jian-min; Hu, Zhi-qiang; Xiao, Long-fei; Peng, Tao
2012-03-01
Hydrodynamic performance of an ultra deep turret-moored Floating Liquefied Natural Gas (FLNG) system is investigated. Hydrodynamic modeling of a turret-moored FLNG system, in consideration of the coupling effects of the vessel and its mooring lines, has been addressed in details. Based on the boundary element method, a 3-D panel model of the FLNG vessel and the related free water surface model are established, and the first-order and second-order mean-drift wave loads and other hydrodynamic coefficients are calculated. A systematic model test program consisting of the white noise wave test, offset test and irregular wave test combined with current and wind, etc. is performed to verify the numerical model. Owing to the depth limit of the water basin, the model test is carried out for the hydrodynamics of the FLNG coupled with only the truncated mooring system. The numerical simulation model features well the hydrodynamic performance of the FLNG system obtained from the model tests. The hydrodynamic characteristics presented in both the numerical simulations and the physical model tests would serve as the guidance for the ongoing project of FLNG system.
The hydrodynamics of colloidal gelation.
Varga, Zsigmond; Wang, Gang; Swan, James
2015-12-14
Colloidal gels are formed during arrested phase separation. Sub-micron, mutually attractive particles aggregate to form a system spanning network with high interfacial area, far from equilibrium. Models for microstructural evolution during colloidal gelation have often struggled to match experimental results with long standing questions regarding the role of hydrodynamic interactions. In nearly all models, these interactions are neglected entirely. In the present work, we report simulations of gelation with and without hydrodynamic interactions between the suspended particles executed in HOOMD-blue. The disparities between these simulations are striking and mirror the experimental-theoretical mismatch in the literature. The hydrodynamic simulations agree with experimental observations, however. We explore a simple model of the competing transport processes in gelation that anticipates these disparities, and conclude that hydrodynamic forces are essential. Near the gel boundary, there exists a competition between compaction of individual aggregates which suppresses gelation and coagulation of aggregates which enhances it. The time scale for compaction is mildly slowed by hydrodynamic interactions, while the time scale for coagulation is greatly accelerated. This enhancement to coagulation leads to a shift in the gel boundary to lower strengths of attraction and lower particle concentrations when compared to models that neglect hydrodynamic interactions. Away from the gel boundary, differences in the nearest neighbor distribution and fractal dimension persist within gels produced by both simulation methods. This result necessitates a fundamental rethinking of how dynamic, discrete element models for gelation kinetics are developed as well as how collective hydrodynamic interactions influence the arrest of attractive colloidal dispersions. PMID:26406284
Group-invariant solutions of hydrodynamics and radiation hydrodynamics
Coggeshall, S.V.
1993-08-01
Using the property of invariance under Lie groups of transformations, the equations of hydrodynamics are transformed from partial differential equations to ordinary differential equations, for which special analytic solutions can be found. These particular solutions can be used for (1) numerical benchmarks, (2) the basis for analytic models, and (3) insight into more general solutions. Additionally, group transformations can be used to construct new solutions from existing ones. A space-time projective group is used to generate complicated solutions from simpler solutions. Discussion of these procedures is presented along with examples of analytic of 1,2 and 3-D hydrodynamics.
What Controls the Hydrodynamics of the Central Congo River?
NASA Astrophysics Data System (ADS)
O'Loughlin, F.; Bates, P. D.
2014-12-01
Despite being the second largest river basin in the world, with a drainage area greater than 3.7 million square kilometres, little is known about the hydraulics of the Congo River. This lack of knowledge is mainly due to a mixture of conflicts and the difficulty of accessing existing data. We present results of studies which have focused primarily on the middle reach of the Congo River, located between Kisangani and Kinshasa, and its six main tributaries (Kasai, Ubangai, Sangha, Ruki, Lulonga and Lomami rivers). Through a combination of remotely sensed datasets and a hydrodynamic model we investigated what factors control the hydrodynamics of the middle reach. From the analysis of the remotely sensed datasets, we discover that variability in river width of the middle reach of the Congo is large and cannot be represented by empirical equations which relate channel geometry to basin area and discharge. Water surface slopes vary from 3.5 cm/km to 9 cm/km, which is far more than previous studies suggest. The remote datasets indicate that there exist 5 large constrictions in the river width which may result in backwater affecting between 11 and 33 percent of middle reach at low and high water respectively. These results were corroborated by the hydrodynamic model. In fact, when all constrictions caused by a narrowing in width of 1 km or more are considered, water levels along 43 percent of the middle reach change by at least 0.5 m. Using the hydrodynamic model we also investigated the importance of the wetlands to the attenuation of the flood wave through the system. Initial results suggest that for the Congo River, floodplains have far more impact on the peak magnitude than the timing of the flood wave. When the model was run with no floodplain interactions an increase in the magnitude of flood peak was observed, with the timing of the waves being consistent with observed measurements.
Comparative hydrodynamics of bacterial polymorphism
Spagnolie, Saverio E
2011-01-01
Most bacteria swim through fluids by rotating helical flagella which can take one of twelve distinct polymorphic shapes. The most common helical waveform 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 hydrodynamically efficient of the twelve 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. The hydrodynamic optimality of the normal polymorph suggests that, although energetic costs of locomotion are small for bacteria, fluid mechanical forces may have played a significant role in the evolution of the flagellum.
Hydrodynamics of fractal continuum flow.
Balankin, Alexander S; Elizarraraz, Benjamin Espinoza
2012-02-01
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
Abnormal pressures as hydrodynamic phenomena
Neuzil, C.E.
1995-01-01
So-called abnormal pressures, subsurface fluid pressures significantly higher or lower than hydrostatic, have excited speculation about their origin since subsurface exploration first encountered them. Two distinct conceptual models for abnormal pressures have gained currency among earth scientists. The static model sees abnormal pressures generally as relict features preserved by a virtual absence of fluid flow over geologic time. The hydrodynamic model instead envisions abnormal pressures as phenomena in which flow usually plays an important role. This paper develops the theoretical framework for abnormal pressures as hydrodynamic phenomena, shows that it explains the manifold occurrences of abnormal pressures, and examines the implications of this approach. -from Author
Spin current evolution in the separated spin-up and spin-down quantum hydrodynamics
NASA Astrophysics Data System (ADS)
Trukhanova, Mariya, Iv.
2015-10-01
We have developed a method of quantum hydrodynamics (QHD) that describes particles with spin-up and with spin-down in separate. We have derived the equation of the spin current evolution as a part of the set of the quantum hydrodynamics equations that treat particles with different projection of spin on the preferable direction as two different species. We have studied orthogonal propagation of waves in the external magnetic field and determined the contribution of quantum corrections due to the Bohm potential and to magnetization energy of particles with different projections of spin in the spin-current wave dispersion. We have analyzed the limits of weak and strong magnetic fields.
THE RECIPROCAL RELATIONSHIP BETWEEN HYDRODYNAMICS AND BIVALVES
THE RECIPROCAL RELATIONSHIP BETWEEN HYDRODYNAMICS AND BIVALVES A Thesis Presented to The Academic #12;THE RECIPROCAL RELATIONSHIP BETWEEN HYDRODYNAMICS AND BIVALVES Approved by: Dr. Donald R. Webster . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2.1 Unsteady Jets . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.3 Bivalve Clams
Hydrodynamics of Coalescing Binary Neutron Stars: Ellipsoidal Treatment
Dong Lai; Stu Shapiro
1994-08-17
We employ an approximate treatment of dissipative hydrodynamics in three dimensions to study the coalescence of binary neutron stars driven by the emission of gravitational waves. The stars are modeled as compressible ellipsoids obeying a polytropic equation of state; all internal fluid velocities are assumed to be linear functions of the coordinates. The hydrodynamic equations then reduce to a set of coupled ordinary differential equations for the evolution of the principal axes of the ellipsoids, the internal velocity parameters and the binary orbital parameters. Gravitational radiation reaction and viscous dissipation are both incorporated. We set up exact initial binary equilibrium configurations and follow the transition from the quasi-static, secular decay of the orbit at large separation to the rapid dynamical evolution of the configurations just prior to contact. A hydrodynamical instability resulting from tidal interactions significantly accelerates the coalescence at small separation, leading to appreciable radial infall velocity and tidal lag angles near contact. This behavior is reflected in the gravitational waveforms and may be observable by gravitational wave detectors under construction.
From Field Theory to the Hydrodynamics of Relativistic Superfluids
Stephan Stetina
2015-01-31
The hydrodynamic description of a superfluid is usually based on a two-fluid picture. In this thesis, basic properties of such a relativistic two-fluid system are derived from the underlying microscopic physics of a complex scalar quantum field theory. To obtain analytic results of all non-dissipative hydrodynamic quantities in terms of field theoretic variables, calculations are first carried out in a low-temperature and weak-coupling approximation. In a second step, the 2-particle-irreducible formalism is applied: This formalism allows for a numerical evaluation of the hydrodynamic parameters for all temperatures below the critical temperature. In addition, a system of two coupled superfluids is studied. As an application, the velocities of first and second sound in the presence of a superflow are calculated. The results show that first (second) sound evolves from a density (temperature) wave at low temperatures to a temperature (density) wave at high temperatures. This role reversal is investigated for ultra-relativistic and near-nonrelativistic systems for zero and nonzero superflow. The studies carried out in this thesis are of a very general nature as one does not have to specify the system for which the microscopic field theory is an effective description. As a particular example, superfluidity in dense quark and nuclear matter in compact stars are discussed.
Hydrodynamic focusing – a versatile tool
Golden, Joel P.; Justin, Gusphyl A.; Nasir, Mansoor; Ligler, Frances S.
2011-01-01
The control of hydrodynamic focusing in a microchannel has inspired new approaches for microfluidic mixing, separations, sensors, cell analysis and microfabrication. Achieving a flat interface between the focusing and focused fluids is dependent on Reynolds number and device geometry, and many hydrodynamic focusing systems can benefit from this understanding. For applications where a specific cross-sectional shape is desired for the focused flow, advection generated by grooved structures in the channel walls can be used to define the shape of the focused flow. Relative flow rates of the focused flow and focusing streams can be manipulated to control the crosssectional area of the focused flows. This manuscript discusses the principles for defining the shape of the interface between the focused and focusing fluids and provides examples from our lab that use hydrodynamic focusing for impedance-based sensors, flow cytometry, and microfabrication to illustrate the breadth of opportunities for introducing new capabilities into microfluidic systems. We evaluate each example for the advantages and limitations integral to utilization of hydrodynamic focusing for that particular application. PMID:21952728
Meat Products, Hydrodynamic Pressure Processing
Technology Transfer Automated Retrieval System (TEKTRAN)
The hydrodynamic pressure process (HDP) has been shown to be very effective at improving meat tenderness in a variety of meat cuts. When compared to conventional aging for tenderization, HDP was more effective. The HDP process may offer the meat industry a new alternative for tenderizing meat in add...
Formation Interuniversitaire de Physique Hydrodynamics
Balbus, Steven
" . . . . . . . . . . . . . . . . . . . . 16 3.2 Rotating Frames . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.3 Manipulating Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4.2.1 Hydraulic Jumps
Low torque hydrodynamic lip geometry for rotary seals
Dietle, Lannie L.; Schroeder, John E.
2015-07-21
A hydrodynamically lubricating geometry for the generally circular dynamic sealing lip of rotary seals that are employed to partition a lubricant from an environment. The dynamic sealing lip is provided for establishing compressed sealing engagement with a relatively rotatable surface, and for wedging a film of lubricating fluid into the interface between the dynamic sealing lip and the relatively rotatable surface in response to relative rotation that may occur in the clockwise or the counter-clockwise direction. A wave form incorporating an elongated dimple provides the gradual convergence, efficient impingement angle, and gradual interfacial contact pressure rise that are conducive to efficient hydrodynamic wedging. Skewed elevated contact pressure zones produced by compression edge effects provide for controlled lubricant movement within the dynamic sealing interface between the seal and the relatively rotatable surface, producing enhanced lubrication and low running torque.
Enhanced Heat Flow in the Hydrodynamic Collisionless Regime
Meppelink, R.; Rooij, R. van; Vogels, J. M.; Straten, P. van der
2009-08-28
We study the heat conduction of a cold, thermal cloud in a highly asymmetric trap. The cloud is axially hydrodynamic, but due to the asymmetric trap radially collisionless. By locally heating the cloud we excite a thermal dipole mode and measure its oscillation frequency and damping rate. We find an unexpectedly large heat conduction compared to the homogeneous case. The enhanced heat conduction in this regime is partially caused by atoms with a high angular momentum spiraling in trajectories around the core of the cloud. Since atoms in these trajectories are almost collisionless they strongly contribute to the heat transfer. We observe a second, oscillating hydrodynamic mode, which we identify as a standing wave sound mode.
A hydrodynamic approach to non-equilibrium conformal field theories
Bernard, Denis
2015-01-01
We develop a hydrodynamic approach to non-equilibrium conformal field theory. We study non-equilibrium steady states in the context of one-dimensional conformal field theory perturbed by the $T\\bar T$ irrelevant operator. By direct quantum computation, we show, to first order in the coupling, that a relativistic hydrodynamic emerges, which is a simple modification of one-dimensional conformal fluids. We show that it describes the steady state and its approach, and we provide the main characteristics of the steady state, which lies between two shock waves. The velocities of these shocks are modified by the perturbation and equal the sound velocities of the asymptotic baths. Pushing further this approach, we are led to conjecture that the approach to the steady state is generically controlled by the power law $t^{-1/2}$, and that the widths of the shocks increase with time according to $t^{1/3}$.
A hydrodynamic approach to non-equilibrium conformal field theories
Denis Bernard; Benjamin Doyon
2015-07-27
We develop a hydrodynamic approach to non-equilibrium conformal field theory. We study non-equilibrium steady states in the context of one-dimensional conformal field theory perturbed by the $T\\bar T$ irrelevant operator. By direct quantum computation, we show, to first order in the coupling, that a relativistic hydrodynamic emerges, which is a simple modification of one-dimensional conformal fluids. We show that it describes the steady state and its approach, and we provide the main characteristics of the steady state, which lies between two shock waves. The velocities of these shocks are modified by the perturbation and equal the sound velocities of the asymptotic baths. Pushing further this approach, we are led to conjecture that the approach to the steady state is generically controlled by the power law $t^{-1/2}$, and that the widths of the shocks increase with time according to $t^{1/3}$.
NASA Astrophysics Data System (ADS)
Mosher, Nathaniel; Perkins-Harbin, Emily; Aho, Brandon; Wang, Lihua; Kumon, Ronald; Rablau, Corneliu; Vaishnava, Prem; Tackett, Ronald; Therapeutic Biomaterials Group Team
2015-03-01
Colloidal suspensions of superparamagnetic nanoparticles, known as ferrofluids, are promising candidates for the mediation of magnetic fluid hyperthermia (MFH). In such materials, the dissipation of heat occurs as a result of the relaxation of the particles in an applied ac magnetic field via the Brownian and Neel mechanisms. In order to isolate and study the role of the Neel mechanism in this process, the sample can be frozen, using liquid nitrogen, in order to suppress the Brownian relaxation. In this experiment, dextran-coated Fe3O4 nanoparticles synthesized via co-precipitation and characterized via transmission electron microscopy and dc magnetization are used as MFH mediators over the temperature range between -70 °C to -10 °C (Brownian-suppressed state). Heating the nanoparticles using ac magnetic field (amplitude ~300 Oe), the frequency dependence of the specific absorption rate (SAR) is calculated between 150 kHz and 350 kHz and used to determine the magnetocrystalline anisotropy of the sample. We would like to thank Fluxtrol, Inc. for their help with this project
Fasih Ramandi, Negin; Shemirani, Farzaneh
2015-10-15
Surfacted ferrofluid (S-FF) is a stable colloid dispersion of magnetic nanoparticles in a carrier liquid which possesses magnetic properties and fluidity simultaneously. Specifically in S-FF coating magnetic nanoparticles with a suitable surfactant provides steric repulsions to prevent particles agglomeration. Selecting the function of surfactant can be engineered according to its application. In the present study, for the first time the application of S-FF in dispersive solid phase extraction of methylene blue (as a cationic dye model) in water and shrimp samples was investigated. For this purpose, in order to use ionic liquid as carrier fluid, the surface of Fe3O4 nanoparticles was coated by an anionic surfactant in a polar medium to form a hydrophilic layer around magnetic nanoparticles. In addition to hydrophobic interactions between the analyte and carbonic chain of surfactant, the retention of cationic dye was mainly governed by attractive electrostatic interactions between polar head of surfactant and dye. Under optimized conditions, the relative standard deviation is 2.9%, the limit of detection is 2.5 ?g L(-1), and the preconcentration factor is 135. PMID:25952885
Qasim, Muhammad; Khan, Zafar Hayat; Khan, Waqar Ahmad; Ali Shah, Inayat
2014-01-01
This study investigates the magnetohydrodynamic (MHD) flow of ferrofluid along a stretching cylinder. The velocity slip and prescribed surface heat flux boundary conditions are employed on the cylinder surface. Water as conventional base fluid containing nanoparticles of magnetite (Fe3O4) is used. Comparison between magnetic (Fe3O4) and non-magnetic (Al2O3) nanoparticles is also made. The governing non-linear partial differential equations are reduced to non-linear ordinary differential equations and then solved numerically using shooting method. Present results are compared with the available data in the limiting cases. The present results are found to be in an excellent agreement. It is observed that with an increase in the magnetic field strength, the percent difference in the heat transfer rate of magnetic nanoparticles with Al2O3 decreases. Surface shear stress and the heat transfer rate at the surface increase as the curvature parameter increases, i.e curvature helps to enhance the heat transfer. PMID:24465388
Qasim, Muhammad; Khan, Zafar Hayat; Khan, Waqar Ahmad; Ali Shah, Inayat
2014-01-01
This study investigates the magnetohydrodynamic (MHD) flow of ferrofluid along a stretching cylinder. The velocity slip and prescribed surface heat flux boundary conditions are employed on the cylinder surface. Water as conventional base fluid containing nanoparticles of magnetite (Fe3O4) is used. Comparison between magnetic (Fe3O4) and non-magnetic (Al2O3) nanoparticles is also made. The governing non-linear partial differential equations are reduced to non-linear ordinary differential equations and then solved numerically using shooting method. Present results are compared with the available data in the limiting cases. The present results are found to be in an excellent agreement. It is observed that with an increase in the magnetic field strength, the percent difference in the heat transfer rate of magnetic nanoparticles with Al2O3 decreases. Surface shear stress and the heat transfer rate at the surface increase as the curvature parameter increases, i.e curvature helps to enhance the heat transfer. PMID:24465388
NASA Astrophysics Data System (ADS)
Hong, Ruo-Yu; Li, Jian-Hua; Zhang, Shi-Zhong; Li, Hong-Zhong; Zheng, Ying; Ding, Jian-min; Wei, Dong-Guang
2009-01-01
Fe 3O 4 magnetic nanoparticles (MNPs) were synthesized by the co-precipitation of Fe 3+ and Fe 2+ with ammonium hydroxide. The sodium citrate-modified Fe 3O 4 MNPs were prepared under Ar protection and were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM). To improve the oxidation resistance of Fe 3O 4 MNPs, a silica layer was coated onto the modified and unmodified MNPs by the hydrolysis of tetraethoxysilane (TEOS) at 50 °C and pH 9. Afterwards, the silica-coated Fe 3O 4 core/shell MNPs were modified by oleic acid (OA) and were tested by IR and VSM. IR results revealed that the OA was successfully grafted onto the silica shell. The Fe 3O 4/SiO 2 core/shell MNPs modified by OA were used to prepare water-based ferrofluids (FFs) using PEG as the second layer of surfactants. The properties of FFs were characterized using a UV-vis spectrophotometer, a Gouy magnetic balance, a laser particle size analyzer and a Brookfield LVDV-III+ rheometer.
Hydrodynamic correlations in shear flow: Multiparticle-collision-dynamics simulation study
NASA Astrophysics Data System (ADS)
Varghese, Anoop; Huang, Chien-Cheng; Winkler, Roland G.; Gompper, Gerhard
2015-11-01
The nonequilibrium hydrodynamic correlations of a multiparticle-collision-dynamics (MPC) fluid in shear flow are studied by analytical calculations and simulations. The Navier-Stokes equations for a MPC fluid are linearized about the shear flow and the hydrodynamic modes are evaluated as an expansion in the wave vector. The shear-rate dependence and anisotropy of the transverse and longitudinal velocity correlations are analyzed. We demonstrate that hydrodynamic correlations in shear flow are anisotropic, specifically, the two transverse modes are no longer identical. In addition, our simulations reveal the directional dependence of the frequency and attenuation of the longitudinal velocity correlation function. Furthermore, the velocity autocorrelation functions of a tagged fluid particle in shear flow are determined. The simulation results for various hydrodynamic correlations agree very well with the theoretical predictions.
Computations of fully nonlinear three-dimensional wave-body interactions
Yan, Hongmei
2010-01-01
Nonlinear effects in hydrodynamics of wave-body interaction problems become critically important when large-amplitude body motions and/or extreme surface waves are involved. Accurate prediction and understanding of these ...
Anomalous hydrodynamics of fractional quantum Hall states
Wiegmann, P.
2013-09-15
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.
Cluster Dynamics of Planetary Waves
Elena Kartashova; Victor S. L'vov
2008-11-05
The dynamics of nonlinear atmospheric planetary waves is determined by a small number of independent wave clusters consisting of a few connected resonant triads. We classified the different types of connections between neighboring triads that determine the general dynamics of a cluster. Each connection type corresponds to substantially different scenarios of energy flux among the modes. The general approach can be applied directly to various mesoscopic systems with 3-mode interactions, encountered in hydrodynamics, astronomy, plasma physics, chemistry, medicine, etc.
Jonkman, J. M.; Sclavounos, P. D.
2006-01-01
Aeroelastic simulation tools are routinely used to design and analyze onshore wind turbines, in order to obtain cost effective machines that achieve favorable performance while maintaining structural integrity. These tools employ sophisticated models of wind-inflow; aerodynamic, gravitational, and inertial loading of the rotor, nacelle, and tower; elastic effects within and between components; and mechanical actuation and electrical responses of the generator and of control and protection systems. For offshore wind turbines, additional models of the hydrodynamic loading in regular and irregular seas, the dynamic coupling between the support platform motions and wind turbine motions, and the dynamic characterization of mooring systems for compliant floating platforms are also important. Hydrodynamic loading includes contributions from hydrostatics, wave radiation, and wave scattering, including free surface memory effects. The integration of all of these models into comprehensive simulation tools, capable of modeling the fully coupled aeroelastic and hydrodynamic responses of floating offshore wind turbines, is presented.
Quantum positron acoustic waves
Metref, Hassina; Tribeche, Mouloud
2014-12-15
Nonlinear quantum positron-acoustic (QPA) waves are investigated for the first time, within the theoretical framework of the quantum hydrodynamic model. In the small but finite amplitude limit, both deformed Korteweg-de Vries and generalized Korteweg-de Vries equations governing, respectively, the dynamics of QPA solitary waves and double-layers are derived. Moreover, a full finite amplitude analysis is undertaken, and a numerical integration of the obtained highly nonlinear equations is carried out. The results complement our previously published results on this problem.
Hydrodynamic interactions in two dimensions
NASA Astrophysics Data System (ADS)
di Leonardo, R.; Keen, S.; Ianni, F.; Leach, J.; Padgett, M. J.; Ruocco, G.
2008-09-01
We measure hydrodynamic interactions between colloidal particles confined in a thin sheet of fluid. The reduced dimensionality, compared to a bulk fluid, increases dramatically the range of couplings. Using optical tweezers we force a two body system along the eigenmodes of the mobility tensor and find that eigenmobilities change logarithmically with particle separation. At a hundred radii distance, the mobilities for rigid and relative motions differ by a factor of 2, whereas in bulk fluids, they would be practically indistinguishable. A two dimensional counterpart of Oseen hydrodynamic tensor quantitatively reproduces the observed behavior, once the relevant boundary conditions are recognized. These results highlight the importance of dimensionality for transport and interactions in colloidal systems and proteins in biological membranes.
Hydrodynamic damage to animal cells.
Chisti, Y
2001-01-01
Animal cells are affected by hydrodynamic forces that occur in culture vessel, transfer piping, and recovery operations such as microfiltration. Depending on the type, intensity, and duration of the force, and the specifics of the cell, the force may induce various kinds of responses in the subject cells. Both biochemical and physiological responses are observed, including apoptosis and purely mechanical destruction of the cell. This review examines the kinds of hydrodynamic forces encountered in bioprocessing equipment and the impact of those forces on cells. Methods are given for quantifying the magnitude of the specific forces, and the response thresholds are noted for the common types of cells cultured in free suspension, supported on microcarriers, and anchored to stationary surfaces. PMID:11451047
Membrane Paradigm and Holographic Hydrodynamics
Christopher Eling; Yasha Neiman; Yaron Oz
2010-12-12
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.
Some open questions in hydrodynamics
Mateusz Dyndal; Laurent Schoeffel
2014-12-16
When speaking of unsolved problems in physics, this is surprising at first glance to discuss the case of fluid mechanics. However, there are many deep open questions that come with the theory of fluid mechanics. In this paper, we discuss some of them that we classify in two categories, the long term behavior of solutions of equations of hydrodynamics and the definition of initial (boundary) conditions. The first set of questions come with the non-relativistic theory based on the Navier-Stokes equations. Starting from smooth initial conditions, the purpose is to understand if solutions of Navier-Stokes equations remain smooth with the time evolution. Existence for just a finite time would imply the evolution of finite time singularities, which would have a major influence on the development of turbulent phenomena. The second set of questions come with the relativistic theory of hydrodynamics. There is an accumulating evidence that this theory may be relevant for the description of the medium created in high energy heavy-ion collisions. However, this is not clear that the fundamental hypotheses of hydrodynamics are valid in this context. Also, the determination of initial conditions remains questionable. The purpose of this paper is to explore some ideas related to these questions, both in the non-relativistic and relativistic limits of fluid mechanics. We believe that these ideas do not concern only the theory side but can also be useful for interpreting results from experimental measurements.
NASA Technical Reports Server (NTRS)
Lee, Jeongwoo W.
1993-01-01
In this paper we analyze the generation of waves in a sunspot by extending Stein's hydrodynamic approach to the turbulent medium permeated by a strong uniform magnetic field oriented parallel to the gravity. For wave sources appropriate to the sunspot, we consider magnetic perturbations and entropy changes as well as turbulent convection. To describe the anisotropy imposed by the sunspot, we use a one-dimensional correlation function relating the turbulent eddies separated along the symmetry axis of the spot. This treatment yields several interesting possibilities for wave generation in a sunspot. First, it is demonstrated that the entropy change and magnetic perturbation can lead to a relative enhancement of acoustic wave emission. Second, the energy flux of Alfven waves may be comparable to that of acoustic waves in sunspots. Third, the anisotropy of the sunspot dynamics can lead to wave energy spectrum in a form which may explain the origin of umbral atmospheric oscillations.
XXII ICTAM, 2529 August 2008, Adelaide, Australia PERISTALSIS AND HYDRODYNAMIC INSTABILITIES
Hoepffner, Jérôme
in hydrodynamic instabilities. A propagating wall deformation generates pressure gradients in the flow, which act studied assuming low inertia effects. The domain of validity of asymptotic expansion analyses frequency vibrational motion into rotation. At high Reynolds number, waves of finite amplitude resulting
Symposium on Naval Hydrodynamics Rome, Italy, 17-22 September 2006
Yang, Jianming
applications. Two-phase level set approaches are being implemented in CFDShip-Iowa to extend the modeling data. A computation of non-breaking waves generated by a submerged hydrofoil has also been carried out for both small and large scale ship hydrodynamics applications. Detailed resolution of both air and water
PSEUDO-SPECTRUM OF THE RESISTIVE MAGNETO-HYDRODYNAMICS OPERATOR: RESOLVING THE RESISTIVE ALFV
PSEUDO-SPECTRUM OF THE RESISTIVE MAGNETO-HYDRODYNAMICS OPERATOR: RESOLVING THE RESISTIVE ALFV #19, pseudospectrum, non-normal op- erators, continuous spectrum, Alfv#19;en waves, magnetohydrodynamic stability to the ideal spectrum in the limit of asymptotically small resistiv- ity. As the resistivity, #17;, decreases
PSEUDO-SPECTRUM OF THE RESISTIVE MAGNETO-HYDRODYNAMICS OPERATOR: RESOLVING THE RESISTIVE ALFV, continuous spectrum, Alfv´en waves, magnetohydrodynamic stability. PACS 03.40.Kf, 47.65.+a, 52.30.Jb, 52 would converge to the ideal spectrum in the limit of asymptotically small resistiv- ity
Chrispell, John
November 2015) The synchronization of nearby sperm flagella as they swim in a viscous fluid was observed, models have investigated sperm hydrodynamics where the flagellum is treated as a waving sheet (2D. demonstrate the dy- namic phase-locking of swimming bull sperm4 . Two nearby sperm flagella, initially beating
University of Florida Fall 2004 EOC 6934 Hydrodynamic Stability Civil and Coastal Engineering
Slinn, Donald
12:35 Text Books: Primary: P.G. Drazin, Introduction to Hydrodynamic Stability, Cambridge Texts may be take-home. Course Topics: 1. Introduction to theory of steady flows, their bifurcations Flows, Boundary Layer instabilities, Tolmein-Schlicting waves 7. Routes to Chaos and Turbulence 8
ANALYSIS OF LARGE AMPLITUDE SHOCK PROFILES FOR NON-EQUILIBRIUM RADIATIVE HYDRODYNAMICS: FORMATION OF
Goudon, Thierry
. In the article [10], smooth traveling wave solutions called shock profiles have been constructed under a suitableANALYSIS OF LARGE AMPLITUDE SHOCK PROFILES FOR NON-EQUILIBRIUM RADIATIVE HYDRODYNAMICS: FORMATION) CNRSÂUniversitÂ´e Lille 1 59655 Villeneuve d'Ascq Cedex, France 3 College of science, Hohai University
Weijgaert, Rien van de
flythrough #12;07/04/2015 26 Theory of Supernova Blast Waves Supernovae: Type Ia Subsonic deflagration wave turning into a supersonic detonation wave in outer layers. Mechanism: explosive carbon burning in a mass
Advances in the hydrodynamics solver of CO5BOLD
NASA Astrophysics Data System (ADS)
Freytag, Bernd
Many features of the Roe solver used in the hydrodynamics module of CO5BOLD have recently been added or overhauled, including the reconstruction methods (by adding the new second-order ``Frankenstein's method''), the treatment of transversal velocities, energy-flux averaging and entropy-wave treatment at small Mach numbers, the CTU scheme to combine the one-dimensional fluxes, and additional safety measures. All this results in a significantly better behavior at low Mach number flows, and an improved stability at larger Mach numbers requiring less (or no) additional tensor viscosity, which then leads to a noticeable increase in effective resolution.
Hydrodynamic modeling of tsunamis from the Currituck landslide
Geist, E.L.; Lynett, P.J.; Chaytor, J.D.
2009-01-01
Tsunami generation from the Currituck landslide offshore North Carolina and propagation of waves toward the U.S. coastline are modeled based on recent geotechnical analysis of slide movement. A long and intermediate wave modeling package (COULWAVE) based on the non-linear Boussinesq equations are used to simulate the tsunami. This model includes procedures to incorporate bottom friction, wave breaking, and overland flow during runup. Potential tsunamis generated from the Currituck landslide are analyzed using four approaches: (1) tsunami wave history is calculated from several different scenarios indicated by geotechnical stability and mobility analyses; (2) a sensitivity analysis is conducted to determine the effects of both landslide failure duration during generation and bottom friction along the continental shelf during propagation; (3) wave history is calculated over a regional area to determine the propagation of energy oblique to the slide axis; and (4) a high-resolution 1D model is developed to accurately model wave breaking and the combined influence of nonlinearity and dispersion during nearshore propagation and runup. The primary source parameter that affects tsunami severity for this case study is landslide volume, with failure duration having a secondary influence. Bottom friction during propagation across the continental shelf has a strong influence on the attenuation of the tsunami during propagation. The high-resolution 1D model also indicates that the tsunami undergoes nonlinear fission prior to wave breaking, generating independent, short-period waves. Wave breaking occurs approximately 40-50??km offshore where a tsunami bore is formed that persists during runup. These analyses illustrate the complex nature of landslide tsunamis, necessitating the use of detailed landslide stability/mobility models and higher-order hydrodynamic models to determine their hazard.
Denny, Mark
imposed by ocean waves are thought to limit the size of nearshore plants and animals, but it has provedWave-swept shores are among the most stressful flow environments on earth. Near the shore, ocean hydrodynamic forces on exposed plants and animals, and wave-induced damage is characteristic of intertidal
Hydrodynamics of internal solitons and a comparison of SIR-A and SIR-B data with ocean measurements
NASA Technical Reports Server (NTRS)
Apel, J. R.; Gasparovic, R. F.; Thompson, D. R.
1986-01-01
Large internal solitary waves have been observed by Shuttle SIR-A and SIR-B at locations in the Andaman Sea and the New York Bight. Satellite imagery and oceanographic measurements are used in conjunction with hydrodynamic interaction and electromagnetic scattering models to estimate the expected SAR image intensity modulations associated with the internal waves. There is reasonable agreement between the predicted and observed internal wave signatures.
Hydrodynamic instability mechanism for rip currents
NASA Astrophysics Data System (ADS)
Yu, Jie
2015-04-01
On re-examining the hydrodynamic instability, Yu (J. Fluid Mech., vol. 549, 2006, pp. 403-428) showed that when the fully dynamical interactions are duly accounted for, and proper mathematical analysis is carried out, the positive feedback between the wave and evolving current can initiate and sustain rip current circulations with scales comparable to field observations on alongshore uniform beaches. In this study, we extend that analysis to consider non-planar beaches, and to include a new branch of unstable modes that correspond to alongshore propagating horizontal circulations with the magnitudes of the flow growing in time. This latter has not previously been studied. These propagating unstable modes have typical time periods of tens of minutes and alongshore propagation speeds of a few cm/sec. The physical implications of their spatial and slow time oscillations are discussed, as of relevance to occurrence and recurrence of transient rips, alongshore migration of rip currents and very low frequency pulsations in surf zone eddy circulations.
Constructing higher-order hydrodynamics: The third order
Grozdanov, Sašo
2015-01-01
Hydrodynamics can be formulated as the gradient expansion of conserved currents, in terms of the fundamental fields describing the near-equilibrium fluid flow. In the relativistic case, the Navier-Stokes equations follow from the conservation of the stress-energy tensor to first order in derivatives. In this paper, we go beyond the presently understood second-order hydrodynamics and discuss the systematisation of obtaining the hydrodynamic expansion to an arbitrarily high order. As an example, we fully classify the gradient expansion at third order for neutral fluids in four dimensions, thus finding the most general next-to-leading-order corrections to the relativistic Navier-Stokes equations. In the process, we list $20$ new transport coefficients in the conformal and $68$ in the non-conformal case. We also obtain the third-order corrections to the linear dispersion relations that describe the propagation of diffusion and sound waves in relativistic fluids. We apply our results to the energy-momentum transpo...
a Two-Dimensional Free Lagrangian Hydrodynamics Model.
NASA Astrophysics Data System (ADS)
Trease, Harold Eugene
This thesis describes development of a two-dimensional Lagrangian hydrodynamics computer model. The model numerically integrates the time-dependent, compressible fluid flow equations in two-dimensional Cartesian geometry by using an explicit finite difference scheme on a free Lagrangian grid of Lagrangian mass points. An artificial viscosity tensor is introduced into the flow equations to resolve shock discontinuities in two dimensions. Use of a free Lagrangian grid eliminates the classical mesh tangling problems associated with standard Lagrangian models. This is done by giving each Lagrangian mass point the freedom to associate with a variable set of nearest neighbors. Identifying the nearest neighbors of each mass point is accomplished through the construction of a Voronoi mesh made up of Voronoi cells (convex polygons). The common edges of each Voronoi cell identify pairs of nearest neighbors. Since the change in volume of a Voronoi cell is continuous, two nearest neighbors become associated and disassociated in a continuous manner as the edge of the Voronoi cell separating two neighbors grows and shrinks. The concept of free Lagrangian hydrodynamics, as formulated in this thesis, is tested by modeling several example problems involving the development and propagation of shock waves in various geometric setups. The results of these test problems are compared with both analytic shock relations and experimental data. Through these comparison cases we find the free Lagrangian hydrodynamic scheme used in formulating the Free Lagrangian Model to be both consistent and stable.
Nonlinear density waves in the single-wave model
Marinov, Kiril B.; Tzenov, Stephan I.
2011-03-15
The single-wave model equations are transformed to an exact hydrodynamic closure by using a class of solutions to the Vlasov equation corresponding to the waterbag model. The warm fluid dynamic equations are then manipulated by means of the renormalization group method. As a result, amplitude equations for the slowly varying wave amplitudes are derived. Since the characteristic equation for waves has in general three roots, two cases are examined. If all the three roots of the characteristic equation are real, the amplitude equations for the eigenmodes represent a system of three coupled nonlinear equations. In the case where the dispersion equation possesses one real and two complex conjugate roots, the amplitude equations take the form of two coupled equations with complex coefficients. The analytical results are then compared to the exact system dynamics obtained by solving the hydrodynamic equations numerically.
Foundation of Hydrodynamics of Strongly Interacting Systems
Cheuk-Yin Wong
2014-04-03
Hydrodynamics and quantum mechanics have many elements in common, as the density field and velocity fields are common variables that can be constructed in both descriptions. Starting with the Schroedinger equation and the Klein-Gordon for a single particle in hydrodynamical form, we examine the basic assumptions under which a quantum system of particles interacting through their mean fields can be described by hydrodynamics.
Foundation of Hydrodynamics of Strongly Interacting Systems
Wong, Cheuk-Yin
2014-01-01
Hydrodynamics and quantum mechanics have many elements in common, as the density field and velocity fields are common variables that can be constructed in both descriptions. Starting with the Schroedinger equation and the Klein-Gordon for a single particle in hydrodynamical form, we examine the basic assumptions under which a quantum system of particles interacting through their mean fields can be described by hydrodynamics.
Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications
R. Paul Drake
2005-12-01
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.
Forced wetting and hydrodynamic assist
NASA Astrophysics Data System (ADS)
Blake, Terence D.; Fernandez-Toledano, Juan-Carlos; Doyen, Guillaume; De Coninck, Joël
2015-11-01
Wetting is a prerequisite for coating a uniform layer of liquid onto a solid. Wetting failure and air entrainment set the ultimate limit to coating speed. It is well known in the coating art that this limit can be postponed by manipulating the coating flow to generate what has been termed "hydrodynamic assist," but the underlying mechanism is unclear. Experiments have shown that the conditions that postpone air entrainment also reduce the apparent dynamic contact angle, suggesting a direct link, but how the flow might affect the contact angle remains to be established. Here, we use molecular dynamics to compare the outcome of steady forced wetting with previous results for the spontaneous spreading of liquid drops and apply the molecular-kinetic theory of dynamic wetting to rationalize our findings and place them on a quantitative footing. The forced wetting simulations reveal significant slip at the solid-liquid interface and details of the flow immediately adjacent to the moving contact line. Our results confirm that the local, microscopic contact angle is dependent not simply only on the velocity of wetting but also on the nature of the flow that drives it. In particular, they support an earlier suggestion that during forced wetting, an intense shear stress in the vicinity of the contact line can assist surface tension forces in promoting dynamic wetting, thus reducing the velocity-dependence of the contact angle. Hydrodynamic assist then appears as a natural consequence of wetting that emerges when the contact line is driven by a strong and highly confined flow. Our theoretical approach also provides a self-consistent model of molecular slip at the solid-liquid interface that enables its magnitude to be estimated from dynamic contact angle measurements. In addition, the model predicts how hydrodynamic assist and slip may be influenced by liquid viscosity and solid-liquid interactions.
Effects of Second-Order Hydrodynamics on a Semisubmersible Floating Offshore Wind Turbine: Preprint
Bayati, I.; Jonkman, J.; Robertson, A.; Platt, A.
2014-07-01
The objective of this paper is to assess the second-order hydrodynamic effects on a semisubmersible floating offshore wind turbine. Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of the system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure. Observations of supposed second-order responses in wave-tank tests performed by the DeepCwind consortium at the MARIN offshore basin suggest that these effects might be more important than originally expected. These observations inspired interest in investigating how second-order excitation affects floating offshore wind turbines and whether second-order hydrodynamics should be included in offshore wind simulation tools like FAST in the future. In this work, the effects of second-order hydrodynamics on a floating semisubmersible offshore wind turbine are investigated. Because FAST is currently unable to account for second-order effects, a method to assess these effects was applied in which linearized properties of the floating wind system derived from FAST (including the 6x6 mass and stiffness matrices) are used by WAMIT to solve the first- and second-order hydrodynamics problems in the frequency domain. The method has been applied to the OC4-DeepCwind semisubmersible platform, supporting the NREL 5-MW baseline wind turbine. The loads and response of the system due to the second-order hydrodynamics are analysed and compared to first-order hydrodynamic loads and induced motions in the frequency domain. Further, the second-order loads and induced response data are compared to the loads and motions induced by aerodynamic loading as solved by FAST.
The effects of second-order hydrodynamics on a semisubmersible floating offshore wind turbine
NASA Astrophysics Data System (ADS)
Bayati, I.; Jonkman, J.; Robertson, A.; Platt, A.
2014-06-01
The objective of this paper is to assess the second-order hydrodynamic effects on a semisubmersible floating offshore wind turbine. Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of a floating system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure. Observations of supposed second-order responses in wave-tank tests performed by the DeepCwind consortium at the Maritime Research Institute Netherlands (MARIN) offshore basin suggest that these effects might be more important than originally expected. These observations inspired interest in investigating how second-order excitation affects floating offshore wind turbines and whether second-order hydrodynamics should be included in offshore wind simulation tools like FAST. In this work, the effects of second-order hydrodynamics on a floating semisubmersible offshore wind turbine are investigated. Because FAST is currently unable to account for second-order effects, a method to assess these effects was applied in which linearized properties of the floating wind system derived from FAST (including the 6x6 mass and stiffness matrices) are used by WAMIT to solve the first- and second-order hydrodynamics problems in the frequency domain. The method was applied to the Offshore Code Comparison Collaboration Continuation OC4-DeepCwind semisubmersible platform, supporting the National Renewable Energy Laboratory's 5-MW baseline wind turbine. In this paper, the loads and response of the system caused by the second-order hydrodynamics are analysed and compared to the first-order hydrodynamic loads and induced motions in the frequency domain. Further, the second-order loads and induced response data are compared to the loads and motions induced by aerodynamic loading as solved by FAST.
Collision-dominated nonlinear hydrodynamics in graphene
NASA Astrophysics Data System (ADS)
Briskot, U.; Schütt, M.; Gornyi, I. V.; Titov, M.; Narozhny, B. N.; Mirlin, A. D.
2015-09-01
We present an effective hydrodynamic theory of electronic transport in graphene in the interaction-dominated regime. We derive the emergent hydrodynamic description from the microscopic Boltzmann kinetic equation taking into account dissipation due to Coulomb interaction and find the viscosity of Dirac fermions in graphene for arbitrary densities. The viscous terms have a dramatic effect on transport coefficients in clean samples at high temperatures. Within linear response, we show that viscosity manifests itself in the nonlocal conductivity as well as dispersion of hydrodynamic plasmons. Beyond linear response, we apply the derived nonlinear hydrodynamics to the problem of hot-spot relaxation in graphene.
Collision-dominated nonlinear hydrodynamics in graphene
Briscot, U; Gornyi, I V; Titov, M; Narozhny, B N; Mirlin, A D
2015-01-01
We present an effective hydrodynamic theory of electronic transport in graphene in the interaction-dominated regime. We derive the emergent hydrodynamic description from the microscopic Boltzmann kinetic equation taking into account dissipation due to Coulomb interaction and find the viscosity of Dirac fermions in graphene for arbitrary densities. The viscous terms have a dramatic effect on transport coefficients in clean samples at high temperatures. Within linear response, we show that viscosity manifests itself in the nonlocal conductivity as well as dispersion of hydrodynamic plasmons. Beyond linear response, we apply the derived nonlinear hydrodynamics to the problem of hot spot relaxation in graphene.
Problems in astrophysical radiation hydrodynamics
Castor, J.I.
1983-09-14
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.
Quasi-Static Hydrodynamic Limits
NASA Astrophysics Data System (ADS)
De Masi, Anna; Olla, Stefano
2015-10-01
We consider hydrodynamic limits of interacting particles systems with open boundaries, where the exterior parameters change in a time scale slower than the typical relaxation time scale. The limit deterministic profiles evolve quasi-statically. These limits define rigorously the thermodynamic quasi static transformations also for transitions between non-equilibrium stationary states. We study first the case of the symmetric simple exclusion, where duality can be used, and then we use relative entropy methods to extend to other models like zero range systems. Finally we consider a chain of anharmonic oscillators in contact with a thermal Langevin bath with a temperature gradient and a slowly varying tension applied to one end.
Progress in smooth particle hydrodynamics
Wingate, C.A.; Dilts, G.A.; Mandell, D.A.; Crotzer, L.A.; Knapp, C.E.
1998-07-01
Smooth Particle Hydrodynamics (SPH) is a meshless, Lagrangian numerical method for hydrodynamics calculations where calculational elements are fuzzy particles which move according to the hydrodynamic equations of motion. Each particle carries local values of density, temperature, pressure and other hydrodynamic parameters. A major advantage of SPH is that it is meshless, thus large deformation calculations can be easily done with no connectivity complications. Interface positions are known and there are no problems with advecting quantities through a mesh that typical Eulerian codes have. These underlying SPH features make fracture physics easy and natural and in fact, much of the applications work revolves around simulating fracture. Debris particles from impacts can be easily transported across large voids with SPH. While SPH has considerable promise, there are some problems inherent in the technique that have so far limited its usefulness. The most serious problem is the well known instability in tension leading to particle clumping and numerical fracture. Another problem is that the SPH interpolation is only correct when particles are uniformly spaced a half particle apart leading to incorrect strain rates, accelerations and other quantities for general particle distributions. SPH calculations are also sensitive to particle locations. The standard artificial viscosity treatment in SPH leads to spurious viscosity in shear flows. This paper will demonstrate solutions for these problems that they and others have been developing. The most promising is to replace the SPH interpolant with the moving least squares (MLS) interpolant invented by Lancaster and Salkauskas in 1981. SPH and MLS are closely related with MLS being essentially SPH with corrected particle volumes. When formulated correctly, JLS is conservative, stable in both compression and tension, does not have the SPH boundary problems and is not sensitive to particle placement. The other approach to solving SPH problems, pioneered by Randles and Libersky, is to use a different SPH equation and to renormalize the kernel gradient sums. Finally the authors present results using the SPH statistical fracture model (SPHSFM). It has been applied to a series of ball on plate impacts performed by Grady and Kipp. A description of the model and comparison with the experiments will be given.
Disruptive Innovation in Numerical Hydrodynamics
Waltz, Jacob I.
2012-09-06
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.
Constructing higher-order hydrodynamics: The third order
Sašo Grozdanov; Nikolaos Kaplis
2015-11-04
Hydrodynamics can be formulated as the gradient expansion of conserved currents in terms of the fundamental fields describing the near-equilibrium fluid flow. In the relativistic case, the Navier-Stokes equations follow from the conservation of the stress-energy tensor to first order in derivatives. In this paper, we go beyond the presently understood second-order hydrodynamics and discuss the systematisation of obtaining the hydrodynamic expansion to an arbitrarily high order. As an example of the algorithm that we present, we fully classify the gradient expansion at third order for neutral fluids in four dimensions, thus finding the most general next-to-leading-order corrections to the relativistic Navier-Stokes equations in curved space-time. In doing so, we list $20$ new transport coefficients in the conformal and $68$ in the non-conformal case, without considering any constraints that could potentially arise from the entropy current analysis. To investigate the physical implications of these new transport coefficients, we obtain the third-order corrections to the linear dispersion relations that describe the propagation of diffusion and sound waves in relativistic fluids. We also compute the corrections to the scalar (spin-$2$) two-point correlation function of the third-order stress-energy tensor. Furthermore, as an example of a non-linear hydrodynamic flow, we calculate the third-order corrections to the energy density of a boost-invariant Bjorken flow. Finally, we apply our field theoretic results to the $\\mathcal{N}=4$ supersymmetric Yang-Mills fluid at infinite 't Hooft coupling and infinite number of colours to find the values of five new linear combinations of the conformal transport coefficients.
Hydrodynamic force characteristics of slender cylinders in the splash zone
Haritos, N.; Daliri, M.R.
1995-12-31
This paper presents results from a pilot experimental program of research being performed on segmented vertical surface-piercing cylinders in the Department of Civil and Environmental Engineering at The University of Melbourne. The primary aim of this investigation is to determine the influence of the splash zone on the hydrodynamic force characteristics of such cylinders to wave loading in the Morison regime. This influence is assessed from a comparison of the observed force characteristics of instrumented segments located in the splash zone with the corresponding results obtained from similarly instrumented segments located in the fully submerged zone and from those obtained for the cylinder as a whole via measurements of the cylinder tip restraint force. Results to hand for uni-directional regular waves suggest that there appears to be a mild frequency dependence in the inertia force coefficient in the splash zone which only marginally exceeds the corresponding values observed for a submerged segment immediately below this zone.
Extreme hydrodynamic load calculations for fixed steel structures
Jong, P.R. de; Vugts, J.; Gudmestad, O.T.
1996-12-31
This paper discusses the expected differences between the planned ISO code for design of offshore structures and the present Standard Norwegian Practice (SNP), concerning the extreme hydrodynamic design load calculation for fixed steel space frame structures. Since the ISO code is expected to be similar to the API RP2A LRFD code, the provisions of API RP2A LRFD are used to represent the ISO standard. It should be noted that the new ISO code may include NewWave theory, in addition to the wave theories recommended by the API. Design loads and associated failure probabilities resulting from the application of the code provisions are compared for a typical North Sea structure, the Europipe riser platform 16/11-E.
Cycloidal Wave Energy Converter
Stefan G. Siegel, Ph.D.
2012-11-30
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.
Two dimensional hydrodynamic modeling of a high latitude braided river
NASA Astrophysics Data System (ADS)
Humphries, E.; Pavelsky, T.; Bates, P. D.
2014-12-01
Rivers are a fundamental resource to physical, ecologic and human systems, yet quantification of river flow in high-latitude environments remains limited due to the prevalence of complex morphologies, remote locations and sparse in situ monitoring equipment. Advances in hydrodynamic modeling and remote sensing technology allow us to address questions such as: How well can two-dimensional models simulate a flood wave in a highly 3-dimensional braided river environment, and how does the structure of such a flood wave differ from flow down a similar-sized single-channel river? Here, we use the raster-based hydrodynamic model LISFLOOD-FP to simulate flood waves, discharge, water surface height, and velocity measurements over a ~70 km reach of the Tanana River in Alaska. In order to use LISFLOOD-FP a digital elevation model (DEM) fused with detailed bathymetric data is required. During summer 2013, we surveyed 220,000 bathymetric points along the study reach using an echo sounder system connected to a high-precision GPS unit. The measurements are interpolated to a smooth bathymetric surface, using Topo to Raster interpolation, and combined with an existing five meter DEM (Alaska IfSAR) to create a seamless river terrain model. Flood waves are simulated using varying complexities in model solvers, then compared to gauge records and water logger data to assess major sources of model uncertainty. Velocity and flow direction maps are also assessed and quantified for detailed analysis of braided channel flow. The most accurate model output occurs with using the full two-dimensional model structure, and major inaccuracies appear to be related to DEM quality and roughness values. Future work will intercompare model outputs with extensive ground measurements and new data from AirSWOT, an airborne analog for the Surface Water and Ocean Topography (SWOT) mission, which aims to provide high-resolution measurements of terrestrial and ocean water surface elevations globally.
Hydrodynamic dispersion within porous biofilms
NASA Astrophysics Data System (ADS)
Davit, Y.; Byrne, H.; Osborne, J.; Pitt-Francis, J.; Gavaghan, D.; Quintard, M.
2013-01-01
Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher's equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels' network; (2) the solute's diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport.
Web-based hydrodynamics computing
NASA Astrophysics Data System (ADS)
Shimoide, Alan; Lin, Luping; Hong, Tracie-Lynne; Yoon, Ilmi; Aragon, Sergio R.
2004-12-01
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.
Web-based hydrodynamics computing
NASA Astrophysics Data System (ADS)
Shimoide, Alan; Lin, Luping; Hong, Tracie-Lynne; Yoon, Ilmi; Aragon, Sergio R.
2005-01-01
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.
Active and driven hydrodynamic crystals.
Desreumaux, N; Florent, N; Lauga, E; Bartolo, D
2012-08-01
Motivated by the experimental ability to produce monodisperse particles in microfluidic devices, we study theoretically the hydrodynamic stability of driven and active crystals. We first recall the theoretical tools allowing to quantify the dynamics of elongated particles in a confined fluid. In this regime hydrodynamic interactions between particles arise from a superposition of potential dipolar singularities. We exploit this feature to derive the equations of motion for the particle positions and orientations. After showing that all five planar Bravais lattices are stationary solutions of the equations of motion, we consider separately the case where the particles are passively driven by an external force, and the situation where they are self-propelling. We first demonstrate that phonon modes propagate in driven crystals, which are always marginally stable. The spatial structures of the eigenmodes depend solely on the symmetries of the lattices, and on the orientation of the driving force. For active crystals, the stability of the particle positions and orientations depends not only on the symmetry of the crystals but also on the perturbation wavelengths and on the crystal density. Unlike unconfined fluids, the stability of active crystals is independent of the nature of the propulsion mechanism at the single-particle level. The square and rectangular lattices are found to be linearly unstable at short wavelengths provided the volume fraction of the crystals is high enough. Differently, hexagonal, oblique, and face-centered crystals are always unstable. Our work provides a theoretical basis for future experimental work on flowing microfluidic crystals. PMID:22864543
The hydrodynamics of lamprey locomotion
NASA Astrophysics Data System (ADS)
Leftwich, Megan C.
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.
Active and driven hydrodynamic crystals
Nicolas Desreumaux; Nicolas Florent; Eric Lauga; Denis Bartolo
2012-09-05
Motivated by the experimental ability to produce monodisperse particles in microfluidic devices, we study theoretically the hydrodynamic stability of driven and active crystals. We first recall the theoretical tools allowing to quantify the dynamics of elongated particles in a confined fluid. In this regime hydrodynamic interactions between particles arise from a superposition of potential dipolar singularities. We exploit this feature to derive the equations of motion for the particle positions and orientations. After showing that all five planar Bravais lattices are stationary solutions of the equations of motion, we consider separately the case where the particles are passively driven by an external force, and the situation where they are self-propelling. We first demonstrate that phonon modes propagate in driven crystals, which are always marginally stable. The spatial structure of the eigenmodes depend solely on the symmetries of the lattices, and on the orientation of the driving force. For active crystals, the stability of the particle positions and orientations depends not only on the symmetry of the crystals but also on the perturbation wavelengths and on the crystal density. Unlike unconfined fluids, the stability of active crystals is independent of the nature of the propulsion mechanism at the single particle level. The square and rectangular lattices are found to be linearly unstable at short wavelengths provided the volume fraction of the crystals is high enough. Differently, hexagonal, oblique, and face-centered crystals are always unstable. Our work provides a theoretical basis for future experimental work on flowing microfluidic crystals.
Reliable estimation of shock position in shock-capturing compressible hydrodynamics codes
Nelson, Eric M
2008-01-01
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.
Kelvin-Helmholtz instabilities in Smoothed Particle Hydrodynamics
Valcke, Sander; Roediger, Elke; Dejonghe, Herwig
2010-01-01
In this paper we investigate whether Smoothed Particle Hydrodynamics (SPH), equipped with artificial conductivity, is able to capture the physics of density/energy discontinuities in the case of the so-called shearing layers test, a test for examining Kelvin-Helmholtz (KH) instabilities. We can trace back each failure of SPH to show KH rolls to two causes: i) shock waves travelling in the simulation box and ii) particle clumping, or more generally, particle noise. The probable cause of shock waves is the Local Mixing Instability (LMI), previously identified in the literature. Particle noise on the other hand is a problem because it introduces a large error in the SPH momentum equation. We also investigate the role of artificial conductivity (AC). Including AC is necessary for the long-term behavior of the simulation (e.g. to get $\\lambda=1/2, 1$ KH rolls). In sensitive hydrodynamical simulations great care is however needed in selecting the AC signal velocity, with the default formulation leading to too much ...
Nonlinear acoustics--Coupling between hydrodynamic and acoustic pressure fields
NASA Astrophysics Data System (ADS)
Pazini Brandao, Mauricio
2002-11-01
Linear or Classical Acoustics considers that sound waves propagate essentially without any medium movement. However, in Aeroacoustics we deal with phenomena where there are the simultaneous generation and propagation of sound in a moving medium. Unless the flow velocity is very low, when in aerodynamics the fluid can be modeled as being incompressible, nonlinearities must be taken into account to better model the flow physics. In this paper, by considering the exact mass and momentum equations in the form of a generalized Ffowcs-Williams and Hawkings equation, the coupling between the hydrodynamic and acoustic pressure fields generated by the motion of a solid body in still air is studied. The extent of the validity of linear hypotheses and decoupling between the two pressure fields is discussed. Strategies to consider the coupling for faster movements are indicated. This coupling appears in computations as stepwise linear iterations between the hydrodynamic and acoustic perturbation pressure fields. The goal of this research is to devise a mathematical and computational model where the formation of normal shock waves in transonic flows appears as a nonlinear interaction process between aerodynamics and aeroacoustics.
Hydrodynamic Modeling and the QGP Shear Viscosity
Huichao Song
2012-07-10
In this article, we will briefly review the recent progress on hydrodynamic modeling and the extraction of the quark-gluon plasma (QGP) specific shear viscosity with an emphasis on results obtained from the hybrid model VISHNU that couples viscous hydrodynamics for the macroscopic expansion of the QGP to the hadron cascade model for the microscopic evolution of the late hadronic stage.
Hydrodynamic modeling and the QGP shear viscosity
NASA Astrophysics Data System (ADS)
Song, Huichao
2012-11-01
In this article, we will briefly review the recent progress on hydrodynamic modeling and the extraction of the quark-gluon plasma (QGP) specific shear viscosity with an emphasis on the results obtained from the hybrid model VISHNU that couples viscous hydrodynamics for the macroscopic expansion of the QGP to the hadron cascade model for the microscopic evolution of the late hadronic stage.
Relativistic Hydrodynamics for Heavy-Ion Collisions
ERIC Educational Resources Information Center
Ollitrault, Jean-Yves
2008-01-01
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…
Pilot-wave hydrodynamics in a rotating frame: Exotic orbits
NASA Astrophysics Data System (ADS)
Oza, Anand U.; Wind-Willassen, Øistein; Harris, Daniel M.; Rosales, Rodolfo R.; Bush, John W. M.
2014-08-01
We present the results of a numerical investigation of droplets walking on a rotating vibrating fluid bath. The drop's trajectory is described by an integro-differential equation, which is simulated numerically in various parameter regimes. As the forcing acceleration is progressively increased, stable circular orbits give way to wobbling orbits, which are succeeded in turn by instabilities of the orbital center characterized by steady drifting then discrete leaping. In the limit of large vibrational forcing, the walker's trajectory becomes chaotic, but its statistical behavior reflects the influence of the unstable orbital solutions. The study results in a complete regime diagram that summarizes the dependence of the walker's behavior on the system parameters. Our predictions compare favorably to the experimental observations of Harris and Bush ["Droplets walking in a rotating frame: from quantized orbits to multimodal statistics," J. Fluid Mech. 739, 444-464 (2014)].
Pilot-wave hydrodynamics in a rotating frame: Exotic orbits
Oza, Anand U.; Harris, Daniel M.; Rosales, Rodolfo R.; Bush, John W. M.; Wind-Willassen, Øistein
2014-08-15
We present the results of a numerical investigation of droplets walking on a rotating vibrating fluid bath. The drop's trajectory is described by an integro-differential equation, which is simulated numerically in various parameter regimes. As the forcing acceleration is progressively increased, stable circular orbits give way to wobbling orbits, which are succeeded in turn by instabilities of the orbital center characterized by steady drifting then discrete leaping. In the limit of large vibrational forcing, the walker's trajectory becomes chaotic, but its statistical behavior reflects the influence of the unstable orbital solutions. The study results in a complete regime diagram that summarizes the dependence of the walker's behavior on the system parameters. Our predictions compare favorably to the experimental observations of Harris and Bush [“Droplets walking in a rotating frame: from quantized orbits to multimodal statistics,” J. Fluid Mech. 739, 444–464 (2014)].
Hydrodynamics, Fungal Physiology, and Morphology.
Serrano-Carreón, L; Galindo, E; Rocha-Valadéz, J A; Holguín-Salas, A; Corkidi, G
2015-01-01
Filamentous cultures, such as fungi and actinomycetes, contribute substantially to the pharmaceutical industry and to enzyme production, with an annual market of about 6 billion dollars. In mechanically stirred reactors, most frequently used in fermentation industry, microbial growth and metabolite productivity depend on complex interactions between hydrodynamics, oxygen transfer, and mycelial morphology. The dissipation of energy through mechanically stirring devices, either flasks or tanks, impacts both microbial growth through shearing forces on the cells and the transfer of mass and energy, improving the contact between phases (i.e., air bubbles and microorganisms) but also causing damage to the cells at high energy dissipation rates. Mechanical-induced signaling in the cells triggers the molecular responses to shear stress; however, the complete mechanism is not known. Volumetric power input and, more importantly, the energy dissipation/circulation function are the main parameters determining mycelial size, a phenomenon that can be explained by the interaction of mycelial aggregates and Kolmogorov eddies. The use of microparticles in fungal cultures is also a strategy to increase process productivity and reproducibility by controlling fungal morphology. In order to rigorously study the effects of hydrodynamics on the physiology of fungal microorganisms, it is necessary to rule out the possible associated effects of dissolved oxygen, something which has been reported scarcely. At the other hand, the processes of phase dispersion (including the suspended solid that is the filamentous biomass) are crucial in order to get an integral knowledge about biological and physicochemical interactions within the bioreactor. Digital image analysis is a powerful tool for getting relevant information in order to establish the mechanisms of mass transfer as well as to evaluate the viability of the mycelia. This review focuses on (a) the main characteristics of the two most common morphologies exhibited by filamentous microorganisms; (b) how hydrodynamic conditions affect morphology and physiology in filamentous cultures; and (c) techniques using digital image analysis to characterize the viability of filamentous microorganisms and mass transfer in multiphase dispersions. Representative case studies of fungi (Trichoderma harzianum and Pleurotus ostreatus) exhibiting different typical morphologies (disperse mycelia and pellets) are discussed. PMID:25652005
Hydrodynamic Nambu Brackets derived by Geometric Constraints
Blender, Richard
2015-01-01
A geometric approach to derive the Nambu brackets for ideal two-dimensional (2D) hydrodynamics is suggested. The derivation is based on two-forms with vanishing integrals in a periodic domain, and with resulting dynamics constrained by an orthogonality condition. As a result, 2D hydrodynamics with vorticity as dynamic variable emerges as a generic model, with conservation laws which can be interpreted as enstrophy and energy functionals. Generalized forms like surface quasi-geostrophy and fractional Poisson equations for the stream-function are also included as results from the derivation. The formalism is extended to a hydrodynamic system coupled to a second degree of freedom, with the Rayleigh-B\\'{e}nard convection as an example. This system is reformulated in terms of constitutive conservation laws with two additive brackets which represent individual processes: a first representing inviscid 2D hydrodynamics, and a second representing the coupling between hydrodynamics and thermodynamics. The results can b...
Radiation hydrodynamics in solar flares
Fisher, G.H.
1985-10-18
Solar flares are rather violent and extremely complicated phenomena, and it should be made clear at the outset that a physically complete picture describing all aspects of flares does not exist. From the wealth of data which is available, it is apparent that many different types of physical processes are involved during flares: energetic particle acceleration, rapid magnetohydrodynamic motion of complex field structures, magnetic reconnection, violent mass motion along magnetic field lines, and the heating of plasma to tens of millions of degrees, to name a few. The goal of this paper is to explore just one aspect of solar flares, namely, the interaction of hydrodynamics and radiation processes in fluid being rapidly heated along closed magnetic field lines. The models discussed are therefore necessarily restrictive, and will address only a few of the observed or observable phenomena. 46 refs., 6 figs.
A diffusion hydrodynamic model (DHM)
NASA Astrophysics Data System (ADS)
Hromadka, T. V.; Yen, C. C.
A diffusion hydrodynamic model of coupled two-dimensional overland flow and one-dimensional open channel flow (DHM) is developed. Because of the diffusion form of the governing flow equations is used in this model, several important hydraulic effects are accommodated which are incapable of being handled by the often-used kinematic routing techniques which are used in most watershed models; namely, backwater effects, channel overflow, combined overland flow and storage effects, and ponding. Because these often ignored hydraulic effects are important in drainage studies involving flood control channel deficiencies and subtle grade differences between watershed boundaries (e.g. alluvial fan hydrology), the DHM approach affords the practicing hydrologist a new tool for drainage system evaluations.
Hydrodynamics of vibrated granular monolayer.
Khain, E.; Aranson, I. S.
2011-01-01
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.
Hydrodynamic model for drying emulsions.
Feng, Huanhuan; Sprakel, Joris; van der Gucht, Jasper
2015-08-01
We present a hydrodynamic model for film formation in a dense oil-in-water emulsion under a unidirectional drying stress. Water flow through the plateau borders towards the drying end leads to the buildup of a pressure gradient. When the local pressure exceeds the critical disjoining pressure, the water films between droplets break and the droplets coalesce. We show that, depending on the critical pressure and the evaporation rate, the coalescence can occur in two distinct modes. At low critical pressures and low evaporation rates, coalescence occurs throughout the sample, whereas at high critical pressures and high evaporation rate, coalescence occurs only at the front. In the latter case, an oil layer develops on top of the film, which acts as a diffusive barrier and slows down film formation. Our findings, which are summarized in a state diagram for film formation, are in agreement with recent experimental findings. PMID:26382507
Hydrodynamic model for drying emulsions
NASA Astrophysics Data System (ADS)
Feng, Huanhuan; Sprakel, Joris; van der Gucht, Jasper
2015-08-01
We present a hydrodynamic model for film formation in a dense oil-in-water emulsion under a unidirectional drying stress. Water flow through the plateau borders towards the drying end leads to the buildup of a pressure gradient. When the local pressure exceeds the critical disjoining pressure, the water films between droplets break and the droplets coalesce. We show that, depending on the critical pressure and the evaporation rate, the coalescence can occur in two distinct modes. At low critical pressures and low evaporation rates, coalescence occurs throughout the sample, whereas at high critical pressures and high evaporation rate, coalescence occurs only at the front. In the latter case, an oil layer develops on top of the film, which acts as a diffusive barrier and slows down film formation. Our findings, which are summarized in a state diagram for film formation, are in agreement with recent experimental findings.
Typical geometry of rogue waves
NASA Astrophysics Data System (ADS)
Yudin, Alexander; Shamin, Roman
2015-04-01
Our talk presents geometry results of numerical modeling of rogue waves based on the full nonlinear equations of hydrodynamics. We describe the widespread types of rogue waves in computational experiments. We received a lot of rogue waves in our computing experiments. About 95% of these waves have the typical form of steep ridge ("wall of water"). Other rogue waves have the form of deepest depression ("hole in the sea") or represent several waves of very big height ("three sisters"). Rogue waves from our experiments are one of such individual waves. The most widespread rogue waves have the form of wall of water. Both parts of this wave from the left minimum to the maximum and from the maximum to the right minimum are well-approximated by three-degree polynomials. It gets the follow type after linear transformation when the ordinate of maximum point is transferred to the point with coordinates. References Zakharov V.E., Shamin R.V and Yudin A.V.: Energy Portrait of Rogue Waves, JETP Letters, 2014, Vol. 99, No. 9, pp. 514-517, DOI: 10.1134/S0021364014090136
Early hydrodynamic evolution of a stellar collision
Kushnir, Doron; Katz, Boaz
2014-04-20
The early phase of the hydrodynamic evolution following the collision of two stars is analyzed. Two strong shocks propagate from the contact surface and move toward the center of each star at a velocity that is a small fraction of the velocity of the approaching stars. The shocked region near the contact surface has a planar symmetry and a uniform pressure. The density vanishes at the (Lagrangian) surface of contact, and the speed of sound diverges there. The temperature, however, reaches a finite value, since as the density vanishes, the finite pressure is radiation dominated. For carbon-oxygen white dwarf (CO WD) collisions, this temperature is too low for any appreciable nuclear burning shortly after the collision, which allows for a significant fraction of the mass to be highly compressed to the density required for efficient {sup 56}Ni production in the detonation wave that follows. This property is crucial for the viability of collisions of typical CO WD as progenitors of type Ia supernovae, since otherwise only massive (>0.9 M {sub ?}) CO WDs would have led to such explosions (as required by all other progenitor models). The divergence of the speed of sound limits numerical studies of stellar collisions, as it makes convergence tests exceedingly expensive unless dedicated schemes are used. We provide a new one-dimensional Lagrangian numerical scheme to achieve this. A self-similar planar solution is derived for zero-impact parameter collisions between two identical stars, under some simplifying assumptions (including a power-law density profile), which is the planar version of previous piston problems that were studied in cylindrical and spherical symmetries.
The Korteweg-de Vries soliton in the lattice hydrodynamic model
NASA Astrophysics Data System (ADS)
Ge, H. X.
2009-04-01
The lattice hydrodynamic model is not only a simplified version of the macroscopic hydrodynamic model, but is also closely connected with the microscopic car following model. The modified Korteweg-de Vries (mKdV) equation about the density wave in congested traffic has been derived near the critical point since Nagatani first proposed it. But the Korteweg-de Vries (KdV) equation near the neutral stability line has not been studied, which has been investigated in detail in the car following model. So we devote ourselves to obtaining the KdV equation from the lattice hydrodynamic model and obtaining the KdV soliton solution describing the traffic jam. Numerical simulation is conducted, to demonstrate the nonlinear analysis result.
A hybrid level set/volume-of-fluid approach for simulation of nearshore hydrodynamics
NASA Astrophysics Data System (ADS)
Bakhtyar, R.; Kees, C. E.; Miller, C. T.; Farthing, M. W.
2013-12-01
Wave breaking can play an important role in hydrodynamics near the coast and subsequently can be a factor in beach morphodynamics. However, an accurate understanding of the wave breaking and mixing of water and air at the free surface has yet to be achieved. Numerical models, based on single phase flow, have been used to study the nearshore hydrodynamics, but air-water two-phase flow is not well understood, and so there is a need for additional investigation into the details of this type of flow. The main objective of this study was to de¬velop further understanding of surf-swash zone hydrodynamics under a variety of wave forcing conditions. The main tool used was a com-prehensive two-phase numerical model - combining two-dimensional wave solver with the state-of-the-art 'Eulerian' technique for free surface modeling- of nearshore hydrodynamics. Surf-swash zone hydrodynamics were modeled using the Navier-Stokes equations, combined with turbulence closure model and a hybrid level set/volume-of-fluid approach. The hybrid level set/volume-of-fluid approach combines the accuracy and conceptual simplicity of front-tracking using level set methods with the conservation properties of volume-of fluid methods. The solver was discretized using a finite element method. The model's grid convergence and refinement were investigated in order to obtain high accuracy at an acceptable computational cost while retain robustness. The numerical set-up was tested against the well-known experimental data, with good agreement found. The numerical results showed that the maximum turbulent kinetic energy, turbulence dissipation rate, and velocity components are located near the free surface in the wave breaking area. The model is appropriate for the simulation of air-water mixing flow, undertow distribution, and turbulence characteristics in the nearshore zone. Generally, the analysis shows that, with reasonable hypotheses, it is possible to simulate the surf-swash zone hydrodynamics under wave breaking, consistent with existing understanding of this area.
Low Mach number fluctuating hydrodynamics of multispecies liquid mixtures
Donev, Aleksandar Bhattacharjee, Amit Kumar; Nonaka, Andy; Bell, John B.; Garcia, Alejandro L.
2015-03-15
We develop a low Mach number formulation of the hydrodynamic equations describing transport of mass and momentum in a multispecies mixture of incompressible miscible liquids at specified temperature and pressure, which generalizes our prior work on ideal mixtures of ideal gases [Balakrishnan et al., “Fluctuating hydrodynamics of multispecies nonreactive mixtures,” Phys. Rev. E 89 013017 (2014)] and binary liquid mixtures [Donev et al., “Low mach number fluctuating hydrodynamics of diffusively mixing fluids,” Commun. Appl. Math. Comput. Sci. 9(1), 47-105 (2014)]. In this formulation, we combine and extend a number of existing descriptions of multispecies transport available in the literature. The formulation applies to non-ideal mixtures of arbitrary number of species, without the need to single out a “solvent” species, and includes contributions to the diffusive mass flux due to gradients of composition, temperature, and pressure. Momentum transport and advective mass transport are handled using a low Mach number approach that eliminates fast sound waves (pressure fluctuations) from the full compressible system of equations and leads to a quasi-incompressible formulation. Thermal fluctuations are included in our fluctuating hydrodynamics description following the principles of nonequilibrium thermodynamics. We extend the semi-implicit staggered-grid finite-volume numerical method developed in our prior work on binary liquid mixtures [Nonaka et al., “Low mach number fluctuating hydrodynamics of binary liquid mixtures,” http://arxiv.org/abs/1410.2300 (2015)] and use it to study the development of giant nonequilibrium concentration fluctuations in a ternary mixture subjected to a steady concentration gradient. We also numerically study the development of diffusion-driven gravitational instabilities in a ternary mixture and compare our numerical results to recent experimental measurements [Carballido-Landeira et al., “Mixed-mode instability of a miscible interface due to coupling between Rayleigh–Taylor and double-diffusive convective modes,” Phys. Fluids 25, 024107 (2013)] in a Hele-Shaw cell. We find that giant nonequilibrium fluctuations can trigger the instability but are eventually dominated by the deterministic growth of the unstable mode, in both quasi-two-dimensional (Hele-Shaw) and fully three-dimensional geometries used in typical shadowgraph experiments.
"Oenodynamic": Hydrodynamic of wine swirling
Reclari, Martino; Tissot, Stephanie; Obreschkow, Danail; Wurm, Florian; Farhat, Mohamed
2011-01-01
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. In this fluid dynamics video we show the large variety of waves shapes generated by this simple movement, and we identify a group of dimensionless parameters governing the flow.
The South Carolina Coastal Erosion Study: Nearshore Hydrodynamics Field Experiment
NASA Astrophysics Data System (ADS)
Haas, K. A.; Voulgaris, G.; Demir, H.; Work, P. A.; Hanes, D. M.
2004-12-01
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.
Reena Mary, A P; Narayanan, T N; Sunny, Vijutha; Sakthikumar, D; Yoshida, Yasuhiko; Joy, P A; Anantharaman, M R
2010-01-01
Bio-compatible magnetic fluids having high saturation magnetization find immense applications in various biomedical fields. Aqueous ferrofluids of superparamagnetic iron oxide nanoparticles with narrow size distribution, high shelf life and good stability is realized by controlled chemical co-precipitation process. The crystal structure is verified by X-ray diffraction technique. Particle sizes are evaluated by employing Transmission electron microscopy. Room temperature and low-temperature magnetic measurements were carried out with Superconducting Quantum Interference Device. The fluid exhibits good magnetic response even at very high dilution (6.28 mg/cc). This is an advantage for biomedical applications, since only a small amount of iron is to be metabolised by body organs. Magnetic field induced transmission measurements carried out at photon energy of diode laser (670 nm) exhibited excellent linear dichroism. Based on the structural and magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of radiofrequencies. PMID:21076702
Nemala, H.; Thakur, J. S.; Lawes, G.; Naik, R.; Naik, V. M.; Vaishnava, P. P.
2014-07-21
Rate of heat generated by magnetic nanoparticles in a ferrofluid is affected by their magnetic properties, temperature, and viscosity of the carrier liquid. We have investigated temperature dependent magnetic hyperthermia in ferrofluids, consisting of dextran coated superparamagnetic Fe{sub 3}O{sub 4} nanoparticles, subjected to external magnetic fields of various frequencies (188–375 kHz) and amplitudes (140–235 Oe). Transmission electron microscopy measurements show that the nanoparticles are polydispersed with a mean diameter of 13.8?±?3.1?nm. The fitting of experimental dc magnetization data to a standard Langevin function incorporating particle size distribution yields a mean diameter of 10.6?±?1.2?nm, and a reduced saturation magnetization (?65?emu/g) compared to the bulk value of Fe{sub 3}O{sub 4} (?95?emu/g). This is due to the presence of a finite surface layer (?1?nm thickness) of non-aligned spins surrounding the ferromagnetically aligned Fe{sub 3}O{sub 4} core. We found the specific absorption rate, measured as power absorbed per gram of iron oxide nanoparticles, decreases monotonically with increasing temperature for all values of magnetic field and frequency. Using the size distribution of magnetic nanoparticles estimated from the magnetization measurements, we have fitted the specific absorption rate versus temperature data using a linear response theory and relaxation dissipation mechanisms to determine the value of magnetic anisotropy constant (28?±?2?kJ/m{sup 3}) of Fe{sub 3}O{sub 4} nanoparticles.
Sensitivity Study of Hydrodynamic Parameters During Numerical Simulations of Tsunami Inundation
NASA Astrophysics Data System (ADS)
Ozer, Ceren; Yalciner, Ahmet Cevdet
2011-11-01
This paper describes the analysis of a parameter, "hydrodynamic demand," which can be used to represent the potential for tsunami drag force related damage to structures along coastlines. It is derived from the ratio of drag force to hydrostatic force caused by a tsunami on the structure. It varies according to the instantaneous values of the current velocities and flow depths during a tsunami inundation. To examine the effects of a tsunami in the present study, the analyses were performed using the tsunami numerical model in two altered regular-shaped basins having different bottom slopes. The simulations were implemented using a single sinusoidal wave with particular initial conditions, such as leading elevation wave and leading depression wave profiles with different wave periods. Two different initial wave amplitudes were employed to assess the diversity in the distribution of the square of the Froude number Fr 2 along the coastline. The numerical results were compared quantitatively.
Non abelian hydrodynamics and heavy ion collisions
Calzetta, E.
2014-01-14
The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined by the conservation laws of energy momentum and color currents. Therefore it is possible to describe its main features in hydrodynamic terms, the very short color neutralization time notwithstanding. In this lecture we shall give a simple derivation of the hydrodynamics of a color charged fluid, by generalizing the usual derivation of hydrodynamics from kinetic theory to the non abelian case.
Solving the viscous hydrodynamics order by order
Gao, Jian-Hua
2014-01-01
In this paper, we propose a method of solving the viscous hydrodynamics order by order in a derivative expansion. In such method, the zero order solution is just the one of the ideal hydrodynamics. All the other higher order corrections satisfy the same first-order partial differential equations but with different inhomogeneous terms. We therefore argue that our method could be easily extended to any orders. The problem of causality and stability will be released if the gradient expansion is guaranteed. This method might be of great help to both theoretical and numerical calculations of relativistic hydrodynamics.
Prediction of hydrodynamic performance of an FLNG system in side-by-side offloading operation
NASA Astrophysics Data System (ADS)
Zhao, Wenhua; Yang, Jianmin; Hu, Zhiqiang; Tao, Longbin
2014-04-01
Floating liquefied natural gas (FLNG) is a type of liquefied natural gas (LNG) production system that shows prospects in exploitation of stranded offshore gas fields. The dynamic performance of an FLNG system in side-by-side configuration with a LNG carrier under the combined actions of wave, current and wind can be quite complex. This paper presents a comprehensive study on the hydrodynamics of an FLNG system with a focus on the nonlinear coupling effects of vessels and connection systems based on the concept FLNG prototype recently designed for South China Sea. In this study, the hydrodynamic characteristics of the two floating vessels connected through hawsers and fenders are investigated using a state-of-the-art time-domain simulation code SIMO, considering their mechanical and hydrodynamic coupling effects. The simulation model consisting of FLNG and LNG carrier is developed and calibrated by a series of model tests including a tuned damping and viscous levels. The hydrodynamic performances of the two floating vessels under an extreme sea state during side-by-side offloading operation are obtained, and their relative motions and the force responses of the connection hawsers and fenders are analyzed. Sensitivity studies are conducted to clarify contributions from the pretension and the stiffness of the connection hawsers. The effects on the hydrodynamic performance of the vessels and on the loads of the connection system are also investigated.
Hydrodynamic simulations of He-shell flash convection
Falk Herwig; Bernd Freytag; Robert M. Hueckstaedt; Francis X. Timmes
2006-01-09
We present the first hydrodynamic, multi-dimensional simulations of He-shell flash convection. Specifically, we investigate the properties of shell convection at a time immediately before the He- luminosity peak during the 15th thermal pulse of a stellar evolution track with initially two solar masses and metallicity Z=0.01. This choice is a representative example of a low-mass asymptotic giant branch thermal pulse. We construct the initial vertical stratification with a set of polytropes to resemble the stellar evolution structure. Convection is driven by a constant volume heating in a thin layer at the bottom of the unstable layer. We calculate a grid of 2D simulations with different resolutions and heating rates. Our set of simulations includes one low-resolution 3D run. The computational domain includes 11.4 pressure scale heights. He-shell flash convection is dominated by large convective cells that are centered in the lower half of the convection zone. Convective rolls have an almost circular appearance because focusing mechanisms exist in the form of the density stratification for downdrafts and the heating of localized eddies that generate upflows. Nevertheless, downdrafts appear to be somewhat more focused. The He-shell flash convection generates a rich spectrum of gravity waves in both stable layers above and beneath the convective shell. The magnitude of the convective velocities from our 1D mixing-length theory model and the rms-averaged vertical velocities from the hydrodynamic model are consistent within a factor of a few. However, the velocity profile in the hydrodynamic simulation is more asymmetric, and decays exponentially inside the convection zone. [abbreviated
Nonlinear hydrodynamics of cosmological sheets. 1: Numerical techniques and tests
NASA Technical Reports Server (NTRS)
Anninos, Wenbo Y.; Norman, Michael J.
1994-01-01
We present the numerical techniques and tests used to construct and validate a computer code designed to study the multidimensional nonlinear hydrodynamics of large-scale sheet structures in the universe, especially the fragmentation of such structures under various instabilities. This code is composed of two codes, the hydrodynamical code ZEUS-2D and a particle-mesh code. The ZEUS-2D code solves the hydrodynamical equations in two dimensions using explicit Eulerian finite-difference techniques, with modifications made to incorporate the expansion of the universe and the gas cooling due to Compton scattering, bremsstrahlung, and hydrogen and helium cooling. The particle-mesh code solves the equation of motion for the collisionless dark matter. The code uses two-dimensional Cartesian coordinates with a nonuniform grid in one direction to provide high resolution for the sheet structures. A series of one-dimensional and two-dimensional linear perturbation tests are presented which are designed to test the hydro solver and the Poisson solver with and without the expansion of the universe. We also present a radiative shock wave test which is designed to ensure the code's capability to handle radiative cooling properly. And finally a series of one-dimensional Zel'dovich pancake tests used to test the dark matter code and the hydro solver in the nonlinear regime are discussed and compared with the results of Bond et al. (1984) and Shapiro & Struck-Marcell (1985). Overall, the code is shown to produce accurate and stable results, which provide us a powerful tool to further our studies.
Hydrodynamic phonon transport in suspended graphene.
Lee, Sangyeop; Broido, David; Esfarjani, Keivan; Chen, Gang
2015-01-01
Recent studies of thermal transport in nanomaterials have demonstrated the breakdown of Fourier's law through observations of ballistic transport. Despite its unique features, another instance of the breakdown of Fourier's law, hydrodynamic phonon transport, has drawn less attention because it has been observed only at extremely low temperatures and narrow temperature ranges in bulk materials. Here, we predict on the basis of first-principles calculations that the hydrodynamic phonon transport can occur in suspended graphene at significantly higher temperatures and wider temperature ranges than in bulk materials. The hydrodynamic transport is demonstrated through drift motion of phonons, phonon Poiseuille flow and second sound. The significant hydrodynamic phonon transport in graphene is associated with graphene's two-dimensional features. This work opens a new avenue for understanding and manipulating heat flow in two-dimensional materials. PMID:25693180
Image-Guided Hydrodynamic Gene Delivery
NASA Astrophysics Data System (ADS)
Liu, Dexi
2009-03-01
Gene delivery by rapid injection of a large volume of DNA solution into a blood vessel, commonly called hydrodynamic gene delivery, has become a common method for gene therapy studies in rodents. In this presentation, I will focus on our recent work aiming at establishment of an image-guided hydrodynamic procedure for gene delivery in humans. Our study employed swine as an animal model and the procedure developed includes image-guided insertion of a balloon catheter into the selected blood vessel of the targeted organ from the jugular vein and hydrodynamic injection of plasmid DNA in saline. The talk will cover the rationale of our approach, the effectiveness of procedure for gene delivery to liver and muscle, and the impact of the procedure on physiological functions and serum chemistry of the animals. The results will be discussed with respect to potential applications of the hydrodynamic gene delivery to human gene therapy.
Hydrodynamic trapping of molecules in lipid bilayers.
Jönsson, Peter; McColl, James; Clarke, Richard W; Ostanin, Victor P; Jönsson, Bengt; Klenerman, David
2012-06-26
In this work we show how hydrodynamic forces can be used to locally trap molecules in a supported lipid bilayer (SLB). The method uses the hydrodynamic drag forces arising from a flow through a conical pipette with a tip radius of 1-1.5 ?m, placed approximately 1 ?m above the investigated SLB. This results in a localized forcefield that acts on molecules protruding from the SLB, yielding a hydrodynamic trap with a size approximately given by the size of the pipette tip. We demonstrate this concept by trapping the protein streptavidin, bound to biotin receptors in the SLB. It is also shown how static and kinetic information about the intermolecular interactions in the lipid bilayer can be obtained by relating how the magnitude of the hydrodynamic forces affects the accumulation of protein molecules in the trap. PMID:22699491
Hydrodynamic aspects of fish olfaction
Cox, Jonathan P.L
2008-01-01
Flow into and around the olfactory chamber of a fish determines how odorant from the fish's immediate environment is transported to the sensory surface (olfactory epithelium) lining the chamber. Diffusion times in water are long, even over comparatively short distances (millimetres). Therefore, transport from the external environment to the olfactory epithelium must be controlled by processes that rely on convection (i.e. the bulk flow of fluid). These include the beating of cilia lining the olfactory chamber and the relatively inexpensive pumping action of accessory sacs. Flow through the chamber may also be induced by an external flow. Flow over the olfactory epithelium appears to be laminar. Odorant transfer to the olfactory epithelium may be facilitated in several ways: if the olfactory organs are mounted on stalks that penetrate the boundary layer; by the steep velocity gradients generated by beating cilia; by devices that deflect flow into the olfactory chamber; by parallel arrays of olfactory lamellae; by mechanical agitation of the chamber (or olfactory stalks); and by vortices. Overall, however, our knowledge of the hydrodynamics of fish olfaction is far from complete. Several areas of future research are outlined. PMID:18184629
NASA Astrophysics Data System (ADS)
Yang, G.; Han, X.; Hu, D. A.
2015-11-01
Modified cylindrical smoothed particle hydrodynamics (MCSPH) approximation equations are derived for hydrodynamics with material strength in axisymmetric cylindrical coordinates. The momentum equation and internal energy equation are represented to be in the axisymmetric form. The MCSPH approximation equations are applied to simulate the process of explosively driven metallic tubes, which includes strong shock waves, large deformations and large inhomogeneities, etc. The meshless and Lagrangian character of the MCSPH method offers the advantages in treating the difficulties embodied in these physical phenomena. Two test cases, the cylinder test and the metallic tube driven by two head-on colliding detonation waves, are presented. Numerical simulation results show that the new form of the MCSPH method can predict the detonation process of high explosives and the expansion process of metallic tubes accurately and robustly.
Transition from hydrodynamic to viscoelastic propagation of sound in molten RbBr
NASA Astrophysics Data System (ADS)
Demmel, F.; Szubrin, D.; Pilgrim, W. C.; De Francesco, A.; Formisano, F.
2015-07-01
Inelastic neutron scattering was applied to measure the acoustic-type excitations in the molten alkali halide rubidium bromide. For molten RbBr neutron scattering is mainly sensitive to the number density fluctuation spectrum and is not influenced by charge fluctuations. Utilizing a dedicated Brillouin scattering spectrometer, we focused on the small-wave-vector range. From inelastic excitations in the spectra a dispersion relation was obtained, which shows a large positive dispersion effect. This frequency enhancement is related to a viscoelastic response of the liquid at high frequencies. Towards small wave vectors we identify the transition to hydrodynamic behavior. This observation is supported by a transition of the sound velocity from a viscoelastic enhanced value to the adiabatic speed of sound for the acoustic-type excitations. Furthermore, the spectrum transforms into a line shape compatible with a prediction from hydrodynamics.
Transition from hydrodynamic to viscoelastic propagation of sound in molten RbBr.
Demmel, F; Szubrin, D; Pilgrim, W C; De Francesco, A; Formisano, F
2015-07-01
Inelastic neutron scattering was applied to measure the acoustic-type excitations in the molten alkali halide rubidium bromide. For molten RbBr neutron scattering is mainly sensitive to the number density fluctuation spectrum and is not influenced by charge fluctuations. Utilizing a dedicated Brillouin scattering spectrometer, we focused on the small-wave-vector range. From inelastic excitations in the spectra a dispersion relation was obtained, which shows a large positive dispersion effect. This frequency enhancement is related to a viscoelastic response of the liquid at high frequencies. Towards small wave vectors we identify the transition to hydrodynamic behavior. This observation is supported by a transition of the sound velocity from a viscoelastic enhanced value to the adiabatic speed of sound for the acoustic-type excitations. Furthermore, the spectrum transforms into a line shape compatible with a prediction from hydrodynamics. PMID:26274162
OC5 Project Phase I: Validation of Hydrodynamic Loading on a Fixed Cylinder: Preprint
Robertson, A. N.; Wendt, F. F.; Jonkman, J. M.; Popko, W.; Vorpahl, F.; Stansberg, C. T.; Bachynski, E. E.; Bayati, I.; Beyer, F.; de Vaal, J. B.; Harries, R.; Yamaguchi, A.; Shin, H.; Kim, B.; van der Zee, T.; Bozonnet, P.; Aguilo, B.; Bergua, R.; Qvist, J.; Qijun, W.; Chen, X.; Guerinel, M.; Tu, Y.; Yutong, H.; Li, R.; Bouy, L.
2015-04-23
This paper describes work performed during the first half of Phase I of the Offshore Code Comparison Collaboration Continuation, with Correlation project (OC5). OC5 is a project run under the IEA Wind Research Task 30, and is focused on validating the tools used for modeling offshore wind systems. In this first phase, simulated responses from a variety of offshore wind modeling tools were modeling tools were validated against tank test data of a fixed, suspended cylinder (without a wind turbine) that was tested under regular and irregular wave conditions at MARINTEK. The results from this phase include an examination of different approaches one can use for defining and calibrating hydrodynamic coefficients for a model, and the importance of higher-order wave models in accurately modeling the hydrodynamic loads on offshore substructures.
NASA Astrophysics Data System (ADS)
Yang, G.; Han, X.; Hu, D. A.
2015-08-01
Modified cylindrical smoothed particle hydrodynamics (MCSPH) approximation equations are derived for hydrodynamics with material strength in axisymmetric cylindrical coordinates. The momentum equation and internal energy equation are represented to be in the axisymmetric form. The MCSPH approximation equations are applied to simulate the process of explosively driven metallic tubes, which includes strong shock waves, large deformations and large inhomogeneities, etc. The meshless and Lagrangian character of the MCSPH method offers the advantages in treating the difficulties embodied in these physical phenomena. Two test cases, the cylinder test and the metallic tube driven by two head-on colliding detonation waves, are presented. Numerical simulation results show that the new form of the MCSPH method can predict the detonation process of high explosives and the expansion process of metallic tubes accurately and robustly.
Improvements to SOIL: An Eulerian hydrodynamics code
Davis, C.G.
1988-04-01
Possible improvements to SOIL, an Eulerian hydrodynamics code that can do coupled radiation diffusion and strength of materials, are presented in this report. Our research is based on the inspection of other Eulerian codes and theoretical reports on hydrodynamics. Several conclusions from the present study suggest that some improvements are in order, such as second-order advection, adaptive meshes, and speedup of the code by vectorization and/or multitasking. 29 refs., 2 figs.
Application of practical hydrodynamics to airship design
NASA Technical Reports Server (NTRS)
Upson, Ralph H; Klikoff, W A
1933-01-01
The purpose of the first two parts of this report is to present in concise format all the formulas required for computation of the hydrodynamic forces, so that they can be easily computed for either straight or curvilinear flight. Improved approximations are also introduced having a high degree of accuracy throughout the entire range of practical proportions. The remaining two parts of the report are devoted respectively to stability and skin friction, as functions of the same hydrodynamic forces.
Simple analytic solution of fireball hydrodynamics
NASA Astrophysics Data System (ADS)
Csörg?, Tamás
2004-12-01
A new family of simple analytic solutions of hydrodynamics is found for slowly expanding, rotationally symmetric fireballs assuming an ideal gas equation of state. The temperature profile is position-independent only in the collisionless gas limit. The Zimányi-Bondorf-Garpman solution and the Buda-Lund parameterization of expanding hydrodynamic particle sources are recovered as special cases. The results are applied to predict new features of proton correlations and spectra for 1.93 AGeV Ni+Ni collisions.
Hydrodynamics of Gaseous System in Massive Gravity
Sharif, M
2015-01-01
This paper explores hydrodynamics and hydrostatic of a star in post-Newtonian approximation of massive Bran-Dicke gravity. We study approximated solution of the field equations upto $O(c^{-4})$ and generalize Euler equation of motion. We then formulate equations governing hydrodynamics, stability and instability of the system. Finally, we discuss spherically symmetric stars for a specific barptropic case like dust, cosmic string and domain wall in this scenario.
Quantum ion-acoustic wave oscillations in metallic nanowires
Moradi, Afshin
2015-05-15
The low-frequency electrostatic waves in metallic nanowires are studied using the quantum hydrodynamic model, in which the electron and ion components of the system are regarded as a two-species quantum plasma system. The Poisson equation as well as appropriate quantum boundary conditions give the analytical expressions of dispersion relations of the surface and bulk quantum ion-acoustic wave oscillations.
Starrfield, S.; Kenyon, S.; Truran, J.W.; Sparks, W.M.
1983-01-01
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.
Peculiarities of wave fields in nonlocal media
V. A. Danylenko; S. I. Skurativskyi
2015-03-02
The article summarizes the studies of wave fields in structured non-equilibrium media describing by means of nonlocal hydrodynamic models. Due to the symmetry properties of models, we derived the invariant wave solutions satisfying autonomous dynamical systems. Using the methods of numerical and qualitative analysis, we have shown that these systems possess periodic, multiperiodic, quasiperiodic, chaotic, and soliton-like solutions. Bifurcation phenomena caused by the varying of nonlinearity and nonlocality degree are investigated as well.
CHOLLA: A New Massively Parallel Hydrodynamics Code for Astrophysical Simulation
NASA Astrophysics Data System (ADS)
Schneider, Evan E.; Robertson, Brant E.
2015-04-01
We present Computational Hydrodynamics On ParaLLel Architectures (Cholla ), a new three-dimensional hydrodynamics code that harnesses the power of graphics processing units (GPUs) to accelerate astrophysical simulations. Cholla models the Euler equations on a static mesh using state-of-the-art techniques, including the unsplit Corner Transport Upwind algorithm, a variety of exact and approximate Riemann solvers, and multiple spatial reconstruction techniques including the piecewise parabolic method (PPM). Using GPUs, Cholla evolves the fluid properties of thousands of cells simultaneously and can update over 10 million cells per GPU-second while using an exact Riemann solver and PPM reconstruction. Owing to the massively parallel architecture of GPUs and the design of the Cholla code, astrophysical simulations with physically interesting grid resolutions (?2563) can easily be computed on a single device. We use the Message Passing Interface library to extend calculations onto multiple devices and demonstrate nearly ideal scaling beyond 64 GPUs. A suite of test problems highlights the physical accuracy of our modeling and provides a useful comparison to other codes. We then use Cholla to simulate the interaction of a shock wave with a gas cloud in the interstellar medium, showing that the evolution of the cloud is highly dependent on its density structure. We reconcile the computed mixing time of a turbulent cloud with a realistic density distribution destroyed by a strong shock with the existing analytic theory for spherical cloud destruction by describing the system in terms of its median gas density.
Verification for ALEGRA using magnetized shock hydrodynamics problems.
Rider, William J.; Niederhaus, John H.; Robinson, Allen Conrad; Gardiner, Thomas Anthony
2008-10-01
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.
A Variational approach to thin film hydrodynamics of binary mixtures
NASA Astrophysics Data System (ADS)
Xu, Xinpeng; Thiele, Uwe; Qian, Tiezheng
2015-03-01
In order to model the dynamics of thin films of mixtures, solutions, and suspensions, a thermodynamically consistent formulation is needed such that various coexisting dissipative processes with cross couplings can be correctly described in the presence of capillarity, wettability, and mixing effects. In the present work, we apply Onsager's variational principle to the formulation of thin film hydrodynamics for binary fluid mixtures. We first derive the dynamic equations in two spatial dimensions, one along the substrate and the other normal to the substrate. Then, using long-wave asymptotics, we derive the thin film equations in one spatial dimension along the substrate. This enables us to establish the connection between the present variational approach and the gradient dynamics formulation for thin films. It is shown that for the mobility matrix in the gradient dynamics description, Onsager's reciprocal symmetry is automatically preserved by the variational derivation. Furthermore, using local hydrodynamic variables, our variational approach is capable of introducing diffusive dissipation beyond the limit of dilute solute. Supplemented with a Flory-Huggins-type mixing free energy, our variational approach leads to a thin film model that treats solvent and solute in a symmetric manner. Our approach can be further generalized to include more complicated free energy and additional dissipative processes.
Hydrodynamics of rapidly rotating superfluid neutron stars with mutual friction
A. Passamonti; N. Andersson
2010-04-26
We study time evolutions of superfluid neutron stars, focussing on the nature of the oscillation spectrum, the effect of mutual friction force on the oscillations and the hydrodynamical spin-up phase of pulsar glitches. We linearise the dynamical equations of a Newtonian two-fluid model for rapidly rotating backgrounds. In the axisymmetric equilibrium configurations, the two fluid components corotate and are in beta-equilibrium. We use analytical equations of state that generate stratified and non-stratified stellar models, which enable us to study the coupling between the dynamical degrees of freedom of the system. By means of time evolutions of the linearised dynamical equations, we determine the spectrum of axisymmetric and non-axisymmetric oscillation modes, accounting for the contribution of the gravitational potential perturbations, i.e. without adopting the Cowling approximation. We study the mutual friction damping of the superfluid oscillations and consider the effects of the non-dissipative part of the mutual friction force on the mode frequencies. We also provide technical details and relevant tests for the hydrodynamical model of pulsar glitches discussed by Sidery, Passamonti and Andersson (2010). In particular, we describe the method used to generate the initial data that mimic the pre-glitch state, and derive the equations that are used to extract the gravitational-wave signal.
The hydrodynamics of ribbon-fin propulsion during impulsive motion.
Shirgaonkar, Anup A; Curet, Oscar M; Patankar, Neelesh A; Maciver, Malcolm A
2008-11-01
Weakly electric fish are extraordinarily maneuverable swimmers, able to swim as easily forward as backward and rapidly switch swim direction, among other maneuvers. The primary propulsor of gymnotid electric fish is an elongated ribbon-like anal fin. To understand the mechanical basis of their maneuverability, we examine the hydrodynamics of a non-translating ribbon fin in stationary water using computational fluid dynamics and digital particle image velocimetry (DPIV) of the flow fields around a robotic ribbon fin. Computed forces are compared with drag measurements from towing a cast of the fish and with thrust estimates for measured swim-direction reversals. We idealize the movement of the fin as a traveling sinusoidal wave, and derive scaling relationships for how thrust varies with the wavelength, frequency, amplitude of the traveling wave and fin height. We compare these scaling relationships with prior theoretical work. The primary mechanism of thrust production is the generation of a streamwise central jet and the associated attached vortex rings. Under certain traveling wave regimes, the ribbon fin also generates a heave force, which pushes the body up in the body-fixed frame. In one such regime, we show that as the number of waves along the fin decreases to approximately two-thirds, the heave force surpasses the surge force. This switch from undulatory parallel thrust to oscillatory normal thrust may be important in understanding how the orientation of median fins may vary with fin length and number of waves along them. Our results will be useful for understanding the neural basis of control in the weakly electric knifefish as well as for engineering bio-inspired vehicles with undulatory thrusters. PMID:18931321
Spontaneous waves in muscle fibres
NASA Astrophysics Data System (ADS)
Günther, Stefan; Kruse, Karsten
2007-11-01
Mechanical oscillations are important for many cellular processes, e.g. the beating of cilia and flagella or the sensation of sound by hair cells. These dynamic states originate from spontaneous oscillations of molecular motors. A particularly clear example of such oscillations has been observed in muscle fibers under non-physiological conditions. In that case, motor oscillations lead to contraction waves along the fiber. By a macroscopic analysis of muscle fiber dynamics we find that the spontaneous waves involve non-hydrodynamic modes. A simple microscopic model of sarcomere dynamics highlights mechanical aspects of the motor dynamics and fits with the experimental observations.
Hydrodynamic Instability in an Extended Landau/Levich Model of Liquid-Propellant Combustion
NASA Technical Reports Server (NTRS)
Margolis, Stephen B.; Sackesteder, Kurt (Technical Monitor)
1998-01-01
The classical Landau/Levich models of liquid propellant combustion, which serve as seminal examples of hydrodynamic instability in reactive systems, have been combined and extended to account for a dynamic dependence, absent in the original formulations, of the local burning rate on the local pressure and/or temperature fields. The resulting model admits an extremely rich variety of both hydrodynamic and reactive/diffusive instabilities that can be analyzed in various limiting parameter regimes. In the present work, a formal asymptotic analysis, based on the realistic smallness of the gas-to-liquid density ratio, is developed to investigate the combined effects of gravity, surface tension and viscosity on the hydrodynamic instability of the propagating liquid/gas interface. In particular, a composite asymptotic expression, spanning three distinguished wavenumber regimes, is derived for both cellular and pulsating hydrodynamic neutral stability boundaries A(sub p)(k), where A(sub p) is the pressure sensitivity of the burning rate and k is the disturbance wavenumber. For the case of cellular (Landau) instability, 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 critical negative values of A(sub p). In the limiting case of weak gravity, it is shown that cellular hydrodynamic instability in this context is a long-wave instability phenomenon, whereas at normal gravity, this instability is first manifested through O(l) wavenumber disturbances. It is also demonstrated that, in the large wavenumber regime, surface tension and both liquid and gas viscosity all produce comparable stabilizing effects in the large-wavenumber regime, thereby providing significant modifications to previous analyses of Landau instability in which one or more of these effects were neglected. In contrast, the pulsating hydrodynamic stability boundary is found to be insensitive to gravitational and surface-tension effects, but is more sensitive to the effects of liquid viscosity, which is a significant stabilizing effect for O(l) and higher wavenumbers. Liquid-propellant combustion is predicted to be stable (i.e., steady and planar) only for a range of negative pressure sensitivities that lie between the two types of hydrodynamic stability boundaries.
NASA Technical Reports Server (NTRS)
Margolis, Stephen B.; Sacksteder, Kurt (Technical Monitor)
2000-01-01
A pulsating form of hydrodynamic instability has recently been shown to arise during liquid-propellant deflagration in those parameter regimes where the pressure-dependent burning rate is characterized by a negative pressure sensitivity. This type of instability can coexist with the classical cellular, or Landau form of hydrodynamic instability, with the occurrence of either dependent on whether the pressure sensitivity is sufficiently large or small in magnitude. For the inviscid problem, it has been shown that, when the burning rate is realistically allowed to depend on temperature as well as pressure, sufficiently large values of the temperature sensitivity relative to the pressure sensitivity causes like pulsating form of hydrodynamic instability to become dominant. In that regime, steady, planar burning becomes intrinsically unstable to pulsating disturbances whose wave numbers are sufficiently small. This analysis is extended to the fully viscous case, where it is shown that although viscosity is stabilizing for intermediate and larger wave number perturbations, the intrinsic pulsating instability for small wave numbers remains. Under these conditions, liquid-propellant combustion is predicted to be characterized by large unsteady cells along the liquid/gas interface.
Lefauve, Adrien; Saintillan, David
2014-02-01
Strongly confined active liquids are subject to unique hydrodynamic interactions due to momentum screening and lubricated friction by the confining walls. Using numerical simulations, we demonstrate that two-dimensional dilute suspensions of fore-aft asymmetric polar swimmers in a Hele-Shaw geometry can exhibit a rich variety of novel phase behaviors depending on particle shape, including coherent polarized density waves with global alignment, persistent counterrotating vortices, density shocks and rarefaction waves. We also explain these phenomena using a linear stability analysis and a nonlinear traffic flow model, both derived from a mean-field kinetic theory. PMID:25353410
Marinchio, H.; Sabatini, G.; Palermo, C.; Pousset, J.; Torres, J.; Chusseau, L.; Varani, L.; Shiktorov, P.; Starikov, E.; Gruzinskis, V.
2009-05-11
We present a hydrodynamic model to simulate the excitation by optical beating of plasma waves in nanometric field effect transistors. The biasing conditions are whatever possible from Ohmic to saturation conditions. The model provides a direct calculation of the time-dependent voltage response of the transistors, which can be separated into an average and a harmonic component. These quantities are interpreted by generalizing the concepts of plasma transit time and wave increment to the case of nonuniform channels. The possibilities to tune and to optimize the plasma resonance at room temperature by varying the drain voltage are demonstrated.
Maneuvering hydrodynamics of fish and small underwater vehicles.
Bandyopadhyay, Promode R
2002-02-01
The understanding of fish maneuvering and its application to underwater rigid bodies are considered. The goal is to gain insight into stealth. The recent progress made in NUWC is reviewed. Fish morphology suggests that control fins for maneuverability have unique scalar relationships irrespective of their speed type. Maneuvering experiments are carried out with fish that are fast yet maneuverable. The gap in maneuverability between fish and small underwater vehicles is quantified. The hydrodynamics of a dorsal fin based brisk maneuvering device and a dual flapping foil device, as applied to rigid cylindrical bodies, are described. The role of pectoral wings in maneuvering and station keeping near surface waves is discussed. A pendulum model of dolphin swimming is presented to show that body length and tail flapping frequency are related. For nearly neutrally buoyant bodies, Froude number and maneuverability are related. Analysis of measurements indicates that the Strouhal number of dolphins is a constant. The mechanism of discrete and deterministic vortex shedding from oscillating control surfaces has the property of large amplitude unsteady forcing and an exquisite phase dependence, which makes it inherently amenable to active control for precision maneuvering. Theoretical control studies are carried out to demonstrate the feasibility of maneuverability of biologically inspired bodies under surface waves. The application of fish hydrodynamics to the silencing of propulsors is considered. Two strategies for the reduction of radiated noise are developed. The effects of a reduction of rotational rate are modeled. The active cambering of blades made of digitally programmable artificial muscles, and their thrust enhancement, are demonstrated. Next, wake momentum filling is carried out by artificial muscles at the trailing edge of a stator blade of an upstream stator propulsor, and articulating them like a fish tail. A reduction of radiated noise, called blade tonals, is demonstrated theoretically. PMID:21708699
Three-dimensional hydrodynamic instabilities in stellar core collapses
NASA Astrophysics Data System (ADS)
Lou, Yu-Qing; Lian, Biao
2012-03-01
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.
An integrated coastal model for aeolian and hydrodynamic sediment transport
NASA Astrophysics Data System (ADS)
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.
2012-04-01
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.
Waves, currents, and sediment transport in the surf zone along long, straight beaches
Tajima, Yoshimitsu, 1972-
2004-01-01
This study presents a theoretical model for predictions of near-shore hydrodynamic characteristics and the local sediment transport rate along long, straight beaches. The wave may be periodic or random, the beach may be ...
Wave Energy Extraction from an Oscillating Water Column in a Truncated Circular Cylinder
Wang, Hao
2013-07-19
regular wave is explored. The hydrodynamic coefficients in scattering and radiation potential are solved using Galerkin approximation. The numerical results for the free surface elevation have been verified by a series of experiments conducted...
Truong, Melanie Khanh Phuong
2012-10-19
Hurricanes are one of the primary threats to the Texas coastal environment and economy. They generate large wave and storm surges that have caused much damage on the Texas coast in the past. Understanding both the hydrodynamic ...
Hydrodynamic Nambu Brackets derived by Geometric Constraints
Richard Blender; Gualtiero Badin
2015-10-16
A geometric approach to derive the Nambu brackets for ideal two-dimensional (2D) hydrodynamics is suggested. The derivation is based on two-forms with vanishing integrals in a periodic domain, and with resulting dynamics constrained by an orthogonality condition. As a result, 2D hydrodynamics with vorticity as dynamic variable emerges as a generic model, with conservation laws which can be interpreted as enstrophy and energy functionals. Generalized forms like surface quasi-geostrophy and fractional Poisson equations for the stream-function are also included as results from the derivation. The formalism is extended to a hydrodynamic system coupled to a second degree of freedom, with the Rayleigh-B\\'{e}nard convection as an example. This system is reformulated in terms of constitutive conservation laws with two additive brackets which represent individual processes: a first representing inviscid 2D hydrodynamics, and a second representing the coupling between hydrodynamics and thermodynamics. The results can be used for the formulation of conservative numerical algorithms that can be employed, for example, for the study of fronts and singularities.
Hydrodynamic Approaches in Relativistic Heavy Ion Reactions
Rafael Derradi de Souza; Tomoi Koide; Takeshi Kodama
2015-09-23
We review several facets of the hydrodynamic description of the relativistic heavy ion collisions, starting from the historical motivation to the present understandings of the observed collective aspects of experimental data, especially those of the most recent RHIC and LHC results. In this report, we particularly focus on the conceptual questions and the physical foundations of the validity of the hydrodynamic approach itself. We also discuss recent efforts to clarify some of the points in this direction, such as the various forms of derivations of relativistic hydrodynamics together with the limitations intrinsic to the traditional approaches, variational approaches, known analytic solutions for special cases, and several new theoretical developments. Throughout this review, we stress the role of course-graining procedure in the hydrodynamic description and discuss its relation to the physical observables through the analysis of a hydrodynamic mapping of a microscopic transport model. Several questions to be answered to clarify the physics of collective phenomena in the relativistic heavy ion collisions are pointed out.
New formulation of leading order anisotropic hydrodynamics
NASA Astrophysics Data System (ADS)
Tinti, Leonardo
2015-05-01
Anisotropic hydrodynamics is a reorganization of the relativistic hydrodynamics expansion, with the leading order already containing substantial momentum-space anisotropies. The latter are a cause of concern in the traditional viscous hydrodynamics, since large momentum anisotropies generated in ultrarelativistic heavy-ion collisions are not consistent with the hypothesis of small deviations from an isotropic background, i.e., from the local equilibrium distribution. We discuss the leading order of the expansion, presenting a new formulation for the (1+1)- dimensional case, namely, for the longitudinally boost invariant and cylindrically symmetric flow. This new approach is consistent with the well established framework of Israel and Stewart in the close to equilibrium limit (where we expect viscous hydrodynamics to work well). If we consider the (0+1)-dimensional case, that is, transversally homogeneous and longitudinally boost invariant flow, the new form of anisotropic hydrodynamics leads to better agreement with known solutions of the Boltzmann equation than the previous formulations, especially when we consider massive particles.
Hydrodynamic modulation of pluripotent stem cells
2012-01-01
Controlled expansion and differentiation of pluripotent stem cells (PSCs) using reproducible, high-throughput methods could accelerate stem cell research for clinical therapies. Hydrodynamic culture systems for PSCs are increasingly being used for high-throughput studies and scale-up purposes; however, hydrodynamic cultures expose PSCs to complex physical and chemical environments that include spatially and temporally modulated fluid shear stresses and heterogeneous mass transport. Furthermore, the effects of fluid flow on PSCs cannot easily be attributed to any single environmental parameter since the cellular processes regulating self-renewal and differentiation are interconnected and the complex physical and chemical parameters associated with fluid flow are thus difficult to independently isolate. Regardless of the challenges posed by characterizing fluid dynamic properties, hydrodynamic culture systems offer several advantages over traditional static culture, including increased mass transfer and reduced cell handling. This article discusses the challenges and opportunities of hydrodynamic culture environments for the expansion and differentiation of PSCs in microfluidic systems and larger-volume suspension bioreactors. Ultimately, an improved understanding of the effects of hydrodynamics on the self-renewal and differentiation of PSCs could yield improved bioprocessing technologies to attain scalable PSC culture strategies that will probably be requisite for the development of therapeutic and diagnostic applications. PMID:23168068
Hydrodynamics in Holocene Lake Mega-Chad
NASA Astrophysics Data System (ADS)
Bouchette, Frédéric; Schuster, Mathieu; Ghienne, Jean-François; Denamiel, Cléa; Roquin, Claude; Moussa, Abderamane; Marsaleix, Patrick; Duringer, Philippe
2010-03-01
Holocene Lake Mega-Chad (LMC) was the largest late Quaternary water-body in Africa. The development of this giant paleo-lake is related to a northward shift of the isohyetes interpreted as evidence for an enhanced Monsoon (African Humid Period). Numerous preserved coastal features have been described all around the LMC shore. Such features reveal the main paleo-hydrodynamical tendencies. In the context of a closed water-body like LMC, hydrodynamics are forced mainly by winds. We use a three-dimensional numerical model (SYMPHONIE) to simulate the mean hydrodynamics in LMC under both Harmattan-like (northeasterly trade winds) and Monsoon-like (southwesterly winds) forcings. The northern part of LMC displays coastal features, such as sand spits, that are consistent with the simulations forced by Harmattan-like winds. Geomorphic features related to Monsoon-driven hydrodynamics are not clearly expressed. They could have developed during the early stage of LMC but subsequently reworked. At the time of sand-spit building, Harmattan-like driven hydrodynamics prevailed and related coastal features were preferentially preserved in the sedimentary record.
Hydrodynamic and chemical controls on microbial mat growth in sandy coastal environments
NASA Astrophysics Data System (ADS)
Mariotti, G.; Perron, J.; Bosak, T.
2013-12-01
Photosynthetic microbial mats have stabilized sediments and have contributed to primary production in coastal environments for billions of years, but the hydrodynamic and chemical conditions that influence spatial patterns of mat growth are not well constrained. We investigated these conditions by growing microbial mats in three separate wave tanks, each with a preexisting bed of carbonate sand ripples. In the first tank, large-amplitude waves reworked sediments, inhibited mat growth on the ripples, and allowed growth only in areas of minimal wave motion. The second tank did not experience wave motion, and the mat colonized the sand ripples uniformly. Two opposite spatial patterns developed in the third tank, where small-amplitude waves could not mobilize sand. When nutrients were initially present in the water column, mats colonized mainly the ripple troughs. Instead, when mats colonized sand ripples that had previously been reworked for 40 days by large waves, presumably leading to phosphorous depletion in the water column and adsorption in the sediments, growth was faster at the ripple crests. We attribute these opposite patterns to nutrient fluxes from and to the sediments due to the wave-induced pore water flow, with upwelling in the crests and downwelling in the troughs. In the initially sterile case, downwelling brings nutrient-rich water into the troughs, enabling preferential colonization there. In extensively reworked sediments, upwelling delivers nutrients from anoxic pore water to the ripple crests, promoting the colonization of crests by filamentous cyanobacteria. We conclude that interactions among bed topography, low-energy flows, and biogeochemical processes at the sediment-water interface can influence macroscopic spatial patterns in microbial mats. Similar patterns in living and fossilized mats may record chemical and hydrodynamic conditions of modern and old sedimentary environments. Side view of microbial mats growing on wave ripples. (A) Preferential growth in troughs may result from high nutrient concentrations in the water column. (B) Preferential growth on crests may result from high nutrient concentrations in pore water.
Radiative Hydrodynamic Models of Optical and Ultraviolet Emission from M Dwarf Flares
Joel C. Allred; Suzanne L. Hawley; William P. Abbett; Mats Carlsson
2006-03-08
We report on radiative hydrodynamic simulations of M dwarf stellar flares and compare the model predictions to observations of several flares. The flares were simulated by calculating the hydrodynamic response of a model M dwarf atmosphere to a beam of non-thermal electrons. Radiative backwarming through numerous soft X-ray, extreme ultraviolet, and ultraviolet transitions are also included. The equations of radiative transfer and statistical equilibrium are treated in non-LTE for many transitions of hydrogen, helium and the Ca II ion allowing the calculation of detailed line profiles and continuum radiation. Two simulations were carried out, with electron beam fluxes corresponding to moderate and strong beam heating. In both cases we find the dynamics can be naturally divided into two phases: an initial gentle phase in which hydrogen and helium radiate away much of the beam energy, and an explosive phase characterized by large hydrodynamic waves. During the initial phase, lower chromospheric material is evaporated into higher regions of the atmosphere causing many lines and continua to brighten dramatically. The He II Lya line is especially enhanced, becoming the brightest line in the flaring spectrum. The hydrogen Balmer lines also become much brighter and show very broad line widths, in agreement with observations. We compare our predicted Balmer decrements to decrements calculated for several flare observations and find the predictions to be in general agreement with the observations. During the explosive phase both condensation and evaporation waves are produced. The moderate flare simulation predicts a peak evaporation wave of 130 km/s and a condensation wave of 30 km/s. The velocity of the condensation wave matches velocities observed in several transition region lines.
On Pulsating and Cellular Forms of Hydrodynamic Instability in Liquid-Propellant Combustion
NASA Technical Reports Server (NTRS)
Margolis, Stephen B.; Sacksteder, Kurt (Technical Monitor)
1998-01-01
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 p, analytical formulas for both neutral stability boundaries may be obtained by expanding all quantities in appropriate powers of p in each of three distinguished wave-number regimes. In particular, composite analytical expressions are derived for the neutral stability boundaries A(sub p)(k), where A, is the pressure sensitivity of the burning rate and k is the wave number 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 (both liquid and gas) and surface tension on short-wave perturbations, and the instability associated with intermediate wave numbers 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 because, for typical nonzero values of the latter, the pulsating boundary decreases to larger negative values of A(sub p) as k increases through O(l) values. Thus, liquid-propellant combustion is predicted to be stable (that is, steady and planar) only for a range of negative pressure sensitivities that lie below the cellular boundary that exists for sufficiently small negative values of A(sub p) and above the pulsating boundary that exists for larger negative values of this parameter.
On the Generation of Hydrodynamic Shocks by Mixed Beams and Occurrence of Sunquakes in Flares
NASA Astrophysics Data System (ADS)
Zharkova, Valentina; Zharkov, Sergei
2015-11-01
Observations of solar flares with sunquakes by space- and ground-based instruments reveal essentially different dynamics of seismic events in different flares. Some sunquakes are found to be closely associated with the locations of hard X-ray (HXR) and white-light (WL) emission, while others are located outside either of them. In this article we investigate possible sources causing a seismic response in a form of hydrodynamic shocks produced by the injection of mixed (electron plus proton) beams, discuss the velocities of these shocks, and the depths where they deposit the bulk of their energy and momentum. The simulation of hydrodynamic shocks in flaring atmospheres induced by electron-rich and proton-rich beams reveals that the linear depth of the shock termination is shifted beneath the level of the quiet solar photosphere on a distance from 200 to 5000 km. The parameters of these atmospheric hydrodynamic shocks are used as initial condition for another hydrodynamic model developed for acoustic-wave propagation in the solar interior (Zharkov, Mon. Not. Roy. Astron. Soc. 431, 3414, 2013). The model reveals that the depth of energy and momentum deposition by the atmospheric shocks strongly affects the propagation velocity of the acoustic-wave packet in the interior. The locations of the first bounces from the photosphere of acoustic waves generated in the vicinity of a flare are seen as ripples on the solar surface, or sunquakes. Mixed proton-dominated beams are found to produce a strong supersonic shock at depths 200 - 300 km under the level of the quiet-Sun photosphere and in this way produce well-observable acoustic waves, while electron-dominated beams create a slightly supersonic shock propagating down to 5000 km under the photosphere. This shock can only generate acoustic waves at the top layers beneath the photosphere since the shock velocity very quickly drops below the local sound speed. The distance ? of the first bounce of the generated acoustic waves is discussed in relation to the minimal phase velocities of wave packets defined by the acoustic cutoff frequency and the parameters of atmospheric shock termination beneath the photosphere.
Wave journal bearing. Part 1: Analysis
Dimofte, F.
1995-12-31
A wave journal bearing concept features a waved inner ring diameter and it is an alternative to the plain journal bearing. The wave journal bearing has a significantly increased load capacity in comparison to the plain journal bearing operating at the same eccentricity. It also offers greater stability than the plain circular bearing under all operating conditions. The wave bearing`s design is relatively simple and allows the shaft to rotate in either direction. Three wave bearings are sensitive to the direction of the applied load. Increasing the number of waves reduces the wave bearing`s sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the wave bearing design for a specific application. It is concluded that the stiffness of an air journal bearing, due to hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.
Wave journal bearing. Part 1: Analysis
NASA Astrophysics Data System (ADS)
Dimofte, Florin
1995-01-01
A wave journal bearing concept features a waved inner bearing diameter of the non-rotating bearing side and it is an alternative to the plain journal bearing. The wave journal bearing has a significantly increased load capacity in comparison to the plain journal bearing operating at the same eccentricity. It also offers greater stability than the plain circular bearing under all operating conditions. The wave bearing's design is relatively simple and allows the shaft to rotate in either direction. Three wave bearings are sensitive to the direction of an applied stationary side load. Increasing the number of waves reduces the wave bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the wave bearing design for a specific application. It is concluded that the stiffness of an air journal bearing, due to hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.
Wave Journal Bearing. Part 1: Analysis
NASA Technical Reports Server (NTRS)
Dimofte, Florin
1995-01-01
A wave journal bearing concept features a waved inner bearing diameter of the non-rotating bearing side and it is an alternative to the plain journal bearing. The wave journal bearing has a significantly increased load capacity in comparison to the plain journal bearing operating at the same eccentricity. It also offers greater stability than the plain circular bearing under all operating conditions. The wave bearing's design is relatively simple and allows the shaft to rotate in either direction. Three wave bearings are sensitive to the direction of an applied stationary side load. Increasing the number of waves reduces the wave bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the wave bearing design for a specific application. It is concluded that the stiffness of an air journal bearing, due to hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.
Infragravity waves across the oceans
NASA Astrophysics Data System (ADS)
Rawat, Arshad; Ardhuin, Fabrice; Aucan, Jerome
2014-05-01
The propagation of transoceanic Infragravity (IG) wave was investigated using a global spectral wave model together with deep-ocean pressure recorders. IG waves are generated mostly at the shorelines due to non-linear hydrodynamic effects that transfer energy from the main windsea and swell band, with periods of 1 to 25 s, to periods up to 500 s. IG waves are important for the study of near-shore processes and harbor agitation, and can also be a potential source of errors in satellite altimetry measurements. Setting up a global IG model was motivated by the investigation of these errors for the future planned SWOT mission. Despite the fact that the infragravity waves exhibit much smaller vertical amplitudes than the usual high frequency wind-driven waves, of the order of 1 cm in the deep oceans, their propagation throughout the oceans and signature in the wave spectrum can be clearly observed. Using a simplified empirical parameterization of the nearshore source of free IG waves as a function of the incoming wave parameters we extended to WAVEWATCH III model, used so far for windseas and swell, to the IG band, up to periods of 300 s. The spatial and temporal variability of the modeled IG energy was well correlated to the DART station records, making it useful to interpret the records of IG waves. Open ocean IG wave records appear dominated by trans-oceanic events with well defined sources concentrated on a few days, usually on West coasts, and affecting the entire ocean basin, with amplitude patterns very similar to those of tsunamis. Three particular IG bursts during 2008 are studied, 2 in the Pacific Ocean and 1 in the North Atlantic. It was observed that the liberated IG waves can travel long distances often crossing whole oceans with negligible dissipation. The IG signatures are clearly observed at sensors along their propagation paths.
Hydrodynamics, resurgence and trans-asymptotics
Basar, Gokce
2015-01-01
The second-order hydrodynamical description of a homogeneous conformal plasma that undergoes a boost- invariant expansion is given by a single nonlinear ordinary differential equation, whose resurgent asymptotic properties we study, developing further the recent work of Heller and Spalinski [Phys. Rev. Lett. 115, 072501 (2015)]. Resurgence clearly identifies the non-hydrodynamic modes that are exponentially suppressed at late times, analogous to the quasi-normal-modes in gravitational language, organizing these modes in terms of a trans-series expansion. These modes are analogs of instantons in semi-classical expansions, where the damping rate plays the role of the instanton action. We show that this system displays the generic features of resurgence, with explicit quantitative relations between the fluctuations about different orders of these non-hydrodynamic modes. The imaginary part of the trans-series parameter is identified with the Stokes constant, and the real part with the freedom associated with init...
Hydrodynamics, resurgence and trans-asymptotics
Gokce Basar; Gerald V. Dunne
2015-09-16
The second-order hydrodynamical description of a homogeneous conformal plasma that undergoes a boost- invariant expansion is given by a single nonlinear ordinary differential equation, whose resurgent asymptotic properties we study, developing further the recent work of Heller and Spalinski [Phys. Rev. Lett. 115, 072501 (2015)]. Resurgence clearly identifies the non-hydrodynamic modes that are exponentially suppressed at late times, analogous to the quasi-normal-modes in gravitational language, organizing these modes in terms of a trans-series expansion. These modes are analogs of instantons in semi-classical expansions, where the damping rate plays the role of the instanton action. We show that this system displays the generic features of resurgence, with explicit quantitative relations between the fluctuations about different orders of these non-hydrodynamic modes. The imaginary part of the trans-series parameter is identified with the Stokes constant, and the real part with the freedom associated with initial conditions.
Hydrodynamic stellar interactions in dense star clusters
NASA Technical Reports Server (NTRS)
Rasio, Frederic A.
1993-01-01
Highly detailed HST observations of globular-cluster cores and galactic nuclei motivate new theoretical studies of the violent dynamical processes which govern the evolution of these very dense stellar systems. These processes include close stellar encounters and direct physical collisions between stars. Such hydrodynamic stellar interactions are thought to explain the large populations of blue stragglers, millisecond pulsars, X-ray binaries, and other peculiar sources observed in globular clusters. Three-dimensional hydrodynamics techniques now make it possible to perform realistic numerical simulations of these interactions. The results, when combined with those of N-body simulations of stellar dynamics, should provide for the first time a realistic description of dense star clusters. Here I review briefly current theoretical work on hydrodynamic stellar interactions, emphasizing its relevance to recent observations.
A hydrodynamic approach to cosmology - Methodology
NASA Technical Reports Server (NTRS)
Cen, Renyue
1992-01-01
The present study describes an accurate and efficient hydrodynamic code for evolving self-gravitating cosmological systems. The hydrodynamic code is a flux-based mesh code originally designed for engineering hydrodynamical applications. A variety of checks were performed which indicate that the resolution of the code is a few cells, providing accuracy for integral energy quantities in the present simulations of 1-3 percent over the whole runs. Six species (H I, H II, He I, He II, He III) are tracked separately, and relevant ionization and recombination processes, as well as line and continuum heating and cooling, are computed. The background radiation field is simultaneously determined in the range 1 eV to 100 keV, allowing for absorption, emission, and cosmological effects. It is shown how the inevitable numerical inaccuracies can be estimated and to some extent overcome.
A quaternionic unification of electromagnetism and hydrodynamics
Arbab, Arbab I
2010-01-01
We have derived energy conservation equations from the quaternionic Newton's law that is compatible with Lorentz transformation. This Newton's law yields directly the Euler equation and other relations governing the fluid motion. With this formalism, the pressure contributes positively to the dynamics of the system in the same way mass does. Hydrodynamic equations are derived from Maxwell's equations by adopting an electromagnetohydrodynamics analogy. In this analogy the hydroelectric field is related to the local acceleration of the fluid and the Lorentz gauge is related to the incompressible fluid condition. An analogous Lorentz gauge in hydrodynamics is proposed. We have shown that the vorticity of the fluid is developed whenever the particle local acceleration of the fluid deviates from the velocity direction. We have shown that Lorentz force in electromagnetism corresponds to Euler force for fluids. Moreover, we have obtained a Faraday-like law and Ampere's -like law in Hydrodynamics.
Toward a Fully Consistent Radiation Hydrodynamics
Castor, J I
2009-07-07
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.
On the hydrodynamics of swimming enzymes
NASA Astrophysics Data System (ADS)
Bai, Xiaoyu; Wolynes, Peter G.
2015-10-01
Several recent experiments suggest that rather generally the diffusion of enzymes may be augmented through their activity. We demonstrate that such swimming motility can emerge from the interplay between the enzyme energy landscape and the hydrodynamic coupling of the enzyme to its environment. Swimming thus occurs during the transit time of a transient allosteric change. We estimate the velocity during the transition. The analysis of such a swimming motion suggests the final stroke size is limited by the hydrodynamic size of the enzyme. This limit is quite a bit smaller than the values that can be inferred from the recent experiments. We also show that one proposed explanation of the experiments based on reaction heat effects can be ruled out using an extended hydrodynamic analysis. These results lead us to propose an alternate explanation of the fluorescence correlation measurements.
Nondecaying Hydrodynamic Interactions along Narrow Channels
NASA Astrophysics Data System (ADS)
Misiunas, Karolis; Pagliara, Stefano; Lauga, Eric; Lister, John R.; Keyser, Ulrich F.
2015-07-01
Particle-particle interactions are of paramount importance in every multibody system as they determine the collective behavior and coupling strength. Many well-known interactions such as electrostatic, van der Waals, or screened Coulomb interactions, decay exponentially or with negative powers of the particle spacing r . Similarly, hydrodynamic interactions between particles undergoing Brownian motion decay as 1 /r in bulk, and are assumed to decay in small channels. Such interactions are ubiquitous in biological and technological systems. Here we confine two particles undergoing Brownian motion in narrow, microfluidic channels and study their coupling through hydrodynamic interactions. Our experiments show that the hydrodynamic particle-particle interactions are distance independent in these channels. This finding is of fundamental importance for the interpretation of experiments where dense mixtures of particles or molecules diffuse through finite length, water-filled channels or pore networks.
On the hydrodynamics of swimming enzymes
Xiaoyu Bai; Peter G. Wolynes
2015-10-07
Several recent experiments suggest that rather generally the diffusion of enzymes may be augmented through their activity. We demonstrate that such swimming motility can emerge from the interplay between the enzyme energy landscape and the hydrodynamic coupling of the enzyme to its environment. Swimming thus occurs during the transit time of a transient allosteric change. We estimate the velocity during the transition. The analysis of such a swimming motion suggests the final stroke size is limited by the hydrodynamic size of the enzyme. This limit is quite a bit smaller than the values that can be inferred from the recent experiments. We also show that one proposed explanation of the experiments based on reaction heat effects can be ruled out using an extended hydrodynamic analysis. These results lead us to propose an alternate explanation of the fluorescence correlation measurements.
The RAGE radiation-hydrodynamic code
Gittings, Michael; Clover, Michael; Betlach, Thomas; Byrne, Nelson; Coker, Robert; Dendy, Edward; Hueckstaedt, Robert; New, Kim; Oakes, W Rob; Ranta, Dale; Stefan, Ryan
2008-01-01
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.
Cilia beating patterns are not hydrodynamically optimal
NASA Astrophysics Data System (ADS)
Guo, Hanliang; Nawroth, Janna; Ding, Yang; Kanso, Eva
2014-09-01
We examine the hydrodynamic performance of two cilia beating patterns reconstructed from experimental data. In their respective natural systems, the two beating patterns correspond to: (A) pumping-specialized cilia, and (B) swimming-specialized cilia. We compare the performance of these two cilia beating patterns as a function of the metachronal coordination in the context of two model systems: the swimming of a ciliated cylinder and the fluid pumping by a ciliated carpet. Three performance measures are used for this comparison: (i) average swimming speed/pumping flow rate; (ii) maximum internal moments generated by the cilia; and (iii) swimming/pumping efficiencies. We found that, in both models, pattern (B) outperforms pattern (A) in almost all three measures, including hydrodynamic efficiency. These results challenge the notion that hydrodynamic efficiency dictates the cilia beating kinematics, and suggest that other biological functions and constraints play a role in explaining the wide variety of cilia beating patterns observed in biological systems.
Determining hydrodynamic boundary conditions from equilibrium fluctuations
NASA Astrophysics Data System (ADS)
Chen, Shuyu; Wang, Han; Qian, Tiezheng; Sheng, Ping
2015-10-01
The lack of a first-principles derivation has made the hydrodynamic boundary condition a classical issue for the past century. The fact that the fluid can have interfacial structures adds additional complications and ambiguities to the problem. Here we report the use of molecular dynamics to identify from equilibrium thermal fluctuations the hydrodynamic modes in a fluid confined by solid walls, thereby extending the application of the fluctuation-dissipation theorem to yield not only the accurate location of the hydrodynamic boundary at the molecular scale, but also the relevant parameter value(s) for the description of the macroscopic boundary condition. We present molecular dynamics results on two examples to illustrate the application of this approach—one on the hydrophilic case and one on the hydrophobic case. It is shown that the use of the orthogonality condition of the modes can uniquely locate the hydrodynamic boundary to be inside the fluid in both cases, separated from the molecular solid-liquid interface by a small distance ? that is a few molecules in size. The eigenvalue equation of the hydrodynamic modes directly yields the slip length, which is about equal to ? in the hydrophilic case but is larger than ? in the hydrophobic case. From the decay time we also obtain the bulk viscosity which is in good agreement with the value obtained from dynamic simulations. To complete the picture, we derive the Green-Kubo relation for a finite fluid system and show that the boundary fluctuations decouple from the bulk only in the infinite-fluid-channel limit; and in that limit we recover the interfacial fluctuation-dissipation theorem first presented by Bocquet and Barrat. The coupling between the bulk and the boundary fluctuations provides both the justification and the reason for the effectiveness of the present approach, which promises broad utility for probing the hydrodynamic boundary conditions relevant to structured or elastic interfaces, as well as two-phase immiscible flows.
Ionizing Radiation in Smoothed Particle Hydrodynamics
O. Kessel-Deynet; A. Burkert
2000-02-11
A new method for the inclusion of ionizing radiation from uniform radiation fields into 3D Smoothed Particle Hydrodynamics (SPHI) simulations is presented. We calculate the optical depth for the Lyman continuum radiation from the source towards the SPHI particles by ray-tracing integration. The time-dependent ionization rate equation is then solved locally for the particles within the ionizing radiation field. Using test calculations, we explore the numerical behaviour of the code with respect to the implementation of the time-dependent ionization rate equation. We also test the coupling of the heating caused by the ionization to the hydrodynamical part of the SPHI code.
Supernova hydrodynamics experiments using the Nova laser
Remington, B.A.; Glendinning, S.G.; Estabrook, K.; Wallace, R.J.; Rubenchik, A.; Kane, J.; Arnett, D.; Drake, R.P.; McCray, R.
1997-04-01
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.
Hydrodynamics, horizons, holography and black hole entropy
C. Sivaram
2011-05-20
The usual discussions about black hole dynamics involve analogies with laws of thermodynamics especially in connection with black hole entropy and the associated holographic principle. We explore complementary aspects involving hydrodynamics of the horizon geometry through the membrane paradigm. New conceptual connections complementing usual thermodynamic arguments suggest deep links between diverse topics like black hole decay, quantum circulation and viscosity. Intriguing connections between turbulence cascades, quantum diffusion via quantum paths following Fokker- Planck equation and Hawking decay also result from this combination of thermodynamic and hydrodynamic analogies to black hole dynamics.
CSF hydrodynamics in superior sagittal sinus thrombosis.
Kristensen, B; Malm, J; Markgren, P; Ekstedt, J
1992-01-01
Cerebrospinal fluid hydrodynamics were investigated with a constant pressure infusion method in patients with superior sagittal sinus thrombosis. Ten patients were studied with serial examinations up to 15 years after the onset of the disease. A total of 70 CSF hydrodynamic examinations were performed. A clear increase in intracranial pressure due to raised pressure in the major dural sinus was seen in all patients. A striking feature was the persistent intracranial pressure increase that declined only gradually. This had no obvious clinical impact. Change in CSF resorption facility played only a minor role in the intracranial pressure elevation. None of the patients developed hydrocephalus. PMID:1583513
Effect of Second-Order Hydrodynamics on Floating Offshore Wind Turbines: Preprint
Roald, L.; Jonkman, J.; Robertson, A,; Chokani, N.
2013-07-01
Offshore winds are generally stronger and more consistent than winds on land, making the offshore environment attractive for wind energy development. A large part of the offshore wind resource is however located in deep water, where floating turbines are the only economical way of harvesting the energy. The design of offshore floating wind turbines relies on the use of modeling tools that can simulate the entire coupled system behavior. At present, most of these tools include only first-order hydrodynamic theory. However, observations of supposed second-order hydrodynamic responses in wave-tank tests performed by the DeepCwind consortium suggest that second-order effects might be critical. In this paper, the methodology used by the oil and gas industry has been modified to apply to the analysis of floating wind turbines, and is used to assess the effect of second-order hydrodynamics on floating offshore wind turbines. The method relies on combined use of the frequency-domain tool WAMIT and the time-domain tool FAST. The proposed assessment method has been applied to two different floating wind concepts, a spar and a tension-leg-platform (TLP), both supporting the NREL 5-MW baseline wind turbine. Results showing the hydrodynamic forces and motion response for these systems are presented and analysed, and compared to aerodynamic effects.
The theoretical analysis of the lattice hydrodynamic models for traffic flow theory
NASA Astrophysics Data System (ADS)
Ge, H. X.; Cheng, R. J.; Lei, L.
2010-07-01
The lattice hydrodynamic model is not only a simplified version of the macroscopic hydrodynamic model, but also connected with the microscopic car following model closely. The modified Korteweg-de Vries (mKdV) equation related to the density wave in a congested traffic region has been derived near the critical point since Nagatani first proposed it. But the Korteweg-de Vries (KdV) equation near the neutral stability line has not been studied, which has been investigated in detail for the car following model. We devote ourselves to obtaining the KdV equation from the original lattice hydrodynamic models and the KdV soliton solution to describe the traffic jam. Especially, we obtain the general soliton solution of the KdV equation and the mKdV equation. We review several lattice hydrodynamic models, which were proposed recently. We compare the modified models and carry out some analysis. Numerical simulations are conducted to demonstrate the nonlinear analysis results.
Influence of cavity shape on hydrodynamic noise by a hybrid LES-FW-H method
NASA Astrophysics Data System (ADS)
Wang, Yu; Wang, Shu-Xin; Liu, Yu-Hong; Chen, Chao-Ying
2011-09-01
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.
Ion acoustic shock waves in degenerate plasmas
Akhtar, N.; Hussain, S.
2011-07-15
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.
Passive hydrodynamic synchronization of two-dimensional swimming cells
NASA Astrophysics Data System (ADS)
Elfring, Gwynn J.; Lauga, Eric
2011-01-01
Spermatozoa flagella are known to synchronize when swimming in close proximity. We use a model consisting of two-dimensional sheets propagating transverse waves of displacement to demonstrate that fluid forces lead to such synchronization passively. Using two distinct asymptotic descriptions (small amplitude and long wavelength), we derive the synchronizing dynamics analytically for arbitrarily shaped waveforms in Newtonian fluids, and show that phase-locking will always occur for sufficiently asymmetric shapes. We characterize the effect of the geometry of the waveforms and the separation between the swimmers on the synchronizing dynamics, the final stable conformations, and the energy dissipated by the cells. For two closely swimming cells, synchronization always occurs at the in-phase or opposite-phase conformation, depending solely on the geometry of the cells. In contrast, the work done by the swimmers is always minimized at the in-phase conformation. As the swimmers get further apart, additional fixed points arise at intermediate values of the relative phase. In addition, computations for large amplitude waves using the boundary integral method reveal that the two asymptotic limits capture all the relevant physics of the problem. Our results provide a theoretical framework to address other hydrodynamic interactions phenomena relevant to populations of self-propelled organisms.
Hydrodynamic Simulations of the Bardeen-Petterson Effect
Nelson, R P; Nelson, Richard P.; Papaloizou, John C. B.
2000-01-01
We present SPH simulations of accretion discs in orbit about rotating compact objects such as black holes and neutron stars, and study the structure of warped discs produced by the Bardeen-Petterson effect. We calculate the transition radius out to which the disc specific angular momentum vector is aligned with that of the black hole. We focus on the parameter regime where the warp dynamics are controlled by bending wave propagation, but also consider models in which warps are subject to diffusion rather than wave transport, and are able to consider the fully nonlinear regime. Because of hydrodynamic or pressure effects, for the parameter range investigated, the transition radius is always found to be much smaller than that obtained by Bardeen & Petterson (1975). For discs with midplane Mach numbers of about 10, the transition occurs between 10 - 16 gravitational radii, whereas for a Mach number of about 30 it occurs at around 30 gravitational radii. A thicker disc with a Mach number of 5 is found to prod...
High-order hydrodynamics via lattice Boltzmann methods.
Colosqui, Carlos E
2010-02-01
In this work, closure of the Boltzmann-Bhatnagar-Gross-Krook (Boltzmann-BGK) moment hierarchy is accomplished via projection of the distribution function f onto a space H(N) spanned by N-order Hermite polynomials. While successive order approximations retain an increasing number of leading-order moments of f , the presented procedure produces a hierarchy of (single) N-order partial-differential equations providing exact analytical description of the hydrodynamics rendered by ( N-order) lattice Boltzmann-BGK (LBBGK) simulation. Numerical analysis is performed with LBBGK models and direct simulation Monte Carlo for the case of a sinusoidal shear wave (Kolmogorov flow) in a wide range of Weissenberg number Wi=taunuk(2) (i.e., Knudsen number Kn=lambdak=square root Wi); k is the wave number, [corrected] tau is the relaxation time of the system, and lambda approximately tauc(s) is the mean-free path, where c(s) is the speed of sound. The present results elucidate the applicability of LBBGK simulation under general nonequilibrium conditions. PMID:20365670
Energy Extraction from a Slider-Crank Wave Energy under Irregular Wave Conditions: Preprint
Sang, Yuanrui; Karayaka, H. Bora; Yan, Yanjun; Zhang, James Z.; Muljadi, Eduard; Yu, Yi-Hsiang
2015-08-24
A slider-crank wave energy converter (WEC) is a novel energy conversion device. It converts wave energy into electricity at a relatively high efficiency, and it features a simple structure. Past analysis on this particular WEC has been done under regular sinusoidal wave conditions, and suboptimal energy could be achieved. This paper presents the analysis of the system under irregular wave conditions; a time-domain hydrodynamics model is adopted and a rule-based control methodology is introduced to better serve the irregular wave conditions. Results from the simulations show that the performance of the system under irregular wave conditions is different from that under regular sinusoidal wave conditions, but a reasonable amount of energy can still be extracted.
Sound Waves in (2+1) Dimensional Holographic Magnetic Fluids
Evgeny I. Buchbinder; Alex Buchel; Samuel E. Vazquez
2008-12-22
We use the AdS/CFT correspondence to study propagation of sound waves in strongly coupled (2+1) dimensional conformal magnetic fluids. Our computation provides a nontrivial consistency check of the viscous magneto-hydrodynamics of Hartnoll-Kovtun-Muller-Sachdev to leading order in the external field. Depending on the behavior of the magnetic field in the hydrodynamic limit, we show that it can lead to further attenuation of sound waves in the (2+1) dimensional conformal plasma, or reduce the speed of sound. We present both field theory and dual supergravity descriptions of these phenomena. While to the leading order in momenta the dispersion of the sound waves obtained from the dual supergravity description agrees with the one predicted from field theory, we find a discrepancy at higher order. This suggests that further corrections to HKMS magneto-hydrodynamics are necessary.
Wave-particle interaction in the Faraday waves.
Francois, N; Xia, H; Punzmann, H; Shats, M
2015-10-01
Wave motion in disordered Faraday waves is analysed in terms of oscillons or quasi-particles. The motion of these oscillons is measured using particle tracking tools and it is compared with the motion of fluid particles on the water surface. Both the real floating particles and the oscillons, representing the collective fluid motion, show Brownian-type dispersion exhibiting ballistic and diffusive mean squared displacement at short and long times, respectively. While the floating particles motion has been previously explained in the context of two-dimensional turbulence driven by Faraday waves, no theoretical description exists for the random walk type motion of oscillons. It is found that the r.m.s velocity ???(osc)?(rms) of oscillons is directly related to the turbulent r.m.s. velocity ????(rms) of the fluid particles in a broad range of vertical accelerations. The measured ???(osc)?(rms) accurately explains the broadening of the frequency spectra of the surface elevation observed in disordered Faraday waves. These results suggest that 2D turbulence is the driving force behind both the randomization of the oscillons motion and the resulting broadening of the wave frequency spectra. The coupling between wave motion and hydrodynamic turbulence demonstrated here offers new perspectives for predicting complex fluid transport from the knowledge of wave field spectra and vice versa. PMID:26420468
Gustafsson, Torgny
2011 Waves - 1 STANDING WAVES ON A STRING The objectives of the experiment are: · To show that standing waves can be set up on a string. · To determine the velocity of a standing wave. · To understand the differences between transverse and longitudinal waves. APPARATUS: Buzzer board with string, meter stick
Shao, Yan-Lin Faltinsen, Odd M.
2014-10-01
We propose a new efficient and accurate numerical method based on harmonic polynomials to solve boundary value problems governed by 3D Laplace equation. The computational domain is discretized by overlapping cells. Within each cell, the velocity potential is represented by the linear superposition of a complete set of harmonic polynomials, which are the elementary solutions of Laplace equation. By its definition, the method is named as Harmonic Polynomial Cell (HPC) method. The characteristics of the accuracy and efficiency of the HPC method are demonstrated by studying analytical cases. Comparisons will be made with some other existing boundary element based methods, e.g. Quadratic Boundary Element Method (QBEM) and the Fast Multipole Accelerated QBEM (FMA-QBEM) and a fourth order Finite Difference Method (FDM). To demonstrate the applications of the method, it is applied to some studies relevant for marine hydrodynamics. Sloshing in 3D rectangular tanks, a fully-nonlinear numerical wave tank, fully-nonlinear wave focusing on a semi-circular shoal, and the nonlinear wave diffraction of a bottom-mounted cylinder in regular waves are studied. The comparisons with the experimental results and other numerical results are all in satisfactory agreement, indicating that the present HPC method is a promising method in solving potential-flow problems. The underlying procedure of the HPC method could also be useful in other fields than marine hydrodynamics involved with solving Laplace equation.
Testing different formulations of leading-order anisotropic hydrodynamics
Leonardo Tinti; Radoslaw Ryblewski; Wojciech Florkowski; Michael Strickland
2015-05-24
A recently obtained set of the equations for leading-order (3+1)D anisotropic hydrodynamics is tested against exact solutions of the Boltzmann equation with the collisional kernel treated in the relaxation time approximation. In order to perform the detailed comparisons, the new anisotropic hydrodynamics equations are reduced to the boost-invariant and transversally homogeneous case. The agreement with the exact solutions found using the new anisotropic hydrodynamics equations is similar to that found using previous, less general, formulations of anisotropic hydrodynamics. In addition, we find that, when compared to a state-of-the-art second-order viscous hydrodynamics framework, leading-order anisotropic hydrodynamics better reproduces the exact solution for the pressure anisotropy and gives comparable results for the bulk pressure evolution. Finally, we compare the transport coefficients obtained using linearized anisotropic hydrodynamics with results obtained using second-order viscous hydrodynamics.
The hydrodynamic and radiative properties of low-density foams heated by x-rays
NASA Astrophysics Data System (ADS)
Rosmej, O. N.; Suslov, N.; Martsovenko, D.; Vergunova, G.; Borisenko, N.; Orlov, N.; Rienecker, T.; Klir, D.; Rezack, K.; Orekhov, A.; Borisenko, L.; Krousky, E.; Pfeifer, M.; Dudzak, R.; Maeder, R.; Schaechinger, M.; Schoenlein, A.; Zaehter, S.; Jacoby, J.; Limpouch, J.; Ullschmied, J.; Zhidkov, N.
2015-09-01
An advanced type of hydrodynamic stable plasma targets with homogeneous distribution of plasma parameters has been proposed for application in experiments on heavy ion stopping in plasmas and relativistic laser based particle acceleration. Plasma was created via x-ray heating of polymer aerogels with a mean density 103 times lower than that of solid matter. Hydrodynamic and radiation properties of low-density polymer aerogels heated by x-rays, which were generated due to laser interaction with a gold hohlraum, have been investigated experimentally and numerically. In experiments carried out at the PALS laser facility in Prague, the parameters of the hohlraum based soft x-ray source and the fraction of x-ray energy absorbed by foam layers have been measured. The results of these experiments and numerical simulations show that the x-ray heat process occurs via propagation of supersonic radiation driven heat waves. The measured heat wave velocity of 107?cm?s-1 allows one to estimate the plasma temperature reached as 25?eV. The hydrodynamic stability of x-ray heated plasma layers has been demonstrated by means of an optical streak camera viewing the plasma expansion process. Simulations of the foam heating process denote rather homogeneous distribution of the plasma temperature and density in the x-ray heated plasma layer and sharp plasma boundaries. The investigated features of such plasma targets are a great advantage for experiments with heavy ion and relativistic laser beams.
On pulsating and cellular forms of hydrodynamic instability in liquid-propellant combustion
Margolis, S.B.
1997-11-01
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.
HYDRODYNAMIC ISSUES IN PAMS MANDREL TARGET FABRICATION
McQUILLAN,B.W; PAGUIO,R; SUBRAMANIAN,P; TAKAGI,M; ZEBIB,A
2003-09-01
OAK-B135 Imperfections in PAMS mandrels critically govern the quality of final ICF targets. Imperfections in the mandrels can have a wide range of origins. Here, they present observations of 3 types of imperfections, and data to support the proposal that hydrodynamic factors during the curing of the mandrel are potential causes of these imperfections.
Boundary conditions in tunneling via quantum hydrodynamics
NASA Technical Reports Server (NTRS)
Nassar, Antonio B.
1993-01-01
Via the hydrodynamical formulation of quantum mechanics, an approach to the problem of tunneling through sharp-edged potential barriers is developed. Above all, it is shown how more general boundary conditions follow from the continuity of mass, momentum, and energy.
Hydrodynamic Effects in Multicomponent Fluid Membranes
NASA Astrophysics Data System (ADS)
Komura, Shigeyuki; Ramachandran, Sanoop; Imai, Masayuki
2012-02-01
In this chapter, we deal with hydrodynamic effects on multicomponent fluid membranes. Above the miscibility transition temperature, we focus on the hydrodynamic effects on the dynamics of critical concentration fluctuations in two-component fluid membranes, and the wavenumber dependence of the effective diffusion coefficient is shown. Below the miscibility transition temperature, we study the domain growth exponent in a binary fluid membrane using a particle-based simulation method. A change in the growth exponent from two-dimensional to three-dimensional nature with the addition of bulk solvent is observed. Next, using a simplified hydrodynamic theory, we calculate the drag on a liquid domain diffusing in a two-dimensional membrane. The analytical expression for the diffusion coefficient spans the whole spectrum of size ranges. The dynamics of a Gaussian polymer chain embedded in a liquid membrane surrounded by bulk solvent and walls are also discussed. Using the preaveraging approximation, we can circumvent the non-linearity imposed by the hydrodynamics. Within this approximation, the diffusion coefficient of the polymer in the free membrane geometry is obtained for a size range of several decades in order. The polymer relaxation times as well as structure factor are obtained for both confined and free membranes. Finally, we discuss the coupled in-plane dynamics between point particles embedded in stacked fluid membranes.
Stabilizing geometry for hydrodynamic rotary seals
Dietle, Lannie L. (Houston, TX); Schroeder, John E. (Richmond, TX)
2010-08-10
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.
Simulating Brownian suspensions with fluctuating hydrodynamics.
Delmotte, Blaise; Keaveny, Eric E
2015-12-28
Fluctuating hydrodynamics has been successfully combined with several computational methods to rapidly compute the correlated random velocities of Brownian particles. In the overdamped limit where both particle and fluid inertia are ignored, one must also account for a Brownian drift term in order to successfully update the particle positions. In this paper, we present an efficient computational method for the dynamic simulation of Brownian suspensions with fluctuating hydrodynamics that handles both computations and provides a similar approximation as Stokesian Dynamics for dilute and semidilute suspensions. This advancement relies on combining the fluctuating force-coupling method (FCM) with a new midpoint time-integration scheme we refer to as the drifter-corrector (DC). The DC resolves the drift term for fluctuating hydrodynamics-based methods at a minimal computational cost when constraints are imposed on the fluid flow to obtain the stresslet corrections to the particle hydrodynamic interactions. With the DC, this constraint needs only to be imposed once per time step, reducing the simulation cost to nearly that of a completely deterministic simulation. By performing a series of simulations, we show that the DC with fluctuating FCM is an effective and versatile approach as it reproduces both the equilibrium distribution and the evolution of particulate suspensions in periodic as well as bounded domains. In addition, we demonstrate that fluctuating FCM coupled with the DC provides an efficient and accurate method for large-scale dynamic simulation of colloidal dispersions and the study of processes such as colloidal gelation. PMID:26723653
Laboratory and Astrophysical Radiation Hydrodynamics : An Introduction
Mihalas, Dimitri,
2002-01-01
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.
MS, AIP, Sternphysik, 2001 Hydrodynamical Convection Models
c MS, AIP, Sternphysik, 2001 Hydrodynamical Convection Models -- Sun and Betelgeuse -- Matthias Steffen Convection is a universal feature in astrophysics, essentially all types of stars have one or even several convection zones. The role of stellar convection is farÂreaching: Convective energy transport
Livermore Unstructured Lagrange Explicit Shock Hydrodynamics
Energy Science and Technology Software Center (ESTSC)
2010-09-21
LULESH v1.0 is a 3D unstructured Lagrange hydrodynamics simulation written specifically to solve a standard analytical test problem, known as the Sedov problem. In this problem, a quantum of energy is deposited into a gas and propagates through the gas over time.
ORIGINAL ARTICLE The relationship between hydrodynamic properties
Fortin, Jérôme
the porosity and consequently the permeability and also by increasing water retention. Keywords Physical soil and consequently a growing demand for water. Understanding that the hydrological cycle is fundamental for waterORIGINAL ARTICLE The relationship between hydrodynamic properties and weathering of soils derived
Anisotropic hydrodynamics for conformal Gubser flow
NASA Astrophysics Data System (ADS)
Nopoush, Mohammad; Ryblewski, Radoslaw; Strickland, Michael
2015-02-01
We derive the equations of motion for a system undergoing boost-invariant longitudinal and azimuthally symmetric transverse "Gubser flow" using leading-order anisotropic hydrodynamics. This is accomplished by assuming that the one-particle distribution function is ellipsoidally symmetric in the momenta conjugate to the de Sitter coordinates used to parametrize the Gubser flow. We then demonstrate that the S O (3 )q symmetry in de Sitter space further constrains the anisotropy tensor to be of spheroidal form. The resulting system of two coupled ordinary differential equations for the de Sitter-space momentum scale and anisotropy parameter are solved numerically and compared to a recently obtained exact solution of the relaxation-time-approximation Boltzmann equation subject to the same flow. We show that anisotropic hydrodynamics describes the spatiotemporal evolution of the system better than all currently known dissipative hydrodynamics approaches. In addition, we prove that anisotropic hydrodynamics gives the exact solution of the relaxation-time approximation Boltzmann equation in the ideal, ? /s ?0 , and free-streaming, ? /s ??, limits.
Hydrodynamic Evolution of Chirally Symmetric Nuclear Matter
F. Navarra; U. Ornik
1994-12-15
The equation of state of the linear sigma model in the mean field approximation is used as input in a relativistic hydrodynamical numerical routine. Longitudinal and transverse energy distributions are calculated and compared with those obtained from the QHD-I equation of state.
A Radiation Hydrodynamical for Protostar Formation
Masunaga, Hirohiko
of the Japan Society for the Promotion of Science for Young Scientists. Finally, I thank ism(Pentium II), yso is capable to account for recent observations, we have developed a numerical code for radiation hydrodynamic code is designed to yield the evolution of spectral energy distributions as well as the dynamical
Inverse kinetic theory for quantum hydrodynamic equations
Massimo Tessarotto; Marco Ellero; Piero Nicolini
2006-06-10
We propose a solution for the inverse kinetic theory for quantum hydrodynamic equations associated to the non-relativistic Schr\\"{o}dinger equation. It is shown that an inverse kinetic equation of the form of the Vlasov equation can be non-uniquely determined under suitable mathematical prescriptions.
Microflow Cytometers with Integrated Hydrodynamic Focusing
Frankowski, Marcin; Theisen, Janko; Kummrow, Andreas; Simon, Peter; Ragusch, Hülya; Bock, Nicole; Schmidt, Martin; Neukammer, Jörg
2013-01-01
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. PMID:23571670