Hydrodynamic interactions in colloidal ferrofluids: A lattice Boltzmann study
Eunhye Kim; Kevin Stratford; Philip J. Camp; Michael E. Cates
2009-01-01
We use lattice Boltzmann simulations, in conjunction with Ewald summation methods, to investigate the role of hydrodynamic interactions in colloidal suspensions of dipolar particles, such as ferrofluids. Our work addresses volume fractions $\\\\phi$ of up to 0.20 and dimensionless dipolar interaction parameters $\\\\lambda$ of up to 8. We compare quantitatively with Brownian dynamics simulations, in which many-body hydrodynamic interactions are
Hydrodynamic Interactions in Colloidal Ferrofluids: A Lattice Boltzmann Study †
Eunhye Kim; Kevin Stratford; Philip J. Camp; Michael E. Cates
2009-01-01
We use lattice Boltzmann simulations, in conjunction with Ewald summation\\u000amethods, to investigate the role of hydrodynamic interactions in colloidal\\u000asuspensions of dipolar particles, such as ferrofluids. Our work addresses\\u000avolume fractions $\\\\phi$ of up to 0.20 and dimensionless dipolar interaction\\u000aparameters $\\\\lambda$ of up to 8. We compare quantitatively with Brownian\\u000adynamics simulations, in which many-body hydrodynamic interactions are
Hydrodynamic interactions in colloidal ferrofluids: a lattice Boltzmann study.
Kim, Eunhye; Stratford, Kevin; Camp, Philip J; Cates, Michael E
2009-03-26
We use lattice Boltzmann simulations, in conjunction with Ewald summation methods, to investigate the role of hydrodynamic interactions in colloidal suspensions of dipolar particles, such as ferrofluids. Our work addresses volume fractions phi of up to 0.20 and dimensionless dipolar interaction parameters lambda of up to 8. We compare quantitatively with Brownian dynamics simulations, in which many-body hydrodynamic interactions are absent. Monte Carlo data are also used to check the accuracy of static properties measured with the lattice Boltzmann technique. At equilibrium, hydrodynamic interactions slow down both the long-time and the short-time decays of the intermediate scattering function S(q, t), for wavevectors close to the peak of the static structure factor S(q), by a factor of roughly two. The long-time slowing is diminished at high interaction strengths, whereas the short-time slowing (quantified via the hydrodynamic factor H(q)) is less affected by the dipolar interactions, despite their strong effect on the pair distribution function arising from cluster formation. Cluster formation is also studied in transient data following a quench from lambda = 0; hydrodynamic interactions slow the formation rate, again by a factor of roughly two. PMID:19014186
Hydrodynamic interactions in colloidal ferrofluids: A lattice Boltzmann study
Kim, Eunhye; Camp, Philip J; Cates, Michael E; 10.1021/jp806678m
2009-01-01
We use lattice Boltzmann simulations, in conjunction with Ewald summation methods, to investigate the role of hydrodynamic interactions in colloidal suspensions of dipolar particles, such as ferrofluids. Our work addresses volume fractions $\\phi$ of up to 0.20 and dimensionless dipolar interaction parameters $\\lambda$ of up to 8. We compare quantitatively with Brownian dynamics simulations, in which many-body hydrodynamic interactions are absent. Monte Carlo data are also used to check the accuracy of static properties measured with the lattice Boltzmann technique. At equilibrium, hydrodynamic interactions slow down both the long-time and the short-time decays of the intermediate scattering function $S(q,t)$, for wavevectors close to the peak of the static structure factor $S(q)$, by a factor of roughly two. The long-time slowing is diminished at high interaction strengths whereas the short-time slowing (quantified via the hydrodynamic factor $H(q)$) is less affected by the dipolar interactions, despite their...
Stefan Odenbach
2006-01-01
This issue of Journal of Physics: Condensed Matter is dedicated to results in the field of ferrofluid research. Ferrofluids—suspensions of magnetic nanoparticles—exhibit as a specific feature the magnetic control of their physical parameters and of flows appearing in such fluids. This magnetic control can be achieved by means of moderate magnetic fields with a strength of the order of 10
Experimental and numerical investigation of wave ferrofluid convection
A. A. Bozhko; G. F. Putin; T. Tynjälä; P. Sarkomaa
2007-01-01
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
Commercial applications of ferrofluids
K. Raj; R. Moskowitz
1990-01-01
Ferrofluids have been in the commercial arena for over two decades. In this paper, the most advanced, successful commercial applications of ferrofluids are discussed. These applications center around the tribological characteristics of ferrofluids, e.g., sealing, damping and hydrodynamic bearings. Also, an account of some lesser known applications is presented.
Hyun-Jae Pi; So-yeon Park; Jysoo Lee; Kyoung J. Lee
2000-05-13
Standing wave patterns that arise on the surface of ferrofluids by (single frequency) parametric forcing with an ac magnetic field are investigated experimentally. Depending on the frequency and amplitude of the forcing, the system exhibits various patterns including a superlattice and subharmonic rhombuses as well as conventional harmonic hexagons and subharmonic squares. The superlattice arises in a bicritical situation where harmonic and subharmonic modes collide. The rhombic pattern arises due to the non-monotonic dispersion relation of a ferrofluid.
Stefan Odenbach
2006-01-01
This issue of Journal of Physics: Condensed Matter is dedicated to results in the field of ferrofluid research. Ferrofluids---suspensions of magnetic nanoparticles---exhibit as a specific feature the magnetic control of their physical parameters and of flows appearing in such fluids. This magnetic control can be achieved by means of moderate magnetic fields with a strength of the order of 10
NASA Astrophysics Data System (ADS)
Odenbach, Professor Stefan
2006-09-01
This issue of Journal of Physics: Condensed Matter is dedicated to results in the field of ferrofluid research. Ferrofluids—suspensions of magnetic nanoparticles—exhibit as a specific feature the magnetic control of their physical parameters and of flows appearing in such fluids. This magnetic control can be achieved by means of moderate magnetic fields with a strength of the order of 10 mT. This sort of magnetic control also enables the design of a wide variety of technical applications such as the use of the magnetic forces for basic research in fluid dynamics. The overall field of ferrofluid research is already about 40 years old. Starting with the first patent on the synthesis of magnetic nanoparticle suspensions by S Papell in 1964, a vivid field of research activities has been established. Looking at the long time in which ferrofluids have been the focus of scientific interest, one can ask the question, what kind of recent developments justify a special issue of a scientific journal? New developments in a field, which depends strongly on a certain material class and which opens research possibilities in different scientific fields will nowadays usually require an interdisciplinary approach. This kind of approach starting from the synthesis of magnetic suspensions, including research concerning their basic properties and flow behaviour and focusing on new applications has been the core of a special research programme funded by the Deutsche Forschungsgemeinschaft (DFG) over the past 6 years. Within this programme—entitled `Colloidal Magnetic Fluids: Basics, Synthesis and Applications of New Ferrofluids'—more than 30 different research groups have been coordinated to achieve new results in various fields related to ferrofluid research. The basic approach of the program has been the assumption that new applications well beyond the typical ferrofluid techniques, for example loud speaker cooling or sealing of rotary shafts, will require tailored magnetic suspensions with properties clearly focused towards the need of the application. While such tailoring of fluids to certain well defined properties sounds like a straightforward approach one has to face the fact that it requires a clear definition of the required properties. This definition itself has to be based on a fundamental physical knowledge of the processes determining certain magnetically controlled phenomena in ferrofluids. To make this point concrete one can look into the detailed aims of the mentioned research program. The application areas identified for the future development of research and application of suspensions of magnetic nanoparticles have been on the one hand the biomedical application—especially with respect to cancer treatment—and on the other hand the use of magnetically controlled rheological properties of ferrofluids for new active technical devices. Both directions require, as mentioned, as a basis for success the synthesis of new ferrofluids with dedicated properties. While the medical applications have to rely on biocompatibility as well as on stability of the suspensions in a biomedical environment, the use of ferrofluids in technical devices employing their magnetically controlled rheological properties will depend on an enhancement of the changes of the fluid's viscous properties in the presence of moderate magnetic fields. For both requirements ferrofluids with a make up clearly different from the usual magnetite based fluids have to be synthesized. The question of how the detailed microscopic make up of the fluids would have to look has to be answered on the basis of basic research results defining the physics background of the respective phenomena. Taking these aspects together it becomes obvious that the aforementioned research program had goals aiming far beyond the state of the art of classical ferrofluid research. These goals as well as the basic strategy to achieve them is in a way reflected by the structure of this issue of Journal of Physics: Condensed Matter. The issue contains results emerging from the research pr
A ferrofluidic magnetic micropump
Anson Hatch; Andrew Evan Kamholz; Gary Holman; Paul Yager; Karl F. Böhringer
2001-01-01
A microfluidic pump is described that uses magnetic actuation to push fluid through a microchannel. Operation relies on the use of magnetically-actuated plugs of ferrofluid, a suspension of nanosize ferromagnetic particles. The ferrofluid contacts but is immiscible with the pumped fluid. The prototype circular design demonstrates continuous pumping by regenerating a translating ferrofluidic plug at the conclusion of each pumping
Symposium: Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas
Ildar R. Gabitov; Pavel M. Lushnikov
2009-01-01
Progress in the development of new tools for modem apphed mathematics resulted in a better scientific under standing of nonlinear waves in various fields of nonlinear optics, hydrodynamics, and plasmas. The universahty of the equations describing wave processes is one of the most important components of this success. Nonlinear Schrodinger equation (NLS) and Korteweg de Vries equation are among best
Hydrodynamic waves and correlation functions in dusty plasmas
Xiaogang Wang; A. Bhattacharjee
1997-01-01
A hydrodynamic description of strongly coupled dusty plasmas is given when physical quantities vary slowly in space and time and the system can be assumed to be in local thermodynamic equilibrium. The linear waves in such a system are analyzed. In particular, a dispersion equation is derived for low-frequency dust acoustic waves, including collisional damping effects, and compared with experimental
Hydrodynamic Waves and Correlation Functions in Dusty Plasmas
A. Bhattacharjee; Xiaogang Wang
1997-01-01
A hydrodynamic description of strongly coupled dusty plasmas is given when physical quantities vary slowly in space and time and the system can be assumed to be in local thermodynamic equilibrium. The linear waves in such a system are analyzed. In particular, a dispersion equation is derived for low-frequency dust acoustic waves, including collisional damping effects, and compared with experimental
Anderson, Mary Elizabeth
2011-10-21
Wave attenuation by vegetation is a highly dynamic process and its quantification is important for accurately understanding and predicting coastal hydrodynamics. However, the influence of vegetation on wave dissipation is not yet fully established...
Electron magneto-hydrodynamic waves bounded by magnetic bubble
NASA Astrophysics Data System (ADS)
Anitha, V. P.; Sharma, D.; Banerjee, S. P.; Mattoo, S. K.
2012-08-01
The propagation of electron magneto-hydrodynamic (EMHD) waves is studied experimentally in a 3-dimensional region of low magnetic field surrounded by stronger magnetic field at its boundaries. We report observations where bounded left hand polarized Helicon like EMHD waves are excited, localized in the region of low magnetic field due to the boundary effects generated by growing strengths of the ambient magnetic field rather than a conducting or dielectric material boundary. An analytical model is developed to include the effects of radially nonuniform magnetic field in the wave propagation. The bounded solutions are compared with the experimentally obtained radial wave magnetic field profiles explaining the observed localized propagation of waves.
Ferrofluids: Thermophysical properties and formation of microstructures
NASA Astrophysics Data System (ADS)
Mousavi Khoeini, NargesSadat Susan
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
Transition to turbulence in ferrofluids
Altmeyer, Sebastian; Lai, Ying-Cheng
2015-01-01
It is known that in classical fluids turbulence typically occurs at high Reynolds numbers. But can turbulence occur at low Reynolds numbers? Here we investigate the transition to turbulence in the classic Taylor-Couette system in which the rotating fluids are manufactured ferrofluids with magnetized nanoparticles embedded in liquid carriers. We find that, in the presence of a magnetic field turbulence can occur at Reynolds numbers that are at least one order of magnitude smaller than those in conventional fluids. This is established by extensive computational ferrohydrodynamics through a detailed bifurcation analysis and characterization of behaviors of physical quantities such as the energy, the wave number, and the angular momentum through the bifurcations. A striking finding is that, as the magnetic field is increased, the onset of turbulence can be determined accurately and reliably. Our results imply that experimental investigation of turbulence can be greatly facilitated by using ferrofluids, opening up...
Nonlinear Generalized Hydrodynamic Wave Equations in Strongly Coupled Dusty Plasmas
Veeresha, B. M.; Sen, A.; Kaw, P. K. [Institute for Plasma Research, Bhat, Gandhinagar-382428 (India)
2008-09-07
A set of nonlinear equations for the study of low frequency waves in a strongly coupled dusty plasma medium is derived using the phenomenological generalized hydrodynamic (GH) model and is used to study the modulational stability of dust acoustic waves to parallel perturbations. Dust compressibility contributions arising from strong Coulomb coupling effects are found to introduce significant modifications in the threshold and range of the instability domain.
Hydrodynamic waves and correlation functions in dusty plasmas
Wang, X.; Bhattacharjee, A. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)] [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)
1997-11-01
A hydrodynamic description of strongly coupled dusty plasmas is given when physical quantities vary slowly in space and time and the system can be assumed to be in local thermodynamic equilibrium. The linear waves in such a system are analyzed. In particular, a dispersion equation is derived for low-frequency dust acoustic waves, including collisional damping effects, and compared with experimental results. The linear response of the system is calculated from the fluctuation-dissipation theorem and the hydrodynamic equations. The requirement that these two calculations coincide constrains the particle correlation function for slowly varying perturbations. It is shown that in the presence of weakly damped, long-wavelength dust-acoustic waves, the dust autocorrelation function is of the Debye{endash}H{umlt u}ckel form and the characteristic shielding distance is the dust Debye length. {copyright} {ital 1997 American Institute of Physics.}
Hydrodynamic waves and correlation functions in dusty plasmas
NASA Astrophysics Data System (ADS)
Wang, Xiaogang; Bhattacharjee, A.
1997-11-01
A hydrodynamic description of strongly coupled dusty plasmas is given when physical quantities vary slowly in space and time and the system can be assumed to be in local thermodynamic equilibrium. The linear waves in such a system are analyzed. In particular, a dispersion equation is derived for low-frequency dust acoustic waves, including collisional damping effects, and compared with experimental results. The linear response of the system is calculated from the fluctuation-dissipation theorem and the hydrodynamic equations. The requirement that these two calculations coincide constrains the particle correlation function for slowly varying perturbations. It is shown that in the presence of weakly damped, long-wavelength dust-acoustic waves, the dust autocorrelation function is of the Debye-Hückel form and the characteristic shielding distance is the dust Debye length.
Identification of gravity waves in hydrodynamical simulations
Boris Dintrans; Axel Brandenburg
2004-08-10
The excitation of internal gravity waves by an entropy bubble oscillating in an isothermal atmosphere is investigated using direct two-dimensional numerical simulations. The oscillation field is measured by a projection of the simulated velocity field onto the anelastic solutions of the linear eigenvalue problem for the perturbations. This facilitates a quantitative study of both the spectrum and the amplitudes of excited g-modes.
Nonlinear hydrodynamic Langmuir waves in fully degenerate relativistic plasma
NASA Astrophysics Data System (ADS)
Haas, F.; Kourakis, I.
2015-04-01
The combined effect of special relativity and electron degeneracy on Langmuir waves is analyzed by utilizing a rigorous fully relativistic hydrodynamic model. Assuming a traveling wave solution form, a set of conservation laws is identified, together with a pseudo-potential function depending on the relativistic parameter pF/(m c) (where pF is the Fermi momentum, m is the mass of the charge carriers and c the speed of light), as well as on the amplitude of the electrostatic energy perturbation.
Hydrodynamic Waves and Correlation Functions in Dusty Plasmas
NASA Astrophysics Data System (ADS)
Bhattacharjee, A.; Wang, Xiaogang
1997-11-01
A hydrodynamic description of strongly coupled dusty plasmas is given when physical quantities vary slowly in space and time and the system can be assumed to be in local thermodynamic equilibrium. The linear waves in such a system are analyzed. In particular, a dispersion equation is derived for low-frequency dust acoustic waves, including collisional damping effects, and compared with experimental results. The linear response of the system is calculated from the fluctuation-dissipation theorem and the hydrodynamic equations. The requirement that these two calculations coincide constrains the particle correlation function for slowly varying perturbations [L. P. Kadanoff and P. C. Martin, Ann. Phys. 24, 419 (1963)]. It is shown that in the presence of the slow dust-acoustic waves, the dust auto-correlation function is of the Debye-Hekel form and the shielding distance is the dust Debye length. In the short-wavelength regime, an integral equation is derived from kinetic theory and solved numerically to yield particle correlation functions that display ``liquid-like'' behavior and have been observed experimentally [R. A.. Quinn, C. Cui, J. Goree, J. B. Pieper, H. Thomas and G. E. Morfill, Phys. Rev. E 53, R2049 (1996)].
Hydrodynamic Modes of a holographic $p-$ wave superfluid
Raul E. Arias; Ignacio Salazar Landea
2014-11-04
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.
Negative magnetophoresis in diluted ferrofluid flow.
Hejazian, Majid; Nguyen, Nam-Trung
2015-06-30
We report magnetic manipulation of non-magnetic particles suspended in diluted ferrofluid. Diamagnetic particles were introduced into a circular chamber to study the extent of their deflection under the effect of a non-uniform magnetic field of a permanent magnet. Since ferrofluid is a paramagnetic medium, it also experiences a bulk magnetic force that in turn induces a secondary flow opposing the main hydrodynamic flow. Sheath flow rate, particle size, and magnetic field strength were varied to examine this complex behaviour. The combined effect of negative magnetophoresis and magnetically induced secondary flow leads to various operation regimes, which can potentially find applications in separation, trapping and mixing of diamagnetic particles such as cells in a microfluidic system. PMID:26054840
Smoothed Particle Hydrodynamics for water wave propagation in a channel
NASA Astrophysics Data System (ADS)
Omidvar, Pourya; Norouzi, Hossein; Zarghami, Ahad
2015-01-01
In this paper, Smoothed Particle Hydrodynamics (SPH) is used to simulate the propagation of waves in an intermediate depth water channel. The major advantage of using SPH is that no special treatment of the free surface is required, which is advantageous for simulating highly nonlinear flows with possible wave breaking. The SPH method has an option of different formulations with their own advantages and drawbacks to be implemented. Here, we apply the classical and Arbitrary Lagrange-Euler (ALE) formulation for wave propagation in a water channel. The classical SPH should come with an artificial viscosity which stabilizes the numerical algorithm and increases the accuracy. Here, we will show that the use of classical SPH with an artificial viscosity may cause the waves in the channel to decay. On the other hand, we will show that using the ALE-SPH algorithm with a Riemann solver is more stable, and in addition to producing the pressure fields with much less numerical noise, the waves propagate in the channel without dissipation.
NASA Astrophysics Data System (ADS)
Benson, P.; Meredith, P.; Platzman, E.; White, R.
2003-12-01
Pore fabric geometry is a key feature of sedimentary rocks. Anisotropy arising from pore fabric has been commonly studied in terms of acoustic-wave (seismic) anisotropy, fluid flow (permeability) anisotropy and magnetic anisotropy (Anisotropy of Magnetic Susceptibility - AMS). However, combined approaches are relatively few, and often concentrate on grain fabric AMS. Here, we present results from an experimental study in which the AMS technique is used to determine the average 3D void space geometry in porous rock saturated with a high susceptibility magnetic ferrofluid. Using this approach, we independently show that the acoustic wave anisotropy and permeability anisotropy are well described by knowledge of the pore fabric anisotropy. We also demonstrate that pressure produces marked changes in both permeability and acoustic wave velocity, and that pore fabric is a useful tool with which to explain such changes. Measurements were made on Crab Orchard sandstone (COS) and Bentheim sandstone (BHS), chosen specifically for their contrasting strong (COS) and weak (BHS) anisotropy. COS is fine-grained and exhibits layering on a mm scale. It has a high cement content, resulting in a porosity of 4.5%. By contrast, BHS comprises 95% quartz grains in an open structure, resulting in a porosity of 22%. AMS was determined by measuring the susceptibility of ferrofluid saturated samples in 15 different orientations. A least squares ellipsoidal fit was then applied to this data to calculate the principal directions. Comparative elastic wave velocity measurements were then made in 10 degree increments around the circumferences of sets of three orthogonal cores. An equivalent 3D velocity ellipsoid was then determined, allowing for direct comparison of the velocity and AMS data. The error in using an ellipsoidal fit, rather than a fourth rank tensor, is estimated as less than 1.5%; approximately equal to the error in velocity measurement. Finally, measurements of permeability anisotropy, together with simultaneous ultrasonic velocity measurements, were made in a servo-controlled permeameter at effective pressures from 5 to 90MPa. In general, the permeability of COS parallel to bedding is some 3 times higher than that normal to bedding; whereas the permeability of BHS exhibits no discernible anisotropy. We find a strong positive correlation between the principal directions given by pore space AMS, velocity anisotropy, and permeability anisotropy. P-wave velocity anisotropy on dry samples was 19% and 5% for COS and BHS, respectively. This compares with a pore fabric anisotropy of 3.8% (COS) and 1.4% (BHS). The permeability of COS decreases from 75 to 8 mDarcy as effective pressure is increased from 5 to 90 MPa, a corresponding increase in acoustic wave velocity is also observed. BHS has a considerably higher permeability (830 mDarcy), but this changes little as pressure is increased. Our results clearly demonstrate that the overall anisotropy in these sedimentary rocks is dominated by the average pore fabric shape and orientation. Hence, the analysis of this fabric provides a good indicator of the anisotropy of other related physical properties, such as mechanical strength.
Flow control using ferrofluids
NASA Astrophysics Data System (ADS)
Cornat, Francois; Beck, David; Jacobi, Ian; Stone, Howard
2013-11-01
A novel flow control technique is proposed which employs a ferrofluidic lubricant infused in a micro-patterned substrate as a ``morphing surface'' for control of wall-bounded flows. Traditionally, morphing surfaces produce dynamic changes in the curvature and roughness of solid substrates for active control of high Reynolds number flow features such as boundary layer separation and turbulent streaks. We show how these surface modifications can be achieved with a thin liquid layer in the presence of a normal magnetic field. By impregnating a chemically-treated, micro-patterned surface with a fluorinated ferrofluid, the fluid is maintained as a thin super-hydrophobic film and can be redistributed on the substrate by magnetic forces to dynamically reveal or conceal the underlying surface roughness. Moreover, the surface topography of the ferrofluid film itself can be modified to produce an enhanced roughness, beyond the scale of the underlying substrate pattern. Both types of ferrofluidic surface modifications are studied in micro- and macro- scale channels in order to assess the feasibility of flow modification at low to moderate Reynolds numbers.
Exploring Materials: Ferrofluid
NSDL National Science Digital Library
2014-06-18
In this activity, learners discover that a material can act differently when it's nanometer-sized. Learners investigate the properties of ferrofluid and magnetic black sand and learn that the surprising difference in the behavior of these two materials is due to size. Use this activity to talk about the differences in nanoscale materials.
Nanomagnets: Fun with Ferrofluid
NSDL National Science Digital Library
Amy R. Taylor
2007-01-01
Ferrofluid provides an easy opportunity to introduce students to the fascinating properties of the nanoscale. It is essentially a liquid magnet made of nanosized magnetic particles suspended in water or oil. Not only does it demonstrate the strange and beautiful properties of the nanoscale, but it also illustrates a case where nanoparticles and their associated properties provide interesting opportunities for technological applications.
Plastic micropump with ferrofluidic actuation
Christophe Yamahata; Mathieu Chastellain; Virendra K. Parashar; Alke Petri; Heinrich Hofmann; Martin A. M. Gijs
2005-01-01
We present the realization and characterization of a new type of plastic micropump based on the magnetic actuation of a magnetic liquid. The pump consists of two serial check-valves that convert the periodic motion of a ferrofluidic plug into a pulsed quasi-continuous flow. The ferrofluid is actuated by the mechanical motion of an external NdFeB permanent magnet. The water-based ferrofluid
NASA Astrophysics Data System (ADS)
Bruinsma, Robijn
2015-03-01
The talk will present a hydrodynamic description of large-scale cooperative movement of chromatin that have been observed by particle tracking methods. The results of the hydrodynamic description will be compared with the tracking data. Passive thermal fluctuations and active ``scalar'' events - associated with local chromatin condensation - are found to dominate cooperative motion at shorter length scales while active ``vector events'' - associated with chromatin remodeling - driving transverse hydrodynamic modes dominate at large length scales.
Hydrodynamic forces on larvae affect their settlement on coral reefs in turbulent, wave-driven flow
Reidenbach, Matthew A.
Hydrodynamic forces on larvae affect their settlement on coral reefs in turbulent, wave- driven, California 94720-3140 Abstract This study investigates a key aspect of how ambient flow affects interact with a complex substratum to affect hydrodynamic forces encountered by microscopic larvae sitting
Marques, Francisco
Symmetry Breaking Via Global Bifurcations of Modulated Rotating Waves in Hydrodynamics Jan Abshagen 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
Effect of Interaction of Wave And Forward Speed On Hydrodynamic Forces On Marine Structures
Makoto Ohkusu
1991-01-01
First an overview is given of researches on the prediction methods of hydrodynamic forces on a body moving in waves at a steady forward speed. Then two methods developed by the author are presented, and their results are discussed. These two methods are based on different assumptions of the steady flow field around the body. OVERVIEW The prediction of hydrodynamic
Hydrodynamical simulations of penetrative convection and generation of internal gravity waves
Stêpieñ, Kazimierz
Hydrodynamical simulations of penetrative convection and generation of internal gravity waves M investigate the generation of internal gravity waves in the stable region below a convective layer by means interiors that can be affected by internal gravity waves. Considered so far are: mixing of chemical elements
Goldstein, Raymond E.
Hydrodynamic Synchronization and Metachronal Waves on the Surface of the Colonial Alga Volvox of the colonial alga Volvox carteri, whose large size and ease of visualization make it an ideal model organism
Hydrodynamics of the double-wave structure of insect spermatozoa flagella
Pak, On Shun; Spagnolie, Saverio E.; Lauga, Eric
2012-01-01
In addition to conventional planar and helical flagellar waves, insect sperm flagella have also been observed to display a double-wave structure characterized by the presence of two superimposed helical waves. In this paper, we present a hydrodynamic investigation of the locomotion of insect spermatozoa exhibiting the double-wave structure, idealized here as superhelical waves. Resolving the hydrodynamic interactions with a non-local slender body theory, we predict the swimming kinematics of these superhelical swimmers based on experimentally collected geometric and kinematic data. Our consideration provides insight into the relative contributions of the major and minor helical waves to swimming; namely, propulsion is owing primarily to the minor wave, with negligible contribution from the major wave. We also explore the dependence of the propulsion speed on geometric and kinematic parameters, revealing counterintuitive results, particularly for the case when the minor and major helical structures are of opposite chirality. PMID:22298815
On features of ferrofluid convection caused by barometrical sedimentation
T. Tynjälä; A. Bozhko; P. Bulychev; G. Putin; P. Sarkomaa
2006-01-01
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
Oldenburg, Curtis; Moridis, George
1998-03-24
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.
Magnetization of multicomponent ferrofluids.
Szalai, I; Dietrich, S
2011-08-17
The solution of the mean spherical approximation (MSA) integral equation for isotropic multicomponent dipolar hard sphere fluids without external fields is used to construct a density functional theory (DFT), which includes external fields, in order to obtain an analytical expression for the external field dependence of the magnetization of ferrofluidic mixtures. This DFT is based on a second-order Taylor series expansion of the free energy density functional of the anisotropic system around the corresponding isotropic MSA reference system. The ensuing results for the magnetic properties are in quantitative agreement with our canonical ensemble Monte Carlo simulation data presented here. PMID:21795777
Quasi-simple waves in Korteweg-De Vries hydrodynamics
NASA Astrophysics Data System (ADS)
Gurevich, A. V.; Krylov, A. L.; Mazur, N. G.
1989-05-01
The formation and development of a dissipationless shock wave resulting from the 'overturning' of a nonlinear wave is studied using the modulation equation technique. The case when the wave propagates along an unperturbed medium and two Riemann variables suffice to describe a dissipationless shock wave is studied. Consideration is given to both a monotonously increasing and nonmonotonous (localized) initial perturbation. In both cases, a common solution is found by linearizing the modulation equations via the holograph method.
Synthesis of Aqueous Ferrofluid
NSDL National Science Digital Library
Breitzer, Jonathan
This video lab manual, by the Interdisciplinary Education Group of the University of Wisconsin â?? Madison Materials Research Science and Engineering Center (MRSEC), walks students through the process synthesizing aqueous ferrofluids, which "respond to an external magnetic field enabling the solution's location to be controlled through the application of a magnetic field." Each step of the procedure is detailed and accompanied with a video showing it as it is performed. A brief background of the procedure and the necessary safety and laboratory materials are also given. This detailed resource helps students to explore nanotechnology and advanced materials science through hands-on laboratory activities. A printer-friendly version with an example image for each step is also available, perfect for an in-class handout.
Synthesis of ferrofluid with magnetic nanoparticles by sonochemical method for MRI contrast agent
Eun Hee Kim; Hyo Sook Lee; Byung Kook Kwak; Byung-Kee Kim
2005-01-01
Superparamagnetic iron oxide nanoparticles (SPIO) having high magnetization (83 emu\\/g) and crystallinity were synthesized by using a sonochemical method. Ferrofluids from these nanoparticles coated with oleic acid as a surfactant were prepared for magnetic resonance imaging (MRI) contrast agent. The coated SPIO could be easily dispersed in chitosan, and the hydrodynamic diameter of the coated SPIO in the chitosan solution
Synthesis of ferrofluid with magnetic nanoparticles by sonochemical method for MRI contrast agent
Eun Hee Kim; Hyo Sook Lee; Byung Kook Kwak; Byung-Kee Kim
2005-01-01
Superparamagnetic iron oxide nanoparticles (SPIO) having high magnetization (83emu\\/g) and crystallinity were synthesized by using a sonochemical method. Ferrofluids from these nanoparticles coated with oleic acid as a surfactant were prepared for magnetic resonance imaging (MRI) contrast agent. The coated SPIO could be easily dispersed in chitosan, and the hydrodynamic diameter of the coated SPIO in the chitosan solution was
Hydrodynamic analysis of elastic floating collars in random waves
NASA Astrophysics Data System (ADS)
Bai, Xiao-dong; Zhao, Yun-peng; Dong, Guo-hai; Li, Yu-cheng
2015-06-01
As the main load-bearing component of fish cages, the floating collar supports the whole cage and undergoes large deformations. In this paper, a mathematical method is developed to study the motions and elastic deformations of elastic floating collars in random waves. The irregular wave is simulated by the random phase method and the statistical approach and Fourier transfer are applied to analyze the elastic response in both time and frequency domains. The governing equations of motions are established by Newton's second law, and the governing equations of deformations are obtained based on curved beam theory and modal superposition method. In order to validate the numerical model of the floating collar attacked by random waves, a series of physical model tests are conducted. Good relationship between numerical simulation and experimental observations is obtained. The numerical results indicate that the transfer function of out-of-plane and in-plane deformations increase with the increasing of wave frequency. In the frequency range between 0.6 Hz and 1.1 Hz, a linear relationship exists between the wave elevations and the deformations. The average phase difference between the wave elevation and out-of-plane deformation is 60° with waves leading and the phase between the wave elevation and in-plane deformation is 10° with waves lagging. In addition, the effect of fish net on the elastic response is analyzed. The results suggest that the deformation of the floating collar with fish net is a little larger than that without net.
Hydrodynamic responses of a thin floating disk to regular waves
Yiew, Lucas; Meylan, Michael; French, Ben; Thomas, Giles
2015-01-01
Laboratory wave basin measurements of the surge, heave and pitch of a floating plastic disk caused by regular incident waves are presented. The measurements are used to validate two theoretical models: one based on slope-sliding theory and the other on combined potential-flow and thin-plate theories.
Hydrodynamic forces induced by a solitary wave on a submerged circular cylinder
Clement, A.; Mas, S. [Lab. de Mecanique des Fluides, Nantes (France)
1995-12-31
A numerical two dimensional wave basin has been developed in the framework of potential theory on nonlinear free-surface flows. This general purpose computer code was used in this study to investigate systematically the interaction between a solitary wave and a fixed submerged circular cylinder. For a given submergence, different flow evolutions were encountered; their features are shown to depend on soliton amplitude and cylinder diameter. A quantitative study of hydrodynamic forces during the interaction is also presented.
Energy Flow and Group Velocity of Electromagnetic Surface Wave in Hydrodynamic Approximation
Etsuo Matsuo; Mikio Tsuji
1978-01-01
Expressions for the energy density and the energy flow are derived for the electromagnetic surface wave (surface plasmon) on a semi-infinite metal surface by using the hydrodynamic approximation. A proof is given for the equality between the group velocity and the energy velocity. It is also shown that the direction of the energy flow in the metal is the same
Technology Transfer Automated Retrieval System (TEKTRAN)
Longissimus lumborum samples were removed 24 h postmortem from six U.S. Utility carcasses to be utilized in determining the effects of tenderness enhancement methods and aging time on quality attributes of beef. Within each sample, sections were randomly assigned to hydrodynamic shock waves (HSW), b...
Wake II model for hydrodynamic forces on marine pipelines for the wave plus current case
Ramirez Sabag, Said
1999-01-01
The concept of the Wake II model for the determination of the hydrodynamic forces on marine pipelines is extended to include the wave plus current case. There are two main differences between the Wake II and the traditional model that uses Morison...
Wake II model for hydrodynamic forces on marine pipelines for the wave plus current case
Ramirez Sabag, Said
1999-01-01
The concept of the Wake II model for the determination of the hydrodynamic forces on marine pipelines is extended to include the wave plus current case. There are two main differences between the Wake II and the traditional model that uses Morison...
Using a ferro-fluid pad to climb walls
Buchman, Michael (Michael R.)
2013-01-01
The goal of this thesis is to build a wall climbing system that utilizes the viscosity property of ferrofluids. Ferrofluid viscosity is varies based on the magnetic field applied to it and this property enables ferrofluids ...
Ferrofluids prepared by spark erosion
NASA Astrophysics Data System (ADS)
Berkowitz, A. E.; Walter, J. L.
1983-11-01
Spark erosion was used to prepare ferrofluids from metallic alloy particles. The particles are mostly <100 Å diameter and are enmeshed in the organic reaction products of the spark discharge in the organic dielectric liquid. The preparation, structural characterization and magnetic properties of these particles are discussed.
Hydrodynamic sensing and behavior by oyster larvae in turbulence and waves.
Fuchs, Heidi L; Gerbi, Gregory P; Hunter, Elias J; Christman, Adam J; Diez, F Javier
2015-05-01
Hydrodynamic signals from turbulence and waves may provide marine invertebrate larvae with behavioral cues that affect the pathways and energetic costs of larval delivery to adult habitats. Oysters (Crassostrea virginica) live in sheltered estuaries with strong turbulence and small waves, but their larvae can be transported into coastal waters with large waves. These contrasting environments have different ranges of hydrodynamic signals, because turbulence generally produces higher spatial velocity gradients, whereas waves can produce higher temporal velocity gradients. To understand how physical processes affect oyster larval behavior, transport and energetics, we exposed larvae to different combinations of turbulence and waves in flow tanks with (1) wavy turbulence, (2) a seiche and (3) rectilinear accelerations. We quantified behavioral responses of individual larvae to local instantaneous flows using two-phase, infrared particle-image velocimetry. Both high dissipation rates and high wave-generated accelerations induced most larvae to swim faster upward. High dissipation rates also induced some rapid, active dives, whereas high accelerations induced only weak active dives. In both turbulence and waves, faster swimming and active diving were achieved through an increase in propulsive force and power output that would carry a high energetic cost. Swimming costs could be offset if larvae reaching surface waters had a higher probability of being transported shoreward by Stokes drift, whereas diving costs could be offset by enhanced settlement or predator avoidance. These complex behaviors suggest that larvae integrate multiple hydrodynamic signals to manage dispersal tradeoffs, spending more energy to raise the probability of successful transport to suitable locations. PMID:25788721
On the consistency of the drag between air and water in meteorological, hydrodynamic and wave models
NASA Astrophysics Data System (ADS)
van Nieuwkoop, Joana; Baas, Peter; Caires, Sofia; Groeneweg, Jacco
2015-05-01
For the design, assessment and flood control of water defences, hydraulic loads in terms of water levels and wave conditions are required and often obtained from numerical models. For these hydraulic loads to be reliable, accurate atmospheric forcing is required. Waves and surges are typically forced by surface stress. However, in most cases, the input for these models consists of 10-m wind velocities that are internally converted to surface stress by applying a particular drag relation. This procedure generally leads to inconsistencies, since the hydrodynamic, wave and atmospheric models often apply different drag relations. By means of a case study, we explored the consequences of this inconsistency in the drag formulation for a North Sea storm wave and surge hindcast. This was done by forcing the hydrodynamic and wave models using both the 10-m wind velocity and the surface stress fields computed by the atmospheric model. Our study results show significant differences between the wave parameter values and water levels computed with surface stress input and 10-m wind velocity input. Our goal is not to assess different drag parameterizations but to raise awareness for this issue and to plea for the use of a consistent drag relation in meteorological and hydrodynamic/wave models. The consistent use of one drag formulation facilitates the identification of problems and the eventual improvement of the drag formulation. Furthermore, we suggest using the so-called pseudo-wind, which is a translation of the surface stress to the 10-m wind speed using a reference drag relation.
Mader, C.L.; Kershner, J.D.
1985-01-01
The interaction of a shock wave with a single air hole and a matrix of air holes in PETN, HMX, and TATB has been numerically modeled. The hot-spot formation, interaction, and the resulting buildup toward detonation were computed using three-dimensional numerical Eulerian hydrodynamics with Arrhenius chemical reaction and accurate equations of state according to the hydrodynamic hot-spot model. The basic differences between shock sensitive explosives (PETN, HMX) and shock insensitive explosives (TATB, NQ) may be described using the hydrodynamic hot-spot model. The reactive hydrodynamics of desensitization of heterogeneous explosives by a weak preshock has been numerically modeled. The preshock desensitizes the heterogeneous explosive by closing the air holes and making it more homogeneous. A higher pressure second shock has a lower temperature in the multiple shocked explosive than in single shocked explosives. The multiple shock temperature may be low enough to cause a detonation wave to fail to propagate through the preshocked explosive. 10 refs., 12 figs.
NASA Astrophysics Data System (ADS)
Degtyarev, A.; Gankevich, I.
2015-05-01
Determining the impact of external excitations on a dynamic marine object such as ship hull in a seaway is the main goal of simulations. Now such simulations is most often based on approximate mathematical models that use results of the theory of small amplitude waves. The most complicated software for marine objects behavior simulation LAMP IV (Large amplitude motion program) uses numerical solution of traditional hydrodynamic problem without often used approximations but on the basis of theory of small amplitude waves. For efficiency reasons these simulations can be based on autoregressive model to generate real wave surface. Such a surface possesses all the hydrodynamic characteristics of sea waves, preserves dispersion relation and also shows superior performance compared to other wind wave models. Naturally, the known surface can be used to compute velocity field and in turn to determine pressures in any point under sea surface. The resulting computational algorithm can be used to determine pressures without use of theory of small-amplitude waves.
Computer program for calculating hydrodynamic properties of shock waves in sea water
NASA Astrophysics Data System (ADS)
Fuhs, A. E.
1982-02-01
J. M. Richardson, A. B. Arons, and R. R. Halverson developed a calculation procedure for determining the hydrodynamic properties of sea water at the front of a shock wave. The procedure has been programmed for the HP41CV, which is a hand-held programmable calculator. The program, which uses 374 lines of code, reproduces the values for a shock wave as tabulated by Richardson, et al. The advantage of the HP41CV program is that properties can be calculated without use of tables.
Numerical Simulation of Ferrofluid Flow for Subsurface Environmental Engineering Applications
Curtis M. Oldenburg; Sharon E. Borglin; George J. Moridis
2000-01-01
Ferrofluids are suspensions of magnetic particles of diameter approximately 10?nm stabilized by surfactants in carrier liquids. The large magnetic susceptibility of ferrofluids allows the mobilization of ferrofluid through permeable rock and soil by the application of strong external magnetic fields. We have developed simulation capabilities for both miscible and immiscible conceptualizations of ferrofluid flow through porous media in response to
Transition to turbulence in Taylor-Couette ferrofluidic flow.
Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng
2015-01-01
It is known that in classical fluids turbulence typically occurs at high Reynolds numbers. But can turbulence occur at low Reynolds numbers? Here we investigate the transition to turbulence in the classic Taylor-Couette system in which the rotating fluids are manufactured ferrofluids with magnetized nanoparticles embedded in liquid carriers. We find that, in the presence of a magnetic field transverse to the symmetry axis of the system, turbulence can occur at Reynolds numbers that are at least one order of magnitude smaller than those in conventional fluids. This is established by extensive computational ferrohydrodynamics through a detailed investigation of transitions in the flow structure, and characterization of behaviors of physical quantities such as the energy, the wave number, and the angular momentum through the bifurcations. A finding is that, as the magnetic field is increased, onset of turbulence can be determined accurately and reliably. Our results imply that experimental investigation of turbulence may be feasible by using ferrofluids. Our study of transition to and evolution of turbulence in the Taylor-Couette ferrofluidic flow system provides insights into the challenging problem of turbulence control. PMID:26065572
Transition to turbulence in Taylor-Couette ferrofluidic flow
Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng
2015-01-01
It is known that in classical fluids turbulence typically occurs at high Reynolds numbers. But can turbulence occur at low Reynolds numbers? Here we investigate the transition to turbulence in the classic Taylor-Couette system in which the rotating fluids are manufactured ferrofluids with magnetized nanoparticles embedded in liquid carriers. We find that, in the presence of a magnetic field transverse to the symmetry axis of the system, turbulence can occur at Reynolds numbers that are at least one order of magnitude smaller than those in conventional fluids. This is established by extensive computational ferrohydrodynamics through a detailed investigation of transitions in the flow structure, and characterization of behaviors of physical quantities such as the energy, the wave number, and the angular momentum through the bifurcations. A finding is that, as the magnetic field is increased, onset of turbulence can be determined accurately and reliably. Our results imply that experimental investigation of turbulence may be feasible by using ferrofluids. Our study of transition to and evolution of turbulence in the Taylor-Couette ferrofluidic flow system provides insights into the challenging problem of turbulence control. PMID:26065572
Brumley, Douglas R; Polin, Marco; Pedley, Timothy J; Goldstein, Raymond E
2012-12-28
From unicellular ciliates to the respiratory epithelium, carpets of cilia display metachronal waves, long-wavelength phase modulations of the beating cycles, which theory suggests may arise from hydrodynamic coupling. Experiments have been limited by a lack of organisms suitable for systematic study of flagella and the flows they create. Using time-resolved particle image velocimetry, we report the discovery of metachronal waves on the surface of the colonial alga Volvox carteri, whose large size and ease of visualization make it an ideal model organism for these studies. An elastohydrodynamic model of weakly coupled compliant oscillators, recast as interacting phase oscillators, reveals that orbit compliance can produce fast, robust synchronization in a manner essentially independent of boundary conditions, and offers an intuitive understanding of a possible mechanism leading to the emergence of metachronal waves. PMID:23368623
NASA Astrophysics Data System (ADS)
Brumley, Douglas R.; Polin, Marco; Pedley, Timothy J.; Goldstein, Raymond E.
2012-12-01
From unicellular ciliates to the respiratory epithelium, carpets of cilia display metachronal waves, long-wavelength phase modulations of the beating cycles, which theory suggests may arise from hydrodynamic coupling. Experiments have been limited by a lack of organisms suitable for systematic study of flagella and the flows they create. Using time-resolved particle image velocimetry, we report the discovery of metachronal waves on the surface of the colonial alga Volvox carteri, whose large size and ease of visualization make it an ideal model organism for these studies. An elastohydrodynamic model of weakly coupled compliant oscillators, recast as interacting phase oscillators, reveals that orbit compliance can produce fast, robust synchronization in a manner essentially independent of boundary conditions, and offers an intuitive understanding of a possible mechanism leading to the emergence of metachronal waves.
S. R. Massel; T. J. Done
1993-01-01
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
NASA Astrophysics Data System (ADS)
Behdadfar, Behshid; Kermanpur, Ahmad; Sadeghi-Aliabadi, Hojjat; Morales, Maria del Puerto; Mozaffari, Morteza
2012-03-01
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.
A new experiment for the study of hydrodynamic waves and turbulence
NASA Astrophysics Data System (ADS)
Edlund, E.; Humanik, P.; Roach, A.; Schartman, E.; Sloboda, P.; Spence, E.; Ji, H.
2010-11-01
As a complement to the existing Princeton MRI Experiment, which is used for studies of MHD waves in a rotating liquid metal, a new device is being constructed by modifying the existing Couette water experiment for the study of purely hydrodynamic waves and turbulence. A primary objective of this new device is the study of Rossby waves, which will be excited by forcing a potential vorticity gradient through surfaces which are inclined relative to the azimuthal plane. A modular design allows for change of these fluid interfaces to study of Rossby waves under different forcing conditions. The experiment will be equipped with a two dimensional laser Doppler velocimetry (LDV) system, which can measure correlated fluctuations of radial and azimuthal velocities to form a measure of the Reynolds stress. The additional use of an ultrasonic Doppler velocimetry (UDV) system will allow for instantaneous measurement of the azimuthal and radial velocity profile at multiple locations to identify bulk flow characteristics and low-order wave structures. These measurement techniques allow for detailed study of the interplay between large scale waves, turbulence and angular momentum transport.
NASA Astrophysics Data System (ADS)
Bever, A. J.; MacWilliams, M.
2012-12-01
Under the conceptual model of sediment transport in San Pablo Bay, a sub-embayment of San Francisco Bay, proposed by Krone (1979), sediment typically enters San Pablo Bay during large winter and spring flows and is redistributed during summer conditions through wind wave resuspension and transport by tidal currents. A detailed understanding of how the waves and tides redistribute sediment within San Francisco Bay is critical for predicting how future sea level rise and a reduction in the sediment supply to the Bay will impact existing marsh and mudflat habitat, tidal marsh restoration projects, and ongoing maintenance dredging of the navigation channels. The three-dimensional UnTRIM San Francisco Bay-Delta Model was coupled with the Simulating WAves Nearshore (SWAN) wave model and the SediMorph morphological model, to develop a three-dimensional hydrodynamic, wind wave, and sediment transport model of the San Francisco Bay and the Sacramento-San Joaquin Delta. Numerical simulations of sediment resuspension due to tidal currents and wind waves and the subsequent transport of this sediment by tidal currents are used to quantify the spatial and temporal variability of sediment fluxes on the extensive shoals in San Pablo Bay under a range of tidal and wind conditions. The results demonstrate that suspended sediment concentration and sediment fluxes within San Pablo Bay are a complex product of tides and waves interacting spatially throughout the Bay, with concentrations responding to local resuspension and sediment advection. Sediment fluxes between the San Pablo Bay shoals and the deeper channel are highest during spring tides, and are elevated for up to a week following wave events, even though the greatest influence of the wave event occurs abruptly.
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
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.
Smoothed-particle-hydrodynamics modeling of dissipation mechanisms in gravity waves.
Colagrossi, Andrea; Souto-Iglesias, Antonio; Antuono, Matteo; Marrone, Salvatore
2013-02-01
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
Ferrofluid-based reconfigurable optofluidic switch
NASA Astrophysics Data System (ADS)
Valentino, Gianna; Mongeau, Eric; Gu, Yu
2014-03-01
We present a low-cost, reconfigurable optofluidic switch exploiting both the optical and magnetic properties of a water-based ferrofluid. This switch is composed of an integrated waveguide orthogonally crossing a microfluidic channel containing high-index oil and a ferrofluid plug. The switch is turned ``ON'' or ``OFF'' by the movement of the ferrofluid plug in response to an external magnetic field. Each switch exhibits a high contrast ratio and millisecond response time. Parallel geometries for both mode and multi-mode waveguides are shown. Saint Joseph's University summer research fund, McNulty Fellows Program.
Metachronal waves in the flagellar beating of $Volvox$ and their hydrodynamic origin
Douglas R. Brumley; Marco Polin; Timothy J. Pedley; Raymond E. Goldstein
2015-05-10
Groups of eukaryotic cilia and flagella are capable of coordinating their beating over large scales, routinely exhibiting collective dynamics in the form of metachronal waves. The origin of this behaviour -- possibly influenced by both mechanical interactions and direct biological regulation -- is poorly understood, in large part due to lack of quantitative experimental studies. Here we characterise in detail flagellar coordination on the surface of the multicellular alga $Volvox~carteri$, an emerging model organism for flagellar dynamics. Our studies reveal for the first time that the average metachronal coordination observed is punctuated by periodic phase defects during which synchrony is partial and limited to specific groups of cells. A minimal model of hydrodynamically coupled oscillators can reproduce semi-quantitatively the characteristics of the average metachronal dynamics, and the emergence of defects. We systematically study the model's behaviour by assessing the effect of changing intrinsic rotor characteristics, including oscillator stiffness and the nature of their internal driving force, as well as their geometric properties and spatial arrangement. Our results suggest that metachronal coordination follows from deformations in the oscillators' limit cycles induced by hydrodynamic stresses, and that defects result from sufficiently steep local biases in the oscillators' intrinsic frequencies. Additionally, we find that random variations in the intrinsic rotor frequencies increase the robustness of the average properties of the emergent metachronal waves.
Metachronal waves in the flagellar beating of Volvox and their hydrodynamic origin.
Brumley, Douglas R; Polin, Marco; Pedley, Timothy J; Goldstein, Raymond E
2015-07-01
Groups of eukaryotic cilia and flagella are capable of coordinating their beating over large scales, routinely exhibiting collective dynamics in the form of metachronal waves. The origin of this behaviour-possibly influenced by both mechanical interactions and direct biological regulation-is poorly understood, in large part due to a lack of quantitative experimental studies. Here we characterize in detail flagellar coordination on the surface of the multicellular alga Volvox carteri, an emerging model organism for flagellar dynamics. Our studies reveal for the first time that the average metachronal coordination observed is punctuated by periodic phase defects during which synchrony is partial and limited to specific groups of cells. A minimal model of hydrodynamically coupled oscillators can reproduce semi-quantitatively the characteristics of the average metachronal dynamics, and the emergence of defects. We systematically study the model's behaviour by assessing the effect of changing intrinsic rotor characteristics, including oscillator stiffness and the nature of their internal driving force, as well as their geometric properties and spatial arrangement. Our results suggest that metachronal coordination follows from deformations in the oscillators' limit cycles induced by hydrodynamic stresses, and that defects result from sufficiently steep local biases in the oscillators' intrinsic frequencies. Additionally, we find that random variations in the intrinsic rotor frequencies increase the robustness of the average properties of the emergent metachronal waves. PMID:26040592
Anderson, Mary Elizabeth
2011-10-21
ratio (Hs/h) may dominate over vegetation characteristics such as density or structure. For transects with the greatest proportion of Spartina anglica, when Hs/h exceeded 0.55, further increase in maximum observed wave attenuation ceased, suggesting...
NASA Astrophysics Data System (ADS)
Griv, Evgeny; Wang, Hsiang-Hsu
2014-07-01
Most rapidly and differentially rotating disk galaxies, in which the sound speed (thermal velocity dispersion) is smaller than the orbital velocity, display graceful spiral patterns. Yet, over almost 240 yr after their discovery in M51 by Charles Messier, we still do not fully understand how they originate. In this first paper of a series, the dynamical behavior of a rotating galactic disk is examined numerically by a high-order Godunov hydrodynamic code. The code is implemented to simulate a two-dimensional flow driven by an internal Jeans gravitational instability in a nonresonant wave-“fluid” interaction in an infinitesimally thin disk composed of stars or gas clouds. A goal of this work is to explore the local and linear regimes of density wave formation, employed by Lin, Shu, Yuan and many others in connection with the problem of spiral pattern of rotationally supported galaxies, by means of computer-generated models and to compare those numerical results with the generalized fluid-dynamical wave theory. The focus is on a statistical analysis of time-evolution of density wave structures seen in the simulations. The leading role of collective processes in the formation of both the circular and spiral density waves (“heavy sound”) is emphasized. The main new result is that the disk evolution in the initial, quasilinear stage of the instability in our global simulations is fairly well described using the local approximation of the generalized wave theory. Certain applications of the simulation to actual gas-rich spiral galaxies are also explored.
Magnetic detection of ferrofluid injection zones
Borglin, S.; Moridis, G.; Becker, A.
1998-03-01
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.
A Lagrangian description of nearshore hydrodynamics and rip currents forced by a random wave field
NASA Astrophysics Data System (ADS)
Leandro, S.; Cienfuegos, R.; Escauriaza, C. R.
2011-12-01
Nonlinear processes become important for waves propagating in the shoaling and surf zones. Wave shape changes when approaching the coast under the influence of bathymetry, becoming increasingly asymmetric until reaching the breaking limit. In the shoaling zone, non-linearities induce a net velocity in the direction of wave propagation, a phenomenon called Stokes drift, while in the surf zone, currents are mainly driven by spatio-temporal variations in energy dissipation gradients. In this work we aim at investigating and characterizing the nearshore circulation forced by a random wave field propagating over a variable bathymetry. We carry out numerical simulations over a laboratory experiment conducted in a wave basin over a realistic bathymetry [Michallet et al. 2010]. For the hydrodynamics, we use a 2D shock-capturing finite-volume model that solves the non-linear shallow water equations, taking into account energy dissipation by breaking, friction, bed-slope variations, and an accurate description for the moving shoreline in the swash zone [Marche et al. 2007;Guerra et al. 2010]. Model predictions are compared and validated against experimental data giving confidence for its use in the description of wave propagation in the surf/swash zone, together with mean eulerian velocities. The resulting wave propagation and circulation provided by the 2D model will then be used to describe drifter's patterns in the surf zone and construct Lagrangian particle tracking. The chosen experimental configuration is of great interest due to the random wave forcing (slowly modulated), the beach non-uniformities, and the existence of several bar-rip channels that enhance quasi-periodic rip instabilities. During the experiment, balloons filled with water, with a diameter between 5 and 10 cm, were placed in the surf zone in order to characterize circulation in a Lagrangian framework [Castelle et al. 2010]. The time-location of the balloons was continuously tracked by a shore-mounted video camera, and the images were processed to obtain the trajectories and mean velocities. The Lagrangian description provided by the numerical model will be thus confronted to experimental data, and then used to characterize circulation patterns, rip instabilities and infragravity wave pulsations.
NASA Astrophysics Data System (ADS)
Lasky, Paul D.; Bennett, Mark F.; Melatos, Andrew
2013-03-01
Hydrodynamic turbulence driven by crust-core differential rotation imposes a fundamental noise floor on gravitational wave observations of neutron stars. The gravitational wave emission peaks at the Kolmogorov decoherence frequency which, for reasonable values of the crust-core shear, ??, occurs near the most sensitive part of the frequency band for ground-based, long-baseline interferometers. We calculate the energy density spectrum of the stochastic gravitational wave background from a cosmological population of turbulent neutron stars generalizing previous calculations for individual sources. The spectrum resembles a piecewise power law, ?gw(?)=????, with ?=-1 and 7 above and below the decoherence frequency respectively, and its normalization scales as ???(??)7. Nondetection of a stochastic signal by Initial LIGO implies an upper limit on ?? and hence by implication on the internal relaxation time scale for the crust and core to come into corotation, ?d=??/??, where ?? is the observed electromagnetic spin-down rate, with ?d?107yr for accreting millisecond pulsars and ?d?105yr for radio-loud pulsars. Target limits on ?d are also estimated for future detectors, namely Advanced LIGO and the Einstein Telescope, and are found to be astrophysically interesting.
NASA Astrophysics Data System (ADS)
Marques, Wilson, Jr.; Jacinta Soares, Ana; Pandolfi Bianchi, Miriam; Kremer, Gilberto M.
2015-06-01
A shock wave structure problem, like the one which can be formulated for the planar detonation wave, is analyzed here for a binary mixture of ideal gases undergoing the symmetric reaction {{A}1}+{{A}1}\\rightleftharpoons {{A}2}+{{A}2}. The problem is studied at the hydrodynamic Euler limit of a kinetic model of the reactive Boltzmann equation. The chemical rate law is deduced in this frame with a second-order reaction rate, in a chemical regime such that the gas flow is not far away from the chemical equilibrium. The caloric and the thermal equations of state for the specific internal energy and temperature are employed to close the system of balance laws. With respect to other approaches known in the kinetic literature for detonation problems with a reversible reaction, this paper aims to improve some aspects of the wave solution. Within the mathematical analysis of the detonation model, the equation of the equilibrium Hugoniot curve of the final states is explicitly derived for the first time and used to define the correct location of the equilibrium Chapman–Jouguet point in the Hugoniot diagram. The parametric space is widened to investigate the response of the detonation solution to the activation energy of the chemical reaction. Finally, the mathematical formulation of the linear stability problem is given for the wave detonation structure via a normal-mode approach, when bidimensional disturbances perturb the steady solution. The stability equations with their boundary conditions and the radiation condition of the considered model are explicitly derived for small transversal deviations of the shock wave location. The paper shows how a second-order chemical kinetics description, derived at the microscopic level, and an analytic deduction of the equilibrium Hugoniot curve, lead to an accurate picture of the steady detonation with reversible reaction, as well as to a proper bidimensional linear stability analysis.
Numerical modeling on hydrodynamic performance of a bottom-hinged flap wave energy converter
NASA Astrophysics Data System (ADS)
Zhao, Hai-tao; Sun, Zhi-lin; Hao, Chun-ling; Shen, Jia-fa
2013-03-01
The hydrodynamic performance of a bottom-hinged flap wave energy converter (WEC) is investigated through a frequency domain numerical model. The numerical model is verified through a two-dimensional analytic solution, as well as the qualitative analysis on the dynamic response of avibrating system. The concept of "optimum density" of the bottom-hinged flap is proposed, and its analytic expression is derived as well. The frequency interval in which the optimum density exists is also obtained. The analytic expression of the optimum linear damping coefficient is obtained by a bottom-hinged WEC. Some basic dynamic properties involving natural period, excitation moment, pitch amplitude, and optimum damping coefficient are analyzed and discussed in detail. In addition, this paper highlights the analysis of effects on the conversion performance of the device exerted by some important parameters. The results indicate that "the optimum linear damping period of 5.0 s" is the most ideal option in the short wave sea states with the wave period below 6.0 s. Shallow water depth, large flap thickness and low flap density are advised in the practical design of the device in short wave sea states in order to maximize power capture. In the sea state with water depth of 5.0 m and wave period of 5.0 s, the results of parametric optimization suggest a flap with the width of 8.0 m, thickness of 1.6 m, and with the density as little as possible when the optimum power take-off (PTO) damping coefficient is adopted.
Small, medium and large shock waves for non-equilibrium radiation hydrodynamic
Corrado Mascia
2012-02-13
We examine the existence of shock profiles for a hyperbolic-elliptic system arising in radiation hydrodynamics. The algebraic-differential system for the wave profile is reduced to a standard two-dimensional form that is analyzed in details showing the existence of heteroclinic connection between the two singular points of the system for any distance between the corresponding asymptotic states of the original model. Depending on the location of these asymptotic states, the profile can be either continuous or possesses at most one point of discontinuity. Moreover, a sharp threshold relative to presence of an internal absolute maximum in the temperature profile --also called {\\sf Zel'dovich spike}-- is rigourously derived.
From AdS/CFT correspondence to hydrodynamics. II. Sound waves
G. Policastro; D. T. Son; A. O. Starinets
2005-07-26
As a non-trivial check of the non-supersymmetric gauge/gravity duality, we use a near-extremal black brane background to compute the retarded Green's functions of the stress-energy tensor in N=4 super-Yang-Mills (SYM) theory at finite temperature. For the long-distance, low-frequency modes of the diagonal components of the stress-energy tensor, hydrodynamics predicts the existence of a pole in the correlators corresponding to propagation of sound waves in the N=4 SYM plasma. The retarded Green's functions obtained from gravity do indeed exhibit this pole, with the correct values for the sound speed and the rate of attenuation.
Enzo Marino; Claudio Borri; Claudio Lugni
2011-01-01
This paper draws some preliminary considerations about the direct wind effects on the kinematics and dynamics of steep extreme waves propagating near offshore wind turbines. Most of the hydrodynamic load models currently employed in designing offshore wind turbines take into account only indirectly the role of the wind. In fact, once the sea severity upon a certain wind speed is
Structural studies of ferrofluids by small-angle neutron scattering
M. Balasoiu; M. V. Avdeev; A. I. Kuklin; V. L. Aksenov; D. Bica; L. Vekas; D. Hasegan; Gy. Torok; L. Rosta; V. Garamus; J. Kohlbrecher
2004-01-01
Small-angle neutron scattering (SANS) is a powerful technique for studying the microstructure of ferrofluids under different conditions. The paper reviews recent results obtained from the analysis of SANS data for a number of ferrofluids based on non-polar and polar carriers. Specific features revealed by SANS and their comparison for different types of ferrofluids are discussed. Problems to be solved are
Wave-driven Hydrodynamics for Different Reef Geometries and Roughness Scenarios
NASA Astrophysics Data System (ADS)
Franklin, G. L.; Marino-Tapia, I.; Torres-Freyermuth, A.
2013-05-01
In fringing reef systems where a shallow lagoon is present behind the reef crest, wave breaking appears to dominate circulation, controlling numerous key processes such as the transport and dispersion of larvae, nutrients and sediments. Despite their importance, there is a need for more detailed knowledge on the hydrodynamic processes that take place within the surf zone of these systems and the effects different combinations of geometries and roughness have on them. The present study focuses on the use of two-dimensional (2DV) numerical model simulations and data obtained during a field campaign in Puerto Morelos, Quintana Roo, Mexico to better understand the detailed surf zone processes that occur over a fringing reef. The model used is Cornell Breaking Wave and Structures (COBRAS), which solves Reynolds-Averaged Navier-Stokes (RANS) equations. Reef geometries implemented in the model include a reef flat and two different reef crests. The effect of roughness on wave setup, radiation stress, mean flows, and cross-shore spectral evolution for the model results was studied using different roughness coefficients (Nikuradse) and a bathymetric profile obtained in the field using the bottom track option of an Acoustic Doppler Current Profiler. Field data were also analysed for the configuration and roughness of Puerto Morelos. Model results reveal that for all profiles wave setup increased significantly (~22%) with increasing bed roughness, in agreement with previous findings for sandy beaches.For all wave heights and periods studied, increasing roughness also affected spectral wave evolution across the reef, with a significant reduction in energy, particularly at infragravity frequencies. The presence of a reef crest in the profile resulted in differences in behaviour at infragravity frequencies. For example, preliminary results suggest that there is a shift towards higher frequencies as waves progress into the lagoon when a crest is present, something that does not appear to occur over the reef flat. Time-averaged velocities exhibited a dominant onshore flow due to waves at the surface, as is generally reported for coral reefs. Model results also suggest the presence of offshore velocities, which were slightly greater over the reef flat compared to the reef crest. Maximum offshore velocities appear to be more localised in the case of the reef flat whereas they extended over a larger area in the case of the reef crest. In all cases, increased roughness resulted in reduced velocities. These results are important since they concern processes that affect the circulation within the lagoon, which has implications in terms of the lagoon's residence time and hence heat dispersion and exposure to pollutants.
Atis, S; Saha, S; Auradou, H; Martin, J; Rakotomalala, N; Talon, L; Salin, D
2012-09-01
Autocatalytic reaction fronts between two reacting species in the absence of fluid flow, propagate as solitary waves. The coupling between autocatalytic reaction front and forced simple hydrodynamic flows leads to stationary fronts whose velocity and shape depend on the underlying flow field. We address the issue of the chemico-hydrodynamic coupling between forced advection in porous media and self-sustained chemical waves. Towards that purpose, we perform experiments over a wide range of flow velocities with the well characterized iodate arsenious acid and chlorite-tetrathionate autocatalytic reactions in transparent packed beads porous media. The characteristics of these porous media such as their porosity, tortuosity, and hydrodynamics dispersion are determined. In a pack of beads, the characteristic pore size and the velocity field correlation length are of the order of the bead size. In order to address these two length scales separately, we perform lattice Boltzmann numerical simulations in a stochastic porous medium, which takes into account the log-normal permeability distribution and the spatial correlation of the permeability field. In both experiments and numerical simulations, we observe stationary fronts propagating at a constant velocity with an almost constant front width. Experiments without flow in packed bead porous media with different bead sizes show that the front propagation depends on the tortuous nature of diffusion in the pore space. We observe microscopic effects when the pores are of the size of the chemical front width. We address both supportive co-current and adverse flows with respect to the direction of propagation of the chemical reaction. For supportive flows, experiments and simulations allow observation of two flow regimes. For adverse flow, we observe upstream and downstream front motion as well as static front behaviors over a wide range of flow rates. In order to understand better these observed static state fronts, flow experiments around a single obstacle were used to delineate the range of steady state behavior. A model using the "eikonal thin front limit" explains the observed steady states. PMID:23020499
Magnetic relaxation and dissipative heating in ferrofluids
NASA Astrophysics Data System (ADS)
Vaishnava, P. P.; Tackett, R.; Dixit, A.; Sudakar, C.; Naik, R.; Lawes, G.
2007-09-01
We have investigated the ac magnetic susceptibility and magnetic heating of aqueous suspensions of ?-Fe2O3 nanoparticles embedded in alginate hydrogel matrix and isolated ?-Fe2O3 and Fe3O4 nanoparticles coated with tetramethyl ammonium hydroxide. All three ferrofluids were characterized by measuring the dc magnetization, ac susceptibility, and magnetic heating. We found that significant Néel relaxation is present in all samples, but only the isolated nanoparticle ferrofluids show any significant feature associated with Brownian relaxation near the freezing temperature of the carrier liquid. The heating rate of the ferrofluids varies systematically with the magnitude of the Brownian relaxation peak, despite similar values of the absolute magnetization. These results highlight the importance of the Brownian relaxation for heating applications incorporating magnetic nanoparticles.
Flow and heat transfer of ferrofluids over a flat plate with uniform heat flux
NASA Astrophysics Data System (ADS)
Khan, W. A.; Khan, Z. H.; Haq, R. U.
2015-04-01
The present work is dedicated to analyze the flow and heat transport of ferrofluids along a flat plate subjected to uniform heat flux and slip velocity. A magnetic field is applied in the transverse direction to the plate. Moreover, three different kinds of magnetic nanoparticles (Fe3O4, CoFe2O4, Mn-ZnFe2O4 are incorporated within the base fluid. We have considered two different kinds of base fluids (kerosene and water) having poor thermal conductivity as compared to solid magnetic nanoparticles. Self-similar solutions are obtained and are compared with the available data for special cases. A simulation is performed for each ferrofluid mixture by considering the dominant effects of slip and uniform heat flux. It is found that the present results are in an excellent agreement with the existing literature. The variation of skin friction and heat transfer is also performed at the surface of the plate and then the better heat transfer and of each mixture is analyzed. Kerosene-based magnetite Fe3O4 provides the higher heat transfer rate at the wall as compared to the kerosene-based cobalt ferrite and Mn-Zn ferrite. It is also concluded that the primary effect of the magnetic field is to accelerate the dimensionless velocity and to reduce the dimensionless surface temperature as compared to the hydrodynamic case, thereby increasing the skin friction and the heat transfer rate of ferrofluids.
Magnetic pressure and shape of ferrofluid seals in cylindrical structures
NASA Astrophysics Data System (ADS)
Ravaud, R.; Lemarquand, G.; Lemarquand, V.
2009-08-01
This paper presents a three-dimensional analytical model for studying the shape and the pressure of ferrofluid seals in totally ironless structures. This three-dimensional analytical approach is based on the exact calculation of the magnetic field components created by ring permanent magnets whose polarizations are either radial or axial. We assume that the ferromagnetic particles of the ferrofluid are saturated. Moreover, the permanent magnets (neodymium iron boron) used in the considered applications create a magnetic field which is much higher than the magnetic field created by the magnetic particles in the ferrofluid so the latter is neglected. Nevertheless, the static behavior of the ferrofluid seal depends on both the magnetic field produced by the permanent magnets and the saturation magnetization of the ferrofluid particles. Furthermore, the accurate knowledge of the ferrofluid seal shape as well as the magnetic pressure inside the ferrofluid seal is very useful for the design of devices using both permanent magnets and ferrofluid seals. It is emphasized here that our structures are completely ironless and thus, there are no iron-base piston for these structures. Then, this paper makes a review of the main structures using ring permanent magnets and ferrofluid seals. For each ironless structure, the shape and the pressure of the ferrofluid seals are determined.
Zablotsky, Dmitry; Blums, Elmars
2011-08-01
In this paper, we consider a concentration grating of magnetic nanoparticles optically induced by thermodiffusion in a layer of ferrofluid in the presence of the external homogeneous magnetic field. The applied field is directed along the concentration gradient and leads to the appearance of the internal nonhomogeneous demagnetizing fields. When the system reaches equilibrium, the optical pumping is switched off, and the grating is allowed to relax. We carry out a stability analysis using the Galerkin approach and numerical simulations of the full system of equations to determine the growth rates and the mode amplitudes of the hydrodynamic and concentration perturbations during the relaxation stage. PMID:21929102
Passive Magnetic Bearing With Ferrofluid Stabilization
NASA Technical Reports Server (NTRS)
Jansen, Ralph; DiRusso, Eliseo
1996-01-01
A new class of magnetic bearings is shown to exist analytically and is demonstrated experimentally. The class of magnetic bearings utilize a ferrofluid/solid magnet interaction to stabilize the axial degree of freedom of a permanent magnet radial bearing. Twenty six permanent magnet bearing designs and twenty two ferrofluid stabilizer designs are evaluated. Two types of radial bearing designs are tested to determine their force and stiffness utilizing two methods. The first method is based on the use of frequency measurements to determine stiffness by utilizing an analytical model. The second method consisted of loading the system and measuring displacement in order to measure stiffness. Two ferrofluid stabilizers are tested and force displacement curves are measured. Two experimental test fixtures are designed and constructed in order to conduct the stiffness testing. Polynomial models of the data are generated and used to design the bearing prototype. The prototype was constructed and tested and shown to be stable. Further testing shows the possibility of using this technology for vibration isolation. The project successfully demonstrated the viability of the passive magnetic bearing with ferrofluid stabilization both experimentally and analytically.
A Novel Application of Ferrofluid Actuation with PDMS Microchannel
Yaw-Jen Chang; Chih-Yu Hu; Chu-Hsuan Lin
2010-01-01
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
Microstructure of bidisperse ferrofluids in a thin layer
Minina, E. S., E-mail: alla2307@gmail.com; Muratova, A. B. [Ural Federal University, Department of Mathematical Physics (Russian Federation)] [Ural Federal University, Department of Mathematical Physics (Russian Federation); Cerda, J. J. [Campus University de les Illes Balears, Institute for Cross-Disciplinary Physics and Complex Systems (Spain)] [Campus University de les Illes Balears, Institute for Cross-Disciplinary Physics and Complex Systems (Spain); Kantorovich, S. S., E-mail: sue.kantorovich@usu.ru [Ural Federal University, Department of Mathematical Physics (Russian Federation)
2013-03-15
In this work we present a characterization of the bidisperse ferrofluid microstructures that appear in thin layers of ferrofluid. These layers have been studied by a combination of Langevin dynamics simulations and density functional theory. Our results allow us to compare the microstructures that exist in quasi-two-dimensional ferrofluid nanolayers with the microstructures found in three-dimensional bidisperse ferrofluids. Furthermore, our results allow us to explain the influence of the geometry of the sample on the topology and size-distribution of the observed aggregates of magnetic nanoparticles.
Lacy, J.R.; Sherwood, C.R.; Wilson, D.J.; Chisholm, T.A.; Gelfenbaum, G.R.
2005-01-01
Hydrodynamic roughness is a critical parameter for characterizing bottom drag in boundary layers, and it varies both spatially and temporally due to variation in grain size, bedforms, and saltating sediment. In this paper we investigate temporal variability in hydrodynamic roughness using velocity profiles in the bottom boundary layer measured with a high-resolution acoustic Doppler profiler (PCADP). The data were collected on the ebb-tidal delta off Grays Harbor, Washington, in a mean water depth of 9 m. Significant wave height ranged from 0.5 to 3 m. Bottom roughness has rarely been determined from hydrodynamic measurements under conditions such as these, where energetic waves and medium-to-fine sand produce small bedforms. Friction velocity due to current u*c and apparent bottom roughness z0a were determined from the PCADP burst mean velocity profiles using the law of the wall. Bottom roughness kB was estimated by applying the Grant-Madsen model for wave-current interaction iteratively until the model u*c converged with values determined from the data. The resulting kB values ranged over 3 orders of magnitude (10-1 to 10-4 m) and varied inversely with wave orbital diameter. This range of kB influences predicted bottom shear stress considerably, suggesting that the use of time-varying bottom roughness could significantly improve the accuracy of sediment transport models. Bedform height was estimated from kB and is consistent with both ripple heights predicted by empirical models and bedforms in sonar images collected during the experiment. Copyright 2005 by the American Geophysical Union.
Chabchoub, A; Hoffmann, N; Onorato, M; Genty, G; Dudley, J M; Akhmediev, N
2013-08-01
We report the experimental observation of multi-bound-soliton solutions of the nonlinear Schrödinger equation (NLS) in the context of hydrodynamic surface gravity waves. Higher-order N-soliton solutions with N=2, 3 are studied in detail and shown to be associated with self-focusing in the wave group dynamics and the generation of a steep localized carrier wave underneath the group envelope. We also show that for larger input soliton numbers, the wave group experiences irreversible spectral broadening, which we refer to as a hydrodynamic supercontinuum by analogy with optics. This process is shown to be associated with the fission of the initial multisoliton into individual fundamental solitons due to higher-order nonlinear perturbations to the NLS. Numerical simulations using an extended NLS model described by the modified nonlinear Schrödinger equation, show excellent agreement with experiment and highlight the universal role that higher-order nonlinear perturbations to the NLS play in supercontinuum generation. PMID:23952405
NASA Astrophysics Data System (ADS)
Miura, Hitoshi; Nakamoto, Taishi
2007-05-01
Millimeter-sized, spherical silicate grains abundant in chondritic meteorites, which are called as chondrules, are considered to be a strong evidence of the melting event of the dust particles in the protoplanetary disk. One of the most plausible scenarios is that the chondrule precursor dust particles are heated and melt in the high-velocity gas flow (shock-wave heating model). We developed the non-linear, time-dependent, and three-dimensional hydrodynamic simulation code for analyzing the dynamics of molten droplets exposed to the gas flow. We confirmed that our simulation results showed a good agreement in a linear regime with the linear solution analytically derived by Sekyia et al. [Sekyia, M., Uesugi, M., Nakamoto, T., 2003. Prog. Theor. Phys. 109, 717-728]. We found that the non-linear terms in the hydrodynamical equations neglected by Sekiya et al. [Sekiya, M., Uesugi, M., Nakamoto, T., 2003. Prog. Theor. Phys. 109, 717-728] can cause the cavitation by producing negative pressure in the droplets. We discussed that the fragmentation through the cavitation is a new mechanism to determine the upper limit of chondrule sizes. We also succeeded to reproduce the fragmentation of droplets when the gas ram pressure is stronger than the effect of the surface tension. Finally, we compared the deformation of droplets in the shock-wave heating with the measured data of chondrules and suggested the importance of other effects to deform droplets, for example, the rotation of droplets. We believe that our new code is a very powerful tool to investigate the hydrodynamics of molten droplets in the framework of the shock-wave heating model and has many potentials to be applied to various problems.
Ferrofluid-based microchip pump and valve
Herb Hartshorne; Christopher J. Backhouse; William E. Lee
2004-01-01
Fluid control is a key element in the performance of microfluidic “lab-on-a-chip” devices. The development of integrated multi-function micro-chemical reactors and analysis platforms depends upon on-chip valving and pumping. In this work, microfluidic valves and pumps were fabricated from etched glass substrates each bonded to a second glass substrate lid that had ultrasonically drilled access holes. The devices contained ferrofluid
Magnetic Pressure and Shape of Ferrofluid Seals in Cylindrical Structures
Paris-Sud XI, Université de
of the magnetic field components4 created by ring permanent magnets whose polarizations are either radial or axial as the magnetic pressure inside9 the ferrofluid seal is very useful for the design of devices using both permanent1 Magnetic Pressure and Shape of Ferrofluid Seals in Cylindrical Structures R. Ravaud, G
Magnetic Pressure and Shape of Ferrofluid Seals in Cylindrical Structures
Paris-Sud XI, Université de
-dimensional analytical approach is based on the3 exact calculation of the magnetic field components created by ring as well as the magnetic pressure10 inside the ferrofluid seal is very useful for the design of devices1 Magnetic Pressure and Shape of Ferrofluid Seals in Cylindrical Structures R. Ravaud, G
Aqueous ferrofluids based on manganese and cobalt ferrites
Francisco Augusto Tourinho; Raymonde Franck; René Massart
1990-01-01
Synthesis of two new aqueous ferrofluids is performed chemically according to Massart's procedure. Manganese and cobalt ferrite magnetic particles are precipitated and treated in order to obtain colloidal sols by creating a charge density on their surface. Such “ionic” ferrofluids can be prepared in an acidic (after a treatment by ferric nitrate) or in an alkaline medium at a concentration
Magnetic transient birefringence of ferrofluids : particle size determination
Paris-Sud XI, Université de
E 1385 Magnetic transient birefringence of ferrofluids : particle size determination J.-C. Bacri, R birefringence of ferrofluid solutions are performed with samples of various polydispersities. d-normal distribution. Dynamic magnetic birefringence appears to be a good test of the tail of the sample size
Ferrofluid based micro-electrical energy harvesting
NASA Astrophysics Data System (ADS)
Purohit, Viswas; Mazumder, Baishakhi; Jena, Grishma; Mishra, Madhusha; Materials Department, University of California, Santa Barbara, CA93106 Collaboration
2013-03-01
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.
Some results of the hydrodynamic theory of finite-amplitude waves
NASA Technical Reports Server (NTRS)
Sekerzh-Zenkovich, Y. I.
1975-01-01
Standing waves can be interpreted as free waves between two vertical walls; for a standing wave in an unlimited container there is no transport of liquid mass in the horizontal direction. Standing waves of finite amplitude also possess the following properties not possessed by the waves of the linear theory: (1) there are no motionless points, (2) the points of maximum amplitude (crests and troughs) are fixed, and coincide with the antinodes of the original linear wave, (3) the ordinates of the wave crests are greater in absolute magnitude than the ordinates of the troughs; the wave is similar to a trochoid curve; (4) the wave profile never becomes straight; and (5) the frequency of the oscillations depends not only on the wave length but also on the amplitude.
Tetsu Hara; William J. Plant
1994-01-01
In this paper we use results of microwave backscattering experiments over the past decade to attempt to present a coherent picture of the ocean wave-radar modulation transfer function (MTF) based on composite surface theory, short-wave modulation, and modulated wind stress. A simplified relaxation model is proposed for the modulation of the gravity-capillary wavenumber spectrum by long waves. The model is
From AdS\\/CFT correspondence to hydrodynamics. II. Sound waves
Giuseppe Policastro; Dam T. Son; Andrei O. Starinets
2002-01-01
As a non-trivial check of the non-supersymmetric gauge\\/gravity duality, we use a near-extremal black brane background to compute the retarded Green's functions of the stress-energy tensor in = 4 super-Yang-Mills (SYM) theory at finite temperature. For the long-distance, low-frequency modes of the diagonal components of the stress-energy tensor, hydrodynamics predicts the existence of a pole in the correlators corresponding to
Gr?bel, Klaudiusz; Machnicka, Alicja
2014-01-01
The efficiency of disintegration of sewage sludge cells microorganisms were characterized using biochemical parameters such as COD, phosphate, ammonium nitrogen and proteins. The investigated process was additionally assessed using the coefficient DD (Degree of Disintegration). It has been demonstrated that a 30-min of hydrodynamic and ultrasonic disintegration causes the soluble COD value increased about 300 mg /L and 190 mg /L (average), while the degree of disintegration reached 24% and 21%, respectively. The efficiency of sewage sludge hydrodynamic and ultrasonic disintegration was confirmed by increased release of phosphate (V) (from 4 to 54 mg PO?(3-) /L and to 50 mg PO?(3-) /L, respectively), ammonium nitrogen (from 1.5 to 4 mg N-NH?(+) /L and to 3.5 mg N-NH?(+) /L, respectively) and proteins (from 5 to 70 mg/L and to 60 mg/L, respectively). The effectiveness of surplus activated sludge disintegration was tested in the infrared spectrum. Changes in absorbance at the specified wavelength attest to a release of i.e., amines, amino acids, amide groups (proteins), phosphates, ammonium salts of carboxylic acid, etc. during disintegration time. Revealing these chemical groups in over-sludge liquids attests to a destructive influence of hydrodynamic and ultrasonic cavitation on activated sludge microorganisms and effective cells lysis. PMID:24117089
The hydrodynamic forces acting on a cylinder array oscillating in waves and current
Takeshi Kinoshita; Weiguang Bao; Shunji Sunahara
1997-01-01
The problem of the interaction of multiple cylinders oscillating in waves and slow current is considered. The interaction\\u000a is represented by waves emitted from adjacent cylinders towards the cylinder under consideration. Wave drift forces and moment\\u000a in the horizontal plane are calculated by the far-field method based on the conservation of momentum or angular momentum.\\u000a A semianalytical formula for the
Electromagnetic induction by ferrofluid in an oscillating heat pipe
NASA Astrophysics Data System (ADS)
Monroe, J. G.; Vasquez, E. S.; Aspin, Z. S.; Walters, K. B.; Berg, M. J.; Thompson, S. M.
2015-06-01
Thermal-to-electrical energy conversion was demonstrated using an oscillating heat pipe (OHP) filled with ferrofluid and equipped with an annular-type solenoid. The OHP was subjected to a 100 °C axial temperature difference allowing the ferrofluid to passively oscillate through the solenoid, thus accomplishing electromagnetic induction. The measured solenoid voltage consisted of aperiodic pulses with dominant frequencies between 2 and 5 Hz and peak-to-peak amplitudes approaching 1 mV. Despite exposure to the thermal and phase change cycling within the OHP, nanoparticle morphologies and magnetic properties of the ferrofluid remained intact. This energy harvesting method allows for combined thermal management and in-situ power generation.
The Four-Wave Mixing and the Hydrodynamic Excitations in Smectic A Liquid Crystals
G. F. Kventsel; B. I. Lembrikov
1995-01-01
A nondegenerate four-wave mixing (FWM) on a new type of Kerr nonlinearity determined by the layer deformations in smectic A liquid crystal (SmA) is considered. It is shown that in the case when the frequency difference of the coupled electromagnetic waves (EMW) is close to the frequency of the second sound (SS), a strong parametric coupling among EMW through the
Experimental study of the hydrodynamics of high Mach number blast waves
Aaron Douglas Edens
2005-01-01
We have performed a series of experiments examining the properties of high Mach number blast waves. Preliminary experiments were conducted on the Janus laser at Lawrence Livermore National Laboratory while the majority of experiments were carried out on the Z-Beamlet laser at Sandia National Laboratories. We created blast waves in the laboratory by using 10 J - 1000 J laser
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
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.
Hydrodynamic Models of Bipolar Semiconductors Best Asymptotic Profiles
Hydrodynamic Models of Bipolar Semiconductors Best Asymptotic Profiles Convergence to Stationary Waves Asymptotic Profiles for Bipolar Hydrodynamic System of Semiconductors Ming Mei Champlain College for Bipolar Hydrodynamic System of Semicon #12;Hydrodynamic Models of Bipolar Semiconductors Best Asymptotic
Preparation of magnetic ferrofluids in alternative carrier liquids
NASA Technical Reports Server (NTRS)
Rosensweig, R. E.
1970-01-01
Ferrofluids are made by grinding magnetic particles together with a polar surfactant and a nonpolar solvent. The surfactant is adsorbed on the particle surfaces and acts as a coupling agent between the particles and the solvent.
Ferrofluid surface and volume flows in uniform rotating magnetic fields
Elborai, Shihab M. (Shihab Mahmoud), 1977-
2006-01-01
Ferrofluid surface and volume effects in uniform dc and rotating magnetic fields are studied. Theory and corroborating measurements are presented for meniscus shapes and resulting surface driven flows, spin-up flows, and ...
Static and Dynamic Contact Angles of Immersed Ferrofluid Droplets
NASA Astrophysics Data System (ADS)
Chatterjee, Souvick; Bhowmik, Dipanwita; Mukhopadhyay, Achintya; Ganguly, Ranjan
2013-11-01
Ferrofluid plug driven micro-pumps are useful for manipulating micro-volume of liquids by providing remote actuation using a localized magnetic field gradient. Inside a microchannel, the ferrofluid experiences combined actions of different relevant body forces. While the pressure, viscous and magnetic forces can be estimated using established techniques, the surface tension force requires information about the contact angle between the ferrofluid and glass capillary wall. We address this phenomenon through experimental characterization of static and dynamic contact angles of oil based ferrofluid (EFH3) droplets on glass surface immersed in pure or surfacted distilled water. The equilibrium static contact angle is found to significantly reduce in presence of a magnetic field. Dynamic contact angles are measured through high-speed imaging as the ferrofluid droplets slide along an inclined glass surface. Variation of contact angle hysteresis, which falls outside the Hoffmann Tanner equation for this case, is also investigated as a function of contact line velocity. A strong dependence is found between the contact angle hysteresis and the wetting time. Findings of the work is useful for designing ferrofluid plug-driven microfluidic plugs for different lab-on-a-chip applications.
Characterizing ferrofluid spin-up flow in rotating uniform magnetic fields
Dozier, Kahlil A
2014-01-01
A ferrofluid is a collection of nanoscale ferromagnetic particles with a stabilizing surfactant in a liquid to form a colloid. The dynamic behavior of ferrofluids in the presence of magnetic fields has long been an area ...
Ferrofluid spin-up flows from uniform and non-uniform rotating magnetic fields
Khushrushahi, Shahriar Rohinton
2010-01-01
When ferrofluid in a cylindrical container is subjected to a rotating azimuthally directed magnetic field, the fluid "spins up" into an almost rigid-body rotation where ferrofluid nanoparticles have both a linear and an ...
NASA Astrophysics Data System (ADS)
Suslov, Sergey A.; Bozhko, Alexandra A.; Putin, Gennady F.; Sidorov, Alexander S.
2012-11-01
Study of Boussinesq convection in a vertical differentially heated fluid layer is one of classical problems in hydrodynamics. It is well known that as the value of fluid's Grashof number increases the basic flow velocity profile becomes unstable with respect to stationary shear-driven disturbances (at Prandtl numbers Pr < 12.5) or thermogravitational waves propagating vertically (at larger values of Prandtl number). However linear stability studies of a similar flow of magnetopolarizable nanosuspensions (ferrofluids) placed in a uniform magnetic field perpendicular to a fluid layer predicted the existence of a new type of instability, oblique waves, that arise due to the differential local magnetisation of a non-uniformly heated fluid. The existence of such (thermomagnetic) waves has now been confirmed experimentally using a kerosene-based ferrofluid with magnetite particles of the average size of 10 nm stabilized with oleic acid. The heat transfer rate measurements using thermocouples and flow visualization using a thermosensitive film and an infrared camera have been performed. Perturbation energy analysis has been used to determine the physical nature of various observed instability patterns and quantitatively distinguish between thermogravitational and thermomagnetic waves.
NASA Astrophysics Data System (ADS)
Behdadfar, Behshid; Kermanpur, Ahmad; Sadeghi-Aliabadi, Hojjat; Morales, Maria del Puerto; Mozaffari, Morteza
2012-07-01
Superparamagnetic and monodispersed aqueous ferrofluids of Zn substituted magnetite nanoparticles (ZnxFe3-xO4, x=0, 0.25, 0.3, 0.37 and 0.4) were synthesized via hydrothermal-reduction route in the presence of citric acid, which is a facile, low energy and environmental friendly method. The synthesized nanoparticles were characterized by X ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, scanning and transmission electron microscopy (SEM and TEM) and the dynamic light scattering (DLS) method. The results showed that a certain amount of citric acid was required to obtain single phase Zn substituted magnetite nanoparticles. Citric acid acted as a modulator and reducing agent in the formation of spinel structure and controlled nanoparticle size and crystallinity. Mean particle sizes of the prepared nanoparticles were around 10 nm. The results that are obtained from XRD, magnetic and power loss measurements showed that the crystallinity, saturation magnetization (MS) and loss power of the synthesized ferrofluids were all influenced by the substitution of Zn in the structure of magnetite. The Zn substituted magnetite nanoparticles obtained by this route showed a good stability in aqueous medium (pH 7) and hydrodynamic sizes below 100 nm and polydispersity indexes below 0.2. The calculated intrinsic loss power (ILP) for the sample x=0.3 (e.g. 2.36 nH m2/kg) was comparable to ILP of commercial ferrofluids with similar hydrodynamic sizes.
NASA Astrophysics Data System (ADS)
Mathis, S.; Decressin, T.; Eggenberger, P.; Charbonnel, C.
2013-10-01
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.
The extrinsic hysteresis behavior of dilute binary ferrofluids.
Lin, Lihua; Li, Jian; Lin, Yueqiang; Liu, Xiaodong; Chen, Longlong; Li, Junming; Li, Decai
2014-10-01
We report on the magnetization behavior of dilute binary ferrofluids based on ?-Fe(2)O(3)/Ni(2)O(3) composite nanoparticles (A particles), with diameter about 11 nm, and ferrihydrite (Fe(5)O(7)(OH) ?4H2O) nanoparticles (B particles), with diameter about 6 nm. The results show that for the binary ferrofluids with A-particle volume fraction ?(A) = 0.2% and B-particle volume fractions ?(B) = 0.1% and ?(B) = 0.6%, the magnetization curves exhibit quasi-magnetic hysteresis behavior. The demagnetizing curves coincide with the magnetizing curves at high fields. However, for single ?-Fe(2)O(3)/Ni(2)O(3) ferrofluids with ?(A) = 0.2% and binary ferrofluids with ?(A) = 0.2% and ?(B) = 1.0%, the magnetization curves do not behave in this way. Additionally, at high field (750 kA/m), the binary ferrofluid with ?(B) = 1.0% has the smallest magnetization. From the model-of-chain theory, the extrinsic hysteresis behavior of these samples is attributed to the field-induced effects of pre-existing A particle chains, which involve both Brownian rotation of the chains'moments and a Néel rotation of the particles' moments in the chains. The loss of magnetization for the ferrofluids with ?(B) = 1.0% is attributed to pre-existing ring-like A-particle aggregates. These magnetization behaviors of the dilute binary ferrofluids not only depend on features of the strongly magnetic A-particle system, but also modifications of the weaker magnetic B-particle system. PMID:25365919
Resistive magneto-hydrodynamical cut-off of Alfvén wave in fully ionized plasmas
Vranjes, J., E-mail: jvranjes@yahoo.com [Institute of Physics Belgrade, Pregrevica 118, 11080 Zemun (Serbia); Kono, M., E-mail: kono@fps.chuo-u.ac.jp [Faculty of Policy Studies, Chuo University, Tokyo (Japan)
2014-01-15
The term cut-off in the theory of the Alfvén wave is used to describe several different phenomena. In this work, the cut-off due to magnetohydrodynamic resistive damping in fully ionized plasmas is revisited. This cut-off requires short enough wavelengths, it is routinely discussed in numerous works, and graphs depicting it are available even in textbooks. We show that this cut-off is hardly ever possible in real plasmas. This is due to the fact that some essential criteria and conditions become strongly violated in order to achieve the cut-off.
NASA Astrophysics Data System (ADS)
Omang, M.; Børve, S.; Trulsen, J.
2006-12-01
In this paper we wish to demonstrate to what extent the numerical method regularized smoothed particle hydrodynamics (RSPH) is capable of modelling shocks and shock reflection patterns in a satisfactory manner. The use of SPH based methods to model shock wave problems has been relatively sparse, both due to historical reasons, as the method was originally developed for studies of astrophysical gas dynamics, but also due to the fact that boundary treatment in Lagrangian methods may be a difficult task. The boundary conditions have therefore been given special attention in this paper. Results presented for one quasi-stationary and three non-stationary flow tests reveal a high degree of similarity, when compared to published numerical and experimental data. The difference is found to be below 5, in the case where experimental data was found tabulated. The transition from regular reflection (RR) to Mach reflection (MR) and the opposite transition from MR to RR are studied. The results are found to be in close agreement with the results obtained from various empirical and semi-empirical formulas published in the literature. A convergence test shows a convergence rate slightly steeper than linear, comparable to what is found for other numerical methods when shocks are involved.
Stress relaxation in a ferrofluid with clustered nanoparticles.
Borin, Dmitry Yu; Zubarev, Andrey Yu; Chirikov, Dmitry N; Odenbach, Stefan
2014-10-01
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
NASA Astrophysics Data System (ADS)
Hostache, R.; Matgen, P.; Giustarini, L.; Tailliez, C.; Iffly, J.-F.
2011-11-01
The main objective of this study is to contribute to the development and the improvement of flood forecasting systems. Since hydrometric stations are often poorly distributed for monitoring the propagation of extreme flood waves, the study aims at evaluating the hydrometric value of the Global Navigation Satellite System (GNSS). Integrated with satellite telecommunication systems, drifting or anchored floaters equipped with navigation systems such as GPS and Galileo, enable the quasi-continuous measurement and near real-time transmission of water level and flow velocity data, from virtually any point in the world. The presented study investigates the effect of assimilating GNSS-derived water level and flow velocity measurements into hydraulic models in order to reduce the associated predictive uncertainty.
NASA Astrophysics Data System (ADS)
Larmat, C. S.; Rougier, E.; Knight, E.; Yang, X.; Patton, H. J.
2013-12-01
A goal of the Source Physics Experiments (SPE) is to develop explosion source models expanding monitoring capabilities beyond empirical methods. The SPE project combines field experimentation with numerical modelling. The models take into account non-linear processes occurring from the first moment of the explosion as well as complex linear propagation effects of signals reaching far-field recording stations. The hydrodynamic code CASH is used for modelling high-strain rate, non-linear response occurring in the material near the source. Our development efforts focused on incorporating in-situ stress and fracture processes. CASH simulates the material response from the near-source, strong shock zone out to the small-strain and ultimately the elastic regime where a linear code can take over. We developed an interface with the Spectral Element Method code, SPECFEM3D, that is an efficient implementation on parallel computers of a high-order finite element method. SPECFEM3D allows accurate modelling of wave propagation to remote monitoring distance at low cost. We will present CASH-SPECFEM3D results for SPE1, which was a chemical detonation of about 85 kg of TNT at 55 m depth in a granitic geologic unit. Spallation was observed for SPE1. Keeping yield fixed we vary the depth of the source systematically and compute synthetic seismograms to distances where the P and Rg waves are separated, so that analysis can be performed without concern about interference effects due to overlapping energy. We study the time and frequency characteristics of P and Rg waves and analyse them in regard to the impact of free-surface interactions and rock damage resulting from those interactions. We also perform traditional CMT inversions as well as advanced CMT inversions, developed at LANL to take into account the damage. This will allow us to assess the effect of spallation on CMT solutions as well as to validate our inversion procedure. Further work will aim to validate the developed models with the data recorded on SPEs. This long-term goal requires taking into account the 3D structure and thus a comprehensive characterization of the site.
Ferrofluid clustering driven by dilution: An alternating current susceptibility investigation
NASA Astrophysics Data System (ADS)
Zhong, Jing; Liu, Wenzhong; Li, Yin; Wu, Mian; Morais, Paulo Cesar
2012-03-01
The influence of sample dilution upon cluster disruption/formation within a ferrofluid sample is investigated by monitoring the temperature dependence of the initial AC susceptibility. The effective magnetic response of the ferrofluid sample is described by a combination of Langevin's functions modulated by the relative content of monomers and clusters. Deviations from the linearity found in the inverse susceptibility versus temperature (?-1-T) data were successfully described via the disruption of clusters into monomers within the approach of a second order phase transition at the critical temperature T*. We found T* increasing monotonically from 386 K to 412 K as the stock ferrofluid sample is diluted up to a factor of 5. In the same dilution range, we found the normalized relative content of clusters increasing from about 38% up to 42%, whereas the average effective magnetic moment of the clusters increased by a factor of 1.7.
Structure, synthetic methods, magnetic properties and biomedical applications of ferrofluids.
Shokrollahi, H
2013-07-01
This paper is aimed at conducting a survey of the synthetic methods and magnetic properties of nanoparticles as ferrofluids used in biomedicine. As compared with other works in the field, the distinctive feature of the current work is the systematic study of recent advances in ferrofluids utilized in hyperthermia and magnetic resonance imaging (MRI). The most important feature for application of ferrofluids is super-paramagnetic behavior of magnetic cores with relatively high saturation magnetization. Although Fe3O4 nanoparticles have traditionally been used in medicine; the modified Mn-ferrite has recently received special attention due to its higher saturation magnetization and r2-relaxivity as a contrast agent in MRI. Co-ferrite nanoparticles are also good candidates for hyperthermia treatment because of their high coercivity and magnetocrystalline anisotropy. The thermal decomposition and hydrothermal methods are good candidates for obtaining appropriate super-paramagnetic particles. PMID:23623058
Hydrodynamic model of wave-ordered structures formed by ion bombardment of solids
NASA Astrophysics Data System (ADS)
Rudy, A. S.; Smirnov, V. K.
1999-10-01
The model of a wave-ordered structures (WOS) formed by ion-bombardment on a surfaces of amorphous materials is put forward. The model is based on the assumption that amorphous layer under ion-bombardment may be considered as Newtonian fluid on a hard substrate in the field of external force. Within this approach the mathematical model of an amorphous layer is formulated as a boundary value problem for Navier-Stokes and continuity equations for incompressible liquid. Analysis of the problem results in two quasi-stationary spatial-periodic solutions governed by two control parameters: one of them a? is a capillary constant under a vertical ion beam incidence, normalized to layer thickness, another is an angle of incidence ?. In the general case a capillary constant a?(L,?) is a convex function of both variables viz. normalized spatial-period L and an angle of incidence ?. With energy E0=9 keV this function exhibits a local maximum at L=1.77,?=50.4? which is already global a?c=0.375 when E0=5 keV and (as judged by indirect measurements) becomes more convex with further energy reduction. Collation of a?(L,?) with experimental data reveals that the observed maximum value of capillary constant a?ob=0.367, which due to an inherent supercriticality is a little bit lower than a?c, falls at ?=55?, i.e., with energy diminution angular range should contract to this point. This outcome is consistent with our experimental results on N2+-Si system, manifesting that angular range reduces to a small vicinity of ?cin=55? when ion energy tends to minimum energy of WOS formation E0=1.5 keV.
Azimuthal field instability in a confined ferrofluid.
Dias, Eduardo O; Miranda, José A
2015-02-01
We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes. PMID:25768610
Azimuthal field instability in a confined ferrofluid
NASA Astrophysics Data System (ADS)
Dias, Eduardo O.; Miranda, José A.
2015-02-01
We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes.
Stone, G.W.; Pepper, D.A.; Xu, J.; Zhang, X.
2004-01-01
Ship Shoal, a transgressive sand body located at the 10 m isobath off south-central Louisiana, is deemed a potential sand source for restoration along the rapidly eroding Isles Dernieres barrier chain and possibly other sites in Louisiana. Through numerical wave modeling we evaluate the potential response of mining Ship Shoal on the wave field. During severe and strong storms, waves break seaward of the western flank of Ship Shoal. Therefore, removal of Ship Shoal (approximately 1.1 billion m3) causes a maximum increase of the significant wave height by 90%-100% and 40%-50% over the shoal and directly adjacent to the lee of the complex for two strong storm scenarios. During weak storms and fair weather conditions, waves do not break over Ship Shoal. The degree of increase in significant wave height due to shoal removal is considerably smaller, only 10%-20% on the west part of the shoal. Within the context of increasing nearshore wave energy levels, removal of the shoal is not significant enough to cause increased erosion along the Isles Dernieres. Wave approach direction exerts significant control on the wave climate leeward of Ship Shoal for stronger storms, but not weak storms or fairweather. Instrumentation deployed at the shoal allowed comparison of measured wave heights with numerically derived wave heights using STWAVE. Correlation coefficients are high in virtually all comparisons indicating the capability of the model to simulate wave behavior satisfactorily at the shoal. Directional waves, currents and sediment transport were measured during winter storms associated with frontal passages using three bottom-mounted arrays deployed on the seaward and landward sides of Ship Shoal (November, 1998-January, 1999). Episodic increases in wave height, mean and oscillatory current speed, shear velocity, and sediment transport rates, associated with recurrent cold front passages, were measured. Dissipation mechanisms included both breaking and bottom friction due to variable depths across the shoal crest and variable wave amplitudes during storms and fair-weather. Arctic surge fronts were associated with southerly storm waves, and southwesterly to westerly currents and sediment transport. Migrating cyclonic fronts generated northerly swell that transformed into southerly sea, and currents and sediment transport that were southeasterly overall. Waves were 36% higher and 9% longer on the seaward side of the shoal, whereas mean currents were 10% stronger landward, where they were directed onshore, in contrast to the offshore site, where seaward currents predominated. Sediment transport initiated by cold fronts was generally directed southeasterly to southwesterly at the offshore site, and southerly to westerly at the nearshore site. The data suggest that both cold fronts and the shoal, exert significant influences on regional hydrodynamics and sediment transport.
Detection of magnetic microbeads and ferrofluid with giant magnetoresistance sensors
NASA Astrophysics Data System (ADS)
Feng, J.; Wang, Y. Q.; Li, F. Q.; Shi, H. P.; Chen, X.
2011-01-01
Giant magnetoresistance sensors based on multilayers [Cu/NiFeCo]×10/ Ta were fabricated by microfabrication technology. A GMR-bridge was used to detect the magnetic MyOne beads and Ferro fluid. The dependence of the GMR-bridge signals on the surface coverage of MyOne beads was studied. The results show that the GMR sensor is capable of detecting the magnetic beads. The detectable limit of MyOne beads is about 100, and the corresponding signal output is 8 ?V. The GMR bridge signal is proportional to the surface coverage of the MyOne beads. The sensitivity of the GMR bridge is inversely proportional to the feature size of the GMR sensor. The GMR bridge integrated with microfludic channel was also used for dynamic detection of ferrofluid (suspension of Fe3O4 particles). The results show that the GMR bridge is capable of detecting the flow of ferrofluid, and the sensor signals are proportional to the concentration of the ferrofluid. The detection limit of concentration of the ferrofluid is 0.56 mg/ml, and the corresponding signal is 6.2 ?V.
Numerical investigation of optically induced microconvection in thin ferrofluid layers
D. Zablotsky; E. Blums
2011-01-01
We consider a periodic concentration grating induced in a thin layer of ferrofluid by an optical grating of interfering laser beams under the action of an externally applied uniform magnetic field. The direction of the applied field is parallel to the concentration gradient. Under certain conditions microconvective instability may develop during relaxation of the grating, driven by the internal demagnetizing
Rotating Ferrofluid Drops Andreas Engel, Alexander V. Lebedeva
Engel, Andreas
Rotating Ferrofluid Drops Andreas Engel, Alexander V. Lebedeva , and Konstantin I. Morozova of Continuous Media Mechanics, 1 Korolev Street, 614013 Perm, Russia Reprint requests to A. E.; E-mail: engel-particles which in turn, due to their viscous coupling to the surrounding liquid, trans- #12;704 A. Engel et al
Ferrofluid drops in rotating magnetic fields Alexander V Lebedev1
Engel, Andreas
recent interest concern rotating non-neutral plasmas, laser cooled in a Penning trap [3], and tank with the magnetic properties of super-paramagnets [11]. In the absence of an external magnetic field-range order. For a non-zero external field the magnetization of the ferrofluid builds up with magnetic
Numerical Modeling of Ferrofluid Droplets in Magnetic Fields
Renardy, Yuriko
Numerical Modeling of Ferrofluid Droplets in Magnetic Fields S. Afkhami , Y. Renardy , M. Renardy viscous fluid and driven by a magnetic field are modeled numerically. The governing equations in the drop under non-uniform magnetic fields are simulated. Droplets exhibit shape changes along the applied
A rheological and microscopical characterization of biocompatible ferrofluids
NASA Astrophysics Data System (ADS)
Nowak, J.; Wolf, D.; Odenbach, S.
2014-03-01
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.
Thermodynamics of ferrofluids in applied magnetic fields.
Elfimova, Ekaterina A; Ivanov, Alexey O; Camp, Philip J
2013-10-01
The thermodynamic properties of ferrofluids in applied magnetic fields are examined using theory and computer simulation. The dipolar hard sphere model is used. The second and third virial coefficients (B(2) and B(3)) are evaluated as functions of the dipolar coupling constant ?, and the Langevin parameter ?. The formula for B(3) for a system in an applied field is different from that in the zero-field case, and a derivation is presented. The formulas are compared to results from Mayer-sampling calculations, and the trends with increasing ? and ? are examined. Very good agreement between theory and computation is demonstrated for the realistic values ??2. The analytical formulas for the virial coefficients are incorporated in to various forms of virial expansion, designed to minimize the effects of truncation. The theoretical results for the equation of state are compared against results from Monte Carlo simulations. In all cases, the so-called logarithmic free energy theory is seen to be superior. In this theory, the virial expansion of the Helmholtz free energy is re-summed in to a logarithmic function. Its success is due to the approximate representation of high-order terms in the virial expansion, while retaining the exact low-concentration behavior. The theory also yields the magnetization, and a comparison with simulation results and a competing modified mean-field theory shows excellent agreement. Finally, the putative field-dependent critical parameters for the condensation transition are obtained and compared against existing simulation results for the Stockmayer fluid. Dipolar hard spheres do not undergo the transition, but the presence of isotropic attractions, as in the Stockmayer fluid, gives rise to condensation even in zero field. A comparison of the relative changes in critical parameters with increasing field strength shows excellent agreement between theory and simulation, showing that the theoretical treatment of the dipolar interactions is robust. PMID:24229175
Thermodynamics of ferrofluids in applied magnetic fields
NASA Astrophysics Data System (ADS)
Elfimova, Ekaterina A.; Ivanov, Alexey O.; Camp, Philip J.
2013-10-01
The thermodynamic properties of ferrofluids in applied magnetic fields are examined using theory and computer simulation. The dipolar hard sphere model is used. The second and third virial coefficients (B2 and B3) are evaluated as functions of the dipolar coupling constant ?, and the Langevin parameter ?. The formula for B3 for a system in an applied field is different from that in the zero-field case, and a derivation is presented. The formulas are compared to results from Mayer-sampling calculations, and the trends with increasing ? and ? are examined. Very good agreement between theory and computation is demonstrated for the realistic values ??2. The analytical formulas for the virial coefficients are incorporated in to various forms of virial expansion, designed to minimize the effects of truncation. The theoretical results for the equation of state are compared against results from Monte Carlo simulations. In all cases, the so-called logarithmic free energy theory is seen to be superior. In this theory, the virial expansion of the Helmholtz free energy is re-summed in to a logarithmic function. Its success is due to the approximate representation of high-order terms in the virial expansion, while retaining the exact low-concentration behavior. The theory also yields the magnetization, and a comparison with simulation results and a competing modified mean-field theory shows excellent agreement. Finally, the putative field-dependent critical parameters for the condensation transition are obtained and compared against existing simulation results for the Stockmayer fluid. Dipolar hard spheres do not undergo the transition, but the presence of isotropic attractions, as in the Stockmayer fluid, gives rise to condensation even in zero field. A comparison of the relative changes in critical parameters with increasing field strength shows excellent agreement between theory and simulation, showing that the theoretical treatment of the dipolar interactions is robust.
Karpitschka, Stefan
2015-01-01
Capillarity always favors drop fusion. Nevertheless sessile drops from different but completely miscible liquids often do not fuse instantaneously upon contact. Rather, intermediate non-coalescence is observed. Two separate drop bodies, connected by a thin liquid neck move over the substrate. Supported by new experimental data a thin film hydrodynamic analysis of this state is presented. Presumably advective and diffusive volume fluxes in the neck region establish a localized and temporarily stable surface tension gradient. This induces a local surface (Marangoni) flow that stabilizes a traveling wave i.e., the observed moving twin drop configuration. The theoretical predictions are in excellent agreement with the experimental findings.
NASA Astrophysics Data System (ADS)
Andreev, Pavel A.
2015-06-01
We discuss the 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 the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular to an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the 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 the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction.
NASA Astrophysics Data System (ADS)
Gaeta, M. Gabriella; Samaras, Achilleas; Archetti, Renata
2015-04-01
Wave propagation with the open-source suite TELEMAC is modelled by means of a finite-element type approach. The module TOMAWAC solves a simplified equation for the spectroangular density of wave action and is coupled to TELEMAC2D and 3D, solving the Navier-Stokes equations. Coastal areas and the harbor of Bari in the Puglia region (south of Italy) are implemented. The physical processes modelled comprise (i) energy source/dissipation processes (wind driven interactions with atmosphere, dissipation through wave breaking / whitecapping / waveblocking due to strong opposing currents, bottom friction induced dissipation), (ii) non-linear energy transfer conservative processes (resonant quadruplet interactions, triad interactions), and (iii) wave propagation-related processes due to the wave group / current velocity, depth-/current-induced. Preliminary results show the effect of the wave- and current- related processes: the simulations reproduce different extreme wave scenarios and the coupling modelling leads to an increase in wave disturbance inside the port.
Tritium test of a ferro-fluidic rotary seal
Antipenkov, A.; Day, C.; Adami, H. D. [Forschungszentrum Karlsruhe, Inst. for Technical Physics, Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, 76344 (Germany)
2008-07-15
The ferro-fluidic seal is being investigated as an internal rotary seal for tritium compatible mechanical roots type vacuum pumps. After its successful testing with helium and integration into a small (250 m{sup 3}/h) test roots pump, the seal, made as a cartridge, has been integrated into a special test unit and is currently being tested with tritium in order to define the leak rates and the possible degradation of the ferro-fluid under long term exposure to tritium radiation. The tritium pressure from one side of the seal is 0.125 MPa, the nitrogen pressure from the other side is 0.075 MPa, the rotation speed is maintained at 1500 rpm. The tritium leak through the cartridge contributes to the tritium concentration in the nitrogen, which is continuously measured by an ionisation chamber; the pressure in both chambers is continuously registered by precise pressure gauges. The experimental program is discussed. (authors)
Preparation of a biocompatible magnetic film from an aqueous ferrofluid
NASA Astrophysics Data System (ADS)
Albornoz, Cecilia; Jacobo, Silvia E.
2006-10-01
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.
Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles
NASA Astrophysics Data System (ADS)
Brullot, W.; Reddy, N. K.; Wouters, J.; Valev, V. K.; Goderis, B.; Vermant, J.; Verbiest, T.
2012-06-01
Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles were obtained by a facile protocol and thoroughly characterized. Superparamagnetic iron oxide nanoparticles synthesized using a modified forced hydrolysis method were functionalized with polyethylene glycol silane (PEG silane), precipitated and dried. These functionalized particles are dispersable in a range of solvents and concentrations depending on the desired properties. Examples of tunable properties are magnetic behavior, optical and magneto-optical response, thermal features and rheological behavior. As such, PEG silane functionalized particles represent a platform for the development of new materials that have broad applicability in e.g. biomedical, industrial or photonic environments. Magnetic, optical, magneto-optical, thermal and rheological properties of several ferrofluids based on PEG coated particles with different concentrations of particles dispersed in low molecular mass polyethylene glycol were investigated, establishing the applicability of such materials.
Moridis, George J. (Oakland, CA); Oldenburg, Curtis M. (Mill Valley, CA)
2001-01-01
Disclosed are processes for monitoring and control of underground contamination, which involve the application of ferrofluids. Two broad uses of ferrofluids are described: (1) to control liquid movement by the application of strong external magnetic fields; and (2) to image liquids by standard geophysical methods.
F. de Hoffmann; E. Teller
1950-01-01
A mathematical treatment of the coupled motion of hydrodynamic flow and electromagnetic fields is given. Two simplifying assumptions are introduced: first, the conductivity of the medium is infinite, and second, the motion is described by a plane shock wave. Various orientations of the plane of the shock and the magnetic field are discussed separately, and the extreme relativistic and unrelativistic
S. I. Gorlov
1998-01-01
A method of solving the problem of the motion of an elliptic contour in a three-layer fluid is developed within the framework\\u000a of the linear theory. The results of calculating the hydrodynamic contour loads and the shape of the interfaces are presented\\u000a for the following problems: the motion of a contour beneath an interface between two media and in a
Nakamura, F; Klein, R I; Fisher, R T; Nakamura, Fumitaka; Kee, Christopher F. Mc; Klein, Richard I.; Fisher, Robert T.
2005-01-01
The effect of smooth cloud boundaries on the interaction of steady planar shock waves with interstellar clouds is studied using a high-resolution local AMR technique with a second-order accurate axisymmetric Godunov hydrodynamic scheme. A 3D calculation is also done to confirm the results of the 2D ones. We consider an initially spherical cloud whose density distribution is flat near the cloud center and has a power-law profile in the cloud envelope. When an incident shock is transmitted into a smooth cloud, velocity gradients in the cloud envelope steepen the smooth density profile at the upstream side, resulting in a sharp density jump having an arc-like shape. Such a ``slip surface'' forms immediately when a shock strikes a cloud with a sharp boundary. For smoother boundaries, the formation of slip surface and therefore the onset of hydrodynamic instabilities are delayed. Since the slip surface is subject to the Kelvin-Helmholtz and Rayleigh-Taylor instabilities, the shocked cloud is eventually destroyed i...
L. Berggren
1992-01-01
A method for calculating the energy take-out from a single wave energy converter is presented. The converter consists of a buoy connected via a hose pump to a submerged plate. The equations of motion of the buoy and plate are solved linearly in the frequency domain, which shows that frequency dependent hydrodynamic properties can be used. The emphasis in the
Synchronization via Hydrodynamic Interactions
NASA Astrophysics Data System (ADS)
Kendelbacher, Franziska; Stark, Holger
2013-12-01
An object moving in a viscous fluid creates a flow field that influences the motion of neighboring objects. We review examples from nature in the microscopic world where such hydrodynamic interactions synchronize beating or rotating filaments. Bacteria propel themselves using a bundle of rotating helical filaments called flagella which have to be synchronized in phase. Other micro-organisms are covered with a carpet of smaller filaments called cilia on their surfaces. They beat highly synchronized so that metachronal waves propagate along the cell surfaces. We explore both examples with the help of simple model systems and identify generic properties for observing synchronization by hydrodynamic interactions.
Hydrodynamic forces due to waves and a current induced on a pipeline placed in an open trench
Lee, Jaeyoung
1991-01-01
are 150. 0 ft (45. 72 m) in length, 1. 51 ft (0. 46 m) in width and 4. 0 ft (1. 22 m) in depth. The wave flume is constructed of a metal and wood frame with one side wall of plywood and the other of Plexiglass. Figures 6 and 7 show the general side view... to propagate in the same direction in a two ? dimensional domain. Thirdly, the trench was assumed to be stable under wave and current action. In other words, sediment or erosion around the trench was not accounted for in this experiment. Wave profile, water...
Castor
2003-01-01
The discipline of radiation hydrodynamics is the branch of hydrodynamics in which the moving fluid absorbs and emits electromagnetic radiation, and in so doing modifies its dynamical behavior. That is, the net gain or loss of energy by parcels of the fluid material through absorption or emission of radiation are sufficient to change the pressure of the material, and therefore
Hydrodynamics of insect spermatozoa
NASA Astrophysics Data System (ADS)
Pak, On Shun; Lauga, Eric
2010-11-01
Microorganism motility plays important roles in many biological processes including reproduction. Many microorganisms propel themselves by propagating traveling waves along their flagella. Depending on the species, propagation of planar waves (e.g. Ceratium) and helical waves (e.g. Trichomonas) were observed in eukaryotic flagellar motion, and hydrodynamic models for both were proposed in the past. However, the motility of insect spermatozoa remains largely unexplored. An interesting morphological feature of such cells, first observed in Tenebrio molitor and Bacillus rossius, is the double helical deformation pattern along the flagella, which is characterized by the presence of two superimposed helical flagellar waves (one with a large amplitude and low frequency, and the other with a small amplitude and high frequency). Here we present the first hydrodynamic investigation of the locomotion of insect spermatozoa. The swimming kinematics, trajectories and hydrodynamic efficiency of the swimmer are computed based on the prescribed double helical deformation pattern. We then compare our theoretical predictions with experimental measurements, and explore the dependence of the swimming performance on the geometric and dynamical parameters.
Single-mode fiber variable optical attenuator based on a ferrofluid shutter.
Dudu?, Anna; Blue, Robert; Uttamchandani, Deepak
2015-03-10
We report on the fabrication and characterization of a single-mode fiber variable optical attenuator (VOA) based on a ferrofluid shutter actuated by a magnetic field created by a low voltage electromagnet. We compare the performance of a VOA using oil-based ferrofluid, with one VOA using water-based 12 ferrofluid, and demonstrate broadband optical attenuation of up to 28 dB with polarization dependent 13 loss of 0.85 dB. Our optofluidic VOA has advantages over MEMS-based VOAs such as simple construction and the absence of mechanical moving parts. PMID:25968370
The effect of suspended Fe3O4 nanoparticle size on magneto-optical properties of ferrofluids
NASA Astrophysics Data System (ADS)
Brojabasi, Surajit; Muthukumaran, T.; Laskar, J. M.; Philip, John
2015-02-01
We investigate the effect of hydrodynamic particle size on the magnetic field induced light transmission and transmitted speckle pattern in water based ferrofluids containing functionalized Fe3O4 nanoparticles of size ranging from 15 to 46 nm. Three water-based magnetic nanofluids, containing Fe3O4 nanoparticles functionalized with poly-acrylic acid (PAA), tetra-methyl ammonium hydroxide (TMAOH) and phosphate, are used in the present study. In all three cases, the transmitted light intensity starts decreasing above a certain magnetic field (called first critical field) and becomes a minimum at another field (second critical field). These two critical fields signify the onset of linear aggregation process and zippering transitions between fully grown chains, respectively. Both these critical fields shift towards a lower magnetic field with increasing hydrodynamic diameter, due to stronger magnetic dipolar interactions. The first and the second critical fields showed a power law dependence on the hydrodynamic diameters. The dipolar resonances occurring at certain values of the scatterer size, leads to the field induced extinction of light. Both the onset of chaining and zippering transitions were clearly evident in the time dependent transmitted light intensity. Above the first critical field, the lobe part of the transmitted intensity and the lobe speckle contrast values increase with increasing external magnetic field due to reduced Brownian motion of the field induced aggregates. The speckle contrast was highest for nanoparticle with the largest hydrodynamic diameter, due to reduced Brownian motion. These results provide better insight into field dependent light control in magnetic colloids, which may find interesting applications in magneto-optical devices.
Diffraction patterns in ferrofluids: Effect of magnetic field and gravity
NASA Astrophysics Data System (ADS)
Radha, S.; Mohan, Shalini; Pai, Chintamani
2014-09-01
In this paper, we report the experimental observation of diffraction patterns in a ferrofluid comprising of Fe3O4 nanoparticles in hexane by a 10 mW He-Ne laser beam. An external dc magnetic field (0-2 kG) was applied perpendicular to the beam. The diffraction pattern showed a variation at different depths of the sample in both zero and applied magnetic field. The patterns also exhibit a change in shape and size as the external field is varied. This effect arises due to thermally induced self-diffraction under the influence of gravity and external magnetic field.
Investigations of field instability of ferrofluid in hypergravity and microgravity
NASA Astrophysics Data System (ADS)
Chong, Theng Yee; Ho, Kent Loong; Ong, Boon Hoong
2012-03-01
The field instability of the free surface of ferrofluid was investigated under microgravity and hypergravity environments conducted by parabolic flight. It is observed that the perturbation was suppressed under hypergravity, whereas at the microgravity condition, it appeared to have only slight increase in the amplitude of the perturbation peaks compared to the case of ground condition. Besides, an observation of peak-trough distance showed that not only the peak, but the trough was also very much dependent on the applied magnetic field. The difference of magnetic pole (north and south) had shown to be a factor to the perturbation as well.
A Ferrofluidic Magnetic Micropump for Variable-Flow-Rate Applications
NASA Astrophysics Data System (ADS)
Lee, Chia-Yen; Leong, Jik-Chang; Wang, Yao-Nan; Fu, Lung-Ming; Chen, Sih-Jia
2012-04-01
A novel micropump is proposed comprising two ferrofluidic plugs contained within a circular poly(methyl methacrylate) (PMMA) microchannel and a permanent magnet positioned beneath one of the plugs and driven by a rotating stepping motor. The ferrofluidic plugs are immiscible with the sample fluid. Thus, as the stepping motor rotates, the sample trapped between the two plugs is driven through the circular microchannel and exits the pump via the outlet diffuser. Meanwhile, more sample fluid is drawn into the microchannel on the inlet side. As a result, a continuous pumping effect is achieved. It is shown that the flow rate in the proposed device can be easily controlled by adjusting the rotational velocity of the stepping motor. In addition, for a constant motor velocity, the flow rate can be improved by increasing the circular channel width. The experimental results show that a maximum flow rate of 93 µl/min is obtained given a channel width of 1000 µm and a rotational velocity of 8 rpm. In addition, it is shown that the pump is capable of developing a maximum pressure head of 75 mm water (0.66 kPa) with channel width of 500 µm.
Ferrofluid dynamics in a Hele-Shaw cell simultaneously stressed by DC and rotating magnetic fields
Orji, Uzoma A
2007-01-01
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 ...
NASA Astrophysics Data System (ADS)
Berggren, L.
1992-02-01
A method for calculating the energy take-out from a single wave energy converter is presented. The converter consists of a buoy connected via a hose pump to a submerged plate. The equations of motion of the buoy and plate are solved linearly in the frequency domain, which shows that frequency dependent hydrodynamic properties can be used. The emphasis in the report is placed on the calculation of the frequency dependent hydrodynamic properties, such as the wave excited forces and the hydrodynamic coefficients. The structure is considered to be large in comparison with the wave length and, therefore, the diffraction theory was used. A method of calculating the forces that act on the bodies is presented, as well as the interaction between the bodies. The two-body problem is solved analytically. The present solution is compared with a numerical one and an analytical one, the latter, however, treats simply a single buoy riding in the waves. The calculated energy take-out of the present model is compared with a time domain dependent model, and reasonable agreement was found.
The effect of particle interactions on Curie-Weiss behavior in ferrofluids
J. Popplewell; B. Abu Aisheh; N. Y. Ayoub
1988-01-01
The initial susceptibility of a number of Fe3 O4 particle ferrofluids with volume concentrations, &egr;=0.08, 0.07, 0.05, 0.03, 0.02, and 0.01 (prepared by diluting a stock fluid of Ms =40 kA m?1) has been measured in the temperature range 220–450 K. The mean particle sizes Dm (magnetic) and Dp (physical) are 74 and 81 A?, respectively. The ferrofluids exhibit Curie–Weiss-type
From Rust To High Tech: SemiSynthesis Of A Ferrofluid Using FeO Nanoparticles
Lisa M. Stuber; Elizabeth M. Rachford; Christopher S. Jordan; Scott J. Mitchell; Crystal Tabron; Thomas J. Manning
Metal oxide nanoparticles are an important material in nanotechnology. Ferrofluids, which are typically made from iron oxide (Fe3O4) nanoparticles, have found commercial applications and are widely used in academic research and educational activities. This study describes the novel semisynthesis of a ferrofluid using commercially available iron oxide nanoparticles (FeO) as the starting material. It forms the spiked solution indicative of
General Relativistic Hydrodynamics on Overlapping Curvilinear Grids
Blakely, P. M.; Nikiforakis, N.; Henshaw, W. D.
2015-03-04
- ably hope that propagation of numerical errors outside the event horizon will be limited. In general, however, note that numerical waves can propagate faster than any of the physical wave-speeds. This means that we can excise part of the domain inside... – hydrodynamics – shock waves 1. Introduction The simulation of general relativistic hydrodynamical (GRHD) problems is of great importance to the astrophysics commu- nity. Although special relativistic and post Newtonian approx- imations can be used in some cases...
Relaxation mechanisms of photoinduced periodic microstructures in ferrofluid layers.
Zablotsky, Dmitry; Blums, Elmars
2011-12-01
We consider theoretically and numerically a periodic concentration grating induced in a layer of ferrofluid in the presence of the external magnetic field by nonuniform optical heating through photoabsorption. The stationary profiles of the periodic microstructures are governed by the equilibrium of the diffusive, thermodiffusive, and magnetic fluxes. The anisotropy of the diffusion coefficient and the magnetically driven microconvection contribute to the relaxation of these structures. The temperature-concentration coupling is shown to increase the initial effective diffusive relaxation rate by up to 50%. Microconvection dominates in the relaxation process even at small values of the control parameter and rapidly destroys the periodic part of the concentration grating. We describe this process in the weakly nonlinear regime by an approximate Galerkin model. PMID:22304188
Optical imaging using spatial grating effects in ferrofluids
NASA Astrophysics Data System (ADS)
Dave, Vishakha; Virpura, Hiral; Patel, Rajesh
2015-06-01
Under the effect of magnetic field the magnetic nanoparticles of the ferrofluid tend to align in the direction of the magnetic field. This alignment of the magnetic nanoparticles behaves as a spatial grating and diffract light, when light is propagating perpendicular to the direction of the applied magnetic field. The chains of the magnetic nanoparticles represents a linear series of fringes like those observed in a grating/wire. Under applied magnetic field the circular beam of light transforms into a prominent diffraction line in the direction perpendicular to the applied magnetic field. This diffracted light illuminates larger area on the screen. This behavior can be used as magneto controlled illumination of the object and image analysis.
Label-free cellular manipulation and sorting via biocompatible ferrofluids
Kose, Ayse R.; Fischer, Birgit; Mao, Leidong; Koser, Hur
2009-01-01
We present a simple microfluidic platform that uses biocompatible ferrofluids for the controlled manipulation and rapid separation of both microparticles and live cells. This low-cost platform exploits differences in particle size, shape, and elasticity to achieve rapid and efficient separation. Using microspheres, we demonstrate size-based separation with 99% separation efficiency and sub-10-?m resolution in <45 s. We also show continuous manipulation and shape-based separation of live red blood cells from sickle cells and bacteria. These initial demonstrations reveal the potential of ferromicrofluidics in significantly reducing incubation times and increasing diagnostic sensitivity in cellular assays through rapid separation and delivery of target cells to sensor arrays. PMID:19995975
Magnetocoalescence of ferrofluid droplets in a flat microfluidic channel
NASA Astrophysics Data System (ADS)
Kadivar, Erfan
2014-04-01
In this work we present the numerical study of the deformation and the coalescence of two ferrofluid droplets in a uniform applied magnetic field. Employing the boundary element method (BEM), we numerically solve the Darcy equation in a flat microfluidic channel by applying the magnetic normal stress as a boundary condition at the interfaces of droplets. The occurrence of different numerical regimes is summarized in the two phase diagrams scanned by the distance between two droplets, magnetic capillary number, and magnetic permeability. We also show the existence of the critical separation of two droplets where the coalescence of the droplets is inhibited. This critical value is independent of the applied-magnetic-field intensity, although it depends on the permeability ratio of droplet and continuous phase.
Paris-Sud XI, Université de
1 Radial Stiffness of a ferrofluid seal R. Ravaud, M. Pinho, G. Lemarquand Senior IEEE, N. Dauchez for calculating the shape and the radial stiffness of ferrofluid seals used as radial bearings for the design of loudspeakers. Moreover, the concept of magnetic pressure is used to determine the seal shape
Probst, R; Lin, J; Komaee, A; Nacev, A; Cummins, Z; Shapiro, B
2011-04-01
Any single permanent or electro magnet will always attract a magnetic fluid. For this reason it is difficult to precisely position and manipulate ferrofluid at a distance from magnets. We develop and experimentally demonstrate optimal (minimum electrical power) 2-dimensional manipulation of a single droplet of ferrofluid by feedback control of 4 external electromagnets. The control algorithm we have developed takes into account, and is explicitly designed for, the nonlinear (fast decay in space, quadratic in magnet strength) nature of how the magnets actuate the ferrofluid, and it also corrects for electro-magnet charging time delays. With this control, we show that dynamic actuation of electro-magnets held outside a domain can be used to position a droplet of ferrofluid to any desired location and steer it along any desired path within that domain - an example of precision control of a ferrofluid by magnets acting at a distance. PMID:21218157
NASA Astrophysics Data System (ADS)
Florkowski, W.; Martinez, M.; Ryblewski, R.; Strickland, M.
2013-05-01
The recently formulated framework of anisotropic hydrodynamics is used in 3+1 dimensions to study behavior of matter created in relativistic heavy-ion collisions. The model predictions for various hadronic observables show that the effects of the initial anisotropy of pressure may be compensated by appropriate adjustment of the initial energy density. In this way, the final hadronic observables become insensitive to the early stage dynamics and the early thermalization/isotropization puzzle may be circumvented.
López, J., E-mail: javier.lopez@correounivalle.edu.co; González, Luz E.; Quiñonez, M. F.; Gómez, M. E.; Porras-Montenegro, N.; Zambrano, G. [Departamento de Física, Universidad del Valle, A.A. 25360, Cali (Colombia)
2014-05-21
Ferrofluids based on magnetic Co{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} ferrite nanoparticles were prepared by co-precipitation method from aqueous salt solutions of Co (II), ZnSO{sub 4}, and Fe (III) in an alkaline medium. Ferrofluids placed in an external magnetic field show properties that make them interesting as magneto-controllable soft photonic crystals. Morphological and structural characterizations of the samples were obtained from Scanning Electron Microscopy and Transmission Electron Microscopy studies. Magnetic properties were investigated with the aid of a vibrating sample magnetometer at room temperature. Herein, the Co{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} samples showed superparamagnetic behavior, according to hysteresis loop results. Taking in mind that the Co-Zn ferrite hysteresis loop is very small, our magnetic nanoparticles can be considered soft magnetic material with interesting technological applications. In addition, by using the plane-wave expansion method, we studied the photonic band structure of 2D photonic crystals made of ferrofluids with the same nanoparticles. Previous experimental results show that a magnetic field applied perpendicular to the ferrofluid plane agglomerates the magnetic nanoparticles in parallel rods to form a hexagonal 2D photonic crystal. We calculated the photonic band structure of photonic crystals by means of the effective refractive index of the magnetic fluid, basing the study on the Maxwell-Garnett theory, finding that the photonic band structure does not present any band gaps under the action of applied magnetic field strengths used in our experimental conditions.
Interfacial stress balances in structured continua and free surface flows in ferrofluids
Chaves, Arlex [School of Chemical Engineering, Universidad Industrial de Santander, Calle 9 Cra. 27, Edificio 24, Bucaramanga, Santander (Colombia)] [School of Chemical Engineering, Universidad Industrial de Santander, Calle 9 Cra. 27, Edificio 24, Bucaramanga, Santander (Colombia); Rinaldi, Carlos, E-mail: carlos.rinaldi@bme.ufl.edu [J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611, USA and Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611, USA and Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)
2014-04-15
Interfacial linear and internal angular momentum balances are obtained for a structured continuum and for the special case of a ferrofluid, a suspension of magnetic nanoparticles in a Newtonian fluid. The interfacial balance equations account for the effects of surface tension and surface tension gradient, magnetic surface excess forces, antisymmetric stresses, and couple stresses in driving interfacial flows in ferrofluids. Application of the interfacial balance equations is illustrated by obtaining analytical expressions for the translational and spin velocity profiles in a thin film of ferrofluid on an infinite flat plate when a rotating magnetic field is applied with axis of rotation parallel to the ferrofluid/air interface. The cases of zero and non-zero spin viscosity are considered for small applied magnetic field amplitude. Expressions for the maximum translational velocity, slope of the translational velocity profile at the ferrofluid/air interface, and volumetric flow rate are obtained and their use to test the relevance of spin viscosity and couple stresses in the flow situation under consideration is discussed.
Hydrodynamic interactions in colloidal crystals
J. M. A. Hofman; H. J. H. Clercx; P. P. J. M. Schram
1999-01-01
Wavevector dependent friction factors, which together with the elastic properties determine the hydrodynamic damping of harmonic lattice waves in colloidal crystals, are calculated for cubic arrays of rigid spheres at low, intermediate and high sphere volume fractions, including simple cubic (SC), body-centred cubic (BCC) and face-centred cubic (FCC) lattices. Exact numerical data are presented for the rheological coefficient appropriate to
Investigating the energy harvesting potential of ferro-fluids sloshing in base-excited containers
NASA Astrophysics Data System (ADS)
Bibo, A.; Masana, R.; King, A.; Li, G.; Daqaq, M. F.
2012-04-01
This paper investigates the potential of designing a vibratory energy harvester which utilizes a ferrofluid sloshing in a seismically excited tank to generate electric power. Mechanical vibrations change the orientational order of the magnetic dipoles in the ferrofluid and create a varying magnetic flux which induces an electromotive force in a coil wound around the tank, thereby generating an electric current according to Faraday's law. Several experiments are performed on a cylindrical container of volume 5x10-5 m3 carrying a ferrofluid and subjected to different base excitation levels. Initial results illustrate that the proposed device can be excited at one or multiple modal frequencies depending on the container's size, can exhibit tunable characteristics by adjusting the external magnetic field, and currently produces 28 mV of open-circuit voltage using a base excitation of 2.5 m/s2 at a frequency of 5.5 Hz.
Experimental and numerical determination of the static critical pressure in ferrofluid seals
NASA Astrophysics Data System (ADS)
Horak, W.; Szcz?ch, M.
2013-02-01
Ferrofluids have various engineering applications; one of them are magnetic fluid seals for rotating shafts. There are various constructions of this type of seals, but the main difference is the number of sealing stages. The development of this construction is a complex process which requires knowledge of ferrofluid physical and rheological properties and the magnetic field distribution inside the sealing gap. One of the most important parameters of ferrofluid seals is the critical (burst) pressure. It is the pressure value at which a leak will occur. This study presents results of numerical simulation of magnetic field distribution inside the seal gap and calculations of the critical pressure value. The obtained pressure values were verified by experiments.
Sangyong Jeon; Ulrich Heinz
2015-03-13
We give a pedagogical review of relativistic hydrodynamics relevant to relativistic heavy ion collisions. Topics discussed include linear response theory derivation of 2nd order viscous hydrodynamics including the Kubo formulas, kinetic theory derivation of 2nd order viscous hydrodynamics, anisotropic hydrodynamics and a brief review of numerical algorithms. Emphasis is given to the theory of hydrodynamics rather than phenomenology.
Jeon, Sangyong
2015-01-01
We give a pedagogical review of relativistic hydrodynamics relevant to relativistic heavy ion collisions. Topics discussed include linear response theory derivation of 2nd order viscous hydrodynamics including the Kubo formulas, kinetic theory derivation of 2nd order viscous hydrodynamics, anisotropic hydrodynamics and a brief review of numerical algorithms. Emphasis is given to the theory of hydrodynamics rather than phenomenology.
Mössbauer evidence of 57Fe3O4 based ferrofluid biodegradation in the brain
NASA Astrophysics Data System (ADS)
Polikarpov, D.; Cherepanov, V.; Chuev, M.; Gabbasov, R.; Mischenko, I.; Nikitin, M.; Vereshagin, Y.; Yurenia, A.; Panchenko, V.
2014-04-01
The ferrofluid, based on 57Fe isotope enriched Fe3O4 nanoparticles, was synthesized, investigated by Mössbauer spectroscopy method and injected transcranially in the ventricle of the rat brain. The comparison of the Mössbauer spectra of the initial ferrofluid and the rat brain measured in two hours and one week after the transcranial injection allows us to state that the synthesized magnetic 57Fe3O4 nanoparticles undergo intensive biodegradation in live brain and, therefore, they can be regarded as a promising target for a new method of radionuclide-free Mössbauer brachytherapy.
Co–Zn ferrite nanoparticles for ferrofluid preparation: Study on magnetic properties
R. Arulmurugan; G. Vaidyanathan; S. Sendhilnathan; B. Jeyadevan
2005-01-01
Co–Zn substituted nanoferrites having stoichiometric composition Co1?xZnxFe2O4 with x ranging from 0.1 to 0.5 were prepared by chemical coprecipitation method. The precipitated particles were used for the preparation of ferrofluid. Ferrofluids having Co0.5Zn0.5Fe2O4 particles could be used for the energy conversion application utilizing the magnetically induced convection for thermal dissipation. The final estimated cation contents, agreed with the initial degree
Cross-shore hydrodynamics within an unsaturated surf zone
T. E. Baldock; P. Holmes; S. Bunker; P. Van Weert
1998-01-01
This paper concerns the hydrodynamics induced by random waves incident on a steep beach. New experimental results are presented on surface elevation and kinematic probability density functions, cross-shore variation in wave heights, the fraction of broken waves and velocity moments. The surf zone is found to be unsaturated at incident wave frequencies, with a significant proportion of the incident wave
Stable ferrofluids of magnetite nanoparticles in hydrophobic ionic liquids
NASA Astrophysics Data System (ADS)
Mestrom, Luuk; Lenders, Jos J. M.; de Groot, Rick; Hooghoudt, Tonnis; Sommerdijk, Nico A. J. M.; Vilaplana Artigas, Marcel
2015-07-01
Ferrofluids (FFs) of metal oxide nanoparticles in ionic liquids (ILs) are a potentially useful class of magnetic materials for many applications because of their properties related to temperature/pressure stability, hydrophobicity, viscosity and recyclability. In this work, the screening of several designer surfactants for their stabilizing capabilities has resulted in the synthesis of stable FFs of superparamagnetic 7 ± 2 nm magnetite (Fe3O4) nanoparticles in the hydrophobic IL 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([CRMIM][NTf2]). The designed and synthesized 1-butyl-3-(10-carboxydecyl)-1H-imidazol-3-ium bromide (ILC10-COOH) surfactant that combines the same imidazole moiety as the IL with a long alkyl chain ensured compatibility with the IL and increased the steric repulsion between the magnetite nanoparticles sufficiently such that stable dispersions of up to 50 wt% magnetite were obtained according to stability tests in the presence of a magnetic field (0.5–1 Tesla). Cryo-transmission electron microscopy (cryo-TEM) of the IL-based FFs allowed direct visualization of the surfactant-stabilized nanoparticles in the ILs and the native, hardly aggregated state of their dispersion.
Stable ferrofluids of magnetite nanoparticles in hydrophobic ionic liquids.
Mestrom, Luuk; Lenders, Jos J M; de Groot, Rick; Hooghoudt, Tonnis; Sommerdijk, Nico A J M; Artigas, Marcel Vilaplana
2015-07-17
Ferrofluids (FFs) of metal oxide nanoparticles in ionic liquids (ILs) are a potentially useful class of magnetic materials for many applications because of their properties related to temperature/pressure stability, hydrophobicity, viscosity and recyclability. In this work, the screening of several designer surfactants for their stabilizing capabilities has resulted in the synthesis of stable FFs of superparamagnetic 7 ± 2 nm magnetite (Fe3O4) nanoparticles in the hydrophobic IL 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([CRMIM][NTf2]). The designed and synthesized 1-butyl-3-(10-carboxydecyl)-1H-imidazol-3-ium bromide (ILC10-COOH) surfactant that combines the same imidazole moiety as the IL with a long alkyl chain ensured compatibility with the IL and increased the steric repulsion between the magnetite nanoparticles sufficiently such that stable dispersions of up to 50 wt% magnetite were obtained according to stability tests in the presence of a magnetic field (0.5-1 Tesla). Cryo-transmission electron microscopy (cryo-TEM) of the IL-based FFs allowed direct visualization of the surfactant-stabilized nanoparticles in the ILs and the native, hardly aggregated state of their dispersion. PMID:26118409
Micropump Anson Hatch, Andrew Evan Kamholz, Gary Holman, Paul Yager, and Karl F. Böhringer, Member, IEEE water (1.2 kPa). [558] Index Terms--Ferrofluid, ferromagnetic, MEMS, microfluidic, micropump, microvalve]. Although several different micropumping mechanisms have been realized using a variety of actuation methods
IDENTIFICATION OF MAGNETIC MINERALS BY SCANNING ELECTRON MICROSCOPE AND APPLICATION OF FERROFLUID
Kletetschka, Gunther
IDENTIFICATION OF MAGNETIC MINERALS BY SCANNING ELECTRON MICROSCOPE AND APPLICATION OF FERROFLUID G in combination with an optical microscope was applied during the last decades. But today, scanning electron are easily identifiable under the scanning electron microscope. The different mineralogy observed
XRD, SEM, EPR and microwave investigations of ferrofluid-PVA composite films
R. P. Pant; R. M. Krishna; P. S. Negi; K. Ravat; D. K. Suri; S. K. Gupta; U. Dhawan
1995-01-01
Ferrofluid-polymer composite films, prepared under the influence of a magnetic field and without magnetic field, have been studied for their physical characteristics. Results of X-ray diffraction, electron paramagnetic resonance, surface structure and microwave absorption studies are reported in this paper and the experimental data correlated with the crystallite size and relatively cluster size variation in the applied field direction.
Dmitry Zablotsky; Elmars Blums
2011-01-01
In this paper, we consider a concentration grating of magnetic nanoparticles optically induced by thermodiffusion in a layer of ferrofluid in the presence of the external homogeneous magnetic field. The applied field is directed along the concentration gradient and leads to the appearance of the internal nonhomogeneous demagnetizing fields. When the system reaches equilibrium, the optical pumping is switched off,
Engel, Andreas
THERMAL RATCHET EFFECT IN FERROFLUIDS A. Engel Institute for Physics, University of Oldenburg, D-26111 Oldenburg, Germany (engel@theorie.physik.uni-oldenburg.de) Introduction. The extraction. Engel y-direction H = (H x ; H y (t); 0) ; H y (t + 2#25;=!) = H y (t) : (1) Di#11;erent choices
Coupling of blocking and melting in cobalt ferrofluids Tianlong Wen,1,a
Krishnan, Kannan M.
at the melting point of the organic solvent was obtained. This observation is explained by applying the M at the melting point of the solvent. Associated with the first order phase transition and the supercooling effectCoupling of blocking and melting in cobalt ferrofluids Tianlong Wen,1,a Wenkel Liang,2 and Kannan M
Optimization of ferrofluid motion on solid substrate and its application to micro-mirror device
NASA Astrophysics Data System (ADS)
Yu, Seonuk; Kim, Dongil; Cho, Il-Joo; Yun, Kwang-Seok
2015-06-01
This paper presents and demonstrates the optimization of an oil-based ferrofluid droplet on a solid surface and its application to a micro-mirror device with a fast switching time. The motion of the ferrofluid droplet on a hydrophilic surface was examined at various surfactant concentrations for both rotational and linear reciprocating actuations. A maximum moving speed of 0.733 m/s was measured at a poly(vinyl alcohol) (PVA) concentration of 0.1 wt % during the rotational motion of the ferrofluid droplet. In addition, a fast reciprocating motion was successfully demonstrated during the linear operation experiment without droplet separation or surface contamination. A maximum acceleration and deceleration of 28 m/s2 was measured at a PVA concentration of 0.1 wt %. As an application of the fast motion of the ferrofluid, a current-driven micro-mirror was proposed and experimentally demonstrated. Switching times of 25 and 18 ms were measured for the closing and opening phases of the mirror, respectively.
Applications of ferrofluids in Micro Electro Mechanical Systems (MEMS) and micropumps
NASA Astrophysics Data System (ADS)
Jain, V. K.; Pant, R. P.; Vinod Kumar, .
2008-12-01
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.
Perspectives in coral reef hydrodynamics
NASA Astrophysics Data System (ADS)
Hearn, Clifford J.
2011-06-01
Some developments in coral reef hydrodynamics over the last decade are reviewed with an overview of papers in this special issue. Advances in hydrodynamics based on improved understanding of topographic complexity are illustrated for the reef at Kilo Nalu Observatory and Kaneohe Bay (both in Hawaii). Models of the roughness layer are discussed as a background to numerical models of reef hydrodynamics for Molokai and Guam. Topographic complexity produces spatial temperature variability over reefs creating thermal microclimates which are reported in this issue for the Red Sea. Uptake of ocean nutrients by reefs is controlled by hydrodynamics, and papers in this issue show its critical role in the ecology of a fringing reef at La Réunion Island; nutrient uptake rates are discussed here using new data for Hearn Roughness and Decadal Rugosity. The role of upwelled water by large amplitude internal waves on reefs is reported for the Similan Islands, providing major new evidence for the role of hydrodynamics in the ecology of reefs and its importance to climate change. The review suggests some important areas for new research including simulated corals used in flumes and the field. Major new modeling based on measured roughness maps combined with small scale lattice Boltzmann simulations should be possible in the next decade.
V. Socoliuc; L. B. Popescu
2014-10-09
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.
Visualizing complex hydrodynamic features
NASA Astrophysics Data System (ADS)
Kempf, Jill L.; Marshall, Robert E.; Yen, Chieh-Cheng
1990-08-01
The Lake Erie Forecasting System is a cooperative project by university, private and governmental institutions to provide continuous forecasting of three-dimensional structure within the lake. The forecasts will include water velocity and temperature distributions throughout the body of water, as well as water level and wind-wave distributions at the lake's surface. Many hydrodynamic features can be extracted from this data, including coastal jets, large-scale thermocline motion and zones of upwelling and downwelling. A visualization system is being developed that will aid in understanding these features and their interactions. Because of the wide variety of features, they cannot all be adequately represented by a single rendering technique. Particle tracing, surface rendering, and volumetric techniques are all necessary. This visualization effortis aimed towards creating a system that will provide meaningful forecasts for those using the lake for recreational and commercial purposes. For example, the fishing industry needs to know about large-scale thermocline motion in order to find the best fishing areas and power plants need to know water intAke temperatures. The visualization system must convey this information in a manner that is easily understood by these users. Scientists must also be able to use this system to verify their hydrodynamic simulation. The focus of the system, therefore, is to provide the information to serve these diverse interests, without overwhelming any single user with unnecessary data.
Hydrodynamics of Turning Flocks
NASA Astrophysics Data System (ADS)
Yang, Xingbo; Marchetti, M. Cristina
2015-03-01
We present a hydrodynamic model of flocking that generalizes the familiar Toner-Tu equations to incorporate turning inertia of well polarized flocks. The continuum equations are derived by coarse graining the inertial spin model recently proposed by Cavagna et al. The interplay between orientational inertia and bend elasticity of the flock yields spin waves that mediate the propagation of turning information throughout the flock. When the inertia is large, we find a novel instability that signals the transition to complex spatio-temporal patterns of continuously turning and swirling flocks. This work was supported by the NSF Awards DMR-1305184 and DGE-1068780 at Syracuse University and NSF Award PHY11-25915 and the Gordon and Betty Moore Foundation Grant No. 2919 at the KITP at the University of California, Santa Barbara.
Hydrodynamic compressibility of high-strength ceramics
Grady, D.E.
1993-08-01
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.
Thermal ratchet effects in ferrofluids Andreas Engel1,
Engel, Andreas
- sequences of the rotational diffusion of the constituting par- ticles. In particular, in the well developed or oil. They combine the hydrodynamic properties of Newtonian fluids with the magnetic behavior experimentally in a previous short communication [10]. In the present paper, we provide many more details
NSDL National Science Digital Library
Mr. Hansen
2010-11-12
The following websites are useful tools in understanding how energy is transferred from place to place through waves. Start by downloading the assignment and then begin with website number 1 and continue until you have visited all three websites. Begin by downloading the IA Waves Internet Assignment: IA Waves Internet Assignment You will answer the questions in Microsoft Word and then e-mail the assignment to me. Website #1: Read about basic information on waves and answer the questions from part 1 of the IA Waves Guide: Basic Wave Information Website #2: Follow the instructions for the following ...
Modeling of retardance in ferrofluid with Taguchi-based multiple regression analysis
NASA Astrophysics Data System (ADS)
Lin, Jing-Fung; Wu, Jyh-Shyang; Sheu, Jer-Jia
2015-03-01
The citric acid (CA) coated Fe3O4 ferrofluids are prepared by a co-precipitation method and the magneto-optical retardance property is measured by a Stokes polarimeter. Optimization and multiple regression of retardance in ferrofluids are executed by combining Taguchi method and Excel. From the nine tests for four parameters, including pH of suspension, molar ratio of CA to Fe3O4, volume of CA, and coating temperature, influence sequence and excellent program are found. Multiple regression analysis and F-test on the significance of regression equation are performed. It is found that the model F value is much larger than Fcritical and significance level P <0.0001. So it can be concluded that the regression model has statistically significant predictive ability. Substituting excellent program into equation, retardance is obtained as 32.703°, higher than the highest value in tests by 11.4%.
On stationary convection and oscillatory motions in ferromagnetic convection in a ferrofluid layer
NASA Astrophysics Data System (ADS)
Prakash, Jyoti
2012-04-01
It is shown analytically that the 'principle of the exchange of stabilities' (PES), in general, is not valid in ferromagnetic convection in a ferrofluid layer, for the case of free boundaries and hence a sufficient condition is derived for the validity of the PES. Upper bounds for the complex growth rate are then obtained. It is proved that the complex growth rate ?=?r+i?i (where ?r and ?i are, respectively, the real and imaginary parts of ?) of an arbitrary oscillatory motion of growing amplitude, in ferromagnetic convection in a ferrofluid layer, for the case of free boundaries lies inside a semicircle in the right half of the ?r?i-plane whose center is at the origin and (=RM1/Pr, where R is the Rayleigh number,M1 is the magnetic number and Pr is the Prandtl number. Further, bounds for the case of rigid ferromagnetic boundaries are also derived separately.
Active surfaces: Ferrofluid-impregnated surfaces for active manipulation of droplets
NASA Astrophysics Data System (ADS)
Khalil, Karim S.; Mahmoudi, Seyed Reza; Abu-dheir, Numan; Varanasi, Kripa K.
2014-07-01
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.
Rheological investigations on the theoretical predicted “Poisoning” effect in bidisperse ferrofluids
NASA Astrophysics Data System (ADS)
Siebert, E.; Dupuis, V.; Neveu, S.; Odenbach, S.
2015-01-01
Interparticle interactions in ferrofluids especially the influence of small particles on the agglomeration behaviour of large particles were the topic of numerous theoretical predictions and simulations as well as of experimental investigations. In this context the "Poisoning" effect describes the decrease of the magnetoviscous effect in the presence of small particles in a bidisperse model fluid. In order to examine this effect rheological experiments have been carried out by means of a specially designed rheometer, which allows measurements under the influence of an applied magnetic field. We were able to synthesize ferrofluids with a narrow particle size distribution containing only small or large cobalt ferrite nanoparticles, which were mixed to receive various bidisperse fluid samples. With these fluids changes of the viscous behaviour in a magnetic field have been measured and compared according to their individual compositions.
Synthesis and characterization of size-controlled cobalt-ferrite-based ionic ferrofluids
P. C. Morais; V. K. Garg; A. C. Oliveira; L. P. Silva; R. B. Azevedo; A. M. L. Silva; E. C. D. Lima
2001-01-01
Size-controlled synthesis of cobalt-ferrite nanoparticles, their passivation and peptization as stable ferrofluids are reported. Transmission electron microscopy and Mössbauer spectroscopy were used as characterization techniques. Particles with little change in size distribution, in the 10–15nm diameter ranges, were obtained using stirring speeds between 2700 and 8100rpm. The anomalous diffusion has been used to explain the nanoparticle size-control mechanism.
Mn–Zn ferrite nanoparticles for ferrofluid preparation: Study on thermal–magnetic properties
R. Arulmurugan; G. Vaidyanathan; S. Sendhilnathan; B. Jeyadevan
2006-01-01
Mn1?xZnxFe2O4 (with x varying from 0.1 to 0.5) ferrite nanoparticles used for ferrofluid preparation have been prepared by chemical co-precipitation method and characterized. Characterization techniques like elemental analysis by atomic absorption spectroscopy and spectrophotometry, thermal analysis using simultaneous TG-DTA, XRD, TEM, VSM and Mossbauer spectroscopy have been utilized. The final cation contents estimated agree with the initial degree of substitution.
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
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.
Investigation of the Magnetic Behavior in Fe3O4 Ferrofluid Functionalized by Carapa Guianensis Oil
Jorge Luis López; Anselmo Fortunato Ruiz Rodriguez; Maria de Jesus Nascimento Pontes; Paulo Cesar de Morais; Ricardo Bentes de Azevedo; Hans Dieter Pfannes; José Higino Dias Filho
2010-01-01
A ferrofluid based on Fe3O4 has been synthesized using the condensation method by coprecipitating aqueous solutions of FeSO4 and FeCl3 mixtures in NH4OH and treated further in order to obtain colloidal sols by creating a charge density on their surface and functionalized by carapa guianensis (andiroba oil). Aqueous sample with an average particle diameter ~7 nm were studied by Mössbauer
Low-temperature magnetic susceptibility of concentrated ferrofluids: The influence of polydispersity
NASA Astrophysics Data System (ADS)
Ivanov, Alexey O.; Elfimova, Ekaterina A.
2015-01-01
In this paper we address the question of theoretical explanation of extremely high low-temperature initial magnetic susceptibility of concentrated ferrofluids. These laboratory synthesized samples [A.F. Pshenichnikov, A.V. Lebedev, J. Chem. Phys. 121(11) (2004) 5455; Colloid J. 67(2) (2005) 189] demonstrated the record-breaking values ? ~ 120 - 150 at temperatures ~ 230-240 K. The existing models predict such high susceptibility only under the assumption of unreasonably large dipolar coupling constant, which is out of the range of applicability. Here we calculate the second virial contribution to susceptibility for polydisperse ferrofluid, modeled by the dipolar hard sphere fluid. In the resulting expression there exists the parameter, which plays a part of dipolar coupling constant and which is defined in a form of double averaging of high powers of particle sizes over the granulometric distribution. For real particle size distribution this effective parameter at least twice exceeds the commonly defined polydisperse dipolar coupling constant. We show that the low-temperature magnetic susceptibility of the record-breaking ferrofluids could be explained theoretically on the basis of the first terms of the polydisperse second virial contribution in combination with the second-order modified mean field model.
Theory and simulation of anisotropic pair correlations in ferrofluids in magnetic fields
NASA Astrophysics Data System (ADS)
Elfimova, Ekaterina A.; Ivanov, Alexey O.; Camp, Philip J.
2012-05-01
Anisotropic pair correlations in ferrofluids exposed to magnetic fields are studied using a combination of statistical-mechanical theory and computer simulations. A simple dipolar hard-sphere model of the magnetic colloidal particles is studied in detail. A virial-expansion theory is constructed for the pair distribution function (PDF) which depends not only on the length of the pair separation vector, but also on its orientation with respect to the field. A detailed comparison is made between the theoretical predictions and accurate simulation data, and it is found that the theory works well for realistic values of the dipolar coupling constant (? = 1), volume fraction (? ? 0.1), and magnetic field strength. The structure factor is computed for wavevectors either parallel or perpendicular to the field. The comparison between theory and simulation is generally very good with realistic ferrofluid parameters. For both the PDF and the structure factor, there are some deviations between theory and simulation at uncommonly high dipolar coupling constants, and with very strong magnetic fields. In particular, the theory is less successful at predicting the behavior of the structure factors at very low wavevectors, and perpendicular Gaussian density fluctuations arising from strongly correlated pairs of magnetic particles. Overall, though, the theory provides reliable predictions for the nature and degree of pair correlations in ferrofluids in magnetic fields, and hence should be of use in the design of functional magnetic materials.
Theory and simulation of anisotropic pair correlations in ferrofluids in magnetic fields.
Elfimova, Ekaterina A; Ivanov, Alexey O; Camp, Philip J
2012-05-21
Anisotropic pair correlations in ferrofluids exposed to magnetic fields are studied using a combination of statistical-mechanical theory and computer simulations. A simple dipolar hard-sphere model of the magnetic colloidal particles is studied in detail. A virial-expansion theory is constructed for the pair distribution function (PDF) which depends not only on the length of the pair separation vector, but also on its orientation with respect to the field. A detailed comparison is made between the theoretical predictions and accurate simulation data, and it is found that the theory works well for realistic values of the dipolar coupling constant (? = 1), volume fraction (? ? 0.1), and magnetic field strength. The structure factor is computed for wavevectors either parallel or perpendicular to the field. The comparison between theory and simulation is generally very good with realistic ferrofluid parameters. For both the PDF and the structure factor, there are some deviations between theory and simulation at uncommonly high dipolar coupling constants, and with very strong magnetic fields. In particular, the theory is less successful at predicting the behavior of the structure factors at very low wavevectors, and perpendicular Gaussian density fluctuations arising from strongly correlated pairs of magnetic particles. Overall, though, the theory provides reliable predictions for the nature and degree of pair correlations in ferrofluids in magnetic fields, and hence should be of use in the design of functional magnetic materials. PMID:22612098
Optical monitoring study on estuarine sediment incipient under marine hydrodynamic
Hao Qin; Shucai Li; Lei Zhang
2009-01-01
For the deserted estuary without sediment inflow, ocean hydrodynamic has become the main force for coastal erosion. This paper utilizes wave-tide gauge and current meter to monitor the hydrodynamic within the experimental area and also, turbidity meter is used to conduct indirect monitoring to the sediment concentration (the corresponding relation between the turbidity value and the content of suspended particles
Studies of oil retention boom hydrodynamics
W. T. Lindenmuth; E. R. Jr. Miller; C. C. Hsu
1970-01-01
Results of an experimental investigation of oil containment hydrodynamics are presented with theoretical analysis to help explain the experimental findings. Two-dimensional model tests were performed using several petroleum products including diesel fuel and motor oil. Test variables in addition to oil properties were current, interfacial tension, gravity waves, slick volume, containment boom geometry, and boom depth. Also studied were three-dimensional
LaCure, Mari Mae
2010-04-29
travel as waves through space and time. Waves can also manifest visibly through other mediums, water for example, as they travel outward from where an object disturbs the surface. As the title of my thesis exhibit, Waves refers to my aim to imbue.... As a viewer approaches a drawing from different angles the light reflected by the image subtly changes intensity. 4 Sewing by hand further adds dimension where it is seen in the front, and creates a shadow where it can be seen through the back...
NASA Astrophysics Data System (ADS)
Cristaldo, C. F. C.; Fachini, F. F.
2013-03-01
In this work, heating and vaporization of a liquid droplet with dispersed magnetic nanoparticles (ferrofluid) are analyzed. The ferrofluid droplet is in a quiescent inert gas phase with a temperature which is set down equal to, higher and lower than the liquid boiling temperature. Under these conditions, an alternating magnetic field is applied and, as a result, the magnetic nanoparticles generate heat by the Brownian relaxation mechanism. In this mechanism, the magnetic dipoles present a random orientation due to collisions between the fluid molecules and nanoparticles. The magnetic dipoles tend to align to the magnetic field causing rotation of the nanoparticles. Consequently the temperature increases due to the energy dissipated by the friction between the resting fluid and the rotating nanoparticles. Assuming a very large magnetic power and a uniform distribution of nanoparticles, the droplet core is uniformly heated. A thermal boundary layer is established in the liquid-phase adjacent to the droplet surface due to heat flux from the ambient atmosphere. The temperature profile inside the thermal boundary layer is obtained in appropriate time and length scales. In the present model, the ferrofluid droplet is heated up to its boiling temperature in a very short time. In addition, the combination of the heat generated by magnetic nanoparticles and heat conduction from gas phase results in a higher vaporization rate. Under specific conditions, the boiling temperature is achieved not at the surface but inside the thermal boundary layer. Moreover, the results point out that the thermal boundary layer depends directly on the vapor Lewis number but the vaporization rate reciprocally on it.
Blast-Driven Hydrodynamic Instability
NASA Astrophysics Data System (ADS)
Henry de Frahan, Marc T.; Johnsen, Eric
2013-11-01
Accurate characterization of mixing from hydrodynamic instabilities, such as Richtmyer-Meshkov, Rayleigh-Taylor, and Kelvin-Helmholtz, is important to many multi-fluid applications, particularly, inertial confinement fusion, supernova collapse, and scramjet combustion. We investigate the dynamics of a perturbed interface between two fluids subjected to a planar blast wave. An initial point source explosion initiates a blast, which can be described as a shock front followed by a rarefaction wave. The interface, therefore, experiences an instantaneous acceleration (a pressure increase) followed by a gradual, time-dependent deceleration (a pressure decrease). The resulting interaction gives rise to Richtmyer-Meshkov and Rayleigh-Taylor growth, depending on the shock strength and blast profile. Using a high-order accurate numerical method that prevents pressure errors at interfaces when simulating variable specific heats ratios, we identify regimes in which one or the other instability dominates. Accurate characterization of mixing from hydrodynamic instabilities, such as Richtmyer-Meshkov, Rayleigh-Taylor, and Kelvin-Helmholtz, is important to many multi-fluid applications, particularly, inertial confinement fusion, supernova collapse, and scramjet combustion. We investigate the dynamics of a perturbed interface between two fluids subjected to a planar blast wave. An initial point source explosion initiates a blast, which can be described as a shock front followed by a rarefaction wave. The interface, therefore, experiences an instantaneous acceleration (a pressure increase) followed by a gradual, time-dependent deceleration (a pressure decrease). The resulting interaction gives rise to Richtmyer-Meshkov and Rayleigh-Taylor growth, depending on the shock strength and blast profile. Using a high-order accurate numerical method that prevents pressure errors at interfaces when simulating variable specific heats ratios, we identify regimes in which one or the other instability dominates. This research was supported by the DOE NNSA/ASC under the predictive Science Academic Alliance Program by Grant No. DEFC52-08NA28616.
Avdeev, M V; Bica, D; Vékás, L; Aksenov, V L; Feoktystov, A V; Marinica, O; Rosta, L; Garamus, V M; Willumeit, R
2009-06-01
The structure of ferrofluids (magnetite in decahydronaphtalene) stabilized with saturated mono-carboxylic acids of different chain lengths (lauric, myristic, palmitic and stearic acids) is studied by means of magnetization analysis and small-angle neutron scattering. It is shown that in case of saturated acid surfactants, magnetite nanoparticles are dispersed in the carrier approximately with the same size distribution whose mean value and width are significantly less as compared to the classical stabilization with non-saturated oleic acid. The found thickness of the surfactant shell around magnetite is analyzed with respect to stabilizing properties of mono-carboxylic acids. PMID:19376524
Candiani, A. [Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), Heraklion 70013 Greece (Greece); Department of Information Engineering (DII), University of Parma, Parma 43124 (Italy); Argyros, A.; Leon-Saval, S. G.; Lwin, R. [Institute of Photonics and Optical Science (IPOS), School of Physics, The University of Sydney, Sydney (Australia); Selleri, S. [Department of Information Engineering (DII), University of Parma, Parma 43124 (Italy); Pissadakis, S., E-mail: pissas@iesl.forth.gr [Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), Heraklion 70013 Greece (Greece)
2014-03-17
We report an in-fiber magnetic field sensor based on magneto-driven optical loss effects, while being implemented in a ferrofluid infiltrated microstructured polymer optical fiber. We demonstrate that magnetic field flux changes up to 2000 gauss can be detected when the magnetic field is applied perpendicular to the fiber axis. In addition, the sensor exhibits high polarization sensitivity for the interrogated wavelengths, providing the possibility of both field flux and direction measurements. The underlying physical and guidance mechanisms of this sensing transduction are further investigated using spectrophotometric, light scattering measurements, and numerical simulations, suggesting photonic Hall effect as the dominant physical, transducing mechanism.
NASA Astrophysics Data System (ADS)
Candiani, A.; Argyros, A.; Leon-Saval, S. G.; Lwin, R.; Selleri, S.; Pissadakis, S.
2014-03-01
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.
NASA Astrophysics Data System (ADS)
Fannin, P. C.; Kinsella, L.; Charles, S. W.
1997-02-01
Application of the fluctuation dissipation theorem to the frequency-dependent, complex magnetic susceptibility data, 0022-3727/30/4/006/img6, allows the after-effect function or magnetization decay, b(t), of ferrofluids or other particulate systems to be determined. Here it is demonstrated that, by means of the simple expedient of fitting the measured complex susceptibility profiles to suitably adapted classical models, data in the 10 - 100 GHz frequency band can be determined from measurements made in the 100 MHz to 6 GHz frequency range. Transformation of the fitted data thus, for the first time, allows b(t) to be investigated in the 0022-3727/30/4/006/img7 and 0022-3727/30/4/006/img8 time regions. The results of applying this technique to two ferrofluid samples and a magnetic tape sample are presented; in the case of the ferrofluids the complex susceptibility data, 0022-3727/30/4/006/img9, are fitted to the equations of Raikher and Shliomis and of Debye, suitably modified to include a distribution of particle size, r, and anisotropy constant, K, whereas for the magnetic tape sample, the fit is realized by means of the Landau - Lifshitz equations suitably modified to cater for a distribution of K. It is demonstrated that a more accurate after-effect function is obtained in the cases in which the fitted profiles are transformed and that, by application of a varying polarizing magnetic field to the ferrofluid samples, b(t) of the fitted data is shown to be oscillatory in form with the transverse relaxation time, 0022-3727/30/4/006/img10, having a periodic time approximately equal to the time obtained from the resonant frequency, 0022-3727/30/4/006/img11, 0022-3727/30/4/006/img12 corresponding to the frequency at which the 0022-3727/30/4/006/img13 component goes from a positive to a negative value. The region of 0022-3727/30/4/006/img7 to 0022-3727/30/4/006/img8 corresponds to a time region which is generally associated with the precessional decay time, 0022-3727/30/4/006/img16, which is a pre-factor of Brown's equations for Néel relaxation. It is considered that the technique presented has the potential to be a useful tool for investigating and verifying the value of this parameter.
Magnetic field effects on viscous fingering of a ferrofluid in a radial Hele Shaw cell
NASA Astrophysics Data System (ADS)
Herreman, Wietze; Molho, Pierre; Neveu, Sophie
2005-03-01
We have studied the effects of a magnetic field on viscous fingering when a ferrofluid is pushed in a more viscous liquid in a circular Hele-Shaw cell. The main effect of the magnetic field, as already known, is to stabilize interfaces parallel to the field and to destabilize interfaces normal to the field. Depending on the growth regime (quasi static, fingering, dendritic growth), which depends on parameters like the cell thickness and oil viscosity, the combination of field effect and anisotropy is analyzed through the various observed patterns.
Torres-Diaz, I.; Cortes, A.; Rinaldi, C., E-mail: carlos.rinaldi@bme.ufl.edu [Department of Chemical Engineering, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9000 (United States); Cedeño-Mattei, Y. [Department of Chemistry, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9019 (United States)] [Department of Chemistry, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9019 (United States); Perales-Perez, O. [Department of Engineering Science and Materials, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9044 (United States)] [Department of Engineering Science and Materials, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9044 (United States)
2014-01-15
Ferrofluid flow in cylindrical and annular geometries under the influence of a uniform rotating magnetic field was studied experimentally using aqueous ferrofluids consisting of low concentrations (<0.01 v/v) of cobalt ferrite nanoparticles with Brownian relaxation to test the ferrohydrodynamic equations, elucidate the existence of couple stresses, and determine the value of the spin viscosity in these fluids. An ultrasound technique was used to measure bulk velocity profiles in the spin-up (cylindrical) and annular geometries, varying the intensity and frequency of the rotating magnetic field generated by a two pole stator winding. Additionally, torque measurements in the cylindrical geometry were made. Results show rigid-body like velocity profiles in the bulk, and no dependence on the axial direction. Experimental velocity profiles were in quantitative agreement with the predictions of the spin diffusion theory, with a value of the spin viscosity of ?10{sup ?8} kg m/s, two orders of magnitude larger than the value estimated earlier for iron oxide based ferrofluids, and 12 orders of magnitude larger than estimated using dimensional arguments valid in the infinite dilution limit. These results provide further evidence of the existence of couple stresses in ferrofluids and their role in driving the spin-up flow phenomenon.
Paris-Sud XI, Université de
Instability of the origami of a ferrofluid drop in a magnetic field Timoth´ee Jamin, Charlotte Py: October 26, 2011) Capillary origami is the wrapping of an usual fluid drop by a planar elastic membrane- ical behaviors of such a magnetic capillary origami. We report the observation of an overturning
Falcon, Eric
Instability of the Origami of a Ferrofluid Drop in a Magnetic Field Timothe´e Jamin, Charlotte Py origami is the wrapping of a usual fluid drop by a planar elastic membrane due to the interplay between origami. We report the observation of an overturning instability that the origami undergoes at a critical
New nonlinear optical materials based on ferrofluids J. P. Huang1,2,3, K. W. Yu2,4
Huang, Ji-Ping
Kong, Shatin, NT, Hong Kong 3 Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz optical material based on ferrofluids in which ferromagnetic nanoparticles are coated with a non- magnetic nonlinear optical materials with large nonlinear susceptibilities and fast responses is up to now
Hydrodynamics of the Chiral Dirac Spectrum
Liu, Yizhuang; Zahed, Ismail
2015-01-01
We derive a hydrodynamical description of the eigenvalues of the chiral Dirac spectrum in the vacuum and in the large $N$ (volume) limit. The linearized hydrodynamics supports sound waves. The stochastic relaxation of the eigenvalues is captured by a hydrodynamical instanton configuration which follows from a pertinent form of Euler equation. The relaxation from a phase of localized eigenvalues and unbroken chiral symmetry to a phase of de-localized eigenvalues and broken chiral symmetry occurs over a time set by the speed of sound. We show that the time is $\\Delta \\tau=\\pi\\rho(0)/2\\beta N$ with $\\rho(0)$ the spectral density at zero virtuality and $\\beta=1,2,4$ for the three Dyson ensembles that characterize QCD with different quark representations in the ergodic regime.
Hydrodynamics of the Chiral Dirac Spectrum
Yizhuang Liu; Piotr Warchol; Ismail Zahed
2015-06-29
We derive a hydrodynamical description of the eigenvalues of the chiral Dirac spectrum in the vacuum and in the large $N$ (volume) limit. The linearized hydrodynamics supports sound waves. The stochastic relaxation of the eigenvalues is captured by a hydrodynamical instanton configuration which follows from a pertinent form of Euler equation. The relaxation from a phase of localized eigenvalues and unbroken chiral symmetry to a phase of de-localized eigenvalues and broken chiral symmetry occurs over a time set by the speed of sound. We show that the time is $\\Delta \\tau=\\pi\\rho(0)/2\\beta N$ with $\\rho(0)$ the spectral density at zero virtuality and $\\beta=1,2,4$ for the three Dyson ensembles that characterize QCD with different quark representations in the ergodic regime.
Takahashi, Hayato; Nagao, Daisuke; Watanabe, Kanako; Ishii, Haruyuki; Konno, Mikio
2015-05-26
Monodisperse, nonmagnetic, asymmetrical composite dumbbells in a suspension of magnetic nanoparticles (ferrofluid) were aligned by application of an external magnetic field to the ferrofluid. The asymmetrical composite dumbbells were prepared by two-step soap-free emulsion polymerization consisting of the first polymerization to coat spherical silica cores with cross-linked poly(methyl methacrylate) (PMMA) shell and the second polymerization to protrude a polystyrene (PSt) lobe from the core-shell particles. A chain structure of nonmagnetic dumbbells oriented to the applied magnetic field was observed at nanoparticle content of 2.0 vol % and field strengths higher than 1.0 mT. A similar chain structure of the dumbbells was observed under application of alternating electric field at strengths higher than 50 V/mm. Parallel and orthogonally combined applications of the electric and magnetic fields were also conducted to examine independence of the electric and magnetic applications as operational factors in the dumbbell assembling. Dumbbell chains stiffer than those in a single application of external field were formed in the parallel combined application of electric and magnetic fields. The orthogonal combination of the different applied fields could form a magnetically aligned chain structure of the nonmagnetic dumbbells oriented to the electric field. The present work experimentally indicated that the employment of inverse magnetorheological effect for nonmagnetic, anisotropic particles can be a useful method for the simultaneous controls over the orientation and the positon of anisotropic particles in their assembling. PMID:25927488
One-dimensional actuation of a ferrofluid droplet by planar microcoils
NASA Astrophysics Data System (ADS)
Beyzavi, Ali; Nguyen, Nam-Trung
2009-01-01
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. The coils on the top create a virtual channel to confine the motion of the droplet along a straight line. The paper first formulates the model of the magnetic field of the coils. With the modelled magnetic field, the corresponding forces acting on the droplet were calculated. The equation of the motion of a ferrofluid droplet immersed in silicone oil is solved numerically. The influence of different parameters such as driving current, droplet diameter and viscosity of the carrier fluid is investigated. Theoretical and experimental results agree well quantitatively and qualitatively. Both theoretical and experimental results show that a higher magnetic field, a lower oil viscosity and a bigger droplet size will increase the peak velocity of the droplet.
Spreading of a ferrofluid core in three-stream micromixer channels
NASA Astrophysics Data System (ADS)
Wang, Zhaomeng; Varma, V. B.; Xia, Huan Ming; Wang, Z. P.; Ramanujan, R. V.
2015-05-01
Spreading of a water based ferrofluid core, cladded by a diamagnetic fluid, in three-stream micromixer channels was studied. This spreading, induced by an external magnetic field, is known as magnetofluidic spreading (MFS). MFS is useful for various novel applications where control of fluid-fluid interface is desired, such as micromixers or micro-chemical reactors. However, fundamental aspects of MFS are still unclear, and a model without correction factors is lacking. Hence, in this work, both experimental and numerical analyses were undertaken to study MFS. We show that MFS increased for higher applied magnetic fields, slower flow speed of both fluids, smaller flow rate of ferrofluid relative to cladding, and higher initial magnetic particle concentration. Spreading, mainly due to connective diffusion, was observed mostly near the channel walls. Our multi-physics model, which combines magnetic and fluidic analyses, showed, for the first time, excellent agreement between theory and experiment. These results can be useful for lab-on-a-chip devices.
Ramos Heredia, Rafael Juda
1995-01-01
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
1995-01-01
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...
Anisotropic Hydrodynamics: Three Lectures
NASA Astrophysics Data System (ADS)
Strickland, M.
Anisotropic hydrodynamics is a non-perturbative reorganization of relativistic hydrodynamics that takes into account the large momentum-space anisotropies generated in ultrarelativistic heavy-ion collisions. As a result, it allows one to extend the regime of applicability of hydrodynamic treatments to situations that can be quite far from isotropic thermal equilibrium. In this paper, I review the material presented in a series of three introductory lectures. I review the derivation of ideal and second-order viscous hydrodynamics from kinetic theory. I then show how to extend the methods used to a system that can be highly anisotropic in local-rest-frame momenta. I close by discussing recent work on this topic and then present an outlook to the future.
NASA Astrophysics Data System (ADS)
Hirano, Tetsufumi; van der Kolk, Naomi; Bilandzic, Ante
The main purpose of the lecture was to lead students and young postdocs to the frontier of the hydrodynamic description of relativistic heavy-ion collisions (H.I.C.) in order for them to understand talks and posters presented in the Quark Matter 2008 (QM08) conference in Jaipur, India [1]. So the most recent studies were not addressed in this lecture as they would be presented during the QM08 conference itself. Also, we try to give a very pedagogical lecture here. For the readers who may want to study relativistic hydrodynamics and its application to H.I.C. as an advanced course, we strongly recommend them to consult the references. This lecture note is divided into three parts. In the first part we give a brief introduction to relativistic hydrodynamics in the context of H.I.C. In the second part we present the formalism and some fundamental aspects of relativistic ideal and viscous hydrodynamics.
Nonconformal viscous anisotropic hydrodynamics
NASA Astrophysics Data System (ADS)
Bazow, Dennis; Heinz, Ulrich; Martinez, Mauricio
2015-06-01
We generalize the derivation of viscous anisotropic hydrodynamics from kinetic theory to allow for nonzero particle masses. The macroscopic theory is obtained by taking moments of the Boltzmann equation after expanding the distribution function around a spheroidally deformed local momentum distribution whose form has been generalized by the addition of a scalar field that accounts nonperturbatively (i.e., already at leading order) for bulk viscous effects. Hydrodynamic equations for the parameters of the leading-order distribution function and for the residual (next-to-leading order) dissipative flows are obtained from the three lowest moments of the Boltzmann equation. The approach is tested for a system undergoing (0 +1 )-dimensional boost-invariant expansion for which the exact solution of the Boltzmann equation in the relaxation time approximation is known. Nonconformal viscous anisotropic hydrodynamics is shown to approximate this exact solution more accurately than any other known hydrodynamic approximation.
Hydrodynamics of vegetated channels
Nepf, Heidi
This paper highlights some recent trends in vegetation hydrodynamics, focusing on conditions within channels and spanning spatial scales from individual blades, to canopies or vegetation patches, to the channel reach. At ...
Hydrodynamical evolution of coalescing binary neutron stars
NASA Technical Reports Server (NTRS)
Rasio, Frederic A.; Shapiro, Stuart L.
1992-01-01
The hydrodynamics of the final merging of two neutron stars and the corresponding gravitational wave emission is studied in detail. Various test calculations are presented, including the compressible Roche and Darwin problems and the head-on collision of two polytropes. A complete coalescence calculation is presented for the simplest case of two identical neutron stars, represented by Gamma = 2 polytropes, in a circular orbit, with their spins aligned and synchronized with the orbital rotation.
Stellar Hydrodynamics in Radiative Regions
Patrick A. Young; Karen A. Knierman; Jane R. Rigby; David Arnett
2003-06-11
We present an analysis of the response of a radiative region to waves generated by a convective region of the star; this wave treatment of the classical problem of ``overshooting'' gives extra mixing relative to the treatment traditionally used in stellar evolutionary codes. The interface between convectively stable and unstable regions is dynamic and nonspherical, so that the nonturbulent material is driven into motion, even in the absence of ``penetrative overshoot.'' These motions may be described by the theory of nonspherical stellar pulsations, and are related to motion measured by helioseismology. Multi-dimensional numerical simulations of convective flow show puzzling features which we explain by this simplified physical model. Gravity waves generated at the interface are dissipated, resulting in slow circulation and mixing seen outside the formal convection zone. The approach may be extended to deal with rotation and composition gradients. Tests of this description in the stellar evolution code TYCHO produce carbon stars on the asymptotic giant branch (AGB), an isochrone age for the Hyades and three young clusters with lithium depletion ages from brown dwarfs, and lithium and beryllium depletion consistent with observations of the Hyades and Pleiades, all without tuning parameters. The insight into the different contributions of rotational and hydrodynamic mixing processes could have important implications for realistic simulation of supernovae and other questions in stellar evolution.
NASA Astrophysics Data System (ADS)
Rablau, Corneliu; Vaishnava, Prem; Sudakar, Chandran; Tackett, Ronald; Lawes, Gavin; Naik, Ratna
2008-11-01
We report an experimental investigation of time dependent anisotropic light scattering by an aqueous suspension of tetramethyl ammonium hydroxide coated Fe3O4 nanoparticles (˜6nm) under the ON-OFF transient of an external dc magnetic field. The study employs the synchronized recording and measurement of the two magnetic-field-induced light-scattering patterns produced by two identical orthogonal He-Ne laser beams passing through the ferrofluid sample and propagating parallel and perpendicular to the applied field, respectively. From these patterns, we extract the time dependence of the induced optical anisotropy, which provides a measure of the characteristic time scale and kinematic response for field-induced structure formation in the sample. We propose that the time evolution of the scattering patterns, which is very fast at short times and significantly slower at long times, can be explained using a model based on a two-stage chain formation and coarsening processes.
NASA Astrophysics Data System (ADS)
Linke, J. M.; Odenbach, S.
2015-05-01
The anisotropy of the magnetoviscous effect of a ferrofluid has been studied in a specially designed slit die viscometer, which allows three distinct orientations of the magnetic field with respect to the fluid flow. The corresponding Miesowicz viscosity coefficients were determined in dependence of the shear rate and the magnetic field intensity to gain a comprehensive magnetorheological characterization of the fluid. The particles in the fluid have a mean diameter of 13 nm corresponding to an interaction parameter of ? ? 1.3 for magnetite. Thus, the fluid can be expected to show a transition from non-interacting individual particles to microstructures with chain-like associated particles when the magnetic field intensity is increased and the shear rate is decreased. The observed field and shear dependent anisotropy of the magnetoviscous effect is explained coherently in terms of these microstructural changes in the fluid.
Ju, D Y; Bian, P; Kumazawa, T; Nakano, M; Matsuura, H; Umetani, K; Komdo, T; Uozumi, Y; Makino, K; Noda, N; Koide, K; Akutsu, M; Masuyama, K
2011-10-01
In this study, the composite magnetic nanoparticles of coated SiO nano film with about 8 nm size and high saturation magnetization value, were synthesized by liquid phase precipitation method. The magnetic nanoparticles can be dispersed in various liquid media, widely known as magnetic fluids or ferrofluids with both magnetic and liquid properties. The materials been collected great interests and more and more attentions to focus into Drug Delivery System (DDS) as a new technology in this paper. We use the composite nanoparticles to disperse H2O and inject the solutions into rat's in-vivo organs. And, in the experiments by using a strong photon beam of SPring-8 Synchrotron Radiation facility, the distribution stat and the effects of magnetic field as well as drug delivery behaviour of nanoparticles in the rat' kidney are verified by the in-vivo observations. PMID:22400252
Hydrodynamics of spin-polarized transport and spin pendulum
Gurzhi, R. N., E-mail: gurzhi@ilt.kharkov.ua; Kalinenko, A. N.; Kopeliovich, A. I.; Pyshkin, P. V.; Yanovsky, A. V. [Verkin Institute for Low-Temperature Physics and Engineering (Ukraine)
2007-07-15
The dynamics of a nonequilibrium spin system dominated by collisions preserving the total quasimomentum of the interacting electrons and quasiparticles is considered. An analysis of the derived hydrodynamic equations shows that weakly attenuated spin-polarization waves associated with an oscillating drift current can exist in a magnetically inhomogeneous conducting ring. Spin-polarized transport in a ballistic regime of wave propagation through a conductor is also considered, and a simple method is proposed for distinguishing these waves from spin and current oscillations that develop in the hydrodynamic regime. It is shown that a potential difference arises between the leads of an open nonuniformly spin-polarized conductor as a manifestation of spin polarization of electron density. This spin-mediated electrical phenomenon occurs in both hydrodynamic and diffusive limits.
Stretching of a confined ferrofluid: Influence of viscous stresses and magnetic field
NASA Astrophysics Data System (ADS)
Oliveira, Rafael M.; Miranda, José A.
2006-03-01
An analytical investigation is presented for the stretch flow of a viscous Newtonian ferrofluid highly confined between parallel plates. We focus on the development of interfacial instabilities when the upper plate is lifted at a described rate, under the action of an applied magnetic field. We derive the mode-coupling differential equation for the interface perturbation amplitudes and study both linear and nonlinear flow regimes. In contrast to the great majority of works in stretch flow we take into account stresses originated from velocity gradients normal to the ferrofluid interface. The impact of such normal stresses is accounted for through a modified Young-Laplace pressure jump interfacial boundary condition, which also includes the contribution from magnetic normal traction. We study how the stability properties of the interface and the shape of the emerging patterns respond to the combined action of normal stresses and magnetic field, both in the presence and absence of surface tension. We show that the inclusion of normal viscous stresses introduces a pertinent dependence on the initial aspect ratio, indicating that the number of fingers formed would be overestimated if such stresses are not taken into account. At early linear stages it is found that such stresses regularize the system, acting as an effective interfacial tension. At weakly nonlinear stages we verified that normal stresses reduce finger competition, which can be completely suppressed with the assistance of an azimuthal magnetic field. We have also found that the magnetic normal traction introduces a purely nonlinear contribution to the problem, revealing the key role played by the magnetic susceptibility in the control of finger competition.
Synthesis and characterization of iron-rich FexPt1-x ferrofluid for magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Jha, Deepak K.; Deb, P.; Kalita, E.; Shameem, M.; Patel, Anant B.
2012-03-01
Iron-rich FexPt1-x ultrafine nanodots were prepared by a simple and versatile polyol process using a combinatorial strategy of introducing a strong reducing agent and decreasing the synthesis temperature. The native hydrophobic nanodots were converted into a wettable dispersion by ligand exchange-mediated phase transformation using tetramethyl ammonium hydroxide. The microstructural study confirmed the formation of Fe-rich FePt nanodots having an average particle size of ~3.5 nm with a narrow size distribution. An MTT (methylthiazolyldiphenyl-tetrazolium bromide [3- (4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide]) study on mammalian leukocyte cultures confirmed the high degree of biocompatibility for the ferrofluid. The ferrofluid, when studied for its concentration-dependent transverse relaxation time and contrast properties, was found to exhibit promising properties as a magnetic resonance imaging T2 contrast agent.
Hydrodynamics with Triangle Anomalies
Dam T. Son; Piotr Surowka
2009-07-13
We consider the hydrodynamic regime of theories with quantum anomalies for global currents. We show that a hitherto discarded term in the conserve current is not only allowed by symmetries, but is in fact required by triangle anomalies and the second law of thermodynamics. This term leads to a number of new effects, one of which is chiral separation in a rotating fluid at nonzero chemical potential. The new kinetic coefficients can be expressed, in a unique fashion, through the anomalies coefficients and the equation of state. We briefly discuss the relevance of this new hydrodynamic term for physical situations, including heavy ion collisions.
Hydrodynamics with Triangle Anomalies
Son, Dam T. [Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550 (United States); Surowka, Piotr [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)
2009-11-06
We consider the hydrodynamic regime of theories with quantum anomalies for global currents. We show that a hitherto discarded term in the conserved current is not only allowed by symmetries, but is in fact required by triangle anomalies and the second law of thermodynamics. This term leads to a number of new effects, one of which is chiral separation in a rotating fluid at nonzero chemical potential. The new kinetic coefficients can be expressed, in a unique fashion, through the anomaly coefficients and the equation of state. We briefly discuss the relevance of this new hydrodynamic term for physical situations, including heavy-ion collisions.
Allen M. Teeter; Billy H. Johnson; Charlie Berger; Guus Stelling; Norman W. Scheffner; Marcelo H. Garcia; T. M. Parchure
2001-01-01
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
Skew resisting hydrodynamic seal
Conroy, William T. (Pearland, TX); Dietle, Lannie L. (Sugar Land, TX); Gobeli, Jeffrey D. (Houston, TX); Kalsi, Manmohan S. (Houston, TX)
2001-01-01
A novel hydrodynamically lubricated compression type rotary seal that is suitable for lubricant retention and environmental exclusion. Particularly, the seal geometry ensures constraint of a hydrodynamic seal in a manner preventing skew-induced wear and provides adequate room within the seal gland to accommodate thermal expansion. The seal accommodates large as-manufactured variations in the coefficient of thermal expansion of the sealing material, provides a relatively stiff integral spring effect to minimize pressure-induced shuttling of the seal within the gland, and also maintains interfacial contact pressure within the dynamic sealing interface in an optimum range for efficient hydrodynamic lubrication and environment exclusion. The seal geometry also provides for complete support about the circumference of the seal to receive environmental pressure, as compared the interrupted character of seal support set forth in U.S. Pat. Nos. 5,873,576 and 6,036,192 and provides a hydrodynamic seal which is suitable for use with non-Newtonian lubricants.
Yuri N. Obukhov
2003-09-23
The curved geometry of a spacetime manifold arises as a solution of Einstein's gravitational field equation. We show that the metric of a spherically symmetric gravitational field configuration can be viewed as an optical metric created by the moving material fluid with nontrivial dielectric and magnetic properties. Such a "hydrodynamical" approach provides a simple physical interpretation of a horizon.
Hydrodynamic particle interactions
W. Brent Daniel; Michael K. Rivera; Robert E. Ecke
2003-01-01
The interaction of particles at moderate Reynolds numbers has many important commercial and industrial applications ranging from fluidized beds, to bioreactors, to the dispersion of pollutants. Underlying the gross characteristics of such systems is a set of complex hydrodynamic interactions that is poorly understood. These interactions may be either attractive or repulsive depending on the angular and radial configuration of
Hydrodynamically coupled rigid bodies
Sujit Nair; Eva Kanso
2007-01-01
This paper considers a finite number of rigid bodies moving in potential flow. The dynamics of the solid--fluid system is described in terms of the solid variables only using Kirchhoff potentials. The equations of motion are first derived for the problem of two submerged bodies where one is forced into periodic oscillations. The hydrodynamic coupling causes the free body to
Heat capacity of liquids: A hydrodynamic approach
T. Bryk; T. Scopigno; G. Ruocco
2015-04-06
We study autocorrelation functions of energy, heat and entropy densities obtained by molecular dynamics simulations of supercritical Ar and compare them with the predictions of the hydrodynamic theory. It is shown that the predicted by the hydrodynamic theory single-exponential shape of the entropy density autocorrelation functions is perfectly reproduced for small wave numbers by the molecular dynamics simulations and permits the calculation of the wavenumber-dependent specific heat at constant pressure. The estimated wavenumber-dependent specific heats at constant volume and pressure, $C_{v}(k)$ and $C_{p}(k)$, are shown to be in the long-wavelength limit in good agreement with the macroscopic experimental values of $C_{v}$ and $C_{p}$ for the studied thermodynamic points of supercritical Ar.
The Radiation Transport Conundrum in Radiation Hydrodynamics
Castor, J I
2005-03-18
The summary of this paper is: (1) The conundrum in the title is whether to treat radiation in the lab frame or the comoving frame in a radiation-hydrodynamic problem; (2) Several of the difficulties are associated with combining a somewhat relativistic treatment of radiation with a non-relativistic treatment of hydrodynamics; (3) The principal problem is a tradeoff between easily obtaining the correct diffusion limit and describing free-streaming radiation with the correct wave speed; (4) The computational problems of the comoving-frame formulation in more than one dimension, and the difficulty of obtaining both exact conservation and full u/c accuracy argue against this method; (5) As the interest in multi-D increases, as well as the power of computers, the lab-frame method is becoming more attractive; and (6) The Monte Carlo method combines the advantages of both lab-frame and comoving-frame approaches, its only disadvantage being cost.
Modeling of textural changes in beef loins subjected to hydrodynamic pressure
Technology Transfer Automated Retrieval System (TEKTRAN)
High hydrodynamic pressure has been considered as a new novel food processing technique to impart favorable textural changes in meat. It is believed that a hydrodynamic pressure wave could be used to tenderize otherwise unacceptably tough cuts of beef, and allow them to be used in more valuable prod...
Fluctuations in relativistic causal hydrodynamics
NASA Astrophysics Data System (ADS)
Kumar, Avdhesh; Bhatt, Jitesh R.; Mishra, Ananta P.
2014-05-01
Formalism to calculate the hydrodynamic fluctuations by applying the Onsager theory to the relativistic Navier-Stokes equation is already known. In this work, we calculate hydrodynamic fluctuations within the framework of the second order hydrodynamics of Müller, Israel and Stewart and its generalization to the third order. We have also calculated the fluctuations for several other causal hydrodynamical equations. We show that the form for the Onsager-coefficients and form of the correlation functions remain the same as those obtained by the relativistic Navier-Stokes equation and do not depend on any specific model of hydrodynamics. Further we numerically investigate evolution of the correlation function using the one dimensional boost-invariant (Bjorken) flow. We compare the correlation functions obtained using the causal hydrodynamics with the correlation function for the relativistic Navier-Stokes equation. We find that the qualitative behavior of the correlation functions remains the same for all the models of the causal hydrodynamics.
Optical monitoring study on estuarine sediment incipient under marine hydrodynamic
NASA Astrophysics Data System (ADS)
Qin, Hao; Li, Shucai; Zhang, Lei
2009-12-01
For the deserted estuary without sediment inflow, ocean hydrodynamic has become the main force for coastal erosion. This paper utilizes wave-tide gauge and current meter to monitor the hydrodynamic within the experimental area and also, turbidity meter is used to conduct indirect monitoring to the sediment concentration (the corresponding relation between the turbidity value and the content of suspended particles in the water is pre-calibrated indoors). Statistical means is adopted to calculate the correlativity between the turbidity and hydropower factors, such as wave height, tide height and flow meter which are determined on site and then the determining factors for sediment incipient are obtained. The conclusion is that the eddy and turbulent flow caused by broken wave constitute the main dynamic factors for the sediment incipient and the incipient velocity mainly comes from the flow rate of the eddy and turbulence resulting from the broken wave.
Optical monitoring study on estuarine sediment incipient under marine hydrodynamic
NASA Astrophysics Data System (ADS)
Qin, Hao; Li, Shucai; Zhang, Lei
2010-03-01
For the deserted estuary without sediment inflow, ocean hydrodynamic has become the main force for coastal erosion. This paper utilizes wave-tide gauge and current meter to monitor the hydrodynamic within the experimental area and also, turbidity meter is used to conduct indirect monitoring to the sediment concentration (the corresponding relation between the turbidity value and the content of suspended particles in the water is pre-calibrated indoors). Statistical means is adopted to calculate the correlativity between the turbidity and hydropower factors, such as wave height, tide height and flow meter which are determined on site and then the determining factors for sediment incipient are obtained. The conclusion is that the eddy and turbulent flow caused by broken wave constitute the main dynamic factors for the sediment incipient and the incipient velocity mainly comes from the flow rate of the eddy and turbulence resulting from the broken wave.
From Field Theory to the Hydrodynamics of Relativistic Superfluids
Stetina, Stephan
2015-01-01
The hydrodynamic description of a superfluid is usually based on a two-fluid picture. In this thesis, basic properties of such a relativistic two-fluid system are derived from the underlying microscopic physics of a complex scalar quantum field theory. To obtain analytic results of all non-dissipative hydrodynamic quantities in terms of field theoretic variables, calculations are first carried out in a low-temperature and weak-coupling approximation. In a second step, the 2-particle-irreducible formalism is applied: This formalism allows for a numerical evaluation of the hydrodynamic parameters for all temperatures below the critical temperature. In addition, a system of two coupled superfluids is studied. As an application, the velocities of first and second sound in the presence of a superflow are calculated. The results show that first (second) sound evolves from a density (temperature) wave at low temperatures to a temperature (density) wave at high temperatures. This role reversal is investigated for ult...
Spin-Electromagnetic Hydrodynamics
Koide, T
2013-01-01
The hydrodynamic model including the spin degree of freedom and the electromagnetic field was discussed. In this derivation, we applied electromagnetism for macroscopic medium proposed by Minkowski. For the equation of motion of spin, we assumed that the hydrodynamic equation of the Pauli equation is reproduced when the many-body effect is neglected. The fluid and spin stress tensors induced by the many-body effect were obtained by employing the algebraic positivity of the entropy production in the framework of linear irreversible thermodynamics. In our model, the effect of the spin-magnetic interaction is absorbed into the magnetic polarization so as to satisfy the momentum and angular momentum conservations. We further compared our result with other existing models.
Relativistic cosmological hydrodynamics
J. Hwang; H. Noh
1997-11-29
We investigate the relativistic cosmological hydrodynamic perturbations. We present the general large scale solutions of the perturbation variables valid for the general sign of three space curvature, the cosmological constant, and generally evolving background equation of state. The large scale evolution is characterized by a conserved gauge invariant quantity which is the same as a perturbed potential (or three-space curvature) in the comoving gauge.
Blaedel, Kenneth L. (Dublin, CA); Davis, Pete J. (Pleasanton, CA); Landram, Charles S. (Livermore, CA)
2000-01-01
A saw having a self-pumped hydrodynamic blade guide or bearing for retaining the saw blade in a centered position in the saw kerf (width of cut made by the saw). The hydrodynamic blade guide or bearing utilizes pockets or grooves incorporated into the sides of the blade. The saw kerf in the workpiece provides the guide or bearing stator surface. Both sides of the blade entrain cutting fluid as the blade enters the kerf in the workpiece, and the trapped fluid provides pressure between the blade and the workpiece as an inverse function of the gap between the blade surface and the workpiece surface. If the blade wanders from the center of the kerf, then one gap will increase and one gap will decrease and the consequent pressure difference between the two sides of the blade will cause the blade to re-center itself in the kerf. Saws using the hydrodynamic blade guide or bearing have particular application in slicing slabs from boules of single crystal materials, for example, as well as for cutting other difficult to saw materials such as ceramics, glass, and brittle composite materials.
Intersections Between Marine Hydrodynamics and Optimal Control Theory
Paul D. Sclavounos
1 Background The fleld of marine hydrodynamics has witnessed remarkable progress over the past 50 years both at the theoretical, experimental and computational fronts. Reliable analytical techniques and computer programs have been developed and are in routine use in practice for the modelling of steady and un- steady ?ows around ships and the interaction of sur- face waves with ?oating
Stonefly nymphs use hydrodynamic cues to discriminate between prey
Barbara L. Peckarsky; R. Stimson Wilcox
1989-01-01
Playback experiments conducted in a Rocky Mountain, USA, stream determined whether predatory stonefly nymphs (Kogotus modestus; Plecoptera: PerlodiMae) used hydrodynamic cues to discriminate prey species from nonprey species. In the laboratory we recorded pressure wave patterns associated with swimming escape behavior of Baetis bicaudatus (Baetidae), the favored mayfly prey species, and those of a nonprey mayfly, Ephemerella infrequens (Ephemerellidae). We
Effect of hydrodynamic pressure processing on chevon quality characteristics
Technology Transfer Automated Retrieval System (TEKTRAN)
Hydrodynamic pressure processing (HDP) technology, which involves exposure of packaged meat to a supersonic shock wave under water created by a small amount of explosive, has been shown to improve meat tenderness, but its effect on chevon tenderness has not been studied so far. The objective of this...
Inactivation and injury of pathogenic bacteria by hydrodynamic pressure treatment
Technology Transfer Automated Retrieval System (TEKTRAN)
Hydrodynamic pressure processing (HDP) is an innovative non-thermal technology developed for improving meat tenderness. The shock waves generated in the HDP process cause significant disruption of myofibrillar proteins in muscle tissue resulting in improved tenderness of various beef cuts. The same ...
Nonlinear Evolution of Hydrodynamical Shear Flows in Two Dimensions
Yoram Lithwick
2007-01-01
We examine how perturbed shear flows evolve in two-dimensional, incompressible, inviscid hydrodynamical fluids, with the ultimate goal of understanding the dynamics of accretion disks. To linear order, vorticity waves are swung around by the background shear, and their velocities are amplified transiently before decaying. It has been speculated that sufficiently amplified modes might couple nonlinearly, leading to turbulence. Here we
A new shock-capturing numerical scheme for ideal hydrodynamics
Feckova, Zuzana
2015-01-01
We present a new algorithm for solving ideal relativistic hydrodynamics based on Godunov method with an exact solution of Riemann problem for an arbitrary equation of state. Standard numerical tests are executed, such as the sound wave propagation and the shock tube problem. Low numerical viscosity and high precision are attained with proper discretization.
A new shock-capturing numerical scheme for ideal hydrodynamics
Zuzana Feckova; Boris Tomasik
2015-01-07
We present a new algorithm for solving ideal relativistic hydrodynamics based on Godunov method with an exact solution of Riemann problem for an arbitrary equation of state. Standard numerical tests are executed, such as the sound wave propagation and the shock tube problem. Low numerical viscosity and high precision are attained with proper discretization.
A new shock-capturing numerical scheme for ideal hydrodynamics
NASA Astrophysics Data System (ADS)
Fecková, Z.; Tomášik, B.
2015-05-01
We present a new algorithm for solving ideal relativistic hydrodynamics based on Godunov method with an exact solution of Riemann problem for an arbitrary equation of state. Standard numerical tests are executed, such as the sound wave propagation and the shock tube problem. Low numerical viscosity and high precision are attained with proper discretization.
Hydrodynamic damping contributions for an advanced floating production system design
D. T. Brown; J. Fang
1996-01-01
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
NASA Astrophysics Data System (ADS)
Wang, Xianping; Yin, Cheng; Sun, Jingjing; Li, Honggen; Sang, Minghuang; Yuan, Wen; Cao, Zhuangqi; Huang, Meizhen
2013-10-01
We report on the observation of all-optically tunable Goos-Hänchen (GH) shift in a symmetrical metal-cladding waveguide, whose guiding layer is filled with the water-based ferrofluid. The strong dependence of the GH shift and its switching time on the control beam power is suggested to be arising from the light-induced periodic-like microstructure transitions of ferrofluid in virtue of the competition between the optical trapping effect and the Soret effect. The indirect evidence of our qualitative hypothesis is given. The presented tunability of GH shift may have potential applications in optical switching and sensing.
Computational Naval Ship Hydrodynamics
Kyle A. Brucker; Douglas G. Dommermuth; Thomas T. O'Shea; Dick K. P. Yue; Kelli Hendrickson; Gabriel Weymouth
2010-01-01
The primary purpose of our research efforts is to improve naval design and detection capabilities. Our current research efforts leverage high performance computing (HPC) resources to perform high-resolution numerical simulations with hundreds-of-millions to billions of unknowns to study wave breaking behind a transom stern, wave-impact loading, the generation of spray by high-speed planing craft, air entrainment by plunging breaking waves,
Fast Lattice Boltzmann Solver for Relativistic Hydrodynamics
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
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.
Hydrodynamic phase locking of swimming microorganisms.
Elfring, Gwynn J; Lauga, Eric
2009-08-21
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 coswimming cells depends only on the nature of this geometrical asymmetry, and microorganisms can phase lock into conformations which minimize or maximize energy dissipation. PMID:19792766
Hydrodynamic Phase Locking of Swimming Microorganisms
NASA Astrophysics Data System (ADS)
Elfring, Gwynn J.; Lauga, Eric
2009-08-01
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 coswimming cells depends only on the nature of this geometrical asymmetry, and microorganisms can phase lock into conformations which minimize or maximize energy dissipation.
Fast lattice Boltzmann solver for relativistic hydrodynamics.
Mendoza, M; Boghosian, B M; Herrmann, H J; Succi, S
2010-07-01
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
Postexplosion hydrodynamics of supernovae in red supergiants
NASA Technical Reports Server (NTRS)
Herant, Marc; Woosley, S. E.
1994-01-01
Shock propagation, mixing, and clumping are studied in the explosion of red supergiants as Type II supernovae using a two-dimensional smooth particle hydrodynamic (SPH) code. We show that extensive Rayleigh-Talor instabilities develop in the ejecta in the wake of the reverse shock wave. In all cases, the shell structure of the progenitor is obliterated to leave a clumpy, well-mixed supernova remnant. However, the occurrence of mass loss during the lifetime of the progenitor can significantly reduce the amount of mixing. These results are independent of the Type II supernova explosion mechanism.
Hydrodynamic force characteristics in the splash zone
Daliri, M.R.; Haritos, N. [Univ. of Melbourne, Parkville, Victoria (Australia). Dept. of Civil and Environmental Engineering
1996-12-31
A comprehensive experimental study concerned with the hydrodynamic force characteristics of both rigid and compliant surface piercing cylinders, with a major focus on the local nature of these characteristics as realized in the splash zone and in the fully submerged zone immediately below this region, has been in progress at the University of Melbourne for the last three years. This paper concentrates on a portion of this study associated with uni-directional regular wave inputs with wave steepness (H/{lambda}) in the range 0.0005--0.1580 and Keulegan-Carpenter (KC) numbers in the range 2--15 which encompasses inertia force dominant (KC<5) to drag force significant conditions (5
Hydrodynamic Simulations of Giant Impacts
NASA Astrophysics Data System (ADS)
Reinhardt, Christian; Stadel, Joachim
2013-07-01
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.
On the self-assembly of net-like nanostructures in ferrofluids
NASA Astrophysics Data System (ADS)
Elkady, Ashraf S.; Iskakova, Larisa; Zubarev, Andrey
2015-06-01
Understanding the physical forces that govern nanoparticles self-assembly is central to the ability to engineer super-nanostructures for advanced nanotechnology applications. Magnetic force represents one of such important forces that is responsible for structural transformations and condensation in ferrofluids (FF). In this work, we study internal structural transformations in FF in the absence of external magnetic field by introducing the first direct statistical model that takes into account formation of linear chains, Y-forks and net-like nanostructures. The results show that, in agreement with experiments, when the concentration of the magnetic nanoparticles and their magnetic interaction energy are small enough, majority of the particles are united in individual linear chains. But, when these parameters exceed some threshold magnitude, the main particles population switches to net-like nanostructures. These results highlight the importance of magnetic dipole interactions in the absence of external magnetic field, and their essential role in the bottom-up construction of hierarchical nano-architectures of viable fundamental and practical implications.
Enhanced magneto-optic activity of magnetite-based ferrofluids subjected to gamma irradiation
NASA Astrophysics Data System (ADS)
Devi, Manasi; Das, Rupali; Mohanta, Dambarudhar; Baruah, Kishor Kumar; Saha, Abhijit
2012-03-01
We report here the effect of ?-irradiation on the particle size and size distribution dependent spectroscopic and magneto-optic properties of ferrofluids, synthesized by a co-precipitation method. The X-ray diffraction (XRD) study exhibits magnetite (Fe3O4) phase of the particles while electron microscopic and dynamic light scattering (DLS) studies have predicted particle growth upon ?-irradiation. Further, Fourier transform infrared (FT-IR) spectroscopy studies ensured that no dissociation has occurred due to irradiation effect. As a consequence of magneto-optic behavior reflected in the Faraday rotation (FR) measurement, the Verdet constant increased from a value of 0.64×10-2 for the pristine sample to 5.6×10-2 deg/Gauss-cm for the sample irradiated with the highest dose (2.635 kGy). The substantial enhancement in the FR is assigned to the improvement in associated chaining effect owing to adequate particle growth where an increased stoichiometry variation of Fe2+/Fe3+ is assured.
Modeling multiphase flow using fluctuating hydrodynamics.
Chaudhri, Anuj; Bell, John B; Garcia, Alejandro L; Donev, Aleksandar
2014-09-01
Fluctuating hydrodynamics provides a model for fluids at mesoscopic scales where thermal fluctuations can have a significant impact on the behavior of the system. Here we investigate a model for fluctuating hydrodynamics of a single-component, multiphase flow in the neighborhood of the critical point. The system is modeled using a compressible flow formulation with a van der Waals equation of state, incorporating a Korteweg stress term to treat interfacial tension. We present a numerical algorithm for modeling this system based on an extension of algorithms developed for fluctuating hydrodynamics for ideal fluids. The scheme is validated by comparison of measured structure factors and capillary wave spectra with equilibrium theory. We also present several nonequilibrium examples to illustrate the capability of the algorithm to model multiphase fluid phenomena in a neighborhood of the critical point. These examples include a study of the impact of fluctuations on the spinodal decomposition following a rapid quench, as well as the piston effect in a cavity with supercooled walls. The conclusion in both cases is that thermal fluctuations affect the size and growth of the domains in off-critical quenches. PMID:25314536
Modeling multiphase flow using fluctuating hydrodynamics
NASA Astrophysics Data System (ADS)
Chaudhri, Anuj; Bell, John B.; Garcia, Alejandro L.; Donev, Aleksandar
2014-09-01
Fluctuating hydrodynamics provides a model for fluids at mesoscopic scales where thermal fluctuations can have a significant impact on the behavior of the system. Here we investigate a model for fluctuating hydrodynamics of a single-component, multiphase flow in the neighborhood of the critical point. The system is modeled using a compressible flow formulation with a van der Waals equation of state, incorporating a Korteweg stress term to treat interfacial tension. We present a numerical algorithm for modeling this system based on an extension of algorithms developed for fluctuating hydrodynamics for ideal fluids. The scheme is validated by comparison of measured structure factors and capillary wave spectra with equilibrium theory. We also present several nonequilibrium examples to illustrate the capability of the algorithm to model multiphase fluid phenomena in a neighborhood of the critical point. These examples include a study of the impact of fluctuations on the spinodal decomposition following a rapid quench, as well as the piston effect in a cavity with supercooled walls. The conclusion in both cases is that thermal fluctuations affect the size and growth of the domains in off-critical quenches.
EUNHA: a New Cosmological Hydrodynamic Simulation Code
NASA Astrophysics Data System (ADS)
Shin, Jihye; Kim, Juhan; Kim, Sungsoo S.; Park, Changbom
2014-06-01
We develop a parallel cosmological hydrodynamic simulation code designed for the study of formation and evolution of cosmological structures. The gravitational force is calculated using the TreePM method and the hydrodynamics is implemented based on the smoothed particle hydrodynamics. The initial displacement and velocity of simulation particles are calculated according to second-order Lagrangian perturbation theory using the power spectra of dark matter and baryonic matter. The initial background temperature is given by Recfast and the temperature fluctuations at the initial particle position are assigned according to the adiabatic model. We use a time-limiter scheme over the individual time steps to capture shock-fronts and to ease the time-step tension between the shock and preshock particles. We also include the astrophysical gas processes of radiative heating/cooling, star formation, metal enrichment, and supernova feedback. We test the code in several standard cases such as one-dimensional Riemann problems, Kelvin-Helmholtz, and Sedov blast wave instability. Star formation on the galactic disk is investigated to check whether the Schmidt-Kennicutt relation is properly recovered. We also study global star formation history at different simulation resolutions and compare them with observations.
Topics in Fluctuating Nonlinear Hydrodynamics
Scott Thomas Milner
1986-01-01
Models of fluctuating nonlinear hydrodynamics have enjoyed much success in explaining the effects of long-wavelength fluctuations in diverse hydrodynamic systems. This thesis explores two such problems; in both, the body of hydrodynamic assumptions powerfully constrains the predictions of a well-posed theory. We first examine the effects of layer fluctuations in smectic-A liquid crystals. The static theory (introduced by Grinstein and
Latest developments in anisotropic hydrodynamics
Tinti, Leonardo
2015-01-01
We discuss the leading order of anisotropic hydrodynamics expansion. It has already been shown that in the (0+1) and (1+1)-dimensional cases it is consistent with the second order viscous hydrodynamics, and it provides a striking agreement with the exact solutions of the Boltzmann equation. Quite recently, a new set of equations has been proposed for the leading order of anisotropic hydrodynamics, which is consistent with the second order viscous hydrodynamics in the most general (3+1)-dimensional case, and does not require a next-to-leading treatment for describing pressure anisotropies in the transverse plane.
Highly anisotropic dissipative hydrodynamics
NASA Astrophysics Data System (ADS)
Strickland, Michael
2013-10-01
The quark gluon plasma generated in ultrarelativistic heavy ion collisions may possess sizable momentum-space anisotropies that cause the longitudinal and transverse pressures in the local rest frame to be significantly different. We review recent attempts to derive a dynamical framework that can reliably describe systems that possess a high degree of momentum-space anisotropy. The dynamical framework that has been developed can describe the evolution of the quark gluon plasma ranging from the longitudinal free-streaming limit to the ideal hydrodynamical limit.
R. Tackett; C. Sudakar; R. Naik; G. Lawes; C. Rablau; P. P. Vaishnava
2008-01-01
CoxFe3?xO4 (0?x?0.10) nanoparticles coated with tetramethyl ammonium hydroxide as a surfactant were synthesized by a co-precipitation technique. The Fe:Co ratio was tuned up to x=0.10 by controlling the Co2+ concentration during synthesis. The mean particle size, determined by transmission electron microscopy, ranged between 15±4 and 18±4nm. The superparamagnetic blocking temperature and the magnetocrystalline anisotropy constant of the ferrofluids, determined using
The Quantum Hydrodynamic Description of Tunneling
Kendrick, Brian K. [Los Alamos National Laboratory
2012-06-15
The quantum hydrodynamic approach is based on the de Broglie-Bohm formulation of quantum mechanics. The resulting fluid-like equations of motion describe the flow of probability and an accurate solution to these equations is equivalent to solving the time-dependent Schroedinger equation. Furthermore, the hydrodynamic approach provides new insight into the mechanisms as well as an alternative computational approach for treating tunneling phenomena. New concepts include well-defined 'quantum trajectories', 'quantum potential', and 'quantum force' all of which have classical analogues. The quantum potential and its associated force give rise to all quantum mechanical effects such as zero point energy, tunneling, and interference. A new numerical approach called the Iterative Finite Difference Method (IFDM) will be discussed. The IFDM is used to solve the set of non-linear coupled hydrodynamic equations. It is 2nd-order accurate in both space and time and exhibits exponential convergence with respect to the iteration count. The stability and computational efficiency of the IFDM is significantly improved by using a 'smart' Eulerian grid which has the same computational advantages as a Lagrangian or Arbitrary Lagrangian Eulerian (ALE) grid. The IFDM is also capable of treating anharmonic potentials. Example calculations using the IFDM will be presented which include: a one-dimensional Gaussian wave packet tunneling through an Eckart barrier, a one-dimensional bound-state Morse oscillator, and a two-dimensional (2D) model collinear reaction using an anharmonic potential energy surface. Approximate treatments of the quantum hydrodynamic equations will also be discussed which could allow scaling of the calculations to hundreds of degrees of freedom which is important for treating tunneling phenomena in condensed phase systems.
Superfluid Hydrodynamics in Neutron Stars
NASA Astrophysics Data System (ADS)
Mendell, Gregory Allen
Superfluidity is predicted to exist in neutron stars. Superfluid effects on the dynamics of these stars have not been investigated in depth in the past. In this thesis, superfluid hydrodynamics in neutron stars is developed extensively. It is shown that superfluidity has important effects on the oscillation modes, dissipative properties, and stability of these stars. Very general hydrodynamic equations are derived which describe superfluid mixtures. The fluid equations are coupled to the electromagnetic and gravitational fields. Forces due to the quantized vortices of the superfluids are also included. It is shown that new vorticity-preserving forces can be introduced into the superfluid-mixture equations. The equations are then adapted to describe neutron stars composed primarily of superfluid neutrons, superconducting protons, and degenerate electrons and muons. The set of equations is closed by constructing a model of the total energy density and using it to express the dependent variables in terms of the independent variables. The low-frequency long-wavelength limit of the equations is determined. The results can be used to study superfluid effects on the global oscillations of neutron stars. The equations are generalized further to include dissipative effects. Most important is a form of dissipation known as mutual friction, which occurs only in superfluids. In neutron stars, mutual friction is due to electron scattering off the neutron and proton vortices. An energy functional is constructed which determines the damping time of a mode due to the various forms of dissipation, including mutual friction. Plane-wave solutions are found to the equations. Mutual friction is shown to be the dominant form of dissipation in neutron stars for sufficiently large angular velocities. Gravitational radiation tends to make all rotating stars unstable, while internal dissipation tends to counteract this instability. This, gravitational radiation can limit the maximum angular velocity of neutron stars. The most important conclusion of this thesis is that mutual friction completely suppresses the gravitational-radiation instability in rotating neutron stars cooler than the superfluid-transition temperature.
Klein-Gordon Equation in Hydrodynamical Form
Cheuk-Yin Wong
2010-12-22
We follow and modify the Feshbach-Villars formalism by separating the Klein-Gordon equation into two coupled time-dependent Schroedinger equations for particle and antiparticle wave function components with positive probability densities. We find that the equation of motion for the probability densities is in the form of relativistic hydrodynamics where various forces have their classical counterparts, with the additional element of the quantum stress tensor that depends on the derivatives of the amplitude of the wave function. We derive the equation of motion for the Wigner function and we find that its approximate classical weak-field limit coincides with the equation of motion for the distribution function in the collisionless kinetic theory.
Load responsive hydrodynamic bearing
Kalsi, Manmohan S. (Houston, TX); Somogyi, Dezso (Sugar Land, TX); Dietle, Lannie L. (Stafford, TX)
2002-01-01
A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.
Efficient calculation of hydrodynamic properties of OWC-type devices
Evans, D.V.; Porter, R. [Univ. of Bristol (United Kingdom). School of Mathematics
1996-12-31
A simple model of an OWC-type wave-energy device is used to illustrate a powerful accurate method for computing the hydrodynamic coefficients when sharp edges are present. The device consists simply of a vertical partially-immersed circular cylinder open at either end, with power being extracted by constricting the flow of the air trapped in the cylinder above the internal free surface. The method involves the use of the theory of pressure distributions for OWC devices and the hydrodynamical coefficients are computed using an accurate Galerkin method which preserves the reciprocity relations.
Active Carbon and Oxygen Shell Burning Hydrodynamics
Casey Meakin; David Arnett
2006-01-16
We have simulated 2.5$\\times10^3$ s of the late evolution of a $23 \\rm M_\\odot$ star with full hydrodynamic behavior. We present the first simulations of a multiple-shell burning epoch, including the concurrent evolution and interaction of an oxygen and carbon burning shell. In addition, we have evolved a 3D model of the oxygen burning shell to sufficiently long times (300 s) to begin to assess the adequacy of the 2D approximation. We summarize striking new results: (1) strong interactions occur between active carbon and oxygen burning shells, (2) hydrodynamic wave motions in nonconvective regions, generated at the convective-radiative boundaries, are energetically important in both 2D and 3D with important consequences for compositional mixing, and (3) a spectrum of mixed p- and g-modes are unambiguously identified with corresponding adiabatic waves in these computational domains. We find that 2D convective motions are exaggerated relative to 3D because of vortex instability in 3D. We discuss the implications for supernova progenitor evolution and symmetry breaking in core collapse.
Fasih Ramandi, Negin; Shemirani, Farzaneh
2015-01-01
For the first time, a selective ionic liquid ferrofluid has been used in dispersive solid phase extraction (IL-FF-D-SPE) for simultaneous preconcentration and separation of lead and cadmium in milk and biological samples combined with flame atomic absorption spectrometry. To improve the selectivity of the ionic liquid ferrofluid, the surface of TiO2 nanoparticles with a magnetic core as sorbent was modified by loading 1-(2-pyridylazo)-2-naphtol. Due to the rapid injection of an appropriate amount of ionic liquid ferrofluid into the aqueous sample by a syringe, extraction can be achieved within a few seconds. In addition, based on the attraction of the ionic liquid ferrofluid to a magnet, no centrifugation step is needed for phase separation. The experimental parameters of IL-FF-D-SPE were optimized using a Box-Behnken design (BBD) after a Plackett-Burman screening design. Under the optimum conditions, the relative standard deviations of 2.2% and 2.4% were obtained for lead and cadmium, respectively (n=7). The limit of detections were 1.21 µg L(-1) for Pb(II) and 0.21 µg L(-1) for Cd(II). The preconcentration factors were 250 for lead and 200 for cadmium and the maximum adsorption capacities of the sorbent were 11.18 and 9.34 mg g(-1) for lead and cadmium, respectively. PMID:25281121
Algorithm refinement for fluctuating hydrodynamics
This paper introduces an adaptive mesh and algorithm refinement method for fluctuating hydrodynamics, specifically for the non-hydrodynamic (kinetic) time scales. 1 Introduction Adaptive mesh refinement (AMR for mesh refinement may change over time, so methods have been developed to adaptively identify
General formulation of transverse hydrodynamics
Radoslaw Ryblewski; Wojciech Florkowski
2008-04-15
General formulation of hydrodynamics describing transversally thermalized matter created at the early stages of ultra-relativistic heavy-ion collisions is presented. Similarities and differences with the standard three-dimensionally thermalized relativistic hydrodynamics are discussed. The role of the conservation laws as well as the thermodynamic consistency of two-dimensional thermodynamic variables characterizing transversally thermalized matter is emphasized.
Gorban, Alexander N.
in balance equations for density, momentum, and energy. Retaining the first order term (e) in the latter of the acoustic spectrum in the short-wave domain is obtained. [S0031-9007(96)00642-4] PACS numbers: 47.10.+g, 05- dynamics violate the basic physics behind the Boltzmann equation. Namely, sufficiently short acoustic waves
NASA Astrophysics Data System (ADS)
Vales-Pinzón, C.; Alvarado-Gil, J. J.; Medina-Esquivel, R.; Martínez-Torres, P.
2014-11-01
Magneto-optic phenomena in ferrofluids have been shown to be related to the formation of chain structures, due to the arrangement of the ferromagnetic particles, induced by an applied magnetic field. In this work, the effects on transmission of polarized light due to anisotropic effects induced by an external magnetic field in ferrofluids with carbon nanotubes are studied. The time response of the system presents two well defined stages, in the first one, which is very short, the fluid behaves as a polarizer. In contrast in the second stage, the effects of light transmission dominate. In this stage the transmitted light intensity grows with time and after a long time reaches a constant stable value. It is shown that these phenomena depend on the carbon nanotubes concentration as well as on the strength of the applied magnetic field. Using a simple model that considers a chain-like structure formation, it is possible to determine the rate of agglomeration of the formed structures and the attenuation coefficient of the transmitted light. The formation of nanostructures leads to variation in the transmitted light, depending on the polarization of the incident light. These magnetic nanostructures can find numerous applications in nanotechnology, optical devices and medicine.
Jain, Dr Nirmesh [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
The optical magnetic chaining technique (MCT) developed by Leal-Calderon, Bibette and co-workers in the 1990 s allows precise measurements of force profiles between droplets in monodisperse ferrofluid emulsions. However, the method lacks an in-situ determination of droplet size and therefore requires the combination of separately acquired measurements of droplet chain periodicity versus an applied magnetic field from optical Bragg scattering and droplet diameter inferred from dynamic light scattering (DLS) to recover surface force-distance profiles between the colloidal particles. Compound refractive lens (CRL) focussed small-angle scattering (SANS) MCT should result in more consistent measurements of droplet size (form factor measurements in the absence of field) and droplet chaining period (from structure factor peaks when the magnetic field is applied); and, with access to shorter length scales, extend force measurements to closer approaches than possible by optical measurements. We report on CRL-SANS measurements of monodisperse ferrofluid emulsion droplets aligned in straight chains by an applied field perpendicular to the incident beam direction. Analysis of the scattering from the closely spaced droplets required algorithms that carefully treated resolution and its effect on mean scattering vector magnitudes in order to determine droplet size and chain periods to sufficient accuracy. At lower applied fields scattering patterns indicate structural correlations transverse to the magnetic field direction due to the formation of intermediate structures in early chain growth.
The relativistic Rindler hydrodynamics
NASA Astrophysics Data System (ADS)
Eling, Christopher; Meyer, Adiel; Oz, Yaron
2012-05-01
We consider a (d + 2)-dimensional class of Lorentzian geometries holograph- ically dual to a relativistic fluid flow in (d + 1) dimensions. The fluid is defined on a (d + 1)-dimensional time-like surface which is embedded in the (d + 2)-dimensional bulk space-time and equipped with a flat intrinsic metric. We find two types of geometries that are solutions to the vacuum Einstein equations: the Rindler metric and the Taub plane symmetric vacuum. These correspond to dual perfect fluids with vanishing and negative energy densities respectively. While the Rindler geometry is characterized by a causal hori- zon, the Taub geometry has a timelike naked singularity, indicating pathological behavior. We construct the Rindler hydrodynamics up to second order in derivatives of the fluid variables and show the positivity of its entropy current divergence.
Synchronization and hydrodynamic interactions
NASA Astrophysics Data System (ADS)
Powers, Thomas; Qian, Bian; Breuer, Kenneth
2008-03-01
Cilia and flagella commonly beat in a coordinated manner. Examples include the flagella that Volvox colonies use to move, the cilia that sweep foreign particles up out of the human airway, and the nodal cilia that set up the flow that determines the left-right axis in developing vertebrate embryos. In this talk we present an experimental study of how hydrodynamic interactions can lead to coordination in a simple idealized system: two nearby paddles driven with fixed torques in a highly viscous fluid. The paddles attain a synchronized state in which they rotate together with a phase difference of 90 degrees. We discuss how synchronization depends on system parameters and present numerical calculations using the method of regularized stokeslets.
Hydrodynamic effects on coalescence.
Dimiduk, Thomas G.; Bourdon, Christopher Jay; Grillet, Anne Mary; Baer, Thomas A.; de Boer, Maarten Pieter; Loewenberg, Michael (Yale University, New Haven, CT); Gorby, Allen D.; Brooks, Carlton, F.
2006-10-01
The goal of this project was to design, build and test novel diagnostics to probe the effect of hydrodynamic forces on coalescence dynamics. Our investigation focused on how a drop coalesces onto a flat surface which is analogous to two drops coalescing, but more amenable to precise experimental measurements. We designed and built a flow cell to create an axisymmetric compression flow which brings a drop onto a flat surface. A computer-controlled system manipulates the flow to steer the drop and maintain a symmetric flow. Particle image velocimetry was performed to confirm that the control system was delivering a well conditioned flow. To examine the dynamics of the coalescence, we implemented an interferometry capability to measure the drainage of the thin film between the drop and the surface during the coalescence process. A semi-automated analysis routine was developed which converts the dynamic interferogram series into drop shape evolution data.
Truong, Melanie Khanh Phuong
2012-10-19
during passage of the waves. The experimental measurements were able to describe the wave transformations over the marsh segments. The influence of coastal wetlands was identified to affect the hydrodynamic process and reduce the total wave energy which...
Anisotropic hydrodynamics: Motivation and methodology
NASA Astrophysics Data System (ADS)
Strickland, Michael
2014-06-01
In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can be made around an anisotropic background, and the resulting dynamical framework has been dubbed “anisotropic hydrodynamics”. I also discuss expectations for the degree of momentum-space anisotropy of the quark-gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches.
Hydrodynamic response of viscous fluids under seismic excitation
Ma, D.C.
1993-08-01
Hydrodynamic response of liquid-tank systems, such as reactor vessels, spent-fuel pools and liquid storage tanks have been studied extensively in the last decade (Chang et al. 1988; Ma et al. 1991). However, most of the studies are conducted with the assumption of an inviscid fluid. In recent years, the hydrodynamic response of viscous fluids has received increasing attention in high level waste storage tanks containing viscous waste material. This paper presents a numerical study on the hydrodynamic response of viscous fluids in a large 2-D fluid-tank system under seismic excitation. Hydrodynamic responses (i.e. sloshing wave height, fluid pressures, shear stress, etc.) are calculated for a fluid with various viscosities. Four fluid viscosities are considered. They are 1 cp, 120 cp, 1,000 cp and 12,000 cp (1 cp = 1.45 {times} 10{sup {minus}7} lb-sec/in{sup 2}). Note that the liquid sodium of the Liquid-Metal Reactor (LMR) reactor has a viscosity of 1.38 {times} 10{sup {minus}5} lb-sec/in{sup 2} (about 95 cp) at an operational temperature of 900{degree}F. Section 2 describes the pertinent features of the mathematical model. In Section 3, the fundamental sloshing phenomena of viscous fluid are examined. Sloshing wave height and shear stress for fluid with different viscosities are compared. The conclusions are given in Section 4.
Hydrodynamic theories of relaxation in liquids
J. A. Montgomery Jr.
1978-01-01
Molecular hydrodynamics is used to theoretically describe recent computer experiments on rough and partially rough sphere fluids. The long time behavior of hydrodynamic AVCF (angular velocity correlation function) is discussed. A theory of coupled translational and rotational relaxation in solution including the effects of hydrodynamic interaction is presented. The translational, translational-rotational diffusion tensors are computed using the method of hydrodynamic
Frictionless Random Dynamics: Hydrodynamical Formalism
Piotr Garbaczewski
We investigate an undamped random phase-space dynamics in deterministic external force fields (conservative and magnetic ones). By employing the hydrodynamical formalism for those stochastic processes we analyze microscopic kinetic-type \\
Perfusion effects and hydrodynamics.
Peattie, Robert A; Fisher, Robert J
2007-01-01
Biological processes within living systems are significantly influenced by the motion of the liquids and gases to which those tissues are exposed. Accordingly, tissue engineers must not only understand hydrodynamic phenomena, but also appreciate the vital role of those phenomena in cellular and physiologic processes both in vitro and in vivo. In particular, understanding the fundamental principles of fluid flow underlying perfusion effects in the organ-level internal environment and their relation to the cellular microenvironment is essential to successfully mimicking tissue behavior. In this work, the major principles of hemodynamic flow and transport are summarized, to provide readers with a physical understanding of these important issues. In particular, since quantifying hemodynamic events through experiments can require expensive and invasive techniques, the benefits that can be derived from the use of computational fluid dynamics (CFD) packages and neural networking (NN) models are stressed. A capstone illustration based on analysis of the hemodynamics of aortic aneurysms is presented as a representative example of this approach, to stress the importance of tissue responses to flow-induced events. PMID:17195462
NASA Astrophysics Data System (ADS)
Kolb, Peter
2002-04-01
A wealth of low pT observables has been extracted from RHIC's year 2000 run with Au nuclei colliding at energies of 130 GeV per nucleon [1]. We summarize the indications given by the experimental particle spectra, their slope parameters, and anisotropies in the case of non-central collisions (elliptic flow), which suggest that the amount of transverse flow at RHIC is strongly increased compared to experiments at lower beam energies. In fact, we find that rescattering in the created fireball is strong enough that flow observables coincide with results given by an ideal hydrodynamic expansion [2]. This indicates that local thermal equilibrium is established at very short timescales after the collision with temperatures reaching well above the predicted QCD phase transition temperature - even in non-central collisions. We discuss the limitations and shortcomings of the idealized approach and give an outlook and expectations for results from the recent run at 200 AGeV. References: [1] Proceedings of 15th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions, 2001, Nucl. Phys. A, in press; Publications by the BRAHMS-, PHENIX-, PHOBOS-, and STAR-Collaborations. [2] P.F. Kolb et al., PLB 500 (2001) 232; P. Huovinen et al., PLB 503 (2001) 58; P.F. Kolb et al., NPA 696 (2001) 197.
Hydrodynamics of micropipette aspiration.
Drury, J L; Dembo, M
1999-01-01
The dynamics of human neutrophils during micropipette aspiration are frequently analyzed by approximating these cells as simple slippery droplets of viscous fluid. Here, we present computations that reveal the detailed predictions of the simplest and most idealized case of such a scheme; namely, the case where the fluid of the droplet is homogeneous and Newtonian, and the surface tension of the droplet is constant. We have investigated the behavior of this model as a function of surface tension, droplet radius, viscosity, aspiration pressure, and pipette radius. In addition, we have tabulated a dimensionless factor, M, which can be utilized to calculate the apparent viscosity of the slippery droplet. Computations were carried out using a low Reynolds number hydrodynamics transport code based on the finite-element method. Although idealized and simplistic, we find that the slippery droplet model predicts many observed features of neutrophil aspiration. However, there are certain features that are not observed in neutrophils. In particular, the model predicts dilation of the membrane past the point of being continuous, as well as a reentrant jet at high aspiration pressures. PMID:9876128
A hybrid Godunov method for radiation hydrodynamics
Sekora, Michael D., E-mail: sekora@math.princeton.ed [Program in Applied and Computational Mathematics, Princeton University, Princeton, NJ 08544 (United States); Stone, James M. [Program in Applied and Computational Mathematics, Princeton University, Princeton, NJ 08544 (United States); Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
2010-09-20
From a mathematical perspective, radiation hydrodynamics can be thought of as a system of hyperbolic balance laws with dual multiscale behavior (multiscale behavior associated with the hyperbolic wave speeds as well as multiscale behavior associated with source term relaxation). With this outlook in mind, this paper presents a hybrid Godunov method for one-dimensional radiation hydrodynamics that is uniformly well behaved from the photon free streaming (hyperbolic) limit through the weak equilibrium diffusion (parabolic) limit and to the strong equilibrium diffusion (hyperbolic) limit. Moreover, one finds that the technique preserves certain asymptotic limits. The method incorporates a backward Euler upwinding scheme for the radiation energy density E{sub r} and flux F{sub r} as well as a modified Godunov scheme for the material density {rho}, momentum density m, and energy density E. The backward Euler upwinding scheme is first-order accurate and uses an implicit HLLE flux function to temporally advance the radiation components according to the material flow scale. The modified Godunov scheme is second-order accurate and directly couples stiff source term effects to the hyperbolic structure of the system of balance laws. This Godunov technique is composed of a predictor step that is based on Duhamel's principle and a corrector step that is based on Picard iteration. The Godunov scheme is explicit on the material flow scale but is unsplit and fully couples matter and radiation without invoking a diffusion-type approximation for radiation hydrodynamics. This technique derives from earlier work by Miniati and Colella (2007) . Numerical tests demonstrate that the method is stable, robust, and accurate across various parameter regimes.
Triangle Anomalies, Thermodynamics, and Hydrodynamics
Kristan Jensen
2012-04-11
We consider 3+1-dimensional fluids with U(1)^3 anomalies. We use Ward identities to constrain low-momentum Euclidean correlation functions and obtain differential equations that relate two and three-point functions. The solution to those equations yields, among other things, the chiral magnetic conductivity. We then compute zero-frequency functions in hydrodynamics and show that the consistency of the hydrodynamic theory also fixes the anomaly-induced conductivities.
Eightfold Classification of Hydrodynamic Dissipation.
Haehl, Felix M; Loganayagam, R; Rangamani, Mukund
2015-05-22
We provide a complete characterization of hydrodynamic transport consistent with the second law of thermodynamics at arbitrary orders in the gradient expansion. A key ingredient in facilitating this analysis is the notion of adiabatic hydrodynamics, which enables isolation of the genuinely dissipative parts of transport. We demonstrate that most transport is adiabatic. Furthermore, in the dissipative part, only terms at the leading order in gradient expansion are constrained to be sign definite by the second law (as has been derived before). PMID:26047219
Eightfold Classification of Hydrodynamic Dissipation
NASA Astrophysics Data System (ADS)
Haehl, Felix M.; Loganayagam, R.; Rangamani, Mukund
2015-05-01
We provide a complete characterization of hydrodynamic transport consistent with the second law of thermodynamics at arbitrary orders in the gradient expansion. A key ingredient in facilitating this analysis is the notion of adiabatic hydrodynamics, which enables isolation of the genuinely dissipative parts of transport. We demonstrate that most transport is adiabatic. Furthermore, in the dissipative part, only terms at the leading order in gradient expansion are constrained to be sign definite by the second law (as has been derived before).
Purely hydrodynamic origin for swarming of swimming particles
Norihiro Oyama; John Jairo Molina; Ryoichi Yamamoto
2015-06-04
Understanding the process of group formation, from individual dynamics to collective motion, is a key issue in biology. However, we still do not fully understand the underlying mechanisms behind the complex collective behaviours seen even in very simple systems, such as crawling cells or swimming bacteria. In this work, three-dimensional simulations with fully resolved hydrodynamics are performed to study the collective motion of model swimming particles in confinement. We show that certain swimming mechanisms can lead to travelling wave-like collective motion even without any direct alignment mechanism. It is also shown that by varying the swimming mechanism, this collective motion can be suppressed, contrary to the perception that hydrodynamic effects are completely screened. From an analysis of bulk systems, it is shown that this travelling wave-like motion, which can be characterized as a pseudo-acoustic mode, is mainly due to the intrinsic property of the swimmers.
Vegetation Hydrodynamics - Recent Developments and Future Challenges
NASA Astrophysics Data System (ADS)
Nepf, H. M.
2014-12-01
For over a century vegetation has been removed from channels and coastal zones to facilitate navigation and development. In recent decades, however, we have recognized the ecologic and economic benefits of aquatic vegetation. It buffers against coastal eutrophication, damps waves and coastal storm surge, provides habitat, inhibits bank erosion, and provides significant carbon storage. The management of watersheds and coastal zones has turned from vegetation removal to restoration. In the past 20 years, the study of vegetation hydrodynamics has accelerated to meet the need to understand feedbacks between vegetation, flow and sediment transport. This presentation will describe key features of vegetation hydrodynamics, first at the meadow scale and then at the scale of individual patches, examining how vegetation density and meadow (or patch) morphology impact flow, with subsequent implications for sediment fate. Finally, the talk highlights differences in turbulence generation between bare and vegetated beds that may limit the transfer of open channel sediment transport models to vegetated channels, creating the future challenge of defining sediment transport models appropriate for vegetated regions.
Multiscale temporal integrators for fluctuating hydrodynamics.
Delong, Steven; Sun, Yifei; Griffith, Boyce E; Vanden-Eijnden, Eric; Donev, Aleksandar
2014-12-01
Following on our previous work [S. Delong, B. E. Griffith, E. Vanden-Eijnden, and A. Donev, Phys. Rev. E 87, 033302 (2013)], we develop temporal integrators for solving Langevin stochastic differential equations that arise in fluctuating hydrodynamics. Our simple predictor-corrector schemes add fluctuations to standard second-order deterministic solvers in a way that maintains second-order weak accuracy for linearized fluctuating hydrodynamics. We construct a general class of schemes and recommend two specific schemes: an explicit midpoint method and an implicit trapezoidal method. We also construct predictor-corrector methods for integrating the overdamped limit of systems of equations with a fast and slow variable in the limit of infinite separation of the fast and slow time scales. We propose using random finite differences to approximate some of the stochastic drift terms that arise because of the kinetic multiplicative noise in the limiting dynamics. We illustrate our integrators on two applications involving the development of giant nonequilibrium concentration fluctuations in diffusively mixing fluids. We first study the development of giant fluctuations in recent experiments performed in microgravity using an overdamped integrator. We then include the effects of gravity and find that we also need to include the effects of fluid inertia, which affects the dynamics of the concentration fluctuations greatly at small wave numbers. PMID:25615227
Hydrodynamic modelling of small upland lakes under strong wind forcing
NASA Astrophysics Data System (ADS)
Morales, L.; French, J.; Burningham, H.
2012-04-01
Small lakes (Area < 1 km2) represent 46.3% of the total lake surface globally and constitute an important source of water supply. Lakes also provide an important sedimentary archive of environmental and climate changes and ecosystem function. Hydrodynamic controls on the transport and distribution of lake sediments, and also seasonal variations in thermal structure due to solar radiation, precipitation, evaporation and mixing and the complex vertical and horizontal circulation patterns induced by the action of wind are not very well understood. The work presented here analyses hydrodynamic motions present in small upland lakes due to circulation and internal scale waves, and their linkages with the distribution of bottom sediment accumulation in the lake. For purpose, a 3D hydrodynamic is calibrated and implemented for Llyn Conwy, a small oligotrophic upland lake in North Wales, UK. The model, based around the FVCOM open source community model code, resolves the Navier-Stokes equations using a 3D unstructured mesh and a finite volume scheme. The model is forced by meteorological boundary conditions. Improvements made to the FVCOM code include a new graphical user interface to pre- and post process the model input and results respectively, and a JONSWAT wave model to include the effects of wind-wave induced bottom stresses on lake sediment dynamics. Modelled internal scale waves are validated against summer temperature measurements acquired from a thermistor chain deployed at the deepest part of the lake. Seiche motions were validated using data recorded by high-frequency level sensors around the lake margins, and the velocity field and the circulation patterns were validated using the data recorded by an ADCP and GPS drifters. The model is shown to reproduce the lake hydrodynamics and reveals well-developed seiches at different frequencies superimposed on wind-driven circulation patterns that appear to control the distribution of bottom sediments in this small upland lake.
Hydrodynamic aspects of caldera-forming eruptions: Numerical models
K. H. Wohletz; T. R. McGetchin; M. T. Sandford II; E. M. Jones
1984-01-01
Compariosn of results from a two-dimensional numerical eruption simulation (KACHINA) to calculations based upon a shock tube analog supports the conclusion that the hydrodynamics during the initial minutes of large caldrs-forming ash flow ruptions may be dominated by blast wave phenomena. Field evidence for this phenomonology is pyroclastic surge deposits commonly occurring both directly below caldera-related ash flow sheets, on
Hamiltonian Hydrodynamics and Irrotational Binary Inspiral
Charalampos M. Markakis
2014-10-28
Gravitational waves from neutron-star and black-hole binaries carry valuable information on their physical properties and probe physics inaccessible to the laboratory. Although development of black-hole gravitational-wave templates in the past decade has been revolutionary, the corresponding work for double neutron-star systems has lagged. Neutron stars can be well-modelled as simple barotropic fluids during the part of binary inspiral most relevant to gravitational wave astronomy, but the crucial geometric and mathematical consequences of this simplification have remained computationally unexploited. In particular, Carter and Lichnerowicz have described barotropic fluid motion via classical variational principles as conformally geodesic. Moreover, Kelvin's circulation theorem implies that initially irrotational flows remain irrotational. Applied to numerical relativity, these concepts lead to novel Hamiltonian or Hamilton-Jacobi schemes for evolving relativistic fluid flows. Hamiltonian methods can conserve not only flux, but also circulation and symplecticity, and moreover do not require addition of an artificial atmosphere typically required by standard conservative methods. These properties can allow production of high-precision gravitational waveforms at low computational cost. This canonical hydrodynamics approach is applicable to a wide class of problems involving theoretical or computational fluid dynamics.
Application of Multi-block Grid and Parallelization Techniques in Hydrodynamic Modelling
Phu V. Luong; Raymond S. Chapman
2009-01-01
The Curvilinear Hydrodynamic 3-D (CH3D-WES) model is routinely applied in three-dimensional (3D) hydrodynamic and water quality modeling studies at the Engineering Research and Development Center (ERDC), Mississippi. Recent model improvements include the implementation of multiple grain size class sediment transport, grid wetting\\/drying, spatially and temporally varying wind and wave radiation stress gradient forcing. The practical application of the original single-block
Waves and Instabilities in Magnetized Dusty Plasmas
Padma K. Shukla
1998-01-01
The status of waves and instabilities in magnetized dusty plasmas is summarized. The effects of an external magnetic field on low-frequency electrostatic and electromagnetic waves in dusty plasmas are discussed. The kinetic and hydrodynamic instabilities are shown to excite magnetized dusty plasma waves. The presence of the latter can give rise to an oscillatory wake-potential which can be responsible for
Waves and Instabilities in Magnetized Dusty Plasmas
Padma K. Shukla
1999-01-01
The status of waves and instabilities in magnetized dusty plasmas is summarized. The effects of an external magnetic field on low-frequency electrostatic and electromagnetic waves in dusty plasmas are discussed. The kinetic and hydrodynamic instabilities are shown to excite magnetized dusty plasma waves. The presence of the latter can give rise to an oscillatory wake-potential which can be responsible for
A new hydrodynamic analysis of double layers
NASA Technical Reports Server (NTRS)
Hora, Heinrich
1987-01-01
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.
Phonon hydrodynamics in two-dimensional materials.
Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola
2015-01-01
The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane. PMID:25744932
Hydrodynamics of coalescing binary neutron stars: Ellipsoidal treatment
NASA Astrophysics Data System (ADS)
Lai, Dong; Shapiro, Stuart L.
1995-04-01
We employ an approximate treatment of dissipative hydrodynamics in three dimensions to study the coalescence of binary neutron stars driven by the emission of gravitational waves. The stars are modeled as compressible ellipsoids obeying a polytropic equation of state; all internal fluid velocities are assumed to be linear functions of the coordinates. The hydrodynamics equations then reduce to a set of coupled ordinary differential equations for the evolution of the principal axes of the ellipsoids, the internal velocity parameters, and the binary orbital parameters. Gravitational radiation reaction and viscous dissipation are both incorporated. We set up exact initial binary equilibrium configurations and follow the transition from the quasi-static, secular decay of the orbit at large separation to the rapid dynamical evolution of the configurations just prior to contact. A hydrodynamical instability resulting from tidal interactions significantly accelerates the coalescence at small separation, leading to appreciable radial infall velocity and tidal lag angles near contact. This behavior is reflected in the gravitational waveforms and may be observable by gravitational wave detectors under construction. In cases where the neutron stars have spins which are not aligned with the orbital angular momentum, the spin-induced quadrupole moment can lead to precession of the orbital plane and therefore modulation of the gravitational wave amplitude even at large orbital radius. However, the amplitude of the modulation is small for typical neutron star binaries with spins much smaller than the orbital angular momentum.
Effect of Second-Order Hydrodynamics on a Floating Offshore Wind Turbine
Roald, L.; Jonkman, J.; Robertson, A.
2014-05-01
The design of offshore floating wind turbines uses design codes that can simulate the entire coupled system behavior. At the present, most codes include only first-order hydrodynamics, which induce forces and motions varying with the same frequency as the incident waves. Effects due to second- and higher-order hydrodynamics are often ignored in the offshore industry, because the forces induced typically are smaller than the first-order forces. In this report, first- and second-order hydrodynamic analysis used in the offshore oil and gas industry is applied to two different wind turbine concepts--a spar and a tension leg platform.
NASA Astrophysics Data System (ADS)
Ashouri, M.; Ebrahimi, B.; Shafii, M. B.; Saidi, M. H.; Saidi, M. S.
2010-11-01
Magnetic convection heat transfer in a two-dimensional square cavity induced by magnetic field gradient is investigated numerically using a semi-implicit finite volume method. The side walls of the cavity are heated with different temperatures, the top and bottom walls are isolated, and a permanent magnet is located near the bottom wall. Thermal buoyancy-induced flow is neglected due to the nongravity condition on the plane of the cavity. Conditions for the different values of non-dimensional variables in a variety of ferrofluid properties and magnetic field parameters are studied. Based on this numerical analysis, a general correlation for the overall Nusselt number on the side walls is introduced for a wide range of effective parameters. Results showed that maximum error produced by use of this correlation is about 6 percent.
NASA Astrophysics Data System (ADS)
Prakash, Jyoti; Gupta, Sanjay
2013-11-01
It is proved analytically that the complex growth rate ?=?r+ i?i (?r and ?i are respectively the real and imaginary parts of ?) of an arbitrary oscillatory motion of growing amplitude in ferromagnetic convection, with magnetic field dependent viscosity, in a rotating ferrofluid layer for the case of free boundaries, must lie inside a semicircle in the right half of the ?r?i- plane whose center is at the origin and (=max{(RM1/Pr), Ta}, where R is the Rayleigh number, M1 is the magnetic number, Pr is the Prandtl number and Ta is the Taylor number. Further, bounds for the case of rigid boundaries are also derived separately.
Investigation on the hydrodynamic performance of an ultra deep turret-moored FLNG system
NASA Astrophysics Data System (ADS)
Zhao, Wen-hua; Yang, Jian-min; Hu, Zhi-qiang; Xiao, Long-fei; Peng, Tao
2012-03-01
Hydrodynamic performance of an ultra deep turret-moored Floating Liquefied Natural Gas (FLNG) system is investigated. Hydrodynamic modeling of a turret-moored FLNG system, in consideration of the coupling effects of the vessel and its mooring lines, has been addressed in details. Based on the boundary element method, a 3-D panel model of the FLNG vessel and the related free water surface model are established, and the first-order and second-order mean-drift wave loads and other hydrodynamic coefficients are calculated. A systematic model test program consisting of the white noise wave test, offset test and irregular wave test combined with current and wind, etc. is performed to verify the numerical model. Owing to the depth limit of the water basin, the model test is carried out for the hydrodynamics of the FLNG coupled with only the truncated mooring system. The numerical simulation model features well the hydrodynamic performance of the FLNG system obtained from the model tests. The hydrodynamic characteristics presented in both the numerical simulations and the physical model tests would serve as the guidance for the ongoing project of FLNG system.
Cuppo, F L S; Gómez, S L; Figueiredo Neto, A M
2004-04-01
In this paper is reported a systematic experimental study of the linear-optical-absorption coefficient of ferrofluid-doped isotropic lyotropic mixtures as a function of the magnetic-grains concentration. The linear optical absorption of ferrolyomesophases increases in a nonlinear manner with the concentration of magnetic grains, deviating from the usual Beer-Lambert law. This behavior is associated to the presence of correlated micelles in the mixture which favors the formation of small-scale aggregates of magnetic grains (dimers), which have a higher absorption coefficient with respect to that of isolated grains. We propose that the indirect heating of the micelles via the ferrofluid grains (hyperthermia) could account for this nonlinear increase of the linear-optical-absorption coefficient as a function of the grains concentration. PMID:15170531
NASA Astrophysics Data System (ADS)
Cuppo, F. L. S.; Gómez, S. L.; Figueiredo Neto, A. M.
2004-04-01
In this paper is reported a systematic experimental study of the linear-optical-absorption coefficient of ferrofluid-doped isotropic lyotropic mixtures as a function of the magnetic-grains concentration. The linear optical absorption of ferrolyomesophases increases in a nonlinear manner with the concentration of magnetic grains, deviating from the usual Beer-Lambert law. This behavior is associated to the presence of correlated micelles in the mixture which favors the formation of small-scale aggregates of magnetic grains (dimers), which have a higher absorption coefficient with respect to that of isolated grains. We propose that the indirect heating of the micelles via the ferrofluid grains (hyperthermia) could account for this nonlinear increase of the linear-optical-absorption coefficient as a function of the grains concentration.
Group-invariant solutions of hydrodynamics and radiation hydrodynamics
Coggeshall, S.V.
1993-08-01
Using the property of invariance under Lie groups of transformations, the equations of hydrodynamics are transformed from partial differential equations to ordinary differential equations, for which special analytic solutions can be found. These particular solutions can be used for (1) numerical benchmarks, (2) the basis for analytic models, and (3) insight into more general solutions. Additionally, group transformations can be used to construct new solutions from existing ones. A space-time projective group is used to generate complicated solutions from simpler solutions. Discussion of these procedures is presented along with examples of analytic of 1,2 and 3-D hydrodynamics.
Hydrodynamics of polar liquid crystals
William Kung; M. Cristina Marchetti; Karl Saunders
2006-03-01
Starting from a microscopic definition of an alignment vector proportional to the polarization, we discuss the hydrodynamics of polar liquid crystals with local $C_{\\infty v}$-symmetry. The free energy for polar liquid crystals differs from that of nematic liquid crystals ($D_{\\infty h}$) in that it contains terms violating the ${\\bf{n}}\\to -{\\bf{n}}$ symmetry. First we show that these $\\mathcal{Z}_2$-odd terms induce a general splay instability of a uniform polarized state in a range of parameters. Next we use the general Poisson-bracket formalism to derive the hydrodynamic equations of the system in the polarized state. The structure of the linear hydrodynamic modes confirms the existence of the splay instability.
Black brane entropy and hydrodynamics
Booth, Ivan; Heller, Michal P.; Spalinski, Michal [Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, A1C 5S7 (Canada); Instituut voor Theoretische Fysica, Universiteit van Amsterdam, Science Park 904, 1090 GL Amsterdam (Netherlands); Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw (Poland) and Physics Department, University of Bialystok, 15-424 Bialystok (Poland)
2011-03-15
Recent advances in holography have led to the formulation of fluid-gravity duality, a remarkable connection between the hydrodynamics of certain strongly coupled media and dynamics of higher dimensional black holes. This paper introduces a correspondence between phenomenologically defined entropy currents in relativistic hydrodynamics and 'generalized horizons' of near-equilibrium black objects in a dual gravitational description. A general formula is given, expressing the divergence of the entropy current in terms of geometric objects which appear naturally in the gravity dual geometry. The proposed definition is explicitly covariant with respect to boundary diffeomorphisms and reproduces known results when evaluated for the event horizon.
NASA Astrophysics Data System (ADS)
Kuznetsov, N.; Maz'ya, V.; Vainberg, B.
2002-08-01
This book gives a self-contained and up-to-date account of mathematical results in the linear theory of water waves. The study of waves has many applications, including the prediction of behavior of floating bodies (ships, submarines, tension-leg platforms etc.), the calculation of wave-making resistance in naval architecture, and the description of wave patterns over bottom topography in geophysical hydrodynamics. The first section deals with time-harmonic waves. Three linear boundary value problems serve as the approximate mathematical models for these types of water waves. The next section uses a plethora of mathematical techniques in the investigation of these three problems. The techniques used in the book include integral equations based on Green's functions, various inequalities between the kinetic and potential energy and integral identities which are indispensable for proving the uniqueness theorems. The so-called inverse procedure is applied to constructing examples of non-uniqueness, usually referred to as 'trapped nodes.'
RUN UP OF SURFACE AND INTERNAL WAVES H. Branger1
Paris-Sud XI, Université de
RUN UP OF SURFACE AND INTERNAL WAVES H. Branger1 , O. Kimmoun , N. Gavrilov , V. Liapidevskii3 , E as for internal waves is considered. The study is based on the laboratory run up experiments for surface waves in LIH (Lavrentyev Institute of Hydrodynamics) and on the field data describing the internal wave run up
Group-invariant solutions of hydrodynamics and radiation hydrodynamics
S. V. Coggeshall
1993-01-01
Using the property of invariance under Lie groups of transformations, the equations of hydrodynamics are transformed from partial differential equations to ordinary differential equations for which special analytic solutions can be found. These particular solutions can be used for the following: (1) numerical benchmarks; (2) the basis for analytic models; and (3) insight into more general solutions. Additionally, group transformations
Spin current evolution in the separated spin-up and spin-down quantum hydrodynamics
Trukhanova, Mariya Iv
2015-01-01
We have developed the quantum hydrodynamic model that describes particles with spin-up and with spin-down in separate. We have derived the equation of the spin current evolution as a part of the set of the quantum hydrodynamics (QHD) equations that treat particles with different projection of spin on the preferable direction as two different species. We have studied orthogonal propagation of waves in the external magnetic field and determined the contribution of quantum corrections due to the Bohm potential and to magnetization energy of particles with different projections of spin in the spin current wave dispersion. We have analyzed the limits of weak and strong magnetic fields.
From Field Theory to the Hydrodynamics of Relativistic Superfluids
Stephan Stetina
2015-01-31
The hydrodynamic description of a superfluid is usually based on a two-fluid picture. In this thesis, basic properties of such a relativistic two-fluid system are derived from the underlying microscopic physics of a complex scalar quantum field theory. To obtain analytic results of all non-dissipative hydrodynamic quantities in terms of field theoretic variables, calculations are first carried out in a low-temperature and weak-coupling approximation. In a second step, the 2-particle-irreducible formalism is applied: This formalism allows for a numerical evaluation of the hydrodynamic parameters for all temperatures below the critical temperature. In addition, a system of two coupled superfluids is studied. As an application, the velocities of first and second sound in the presence of a superflow are calculated. The results show that first (second) sound evolves from a density (temperature) wave at low temperatures to a temperature (density) wave at high temperatures. This role reversal is investigated for ultra-relativistic and near-nonrelativistic systems for zero and nonzero superflow. The studies carried out in this thesis are of a very general nature as one does not have to specify the system for which the microscopic field theory is an effective description. As a particular example, superfluidity in dense quark and nuclear matter in compact stars are discussed.
Anisotropic hydrodynamics for rapidly expanding systems
NASA Astrophysics Data System (ADS)
Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael
2013-10-01
We exactly solve the relaxation-time approximation Boltzmann equation for a system which is transversely homogeneous and undergoing boost-invariant longitudinal expansion. We compare the resulting exact numerical solution with approximate solutions available in the anisotropic hydrodynamics and second order viscous hydrodynamics frameworks. In all cases studied, we find that the anisotropic hydrodynamics framework is a better approximation to the exact solution than traditional viscous hydrodynamical approaches.
Hydrodynamic instabilities in inertial fusion
Hoffman, N.M.
1994-09-01
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.
Hydrodynamic focusing – a versatile tool
Golden, Joel P.; Justin, Gusphyl A.; Nasir, Mansoor; Ligler, Frances S.
2011-01-01
The control of hydrodynamic focusing in a microchannel has inspired new approaches for microfluidic mixing, separations, sensors, cell analysis and microfabrication. Achieving a flat interface between the focusing and focused fluids is dependent on Reynolds number and device geometry, and many hydrodynamic focusing systems can benefit from this understanding. For applications where a specific cross-sectional shape is desired for the focused flow, advection generated by grooved structures in the channel walls can be used to define the shape of the focused flow. Relative flow rates of the focused flow and focusing streams can be manipulated to control the crosssectional area of the focused flows. This manuscript discusses the principles for defining the shape of the interface between the focused and focusing fluids and provides examples from our lab that use hydrodynamic focusing for impedance-based sensors, flow cytometry, and microfabrication to illustrate the breadth of opportunities for introducing new capabilities into microfluidic systems. We evaluate each example for the advantages and limitations integral to utilization of hydrodynamic focusing for that particular application. PMID:21952728
Analytic solutions of hydrodynamics equations
S. V. Coggeshall
1991-01-01
Many similarity solutions have been found for the equations of one-dimensional (1-D) hydrodynamics. These special combinations of variables allow the partial differential equations to be reduced to ordinary differential equations, which must then be solved to determine the physical solutions. Usually, these reduced ordinary differential equations are solved numerically. In some cases it is possible to solve these reduced equations
Frictionless random dynamics: hydrodynamical formalism
Radoslaw Czopnik; Piotr Garbaczewski
2003-01-01
We investigate an undamped random phase-space dynamics in deterministic external force fields (conservative and magnetic ones). By employing the hydrodynamical formalism for those stochastic processes we analyze microscopic kinetic-type “collision invariants” and their relationship to local conservation laws (moment equations) in the fully nonequilibrium context.
Axially symmetric pseudo-Newtonian hydrodynamics code
Jinho Kim; Hee Il Kim; Matthew William Choptuik; Hyung Mok Lee
2012-04-17
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 (HRSC) techniques. We implement several different slope limiters for second order reconstruction schemes and also investigate higher order reconstructions. We use the method of lines (MoL) to convert the mixed spatial-time partial differential equations into ordinary differential equations (ODEs) that depend only on time. These ODEs are solved using 2nd and 3rd order Runge-Kutta methods. The Poisson equation for the gravitational potential is solved with a multigrid method. 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 $3 \\times 10^{-6}$, $5 \\times 10^{-7}$ and $2 \\times 10^{-6}$, 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.
Magnetohydrodynamic shock waves in molecular clouds
B. T. Draine; W. G. Roberge; A. Dalgarno
1983-01-01
Calculations for the structure of shock waves in molecular clouds are presented which include the effects of ion-neutral streaming driven by the magnetic field. Results show that shock waves in molecular clouds will usually be C-type shock waves, mediated entirely by the dissipation accompanying ion-neutral streaming, and in which all of the hydrodynamic variables are continuous. The magnetohydrodynamic shock waves
Hydrodynamic variability on megatidal beaches, Normandy, France
NASA Astrophysics Data System (ADS)
Levoy, Franck; Monfort, Olivier; Larsonneur, Claude
2001-04-01
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 9.3 and 11.4 m. The results show the prevalence of strong longshore currents, with velocities up to 0.5 m s -1, on the low- and mid-tidal beach zones. Mostly oriented northward, these currents reflect both a progressive tidal wave and a strong longshore gradient in water level between the Channel Islands embayment and the English Channel. While varying largely during a typical tidal cycle, these longshore velocities are maximum at high tide, reflecting the progressive nature of the tides. This high-tide maximum velocity increases by a factor of 1.5 between the mean tide and mean spring tide, and between the mid- and low-tidal zones due to bed friction effects. Cross-shore velocities are generally weak (<0.1 m s -1), but sometimes stronger in smaller water depths. In the low-tidal zone, they are commonly oriented onshore at the beginning of the rising tide and offshore during the falling tide. This circulation results from a west-east cross-shore gradient in water level that is particularly important around the mean water level. Towards high tides, weak offshore steady flows were observed in the presence of waves. Site-specific relationships were defined in order to characterise the modulation of significant wave height by sea level fluctuations both on the shoreface and in the intertidal zone. The water depth variability during the tidal cycle induces fluctuations in the dissipation by bottom friction, resulting in wave height changes. The influence of tidal currents on the wave height proved to be very small in this context. The tidal fluctuations also influence the instantaneous near-bed currents induced by simultaneous action of non-breaking waves and the tides. During stormy conditions, wave-induced gravity orbital motions dominate the steady flows in the mid-tidal zone, outside the surf zone. At this location, the shallow water friction effect results in weak steady longshore currents, and low water depths explain strong orbital motions. The opposite conditions prevail in the low-tidal zone, where the steady tidal currents are stronger than gravity orbital velocities during a few hours around high tide. Outside this period, with the decrease in water depth and in steady current intensity due to friction effects, the tidal and gravity wave-induced currents have comparable intensities. In both the low- and mid-tidal zones, infragravity motions are weak outside the surf zone. The foregoing results show that outside the surf zone, these megatidal beaches are characterised by wave-dominated mid-tidal zones and tide-dominated low-tidal zones during spring tides. We suggest the term "mixed wave-tide-dominated" for these beaches with very large tidal ranges.
Formation Interuniversitaire de Physique Hydrodynamics
Balbus, Steven
: ... Nonlinear Classical Hydro -- From the final blackboard of R. P. Feynman 2 #12;Contents 1 Opening Comment 9 2 . . . . . . . . . . . . . . . . . . . . . . . . 47 4.5 Incompressible Waves: the Boussinesq Approximation . . . . . 48 3 #12;4.5.1 Internal Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4.8 Nonlinear Acoustic Waves . . . . . . . . . . . . . . . . . . . . 69 4.8.1 Quasilinear Theory
Shear-bulk coupling in nonconformal hydrodynamics
NASA Astrophysics Data System (ADS)
Denicol, Gabriel S.; Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael
2014-10-01
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.
Hydrodynamic simulations with the Godunov smoothed particle hydrodynamics
NASA Astrophysics Data System (ADS)
Murante, G.; Borgani, S.; Brunino, R.; Cha, S.-H.
2011-10-01
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.
Jonkman, J. M.; Sclavounos, P. D.
2006-01-01
Aeroelastic simulation tools are routinely used to design and analyze onshore wind turbines, in order to obtain cost effective machines that achieve favorable performance while maintaining structural integrity. These tools employ sophisticated models of wind-inflow; aerodynamic, gravitational, and inertial loading of the rotor, nacelle, and tower; elastic effects within and between components; and mechanical actuation and electrical responses of the generator and of control and protection systems. For offshore wind turbines, additional models of the hydrodynamic loading in regular and irregular seas, the dynamic coupling between the support platform motions and wind turbine motions, and the dynamic characterization of mooring systems for compliant floating platforms are also important. Hydrodynamic loading includes contributions from hydrostatics, wave radiation, and wave scattering, including free surface memory effects. The integration of all of these models into comprehensive simulation tools, capable of modeling the fully coupled aeroelastic and hydrodynamic responses of floating offshore wind turbines, is presented.
Brain vascular and hydrodynamic physiology
Tasker, Robert C.
2013-01-01
Protecting the brain in vulnerable infants undergoing surgery is a central aspect of perioperative care. Understanding the link between blood flow, oxygen delivery and oxygen consumption leads to a more informed approach to bedside care. In some cases, we need to consider how high can we let the partial pressure of carbon dioxide go before we have concerns about risk of increased cerebral blood volume and change in intracranial hydrodynamics? Alternatively, in almost all such cases, we have to address the question of how low can we let the blood pressure drop before we should be concerned about brain perfusion? This review, provides a basic understanding of brain bioenergetics, hemodynamics, hydrodynamics, autoregulation and vascular homeostasis to changes in blood gases that is fundamental to our thinking about bedside care and monitoring. PMID:24331089
Analytic solutions of hydrodynamics equations
Coggeshall, S.V. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (US))
1991-05-01
Many similarity solutions have been found for the equations of one-dimensional (1-D) hydrodynamics. These special combinations of variables allow the partial differential equations to be reduced to ordinary differential equations, which must then be solved to determine the physical solutions. Usually, these reduced ordinary differential equations are solved numerically. In some cases it is possible to solve these reduced equations analytically to obtain explicit solutions. In this work a collection of analytic solutions of the 1-D hydrodynamics equations is presented. These can be used for a variety of purposes, including (i) numerical benchmark problems, (ii) as a basis for analytic models, and (iii) to provide insight into more complicated solutions.
Hydrodynamic consequences of barnacle colonization
J. C. Thomason; J. M. Hills; A. S. Clare; A. Neville; M. Richardson
1998-01-01
The aim of this project was to study the hydrodynamic consequences of substratum colonization by barnacles. Replicas of individual\\u000a barnacles and barnacle colonies, and living colonies were studied in a 5 m seawater flume using tracer dyes, macro video-photography\\u000a and image digitization and in a small flume fitted with differential pressure sensors. Using replicas, colonization densities\\u000a were manipulated to determine
Hydrodynamics of catheter biofilm formation
Sotolongo-Costa, Oscar; Rodriguez-Perez, Daniel; Martinez-Escobar, Sergio; Fernandez-Barbero, Antonio
2009-01-01
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.
Numerical hydrodynamics in special relativity
Jose M. Marti; E. Muller
1999-01-01
This review is concerned with a discussion of numerical methods for the\\u000asolution of the equations of special relativistic hydrodynamics (SRHD).\\u000aParticular emphasis is put on a comprehensive review of the application of\\u000ahigh-resolution shock-capturing methods in SRHD. Results obtained with\\u000adifferent numerical SRHD methods are compared, and two astrophysical\\u000aapplications of SRHD flows are discussed. An evaluation of the
The Gulf of Lions' hydrodynamics
NASA Astrophysics Data System (ADS)
Millot, Claude
1990-09-01
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 meteorological conditions. The cloudless atmospheric conditions encountered generally in the northwestern Mediterranean Sea have enabled us to make use of, over more than 10 years, large use of various satellite imageries. The large space and time variability of the hydrodynamical features, a complex topography and a noticeable fishing activity, represent certain difficulties to the collection of observations in situ. We have obtained, therefore, only a few current time series on the slope; those obtained on the shelf only cover the summer period. Models have been elaborated to help us understand the reasons for the general circulation. Observational programmes to be carried out in the forthcoming years will probably provide us with more definitive results on the Gulf of Lions' hydrodynamics.
Near-critical fluid hydrodynamics
NASA Astrophysics Data System (ADS)
Zappoli, Bernard
2003-10-01
In the vicinity of the gas-liquid critical point, transport coefficients of pure fluids experience important changes. In particular, the thermal diffusivity tends to zero whereas the isothermal compressibility tends to infinity. Supercritical fluids are thus as dense as liquids and much more expandable than gases. These properties make the hydrodynamic similarity parameters vary over orders of magnitude when nearing the critical point, thus leading to a large field of research. We review here four main fields: heat transfer, cavity flows, interfaces and hydrodynamic instabilities. In the first, we present a fourth adiabatic heat transfer mechanism, called the piston effect, which carries heat much faster than diffusion, in the absence of convection. In the second, we show how this heat transfer mechanism interacts with buoyant convection. In the third, we basically show that a thermally non-homogeneous near-critical fluid behaves as a two miscible-phases fluid. In the fourth, we present some specific behavior of the Rayleigh-Benard convection, as recent experiments and numerical simulations have indicated. The last part gives some pathways in the continuation of the current research. We stress the need to fully develop the hydrodynamic of highly expandable, low heat diffusing fluids since the subject is both a bearer of new physics and is needed for the development of processes in chemical engineering. To cite this article: B. Zappoli, C. R. Mecanique 331 (2003).
NASA Astrophysics Data System (ADS)
Hong, Ruo-Yu; Li, Jian-Hua; Zhang, Shi-Zhong; Li, Hong-Zhong; Zheng, Ying; Ding, Jian-min; Wei, Dong-Guang
2009-01-01
Fe 3O 4 magnetic nanoparticles (MNPs) were synthesized by the co-precipitation of Fe 3+ and Fe 2+ with ammonium hydroxide. The sodium citrate-modified Fe 3O 4 MNPs were prepared under Ar protection and were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM). To improve the oxidation resistance of Fe 3O 4 MNPs, a silica layer was coated onto the modified and unmodified MNPs by the hydrolysis of tetraethoxysilane (TEOS) at 50 °C and pH 9. Afterwards, the silica-coated Fe 3O 4 core/shell MNPs were modified by oleic acid (OA) and were tested by IR and VSM. IR results revealed that the OA was successfully grafted onto the silica shell. The Fe 3O 4/SiO 2 core/shell MNPs modified by OA were used to prepare water-based ferrofluids (FFs) using PEG as the second layer of surfactants. The properties of FFs were characterized using a UV-vis spectrophotometer, a Gouy magnetic balance, a laser particle size analyzer and a Brookfield LVDV-III+ rheometer.
NASA Astrophysics Data System (ADS)
Nanjundappa, C. E.; Shivakumara, I. S.; Prakash, H. N.
2014-12-01
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.
Fasih Ramandi, Negin; Shemirani, Farzaneh
2015-10-15
Surfacted ferrofluid (S-FF) is a stable colloid dispersion of magnetic nanoparticles in a carrier liquid which possesses magnetic properties and fluidity simultaneously. Specifically in S-FF coating magnetic nanoparticles with a suitable surfactant provides steric repulsions to prevent particles agglomeration. Selecting the function of surfactant can be engineered according to its application. In the present study, for the first time the application of S-FF in dispersive solid phase extraction of methylene blue (as a cationic dye model) in water and shrimp samples was investigated. For this purpose, in order to use ionic liquid as carrier fluid, the surface of Fe3O4 nanoparticles was coated by an anionic surfactant in a polar medium to form a hydrophilic layer around magnetic nanoparticles. In addition to hydrophobic interactions between the analyte and carbonic chain of surfactant, the retention of cationic dye was mainly governed by attractive electrostatic interactions between polar head of surfactant and dye. Under optimized conditions, the relative standard deviation is 2.9%, the limit of detection is 2.5?gL(-1), and the preconcentration factor is 135. PMID:25952885
Qasim, Muhammad; Khan, Zafar Hayat; Khan, Waqar Ahmad; Ali Shah, Inayat
2014-01-01
This study investigates the magnetohydrodynamic (MHD) flow of ferrofluid along a stretching cylinder. The velocity slip and prescribed surface heat flux boundary conditions are employed on the cylinder surface. Water as conventional base fluid containing nanoparticles of magnetite (Fe3O4) is used. Comparison between magnetic (Fe3O4) and non-magnetic (Al2O3) nanoparticles is also made. The governing non-linear partial differential equations are reduced to non-linear ordinary differential equations and then solved numerically using shooting method. Present results are compared with the available data in the limiting cases. The present results are found to be in an excellent agreement. It is observed that with an increase in the magnetic field strength, the percent difference in the heat transfer rate of magnetic nanoparticles with Al2O3 decreases. Surface shear stress and the heat transfer rate at the surface increase as the curvature parameter increases, i.e curvature helps to enhance the heat transfer. PMID:24465388
Qasim, Muhammad; Khan, Zafar Hayat; Khan, Waqar Ahmad; Ali Shah, Inayat
2014-01-01
This study investigates the magnetohydrodynamic (MHD) flow of ferrofluid along a stretching cylinder. The velocity slip and prescribed surface heat flux boundary conditions are employed on the cylinder surface. Water as conventional base fluid containing nanoparticles of magnetite (Fe3O4) is used. Comparison between magnetic (Fe3O4) and non-magnetic (Al2O3) nanoparticles is also made. The governing non-linear partial differential equations are reduced to non-linear ordinary differential equations and then solved numerically using shooting method. Present results are compared with the available data in the limiting cases. The present results are found to be in an excellent agreement. It is observed that with an increase in the magnetic field strength, the percent difference in the heat transfer rate of magnetic nanoparticles with Al2O3 decreases. Surface shear stress and the heat transfer rate at the surface increase as the curvature parameter increases, i.e curvature helps to enhance the heat transfer. PMID:24465388
Tristan Perez; Thor I. Fossen
2011-01-01
The motion response of marine structures in waves can be studied using finite-dimensional linear-time-invariant approximating models. These models, obtained using system identification with data computed by hydrodynamic codes, find application in offshore training simulators, hardware-in-the-loop simulators for positioning control testing, and also in initial designs of wave-energy conversion devices. Different proposals have appeared in the literature to address the identification
Symposium on Naval Hydrodynamics Rome, Italy, 17-22 September 2006
Yang, Jianming
a first step towards the development of two-phase CFD methods for small and large scale ship hydrodynamic surface and waves. Additionally, detailed experiments for physics, model development, and CFD validation the development of two-phase CFD methods for such problems and complementary PIV EFD with specific focus
PSEUDO-SPECTRUM OF THE RESISTIVE MAGNETO-HYDRODYNAMICS OPERATOR: RESOLVING THE RESISTIVE ALFV, continuous spectrum, Alfv´en waves, magnetohydrodynamic stability. PACS 03.40.Kf, 47.65.+a, 52.30.Jb, 52 would converge to the ideal spectrum in the limit of asymptotically small resistiv- ity
PSEUDO-SPECTRUM OF THE RESISTIVE MAGNETO-HYDRODYNAMICS OPERATOR: RESOLVING THE RESISTIVE ALFV
PSEUDO-SPECTRUM OF THE RESISTIVE MAGNETO-HYDRODYNAMICS OPERATOR: RESOLVING THE RESISTIVE ALFV #19, pseudospectrum, non-normal op- erators, continuous spectrum, Alfv#19;en waves, magnetohydrodynamic stability to the ideal spectrum in the limit of asymptotically small resistiv- ity. As the resistivity, #17;, decreases
Thermodynamic entropy and chaos in a discrete hydrodynamical system.
Bagnoli, Franco; Rechtman, Raúl
2009-04-01
We show that the thermodynamic entropy density is proportional to the largest Lyapunov exponent (LLE) of a discrete hydrodynamical system, a deterministic two-dimensional lattice gas automaton. The definition of the LLE for cellular automata is based on the concept of Boolean derivatives and is formally equivalent to that of continuous dynamical systems. This relation is justified using a Markovian model. In an irreversible process with an initial density difference between both halves of the system, we find that Boltzmann's H function is linearly related to the expansion factor of the LLE although the latter is more sensitive to the presence of traveling waves. PMID:19518181
Anderson localization and breakdown of hydrodynamics in random ferromagnets
Bruinsma, R.; Coppersmith, S.N.
1986-05-01
The dynamic structure factor of Heisenberg magnets with weak randomness is computed. Under circumstances which are explained in detail, we find failure of hydrodynamic theory in the longitudinal structure factor due to localization of spin waves. Localization induces a power-law dependence on q and ..omega.. for the neutron scattering line shape near magnetic Bragg spots. The exponent describing the power law is related to the correlation-length exponent of Anderson localization. Random anisotropy magnets appear to be promising candidates for experimental investigations.
Cluster Dynamics of Planetary Waves
Elena Kartashova; Victor S. L'vov
2008-11-05
The dynamics of nonlinear atmospheric planetary waves is determined by a small number of independent wave clusters consisting of a few connected resonant triads. We classified the different types of connections between neighboring triads that determine the general dynamics of a cluster. Each connection type corresponds to substantially different scenarios of energy flux among the modes. The general approach can be applied directly to various mesoscopic systems with 3-mode interactions, encountered in hydrodynamics, astronomy, plasma physics, chemistry, medicine, etc.
A. O. Lebeck; K. L. Wong
1984-01-01
This paper presents a new concept for a self-acting, rotating-shaft gas seal. One of the seal faces is elastically distorted to provide a converging tilt and wavy shape on the face. The tilt enhances hydrostatic load support while the waviness enhances hydrodynamic load support. By moving the wave slowly elastically, this unique shape is preserved in spite of any wear.
Hydrodynamic modeling of tsunamis from the Currituck landslide
Geist, E.L.; Lynett, P.J.; Chaytor, J.D.
2009-01-01
Tsunami generation from the Currituck landslide offshore North Carolina and propagation of waves toward the U.S. coastline are modeled based on recent geotechnical analysis of slide movement. A long and intermediate wave modeling package (COULWAVE) based on the non-linear Boussinesq equations are used to simulate the tsunami. This model includes procedures to incorporate bottom friction, wave breaking, and overland flow during runup. Potential tsunamis generated from the Currituck landslide are analyzed using four approaches: (1) tsunami wave history is calculated from several different scenarios indicated by geotechnical stability and mobility analyses; (2) a sensitivity analysis is conducted to determine the effects of both landslide failure duration during generation and bottom friction along the continental shelf during propagation; (3) wave history is calculated over a regional area to determine the propagation of energy oblique to the slide axis; and (4) a high-resolution 1D model is developed to accurately model wave breaking and the combined influence of nonlinearity and dispersion during nearshore propagation and runup. The primary source parameter that affects tsunami severity for this case study is landslide volume, with failure duration having a secondary influence. Bottom friction during propagation across the continental shelf has a strong influence on the attenuation of the tsunami during propagation. The high-resolution 1D model also indicates that the tsunami undergoes nonlinear fission prior to wave breaking, generating independent, short-period waves. Wave breaking occurs approximately 40-50??km offshore where a tsunami bore is formed that persists during runup. These analyses illustrate the complex nature of landslide tsunamis, necessitating the use of detailed landslide stability/mobility models and higher-order hydrodynamic models to determine their hazard.
Hydrodynamic instability in eccentric astrophysical discs
NASA Astrophysics Data System (ADS)
Barker, A. J.; Ogilvie, G. I.
2014-12-01
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.
Hydrodynamic instability mechanism for rip currents
NASA Astrophysics Data System (ADS)
Yu, Jie
2015-04-01
On re-examining the hydrodynamic instability, Yu (J. Fluid Mech., vol. 549, 2006, pp. 403-428) showed that when the fully dynamical interactions are duly accounted for, and proper mathematical analysis is carried out, the positive feedback between the wave and evolving current can initiate and sustain rip current circulations with scales comparable to field observations on alongshore uniform beaches. In this study, we extend that analysis to consider non-planar beaches, and to include a new branch of unstable modes that correspond to alongshore propagating horizontal circulations with the magnitudes of the flow growing in time. This latter has not previously been studied. These propagating unstable modes have typical time periods of tens of minutes and alongshore propagation speeds of a few cm/sec. The physical implications of their spatial and slow time oscillations are discussed, as of relevance to occurrence and recurrence of transient rips, alongshore migration of rip currents and very low frequency pulsations in surf zone eddy circulations.
Hydrodynamics of internal solitons and a comparison of SIR-A and SIR-B data with ocean measurements
NASA Technical Reports Server (NTRS)
Apel, J. R.; Gasparovic, R. F.; Thompson, D. R.
1986-01-01
Large internal solitary waves have been observed by Shuttle SIR-A and SIR-B at locations in the Andaman Sea and the New York Bight. Satellite imagery and oceanographic measurements are used in conjunction with hydrodynamic interaction and electromagnetic scattering models to estimate the expected SAR image intensity modulations associated with the internal waves. There is reasonable agreement between the predicted and observed internal wave signatures.
Direct evidence of flagellar synchronization through hydrodynamic interactions
NASA Astrophysics Data System (ADS)
Brumley, Douglas; Polin, Marco; Wan, Kirsty; Goldstein, Raymond
2013-11-01
Eukaryotic cilia and flagella exhibit striking coordination, from the synchronous beating of two flagella in Chlamydomonas to the metachronal waves and large-scale flows displayed by carpets of cilia. However, the precise mechanisms responsible for flagellar synchronization remain unclear. We perform a series of experiments involving two individual flagella in a quiescent fluid. Cells are isolated from the colonial alga Volvox carteri, held in place at a fixed distance d, and oriented so that their flagellar beating planes coincide. In this fashion, we are able to explicitly assess the role of hydrodynamics in achieving synchronization. For closely separated cells, the flagella are capable of exhibiting a phase-locked state for thousands of beats at a time, despite significant differences in their intrinsic frequencies. For intermediate values of d, synchronous periods are interrupted by brief phase slips, while for d >> 1 the flagellar phase difference drifts almost linearly with time. The coupling strength extracted through analysis of the synchronization statistics exhibits excellent agreement with hydrodynamic predictions. This study unambiguously reveals that flagella coupled only through hydrodynamics are capable of exhibiting robust synchrony.
NASA Technical Reports Server (NTRS)
Lee, Jeongwoo W.
1993-01-01
In this paper we analyze the generation of waves in a sunspot by extending Stein's hydrodynamic approach to the turbulent medium permeated by a strong uniform magnetic field oriented parallel to the gravity. For wave sources appropriate to the sunspot, we consider magnetic perturbations and entropy changes as well as turbulent convection. To describe the anisotropy imposed by the sunspot, we use a one-dimensional correlation function relating the turbulent eddies separated along the symmetry axis of the spot. This treatment yields several interesting possibilities for wave generation in a sunspot. First, it is demonstrated that the entropy change and magnetic perturbation can lead to a relative enhancement of acoustic wave emission. Second, the energy flux of Alfven waves may be comparable to that of acoustic waves in sunspots. Third, the anisotropy of the sunspot dynamics can lead to wave energy spectrum in a form which may explain the origin of umbral atmospheric oscillations.
Foundation of Hydrodynamics of Strongly Interacting Systems
Wong, Cheuk-Yin [ORNL] [ORNL
2014-01-01
Hydrodynamics and quantum mechanics have many elements in common, as the density field and velocity fields are common variables that can be constructed in both descriptions. Starting with the Schroedinger equation and the Klein-Gordon for a single particle in hydrodynamical form, we examine the basic assumptions under which a quantum system of particles interacting through their mean fields can be described by hydrodynamics.
Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications
R. Paul Drake
2005-12-01
We report the ongoing work of our group in hydrodynamics and radiative hydrodynamics with astrophysical applications. During the period of the existing grant, we have carried out two types of experiments at the Omega laser. One set of experiments has studied radiatively collapsing shocks, obtaining high-quality scaling data using a backlit pinhole and obtaining the first (ever, anywhere) Thomson-scattering data from a radiative shock. Other experiments have studied the deeply nonlinear development of the Rayleigh-Taylor (RT) instability from complex initial conditions, obtaining the first (ever, anywhere) dual-axis radiographic data using backlit pinholes and ungated detectors. All these experiments have applications to astrophysics, discussed in the corresponding papers either in print or in preparation. We also have obtained preliminary radiographs of experimental targets using our x-ray source. The targets for the experiments have been assembled at Michigan, where we also prepare many of the simple components. The above activities, in addition to a variety of data analysis and design projects, provide good experience for graduate and undergraduates students. In the process of doing this research we have built a research group that uses such work to train junior scientists.
Hydrodynamic excitations in a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Meppelink, R.
2009-10-01
The field of Bose-Einstein condensation (BEC) in dilute atomic gases provides a fruitful playground to test well-developed theories of quantum fluids. Research using BECs can address open questions relating to the many-body aspects of two-component quantum liquids, namely the interaction between the hydrodynamic normal and the superfluid component at finite temperatures. After the first realization of BEC some pilot experiments have been carried out, but detailed experiments are missing. This has to be compared to the case of liquid helium II, where many experiments since the 1950s have added to our understanding of novel phenomena in quantum liquids, like collective excitations, first and second sound, and others. One of the drawbacks of liquid helium is that the interactions are so strong that a clear distinction between the two components is difficult and the interpretation of the phenomena remains ambiguous. Most experimental studies of dilute Bose-Einstein condensed gases use clouds, which are in the collisionless regime. The reason for the lack of detailed experiments in BECs to study quantum liquids and in particular the hydrodynamical aspects of it, is the limited number of atoms (typically 1--10 million) in the experiments leaving the thermal atoms virtually collisionless. Efforts to decrease the mean free path by increasing the confinement limits the lifetime of the sample, since the density is limited by three-body decay. Experiments on dilute clouds of cold atoms are generally conducted in highly asymmetric traps. In these elongated, cigar-shaped geometries the mean free path of the atoms can become much shorter than the size of the cloud in the long, axial direction, but at the same time exceeds the size in the other, radial directions. In this so-called hydrodynamic-collisionless regime the system can be considered radially collisionless and axially hydrodynamic. In our setup we have created BECs containing up to 300 million sodium atoms by evaporation of atoms in an axially strongly decompressed trap with an aspect ratio of 1:65. Hot atoms created in three-body collisions are able to leave the sample in this highly asymmetric trap, before they can heat other atoms in an avalanche. The sample is axially hydrodynamic, but due to the large aspect ratio collisionless in the radial direction. Such samples are ideal for the observation of the interaction between the superfluid and normal fluid component of the cloud. In this thesis we describe the setup which is used to reach the hydrodynamic regime and we describe a novel implementation of the well-known phase contrast imaging technique. Next, we study collective excitations in the crossover from the collisionless toward the hydrodynamic regime, we determine the heat conduction in a cold, hydrodynamic thermal cloud and observe the propagation of a thermal wave in the two-fluid regime. Furthermore, we study the friction between the superfluid and normal fluid component of the cloud. In the final chapters of this thesis we study the propagation of second sound, as well as the formation and propagation of shock waves.
Disruptive Innovation in Numerical Hydrodynamics
Waltz, Jacob I. [Los Alamos National Laboratory
2012-09-06
We propose the research and development of a high-fidelity hydrodynamic algorithm for tetrahedral meshes that will lead to a disruptive innovation in the numerical modeling of Laboratory problems. Our proposed innovation has the potential to reduce turnaround time by orders of magnitude relative to Advanced Simulation and Computing (ASC) codes; reduce simulation setup costs by millions of dollars per year; and effectively leverage Graphics Processing Unit (GPU) and future Exascale computing hardware. If successful, this work will lead to a dramatic leap forward in the Laboratory's quest for a predictive simulation capability.
Hydrodynamics of Active Permeating Gels
NASA Astrophysics Data System (ADS)
Callan-Jones, Andrew; Jülicher, Frank
2012-02-01
We present a hydrodynamic theory of active viscoelastic gels in which a polymer network is embedded in a background fluid. This work is motivated by active processes in the cell cytoskeleton in which motor molecules generate elastic stresses in the network which can drive permeation flows of the cytosol. Our approach differs from earlier ones by considering the elastic strain in the polymer network as a slowly relaxing dynamical variable. We discuss a specific case that illustrates the role of permeation in active gels: the self-propulsion of a thin slab of gel relative to a substrate driven by filament polymerization and depolymerization.
The effects of second-order hydrodynamics on a semisubmersible floating offshore wind turbine
NASA Astrophysics Data System (ADS)
Bayati, I.; Jonkman, J.; Robertson, A.; Platt, A.
2014-06-01
The objective of this paper is to assess the second-order hydrodynamic effects on a semisubmersible floating offshore wind turbine. Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of a floating system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure. Observations of supposed second-order responses in wave-tank tests performed by the DeepCwind consortium at the Maritime Research Institute Netherlands (MARIN) offshore basin suggest that these effects might be more important than originally expected. These observations inspired interest in investigating how second-order excitation affects floating offshore wind turbines and whether second-order hydrodynamics should be included in offshore wind simulation tools like FAST. In this work, the effects of second-order hydrodynamics on a floating semisubmersible offshore wind turbine are investigated. Because FAST is currently unable to account for second-order effects, a method to assess these effects was applied in which linearized properties of the floating wind system derived from FAST (including the 6x6 mass and stiffness matrices) are used by WAMIT to solve the first- and second-order hydrodynamics problems in the frequency domain. The method was applied to the Offshore Code Comparison Collaboration Continuation OC4-DeepCwind semisubmersible platform, supporting the National Renewable Energy Laboratory's 5-MW baseline wind turbine. In this paper, the loads and response of the system caused by the second-order hydrodynamics are analysed and compared to the first-order hydrodynamic loads and induced motions in the frequency domain. Further, the second-order loads and induced response data are compared to the loads and motions induced by aerodynamic loading as solved by FAST.
Effects of Second-Order Hydrodynamics on a Semisubmersible Floating Offshore Wind Turbine: Preprint
Bayati, I.; Jonkman, J.; Robertson, A.; Platt, A.
2014-07-01
The objective of this paper is to assess the second-order hydrodynamic effects on a semisubmersible floating offshore wind turbine. Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of the system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure. Observations of supposed second-order responses in wave-tank tests performed by the DeepCwind consortium at the MARIN offshore basin suggest that these effects might be more important than originally expected. These observations inspired interest in investigating how second-order excitation affects floating offshore wind turbines and whether second-order hydrodynamics should be included in offshore wind simulation tools like FAST in the future. In this work, the effects of second-order hydrodynamics on a floating semisubmersible offshore wind turbine are investigated. Because FAST is currently unable to account for second-order effects, a method to assess these effects was applied in which linearized properties of the floating wind system derived from FAST (including the 6x6 mass and stiffness matrices) are used by WAMIT to solve the first- and second-order hydrodynamics problems in the frequency domain. The method has been applied to the OC4-DeepCwind semisubmersible platform, supporting the NREL 5-MW baseline wind turbine. The loads and response of the system due to the second-order hydrodynamics are analysed and compared to first-order hydrodynamic loads and induced motions in the frequency domain. Further, the second-order loads and induced response data are compared to the loads and motions induced by aerodynamic loading as solved by FAST.
NSDL National Science Digital Library
Michael Horton
2009-05-30
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
Extreme hydrodynamic load calculations for fixed steel structures
Jong, P.R. de; Vugts, J. [Delft Univ. of Technology (Netherlands); Gudmestad, O.T. [Statoil, Stavanger (Norway)
1996-12-31
This paper discusses the expected differences between the planned ISO code for design of offshore structures and the present Standard Norwegian Practice (SNP), concerning the extreme hydrodynamic design load calculation for fixed steel space frame structures. Since the ISO code is expected to be similar to the API RP2A LRFD code, the provisions of API RP2A LRFD are used to represent the ISO standard. It should be noted that the new ISO code may include NewWave theory, in addition to the wave theories recommended by the API. Design loads and associated failure probabilities resulting from the application of the code provisions are compared for a typical North Sea structure, the Europipe riser platform 16/11-E.
Physics-Based Learning Models for Ship Hydrodynamics
Weymouth, Gabriel D
2014-01-01
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 ...
Hydrodynamic dispersion within porous biofilms
NASA Astrophysics Data System (ADS)
Davit, Y.; Byrne, H.; Osborne, J.; Pitt-Francis, J.; Gavaghan, D.; Quintard, M.
2013-01-01
Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher's equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels' network; (2) the solute's diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport.
Active and driven hydrodynamic crystals.
Desreumaux, N; Florent, N; Lauga, E; Bartolo, D
2012-08-01
Motivated by the experimental ability to produce monodisperse particles in microfluidic devices, we study theoretically the hydrodynamic stability of driven and active crystals. We first recall the theoretical tools allowing to quantify the dynamics of elongated particles in a confined fluid. In this regime hydrodynamic interactions between particles arise from a superposition of potential dipolar singularities. We exploit this feature to derive the equations of motion for the particle positions and orientations. After showing that all five planar Bravais lattices are stationary solutions of the equations of motion, we consider separately the case where the particles are passively driven by an external force, and the situation where they are self-propelling. We first demonstrate that phonon modes propagate in driven crystals, which are always marginally stable. The spatial structures of the eigenmodes depend solely on the symmetries of the lattices, and on the orientation of the driving force. For active crystals, the stability of the particle positions and orientations depends not only on the symmetry of the crystals but also on the perturbation wavelengths and on the crystal density. Unlike unconfined fluids, the stability of active crystals is independent of the nature of the propulsion mechanism at the single-particle level. The square and rectangular lattices are found to be linearly unstable at short wavelengths provided the volume fraction of the crystals is high enough. Differently, hexagonal, oblique, and face-centered crystals are always unstable. Our work provides a theoretical basis for future experimental work on flowing microfluidic crystals. PMID:22864543
Wave excited cable mooring dynamics by modal analysis
Davis, Richard Earl
1977-01-01
experiments are also presented. TABLE OF CONTENTS ABSTRACT TABLE OF CONTL'NTS 1V LIST OF FIGURES INTRODUCTION ANALYTICAL ANALYSIS Structural Nodel Govern ng Equations Hydrodynamic Forces 12 17 ANALYTICAT, AND EXPER:-', E & TAL PESUL' S 22... of the wave forces in the equations of motion. Specifically, the in- clusion of the hydrodynamic wave forces i. n the external load distribution on the cable was addressed. The modal analysis technique was utilized to yield the time dependent displace...
Waves and Instabilities in Magnetized Dusty Plasmas
Padma K. Shukla
1998-01-01
The status of waves and instabilities in magnetized dusty plasmas is summarized. The effects of an external magnetic field\\u000a on low-frequency electrostatic and electromagnetic waves in dusty plasmas are discussed. The kinetic and hydrodynamic instabilities\\u000a are shown to excite magnetized dusty plasma waves. The presence of the latter can give rise to an oscillatory wake-potential\\u000a which can be responsible for
Magnetohydrodynamic shock waves in molecular clouds
B. T. Draine; W. G. Roberge; A. Dalgarno
1983-01-01
The structure of shock waves in molecular clouds is calculated, including the effects of ion-neutral streaming driven by the magnetic field. It is found that shock waves in molecular clouds will usually be C-type shock waves, mediated entirely by the dissipation accompanying ion-neutral streaming, and in which all of the hydrodynamic variables are continuous. Detailed results are presented for magnetohydrodynamic
Piero Chiarelli
2014-08-14
The quantum hydrodynamic like equations as a function of two real sets of variables, the 4x4 action matrix and the 4 dimensional wave function modulus vector of the Dirac equation, are derived in the present work. The paper shows that in the low velocity limit the equations lead to the hydrodynamic representation of the Pauli equation for charged particle with spin given by Janossy and by Bialynicki.The Lorentz invariance of the relativistic quantum potential that generates the non-local behavior of the quantum mechanics is discussed.
NASA Astrophysics Data System (ADS)
Belyakov, Vladimir; Makarov, Vladimir; Zezyulin, Denis; Kurkin, Andrey; Pelinovsky, Efim
2015-04-01
Hazardous phenomena in the coastal zone lead to the topographic changing which are difficulty inspected by traditional methods. It is why those autonomous robots are used for collection of nearshore topographic and hydrodynamic measurements. The robot RTS-Hanna is well-known (Wubbold, F., Hentschel, M., Vousdoukas, M., and Wagner, B. Application of an autonomous robot for the collection of nearshore topographic and hydrodynamic measurements. Coastal Engineering Proceedings, 2012, vol. 33, Paper 53). We describe here several constructions of mobile systems developed in Laboratory "Transported Machines and Transported Complexes", Nizhny Novgorod State Technical University. They can be used in the field surveys and monitoring of wave regimes nearshore.
Variational description of multifluid hydrodynamics: Uncharged fluids
Reinhard Prix
2004-01-01
We present a formalism for Newtonian multifluid hydrodynamics derived from an unconstrained variational principle. This approach provides a natural way of obtaining the general equations of motion for a wide range of hydrodynamic systems containing an arbitrary number of interacting fluids and superfluids. In addition to spatial variations we use ``time shifts'' in the variational principle, which allows us to
Hydrodynamic Modeling and the QGP Shear Viscosity
Huichao Song
2012-07-10
In this article, we will briefly review the recent progress on hydrodynamic modeling and the extraction of the quark-gluon plasma (QGP) specific shear viscosity with an emphasis on results obtained from the hybrid model VISHNU that couples viscous hydrodynamics for the macroscopic expansion of the QGP to the hadron cascade model for the microscopic evolution of the late hadronic stage.
Hydrodynamics of prey capture in sharks: effects
Nauwelaerts, Sandra
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
Hydrodynamic description for ballistic annihilation systems
Garcia de Soria, Maria Isabel; Trizac, Emmanuel [LPTMS (CNRS UMR 8626), Universite Paris-Sud, Orsay Cedex, F-91405 (France); Maynar, Pablo [LPT - CNRS UMR 8627, Universite Paris-Sud, Orsay Cedex, F-91405 (France) and Fisica Teorica, Universidad de Sevilla, Apartado de Correos 1065, E-41080, Sevilla (Spain); Schehr, Gregory; Barrat, Alain [LPT - CNRS UMR 8627, Universite Paris-Sud, Orsay Cedex, F-91405 (France)
2009-01-21
The problem of the validity of a hydrodynamic description for a system in which there are no collisional invariants is addressed. Hydrodynamic equations have been derived and successfully tested against simulation data for a system where particles annihilate with a probability p, or collide elastically otherwise. The response of the system to a linear perturbation is analyzed as well.
Many-body Oseen hydrodynamic interactions
Izabela Pienkowska
2004-01-01
We consider the many-sphere hydrodynamic interactions in the incompressible, viscous fluid, under small Reynolds number Re conditions. The interactions are analysed in the framework of the Oseen equation of motion, with the aid of the respective Green tensor, accounting for the convective inertia of the fluid. The hydrodynamic forces, exerted by the fluid on the spheres, are described by means
General relativistic hydrodynamics in multiple coordinate systems
Chongming Xu; Xuejun Wu
2001-01-01
In this paper, the general relativistic hydrodynamic equations of a thermally conducting, viscous and compressible fluid in multiple coordinate systems are deduced in terms of the scheme developed by Damour, Sofel, and Xu (DSX scheme). Our paper is the first one to describe the hydrodynamic equations of a nonperfect fluid in every local coordinate system at the first post-Newtonian approximation
Hydrodynamic Approaches in Relativistic Heavy Ion Reactions
de Souza, Rafael Derradi; Kodama, Takeshi
2015-01-01
We review several facets of the hydrodynamic description of the relativistic heavy ion collisions, starting from the historical motivation to the present understandings of the observed collective aspects of experimental data, especially those of the most recent RHIC and LHC results. In this report, we particularly focus on the conceptual questions and the physical foundations of the validity of the hydrodynamic approach itself. We also discuss recent efforts to clarify some of the points in this direction, such as the various forms of derivations of relativistic hydrodynamics together with the limitations intrinsic to the traditional approaches, variational approaches, known analytic solutions for special cases, and several new theoretical developments. Throughout this review, we stress the role of course-graining procedure in the hydrodynamic description and discuss its relation with the physical observables through the analysis of a hydrodynamic mapping of a microscopic transport model. Several questions to...
Hydrodynamics, Fungal Physiology, and Morphology.
Serrano-Carreón, L; Galindo, E; Rocha-Valadéz, J A; Holguín-Salas, A; Corkidi, G
2015-01-01
Filamentous cultures, such as fungi and actinomycetes, contribute substantially to the pharmaceutical industry and to enzyme production, with an annual market of about 6 billion dollars. In mechanically stirred reactors, most frequently used in fermentation industry, microbial growth and metabolite productivity depend on complex interactions between hydrodynamics, oxygen transfer, and mycelial morphology. The dissipation of energy through mechanically stirring devices, either flasks or tanks, impacts both microbial growth through shearing forces on the cells and the transfer of mass and energy, improving the contact between phases (i.e., air bubbles and microorganisms) but also causing damage to the cells at high energy dissipation rates. Mechanical-induced signaling in the cells triggers the molecular responses to shear stress; however, the complete mechanism is not known. Volumetric power input and, more importantly, the energy dissipation/circulation function are the main parameters determining mycelial size, a phenomenon that can be explained by the interaction of mycelial aggregates and Kolmogorov eddies. The use of microparticles in fungal cultures is also a strategy to increase process productivity and reproducibility by controlling fungal morphology. In order to rigorously study the effects of hydrodynamics on the physiology of fungal microorganisms, it is necessary to rule out the possible associated effects of dissolved oxygen, something which has been reported scarcely. At the other hand, the processes of phase dispersion (including the suspended solid that is the filamentous biomass) are crucial in order to get an integral knowledge about biological and physicochemical interactions within the bioreactor. Digital image analysis is a powerful tool for getting relevant information in order to establish the mechanisms of mass transfer as well as to evaluate the viability of the mycelia. This review focuses on (a) the main characteristics of the two most common morphologies exhibited by filamentous microorganisms; (b) how hydrodynamic conditions affect morphology and physiology in filamentous cultures; and (c) techniques using digital image analysis to characterize the viability of filamentous microorganisms and mass transfer in multiphase dispersions. Representative case studies of fungi (Trichoderma harzianum and Pleurotus ostreatus) exhibiting different typical morphologies (disperse mycelia and pellets) are discussed. PMID:25652005
Wave synchronizing crane control during water entry in offshore moonpool operations
Svein I. Sagatun; Tor A. Johansen; Thor I. Fossen; Finn G. Nielsen
2002-01-01
A new strategy for active control in heavy-lift offshore crane operations is suggested, by introducing a new concept referred to as wave synchronization. Wave synchronization reduces the hydrodynamic forces by minimization of variations in the relative vertical velocity between payload and water using a wave amplitude measurement. Wave synchronization is combined with conventional heave compensation to obtain accurate control. Experimental
Tor A. Johansen; Thor I. Fossen; Svein I. Sagatun; Finn G. Nielsen
2003-01-01
A new strategy for active control in heavy-lift offshore crane operations is suggested by introducing a new concept referred to as wave synchronization. Wave synchronization reduces the hydrodynamic forces by minimizing variations in the relative vertical velocity between payload and water using a wave-amplitude measurement. Wave synchronization is combined with conventional active heave compensation to obtain accurate control. Experimental results
Incompressible wave motion of compressible fluids.
Godin, Oleg A
2012-05-11
We consider linear waves in compressible fluids in a uniform potential field, such as a gravity field, and demonstrate that a particular type of wave motion, in which pressure remains constant in each fluid parcel, is supported by inhomogeneous fluids occupying bounded or unbounded domains. We present elementary, exact solutions of linearized hydrodynamics equations, which describe the new type of waves in the coupled ocean-atmosphere system. The solutions provide an extension of surface gravity waves in an incompressible fluid half-space with a free boundary to waves in compressible, three-dimensionally inhomogeneous, rotating fluids. PMID:23003046
Cycloidal Wave Energy Converter
Stefan G. Siegel, Ph.D.
2012-11-30
This program allowed further advancing the development of a novel type of wave energy converter, a Cycloidal Wave Energy Converter or CycWEC. A CycWEC consists of one or more hydrofoils rotating around a central shaft, and operates fully submerged beneath the water surface. It operates under feedback control sensing the incoming waves, and converts wave power to shaft power directly without any intermediate power take off system. Previous research consisting of numerical simulations and two dimensional small 1:300 scale wave flume experiments had indicated wave cancellation efficiencies beyond 95%. The present work was centered on construction and testing of a 1:10 scale model and conducting two testing campaigns in a three dimensional wave basin. These experiments allowed for the first time for direct measurement of electrical power generated as well as the interaction of the CycWEC in a three dimensional environment. The Atargis team successfully conducted two testing campaigns at the Texas A&M Offshore Technology Research Center and was able to demonstrate electricity generation. In addition, three dimensional wave diffraction results show the ability to achieve wave focusing, thus increasing the amount of wave power that can be extracted beyond what was expected from earlier two dimensional investigations. Numerical results showed wave cancellation efficiencies for irregular waves to be on par with results for regular waves over a wide range of wave lengths. Using the results from previous simulations and experiments a full scale prototype was designed and its performance in a North Atlantic wave climate of average 30kW/m of wave crest was estimated. A full scale WEC with a blade span of 150m will deliver a design power of 5MW at an estimated levelized cost of energy (LCOE) in the range of 10-17 US cents per kWh. Based on the new results achieved in the 1:10 scale experiments these estimates appear conservative and the likely performance at full scale will exceed this initial performance estimates. In advancing the Technology Readiness Level (TRL) of this type of wave energy converter from 3 to 4, we find the CycWEC to exceed our initial estimates in terms of hydrodynamic performance. Once fully developed and optimized, it has the potential to not just outperform all other WEC technologies, but to also deliver power at a lower LCOE than competing conventional renewables like wind and solar. Given the large wave power resource both domestically and internationally, this technology has the potential to lead to a large improvement in our ability to produce clean electricity at affordable cost.
Anomalous hydrodynamics kicks neutron stars
Matthias Kaminski; Christoph F. Uhlemann; Marcus Bleicher; Jürgen Schaffner-Bielich
2014-10-14
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.
Hydrodynamics of active permeating gels
NASA Astrophysics Data System (ADS)
Callan-Jones, A. C.; Jülicher, F.
2011-09-01
We develop a hydrodynamic theory of active permeating gels with viscoelasticity in which a polymer network is embedded in a background fluid. This situation is motivated by active processes in the cell cytoskeleton in which motor molecules generate elastic stresses in the network, which can drive permeation flows of the cytosol. Our approach differs from earlier ones by considering the elastic strain in the polymer network as a slowly relaxing dynamical variable. We first present the general ideas for the case of a passive, isotropic gel and then extend this description to a polar, active gel. We discuss two specific cases to illustrate the role of permeation in active gels: self-propulsion of a thin slab of gel relative to a substrate driven by filament polymerization and depolymerization; and non-equilibrium deswelling of a gel driven by molecular motors.
Smoothed Particle Hydrodynamics Code Basics
NASA Astrophysics Data System (ADS)
Monaghan, J. J.
2001-12-01
SPH is the shorthand for Smoothed Particle Hydrodynamics. This method is a Lagrangian method which means that it involves following the motion of elements of fluid. These elements have the characteristics of particles and the method is called a particle method. A useful review of SPH (Monaghan 1992) gives the basic technique and how it can be applied to numerous problems relevant to astrophysics. You can get some basic SPH programs from http://www.maths.monash.edu.au/~jjm/sphlect. In the present lecture I will assume that the student has studied this review and therefore understands the basic principles. In today's lecture I plan to approach the equations from a different perspective by using a variational principle.
Identified particles from viscous hydrodynamics
NASA Astrophysics Data System (ADS)
Molnar, Denes
2011-12-01
Identified particle observables from viscous hydrodynamics are sensitive to the fluid-to-particle conversion. Instead of the commonly assumed 'democratic' Grad ansatz for phase space corrections ?f, we utilize corrections calculated from linearized covariant transport theory. Estimates based on a ?-p system with binary collisions indicate that protons are much closer to equilibrium than pions, significantly affecting the dissipative reduction of differential elliptic flow in Au+Au at the RHIC. In addition, we test the linear response against fully nonlinear transport for a two-component massless system in a Bjorken scenario. Strikingly, we find that, while linear response accounts well for the dynamical sharing of shear stress, the momentum dependence of phase space corrections is best described by Grad's quadratic ansatz, and not the linear response solution.
Hydrodynamic enhanced dielectrophoretic particle trapping
Miles, Robin R.
2003-12-09
Hydrodynamic enhanced dielectrophoretic particle trapping carried out by introducing a side stream into the main stream to squeeze the fluid containing particles close to the electrodes producing the dielelectrophoretic forces. The region of most effective or the strongest forces in the manipulating fields of the electrodes producing the dielectrophoretic forces is close to the electrodes, within 100 .mu.m from the electrodes. The particle trapping arrangement uses a series of electrodes with an AC field placed between pairs of electrodes, which causes trapping of particles along the edges of the electrodes. By forcing an incoming flow stream containing cells and DNA, for example, close to the electrodes using another flow stream improves the efficiency of the DNA trapping.
Symposium: Nonlinear Waves and Singularities in Optics, Hydrodynamics and Plasmas
Lushnikov, Pavel
carriers in optical lines. NLS in 2D describes a stationary self-focusing of light in optical media to self-focusing the amplitude of an NLS solution tends to infinity after finite distance of propagation
Suspended sediment and hydrodynamics above mildly sloped long wave ripples
Kirby, James T.
of Miami, Miami, Florida, USA Daniel M. Hanes1 Coastal and Marine Geology, U.S. Geological Survey Pacific with the entrainment of sediment on the offshore flank of the ripple, and rapid vertical mixing at the time of flow of the ripple crest, near the time of flow reversal. The simulations indicate that only one vortex is formed
Pilot-wave hydrodynamics in a rotating frame: Exotic orbits
Oza, Anand U.; Harris, Daniel M.; Rosales, Rodolfo R.; Bush, John W. M., E-mail: bush@math.mit.edu [Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Wind-Willassen, Øistein [Department of Applied Mathematics and Computer Science, Technical University of Denmark, 2800 Kongens Lyngby (Denmark)
2014-08-15
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)].
An overview of seismic-induced hydrodynamic phenomena in LMR reactor tanks
Ma, D.C.; Chang, Y.W.; Seidensticker, R.W.
1991-01-01
Liquid metal reactors (LMTs) usually contain a huge volume of liquid sodium as reactor coolant. Since most reactor components are submerged in the sodium coolant, the seismic-induced hydrodynamic effects are of great importance in the design of LMR reactor components. Because LMRs operate at low pressures, the reactor components are made of thin-walled structures. Of interest in reactor design, in particular, are the hydrodynamic pressures imposed on various components, such as the reactor vessel wall, thermal liner, and components projecting down into the liquid sodium. The sloshing wave height and impact forces on the reactor cover are also important in assessing the safety of the reactor system. This paper presents an overview of the seismic-induced hydrodynamic phenomena in the LMR reactor tanks. 10 refs., 14 figs., 2 tabs.
Conservative, special-relativistic smoothed particle hydrodynamics
Rosswog, Stephan, E-mail: s.rosswog@jacobs-university.d [School of Engineering and Science, Jacobs University Bremen, 28759 Bremen (Germany)
2010-11-01
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.
Early Hydrodynamic Evolution of a Stellar Collision
NASA Astrophysics Data System (ADS)
Kushnir, Doron; Katz, Boaz
2014-04-01
The early phase of the hydrodynamic evolution following the collision of two stars is analyzed. Two strong shocks propagate from the contact surface and move toward the center of each star at a velocity that is a small fraction of the velocity of the approaching stars. The shocked region near the contact surface has a planar symmetry and a uniform pressure. The density vanishes at the (Lagrangian) surface of contact, and the speed of sound diverges there. The temperature, however, reaches a finite value, since as the density vanishes, the finite pressure is radiation dominated. For carbon-oxygen white dwarf (CO WD) collisions, this temperature is too low for any appreciable nuclear burning shortly after the collision, which allows for a significant fraction of the mass to be highly compressed to the density required for efficient 56Ni production in the detonation wave that follows. This property is crucial for the viability of collisions of typical CO WD as progenitors of type Ia supernovae, since otherwise only massive (>0.9 M ?) CO WDs would have led to such explosions (as required by all other progenitor models). The divergence of the speed of sound limits numerical studies of stellar collisions, as it makes convergence tests exceedingly expensive unless dedicated schemes are used. We provide a new one-dimensional Lagrangian numerical scheme to achieve this. A self-similar planar solution is derived for zero-impact parameter collisions between two identical stars, under some simplifying assumptions (including a power-law density profile), which is the planar version of previous piston problems that were studied in cylindrical and spherical symmetries.
Low Mach number fluctuating hydrodynamics of multispecies liquid mixtures
NASA Astrophysics Data System (ADS)
Donev, Aleksandar; Nonaka, Andy; Bhattacharjee, Amit Kumar; Garcia, Alejandro L.; Bell, John B.
2015-03-01
We develop a low Mach number formulation of the hydrodynamic equations describing transport of mass and momentum in a multispecies mixture of incompressible miscible liquids at specified temperature and pressure, which generalizes our prior work on ideal mixtures of ideal gases [Balakrishnan et al., "Fluctuating hydrodynamics of multispecies nonreactive mixtures," Phys. Rev. E 89 013017 (2014)] and binary liquid mixtures [Donev et al., "Low mach number fluctuating hydrodynamics of diffusively mixing fluids," Commun. Appl. Math. Comput. Sci. 9(1), 47-105 (2014)]. In this formulation, we combine and extend a number of existing descriptions of multispecies transport available in the literature. The formulation applies to non-ideal mixtures of arbitrary number of species, without the need to single out a "solvent" species, and includes contributions to the diffusive mass flux due to gradients of composition, temperature, and pressure. Momentum transport and advective mass transport are handled using a low Mach number approach that eliminates fast sound waves (pressure fluctuations) from the full compressible system of equations and leads to a quasi-incompressible formulation. Thermal fluctuations are included in our fluctuating hydrodynamics description following the principles of nonequilibrium thermodynamics. We extend the semi-implicit staggered-grid finite-volume numerical method developed in our prior work on binary liquid mixtures [Nonaka et al., "Low mach number fluctuating hydrodynamics of binary liquid mixtures," arXiv:1410.2300 (2015)] and use it to study the development of giant nonequilibrium concentration fluctuations in a ternary mixture subjected to a steady concentration gradient. We also numerically study the development of diffusion-driven gravitational instabilities in a ternary mixture and compare our numerical results to recent experimental measurements [Carballido-Landeira et al., "Mixed-mode instability of a miscible interface due to coupling between Rayleigh-Taylor and double-diffusive convective modes," Phys. Fluids 25, 024107 (2013)] in a Hele-Shaw cell. We find that giant nonequilibrium fluctuations can trigger the instability but are eventually dominated by the deterministic growth of the unstable mode, in both quasi-two-dimensional (Hele-Shaw) and fully three-dimensional geometries used in typical shadowgraph experiments.
Hydrodynamical processes in coalescing binary stars
NASA Astrophysics Data System (ADS)
Lai, Dong
1994-01-01
Coalescing neutron star binaries are considered to be the most promising sources of gravitational waves that could be detected by the planned laser-interferometer LIGO/VIRGO detectors. Extracting gravity wave signals from noisy data requires accurate theoretical waveforms in the frequency range 10-1000 Hz end detailed understanding of the dynamics of the binary orbits. We investigate the quasi-equilibrium and dynamical tidal interactions in coalescing binary stars, with particular focus on binary neutron stars. We develop a new formalism to study the equilibrium and dynamics of fluid stars in binary systems. The stars are modeled as compressible ellipsoids, and satisfy polytropic equation of state. The hydrodynamic equations are reduced to a set of ordinary differential equations for the evolution of the principal axes and other global quantities. The equilibrium binary structure is determined by a set of algebraic equations. We consider both synchronized and nonsynchronized systems, obtaining the generalizations to compressible fluid of the classical results for the ellipsoidal binary configurations. Our method can be applied to a wide variety of astrophysical binary systems containing neutron stars, white dwarfs, main-sequence stars and planets. We find that both secular and dynamical instabilities can develop in close binaries. The quasi-static (secular) orbital evolution, as well as the dynamical evolution of binaries driven by viscous dissipation and gravitational radiation reaction are studied. The development of the dynamical instability accelerates the binary coalescence at small separation, leading to appreciable radial infall velocity near contact. We also study resonant excitations of g-mode oscillations in coalescing binary neutron stars. A resonance occurs when the frequency of the tidal driving force equals one of the intrinsic g-mode frequencies. Using realistic microscopic nuclear equations of state, we determine the g-modes in a cold neutron atar. Resonant excitations of these g-modes during the last few minutes of the binary coalescence result in energy transfer and angular momentum transfer from the binary orbit to the neutron star. Because of the weak coupling between the g-modes and the tidal potential, the induced orbital phase errors due to resonances are small. However, resonant excitations of the g-modes play an important role in the tidal heating of binary neutron stars.
The South Carolina Coastal Erosion Study: Nearshore Hydrodynamics Field Experiment
NASA Astrophysics Data System (ADS)
Haas, K. A.; Voulgaris, G.; Demir, H.; Work, P. A.; Hanes, D. M.
2004-12-01
As part of the South Carolina Coastal Erosion Study (SCCES) a nearshore field experiment was carried out for five days in December 2003 just north of Myrtle Beach, South Carolina, providing measurements of the waves, currents and morphological evolution. This experiment occurred concurrently with an extensive field campaign several kilometers offshore which included measurements of the waves and currents on and near a significant sand shoal. The purpose of the nearshore experiment was to aid in the identification of the effect of the offshore shoal on the nearshore processes. The resulting dataset will be used for verification of numerical models being used to investigate the hydrodynamics of the region. The experiment was carried out from December 10 to December 15 and consisted of measurements of the waves and currents, extensive surveys of the bathymetry every day, grab samples of the sediments, and video imagery. The hydrodynamics were measured using two Sontek Triton downward-looking Acoustic Doppler Velocimeters and two Nortek AquaDopp profilers arranged in a cross-shore line from inside the swash to several surf zone widths past the breakers. The bathymetric surveying was accomplished using both a differential GPS system and a total station. Surveying was performed each day in order to capture the morphological changes. On the last day, seven sediment samples were taken along a single cross-section to determine the sediment characteristics across the beach. Additionally, a video camera was located on a balcony of the top floor of a nearby hotel providing an excellent field of view of the entire experimental area. Digital video was captured directly onto a computer during all daylight hours and many control points were surveyed in each day to facilitate rectification of the imagery. A variety of conditions were encountered during the experiment, including two storm fronts which passed through, generating wind speeds up to 15 m/s. The first storm generated waves from the south driving a longshore current towards the north. After several relatively calm days with nearly normal incident waves the second front passed through the area with strong wind and waves approaching the shore with a large angle of incidence from the north. This drove an extremely strong longshore current in excess of 1.4 m/s and caused significant morphological changes.
Viscous hydrodynamics for strongly anisotropic expansion
NASA Astrophysics Data System (ADS)
Heinz, Ulrich; Bazow, Dennis; Strickland, Michael
2014-11-01
A new formulation of second-order viscous hydrodynamics, based on an expansion around a locally anisotropic momentum distribution, is presented. It generalizes the previously developed formalism of anisotropic hydrodynamics (AHYDRO) to include a complete set of dissipative currents for which equations of motion are derived by solving the Boltzmann equation in the 14-moment approximation. By solving the VAHYDRO equations for a transversally homogeneous, longitudinally boost-invariant system ((0 + 1)-dimensional expansion) and comparing with the exact solution of the Boltzmann equation in relaxation-time approximation we show that VAHYDRO performs much better than all other known second-order viscous hydrodynamic approximations.
Non abelian hydrodynamics and heavy ion collisions
NASA Astrophysics Data System (ADS)
Calzetta, E.
2014-01-01
The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined by the conservation laws of energy momentum and color currents. Therefore it is possible to describe its main features in hydrodynamic terms, the very short color neutralization time notwithstanding. In this lecture we shall give a simple derivation of the hydrodynamics of a color charged fluid, by generalizing the usual derivation of hydrodynamics from kinetic theory to the non abelian case.
Solving the viscous hydrodynamics order by order
Gao, Jian-Hua
2014-01-01
In this paper, we propose a method of solving the viscous hydrodynamics order by order in a derivative expansion. In such method, the zero order solution is just the one of the ideal hydrodynamics. All the other higher order corrections satisfy the same first-order partial differential equations but with different inhomogeneous terms. We therefore argue that our method could be easily extended to any orders. The problem of causality and stability will be released if the gradient expansion is guaranteed. This method might be of great help to both theoretical and numerical calculations of relativistic hydrodynamics.
Dileptons from transport and hydrodynamical models
Huovinen, P.; Koch, V.
2000-01-01
Transport and hydrodynamical models used to describe the expansion stage of a heavy-ion collision at the CERN SPS give different dilepton spectrum even if they are tuned to reproduce the observed hadron spectra. To understand the origin of this difference we compare the dilepton emission from transport and hydrodynamical models using similar initial states in both models. We find that the requirement of pion number conservation in a hydrodynamical model does not change the dilepton emission. Also the mass distribution from the transport model indicates faster cooling and longer lifetime of the fireball.
Microscopic Diffusion and Hydrodynamic Interactions of Hemoglobin in Red Blood Cells
Doster, Wolfgang; Longeville, Stéphane
2007-01-01
The cytoplasm of red blood cells is congested with the oxygen storage protein hemoglobin occupying a quarter of the cell volume. The high protein concentration leads to a reduced mobility; the self-diffusion coefficient of hemoglobin in blood cells is six times lower than in dilute solution. This effect is generally assigned to excluded volume effects in crowded media. However, the collective or gradient diffusion coefficient of hemoglobin is only weakly dependent on concentration, suggesting the compensation of osmotic and friction forces. This would exclude hydrodynamic interactions, which are of dynamic origin and do not contribute to the osmotic pressure. Hydrodynamic coupling between protein molecules is dominant at short time- and length scales before direct interactions are fully established. Employing neutron spin-echo-spectroscopy, we study hemoglobin diffusion on a nanosecond timescale and protein displacements on the scale of a few nanometers. A time- and wave-vector dependent diffusion coefficient is found, suggesting the crossover of self- and collective diffusion. Moreover, a wave-vector dependent friction function is derived, which is a characteristic feature of hydrodynamic interactions. The wave-vector and concentration dependence of the long-time self-diffusion coefficient of hemoglobin agree qualitatively with theoretical results on hydrodynamics in hard spheres suspensions. Quantitative agreement requires us to adjust the volume fraction by including part of the hydration shell: Proteins exhibit a larger surface/volume ratio compared to standard colloids of much larger size. It is concluded that hydrodynamic and not direct interactions dominate long-range molecular transport at high concentration. PMID:17513357
Prediction of hydrodynamic performance of an FLNG system in side-by-side offloading operation
NASA Astrophysics Data System (ADS)
Zhao, Wenhua; Yang, Jianmin; Hu, Zhiqiang; Tao, Longbin
2014-04-01
Floating liquefied natural gas (FLNG) is a type of liquefied natural gas (LNG) production system that shows prospects in exploitation of stranded offshore gas fields. The dynamic performance of an FLNG system in side-by-side configuration with a LNG carrier under the combined actions of wave, current and wind can be quite complex. This paper presents a comprehensive study on the hydrodynamics of an FLNG system with a focus on the nonlinear coupling effects of vessels and connection systems based on the concept FLNG prototype recently designed for South China Sea. In this study, the hydrodynamic characteristics of the two floating vessels connected through hawsers and fenders are investigated using a state-of-the-art time-domain simulation code SIMO, considering their mechanical and hydrodynamic coupling effects. The simulation model consisting of FLNG and LNG carrier is developed and calibrated by a series of model tests including a tuned damping and viscous levels. The hydrodynamic performances of the two floating vessels under an extreme sea state during side-by-side offloading operation are obtained, and their relative motions and the force responses of the connection hawsers and fenders are analyzed. Sensitivity studies are conducted to clarify contributions from the pretension and the stiffness of the connection hawsers. The effects on the hydrodynamic performance of the vessels and on the loads of the connection system are also investigated.
Hydrodynamic Model of Spatio-Temporal Evolution of Two-Plasmon Decay
Dimitrijevic, D. R.; Maluckov, A. A. [Department of Physics, Faculty of Sciences and Mathematics, University of Nis, P. O. Box 224, 18001 Nis (Serbia)
2010-01-21
A hydrodynamic model of two-plasmon decay in a homogeneous plasma slab near the quarter-critical density is constructed in order to gain better insight into the spatio-temporal evolution of the daughter electron plasma waves in plasma in the course of the instability. The influence of laser and plasma parameters on the evolution of the amplitudes of the participating waves is discussed. The secondary coupling of two daughter electron plasma waves with an ion-acoustic wave is assumed to be the principal mechanism of saturation of the instability. The impact of the inherently nonresonant nature of this secondary coupling on the development of TPD is investigated and it is shown to significantly influence the electron plasma wave dynamics. Its inclusion leads to nonuniformity of the spatial profile of the instability and causes the burst-like pattern of the instability development, which should result in the burst-like hot-electron production in homogeneous plasma.
Typical geometry of rogue waves
NASA Astrophysics Data System (ADS)
Yudin, Alexander; Shamin, Roman
2015-04-01
Our talk presents geometry results of numerical modeling of rogue waves based on the full nonlinear equations of hydrodynamics. We describe the widespread types of rogue waves in computational experiments. We received a lot of rogue waves in our computing experiments. About 95% of these waves have the typical form of steep ridge ("wall of water"). Other rogue waves have the form of deepest depression ("hole in the sea") or represent several waves of very big height ("three sisters"). Rogue waves from our experiments are one of such individual waves. The most widespread rogue waves have the form of wall of water. Both parts of this wave from the left minimum to the maximum and from the maximum to the right minimum are well-approximated by three-degree polynomials. It gets the follow type after linear transformation when the ordinate of maximum point is transferred to the point with coordinates. References Zakharov V.E., Shamin R.V and Yudin A.V.: Energy Portrait of Rogue Waves, JETP Letters, 2014, Vol. 99, No. 9, pp. 514-517, DOI: 10.1134/S0021364014090136
Transonic Hydrodynamic Escape of Hydrogen from Extrasolar Planetary Atmospheres
Feng Tian; Owen B. Toon; Alexander A. Pavlov; H. De Sterck
2005-01-01
Hydrodynamic escape is an important process in the formation and evolution of planetary atmospheres. Tran- sonic steady state solutions of the time-independent hydrodynamic equations are difficult to find because of the existence of a singularity point. A numerical model is developed to study the hydrodynamic escape of neutral gas from planetary atmospheres by solving the time-dependent hydrodynamic equations. The model
Shear viscosity, cavitation and hydrodynamics at LHC
Jitesh R. Bhatt; Hiranmaya Mishra; V. Sreekanth
2011-09-28
We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid become invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early during the evolution of the hydrodynamics in time $\\lesssim 2 $fm/c. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal term used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.
The hydrodynamics of swimming microorganisms
NASA Astrophysics Data System (ADS)
Lauga, Eric; Powers, Thomas R.
2009-09-01
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 micrometers and below. At this scale, inertia is unimportant and the Reynolds number is small. Our emphasis is on the simple physical picture and fundamental flow physics phenomena in this regime. We first give a brief overview of the mechanisms for swimming motility, and of 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, in particular early calculations of swimming kinematics with prescribed stroke and the application of resistive force theory and slender-body theory to flagellar locomotion. After examining 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.
Hydrodynamics from scalar black branes
NASA Astrophysics Data System (ADS)
Roychowdhury, Dibakar
2015-04-01
In this paper, using the Gauge/gravity duality techniques, we explore the hydrodynamic regime of a very special class of strongly coupled QFTs that come up with an emerging UV length scale in the presence of a negative hyperscaling violating exponent. The dual gravitational counterpart for these QFTs consists of scalar dressed black brane solutions of exactly integrable Einstein-scalar gravity model with Domain Wall (DW) asymptotics. In the first part of our analysis we compute the R-charge diffusion for the boundary theory and find that (unlike the case for the pure AdS 4 black branes) it scales quite non trivially with the temperature. In the second part of our analysis, we compute the ?/s ratio both in the non extremal as well as in the extremal limit of these special class of gauge theories and it turns out to be equal to 1 /4 ? in both the cases. These results therefore suggest that the quantum critical systems in the presence of (negative) hyperscaling violation at UV, might fall under a separate universality class as compared to those conventional quantum critical systems with the usual AdS 4 duals.
Hydrodynamic Instabilities Produced by Evaporation
NASA Astrophysics Data System (ADS)
Romo-Cruz, Julio Cesar Ruben; Hernandez-Zapata, Sergio; Ruiz-Chavarria, Gerardo
2012-11-01
When a liquid layer (alcohol in the present work) is in an environment where its relative humidity is less than 100 percent evaporation appears. When RH is above a certain threshold the liquid is at rest. If RH decreases below this threshold the flow becomes unstable, and hydrodynamic cells develop. The aim of this work is to understand the formation of those cells and its main features. Firstly, we investigate how the cell size depends on the layer width. We also study how temperature depends on the vertical coordinate when the cells are present. An inverse temperature gradient is found, that is, the bottom of liquid layer is colder than the free surface. This shows that the intuitive idea that the cells are due to a direct temperature gradient, following a Marangoni-like process, does not work. We propose the hypothesis that the evaporation produce a pressure gradient that is responsible of the cell development. On the other hand, using a Schlieren technique we study the topography of the free surface when cells are present. Finally the alcohol vapor layer adjacent to the liquid surface is explored using scattering experiments, giving some insight on the plausibility of the hypothesis described previously. Authors acknowledge support by DGAPA-UNAM under project IN116312 ``Vorticidad y ondas no lineales en fluidos.''
Hydrodynamics of unitary Fermi gases
NASA Astrophysics Data System (ADS)
Young, Ryan E.
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.
Hydrodynamic aspects of fish olfaction
Cox, Jonathan P.L
2008-01-01
Flow into and around the olfactory chamber of a fish determines how odorant from the fish's immediate environment is transported to the sensory surface (olfactory epithelium) lining the chamber. Diffusion times in water are long, even over comparatively short distances (millimetres). Therefore, transport from the external environment to the olfactory epithelium must be controlled by processes that rely on convection (i.e. the bulk flow of fluid). These include the beating of cilia lining the olfactory chamber and the relatively inexpensive pumping action of accessory sacs. Flow through the chamber may also be induced by an external flow. Flow over the olfactory epithelium appears to be laminar. Odorant transfer to the olfactory epithelium may be facilitated in several ways: if the olfactory organs are mounted on stalks that penetrate the boundary layer; by the steep velocity gradients generated by beating cilia; by devices that deflect flow into the olfactory chamber; by parallel arrays of olfactory lamellae; by mechanical agitation of the chamber (or olfactory stalks); and by vortices. Overall, however, our knowledge of the hydrodynamics of fish olfaction is far from complete. Several areas of future research are outlined. PMID:18184629
Hydrodynamic modeling of detonations for structural design of containment vessels.
Rodriguez, E. A. (Edward A.); Romero, C. (Christopher)
2005-01-01
Los Alamos National Laboratory (LANL), under the auspices of the U.S. Department of Energy (DOE) and the National Nuclear Security Administration (NNSA), has been conducting confined high explosion experiments utilizing large, spherical, steel pressure vessels to contain the reaction products and hazardous materials from high-explosive (HE) events. Structural design of these spherical vessels was originally accomplished by maintaining that the vessel's kinetic energy, developed from the detonation impulse loading, be equilibrated by the elastic strain energy inherent in the vessel. In some cases, the vessel is designed for one-time use only, efficiently utilizing the significant plastic energy absorption capability of ductile vessel materials. Alternatively, the vessel can be designed for multiple use, in which case the material response is restricted to the elastic range. Within the last decade, designs have been accomplished utilizing sophisticated and advanced 3D computer codes that address both the detonation hydrodynamics and the vessel's highly nonlinear structural dynamic response. This paper describes the hydrodynamic modeling of HE reaction products phase, which produces transient pressures resulting in an impulsive load on the vessel shell. Modeling is accomplished through either (a) empirical/analytical methods utilizing a vast experimental database developed primarily for the Department of Defense (DoD) or (b) through application of numerical hydrodynamics codes, such as the Sandia National Laboratories (SNL) shock-wave physics code, CTH, which accurately model the thermochemistry and thermophysics of a detonation. It should be noted that this paper only addresses blast load prediction using the methods stated and does not include an assessment of structural response methods.
RAMSES: A new N-body and hydrodynamical code
NASA Astrophysics Data System (ADS)
Teyssier, Romain
2010-11-01
A new N-body and hydrodynamical code, called RAMSES, is presented. It has been designed to study structure formation in the universe with high spatial resolution. The code is based on Adaptive Mesh Refinement (AMR) technique, with a tree based data structure allowing recursive grid refinements on a cell-by-cell basis. The N-body solver is very similar to the one developed for the ART code (Kravtsov et al. 97), with minor differences in the exact implementation. The hydrodynamical solver is based on a second-order Godunov method, a modern shock-capturing scheme known to compute accurately the thermal history of the fluid component. The accuracy of the code is carefully estimated using various test cases, from pure gas dynamical tests to cosmological ones. The specific refinement strategy used in cosmological simulations is described, and potential spurious effects associated to shock waves propagation in the resulting AMR grid are discussed and found to be negligible. Results obtained in a large N-body and hydrodynamical simulation of structure formation in a low density LCDM universe are finally reported, with 256^3 particles and 4.1 10^7 cells in the AMR grid, reaching a formal resolution of 8192^3. A convergence analysis of different quantities, such as dark matter density power spectrum, gas pressure power spectrum and individual haloes temperature profiles, shows that numerical results are converging down to the actual resolution limit of the code, and are well reproduced by recent analytical predictions in the framework of the halo model.
Numerical Hydrodynamics in Strong-Field General Relativity
NASA Astrophysics Data System (ADS)
East, William Edward
In this thesis we develop and test methods for numerically evolving hydrodynamics coupled to the Einstein field equations, and then apply them to several problems in gravitational physics and astrophysics. The hydrodynamics scheme utilizes high-resolution shock-capturing techniques with flux corrections while the Einstein equations are evolved in the generalized harmonic formulation using finite difference methods. We construct initial data by solving the constraint equations using a multigrid algorithm with free data chosen based on superposing isolated compact objects. One application we consider is the merger of black hole-neutron star and neutron star-neutron star binaries that form through dynamical capture, as may occur in globular clusters or galactic nuclei. These systems can merge with non-negligible orbital eccentricity and display significant variability in dynamics and outcome as a function of initial impact parameter. We study the electromagnetic and gravitational-wave transients that these mergers may produce and their prospects for being detected with upcoming observations. We also introduce a numerical technique that allows solutions to the full Einstein equations to be obtained for extreme-mass-ratio systems where the spacetime is dominated by a known background solution. This technique is based on using the knowledge of a background solution to subtract off its contribution to the truncation error. We use this to study the tidal effects and gravitational radiation from a solar-type star falling into a supermassive black hole. Finally, we utilize general-relativistic hydrodynamics to study ultrarelativistic black hole formation. We study the head-on collision of fluid particles well within the kinetic energy dominated regime (Lorentz factors of 8-12). We find that black hole formation does occur at energies a factor of a few below simple hoop conjecture estimates. We also find that near the threshold for black hole formation, the collision leads to two separate apparent horizons which then merge. Both of these phenomena can be understood in terms of a gravitational focusing effect.
Hydrodynamic simulations of He-shell flash convection
Falk Herwig; Bernd Freytag; Robert M. Hueckstaedt; Francis X. Timmes
2006-01-09
We present the first hydrodynamic, multi-dimensional simulations of He-shell flash convection. Specifically, we investigate the properties of shell convection at a time immediately before the He- luminosity peak during the 15th thermal pulse of a stellar evolution track with initially two solar masses and metallicity Z=0.01. This choice is a representative example of a low-mass asymptotic giant branch thermal pulse. We construct the initial vertical stratification with a set of polytropes to resemble the stellar evolution structure. Convection is driven by a constant volume heating in a thin layer at the bottom of the unstable layer. We calculate a grid of 2D simulations with different resolutions and heating rates. Our set of simulations includes one low-resolution 3D run. The computational domain includes 11.4 pressure scale heights. He-shell flash convection is dominated by large convective cells that are centered in the lower half of the convection zone. Convective rolls have an almost circular appearance because focusing mechanisms exist in the form of the density stratification for downdrafts and the heating of localized eddies that generate upflows. Nevertheless, downdrafts appear to be somewhat more focused. The He-shell flash convection generates a rich spectrum of gravity waves in both stable layers above and beneath the convective shell. The magnitude of the convective velocities from our 1D mixing-length theory model and the rms-averaged vertical velocities from the hydrodynamic model are consistent within a factor of a few. However, the velocity profile in the hydrodynamic simulation is more asymmetric, and decays exponentially inside the convection zone. [abbreviated
Hydrodynamic Cavitation for Food and Water Processing
Parag R. Gogate
2011-01-01
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
Improvements to SOIL: An Eulerian hydrodynamics code
Davis, C.G.
1988-04-01
Possible improvements to SOIL, an Eulerian hydrodynamics code that can do coupled radiation diffusion and strength of materials, are presented in this report. Our research is based on the inspection of other Eulerian codes and theoretical reports on hydrodynamics. Several conclusions from the present study suggest that some improvements are in order, such as second-order advection, adaptive meshes, and speedup of the code by vectorization and/or multitasking. 29 refs., 2 figs.
General Relativistic Hydrodynamic Equations in Multiple Coordinates
Xuejun Wu; Chongming Xu
2002-01-01
General relativistic hydrodynamics is an important subject in classical general relativity1. The importance is not only from theoretical point view, but also in the practical application, e.g., compact star, precise measurement in geophysics and cosmological problems. For first order post-Newtonian (1PN) hydrodynamics it has been investigated by many authors (e.g. Chandrasekhar2; Greenberg3; Blanchet, Damour & Schäfer4). But we should point
NASA Astrophysics Data System (ADS)
Yang, Chun-Cheng; Bian, Xiu-Fang; Yang, Jian-Fei
2014-03-01
Using combination of ferrofluid (FF) and Fe-based amorphous alloy in the advanced treatment of high concentration, organic wastewater was investigated. The addition of Fe73.5Nb3Cu1Si13.5B9 amorphous alloy powders into a FF give rise to a dramatic enhancement in decreasing chemical oxygen demand (COD) and decolorization. The removal rate of COD by using FF that combined Fe73.5Nb3Cu1Si13.5B9 metallic glass (MG) particles reached 92% in the presence of H2O2, nearly more than 50% higher than that by using only FF. Furthermore, compared with the FF, the decolorizing effect of the combination was 20% higher. It has been found that MG powders with the amorphous structures have high efficiency of waste water treatment and lead to high catalytic ability.
Reena Mary, A P; Narayanan, T N; Sunny, Vijutha; Sakthikumar, D; Yoshida, Yasuhiko; Joy, P A; Anantharaman, M R
2010-01-01
Bio-compatible magnetic fluids having high saturation magnetization find immense applications in various biomedical fields. Aqueous ferrofluids of superparamagnetic iron oxide nanoparticles with narrow size distribution, high shelf life and good stability is realized by controlled chemical co-precipitation process. The crystal structure is verified by X-ray diffraction technique. Particle sizes are evaluated by employing Transmission electron microscopy. Room temperature and low-temperature magnetic measurements were carried out with Superconducting Quantum Interference Device. The fluid exhibits good magnetic response even at very high dilution (6.28 mg/cc). This is an advantage for biomedical applications, since only a small amount of iron is to be metabolised by body organs. Magnetic field induced transmission measurements carried out at photon energy of diode laser (670 nm) exhibited excellent linear dichroism. Based on the structural and magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of radiofrequencies. PMID:21076702
2010-01-01
Bio-compatible magnetic fluids having high saturation magnetization find immense applications in various biomedical fields. Aqueous ferrofluids of superparamagnetic iron oxide nanoparticles with narrow size distribution, high shelf life and good stability is realized by controlled chemical co-precipitation process. The crystal structure is verified by X-ray diffraction technique. Particle sizes are evaluated by employing Transmission electron microscopy. Room temperature and low-temperature magnetic measurements were carried out with Superconducting Quantum Interference Device. The fluid exhibits good magnetic response even at very high dilution (6.28 mg/cc). This is an advantage for biomedical applications, since only a small amount of iron is to be metabolised by body organs. Magnetic field induced transmission measurements carried out at photon energy of diode laser (670 nm) exhibited excellent linear dichroism. Based on the structural and magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of radiofrequencies. PMID:21076702
Nemala, H.; Thakur, J. S.; Lawes, G.; Naik, R., E-mail: rnaik@wayne.edu [Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48202 (United States); Naik, V. M. [Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128 (United States); Vaishnava, P. P. [Department of Physics, Kettering University, Flint, Michigan 48504 (United States)
2014-07-21
Rate of heat generated by magnetic nanoparticles in a ferrofluid is affected by their magnetic properties, temperature, and viscosity of the carrier liquid. We have investigated temperature dependent magnetic hyperthermia in ferrofluids, consisting of dextran coated superparamagnetic Fe{sub 3}O{sub 4} nanoparticles, subjected to external magnetic fields of various frequencies (188–375 kHz) and amplitudes (140–235 Oe). Transmission electron microscopy measurements show that the nanoparticles are polydispersed with a mean diameter of 13.8?±?3.1?nm. The fitting of experimental dc magnetization data to a standard Langevin function incorporating particle size distribution yields a mean diameter of 10.6?±?1.2?nm, and a reduced saturation magnetization (?65?emu/g) compared to the bulk value of Fe{sub 3}O{sub 4} (?95?emu/g). This is due to the presence of a finite surface layer (?1?nm thickness) of non-aligned spins surrounding the ferromagnetically aligned Fe{sub 3}O{sub 4} core. We found the specific absorption rate, measured as power absorbed per gram of iron oxide nanoparticles, decreases monotonically with increasing temperature for all values of magnetic field and frequency. Using the size distribution of magnetic nanoparticles estimated from the magnetization measurements, we have fitted the specific absorption rate versus temperature data using a linear response theory and relaxation dissipation mechanisms to determine the value of magnetic anisotropy constant (28?±?2?kJ/m{sup 3}) of Fe{sub 3}O{sub 4} nanoparticles.
Kinematics and hydrodynamics of linear acceleration in eels, Anguilla rostrata.
Tytell, Eric D
2004-12-22
The kinematics and hydrodynamics of routine linear accelerations were studied in American eels, Anguilla rostrata, using high-speed video and particle image velocimetry. Eels were examined both during steady swimming at speeds from 0.6 to 1.9 body lengths (L) per second and during accelerations from -1.4 to 1.3 L s(-2). Multiple regression of the acceleration and steady swimming speed on the body kinematics suggests that eels primarily change their tail-tip velocity during acceleration. By contrast, the best predictor of steady swimming speed is body wave speed, keeping tail-tip velocity an approximately constant fraction of the swimming velocity. Thus, during steady swimming, Strouhal number does not vary with speed, remaining close to 0.32, but during acceleration, it deviates from the steady value. The kinematic changes during acceleration are indicated hydrodynamically by axial fluid momentum in the wake. During steady swimming, the wake consists of lateral jets of fluid and has minimal net axial momentum, which reflects a balance between thrust and drag. During acceleration, those jets rotate to point downstream, adding axial momentum to the fluid. The amount of added momentum correlates with the acceleration, but is greater than the necessary inertial force by 2.8+/-0.6 times, indicating a substantial acceleration reaction. PMID:15615678
Starrfield, S.; Kenyon, S.; Truran, J.W.; Sparks, W.M.
1983-01-01
We have used a Lagrangian, hydrodynamic stellar-evolution computer code to evolve a thermonuclear runaway in the accreted hydrogen rich envelope of a 1.0M, 10-km neutron star. Our simulation produced an outburst which lasted about 2000 sec and peak effective temperature was 3 keV. The peak luminosity exceeded 2 x 10/sup 5/ L. A shock wave caused a precursor in the light curve which lasted 10/sup -5/ sec.
Hydrodynamic Instability in an Extended Landau/Levich Model of Liquid-Propellant Combustion
NASA Technical Reports Server (NTRS)
Margolis, Stephen B.; Sackesteder, Kurt (Technical Monitor)
1998-01-01
The classical Landau/Levich models of liquid propellant combustion, which serve as seminal examples of hydrodynamic instability in reactive systems, have been combined and extended to account for a dynamic dependence, absent in the original formulations, of the local burning rate on the local pressure and/or temperature fields. The resulting model admits an extremely rich variety of both hydrodynamic and reactive/diffusive instabilities that can be analyzed in various limiting parameter regimes. In the present work, a formal asymptotic analysis, based on the realistic smallness of the gas-to-liquid density ratio, is developed to investigate the combined effects of gravity, surface tension and viscosity on the hydrodynamic instability of the propagating liquid/gas interface. In particular, a composite asymptotic expression, spanning three distinguished wavenumber regimes, is derived for both cellular and pulsating hydrodynamic neutral stability boundaries A(sub p)(k), where A(sub p) is the pressure sensitivity of the burning rate and k is the disturbance wavenumber. For the case of cellular (Landau) instability, the results demonstrate explicitly the stabilizing effect of gravity on long-wave disturbances, the stabilizing effect of viscosity and surface tension on short-wave perturbations, and the instability associated with intermediate wavenumbers for critical negative values of A(sub p). In the limiting case of weak gravity, it is shown that cellular hydrodynamic instability in this context is a long-wave instability phenomenon, whereas at normal gravity, this instability is first manifested through O(l) wavenumber disturbances. It is also demonstrated that, in the large wavenumber regime, surface tension and both liquid and gas viscosity all produce comparable stabilizing effects in the large-wavenumber regime, thereby providing significant modifications to previous analyses of Landau instability in which one or more of these effects were neglected. In contrast, the pulsating hydrodynamic stability boundary is found to be insensitive to gravitational and surface-tension effects, but is more sensitive to the effects of liquid viscosity, which is a significant stabilizing effect for O(l) and higher wavenumbers. Liquid-propellant combustion is predicted to be stable (i.e., steady and planar) only for a range of negative pressure sensitivities that lie between the two types of hydrodynamic stability boundaries.
Interaction of three-dimensional hydrodynamic and thermocapillary instabilities in film flows
NASA Astrophysics Data System (ADS)
Scheid, Benoit; Kalliadasis, Serafim; Ruyer-Quil, Christian; Colinet, Pierre
2008-12-01
We study three-dimensional wave patterns on the surface of a film flowing down a uniformly heated wall. Our starting point is a model of four evolution equations for the film thickness h , the interfacial temperature ? , and the streamwise and spanwise flow rates, q and p , respectively, obtained by combining a gradient expansion with a weighted residual projection. This model is shown to be robust and accurate in describing the competition between hydrodynamic waves and thermocapillary Marangoni effects for a wide range of parameters. For small Reynolds numbers, i.e., in the “drag-gravity regime,” we observe regularly spaced rivulets aligned with the flow and preventing the development of hydrodynamic waves. The wavelength of the developed rivulet structures is found to closely match the one of the most amplified mode predicted by linear theory. For larger Reynolds numbers, i.e., in the “drag-inertia regime,” the situation is similar to the isothermal case and no rivulets are observed. Between these two regimes we observe a complex behavior for the hydrodynamic and thermocapillary modes with the presence of rivulets channeling quasi-two-dimensional waves of larger amplitude and phase speed than those observed in isothermal conditions, leading possibly to solitarylike waves. Two subregions are identified depending on the topology of the rivulet structures that can be either “ridgelike” or “groovelike.” A regime map is further proposed that highlights the influence of the Reynolds and the Marangoni numbers on the rivulet structures. Interestingly, this map is found to be related to the variations of amplitude and speed of the two-dimensional solitary-wave solutions of the model. Finally, the heat transfer enhancement due to the increase of interfacial area in the presence of rivulet structures is shown to be significant.
Hydrodynamics of soft active matter
NASA Astrophysics Data System (ADS)
Marchetti, M. C.; Joanny, J. F.; Ramaswamy, S.; Liverpool, T. B.; Prost, J.; Rao, Madan; Simha, R. Aditi
2013-07-01
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.
Electro-hydrodynamic instability of stressed viscoelastic polymer films.
Closa, F; Raphaël, E; Ziebert, F
2013-10-01
We study the stability of a viscoelastic thin polymer film under two destabilization factors: the application of an electric field normal to the surface--as in typical electro-hydrodynamic destabilization experiments--and the presence of a frozen-in internal residual stress, stemming from the preparation process of the film, typically spin-coating. At the film-substrate interface we consider a general boundary condition, containing perfect gliding on slippery substrates, as well as perfect sticking of the film to the substrate as limiting cases. We show that the interplay of the two sources of stress, the viscoelasticity and the boundary condition, leads to a rich behavior, especially as far as the fastest growing wave number (or wavelength) is concerned. The latter determines the initial growth of the instability, and often also the final pattern obtained in small capacitor gaps, and is the main experimental observable. PMID:24158265
Renormalization and universality of blowup in hydrodynamic flows.
Mailybaev, Alexei A
2012-06-01
We consider self-similar solutions describing intermittent bursts in shell models of turbulence and study their relationship with blowup phenomena in continuous hydrodynamic models. First, we show that these solutions are very close to self-similar solution for the Fourier transformed inviscid Burgers equation corresponding to shock formation from smooth initial data. Then, the result is generalized to hyperbolic conservation laws in one space dimension describing compressible flows. It is shown that the renormalized wave profile tends to a universal function, which is independent both of initial conditions and of a specific form of the conservation law. This phenomenon can be viewed as a new manifestation of the renormalization group theory. Finally, we discuss possibilities for application of the developed theory for detecting and describing a blowup in incompressible flows. PMID:23005216
A hydrodynamic model of locomotion in the Basilisk Lizard
NASA Astrophysics Data System (ADS)
Glasheen, J. W.; McMahon, T. A.
1996-03-01
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.
Soft, Hydrodynamically Coupled Particles in a Hele-Shaw Channel
NASA Astrophysics Data System (ADS)
Uspal, William; Doyle, Patrick
2012-02-01
Control of flowing suspensions is central to many emerging microfluidic applications. For instance, manipulation of small clusters is important in the synthesis of functional particles. Via theory and simulations, we study small clusters confined in a microchannel with thin cross section and subject to an external flow. We show that many-body hydrodynamic interactions sustain long-lived bound states with complex dynamics. As these interactions are sensitive to confinement, we investigate modulation of channel geometry as a means to perform sequential operations in a continuous process. We also probe the effects of shape and elasticity via a Lattice Boltzmann/Lattice Spring code, finding spontaneous excitation of elastic waves (``flapping''), and enriched behavior through the orientational effects of shape. Our results demonstrate phenomena that could be exploited for assembly of soft colloids in microchannels.
Sharp shock model for propagating detonation waves
Bukiet, B.; Menikoff, R.
1989-01-01
Recent analyses of the reactive Euler equations have led to an understanding of the effect of curvature on an underdriven detonation wave. This advance can be incorporated into an improved sharp shock model for propagating detonation waves in hydrodynamic calculations. We illustrate the model with two simple examples: time dependent propagation of a diverging detonation wave in 1-D, and the steady 2-D propagation of a detonation wave in a rate stick. Incorporating this model into a 2-D front tracking code is discussed. 20 refs., 3 figs.
NASA Technical Reports Server (NTRS)
Margolis, Stephen B.; Sacksteder, Kurt (Technical Monitor)
2000-01-01
A pulsating form of hydrodynamic instability has recently been shown to arise during liquid-propellant deflagration in those parameter regimes where the pressure-dependent burning rate is characterized by a negative pressure sensitivity. This type of instability can coexist with the classical cellular, or Landau form of hydrodynamic instability, with the occurrence of either dependent on whether the pressure sensitivity is sufficiently large or small in magnitude. For the inviscid problem, it has been shown that, when the burning rate is realistically allowed to depend on temperature as well as pressure, sufficiently large values of the temperature sensitivity relative to the pressure sensitivity causes like pulsating form of hydrodynamic instability to become dominant. In that regime, steady, planar burning becomes intrinsically unstable to pulsating disturbances whose wave numbers are sufficiently small. This analysis is extended to the fully viscous case, where it is shown that although viscosity is stabilizing for intermediate and larger wave number perturbations, the intrinsic pulsating instability for small wave numbers remains. Under these conditions, liquid-propellant combustion is predicted to be characterized by large unsteady cells along the liquid/gas interface.
Quantum ion-acoustic wave oscillations in metallic nanowires
NASA Astrophysics Data System (ADS)
Moradi, Afshin
2015-05-01
The low-frequency electrostatic waves in metallic nanowires are studied using the quantum hydrodynamic model, in which the electron and ion components of the system are regarded as a two-species quantum plasma system. The Poisson equation as well as appropriate quantum boundary conditions give the analytical expressions of dispersion relations of the surface and bulk quantum ion-acoustic wave oscillations.
Hydrodynamic comparison between the north and south of Mallorca Island
NASA Astrophysics Data System (ADS)
Amores, Angel; Monserrat, Sebastià
2014-10-01
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.
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.
Treatment of compounds and alloys in radiation hydrodynamics simulations of ablative laser loading.
Swift, Damian C; Gammel, J Tinka; Clegg, Samuel M
2004-05-01
Different methods were compared for constructing models of the behavior of a prototype intermetallic compound, nickel aluminide, for use in radiation hydrodynamics simulations of shock wave generation by ablation induced by laser energy. The models included the equation of state, ionization, and radiation opacity. The methods of construction were evaluated by comparing the results of simulations of an ablatively generated shock wave in a sample of the alloy. The most accurate simulations were obtained using the "constant number density" mixture model to calculate the equation of state and opacity, and Thomas-Fermi ionization. This model is consistent with that found to be most accurate for simulations of ablatively shocked elements. PMID:15244945
NASA Astrophysics Data System (ADS)
Xu, Da A.; Lacoste, Deanna A.; Rusterholtz, Diane L.; Elias, Paul-Quentin; Stancu, Gabi D.; Laux, Christophe O.
2011-09-01
We report on an experimental study of the hydrodynamic expansion following a nanosecond repetitively pulsed (NRP) discharge in atmospheric pressure air preheated up to 1000 K. Single-shot schlieren images starting from 50 ns after the discharge were recorded to show the shock-wave propagation and the expansion of the heated gas channel. The temporal evolution of the gas temperature behind the shock-front is estimated from the measured shock-wave velocity by using the Rankine-Hugoniot relationships. The results show that a gas temperature increase of up to 1100 K can be observed 50 ns after the nanosecond pulse.
Wave Impact Reduction of Planing Boats
William S. Vorus; Richard A. Royce
The 3-year research effort reported here was dedicated to conception and development of devices for reducing the wave impact shock inherent with high-speed planing craft operating in waves. The first two years focused on assembly of rational methodology for predicting the hydrodynamics of generalized cylinders dropped onto a calm water surface. The generalizations were for a range of cross-section shapes
Relativistic shock waves in viscous gluon matter
I. Bouras; E. Molnar; H. Niemi; Z. Xu; A. El; O. Fochler; C. Greiner; D. H. Rischke
2009-07-22
We solve the relativistic Riemann problem in viscous gluon matter employing a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio $\\eta/s$ from zero to infinity. We show that an $\\eta/s$ ratio larger than 0.2 prevents the development of well-defined shock waves on timescales typical for ultrarelativistic heavy-ion collisions. Comparisons with viscous hydrodynamic calculations confirm our findings.
Relativistic Shock Waves in Viscous Gluon Matter
Bouras, I.; Xu, Z.; El, A.; Fochler, O.; Greiner, C. [Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main (Germany); Molnar, E.; Niemi, H. [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt am Main (Germany); Rischke, D. H. [Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main (Germany); Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt am Main (Germany)
2009-07-17
We solve the relativistic Riemann problem in viscous gluon matter employing a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio eta/s from zero to infinity. We show that an eta/s ratio larger than 0.2 prevents the development of well-defined shock waves on time scales typical for ultrarelativistic heavy-ion collisions. Comparisons with viscous hydrodynamic calculations confirm our findings.
Physical viscosity in smoothed particle hydrodynamics simulations of galaxy clusters
NASA Astrophysics Data System (ADS)
Sijacki, Debora; Springel, Volker
2006-09-01
Most hydrodynamical simulations of galaxy cluster formation carried out to date have tried to model the cosmic gas as an ideal, inviscid fluid, where only a small amount of (unwanted) numerical viscosity is present, arising from practical limitations of the numerical method employed, and with a strength that depends on numerical resolution. However, the physical viscosity of the gas in hot galaxy clusters may in fact not be negligible, suggesting that a self-consistent treatment that accounts for the internal gas friction would be more appropriate. To allow such simulations using the smoothed particle hydrodynamics (SPH) method, we derive a novel SPH formulation of the Navier-Stokes and general heat transfer equations and implement them in the GADGET-2 code. We include both shear and bulk viscosity stress tensors, as well as saturation criteria that limit viscous stress transport where appropriate. Our scheme integrates consistently into the entropy and energy conserving formulation of SPH employed by the code. Using a number of simple hydrodynamical test problems, e.g. the flow of a viscous fluid through a pipe, we demonstrate the validity of our implementation. Adopting Braginskii parametrization for the shear viscosity of hot gaseous plasmas, we then study the influence of viscosity on the interplay between AGN-inflated bubbles and the surrounding intracluster medium (ICM). We find that certain bubble properties like morphology, maximum clustercentric radius reached or survival time depend quite sensitively on the assumed level of viscosity. Interestingly, the sound waves launched into the ICM by the bubble injection are damped by physical viscosity, establishing a non-local heating process. However, we find that the associated heating is rather weak due to the overall small energy content of the sound waves. Finally, we carry out cosmological simulations of galaxy cluster formation with a viscous ICM. We find that the presence of physical viscosity induces new modes of entropy generation, including a significant production of entropy in filamentary regions perpendicular to the direction of the clusters encounter. Viscosity also modifies the dynamics of mergers and the motion of substructures through the cluster atmosphere. Substructures are generally more efficiently stripped of their gas, leading to prominent long gaseous tails behind infalling massive haloes.
An integrated coastal model for aeolian and hydrodynamic sediment transport
NASA Astrophysics Data System (ADS)
Baart, F.; den Bieman, J.; van Koningsveld, M.; Luijendijk, A. P.; Parteli, E. J. R.; Plant, N. G.; Roelvink, J. A.; Storms, J. E. A.; de Vries, S.; van Thiel de Vries, J. S. M.; Ye, Q.
2012-04-01
Dunes are formed by aeolian and hydrodynamic processes. Over the last decades numerical models were developed that capture our knowledge of the hydrodynamic transport of sediment near the coast. At the same time others have worked on creating numerical models for aeolian-based transport. Here we show a coastal model that integrates three existing numerical models into one online-coupled system. The XBeach model simulates storm-induced erosion (Roelvink et al., 2009). The Delft3D model (Lesser et al., 2004) is used for long term morphology and the Dune model (Durán et al., 2010) is used to simulate the aeolian transport. These three models were adapted to be able to exchange bed updates in real time. The updated models were integrated using the ESMF framework (Hill et al., 2004), a system for composing coupled modeling systems. The goal of this integrated model is to capture the relevant coastal processes at different time and spatial scales. Aeolian transport can be relevant during storms when the strong winds are generating new dunes, but also under relative mild conditions when the dunes are strengthened by transporting sand from the intertidal area to the dunes. Hydrodynamic transport is also relevant during storms, when high water in combination with waves can cause dunes to avalanche and erode. While under normal conditions the hydrodynamic transport can result in an onshore transport of sediment up to the intertidal area. The exchange of sediment in the intertidal area is a dynamic interaction between the hydrodynamic transport and the aeolian transport. This dynamic interaction is particularly important for simulating dune evolution at timescales longer than individual storm events. The main contribution of the integrated model is that it simulates the dynamic exchange of sediment between aeolian and hydrodynamic models in the intertidal area. By integrating the numerical models, we hope to develop a model that has a broader scope and applicability than existing models and is capable of simulating both the growth and destruction of coastal dunes. The integrated version of XBeach and Dune is currently being applied for a test case in Assateague Island in the United States. The integrated version of XBeach, Dune and Delft3D is applied to the Sand Engine in the Netherlands. In the presentation we show the current status of the development, experiences with the first test cases and our plans for future developments. [Durán et al., 2010] Durán, O., Parteli, E. J., and Herrmann, H. J. (2010). A continuous model for sand dunes: Review, new developments and application to barchan dunes and barchan dune fields. Earth Surface Processes and Landforms, 35(13):1591-1600. [Hill et al., 2004] Hill, C., DeLuca, C., Balaji, Suarez, M., and Da Silva, A. (2004). The architecture of the earth system modeling framework. Computing in Science Engineering, 6(1):18 - 28. [Lesser et al., 2004] Lesser, G. R., Roelvink, J. A., van Kester, J. A. T. M., and Stelling, G. S. (2004). Development and validation of a three-dimensional morphological model. Coastal Engineering, 51(8-9):883-915. Coastal Morphodynamic Modeling. [Roelvink et al., 2009] Roelvink, D., Reniers, A., van Dongeren, A., de Vries, J. v. T., McCall, R., and Lescinski, J. (2009). Modelling storm impacts on beaches, dunes and barrier islands. Coastal Engineering, 56(11-12):1133-1152.
L. A. Willson; S. J. Hill
1979-01-01
An analytical description of strictly periodic shock waves passing through a stellar atmosphere is developed which allows predictions to be made of the onset of instability of the system against mass loss by hydrodynamic ejection. This diagnostic method for determining when shock-driven mass loss may be expected is compared to several numerical isothermal hydrodynamical models. The predictions by the analytical
New formulation of leading order anisotropic hydrodynamics
Leonardo Tinti
2014-11-27
Anisotropic hydrodynamics is a reorganization of the relativistic hydrodynamics expansion, with the leading order already containing substantial momentum-space anisotropies. The latter are a cause of concern in the traditional viscous hydrodynamics, since large momentum anisotropies generated in ultrarelativistic heavy-ion collisions are not consistent with the hypothesis of small deviations from an isotropic background, i.e., from the local equilibrium distribution. We discuss the leading order of the expansion, presenting a new formulation for the (1+1)--dimensional case, namely, for the longitudinally boost invariant and cylindrically symmetric flow. This new approach is consistent with the well established framework of Israel and Stewart in the close to equilibrium limit (where we expect viscous hydrodynamics to work well). If we consider the (0+1)--dimensional case, that is, transversally homogeneous and longitudinally boost invariant flow, {the new form of anisotropic hydrodynamics leads to better agreement with known solutions} of the Boltzmann equation than the previous formulations, especially when we consider finite mass particles.
New formulation of leading order anisotropic hydrodynamics
NASA Astrophysics Data System (ADS)
Tinti, Leonardo
2015-05-01
Anisotropic hydrodynamics is a reorganization of the relativistic hydrodynamics expansion, with the leading order already containing substantial momentum-space anisotropies. The latter are a cause of concern in the traditional viscous hydrodynamics, since large momentum anisotropies generated in ultrarelativistic heavy-ion collisions are not consistent with the hypothesis of small deviations from an isotropic background, i.e., from the local equilibrium distribution. We discuss the leading order of the expansion, presenting a new formulation for the (1+1)- dimensional case, namely, for the longitudinally boost invariant and cylindrically symmetric flow. This new approach is consistent with the well established framework of Israel and Stewart in the close to equilibrium limit (where we expect viscous hydrodynamics to work well). If we consider the (0+1)-dimensional case, that is, transversally homogeneous and longitudinally boost invariant flow, the new form of anisotropic hydrodynamics leads to better agreement with known solutions of the Boltzmann equation than the previous formulations, especially when we consider massive particles.
Fluctuating hydrodynamics and direct simulation Monte Carlo
NASA Astrophysics Data System (ADS)
Balakrishnan, Kaushik; Bell, John B.; Donev, Aleksandar; Garcia, Alejandro L.
2012-11-01
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).
Hydrodynamic Nambu brackets derived by geometric constraints
NASA Astrophysics Data System (ADS)
Blender, Richard; Badin, Gualtiero
2015-03-01
A geometric approach to derive the Nambu brackets for ideal two-dimensional (2D) hydrodynamics is suggested. The derivation is based on two-forms with vanishing integrals in a periodic domain, and with resulting dynamics constrained by an orthogonality condition. As a result, 2D hydrodynamics with vorticity as dynamic variable emerges as a generic model, with conservation laws which can be interpreted as enstrophy and energy functionals. Generalized forms like surface quasi-geostrophy and fractional Poisson equations for the stream-function are also included as results from the derivation. The formalism is extended to a hydrodynamic system coupled to a second degree of freedom, with the Rayleigh–Bénard convection as an example. This system is reformulated in terms of constitutive conservation laws with two additive brackets which represent individual processes: a first representing inviscid 2D hydrodynamics, and a second representing the coupling between hydrodynamics and thermodynamics. The results can be used for the formulation of conservative numerical algorithms that can be employed, for example, for the study of fronts and singularities.
Float pump offshore wave energy converters
Nielsen, K. [Danish Wave Power Aps, Virum (Denmark)
1996-12-31
This paper will describe the numerical design models developed by DWP and ES-Consult as part of the Off-shore Wave Energy Converter project OWEC-1 supported by the European Union under the JOULE initiative. Offshore Wave Power Plants composed of float pump systems, has been investigated. Modeling techniques required to provide reliable methods for the predicted hydrodynamic behavior of the floats, their performance has been assessed and standardized criteria and techniques for the design has been provided. The systems investigated and the numerical time domain models developed will be described. The DWP/ES-Consult design models include both heave and surge motion of the device motion. The hydrodynamics are based on the long wave approximation of wave exiting forces as well as nonlinear drag and lift-forces, limits for the buoyancy force and variation of added mass with submergence are included in the calculations. The numerical models developed by DWP/ES-Consult are intended as tools for the structural design. The results in medium waves are compared to more exact hydrodynamic models (heave only) developed at Chalmars University and at NTH norwegian Technical University. Results are compared to model tests and real sea measurements. The design of the float geometry`s and power takeoff has not been optimized. The scope has been to compare and provide tools and guidelines for time domain modeling of offshore wave energy converters as a basis for further optimization.
Breaking of waves in deep water
NASA Astrophysics Data System (ADS)
Ruiz-Chavarria, Gerardo
2013-11-01
The breaking of waves is a nonlinear phenomenon during which a fraction of the energy is dissipated. In the previous stage the wave undergoes a growth of its amplitude and the wave pattern is modified in the sense that the crests become more pronounced than the troughs. The breaking has been extensively studied in the case of waves approaching the shore. However, the wave breaking in deep water remains an open problem in fluid dynamics. In this work we study the wave breaking due to focusing of an initially parabolic wave front. To this end the evolution of wave is numerically investigated using a meshless code (Smoothed Particle Hydrodynamics). We present some results about the evolution of waves excited by a parabolic wave maker, among others, the growth induced by the focusing, the behavior around the Huygens' cusp and the process of wave breaking. Then, we compare the numerical results with the criteria given in the literature about the onset of breaking and we discuss how the energy dissipates, for example by the rise of short waves. In addition we compare the numerical results with data obtained in two different experiments made by our team. The breaking of waves is a nonlinear phenomenon during which a fraction of the energy is dissipated. In the previous stage the wave undergoes a growth of its amplitude and the wave pattern is modified in the sense that the crests become more pronounced than the troughs. The breaking has been extensively studied in the case of waves approaching the shore. However, the wave breaking in deep water remains an open problem in fluid dynamics. In this work we study the wave breaking due to focusing of an initially parabolic wave front. To this end the evolution of wave is numerically investigated using a meshless code (Smoothed Particle Hydrodynamics). We present some results about the evolution of waves excited by a parabolic wave maker, among others, the growth induced by the focusing, the behavior around the Huygens' cusp and the process of wave breaking. Then, we compare the numerical results with the criteria given in the literature about the onset of breaking and we discuss how the energy dissipates, for example by the rise of short waves. In addition we compare the numerical results with data obtained in two different experiments made by our team. Author acknowledges DGAPA-UNAM by support under project IN116312, ``Vorticidad y ondas no lineales en fluidos.''
Water wave problems using null-field boundary integral equations: ill-posedness and remedies
Jeng-Tzong Chen; Jia-Wei Lee
2012-01-01
In this article, we focus on the hydrodynamic scattering of water wave problems containing circular and\\/or elliptical cylinders. Regarding water wave problems, the phenomena of numerical instability due to fictitious frequencies may appear when the boundary element method (BEM) is used. We examine the occurring mechanism of fictitious frequency in the BEM through a water wave problem containing an elliptical
Water wave problems using null-field boundary integral equations: ill-posedness and remedies
Jeng-Tzong Chen; Jia-Wei Lee
2011-01-01
In this article, we focus on the hydrodynamic scattering of water wave problems containing circular and\\/or elliptical cylinders. Regarding water wave problems, the phenomena of numerical instability due to fictitious frequencies may appear when the boundary element method (BEM) is used. We examine the occurring mechanism of fictitious frequency in the BEM through a water wave problem containing an elliptical
Coastal Inundation due to Tide, Surge, Waves, and Sea Level Rise at Naval Station Norfolk
US Army Corps of Engineers
Coastal Inundation due to Tide, Surge, Waves, and Sea Level Rise at Naval Station Norfolk Honghai elevation and storm induced inundation for combined influence of tide, surge, waves, wind, and SLR Stresses CMS-Flow Hydrodynamics Tide, Wind, Waves Coriolis, River flux Sediment Transport Advection
E. Sánchez-Badorrey; M. A. Losada
2006-01-01
This article analyzes the phase-averaged hydrodynamics induced by regular wave groups and the related long waves under reflective conditions outside of the wave-breaking zone. The solutions of the inviscid region and wave-group bottom boundary layer (WGBL) are analytically investigated for a regular wave group at a constant depth, impinging obliquely on an alongshore uniform reflective wall. The problem is formulated
Toward a Fully Consistent Radiation Hydrodynamics
Castor, J I
2009-07-07
Dimitri Mihalas set the standard for all work in radiation hydrodynamics since 1984. The present contribution builds on 'Foundations of Radiation Hydrodynamics' to explore the relativistic effects that have prevented having a consistent non-relativistic theory. Much of what I have to say is in FRH, but the 3-D development is new. Results are presented for the relativistic radiation transport equation in the frame obtained by a Lorentz boost with the fluid velocity, and the exact momentum-integrated moment equations. The special-relativistic hydrodynamic equations are summarized, including the radiation contributions, and it is shown that exact conservation is obtained, and certain puzzles in the non-relativistic radhydro equations are explained.
A quaternionic unification of electromagnetism and hydrodynamics
Arbab I. Arbab
2010-04-06
We have derived energy conservation equations from the quaternionic Newton's law that is compatible with Lorentz transformation. This Newton's law yields directly the Euler equation and other equations governing the fluid motion. With this formalism, the pressure contributes positively to the dynamics of the system in the same way mass does. Hydrodynamic equations are derived from Maxwell's equations by adopting an electromagnetohydrodynamics (EMH) analogy. In this analogy the hydroelectric field is related to the local acceleration of the fluid and the Lorentz gauge is related to the incompressible fluid condition. An analogous Lorentz gauge in hydrodynamics is proposed. We have shown that the vorticity of the fluid is developed whenever the particle local acceleration of the fluid deviates from the velocity direction. We have also shown that Lorentz force in electromagnetism corresponds to Euler force in fluids. Moreover, we have obtained Gauss's, Faraday's and Ampere's -like laws in Hydrodynamics.
Radiation hydrodynamics integrated in the code PLUTO
Kolb, Stefan M; Kley, Wilhelm; Mignone, Andrea
2013-01-01
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...
Cilia beating patterns are not hydrodynamically optimal
NASA Astrophysics Data System (ADS)
Guo, Hanliang; Nawroth, Janna; Ding, Yang; Kanso, Eva
2014-09-01
We examine the hydrodynamic performance of two cilia beating patterns reconstructed from experimental data. In their respective natural systems, the two beating patterns correspond to: (A) pumping-specialized cilia, and (B) swimming-specialized cilia. We compare the performance of these two cilia beating patterns as a function of the metachronal coordination in the context of two model systems: the swimming of a ciliated cylinder and the fluid pumping by a ciliated carpet. Three performance measures are used for this comparison: (i) average swimming speed/pumping flow rate; (ii) maximum internal moments generated by the cilia; and (iii) swimming/pumping efficiencies. We found that, in both models, pattern (B) outperforms pattern (A) in almost all three measures, including hydrodynamic efficiency. These results challenge the notion that hydrodynamic efficiency dictates the cilia beating kinematics, and suggest that other biological functions and constraints play a role in explaining the wide variety of cilia beating patterns observed in biological systems.
Electro-hydrodynamics near Hydrophobic Surfaces
S. R. Maduar; A. V. Belyaev; V. Lobaskin; O. I. Vinogradova
2015-02-20
We show that an electro-osmotic flow near the slippery hydrophobic surface depends strongly on the mobility of surface charges, which are balanced by counter-ions of the electrostatic diffuse layer. For a hydrophobic surface with immobile charges the fluid transport is considerably amplified by the existence of a hydrodynamic slippage. In contrast, near the hydrophobic surface with mobile adsorbed charges it is also controlled by an additional electric force, which increases the shear stress at the slipping interface. To account for this, we formulate electro-hydrodynamic boundary conditions at the slipping interface, which should be applied to quantify electro-osmotic flows instead of hydrodynamic boundary conditions. Our theoretical predictions are fully supported by dissipative particle dynamics simulations with explicit charges. These results lead to a new interpretation of zeta-potential of hydrophobic surfaces.
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.
Numerical Simulations of the Wave Bottom Boundary Layer over Sand Ripples
Slinn, Donald
to hydrodynamics by employing computational fluid dynamics (CFD) to simulate turbulent flows in the wave bottom in the nearshore environment (Voropayev et al. 1999). 1.3 Literature Review Many researchers have investigated
1.138J / 2.062J / 18.376J Wave Propagation, Fall 2004
Akylas, Triantaphyllos R.
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 ...
Supernova hydrodynamics experiments using the Nova laser
Remington, B.A.; Glendinning, S.G.; Estabrook, K.; Wallace, R.J.; Rubenchik, A. [Lawrence Livermore National Lab., CA (United States); Kane, J.; Arnett, D. [Arizona Univ., Tucson, AZ (United States). Stewart Observatory; Drake, R.P. [Michigan Univ., Ann Arbor, MI (United States); McCray, R. [Colorado Univ., Boulder, CO (United States)
1997-04-01
We are developing experiments using the Nova laser to investigate two areas of physics relevant to core-collapse supernovae (SN): (1) compressible nonlinear hydrodynamic mixing and (2) radiative shock hydrodynamics. In the former, we are examining the differences between the 2D and 3D evolution of the Rayleigh-Taylor instability, an issue critical to the observables emerging from SN in the first year after exploding. In the latter, we are investigating the evolution of a colliding plasma system relevant to the ejecta-stellar wind interactions of the early stages of SN remnant formation. The experiments and astrophysical implications are discussed.
Polyelectrolyte electrophoresis: Field effects and hydrodynamic interactions
NASA Astrophysics Data System (ADS)
Frank, S.; Winkler, R. G.
2008-08-01
The dynamical and conformational properties of short polyelectrolytes are studied in salt-free solution exposed to an external electric field taking hydrodynamic interactions into account by a mesoscale simulation technique. As a function of polymer length, we find a non-monotonic electrophoretic mobility, in agreement with experiments, and diffusion coefficients, which are well described by the expression of rodlike objects, both aspects reflect the importance of hydrodynamic interactions. Strong electric fields lead to particular polymer conformations, which are illustrated in a schematic diagram.
Adiabatic hydrodynamics: the eightfold way to dissipation
NASA Astrophysics Data System (ADS)
Haehl, Felix M.; Loganayagam, R.; Rangamani, Mukund
2015-05-01
Hydrodynamics is the low-energy effective field theory of any interacting quantum theory, capturing the long-wavelength fluctuations of an equilibrium Gibbs densitymatrix. Conventionally, one views the effective dynamics in terms of the conserved currents, which should be expressed via the constitutive relations in terms of the fluid velocity and the intensive parameters such as the temperature, chemical potential, etc. . . However, not all constitutive relations are acceptable; one has to ensure that the second law of thermodynamics is satisfied on all physical configurations. In this paper, we provide a complete solution to hydrodynamic transport at all orders in the gradient expansion compatible with the second law constraint.
Bounce-free spherical hydrodynamic implosion
Kagan, Grigory; Tang Xianzhu; Hsu, Scott C.; Awe, Thomas J. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2011-12-15
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.
Bounce-free Spherical Hydrodynamic Implosion
Kagan, Grigory; Hsu, Scott C; Awe, Thomas J
2011-01-01
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.
Ionizing Radiation in Smoothed Particle Hydrodynamics
O. Kessel-Deynet; A. Burkert
2000-02-11
A new method for the inclusion of ionizing radiation from uniform radiation fields into 3D Smoothed Particle Hydrodynamics (SPHI) simulations is presented. We calculate the optical depth for the Lyman continuum radiation from the source towards the SPHI particles by ray-tracing integration. The time-dependent ionization rate equation is then solved locally for the particles within the ionizing radiation field. Using test calculations, we explore the numerical behaviour of the code with respect to the implementation of the time-dependent ionization rate equation. We also test the coupling of the heating caused by the ionization to the hydrodynamical part of the SPHI code.
Hydrodynamic Simulations with the Godunov SPH
NASA Astrophysics Data System (ADS)
Borgani, S.; Murante, G.; Brunino, R.; Cha, S.-H.
2012-07-01
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.
Laboratory blast wave driven instabilities
NASA Astrophysics Data System (ADS)
Kuranz, Carolyn
2008-11-01
This presentation discusses experiments involving the evolution of hydrodynamic instabilities in the laboratory under high-energy-density (HED) conditions. These instabilities are driven by blast waves, which occur following a sudden, finite release of energy, and consist of a shock front followed by a rarefaction wave. When a blast wave crosses an interface with a decrease in density, hydrodynamic instabilities will develop. Instabilities evolving under HED conditions are relevant to astrophysics. These experiments include target materials scaled in density to the He/H layer in SN1987A. About 5 kJ of laser energy from the Omega Laser facility irradiates a 150 ?m plastic layer that is followed by a low-density foam layer. A blast wave structure similar to those in supernovae is created in the plastic layer. The blast wave crosses an interface having a 2D or 3D sinusoidal structure that serves as a seed perturbation for hydrodynamic instabilities. This produces unstable growth dominated by the Rayleigh-Taylor (RT) instability in the nonlinear regime. We have detected the interface structure under these conditions using x-ray backlighting. Recent advances in our diagnostic techniques have greatly improved the resolution of our x-ray radiographic images. Under certain conditions, the improved images show some mass extending beyond the RT spike and penetrating further than previously observed or predicted by current simulations. The observed effect is potentially of great importance as a source of mass transport to places not anticipated by current theory and simulation. I will discuss the amount of mass in these spike extensions, the associated uncertainties, and hypotheses regarding their origin We also plan to show comparisons of experiments using single mode and multimode as well as 2D and 3D initial conditions. This work is sponsored by DOE/NNSA Research Grants DE-FG52-07NA28058 (Stewardship Sciences Academic Alliances) and DE-FG52-04NA00064 (National Laser User Facility).
Influence of cavity shape on hydrodynamic noise by a hybrid LES-FW-H method
NASA Astrophysics Data System (ADS)
Wang, Yu; Wang, Shu-Xin; Liu, Yu-Hong; Chen, Chao-Ying
2011-09-01
The flow past various mechanical cavity, which is a common structure on the surface of the underwater vehicle, and generating hydrodynamic noise has attracted considerable attention in recent years. In this paper, a hybrid method is presented to investigate the hydrodynamic noise induced by mechanical cavities with various shapes. With this method, the noise sources in the near wall turbulences or in the wake are computed by the large eddy simulation (LES) and the generation and propagation of the acoustic waves are solved by the Ffowcs Williams-Hawkings (FW-H) acoustic analogy method with acoustic source terms extracted from the time-dependent solutions of the unsteady flow. The feasibility and reliability of the current method was verified by comparing with experimental data (Wang, 2009). The 2D cavity models with different cross-section shapes and 3D cavity models with different cavity mouth shapes (rectangular and circular) are developed to study the influence of cavity shape on the hydrodynamic noise. By comparing the flow mechanisms, wall pressure fluctuations, near-field and far-field sound propagation distributions, it is found that the quadrangular cavity with equal depths of leading-edge and trailing-edge is preferred for its inducing lower hydrodynamic noise than the cylindrical cavity does.
Effect of Second-Order Hydrodynamics on Floating Offshore Wind Turbines: Preprint
Roald, L.; Jonkman, J.; Robertson, A,; Chokani, N.
2013-07-01
Offshore winds are generally stronger and more consistent than winds on land, making the offshore environment attractive for wind energy development. A large part of the offshore wind resource is however located in deep water, where floating turbines are the only economical way of harvesting the energy. The design of offshore floating wind turbines relies on the use of modeling tools that can simulate the entire coupled system behavior. At present, most of these tools include only first-order hydrodynamic theory. However, observations of supposed second-order hydrodynamic responses in wave-tank tests performed by the DeepCwind consortium suggest that second-order effects might be critical. In this paper, the methodology used by the oil and gas industry has been modified to apply to the analysis of floating wind turbines, and is used to assess the effect of second-order hydrodynamics on floating offshore wind turbines. The method relies on combined use of the frequency-domain tool WAMIT and the time-domain tool FAST. The proposed assessment method has been applied to two different floating wind concepts, a spar and a tension-leg-platform (TLP), both supporting the NREL 5-MW baseline wind turbine. Results showing the hydrodynamic forces and motion response for these systems are presented and analysed, and compared to aerodynamic effects.
G. Rüdiger; R. Arlt; D. Shalybkov
2002-02-13
The hydrodynamic stability of accretion disks is considered. The particular question is whether the combined action of a (stable) vertical density stratification and a (stable) radial differential rotation gives rise to a new instability for nonaxisymmetric modes of disturbances. The existence of such an instability is not suggested by the well-known Solberg-Hoiland criterion. It is also not suggested by a local analysis for disturbances in general stratifications of entropy and angular momentum which is presented in our Section 2 confirming the results of the Solberg-Hoiland criterion also for nonaxisymmetric modes within the frame of ideal hydrodynamics but only in the frame of a short-wave approximation for small m. As a necessary condition for stability we find that only conservative external forces are allowed to influence the stable disk. As magnetic forces are never conservative, linear disk instabilities should only exist in the magnetohydrodynamical regime which indeed contains the magnetorotational instability as a much-promising candidate. To overcome some of the used approximations in a numerical approach,the equations of the compressible adiabatic hydrodynamics are integrated imposing initial nonaxisymmetric velocity perturbations with m=1 to m=200. Only solutions with decaying kinetic energy are found. The system always settles in a vertical equilibrium stratification according to pressure balance with the gravitational potential of the central object. keywords: accretion disks -- hydrodynamic instabilities -- turbulence
Passive hydrodynamic synchronization of two-dimensional swimming cells
NASA Astrophysics Data System (ADS)
Elfring, Gwynn J.; Lauga, Eric
2011-01-01
Spermatozoa flagella are known to synchronize when swimming in close proximity. We use a model consisting of two-dimensional sheets propagating transverse waves of displacement to demonstrate that fluid forces lead to such synchronization passively. Using two distinct asymptotic descriptions (small amplitude and long wavelength), we derive the synchronizing dynamics analytically for arbitrarily shaped waveforms in Newtonian fluids, and show that phase-locking will always occur for sufficiently asymmetric shapes. We characterize the effect of the geometry of the waveforms and the separation between the swimmers on the synchronizing dynamics, the final stable conformations, and the energy dissipated by the cells. For two closely swimming cells, synchronization always occurs at the in-phase or opposite-phase conformation, depending solely on the geometry of the cells. In contrast, the work done by the swimmers is always minimized at the in-phase conformation. As the swimmers get further apart, additional fixed points arise at intermediate values of the relative phase. In addition, computations for large amplitude waves using the boundary integral method reveal that the two asymptotic limits capture all the relevant physics of the problem. Our results provide a theoretical framework to address other hydrodynamic interactions phenomena relevant to populations of self-propelled organisms.