These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Experimental and numerical investigation of wave ferrofluid convection  

Microsoft Academic Search

The stability of buoyancy-driven shear flow in an inclined layer of a ferrocolloid is investigated for different values of inclinations and homogeneous longitudinal magnetic fields. Near the onset of Rayleigh convection of ferrofluid layer inclined with respect to gravity, the wave oscillatory regimes were observed in experiments and numerical simulations. Visualization of convection patterns is provided by a temperature-sensitive liquid

A. A. Bozhko; G. F. Putin; T. Tynjälä; P. Sarkomaa

2007-01-01

2

The influence of hydrodynamic diameter and core composition on the magnetoviscous effect of biocompatible ferrofluids.  

PubMed

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

Nowak, J; Wiekhorst, F; Trahms, L; Odenbach, S

2014-04-30

3

Wave turbulence on the surface of a ferrofluid in a horizontal magnetic field  

E-print Network

We report observations of wave turbulence on the surface of a ferrofluid submitted to a magnetic field parallel to the fluid surface. The magnetic wave turbulence shows several differences compared to the normal field case reported recently. The inertial zone of the magnetic wave turbulence regime is notably found to be strongly increased with respect to the normal field case, and to be well described by our theoretical predictions. The dispersion relation of linear waves is also measured and differs from the normal field case due to the absence of the Rosensweig instability.

Stéphane Dorbolo; Eric Falcon

2011-03-30

4

Pilot-wave hydrodynamics  

E-print Network

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

Bush, John W. M.

5

Wave turbulence on the surface of a ferrofluid submitted to a magnetic field  

E-print Network

We report the observation of wave turbulence on the surface of a ferrofluid mechanically forced and submitted to a static normal magnetic field. We show that magnetic surface waves arise only above a critical field. The power spectrum of their amplitudes displays a frequency-power law leading to the observation of a magnetic wave turbulence regime which is experimentally shown to involve a 4-wave interaction process. The existence of the regimes of gravity, magnetic and capillary wave turbulence is reported in the phase space parameters as well as a triple point of coexistence of these three regimes. Most of these features are understood using dimensional analysis or the dispersion relation of the ferrohydrodynamics surface waves.

François Boyer; Eric Falcon

2008-11-12

6

Generalized hydrodynamics and heat waves  

NASA Astrophysics Data System (ADS)

By using the evolution equations of generalized hydrodynamics we investigate heat-pulse propagation in a Lennard-Jones liquid contained in the annulus between two concentric cylinders at different temperatures. It is found that the heat pulse propagates as a wave of a finite speed when a composite fluid dynamic number N(R) that depends on the thermal conductivity and wall temperature ratio is above a critical value, but in the subcritical region the heat pulse propagates diffusively as if predicted by a parabolic differential equation with an infinite speed of propagation. Therefore the question of the hyperbolicity of the system of differential (evolution) equations used is mainly determined by the parameter N(R). This implies that the hyperbolicity of evolution equations, i.e., the finiteness of pulse-propagation speed, cannot be the main reason for extending the thermodynamics of irreversible processes as believed by some authors in the literature.

Khayat, R. E.; Eu, Byung C.

1992-01-01

7

Ferrofluid Film Bearing for enhancement of rotary scanner performance  

NASA Astrophysics Data System (ADS)

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

Cheever, Charles; Li, Zhixin; Raj, Kuldip

1991-02-01

8

Simple Waves in Ideal Radiation Hydrodynamics  

SciTech Connect

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

Johnson, B M

2008-09-03

9

PREFACE: Ferrofluids  

NASA Astrophysics Data System (ADS)

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

Odenbach, Professor Stefan

2006-09-01

10

Resonant Ferrofluidic Inclinometers  

Microsoft Academic Search

In this paper modeling, prototyping and preliminary characterization of an innovative inclinometer based on ferrofluid is presented. It consists of a glass pipe where a drop of ferrofluid is contained in a water environment, a \\

B. Ando; A. Ascia; S. Baglio; C. Trigona

2007-01-01

11

Ferrofluids: Thermophysical properties and formation of microstructures  

NASA Astrophysics Data System (ADS)

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

Mousavi Khoeini, NargesSadat Susan

12

Existence of Electromagnetic-Hydrodynamic Waves  

Microsoft Academic Search

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

H. Alfvén

1942-01-01

13

Hydrodynamic shock wave studies within a kinetic Monte Carlo approach  

NASA Astrophysics Data System (ADS)

We introduce a massively parallelized test-particle based kinetic Monte Carlo code that is capable of modeling the phase space evolution of an arbitrarily sized system that is free to move in and out of the continuum limit. Our code combines advantages of the DSMC and the Point of Closest Approach techniques for solving the collision integral. With that, it achieves high spatial accuracy in simulations of large particle systems while maintaining computational feasibility. Using particle mean free paths which are small with respect to the characteristic length scale of the simulated system, we reproduce hydrodynamic behavior. To demonstrate that our code can retrieve continuum solutions, we perform a test-suite of classic hydrodynamic shock problems consisting of the Sod, the Noh, and the Sedov tests. We find that the results of our simulations which apply millions of test-particles match the analytic solutions well. In addition, we take advantage of the ability of kinetic codes to describe matter out of the continuum regime when applying large particle mean free paths. With that, we study and compare the evolution of shock waves in the hydrodynamic limit and in a regime which is not reachable by hydrodynamic codes.

Sagert, Irina; Bauer, Wolfgang; Colbry, Dirk; Howell, Jim; Pickett, Rodney; Staber, Alec; Strother, Terrance

2014-06-01

14

Hydrodynamic Modes of a holographic $p-$ wave superfluid  

E-print Network

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

Arias, Raul E

2014-01-01

15

Hydrodynamic Modes of a holographic $p-$ wave superfluid  

E-print Network

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

Raul E. Arias; Ignacio Salazar Landea

2014-09-22

16

The velocities and accelerations accompanying ocean waves can impose large hydrodynamic forces on marine organisms,  

E-print Network

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

Denny, Mark

17

"Photochemical Oscillator": Colored Hydrodynamic Oscillations and Waves in a Photochromic System  

E-print Network

between 15 and 70 s. INTRODUCTION Colored chemical oscillations and waves have been utilized as tools"Photochemical Oscillator": Colored Hydrodynamic Oscillations and Waves in a Photochromic System is sufficiently high, it triggers color oscillations and waves due to hydrodynamic convective motion

Epstein, Irving R.

18

Ferrofluid and cellulolytic fungi  

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

19

On the nonlinear hydrodynamic forces for a ship advancing in waves  

Microsoft Academic Search

In this paper, using a second-order steady-state approach and a three-dimensional (3D) pulsating source distribution method derives the nonlinear hydrodynamic forces on a ship advancing in waves. The nonlinear hydrodynamic forces considered here consist of the mean lateral drifting force and the added resistance, which can be expressed as products of the ship-motion responses, the radiation potential, diffraction potential and

Ming-Chung Fang; Gung-Rong Chen

2006-01-01

20

Smoothed Particle Hydrodynamics (SPH) Method for Stress Wave Propagation Problems  

Microsoft Academic Search

Smoothed particle hydrodynamics (SPH) method is robust to deal with the problems of impact dynamics. Conventional SPH (CSPH) method converts the kernel integral into a volumetric weighted sum straightforwardly and it is named as particle approximation. This method is very simple and pellucid, but it causes phenomena of tensile instability and numerical oscillations and makes the numerical calculation difficulty. Modified

Ji Xiaoyu; Li Yongchi; Huang Xicheng; Yin Yihui

2007-01-01

21

On features of ferrofluid convection caused by barometrical sedimentation  

Microsoft Academic Search

The experimental and numerical studies of Rayleigh convection in a thin cylindrical layer have been conducted for a ferrofluid containing magnetite particles suspended in kerosene carrier liquid. Near the onset of convection, the wave oscillatory convection was observed both in the experiments and in the numerical finite volume simulations. Time periods of temperature oscillations obtained using thermocouples were investigated using

T. Tynjälä; A. Bozhko; P. Bulychev; G. Putin; P. Sarkomaa

2006-01-01

22

Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas  

E-print Network

, from waves on the surface of a lake or a pool and sound waves to the electromagnetic waves propagation propagation can be solved not only in the linear approximation but also with nonlinear effects taken. In the case of direct numerical simulation we have the highest possible control on the parameters

Lushnikov, Pavel

23

Ferrofluid flow for TOUGH2  

SciTech Connect

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

Oldenburg, Curtis; Moridis, George

1998-03-24

24

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

E-print Network

(P) between Wave Front and Pipe Location. (After 10, 11 and 12) 12 CHAPTER III THEORETICAL CONSIDERATIONS A. Hydrodynamic Forces on a Horizontal Circular Cylinder Submarine pipelines are, for the most part, exposed to wave and current action...(P) between Wave Front and Pipe Location. (After 10, 11 and 12) 12 CHAPTER III THEORETICAL CONSIDERATIONS A. Hydrodynamic Forces on a Horizontal Circular Cylinder Submarine pipelines are, for the most part, exposed to wave and current action...

Lee, Jaeyoung

2012-06-07

25

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

Microsoft Academic Search

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

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

2006-01-01

26

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

Microsoft Academic Search

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

Said R Sabag; Billy L Edge; Iwan Soedigdo

2000-01-01

27

Three-wave interaction and Manley-Rowe relations in quantum hydrodynamics  

E-print Network

The theory for nonlinear three-wave interaction in magnetized plasmas is reconsidered using quantum hydrodynamics. The general coupling coefficients are calculated for a generalized Bohm de Broglie term. It is found that the Manley-Rowe relations are fulfilled only if the form of the particle dispersive term coincides with the standard expression. The implications of our results are discussed.

Wallin, Erik; Brodin, Gert

2013-01-01

28

A Dynamic Analysis of Hydrodynamic Wave Journal Bearings  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

29

Smoothed Particle Hydrodynamics method to study water wave breaking and runup  

NASA Astrophysics Data System (ADS)

The problem of determining solitary waves runups is of great interest in studying coastal effects of tsunamis. A relationship between the runup and wave height, for non-breaking waves, exists in the literature (Synolakis, 1987). Nevertheless, it is difficult to predict the runup for breaking waves. Our study aims to numerically determine the runup law for breaking waves. Therefore, we developed a numerical model based on the Smoothed Particle Hydrodynamics method (SPH) in order to study the transformation of a wave propagating over a constant depth and encountering a sloping beach. SPH is a meshfree method, where all fluid quantities are carried out by points, and is very suitable for problems involving large deformations and moving interfaces. Originally developed for astrophysical problems, this numerical method proved its efficiency to simulate free surface flows. The formalism requires to consider fluid being slightly compressible and that pressure is to be evaluated from density variations through a state equation. Our SPH code has been validated with general hydrodynamic flow problems (laminar flows, dam breaking, solitary wave runup on vertical wall, ...) using experimental or theoretical results coming from literature. Depending on problem parameters (the slope of the beach, wave amplitude, water depth,...), wave breaking can be observed and runup can be determined with the use of our numerical program.

Lominé, F.; Chambon, G.; Naaim, M.; Faug, T.

2009-04-01

30

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

SciTech Connect

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

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

1985-01-01

31

Explicit vs. implicit time integration for nonlinear hydrodynamic shock wave propagation  

NASA Astrophysics Data System (ADS)

Two-dimensional nonlinear hydrodynamic equations were discretized using the finite element method and a water medium. A shock wave was generated, and its propagation and reflection were studied using two different shock capturing schemes and two different time integration schemes. The use of the finite-element package ANSYS is discussed, and results obtained using an acoustic element are compared with those based on the nonlinear model.

Jamnia, M. A.; Jackson, J. E.

32

Smoothed Particle Hydrodynamics Simulation of Wave Overtopping Characteristics for Different Coastal Structures  

PubMed Central

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

Pu, Jaan Hui; Shao, Songdong

2012-01-01

33

Application of a Coupled Wave and Hydrodynamic Model over Complex Bathymetry in Eastern Lake Ontario  

NASA Astrophysics Data System (ADS)

The Kingston Basin in eastern Lake Ontario is a region with complex bathymetry including islands, shoals and deeper channels. This area can have waves over 5 m in height and storm surges on the order of 1 m, forced by strong westerly fall and winter storm winds. We characterize the waves, hydrodynamics and thermal structure from observations acquired by acoustic Doppler current profilers, thermistor chains, optical backscatter loggers, water level sensors and wave gauges collected over the 2012 winter period. The SWAN and Delft3D coupled models, validated by the observations, are used to simulate the wave and hydrodynamic conditions for two large storm events. The model was forced with forecast data from the Great Lakes Coastal Forecasting System, observations from the National Oceanographic and Atmospheric Administration and Environment Canada. Results indicate that there is strong spatial variability in wave conditions due to refraction and focusing of the bathymetry. Future work will extend the model to determine the potential environmental impacts of offshore wind farm construction in the region.

McCombs, M. P.; Mulligan, R. P.; Boegman, L.; Yerubandi, R. R.

2012-12-01

34

Hydrodynamic instabilities and transverse waves in propagation mechanism of gaseous detonations  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

35

A Stability Analysis for a Hydrodynamic Three-Wave Journal Bearing  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

36

Measurements and Linear Wave Theory Based Simulations of Vegetated Wave Hydrodynamics for Practical Applications  

E-print Network

wave attenuation is dependent on relative vegetation height, stem density, and stem spacing standard deviation. As stems occupy more of the water column, an increase in attenuation occurred given that the highest wave particle velocities are being...

Anderson, Mary Elizabeth

2011-10-21

37

Experimental study of the hydrodynamic performance of an onshore wave power device in the presence of an underwater mound  

Microsoft Academic Search

The hydrodynamic functioning of an oscillating water column (OWC) in the presence of an underwater tri-dimensional mound (UTDM) through large-scale ocean engineering basin experiments is described. Experiments are carried out with both regular and irregular waves and are compared to numerical models. The analysis is based on the measurements of the wave amplification in the water column for the OWC

F. Gouaud; V. Rey; J. Piazzola; R. Van Hooff

2010-01-01

38

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

Microsoft Academic Search

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

S. R. Massel; T. J. Done

1993-01-01

39

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

PubMed

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

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

2013-02-01

40

Hydrodynamics of the Oscillating Wave Surge Converter in the open ocean  

E-print Network

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

Renzi, E

2012-01-01

41

Symmetry Breaking Via Global Bifurcations of Modulated Rotating Waves in Hydrodynamics  

NASA Astrophysics Data System (ADS)

The combined experimental and numerical study finds a complex mechanism of Z2 symmetry breaking involving global bifurcations for the first time in hydrodynamics. In addition to symmetry breaking via pitchfork bifurcation, the Z2 symmetry of a rotating wave that occurs in Taylor-Couette flow is broken by a global saddle-node-infinite-period (SNIP) bifurcation after it has undergone a Neimark-Sacker bifurcation to a Z2-symmetric modulated rotating wave. Unexpected complexity in the bifurcation structure arises as the curves of cyclic pitchfork, Neimark-Sacker, and SNIP bifurcations are traced towards their apparent merging point. Instead of symmetry breaking due to a SNIP bifurcation, we find a more complex mechanism of Z2 symmetry breaking involving nonsymmetric two-tori undergoing saddle-loop homoclinic bifurcations and complex dynamics in the vicinity of this global bifurcation.

Abshagen, Jan; Lopez, Juan M.; Marques, Francisco; Pfister, Gerd

2005-02-01

42

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

43

Density wave formation in differentially rotating disk galaxies: Hydrodynamic simulation of the linear regime  

NASA Astrophysics Data System (ADS)

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.

Griv, Evgeny; Wang, Hsiang-Hsu

2014-07-01

44

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

NASA Astrophysics Data System (ADS)

Monodispersed aqueous ferrofluids of iron oxide nanoparticle were synthesized by hydrothermal-reduction route. They were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy and dynamic light scattering. The results showed that certain concentrations of citric acid (CA) are required to obtain only magnetic iron oxides with mean particle sizes around 8 nm. CA acts as a modulator and reducing agent in iron oxide formation which controls nanoparticle size. The XRD, magnetic and heating measurements showed that the temperature and time of hydrothermal reaction can affect the magnetic properties of obtained ferrofluids. The synthesized ferrofluids were stable at pH 7. Their mean hydrodynamic size was around 80 nm with polydispersity index (PDI) of 0.158. The calculated intrinsic loss power (ILP) was 9.4 nHm2/kg. So this clean and cheap route is an efficient way to synthesize high ILP aqueous ferrofluids applicable in magnetic hyperthermia.

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

2012-03-01

45

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

SciTech Connect

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

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

2012-03-15

46

Electromagnetic ferrofluid-based energy harvester  

NASA Astrophysics Data System (ADS)

This Letter investigates the use of ferrofluids for vibratory energy harvesting. In particular, an electromagnetic micro-power generator which utilizes the sloshing of a ferrofluid column in a seismically-excited tank is proposed to transform mechanical motions directly into electricity. Unlike traditional electromagnetic generators that implement a solid magnet, ferrofluids can easily conform to different shapes and respond to very small acceleration levels offering an untapped opportunity to design scalable energy harvesters. The feasibility of the proposed concept is demonstrated and its efficacy is discussed through several experimental studies.

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

2012-06-01

47

Wave-driven Hydrodynamics for Different Reef Geometries and Roughness Scenarios  

NASA Astrophysics Data System (ADS)

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.

Franklin, G. L.; Marino-Tapia, I.; Torres-Freyermuth, A.

2013-05-01

48

Anisotropic Light Scattering from Ferrofluids  

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

49

Controlling ferrofluid permeability across the blood-brain barrier model  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

50

The Effect of Morphology, Tides and Wind Waves on the Hydrodynamics of Idealized River-Mouth Systems  

NASA Astrophysics Data System (ADS)

The hydrodynamics and the morphological configuration of estuaries strongly depend on tidal wave propagation, offshore wave climate, and river discharges. Depending of their relative contribution, an estuary can exhibit a wave-dominated morphology, a tidal-dominated configuration, or a river dominated one. This has a direct effect on hydrodynamic parameters relevant from the ecological and biological points of view. Overall, these coastal systems are highly dynamic and complex and the interplay of the physical processes and the resulting dynamics are still not fully understood. The 3D COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) modeling system is applied to analyze numerically wave-tidal hydrodynamics in 3 idealized inlet-estuary configurations. The configurations differ because of the presence/absence of the ebb delta and a main channel crossing the delta and because of the water depths inside the estuary. In essence we consider different wave climates, tidal prisms, and standing/progressive tidal conditions. The goal is to infer the effect of the ebb delta on the combined wave-tidal flows along a whole tidal cycle and its dependency with the characteristics of the tides and the incoming swell waves. The interaction between surface gravity waves and currents is modeled with the 3D vortex force method, which decouples conservative and non-conservative wave forces. We show how the ebb shoal acts as a roughness element increasing energy losses in the inlet area. It also enhances the relative effect of the wave driven forces and circulations in the inlet region. The effect of waves is not confined to the inlet and its influence extends to the inner part of the estuary. These are manifested on increased mean water levels, dissipation of the main tidal harmonics and a more progressive character of the tides inside the estuary. The main forces responsible for these changes are wave breaking induced accelerations and the increase of bed friction. Tidal modulations of the full directional wave spectra are also identified in the inlet region. The wave penetration capacity into the estuary changes during a tidal cycle, because of variations in the energy dissipation over the ebb shoal and because the wave action advection by the tidal currents. The momentum balance analysis performed along the whole tidal cycle shows tidal modulations of the wave induced forces as a consequence of temporal and spatial variations in water depths and tidal currents. This presentation will discuss the relevance of the wave induced forces on the inlet estuarine systems pointing out the limitations and future efforts in these directions.

Olabarrieta, M.; Coco, G.; Zhou, Z.

2012-12-01

51

Integrated Catadioptric Pickup with Ferrofluidic Cooling Structure  

NASA Astrophysics Data System (ADS)

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

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

2006-02-01

52

Exploration of ocean waves created by iceberg calving and capsize using SPH (smoothed particle hydrodynamics)  

NASA Astrophysics Data System (ADS)

The interaction between icebergs, their parent ice shelves and the fluid in which they float (seawater) is one of the most demanding problems in glaciology because the interactions involve multiple widely divergent time scales, a variety of constitutive behaviors along with free surfaces and disconnected domains. As calving begins, compressibility and surface tension of seawater comes into play as free-falling ice encounters the ocean surface, producing jets of spray and filling the water with plumes of bubbles. As calving proceeds, incompressible hydrodynamics describes the interaction between the iceberg and the surface waves (tsunamis) the calving event creates in the ocean. In regions where the Froude number (which inversely measures the ability of the water to relieve pressure on the iceberg, ice shelf and seabed by radiating free-surface gravity waves) is greater than 1, hydraulic pressure coupling can produce extraordinary tensile and compressive stresses in the iceberg and ice shelf, triggering further calving. Eventually, a hydrostatic pressure regime develops in which icebergs may further evolve through capsize, which often produces such strong elastic stress within the iceberg sufficient to cause its disintegration. This presentation will focus on the use of SPH as a means of modeling ice/ocean interaction during iceberg calving. Goals of the investigation will be methodological and will evaluate the efficiency and accuracy of the computation of boundary forces which act on icebergs, ice shelves and seabed/fjord walls during iceberg calving and capsize.

Macayeal, D. R.

2009-12-01

53

Magnetic detection of ferrofluid injection zones  

SciTech Connect

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

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

1998-03-01

54

Investigation into loss in ferrofluid magnetization  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

55

Three-dimensional diamagnetic particle deflection in ferrofluid microchannel flows  

E-print Network

Three-dimensional diamagnetic particle deflection in ferrofluid microchannel flows Litao Liang, and optical methods. This work presents a fundamental study of diamagnetic particle motion in ferrofluid flows relative to the ferrofluid, diamagnetic particles experience negative magnetophoresis and are repelled away

Xuan, Xiangchun "Schwann"

56

Iron(oxide) ferrofluids: synthesis, structure and catalysis  

Microsoft Academic Search

This thesis describes a study on two connecting research subjects concerning ferrofluids, i.e. the synthesis and use of catalytic magnetic colloids and the microstructural behaviour of ferrofluids in general. An interesting application of ferrofluids (dispersions of magnetic colloids) would be their use in catalysis; catalysts attached to the surface of small magnetic particles could in principle be separated magnetically for

Karen Butter

2003-01-01

57

Coupled Wave-Hydrodynamic Modeling Over Sorted Grain Size Features (Rippled Scour Depressions) on the Inner Shelf  

NASA Astrophysics Data System (ADS)

Sorted grain-size features, also known as rippled scour depressions, are persistent cross-shore structures found in many nearshore environments, characterized by sharp gradients in grain size and gentle relief in the alongshore direction. The formation of these features is not completely understood, but self-organization and feedback have been proposed as explanations for their persistence. Sorted grain-size features near the Martha's Vineyard Coastal Observatory (MVCO), Massachusetts, are characterized by bathymetric lows with coarse (0.5 mm) sand and large ripples (heights of 0.10-0.15 cm, wavelengths of 0.6 to 0.8 m) and bathymetric highs with fine sand (0.125 mm) and small ripples (heights of 0.01 m, wavelengths of 0.1 m). The features extend from the shallowest region surveyed (6 m) to depths of 17 m, 3 km offshore, with a maximum alongshore width of less than 1 km. Wave-current interaction is an important component of the inner shelf and circulation at MVCO. However, subtle changes in topography and hydrodynamic roughness associated with these features complicate evaluation of numerical models, especially because of the spatial and temporal variability in alongshore flows and wave forcing near MVCO. We have investigated these features and the inner-shelf circulation using nested and coupled wave-hydrodynamic models. The models were calibrated using water-level, current, and wave data from MVCO and several wave buoys. The suite of nested models applied here began with basin- scale (5-km grid for the eastern seaboard) wave models that provided spectral wave forcing to a regional wave model (1-km grid for the southern New England shelf). The regional wave model and a regional hydrodynamic model at the same scale were then run uncoupled, to provide boundary conditions for a cascade of nested, coupled, wave-hydrodynamic models. The final nested model, at an 8-m grid resolution, resolved the sorted grain-size features. At this level, a sediment-transport model with time-dependent ripple geometry and various roughness formulations was applied to investigate the maintenance of these features and their influence on circulation under realistic conditions. Given an initial bed sediment distribution, the roughness introduced by these features significantly alters the quasi-steady-state distribution within the bed, and highlights the concept of feedback and self-organization.

Ganju, N. K.; Sherwood, C. R.; Signell, R. P.

2008-12-01

58

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

SciTech Connect

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

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

2004-03-31

59

Performance analysis of coupled and uncoupled hydrodynamic and wave models in the northern Adriatic Sea  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

60

On the hydrodynamic interaction of shock waves with interstellar clouds. 1: Nonradiative shocks in small clouds  

NASA Technical Reports Server (NTRS)

The interstellar medium (ISM) is inhomogeneous, with clouds of various temperatures and densities embedded in a tenuous intercloud medium. Shocks propagating through the ISM can ablate or destroy the clouds, at the same time significantly altering the properties of the intercloud medium. This paper presents a comprehensive numerical study of the simplest case of the interaction between a shock wave and a spherical cloud, in which the shock far from the cloud is steady and planar, and in which radiative losses, thermal conduction, magnetic fields, and gravitational forces are all neglected. As a result, the problem is completely specified by two numbers: the Mach number of the shock, M, and the ratio of the density of the cloud to that of the intercloud medium, Chi. For strong shocks we show that the dependence on M scales out, so the primary independent parameter is Chi. Variations from this simple case are also considered: the potential effect of radiative losses is assessed by calculations in which the ratio of specific heats in the cloud is 1.1 instead of 5/3; the effect of the initial shape of the cloud is studied by using a cylindrical cloud instead of a spherical one; and the role of the initial shock is determined by considering the case of a cloud embedded in a wind. Local adaptive mesh refinement techniques with a second-order, two-fluid, two-dimensional Godunov hydrodynamic scheme are used to address these problems, allowing heretofore unobtainable numerical resolution. Convergence studies to be described in a subsequent paper demonstrate that about 100 zones per cloud radius are needed for accurate results; previous calculations have generally used about a third of this number. The results of the calculations are analyzed in terms of global quantities which provide an overall description of te shocked cloud: the size and shape of the cloud, the mean density, the mean pressure, the mean velocity, the velocity dispersion, and the total circulation.

Klein, Richard I.; Mckee, Christopher F.; Colella, Philip

1994-01-01

61

Experimental model of topological defects in Minkowski spacetime based on disordered ferrofluid: magnetic monopoles, cosmic strings and the spacetime cloak  

E-print Network

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.

Igor I. Smolyaninov; Vera N. Smolyaninova; Alexei I. Smolyaninov

2014-09-24

62

Experimental model of topological defects in Minkowski spacetime based on disordered ferrofluid: magnetic monopoles, cosmic strings and the spacetime cloak  

E-print Network

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.

Smolyaninov, Igor I; Smolyaninov, Alexei I

2014-01-01

63

Estimating hydrodynamic roughness in a wave-dominated environment with a high-resolution acoustic Doppler profiler  

USGS Publications Warehouse

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

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

2005-01-01

64

Six-dimensional supersymmetric gauge theories, quantum cohomology of instanton moduli spaces and gl( N) Quantum Intermediate Long Wave Hydrodynamics  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

65

Passive Magnetic Bearing With Ferrofluid Stabilization  

NASA Technical Reports Server (NTRS)

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

Jansen, Ralph; DiRusso, Eliseo

1996-01-01

66

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

NASA Astrophysics Data System (ADS)

Millimeter-sized, spherical silicate grains abundant in chondritic meteorites, which are called as chondrules, are considered to be a strong evidence of the melting event of the dust particles in the protoplanetary disk. One of the most plausible scenarios is that the chondrule precursor dust particles are heated and melt in the high-velocity gas flow (shock-wave heating model). We developed the non-linear, time-dependent, and three-dimensional hydrodynamic simulation code for analyzing the dynamics of molten droplets exposed to the gas flow. We confirmed that our simulation results showed a good agreement in a linear regime with the linear solution analytically derived by Sekyia et al. [Sekyia, M., Uesugi, M., Nakamoto, T., 2003. Prog. Theor. Phys. 109, 717-728]. We found that the non-linear terms in the hydrodynamical equations neglected by Sekiya et al. [Sekiya, M., Uesugi, M., Nakamoto, T., 2003. Prog. Theor. Phys. 109, 717-728] can cause the cavitation by producing negative pressure in the droplets. We discussed that the fragmentation through the cavitation is a new mechanism to determine the upper limit of chondrule sizes. We also succeeded to reproduce the fragmentation of droplets when the gas ram pressure is stronger than the effect of the surface tension. Finally, we compared the deformation of droplets in the shock-wave heating with the measured data of chondrules and suggested the importance of other effects to deform droplets, for example, the rotation of droplets. We believe that our new code is a very powerful tool to investigate the hydrodynamics of molten droplets in the framework of the shock-wave heating model and has many potentials to be applied to various problems.

Miura, Hitoshi; Nakamoto, Taishi

2007-05-01

67

A Novel Implantable Glaucoma Valve Using Ferrofluid  

PubMed Central

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

Paschalis, Eleftherios I.; Chodosh, James; Sperling, Ralph A.; Salvador-Culla, Borja; Dohlman, Claes

2013-01-01

68

A Novel Application of Ferrofluid Actuation with PDMS Microchannel  

Microsoft Academic Search

Ferrofluid is usually used as actuation medium in micropump or microvalve where most microchannels were fabricated with PMMA or silicon. The manufacturing is time-consuming and costly. In this paper, we present a novel microchip design based on the magnetic actuation of ferrofluid. The device contains plugs and pistons formed by a ferrofluid which is actuated by an external NdFeB permanent

Yaw-Jen Chang; Chih-Yu Hu; Chu-Hsuan Lin

2010-01-01

69

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

Microsoft Academic Search

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

W. Magda

2000-01-01

70

Solid-Liquid Transition and Hydrodynamic Surface Waves in Vibrated Granular Layers  

Microsoft Academic Search

Experiments on thin layers of granular material subjected to vertical vibration have revealed a series of subharmonic bifurcations from flat surface to standing wave patterns. From pressure and surface dilation measurements we show that a solid-liquid-type transition precedes surface wave bifurcation, indicating that these waves are associated with the fluidlike behavior of the layer. Also, we show that depending on

Nicolás Mujica; Francisco Melo

1998-01-01

71

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

SciTech Connect

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

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

1997-09-01

72

Ferrofluid drops in rotating magnetic fields  

Microsoft Academic Search

Drops of a ferrofluid floating in a non-magnetic liquid of the same density and spun by a rotating magnetic field are investigated experimentally and theoretically. The parameters for the experiment are chosen such that different stationary drop shapes including non-axis-symmetric configurations could be observed. Within an approximate theoretical analysis the character of the occurring shape bifurcations, the different stationary drop

Alexander V. Lebedev; Andreas Engel; Konstantin I. Morozov; Heiko Bauke

2003-01-01

73

Ferrofluid based micro-electrical energy harvesting  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

74

Magnetoviscosity and orientational order parameters of dilute ferrofluids  

NASA Astrophysics Data System (ADS)

The linear and nonlinear rheological behavior of dilute ferrofluids is determined from an underlying kinetic model and the dependence of the viscosity coefficient on the scalar orientational order parameters is obtained. In case of uniaxial symmetry, the antisymmetric contribution to the hydrodynamic stress tensor is of the same form as in the classical Ericksen-Leslie theory of uniaxial nematic liquid crystals and the linear magnetoviscosity is found to coincide with earlier results obtained by the so-called effective field method. While the assumption of uniaxial symmetry is fulfilled exactly in the limit of strong vorticity and weak magnetic field, the exact result for the linear magnetoviscosity shows corrections due to contributions from biaxial symmetry. Measures for the deviations from uniaxial symmetry are introduced and the generalization of the stress tensor in case of biaxial symmetry is obtained. The investigations are accompanied by numerical simulation of the kinetic equation and reveal that the assumption of uniaxial symmetry seems to be a good approximation for most values of the magnetic field and vorticity.

Ilg, Patrick; Kröger, Martin; Hess, Siegfried

2002-05-01

75

Ferrofluid aggregates phase transitions in the planar magnetic field  

E-print Network

The influence of the cyclic heating and cooling on properties of the aggregates (aka "ferrofluid clusters") in a ferrofluid, which made on the basis of magnetite nanoparticles, are investigated. The heating of the ferrofluid layer with such aggregates leads to equalization of the concentration between high- and low-concentrated phases. The temperature of the equalization of the phase concentrations was determined at different values of an external constant magnetic field, which was applied parallel to the layer of the ferrofluid. The temperature of the destruction of a periodic structure of the magnetic aggregates, which were formed during cooling of a homogeneous phase of the ferrofluid, was obtained at the different values of the applied external magnetic field.

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

2014-04-21

76

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

NASA Astrophysics Data System (ADS)

We present a semi-phenomenological treatment of light transmission through and its reflection from a ferrofluid which we regard as a magnetically tunable system of dense random dielectric scatterers with dissipation. Partial spatial ordering is introduced by the application of a transverse magnetic field that superimposes a periodic modulation on the dielectric randomness. This causes Bragg scattering that effectively enhances the scattering due to the disorder alone, and thus reduces the elastic mean free path towards Anderson localization. A theoretical treatment, based on invariant imbedding, gives a simultaneous decrease of the transmission and the reflection without change of incident linear polarisation as the spatial order is tuned magnetically to the Bragg condition, namely the light wave vector being equal to half the Bragg vector (Q). Our experimental observations are in qualitative agreement with these results. We have also given expressions for the transit (sojourn) time of the light, and for the light energy stored in the random medium under a steady illumination. The ferrofluid thus provides an interesting physical realization of effectively a "Lossy Anderson-Bragg" (LAB) cavity with which to study the effect of interplay of the spatial disorder, partial order and the dissipation on light transport. Given current interests in the light propagation, optical limiting and the storage of light in ferrofluids, the present work seems topical.

Shalini, M.; Sharma, D.; Deshpande, A. A.; Mathur, D.; Ramachandran, Hema; Kumar, N.

2012-01-01

77

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

USGS Publications Warehouse

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

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

2011-01-01

78

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

SciTech Connect

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

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

2005-05-15

79

Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas  

E-print Network

We discuss complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider contribution of the annihilation interaction in the quantum hydrodynamic equations and in spectrum of waves in magnetized electron-positron plasmas. We consider propagation of waves parallel and perpendicular to an external magnetic field. We also consider oblique propagation of longitudinal waves. We derive set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory for the linear wave behavior in absence of external fields. We calculate contribution of the Darwin...

Andreev, Pavel A

2014-01-01

80

Wake II model for hydrodynamic forces on marine pipelines for the wave plus current case  

E-print Network

Effective Velocity 1. 4 Objective of the Research. 1. 5 Organization. I 3 4 6 8 12 13 13 II WAKE II MODEL FOR WAVES PLUS CURRENT. . . . 15 2. 1 Wake Velocity for Wave plus Current. . . . . . Phase A. . Phase B. . Local Keulegan... for the Calibration. 3. 2 Cases Covered in the Study. . 3. 3 Determination of the Wake Correction Parameters. . . . . . . . 3. 4 Determination of the Constants for the Start-up Effect. . . 26 27 28 31 IV COMPARISON OF WAKE II MODEL FOR WAVES PLUS CURRENT...

Ramirez Sabag, Said

2012-06-07

81

Preliminary hydrodynamic analysis of landslide-generated waves in Tidal Inlet, Glacier Bay National Park, Alaska  

USGS Publications Warehouse

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

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

2003-01-01

82

Magnetic and rheological characterization of novel ferrofluids  

NASA Astrophysics Data System (ADS)

A new type of magnetic fluid containing silica-coated magnetic nanoparticles has been synthesized. The particles are produced by a flame synthesis and have been dispersed in an oily medium to obtain the magnetic fluid. By means of magnetic and rheological investigations the basic properties of these fluids were determined. It could be seen, that the fluids show the well known paramagnetic behavior of ferrofluids with a small hysteresis due to the large domain size of the magnetic particles. Moreover strong dependencies of the rheological functions on magnetic field strength could be observed.

Kroell, M.; Pridoehl, M.; Zimmermann, G.; Pop, L.; Odenbach, S.; Hartwig, A.

2005-03-01

83

Miscible ferrofluid patterns in a radial magnetic field  

NASA Astrophysics Data System (ADS)

Pattern formation in a miscible ferrofluid system is experimentally investigated. The experiment is performed by immersing a thin ferrofluid droplet in a cylindrical container, overfilling it with a nonmagnetic miscible fluid, and applying an in-plane radial magnetic field. Visually striking patterns are obtained whose morphologies change from circular at zero field to complex starburstlike structures at finite field. The evolution of miscible ferrofluid droplets of various initial diameters subjected to different magnetic-field strengths is considered. Proper rescaling of the experimental data indicates that the time evolution of the droplets’ area increments obeys a universal 4/3 power-law behavior at long times.

Chen, Ching-Yao; Yang, Y.-S.; Miranda, José A.

2009-07-01

84

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

Microsoft Academic Search

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

Ingo HENNINGS; Blandine LURIN; C. VERNEMMEN

85

Waves in Radial Gravity Using Magnetic Fluid  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

87

Stable and water-tolerant ionic liquid ferrofluids.  

PubMed

Ionic liquid ferrofluids have been prepared containing both bare and sterically stabilized 8-12 nm diameter superparamagnetic iron oxide nanoparticles, which remain stable for several months in both protic ethylammonium and aprotic imidazolium room-temperature ionic liquids. These ferrofluids exhibit spiking in static magnetic fields similar to conventional aqueous and nonaqueous ferrofluids. Ferrofluid stability was verified by following the flocculation and settling behavior of dilute nanoparticle dispersions. Although bare nanoparticles showed excellent stability in some ILs, they were unstable in others, and exhibited limited water tolerance. Stability was achieved by incorporating a thin polymeric steric stabilization layer designed to be compatible with the IL. This confers the added benefit of imbuing the ILF with a high tolerance to water. PMID:21338083

Jain, Nirmesh; Zhang, Xiaoli; Hawkett, Brian S; Warr, Gregory G

2011-03-01

88

Ferrofluid surface and volume flows in uniform rotating magnetic fields  

E-print Network

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

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

2006-01-01

89

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

E-print Network

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

Khushrushahi, Shahriar Rohinton

2010-01-01

90

A ferrofluidic deformable mirror for ophthalmology  

NASA Astrophysics Data System (ADS)

Optical aberrations reduce the imaging quality of the human eye. In addition to degrading vision, this limits our ability to illuminate small points of the retina for therapeutic, surgical or diagnostic purposes. When viewing the rear of the eye, aberrations cause structures in the fundus to appear blurred, limiting the resolution of ophthalmoscopes (diagnostic instruments used to image the eye). Adaptive optics, such as deformable mirrors may be used to compensate for aberrations, allowing the eye to work as a diffraction-limited optical element. Unfortunately, this type of correction has not been widely available for ophthalmic applications because of the expense and technical limitations of current deformable mirrors. We present preliminary design and characterisation of a deformable mirror suitable for ophthalmology. In this ferrofluidic mirror, wavefronts are reflected from a fluid whose surface shape is controlled by a magnetic field. Challenges in design are outlined, as are advantages over traditional deformable mirrors.

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

2005-09-01

91

Experimental investigation of magnetically driven flow of ferrofluids in porous media  

SciTech Connect

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

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

1998-08-01

92

Stress relaxation in a ferrofluid with clustered nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

93

Stress relaxation in a ferrofluid with clustered nanoparticles.  

PubMed

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

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

2014-10-01

94

Experimental demonstration of metamaterial "multiverse" in a ferrofluid.  

PubMed

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

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

2013-06-17

95

Magneto-viscosity of MnZn-ferrite ferrofluid  

NASA Astrophysics Data System (ADS)

Mn0.75Zn0.25Fe2O4 (MZF) ferrofluid was synthesized using a precipitation method in ethylene glycol colloidal media. The x-ray diffraction and transmission electron microscope studies show nanophase of the MZF ultra fine nanoparticles. The magnetization (M) vs magnetic field (H) show zero coercivity and high saturation field characteristic of superparamagnetic behavior. The dynamic light scattering (DLS) data show the formation of aggregates or clusters with size distribution ranging from 50 to 600 nm. Magneto-viscosity of the ferrofluid is studied using rheological measurements under magnetic field up to 1.3 T. The behavior of shear rate vs effective shear viscosity (?) plot in zero and higher magnetic field changes from non-Newtonian to Newtonian as shear rate increases. At a steady shear rate irreversible nonlinear behavior is observed in ? vs H plots. The data indicate the particle size distribution and formation of chains in the ferrofluid with increase in magnetic field.

Thirupathi, Gadipelly; Singh, Rajender

2014-09-01

96

Magnetically tunable terahertz magnetoplasmons in ferrofluid-filled photonic crystals  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

97

Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas  

E-print Network

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

Pavel A. Andreev

2014-04-18

98

A rheological and microscopical characterization of biocompatible ferrofluids  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

99

Onset of Particle Rotation in a Ferrofluid Shear Flow  

Microsoft Academic Search

A ferrofluid shear flow subjected to a magnetic field is investigated in the limit where viscous and magnetic forces prevail over thermal fluctuations. When the viscous torque slightly exceeds the magnetic hold torque the nanoparticles start to rotate anharmonically. By means of a weak field modulation, the rotation of the particles can be phase synchronized generating an overproportional ac contribution

Hanns Walter Müller

1999-01-01

100

The effects of polydispersity on the initial susceptibilities of ferrofluids  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

101

The effects of polydispersity on the initial susceptibilities of ferrofluids.  

PubMed

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

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

2014-11-12

102

Two-Dimensional Melting of a Crystal of Ferrofluid Spikes  

Microsoft Academic Search

We report the observation of the transition from an ordered solidlike phase to a disordered liquidlike phase of a lattice of spikes on a ferrofluid surface submitted to horizontal sinusoidal vibrations. The melting transition occurs for a critical spike displacement which is experimentally found to follow the Lindemann criterion, for two different lattice topologies (hexagonal and square) and over a

François Boyer; Eric Falcon

2009-01-01

103

RESPONSE STATISTICS OF OCEAN STRUCTURES TO NON-LINEAR HYDRODYNAMIC LOADING PART II: NON-GAUSSIAN OCEAN WAVES  

Microsoft Academic Search

In this second part, the response statistics of ocean elastic systems to non-linear hydrodynamic loading represented by a non-Gaussian random process are considered. The non-Gaussian process is generated from a non-linear filter excited by a white noise process. The filter non-linearity is represented by a gradient of a potential function where an exact closed form solution of the stationary probability

N. Moshchuk; R. A. Ibrahim

1996-01-01

104

Wave Control Introduction  

E-print Network

Waves Conclusion Appendix 1. Introduction Some hydrodynamics . . . rogue waves are anomalously high focussing: in crossing seas due to coastal or submarine convergences. Moreover, (rogue) wave energy devices

Wirosoetisno, Djoko

105

Penetration of surface-inoculated bacteria as a result of electrically generated hydrodynamic shock wave treatment of boneless skinless chicken breasts.  

PubMed

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

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

2003-07-01

106

Preparation of a biocompatible magnetic film from an aqueous ferrofluid  

NASA Astrophysics Data System (ADS)

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

Albornoz, Cecilia; Jacobo, Silvia E.

2006-10-01

107

Study on the Ferrofluid Lubrication with an External Magnetic Field  

Microsoft Academic Search

Ferrofluids (FFs) are stable colloidal systems consisting of single-domain magnetic particles with a diameter of approximately\\u000a 10 nm coated with surfactants and dispersed in a carrier liquid. By applying an external magnetic field, these fluids can\\u000a be confined, positioned, shaped and, controlled at desired places. The load capacity of a lubricant film of FF can also be\\u000a increased with an appropriate

Wei Huang; Cong Shen; Sijie Liao; Xiaolei Wang

2011-01-01

108

Magnetic Soret effect: Application of the ferrofluid dynamics theory  

E-print Network

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

Adrian Lange

2004-11-11

109

Accelerated thermal aging of petroleum-based ferrofluids  

NASA Astrophysics Data System (ADS)

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

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

1999-07-01

110

Immunomagnetic cell separation, imaging, and analysis using Captivate ferrofluids  

NASA Astrophysics Data System (ADS)

We have developed applications of CaptivateTM ferrofluids, paramagnetic particles (approximately 200 nm diameter), for isolating and analyzing cell populations in combination with fluorescence-based techniques. Using a microscope-mounted magnetic yoke and sample insertion chamber, fluorescent images of magnetically captured cells were obtained in culture media, buffer, or whole blood, while non-magnetically labeled cells sedimented to the bottom of the chamber. We combined this immunomagnetic cell separation and imaging technique with fluorescent staining, spectroscopy, and analysis to evaluate cell surface receptor-containing subpopulations, live/dead cell ratios, apoptotic/dead cell ratios, etc. The acquired images were analyzed using multi-color parameters, as produced by nucleic acid staining, esterase activity, or antibody labeling. In addition, the immunomagnetically separated cell fractions were assessed through microplate analysis using the CyQUANT Cell Proliferation Assay. These methods should provide an inexpensive alternative to some flow cytometric measurements. The binding capacities of the streptavidin- labled Captivate ferrofluid (SA-FF) particles were determined to be 8.8 nmol biotin/mg SA-FF, using biotin-4- fluorescein, and > 106 cells/mg SA-FF, using several cell types labeled with biotinylated probes. For goat anti- mouse IgG-labeled ferrofluids (GAM-FF), binding capacities were established to be approximately 0.2 - 7.5 nmol protein/mg GAM-FF using fluorescent conjugates of antibodies, protein G, and protein A.

Jones, Laurie; Beechem, Joseph M.

2002-05-01

111

Study of the deformation of ferrofluid droplets in a magnetic field  

E-print Network

L-179 Study of the deformation of ferrofluid droplets in a magnetic field J.-C. Bacri, D. Salin) in a weak magnetic field (up to 10 gauss) for a new kind of ferrofluid. The ellipsoid shape of the agglomerate is due to a competition between magnetic energy which favours elongated agglomerates in the field

Boyer, Edmond

112

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

DOEpatents

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

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

2001-01-01

113

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

Microsoft Academic Search

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

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

2003-01-01

114

3D hydrodynamic modelling of fixed oscillating water column wave power plant by a boundary element methods  

Microsoft Academic Search

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

Y. M. C. Delauré; A. Lewis

2003-01-01

115

Two-Dimensional Melting of a Crystal of Ferrofluid Spikes  

E-print Network

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

François Boyer; Eric Falcon

2009-09-18

116

Hydrodynamic Simulation  

NASA Astrophysics Data System (ADS)

The main aim of this lecture is to provide a broad overview of the area of hydrodynamic simulation. The provision of introductions to a couple of basic algorithms for solving the equations of gas dynamics is a secondary objective. Hydrodynamic simulation in the context of laser-plasma physics and inertial fusion is now a large and mature field, deserving of an entire book (or books…) for a proper treatment. Individual topics will not be treated in great depth, and mathematical detail is avoided where possible. It is hoped that the reader will understand the key aspects of hydrodynamic simulation and the ability to write a very simple 1D hydro-solver with a view to using this knowledge as a "springboard" for more in-depth study.

Robinson, Alex P. L.

117

Use of a ferrofluid as the heat-exchange fluid in a magnetic refrigerator  

SciTech Connect

The use of a ferrofluid is proposed as the heat-exchange fluid in a wheel-type magnetic refrigerator in order to avoid flow-control problems. An equivalent-circuit analysis of the ferrofluid flow path with several different magnetic field profiles indicates that it is possible to obtain the desired flow control in at least one case. Sample design calculations for the revised wheel-type refrigerator are presented. In addition, the results of heat-transfer measurements from kerosene to a stainless-steel screen and from a kerosene-base ferrofluid to the same screen in and out of an 8-T magnetic field are described.

Barclay, J.A.

1982-04-01

118

Ship Hydrodynamics  

ERIC Educational Resources Information Center

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

Lafrance, Pierre

1978-01-01

119

A comparative study of different ferrofluid constitutive equations.  

NASA Astrophysics Data System (ADS)

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

Kaloni, Purna

2011-11-01

120

Rheological investigations of ferrofluids with a shear stress controlled rheometer.  

PubMed

The appearance of field- and shear-dependent changes of viscosity-the magnetoviscous effect-is correlated to the formation of chains and structures of magnetic nanoparticles. Moreover, the formation of these structures leads to the appearance of viscoelastic effects or other non-Newtonian features in ferrofluids in the presence of a magnetic field. In order to describe these phenomena, different theoretical approaches have been developed which explain the mechanism of these effects with different assumptions. One point in which these models differ, and which has to be clarified, is the appearance of yield stress and its dependence on magnetic field strength. With this aim, a stress controlled rheometer has been designed to prove the existence of this very small field-dependent yield stress for ferrofluids. The results presented here show a dependence of the yield stress on the magnetic field strength as well as on the interparticle interaction and particle size distribution. Finally, yield stress experiments have been performed for different geometries of the shear cell in order to get more information about the microstructure formed by the magnetic particles. PMID:21694266

Shahnazian, Hamid; Odenbach, Stefan

2008-05-21

121

Effects of demagnetizing factors on transient motion of ferrofluid in a uniform rotating magnetic field  

E-print Network

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

Snively, Michael John

2011-01-01

122

Design and manufacture of a modular cylindrical apparatus for ferrofluid experimentation  

E-print Network

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

Schoen, Katrina Leigh

2011-01-01

123

Ferrofluid dynamics in a Hele-Shaw cell simultaneously stressed by DC and rotating magnetic fields  

E-print Network

Earlier experiments have been repeated to evaluate magnetic fluid behavior in DC, AC and rotating magnetic fields. Understanding these behaviors are essential to the ferrohydrodynamic applications of ferrofluids in ...

Orji, Uzoma A

2007-01-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

125

Effect of an alternating nonuniform magnetic field on ferrofluid flow and heat transfer in a channel  

NASA Astrophysics Data System (ADS)

Forced convective heat transfer of water based Fe3O4 nanofluid (ferrofluid) in the presence of an alternating non-uniform magnetic field is investigated numerically. The geometry is a two-dimensional channel which is subjected to a uniform heat flux at the top and bottom surfaces. Nonuniform magnetic field produced by eight line source dipoles is imposed on several parts of the channel. Also, a rectangular wave function is applied to the dipoles in order to turn them on and off alternatingly. The effects of the alternating magnetic field strength and frequency on the convective heat transfer are investigated for four different Reynolds numbers (Re=100, 600, 1200 and 2000) in the laminar flow regime. Comparing the results with zero magnetic field case, show that the heat transfer enhancement increases with the Reynolds number and reaches a maximum of 13.9% at Re=2000 and f=20 Hz. Moreover, at a constant Reynolds number, it increases with the magnetic field intensity while an optimum value exists for the frequency. Also, the optimum frequency increases with the Reynolds number. On the other hand, the heat transfer enhancement due to the magnetic field is always accompanied by a pressure drop penalty. A maximum pressure drop increase of 6% is observed at Re=2000 and f=5 Hz which shows that the pressure drop increase is not as significant as the heat transfer enhancement.

Goharkhah, Mohammad; Ashjaee, Mehdi

2014-08-01

126

On the Hydrodynamic Interaction of Shock Waves with Interstellar Clouds. II. The Effect of Smooth Cloud Boundaries on Cloud Destruction and Cloud Turbulence  

NASA Astrophysics Data System (ADS)

The effect of smooth cloud boundaries on the interaction of steady planar shock waves with interstellar clouds is studied using a local adaptive mesh refinement technique with an axisymmetric Godunov hydrodynamic scheme. A three-dimensional calculation is also done to confirm the two-dimensional results. We find that smooth cloud boundaries significantly affect cloud morphology and retard cloud destruction. After shock passage, a sharp density jump forms due to velocity gradients generated in the smooth cloud boundary. We refer to this density jump as a ``slip surface'' because the velocity is sheared parallel to its surface. The formation of a slip surface leads to complete cloud destruction because of the Kelvin-Helmholtz and Rayleigh-Taylor instabilities. We construct analytic models of cloud drag and vorticity generation that compare well with the numerical results. Small shreds formed by the instabilities have significant velocity dispersions of 10%-20% of the ambient shock velocity. They could be related to the small cold H I clouds recently observed by Stanimirovi? & Heiles. The dependence of the velocity dispersion on region size, the so-called line width-size relation, is found to be time-dependent. In the early stages, the line width-size relation is more or less flat because of the significant small-scale fluctuations generated by the Kelvin-Helmholtz instability. In the later stages, the small-scale fluctuations tend to damp, leading to a line width that increases with size. The possibility of gravitational instability triggered by shock compression is discussed. We show that gravitational collapse can be induced in an initially uniform cloud by a radiative shock (?<4/3) only if it is not too strong and nonthermal motions are weak.

Nakamura, Fumitaka; McKee, Christopher F.; Klein, Richard I.; Fisher, Robert T.

2006-06-01

127

A NEW MULTI-DIMENSIONAL GENERAL RELATIVISTIC NEUTRINO HYDRODYNAMICS CODE OF CORE-COLLAPSE SUPERNOVAE. III. GRAVITATIONAL WAVE SIGNALS FROM SUPERNOVA EXPLOSION MODELS  

SciTech Connect

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

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

2013-03-20

128

Concentration and temperature effect in microstructure of ferrofluids  

NASA Astrophysics Data System (ADS)

The spatial correlations in magnetite-based ferrofluids (FF) with pentanol carrier have been investigated by small-angle neutron scattering, as dependent on the concentration of magnetic phase ( C=0.6-20 vol%) and temperature (20-85 °C). Some peculiarities in the structure of FF were detected. An anomalous increase of short range order by heating of low-concentrated FF ( C˜0.6-4.0 vol%); the formation of short range order at ambient temperature which weakens at growing concentrations C=7-14 vol% and the existence of a stable structure at the highest concentration C˜20 vol% when particles' shell interpenetrate. Neutron scattering data are discussed with regard to the particles' intrinsic magnetisation enhancement induced by ordering.

Török, Gy.; Lebedev, V. T.; Bica, D.; Vékás, L.; Avdeev, M. V.

2006-05-01

129

Photonic Dipole Contours of Ferrofluid Hele-Shaw Cell  

E-print Network

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.

Michael Snyder; Jonathan Frederick

2008-05-28

130

Planar Steering of a Single Ferrofluid Drop by Optimal Minimum Power Dynamic Feedback Control of Four Electromagnets at a Distance  

PubMed Central

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

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

2010-01-01

131

Magnetic field role on the structure and optical response of photonic crystals based on ferrofluids containing Co0.25Zn0.75Fe2O4 nanoparticles  

NASA Astrophysics Data System (ADS)

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.

2014-05-01

132

No aging phenomena in ferrofluids: the influence of coating on interparticle interactions of maghemite nanoparticles.  

PubMed

The influence of coating on interparticle interactions in ferrofluids has been investigated using various techniques such as Mossbauer spectroscopy, magnetometry, transmission electron microscopy, photon correlation spectroscopy, X-ray diffraction, X-ray photoelectron, and resonance micro-Raman spectroscopy. Aging and spin-glass-like behavior was investigated in frozen ferrofluids of various concentrations from dense, initial value of 40 mg of coated nanoparticles per 1 mL of water, to dilute 1:10 (4 mg/mL). The as-prepared nanoparticles, core size 7-8 nm, were subsequently coated with a gummic acid corona of 20 nm thickness, which was observed to prevent agglomeration and to delay aggregation even in dense ferrofluids. The resulting separation of magnetic cores due to the coating eliminated all magnetic interparticle interaction mechanisms, such as exchange and dipoledipole, thus ensuring no aging effects of the magnetic particle system, as manifested in particle agglomeration and precipitation. PMID:19206495

Rabias, Ioannis; Fardis, Michael; Devlin, Eamonn; Boukos, Nikos; Tsitrouli, Danai; Papavassiliou, George

2008-05-01

133

Flow in isothermal layers of ferrofluid by action of uniform rotating magnetic field  

SciTech Connect

The author attempts to determine how intense the flow of a ferrofluid in a rotating magnetic field can become owing to the temperature dependence of the properties when a nonuniform temperature field has been produced within the volume of such a fluid. It was found that in a channel with a strong temperature dependence of viscosity, a uniform rotating magnetic field is capable of effectively influencing the flow of a ferrofluid within nonisothermal layers, which may be of interest in solving problems of heat transfer.

Kashevskii, B.E.

1986-01-01

134

Meniscus of a ferrofluid around a vertical cylindrical wire carrying electric current  

NASA Astrophysics Data System (ADS)

We study the meniscus profiles of ferrofluids in the magnetic field of a vertical current-carrying wire. Measurements of the free ferrofluid surface profile are quantitatively compared with numerical calculations. The theoretical model leads to a second-order ordinary differential equation. All material parameters are determined in independent experiments, therefore no fitting parameters are involved in the calculations. The experimental results can be modeled by the equilibrium of magnetic, gravitational, and interface tension forces. The classical model that neglects interface tension yields significant deviations from the experimental profiles in the parameter range studied.

John, Thomas; May, Kathrin; Stannarius, Ralf

2011-05-01

135

Perspectives in coral reef hydrodynamics  

NASA Astrophysics Data System (ADS)

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

Hearn, Clifford J.

2011-06-01

136

Magnetic-field-induced structural transitions in a ferrofluid emulsion  

NASA Astrophysics Data System (ADS)

A ferrofluid emulsion, subjected to a slowly increasing magnetic field, exhibits a complicated structural behavior: a gas of Brownian particles changes to columnar solid structures due to induced dipole interaction. Two transition (intermediate) structural regimes are observed: (i) randomly distributed chains and particles and (ii) distinct thin columns and randomly distributed chains and particles. Three structural transition magnetic fields are found, one marking each structural transition, from the initial to the final structural regime. A structural diagram of the structural transition magnetic fields, HC, versus particle volume fractions, ?, is constructed experimentally. Theoretical models of scaling calculations, based upon the dominant magnetic interaction in each structural regime, give the three structural transition magnetic-field relations as HC1~?-1/2, HC2~?-1/4, and HC3~(??/G2)exp(?G/ ?(?/2)), where ?=0.39 and G=0.29 for our sample. The final end shape of columns and the relative position between columns show that the end-end repulsion between chains is important in the structural formation.

Ivey, Mark; Liu, Jing; Zhu, Yun; Cutillas, Serge

2001-01-01

137

Natural convection of ferrofluids in partially heated square enclosures  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

138

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

SciTech Connect

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

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

1998-03-01

139

Advances in Wave Turbulence Optical Wave Turbulence  

E-print Network

nonlinear phenomenon which occurs in a variety of nonlinear wave- bearing physical systems. The experimental impediments and the computationally intensive nature of simulating of hydrodynamic or plasma wave turbulence

Turitsyn, Sergei K.

140

Shallow Water Waves and Solitary Waves Willy Hereman  

E-print Network

of nonlinear hydrodynamics. Solitary waves have finite amplitude and propagate with constant speed and constant earthquake, a submarine volcanic eruption, or by a landslide. Wave dispersion Wave dispersion in water waves centuries, Stokes (1847) is considered one of the pioneers of hydrodynamics (see Craik 2005). He carefully

Hereman, Willy A.M.

141

Shallow Water Waves and Solitary Waves Willy Hereman  

E-print Network

of nonlinear hydrodynamics. Solitary waves have finite amplitude and propagate with constant speed and constant earthquake, a submarine volcanic eruption, or by a landslide. Wave dispersion Wave dispersion in water waves century, Stokes (1847) is considered one of the pioneers of hydrodynamics (see Craik 2005). He carefully

Hereman, Willy A.M.

142

Superradiant scattering from a hydrodynamic vortex  

E-print Network

We show that sound waves scattered from a hydrodynamic vortex may be amplified. Such superradiant scattering follows from the physical analogy between spinning black holes and hydrodynamic vortices. However a sonic horizon analogous to the black hole event horizon does not exist unless the vortex possesses a central drain, which is challenging to produce experimentally. In the astrophysical domain, superradiance can occur even in the absence of an event horizon: we show that in the hydrodynamic analogue, a drain is not required and a vortex scatters sound superradiantly. Possible experimental realization in dilute gas Bose-Einstein condensates is discussed.

T. R. Slatyer; C. M. Savage

2005-01-10

143

Hydrodynamic compressibility of high-strength ceramics  

SciTech Connect

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

Grady, D.E.

1993-08-01

144

2 HYDRODYNAMIC MODELING IN THE GREAT LAKES FROM  

E-print Network

friction. Coriolis force Wind waves Hydrologic models Wind stress, wave energy. wave dissipation41 2 HYDRODYNAMIC MODELING IN THE GREAT LAKES FROM 1950 TO 1990 AND PROSPECTS FOR THE 1990S DAVID 1, tidal models. wind wave models, and hydrologic models. The main types of lake circulation and thermal

145

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

146

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

Microsoft Academic Search

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

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

2008-01-01

147

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

NASA Astrophysics Data System (ADS)

The particle structure of ferrofluids is studied in situ, by cryogenic electron microscopy, on vitrified films of iron and magnetite dispersions. By means of synthesis of iron colloids with controlled particle size and different types of surfactant, dipolar particle interactions can be varied over a broad range, which significantly influences the ferrofluid particle structure. Our experiments on iron dispersions (in contrast to magnetite dispersions) for the first time demonstrate, in ferrofluids in zero field, a transition with increasing particle size from separate particles to linear chains of particles (Butter K, Bomans P H, Frederik P M, Vroege G J and Philipse A P 2003 Nature Mater. 2 88). These chains, already predicted theoretically by de Gennes and Pincus (de Gennes P G and Pincus P A 1970 Phys. Kondens. Mater. 11 189), very much resemble the fluctuating chains found in simulations of dipolar fluids (Weis J J 1998 Mol. Phys. 93 361, Chantrell R W, Bradbury A, Popplewell J and Charles S W 1982 J. Appl. Phys. 53 2742). Decreasing the range of steric repulsion between particles by employing a thinner surfactant layer is found to change particle structures as well. The dipolar nature of the aggregation is confirmed by the alignment of existing chains and individual particles in the field direction upon vitrification of dispersions in a saturating magnetic field. Frequency-dependent susceptibility measurements indicate that particle structures in truly three-dimensional ferrofluids are qualitatively similar to those in liquid films.

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

2003-04-01

148

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

Microsoft Academic Search

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

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

2003-01-01

149

One-dimensional actuation of a ferrofluid droplet by planar microcoils  

Microsoft Academic Search

This paper discusses the simulation of a device for actuation of a ferrofluid droplet using planar microcoils. The device with two pairs of planar microcoils was designed and fabricated on a double-sided printed circuit board (PCB). Each pair is placed on each side of the PCB. The coils on the bottom actuate the droplet along the line connecting their centres.

Ali Beyzavi; Nam-Trung Nguyen

2009-01-01

150

Programmable two-dimensional actuation of ferrofluid droplet using planar microcoils  

Microsoft Academic Search

This paper reports the concept and the device for two-dimensional magnetic actuation of a ferrofluid droplet. Four planar microcoils were etched on one side of a printed circuit board (PCB). The magnetic field was digitally controlled by adjusting the magnitude and the polarity of the driving current in the coils. A computer programme generates the control signals, which are conditioned

Ali Beyzavi; Nam-Trung Nguyen

2010-01-01

151

Under consideration for publication in J. Fluid Mech. 1 Field-induced motion of ferrofluid droplets  

E-print Network

system is investigated in Mefford et al. (2007) with a ferrofluid drop, assumed to be a solid sphere, momentum equation and incompressibility. A numerical algorithm is derived to model the interface between-surface-force formulation is used to model the interfacial tension force as a body force, and the placement of the liquids

Renardy, Yuriko

152

Integration of quantum hydrodynamical equation  

NASA Astrophysics Data System (ADS)

Quantum hydrodynamics equations describing the dynamics of quantum fluid are a subject of this report (QFD).These equations can be used to decide the wide class of problem. But there are the calculated difficulties for the equations, which take place for nonlinear hyperbolic systems. In this connection, It is necessary to impose the additional restrictions which assure the existence and unique of solutions. As test sample, we use the free wave packet and study its behavior at the different initial and boundary conditions. The calculations of wave packet propagation cause in numerical algorithm the division. In numerical algorithm at the calculations of wave packet propagation, there arises the problem of division by zero. To overcome this problem we have to sew together discrete numerical and analytical continuous solutions on the boundary. We demonstrate here for the free wave packet that the numerical solution corresponds to the analytical solution.

Ulyanova, Vera G.; Sanin, Andrey L.

2007-04-01

153

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

PubMed

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

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

2011-11-01

154

Waves in Radial Gravity Using Magnetic Fluid  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

155

Gas-dynamic signs of explosive eruptions of volcanoes. 1. Hydrodynamic analogs of the pre-explosion state of volcanoes, dynamics of the three-phase magma state in decompression waves  

NASA Astrophysics Data System (ADS)

Experimental data and results of numerical simulations of the magma state dynamics in explosive eruptions of volcanoes are presented. The pre-explosion state of volcanoes and the cavitation processes developed in the magma under explosive decompression are studied under the assumption that the intensity of explosive volcanoes does not exert any significant effect on the eruption mechanisms. In terms of the structural features of the pre-explosion state, a number of explosive volcanic systems are close to hydrodynamic shock-tube schemes proposed by Glass and Heuckroth. High-velocity processes initiated by shock-wave loading of the liquid may be considered as analogs of natural volcanic processes, which have common gas-dynamic features and common kinetics responsible for their mechanisms, regardless of the eruption intensity.

Kedrinskii, V. K.

2008-11-01

156

Magneto-optical granulometry: on the determination of the statistics of magnetically induced particle chains in concentrated ferrofluids from linear dichroism experiments  

E-print Network

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

V. Socoliuc; L. B. Popescu

2014-10-09

157

Laboratory Experiments on Wave Turbulence  

E-print Network

This review paper is devoted to a presentation of recent progress in wave turbulence. I first present the context and state of the art of this field of research both experimentally and theoretically. I then focus on the case of wave turbulence on the surface of a fluid, and I discuss the main results obtained by our group: caracterization of the gravity and capillary wave turbulence regimes, the first observation of intermittency in wave turbulence, the occurrence of strong fluctuations of injected power in the fluid, the observation of a pure capillary wave turbulence in low gravity environment and the observation of magnetic wave turbulence on the surface of a ferrofluid. Finally, open questions in wave turbulence are discussed.

Eric Falcon

2010-01-05

158

Smoothed Particle Hydrodynamics  

E-print Network

27 Chapter 2 Smoothed Particle Hydrodynamics The smoothed particle hydrodynamics (SPH) technique to solving the time evolution of hydrodynamic equations. Later, a derivation of SPH in terms of interpolation for simulating hydrody­ namic phenomena was first described by Lucy (1977). It was originally developed for use

Bate, Matthew

159

Hydrodynamic Simulations of Planetary Rings  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

160

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

161

Electromagnetic Induction Heat Generation of Nano-ferrofluid and Other Stimulants for Heavy Oil Recovery  

NASA Astrophysics Data System (ADS)

Nano-ferrofluid and graphite-fluid are proposed to be used as stimulants for heavy oil recovery processes using electromagnetic induction. The heat generation in the stimulants will be used for reducing the viscosity of heavy oil. The temperature increase of the stimulants are observed with the presence of electromagnetic induction. These increments are better compared to those of the varying concentration of salt water (brine) usually exist in the oil reservoir.

Pramana, A. A.; Abdassah, D.; Rachmat, S.; Mikrajuddin, A.

2010-10-01

162

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

SciTech Connect

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

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

2008-11-15

163

Magnetic and optical properties of ionic ferrofluids based on nickel ferrite nanoparticles  

Microsoft Academic Search

New ionic ferrofluids containing NiFe2O4 nanoparticles of size <=10 nm are investigated. The crystalline structure of the particles is probed by transmission electron microscopy and x-ray scattering. Static magnetization and field-induced birefringence measurements are performed on three samples differing by particle volume fraction. Cross analyzing of the results of those two types of macroscopic tests completely rejects a simple single-domain

E. Hasmonay; J. Depeyrot; M. H. Sousa; F. A. Tourinho; J.-C. Bacri; R. Perzynski; Yu. L. Raikher; I. Rosenman

2000-01-01

164

Influence of impurities on hydrodynamic solitons  

Microsoft Academic Search

The interaction between impurities and solitary waves has been experimentally observed on the surface of a defective water layer subjected to vertical vibration. A slightly rugged surface on one sidewall of the water layer serves as the impurity, making the layer breadth at the defect slightly different elsewhere. A wide-breadth impurity will attract or pin not only the hydrodynamic breather

Weizhong Chen; Lei Lu; Yifei Zhu

2005-01-01

165

Fractional hydrodynamic equations for fractal media  

E-print Network

Fractional hydrodynamic equations for fractal media Vasily E. Tarasov * Skobeltsyn Institute for the fractal media and derive the fractional generalization of the equations of balance of mass density are considered. We derive the equilibrium equation for fractal media. The sound waves in the con- tinuous medium

Tarasov, Vasily E.

166

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

PubMed

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

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

2003-02-01

167

Waves  

E-print Network

WAVES BY Mari LaCure Submitted to the graduate degree program in Visual Art and the Graduate Faculty of the University of Kansas in partial fulfillment of the requirements for the degree of Master’s of Fine Arts. Yoonmi Nam Chairperson... Committee members: Shawn Bitters Michael Krueger Date Defended: March 10, 2010 2 The Thesis Committee for Mari LaCure certifies that this is the approved Version of the following thesis: WAVES...

LaCure, Mari Mae

2010-04-29

168

Static and quasi-elastic small angle neutron scattering on biocompatible ionic ferrofluids: magnetic and hydrodynamic interactions  

Microsoft Academic Search

We investigate the structure and dynamics of ionic magnetic fluids (MFs), based on ferrite nanoparticles, dispersed at pH ? 7 either in H2O or in D2O. Polarized and non-polarized static small angle neutron scattering (SANS) experiments in zero magnetic field allow us to study both the magnetic and the nuclear contributions to the neutron scattering. The magnetic interparticle attraction is

F Gazeau; F Boué; E Dubois; R Perzynski

2003-01-01

169

Modulation of short waves by long waves. [ocean wave interactions  

NASA Technical Reports Server (NTRS)

Wave-tank experiments were performed to investigate the cyclic short-wave energy changes, related in phase to an underlying long wave, which occur during active generation of the short-wave field by wind. Measurements of time series of the short-wave slope were made by a laser-optical system, where the basic long-wave parameters were controlled and wind speeds were accurately reproducible. The short-wave slope variances were found to exhibit cyclic variations that are related to the phase of the long wave. The variations result from two combined effects: (1) the short wave frequency is varied by the long-wave orbital velocity; (2) the energy of the short waves is modulated by the actions of aerodynamic and hydrodynamic couplings that operate on the short waves in a manner related to the long-wave phase.

Reece, A. M., Jr.

1978-01-01

170

Hydrodynamics of vegetated channels  

E-print Network

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

Nepf, Heidi

171

Structurization of ferrofluids in the absence of an external magnetic field  

SciTech Connect

Structural transformations in a model ferrofluid in the absence of an external magnetic field have been theoretically studied. The results agree with well-known laboratory experiments and computer simulations in showing that, if the concentration of particles and their magnetic interaction energy are below certain critical values, most particles form separate linear chains. If these parameters exceed the critical values, most particles concentrate so as to form branched network structures. The passage from chains to network has a continuous character rather than represents a discontinuous first-order phase transition.

Zubarev, A. Yu., E-mail: Andrey.Zubarev@usu.ru; Iskakova, L. Yu. [Ural Federal University (Russian Federation)] [Ural Federal University (Russian Federation)

2013-02-15

172

Effect of Anisotropy in Two-dimensional Dimer model of magnetic ferrofluids  

NASA Astrophysics Data System (ADS)

The magnetization and the Initial susceptibility have been calculated using statistical mechanics for two-dimensional structured dilute ferro-fluid taking the effect of the magnetic anisotropy and inter-particle interaction. We assumed the assembly consists of N/2 non-interacting systems. Each system is composed of 2 interacting single domain fine magnetic spherical particles. We referred to this model as a Dimer-model. We found that when the easy axis is fixed with respect to the external magnetic field, the ordering temperature depend on the anisotropy constant K in both parallel and perpendicular cases.

Obeidat, Abdalla; Al-Sharo, Wesam

2009-03-01

173

Mechanism of homeotropic alignment of ferroelectric liquid crystals doped with ferro-fluid and applications  

NASA Astrophysics Data System (ADS)

We report homeotropic (HT) alignment of ferroelectric liquid crystal (FLC) doped with various concentrations of ferro-fluid (FF) without using any type of alignment layer. The FF induced HT alignment of FLC was found to be dependent on the doping concentration as revealed by optical micrographs, contact angle, and dielectric spectroscopy studies. Higher water contact angle of FF doped FLC films with respect to pure FLC film suggests higher surface energy of FF doped FLC than the surface energy of substrate. The physico-chemical mechanism together with steric model successfully explains the HT alignment of the studied FLC on the ITO substrate.

Joshi, Tilak; Singh, Shri; Choudhary, Amit; Pant, R. P.; Biradar, A. M.

2013-07-01

174

A loss-based, magnetic field sensor implemented in a ferrofluid infiltrated microstructured polymer optical fiber  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

175

Orientational dynamics of ferrofluids with finite magnetic anisotropy of the particles: Relaxation of magneto-birefringence in crossed fields  

Microsoft Academic Search

Dynamic birefringence in a ferrofluid subjected to crossed bias (constant) and probing (pulse or ac) fields is considered, assuming that the nanoparticles have finite magnetic anisotropy. This is done on the basis of the general Fokker-Planck equation that takes into account both internal magnetic and external mechanical degrees of freedom of the particle. We describe the orientation dynamics in terms

Yu. L. Raikher; V. I. Stepanov; J.-C. Bacri; R. Perzynski

2002-01-01

176

Gyromagnetic resonance in ferrofluids made from manganese ferrite or magnetite particles: influence of a constant axial magnetic field  

Microsoft Academic Search

We have measured the susceptibility of two ferrofluids in the frequency range 0.1–20 GHz. We confine the liquid under test in a coaxial line cell and we use the reflection\\/transmission method to obtain ??. If we add a constant axial magnetic field to the microwave field we evidence an increase of the gyromagnetic resonance phenomenon appearing as a consequence of

D. Vincent; S. Neveu; L. Jorat; G. Noyel

1996-01-01

177

Orientational dynamics of ferrofluids with finite magnetic anisotropy of the particles: Relaxation of magneto-birefringence in crossed fields  

Microsoft Academic Search

Dynamic birefringence in a ferrofluid subjected to crossed bias ~constant! and probing ~pulse or ac! fields is considered, assuming that the nanoparticles have finite magnetic anisotropy. This is done on the basis of the general Fokker-Planck equation that takes into account both internal magnetic and external mechanical degrees of freedom of the particle. We describe the orientation dynamics in terms

Yu. L. Raikher; V. I. Stepanov; J.-C. Bacri; R. Perzynski

2002-01-01

178

Flows and torques in Brownian ferrofluids subjected to rotating uniform magnetic fields in a cylindrical and annular geometry  

NASA Astrophysics Data System (ADS)

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 ˜10-8 kg m/s, two orders of magnitude larger than the value estimated earlier for iron oxide based ferrofluids, and 12 orders of magnitude larger than estimated using dimensional arguments valid in the infinite dilution limit. These results provide further evidence of the existence of couple stresses in ferrofluids and their role in driving the spin-up flow phenomenon.

Torres-Diaz, I.; Cortes, A.; Cedeño-Mattei, Y.; Perales-Perez, O.; Rinaldi, C.

2014-01-01

179

The Evolution of Field-Induced Structure of Confined Ferrofluid Emulsions  

NASA Astrophysics Data System (ADS)

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.

Mou, T.; Flores, G. A.; Liu, J.; Bibette, J.; Richard, J.

180

Protein-polymer functionalized aqueous ferrofluids showing high T2 relaxivity.  

PubMed

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

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

2014-05-01

181

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

PubMed

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

Felicia, Leona J; Philip, John

2014-10-21

182

Comparisons on offshore structure responses to random waves using linear and high-order wave theories  

E-print Network

methodology for wave kinematics prediction. While the methods commonly used by the offshore industry are empirical and semi-empirical modifications of Linear (random) Wave Theory, the new approach (Hybrid Wave Model) satisfies the principles of hydrodynamics...

Ramos Heredia, Rafael Juda

2012-06-07

183

Molecular quantum wakes in the hydrodynamic plasma waveguide in air  

SciTech Connect

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

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

2010-10-15

184

Enhanced bio-compatibility of ferrofluids of self-assembled superparamagnetic iron oxide-silica core-shell nanoparticles.  

PubMed

Self-assembled magnetic colloidal suspensions are sought after by material scientists owing to its huge application potential. The biomedical applications of colloidal nanoparticles necessitate that they are biocompatible, non-interacting, monodispersed and hence the synthesis of such nanostructures has great relevance in the realm of nanoscience. Silica-coated superparamagnetic iron oxide nanoparticles based ferrofluids were prepared using polyethylene glycol as carrier fluid by employing a controlled co-precipitation technique followed by a modified sol-gel synthesis. A plausible mechanism for the formation of stable suspension of SiO2-coated Iron Oxide nanoparticles with a size of about 9 nm dispersed in polyethylene glycol (PEG) is proposed. Core-shell nature of the resultant SiO2-Iron Oxide nanocomposite was verified using transmission electron microscopy. Fourier transform-infrared spectroscopy studies were carried out to understand the structure and nature of chemical bonds. The result suggests that Iron Oxide exist in an isolated state inside silica matrix. Moreover, the presence of silanol bonds establishes the hydrophilic nature of silica shell confirming the formation of stable ferrofluid with PEG as carrier fluid. The magnetic characterization reveals the superparamagnetic behavior of the nanoparticles with a rather narrow distribution of blocking temperatures. These properties are not seen in ferrofluids prepared from Iron Oxide nanoparticles without SiO2 coating. The latter suggests the successful tuning of the inter-particle interactions preventing agglomeration of nanoparticles. Cytotoxicity studies on citric acid coated water based ferrofluid and silica-coated PEG-based ferrofluid were evaluated by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium chloride assay and it shows an enhanced compatibility for silica modified nanoparticles. PMID:21449334

Narayanan, T N; Mary, A P Reena; Swalih, P K Anas; Kumar, D Sakthi; Makarov, D; Albrecht, M; Puthumana, Jayesh; Anas, Abdulaziz; Anantharaman, M R

2011-03-01

185

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

186

Hydrodynamics of Semiconvection in Massive Stars  

NASA Astrophysics Data System (ADS)

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

Merryfield, W. J.

1993-12-01

187

Numerical Simulations of Wave Generation by a Vertical Plunger Using RANS and SPH Models  

E-print Network

uses the smoothed particle hydrodynamics SPH method. Numerical simulations using several differentNumerical Simulations of Wave Generation by a Vertical Plunger Using RANS and SPH Models S. C. Yim Database subject headings: Simulation; Numerical models; Hydrodynamics; Wave generation. Introduction

Yim, Solomon C.

188

Hydrodynamics and universality in cold atomic gases  

NASA Astrophysics Data System (ADS)

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

Abanov, Alexander; Kulkarni, Manas

2013-03-01

189

Hydrodynamics of Lake Lugano  

Microsoft Academic Search

The hydrodynamic processes in the Lake of Lugano (Lago di Lugano) have been the object of three major measuring campaigns. The first during summer 1979 in the North Basin, the second in the autumn of 1984 in the South Basin and the last in 1989 again in the North Basin. It is expected that analysis of the collected data in

G. Salvadè; K. Stocker; J. Trösch; F. Zamboni

1992-01-01

190

Skew resisting hydrodynamic seal  

DOEpatents

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

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

2001-01-01

191

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

SciTech Connect

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

Lee, W.; X-Ray Science Division

2010-09-01

192

Total-reflection X-ray fluorescence: An alternative tool for the analysis of magnetic ferrofluids  

NASA Astrophysics Data System (ADS)

This work presents the first application of the total-reflection X-ray fluorescence (TXRF) to the compositional study of magnetic ferrofluids. With the aims of validating the best analytical conditions and also, limitations of the TXRF in the compositional study of these materials, an alternative empirical method, based in the use of angle-dependence TXRF (AD-TXRF) measurements, is proposed. Three kinds of ferromagnetic nanoparticles, with different morphologies, have been studied. The techniques of inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectroscopy (ICP-OES) have been used to validate the TXRF results. In contrast with the plasma techniques, the developed TXRF procedure need not of previous chemical acid digestion. Additionally, two procedures of magnetic nanoparticles synthesis, co-precipitation and laser-pyrolysis, have been checked for the contaminants trace metals Zn, Mn and Cr. It has been found that the method of laser-pyrolysis produces nanoparticles of higher purity.

Fernández-Ruiz, R.; Costo, R.; Morales, M. P.; Bomatí-Miguel, O.; Veintemillas-Verdaguer, S.

2008-12-01

193

InSitu Imaging of Field-Induced Hexagonal Columns in Magnetite Ferrofluids  

NASA Astrophysics Data System (ADS)

Field-induced structures in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment are analyzed on a single-particle level by in situ cryogenic transmission electron microscopy (2D). The field-induced columnar phase locally exhibits hexagonal symmetry and confirms the structures observed in simulations for ferromagnetic dipolar fluids in 2D. The columns are distorted by lens-shaped voids, due to the weak interchain attraction relative to field-directed dipole-dipole attraction. Both dipolar coupling and the dipole concentration determine the dimensions and the spatial arrangement of the columns. Their regular spacing manifests long-range end-pole repulsions that eventually dominate the fluctuation-induced attractions between dipole chains that initiate the columnar transition.

Klokkenburg, Mark; Erné, Ben H.; Meeldijk, Johannes D.; Wiedenmann, Albrecht; Petukhov, Andrei V.; Dullens, Roel P. A.; Philipse, Albert P.

2006-11-01

194

Reference hypernetted chain theory for ferrofluid bilayer: Distribution functions compared with Monte Carlo  

NASA Astrophysics Data System (ADS)

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.

Polyakov, Evgeny A.; Vorontsov-Velyaminov, Pavel N.

2014-08-01

195

Influence of impurities on hydrodynamic solitons  

NASA Astrophysics Data System (ADS)

The interaction between impurities and solitary waves has been experimentally observed on the surface of a defective water layer subjected to vertical vibration. A slightly rugged surface on one sidewall of the water layer serves as the impurity, making the layer breadth at the defect slightly different elsewhere. A wide-breadth impurity will attract or pin not only the hydrodynamic breather at lower driving frequency, but also the kink at higher driving frequency, while a narrow-breadth one will repel them. Using a multiple scale expansion method, a nonlinear Schrödinger equation with an impurity term (NLSI) was derived from the basic hydrodynamic equation. Furthermore, we present numerical calculations that show good agreement between the NLSI-based theoretical model and the experimental results.

Chen, Weizhong; Lu, Lei; Zhu, Yifei

2005-03-01

196

Influence of impurities on hydrodynamic solitons.  

PubMed

The interaction between impurities and solitary waves has been experimentally observed on the surface of a defective water layer subjected to vertical vibration. A slightly rugged surface on one sidewall of the water layer serves as the impurity, making the layer breadth at the defect slightly different elsewhere. A wide-breadth impurity will attract or pin not only the hydrodynamic breather at lower driving frequency, but also the kink at higher driving frequency, while a narrow-breadth one will repel them. Using a multiple scale expansion method, a nonlinear Schro dinger equation with an impurity term (NLSI) was derived from the basic hydrodynamic equation. Furthermore, we present numerical calculations that show good agreement between the NLSI-based theoretical model and the experimental results. PMID:15903620

Chen, Weizhong; Lu, Lei; Zhu, Yifei

2005-03-01

197

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

Microsoft Academic Search

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

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

2001-01-01

198

Hydrodynamics and viscosity  

NSDL National Science Digital Library

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

2008-09-22

199

Hydrodynamic blade guide  

DOEpatents

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

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

2000-01-01

200

Hydrodynamic blade guide  

SciTech Connect

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

Blaedel, K.L.; Davis, P.J.; Landram, C.S.

2000-07-04

201

Hydrodynamics of fossil fishes  

PubMed Central

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

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

2014-01-01

202

Experimental investigation of longitudinal magneto-optic effects in four ferrite ferrofluids in visible-near infrared spectrum  

Microsoft Academic Search

We present an extensive experimental work concerning measurement of longitudinal magneto-optic effects (Faraday rotation and circular dichroism) induced in magnetic liquids. Seven ferrofluid samples allow the study of the influence of numerous parameters: magnetic suspension and carrier liquid characteristics, magnetic field strength (up to 10 kOe) and frequency (dc to 50 kHz), light wavelength (400 to 2000 nm) and, temperature

F. Donatini; D. Jamon; J. Monin; S. Neveu

1999-01-01

203

Multiscale Measurements of Ocean Wave Breaking Probability  

Microsoft Academic Search

Recent numerical model studies of nonlinear deep water wave group evolution suggest that wave breaking onset is associated primarily with a threshold behavior linked to the nonlinear wave group hydrodynamics. Motivated by these findings, a recently published probability analysis of observed dominant ocean wind wave breaking events reported a threshold behavior using the significant wave steepness as a measure of

Michael L. Banner; Johannes R. Gemmrich; David M. Farmer

2002-01-01

204

Carbonate sedimentation and hydrodynamic pattern on a modern temperate shelf: The strait of Bonifacio (western Mediterranean)  

Microsoft Academic Search

The sedimentary features of the inner-middle shelf of the strait of Bonifacio (western Mediterranean) were analyzed to evaluate the relationship between the production and transport of biogenic carbonate sediments and the basin morphology and hydrodynamics. A three-dimensional hydrodynamic modeling was performed in order to simulate the influence of waves and currents at seabed level. Superficial sediments were collected at depths

Giovanni De Falco; Sandro De Muro; Tiziana Batzella; Andrea Cucco

2011-01-01

205

Molecular Dynamics simulations of polymer/post collisions with explicit hydrodynamic interactions.  

NASA Astrophysics Data System (ADS)

Micro-- or nano--scopic arrays of posts, made using either microlithography or magnetically self--assembled arrays of ferro--fluids represent a promising new media for the electrophoretic separation of DNA. In order to optimize these systems we require a better understanding of the underlying mechanisms involved in separation. In light of this we carry out a systematic examination of the collision of polymers with fixed posts using large scale Molecular Dynamics simulations. These simulations explicitly include solvent, i.e., hydrodynamic interactions, in order to gain a better understanding of polymer dynamics involved in these media. In particular we examine the effects of field strength on polymer deformation, mean extension and escape time. Also we examine the effects of hydrodynamic interactions on the escape of polymers from entangled states and mean escape times of polymers as a function of molecular weight. We compare the results from the MD simulations with theoretical predictions for the escape time of a polymer derived within a non--local friction model.

Kenward, Martin; Slater, Gary W.

2003-03-01

206

How (non-) linear is the hydrodynamics of heavy ion collisions?  

E-print Network

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.

Stefan Floerchinger; Urs Achim Wiedemann; Andrea Beraudo; Luca Del Zanna; Gabriele Inghirami; Valentina Rolando

2013-12-19

207

Hydrodynamic damping contributions for an advanced floating production system design  

Microsoft Academic Search

Catenary moored floating vessels used for hydrocarbon production and storage exhibit low frequency, large amplitude resonant motions predominantly in the surge direction. These motions are caused by slow drift forces resulting primarily from random wave action. Accurate predictions of the damping forces are required in order to design fit for purpose moorings. This paper considers the contribution caused by hydrodynamic

D. T. Brown; J. Fang

1996-01-01

208

Fast lattice Boltzmann solver for relativistic hydrodynamics.  

PubMed

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

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

2010-07-01

209

Fast Lattice Boltzmann Solver for Relativistic Hydrodynamics  

SciTech Connect

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

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

2010-07-02

210

Hydrodynamic phase-locking of swimming microorganisms  

E-print Network

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.

Elfring, Gwynn J

2009-01-01

211

Hydrodynamic phase-locking of swimming microorganisms  

E-print Network

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.

Gwynn J. Elfring; Eric Lauga

2009-07-06

212

Hydrodynamic Simulations of Giant Impacts  

NASA Astrophysics Data System (ADS)

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

Reinhardt, Christian; Stadel, Joachim

2013-07-01

213

COCHLEAR HYDRODYNAMICS DEMYSTIFIED  

E-print Network

Technical Report Caltech-CS-TR-88-4 February 1988 revised September 1988 and January 1989 Abstract: Wave. The transfer functions of the low-order filter stages are completely determined by the wave-number vs 45], and of J. W. S. Rayleigh, The Theory of Sound [Rayleigh 45], which explain fluid flow problems

Allen, Jont

214

Hydrodynamics of confined membranes.  

PubMed

We calculate the hydrodynamic interaction Lambdak (Oseen interaction kernel) and relaxation frequency omegak for the fluctuations of a membrane that is harmonically bounded to a permeable or impermeable wall. We show that due to the confining wall there is an increase in the effective viscosity of the fluid surrounding the membrane. This has been observed in experiments on confined membranes, such as lamellar phases and the red-blood cell membrane. Our results allow a quantitative analysis of these experiments, in terms of the strength of the membrane confining potential and dislocations. PMID:15324039

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

2004-07-01

215

Inertial coupling for point particle fluctuating hydrodynamics  

NASA Astrophysics Data System (ADS)

A method for particle hydrodynamics based on an hybrid Eulerian-Lagrangian approach is presented. Particle dynamics are solved in continuum space while the fluid equations are solved in an Eulerian mesh, and described by finite volume fluctuating hydrodynamics. This set-up is particularly suited for micron-size devices where the Reynolds number is small but thermal fluctuations are important. The particle-fluid coupling force is obtained by imposing zero relative (particle-fluid) velocity at a local average over the particle volume. In doing so the momentum exchanged between fluid and particle is transferred instantaneously ensuring a correct treatment of inertia and correct particle velocity fluctuations uniquely driven by fluid thermal forces. Consistency between the Eulerian and Lagrangian momentum balance is shown to be essential. The scheme is applied to compressible fluids at low Mach number and moderate Reynolds number. A series of tests show that the near velocity field around the particle is correctly captured up to distances of about one particle hydrodynamic diameter. Also, acoustic forces measured under ultrasound waves are in excellent agreement with the theoretical expressions.

Usabiaga, F. Balboa; Pagonabarraga, I.; Delgado-Buscalioni, R.

2013-02-01

216

Modeling multiphase flow using fluctuating hydrodynamics  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

217

Load responsive hydrodynamic bearing  

DOEpatents

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

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

2002-01-01

218

Hydrodynamic simulations with the Godunov smoothed particle hydrodynamics  

Microsoft Academic Search

We present results based on an implementation of the Godunov smoothed particle hydrodynamics (GSPH), originally developed by Inutsuka, in the GADGET-3 hydrodynamic code. We first review the derivation of the GSPH discretization of the equations of moment and energy conservation, starting from the convolution of these equations with the interpolating kernel. The two most important aspects of the numerical implementation

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

2011-01-01

219

The Quantum Hydrodynamic Description of Tunneling  

SciTech Connect

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.

Kendrick, Brian K. [Los Alamos National Laboratory

2012-06-15

220

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

NASA Technical Reports Server (NTRS)

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

Leslie, F.; Ramachandran, N.

2000-01-01

221

Dielectric-spectroscopy approach to ferrofluid nanoparticle clustering induced by an external electric field  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

222

Oscillations in the solar atmosphere: a result of hydrodynamical simulations.  

NASA Astrophysics Data System (ADS)

Using a time-dependent hydrodynamic code, we follow the propagation of acoustic waves in the solar atmosphere to study the origin of chromospheric 3 minute oscillations. In the calculations, the spectral analysis method is used and the effects of radiative losses, mechanical heating, thermal conduction and ionization of hydrogen are considered. We found that the observed 3-min oscillations are actually the acoustic waves at periods around 3 minutes which appear as propagating waves (Liu 1984) and become dominant in the chromosphere. We suggest that the 3-min oscillation is caused by an incident acoustic wave spectrum in the 3-min band at the subphotospheric region. The excitation of photospheric 5-min evanescent waves or the shock overtaking process of high frequency waves is minor in the generation of chromospheric 3-min oscillations.

Cheng, Q.-Q.; Yi, Z.

1996-09-01

223

Air–water two-phase flow modeling of turbulent surf and swash zone wave motions  

Microsoft Academic Search

Wave breaking and wave runup\\/rundown have a major influence on nearshore hydrodynamics, morphodynamics and beach evolution. In the case of wave breaking, there is significant mixing of air and water at the wave crest, along with relatively high kinetic energy, so prediction of the free surface is complicated. Most hydrodynamic studies of surf and swash zone are derived from single-phase

R. Bakhtyar; A. M. Razmi; D. A. Barry; A. Yeganeh-Bakhtiary; Q.-P. Zou

224

Thermodiffusion in concentrated ferrofluids: A review and current experimental and numerical results on non-magnetic thermodiffusion  

SciTech Connect

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

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

2013-12-15

225

Modeling Multi-phase Flow using Fluctuating Hydrodynamics  

E-print Network

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 non-equilibrium examples to illustrate the capability of the algorithm to model multi-phase 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 ...

Chaudhri, Anuj; Garcia, Alejandro L; Donev, Aleksandar

2014-01-01

226

Selective ionic liquid ferrofluid based dispersive-solid phase extraction for simultaneous preconcentration/separation of lead and cadmium in milk and biological samples.  

PubMed

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 1.21µgL(-1) for Pb(II) and 0.21µgL(-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 9.34mgg(-1) for lead and cadmium, respectively. PMID:25281121

Fasih Ramandi, Negin; Shemirani, Farzaneh

2015-01-01

227

Forces on a fixed barge due to Stokes 5th-Order laboratory waves  

E-print Network

This paper presents the results of experiment of nonlinear Stokes 5th order waves and forces measured in the Ocean Engineering Hydrodynamic Laboratory. It also presents analysis of the data and the comparison with hydrodynamic theory. We...

Choi, Nag Joon

2012-06-07

228

Influence of large size magnetic particles on the magneto-viscous properties of ferrofluid  

NASA Astrophysics Data System (ADS)

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.

Shah, Kruti; Upadhyay, R. V.; Aswal, V. K.

2012-07-01

229

Hydrodynamic fluctuations in relativistic superfluids  

SciTech Connect

The Hamiltonian formulation of superfluids based on noncanonical Poisson brackets is studied in detail. The assumption that the momentum density is proportional to the flow of the conserved energy is shown to lead to the covariant relativistic theory previously suggested by Khalatnikov, Lebedev, and Carter, and some potentials in this theory are given explicitly. We discuss hydrodynamic fluctuations in the presence of dissipative effects, and we derive the corresponding set of hydrodynamic correlation functions. Kubo relations for the transport coefficients are obtained.

Valle, Manuel A. [Departamento de Fisica Teorica, Universidad del Pais Vasco, Apartado 644, E-48080 Bilbao (Spain)

2008-01-15

230

Numerical Studies of Backscattering from Time Evolving Sea Surfaces: Comparison of Hydrodynamic Models  

E-print Network

spectrum. Measured microwave Doppler spectra however show more features than a single Bragg line, and also relation, taken to be the deep water gravity wave equation for this paper. More complete hydrodynamic theories can be applied to predict interaction effects between these sinusoidal waves, but the non

231

Polarized light transmission in ferrofluids loaded with carbon nanotubes in the presence of a uniform magnetic field  

NASA Astrophysics Data System (ADS)

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.

Vales-Pinzón, C.; Alvarado-Gil, J. J.; Medina-Esquivel, R.; Martínez-Torres, P.

2014-11-01

232

Application of small-angle neutron scattering to the study of forces between magnetically chained monodisperse ferrofluid emulsion droplets  

SciTech Connect

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

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

2014-01-01

233

Investigation of magnetic properties of Fe3O4 nanoparticles using temperature dependent magnetic hyperthermia in ferrofluids  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

234

On the choice of random wave simulation in the surf zone processes  

E-print Network

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 ...

Yuan, Jing

2010-01-01

235

Simulation of astrophysical jet using the special relativistic hydrodynamics code  

E-print Network

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.

Orhan Donmez; Refik Kayali

2006-02-14

236

In this paper, we represent numerical results which, validate our former work on the hydrodynamic effect (nonlinear)  

E-print Network

, the scattering of breaking waves which cause non-linear phenomena. In our case, we could consider that the ocean the experimental radar measurement validations considering targets in the form of breaking waves. II. BREAKING on the hydrodynamic effect (nonlinear) produced by breaking waves [1] in EM bistatic scattering coefficients. We

Paris-Sud XI, Université de

237

A new hydrodynamic analysis of double layers  

NASA Technical Reports Server (NTRS)

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

Hora, Heinrich

1987-01-01

238

Polariton superfluids reveal quantum hydrodynamic solitons.  

PubMed

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

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

2011-06-01

239

Formulating Viscous Hydrodynamics for Large Velocity Gradients  

E-print Network

Viscous corrections to relativistic hydrodynamics, which are usually formulated for small velocity g radients, have recently been extended from Navier-Stokes formulations to a class of treatments based on Israel-Stewart equations. Israel-Stewart treatments, which treat the spatial components of the s tress-energy tensor tau_ij as dynamical objects, introduce new parameters, such as the relaxati on times describing non-equilibrium behavior of the elements tau_ij. By considering linear resp onse theory and entropy constraints, we show how the additional parameters are related to fluctuatio ns of tau_ij. Furthermore, the Israel-Stewart parameters are analyzed for their ability to prov ide stable and physical solutions for sound waves. Finally, it is shown how these parameters, which are naturally described by correlation functions in real time, might be constrained by lattice calcu lations, which are based on path-integral formulations in imaginary time.

Scott Pratt

2007-11-25

240

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

SciTech Connect

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

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

2012-09-26

241

Hydrodynamic Stability of Liquid-Propellant Combustion: Landau's Problem Revisited  

NASA Technical Reports Server (NTRS)

Hydrodynamic, or Landau, instability in combustion is typically associated with the onset of wrinkling of a flame surface, corresponding to the formation of steady cellular structures as the stability threshold is crossed. As its name suggests, it stems from hydrodynamic effects connected with thermal expansion across the reaction region. In the context of liquid-propellant combustion, the classical models that originally predicted this phenomenon have been extended to include the important effects that arise from a dynamic dependence of the burning rate on the local pressure and temperature fields. Thus, the onset of Landau instability has now been shown to occur for sufficiently small negative values of the pressure sensitivity of the burning rate, significantly generalizing previous classical results for this problem that assumed a constant normal burning rate. It has also been shown that the onset of instability occurs for decreasing values of the disturbance wave number as the gravitational-acceleration parameter decreases. Consequently, in an appropriate weak-gravity limit, Landau instability becomes a long-wave phenomena associated with the formation of large cells on the liquid-propellant surface. Additionally, a pulsating form of hydrodynamic instability has been shown to occur as well, corresponding to the onset of temporal oscillations in the location of the liquid/gas interface. This instability occurs for sufficiently large negative values of the pressure sensitivity, and is enhanced by increasing values of the burning-rate temperature sensitivity. It is further shown that for sufficiently small values of this parameter, there exists a stable range of pressure sensitivities for steady, planar burning such that the classical cellular form of hydrodynamic instability and the more recent pulsating form of hydrodynamic instability can each occur as the corresponding stability threshold is crossed. For larger thermal sensitivities, however, the pulsating stability boundary evolves into a C-shaped curve in the (disturbance-wave number, pressure-sensitivity) plane, indicating loss of stability to pulsating perturbations for all sufficiently large disturbance wavelengths. It is thus concluded, based on characteristic parameter values that an equally likely form of hydrodynamic instability in liquid-propellant combustion is of a nonsteady, long-wave nature, distinct from the steady, cellular form originally predicted by Landau.

Margolis, S. B.

2001-01-01

242

Mon. Not. R. Astron. Soc. 000, 1--?? (0000) Printed 28 June 1999 (MN L a T E X style file v1.4) Hydrodynamic Simulations of Propagating Warps and  

E-print Network

in accretion discs. Three dimensional hydrodynamic simulations were performed using SPH, and the results.4) Hydrodynamic Simulations of Propagating Warps and Bending Waves in Accretion Discs Richard P. Nelson ? & John C indicate that SPH can model the hydrodynamics of warped discs, even when using rather modest numbers

Nelson, Richard

243

Hydrodynamic spinning of hydrogel fibers.  

PubMed

Hydrogel scaffolds are highly hydrated polymer networks that allow cells to adhere, proliferate and differentiate in the treatment of diseased or injured tissues and organs. Using hydrodynamic shaping and in situ cross-linking of hydrogel precursors, we have developed a highly efficient "hydrodynamic spinning" approach for synthesizing hydrogel fibers of different diameters in a multiphase coaxial flow. A triple-orifice spinneret has been created, and three different types of hydrogel precursors have been examined. Without changing the spinning head, hollow and solid hydrogel fibers with different diameters have been spun by simply manipulating the ratio of input flow rates. Together with the ability of simultaneous cell-seeding in the hydrogel matrix, hydrodynamic spinning can be broadly applied to many hydrogel materials, providing a powerful technique in the preparation of fiber-like and tubule-like hydrogel constructs for tissue engineering. PMID:19878994

Hu, Min; Deng, Rensheng; Schumacher, Karl M; Kurisawa, Motoichi; Ye, Hongye; Purnamawati, Kristy; Ying, Jackie Y

2010-02-01

244

Hydrodynamic description of protein folding.  

PubMed

A hydrodynamic description of protein folding is proposed and illustrated with a lattice protein model, which has a free energy surface (FES) typical of proteins with two-state folding kinetics. The flows from the unfolded to the native state are concentrated in a limited region of the FES. The rest is occupied by a flow "vortex", which does not lead to the native state. In contrast with intermediates that are associated with local minima, the vortex is not visible on the FES. The hydrodynamic interpretation thus provides new insights into the mechanism of protein folding and can be a useful complement to standard analyses. PMID:18232827

Chekmarev, Sergei F; Palyanov, Andrey Yu; Karplus, Martin

2008-01-11

245

Kinetics of cavitation and luminescence for spherically focusing shock waves in liquids  

Microsoft Academic Search

The hydrodynamic processes due to spherically focusing acoustic shock waves in liquids are discussed. Luminescence recording has been combined with pressure measurement and high-speed photo recording. An electromagnetic generator of shock waves, shaped as a sphere segment, is used in the experiments. The complex nonlinear hydrodynamic processes are caused by cavitation in the shock wave (?1 ?s) focus both in

Vyacheslav S. Teslenko; Georgii N. Sankin; Aleksey P. Drozhzhin

2000-01-01

246

Kinetics of cavitation and luminescence for spherically focusing shock waves in liquids  

Microsoft Academic Search

The hydrodynamic processes due to spherically focusing acoustic shock waves in liquids are discussed. Luminescence recording has been combined with pressure measurement and high-speed photo recording. An electromagnetic generator of shock waves, shaped as a sphere segment, is used in the experiments. The complex nonlinear hydrodynamic processes are caused by cavitation in the shock wave (~1 mus) focus both in

Vyacheslav S. Teslenko; Georgii N. Sankin; Aleksey P. Drozhzhin

2000-01-01

247

Hydrodynamic focusing - a versatile tool  

PubMed Central

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

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

2011-01-01

248

Hydrodynamic instabilities in inertial fusion  

SciTech Connect

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

Hoffman, N.M.

1994-09-01

249

Millifluidics: Capillarity and Interfacial Hydrodynamics  

E-print Network

of " ? " clean glass water " greasy glass (or silanized) grease ! %SV %SL ! cos" problem: measuring independentlyMillifluidics: Capillarity and Interfacial Hydrodynamics 1: Surface tension: the basics 2: Liquid in contact with a solid 3: Capillary rise 4: Actual surfaces 5: Interfacial flows 6: Interfacial

Bico,José

250

Smoothed Particle Hydrodynamics on GPUs  

Microsoft Academic Search

In this paper, we present a Smoothed Parti- cle Hydrodynamics (SPH) implementation algorithm on GPUs. To compute a force on a particle, neighboring par- ticles have to be searched. However, implementation of a neighboring particle search on GPUs is not straightfor- ward. We developed a method that can search for neigh- boring particles on GPUs, which enabled us to imple-

Takahiro Harada; Seiichi Koshizuka; Yoichiro Kawaguchi

251

The Gulf of Lions' hydrodynamics  

Microsoft Academic Search

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

Claude Millot

1990-01-01

252

Hydrodynamic Modeling of Sailing Yachts  

Microsoft Academic Search

In modern yacht design geometric modeling is regarded to be directly related to the hydrodynamic performance of the shape of the hull and its appending elements - usually the keel, often with winglets, and the rudder. While the traditional way of shape design - i.e., draw- ing, model building, tank testing, modifying . . . - is both time consuming

Stefan Harries; Claus Abt; Karsten Hochkirch

253

Stochastic sedimentation and hydrodynamic diffusion  

Microsoft Academic Search

Molecular collisions with very small particles induce Brownian motion. Consequently, such particles exhibit classical diffusion during their sedimentation. However, identical particles too large to be affected by Brownian motion also change their relative positions. This phenomenon is called hydrodynamic diffusion. Long before this term was coined, the variability of individual particle trajectories had been recognized and a stochastic model had

Elmer M. Tory

2000-01-01

254

Research on the unsteady hydrodynamic characteristics of vertical axis tidal turbine  

NASA Astrophysics Data System (ADS)

The unsteady hydrodynamic characteristics of vertical axis tidal turbine are investigated by numerical simulation based on viscous CFD method. The starting mechanism of the turbine is revealed through analyzing the interaction of its motion and dynamics during starting process. The operating hydrodynamic characteristics of the turbine in wave-current condition are also explored by combining with the linear wave theory. According to possible magnification of the cyclic loads in the maximum power tracking control of vertical axis turbine, a novel torque control strategy is put forward, which can improve the structural characteristics significantly without effecting energy efficiency.

Zhang, Xue-wei; Zhang, Liang; Wang, Feng; Zhao, Dong-ya; Pang, Cheng-yan

2014-03-01

255

Axisymmetric solitary waves on the surface of a ferrofluid E. Bourdin, J.-C. Bacri, and E. Falcon  

E-print Network

predictions [9]. The experimental setup is shown in Fig. 1. It consists of a cylindrical copper tube (50 cm through hollow waterproof screws. A dc electrical current, I, in the range 0�100 A is applied to the cylindrical conductor by means of a power supply. The current generates circular magnetic field lines around

Paris-Sud XI, Université de

256

On Faraday Instability in Magnetic Liquids: Ince-Erdelyi Approach Applied to the Hill Equation Describing Oscillations of a Ferrofluid Free Surface  

NASA Astrophysics Data System (ADS)

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.

Hennenberg, M.; Slavtchev, S.; Valchev, G.

2013-12-01

257

Axially symmetric pseudo-Newtonian hydrodynamics code  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

258

Viscoelastic surface waves and the surface structure of liquids  

Microsoft Academic Search

The dispersion relations for surface waves on a planar liquid surface are obtained from first principles. The high-frequency elastic, low-frequency hydrodynamic and intermediate viscoelastic regimes are investigated separately. It is shown that the structure of the liquid surface modifies the expression for Rayleigh's elastic surface waves and Kelvin's capillary waves and allows for the existence of new surface waves besides

C. F. Tejero; M. Baus

1985-01-01

259

Anomalous hydrodynamics of fractional quantum Hall states  

SciTech Connect

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

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

2013-09-15

260

A stochastic analysis approach for the calculation of hydrodynamic dampings  

SciTech Connect

This paper introduces an alternative linearization algorithm for nonlinear loading terms occurring in the spectral analysis of offshore structures. The algorithm makes use of member consistent forces for the linearization unlike the traditional linearization method. Different linearization criteria are used for different components of the member consistent forces. An equivalent second moment criterion is used to linearize the force component due to wave velocities while the components due to current and structural velocities are kept being stochastic. Calculation of their mean values is presented for the analysis. A deterministic added mass matrix and a stochastic hydrodynamic damping matrix are derived from the force component due to structural deformations. It is demonstrated that the mean value hydrodynamic damping ratios which are calculated in the paper are more realistic than those resulted from the linearization of the Morison`s equation.

Karadeniz, H. [Delft Univ. of Technology (Netherlands). Dept. of Civil Engineering

1995-12-31

261

Hydrodynamic model of Fukushima-Daiichi NPP Industrial site flooding  

E-print Network

While the Fukushima-Daiichi was designed and constructed the maximal tsunami height estimate was about 3 m based on analysis of statistical data including Chile earthquake in 1960. The NPP project industrial site height was 10 m. The further deterministic estimates TPCO-JSCE confirmed the impossibility of the industrial site flooding by a tsunami and therefore confirmed ecological safety of the NPP. However, as a result of beyond design earthquake of 11 March 2011 the tsunami height at the shore near the Fukushima-Daiichi NPP reached 15 m. This led to flooding and severe emergencies having catastrophic environmental consequences. This paper proposes hydrodynamic model of tsunami emerging and traveling based on conservative assumptions. The possibility of a tsunami wave reaching 15 m height at the Fukushima-Daiichi NPP shore was confirmed for deduced hydrodynamic resistance coefficient of 1.8. According to the model developed a possibility of flooding is determined not only by the industrial site height, magni...

Vaschenko, V N; Gerasimenko, T V; Vachev, B

2014-01-01

262

Hydrodynamic simulations with the Godunov smoothed particle hydrodynamics  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

263

Shear-bulk coupling in nonconformal hydrodynamics  

NASA Astrophysics Data System (ADS)

We compute the temporal evolution of the pressure anisotropy and bulk pressure of a massive gas using second-order viscous hydrodynamics and anisotropic hydrodynamics. We then compare our results with an exact solution of the Boltzmann equation for a massive gas in the relaxation time approximation. We demonstrate that, within second-order viscous hydrodynamics, the inclusion of the full set of kinetic coefficients, particularly the shear-bulk couplings, is necessary to properly describe the time evolution of the bulk pressure. We also compare the results of second-order hydrodynamics with those obtained using the anisotropic hydrodynamics approach. We find that anisotropic hydrodynamics and second-order viscous hydrodynamics including the shear-bulk couplings are both able to reproduce the exact evolution with comparable accuracy.

Denicol, Gabriel S.; Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael

2014-10-01

264

Hydrodynamics of catheter biofilm formation  

E-print Network

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

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

2009-01-01

265

Hydrodynamic sensory stressors produce nonlinear predation patterns.  

PubMed

Predators often have large effects on community structure, but these effects can be minimized in habitats subjected to intense physical stress. For example, predators exert large effects on rocky intertidal communities on wave-protected shores but are usually absent from wave-swept shores where hydrodynamic forces prevent them from foraging effectively. The physical environment also can affect predation levels when stressors are not severe enough to be physically risky. In these situations, environmental conditions may constrain a predator's ability to locate prey and alleviate predation pressure. Yet, stress models of community structure have rarely considered the implications of such sensory or behavioral stressors, particularly when the sensory abilities of both predators and prey are affected by the same types of environmental conditions. Ecologists may classify certain environmental conditions as refuges if they impede predator foraging, but these conditions may not actually decrease predation levels if they simultaneously increase prey vulnerability to consumers. Using blue crabs (Callinectes sapidus) and hard clams (Mercenaria mercenaria) as a model system, we investigated the relationship between predation intensity and environmental stress in the form of hydrodynamics (i.e., flow velocity and turbulence). Blue crabs and hard clams are less responsive to each other in faster, more turbulent flows, but studies exploring how flow modulates the outcomes of crab-clam interactions in the field are lacking. We manipulated turbulence within field sites and compared predation levels within and between sites that differed in flow velocity and turbulence. Our results suggest that blue crabs are most effective foragers in flows with intermediate velocities and turbulence levels. Although these conditions are not ideal for blue crabs, lab studies indicate that they also compromise the ability of clams to detect and react to approaching crabs and, thereby, increase clam vulnerability to predators. Our results suggest that environmental stresses on perception (sensory stressors) may not cause a steady decay in predation rates when they simultaneously affect the behaviors of both predators and prey. Moreover, the relative contribution of lethal vs. nonlethal predator effects in communities also may be influenced by environmental forces that enhance the predator-avoidance abilities of prey or the foraging efficiency of predators. PMID:20503871

Smee, Delbert L; Ferner, Matthew C; Weissburg, Marc J

2010-05-01

266

Development of Fully Coupled Aeroelastic and Hydrodynamic Models for Offshore Wind Turbines: Preprint  

SciTech Connect

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

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

2006-01-01

267

Fundamental Characteristics of Breather Hydrodynamics  

NASA Astrophysics Data System (ADS)

The formation of oceanic rogue waves can be explained by the modulation instability of deep-water Stokes waves. In particular, being doubly-localized and amplifying the background wave amplitude by a factor of three or higher, the class of Peregrine-type breather solutions of the nonlinear Schrödinger equation (NLS) are considered to be appropriate models to describe extreme ocean wave dynamics. Here, we present an experimental validation of fundamental properties of the NLS within the context of Peregrine breather dynamics and we discuss the long-term behavior of such in time and space localized structures.

Chabchoub, Amin

2014-05-01

268

Tidal hydrodynamics and erosional power in the Fly River delta, Papua New Guinea  

Microsoft Academic Search

A two-dimensional numerical model is used to study tidal hydrodynamics and distribution of bed shear stresses in the Fly River delta, Papua New Guinea. The model describes the propagation of the tidal wave within the delta and along the river. Model results indicate that tidal discharge at the mouths of the distributary channels is between 10 and 30 times larger

A. Canestrelli; S. Fagherazzi; A. Defina; S. Lanzoni

2010-01-01

269

Eigenvalues, Eigenvectors and Symmetrization of the Magneto-Hydrodynamic (MHD) Equations  

E-print Network

Eigenvalues, Eigenvectors and Symmetrization of the Magneto-Hydrodynamic (MHD) Equations Antony, the eight wave MHD equations proposed by Powell [1] and also studied by Roe [2,3] can be written as t + xj of the conservative variables w, the MHD equations can be written as w t + xi Fi(w) + S(w) = 0 where w

Stanford University

270

Hydrodynamic consequences of maintaining an upright posture by different magnitudes of stiffness and buoyancy in  

E-print Network

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

Stewart, Hannah Louise

271

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

Microsoft Academic Search

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

M. L. FRANKEL; G. I. SIVASHINSKY

1982-01-01

272

MODELING AND SIMULATION OF TSUNAMI AND STORM SURGE HYDRODYNAMIC LOADS ON COASTAL BRIDGE STRUCTURES  

Microsoft Academic Search

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

Solomon C. Yim

273

No-Slip Hydrodynamic Boundary Condition for Hydrophilic Particles  

NASA Astrophysics Data System (ADS)

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

Honig, Christopher D. F.; Ducker, William A.

2007-01-01

274

Hydrodynamic stability of rockets with headwall injection  

NASA Astrophysics Data System (ADS)

We investigate the hydrodynamic instability of the full-length, cylindrical models of solid and hybrid rockets with headwall injection. Our baseline is the rotational incompressible flowfield proposed in a recent study (Majdalani and Vyas, "Inviscid models of the classic hybrid rocket," AIAA Paper 2004-3474). The local nonparallel approach is implemented in which the amplitude functions are assumed to be radially dependent at fixed streamwise locations. The usual singularity along the chamber axis is eliminated using Taylor series expansions. As a result, three compatibility relations are derived and substituted for the local boundary conditions along the axis. These depend on whether the tangential wave number q is 0, 1, or larger. Our rotational model is shown to exhibit a range of instability that broadens with successive increases in headwall injection. The lowest frequency below which the flow remains unconditionally stable is observed at ? =28.5 regardless of the headwall injection rate. As usual, the zeroth order tangential mode is found to be the most amplified. Using a representative headwall injection velocity for hybrid rockets, we identify a range of frequencies along which large excursions in pressure and velocity amplitudes are possible. These surges signal the presence of a resonant-like mechanism that is akin to an acoustic instability response. The most excited frequencies vary between 387 and 415 in the vicinity of the headwall. These frequencies are spatially delayed and lowered to 93.8-163.5 when the headwall injection rate is reduced to the level associated with solid rockets. For the most critical streamwise stations, these resurging wave amplitudes are quantified and shown to exhibit spectra that mimic the waterfall data acquired in acoustic instability tests.

Abu-Irshaid, Esam M.; Majdalani, Joseph; Casalis, Grégoire

2007-02-01

275

Hydrodynamic instability in eccentric astrophysical discs  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

276

Hydrodynamics  

NSDL National Science Digital Library

This lab is an inquiry activity in that students do not know the answer and have probably never experienced this phenomenon. Most students have seen that water in U-tubes is always equal height on both sides. This lab will be both a discrepant event as we

Horton, Michael

2009-05-30

277

Computations of fully nonlinear three-dimensional wave-body interactions  

E-print Network

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

Yan, Hongmei

2010-01-01

278

Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications  

SciTech Connect

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

R. Paul Drake

2005-12-01

279

Hydrodynamic Simulations of Galaxy Formation  

E-print Network

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

A. A. Thoul

1994-12-09

280

Problems in astrophysical radiation hydrodynamics  

SciTech Connect

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

Castor, J.I.

1983-09-14

281

Progress in smooth particle hydrodynamics  

SciTech Connect

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

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

1998-07-01

282

Hydrodynamic anomalies in supercritical fluid.  

PubMed

Using the molecular dynamics simulations we investigate properties of velocity autocorrelation function of Lennard-Jones fluid at long and intermediate time scales in wide ranges of temperature and density. We show that the amplitudes of both the leading and the subleading time asymptotic terms of velocity autocorrelation function, a1 and a2, show essentially non-monotonic temperature and density dependence. There are two lines on temperature-density plain corresponding to maxima of a1 (a2) along isochors and isotherms situated in the supercritical fluid (hydrodynamic anomalies). These lines give insight into the stages of the fluid evolution into gas. PMID:25273453

Ryltsev, R E; Chtchelkatchev, N M

2014-09-28

283

Disruptive Innovation in Numerical Hydrodynamics  

SciTech Connect

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

Waltz, Jacob I. [Los Alamos National Laboratory

2012-09-06

284

Foundation of Hydrodynamics of Strongly Interacting Systems  

SciTech Connect

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

Wong, Cheuk-Yin [ORNL] [ORNL

2014-01-01

285

A hydrodynamic sensory antenna used by killifish for nocturnal hunting  

PubMed Central

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

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

2011-01-01

286

Oil film pressure in hydrodynamic journal bearings.  

E-print Network

??Hydrodynamic journal bearings are critical power transmission components that are carrying increasingly high loads because of the increasing power density in various machines. Therefore, knowing… (more)

Valkonen, Antti

2009-01-01

287

Hydrodynamic interactions in active colloidal crystal microrheology  

E-print Network

In dense colloids it is commonly assumed that hydrodynamic interactions do not play a role. However, a found theoretical quantification is often missing. We present computer simulations that are motivated by experiments where a large colloidal particle is dragged through a colloidal crystal. To qualify the influence of long-ranged hydrodynamics, we model the setup by conventional Langevin dynamics simulations and by an improved scheme with limited hydrodynamic interactions. This scheme significantly improves our results and allows to show that hydrodynamics strongly impacts on the development of defects, the crystal regeneration as well as on the jamming behavior.

Rudolf Weeber; Jens Harting

2011-12-04

288

Hydrodynamic interactions in active colloidal crystal microrheology  

NASA Astrophysics Data System (ADS)

In dense colloids it is commonly assumed that hydrodynamic interactions do not play a role. However, a found theoretical quantification is often missing. We present computer simulations that are motivated by experiments where a large colloidal particle is dragged through a colloidal crystal. To qualify the influence of long-ranged hydrodynamics, we model the setup by conventional Langevin dynamics simulations and by an improved scheme with limited hydrodynamic interactions. This scheme significantly improves our results and allows to show that hydrodynamics strongly impacts the development of defects, the crystal regeneration, as well as the jamming behavior.

Weeber, R.; Harting, J.

2012-11-01

289

Hydrodynamic interactions in active colloidal crystal microrheology.  

PubMed

In dense colloids it is commonly assumed that hydrodynamic interactions do not play a role. However, a found theoretical quantification is often missing. We present computer simulations that are motivated by experiments where a large colloidal particle is dragged through a colloidal crystal. To qualify the influence of long-ranged hydrodynamics, we model the setup by conventional Langevin dynamics simulations and by an improved scheme with limited hydrodynamic interactions. This scheme significantly improves our results and allows to show that hydrodynamics strongly impacts the development of defects, the crystal regeneration, as well as the jamming behavior. PMID:23214913

Weeber, R; Harting, J

2012-11-01

290

Petascale Cosmological Hydrodynamic Simulation of Quasars.  

E-print Network

??This thesis presents a theoretical investigation of supermassive black holes and the quasars they power through cosmological hydrodynamic simulations on petascale supercomputers. As the size… (more)

Feng, Yu

2014-01-01

291

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

NASA Astrophysics Data System (ADS)

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

Long, Joseph W.

292

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

SciTech Connect

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

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

2002-01-01

293

INTRODUCTION Wave-swept rocky shores present organisms with physical rigors  

E-print Network

and desiccation (Denny and Wethey, 2001; Tomanek and Helmuth, 2002). At high tide, hydrodynamic forces exerted nature of wave-imposed loadings may have a bearing on macroalgal failure. Hale (Hale, 2001) and Mach Seaweeds inhabiting the extreme hydrodynamic environment of wave-swept shores break frequently. However

Denny, Mark

294

Some problems in hydrodynamic lubrication  

SciTech Connect

Several computational and mathematical modeling problems in the areas of compressible and incompressible hydrodynamic lubrication are addressed. The first problem involves application of the collocation method for static and dynamic analyses of finite-length gas journal bearings. The method is shown to be an order of magnitude computationally faster than the finite-difference method. Squeeze-film dampers of finite-length with variable clearance is next investigated using the collocation method. It is shown that by suitably varying the two parameters than control the nature of axial clearance variation, the secant stiffness and damping coefficient variation with journal eccentricity ratio can be altered to better suit specific design needs. Surface-roughness effects on the hydrodynamic lubrication characteristics of finite-length gas journal bearings is studied next by numerically solving the ensemble averaged compressible Reynolds equation. The last problem deals with gas-lubricated finite-length foil-journal bearings. An elasticity solution that solves for the deflection of the compliant foil-bearing surface for applied loads is first developed, and used for the study of load-deflection characteristics of the foil bearing with a non-rotating journal.

Arakere, N.K.

1988-01-01

295

Active and driven hydrodynamic crystals  

E-print Network

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.

Nicolas Desreumaux; Nicolas Florent; Eric Lauga; Denis Bartolo

2012-09-05

296

Inducer Hydrodynamic Load Measurement Devices  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

297

Inducer Hydrodynamic Load Measurement Devices  

NASA Technical Reports Server (NTRS)

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

Skelley, Stephen E.; Zoladz, Thomas F.

2002-01-01

298

Web-based hydrodynamics computing  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

299

Web-based hydrodynamics computing  

NASA Astrophysics Data System (ADS)

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

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

2005-01-01

300

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

301

Effect of Coriolis force on thermomagnetic convection in a ferrofluid saturating porous medium: A weakly nonlinear stability analysis  

NASA Astrophysics Data System (ADS)

We investigate the influence of Coriolis force on the onset of thermomagnetic convection in ferrofluid saturating a porous layer in the presence of a uniform vertical magnetic field using both linear and weakly non-linear analyses. The modified Brinkman-Forchheimer-extended Darcy equation with Coriolis term has been used to describe the fluid flow. The linear theory based on normal mode method is considered to find the criteria for the onset of stationary thermomagnetic Convection and weakly non-linear analysis based on minimal representation of truncated Fourier series analysis containing only two terms has been used to find the Nusselt number Nu as functions of time. The range of thermal Rayleigh number R beyond which the bifurcation becomes subcritical increases with increasing ?, Da-1 and Ta. The global quantity of the heat transfer rate decreases by increasing the Taylor number Ta. The results obtained, during the above analyses, have been presented graphically and the effects of various parameters on heat and mass transfer have been discussed. Finally, we have drawn the steady streamlines for various parameters.

Nanjundappa, C. E.; Shivakumara, I. S.; Prakash, H. N.

2014-12-01

302

Preparation and characterization of silica-coated Fe 3O 4 nanoparticles used as precursor of ferrofluids  

NASA Astrophysics Data System (ADS)

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.

Hong, Ruo-Yu; Li, Jian-Hua; Zhang, Shi-Zhong; Li, Hong-Zhong; Zheng, Ying; Ding, Jian-min; Wei, Dong-Guang

2009-01-01

303

Hydrodynamics of weakly deformed soliton lattices. Differential geometry and Hamiltonian theory  

NASA Astrophysics Data System (ADS)

CONTENTS Introduction Chapter I. Hamiltonian theory of systems of hydrodynamic type § 1. General properties of Poisson brackets § 2. Hamiltonian formalism of systems of hydrodynamic type and Riemannian geometry § 3. Generalizations: differential-geometric Poisson brackets of higher orders, differential-geometric Poisson brackets on a lattice, and the Yang-Baxter equation § 4. Riemann invariants and the Hamiltonian formalism of diagonal systems of hydrodynamic type. Novikov's conjecture. Tsarev's theorem. The generalized hodograph method Chapter II. Equations of hydrodynamics of soliton lattices § 5. The Bogolyubov-Whitham averaging method for field-theoretic systems and soliton lattices. The results of Whitham and Hayes for Lagrangian systems § 6. The Whitham equations of hydrodynamics of weakly deformed soliton lattices for Hamiltonian field-theoretic systems. The principle of conservation of the Hamiltonian structure under averaging § 7. Modulations of soliton lattices of completely integrable evolutionary systems. Krichever's method. The analytic solution of the Gurevich-Pitaevskii problem on the dispersive analogue of a shock wave § 8. Evolution of the oscillatory zone in the KdV theory. Multi-valued functions in the hydrodynamics of soliton lattices. Numerical studies § 9. Influence of small viscosity on the evolution of the oscillatory zone References

Dubrovin, B. A.; Novikov, S. P.

1989-12-01

304

Wave generation in a sunspot  

NASA Technical Reports Server (NTRS)

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.

Lee, Jeongwoo W.

1993-01-01

305

Extreme hydrodynamic load calculations for fixed steel structures  

SciTech Connect

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.

Jong, P.R. de; Vugts, J. [Delft Univ. of Technology (Netherlands); Gudmestad, O.T. [Statoil, Stavanger (Norway)

1996-12-31

306

Physics-Based Learning Models for Ship Hydrodynamics  

E-print Network

We present the concepts of physics-based learning models (PBLM) and their relevance and application to the field of ship hydrodynamics. The utility of physics-based learning is motivated by contrasting generic learning models for regression predictions, which do not presume any knowledge of the system other than the training data provided with methods such as semi-empirical models, which incorporate physical insights along with data-fitting. PBLM provides a framework wherein intermediate models, which capture (some) physical aspects of the problem, are incorporated into modern generic learning tools to substantially improve the predictions of the latter, minimizing the reliance on costly experimental measurements or high-resolution high-fidelity numerical solutions. To illustrate the versatility and efficacy of PBLM, we present three wave-ship interaction problems: 1) at speed waterline profiles; 2) ship motions in head seas; and 3) three-dimensional breaking bow waves. PBLM is shown to be robust and produce ...

Weymouth, Gabriel D

2014-01-01

307

Mirror-type Boundary Condition in Smoothed Particle Hydrodynamics  

NASA Astrophysics Data System (ADS)

The main purpose of this study is to enhance the Smoothed Particle Hydrodynamics (SPH) method that can accurately simulate the hydrodynamic forces on a structure and can be used for determining efficient designs for wave energy devices. Smoothed particle hydrodynamics is a method used in various fields of study. Unlike the finite difference method (FDM), SPH is a Lagrangian mesh-free method in which each particle moves according to the property of the surrounding flow and governing conservation equations, and carries the properties of water such as density, pressure and mass. Smoothed Particle Hydrodynamics is recently applied to a wide range of fluid mechanics problems. Although it is known as a highly accurate model, slow performance in 3D interface is one of its drawbacks. Not only the computational time becomes very long but also the number of processors and required memory are not easily available. Practical applications deal with high Reynolds numbers that requires high resolution to achieve adequate accuracy. A large number of coastal engineering problems are geometrically symmetric; hence, as a solution, mirror boundary condition is introduced and applied to two different tests in this paper, one is the impact of solitary wave on a large circular cylinder and the other is the interaction of dam break wave and structure. Mirror boundary condition can either produce a remarkable speedup with the same number of processors or the same running time with less number of processors. Regarding the fact that SPH algorithm yields Np log(Np) particle interactions at each time step, reducing the number of particles by a factor of 2 decreases the total number of interactions by a factor greater than 2. In other words, the relation between computational time and the number of particles does not behave like a linear function. Results show that smaller number of particles results in fewer particle interactions and less communications between processors. We believe that this technique is one of the best approaches to reduce the total number of particles by half. Simulating the half-basin model leads to a significant speedup of about 2.7. Half-basin model reproduces the laboratory data as precisely as full-size model does. Dam Break test by SPH - Half basin

Marjani, A.; Edge, B. L.

2013-12-01

308

Oscillations and Waves  

NASA Astrophysics Data System (ADS)

This book emerged from a course given at Moscow State University and provides an introduction to current research in general relativity, relativistic gas dynamics, and cosmology, touching as well on the different methods used in wave theory. Each chapter begins with an elementary introduction and then proceeds to a more sophisticated discussion including a presentation of the current state of the art. Topics covered include: original results of and approaches to the mathematical theory of strong gravitational and electromagnetic fields in general relativity which reduce the problem to a single linear integral equation; the theory of black holes; wave propagation in the vicinity of black holes; the effect of strong external electromagnetic fields on gravitational and electromagnetic waves of short length; the theory of integrable nonlinear two-dimensional systems in theoretical physics; methods of relativistic and magneto gas dynamics in cosmology including shock and acoustic waves; hydrodynamical effects due to the rotation of a pulsar in a closed binary system.

Sibgatullin, Nail R.; Queen, N. M.

309

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

E-print Network

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

Denny, Mark

310

Probabilistic analysis for wave?induced submarine landslides  

Microsoft Academic Search

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

M. S. Rahman; F. M. Layas

1985-01-01

311

Dynamic coupling of a three-dimensional hydrodynamic model with a laterally averaged, two-dimensional hydrodynamic model  

NASA Astrophysics Data System (ADS)

An efficient method to dynamically couple a three-dimensional (3D) hydrodynamic model with a laterally averaged, two-dimensional (2DV) hydrodynamic model is described. The method is a useful tool to incorporate narrow tributaries that have vertically 2D flow patterns into a three-dimensional hydrodynamic simulation for a shallow and large water body that has a 3D flow pattern. The coupling of the two models is facilitated with a free-surface correction (FSC) method that is unconditionally stable with respect to gravity waves, wind and bottom shear stresses, and vertical eddy viscosity terms. The coupled model solves laterally averaged (2DV) Reynolds-averaged Navier-Stokes (RANS) equations for the narrow tributaries and three-dimensional RANS equations for the larger water body. The coupled 3D-2DV model was used to simulate hydrodynamics and salinity transport processes in an idealized estuary with a large water body and two narrow tributaries. In the 3D-2DV simulation, the entire simulation domain was split into one 3D subdomain and two 2DV subdomains. To illustrate the efficiency of the coupled 3D-2DV model, a 3D simulation was also conducted for the entire simulation domain. It was found that the coupled 3D-2DV model can generate the same model results as those by the 3D model but uses less than half of the computer time of the 3D simulation for this particular case. An application of the coupled 3D-2DV model to the Lower Peace River-Upper Charlotte Harbor (LPR-UCH) system in southwest Florida, USA, shows that the dynamically coupled model retains the efficiency of both the 3D model and the 2DV model.

Chen, Xinjian

2007-07-01

312

The magneto-optical behaviors modulated by unaggregated system for ?-Fe2O3-ZnFe2O4 binary ferrofluids  

NASA Astrophysics Data System (ADS)

Under an external magnetic field, when circularly polarized light was transmitted through binary ferrofluids based on strongly magnetic ?-Fe2O3 and weakly magnetic ZnFe2O4 nanoparticles, the birefringence ?n and dichroism ?k arising from the chains of ?-Fe2O3 particles system were modulated and decreased by the unchained ZnFe2O4 particles. In our experiments, we used two types of ZnFe2O4 nanoparticles: one consisted of ZnFe2O4(1) particles with higher moments, and the other consisted of ZnFe2O4(2) particles with lower moments. Comparing the birefringence and dichroism of the ?-Fe2O3-ZnFe2O4(1) and ?-Fe2O3-ZnFe2O4(2) binary ferrofluids, it was found that the modulating action of the ZnFe2O4(2) particle system with lower moments was larger than that of the ZnFe2O4(1) particle system with higher moments. Using a model for a bi-dispersed system based on chained and unchained particles, the behavior of the modulating action was explained by an additional effective relative magnetic permeability, which depends on the background of the unchained ZnFe2O4 particles for the chained ?-Fe2O3 particles and a field-induced demixing phase transition. These results showed that for binary ferrofluids based on both strong and weak magnetic nanoparticles, the power of the modulation of the magneto-optical effects depends on the difference in magnetization between the particles.

Li, Jian; Fu, Jun; Lin, Yueqiang; Liu, Xiaodong; Lin, Lihua; Chen, Longlong

2012-12-01

313

Hydroporation as the mechanism of hydrodynamic delivery  

Microsoft Academic Search

We have reported that a rapid tail vein injection of a large volume of plasmid DNA solution into a mouse results in high level of transgene expression in the liver. Gene transfer efficiency of this hydrodynamics-based procedure is determined by the combined effect of a large volume and high injection speed. Here, we show that the hydrodynamic injection induces a

G Zhang; X Gao; Y K Song; R Vollmer; D B Stolz; J Z Gasiorowski; D A Dean; D Liu

2004-01-01

314

An overview of hydrodynamic studies of mineralization  

Microsoft Academic Search

Fluid flow is an integral part of hydrothermal mineralization, and its analysis and characterization constitute an important part of a mineralization model. The hydrodynamic study of mineralization deals with analyzing the driving forces, fluid pressure regimes, fluid flow rate and direction, and their relationships with localization of mineralization. This paper reviews the principles and methods of hydrodynamic studies of mineralization,

Guoxiang Chi; Chunji Xue

2011-01-01

315

Hydrodynamics of prey capture in sharks: effects  

E-print Network

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

Nauwelaerts, Sandra

316

Relativistic Hydrodynamics for Heavy-Ion Collisions  

ERIC Educational Resources Information Center

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

Ollitrault, Jean-Yves

2008-01-01

317

Lattice Boltzmann simulations of liquid crystal hydrodynamics  

NASA Astrophysics Data System (ADS)

We describe a lattice Boltzmann algorithm to simulate liquid crystal hydrodynamics. The equations of motion are written in terms of a tensor order parameter. This allows both the isotropic and the nematic phases to be considered. Backflow effects and the hydrodynamics of topological defects are naturally included in the simulations, as are non-Newtonian flow properties such as shear thinning and shear banding.

Denniston, Colin; Orlandini, Enzo; Yeomans, J. M.

2001-05-01

318

Hydrodynamic simulations with the Godunov SPH  

Microsoft Academic Search

We present results based on an implementation of the Godunov Smoothed Particle Hydrodynamics (GSPH), originally developed by Inutsuka (2002), in the GADGET-3 hydrodynamic code. We first review the derivation of the GSPH discretization of the equations of moment and energy conservation, starting from the convolution of these equations with the interpolating kernel. The two most important aspects of the numerical

Giuseppe Murante; Stefano Borgani; Riccardo Brunino; Suneg-Hoon Cha

2011-01-01

319

Weakly nonlocal hydrodynamics and the origin of viscosity in the adhesion model  

SciTech Connect

We use the weakly nonlocal hydrodynamics approach to obtain a dynamical equation for the peculiar velocity field in which the viscosity term is physically motivated. Based on some properties of the Ginzburg-Landau equation and the wave mechanics analog of hydrodynamics we find the nonlocal adhesion approximation taking into account the internal structures of the Zeldovich pancakes. If the internal structures correspond to significant mesoscopic fluctuations, viscosity is probably driven by a stochastic force and dynamics is given by the noisy Burgers equation.

Ribeiro, A.L.B.; Peixoto de Faria, J.G. [Laboratorio de Astrofisica Teorica e Observacional, Departamento de Ciencias Exatas e Tecnologicas, Universidade Estadual de Santa Cruz, Ilheus-BA (45650-000) (Brazil)

2005-03-15

320

Weakly Nonlocal Hydrodynamics and the Origin of Viscosity in the Adhesion Model  

E-print Network

We use the weakly nonlocal hydrodynamics approach to obtain a dynamical equation for the peculiar velocity field in which the viscosity term is physically motivated. Based on some properties of the Ginzburg-Landau equation and the wave mechanics analog of hydrodynamics we find the nonlocal adhesion approximation taking into account the internal structures of the Zeldovich pancakes. If the internal structures correspond to significant mesoscopic fluctuations, viscosity is probably driven by a stochastic force and dynamics is given by the noisy Burgers equation.

Ribeiro, A L B

2005-01-01

321

Weakly Nonlocal Hydrodynamics and the Origin of Viscosity in the Adhesion Model  

E-print Network

We use the weakly nonlocal hydrodynamics approach to obtain a dynamical equation for the peculiar velocity field in which the viscosity term is physically motivated. Based on some properties of the Ginzburg-Landau equation and the wave mechanics analog of hydrodynamics we find the nonlocal adhesion approximation taking into account the internal structures of the Zeldovich pancakes. If the internal structures correspond to significant mesoscopic fluctuations, viscosity is probably driven by a stochastic force and dynamics is given by the noisy Burgers equation.

A. L. B. Ribeiro; J. G. Peixoto de Faria

2005-02-28

322

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

SciTech Connect

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

Nelson, Eric M [Los Alamos National Laboratory

2008-01-01

323

Effect of Surface Roughness on Hydrodynamic Bearings  

NASA Technical Reports Server (NTRS)

A theoretical analysis on the performance of hydrodynamic oil bearings is made considering surface roughness effect. The hydrodynamic as well as asperity contact load is found. The contact pressure was calculated with the assumption that the surface height distribution was Gaussian. The average Reynolds equation of partially lubricated surface was used to calculate hydrodynamic load. An analytical expression for average gap was found and was introduced to modify the average Reynolds equation. The resulting boundary value problem was then solved numerically by finite difference methods using the method of successive over relaxation. The pressure distribution and hydrodynamic load capacity of plane slider and journal bearings were calculated for various design data. The effects of attitude and roughness of surface on the bearing performance were shown. The results are compared with similar available solution of rough surface bearings. It is shown that: (1) the contribution of contact load is not significant; and (2) the hydrodynamic and contact load increase with surface roughness.

Majumdar, B. C.; Hamrock, B. J.

1981-01-01

324

Nonlinear waves in strongly interacting relativistic fluids  

E-print Network

During the past decades the study of strongly interacting fluids experienced a tremendous progress. In the relativistic heavy ion accelerators, specially the RHIC and LHC colliders, it became possible to study not only fluids made of hadronic matter but also fluids of quarks and gluons. Part of the physics program of these machines is the observation of waves in this strongly interacting medium. From the theoretical point of view, these waves are often treated with li-nearized hydrodynamics. In this text we review the attempts to go beyond linearization. We show how to use the Reductive Perturbation Method to expand the equations of (ideal and viscous) relativistic hydrodynamics to obtain nonlinear wave equations. These nonlinear wave equations govern the evolution of energy density perturbations (in hot quark gluon plasma) or baryon density perturbations (in cold quark gluon plasma and nuclear matter). Different nonlinear wave equations, such as the breaking wave, Korteweg-de Vries and Burgers equations, are...

Fogaça, D A; Filho, L G Ferreira

2013-01-01

325

Self-assembly of polymers or copolymers and ferrofluids leading to either 1-d, 2-d or 3-d aggregates decorated with magnetic nanoparticles  

E-print Network

A novel type of hybrid colloids is presented, based on the association of several polymeric systems and ferrofluids. On the one hand, we use inorganic nanoparticles made of magnetic iron oxide prepared at the LI2C, which response to a magnetic field of low intensity. On the other hand the organic part is made either of long linear polyacrylamide chains or of mesoscopic structures (vesicles and micelles) self-assembled from amphiphile polybutadiene-b-poly(glutamic acid) di-block copolymers, which conformation is pH-sensitive.

Delphine El Kharrat; Olivier Sandre; Régine Perzynski; Frédéric Chécot; Sébastien Lecommandoux

2007-09-21

326

The hydrodynamic theory of detonation  

NASA Technical Reports Server (NTRS)

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

Langweiler, Heinz

1939-01-01

327

Anomalous hydrodynamics kicks neutron stars  

E-print Network

Observations show that, at the beginning of their existence, neutron stars are accelerated briskly to velocities of up to $1000$ km/s. We discuss possible mechanisms contributing to these kicks in a systematic effective-field-theory framework. Anomalies of the underlying microscopic theory result in chiral transport terms in the hydrodynamic description, and we identify these as explanation for the drastic acceleration. In the presence of vorticity or a magnetic field, the chiral transport effects cause neutrino emission along the respective axes. In typical scenarios, the transport effect due to the magnetic field turns out to be strong enough to explain the kicks. Mixed gauge-gravitational anomalies enter in a distinct way, and we also discuss their implications.

Kaminski, Matthias; Bleicher, Marcus; Schaffner-Bielich, Jürgen

2014-01-01

328

Hydrodynamic assembly for Fast Ignition  

NASA Astrophysics Data System (ADS)

We present directly and indirectly driven implosion designs for Fast Ignition. Directly driven designs using various laser illumination wavelengths are described. We compare these designs with simple hydrodynamic efficiency models. Capsules illuminated with less than 1 MJ of light with perfect zooming at low intensity and low contrast ratio in power can assemble 4 mg of fuel to column density in excess of 3 g/cm^2. We contrast these designs with more optimized designs that lead to Guderley-style self similar implosions. Indirectly driven capsules absorbing 75 kJ of xrays can assemble 0.7 mg to column density 2.7 g/cm^2 in 1D simulations. We describe 2-D simulations including both capsules and attached cones driven by radiation. We describe issues in assembling fuel near the cone tip and cone disruption.

Tabak, Max; Clark, Daniel; Town, Richard; Hatchett, Stephen

2007-11-01

329

Radiation hydrodynamics in solar flares  

SciTech Connect

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.

Fisher, G.H.

1985-10-18

330

The hydrodynamics of dolphin drafting  

PubMed Central

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

Weihs, Daniel

2004-01-01

331

Pilot-wave hydrodynamics in a rotating frame: Exotic orbits  

NASA Astrophysics Data System (ADS)

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

Oza, Anand U.; Wind-Willassen, Øistein; Harris, Daniel M.; Rosales, Rodolfo R.; Bush, John W. M.

2014-08-01

332

Nonlinear density waves in the single-wave model  

SciTech Connect

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.

Marinov, Kiril B. [ASTeC, STFC Daresbury Laboratory, Keckwick Lane, Daresbury, Cheshire WA4 4AD (United Kingdom); Cockcroft Institute, Keckwick Lane, Daresbury, Cheshire WA4 4AD (United Kingdom); Tzenov, Stephan I. [Cockcroft Institute, Keckwick Lane, Daresbury, Cheshire WA4 4AD (United Kingdom); Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)

2011-03-15

333

Hydrodynamic construction of the electromagnetic field  

E-print Network

We present an alternative Eulerian hydrodynamic model for the electromagnetic field in which the discrete vector indices in Maxwell\\s equations are replaced by continuous angular freedoms, and develop the corresponding Lagrangian picture in which the fluid particles have rotational and translational freedoms. This enables us to extend to the electromagnetic field the exact method of state construction proposed previously for spin 0 systems, in which the time-dependent wavefunction is computed from a single-valued continuum of deterministic trajectories where two spacetime points are linked by at most a single orbit. The deduction of Maxwell\\s equations from continuum mechanics is achieved by generalizing the spin 0 theory to a general Riemannian manifold from which the electromagnetic construction is extracted as a special case. In particular, the flat-space Maxwell equations are represented as a curved-space Schr\\"odinger equation for a massive system. The Lorentz covariance of the Eulerian field theory is obtained from the non-covariant Lagrangian-coordinate model as a kind of collective effect. The method makes manifest the electromagnetic analogue of the quantum potential that is tacit in Maxwell\\s equations. This implies a novel definition of the \\classical limit\\ of Maxwell\\s equations that differs from geometrical optics. It is shown that Maxwell\\s equations may be obtained by canonical quantization of the classical model. Using the classical trajectories a novel expression is derived for the propagator of the electromagnetic field in the Eulerian picture. The trajectory and propagator methods of solution are illustrated for the case of a light wave.

Peter Holland

2004-11-18

334

Conservative, special-relativistic smoothed particle hydrodynamics  

SciTech Connect

We present and test a new, special-relativistic formulation of smoothed particle hydrodynamics (SPH). Our approach benefits from several improvements with respect to earlier relativistic SPH formulations. It is self-consistently derived from the Lagrangian of an ideal fluid and accounts for the terms that stem from non-constant smoothing lengths, usually called 'grad-h terms'. In our approach, we evolve the canonical momentum and the canonical energy per baryon and thus circumvent some of the problems that have plagued earlier formulations of relativistic SPH. We further use a much improved artificial viscosity prescription which uses the extreme local eigenvalues of the Euler equations and triggers selectively on (a) shocks and (b) velocity noise. The shock trigger accurately monitors the relative density slope and uses it to fine-tune the amount of artificial viscosity that is applied. This procedure substantially sharpens shock fronts while still avoiding post-shock noise. If not triggered, the viscosity parameter of each particle decays to zero. None of these viscosity triggers is specific to special relativity, both could also be applied in Newtonian SPH. The performance of the new scheme is explored in a large variety of benchmark tests where it delivers excellent results. Generally, the grad-h terms deliver minor, though worthwhile, improvements. As expected for a Lagrangian method, it performs close to perfect in supersonic advection tests, but also in strong relativistic shocks, usually considered a particular challenge for SPH, the method yields convincing results. For example, due to its perfect conservation properties, it is able to handle Lorentz factors as large as {gamma} = 50,000 in the so-called wall shock test. Moreover, we find convincing results in a rarely shown, but challenging test that involves so-called relativistic simple waves and also in multi-dimensional shock tube tests.

Rosswog, Stephan, E-mail: s.rosswog@jacobs-university.d [School of Engineering and Science, Jacobs University Bremen, 28759 Bremen (Germany)

2010-11-01

335

Conservative, special-relativistic smoothed particle hydrodynamics  

NASA Astrophysics Data System (ADS)

We present and test a new, special-relativistic formulation of smoothed particle hydrodynamics (SPH). Our approach benefits from several improvements with respect to earlier relativistic SPH formulations. It is self-consistently derived from the Lagrangian of an ideal fluid and accounts for the terms that stem from non-constant smoothing lengths, usually called “grad-h terms”. In our approach, we evolve the canonical momentum and the canonical energy per baryon and thus circumvent some of the problems that have plagued earlier formulations of relativistic SPH. We further use a much improved artificial viscosity prescription which uses the extreme local eigenvalues of the Euler equations and triggers selectively on (a) shocks and (b) velocity noise. The shock trigger accurately monitors the relative density slope and uses it to fine-tune the amount of artificial viscosity that is applied. This procedure substantially sharpens shock fronts while still avoiding post-shock noise. If not triggered, the viscosity parameter of each particle decays to zero. None of these viscosity triggers is specific to special relativity, both could also be applied in Newtonian SPH.The performance of the new scheme is explored in a large variety of benchmark tests where it delivers excellent results. Generally, the grad-h terms deliver minor, though worthwhile, improvements. As expected for a Lagrangian method, it performs close to perfect in supersonic advection tests, but also in strong relativistic shocks, usually considered a particular challenge for SPH, the method yields convincing results. For example, due to its perfect conservation properties, it is able to handle Lorentz factors as large as ? = 50,000 in the so-called wall shock test. Moreover, we find convincing results in a rarely shown, but challenging test that involves so-called relativistic simple waves and also in multi-dimensional shock tube tests.

Rosswog, Stephan

2010-11-01

336

Waves and Wave Properties  

NSDL National Science Digital Library

Students learn about the types of waves and how they change direction, as well as basic wave properties such as wavelength, frequency, amplitude and speed. During the presentation of lecture information on wave characteristics and properties, students take notes using a handout. Then they label wave parts on a worksheet diagram and draw their own waves with specified properties (crest, trough and wavelength). They also make observations about the waves they drew to determine which has the highest and the lowest frequency. With this knowledge, students better understand waves and are a step closer to understanding how humans see color.

Research Experience for Teachers (RET) Program, Center of Advancement of Engineering Fibers and Films,

337

Algorithm refinement for fluctuating hydrodynamics  

E-print Network

refinement by the com- putation of a moving shock wave. Mean system behavior and second moment statistics. As an example, consider the classical Rayleigh-Taylor prob- lem and the related Richtmyer-Meshkov instability, in stochastic atomistic simula- tions of Rayleigh-Taylor, and in laboratory experiments, spikes of

338

Cycloidal Wave Energy Converter  

SciTech Connect

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

Stefan G. Siegel, Ph.D.

2012-11-30

339

Quantum ideal hydrodynamics on the lattice  

E-print Network

After discussing the problem of defining the hydrodynamic limit from microscopic scales, we give an introduction to ideal hydrodynamics in the Lagrange picture, and show that it can be viewed as a field theory, which can be quantized using the usual Feynman sum-over-paths prescription. We then argue that this picture can be connected to the usually neglected thermal microscopic scale in the hydrodynamic expansion. After showing that this expansion is generally non-perturbative, we show how the lattice can be used to understand the impact quantum and thermal fluctuations can have on the fluid behavior.

Tommy Burch; Giorgio Torrieri

2013-11-13

340

A hybrid level set/volume-of-fluid approach for simulation of nearshore hydrodynamics  

NASA Astrophysics Data System (ADS)

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.

Bakhtyar, R.; Kees, C. E.; Miller, C. T.; Farthing, M. W.

2013-12-01

341

SAR imagery of ocean-wave swell traveling in an arbitrary direction  

Microsoft Academic Search

The intensity wave like patterns observed in Synthetic Aperture Radar (SAR) are known to be caused by two mechanisms: the microwave radar cross sectional amplitude modulation due to tilt and hydrodynamic interaction of the long ocean waves, and intensity modulation due to the motion of the long ocean waves. Two dimensional closed form expressions of intensity wave patterns based on

C. L. Rufenach; R. A. Shuchman; D. R. Lyzenga

1984-01-01

342

Hydrodynamics of unitary Fermi gases  

NASA Astrophysics Data System (ADS)

Unitary fermi gases have been widely studied as they provide a tabletop archetype for re- search on strongly coupled many body systems and perfect fluids. Research into unitary fermi gases can provide insight into may other strongly interacting systems including high temperature superconductor, quark-gluon plasmas, and neutron stars. Within the unitary regime, the equilib- rium transport coefficients and thermodynamic properties are universal functions of density and temperature. Thus, unitary fermi gases provide a archetype to study nonperturbative many-body physics, which is of fundamental significance and crosses several fields. This thesis reports on two topics regarding unitary fermi gases. A recent string theory conjecture gives a lower bound for the dimensionless ratio of shear viscosity of entropy, ?/s ? 4pi /kb . Unitary fermi gases are a candidate for prefect fluids, yet ?/s is well above the string theory bound. Using a stochastic formulation of hydrodynamics, we calculate a lower bound for this ratio accounting for the momentum dissipation from fluctuations. This lower bound is in good agreement with both theoretical and experimental results. The second question addressed is the simulation of elliptic flow. Elliptic flow, first observed in 2002, is a characteristic of strongly coupled systems and has been studied in both quark-gluon plasmas and unitary fermi gases. As such, simulations of these systems are of interest. We test a variety of lattice Boltzmann models and compare the simulation results to the theoretical and experimental findings.

Young, Ryan E.

343

The hydrodynamics of swimming microorganisms  

E-print Network

Cell motility in viscous fluids is ubiquitous and affects many biological processes, including reproduction, infection, and the marine life ecosystem. Here we review the biophysical and mechanical principles of locomotion at the small scales relevant to cell swimming (tens of microns and below). The focus is on the fundamental flow physics phenomena occurring in this inertia-less realm, and the emphasis is on the simple physical picture. We review the basic properties of flows at low Reynolds number, paying special attention to aspects most relevant for swimming, such as resistance matrices for solid bodies, flow singularities, and kinematic requirements for net translation. Then we review classical theoretical work on cell motility: early calculations of the speed of a swimmer with prescribed stroke, and the application of resistive-force theory and slender-body theory to flagellar locomotion. After reviewing the physical means by which flagella are actuated, we outline areas of active research, including hydrodynamic interactions, biological locomotion in complex fluids, the design of small-scale artificial swimmers, and the optimization of locomotion strategies.

Eric Lauga; Thomas R. Powers

2008-12-15

344

Differential geometry of hydrodynamic Vlasov equations  

NASA Astrophysics Data System (ADS)

We consider hydrodynamic chains in (1+1) dimensions which are Hamiltonian with respect to the Kupershmidt-Manin Poisson bracket. These systems can be derived from single (2+1) equations, here called hydrodynamic Vlasov equations, under the map An=?-??pnfdp. For these equations an analogue of the Dubrovin-Novikov Hamiltonian structure is constructed. The Vlasov formalism allows us to describe objects like the Haantjes tensor for such a chain in a much more compact and computable way. We prove that the necessary conditions found by Ferapontov and Marshall in [E.V. Ferapontov, D.G. Marshall, Differential-geometric approach to the integrability of hydrodynamic chains: The Haantjes tensor. arXiv:nlin.SI/0505013, 2005] for the integrability of these hydrodynamic chains are also sufficient.

Gibbons, John; Raimondo, Andrea

2007-08-01

345

Geometry and Starvation Effects in Hydrodynamic Lubrication.  

National Technical Information Service (NTIS)

Numerical methods were used to determine the effects of lubricant starvation on the minimum film thickness under conditions of a hydrodynamic point contact. Starvation was effected by varying the fluid inlet level. The Reynolds boundary conditions were ap...

D. E. Brewe, B. J. Hamrock

1982-01-01

346

Anisotropic hydrodynamics for conformal Gubser flow  

E-print Network

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 SO(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 spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches. In addition, we prove that anisotropic hydrodynamics gives t...

Nopoush, Mohammad; Strickland, Michael

2014-01-01

347

Quantum dynamics using hydrodynamic trajectories  

NASA Astrophysics Data System (ADS)

In this talk we will give a brief overview of our recent work in developing a causal trajectory approach for simulating quantum dynamics in a variety of systems. These trajectories arise as solutions to the de Broglie/Bohm equations, which replace the Schrödinger wave equation with the continuity equation for the quantum density and a quantum Hamilton-Jacobi equation for a set of ray-like trajectories. Whereas typical applications of this approach have focused upon the use of a "pilot wave" approach whereby the trajectories are obtained from quantum wavefunction, i.e. p[?] =hbar Im[nablalog?], our approach discretizes the density and allowes the discretization points to move according Lagrangian equations of motion derived from the quantum Hamilton-Jacobi equation. We demonstrate the approach via a series of test cases and comment upon the various strengths and difficulties of the approach. In particular, we will discuss what happens when nodes form in the quantum density.

Bittner, Eric

2000-03-01

348

Hydrodynamic Cavitation for Food and Water Processing  

Microsoft Academic Search

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

Parag R. Gogate

2011-01-01

349

Micro-Roughness Effects in (Elasto)Hydrodynamic Lubrication Including  

E-print Network

on the model are presented for the case of a hydrodynamically lubricated journal bearings and an elasto-hydrodynamicallyMicro-Roughness Effects in (Elasto)Hydrodynamic Lubrication Including a Mass-Flow Preserving roughness, taking JFO mass flow preserving cavitation model and elasto- hydrodynamic effects into account

Paris-Sud XI, Université de

350

Hydrodynamic simulations of He-shell flash convection  

E-print Network

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

Falk Herwig; Bernd Freytag; Robert M. Hueckstaedt; Francis X. Timmes

2006-01-09

351

Numerical simulation of the hydrodynamic instability experiments and flow mixing  

NASA Astrophysics Data System (ADS)

Based on the numerical methods of volume of fluid (VOF) and piecewise parabolic method (PPM) and parallel circumstance of Message Passing Interface (MPI), a parallel multi-viscosity-fluid hydrodynamic code MVPPM (Multi-Viscosity-Fluid Piecewise Parabolic Method) is developed and performed to study the hydrodynamic instability and flow mixing. Firstly, the MVPPM code is verified and validated by simulating three instability cases: The first one is a Riemann problem of viscous flow on the shock tube; the second one is the hydrodynamic instability and mixing of gaseous flows under re-shocks; the third one is a half height experiment of interfacial instability, which is conducted on the AWE’s shock tube. By comparing the numerical results with experimental data, good agreement is achieved. Then the MVPPM code is applied to simulate the two cases of the interfacial instabilities of jelly models accelerated by explosion products of a gaseous explosive mixture (GEM), which are adopted in our experiments. The first is implosive dynamic interfacial instability of cylindrical symmetry and mixing. The evolving process of inner and outer interfaces, and the late distribution of mixing mass caused by Rayleigh-Taylor (RT) instability in the center of different radius are given. The second is jelly layer experiment which is initialized with one periodic perturbation with different amplitude and wave length. It reveals the complex processes of evolution of interface, and presents the displacement of front face of jelly layer, bubble head and top of spike relative to initial equilibrium position vs. time. The numerical results are in excellent agreement with that experimental images, and show that the amplitude of initial perturbations affects the evolvement of fluid mixing zone (FMZ) growth rate extremely, especially at late times.

Bai, Jingsong; Wang, Tao; Li, Ping; Zou, Liyong; Liu, Cangli

2009-12-01

352

Hydrodynamics of soft active matter  

NASA Astrophysics Data System (ADS)

This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: biofilaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semimicroscopic to phenomenological. In particular, first considered are “dry” systems, defined as those where momentum is not conserved due to friction with a substrate or an embedding porous medium. The differences and similarities between two types of orientationally ordered states, the nematic and the polar, are clarified. Next, the active hydrodynamics of suspensions or “wet” systems is discussed and the relation with and difference from the dry case, as well as various large-scale instabilities of these nonequilibrium states of matter, are highlighted. Further highlighted are various large-scale instabilities of these nonequilibrium states of matter. Various semimicroscopic derivations of the continuum theory are discussed and connected, highlighting the unifying and generic nature of the continuum model. Throughout the review, the experimental relevance of these theories for describing bacterial swarms and suspensions, the cytoskeleton of living cells, and vibrated granular material is discussed. Promising extensions toward greater realism in specific contexts from cell biology to animal behavior are suggested, and remarks are given on some exotic active-matter analogs. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized.

Marchetti, M. C.; Joanny, J. F.; Ramaswamy, S.; Liverpool, T. B.; Prost, J.; Rao, Madan; Simha, R. Aditi

2013-07-01

353

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

Microsoft Academic Search

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

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

2011-01-01

354

RICH: Numerical simulation of compressible hydrodynamics on a moving Voronoi mesh  

NASA Astrophysics Data System (ADS)

RICH (Racah Institute Computational Hydrodynamics) is a 2D hydrodynamic code based on Godunov's method. The code, largely based on AREPO, acts on an unstructured moving mesh. It differs from AREPO in the interpolation and time advancement scheme as well as a novel parallelization scheme based on Voronoi tessellation. Though not universally true, in many cases a moving mesh gives better results than a static mesh: where matter moves one way and a sound wave is traveling in the other way (such that relative to the grid the wave is not moving), a static mesh gives better results than a moving mesh. RICH is designed in an object oriented, user friendly way that facilitates incorporation of new algorithms and physical processes.

Yalinewich, Almog; Steinberg, Elad; Sari, Re'em

2014-10-01

355

Advanced multi-dimensional method for structural and hydrodynamic analyses of LMFBR piping systems  

SciTech Connect

Maintaining the structural integrity of the piping system of Liquid Metal Fast Breeder Reactors (LMFBRs) is essential to the safe operation of the reactor and steam supply systems. In the safety analysis various transient loads can be imposed on the piping systems, which may pose threats to the integrity of the piping structure. These transient loads can be classified into two categories. The first represents dynamic loads resulting from the hydrodynamic pressure-wave propagation or seismic events. The second represents static or quasi-dynamic loads generated by thermal wave propagation, normal operation transient, or creep phenomena. At Argonne National Laboratory, a multi-dimensional method has been developed for the integrated analysis of piping systems under these transient loading conditions. It utilizes a 2-D implicit finite-difference hydrodynamics in conjunction with a 3-D explicit finite-element structural analysis.

Wang, C.Y.; Zeuch, W.R.

1985-04-09

356

Rich: Open Source Hydrodynamic Simulation on a Moving Voronoi Mesh  

E-print Network

We present here RICH, a state of the art 2D hydrodynamic code based on Godunov's method, on an unstructured moving mesh (the acronym stands for Racah Institute Computational Hydrodynamics). This code is largely based on the code AREPO. It differs from AREPO in the interpolation and time advancement scheme as well as a novel parallelization scheme based on Voronoi tessellation. Using our code we study the pros and cons of a moving mesh (in comparison to a static mesh). We also compare its accuracy to other codes. Specifically, we show that our implementation of external sources and time advancement scheme is more accurate and robust than AREPO's, when the mesh is allowed to move. We performed a parameter study of the cell rounding mechanism (Llyod iterations) and it effects. We find that in most cases a moving mesh gives better results than a static mesh, but it is not universally true. In the case where matter moves in one way, and a sound wave is traveling in the other way (such that relative to the grid the...

Yalinewich, Almog; Sari, Re'em

2014-01-01

357

Hydrodynamics of rapidly rotating superfluid neutron stars with mutual friction  

E-print Network

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.

A. Passamonti; N. Andersson

2010-04-26

358

O the Nonlinear Dynamics of Ocean Wave Systems  

Microsoft Academic Search

The thesis is composed of three subjects, independent yet interrelated. The first part deals with the surface wave breaking problem, in which a mechanism of wave-breaking through intrinsic hydrodynamic instability is discovered. The second part is a general theory for non-linear evolution of three-dimensional resonant side-band wave systems. In part three, dynamics of nonlinear wave systems is generalized for non-conservative

Jiyue J. Li

1992-01-01

359

``Oenodynamic'': hydrodynamic of wine swirling  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

360

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

Microsoft Academic Search

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

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

2007-01-01

361

Analysis and design of hydrodynamic journal air bearings for high performance HDD spindle  

Microsoft Academic Search

In this paper, we proposed the design concept of NRRO-free non-contact bearings for a high performance hard disk drive (HDD) spindle. We numerically analyzed three types of hydrodynamic journal air bearings [gas dynamic bearing (GDB)], such as a partial herringbone groove, a sinusoidal wave, and a taper-flat type. And we compared their performances in terms of pressure distribution, load capacity,

T. Hwang; K. Ono

2003-01-01

362

Granular Solid Hydrodynamics (GSH): a broad-ranged macroscopic theory of granular media  

E-print Network

A unified continuum-mechanical theory has been until now lacking for granular media, some believe it could not exist. Derived employing the hydrodynamic approach, GSH is such a theory, though as yet a qualitative one. The behavior being accounted for includes static stress distribution, elastic wave, elasto-plastic motion, the critical state and rapid dense flow. The equations and application to a few typical experiments are presented here.

Yimin Jiang; Mario Liu

2014-07-27

363

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

SciTech Connect

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

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

2010-12-15

364

First step toward numerical hydrodynamics: SPH and Finite Differences with artificial dissipative terms  

NASA Astrophysics Data System (ADS)

In this academic work, we present a comparison between the Smoothed Particles Hydrodynamics (SPH) method and the standard finite differences (FD). As the test case for this comparison we use the Sod shock tube. In order to deal with the shock waves without using Riemann solvers, we add artificial viscosity to SPH and dissipation to the finite differences. We compare the numerical results with the exact solution and show the convergence of both methods.

Cruz-Pérez, J. P.; González, J. A.; Guzmán, F. S.; Lora-Clavijo, F. D.

2010-07-01

365

An application of unstructured grid system in hydrodynamic simulation  

SciTech Connect

The objective of this research is to develop a finite volume algorithm by utilizing an unstructured grid system to solve the integral form of free surface shallow water hydrodynamic equations. The algorithm is applicable to a triangular grid system or a hybrid grid system composed of a mixture of triangular and quadrilateral cells. Cell-centered discretization strategy is selected. A quadrature formula is used in the approximation of the integrals and the evaluation of various variables. An implicit scheme is employed for solving the governing equation system. The triangular grids are generated using a Delauney triangulation scheme based on Voronoi Diagrams. Long-term wave profiles obtained from a flow field simulation for coastal areas are presented to demonstrate the success of the algorithm.

Liu, J.J.; Soni, B.K. [Mississippi State Univ., MS (United States)

1996-12-31

366

A hydrodynamic model of locomotion in the Basilisk Lizard  

NASA Astrophysics Data System (ADS)

ORGANISMS with a body mass of more than one gram and which live at the air-water interface generally support their weight with their buoyant bodies. The maximum swimming speed these animals can attain is limited by wave-making resistance1-3. For high-speed progression across a body of water, shore birds and basilisk lizards (Basiliscus basiliscus) support their bodies above the water surface by repeatedly striking the surface with their feet. Here we investigate the mechanism of support in moderately sized basilisk lizards (about 90 g) by combining hydrodynamic measurements of a physical model of the lizards' feet with an analysis of video records of foot movements. We find basilisks of intermediate size obtain little support for their body weight by slapping the water surface; most of the support comes from stroking the foot downwards while expanding an air cavity underwater. The lizard minimizes downward forces by pulling its foot upward before the cavity collapses.

Glasheen, J. W.; McMahon, T. A.

1996-03-01

367

Post-Newtonian Hydrodynamics of Merging Neutron Stars  

NASA Astrophysics Data System (ADS)

We present results from our new Post-Newtonian (PN) Smoothed Particle Hydrodynamics (SPH) code, which has been used to study the coalescence of binary neutron star (NS) systems. The Lagrangian particle-based code incorporates consistently all lowest-order (1PN) relativistic effects, as well as gravitational radiation reaction, the lowest-order dissipative term in general relativity. We compare calculations of initially synchronized and nonsynchronized binaries, with and without 1PN effects, for NS with stiff equations of state, modeled as polytropes with ? =2-3, and for a range of binary mass ratios. We find that 1PN effects can play a major role in the coalescence, accelerating the final inspiral and causing a characteristic modulation of the gravitational wave signal at late times. This work was partially supported by the National Computational Science Alliance under grant AST980014N and utilized the NCSA SGI/CRAY Origin2000.

Faber, J. A.; Manor, J.; Rasio, F. A.

2000-05-01

368

Hydrodynamic Instability in an Extended Landau/Levich Model of Liquid-Propellant Combustion  

NASA Technical Reports Server (NTRS)

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.

Margolis, Stephen B.; Sackesteder, Kurt (Technical Monitor)

1998-01-01

369

Hydrodynamic comparison between the north and south of Mallorca Island  

NASA Astrophysics Data System (ADS)

A hydrodynamic comparison between two zones of fishing interest, one located to the north and the other to the south of Mallorca Island (Balearic Islands, Western Mediterranean) was done. The comparison was conducted using the data from two moorings, one placed in the middle of the Balearic Current, in the Balearic subbasin (herein, Sóller) and the other in the Mallorca Channel, near the Algerian subbasin (called Cabrera). The instruments moored, continuously recorded the temperature, salinity and currents at different depths, for over 15 months. The data analysis suggests that Sóller is hydrodynamically more active than Cabrera, at least during the time of recording the measurements. The mean currents were higher at Sóller than at Cabrera at all depths, also showing greater maximum speeds and variability. In addition, the presence of more mesoscale eddies in Sóller became evident from the altimetry data. These eddies were not only significantly more energetic near the surface, they also generally reached to greater depths, affecting the velocities of the seabed currents. Subsequent to each significant eddy episode, strong changes in temperature and/or salinity were observed, along the entire water column. Spectral analysis revealed the presence of high frequency oscillations with periods of a few hours. One energy peak, with a period around 3.7 h, was observed at both locations, probably related to trapped waves around Mallorca or the Balearic Islands, while others (3 h and 2 h) were reflected only in Sóller, suggesting they could be associated with some standing resonance waves between the Iberian Peninsula and Mallorca.

Amores, Angel; Monserrat, Sebastià

2014-10-01

370

Viscous Analysis of Pulsating Hydrodynamic Instability and Thermal Coupling Liquid-Propellant Combustion  

NASA Technical Reports Server (NTRS)

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.

Margolis, Stephen B.; Sacksteder, Kurt (Technical Monitor)

2000-01-01

371

Hydrodynamic modulation of pluripotent stem cells  

PubMed Central

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

2012-01-01

372

Fluctuating hydrodynamics and direct simulation Monte Carlo  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

373

Globally aligned states and hydrodynamic traffic jams in confined suspensions of active asymmetric particles  

NASA Astrophysics Data System (ADS)

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.

Lefauve, Adrien; Saintillan, David

2014-02-01

374

Hydrodynamic modeling of optically excited terahertz plasma oscillations in nanometric field effect transistors  

SciTech Connect

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.

Marinchio, H.; Sabatini, G.; Palermo, C.; Pousset, J.; Torres, J.; Chusseau, L.; Varani, L. [Institut d'Electronique du Sud, UMR 5214 CNRS, Universite Montpellier 2, 34095 Montpellier (France); Shiktorov, P.; Starikov, E.; Gruzinskis, V. [Semiconductor Physics Institute, A. Gostauto 11, 2600 Vilnius (Lithuania)

2009-05-11

375

Seismic Waves  

NSDL National Science Digital Library

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

376

Three-dimensional hydrodynamic instabilities in stellar core collapses  

NASA Astrophysics Data System (ADS)

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

Lou, Yu-Qing; Lian, Biao

2012-03-01

377

Kelvin-Helmholtz instabilities in smoothed particle hydrodynamics  

NASA Astrophysics Data System (ADS)

In this paper we investigate whether smoothed particle hydrodynamics (SPH), equipped with artificial conductivity (AC), 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, 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. The shocks are hard to avoid in SPH simulations with initial density gradients because the most straightforward way of removing them, i.e. relaxing the initial conditions, is not viable. Indeed, by the time sufficient relaxing has taken place the density and energy gradients have become prohibitively wide. The particle disorder introduced by the relaxation is also a problem. We show that setting up initial conditions with a suitably smoothed density gradient dramatically improves results: shock waves are reduced whilst retaining relatively sharp gradients and avoiding unnecessary particle disorder. Particle clumping is easy to overcome, the most straightforward method being the use of a suitable smoothing kernel with non-zero first central derivative. We present results to that effect using a new smoothing kernel: the linear quartic kernel. We also investigate the role of AC. Although AC is necessary in the simulations to avoid `oily' features in the gas due to artificial surface tension, we fail to find any relation between using AC and the appearance of seeded KH rolls. Including AC is necessary for the long-term behaviour of the simulation (e.g. to get ? = 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 energy diffusion. We present new signal velocities that lead to less diffusion. The effects of the shock waves and of particle disorder become less important as the time-scale of the physical problem (for the shearing layers problem: lower density contrast and higher Mach numbers) decreases. At the resolution of current galaxy formation simulations mixing is probably not important. However, mixing could become crucial for next-generation simulations.

Valcke, S.; de Rijcke, S.; Rödiger, E.; Dejonghe, H.

2010-10-01

378

An integrated coastal model for aeolian and hydrodynamic sediment transport  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

379

Dispersion Relation for MHD Waves  

NASA Astrophysics Data System (ADS)

We have derived a seventh degree polynomial for the dispersion relation, using the same set of basic equations which is used in Dwivedi & Pandey and Kumar et al.. Further, we have shown that the results for the fast and slow modes of magneto hydrostatic waves are independent of the degree of polynomial for the dispersion relation and the fifth degree polynomial is sufficient. For application of magneto hydrodynamics (MHD) in solar physics as well as in plasma physics, dispersion relation plays key role.

Dak, Ganpat

380

Radiation hydrodynamics integrated in the code PLUTO  

E-print Network

The transport of energy through radiation is very important in many astrophysical phenomena. In dynamical problems the time-dependent equations of radiation hydrodynamics have to be solved. We present a newly developed radiation-hydrodynamics module specifically designed for the versatile MHD code PLUTO. The solver is based on the flux-limited diffusion approximation in the two-temperature approach. All equations are solved in the co-moving frame in the frequency independent (grey) approximation. The hydrodynamics is solved by the different Godunov schemes implemented in PLUTO, and for the radiation transport we use a fully implicit scheme. The resulting system of linear equations is solved either using the successive over-relaxation (SOR) method (for testing purposes), or matrix solvers that are available in the PETSc library. We state in detail the methodology and describe several test cases in order to verify the correctness of our implementation. The solver works in standard coordinate systems, such as Ca...

Kolb, Stefan M; Kley, Wilhelm; Mignone, Andrea

2013-01-01

381

On Hydrodynamical Description of Thermal Photons  

E-print Network

The WA98 collaboration in the CERN SPS has reported an excess of photons over those originating from the decays of final hadrons in the lead-lead collisions. These photons can originate either from primary interactions of partons from colliding nuclei or from secondary interactions among produced particles. Photons produced in the secondary interactions, often called thermal photons, can be calculated by using thermal production rates and equilibrium hydrodynamics for the evolution of the expanding matter. I will review the main features of hydrodynamical studies for the WA98 data. The data can be reproduced both with or without a phase transition to the QGP, but high initial temperature, over the values predicted for the phase transition temperature, is required by the data. I will also show a prediction for the photon excess for central gold-gold collisions at the Brookhaven RHIC collider. In this prediction, the initial state for the hydrodynamical expansion is obtained from a perturbative QCD calculation.

S. S. Rasanen

2002-10-03

382

A hydrodynamic approach to cosmology - Methodology  

NASA Technical Reports Server (NTRS)

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.

Cen, Renyue

1992-01-01

383

Hydrodynamic simulations with the Godunov SPH  

E-print Network

We present results based on an implementation of the Godunov Smoothed Particle Hydrodynamics (GSPH), originally developed by Inutsuka (2002), in the GADGET-3 hydrodynamic code. We first review the derivation of the GSPH discretization of the equations of moment and energy conservation, starting from the convolution of these equations with the interpolating kernel. The two most important aspects of the numerical implementation of these equations are (a) the appearance of fluid velocity and pressure obtained from the solution of the Riemann problem between each pair of particles, and (b the absence of an artificial viscosity term. We carry out three different controlled hydrodynamical three-dimensional tests, namely the Sod shock tube, the development of Kelvin-Helmholtz instabilities in a shear flow test, and the "blob" test describing the evolution of a cold cloud moving against a hot wind. The results of our tests confirm and extend in a number of aspects those recently obtained by Cha (2010): (i) GSPH provi...

Murante, Giuseppe; Brunino, Riccardo; Cha, Suneg-Hoon

2011-01-01

384

Cilia beating patterns are not hydrodynamically optimal  

NASA Astrophysics Data System (ADS)

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.

Guo, Hanliang; Nawroth, Janna; Ding, Yang; Kanso, Eva

2014-09-01

385

Toward a Fully Consistent Radiation Hydrodynamics  

SciTech Connect

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

Castor, J I

2009-07-07

386

MLSPH: An Alternative to Smoothed Particle Hydrodynamics  

NASA Astrophysics Data System (ADS)

Smoothed Particle Hydrodynamics (SPH) is the primary numerical tool used to simulate galaxy interactions, and is extensively used in other fields of astrophysics and high-strain hydrodynamics. The reliability of SPH simulations is limited by consistency, accuracy, and artificial viscosity. These limitations can create results which depend on rather arbitrary numerical parameters rather than on the physical behavior of the modelled system. We have been studying alternatives to traditional SPH based on local polynomial modeling. These methods, including ``Moving Least-Squares Particle Hydrodynamics,'' show great promise in improving or eliminating the problems found in traditional SPH. We present an overview of this methods along with preliminary results obtained during the validation of these methods.

Wallin, J. F.; Dilts, G. A.; Haque, A.

2000-05-01

387

Wave reflection characteristics of plane, dentated and serrated seawalls  

Microsoft Academic Search

The hydrodynamic performance of vertical and sloped plane, dentated and serrated seawalls were investigated using physical model studies. Regular and random waves of wide range of heights and periods were used. Tests were carried out for different inclinations of the seawall (i.e. ?=30, 40, 50, 60 and 90°) and for a constant water depth of 0.7 m. The wave reflection

S. Neelamani; N. Sandhya

2003-01-01

388

Hydrodynamic Simulations with the Godunov SPH  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

389

Bounce-free spherical hydrodynamic implosion  

NASA Astrophysics Data System (ADS)

In a bounce-free spherical hydrodynamic implosion, the post-stagnation hot core plasma does not expand against the imploding flow. Such an implosion scheme has the advantage of improving the dwell time of the burning fuel, resulting in a higher fusion burn-up fraction. The existence of bounce-free spherical implosions is demonstrated by explicitly constructing a family of self-similar solutions to the spherically symmetric ideal hydrodynamic equations. When applied to a specific example of plasma liner driven magneto-inertial fusion, the bounce-free solution is found to produce at least a factor of four improvement in dwell time and fusion energy gain.

Kagan, Grigory; Tang, Xian-Zhu; Hsu, Scott C.; Awe, Thomas J.

2011-12-01

390

Hydrodynamic instabilities and the transition to turbulence  

NASA Astrophysics Data System (ADS)

Topics in hydrodynamic instability and the transition to turbulence covered include strange attractors and turbulence; hydrodynamic stability and bifurcation, with attention to the Navier-Stokes equations; chaotic behavior and fluid dynamics, with reference to the Lorenz equations and Landau's idea; and the transition to turbulence in Rayleigh-Benard convection. Also considered are instabilities and transition flow between concentric rotating cylinders; shear flow instabilities and transition; instabilities in geophysical fluid dynamics; and instabilities and chaos in nonhydrodynamic systems, such as those of the Rikitake dynamo model for the earth's magnetic field and the Belousov-Zhabotinskii chemical reaction.

Swinney, H. L.; Gollub, J. P.

391

Hydrodynamics, horizons, holography and black hole entropy  

E-print Network

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.

C. Sivaram

2011-05-20

392

A Numerical Model for Multigroup Radiation Hydrodynamics  

NASA Astrophysics Data System (ADS)

We present in this paper a multigroup model for radiation hydrodynamics to account for variations of the gas opacity as a function of frequency. The entropy closure model (M1) is applied to multigroup radiation transfer in a radiation hydrodynamics code. In difference from the previous grey model, we are able to reproduce the crucial effects of frequency-variable gas opacities, a situation omnipresent in physics and astrophysics. We also account for the energy exchange between neighbouring groups which is important in flows with strong velocity divergence. We presents some test problems as well as realistic frequency-dependent simulations of radiative shocks.

Vaytet, N.; Audit, E.; Dubroca, B.; González, M.

2012-07-01

393

Impact of Synoptic Meteorological Variations on Nearshore Hydrodynamics  

NASA Astrophysics Data System (ADS)

Passage of low pressure atmospheric frontal systems over the Southeast US introduces synoptic variation in meteorological parameters. Nearshore wave climate in this region is influenced by locally generated winds, showing a strong response to moving frontal systems. Accurate prediction of surf-zone response to wave forcing and wind forcing in general and atmospheric fronts in particular is important in quantifying sediment mobility and changes in beach morphodynamics. Energetic wave conditions can be attributed to three atmospheric front systems: 1) Cold Fronts, 2) Warm Fronts, and 3) Tropical Storms. Low pressure systems associated with cold fronts moving from west to east-northeast, change the wind direction from northeast to southwest. Conversely, warm fronts are accompanied by an opposite change in wind direction. Tropical storms moving nearshore rotate the wind direction slowly from southwest to southeast. Long term (2004- 2007) nearshore wind, wave and current information is analyzed from a station located at mean water depth of 5 meters on the coast of SC (Springmaid Pier) to examine the relationship between meteorological forcing and nearshore hydrodynamic conditions. Atmospheric pressure, temperature and wind velocity from the same station were used to identify, 24 cold fronts, 18 warm fronts and 14 tropical storms on average for each year from 2004-2007. In this contribution, a 2-D wave propagation model, Simulating WAves Nearshore (SWAN), coupled with the coastal-circulation model Regional Ocean Modeling System (ROMS v 3.0) is being used to predict longshore current and sediment transport in the surf zone in response to different types of fronts. The performance of the wave propagation model is evaluated with in-situ measurements collected as a part of South Carolina Coastal Erosion Study (SCCES) along the coast. Synthetic atmospheric fronts and tropical storms, developed from the climatic analysis, are used as input to the coupled models. The results are used to examine the overall impact of the different type of atmospheric fronts and tropical storms over a year in terms of net alongshelf sediment transport in surf zone.

Kumar, N.; Voulgaris, G.; Warner, J. C.

2008-12-01

394

On Pulsating and Cellular Forms of Hydrodynamic Instability in Liquid-Propellant Combustion  

NASA Technical Reports Server (NTRS)

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.

Margolis, Stephen B.; Sacksteder, Kurt (Technical Monitor)

1998-01-01

395

Radiative Hydrodynamic Models of Optical and Ultraviolet Emission from M Dwarf Flares  

E-print Network

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.

Joel C. Allred; Suzanne L. Hawley; William P. Abbett; Mats Carlsson

2006-03-08

396

Twisted electrostatic ion-cyclotron waves in dusty plasmas.  

PubMed

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

Shukla, P K

2013-01-01

397

Wave Properties  

NSDL National Science Digital Library

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

398

Roll-waves in bi-layer flows February 23, 2011  

E-print Network

frequency regime and show the occurence of hydrodynamic instabilities, so called roll-waves, when steady describe a lot of situations in geophysics and engineering: mud flows, submarine avalanches, transport of hydrodynamical instabilities in shallow waters. Moreover, the derivation of Kuramoto Sivashnisky equations

Paris-Sud XI, Université de

399

Unravelling the influence of water depth and wave energy on the facies diversity of shelf carbonates  

E-print Network

processes of storm and wave reworking influence the seabed through submarine erosion and sediment of a greater diversity in grain producers. Remote sensing imagery, field observa- tions and hydrodynamic models lithofacies, while highlighting the importance of hydrodynamics in directing the accumulation of carbonate

Purkis, Sam

400

NOAA Fisheries Protocols For Hydro-dynamic Dredge Surveys  

E-print Network

NOAA Fisheries Protocols For Hydro-dynamic Dredge Surveys: Surf Clams and Ocean Quahogs December 19..................................................................................................................................... 1 NOAA Fisheries Hydro-dynamic Clam Dredge Survey Protocols........................................................................... 5 Clam Dredge Construction and Repair

401

Dilepton production in schematic causal viscous hydrodynamics  

NASA Astrophysics Data System (ADS)

Assuming that in the hot dense matter produced in relativistic heavy-ion collisions, the energy density, entropy density, and pressure as well as the azimuthal and space-time rapidity components of the shear tensor are uniform in the direction transversal to the reaction plane, we derive a set of schematic equations from the Isreal-Stewart causal viscous hydrodynamics. These equations are then used to describe the evolution dynamics of relativistic heavy-ion collisions by taking the shear viscosity to entropy density ratio of 1/4? for the initial quark-gluon plasma (QGP) phase and of 10 times this value for the later hadron-gas (HG) phase. Using the production rate evaluated with particle distributions that take into account the viscous effect, we study dilepton production in central heavy-ion collisions. Compared with results from the ideal hydrodynamics, we find that although the dilepton invariant mass spectra from the two approaches are similar, the transverse momentum spectra are significantly enhanced at high transverse momenta by the viscous effect. We also study the transverse momentum dependence of dileptons produced from QGP for a fixed transverse mass, which is essentially absent in the ideal hydrodynamics, and find that this so-called transverse mass scaling is violated in the viscous hydrodynamics, particularly at high transverse momenta.

Song, Taesoo; Han, Kyong Chol; Ko, Che Ming

2011-02-01

402

Characteristic analysis of hydrodynamic bearings for HDDs  

Microsoft Academic Search

In this paper we describe the application of Hydrodynamic Bearings (HDBs) to conventional products and discuss the technical distinctions of HDBs between HDD applications and another applications. We also report on numerical analytical and experiments aimed at solving the characteristic problems of high-speed HDDs

Takafumi Asada; Hiroaki Saitou; Yasuhiro Asaida; Kaiji Itoh

2001-01-01

403

Hydrodynamic squeeze-film bearings for gyroscopes  

NASA Technical Reports Server (NTRS)

Experimental tests are conducted on squeeze-film bearings by applying electricity to piezoelectric ceramics, causing vibrations at thousands or millions of Hz that are amplified and transmitted to the bearing. Rotor operation through 24,000 rpm without whirl instability proved bearing ability to support rotor weight without hydrodynamic action.

Chiang, T.; Smith, R. L.

1970-01-01

404

Hydrodynamics of Falling Mine in Water Column  

E-print Network

Vinit #12;Mine Injector Mine Shapes: Length: 15, 12, 9 cm Diameter: 4 cm Light Sensor To Universal Technologies (Multiple Sensors, Ship Count Routines, Anechoic Coatings Non-Ferrous Materials) #12;Hydrodynamic disparity. 3. Air cavity affects on mine motion not considered in calculations. 4. Camera plane not parallel

Chu, Peter C.

405

Relativistic hydrodynamics in a global fashion  

NASA Astrophysics Data System (ADS)

After a long and controversial tradition of applications to high-energy hadron-hadron and hadron-nucleus collisions, relativistic hydrodynamics may finally become a convincing concept when applied to ultrarelativistic nuclear collisions with large projectiles and targets. We propose a new method, which we call global hydrodynamics, for solving the hydrodynamic equations, with two objectives in mind: first to make the calculations easier by using an approximate but very efficient scheme, and second to gain new insights into the dynamics by establishing the global expansion characteristics as a new viewpoint. The method consists of integrating the partial differential equations of hydrodynamics over an azimuthally symmetric region to obtain global conservation laws from the local ones. Assuming specific thermal and velocity profiles we derive ordinary differential equations for the most relevant dynamical quantities which are easy to solve. This enables us to do large numbers of runs easily and thus to perform a systematic scan of the whole range of possible initial conditions, following each case individually until freeze-out. By comparing the computed particle spectra to experiments it is possible to restrict the initial conditions and obtain quantitative information on the early dynamics of relativistic nuclear collisions.

Schnedermann, Ekkard; Heinz, Ulrich

1993-04-01

406

Hydrodynamic synchronization of colloidal oscillators Jurij Kotara  

E-print Network

Hydrodynamic synchronization of colloidal oscillators Jurij Kotara , Marco Leonia,b,c , Bruno for review October 28, 2009) Two colloidal spheres are maintained in oscillation by switching the position of an optical trap when a sphere reaches a limit position, leading to oscillations that are bounded in amplitude

Cicuta, Pietro

407

Microflow cytometers with integrated hydrodynamic focusing.  

PubMed

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

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

2013-01-01

408

Boundary conditions in tunneling via quantum hydrodynamics  

NASA Technical Reports Server (NTRS)

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.

Nassar, Antonio B.

1993-01-01

409

Modeling and estimation of hydrodynamic potentials  

Microsoft Academic Search

In order for underwater vehicles to fully realize the potential of utilizing oscillating foils as propulsion mechanisms, it is necessary for the control scheme to be aware of the state of the water environment, especially the vorticity in the water. In this paper, we investigate the problem of estimating the hydrodynamic potentials based on pressure measurement on a submerged body.

Perry Y. Li; Saroj Saimek

1999-01-01

410

DIFFERENTIAL GEOMETRY AND HYDRODYNAMICS OF SOLITON LATTICES  

E-print Network

) + c. Here we have u1 = c, u2 = k, u3 = . We write KDV in the form (0.3) (0.3) t - 6x + xxx = 0 to the discovery of some deep and natural differentially-geometric structure for the hamiltonian hydrodynamic type

Novikov, Sergei Petrovich

411

Hydrodynamics of maneuvering bodies: LDRD Final Report  

Microsoft Academic Search

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

S. N. Kempka; J. H. Strickland

1994-01-01

412

A Hydrodynamic Theory of Turbidity Currents  

Microsoft Academic Search

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

John E. Plapp; James P. Mitchell

1960-01-01

413

Hydrodynamic implications for submarine launched underwater gliders  

Microsoft Academic Search

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

Joshua D. Rodgers; John M. Wharington

2010-01-01

414

First order and stable relativistic dissipative hydrodynamics  

E-print Network

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

P. Ván; T. S. Biró

2011-09-05

415

Hydrodynamic self-similar cosmological models  

SciTech Connect

Hydrodynamic self-similar solutions, as obtained by Chi (J. Math. Phys. 24, 2532 (1983)) have been generalized by introducing new variables in place of the old space and time variables. A systematic procedure of obtaining a complete set of solutions has been suggested. The Newtonian analogs of all homogeneous isotropic Friedmann dust universes with spatial curvature k = 0 and +- 1 have been given.

Sanyal, A.K.; Banerjee, A.; Ray, D.

1985-10-01

416

A HYDRODYNAMIC MODEL FOR NUCLEATE POOL BOILING  

Microsoft Academic Search

A hydrodynamic model of stagnation flow is proposed for saturated ; nucleate boiling over a flat surface, Using analytical results from ; axisymmetrical stagnation flow, a relation between the heat-transfer coefficient ; and the thermal boundary-layer thickness induced by rising bubbles is obtained, ; and agreement with measured results in the low heat-flux region is indicated. ; The predicted heat-transfer

C Tien

1962-01-01

417

On Hydrodynamics of Bionic Flapping Hydrofoil Propeller  

Microsoft Academic Search

The bionic flapping hydrofoil propulsion, as a new propulsion mode, is different with the traditionary screw propeller, and it has attract the interest of the technologist in the aeronautics, astronautics and marine field. The underwater bionic flapping hydrofoil propeller is a system which can produce the thrust and can also produce the control force. This paper describes a hydrodynamics model

Du Xiao-xu; Song Bao-wei; Pan Guang

2010-01-01

418

(Non)-dissipative hydrodynamics on embedded surfaces  

NASA Astrophysics Data System (ADS)

We construct the theory of dissipative hydrodynamics of uncharged fluids living on embedded space-time surfaces to first order in a derivative expansion in the case of codimension-1 surfaces (including fluid membranes) and the theory of non-dissipative hydrodynamics to second order in a derivative expansion in the case of codimension higher than one under the assumption of no angular momenta in transverse directions to the surface. This construction includes the elastic degrees of freedom, and hence the corresponding transport coefficients, that take into account transverse fluctuations of the geometry where the fluid lives. Requiring the second law of thermodynamics to be satisfied leads us to conclude that in the case of codimension-1 surfaces the stress-energy tensor is characterized by 2 hydrodynamic and 1 elastic independent transport coefficient to first order in the expansion while for codimension higher than one, and for non-dissipative flows, the stress-energy tensor is characterized by 7 hydrodynamic and 3 elastic independent transport coefficients to second order in the expansion. Furthermore, the constraints imposed between the stress-energy tensor, the bending moment and the entropy current of the fluid by these extra non-dissipative contributions are fully captured by equilibrium partition functions. This analysis constrains the Young modulus which can be measured from gravity by elastically perturbing black branes.

Armas, Jay

2014-09-01

419

Quantum Moment Hydrodynamics and the Entropy Principle  

Microsoft Academic Search

This paper presents how a non-commutative version of the entropy extremalization principle allows to construct new quantum hydrodynamic models. Our starting point is the moment method, which consists in integrating the quantum Liouville equation with respect to momentum p against a given vector of monomials of p. Like in the classical case, the so-obtained moment system is not closed. Inspired

P. Degond; C. Ringhofer

2003-01-01

420

Hydrodynamic variability on megatidal beaches, Normandy, France  

Microsoft Academic Search

Several experiments aimed at characterising the hydrodynamics of megatidal beaches outside the surf zone were carried out between 1990 and 1994 on the Cotentin coast of the Cherbourg Peninsula in Normandy. The database was established from the records of several electromagnetic current meters and pressure sensors and from field surveys. The mean spring tidal range on these beaches varies between

Franck Levoy; Olivier Monfort; Claude Larsonneur

2001-01-01

421

Wind Speed Dependence of Single-Site Wave-Height Retrievals from High-Frequency Radars  

E-print Network

-order returns to the ocean surface wave energy spectra. Methods to invert the Barrick (1972) equations and retrieve the surface wave directional energy spectrum have been developed by Lipa (1978), Lipa and Barrick signal as well as from the hydrodynamic interaction between surface waves to produce a Bragg scattering

Miami, University of

422

A three-scale composite surface model for the ocean wave-radar modulation transfer function  

Microsoft Academic Search

An improved three-scale composite surface model for the modulation of the radar backscatter from the ocean surface by long ocean waves is presented. The model is based on Bragg scattering theory. In the conventional two-scale model, only the geometric modulation of the radar backscatter and the hydrodynamic modulation of the short Bragg waves by the long waves is considered. In

Roland Romeiser; Anke Schmidt; Werner Alpers

1994-01-01

423

High-Fidelity Simulations of Bubble, Droplet, and Spray Formation in Breaking Waves  

E-print Network

, Iowa Background and Objective Plunging wave breaking is of great importance to ship hydrodynamics. Previous experimental fluid dynamics (EFD) and computational fluid dynamics (CFD) studies on plunging wave conditions that drive bubble creation in breaking waves: jet plunging and collapse of the cavity. The bubble

Yang, Jianming

424

Observation of Optical Undular Bores in Multiple Four-Wave Mixing J. Fatome,1,*  

E-print Network

Observation of Optical Undular Bores in Multiple Four-Wave Mixing J. Fatome,1,* C. Finot,1 G to the formation of undular bores (dispersive shock waves) that mimic the typical behavior of dispersive hydrodynamics exhibited, e.g., by gravity waves and tidal bores. Thanks to the nonpulsed nature of the beat

Paris-Sud XI, Université de

425

Simulation of Helical Flow Hydrodynamics in Meanders and Advection-Turbulent Diffusion Using Smoothed Particle Hydrodynamics  

NASA Astrophysics Data System (ADS)

Particle-based numerical methods, such as Smoothed Particle Hydrodynamics (SPH), may be able to simulate some hydrodynamic and morphodynamic behaviors better than grid-based numerical methods. This study simulates hydrodynamics in meanders and advection and turbulent diffusion in straight river channels using Microsoft Excel and Visual Basic. The simulators generate three-dimensional data for hydrodynamics and one-dimensional data for advection-turbulent diffusion. Fluid at rest, sloshing, and helical flow are simulated in the river meanders. Spill loading and step loading are done to simulate concentration patterns associated with advection-turbulent diffusion. Results indicate that helical flow is formed due to disturbance in morphology and particle velocity in the stream and the number of particles does not have a significant effect on the pattern of advection-turbulent diffusion concentration.

Gusti, T. P.; Hertanti, D. R.; Bahsan, E.; Soeryantono, H.

2013-12-01

426

Simple kinetic-theory tests of dissipative and anisotropic hydrodynamics  

NASA Astrophysics Data System (ADS)

We solve the one-dimensional boost-invariant Boltzmann equation in the relaxation time approximation and compare the results with the predictions of dissipative and anisotropic hydrodynamics. We observe that recent formulations of second-order viscous hydrodynamics agree better with the exact solutions than the standard Israel-Stewart approach. In addition, we find that the anisotropic hydrodynamics gives a very good approximation to the exact results provided the appropriate connection between the kinetic and anisotropic hydrodynamics relaxation times is introduced.

Florkowski, Wojciech

2014-04-01

427

SRTM vegetation removal and hydrodynamic modeling accuracy  

NASA Astrophysics Data System (ADS)

Hydrodynamic modeling of large remote forested floodplains, such as the Amazon, is hindered by the vegetation signal contained within Digital Elevation Models (DEMs) such as the Shuttle Radar Topography Mission (SRTM). Not removing the vegetation signal causes DEMs to be overelevated preventing the correct simulation of overbank inundation. Previous efforts to remove this vegetation signal have either not accounted for its spatial variability or relied upon single assumed error values. As a possible solution, a systematic approach to removing the vegetation signal which accounts for spatial variability using recently published estimates of global vegetation heights is proposed. The proposed approach is applied to a well-studied reach of the Amazon floodplain where previous hydrodynamic model applications were affected by the SRTM vegetation signal. Greatest improvements to hydrodynamic model accuracy were obtained by subtracting 50-60% of the vegetation height from the SRTM. The vegetation signal removal procedure improved the RMSE (Root-Mean-Square Error) accuracy of the hydrodynamic model than when using the original SRTM in three ways: (1) seasonal floodplain water elevation predictions against TOPEX/Poseidon observations improved from 6.61 to 1.84 m; (2) high water inundation extent prediction accuracy improved from 0.52 to 0.07 against a JERS (Japanese Earth Resources Satellite) observation; (3) low water inundation extent accuracy against a JERS observation improved from 0.22 to 0.12. The simple data requirements of this vegetation removal method enable it to be applied to any remote floodplain for which hydrodynamic model accuracy is hindered by vegetation present in the DEM.

Baugh, Calum A.; Bates, Paul D.; Schumann, Guy; Trigg, Mark A.

2013-09-01

428

Scaling supernova hydrodynamics to the laboratory  

NASA Astrophysics Data System (ADS)

Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported in J. Kane et al. [Astrophys. J. 478, L75 (1997) and B. A. Remington et al., Phys. Plasmas 4, 1994 (1997)]. The Nova laser is used to generate a 10-15 Mbar shock at the interface of a two-layer planar target, which triggers perturbation growth due to the Richtmyer-Meshkov instability, and to the Rayleigh-Taylor instability as the interface decelerates. This resembles the hydrodynamics of the He-H interface of a Type II supernova at intermediate times, up to a few ×103 s. The scaling of hydrodynamics on microscopic laser scales to the SN-size scales is presented. The experiment is modeled using the hydrodynamics codes HYADES [J. T. Larson and S. M. Lane, J. Quant. Spect. Rad. Trans. 51, 179 (1994)] and CALE [R. T. Barton, Numerical Astrophysics (Jones and Bartlett, Boston, 1985), pp. 482-497], and the supernova code PROMETHEUS [P. R. Woodward and P. Collela, J. Comp. Phys. 54, 115 (1984)]. Results of the experiments and simulations are presented. Analysis of the spike-and-bubble velocities using potential flow theory and Ott thin-shell theory is presented, as well as a study of 2D versus 3D differences in perturbation growth at the He-H interface of SN 1987A.

Kane, J.; Arnett, D.; Remington, B. A.; Glendinning, S. G.; Bazan, G.; Drake, R. P.; Fryxell, B. A.; Teyssier, R.; Moore, K.

1999-05-01

429

1.138J / 2.062J / 18.376J Wave Propagation, Fall 2004  

E-print Network

This course discusses the Linearized theory of wave phenomena in applied mechanics. Examples are chosen from elasticity, acoustics, geophysics, hydrodynamics and other subjects. The topics include: basic concepts, one ...

Akylas, Triantaphyllos R.

430

Investigations on a permanent magnetic–hydrodynamic hybrid journal bearing  

Microsoft Academic Search

In the present work, a permanent magnetic–hydrodynamic hybrid journal bearing is developed. The force of the journal bearing comes from the hydrodynamic film and the permanent magnetic field. When a hydrodynamic film does not form, such as during starting and stopping a machine, the journal bearing relies on the magnetic force to support the rotor system. This paper studies a

Qingchang Tan; Wei Li; Bo Liu

2002-01-01

431

Friction characteristics of microtextured surfaces under mixed and hydrodynamic lubrication  

E-print Network

perfor- mance of mechanical parts [2,3]. Microtextures act as micro- hydrodynamic bearings, enhancingFriction characteristics of microtextured surfaces under mixed and hydrodynamic lubrication Ashwin Keywords: Surface engineering Microtexturing Hydrodynamic lubrication Mixed lubrication a b s t r a c t We

King, William P.

432

Thermal Conduction in a 2D FCT Plasma Hydrodynamic Code  

E-print Network

Thermal Conduction in a 2­D FCT Plasma Hydrodynamic Code F. Reale Istituto e Osservatorio of thermal conduction in a 2­D hydrodynamic code for compressible inviscid plasmas. The code is flexible describes the extension of the 2­D FCT hydrodynamic code to include the description of plasma thermal

433

SPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations  

E-print Network

Particle Hydrodynamics (SPH) simulations. Visualisation of SPH data is more compli- cated than for gridSPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations Daniel J and meaningful visualisation of one, two and three dimensional SPH results. Keywords: hydrodynamics ­ methods

Price, Daniel

434

Technical Report 2010-2 Smoothed Particle Hydrodynamics in Acoustic  

E-print Network

Lagrangian technique, called Smoothed Particle Hydrodynamics (SPH), as a method for acoustic simulation Lagrangian technique, called Smoothed Particle Hydrodynamics (SPH), as a method for acoustic simulationTechnical Report 2010-2 Smoothed Particle Hydrodynamics in Acoustic Simulations Philipp Hahn, Dan

Negrut, Dan

435

Hydrodynamic Tesla Wheel Flume for Model and Prototype Testing  

E-print Network

Hydrodynamic Tesla Wheel Flume for Model and Prototype Testing Spencer Jenkins, Chris Scott, Jacob Engineering department at Florida Institute of Technology (Florida Tech) has developed a Hydrodynamic Tesla, hydrodynamic, laminar, fluid, flow, model, prototype testing, Tesla wheel. I. INTRODUCTION The southeast region

Wood, Stephen L.

436

Wave-Wave Coupling: A Nonlinear Phenomenon of Classical Physics  

NASA Astrophysics Data System (ADS)

Linear physics does not admit the possibility of wave coupling. With the advent of nonlinear research, wave-wave coupling has been observed and described theoretically in many media. For example, in hydrodynamics the Euler equations can lead to the Nonlinear Schroedinger Equation (NLS), which in turn admits three-wave coupling. Simple theory yields surprisingly good results [1, 2]. In plasma physics, the wave coupling phenomenon can be derived directly from the Vlasov equation [3]. Recent interest has been renewed when four-wave coupling was observed in experiments on Bose-Einstein condensates. Here, a successful theory has recently been developed based on the Gross-Pitayevski equation, a NLS for this condensate. Although now four waves may couple instead of three, the ideas and even the formalisms are almost identical [4]. Other fields in which the phenomenon is observed include optics and even population studies. When looking for this effect in new fields, one should ask whether similar coupling mechanisms are in place. References [1] E Infeld, Phys Rev Letters 47 717, 1981 [2] E Infeld and G Rowlands, Nonlinear Waves, Solitons and Chaos, CUP, 1990, second edition, Chapter 5. [3] R C Davidson, Methods in Nonlinear Plasma Theory, Academic, NY, 1972, chapter 6. [4] M. Trippenbach et al., Phys. Rev. A 62, 023608, 2000.

Infeld, E.

2002-12-01

437

A harmonic polynomial cell (HPC) method for 3D Laplace equation with application in marine hydrodynamics  

NASA Astrophysics Data System (ADS)

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.

Shao, Yan-Lin; Faltinsen, Odd M.

2014-10-01

438

Seismic Waves  

NSDL National Science Digital Library

This demonstration elucidates the concept of propagation of compressional waves (primary or P waves) and shear waves (secondary or S waves), which constitute the seismic waves used in locating and modeling earthquakes and underground nuclear explosions, and for imaging the interior structure of the Earth. The demonstration uses a slinky, pushed along its axis to create a compressional (longitudinal) wave, and moved up and down on one end to create a shear (transverse) wave.

Barker, Jeffrey

439

High Resolution Simulations of Relativistic Hydrodynamic and MHD Turbulence  

NASA Astrophysics Data System (ADS)

We present a program of simulations designed to investigate the basic properties of relativistic hydrodynamic and magnetohydrodynamic (MHD) turbulence. We employ a well-tested 5th-order accurate numerical scheme at resolutions of up to 2048^3 zones for hydrodynamic turbulence, and a minimally diffusive 2nd-order scheme at resolutions of up to 1024^3 in the case of relativistic MHD. For the hydrodynamic case, we simulate a relativistically hot gas in a cubic periodic domain continuously driven at large scales with Lorentz factor of about 3. We find that relativistic turbulent velocity fluctuations with ? ? > 1 persist from the driving scale down to scales an order of magnitude smaller, demonstrating the existence of a sustained relativistic turbulent cascade. The power spectrum of the fluid 4-velocity is broadly Kolmogorov-like, roughly obeying a power law with 5/3 index between scales 1/10 and 1/100 of the domain. Departures from 5/3 scaling are larger for the power spectrum of 3-velocity. We find that throughout the inertial interval, 25% of power is in dilatational modes, which obey strict power law scaling between 1/2 and 1/100 of the domain with an index of 1.88. Our program also explores turbulent amplification of magnetic fields in the conditions of merging neutron stars, using a realistic equation of state for dense nuclear matter (? ˜ 10^13 g/cm^3). We find that very robustly, seed fields are amplified to magnetar strength (? 4 * 10^16 Gauss) within ˜1 micro-second for fluid volumes near the size of the NS crust thickness <10 meters. We present power spectra of the kinetic and magnetic energy taken long into the fully stationary evolution of the highest resolution models, finding the magnetic energy to be in super-equipartition (4 times larger) with the kinetic energy through the inertial range. We believe that current global simulations of merging NS binaries are insufficiently resolved for studying field amplification via turbulent processes. Larger magnetic fields, as found in our high resolution local simulations, may have consequences for gravitational wave signals, GRB precursor events, radio afterglows, and optical afterglows due to emission from ejected radioactive r-process material.

Zrake, Jonathan; MacFadyen, A.

2013-01-01

440

Wave Journal Bearing. Part 1: Analysis  

NASA Technical Reports Server (NTRS)

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.

Dimofte, Florin

1995-01-01