Abrikosov Gluon Vortices in Color Superconductors
NASA Astrophysics Data System (ADS)
Ferrer, Efrain J.
2011-09-01
In this talk I will discuss how the in-medium magnetic field can influence the gluon dynamics in a three-flavor color superconductor. It will be shown how at field strengths comparable to the charged gluon Meissner mass a new phase can be realized, giving rise to Abrikosov's vortices of charged gluons. In that phase, the inhomogeneous gluon condensate anti-screens the magnetic field due to the anomalous magnetic moment of these spin-1 particles. This paramagnetic effect can be of interest for astrophysics, since due to the gluon vortex antiscreening mechanism, compact stars with color superconducting cores could have larger magnetic fields than neutron stars made up entirely of nuclear matter. I will also discuss a second gluon condensation phenomenon connected to the Meissner instability attained at moderate densities by two-flavor color superconductors. In this situation, an inhomogeneous condensate of charged gluons emerges to remove the chromomagnetic instability created by the pairing mismatch, and as a consequence, the charged gluonic currents induce a magnetic field. Finally, I will point out a possible relation between glitches in neutron stars and the existence of the gluon vortices.
Single Abrikosov vortices as quantized information bits
NASA Astrophysics Data System (ADS)
Golod, T.; Iovan, A.; Krasnov, V. M.
2015-10-01
Superconducting digital devices can be advantageously used in future supercomputers because they can greatly reduce the dissipation power and increase the speed of operation. Non-volatile quantized states are ideal for the realization of classical Boolean logics. A quantized Abrikosov vortex represents the most compact magnetic object in superconductors, which can be utilized for creation of high-density digital cryoelectronics. In this work we provide a proof of concept for Abrikosov-vortex-based random access memory cell, in which a single vortex is used as an information bit. We demonstrate high-endurance write operation and two different ways of read-out using a spin valve or a Josephson junction. These memory cells are characterized by an infinite magnetoresistance between 0 and 1 states, a short access time, a scalability to nm sizes and an extremely low write energy. Non-volatility and perfect reproducibility are inherent for such a device due to the quantized nature of the vortex.
Single Abrikosov vortices as quantized information bits
Golod, T.; Iovan, A.; Krasnov, V. M.
2015-01-01
Superconducting digital devices can be advantageously used in future supercomputers because they can greatly reduce the dissipation power and increase the speed of operation. Non-volatile quantized states are ideal for the realization of classical Boolean logics. A quantized Abrikosov vortex represents the most compact magnetic object in superconductors, which can be utilized for creation of high-density digital cryoelectronics. In this work we provide a proof of concept for Abrikosov-vortex-based random access memory cell, in which a single vortex is used as an information bit. We demonstrate high-endurance write operation and two different ways of read-out using a spin valve or a Josephson junction. These memory cells are characterized by an infinite magnetoresistance between 0 and 1 states, a short access time, a scalability to nm sizes and an extremely low write energy. Non-volatility and perfect reproducibility are inherent for such a device due to the quantized nature of the vortex. PMID:26456592
Gamma-ray superconducting detector based on Abrikosov vortices: Principle of operation
Lisitskiy, M. P.
2009-11-15
The high atomic number of some superconducting elements such as niobium (Z=41) and tantalum (Z=73) and a high material thickness (e.g., t=300 mum) are emphasized as essential properties for development of a gamma-ray solid state detector with high intrinsic detection efficiency in the energy range up to 100 keV. To exploit these properties, a new detection principle based on the interaction of a single gamma-ray photon with Abrikosov vortex is proposed. The interaction of gamma-ray photon with a superconductor is discussed in terms of the photoelectric absorption and a hot-spot formation, the last acts as a short-time pinning center on an Abrikosov vortex and activates its motion, namely, a jump or damped vibration. Both types of vortex motion lead to variation (either static or dynamic) in the magnetic field on the absorber surface. The high sensitivity of the Josephson tunneling to weak magnetic field can be exploited for revealing the magnetic field variation and to make the readout of the detector. Main intrinsic properties of a gamma-ray detector based on Abrikosov vortices are evaluated, including the possibility to measure the energy deposited in the detector. A single Josephson tunnel junction configuration or a superconducting quantum interference device (SQUID) configuration is proposed and discussed as possible realization of working gamma-ray detector both in the counter operation mode and in the radiation spectroscopy operation mode.
DC to AC converter on Abrikosov vortices in a washboard pinning potential
NASA Astrophysics Data System (ADS)
Shklovskij, Valerij A.; Dobrovolskiy, Oleksandr V.
2014-05-01
The nonlinear dynamics of Abrikosov vortices in a cosine dc-biased washboard pinning potential at nonzero temperature is theoretically investigated. The problem is treated relying upon the exact solution of the Langevin equation for non-interacting vortices by using the Fokker-Planck method combined with the scalar continued fractions technique. The time variation of the local mean vortex velocity v(t) is calculated. The time voltage E(t) ~ v(t) is predicted to oscillate with a dc current-dependent frequency and a tunable pulse shape. Formulas for v(t) are discussed as functions of dc transport current and temperature, in a wide range of the corresponding dimensionless parameters. The derived expressions can be adapted for a number of physical applications utilizing the overdamped motion of a Brownian particle in a tilted cosine potential, e.g., the resistively shunted Josephson junction model.
Rakhmanov, A L; Savel'ev, Sergey; Kusmartsev, F V
2008-11-01
We describe the decomposition of Abrikosov vortices into decoupled pancake vortices in superconductors having both electron and hole charge carriers. We estimate the critical current of such a decomposition, at which a superconducting-normal state transition occurs, and find that it is very sensitive to the magnetic field and temperature. The effect can be observed in recently synthesized self-doped high-Tc layered superconductors with electrons and holes coexisting in different Cu-O planes and in artificial p-n superconductor heterostructures. The sensitivity of the critical current to a magnetic field may be used for sensors and detectors of a magnetic field, which can be built up from the superconductor heterostructures. PMID:19113298
Cristiano, R.; Frunzio, L.; Pagano, S.; Palmieri, V.G.; Lisitskii, M.P.
1997-11-01
We report on a new experimental approach to the size estimation of the hot spot induced by ionizing particles in a Josephson tunnel junction. Here, in contrast to the case of a superconducting strip, it is possible to investigate the hot spot dynamics in absence of effects due to the heating induced by the bias current. The reported experiment is based on the motion of Abrikosov vortices, trapped in the thin films constituting the junction electrodes, under 5.6 MeV {alpha}-particle irradiation. The fast time evolution of a hot spot, combined with the presence of Abrikosov vortices, produces a change of the static magnetic field in the junction area and thus a change of the critical current value, I{sub c}. Measurements of I{sub c} during the {alpha}-particle irradiation and in presence of trapped Abrikosov vortices allow to determine the rate of appearance of those I{sub c} changes. The behavior of the average appearance rate as function of the Abrikosov vortices density provides a direct determination of the maximum hot spot area. The experiment is performed on a high quality Nb/Al{endash}AlO{sub x}/Nb junction of circular geometry and with {open_quotes}small{close_quotes} dimensions with respect to the Josephson penetration depth. A value of 4.7{plus_minus}1.2{mu}m{sup 2} is found for the maximum hot spot area. {copyright} {ital 1997 American Institute of Physics.}
NASA Astrophysics Data System (ADS)
Flis, V. S.; Kalenyuk, A. A.; Kasatkin, A. L.; Moskalyuk, V. O.; Rebikov, A. I.; Svechnikov, V. L.; Tret'yachenko, K. G.; Pan, V. M.
2010-01-01
This paper presents the results of a comprehensive study of the relationship of the structural and electrodynamic characteristics of quasi-single-crystal films of the HTSC cuprate YBa2Cu3O7-δ (YBCO) with various concentrations (several mass percent) of nanosize inclusions of the perovskitelike phase of BaZrO3 (BZO). High-resolution electron microscopy is used to investigate the nanostructure of the fabricated films and to determine the main types of defects that cause strong pinning of Abrikosov vortices and, accordingly, large critical current densities. The results of theoretically modelling the genesis of the defect nanostructure that appears in such films and its influence on the critical current are presented. The magnetic and transport properties of HTSC films made from YBCO(BZO) have been experimentally studied. The temperature, magnetic-field, and magnetic-orientation dependences of the critical current density of the test films are found. The results of an experimental investigation of the high-frequency properties of YBZO(BZO) films—the surface microwave impedance of the films in the linear and nonlinear regimes—are also given. The experimental results are discussed, and the influence of the nanostructure of the impurity phase on the electrodynamic characteristics of the HTSC films is analyzed.
Chiral vortical wave and induced flavor charge transport in a rotating quark-gluon plasma
NASA Astrophysics Data System (ADS)
Jiang, Yin; Huang, Xu-Guang; Liao, Jinfeng
2015-10-01
We show the existence of a new gapless collective excitation in a rotating fluid system with chiral fermions, named the chiral vortical wave (CVW). The CVW has its microscopic origin at the quantum anomaly and macroscopically arises from interplay between vector and axial charge fluctuations induced by vortical effects. The wave equation is obtained both from hydrodynamic current equations and from chiral kinetic theory, and its solutions show nontrivial CVW-induced charge transport from different initial conditions. Using the rotating quark-gluon plasma in heavy ion collisions as a concrete example, we show the formation of an induced flavor quadrupole in quark-gluon plasma and estimate the elliptic flow splitting effect for Λ baryons that may be experimentally measured.
Numerical calculations of the driving force on an Abrikosov vortex
NASA Astrophysics Data System (ADS)
Chen, D.-X.; Pardo, E.; Sanchez, A.
2010-05-01
The driving force on an Abrikosov vortex is calculated numerically from the London equation and involved energies for a vortex perpendicular to the screening current near the surface of a superconductor. Compared with previous analytical derivation of the total force, the partial magnetic, kinematic, and external forces are also obtained so that the nature of the driving force may be deeply discussed. It is shown that the force is neither a Lorentz force nor a Magnus force as often believed and that in order to get a correct result, the image effects and the work done by the applied field must be taken into account. A name of London force is suggested for the driving force. A deep understanding of the nature of the driving force on Abrikosov vortices may also be important in the study of vortex pinning and dynamics in type-II superconductors.
Vortices in normal part of proximity system
Kogan, V. G.
2015-05-26
It is shown that the order parameter Δ induced in the normal part of superconductor-normal-superconductor proximity system is modulated in the magnetic field differently from vortices in bulk superconductors. Whereas Δ turns zero at vortex centers, the magnetic structure of these vortices differs from that of Abrikosov's.
Hierarchy of gaps and magnetic minibands in graphene in the presence of the Abrikosov vortex lattice
NASA Astrophysics Data System (ADS)
Chen, Xi; Fal'ko, Vladimir I.
2016-01-01
We determine the bands and gaps in graphene subjected to the magnetic field of an Abrikosov lattice of vortices in the underlying superconducting film. The spectrum features one nondispersive magnetic miniband at zero energy, separated by the largest gaps in the miniband spectrum from a pair of minibands resembling a slightly broadened first Landau level in graphene, suggesting the persistence of ν =±2 and ±6 quantum Hall effect states. Also, we identify an occasional merging point of magnetic minibands with a Dirac-type dispersion at the miniband edges.
Superconducting vortices in semilocal models.
Forgács, Péter; Reuillon, Sébastien; Volkov, Mikhail S
2006-02-01
It is shown that the SU(2) semilocal model--the Abelian Higgs model with two complex scalars--admits a new class of stationary, straight string solutions carrying a persistent current and having finite energy per unit length. In the plane orthogonal to their direction they correspond to a nontrivial deformation of the embedded Abrikosov-Nielsen-Olesen (ANO) vortices by the current flowing through them. The new solutions bifurcate with the ANO vortices in the limit of vanishing current. They can be either static or stationary. In the stationary case, the relative phase of the two scalars rotates at constant velocity, giving rise to an electric field and angular momentum, while the energy remains finite. The new static vortex solutions have lower energy than the ANO vortices and could be of considerable importance in various physical systems (from condensed matter to cosmic strings). PMID:16486806
Melting of the Abrikosov flux lattice in anisotropic superconductors
NASA Technical Reports Server (NTRS)
Beck, R. G.; Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.; Kogan, V. G.
1992-01-01
It has been proposed that the Abrikosov flux lattice in high-Tc superconductors is melted over a significant fraction of the phase diagram. A thermodynamic argument is provided which establishes that the angular dependence of the melting temperature is controlled by the superconducting mass anisotropy. Using a low-frequency torsional-oscillator technique, this relationship has been tested in untwinned single-crystal YBa2Cu3O(7-delta). The results offer decisive support for the melting proposal.
Interaction of half-quantized vortices in two-component Bose-Einstein condensates
Eto, Minoru; Kasamatsu, Kenichi; Nitta, Muneto; Takeuchi, Hiromitsu; Tsubota, Makoto
2011-06-15
We study the asymptotic interaction between two half-quantized vortices in two-component Bose-Einstein condensates. When two vortices in different components are placed at distance 2R, the leading order of the force between them is found to be (lnR/{xi}-1/2)/R{sup 3}, in contrast to 1/R between vortices placed in the same component. We derive it analytically using the Abrikosov ansatz and the profile functions of the vortices, confirmed numerically with the Gross-Pitaevskii model. We also find that the short-range cutoff of the intervortex potential linearly depends on the healing length.
Nielsen-Olesen vortices for large Ginzburg-Landau parameter
NASA Astrophysics Data System (ADS)
Burzlaff, Jürgen; Navarro-Lérida, F.
2010-12-01
Using analytic and numerical techniques Nielsen-Olesen vortices, which in the context of Ginzburg-Landau theory are known as Abrikosov vortices of type-II superconductors, are studied for large Ginzburg-Landau parameter λ. We show that their energy is equal to (πn2/2)logλ to leading order, where n is the winding number of the vortex, and find that the limit of the gauge field can be expressed in terms of the modified Bessel function K1. The leading terms of the asymptotic expansion of the solution are given, and the different contributions to the energy are analyzed.
Stirring vortices with vorticity holes
NASA Astrophysics Data System (ADS)
Velasco Fuentes, Oscar
2012-11-01
A vorticity hole is a region with, in absolute value, significantly lower vorticity than its surroundings. Here we discuss the dynamics of a Rankine vortex with two equal circular holes. If a symmetric initial condition is assumed, the evolution depends on three parameters: the vorticity drop, the hole size and the distance between the holes. We computed the evolution with a contour-dynamics model and quantified the stirring of fluid particles using finite-time Lyapunov exponents and Melnikov's method. The vorticity holes evolve similarly to a pair of vortices in an otherwise quiescent fluid, although they are additionally affected by their interaction with the boundary of the Rankine vortex. The strongest stirring occurs when the holes interact elastically and then always in the center of the vortex. This result contradicts the generally accepted notion that vortices are regions of null to weak stirring.
Beyond the simple hexagonal Abrikosov vortex lattice in layered superconductors
NASA Astrophysics Data System (ADS)
Feinberg, D.; Ettouhami, A. M.
1993-01-01
In layered superconductors as high-Tc materials but also organic superconductors, chalcogenides and superlattices, the simple concept of an distorted hexagonal lattice of straight vortices becomes unsufficient. Due to anisotropy and short coherence lengths, quite new vortex structures may arise. Some of them, as staircase vortices, simply add a modulation in the direction of vortex lines. This phenomenon is reviewed, together with the resulting lock-in transition, especially when the effects of the layered structure are weak. More exotic structures like a decomposed vortex lattice can also occur in specific situations: they involve two perpendicular sublattices, one parallel and one normal to the layers. We propose that extended defects as twin boundaries or irradiation tracks can trigger such a structure even in moderately anisotropic compounds as Y:123.
Monopoles and fractional vortices in chiral superconductors
Volovik, G. E.
2000-01-01
I discuss two exotic objects that must be experimentally identified in chiral superfluids and superconductors. These are (i) the vortex with a fractional quantum number (N = 1/2 in chiral superfluids, and N = 1/2 and N = 1/4 in chiral superconductors), which plays the part of the Alice string in relativistic theories and (ii) the hedgehog in the ^l field, which is the counterpart of the Dirac magnetic monopole. These objects of different dimensions are topologically connected. They form the combined object that is called a nexus in relativistic theories. In chiral superconductors, the nexus has magnetic charge emanating radially from the hedgehog, whereas the half-quantum vortices play the part of the Dirac string. Each half-quantum vortex supplies the fractional magnetic flux to the hedgehog, representing 1/4 of the “conventional” Dirac string. I discuss the topological interaction of the superconductor's nexus with the ‘t Hooft–Polyakov magnetic monopole, which can exist in Grand Unified Theories. The monopole and the hedgehog with the same magnetic charge are topologically confined by a piece of the Abrikosov vortex. Such confinement makes the nexus a natural trap for the magnetic monopole. Other properties of half-quantum vortices and monopoles are discussed as well, including fermion zero modes. PMID:10716980
Sugano, K.
1986-09-01
The properties of gluon jets are reviewed from an experimental point of view. The measured characteristics are compared to theoretical expectations. Although neither data nor models for the gluon jets are in the mature stage, there are remarkable agreements and also intriguing disagreements between experiment and theory. Since much interesting data have begun to emerge from various experiments and the properties of gluon jets are deeply rooted in the basic structure of non-Abelian gauge theory, the study of gluon jets casts further light on our understanding of QCD. Finally, the future prospects are discussed.
A single Abrikosov vortex trapped in a mesoscopic superconducting cylindrical surface
NASA Astrophysics Data System (ADS)
Carapella, G.; Sabatino, P.; Costabile, G.
2011-11-01
We investigate the behaviour of a single Abrikosov vortex trapped in a mesoscopic superconducting cylindrical surface with a magnetic field applied transverse to its axis. In the framework of the time-dependent Ginzburg-Landau formalism we show that, provided the transport current and the magnetic field are not large, the vortex behaves as an overdamped quasi-particle in a tilted washboard potential. The cylindrical thin strip with the trapped vortex exhibits E(J) curves and time-dependent electric fields very similar to the ones exhibited by a resistively shunted Josephson weak link.
Dowling, T.E.; Spiegel, E.A. )
1990-12-01
The characteristics of 'Jovian' vortices (the large vortices observed in the atmospheres of Jupiter, Saturn, Neptune) are summarized, and the existence of similar structures in the atmospheres of stars is considered theoretically. The problem of vortex maintenance is addressed, including potential vorticity, numerical simulations of Jovian vortices, and cyclones and anticyclones; the Great Red Spot of Jupiter is described on the basis of Voyager data; the evidence for convective generation of vertical vorticity in the sun is examined; the possibly vortical nature of the large spots of RS CVn stars is discussed; and models of spots on rapidly rotating hot stars are surveyed. 62 refs.
Gluon Vortices and Induced Magnetic Field in Compact Stars
Ferrer, Efrain J.
2007-10-26
The natural candidates for the realization of color superconductivity are the extremely dense cores of compact stars, many of which have very large magnetic fields, especially the so called magnetars. In this paper we discuss how a color superconducting core can serve to generate and enhance the stellar magnetic field without appealing to a magnetohydrodynamic dynamo mechanism.
Defining coherent vortices objectively from the vorticity
NASA Astrophysics Data System (ADS)
Haller, G.; Hadjighasem, A.; Farazmand, M.; Huhn, F.
2016-05-01
Rotationally coherent Lagrangian vortices are formed by tubes of deforming fluid elements that complete equal bulk material rotation relative to the mean rotation of the deforming fluid volume. We show that initial positions of such tubes coincide with tubular level surfaces of the Lagrangian-Averaged Vorticity Deviation (LAVD), the trajectory integral of the normed difference of the vorticity from its spatial mean. LAVD-based vortices are objective, i.e., remain unchanged under time-dependent rotations and translations of the coordinate frame. In the limit of vanishing Rossby numbers in geostrophic flows, cyclonic LAVD vortex centers are precisely the observed attractors for light particles. A similar result holds for heavy particles in anticyclonic LAVD vortices. We also establish a relationship between rotationally coherent Lagrangian vortices and their instantaneous Eulerian counterparts. The latter are formed by tubular surfaces of equal material rotation rate, objectively measured by the Instantaneous Vorticity Deviation (IVD). We illustrate the use of the LAVD and the IVD to detect rotationally coherent Lagrangian and Eulerian vortices objectively in several two- and three-dimensional flows.
NASA Astrophysics Data System (ADS)
Shahveh, Abolfazl; Taghavi-Shahri, Fatemeh; Arash, Firooz
2010-07-01
In the context of the so-called valon model, we calculate δg/g and show that although it is small and compatible with the measured values, the gluon contribution to the spin of nucleon can be sizable. The smallness of δg/g in the measured kinematical region should not be interpreted as δg being small. In fact, δg itself at small x, and the first moment of the polarized gluon distribution in the nucleon, Δg (Q2), are large.
NASA Astrophysics Data System (ADS)
Boer, Daniël
2016-03-01
A high-energy Electron-Ion Collider (EIC) would offer a most promising tool to study in detail the transverse momentum distributions of gluons inside hadrons. This applies to unpolarized as well as linearly polarized gluons inside unpolarized protons, and to left-right asymmetric distributions of gluons inside transversely polarized protons, the so-called gluon Sivers effect. The inherent process dependence of these distributions can be studied by comparing to similar, but often complementary observables at LHC.
Macroscopic evidence for Abrikosov-type magnetic vortexes in MnSi A-phase
Lobanova, I. I.; Glushkov, V. V.; Sluchanko, N. E.; Demishev, S. V.
2016-01-01
Intrinsic phase coherence between individual topologically stable knots in spin arrangement – skyrmions – is known to induce the crystalline-like structure in the A-phase of non-centrosymmetric MnSi with chiral spin-orbit interaction. Here we report the experimental evidence for two types of the skyrmion lattice (SL) inside the A-phase of MnSi, which are distinguished by different coupling to the anisotropic magnetic interactions. The transition between these SLs is shown to induce a change in magnetic scattering between isotropic MR discovered in the area inside the A-phase (the A-phase core) and anisotropic MR found on the border of the A-phase. We argue that the SL in the A-phase core corresponds to the dense skyrmion state built from individual skyrmions in a way similar to Abrikosov-type magnetic vortexes. PMID:26915818
Macroscopic evidence for Abrikosov-type magnetic vortexes in MnSi A-phase
NASA Astrophysics Data System (ADS)
Lobanova, I. I.; Glushkov, V. V.; Sluchanko, N. E.; Demishev, S. V.
2016-02-01
Intrinsic phase coherence between individual topologically stable knots in spin arrangement - skyrmions - is known to induce the crystalline-like structure in the A-phase of non-centrosymmetric MnSi with chiral spin-orbit interaction. Here we report the experimental evidence for two types of the skyrmion lattice (SL) inside the A-phase of MnSi, which are distinguished by different coupling to the anisotropic magnetic interactions. The transition between these SLs is shown to induce a change in magnetic scattering between isotropic MR discovered in the area inside the A-phase (the A-phase core) and anisotropic MR found on the border of the A-phase. We argue that the SL in the A-phase core corresponds to the dense skyrmion state built from individual skyrmions in a way similar to Abrikosov-type magnetic vortexes.
Confined vortices in topologically massive U (1 )×U (1 ) theory
NASA Astrophysics Data System (ADS)
Anber, Mohamed M.; Burnier, Yannis; Sabancilar, Eray; Shaposhnikov, Mikhail
2015-09-01
We report on a new topological vortex solution in U (1 )×U (1 ) Maxwell-Chern-Simons theory. The existence of the vortex is envisaged by analytical means, and a numerical solution is obtained by integrating the equations of motion. These vortices have a long-range force because one of the U(1)'s remains unbroken in the infrared, which is guarded by the Coleman-Hill theorem. The sum of the winding numbers of an ensemble of vortices has to vanish; otherwise the system would have a logarithmically divergent energy. In turn, these vortices exhibit classical confinement. We investigate the rich parameter space of the solutions, and show that one recovers the Abrikosov-Nielsen-Olesen, U(1) Maxwell-Chern-Simons, U(1) pure Chern-Simons, and global vortices as various limiting cases. Unlike these limiting cases, the higher winding solutions of our vortices carry noninteger charges under the broken U(1). This is the first vortex solution exhibiting such behavior.
NASA Astrophysics Data System (ADS)
Anikin, I. V.; Teryaev, O. V.
2015-12-01
In this letter, we revise the QED gauge invariance for the hadron tensor of Drell-Yan type processes with the transversely polarized hadron. We perform our analysis within the Feynman gauge for gluons and make a comparison with the results obtained within the light-cone gauge. We demonstrate that QED gauge invariance leads, first, to the need of a non-standard diagram and, second, to the absence of gluon poles in the correlators < ψ bar γ⊥A+ ψ > related traditionally to dT (x , x) / dx. As a result, these terms disappear from the final QED gauge invariant hadron tensor. We also verify the absence of such poles by analyzing the corresponding light-cone Dirac algebra.
Ayala, A.L.; Ducati, M.B.G.; Levin, E.M.
1996-10-01
In this talk we present our detailed study (theory and numbers) on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather controversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula and estimate the value of the shadowing corrections in this case. Then we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus-nucleus cascade. The initial conditions should be fixed both theoretically and phenomenologically before to attack such complicated problems as the mixture of hard and soft processes in nucleus-nucleus interactions at high energy or the theoretically reliable approach to hadron or/and parton cascades for high energy nucleus-nucleus interaction. 35 refs., 24 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Chagoya, Javier; Tasinato, Gianmassimo
2016-02-01
Vortex solutions are topologically stable field configurations that can play an important role in condensed matter, field theory, and cosmology. We investigate vortex configuration in a 2+1 dimensional Abelian Higgs theory supplemented by higher order derivative self-interactions, related with Galileons. Our vortex solutions have features that make them qualitatively different from well-known Abrikosov-Nielsen-Olesen configurations, since the derivative interactions turn on gauge invariant field profiles that break axial symmetry. By promoting the system to a 3+1 dimensional string configuration, we study its gravitational backreaction. Our results are all derived within a specific, analytically manageable system, and might offer indications for understanding Galileonic interactions and screening mechanisms around configurations that are not spherically symmetric, but only at most cylindrically symmetric.
Constraining the double gluon distribution by the single gluon distribution
NASA Astrophysics Data System (ADS)
Golec-Biernat, Krzysztof; Lewandowska, Emilia; Serino, Mirko; Snyder, Zachary; Staśto, Anna M.
2015-11-01
We show how to consistently construct initial conditions for the QCD evolution equations for double parton distribution functions in the pure gluon case. We use to momentum sum rule for this purpose and a specific form of the known single gluon distribution function in the MSTW parameterization. The resulting double gluon distribution satisfies exactly the momentum sum rule and is parameter free. We also study numerically its evolution with a hard scale and show the approximate factorization into product of two single gluon distributions at small values of x, whereas at large values of x the factorization is always violated in agreement with the sum rule.
Annihilation of strained vortices
NASA Astrophysics Data System (ADS)
Kimura, Yoshifumi
2014-11-01
As an initial stage of vortex reconnection, approach of nearly anti-parallel vortices has often been observed experimentally and studied numerically. Inspired by the recent experiment by Kleckner and Irvine on the dynamics of knotted vortices, we have studied the motion of two anti-parellel Burgers vortices driven by an axisymmetric linear straining field. We first extend the Burgers vortex solution which is a steady exact solution of the Navier-Stokes equation to a time-dependent exact solution. Then by superposing two such solutions, we investigate the annihilation process analytically. We can demonstrate that during the annihilation process the total vorticity decays exponentially on a time-scale proportional to the inverse of the rate of strain, even as the kinematic viscosity tends to 0. The analytic results are compared with the numerical simulations of two strained vortices with the vortex-vortex nonlinear interaction by Buntine and Pullin.
NASA Astrophysics Data System (ADS)
Peshier*, André; Giovannoni, Dino
2016-01-01
We put forward the idea that the quark-gluon plasma might exist way below the usual confinement temperature Tc. Our argument rests on the possibility that the plasma produced in heavy-ion collisions could reach a transient quasi-equilibrium with ‘over-occupied’ gluon density, as advocated by Blaizot et al. Taking further into account that gluons acquire an effective mass by interaction effects, they can have a positive chemical potential and therefore behave similarly to non-relativistic bosons. Relevant properties of this dense state of interacting gluons, which we dub serried glue, can then be inferred on rather general grounds from Maxwell's relation.
Lincoln, Don
2015-05-07
Matter is malleable and can change its properties with temperature. This is most familiar when comparing ice, liquid water and steam, which are all different forms of the same thing. However beyond the usual states of matter, physicists can explore other states, both much colder and hotter. In this video, Fermilab’s Dr. Don Lincoln explains the hottest known state of matter – a state that is so hot that protons and neutrons from the center of atoms can literally melt. This form of matter is called a quark gluon plasma and it is an important research topic being pursued at the LHC.
Quark and Gluon Relaxation in Quark-Gluon Plasmas
NASA Technical Reports Server (NTRS)
Heiselberg, H.; Pethick, C. J.
1993-01-01
The quasiparticle decay rates for quarks and gluons in quark-gluon plasmas are calculated by solving the kinetic equation. Introducing an infrared cutoff to allow for nonperturbative effects, we evaluate the quasiparticle lifetime at momenta greater than the inverse Debye screening length to leading order in the coupling constant.
NASA Technical Reports Server (NTRS)
Holmes, Bruce J. (Inventor); Carraway, Debra L. (Inventor); Holmes, Harlan K. (Inventor); Moore, Thomas C. (Inventor)
1988-01-01
A crossflow vorticity sensor for the detection of crossflow vorticity characteristics is described. The sensor is comprised of crossflow sensors which are noninvasively adhered to a swept wing laminar surface either singularly, in multi-element strips, in polar patterns, or in orthogonal patterns. These crossflow sensors are comprised of hot-film sensor elements which operate as a constant temperature anemometer circuit to detect heat transfer rate changes. Accordingly, crossflow vorticity characteristics are determined via cross-correlation. In addition, the crossflow sensors have a thickness which does not exceed a maximum value h in order to avoid contamination of downstream crossflow sensors.
The distribution of vorticity in a large vortical motion
NASA Technical Reports Server (NTRS)
Disimile, Peter J.
1988-01-01
An experimental investigation into the distribution of vorticity in the large scale vortical motions which are found in free shear layers was undertaken. Using hot-wire anemometry, both quasi-instantaneous and phase averaged transverse vorticity were acquired. These results appear to indicate that the transverse vorticity in a large scale vortical motion is distributed in a marble cake manner and not in laminated sheets spooled up into a coil or helical spring. Also, levels of vorticity were found to vary by as much as an order of magnitude in these concentrated vortical cores.
Unitarity bound for gluon shadowing
Kopeliovich, B. Z.; Levin, E.; Potashnikova, I. K.; Schmidt, Ivan
2009-06-15
Although at small Bjorken x gluons originated from different nucleons in a nucleus overlap in the longitudinal direction, most of them are still well separated in the transverse plane and therefore cannot fuse. For this reason the gluon density in nuclei cannot drop at small x below a certain bottom bound, which we evaluated in a model independent manner assuming the maximal strength of gluon fusion. We also calculated gluon shadowing in the saturated regime using the Balitsky-Kovchegov equation and found the nuclear ratio to be well above the unitarity bound. The recently updated analysis of parton distributions in nuclei, including BNL Relativistic Heavy Ion Collider (RHIC) data on high-p{sub T} hadron production at forward rapidities, led to strong gluon shadowing. Such strong shadowing and therefore the interpretation of the nuclear modification of the p{sub T} spectra in dA collisions at RHIC seem to be inconsistent with this unitarity bound.
Effect of fluctuations on the NMR relaxation beyond the Abrikosov vortex state
NASA Astrophysics Data System (ADS)
Glatz, A.; Galda, A.; Varlamov, A. A.
2015-08-01
The effect of fluctuations on the nuclear magnetic resonance (NMR) relaxation rate W =T1-1 is studied in a complete phase diagram of a two-dimensional superconductor above the upper critical field line Hc 2(T ) . In the region of relatively high temperatures and low magnetic fields, the relaxation rate W is determined by two competing effects. The first one is its decrease in the result of suppression of the quasiparticle density of states (DOS) due to formation of fluctuation Cooper pairs (FCPs). The second one is a specific, purely quantum relaxation process of the Maki-Thompson (MT) type, which for low field leads to an increase of the relaxation rate. The latter describes particular fluctuation processes involving self-pairing of a single electron on self-intersecting trajectories of a size up to phase-breaking length ℓϕ which becomes possible due to an electron spin-flip scattering event at a nucleus. As a result, different scenarios with either growth or decrease of the NMR relaxation rate are possible upon approaching the normal-metal-type-II superconductor transition. The character of fluctuations changes along the line Hc 2(T ) from the thermal long-wavelength type in weak magnetic fields to the clusters of rotating FCPs in fields comparable to Hc 2(0 ) . We find that below the well-defined temperature T0*≈0.6 Tc 0 , the MT process becomes ineffective even in the absence of intrinsic pair breaking. The small scale of the FCP rotations ξxy in such high fields impedes formation of long (≲ℓϕ) self-intersecting trajectories, causing the corresponding relaxation mechanism to lose its efficiency. This reduces the effect of superconducting fluctuations in the domain of high fields and low temperatures to just the suppression of quasiparticle DOS, analogous to the Abrikosov vortex phase below the Hc 2(T ) line.
Macek, Joseph H ORNL
2012-01-01
The time-dependent Schrodinger equation describes dynamical processes of one-electron species in terms of a complex wave function. The function is inherently complex, therefore zeros occur only when both the real and imaginary parts of the wave function vanish. If this happens at isolated points rather than on a nodal surface one can show the zero must correspond to a vortex. An imaging theorem is given which shows how such vortices can be seen experimentally. Since the theorem requires time propagation from microscopic to macroscopic scales, a method is developed that does just that. Examples of vortices that emerge in dynamical processes are given. The vortices that we nd are linked to the hydrodynamic interpretation of Schrodinger's time-dependent equation.
Relaminarization under stationary vortices
NASA Astrophysics Data System (ADS)
Breidenthal, Robert
2005-11-01
Flow visualization reveals that a turbulent boundary layer is relaminarized when stationary streamwise vortices are introduced. Following a suggestion of Balle, the vortices are stabilized by large streamwise ``Karman'' grooves in a wavy wall. In a water tunnel, upstream vortex generators place a large streamwise vortex in the middle of each groove, at the stationary point where Prandtl's vortex force vanishes. According to a theory by Cotel, the wall fluxes of a turbulent boundary layer should decline to laminar values under such ``persistent'' vortices. The observed relaminarization is consistent with this theory and with previous measurements of heat transfer by Touel and Balle. However, the structure of the transverse flow resembles the cats-eye pattern of a temporal shear layer rather than the anticipated von Karman wake. The cats-eye pattern corresponds to the forced shear layers of Oster-Wygnanski and Roberts, who found that the Reynolds stresses and mixing rate also decline to laminar values.
NASA Astrophysics Data System (ADS)
Olson Reichhardt, C. J.; Hastings, M. B.
2004-04-01
We propose an experiment for directly constructing and locally probing topologically entangled states of superconducting vortices which can be performed with present-day technology. Calculations using an elastic string vortex model indicate that as the pitch (the winding angle divided by the vertical distance) increases, the vortices approach each other. At values of the pitch higher than a maximum value the entangled state becomes unstable to collapse via a singularity of the model. We provide predicted experimental signatures for both vortex entanglement and vortex cutting. The local probe we propose can also be used to explore a wide range of other quantities.
Continuously tailored Taylor vortices
NASA Astrophysics Data System (ADS)
Sprague, M. A.; Weidman, P. D.
2009-11-01
Modified axisymmetric, finite-length Taylor-Couette (TC) cells with stationary outer cylinder and rotating inner cylinder are designed in an effort to produce simultaneous onset of toroidal vortices of continuously varying wavelength along the gap. For a given axial variation in the inner radius, the axial variation in the outer radius can be chosen such that at every axial position, the criterion for the onset of Taylor vortices in a corresponding classical TC cell is met. In one scenario, a conical inner cylinder is chosen and the shape of the outer cylinder is then determined by locally satisfying the onset criterion. In another scenario, the inner and outer radii are chosen such that the onset criterion is locally satisfied and the axial rate of change in the classical onset wave number is held constant. In both cases, the modified cells possess a large-scale meridional circulation wrought by the finite Ekman (Bödewadt) pumping on the inner (outer) cylinder walls. Using direct numerical simulation, it is found that for sufficiently large aspect ratio, there exists a critical rotation rate for the simultaneous transition from the base flow to counter-rotating toroidal vortices throughout the varying-radius region. The vortices propagate in the direction of decreasing gap width with a phase speed that decreases with increasing aspect ratio.
One gluon, two gluon: multigluon production via high energy evolution
NASA Astrophysics Data System (ADS)
Kovner, Alex; Lublinsky, Michael
2006-11-01
We develop an approach for calculating the inclusive multigluon production within the JIMWLK high energy evolution. We give a formal expression of multigluon cross section in terms of a generating functional for arbitrary number of gluons n. In the dipole limit the expression simplifies dramatically. We recover the previously known results for single and double gluon inclusive cross section and generalize those for arbitrary multigluon amplitude in terms of Feynman diagramms of Pomeron - like objects coupled to external rapidity dependent field s(η). We confirm the conclusion that the AGK cutting rules in general are violated in multigluon production. However we present an argument to the effect that for doubly inclusive cross section the AGK diagramms give the leading contribution at high energy, while genuine violation only occurs for triple and higher inclusive gluon production. We discuss some general properties of our expressions and suggest a line of argument to simplify the approach further.
Shining a gluon beam through quark-gluon plasma
NASA Astrophysics Data System (ADS)
Chesler, Paul M.; Ho, Ying-Yu; Rajagopal, Krishna
2012-06-01
We compute the energy density radiated by a quark undergoing circular motion in strongly coupled N=4 supersymmetric Yang-Mills plasma. If it were in vacuum, this quark would radiate a beam of strongly coupled radiation whose angular distribution has been characterized and is very similar to that of synchrotron radiation produced by an electron in circular motion in electrodynamics. Here, we watch this beam of gluons getting quenched by the strongly coupled plasma. We find that a beam of gluons of momenta ˜q≫πT is attenuated rapidly, over a distance ˜q1/3(πT)-4/3 in a plasma with temperature T. As the beam propagates through the plasma at the speed of light, it sheds trailing sound waves with momenta ≲πT. Presumably these sound waves would thermalize in the plasma if they were not hit soon after their production by the next pulse of gluons from the lighthouselike rotating quark. At larger and larger q, the trailing sound wave becomes less and less prominent. The outward-going beam of gluon radiation itself shows no tendency to spread in angle or to shift toward larger wavelengths, even as it is completely attenuated. In this regard, the behavior of the beam of gluons which we analyze is reminiscent of the behavior of jets produced in heavy ion collisions at the LHC which lose a significant fraction of their energy without appreciable change in their angular distribution or their momentum distribution as they plow through the strongly coupled quark-gluon plasma produced in these collisions.
Scale evolution of gluon TMDPDFs
NASA Astrophysics Data System (ADS)
Echevarria, Miguel G.; Kasemets, Tomas; Mulders, Piet J.; Pisano, Cristian
2015-01-01
By applying the effective field theory machinery we factorize the transverse momentum spectrum of Higgs boson production, where the main hadronic quantities are the gluon transverse momentum dependent parton distribution functions (TMDPDFs). We properly define those quantities, showing explicitly, in the case of an unpolarized hadron, that they are free from rapidity divergences, and extract their evolution properties. It turns out that the evolution for all eight (un-)polarized leading-twist gluon TMDPDFs is driven by the same evolution kernel, for which we derive the necessary ingredients to obtain a resummation of large logarithms at next-tonext-to-leading-logarithmic accuracy. We make predictions for the contribution of linearly polarized gluons to the Higgs boson qT -spectrum.
Vorticity production in shock diffraction
NASA Astrophysics Data System (ADS)
Sun, M.; Takayama, K.
2003-03-01
The production of vorticity or circulation production in shock wave diffraction over sharp convex corners has been numerically simulated and quantified. The corner angle is varied from 5° to 180°. Total vorticity is represented by the circulation, which is evaluated by integrating the velocity along a path enclosing the perturbed region behind a diffracting shock wave. The increase of circulation in unit time, or the rate of circulation production, depends on the shock strength and wall angle if the effects of viscosity and heat conductivity are neglected. The rate of vorticity production is determined by using a solution-adaptive code, which solves the Euler equations. It is shown that the rate of vorticity production is independent of the computational mesh and numerical scheme by comparing solutions from two different codes. It is found that larger wall angles always enhance the vorticity production. The vorticity production increases sharply when the corner angle is varied from 15° to 45°. However, for corner angles over 90°, the rate of vorticity production hardly increases and reaches to a constant value. Strong shock waves produce vorticity faster in general, except when the slipstream originating from the shallow corner attaches to the downstream wall. It is found that the vorticity produced by the slipstream represents a large proportion of the total vorticity. The slipstream is therefore a more important source of vorticity than baroclinic effects in shock diffraction.
NASA Astrophysics Data System (ADS)
Mironov, A. D.; Morozov, A.; Tomaras, T. N.
2005-08-01
Usually the intuition from condensed-matter physics is used to provide ideas for possible confinement mechanisms in gauge theories. Today, with a clear but puzzling ``spaghetti'' confinement pattern, arising after a decade of lattice computer experiments, which implies formation of a fluctuating net of peculiar magnetic vortices rather than condensation of the homogeneously distributed magnetic monopoles, the time is coming to reverse the logic and search for similar patterns in condensed matter systems. The main thing to look for in a condensed matter setup is the simultaneous existence of narrow tubes ($P$-vortices or 1-branes) of direction-changing electric field and broader tubes (Abrikosov lines) of magnetic field, a pattern dual to the one, presumably underlying confinement in gluodynamics. As a possible place for this search we suggest systems with coexisting charge-density waves and superconductivity.
NASA Astrophysics Data System (ADS)
Sprague, M. A.; Weidman, P. D.; Macumber, S.; Fischer, P. F.
2008-01-01
The stability of circular Couette flow in discontinuous axisymmetric geometries is investigated using numerical simulations and physical experiments. By contouring the geometry of the inner cylinder, Taylor vortices can be made to appear in discrete sections along the length of the cylinder while adjoining sections remain stable. The disparate flows are connected by transition regions that arise from the stability of the axially nonuniform base flow state. The geometry of the inner cylinder can be tailored to produce the simultaneous onset of Taylor vortices of different wavelength in neighboring sections. In another variant, a stack of inner cylinders of common radius are made to rotate independently to produce adjacent regions of stable and unstable flow.
Toward modeling wingtip vortices
NASA Technical Reports Server (NTRS)
Zeman, O.
1993-01-01
Wingtip vortices are generated by lifting airfoils; their salient features are compactness and relatively slow rate of decay. The principal motivation for studying the far field evolution of wingtip vortices is the need to understand and predict the extent of the vortex influence during aircraft take-off or landing. On submarines a wingtip vortex ingested into a propeller can be a source of undesirable noise. The main objectives of this research are (1) to establish theoretical understanding of the principal mechanisms that govern the later (diffusive) stages of a turbulent vortex, (2) to develop a turbulence closure model representing the basic physical mechanisms that control the vortex diffusive stage, and further (3) to investigate coupling between the near and far field evolutions; in other words, to study the effect of initial conditions on the vortex lifetime and the ultimate state.
NASA Astrophysics Data System (ADS)
Cropp, Bethan; Liberati, Stefano; Turcati, Rodrigo
2016-06-01
In the analog gravity framework, the acoustic disturbances in a moving fluid can be described by an equation of motion identical to a relativistic scalar massless field propagating in curved space-time. This description is possible only when the fluid under consideration is barotropic, inviscid, and irrotational. In this case, the propagation of the perturbations is governed by an acoustic metric that depends algebrically on the local speed of sound, density, and the background flow velocity, the latter assumed to be vorticity-free. In this work we provide a straightforward extension in order to go beyond the irrotational constraint. Using a charged—relativistic and nonrelativistic—Bose–Einstein condensate as a physical system, we show that in the low-momentum limit and performing the eikonal approximation we can derive a d’Alembertian equation of motion for the charged phonons where the emergent acoustic metric depends on flow velocity in the presence of vorticity.
Untangling Superfluid Vortices
NASA Astrophysics Data System (ADS)
Kleckner, Dustin; Scheeler, Martin W.; Proment, Davide; Irvine, William T. M.
2015-03-01
What is the role of topology, or knottedness, in superfluid phase defects (quantum vortices)? In ideal classical fluids, vortex knots may never untie, and so there is an associated conserved quantity - helicity - which measures how tangled a flow is. One might expect a similar robustness for superfluid defects, however, simulations of the Gross-Pitevskii equation demonstrate that vortex knots and links spontaneously untie and unlink. Nonetheless, the topology dramatically affects the vortex evolution, and a component of the initial helicity is transferred to helical coils as the knots unravel. These effects are remarkably similar to the behavior of tangled vortices in viscous fluids, suggesting they are universal features of non-ideal fluids.
NASA Technical Reports Server (NTRS)
Perry, A. E.; Chong, M. S.; Lim, T. T.
1982-01-01
Theoretical and experimental results of studies to determine the flow parameters and structures of plane mixing layers are reported. Smoke visualization, combined with hot-wire anemometry, sheets of laser light, and photography were used to gather data from the wall flow. The behavior of vortex rods was examined, noting that the rods persisted only if new vortex energy was supplied from the sublayer. A power spectral density was defined for the velocity fluctuations, as was a hierarchy of velocity scales for geometrically similar vortices. The length scale grows linearly with downstream distance, where the flow structures are fed by longitudinal vortices. A model is developed for vortex pairing in sequential order from the bottom of the mixing layer outward in a repetitive process involving vortex stretching. The model is actually a migration strategy that satisfies the flow self-preservation constraints.
Haymaker, Richard W.; Matsuki, Takayuki
2007-01-01
We address the problem of determining the type I, type II or borderline dual superconductor behavior in maximal Abelian gauge SU(2) through the study of the dual Abrikosov vortex. We find that significant electric currents in the simulation data call into question the use of the dual Ginzburg-Landau Higgs model in interpreting the data. Further, two definitions of the penetration depth parameter take two different values. The splitting of this parameter into two is intricately connected to the existence of electric currents. It is important in our approach that we employ definitions of flux and electric and magnetic currents that respect Maxwell equations exactly for lattice averages independent of lattice spacings. Applied to specific Wilson loop sizes, our conclusions differ from those that use the dual GLH model.
Dynamic Melting of Driven Abrikosov Lattices in an Amorphous MoxGe1-x Film in Tilted Field
NASA Astrophysics Data System (ADS)
Ochi, Aguri; Kawamura, Yasuki; Inoue, Toshiki; Kaji, Tetsuya; Mihaly, Dobroka; Kaneko, Shin-ichi; Kokubo, Nobuhito; Okuma, Satoshi
2016-03-01
We report a comparative study of the dynamic melting of driven vortex lattices in magnetic field tilted (by θ = 36°) from the normal to the film surface and that of a driven Abrikosov lattice in untilted field (θ = 0). From the mode-locking (ML) resonance, we confirm that vortex lattices in tilted field are stretched in the tilt direction and that, with increasing dc velocity at ML, the shape and orientation of the driven lattice change. Associated with this structural change, the dynamic melting field at which the driven lattice melts also changes. Our results show that, regardless of the lattice shape and orientation, dynamic melting occurs as the shorter side of the distorted lattices reaches close to the side at which the isotropic lattice melts dynamically.
Axisymmetric Vortices with Swirl
NASA Astrophysics Data System (ADS)
Elcrat, A.
2007-11-01
This talk is concerned with finding solutions of the Euler equations by solving elliptic boundary value problems for the Bragg-Hawthorne equation L u= -urr -(1/r)ur - = r^2f (u) + h(u). Theoretical results have been given for previously (Elcrat and Miller, Differential and Integral Equations 16(4) 2003, 949-968) for problems with swirl and general classes of profile functions f, h by iterating Lu(n+1)= rf(u)n)) + h(u(n)), and showing u(n) converges montonically to a solution. The solutions obtained depend on the initial guess, which can be thought of as prescribing level sets of the vortex. When a computational program was attempted these monotone iterations turned out to be numerically unstable, and a stable computation was acheived by fixing the moment of the cross section of a vortex in the merideanal plane. (This generalizes previous computational results in Elcrat, Fornberg and Miller, JFM 433 2001, (315-328) We obtain famillies of vortices related to vortex rings with swirl, Moffatt's generalization of Hill's vortex and tubes of vorticity with swirl wrapped around the symmetry axis. The vortices are embedded in either an irrotational flow or a flow with shear, and we deal with the transition form no swirl in the vortex to flow with only swirl, a Beltrami flow.
Vorticity in the solar photosphere
NASA Astrophysics Data System (ADS)
Shelyag, S.; Keys, P.; Mathioudakis, M.; Keenan, F. P.
2011-02-01
Aims: We use magnetic and non-magnetic 3D numerical simulations of solar granulation and G-band radiative diagnostics from the resulting models to analyse the generation of small-scale vortex motions in the solar photosphere. Methods: Radiative MHD simulations of magnetoconvection are used to produce photospheric models. Our starting point is a non-magnetic model of solar convection, where we introduce a uniform magnetic field and follow the evolution of the field in the simulated photosphere. We find two different types of photospheric vortices, and provide a link between the vorticity generation and the presence of the intergranular magnetic field. A detailed analysis of the vorticity equation, combined with the G-band radiative diagnostics, allows us to identify the sources and observational signatures of photospheric vorticity in the simulated photosphere. Results: Two different types of photospheric vorticity, magnetic and non-magnetic, are generated in the domain. Non-magnetic vortices are generated by the baroclinic motions of the plasma in the photosphere, while magnetic vortices are produced by the magnetic tension in the intergranular magnetic flux concentrations. The two types of vortices have different shapes. We find that the vorticity is generated more efficiently in the magnetised model. Simulated G-band images show a direct connection between magnetic vortices and rotary motions of photospheric bright points, and suggest that there may be a connection between the magnetic bright point rotation and small-scale swirl motions observed higher in the atmosphere.
Gluon polarization in the proton
Bass, Steven D.; Casey, Andrew; Thomas, Anthony W.
2011-03-15
We combine heavy-quark renormalization group arguments with our understanding of the nucleon's wave function to deduce a bound on the gluon polarization {Delta}g in the proton. The bound is consistent with the values extracted from spin experiments at COMPASS and RHIC.
Interaction of Atmospheric Plasma Vortices
NASA Astrophysics Data System (ADS)
Izhovkina, N. I.; Artekha, S. N.; Erokhin, N. S.; Mikhailovskaya, L. A.
2016-06-01
Atmospheric electric fields, connected with the ionization of particles and plasma processes, occur in the fields of pressure gradients of mosaic mesh topology. Atmospheric aerosol particles play a significant role in the vortex generation. The Coriolis force and the motion of charged particles in the geomagnetic field lead to gyrotropy of the atmosphere and ionosphere. Occurrence of plasma vortices is stochastically determined for such an inhomogeneous gyrotropic medium. The geomagnetic field influences the change of structures of inhomogeneous media in the process of excitation of plasma vortices and their interaction. If colliding vortices are centered on the one geomagnetic line, the merge of vortices and the generation of a joint powerful vortex are possible. If a collision of vortices with centers at different geomagnetic field lines occurs, then the emergence of areas of heating and jet streams and the generation of new vortices are possible.
Interaction of Atmospheric Plasma Vortices
NASA Astrophysics Data System (ADS)
Izhovkina, N. I.; Artekha, S. N.; Erokhin, N. S.; Mikhailovskaya, L. A.
2016-08-01
Atmospheric electric fields, connected with the ionization of particles and plasma processes, occur in the fields of pressure gradients of mosaic mesh topology. Atmospheric aerosol particles play a significant role in the vortex generation. The Coriolis force and the motion of charged particles in the geomagnetic field lead to gyrotropy of the atmosphere and ionosphere. Occurrence of plasma vortices is stochastically determined for such an inhomogeneous gyrotropic medium. The geomagnetic field influences the change of structures of inhomogeneous media in the process of excitation of plasma vortices and their interaction. If colliding vortices are centered on the one geomagnetic line, the merge of vortices and the generation of a joint powerful vortex are possible. If a collision of vortices with centers at different geomagnetic field lines occurs, then the emergence of areas of heating and jet streams and the generation of new vortices are possible.
Gluon mass generation without seagull divergences
Aguilar, Arlene C.; Papavassiliou, Joannis
2010-02-01
Dynamical gluon mass generation has been traditionally plagued with seagull divergences, and all regularization procedures proposed over the years yield finite but scheme-dependent gluon masses. In this work we show how such divergences can be eliminated completely by virtue of a characteristic identity, valid in dimensional regularization. The ability to trigger the aforementioned identity hinges crucially on the particular Ansatz employed for the three-gluon vertex entering into the Schwinger-Dyson equation governing the gluon propagator. The use of the appropriate three-gluon vertex brings about an additional advantage: one obtains two separate (but coupled) integral equations, one for the effective charge and one for the gluon mass. This system of integral equations has a unique solution, which unambiguously determines these two quantities. Most notably, the effective charge freezes in the infrared, and the gluon mass displays power-law running in the ultraviolet, in agreement with earlier considerations.
Defining and Computing Vortices Objectively from the Vorticity
NASA Astrophysics Data System (ADS)
Haller, George; Hadjighasem, Alireza; Farazmand, Mohammad; Huhn, Florian
2015-11-01
We introduce the notion of rotationally coherent Lagrangian vortices as tubular material surfaces in which fluid elements complete equal bulk material rotation relative to the mean rotation of the fluid. We find that initial positions of such tubes coincide with tubular level surfaces of the Lagrangian-Averaged Vorticity Deviation (LAVD), the trajectory integral of the normed difference of the vorticity from its spatial mean. LAVD-based vortices turn out to be objective, i.e., invariant under time-dependent rotations and translations of the reference frame. In the limit of vanishing Rossby numbers in geostrophic flows, cyclonic LAVD vortex centers can be proven to coincide with the observed attractors for light particles. A similar result holds for heavy particles in anticyclonic LAVD vortices. We also discuss a relationship between rotationally coherent Lagrangian vortices and their instantaneous Eulerian counterparts. The latter are formed by tubular surfaces of equal material rotation rate, objectively measured by the Instantaneous Vorticity Deviation (IVD). We show how the LAVD and the IVD detect rotationally coherent Lagrangian and Eulerian vortices objectively in analytic flow models and numerical flow data.
NASA Technical Reports Server (NTRS)
Greenblatt, David
2005-01-01
A wind tunnel investigation was carried out on a semi-span wing model to assess the feasibility of controlling vortices emanating from outboard flaps and tip-flaps by actively varying the degree of boundary layer separation. Separation was varied by means of perturbations produced from segmented zero-efflux oscillatory blowing slots, while estimates of span loadings and vortex sheet strengths were obtained by integrating wing surface pressures. These estimates were used as input to inviscid rollup relations as a means of predicting changes to the vortex characteristics resulting from the perturbations. Surveys of flow in the wake of the outboard and tip-flaps were made using a seven-hole probe, from which the vortex characteristics were directly deduced. Varying the degree of separation had a marked effect on vortex location, strength, tangential velocity, axial velocity and size for both outboard and tip-flaps. Qualitative changes in vortex characteristics were well predicted by the inviscid rollup relations, while the failure to account for viscosity was presumed to be the main reason for observed discrepancies. Introducing perturbations near the outboard flap-edges or on the tip-flap exerted significant control over vortices while producing negligible lift excursions.
Gluon TMDs in Quarkonium Production
NASA Astrophysics Data System (ADS)
Signori, Andrea
2016-04-01
I report on our investigations into the impact of (un)polarized transverse momentum dependent parton distribution functions (TMD PDFs or TMDs) for gluons at hadron colliders, especially at A Fixed Target Experiment at the LHC (AFTER@LHC). In the context of high energy proton-proton collisions, we look at final states with low mass (e.g. η _b ) in order to investigate the nonperturbative part of TMD PDFs. We study the factorization theorem for the q_T spectrum of η _b produced in proton-proton collisions relying on the effective field theory approach, defining the tools to perform phenomenological investigations at next-to-next-to-leading log and next-to-leading order accuracy in the perturbation theory. We provide predictions for the unpolarized cross section and comment on the possibility of extracting nonperturbative information about the gluon content of the proton once data at low transverse momentum are available.
Gluon TMDs in Quarkonium Production
NASA Astrophysics Data System (ADS)
Signori, Andrea
2016-08-01
I report on our investigations into the impact of (un)polarized transverse momentum dependent parton distribution functions (TMD PDFs or TMDs) for gluons at hadron colliders, especially at A Fixed Target Experiment at the LHC (AFTER@LHC). In the context of high energy proton-proton collisions, we look at final states with low mass (e.g. η _b) in order to investigate the nonperturbative part of TMD PDFs. We study the factorization theorem for the q_T spectrum of η _b produced in proton-proton collisions relying on the effective field theory approach, defining the tools to perform phenomenological investigations at next-to-next-to-leading log and next-to-leading order accuracy in the perturbation theory. We provide predictions for the unpolarized cross section and comment on the possibility of extracting nonperturbative information about the gluon content of the proton once data at low transverse momentum are available.
Dynamics of vortices in superconductors
Weinan, E.
1992-12-31
We study the dynamics of vortices in type-II superconductors from the point of view of time-dependent Ginzburg-Landau equations. We outline a proof of existence, uniqueness and regularity of strong solutions for these equations. We then derive reduced systems of ODEs governing the motion of the vortices in the asymptotic limit of large Ginzburg-Landau parameter.
Quantised vortices in polariton lattices
NASA Astrophysics Data System (ADS)
Berloff, Natalia
2015-11-01
The first comprehensive treatment of quantised vorticity in the light of research on vortices in modern fluid mechanics appeared in Russell Donnelly seminal research papers and summarized in his 1991 book ``Quantized Vortices in Helium II''. Recently quantized vortices have been studied in polariton condensates. Polaritons are the mixed light-matter quasi-particles that are formed in the strong exciton-photon coupling regime. Under non-resonant optical excitation rapid relaxation of carriers and bosonic stimulation result in the formation of a non-equilibrium polariton condensate characterized by a single many-body wave-function, therefore, naturally possessing quantized vortices. Polariton condensates can be imprinted into any two-dimensional lattice by spatial modulation of the pumping laser and form vortices via interacting outfows from the pumping sites. Optically pumped polariton condensates can be injected in lattice configurations with arbitrary density profiles offering the possibility to control the kinetics of the condensate and therefore the number and location of vortices. I will present some new developments in theoretical and experimental studies of quantized vortices in polariton condensates and discuss possible practical implementations of polariton lattices.
Flame propagation through periodic vortices
Dold, J.W.; Kerr, O.S.; Nikolova, I.P.
1995-02-01
The discovery of a new class of Navier-Stokes solutions representing steady periodic stretched vortices offers a useful test-bed for examining interactions between flames and complex flow-fields. After briefly describing these vortex solutions and their wide-ranging parameterization in terms of wavelength and amplitude, this article examines their effect on flames of constant normal propagation speed as observed through numerical solutions of an eikonal equation. Over certain ranges of vortex amplitude and flame-speed, a corridor of enhanced flame passage is seen to be created as a leading flame-tip managers to leap-frog between successive vortices. However, for large enough amplitudes of vorticity or small enough flame-speeds, the flame fails to be able to benefit from the advection due to the vortices. It is shown that the leading tips of such flames are effectively trapped by the stretched vortices.
Vorticity flux from active dimples
NASA Astrophysics Data System (ADS)
McKeon, Beverley; Sherwin, Spencer; Morrison, Jonathan
2004-11-01
The effect of surface depressions, or dimples, in reducing drag on golf balls is well-known. Here this concept is extended to using ``active" dimples to manipulate vorticity flux at the wall. Surface vorticity flux is governed by surface accelerations, pressure and shear stress gradients, and surface curvature. ``Active" (or vibrating) dimples may generate vorticity flux by each of these terms, making them an excellent candidate for a basic study of flux manipulation, by which flow control may be achieved. Flow over an active dimple in fully-developed laminar channel flow is simulated with velocity boundary conditions developed from a linearized perturbation method imposed at the wall. This simple model cannot capture flow separation, but gives insight into the most straightforward means of flux generation from the concave surface. Vorticity flux due to dimple geometry and motion is quantified, and enhancements of two to three orders of magnitude in peak vorticity over the static dimple case are observed.
Potential vorticity in magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Webb, G. M.; Mace, R. L.
2015-01-01
A version of Noether's second theorem using Lagrange multipliers is used to investigate fluid relabelling symmetries conservation laws in magnetohydrodynamics (MHD). We obtain a new generalized potential vorticity type conservation equation for MHD which takes into account entropy gradients and the J × B force on the plasma due to the current J and magnetic induction B. This new conservation law for MHD is derived by using Noether's second theorem in conjunction with a class of fluid relabelling symmetries in which the symmetry generator for the Lagrange label transformations is non-parallel to the magnetic field induction in Lagrange label space. This is associated with an Abelian Lie pseudo algebra and a foliated phase space in Lagrange label space. It contains as a special case Ertel's theorem in ideal fluid mechanics. An independent derivation shows that the new conservation law is also valid for more general physical situations.
A study of vorticity formation in high energy nuclear collisions
NASA Astrophysics Data System (ADS)
Becattini, F.; Inghirami, G.; Rolando, V.; Beraudo, A.; Del Zanna, L.; De Pace, A.; Nardi, M.; Pagliara, G.; Chandra, V.
2015-09-01
We present a quantitative study of vorticity formation in peripheral ultrarelativistic heavy-ion collisions at GeV by using the ECHO-QGP numerical code, implementing relativistic dissipative hydrodynamics in the causal Israel-Stewart framework in dimensions with an initial Bjorken flow profile. We consider different definitions of vorticity which are relevant in relativistic hydrodynamics. After demonstrating the excellent capabilities of our code, which proves to be able to reproduce Gubser flow up to 8 fm/ c, we show that, with the initial conditions needed to reproduce the measured directed flow in peripheral collisions corresponding to an average impact parameter fm and with the Bjorken flow profile for a viscous Quark Gluon Plasma with fixed, a vorticity of the order of some /fm can develop at freeze-out. The ensuing polarization of baryons does not exceed 1.4 % at midrapidity. We show that the amount of developed directed flow is sensitive to both the initial angular momentum of the plasma and its viscosity.
Gluon Contribution To The Nucleon Spin
NASA Astrophysics Data System (ADS)
Arash, Firooz; Taghavi-Shahri, Fatemeh; Shahveh, Abolfazl
2011-07-01
Gluon polarization in Nucleon is evaluated in the valon representation of hadrons. It is shown that although δg/g is small at the currently measured kinematics, it does not imply that the gluon contribution to the nucleon spin is small. In fact the first moment of gluon polarization in the nucleon, Δg(Q2), is sizable. We also notice that the majority of Δg is concentrated at around x = 0.08.
Quark ACM with topologically generated gluon mass
NASA Astrophysics Data System (ADS)
Choudhury, Ishita Dutta; Lahiri, Amitabha
2016-03-01
We investigate the effect of a small, gauge-invariant mass of the gluon on the anomalous chromomagnetic moment (ACM) of quarks by perturbative calculations at one-loop level. The mass of the gluon is taken to have been generated via a topological mass generation mechanism, in which the gluon acquires a mass through its interaction with an antisymmetric tensor field Bμν. For a small gluon mass ( < 10 MeV), we calculate the ACM at momentum transfer q2 = -M Z2. We compare those with the ACM calculated for the gluon mass arising from a Proca mass term. We find that the ACM of up, down, strange and charm quarks vary significantly with the gluon mass, while the ACM of top and bottom quarks show negligible gluon mass dependence. The mechanism of gluon mass generation is most important for the strange quarks ACM, but not so much for the other quarks. We also show the results at q2 = -m t2. We find that the dependence on gluon mass at q2 = -m t2 is much less than at q2 = -M Z2 for all quarks.
Asymptocic Freedom of Gluons in Hamiltonian Dynamics
NASA Astrophysics Data System (ADS)
Gómez-Rocha, María; Głazek, Stanisław D.
2016-07-01
We derive asymptotic freedom of gluons in terms of the renormalized SU(3) Yang-Mills Hamiltonian in the Fock space. Namely, we use the renormalization group procedure for effective particles to calculate the three-gluon interaction term in the front-form Yang-Mills Hamiltonian using a perturbative expansion in powers of g up to third order. The resulting three-gluon vertex is a function of the scale parameter s that has an interpretation of the size of effective gluons. The corresponding Hamiltonian running coupling constant exhibits asymptotic freedom, and the corresponding Hamiltonian {β} -function coincides with the one obtained in an earlier calculation using a different generator.
NASA Technical Reports Server (NTRS)
Rossow, Vernon J.
2011-01-01
As part of an ongoing effort to find ways to make vortex flow fields decompose more quickly, photographs and observations are presented of vortex flow fields that indicate the presence of multiple layers of fluid rotating about a common axis. A survey of the literature indicates that multiple-layered vortices form in waterspouts, tornadoes and lift-generated vortices of aircraft. An explanation for the appearance of multiple-layered structures in vortices is suggested. The observations and data presented are intended to improve the understanding of the formation and persistence of vortex flow fields.
Ordering Multiple Soft Gluon Emissions.
Ángeles Martínez, René; Forshaw, Jeffrey R; Seymour, Michael H
2016-05-27
We present an expression for the QCD amplitude for a general hard scattering process with any number of soft gluon emissions, to one-loop accuracy. The amplitude is written in two different but equivalent ways: as a product of operators ordered in dipole transverse momentum and as a product of loop-expanded currents. We hope that these results will help in the development of an all-orders algorithm for multiple emissions that includes the full color structure and both the real and imaginary contributions to the amplitude. PMID:27284651
Gluon Evolution and Saturation Proceedings
McLerran, L.D.
2010-05-26
Almost 40 years ago, Gribov and colleagues at the Leningrad Nuclear Physics Institute developed the ideas that led to the Dokhsitzer-Gribov-Altarelli-Parisi the Baltisky-Fadin-Kuraev-Lipatov equations. These equations describe the evolution of the distributions for quarks and gluon inside a hadron to increased resolution scale of a probe or to smaller values of the fractional momentum of a hadronic constituent. I motivate and discuss the generalization required of these equations needed for high energy processes when the density of constituents is large. This leads to a theory of saturation realized by the Color Glass Condensate
Vorticity Transfer in Shock Wave Interactions with Turbulence and Vortices
NASA Astrophysics Data System (ADS)
Agui, J. H.; Andreopoulos, J.
1998-11-01
Time-dependent, three-dimensional vorticity measurements of shock waves interacting with grid generated turbulence and concentrated tip vortices were conducted in a large diameter shock tube facility. Two different mesh size grids and a NACA-0012 semi-span wing acting as a tip vortex generator were used to carry out different relative Mach number interactions. The turbulence interactions produced a clear amplification of the lateral and spanwise vorticity rms, while the longitudinal component remained mostly unaffected. By comparison, the tip vortex/shock wave interactions produced a two fold increase in the rms of longitudinal vorticity. Considerable attention was given to the vorticity source terms. The mean and rms of the vorticity stretching terms dominated by 5 to 7 orders of magnitude over the dilitational compression terms in all the interactions. All three signals of the stretching terms manifested very intermittent, large amplitude peak events which indicated the bursting character of the stretching process. Distributions of these signals were characterized by extremely large levels of flatness with varying degrees of skewness. These distribution patterns were found to change only slightly through the turbulence interactions. However, the tip vortex/shock wave interactions brought about significant changes in these distributions which were associated with the abrupt structural changes of the vortex after the interaction.
NASA Astrophysics Data System (ADS)
Papanicolaou, N.; Tomaras, T. N.
1991-08-01
The canonical conservation laws of linear and angular momentum in the ferromagnetic continuum have been known to be plagued by certain ambiguities which are resolved in this paper by constructing conservation laws as suitable moments of a topological density. The resulting canonical structure is then shown to be analogous to that encountered in the familiar Hall effect and explains the unusual features of the dynamics of magnetic vortices without resorting to a detailed solution of the underlying nonlinear equations. Thus, in the absence of external magnetic fields, a magnetic vortex is shown to be spontaneously pinned around a fixed guiding center. The guiding center would drift in a direction perpendicular to an applied magnetic field gradient, provided that dissipation can be neglected, with a Hall velocity that is calculated explicitly in terms of the initial configuration of the vortex. In the presence of dissipation, the vortex undergoes skew deflection at an angle δ ≠ 90° with respect to the applied field gradient. The angle δ is related to the winding number of the vortex according to the well-known golden rule of bubble dynamics.
Consequences Of Fully Dressing Quark-Gluon Vertex Function With Two-Point Gluon Lines
Hrayr Matevosyan; Anthony Thomas; Peter Tandy
2007-06-18
We extend recent studies of the effects of quark-gluon vertex dressing upon the solutions of the Dyson-Schwinger equation for the quark propagator. A momentum delta function is used to represent the dominant infrared strength of the effective gluon propagator so that the resulting integral equations become algebraic. The guark-gluon vertex is constructed from the complete set of diagrams involving only 2-point gluon lines. The additional diagrams, including those with crossed gluon lines, are shown to make an important contribution to the DSE solutions for the quark propagator, because of their large color factors and the rapid growth in their number.
Gluon Spin Contribution to The Nucleon Spin
NASA Astrophysics Data System (ADS)
Arash, Firooz; Shahveh, Abolfazl; Taghavi-Shahri, Fateme
2010-10-01
We have calculated δg/ g in the nucleon at all measured kinematics. The smallness of δg/ g in the measured kinematics should not be interpreted as the the gluon contribution to the nucleon spin is small. In fact the first moment of gluon polarization in the nucleon, Δ g( Q2) can be sizable.
HUNTING THE QUARK GLUON PLASMA.
LUDLAM, T.; ARONSON, S.
2005-04-11
The U.S. Department of Energy's Relativistic Heavy Ion Collider (RHIC) construction project was completed at BNL in 1999, with the first data-taking runs in the summer of 2000. Since then the early measurements at RHIC have yielded a wealth of data, from four independent detectors, each with its international collaboration of scientists: BRAHMS, PHENIX, PHOBOS, and STAR [1]. For the first time, collisions of heavy nuclei have been carried out at colliding-beam energies that have previously been accessible only for high-energy physics experiments with collisions of ''elementary'' particles such as protons and electrons. It is at these high energies that the predictions of quantum chromodynamics (QCD), the fundamental theory that describes the role of quarks and gluons in nuclear matter, come into play, and new phenomena are sought that may illuminate our view of the basic structure of matter on the sub-atomic scale, with important implications for the origins of matter on the cosmic scale. The RHIC experiments have recorded data from collisions of gold nuclei at the highest energies ever achieved in man-made particle accelerators. These collisions, of which hundreds of millions have now been examined, result in final states of unprecedented complexity, with thousands of produced particles radiating from the nuclear collision. All four of the RHIC experiments have moved quickly to analyze these data, and have begun to understand the phenomena that unfold from the moment of collision as these particles are produced. In order to provide benchmarks of simpler interactions against which to compare the gold-gold collisions, the experiments have gathered comparable samples of data from collisions of a very light nucleus (deuterium) with gold nuclei, as well as proton-proton collisions, all with identical beam energies and experimental apparatus. The early measurements have revealed compelling evidence for the existence of a new form of nuclear matter at extremely high
Jupiter's Great Red Spot and other vortices
NASA Technical Reports Server (NTRS)
Marcus, Philip S.
1993-01-01
A theoretical explanation of Jupiter's Great Red Spot (GRS) as the self-organization of vorticity in turbulence is presented. A number of properties of the GRS and other Jovian vortices that are unambiguous from the data are listed. The simplest possible model that explains these properties one at a time rather than in a difficult all-encompassing planetary global circulation model is presented. It is shown that Jovian vortices reflect the behavior of quasi-geostrophic (QG) vortices embedded in an east-west wind with bands of uniform potential vorticity. It is argued that most of the properties of the Jovian vortices can be easily explained and understood with QG theory. Many of the signatures of QG vortices are apparent on Voyager images. In numerical and laboratory experiments, QG vortices relax to approximately steady states like the Jovian vortices, rather than oscillating or rotating Kida ellipses.
How rotational vortices enhance transfers
NASA Astrophysics Data System (ADS)
Griffani, D.; Rognon, P.; Metzger, B.; Einav, I.
2013-09-01
Inspired by recent observations of granular flow, we examine how rotational vortices contribute to heat or mass transfer enhancement in a fluid. We use a tracer method to simulate both diffusion and advection in systems of differing intrinsic diffusivities D0, vortex sizes R, vortex rotation frequencies f, and vortex lifetimes ℓ. The results reveal that these systems exhibit an effective diffusive behavior, characterized by an effective diffusivity Deff. A striking finding is the existence of two regimes, dichotomised by the Péclet number Pe = R2f/D0. When the Péclet number is less than one, there is no transfer enhancement, Deff = D0. For higher values, vortices produce some transfer enhancement with a corresponding power law Deff/D0 ≈ Pen. The power n ranges from a lower bound of 0.5 for stationary vortices of lifetime infinity, to an upper bound of 1 for vortices of lifetimes shorter than half a rotation. This difference is attributed to two different internal mechanisms involving the coupling of diffusion and advection. These results could provide new insights on the transfer properties of fluid systems comprising rotational vortices, such as granular materials, suspensions, foams, and emulsions, as well as low Reynolds number stirred flows.
Filamentation with nonlinear Bessel vortices.
Jukna, V; Milián, C; Xie, C; Itina, T; Dudley, J; Courvoisier, F; Couairon, A
2014-10-20
We present a new type of ring-shaped filaments featured by stationary nonlinear high-order Bessel solutions to the laser beam propagation equation. Two different regimes are identified by direct numerical simulations of the nonlinear propagation of axicon focused Gaussian beams carrying helicity in a Kerr medium with multiphoton absorption: the stable nonlinear propagation regime corresponds to a slow beam reshaping into one of the stationary nonlinear high-order Bessel solutions, called nonlinear Bessel vortices. The region of existence of nonlinear Bessel vortices is found semi-analytically. The influence of the Kerr nonlinearity and nonlinear losses on the beam shape is presented. Direct numerical simulations highlight the role of attractors played by nonlinear Bessel vortices in the stable propagation regime. Large input powers or small cone angles lead to the unstable propagation regime where nonlinear Bessel vortices break up into an helical multiple filament pattern or a more irregular structure. Nonlinear Bessel vortices are shown to be sufficiently intense to generate a ring-shaped filamentary ionized channel in the medium which is foreseen as opening the way to novel applications in laser material processing of transparent dielectrics. PMID:25401574
Gluons and the NJL coupling constant
Braghin, Fábio L.; Barros Jr, Ednaldo; Paulo Jr, Ademar
2014-11-11
The QCD origin of the NJL model is re-analysed by considering the gluon condensate of order two . The key point is the treatment of the gluon interactions. To linearize the action the auxiliary variable method is employed to introduce a scalar variable φ(x) that yield such condensate by means of its value in the vacuum, and then another auxiliary variable that corresponds to an antisymmetric gluon configuration φ(x). For that, besides that, two different possible limits of the fourth order non local quark interaction that may contribute to the NJL coupling are compared.
Froissart bound and gluon number fluctuations
Xiang Wenchang
2010-05-01
We study the effect of gluon number fluctuations (Pomeron loops) on the impact parameter behavior of the scattering amplitude in the fixed coupling case. We demonstrate that the dipole-hadron cross section computed from gluon number fluctuations saturates the Froissart bound and the growth of the radius of the black disk with rapidity is enhanced by an additional term as compared to the single event case. We find that the physical amplitude has a Gaussian impact parameter dependence once the gluon number fluctuations are included. This indicates that the fluctuations may be the microscopic origin for the Gaussian impact parameter dependence of the scattering amplitude.
Quark and gluon condensates in isospin matter
He Lianyi; Jiang Yin; Zhuang Pengfei
2009-04-15
By applying the Hellmann-Feynman theorem to a charged pion gas, the quark and gluon condensates at low isospin density are determined by precise pion properties. At intermediate density around f{sub {pi}}{sup 2}m{sub {pi}}, from both the estimation for the dilute pion gas and the calculation with the Nambu-Jona-Lasinio model, the quark condensate is strongly and monotonously suppressed, while the gluon condensate is enhanced and can be larger than its vacuum value. This unusual behavior of the gluon condensate is universal for Bose condensed matter of mesons. Our results can be tested by lattice calculations at finite isospin density.
Hairpin Vortices: Autogeneration and Interaction
NASA Astrophysics Data System (ADS)
Sabatino, Daniel; Maharjan, Rijan; Sanders, Andrew
2013-11-01
The regeneration of hairpin vortices is examined in a free-surface water channel where vortices are artificially generated by means of injection in a laminar boundary layer. The process is visualized with dye and hydrogen bubble-wire techniques. The strength of an isolated hairpin required to begin the autogeneration process is established by means of PIV measurements on the symmetry plane. Because hairpins are in close proximity in a fully-turbulent boundary layer, two hairpins are generated at different streamwise locations and allowed to interact at different stages of development. The relative position, strength and maturity of the interacting hairpins that generate secondary vortices are examined. The morphology of the generation process and of the resulting secondary hairpin for both the isolated and interacting cases are discussed and compared to previous work. Supported by the National Science Foundation under Grant CBET-1040236.
Higgs boson production via gluon fusion: Soft-gluon resummation including mass effects
NASA Astrophysics Data System (ADS)
Schmidt, Timo; Spira, Michael
2016-01-01
We analyze soft and collinear gluon resummation effects at the N3LL level for Standard Model Higgs boson production via gluon fusion g g →H and the neutral scalar and pseudoscalar Higgs bosons of the minimal supersymmetric extension at the next-to-next-to-next-to-leading-log (N3LL ) and next-to-next-to-leading-log (NNLL) level, respectively. We introduce refinements in the treatment of quark mass effects and subleading collinear gluon effects within the resummation. Soft and collinear gluon resummation effects amount to up to about 5% beyond the fixed-order results for scalar and pseudoscalar Higgs boson production.
Transport properties of quark and gluon plasmas
Heiselberg, H.
1993-12-01
The kinetic properties of relativistic quark-gluon and electron-photon plasmas are described in the weak coupling limit. The troublesome Rutherford divergence at small scattering angles is screened by Debye screening for the longitudinal or electric part of the interactions. The transverse or magnetic part of the interactions is effectively screened by Landau damping of the virtual photons and gluons transferred in the QED and QCD interactions respectively. Including screening a number of transport coefficients for QCD and QED plasmas can be calculated to leading order in the interaction strength, including rates of momentum and thermal relaxation, electrical conductivity, viscosities, flavor and spin diffusion of both high temperature and degenerate plasmas. Damping of quarks and gluons as well as color diffusion in quark-gluon plasmas is, however, shown not to be sufficiently screened and the rates depends on an infrared cut-off of order the ``magnetic mass,`` m{sub mag} {approximately} g{sup 2}T.
Gluon saturation in a saturated environment
Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Ivan
2011-07-15
A bootstrap equation for self-quenched gluon shadowing leads to a reduced magnitude of broadening for partons propagating through a nucleus. Saturation of small-x gluons in a nucleus, which has the form of transverse momentum broadening of projectile gluons in pA collisions in the nuclear rest frame, leads to a modification of the parton distribution functions in the beam compared with pp collisions. In nucleus-nucleus collisions all participating nucleons acquire enhanced gluon density at small x, which boosts further the saturation scale. Solution of the reciprocity equations for central collisions of two heavy nuclei demonstrate a significant, up to several times, enhancement of Q{sub sA}{sup 2}, in AA compared with pA collisions.
Gluon saturation in a saturated environment
NASA Astrophysics Data System (ADS)
Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Ivan
2011-07-01
A bootstrap equation for self-quenched gluon shadowing leads to a reduced magnitude of broadening for partons propagating through a nucleus. Saturation of small-x gluons in a nucleus, which has the form of transverse momentum broadening of projectile gluons in pA collisions in the nuclear rest frame, leads to a modification of the parton distribution functions in the beam compared with pp collisions. In nucleus-nucleus collisions all participating nucleons acquire enhanced gluon density at small x, which boosts further the saturation scale. Solution of the reciprocity equations for central collisions of two heavy nuclei demonstrate a significant, up to several times, enhancement of QsA2, in AA compared with pA collisions.
The gluon Sivers distribution: Status and future prospects
Boer, Daniël; Lorcé, Cédric; Pisano, Cristian; Zhou, Jian
2015-06-28
In this study, we review what is currently known about the gluon Sivers distribution and what are the opportunities to learn more about it. Because single transverse spin asymmetries in p↑p → πX provide only indirect information about the gluon Sivers function through the relation with the quark-gluon and tri-gluon Qiu-Sterman functions, current data from hadronic collisions at RHIC have not yet been translated into a solid constraint on the gluon Sivers function.
Role of monopoles in a gluon plasma
Ratti, Claudia; Shuryak, Edward
2009-08-01
We study the role of magnetic monopoles at high enough temperature T>2T{sub c}, when they can be considered heavy, rare objects embedded into matter consisting mostly of the usual 'electric' quasiparticles, quarks, and gluons. We review available lattice results on monopoles at finite temperatures. Then we proceed to classical and quantum charge-monopole scattering, solving the problem of gluon-monopole scattering for the first time. The explicit calculations are performed in the framework of the Georgi-Glashow model; the results that we obtain are nevertheless quite general. Connections to QCD are carefully discussed. We find that, while the gluon-monopole scattering hardly influences thermodynamic quantities, it does produce a large transport cross section, significantly exceeding that for pQCD gluon-gluon scattering up to quite high T. Thus, in spite of their relatively small density at high T, monopoles are extremely important for quark-gluon plasma transport properties, keeping viscosity small enough for hydrodynamics to work at the LHC.
Paraboloids and Vortices in Hydrodynamics
ERIC Educational Resources Information Center
Goodman, John M.
1969-01-01
Describes an apparatus designed to demonstrate vortical flow of a fluid. The apparatus consists of a transparent acrylic cylinder, with a drain hole, and mounted so that it can be rotated about its axis at speeds up to 1000 rpm. Experimental observations with water as the fluid under study are reported. (LC)
Combustor with multistage internal vortices
Shang, Jer Y.; Harrington, Richard E.
1989-01-01
A fluidized bed combustor is provided with a multistage arrangement of vortex generators in the freeboard area. The vortex generators are provided by nozzle means which extend into the interior of the freeboard for forming vortices within the freeboard area to enhance the combustion of particulate material entrained in product gases ascending into the freeboard from the fluidized bed. Each of the nozzles are radially inwardly spaced from the combustor walls defining the freeboard to provide for the formation of an essentially vortex-free, vertically extending annulus about the vortices whereby the particulate material centrifuged from the vortices against the inner walls of the combustor is returned through the annulus to the fluidized bed. By adjusting the vortex pattern within the freeboard, a significant portion of the full cross-sectional area of the freeboard except for the peripheral annulus can be contacted with the turbulent vortical flow for removing the particulate material from the gaseous products and also for enhancing the combustion thereof within the freeboard.
Combustor with multistage internal vortices
Shang, Jer Yu; Harrington, R.E.
1987-05-01
A fluidized bed combustor is provided with a multistage arrangement of vortex generators in the freeboard area. The vortex generators are provided by nozzle means which extend into the interior of the freeboard for forming vortices within the freeboard areas to enhance the combustion of particulate material entrained in product gases ascending into the freeboard from the fluidized bed. Each of the nozzles are radially inwardly spaced from the combustor walls defining the freeboard to provide for the formation of an essentially vortex-free, vertically extending annulus about the vortices whereby the particulate material centrifuged from the vortices against the inner walls of the combustor is returned through the annulus to the fluidized bed. By adjusting the vortex pattern within the freeboard, a significant portion of the full cross-sectional area of the freeboard except for the peripheral annulus can be contacted with the turbulent vortical flow for removing the particulate material from the gaseous products and also for enhancing the combustion thereof within the freeboard. 2 figs.
Adiabatic dynamics of magnetic vortices
NASA Astrophysics Data System (ADS)
Papanicolaou, N.
1994-03-01
We formulate a reasonably detailed adiabatic conjecture concerning the dynamics of skew deflection of magnetic vortices in a field gradient, which is expected to be valid at sufficiently large values of the winding number. The conjecture is consistent with the golden rule used to describe the dynamics of realistic magnetic bubbles and is verified here numerically within the 2-D isotropic Heisenberg model.
Stochastic Vorticity and Associated Filtering Theory
Amirdjanova, A.; Kallianpur, G.
2002-12-19
The focus of this work is on a two-dimensional stochastic vorticity equation for an incompressible homogeneous viscous fluid. We consider a signed measure-valued stochastic partial differential equation for a vorticity process based on the Skorohod-Ito evolution of a system of N randomly moving point vortices. A nonlinear filtering problem associated with the evolution of the vorticity is considered and a corresponding Fujisaki-Kallianpur-Kunita stochastic differential equation for the optimal filter is derived.
Bugaev, K. A.; Petrov, V. K.; Zinovjev, G. M.
2009-05-15
The influence of the medium-dependent finite width of quark gluon plasma (QGP) bags on their equation of state is analyzed within an exactly solvable model. It is argued that the large width of the QGP bags not only explains the observed deficit in the number of hadronic resonances but also clarifies the reason why the heavy QGP bags cannot be directly observed as metastable states in a hadronic phase. The model allows us to estimate the minimal value of the width of QGP bags being heavier than 2 GeV from a variety of the lattice QCD data and get that the minimal resonance width at zero temperature is about 600 MeV, whereas the minimal resonance width at the Hagedorn temperature is about 2000 MeV. As shown, these estimates are almost insensitive to the number of the elementary degrees of freedom. The recent lattice QCD data are analyzed and it is found that in addition to the {sigma}T{sup 4} term the lattice QCD pressure contains T-linear and T{sup 4}lnT terms in the range of temperatures between 240 and 420 MeV. The presence of the last term in the pressure bears almost no effect on the width estimates. Our analysis shows that at high temperatures the average mass and width of the QGP bags behave in accordance with the upper bound of the Regge trajectory asymptotics (the linear asymptotics), whereas at low temperatures they obey the lower bound of the Regge trajectory asymptotics (the square root one). Since the model explicitly contains the Hagedorn mass spectrum, it allows us to remove an existing contradiction between the finite number of hadronic Regge families and the Hagedorn idea of the exponentially growing mass spectrum of hadronic bags.
Vorticity from Isocurvature in the Early Universe
NASA Astrophysics Data System (ADS)
Christopherson, Adam J.; Malik, Karim A.
2015-01-01
Vorticity is ubiquitous in nature however, to date, studies of vorticity in cosmology and the early universe have been quite rare. In this paper, based on a talk in session CM1 of the 13th Marcel Grossmann Meeting, we consider vorticity generation from scalar cosmological perturbations of a perfect fluid system. We show that, at second order in perturbation theory, vorticity is sourced by a coupling between energy density and entropy gradients, thus extending a well-known feature of classical fluid dynamics to a relativistic cosmological framework. This induced vorticity, sourced by isocurvature perturbations, may prove useful in the future as an additional discriminator between inflationary models.
Potential Vorticity Structure of the Mars Polar Vortices
NASA Astrophysics Data System (ADS)
Guzewich, S.; Toigo, A. D.; Waugh, D.; Montabone, L.; Greybush, S. J.
2015-12-01
The increasing sophistication of Mars general circulation models (MGCMs) and the availability of regular atmospheric observations have allowed several teams to begin to assimilate these observations into their MGCMs and produce atmospheric reanalyses that enable, among other things, the potential vorticity (PV) structure of the Martian polar vortices to be examined. Here we perform such an analysis using the Mars Analysis Correction Data Assimilation (MACDA, Montabone et al., 2013) and the Ensembles Mars Reanalysis System (EMARS, Greybush et al., 2012) reanalyses together with free-running MGCM simulations. Monthly-mean fields from the reanalyses and MGCMs show strong westerly winds in northern mid-high latitudes during NH winter, with near-zero PV at and equatorward of the maximum winds (jet core) and steep meridional PV gradients poleward of the jet core. Furthermore, in the lower atmosphere the maximum PV occurs off the pole and monthly-mean maps show a continuous ring (annulus) of high PV. On shorter (e.g., daily) time scales a different picture emerges, with maps showing multiple small-scale coherent regions of high PV that rotate around the pole, and only when averaged over monthly times does a high PV annulus appear. A PV budget analysis is performed to examine the cause of the annulus of high PV. We also relate the ring of small-scale vortices to the stability of the PV annulus, and discuss the implications on meridional transport between mid and high latitudes.
Jupiter's closed cyclones and anticyclones vorticity
NASA Astrophysics Data System (ADS)
Legarreta, J.; Sánchez-Lavega, A.
2003-05-01
We have measured the motions and derived de velocity field tracking the cloud elements present in Jovian large-scale cyclones and anticyclones. We have used very high spatial resolution images obtained by the Voyager 1 and 2 (in 1979) and the Galileo (1997-1999) spacecrafts. In total we measured motions in 13 vortices covering a range of latitudes from -59 deg to + 41 deg. The tangential component of the velocity as a function of the distance to the vortex centre and position angle is used to retrieve the vorticity field. Then, we compare each vortex mean vorticity with the ambient and planetary vorticities (i. e. with latitude). For most cases studied (11), the vortex vorticity is greater than the ambient vorticity, although two types of vortices showed the same vorticity than the ambient, suggesting that their periphery motions can be entrained by the ambient shear. We present an analysis of the correlations between the mean vorticity and mean zonal motion of each vortex, and the relationship between the ambient to intrinsic vorticity versus the zonal to meridional size ratio. This is used to demonstrate that most vortices do not follow the Kida type vortex relationship. Acknowledgements: This work was supported by the Spanish MCYT PNAYA 2000-0932 and Grupos-UPV/EHU. We acknowledge the access to the Voyager and Galileo images through the NASA - PDS Atmospheric node at NMSU.
Mechanical Control of Individual Superconducting Vortices.
Kremen, Anna; Wissberg, Shai; Haham, Noam; Persky, Eylon; Frenkel, Yiftach; Kalisky, Beena
2016-03-01
Manipulating individual vortices in a deterministic way is challenging; ideally, manipulation should be effective, local, and tunable in strength and location. Here, we show that vortices respond to local mechanical stress applied in the vicinity of the vortex. We utilized this interaction to move individual vortices in thin superconducting films via local mechanical contact without magnetic field or current. We used a scanning superconducting quantum interference device to image vortices and to apply local vertical stress with the tip of our sensor. Vortices were attracted to the contact point, relocated, and were stable at their new location. We show that vortices move only after contact and that more effective manipulation is achieved with stronger force and longer contact time. Mechanical manipulation of vortices provides a local view of the interaction between strain and nanomagnetic objects as well as controllable, effective, and reproducible manipulation technique. PMID:26836018
Mechanical Control of Individual Superconducting Vortices
2016-01-01
Manipulating individual vortices in a deterministic way is challenging; ideally, manipulation should be effective, local, and tunable in strength and location. Here, we show that vortices respond to local mechanical stress applied in the vicinity of the vortex. We utilized this interaction to move individual vortices in thin superconducting films via local mechanical contact without magnetic field or current. We used a scanning superconducting quantum interference device to image vortices and to apply local vertical stress with the tip of our sensor. Vortices were attracted to the contact point, relocated, and were stable at their new location. We show that vortices move only after contact and that more effective manipulation is achieved with stronger force and longer contact time. Mechanical manipulation of vortices provides a local view of the interaction between strain and nanomagnetic objects as well as controllable, effective, and reproducible manipulation technique. PMID:26836018
Dynamical equation of the effective gluon mass
Aguilar, A. C.; Binosi, D.; Papavassiliou, J.
2011-10-15
In this article, we derive the integral equation that controls the momentum dependence of the effective gluon mass in the Landau gauge. This is accomplished by means of a well-defined separation of the corresponding ''one-loop dressed'' Schwinger-Dyson equation into two distinct contributions, one associated with the mass and one with the standard kinetic part of the gluon. The entire construction relies on the existence of a longitudinally coupled vertex of nonperturbative origin, which enforces gauge invariance in the presence of a dynamical mass. The specific structure of the resulting mass equation, supplemented by the additional requirement of a positive-definite gluon mass, imposes a rather stringent constraint on the derivative of the gluonic dressing function, which is comfortably satisfied by the large-volume lattice data for the gluon propagator, both for SU(2) and SU(3). The numerical treatment of the mass equation, under some simplifying assumptions, is presented for the aforementioned gauge groups, giving rise to a gluon mass that is a nonmonotonic function of the momentum. Various theoretical improvements and possible future directions are briefly discussed.
Constituent gluons and the static quark potential
NASA Astrophysics Data System (ADS)
Greensite, Jeff; Szczepaniak, Adam P.
2016-04-01
We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a truncated-basis treatment of hadronic states which include constituent gluons. As an illustration, we apply this hybrid approach to the heavy quark potential, for quark-antiquark separations up to 2.4 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of 4 times greater than the asymptotic string tension. In our approach we show that a single constituent gluon is in principle sufficient, up to 2.4 fm, to reduce this overshoot by the factor required. The static potential remains linear, although the precise value of the string tension depends on details of the Couloumb gauge ghost and gluon propagators in the infrared regime. In this connection we present new lattice results for the transverse gluon propagator in position space.
Breathers on quantized superfluid vortices.
Salman, Hayder
2013-10-18
We consider the propagation of breathers along a quantized superfluid vortex. Using the correspondence between the local induction approximation (LIA) and the nonlinear Schrödinger equation, we identify a set of initial conditions corresponding to breather solutions of vortex motion governed by the LIA. These initial conditions, which give rise to a long-wavelength modulational instability, result in the emergence of large amplitude perturbations that are localized in both space and time. The emergent structures on the vortex filament are analogous to loop solitons but arise from the dual action of bending and twisting of the vortex. Although the breather solutions we study are exact solutions of the LIA equations, we demonstrate through full numerical simulations that their key emergent attributes carry over to vortex dynamics governed by the Biot-Savart law and to quantized vortices described by the Gross-Pitaevskii equation. The breather excitations can lead to self-reconnections, a mechanism that can play an important role within the crossover range of scales in superfluid turbulence. Moreover, the observation of breather solutions on vortices in a field model suggests that these solutions are expected to arise in a wide range of other physical contexts from classical vortices to cosmological strings. PMID:24182275
Breathers on Quantized Superfluid Vortices
NASA Astrophysics Data System (ADS)
Salman, Hayder
2013-10-01
We consider the propagation of breathers along a quantized superfluid vortex. Using the correspondence between the local induction approximation (LIA) and the nonlinear Schrödinger equation, we identify a set of initial conditions corresponding to breather solutions of vortex motion governed by the LIA. These initial conditions, which give rise to a long-wavelength modulational instability, result in the emergence of large amplitude perturbations that are localized in both space and time. The emergent structures on the vortex filament are analogous to loop solitons but arise from the dual action of bending and twisting of the vortex. Although the breather solutions we study are exact solutions of the LIA equations, we demonstrate through full numerical simulations that their key emergent attributes carry over to vortex dynamics governed by the Biot-Savart law and to quantized vortices described by the Gross-Pitaevskii equation. The breather excitations can lead to self-reconnections, a mechanism that can play an important role within the crossover range of scales in superfluid turbulence. Moreover, the observation of breather solutions on vortices in a field model suggests that these solutions are expected to arise in a wide range of other physical contexts from classical vortices to cosmological strings.
Vortices in vibrated granular rods
NASA Astrophysics Data System (ADS)
Neicu, Toni; Kudrolli, Arshad
2002-03-01
We report the first experimental observation of vortex patterns in granular rods inside a container that is vibrated vertically . The experiments were carried out with an anodized aluminum circular container which is rigidly attached to an electromagnetic shaker and the patterns are imaged using a high-frame rate digital camera. At low rod numbers and driving amplitudes, the rods are observed to lie horizontally. Above a critical number or packing fraction of rods, moving domains of vertical rods are spontaneously observed to form which coexist with horizontal rods. These small domains of vertical rods coarsen over time to form a few large vortices. The size of the vortices increases with the number of rods. We are able to track the ends of the vertical rods and obtain the velocity fields of the vortices. The mean azimuthal velocity as a function of distance from the center of the vortex is obtained as a function of the packing fraction. We will report the phase diagram of the various patterns observed as function of number of rods and driving amplitude. The mechanism for the formation and motion of the domains of vertical rods will be also discussed.
Buoyancy-Induced, Columnar Vortices
NASA Astrophysics Data System (ADS)
Simpson, Mark; Glezer, Ari
2015-11-01
Free buoyancy-induced, columnar vortices (dust devils) that are driven by thermal instabilities of ground-heated, stratified air in areas with sufficient insolation convert the potential energy of low-grade heat in the surface air layer into a vortex flow with significant kinetic energy. A variant of the naturally-occurring vortex is deliberately triggered and anchored within an azimuthal array of vertical, stator-like flow vanes that form an open-top enclosure and impart tangential momentum to the radially entrained air. This flow may be exploited for power generation by coupling the vortex to a vertical-axis turbine. The fundamental mechanisms associated with the formation, evolution, and dynamics of an anchored, buoyancy-driven columnar vortex within such a facility are investigated experimentally using a heated ground plane. Specific emphasis is placed on the manipulation of the vortex formation and structure and the dependence of the vorticity production and sustainment mechanisms on the thermal resources and characteristic scales of the anchoring flow vanes using stereo-PIV. It is shown that manipulation of the formation and advection of vorticity concentrations within the enclosure can be exploited for increasing the available kinetic energy. Supported by ARPA-E.
Ion-induced quark-gluon implosion.
Frankfurt, L; Strikman, M
2003-07-11
We investigate nuclear fragmentation in the central proton-nucleus and nucleus-nucleus collisions at the energies of CERN LHC. Within the semiclassical approximation we argue that because of the fast increase with energy of the cross sections of soft and hard interactions each nucleon is stripped in the average process off "soft" partons and fragments into a collection of leading quarks and gluons with large p(t). Valence quarks and gluons are streaming in the opposite directions when viewed in the c.m. of the produced system. The resulting pattern of the fragmentation of the colliding nuclei leads to an implosion of the quark and gluon constituents of the nuclei. The nonequilibrium state produced at the initial stage in the nucleus fragmentation region is estimated to have densities >/=50 GeV/fm(3) at the LHC energies and probably >/=10 GeV/fm(3) at BNL RHIC. PMID:12906475
Amplitude for N-Gluon Superstring Scattering
Stieberger, Stephan; Taylor, Tomasz R.
2006-11-24
We consider scattering processes involving N gluonic massless states of open superstrings with a certain Regge slope {alpha}{sup '}. At the semiclassical level, the string world-sheet sweeps a disk and N gluons are created or annihilated at the boundary. We present exact expressions for the corresponding amplitudes, valid to all orders in {alpha}{sup '}, for the so-called maximally helicity violating configurations, with N=4, 5 and N=6. We also obtain the leading O({alpha}{sup '2}) string corrections to the zero-slope N-gluon Yang-Mills amplitudes.
High multiplicity study and gluon dominance model
NASA Astrophysics Data System (ADS)
Kokoulina, E. S.
2016-01-01
Study of high multiplicity events in proton-proton interactions is carried out at the U-70 accelerator (IHEP, Protvino). These events are extremely rare. Usually, Monte Carlo codes underestimate topological cross sections in this region. The gluon dominance model (GDM) was offered to describe them. It is based on QCD and a phenomenological scheme of a hadronization stage. This model indicates a recombination mechanism of hadronization and a gluon fission. Future program of the SVD Collaboration is aimed at studying a long-standing puzzle of excess soft photon yield and its connection with high multiplicity at the U-70 and Nuclotron facility at JINR, Dubna.
Quarks and gluons at hadron colliders
Bodek, A.; CDF Collaboration
1996-08-01
Data from proton-antiproton collisions at high energy provide important information on constraining the quark and gluon distributions in the nucleon and place limits on quark substructure. The S asymmetry data constrains the slope of the d/u quark distributions and significantly reduces the systematic error on the extracted value of the W mass. Drell-Yan data at high invariant mass provides strong limits on quark substructure. Information on {alpha}{sub s} and the gluon distributions can be extracted from high P{sub T} jet data and direct photons.
NASA Astrophysics Data System (ADS)
Deveaud-Plédran, Benoit
2012-02-01
Polariton quantum fluids may be created both spontaneously through a standard phase transition towards a Bose Einstein condensate, or may be resonantly driven with a well-defined speed. Thanks to the photonic component of polaritons, the properties of the quantum fluid may be accessed rather directly with in particular the possibility of detained interferometric studies. Here, I will detail the dynamics of vortices, obtained with a picosecond time resolution, in different configurations, with in particular their phase dynamics. I will show in particular the dynamics the dynamics of spontaneous creation of a vortex, the dissociation of a full vortex into two half vortices as well as the dynamics of the dissociation of a dark soliton line into a street of pairs of vortices. Work done at EPFL by a dream team of Postdocs PhD students and collaborators: K. Lagoudakis, G. Nardin, T. Paraiso, G. Grosso, F. Manni, Y L'eger, M. Portella Oberli, F. Morier-Genoud and the help of our friend theorists V, Savona, M. Vouters and T. Liew.
Jet calculus beyond leading order for the gluon sector
Gunion, J.F.; Kalinowski, J.
1984-04-01
We report results for the order-C/sub A/ /sup 2/..cap alpha../sub s/ /sup 2/ jet calculus three-, two-, and one-gluon distributions of the pure gluon singlet channel. Included is an independent calculation of the C/sub A/ /sup 2/ part of the gluon..-->..gluon inclusive distribution which has been a subject of controversy for several years. We confirm the results of Furmanski and Petronzio for scheme-independent observables.
Plane mixing layer vortical structure kinematics
NASA Technical Reports Server (NTRS)
Leboeuf, Richard L.
1993-01-01
The objective of the current project was to experimentally investigate the structure and dynamics of the streamwise vorticity in a plane mixing layer. The first part of this research program was intended to clarify whether the observed decrease in mean streamwise vorticity in the far-field of mixing layers is due primarily to the 'smearing' caused by vortex meander or to diffusion. Two-point velocity correlation measurements have been used to show that there is little spanwise meander of the large-scale streamwise vortical structure. The correlation measurements also indicate a large degree of transverse meander of the streamwise vorticity which is not surprising since the streamwise vorticity exists in the inclined braid region between the spanwise vortex core regions. The streamwise convection of the braid region thereby introduces an apparent transverse meander into measurements using stationary probes. These results corroborated with estimated secondary velocity profiles in which the streamwise vorticity produces a signature which was tracked in time.
Two applications of potential vorticity thinking
NASA Technical Reports Server (NTRS)
Robinson, Walter A.
1987-01-01
The phenomena of dissipative destabilization of external Rossby waves and the acceleration of the zonal mean jet during baroclinic life cycles are described in terms of potential vorticity. The main principle of the potential temperature variations at rigid boundaries have the same effect on the interior flow as do sheets of potential vorticity located just within the boundaries. It is noted that the potential vorticity theory is useful for understanding the dynamical behavior of meterological phenomena.
SU(3) Landau gauge gluon and ghost propagators using the logarithmic lattice gluon field definition
Ilgenfritz, Ernst-Michael; Menz, Christoph; Mueller-Preussker, Michael; Schiller, Arwed; Sternbeck, Andre
2011-03-01
We study the Landau gauge gluon and ghost propagators of SU(3) gauge theory, employing the logarithmic definition for the lattice gluon fields and implementing the corresponding form of the Faddeev-Popov matrix. This is necessary in order to consistently compare lattice data for the bare propagators with that of higher-loop numerical stochastic perturbation theory. In this paper we provide such a comparison, and introduce what is needed for an efficient lattice study. When comparing our data for the logarithmic definition to that of the standard lattice Landau gauge we clearly see the propagators to be multiplicatively related. The data of the associated ghost-gluon coupling matches up almost completely. For the explored lattice spacings and sizes discretization artifacts, finite size, and Gribov-copy effects are small. At weak coupling and large momentum, the bare propagators and the ghost-gluon coupling are seen to be approached by those of higher-order numerical stochastic perturbation theory.
Exploring Quarks, Gluons and the Higgs Boson
ERIC Educational Resources Information Center
Johansson, K. Erik
2013-01-01
With real particle collision data available on the web, the amazing dynamics of the fundamental particles of the standard model can be explored in classrooms. Complementing the events from the ATLAS experiment with animations of the fundamental processes on the quark and gluon level makes it possible to better understand the invisible world of…
Recent COMPASS results on the gluon polarization
Quintans, Catarina
2009-03-23
The spin structure of the nucleon is studied in the COMPASS experiment at CERN/SPS, from the collisions of 160 GeV polarized muon beam with a {sup 6}LiD target. The data collected from 2002 to 2006 provide an accurate measurement of longitudinal double spin cross-section asymmetries. The latest results on the gluon polarization, accessed from two independent analyses of photon-gluon fusion selected events, are presented. The study of the open-charm production allows to extract the gluon polarization (in LO QCD) from the measurement of the asymmetry, the value obtained being {delta}g/g -0.49{+-}0.27(stat){+-}0.11(syst), at an average x{sub g} 0.11{sub -0.05}{sup +0.11} and a scale <{mu}{sup 2}> = 13(GeV/c){sup 2}. An alternative and independent way to study the gluon polarization, by studying the high transverse momentum hadron pairs produced, leads to a value {delta}g/g 0.08{+-}0.10(stat){+-}0.05(syst), at x{sub g}{sup a{nu}} 0.082{sub -0.027}{sup +0.041} and <{mu}{sup 2}> = 3(GeV/c){sup 2}.
Sambamurti Memorial Lecture: Spotlight on the Gluon
Michael Begelas
2010-09-01
Begel uses results from the Fermilab D0 and E706 experiments to explain how the production rate and energy spectrum of photons produced during proton collisions helped to clarify how the energy inside the proton is shared between quarks and gluons.
Quark-gluon plasma (Selected Topics)
Zakharov, V. I.
2012-09-15
Introductory lectures to the theory of (strongly interacting) quark-gluon plasma given at the Winter School of Physics of ITEP (Moscow, February 2010). We emphasize theoretical issues highlighted by the discovery of the low viscosity of the plasma. The topics include relativistic hydrodynamics, manifestations of chiral anomaly in hydrodynamics, superfluidity, relativistic superfluid hydrodynamics, effective stringy scalars, holographic models of Yang-Mills theories.
Squeezed colour states in gluon jet
NASA Technical Reports Server (NTRS)
Kilin, S. YA.; Kuvshinov, V. I.; Firago, S. A.
1993-01-01
The possibility of the formation of squeezed states of gluon fields in quantum chromodynamics due to nonlinear nonperturbative self interaction during jet evolution in the process of e(+)e(-) annihilation into hadrons, which are analogous to the quantum photon squeezed states in quantum electrodynamics, is demonstrated. Additionally, the squeezing parameters are calculated.
Aircraft trailing vortices: an introduction
NASA Astrophysics Data System (ADS)
Jacquin, Laurent
2005-05-01
Flow momentum that is deflected in a persistent way by a wing, or by another flow, becomes organised in coherent and energetic vortex structures. This phenomenon is briefly introduced here by comparison with other phenomena such as the production of vortices by impulsive forces (e.g. during animal flight), or the production of turbulence by jets. These considerations aim at underlining the fundamental nature of this strange mechanism, which is usually hidden behind engineering models produced by aerodynamic science. The control of these mechanisms, for applications to the safety of the airplanes for example, opens a vast multidisciplinary field of research. To cite this article: L. Jacquin, C. R. Physique 6 (2005).
Making sound vortices by metasurfaces
NASA Astrophysics Data System (ADS)
Ye, Liping; Qiu, Chunyin; Lu, Jiuyang; Tang, Kun; Jia, Han; Ke, Manzhu; Peng, Shasha; Liu, Zhengyou
2016-08-01
Based on the Huygens-Fresnel principle, a metasurface structure is designed to generate a sound vortex beam in airborne environment. The metasurface is constructed by a thin planar plate perforated with a circular array of deep subwavelength resonators with desired phase and amplitude responses. The metasurface approach in making sound vortices is validated well by full-wave simulations and experimental measurements. Potential applications of such artificial spiral beams can be anticipated, as exemplified experimentally by the torque effect exerting on an absorbing disk.
Vortices on surfaces with cylindrical ends
NASA Astrophysics Data System (ADS)
Venugopalan, Sushmita
2015-12-01
We consider Riemann surfaces obtained from nodal curves with infinite cylinders in the place of nodal and marked points, and study the space of finite energy vortices defined on these surfaces. To compactify the space of vortices, we need to consider stable vortices - these incorporate breaking of cylinders and sphere bubbling in the fibers. In this paper, we prove that the space of gauge equivalence classes of stable vortices representing a fixed equivariant homology class is compact and Hausdorff under the Gromov topology. We also show that this space is homeomorphic to the moduli space of quasimaps defined by Ciocan-Fontanine et al. (2014).
Quantized vortices around wavefront nodes, 2
NASA Technical Reports Server (NTRS)
Hirschfelder, J. O.; Goebel, C. J.; Bruch, L. W.
1974-01-01
Quantized vortices can occur around nodal points in wavefunctions. The derivation depends only on the wavefunction being single valued, continuous, and having continuous first derivatives. Since the derivation does not depend upon the dynamical equations, the quantized vortices are expected to occur for many types of waves such as electromagnetic and acoustic. Such vortices have appeared in the calculations of the H + H2 molecular collisions and play a role in the chemical kinetics. In a companion paper, it is shown that quantized vortices occur when optical waves are internally reflected from the face of a prism or particle beams are reflected from potential energy barriers.
Atmospheric Vortices in Shallow Convection.
NASA Astrophysics Data System (ADS)
Hess, G. D.; Spillane, K. T.; Lourensz, R. S.
1988-03-01
Observations of funnel clouds over Port Phillip Bay, Victoria, Australia, indicate that they occur during outbreaks of cool air from the Southern Ocean advecting over the relatively warm bay waters. These clouds act as tracers for shallow convection vortices with dynamics similar to large dust devils. The related phenomena of waterspouts and tornadoes differ from these vortices by requiring deep convection and downdraft and updraft interactions associated with rain processes.Deardorff (1978a) suggests that a necessary condition for the formation of dust devils is /L of the order of 100 or more, where h is the convective boundary layer height and L the Obukhov length. Calculations of /L over the bay and over land for the days of observation are consistent with this suggestion. They indicate that significant rotation may occur at /L as low as 50. This information, if confirmed, may make it possible to use boundary layer numerical models to forecast likely conditions of dust devil occurrence over mesoscale regions, which would be of benefit to pilots of light aircraft and helicopters.
Tunneling decay of false vortices
NASA Astrophysics Data System (ADS)
Lee, Bum-Hoon; Lee, Wonwoo; MacKenzie, Richard; Paranjape, M. B.; Yajnik, U. A.; Yeom, Dong-han
2013-10-01
We consider the decay of vortices trapped in the false vacuum of a theory of scalar electrodynamics in 2+1 dimensions. The potential is inspired by models with intermediate symmetry breaking to a metastable vacuum that completely breaks a U(1) symmetry, while in the true vacuum, the symmetry is unbroken. The false vacuum is unstable through the formation of true vacuum bubbles; however, the rate of decay can be extremely long. On the other hand, the false vacuum can contain metastable vortex solutions. These vortices contain the true vacuum inside in addition to a unit of magnetic flux and the appropriate topologically nontrivial false vacuum outside. We numerically establish the existence of vortex solutions which are classically stable; however, they can decay via tunneling. In general terms, they tunnel to a configuration which is a large, thin-walled vortex configuration that is now classically unstable to the expansion of its radius. We compute an estimate for the tunneling amplitude in the semiclassical approximation. We believe our analysis would be relevant to superconducting thin films or superfluids.
Analytic Structure of the Landau-Gauge Gluon Propagator
NASA Astrophysics Data System (ADS)
Strauss, Stefan; Fischer, Christian S.; Kellermann, Christian
2012-12-01
The analytic structure of the nonperturbative gluon propagator contains information on the absence of gluons from the physical spectrum of the theory. We study this structure from numerical solutions in the complex momentum plane of the gluon and ghost Dyson-Schwinger equations in Landau gauge Yang-Mills theory. The resulting ghost and gluon propagators are analytic apart from a distinct cut structure on the real, timelike momentum axis. The propagator violates the Osterwalder-Schrader positivity condition, confirming the absence of gluons from the asymptotic spectrum of the theory.
Analytic structure of the Landau-gauge gluon propagator.
Strauss, Stefan; Fischer, Christian S; Kellermann, Christian
2012-12-21
The analytic structure of the nonperturbative gluon propagator contains information on the absence of gluons from the physical spectrum of the theory. We study this structure from numerical solutions in the complex momentum plane of the gluon and ghost Dyson-Schwinger equations in Landau gauge Yang-Mills theory. The resulting ghost and gluon propagators are analytic apart from a distinct cut structure on the real, timelike momentum axis. The propagator violates the Osterwalder-Schrader positivity condition, confirming the absence of gluons from the asymptotic spectrum of the theory. PMID:23368451
Discussion on the complete-form vorticity equation and slantwise vorticity development
NASA Astrophysics Data System (ADS)
Wang, Xiuming; Zhou, Xiaogang; Tao, Zuyu; Liu, Hua
2016-02-01
The complete form of the vertical vorticity tendency equation (the complete-form vorticity equation) is derived from the Ertel potential vorticity equation to contain thermodynamic factors. In this study, a new complete-form vorticity equation, which has the same form as the original complete-form vorticity equation, is deduced from the absolute vorticity vector equation combined with the continuity equation and the expression of three-dimensional (3D) entropy gradient. By comparing the complete-form vorticity equation with the classical vertical vorticity equation, it is found that regardless of whether or not the isentropic surface is tilting, the two vorticity equations are in essence the same. The "baroclinic term" of the complete-form vorticity equation is exactly equal to the solenoidal term of the classical one, and there is a significant amount of cancellation between the two baroclinic items (the "slantwise term" and the horizontal vorticity change term) in the complete-form vorticity equation. In operational weather analysis, the tilt of the isentropic surface can be diagnosed according to the density of the isotherm on the upper-level isobaric map. For synoptic-scale motion, the vertical vorticity produced by the tilt of the isentropic surface is due to the contribution of atmospheric baroclinicity, which is measured by the solenoid. The 3D solenoid is parallel to the isentropic surface, so the more tilted the isentropic surface, the bigger the projection of the 3D solenoid in the vertical direction. The baroclinic contribution can be interpreted based on the PV thinking theory, but the relationship between the vorticity field and the potential vorticity field is not immediate.
On relevance of triple-gluon fusion in hadroproduction
NASA Astrophysics Data System (ADS)
Motyka, Leszek; Sadzikowski, Mariusz
2015-05-01
A contribution to hadroproduction is analyzed in which the meson production is mediated by three-gluon partonic state, with two gluons coming from the target and one gluon from the projectile. This mechanism involves double gluon density in one of the protons, hence this contribution enters at a non-leading twist. It is, however, relevant due to an enhancement factor coming from large double gluon density at small . We calculate the three-gluon contribution to hadroproduction within perturbative QCD in the -factorization framework. Results are obtained for differential -dependent cross sections for all polarizations and for the sum over the polarization components. The rescattering contribution is found to provide a significant correction to the standard leading twist cross section at the energies of the Tevatron or the LHC at moderate . We suggest production in proton-nucleus collision as a possible probe of the triple-gluon mechanism.
On generating counter-rotating streamwise vortices
NASA Astrophysics Data System (ADS)
Winoto, S. H.; Mitsudharmadi, H.; Budiman, A. C.; Hasheminejad, S. M.; Nadesan, T.; Tandiono; Low, H. T.; Lee, T. S.
2015-09-01
Counter-rotating streamwise vortices are known to enhance the heat transfer rate from a surface and also to improve the aerodynamic performance of an aerofoil. In this paper, some methods to generate such counter-rotating vortices using different methods or physical conditions will be briefly considered and discussed.
Flute vortices in nonuniform magnetic fields
Yu, M.Y.; Shukla, P.K.; Varma, R.K.
1985-09-01
Localized double vortices associated with the flute modes are shown to exist. Special emphasis is given to the effect of the convective variation of the fluid magnetic moment. It is shown that the latter effect considerably modifies the existence regions of the vortices.
Optical vortices generation using the Wollaston prism
Kurzynowski, Piotr; Wozniak, Wladyslaw A.; Fraczek, Ewa
2006-10-20
A new setup of interferometers is proposed in which the set of specific optical markers - optical vortices - could be generated. The classical Mach-Zender two-beam interferometer has been modernized using the Wollaston prism. In this setup, the optical vortices could be obtained for a wide range of both beam parameters. The numerical analysis and experiments confirm our theoretical predictions.
Nonquasineutral electron vortices in nonuniform plasmas
Angus, J. R.; Richardson, A. S.; Swanekamp, S. B.; Schumer, J. W.; Ottinger, P. F.
2014-11-15
Electron vortices are observed in the numerical simulation of current carrying plasmas on fast time scales where the ion motion can be ignored. In plasmas with nonuniform density n, vortices drift in the B × ∇n direction with a speed that is on the order of the Hall speed. This provides a mechanism for magnetic field penetration into a plasma. Here, we consider strong vortices with rotation speeds V{sub ϕ} close to the speed of light c where the vortex size δ is on the order of the magnetic Debye length λ{sub B}=|B|/4πen and the vortex is thus nonquasineutral. Drifting vortices are typically studied using the electron magnetohydrodynamic model (EMHD), which ignores the displacement current and assumes quasineutrality. However, these assumptions are not strictly valid for drifting vortices when δ ≈ λ{sub B}. In this paper, 2D electron vortices in nonuniform plasmas are studied for the first time using a fully electromagnetic, collisionless fluid code. Relatively large amplitude oscillations with periods that correspond to high frequency extraordinary modes are observed in the average drift speed. The drift speed W is calculated by averaging the electron velocity field over the vorticity. Interestingly, the time-averaged W from these simulations matches very well with W from the much simpler EMHD simulations even for strong vortices with order unity charge density separation.
Relative equilibria of vortices in two dimensions.
Palmore, J I
1982-01-01
An old problem of the evolution of finitely many interacting point vortices in the plane is shown to be amenable to investigation by critical point theory in a way that is identical to the study of the planar n-body problem of celestial mechanics. For any choice of positive circulations of the vortices it is shown by critical point theory applied to Kirchhoff's function that there are many relative equilibria configurations. Each of these configurations gives rise to a stationary configuration of the vortices in a suitably chosen rotating coordinate system. A sharp lower bound on the number of stationary vortex configurations for the problem of point vortices interacting in the plane is given. The problem of point vortices in a circular disk is defined and it is shown that these estimates hold for stationary configurations of small size. PMID:16593155
Vorticity generation by contoured wall injectors
NASA Technical Reports Server (NTRS)
Waitz, Ian A.; Marble, Frank E.; Zukoski, Edward E.
1992-01-01
A class of contoured wall fuel injectors was designed to enable shock-enhancement of hypervelocity mixing for supersonic combustion ramjet applications. Previous studies of these geometries left unresolved questions concerning the relative importance of various axial vorticity sources in mixing the injectant with the freestream. The present study is a numerical simulation of two generic fuel injectors which is aimed at elucidating the relative roles of axial vorticity sources including: baroclinic torque through shock-impingement, cross-stream shear, turning of boundary layer vorticity, shock curvature, and diffusive flux. Both the magnitude of the circulation, and the location of vorticity with respect to the mixing interface were considered. Baroclinic torque and cross-stream shear were found to be most important in convectively mixing the injectant with the freestream, with the former providing for deposition of vorticity directly on the fuel/air interface.
Electrothermal blinking vortices for chaotic mixing
NASA Astrophysics Data System (ADS)
Loire, Sophie; Kauffmann, Paul; Gimenez, Paul; Meinhart, Carl; Mezic, Igor
2012-11-01
We present an experimental and theoretical study of electrothermal chaotic mixing using blinking of asymmetric 2D electrothermal vortices. Electrothermal flows are modelled with 2D finite element method using COMSOL software based on an enhanced electrothermal model. Velocities in top-view and side-view devices are measured by micro particle image velocimetry (μPIV). The experimentally reconstructed velocity profile shows a dramatic asymmetry between the two vortices, in good agreement with the FEM model. The separation line between the two vortices is shifted and tilted making the blinking vortices overlap. We use the mix-variance coefficient (MVC) on experimental particle detection data and numerical trajectory simulations to evaluate mixing at different scales including the layering of fluid interfaces by the flow, a keypoint for efficient mixing. The blinking vortices method greatly improve mixing efficiency. Theoretical, experimental and simulation results of the mixing process will be presented.
Turbulent vortices in stratified fluids
NASA Technical Reports Server (NTRS)
Hecht, A. M.; Bilanin, A. J.; Hirsh, J. E.; Snedeker, R. S.
1979-01-01
In the present paper, calculations, made with the finite difference axisymmetric WAKE computer code, of the influence of turbulence and stratification on the behavior of vortex rings are compared with experimental data. Calculations, made with the two-dimensional version of the code, are used to study the behavior of vortex pairs in stably stratified atmospheres for a range of Froude numbers. Stratification is shown to have a profound effect on the radius of a vortex ring descending into a stably stratified fluid. The separation of the vortices of a vortex pair remains nearly constant or decreases monotonically with increasing penetration of a stably stratified fluid, depending on whether the stratification is discontinuous or linear. An analysis based on an energy balance is used to assess the maximum descent of a vortex pair in a stably stratified fluid.
Twist Helicity in Classical Vortices
NASA Astrophysics Data System (ADS)
Scheeler, Martin W.; Kedia, Hridesh; Kleckner, Dustin; Irvine, William T. M.
2015-11-01
Recent experimental work has demonstrated that a partial measure of fluid Helicity (the sum of linking and writhing of vortex tubes) is conserved even as those vortices undergo topology changing reconnections. Measuring the total Helicity, however, requires additional information about how the vortex lines are locally twisted inside the vortex core. To bridge this gap, we have developed a novel technique for experimentally measuring twist Helicity. Using this method, we are able to measure the production and eventual decay of twist for a variety of vortex evolutions. Remarkably, we observe twist dynamics capable of conserving total Helicity even in the presence of rapidly changing writhe. This work was supported by the NSF MRSEC shared facilities at the University of Chicago (DMR-0820054) and an NSF CAREER award (DMR-1351506). W.T.M.I. further acknowledges support from the A.P. Sloan Foundation and the Packard Foundation.
Quarks and gluons in hadrons and nuclei
Close, F.E. Tennessee Univ., Knoxville, TN )
1989-12-01
These lectures discuss the particle-nuclear interface -- a general introduction to the ideas and application of colored quarks in nuclear physics, color, the Pauli principle, and spin flavor correlations -- this lecture shows how the magnetic moments of hadrons relate to the underlying color degree of freedom, and the proton's spin -- a quark model perspective. This lecture reviews recent excitement which has led some to claim that in deep inelastic polarized lepton scattering very little of the spin of a polarized proton is due to its quarks. This lecture discusses the distribution functions of quarks and gluons in nucleons and nuclei, and how knowledge of these is necessary before some quark-gluon plasma searches can be analyzed. 56 refs., 2 figs.
Quark and Gluon Tagging at the LHC
NASA Astrophysics Data System (ADS)
Gallicchio, Jason; Schwartz, Matthew D.
2011-10-01
Being able to distinguish light-quark jets from gluon jets on an event-by-event basis could significantly enhance the reach for many new physics searches at the Large Hadron Collider. Through an exhaustive search of existing and novel jet substructure observables, we find that a multivariate approach can filter out over 95% of the gluon jets while keeping more than half of the light-quark jets. Moreover, a combination of two simple variables, the charge track multiplicity and the pT-weighted linear radial moment (girth), can achieve similar results. Our study is only Monte Carlo based, so other observables constructed using different jet sizes and parameters are used to highlight areas that deserve further theoretical and experimental scrutiny. Additional information, including distributions of around 10 000 variables, can be found at http://jets.physics.harvard.edu/qvg/.
Running coupling corrections to inclusive gluon production
NASA Astrophysics Data System (ADS)
Horowitz, W. A.; Kovchegov, Y. V.
2011-12-01
We calculate running coupling corrections for the lowest-order gluon production cross section in high energy hadronic and nuclear scattering using the BLM scale-setting prescription. At leading order, there are three powers of fixed coupling; in our final answer, these three couplings are replaced by seven factors of running coupling: five in the numerator and two in the denominator, forming a 'septumvirate' of running couplings, analogous to the 'triumvirate' of running couplings found earlier for the small-x BFKL/BK/JIMWLK evolution equations. It is interesting to note that the two running couplings in the denominator of the 'septumvirate' run with complex-valued momentum scales, which are complex conjugates of each other, such that the production cross section is indeed real. We use our lowest-order result to conjecture how running coupling corrections may enter the full fixed-coupling kT-factorization formula for gluon production which includes nonlinear small-x evolution.
Generation and Growth of Single Hairpin Vortices
NASA Astrophysics Data System (ADS)
Haji-Haidari, Ahmad
The behavior of selectively generated single hairpin vortices are examined within a laminar boundary layer environment over a range of Reynolds numbers, the hairpin vortices are experimentally generated by means of controlled fluid injection from a streamwise slot. Flow visualization using both dye and hydrogen bubble wire is employed in conjunction with hot film anemometry to investigate the growth characteristics and evolution of these single hairpin vortices. Qualitatively, it is established that hairpin vortices form by local destabilization at the interface between the low-speed fluid introduced through the slot and the higher speed boundary layer flow. Kinematical considerations of the hairpin vortex are established. It is observed that a hairpin vortex generally displays visualization and velocity signatures characteristic of those observed for a turbulent boundary layer. Hydrogen-bubble wire visualization results specifically indicate that hairpin vortices generate two purely turbulent-like flow patterns. The first is a low-speed streak pattern developing immediately adjacent to the surface due to surface interaction by the counter -rotating legs of the hairpin vortex; the second pattern is a turbulent pocket-like pattern farther removed from the surface. It is determined from the visualization data that hairpin vortices manifest the necessary flow characteristics which give rise to the regenerative and sustained process required for maintenance of turbulence. The regeneration and the growth process takes place through the formation of similar hairpin-like vortices by one of two means. The first is an inviscid lateral propagation of the initial disturbance which gives rise to outboard (subsidiary), vortices which cause the lateral spreading of the structure. A more complicated and eruptive process occurs by means of viscous-inviscid interactions which give rise to trailing vortices (secondary), which cause the streamwise elongation of the disturbance. A
Measurement of vorticity diffusion by NMR microscopy.
Brown, Jennifer R; Callaghan, Paul T
2010-05-01
In a Newtonian fluid, vorticity diffuses at a rate determined by the kinematic viscosity. Here we use rapid NMR velocimetry, based on a RARE sequence, to image the time-dependent velocity field on startup of a fluid-filled cylinder and therefore measure the diffusion of vorticity. The results are consistent with the solution to the vorticity diffusion equation where the angular velocity on the outside surface of the fluid, at the cylinder's rotating wall, is fixed. This method is a means of measuring kinematic viscosity for low viscosity fluids without the need to measure stress. PMID:20189854
Vortices and turbulence in trapped atomic condensates
White, Angela C.; Anderson, Brian P.; Bagnato, Vanderlei S.
2014-01-01
After more than a decade of experiments generating and studying the physics of quantized vortices in atomic gas Bose–Einstein condensates, research is beginning to focus on the roles of vortices in quantum turbulence, as well as other measures of quantum turbulence in atomic condensates. Such research directions have the potential to uncover new insights into quantum turbulence, vortices, and superfluidity and also explore the similarities and differences between quantum and classical turbulence in entirely new settings. Here we present a critical assessment of theoretical and experimental studies in this emerging field of quantum turbulence in atomic condensates. PMID:24704880
Vortices in magnetically coupled superconducting layered systems
Mints, Roman G.; Kogan, Vladimir G.; Clem, John R.
2000-01-01
Pancake vortices in stacks of thin superconducting films or layers are considered. It is stressed that in the absence of Josephson coupling topological restrictions upon possible configurations of vortices are removed and various examples of structures forbidden in bulk superconductors are given. In particular, it is shown that vortices may skip surface layers in samples of less than a certain size R{sub c} which might be macroscopic. The Josephson coupling suppresses R{sub c} estimates. (c) 2000 The American Physical Society.
Vorticity in heavy-ion collisions
NASA Astrophysics Data System (ADS)
Deng, Wei-Tian; Huang, Xu-Guang
2016-06-01
We study the event-by-event generation of flow vorticity in the BNL Relativistic Heavy Ion Collider Au +Au collisions and CERN Large Hadron Collider Pb +Pb collisions by using the hijing model. Different definitions of the vorticity field and velocity field are considered. A variety of properties of the vorticity are explored, including the impact parameter dependence, the collision energy dependence, the spatial distribution, the event-by-event fluctuation of the magnitude and azimuthal direction, and the time evolution. In addition, the spatial distribution of the flow helicity is also studied.
Hollow vortices in weakly compressible flows
NASA Astrophysics Data System (ADS)
Krishnamurthy, Vikas; Crowdy, Darren
2014-11-01
In a two-dimensional, inviscid and steady fluid flow, hollow vortices are bounded regions of constant pressure with non-zero circulation. It is known that for an infinite row of incompressible hollow vortices, analytical solutions for the flow field and the shape of the hollow vortex boundary can be obtained using conformal mapping methods. In this talk, we show how to derive analytical expressions for a weakly compressible hollow vortex row. This is done by introducing a new method based on the Imai-Lamla formula. We will also touch upon how to extend these results to a von-Karman street of hollow vortices.
Hollow vortices in weakly compressible flows
NASA Astrophysics Data System (ADS)
Krishnamurthy, Vikas; Crowdy, Darren
2015-11-01
In a two-dimensional, inviscid and steady fluid flow, hollow vortices are bounded regions of constant pressure with non-zero circulation. It is known that for an infinite row of incompressible hollow vortices, analytical solutions for the flow field and the shape of the hollow vortex boundary can be obtained using conformal mapping methods. In this talk, we show how to derive analytical expressions for a weakly compressible hollow vortex row. This is done by introducing a new method based on the Imai-Lamla formula. We will also touch upon how to extend these results to a von-Karman street of hollow vortices.
Transonic interactions of unsteady vortical flows
NASA Technical Reports Server (NTRS)
Mccroskey, W. J.; Srinivasan, G. R.
1984-01-01
Unsteady interactions of strong concentrated vortices, distributed gusts, and sharp-edged gusts with stationary airfoils were analyzed in two-dimensional transonic flow. A simple and efficient method for introducing such vortical disturbances was implemented in numerical codes that range from inviscid transonic small disturbance to thin-layer Navier Stokes. The numerical results demonstrate the large distortions in the overall flow field and in the surface air loads that are produced by various vortical interactions. The results of the different codes are in excellent qualitative agreement, but, as might expected, the transonic small-disturbance calculations are deficient in the important region near the leading edge.
Diphoton excess at 750 GeV: gluon-gluon fusion or quark-antiquark annihilation?
NASA Astrophysics Data System (ADS)
Gao, Jun; Zhang, Hao; Zhu, Hua Xing
2016-06-01
Recently, ATLAS and CMS collaborations reported an excess in the measurement of diphoton events, which can be explained by a new resonance with a mass around 750 GeV. In this work, we explored the possibility of identifying if the hypothetical new resonance is produced through gluon-gluon fusion or quark-antiquark annihilation, or tagging the beam. Three different observables for beam tagging, namely the rapidity and transverse-momentum distribution of the diphoton, and one tagged bottom-jet cross section, are proposed. Combining the information gained from these observables, a clear distinction of the production mechanism for the diphoton resonance is promising.
Atmospheric Vortices near Guadalupe Island
NASA Technical Reports Server (NTRS)
2000-01-01
These MISR images from June 11, 2000 (Terra orbit 2569) demonstrate a turbulent atmospheric flow pattern known as the von Karman vortex street. This phenomenon is named after aerodynamicist Theodore von Karman, who theoretically derived the conditions under which it occurs. The alternating double row of vortices can form in the wake of an obstacle, in this instance the eastern Pacific island of Guadalupe. The rugged terrain of this volcanic Mexican island reaches a maximum elevation of 1.3 kilometers. The island is about 35 kilometers long and is located 260 kilometers west of Baja California.
The vortex pattern is made visible by the marine stratocumulus clouds around Guadalupe Island. The upper image is a color view obtained by MISR's vertical-viewing (nadir) camera. North is toward the left. The orientation of the vortex street indicates that the wind direction is from lower left to upper right (northwest to southeast). The areas within the vortex centers tend to be clear because the rotating motions induce a vertical wind component that can break up the cloud deck.
The lower view is a stereo picture generated from data acquired by MISR's fore- and aft-viewing 70-degree cameras. A 3-D effect is obtained by viewing the image with red/blue glasses and placing the red filter over your left eye. Note how the downwelling atmospheric motion (change in elevation from high to low) is accompanied by a clearing in the center of the first vortex. As the vortices propagate downstream, their rotational velocities weaken. As a consequence, the induced vertical motion and cloud-clearing effect weakens as well.
Theodore von Karman was a Professor of Aeronautics at Caltech and Director of Caltech's Guggenheim Aeronautical Laboratory from 1930-1949. He was one of the principal founders of the Jet Propulsion Laboratory.
MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra
Nonperturbative gluon and ghost propagators in d = 3
Papavassiliou, Joannis
2011-05-23
We study the nonperturbative gluon and ghost propagators in d = 3 Yang-Mills, using the Schwinger-Dyson equations of the pinch technique. The use of the Schwinger mechanism leads to the dynamical generation of a gluon mass, which, in turn, gives rise to an infrared finite gluon propagator and ghost dressing function. The propagators obtained are in very good agreement with the results of SU(2) lattice simulations.
Universality of Unintegrated Gluon Distributions at small x
Dominguez, Fabio; Marquet, Cyrille; Xiao, Bowen; Yuan, Feng
2011-01-04
We systematically study dijet production in various processes in the small-x limit and establish an effective kt-factorization for hard processes in a system with dilute probes scattering on a dense target. In the large-Nc limit, the unintegrated gluon distributions involved in different processes are shown to be related to two widely proposed ones: the Weizsacker-Williams gluon distribution and the dipole gluon distribution.
NASA Technical Reports Server (NTRS)
Harrison, D. E.; Holland, W. R.
1981-01-01
A mean vorticity budget analysis is presented of Holland's (1978) numerical ocean general circulation experiment. The stable budgets are compared with classical circulation theory to emphasize the ways in which the mesoscale motions of the model alter (or leave unaltered) classical vorticity balances. The basinwide meridional transports of vorticity by the mean flow and by the mesoscale flow in the mean are evaluated to establish the role(s) of the mesoscale in the larger scale equilibrium vorticity transports. The vorticity equation for this model fluid system is presented and the budget analysis method is described. Vorticity budgets over the selected regions and on a larger scale are given, and a summary of budget results is provided along with remarks about the utility of this type of analysis.
Gluon spectrum in the glasma from JIMWLK evolution
NASA Astrophysics Data System (ADS)
Lappi, T.
2011-09-01
The JIMWLK equation with a "daughter dipole" running coupling is solved numerically, starting from an initial condition given by the McLerran-Venugopalan model. The resulting Wilson line configurations are then used to compute the spectrum of gluons comprising the glasma initial state of a high energy heavy ion collision. The development of a geometrical scaling region makes the spectrum of produced gluons harder. Thus the ratio of the mean gluon transverse momentum to the saturation scale grows with energy. Also the total gluon multiplicity increases with energy slightly faster than the saturation scale squared.
Semirelativistic potential model for three-gluon glueballs
Mathieu, Vincent; Semay, Claude; Silvestre-Brac, Bernard
2008-05-01
The three-gluon glueball states are studied with the generalization of a semirelativistic potential model giving good results for two-gluon glueballs. The Hamiltonian depends only on 3 parameters fixed on two-gluon glueball spectra: the strong coupling constant, the string tension, and a gluon size which removes singularities in the potential. The Casimir scaling determines the structure of the confinement. Our results are in good agreement with other approaches and lattice calculation for the odderon trajectory but differ strongly from lattice in the J{sup +-} sector. We propose a possible explanation for this problem.
Tornadoes and other atmospheric vortices
NASA Technical Reports Server (NTRS)
Deissler, R. G.
1976-01-01
The growth of random vortices in an atmosphere with buoyant instability and vertical wind shear is studied along with the velocities in a single gravity-driven vortex; a frictionless adiabatic model which is supported by laboratory experiments is first considered. The effects of axial drag, heat transfer, and precipitation-induced downdrafts are then calculated. Heat transfer and axial drag tend to have stabilizing effects; they reduce the downdrafts of updrafts due to buoyancy. It is found that downdrafts or tornadic magnitude might occur in negatively-buoyant columns. The radial-inflow velocity required to maintain a given maximum tangential velocity in a tornado is determined by using a turbulent vortex model. Conditions under which radial-inflow velocities become sufficiently large to produce tangential velocities of tornadic magnitude are determined. The radial velocities in the outer regions, as well as the tangential velocities in the inner regions may be large enough to cause damage. The surface boundary layer, which is a region where large radial inflows can occur, is studied, and the thickness of the radial-inflow friction layer is estimated. A tornado model which involves a rotating parent cloud, as well as buoyancy and precipitation effects, is discussed.
Combustion enhancement by axial vortices
NASA Astrophysics Data System (ADS)
Gutmark, E.; Schadow, K. C.; Parr, T. P.; Parr, D. M.; Wilson, K. J.
1987-06-01
A tapered slot jet was studied experimentally in nonreacting and reacting tests using hot-wire anemometry, water-tunnel flow visualization, and Planar Laser Induced Fluorescence (PLIF). The tapered slot jet is a modified elliptic jet which has a conical contraction leading to its outlet. The added contraction changes the entire flow field. The jet spread in the major axis plane is larger than in the minor axis plane, which is the opposite behavior of an elliptic jet. Consequently, no axes switching, typical to an elliptic jet, is observed. The turbulence amplification in the jet core is higher than in circular and elliptic jets. The different behavior is attributed to the change in flow direction, inside the nozzle, from the conical section to the slot outlet. During this transition, the flow acquires angular momentum thereby generating axial vorticity. The influence of the contraction angle and the outlet aspect ratio were investigated. The effect of the augmented turbulence on reactive flow was tested in a premixed flame. The combustion rate was augmented in both the core and edges of the flame relative to a circular burner.
Vorticity matching in superfluid helium
NASA Astrophysics Data System (ADS)
Samuels, David C.
1991-12-01
Recent experiments have rekindled interest in high Reynolds number flows using superfluid helium. In a continuing series of experiments, the flow of helium II through various devices (smooth pipes, corrugated pipes, valves, venturies, turbine flowmeters, and coanda flowmeters for example) was investigated. In all cases, the measured values (typically, mass flow rates and pressure drops) were found to be well described by classical relations for high Reynolds flows. This is unexpected since helium II consists of two interpenetrating fluids; one fluid with nonzero viscosity (the normal fluid) and one with zero viscosity (the superfluid). Only the normal fluid component should directly obey classical relations. Since the experiments listed above only measure the external behavior of the flow (i.e., pressure drops over devices), there is a great deal of room for interpretation of their results. One possible interpretation is that in turbulent flows the normal fluid and the superfluid velocity fields are somehow 'locked' together, presumably by the mutual friction force between the superfluid vortex filaments and the normal fluid. We refer to this locking together of the two fluids as 'vorticity matching.'
Vortices in simulations of solar surface convection
NASA Astrophysics Data System (ADS)
Moll, R.; Cameron, R. H.; Schüssler, M.
2011-09-01
We report on the occurrence of small-scale vortices in simulations of the convective solar surface. Using an eigenanalysis of the velocity gradient tensor, we find the subset of high-vorticity regions in which the plasma is swirling. The swirling regions form an unsteady, tangled network of filaments in the turbulent downflow lanes. Near-surface vertical vortices are underdense and cause a local depression of the optical surface. They are potentially observable as bright points in the dark intergranular lanes. Vortex features typically exist for a few minutes, during which they are moved and twisted by the motion of the ambient plasma. The bigger vortices found in the simulations are possibly, but not necessarily, related to observations of granular-scale spiraling pathlines in "cork animations" or feature tracking. Three movies are available in electronic form at http://www.aanda.org
Rotationally induced vortices in optical cavity modes
NASA Astrophysics Data System (ADS)
Habraken, Steven J. M.; Nienhuis, Gerard
2009-09-01
We show that vortices appear in the modes of an astigmatic optical cavity when it is put into rotation about its optical axis. We study the properties of these vortices and discuss numerical results for a specific realization of such a set-up. Our method is exact up to first order in the time-dependent paraxial approximation and involves bosonic ladder operators in the spirit of the quantum-mechanical harmonic oscillator.
Atmospheric Columnar Vortices (Paper 7R0104)
NASA Astrophysics Data System (ADS)
Snow, John T.
1987-04-01
The family of atmospheric columnar vortices includes tornadoes, waterspouts, firewhirls, dust devils and a variety of other whirlwinds. Each member of the family is characterized by the presence of a relatively tall, concentrated vortical core. Descriptions of such swirling flows are inherently complex, reflecting the presence of a multiplicity of length and velocity scales. In many cases, the flow is both three-dimensional and unsteady.
Compactlike kinks and vortices in generalized models
Bazeia, D.; Hora, E. da; Menezes, R.; Oliveira, H. P. de; Santos, C. dos
2010-06-15
This work deals with the presence of topological defects in k-field models, where the dynamics is generalized to include higher order power in the kinetic term. We investigate kinks in (1, 1) dimensions and vortices in (2, 1) dimensions, focusing on some specific features of the solutions. In particular, we show how the kinks and vortices change to compactlike solutions, controlled by the parameter used to introduce the generalized models.
Potential Vorticity as a Diagnostic of Transport into the Martian Polar Vortices
NASA Astrophysics Data System (ADS)
McConnochie, Timothy H.; Conrath, B. J.; Gierasch, P. J.; Banfield, D.; Smith, M. D.
2009-09-01
Polar vortices dominate the dynamics of the winter mid- and polar latitudes in the martian atmosphere as well as in the terrestrial stratosphere. Polar vortices have also been observed on Venus (Taylor, 2002), Jupiter (Orton, 2002), Saturn (Fletcher, 2008), and Titan (Teanby, 2008). Potential vorticity is the analysis quantity of choice for the terrestrial polar vortices because its vertical component distills the most important features of the wind and temperature fields into a single scalar variable; because it is a conserved tracer under adiabatic conditions; because it serves as the medium for Rossby waves; and because steep potential vorticity gradients are observed to be correlated with steep gradients in the concentrations of chemical species. Using potential vorticity derived from Mars Global Surveyor Thermal Emission Spectrometer (TES) temperature soundings, we find that the northern martian winter polar vortex, just like its terrestrial conterpart, is bounded by a region of very steep potential vorticity gradients and is surrounded by a "surf zone", a region of low potential vorticity and very low potential vorticity gradients. The surf zone concept, as first described for the terrestrial stratosphere by McIntyre and Palmer (1983), implies persistent Rossby wave breaking. In the vicinity of the northern polar vortex, the TES data set provides some examples of local gradient reversals that are suggestive of wave breaking. There is also one case of large-scale wave breaking accompanied by an abrupt polar warming. We also find that the martian southern polar vortex lacks a distinct boundary between the polar vortex and a surf zone. Instead, the potential vorticity field is highly disorganized with local gradient reversals throughout the middle and polar latitudes. In the zonal mean, the southern winter potential vorticity gradient ends up being relatively uniform, although it is somewhat enhanced near 60 degrees latitude.
Strongly coupled quark gluon plasma (SCQGP)
NASA Astrophysics Data System (ADS)
Bannur, Vishnu M.
2006-07-01
We propose that the reason for the non-ideal behaviour seen in lattice simulation of quark gluon plasma (QGP) and ultrarelativistic heavy ion collision experiments is that the QGP near Tc and above is a strongly coupled plasma (SCP), i.e., a strongly coupled quark gluon plasma (SCQGP). It is remarkable that the widely used equation of state of SCP in QED (quantum electrodynamics) very nicely fits lattice results on all QGP systems, with proper modifications to include colour degrees of freedom and the running coupling constant. Results on pressure in pure gauge, 2-flavours and 3-flavours QGP can all be explained by treating QGP as SCQGP, as demonstrated here. Energy density and speed of sound are also presented for all three systems. We further extend the model to systems with finite quark mass and reasonably good fits to lattice results are obtained for (2+1)-flavours and 4-flavours QGP. Hence it is a unified model, namely SCQGP, to explain the non-ideal QGP seen in lattice simulations with just two system dependent parameters.
Gluon production in the Lipatov effective action formalism
NASA Astrophysics Data System (ADS)
Braun, M. A.; Pozdnyakov, S. S.; Salykin, M. Yu.; Vyazovsky, M. I.
2013-09-01
Gluon production on two scattering centers is studied in the formalism of reggeized gluons. Different contributions to the inclusive cross section are derived with the help of the Lipatov effective action. The AGK relations between these contributions are established. The inclusive cross section found is compared to the one in the dipole picture and demonstrated to be the same.
EXPLORING THE POLARIZATION OF GLUONS IN THE NUCLEON.
STRATMANN,M.; VOGELSANG,W.
2007-10-22
We give an overview of the current status of investigations of the polarization of gluons in the nucleon. We describe some of the physics of the spin-dependent gluon parton distribution and its phenomenology in high-energy polarized hadronic scattering. We also review the recent experimental results.
An approach to fast fits of the unintegrated gluon density
Knutsson, Albert; Bacchetta, Alessandro; Kutak, Krzyzstof; Jung, Hannes
2009-01-01
An approach to fast fits of the unintegrated gluon density has been developed and used to determine the unintegrated gluon density by fits to deep inelastic scatting di-jet data from HERA. The fitting method is based on the determination of the parameter dependence by help of interpolating between grid points in the parameter-observable space before the actual fit is performed.
Numerical simulation of baroclinic Jovian vortices
NASA Astrophysics Data System (ADS)
Achterberg, R. K.; Ingersoll, A. P.
1994-02-01
We examine the evolution of baroclinic vortices in a time-dependent, nonlinear numerical model of a Jovian atmosphere. The model uses a normal-mode expansion in the vertical, using the barotropic and first two baroclinic modes. Results for the stability of baroclinic vortices on an f plane in the absence of a mean zonal flow are similar to results of Earth vortex models, although the presence of a fluid interior on the Jovian planets shifts the stability boundaries to smaller length scales. The presence of a barotropic mean zonal flow in the interior stabilizes vortices against instability and significantly modifies the finite amplitude form of baroclinic instabilities. The effect of a zonal flow on a form of barotropic instability produces periodic oscillations in the latitude and longitude of the vortex as observed at the level of the cloud tops. This instability may explain some, but not all, observations of longitudinal oscillations of vortices on the outer planets. Oscillations in aspect ratio and orientation of stable vortices in a zonal shear flow are observed in this baroclinic model, as in simpler two-dimensional models. Such oscillations are also observed in the atmospheres of Jupiter and Neptune. The meridional propagation and decay of vortices on a beta plane is inhibited by the presence of a mean zonal flow. The direction of propagation of a vortex relative to the mean zonal flow depends upon the sign of the meridional potential vorticity gradient; combined with observations of vortex drift rates, this may provide a constraint on model assumption for the flow in the deep interior of the Jovian planets.
A procedure for calculating vorticity boundary conditions in the stream-function-vorticity method
NASA Astrophysics Data System (ADS)
MacKinnon, R. J.; Carey, G. F.; Murray, P.
1990-01-01
A superconvergent projection formula is constructed for determining vorticity boundary data in the stream-function-vorticity method. The approach applies to both straight and curved boundaries and can be used for either finite-element or finite-difference computations.
Initial Circulation and Peak Vorticity Behavior of Vortices Shed from Airfoil Vortex Generators
NASA Technical Reports Server (NTRS)
Wendt, Bruce J.; Biesiadny, Tom (Technical Monitor)
2001-01-01
An extensive parametric study of vortices shed from airfoil vortex generators has been conducted to determine the dependence of initial vortex circulation and peak vorticity on elements of the airfoil geometry and impinging flow conditions. These elements include the airfoil angle of attack, chord length, span, aspect ratio, local boundary layer thickness, and free stream Mach number. In addition, the influence of airfoil-to-airfoil spacing on the circulation and peak vorticity has been examined for pairs of co-rotating and counter-rotating vortices. The vortex generators were symmetric airfoils having a NACA-0012 cross-sectional profile. These airfoils were mounted either in isolation, or in pairs, on the surface of a straight pipe. The turbulent boundary layer thickness to pipe radius ratio was about 17 percent. The circulation and peak vorticity data were derived from cross-plane velocity measurements acquired with a seven-hole probe at one chord-length downstream of the airfoil trailing edge location. The circulation is observed to be proportional to the free-stream Mach number, the angle-of-attack, and the span-to-boundary layer thickness ratio. With these parameters held constant, the circulation is observed to fall off in monotonic fashion with increasing airfoil aspect ratio. The peak vorticity is also observed to be proportional to the free-stream Mach number, the airfoil angle-of-attack, and the span-to-boundary layer thickness ratio. Unlike circulation, however, the peak vorticity is observed to increase with increasing aspect ratio, reaching a peak value at an aspect ratio of about 2.0 before falling off again at higher values of aspect ratio. Co-rotating vortices shed from closely spaced pairs of airfoils have values of circulation and peak vorticity under those values found for vortices shed from isolated airfoils of the same geometry. Conversely, counter-rotating vortices show enhanced values of circulation and peak vorticity when compared to values
Thermalization of gluons with Bose-Einstein condensation.
Xu, Zhe; Zhou, Kai; Zhuang, Pengfei; Greiner, Carsten
2015-05-01
We study the thermalization of gluons far from thermal equilibrium in relativistic kinetic theory. The initial distribution of gluons is assumed to resemble that in the early stage of ultrarelativistic heavy ion collisions. Only elastic scatterings in static, nonexpanding gluonic matter are considered. At first we show that the occurrence of condensation in the limit of vanishing particle mass requires a general constraint for the scattering matrix element. Then the thermalization of gluons with Bose-Einstein condensation is demonstrated in a transport calculation. We see a continuously increasing overpopulation of low energy gluons, followed by a decrease to the equilibrium distribution, when the condensation occurs. The times of the completion of the gluon condensation and of the entropy production are calculated. These times scale inversely with the energy density. PMID:26000996
Interaction of vortices with flexible piezoelectric beams
NASA Astrophysics Data System (ADS)
Goushcha, Oleg; Akaydin, Huseyin Dogus; Elvin, Niell; Andreopoulos, Yiannis
2012-11-01
A cantilever piezoelectric beam immersed in a flow is used to harvest fluidic energy. Pressure distribution induced by naturally present vortices in a turbulent fluid flow can force the beam to oscillate producing electrical output. Maximizing the power output of such an electromechanical fluidic system is a challenge. In order to understand the behavior of the beam in a fluid flow where vortices of different scales are present, an experimental facility was set up to study the interaction of individual vortices with the beam. In our set up, vortex rings produced by an audio speaker travel at specific distances from the beam or impinge on it, with a frequency varied up to the natural frequency of the beam. Depending on this frequency both constructive and destructive interactions between the vortices and the beam are observed. Vortices traveling over the beam with a frequency multiple of the natural frequency of the beam cause the beam to resonate and larger deflection amplitudes are observed compared to excitation from a single vortex. PIV is used to compute the flow field and circulation of each vortex and estimate the effect of pressure distribution on the beam deflection. Sponsored by NSF Grant: CBET #1033117.
NASA Astrophysics Data System (ADS)
Yang, W.; Meng, H.
1999-11-01
The dynamics of vortex structures in the wake of surface-mounted trapezoidal tab at Re=600 based on tab height was studied in detail using time-series, 2D particle image velocimetry. From a total of over 20,000 PIV realizations acquired in x-y, x-z, and y-z planes, we successfully identified vortex structures using the methods proposed by Jeong and Hussain (JFM, vol 285, 1995) and proposed by Chong, Perry, and Cantwell (Phys. Fluids A2, 1990), and cross-checked them with conventional velocity subtraction. Similar to prior measurement at Re=2080, secondary vortices, reverse vortices, and tertiary vortices were observed frequently in the present study. Higher PIV spatial resolution and higher temporal resolution (relative to the flow periodicity) allow us to investigate these dynamical phenomena in much greater detail and confidence. Furthermore, y-z measurements demonstrate that hairpin vortex legs, taking the shape of streamwise vortices, pair with their neighbor counterparts while traveling downstream, and possibly merge with each other. Circulation distribution of the hairpin vortex heads along the x direction shows that it increases at the very near-tab region with the help of pressure induced counter-rotating vortex pairs, but gradually decreases very slowly with the increasing downstream distance, indicating that hairpin vortices are long-lived vortex structures.
3D Vortices in Protoplanetary Disks
NASA Astrophysics Data System (ADS)
Kamal, Samy; Barranco, Joseph; Marcus, Philip
2010-11-01
Like the atmosphere of Jupiter, protoplanetary disks (thin disks of gas & dust in orbit around newly-formed stars) are characterized by rapid rotation and intense shear, inspiring proposals that disks may also be populated with long-lived, robust storms analogous to the Great Red Spot. Such vortices may play key roles in the formation of stars and planets by transporting angular momentum, as well as trapping and concentrating dust grains, seeding the formation of planetesimals, the "building blocks" of planets. In our previous work (Barranco & Marcus 2005), we showed via numerical simulation (with an anelastic spectral code) that vortices near the midplane of the disk suffer an antisymmetric instability and are destroyed. However, internal gravity waves propagate away from the midplane, amplify and break, creating bands of vorticity that roll-up into new long-lived, stable vortices above and below the midplane. We will present new results on 3D vortex dynamics in protoplanetary disks, exploring the role of factors unique to this context: the Coriolis parameter f, the shear rate σ, and the Brunt-Väisälä frequency N are all of the same order of magnitude. In the region around the midplane N
Gluon-initiated production of a Kaluza-Klein gluon in a bulk Randall-Sundrum model
NASA Astrophysics Data System (ADS)
Allanach, Benjamin C.; Mahmoudi, Farvah; Skittrall, Jordan P.; Sridhar, K.
2010-03-01
In the Bulk Randall-Sundrum model, the Kaluza-Klein excitations of the gauge bosons are the primary signatures. In particular, the search for the Kaluza-Klein (KK) excitation of the gluon at hadron colliders is of great importance in testing this model. At the leading order in QCD, the production of this KK-gluon proceeds only via qbar q -initial states. We study the production of KK-gluons from gluon initial states at next-to-leading order in QCD. We find that, even after including the sub-dominant KK-gluon loops at this order, the next-to-leading order (NLO) cross-section is tiny compared to the leading order cross-section and unlikely to impact the searches for this resonance at hardon colliders.
Chiral magnetic and vortical effects in high-energy nuclear collisions-A status report
NASA Astrophysics Data System (ADS)
Kharzeev, D. E.; Liao, J.; Voloshin, S. A.; Wang, G.
2016-05-01
The interplay of quantum anomalies with magnetic field and vorticity results in a variety of novel non-dissipative transport phenomena in systems with chiral fermions, including the quark-gluon plasma. Among them is the Chiral Magnetic Effect (CME)-the generation of electric current along an external magnetic field induced by chirality imbalance. Because the chirality imbalance is related to the global topology of gauge fields, the CME current is topologically protected and hence non-dissipative even in the presence of strong interactions. As a result, the CME and related quantum phenomena affect the hydrodynamical and transport behavior of strongly coupled quark-gluon plasma, and can be studied in relativistic heavy ion collisions where strong magnetic fields are created by the colliding ions. Evidence for the CME and related phenomena has been reported by the STAR Collaboration at Relativistic Heavy Ion Collider at BNL, and by the ALICE Collaboration at the Large Hadron Collider at CERN. The goal of the present review is to provide an elementary introduction into the physics of anomalous chiral effects, to describe the current status of experimental studies in heavy ion physics, and to outline the future work, both in experiment and theory, needed to eliminate the existing uncertainties in the interpretation of the data.
Vorticity, defects and correlations in active turbulence
Thampi, Sumesh P.; Golestanian, Ramin; Yeomans, Julia M.
2014-01-01
We describe a numerical investigation of a continuum model of an active nematic, concentrating on the regime of active turbulence. Results are presented for the effect of three parameters, activity, elastic constant and rotational diffusion constant, on the order parameter and flow fields. Defects and distortions in the director field act as sources of vorticity, and thus vorticity is strongly correlated to the director field. In particular, the characteristic length of decay of vorticity and order parameter correlations is controlled by the defect density. By contrast, the decay of velocity correlations is determined by a balance between activity and dissipation. We highlight the role of microscopic flow generation mechanisms in determining the flow patterns and characteristic scales of active turbulence and contrast the behaviour of extensile and contractile active nematics. PMID:25332382
Characterization of reconnecting vortices in superfluid helium.
Bewley, Gregory P; Paoletti, Matthew S; Sreenivasan, Katepalli R; Lathrop, Daniel P
2008-09-16
When two vortices cross, each of them breaks into two parts and exchanges part of itself for part of the other. This process, called vortex reconnection, occurs in classical and superfluids, and in magnetized plasmas and superconductors. We present the first experimental observations of reconnection between quantized vortices in superfluid helium. We do so by imaging micrometer-sized solid hydrogen particles trapped on quantized vortex cores and by inferring the occurrence of reconnection from the motions of groups of recoiling particles. We show that the distance separating particles on the just-reconnected vortex lines grows as a power law in time. The average value of the scaling exponent is approximately 1/2, consistent with the self-similar evolution of the vortices. PMID:18768790
Vortical mechanism for generation of astrophysical jets
NASA Astrophysics Data System (ADS)
Abrahamyan, M. G.
2008-04-01
A vortical mechanism for generation of astrophysical jets is proposed based on exact solutions of the hydrodynamic equations with a generalized Rankine vortex. It is shown that the development of a Rankine vortex in the polar layer of a rotating gravitating body creates longitudinal fluxes of matter that converge toward the vortex trunk, providing an exponential growth in the angular rotation velocity of the trunk and a pressure drop on its axis. The increased rotational velocity of the vortex trunk and the on-axis pressure drop cease when the discontinuity in the azimuthal velocity at the surface of the trunk reaches the sound speed. During this time, ever deeper layers of the gravitating body are brought into the vortical motion, while the longitudinal velocity of the flow along the vortex trunk builds up, producing jet outflows of mass from its surface. The resulting vortices are essentially dissipationless.
Center vortices as composites of monopole fluxes
NASA Astrophysics Data System (ADS)
Deldar, S.; Nejad, S. M. Hosseini
2016-01-01
We study the relation between the flux of a center vortex obtained from the center vortex model and the flux formed between monopoles from the Abelian gauge fixing method. Motivated by the Monte Carlo simulations which have shown that almost all monopoles are sitting on the top of vortices, we construct the fluxes of center vortices for SU (2) and SU (3) gauge groups using fractional fluxes of monopoles. Then, we compute the potentials in the fundamental representation induced by center vortices and fractional fluxes of monopoles. We show that by combining the fractional fluxes of monopoles one can produce the center vortex fluxes for SU (3) gauge group in a "center vortex model". Comparing the potentials, we conclude that the fractional fluxes of monopoles attract each other.
How center vortices break chiral symmetry
NASA Astrophysics Data System (ADS)
Faber, Manfried; Höllwieser, Roman
2016-01-01
We investigate the chiral properties of near-zero modes for thick classical center vortices in SU(2) lattice gauge theory as examples of the phenomena which may arise in a vortex vacuum. In particular we analyze the creation of near-zero modes from would-be zero modes of various topological charge contributions from center vortices. We show that classical colorful spherical vortex and instanton ensembles have almost identical Dirac spectra and the low-lying eigenmodes from spherical vortices show all characteristic properties for chiral symmetry breaking. We further show that also vortex intersections are able to give rise to a finite density of near-zero modes, leading to chiral symmetry breaking via the Banks-Casher formula. We discuss the mechanism by which center vortex fluxes contribute to chiral symmetry breaking.
Potential Vorticity Analysis of Tropical Cyclone Intensification.
NASA Astrophysics Data System (ADS)
Molinari, John; Skubis, Steven; Vollaro, David; Alsheimer, Frank; Willoughby, Hugh E.
1998-08-01
The interaction of marginal Tropical Storm Danny (1985) with an upper-tropospheric positive potential vorticity anomaly was examined. The intensification mechanism proposed earlier for mature Hurricane Elena appears to be valid for Danny as well, despite significant differences in the synoptic-scale environment and in the stage of the tropical cyclone prior to the interaction. Both storms experienced rapid pressure falls as a relatively small-scale positive upper potential vorticity anomaly began to superpose with the low-level tropical cyclone center.The interaction is described in terms of a complex interplay between vertical wind shear, diabatic heating, and mutual advection among vortices at and below the level of the outflow anticyclone. Despite this complexity, the superposition principle appears to be conceptually useful to describe the intensification of tropical cyclones during such interactions.
A Note on Trapping Moving Vortices
NASA Technical Reports Server (NTRS)
Kao, Hsiao C.
2000-01-01
The topic of stationary configurations of point vortices, also known as vortex equilibrium, has received considerable attention in recent years. By observing numerical results, it is found that a "counterpart" of this system also exists, in which moving vortices may be "trapped" by an inlet-like device to form a stationary pattern with no translational motion. After an intuitive explanation for the process, vortex trajectory maps based on numerical results are presented. These maps exhibit two stationary points under the present conditions, which are the focal points of vortex trajectories. A vortex upstream of these points, if within a certain offset range, will move towards these points spontaneously and be captured there. This proposed device is also capable of trapping spinning vortex pairs and triads. It is possible to impose a uniform stream at infinity, as long as the flow field is still dominated by the moving vortices.
Measurements of Supersonic Wing Tip Vortices
NASA Technical Reports Server (NTRS)
Smart, Michael K.; Kalkhoran, Iraj M.; Benston, James
1994-01-01
An experimental survey of supersonic wing tip vortices has been conducted at Mach 2.5 using small performed 2.25 chords down-stream of a semi-span rectangular wing at angle of attack of 5 and 10 degrees. The main objective of the experiments was to determine the Mach number, flow angularity and total pressure distribution in the core region of supersonic wing tip vortices. A secondary aim was to demonstrate the feasibility of using cone probes calibrated with a numerical flow solver to measure flow characteristics at supersonic speeds. Results showed that the numerically generated calibration curves can be used for 4-hole cone probes, but were not sufficiently accurate for conventional 5-hole probes due to nose bluntness effects. Combination of 4-hole cone probe measurements with independent pitot pressure measurements indicated a significant Mach number and total pressure deficit in the core regions of supersonic wing tip vortices, combined with an asymmetric 'Burger like' swirl distribution.
Vorticity and divergence in the solar photosphere
NASA Technical Reports Server (NTRS)
Wang, YI; Noyes, Robert W.; Tarbell, Theodore D.; Title, Alan M.
1995-01-01
We have studied an outstanding sequence of continuum images of the solar granulation from Pic du Midi Observatory. We have calculated the horizontal vector flow field using a correlation tracking algorithm, and from this determined three scalar field: the vertical component of the curl; the horizontal divergence; and the horizontal flow speed. The divergence field has substantially longer coherence time and more power than does the curl field. Statistically, curl is better correlated with regions of negative divergence - that is, the vertical vorticity is higher in downflow regions, suggesting excess vorticity in intergranular lanes. The average value of the divergence is largest (i.e., outflow is largest) where the horizontal speed is large; we associate these regions with exploding granules. A numerical simulation of general convection also shows similar statistical differences between curl and divergence. Some individual small bright points in the granulation pattern show large local vorticities.
Characterization of reconnecting vortices in superfluid helium
Bewley, Gregory P.; Paoletti, Matthew S.; Sreenivasan, Katepalli R.; Lathrop, Daniel P.
2008-01-01
When two vortices cross, each of them breaks into two parts and exchanges part of itself for part of the other. This process, called vortex reconnection, occurs in classical and superfluids, and in magnetized plasmas and superconductors. We present the first experimental observations of reconnection between quantized vortices in superfluid helium. We do so by imaging micrometer-sized solid hydrogen particles trapped on quantized vortex cores and by inferring the occurrence of reconnection from the motions of groups of recoiling particles. We show that the distance separating particles on the just-reconnected vortex lines grows as a power law in time. The average value of the scaling exponent is approximately ½, consistent with the self-similar evolution of the vortices. PMID:18768790
Identification of vortices in complex flows
NASA Astrophysics Data System (ADS)
Chakraborty, P.; Balachandar, S.; Adrian, R. J.
2007-12-01
Dating back to Leonardo da Vinci's famous sketches of vortices in turbulent flows, fluid dynamicists for over five centuries have continued to visualize and interpret complex flows in terms of motion of vortices. Nevertheless, much debate surrounds the question of how to unambiguously define vortices in complex flows. This debate has resulted in the availability of many vortex identification criteria---mathematical statements of what constitutes a vortex. Here we review the popularly used local or point- wise vortex identification criteria. Based on local flow kinematics, we describe a unified framework to interpret the similarities and differences in the usage of these criteria. We discuss the limitations on the applicability of these criteria when there is a significant component of vortex interactions. Finally, we provide guidelines for applying these criteria to geophysical flows.
Moduli of Vortices and Grassmann Manifolds
NASA Astrophysics Data System (ADS)
Biswas, Indranil; Romão, Nuno M.
2013-05-01
We use the framework of Quot schemes to give a novel description of the moduli spaces of stable n-pairs, also interpreted as gauged vortices on a closed Riemann surface Σ with target {Mat_{r × n}({C})}, where n ≥ r. We then show that these moduli spaces embed canonically into certain Grassmann manifolds, and thus obtain natural Kähler metrics of Fubini-Study type. These spaces are smooth at least in the local case r = n. For abelian local vortices we prove that, if a certain "quantization" condition is satisfied, the embedding can be chosen in such a way that the induced Fubini-Study structure realizes the Kähler class of the usual L 2 metric of gauged vortices.
Longitudinal vortices imbedded in turbulent boundary layers
NASA Astrophysics Data System (ADS)
Mehta, R. D.; Shabaka, I. M. M.; Shibl, A.; Bradshaw, P.
1983-01-01
The attenuation of skew-induced longitudinal vortices by turbulent or viscous stresses is studied for the case of pure, artificially-generated longitudinal vortices entrained into initially two-dimensional boundary layers in nominally zero pressure gradients. Three types of vortex-boundary interactions are studied in detail: (1) an isolated vortex in a two-dimensional boundary layer; (2) a vortex pair in a turbulent boundary layer with the common flow between the vortices moving away from the surface; (3) a vortex pair in a boundary layer with the common flow moving towards the surface. Detailed mean flow and turbulence measurements are made, showing that the eddy viscosities defined for the different shear-stress components behave in different and complicated ways. Terms in the Reynolds stress transport equations, notably the triple products that effect turbulent diffusion of Reynolds stress, also fail to obey simple rules.
Weak quark couplings induced by gluon corrections
NASA Astrophysics Data System (ADS)
Gavela, M. B.; Le Yaouanc, A.; Oliver, L.; Pène, O.; Raynal, J. C.
1980-12-01
We compute the quark couplings in flavor-changing semileptonic transitions induced by lowest-order gluon corrections. We investigate the consequences of these radiative corrections for the quark axial-vector coupling, the deviations from Cabibbo universality for the axial-vector relative to the vector current, and the induced couplings (first-class pseudoscalar and anomalous magnetic moment, and second-class scalar and pseudotensor). The correction lowers the axial-vector coupling and increases the magnetic moment. We study the dependence of the couplings on the quark mass difference. Some of these results, true to all orders in αs, generalize the theorem of Ademollo and Gatto. The effective current is pure V-A to a very good approximation for transitions of heavy quarks (m>~5 GeV).
Gluon Green functions free of quantum fluctuations
NASA Astrophysics Data System (ADS)
Athenodorou, A.; Boucaud, Ph.; De Soto, F.; Rodríguez-Quintero, J.; Zafeiropoulos, S.
2016-09-01
This letter reports on how the Wilson flow technique can efficaciously kill the short-distance quantum fluctuations of 2- and 3-gluon Green functions, remove the ΛQCD scale and destroy the transition from the confining non-perturbative to the asymptotically-free perturbative sector. After the Wilson flow, the behavior of the Green functions with momenta can be described in terms of the quasi-classical instanton background. The same behavior also occurs, before the Wilson flow, at low-momenta. This last result permits applications as, for instance, the detection of instanton phenomenological properties or a determination of the lattice spacing only from the gauge sector of the theory.
Bashir, A.; Gutierrez-Guerrero, L. X.; Tejeda-Yeomans, M. E
2008-07-02
There has been growing evidence that the infra-red enhancement of the form factors defining the quark-gluon vertex plays an important role both in dynamical chiral symmetry breaking and confinement, thus providing an intrinsic link between the the two inherently non-perturbative phenomena. Both lattice and Schwinger-Dyson equation studies have begun to calculate these form factors in various kinematical regimes of momenta involved. A natural consistency check for these studies is that they should match onto the perturbative predictions for large momenta where non-perturbative effects mellow down. In this article, we study this matching by carrying out a numerical analysis of the one loop result for the central Ball-Chiu form factor.
Gluon Polarization and Jet Production at STAR
Djawotho, Pibero
2009-12-17
I will discuss the most recent measurements of the inclusive jet longitudinal spin asymmetry A{sub LL} in polarized proton-proton collisions. STAR collected its largest data sample thus far, 4.7 pb{sup -1} of integrated luminosity at an average beam polarization of {approx}57%, during the 2006 run at a center-of-mass energy of 200 GeV. I will also present previous STAR inclusive jet A{sub LL} and cross section measurements. The results are compared with theoretical calculations of A{sub LL} based on polarized distribution functions in the nucleon with a range of different contributions from the gluon polarization, {delta}G. The STAR data place significant constraints on {delta}G for 0.02
Check of the gluon-reggeization condition in the next-to-leading order: Gluon part
Kozlov, M. G. Reznichenko, A. V. Fadin, V. S.
2012-04-15
The last bootstrap condition whose validity has not been verified to date is considered. This condition is an indispensable element in the unitarity-relation-based proof of themulti-Regge form of highenergy gluon-exchange QCD amplitudes in the next-to-leading-logarithm approximation. The approach used here relies on the s-channel unitarity and makes it possible to reproduce successively, in all orders of perturbation theory, themulti-Regge form of the amplitude, provided that specific nonlinear relations, called bootstrap conditions, hold. All of them were derived, and all, with the exception of one, were tested. An explicit verification of fulfillment of the last condition (the bootstrap condition for the inelastic amplitude of the production of one gluon inmulti-Regge kinematics) is performed. In our preceding study, we performed such a verification for purely fermion contributions, while, in the present study, we complete it for one-loop gluon corrections to the components of the condition being considered.
Aerodynamics and vortical structures in hovering fruitflies
NASA Astrophysics Data System (ADS)
Meng, Xue Guang; Sun, Mao
2015-03-01
We measure the wing kinematics and morphological parameters of seven freely hovering fruitflies and numerically compute the flows of the flapping wings. The computed mean lift approximately equals to the measured weight and the mean horizontal force is approximately zero, validating the computational model. Because of the very small relative velocity of the wing, the mean lift coefficient required to support the weight is rather large, around 1.8, and the Reynolds number of the wing is low, around 100. How such a large lift is produced at such a low Reynolds number is explained by combining the wing motion data, the computed vortical structures, and the theory of vorticity dynamics. It has been shown that two unsteady mechanisms are responsible for the high lift. One is referred as to "fast pitching-up rotation": at the start of an up- or downstroke when the wing has very small speed, it fast pitches down to a small angle of attack, and then, when its speed is higher, it fast pitches up to the angle it normally uses. When the wing pitches up while moving forward, large vorticity is produced and sheds at the trailing edge, and vorticity of opposite sign is produced near the leading edge and on the upper surface, resulting in a large time rate of change of the first moment of vorticity (or fluid impulse), hence a large aerodynamic force. The other is the well known "delayed stall" mechanism: in the mid-portion of the up- or downstroke the wing moves at large angle of attack (about 45 deg) and the leading-edge-vortex (LEV) moves with the wing; thus, the vortex ring, formed by the LEV, the tip vortices, and the starting vortex, expands in size continuously, producing a large time rate of change of fluid impulse or a large aerodynamic force.
Vorticity Confinement Applied to Turbulent Wing Tip Vortices for Wake-Integral Drag Prediction
NASA Astrophysics Data System (ADS)
Pierson, Kristopher; Povitsky, Alex
2013-11-01
In the current study the vorticity confinement (VC) approach was applied to tip vortices shed by edges of stationary wings in order to predict induced drag by far-field integration in Trefftz plane. The VC parameter was evaluated first by application to convection of vortices in 2-D uniform flow and then to tip vortices shed in 3-D simulation of finite-aspect ratio rectangular wing in subsonic flight. Dependence of VC parameter on the flight Mach number and the angle of attack was evaluated. The aerodynamic drag results with application of VC to prevent numerical diffusion are much closer to analytic lifting line theory compared to integration over surface of wing while the viscous profile drag is more accurately evaluated by surface integration. To apply VC to viscous and turbulent flows, it is shown that VC does not affect the physical rate of dissipation of vortices in viscous/turbulent flows at time scales corresponding to convection of vortices from the wing to Trefftz plane of integration. To account for turbulent effects on tip vortices, VC was applied in combination with Spalart-Allmaras, k- ɛ, and six Reynolds stresses models of turbulence. The results are compared to experiments to validate the physical dissipation of tip vortex. This research was supported by The Dayton Area Graduate Studies Institute (DAGSI) and US Air Force Research Laboratory (AFRL) grants in 2009-2013, US Army Research Office (ARO) in 2012-2013 and ASEE/AFRL summer faculty grant.
Conditions for laminar flow in geophysical vortices
NASA Astrophysics Data System (ADS)
Fiedler, Brian H.
1989-01-01
The sufficient condition for inviscid, helical instability at large wavenumbers is applied to solutions for columnar vortices arising from the vortical flow of an end-wall boundary layer. The end-wall vortex arising from the laminar boundary layer under a potential vortex will be unstable at sufficiently high Reynolds number. Hoewever, if the end-wall boundary layer is turbulent, the end-wall vortex can be stable and laminar even at very high Reynolds number; therefore, stable, laminar tornadoes and waterspouts are suggested as theoretical possibilities.
Noise from two-dimensional vortices
NASA Technical Reports Server (NTRS)
Sanders, N. D.; Stockman, N. O.
1972-01-01
The fluctuating flow in an idealized model of a turbulent shear layer composed of many discrete vortices is analyzed. Computer solutions reveal irregular motions which are similar in many respects to observed flows in turbulent three-dimensional layers. The model is further simplified to a pair of equal co-rotating vortices and the noise generation is analyzed in terms of equivalent quadrupole oscillations. Results of the analysis in a uniform medium are consistent with Lighthill's results. New results are obtained for the effects of mean velocity gradients, compressibility, temperature inhomogenities, and gradients of the mean Mach number.
Spatially-partitioned many-body vortices
NASA Astrophysics Data System (ADS)
Klaiman, S.; Alon, O. E.
2016-02-01
A vortex in Bose-Einstein condensates is a localized object which looks much like a tiny tornado storm. It is well described by mean-field theory. In the present work we go beyond the current paradigm and introduce many-body vortices. These are made of spatially- partitioned clouds, carry definite total angular momentum, and are fragmented rather than condensed objects which can only be described beyond mean-field theory. A phase diagram based on a mean-field model assists in predicting the parameters where many-body vortices occur. Implications are briefly discussed.
Linear phase distribution of acoustical vortices
Gao, Lu; Zheng, Haixiang; Ma, Qingyu; Tu, Juan; Zhang, Dong
2014-07-14
Linear phase distribution of phase-coded acoustical vortices was theoretically investigated based on the radiation theory of point source, and then confirmed by experimental measurements. With the proposed criterion of positive phase slope, the possibility of constructing linear circular phase distributions is demonstrated to be determined by source parameters. Improved phase linearity can be achieved at larger source number, lower frequency, smaller vortex radius, and/or longer axial distance. Good agreements are observed between numerical simulations and measurement results for circular phase distributions. The favorable results confirm the feasibility of precise phase control for acoustical vortices and suggest potential applications in particle manipulation.
Quark-gluon vertex model and lattice-QCD data
Bhagwat, M.S.; Tandy, P.C.
2004-11-01
A model for the dressed-quark-gluon vertex, at zero gluon momentum, is formed from a nonperturbative extension of the two Feynman diagrams that contribute at one loop in perturbation theory. The required input is an existing ladder-rainbow model Bethe-Salpeter kernel from an approach based on the Dyson-Schwinger equations; no new parameters are introduced. The model includes an Ansatz for the triple-gluon vertex. Two of the three vertex amplitudes from the model provide a pointwise description of the recent quenched-lattice-QCD data. An estimate of the effects of quenching is made.
Evidence for polarization of gluons in the proton.
de Florian, Daniel; Sassot, Rodolfo; Stratmann, Marco; Vogelsang, Werner
2014-07-01
We discuss the impact of recent high-statistics Relativistic Heavy Ion Collider data on the determination of the gluon polarization in the proton in the context of a global QCD analysis of polarized parton distributions. We find evidence for a nonvanishing polarization of gluons in the region of momentum fraction and at the scales mostly probed by the data. Although information from low momentum fractions is presently lacking, this finding is suggestive of a significant contribution of gluon spin to the proton spin, thereby limiting the amount of orbital angular momentum required to balance the proton spin budget. PMID:25032920
Chromohydrodynamic approach to the unstable quark-gluon plasma
NASA Astrophysics Data System (ADS)
Manuel, Cristina; Mrówczyński, Stanisław
2006-11-01
We derive hydrodynamic-like equations that are applicable to short-time-scale color phenomena in the quark-gluon plasma. The equations are solved in the linear response approximation, and the gluon polarization tensor is derived. As an application, we study the collective modes in a two-stream system and find plasma instabilities when the fluid velocity is larger than the speed of sound in the plasma. The chromohydrodynamic approach, discussed here in detail, should be considered as simpler over other approaches and well-designed for numerical studies of the dynamics of an unstable quark-gluon plasma.
A factor involved in efficient breakdown of supersonic streamwise vortices
NASA Astrophysics Data System (ADS)
Hiejima, Toshihiko
2015-03-01
Spatially developing processes in supersonic streamwise vortices were numerically simulated at Mach number 5.0. The vortex evolution largely depended on the azimuthal vorticity thickness of the vortices, which governs the negative helicity profile. Large vorticity thickness greatly enhanced the centrifugal instability, with consequent development of perturbations with competing wavenumbers outside the vortex core. During the transition process, supersonic streamwise vortices could generate large-scale spiral structures and a number of hairpin like vortices. Remarkably, the transition caused a dramatic increase in the total fluctuation energy of hypersonic flows, because the negative helicity profile destabilizes the flows due to helicity instability. Unstable growth might also relate to the correlation length between the axial and azimuthal vorticities of the streamwise vortices. The knowledge gained in this study is important for realizing effective fuel-oxidizer mixing in supersonic combustion engines.
Evolution of a barotropic shear layer into elliptical vortices.
Guha, Anirban; Rahmani, Mona; Lawrence, Gregory A
2013-01-01
When a barotropic shear layer becomes unstable, it produces the well-known Kelvin-Helmholtz instability (KHI). The nonlinear manifestation of the KHI is usually in the form of spiral billows. However, a piecewise linear shear layer produces a different type of KHI characterized by elliptical vortices of constant vorticity connected via thin braids. Using direct numerical simulation and contour dynamics, we show that the interaction between two counterpropagating vorticity waves is solely responsible for this KHI formation. We investigate the oscillation of the vorticity wave amplitude, the rotation and nutation of the elliptical vortex, and straining of the braids. Our analysis also provides a possible explanation for the formation and evolution of elliptical vortices appearing in geophysical and astrophysical flows, e.g., meddies, stratospheric polar vortices, Jovian vortices, Neptune's Great Dark Spot, and coherent vortices in the wind belts of Uranus. PMID:23410439
The Boltzmann equation for gluons at early times after a heavy ion collision
NASA Astrophysics Data System (ADS)
Mueller, A. H.
2000-03-01
A Boltzmann equation is given for the early stages of evolution of the gluon system produced in a head-on heavy ion collision. The collision term is taken from gluon-gluon scattering in the one-gluon approximation.
and
Cosmological perturbations: Vorticity, isocurvature and magnetic fields
NASA Astrophysics Data System (ADS)
Christopherson, Adam J.
2014-10-01
In this paper, I review some recent, interlinked, work undertaken using cosmological perturbation theory — a powerful technique for modeling inhomogeneities in the universe. The common theme which underpins these pieces of work is the presence of nonadiabatic pressure, or entropy, perturbations. After a brief introduction covering the standard techniques of describing inhomogeneities in both Newtonian and relativistic cosmology, I discuss the generation of vorticity. As in classical fluid mechanics, vorticity is not present in linearized perturbation theory (unless included as an initial condition). Allowing for entropy perturbations, and working to second order in perturbation theory, I show that vorticity is generated, even in the absence of vector perturbations, by purely scalar perturbations, the source term being quadratic in the gradients of first order energy density and isocurvature, or nonadiabatic pressure perturbations. This generalizes Crocco's theorem to a cosmological setting. I then introduce isocurvature perturbations in different models, focusing on the entropy perturbation in standard, concordance cosmology, and in inflationary models involving two scalar fields. As the final topic, I investigate magnetic fields, which are a potential observational consequence of vorticity in the early universe. I briefly review some recent work on including magnetic fields in perturbation theory in a consistent way. I show, using solely analytical techniques, that magnetic fields can be generated by higher order perturbations, albeit too small to provide the entire primordial seed field, in agreement with some numerical studies. I close this paper with a summary and some potential extensions of this work.
Temporal stability of multiple-cell vortices
NASA Technical Reports Server (NTRS)
Khorrami, M. R.; Grosch, C. E.
1989-01-01
The temporal stability of multiple cell vortices is studied with a staggered Chebyshev spectral collocation technique. It is shown that cell multiplicity in the vortex core has a drastic effect on the stability characteristics. While validating the spectral collocation algorithm, two new viscous modes of instability for Batchelor's (1964) vortex were found. These modes are discussed in detail.
Long Term Changes in the Polar Vortices
NASA Astrophysics Data System (ADS)
Braathen, Geir O.
2016-04-01
As the amount of halogens in the stratosphere is slowly declining and the ozone layer slowly recovers it is of interest to see how the meteorological conditions in the vortex develop over the long term since such changes might alter the foreseen ozone recovery. In conjunction with the publication of the WMO Antarctic and Arctic Ozone Bulletins, WMO has acquired the ERA Interim global reanalysis data set for several meteorological parameters. This data set goes from 1979 - present. These long time series of data can be used for several useful studies of the long term development of the polar vortices. Several "environmental indicators" for vortex change have been calculated, and a climatology, as well as trends, for these parameters will be presented. These indicators can act as yardsticks and will be useful for understanding past and future changes in the polar vortices and how these changes affect polar ozone depletion. Examples of indicators are: vortex mean temperature, vortex minimum temperature, vortex mean PV, vortex "importance" (PV*area), vortex break-up time, mean and maximum wind speed. Data for both the north and south polar vortices have been analysed at several isentropic levels from 350 to 850 K. A possible link between changes in PV and sudden stratospheric warmings will be investigated, and the results presented. The unusual meteorological conditions of the 2015 south polar vortex and the 2010/11 and 2015/16 north polar vortices will be compared to other recent years.
Experimental Study of Lift-Generated Vortices
NASA Technical Reports Server (NTRS)
Rossow, Vernon J.; Nixon, David (Technical Monitor)
1998-01-01
The flow fields of vortices, whether bouyancy-driven or lift-generated, are fascinating fluid-dynamic phenomena which often possess intense swirl velocities and complex time-dependent behavior. As part of the on-going study of vortex behavior, this paper presents a historical overview of the research conducted on the structure and modification of the vortices generated by the lifting surfaces of subsonic transport aircraft. It is pointed out that the characteristics of lift-generated vortices are related to the aerodynamic shapes that produce them and that various arrangements of surfaces can be used to produce different vortex structures. The primary purpose of the research to be described is to find a way to reduce the hazard potential of lift-generated vortices shed by subsonic transport aircraft in the vicinity of airports during landing and takeoff operations. It is stressed that lift-generated vortex wakes are so complex that progress towards a solution requires application of a combined theoretical and experimental research program because either alone often leads to incorrect conclusions. It is concluded that a satisfactory aerodynamic solution to the wake-vortex problem at airports has not yet been found but a reduction in the impact of the wake-vortex hazard on airport capacity may become available in the foreseeable future through wake-vortex avoidance concepts currently under study. The material to be presented in this overview is drawn from aerospace journals that are available publicly.
Hairpin vortices in turbulent boundary layers
NASA Astrophysics Data System (ADS)
Eitel-Amor, G.; Flores, O.; Schlatter, P.
2014-04-01
The present work addresses the question whether hairpin vortices are a dominant feature of near-wall turbulence and which role they play during transition. First, the parent-offspring mechanism is investigated in temporal simulations of a single hairpin vortex introduced in a mean shear flow corresponding to turbulent channels and boundary layers up to Reτ = 590. Using an eddy viscosity computed from resolved simulations, the effect of a turbulent background is also considered. Tracking the vortical structure downstream, it is found that secondary hairpins are created shortly after initialization. Thereafter, all rotational structures decay, whereas this effect is enforced in the presence of an eddy viscosity. In a second approach, a laminar boundary layer is tripped to transition by insertion of a regular pattern of hairpins by means of defined volumetric forces representing an ejection event. The idea is to create a synthetic turbulent boundary layer dominated by hairpin-like vortices. The flow for Reτ < 250 is analysed with respect to the lifetime of individual hairpin-like vortices. Both the temporal and spatial simulations demonstrate that the regeneration process is rather short-lived and may not sustain once a turbulent background has formed. From the transitional flow simulations, it is conjectured that the forest of hairpins reported in former DNS studies is an outer layer phenomenon not being connected to the onset of near-wall turbulence.
Two-dimensional vortices and accretion disks
NASA Astrophysics Data System (ADS)
Nauta, Michiel Doede
2000-01-01
Observations show that there are disks around certain stars that slowly rain down on the central (compact) object: accretion disks. The rate of depletion of the disk might be slow but is still larger than was expected on theoretical grounds. That is why it has been suggested that the disks are turbulent. Because the disk is thin and rotating this turbulence might be related to two-dimensional (2D) turbulence which is characterized by energy transfers towards small wave numbers and the formation of 2D-vortices. This hypothesis is investigated in this thesis by numerical simulations. After an introduction, the numerical algorithm that was inplemented is discussed together with its relation to an accretion disk. It performs well under the absence of discontinuities. The code is used to study 2D-turbulence under the influence of background rotation with compressibility and a shearing background flow. The first is found to be of little consequence but the shear flow alters 2D-turbulence siginificantly. Only prograde vortices of enough strength are able to withstand the shear flow. The size of the vortices in the cross stream direction is also found to be smaller than the equivalent of the thickness of an accretion disk. These circulstances imply that the assumption of two-dimensionality is questionable so that 2D-vortices might not abound in accretion disks. However, the existence of such vortices is not ruled out and one such a cortex is studied in detail in chapter 4. The internal structure of the vortex is well described by a balance between Coriolis, centrifugal and pressure forces. The vortex is also accompanied by two spiral compressible waves. These are not responsible for the azimuthal drift of the vortex, which results from secondary vortices, but they might be related to the small radial drift that is observed. Radial drift leads to accretion but it is not very efficient. Multiple vortex interactions are the topic of tha last chapter and though interesting the
Hairpin vortices in turbulent boundary layers
NASA Astrophysics Data System (ADS)
Eitel-Amor, G.; Örlü, R.; Schlatter, P.; Flores, O.
2015-02-01
The present work presents a number of parallel and spatially developing simulations of boundary layers to address the question of whether hairpin vortices are a dominant feature of near-wall turbulence, and which role they play during transition. In the first part, the parent-offspring regeneration mechanism is investigated in parallel (temporal) simulations of a single hairpin vortex introduced in a mean shear flow corresponding to either turbulent channels or boundary layers (Reτ ≲ 590). The effect of a turbulent background superimposed on the mean flow is considered by using an eddy viscosity computed from resolved simulations. Tracking the vortical structure downstream, it is found that secondary hairpins are only created shortly after initialization, with all rotational structures decaying for later times. For hairpins in a clean (laminar) environment, the decay is relatively slow, while hairpins in weak turbulent environments (10% of νt) dissipate after a couple of eddy turnover times. In the second part, the role of hairpin vortices in laminar-turbulent transition is studied using simulations of spatial boundary layers tripped by hairpin vortices. These vortices are generated by means of specific volumetric forces representing an ejection event, creating a synthetic turbulent boundary layer initially dominated by hairpin-like vortices. These hairpins are advected towards the wake region of the boundary layer, while a sinusoidal instability of the streaks near the wall results in rapid development of a turbulent boundary layer. For Reθ > 400, the boundary layer is fully developed, with no evidence of hairpin vortices reaching into the wall region. The results from both the parallel and spatial simulations strongly suggest that the regeneration process is rather short-lived and may not sustain once a turbulent background is developed. From the transitional flow simulations, it is conjectured that the forest of hairpins reported in former direct numerical
Controlled Manipulation of Individual Vortices in a Superconductor
Straver, E.W.J.
2010-04-05
We report controlled local manipulation of single vortices by low temperature magnetic force microscope (MFM) in a thin film of superconducting Nb. We are able to position the vortices in arbitrary configurations and to measure the distribution of local depinning forces. This technique opens up new possibilities for the characterization and use of vortices in superconductors.
An eddy closure for potential vorticity
Ringler, Todd D
2009-01-01
The Gent-McWilliams (GM) parameterization is extended to include a direct influence in the momentum equation. The extension is carried out in two stages; an analysis of the inviscid system is followed by an analysis of the viscous system. In the inviscid analysis the momentum equation is modified such that potential vorticity is conserved along particle trajectories following a transport velocity that includes the Bolus velocity in a manner exactly analogous to the continuity and tracer equations. In addition (and in contrast to traditional GM closures), the new formulation of the inviscid momentum equation results in a conservative exchange between potential and kinetic forms of energy. The inviscid form of the eddy closure conserves total energy to within an error proportional to the time derivative of the Bolus velocity. The hypothesis that the viscous term in the momentum equation should give rise to potential vorticity being diffused along isopycnals in a manner analogous to other tracers is examined in detail. While the form of the momentum closure that follows from a strict adherence to this hypothesis is not immediately interpretable within the constructs of traditional momentum closures, three approximations to this hypothesis results in a form of dissipation that is consistent with traditional Laplacian diffusion. The first two approximations are that relative vorticity, not potential vorticity, is diffused along isopyncals and that the flow is in approximate geostrophic balance. An additional approximation to the Jacobian term is required when the dissipation coefficient varies in space. More importantly, the critique of this hypothesis results in the conclusion that the viscosity parameter in the momentum equation should be identical to the tradition GM closure parameter {Kappa}. Overall, we deem the viscous form of the eddy closure for potential vorticity as a viable closure for use in ocean circulation models.
Bilinear relative equilibria of identical point vortices
NASA Astrophysics Data System (ADS)
Aref, Hassan; Beelen, Peter; Brøns, Morten
2011-11-01
A new class of bilinear relative equilibria of identical point vortices in which the vortices are constrained to be on two perpendicular lines, taken to be the x- and y-axes of a cartesian coordinate system, is introduced and studied. In general we have m vortices on the y-axis and n on the x- axis. We define generating polynomials q (z) and p (z) , respectively, for each set of vortices. A second order, linear ODE for p (z) given q (z) is derived. Several results relating the general solution of the ODE to relative equilibrium configurations are established. Our strongest result, obtained using Sturm's comparison theorem, is that if p (z) satisfies the ODE for a given q (z) with its imaginary zeros symmetric relative to the x-axis, then it must have at least n - m + 2 simple, real zeros. For m = 2 this provides a complete characterization of all zeros, and we study this case in some detail. In particular, we show that given q (z) =z2 +η2 , where η is real, there is a unique p (z) of degree n, and a unique value of η2 =An , such that the zeros of q (z) and p (z) form a relative equilibrium of n + 2 point vortices. We show that An ~2/3 n +1/2 , as n --> ∞ , where the coefficient of n is determined analytically, the next order term numerically. Supported in part by the Danish National Research Foundation through a Niels Bohr visiting professorship.
Rapidity evolution of gluon TMD from low to moderate x
Balitsky, Ian; Tarasov, A.
2015-10-05
In this article, we study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small $x \\ll 1$ to linear evolution at moderate $x \\sim 1$.
Gluon TMD in particle production from low to moderate x
Balitsky, I.; Tarasov, A.
2016-06-28
Here, we study the rapidity evolution of gluon transverse momentum dependent distributions appearing in processes of particle production and show how this evolution changes from small to moderate Bjorken x.
Resummation and the gluon damping rate in hot QCD
Pisarski, R.D.
1990-08-01
At high temperature a consistent perturbative expansion requires the resummation of an infinite subset of loop corrections into an effective expansion. This effective exansion is used to compute the gluon damping rate at leading order. 25 refs.
Rapidity evolution of gluon TMD from low to moderate x
Balitsky, Ian; Tarasov, A.
2015-10-05
In this article, we study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at smallmore » $$x \\ll 1$$ to linear evolution at moderate $$x \\sim 1$$.« less
Veneziano ghost, modified gluon propagator, and gauge copies in QCD
NASA Astrophysics Data System (ADS)
Dudal, D.; Guimaraes, M. S.
2016-04-01
In this short note, we come back to the recent proposal put forward by Kharzeev and Levin [Phys. Rev. Lett. 114, 242001 (2015)], in which they phenomenologically couple the nonperturbative Veneziano ghost to the perturbative gluon, leading to a modified gluon propagator (the "glost") of the Gribov type, with complex poles. As such, a possible link was made between the QCD topological θ -vacuum (Veneziano ghost) and color confinement (no physically observable gluons). We discuss some subtleties concerning gauge (Becchi-Rouet-Stora-Tuytin) invariance of this proposal, related to the choice of Feynman gauge. We draw particular attention to the incompatibility in the longitudinal sector with available nonperturbative results for the linear covariant gauge. We furthermore provide an example in the Landau gauge of a similar phenomenological vertex that also describes the necessary Veneziano ghost but does not affect the Landau gauge gluon propagator.
Gluon TMD in particle production from low to moderate x
NASA Astrophysics Data System (ADS)
Balitsky, I.; Tarasov, A.
2016-06-01
We study the rapidity evolution of gluon transverse momentum dependent distributions appearing in processes of particle production and show how this evolution changes from small to moderate Bjorken x.
Probing the Gluon Self-Interaction in Light Mesons
Fischer, Christian S.; Williams, Richard
2009-09-18
We investigate masses and decay constants of light mesons from a coupled system of Dyson-Schwinger and Bethe-Salpeter equations. We explicitly take into account dominant non-Abelian contributions to the dressed quark-gluon vertex stemming from the gluon self-interaction. We construct the corresponding Bethe-Salpeter kernel that satisfies the axial-vector Ward-Takahashi identity. Our numerical treatment fully includes all momentum dependencies with all equations solved completely in the complex plane. This approach goes well beyond the rainbow-ladder approximation and permits us to investigate the influence of the gluon self-interaction on the properties of mesons. As a first result we find indications of a nonperturbative cancellation of the gluon self-interaction contributions and pion cloud effects in the mass of the rho meson.
Physics of the gluon-helicity contribution to proton spin.
Ji, Xiangdong; Zhang, Jian-Hui; Zhao, Yong
2013-09-13
The total gluon helicity in a polarized proton, measurable in high-energy scattering, is shown to be the large momentum limit of a gauge-invariant but nonlocal, frame-dependent gluon spin E × A⊥ in QCD. This opens a door for a nonperturbative calculation of this quantity in lattice QCD and also justifies using free-field expressions in the light-cone gauge as physical observables. PMID:24074075
Schwinger-Dyson Equations and Dynamical gluon mass generation
Aguilar, A.C.; Natale, A.A.
2004-12-02
We obtain a solution for the gluon propagador in Landau gauge within two distinct approximations for the Schwinger-Dyson equations (SDE). The first, named Mandelstam's approximation, consist in neglecting all contributions that come from fermions and ghosts fields while in the second, the ghosts fields are taken into account leading to a coupled system of integral equations. In both cases we show that a dynamical mass for the gluon propagator can arise as a solution.
Colored plasmons in a quark-gluon plasma near equilibrium
NASA Astrophysics Data System (ADS)
Hein, Ulrich; Siemens, Philip J.
1985-08-01
Within a kinetic theory for QCD plasmas we study the color response function near thermodynamic equilibrium. Its poles yield a longitudinal and a transverse collective mode, both starting at the plasma frequency. Due to the gluon contribution there is no Landau damping for these modes, and creation of gluon or q- overlinep pairs is the dominant damping mechanism. In an electron plasma the generally quoted Landau damping near threshold is shown to be an artifact of the non-relativistic approximation.
Measuring vortical flows in the solar interior
NASA Astrophysics Data System (ADS)
Langfellner, Jan
2015-09-01
This thesis focuses on observations of the effects of rotation on solar convection at the length scales of supergranulation and larger (>30 Mm). Rotation drives vortical flows through the Coriolis force and causes anisotropic velocity correlations that are believed to influence the large-scale solar dynamics. We obtain horizontal flows using photospheric Doppler velocity and continuum intensity images from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) spacecraft via the techniques of time-distance helioseismology (TD) and local correlation tracking (LCT) of granules. In time-distance helioseismology, the local vertical vorticity can be measured by taking the difference between wave travel times measured in the anti-clockwise and clockwise directions along a closed contour. The agreement between the TD and LCT methods is excellent up to Â±60Â° latitude, provided that a center-to-limb correction is applied. Averaging over longitude, one finds that there is a small but significant correlation between the horizontal divergence and the vertical vorticity component of supergranular flows away from the solar equator. By comparison to a noise model, we find that the TD technique can be used to probe the vertical vorticity of flows on spatial scales larger than about 15 Mm, thus including supergranules and also giant cells. We also find that the vertical vorticity signal is much easier to measure using SDO/HMI observations than previous observations. The impact of the Sun's rotation on supergranulation is studied in detail by making spatial maps of the vertical vorticity of the flows associated with the average supergranule. The average supergranule is constructed by co-aligning thousands of individual supergranules in a given latitude band. For the first time, we are able to spatially resolve vorticity associated with inflows and outflow regions. In the northern hemisphere, outflows are on average associated with a clockwise
Recovering the vorticity of a light beam after scattering
Salla, Gangi Reddy Perumangattu, Chithrabhanu; Anwar, Ali; Prabhakar, Shashi; Singh, Ravindra P.
2015-07-13
We generate optical vortices and scatter them through a rough surface. However, the scattered light passing through a lens shows the same vorticity when probed at the Fourier plane. The vorticity is measured using a nonseparable state of polarization and orbital angular momentum of light as it cannot be confirmed by the standard interferometric technique. The observed vorticity is found to be independent of the amount of scattered light collected. Therefore, vortices can be used as information carriers even in the presence of scattering media. The experimental results are well supported by the theoretical results.
Recovering the vorticity of a light beam after scattering
NASA Astrophysics Data System (ADS)
Salla, Gangi Reddy; Perumangattu, Chithrabhanu; Prabhakar, Shashi; Anwar, Ali; Singh, Ravindra P.
2015-07-01
We generate optical vortices and scatter them through a rough surface. However, the scattered light passing through a lens shows the same vorticity when probed at the Fourier plane. The vorticity is measured using a nonseparable state of polarization and orbital angular momentum of light as it cannot be confirmed by the standard interferometric technique. The observed vorticity is found to be independent of the amount of scattered light collected. Therefore, vortices can be used as information carriers even in the presence of scattering media. The experimental results are well supported by the theoretical results.
Inclusive two-gluon and valence-quark-gluon production in DIS and pA collisions
Jalilian-Marian, Jamal; Kovchegov, Yuri V.
2004-12-01
We calculate production cross sections of a forward quark-gluon pair and of two gluons at midrapidity in deep inelastic scattering and in high energy proton-nucleus collisions. The calculation is performed in the framework of the color glass condensate formalism. We first calculate the cross sections in the quasiclassical approximation, which includes multiple rescatterings in the target. We then proceed to include the effects of nonlinear small-x evolution in the production cross sections. It is interesting to note that our result for the two-gluon production cross section appears to be in direct violation of Abramovsky-Gribov-Kanchelli cutting rules, which is the first example of such violation in QCD. The calculated quark-gluon and gluon-gluon production cross sections can be used to construct theoretical predictions for two-particle azimuthal correlations at the Relativistic Heavy Ion Collider and LHC (I{sup p(d)A}) as well as for deep inelastic scattering experiments at the Hadron Electron Ring Accelerator and the Electron-Relativistic Heavy Ion Collider.
Intensity of vortices: from soap bubbles to hurricanes
Meuel, T.; Xiong, Y. L.; Fischer, P.; Bruneau, C. H.; Bessafi, M.; Kellay, H.
2013-01-01
By using a half soap bubble heated from below, we obtain large isolated single vortices whose properties as well as their intensity are measured under different conditions. By studying the effects of rotation of the bubble on the vortex properties, we found that rotation favors vortices near the pole. Rotation also inhibits long life time vortices. The velocity and vorticity profiles of the vortices obtained are well described by a Gaussian vortex. Besides, the intensity of these vortices can be followed over long time spans revealing periods of intensification accompanied by trochoidal motion of the vortex center, features which are reminiscent of the behavior of tropical cyclones. An analysis of this intensification period suggests a simple relation valid for both the vortices observed here and for tropical cyclones. PMID:24336410
Development and Interaction of Artificially Generated Hairpin Vortices
NASA Astrophysics Data System (ADS)
Sabatino, Daniel; McKenna, Christopher
2012-11-01
The development and interaction of hairpin vortices are examined and categorized to better understand their role in fully turbulent boundary layers. Hairpin vortices are generated within an otherwise laminar boundary layer using a free surface water channel. Direct injection is the primary generation method and the behavior of the vortices is first examined using flow visualization. Hydrogen bubble wire is combined with dye injection to help clarify the role of the vorticity in the fluid immediately surrounding the hairpin vortex. PIV data is also used to classify the development and maturity of the vortices for a range of free stream and injection conditions. The interactions of two hairpin vortices of varying maturity are characterized to investigate the potential mechanisms for the formation of hairpin packets beyond autogeneration. Finally, the behavior of hairpin vortices generated with a new technique that uses a transient hemispherical protrusion is also examined. Supported by the National Science Foundation under Grant CBET-1040236.
Instability of isolated hollow vortices with zero circulation
NASA Astrophysics Data System (ADS)
Hiejima, Toshihiko
2016-04-01
Inviscid linear stability analysis and numerical simulations are used to investigate how temporal disturbances evolve in double-annular hollow vortices with an opposite-signed vorticity (the total circulation is zero). Two extrema exist in the vorticity profile and constitute a factor of instability. The dispersion relation is expressed as a simple cubic equation. The results show that the instabilities of vortices are strongly enhanced by the hollow effect of the annular vorticity. In addition, the growth rate of the dominant modes significantly increases with decreasing negative-vorticity thickness. During the initial stage, the dominant unstable modes obtained from simulations are consistent with those obtained from the linear analysis. In nonlinear developments, the flow field stretches out in one direction depending on the motion of the plural vortex pair formed by rolling up the positive and negative vorticities. Once such structures in the vortex are generated, the vortex immediately breaks down and does not become metastable.
Intensity of vortices: from soap bubbles to hurricanes
NASA Astrophysics Data System (ADS)
Meuel, T.; Xiong, Y. L.; Fischer, P.; Bruneau, C. H.; Bessafi, M.; Kellay, H.
2013-12-01
By using a half soap bubble heated from below, we obtain large isolated single vortices whose properties as well as their intensity are measured under different conditions. By studying the effects of rotation of the bubble on the vortex properties, we found that rotation favors vortices near the pole. Rotation also inhibits long life time vortices. The velocity and vorticity profiles of the vortices obtained are well described by a Gaussian vortex. Besides, the intensity of these vortices can be followed over long time spans revealing periods of intensification accompanied by trochoidal motion of the vortex center, features which are reminiscent of the behavior of tropical cyclones. An analysis of this intensification period suggests a simple relation valid for both the vortices observed here and for tropical cyclones.
Emergent vortices in populations of colloidal rollers
Bricard, Antoine; Caussin, Jean-Baptiste; Das, Debasish; Savoie, Charles; Chikkadi, Vijayakumar; Shitara, Kyohei; Chepizhko, Oleksandr; Peruani, Fernando; Saintillan, David; Bartolo, Denis
2015-01-01
Coherent vortical motion has been reported in a wide variety of populations including living organisms (bacteria, fishes, human crowds) and synthetic active matter (shaken grains, mixtures of biopolymers), yet a unified description of the formation and structure of this pattern remains lacking. Here we report the self-organization of motile colloids into a macroscopic steadily rotating vortex. Combining physical experiments and numerical simulations, we elucidate this collective behaviour. We demonstrate that the emergent-vortex structure lives on the verge of a phase separation, and single out the very constituents responsible for this state of polar active matter. Building on this observation, we establish a continuum theory and lay out a strong foundation for the description of vortical collective motion in a broad class of motile populations constrained by geometrical boundaries. PMID:26088835
Trailing vortices from low speed flyers
NASA Astrophysics Data System (ADS)
Waldman, Rye; Kudo, Jun; Breuer, Kenneth
2009-11-01
The structure and strength of the vortex wake behind a airplane or animal flying with a fixed or flapping wing contains valuable information about the aerodynamic load history. However, the amount of vorticity measured in the trailing vortex is not always in agreement with the known lift generated, and the behavior of these vortices at relatively low Reynolds numbers is also not well-understood. We present the results from a series of wind tunnel PIV experiments conducted behind a low-aspect ratio rectangular wing at a chord-Reynolds numbers of 30,000. In addition to wake PIV measurements measured in the cross-stream (Trefftz) plane, we measure the lift and drag directly using a six-axis force-torque transducer. We discuss how vortex size, shape, strength and position vary in time and downstream location, as well as the challenges associated with the use of PIV wake measurements to accurate determine aerodynamic forces.
Emergent vortices in populations of colloidal rollers.
Bricard, Antoine; Caussin, Jean-Baptiste; Das, Debasish; Savoie, Charles; Chikkadi, Vijayakumar; Shitara, Kyohei; Chepizhko, Oleksandr; Peruani, Fernando; Saintillan, David; Bartolo, Denis
2015-01-01
Coherent vortical motion has been reported in a wide variety of populations including living organisms (bacteria, fishes, human crowds) and synthetic active matter (shaken grains, mixtures of biopolymers), yet a unified description of the formation and structure of this pattern remains lacking. Here we report the self-organization of motile colloids into a macroscopic steadily rotating vortex. Combining physical experiments and numerical simulations, we elucidate this collective behaviour. We demonstrate that the emergent-vortex structure lives on the verge of a phase separation, and single out the very constituents responsible for this state of polar active matter. Building on this observation, we establish a continuum theory and lay out a strong foundation for the description of vortical collective motion in a broad class of motile populations constrained by geometrical boundaries. PMID:26088835
Shear-Layer Effects on Trailing Vortices
NASA Technical Reports Server (NTRS)
Zheng, Z. C.; Baek, K.
1998-01-01
Crosswind shear can influence the trailing vortex trajectories significantly, according to both field measurement and numerical simulations. Point vortex models are used in this paper to study the fluid dynamic mechanism in the interactions between trailing vortex pair and shear layers. It has been shown that the shear-layer deformation causes the vortex descent history difference in the two vortices of the vortex pair. When a shear layer is below the vortex pair with the same sign as the left vortex, the right vortex descends less than the left vortex. When the same shear layer is above the vortex pair, the right vortex descends more. The descent altitudes of the two vortices are the same when they go through a constant, non-deformed shear layer. Those trends are in agreement with Navier-Stokes simulations.
Helical vortices: viscous dynamics and instability
NASA Astrophysics Data System (ADS)
Rossi, Maurice; Selcuk, Can; Delbende, Ivan; Ijlra-Upmc Team; Limsi-Cnrs Team
2014-11-01
Understanding the dynamical properties of helical vortices is of great importance for numerous applications such as wind turbines, helicopter rotors, ship propellers. Locally these flows often display a helical symmetry: fields are invariant through combined axial translation of distance Δz and rotation of angle θ = Δz / L around the same z-axis, where 2 πL denotes the helix pitch. A DNS code with built-in helical symmetry has been developed in order to compute viscous quasi-steady basic states with one or multiple vortices. These states will be characterized (core structure, ellipticity, ...) as a function of the pitch, without or with an axial flow component. The instability modes growing in the above base flows and their growth rates are investigated by a linearized version of the DNS code coupled to an Arnoldi procedure. This analysis is complemented by a helical thin-cored vortex filaments model. ANR HELIX.
Motion of vortices outside a cylinder
NASA Astrophysics Data System (ADS)
Tulu, Serdar; Yilmaz, Oguz
2010-12-01
The problem of motion of the vortices around an oscillating cylinder in the presence of a uniform flow is considered. The Hamiltonian for vortex motion for the case with no uniform flow and stationary cylinder is constructed, reduced, and constant Hamiltonian (energy) curves are plotted when the system is shown to be integrable according to Liouville. By adding uniform flow to the system and by allowing the cylinder to vibrate, we model the natural vibration of the cylinder in the flow field, which has applications in ocean engineering involving tethers or pipelines in a flow field. We conclude that in the chaotic case forces on the cylinder may be considerably larger than those on the integrable case depending on the initial positions of vortices and that complex phenomena such as chaotic capture and escape occur when the initial positions lie in a certain region.
Exact Solitary Water Waves with Vorticity
NASA Astrophysics Data System (ADS)
Hur, Vera Mikyoung
2008-05-01
The solitary water wave problem is to find steady free surface waves which approach a constant level of depth in the far field. The main result is the existence of a family of exact solitary waves of small amplitude for an arbitrary vorticity. Each solution has a supercritical parameter value and decays exponentially at infinity. The proof is based on a generalized implicit function theorem of the Nash-Moser type. The first approximation to the surface profile is given by the “KdV” equation. With a supercritical value of the surface tension coefficient, a family of small amplitude solitary waves of depression with subcritical parameter values is constructed for an arbitrary vorticity.
Anomalous energetics and dynamics of moving vortices
NASA Astrophysics Data System (ADS)
Radzihovsky, Leo
Motivated by the general problem of moving topological defects in an otherwise ordered state and specifically, by the anomalous dynamics observed in vortex-antivortex annihilation and coarsening experiments in freely-suspended smectic-C films, I study the deformation, energetics and dynamics of moving vortices in an overdamped xy-model and show that their properties are significantly and qualitatively modified by the motion. Supported by NSF through DMR-1001240, MRSEC DMR-0820579, and by Simons Investigator award from Simons Foundation.
Vortices in rotating superfluid 3He.
Lounasmaa, O V; Thuneberg, E
1999-07-01
In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe. PMID:10393895
Admissible upstream conditions for slender compressible vortices
NASA Technical Reports Server (NTRS)
Liu, C. H.; Krause, E.; Menne, S.
1986-01-01
The influence of the compressibility on the flow in slender vortices is being studied. The dependence of the breakdown of the slender-vortex approximation on the upstream conditions is demonstrated for various Reynolds numbers and Mach numbers. Compatibility conditions, which have to be satisfied if the vortex is to remain slender, are discussed in detail. The general discussions are supplemented by several sample calculations.
Vortices in rotating superfluid 3He
Lounasmaa, Olli V.; Thuneberg, Erkki
1999-01-01
In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe. PMID:10393895
Anomalous Energetics and Dynamics of Moving Vortices
NASA Astrophysics Data System (ADS)
Radzihovsky, Leo
2015-12-01
Motivated by the general problem of moving topological defects in an otherwise ordered state and specifically, by the anomalous dynamics observed in vortex-antivortex annihilation and coarsening experiments in freely suspended smectic-C films, I study the deformation, energetics, and dynamics of moving vortices in an overdamped X Y model and show that their properties are significantly and qualitatively modified by the motion.
Anomalous Energetics and Dynamics of Moving Vortices.
Radzihovsky, Leo
2015-12-11
Motivated by the general problem of moving topological defects in an otherwise ordered state and specifically, by the anomalous dynamics observed in vortex-antivortex annihilation and coarsening experiments in freely suspended smectic-C films, I study the deformation, energetics, and dynamics of moving vortices in an overdamped XY model and show that their properties are significantly and qualitatively modified by the motion. PMID:26705656
Potential vorticity formulation of compressible magnetohydrodynamics.
Arter, Wayne
2013-01-01
Compressible ideal magnetohydrodynamics is formulated in terms of the time evolution of potential vorticity and magnetic flux per unit mass using a compact Lie bracket notation. It is demonstrated that this simplifies analytic solution in at least one very important situation relevant to magnetic fusion experiments. Potentially important implications for analytic and numerical modelling of both laboratory and astrophysical plasmas are also discussed. PMID:23383802
Chiral Self-Gravitating Cosmic Vortices
Rybakov, Yu.P.
2005-06-01
In the framework of general relativity, an exact axisymmetric (vortex) solution of the equations of motion is obtained for the SU(2) symmetric sigma model. This solution is characterized by the topological charge (winding number) and angular deficit. In the linearized approximation, the Lyapunov stability of vortices is proved and the deflection angle of a light ray in the gravitational field of the vortex (gravitational lens effect) is calculated.
Surface Signature of Subsurface-Intensified Vortices
NASA Astrophysics Data System (ADS)
Ciani, D.; Carton, X. J.; Chapron, B.; Bashmachnikov, I.
2014-12-01
The ocean at mesoscale (20-200 km) and submesoscale (0.5-20km) is highly populated by vortices. These recirculating structures are more energetic than the mean flow, they trap water masses from their origin areas and advect them across the ocean, with consequent impact on the 3D distribution of heat and tracers. Mesoscale and submesoscale structures characterize the ocean dynamics both at the sea surface and at intrathermocline depths (0-1500m), and are presently investigated by means of model outputs, in-situ and satellite (surface) data, the latest being the only way to get high resolution and synoptic observations at planetary scale (e.g., thermal-band observations, future altimetric observations given by the SWOT satellite mission). The scientific question arising from this context is related to the role of the ocean surface for inferring informations on mesoscale and submesoscale vortices at depth. This study has also been motivated by the recent detection of subsurface eddies east of the Arabian Peninsula (PHYSINDIEN experiment - 2011).Using analytical models in the frame of the QG theory, we could describe the theoretical altimetric signature of non-drifting and of drifting subsurface eddies. Numerical experiments, using both coupled QG-SQG and primitive equations models, allowed us to investigate the surface expression of intrathermocline eddies interacting with baroclinic currents or evolving under planetary beta-effect. The eddy characteristics (radius, depth, thickness, velocity) were varied, to represent various oceanic examples (Meddies, Swoddies, Reddies, Peddies, Leddies). Idealized simulations with the ROMS model, confirming theoretical estimates, showed that drifting subsurface-intensified vortices can induce dipolar sea level anomalies, up to 3 cm. This result, compatibly with future SWOT measurement accuracies (about 2 cm), is a first step towards systematic and synoptic detection of subsurface vortices.
Gaining (mutual) information about quark/gluon discrimination
NASA Astrophysics Data System (ADS)
Larkoski, Andrew J.; Thaler, Jesse; Waalewijn, Wouter J.
2014-11-01
Discriminating quark jets from gluon jets is an important but challenging problem in jet substructure. In this paper, we use the concept of mutual information to illuminate the physics of quark/gluon tagging. Ideal quark/gluon separation requires only one bit of truth information, so even if two discriminant variables are largely uncorrelated, they can still share the same "truth overlap". Mutual information can be used to diagnose such situations, and thus determine which discriminant variables are redundant and which can be combined to improve performance. Using both parton showers and analytic resummation, we study a two-parameter family of generalized angularities, which includes familiar infrared and collinear (IRC) safe observables like thrust and broadening, as well as IRC unsafe variants like p {/T D } and hadron multiplicity. At leading-logarithmic (LL) order, the bulk of these variables exhibit Casimir scaling, such that their truth overlap is a universal function of the color factor ratio C A /C F . Only at next-to-leading-logarithmic (NLL) order can one see a difference in quark/gluon performance. For the IRC safe angularities, we show that the quark/gluon performance can be improved by combining angularities with complementary angular exponents. Interestingly, LL order, NLL order, Pythia 8, and Herwig++ all exhibit similar correlations between observables, but there are significant differences in the predicted quark/gluon discrimination power. For the IRC unsafe angularities, we show that the mutual information can be calculated analytically with the help of a nonperturbative "weighted-energy function", providing evidence for the complementarity of safe and unsafe observables for quark/gluon discrimination.
Collective Flow signals the Quark Gluon Plasma
NASA Astrophysics Data System (ADS)
Bratkovskaya, E. L.; Bleicher, M.; Greiner, C.; Muronga, A.; Paech, K.; Reiter, M.; Scherer, S.; Soff, S.; Xu, Z.; Zeeb, G.; Zschiesche, D.; Tavares, B.; Portugal, L.; Aguiar, C.; Kodama, T.; Grassi, F.; Hama, Y.; Osada, T.; Sokolowski, O.; Werner, K.; Gallmeister, K.; Cassing, W.; Stöcker, H.
2004-12-01
A critical discussion of the present status of the CERN experiments on charm dynamics and hadron collective flow is given. We emphasize the importance of the flow excitation function from 1 to 50 AṡGeV: here the hydrodynamic model has predicted the collapse of the v1-flow and of the v2-flow at ˜ 10 AṡGeV; at 40 AṡGeV it has been recently observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy we interpret this observation as potential evidence for a first order phase transition at high baryon density ρB. A detailed discussion of the collective flow as a barometer for the equation of state (EoS) of hot dense matter at RHIC follows. Additionally, detailed transport studies show that the away-side jet suppression can only partially (< 50%) be due to hadronic rescattering. We, finally, propose upgrades and second generation experiments at RHIC which inspect the first order phase transition in the fragmentation region, i.e. at μB ≈ 400 MeV (y ≈ 4 - 5), where the collapse of the proton flow should be seen in analogy to the 40 AṡGeV data. The study of Jet-Wake-riding potentials and Bow shocks — caused by jets in the QGP formed at RHIC — can give further information on the equation of state (EoS) and transport coefficients of the Quark Gluon Plasma (QGP).
Collective Flow signals the Quark Gluon Plasma
Bratkovskaya, E.L.; Bleicher, M.; Greiner, C.; Muronga, A.; Paech, K.; Reiter, M.; Scherer, S.; Soff, S.; Xu, Z.; Zeeb, G.; Zschiesche, D.; Tavares, B.; Portugal, L.; Aguiar, C.; Kodama, T.; Grassi, F.; Hama, Y.; Osada, T.; Sokolowski, O.; Werner, K.
2004-12-02
A critical discussion of the present status of the CERN experiments on charm dynamics and hadron collective flow is given. We emphasize the importance of the flow excitation function from 1 to 50 A{center_dot}GeV: here the hydrodynamic model has predicted the collapse of the v1-flow and of the v2-flow at {approx} 10 A{center_dot}GeV; at 40 A{center_dot}GeV it has been recently observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy we interpret this observation as potential evidence for a first order phase transition at high baryon density {rho}B. A detailed discussion of the collective flow as a barometer for the equation of state (EoS) of hot dense matter at RHIC follows. Additionally, detailed transport studies show that the away-side jet suppression can only partially (< 50%) be due to hadronic rescattering. We, finally, propose upgrades and second generation experiments at RHIC which inspect the first order phase transition in the fragmentation region, i.e. at {mu}B {approx_equal} 400 MeV (y {approx_equal} 4 - 5), where the collapse of the proton flow should be seen in analogy to the 40 A{center_dot}GeV data. The study of Jet-Wake-riding potentials and Bow shocks - caused by jets in the QGP formed at RHIC - can give further information on the equation of state (EoS) and transport coefficients of the Quark Gluon Plasma (QGP)
Managing Flap Vortices via Separation Control
NASA Technical Reports Server (NTRS)
Greenblatt, David
2006-01-01
A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management by means of boundary layer separation control. Passive control was achieved using a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressures, was used to predict vortex characteristics based on inviscid rollup relations and vortices trailing the flaps were mapped using a seven-hole probe. Separation control was found to have a marked effect on vortex location, strength, tangential velocity, axial velocity and size over a wide range of angles of attack and control conditions. In general, the vortex trends were well predicted by the inviscid rollup relations. Manipulation of the separated flow near the flap edges exerted significant control over either outboard or inboard edge vortices while producing small lift and moment excursions. Unsteady surface pressures indicated that dynamic separation and attachment control can be exploited to perturb vortices at wavelengths shorter than a typical wingspan. In summary, separation control has the potential for application to time-independent or time-dependent wake alleviation schemes, where the latter can be deployed to minimize adverse effects on ride-quality and dynamic structural loading.
Unsteady vortical structures in porous media flows
NASA Astrophysics Data System (ADS)
Finn, Justin; Apte, Sourabh; Wood, Brian
2011-11-01
The pore scale character of moderate Reynolds number, inertial flow through mono-disperse packed beds of spheres is examined using numerical experiments. Direct numerical simulations are performed for flow through (i) a periodic, 3 × 3 × 6 simple cubic arrangement at Rep = 529 , and (ii) a realistic randomly packed tube containing 326 spheres with dtube /dsp = 5 . 96 at Rep = 600 . At these Reynolds numbers, unsteady vortical regions are dominant features at the pore scale, and can have a profound effect on permeability and dispersion properties at the macro-scale. Despite similar Reynolds numbers and mean void fractions, the vortical structures observed in these two flows are remarkably different. The flow through the arranged packing is characterized by spatially and temporally periodic vortex-ring like structures, while the flow through the random packing contains many elongated helical vortices and a wider spectrum of space and time scales. The sensitive dependence of flow length and time scales and the local pore geometry is investigated using the DNS data. Funding: NSF project #0933857, Inertial Effects in Flow Through Porous Media.
Relative Equilibria of Identical Point Vortices
NASA Astrophysics Data System (ADS)
Aref, Hassan
2006-11-01
The problem of finding relative equilibria of identical point vortices is classical and was considered by Kelvin and J. J. Thomson almost immediately after the model had been introduced by Helmholtz in 1858. At the time relative equilibria of vortices were proposed as models of atoms. Apart from the intrinsic interest of the problem, and its mathematical challenge, such equilibria have been used as models for stationary states of distributed vortices, and have been observed in rotating superfluids, most recently in spectacular images of BECs. Simple equilibria such as regular polygons (both open and centered) were found and analyzed in the 19th century. Double rings and more recently triple rings have been found analytically. However, the numerically known relative equilibria continue to greatly outnumber those that are analytically known. A major numerical exploration was undertaken by Campell & Ziff in 1978 resulting in what is known as the Los Alamos Catalog. We will explore the results in this catalog and what we have learned since then, and present details on the quest for an analytical understanding of these intriguing states.
Two-particle vortices in graphene
NASA Astrophysics Data System (ADS)
Portnoi, Mikhail; Downing, Charles
We show that a pair of two-dimensional massless Dirac-Weyl fermions can form a bound state independently on the sign of the inter-particle interaction potential, as long as this potential decays at large distances faster than Kepler's inverse distance law. The coupling occurs only at the Dirac point, when the charge carriers lose their chirality. These bipartite states must have a non-zero internal angular momentum, meaning that they only exist as stationary vortices. This leads to the emergence of a new type of energetically-favorable quasiparticles: double-charged zero-energy vortices. Their bosonic nature allows condensation and gives rise to Majorana physics without invoking a superconductor. The presence of dark-matter-like silent immobile vortices explains a range of poorly understood experiments in gated graphene structures at low doping. This work was supported by EU H2020 RISE project CoExAN, EU FP7 ITN NOTEDEV and FP7 IRSES project InterNoM.
Self-Similar Compressible Free Vortices
NASA Technical Reports Server (NTRS)
vonEllenrieder, Karl
1998-01-01
Lie group methods are used to find both exact and numerical similarity solutions for compressible perturbations to all incompressible, two-dimensional, axisymmetric vortex reference flow. The reference flow vorticity satisfies an eigenvalue problem for which the solutions are a set of two-dimensional, self-similar, incompressible vortices. These solutions are augmented by deriving a conserved quantity for each eigenvalue, and identifying a Lie group which leaves the reference flow equations invariant. The partial differential equations governing the compressible perturbations to these reference flows are also invariant under the action of the same group. The similarity variables found with this group are used to determine the decay rates of the velocities and thermodynamic variables in the self-similar flows, and to reduce the governing partial differential equations to a set of ordinary differential equations. The ODE's are solved analytically and numerically for a Taylor vortex reference flow, and numerically for an Oseen vortex reference flow. The solutions are used to examine the dependencies of the temperature, density, entropy, dissipation and radial velocity on the Prandtl number. Also, experimental data on compressible free vortex flow are compared to the analytical results, the evolution of vortices from initial states which are not self-similar is discussed, and the energy transfer in a slightly-compressible vortex is considered.
Model flocks in a steady vortical flow.
Baggaley, A W
2015-05-01
We modify the standard Vicsek model to clearly distinguish between intrinsic noise due to imperfect alignment between organisms and extrinsic noise due to fluid motion. We then consider the effect of a steady vortical flow, the Taylor-Green vortex, on the dynamics of the flock, for various flow speeds, with a fixed intrinsic particle speed. We pay particular attention to the morphology of the flow, and quantify its filamentarity. Strikingly, above a critical flow speed there is a pronounced increase in the filamentarity of the flock, when compared to the zero-flow case. This is due to the fact that particles appear confined to areas of low vorticity; a familiar phenomena, commonly seen in the clustering of inertial particles in vortical flows. Hence, the cooperative motion of the particles gives them an effective inertia, which is seen to have a profound effect on the morphology of the flock, in the presence of external fluid motion. Finally, we investigate the angle between the flow and the particles direction of movement and find it follows a power-law distribution. PMID:26066260
Driven motion of vortices in superconductors
Crabtree, G.W.; Leaf, G.K.; Kaper, H.G.; Vinokur, V.M.; Koshelev, A.E.; Braun, D.W.; Levine, D.M.
1995-09-01
The driven motion of vortices in the solid vortex state is analyzed with the time-dependent Ginzburg-Landau equations. In large-scale numerical simulations, carried out on the IBM Scalable POWERparallel (SP) system at Argonne National Laboratory, many hundreds of vortices are followed as they move under the influence of a Lorentz force induced by a transport current in the presence of a planar defect (similar to a twin boundary in YBa{sub 2}CU{sub 3}O{sub 7}). Correlations in the positions and velocities of the vortices in plastic and elastic motion are identified and compared. Two types of plastic motion are observed. Organized plastic motion displaying long-range orientational correlation and shorter-range velocity correlation occurs when the driving forces are small compared to the pinning forces in the twin boundary. Disorganized plastic motion displaying no significant correlation in either the velocities or orientation of the vortex system occurs when the driving and pinning forces axe of the same order.
Model flocks in a steady vortical flow
NASA Astrophysics Data System (ADS)
Baggaley, A. W.
2015-05-01
We modify the standard Vicsek model to clearly distinguish between intrinsic noise due to imperfect alignment between organisms and extrinsic noise due to fluid motion. We then consider the effect of a steady vortical flow, the Taylor-Green vortex, on the dynamics of the flock, for various flow speeds, with a fixed intrinsic particle speed. We pay particular attention to the morphology of the flow, and quantify its filamentarity. Strikingly, above a critical flow speed there is a pronounced increase in the filamentarity of the flock, when compared to the zero-flow case. This is due to the fact that particles appear confined to areas of low vorticity; a familiar phenomena, commonly seen in the clustering of inertial particles in vortical flows. Hence, the cooperative motion of the particles gives them an effective inertia, which is seen to have a profound effect on the morphology of the flock, in the presence of external fluid motion. Finally, we investigate the angle between the flow and the particles direction of movement and find it follows a power-law distribution.
Long term changes in the polar vortices
NASA Astrophysics Data System (ADS)
Braathen, Geir O.
2015-04-01
As the amount of halogens in the stratosphere is slowly declining and the ozone layer slowly recovers it is of interest to see how the meteorological conditions in the vortex develop over the long term since such changes might alter the foreseen ozone recovery. In conjunction with the publication of the WMO Antarctic and Arctic Ozone Bulletins, WMO has acquired the ERA Interim global reanalysis data set for several meteorological parameters. This data set goes from 1979 - present. These long time series of data can be used for several useful studies of the long term development of the polar vortices. Several "environmental indicators" for vortex change have been calculated, and a climatology, as well as trends, for these parameters will be presented. These indicators can act as yardsticks and will be useful for understanding past and future changes in the polar vortices and how these changes affect polar ozone depletion. Examples of indicators are: vortex mean temperature, vortex minimum temperature, vortex mean PV, vortex "importance" (PV*area), vortex break-up time, mean and maximum wind speed. Data for both the north and south polar vortices have been analysed at several isentropic levels from 350 to 850 K. A possible link between changes in PV and sudden stratospheric warmings will be investigated, and the results presented.
Waves and vortices in rotating stratified turbulence
NASA Astrophysics Data System (ADS)
Pouquet, Annick; Herbert, Corentin; Marino, Raffaele; Rosenberg, Duane
2015-04-01
The interactions between vortices and waves is a long-standing problem in fluid turbulence. It can lead to a self-sustaining process that is dominant, for example in pipe flows, and to the prediction of large-scale coherent structures such as baroclinic jets in planetary atmospheres, and it can also be used as a control tool for the onset of turbulence. Similarly, the dynamics of the atmosphere and the ocean is dominated by complex interactions between nonlinear eddies and waves due to a combination of rotation and stratification (characterized respectively by frequencies f and N), as well as shear layers. The waves are faster at large scales, and this leads to a quasi-geostrophic quasi-linear regime in which there is a balance between pressure gradient and the Coriolis and gravity forces. The range of scales in these geophysical flows before dissipation prevails is such that other regimes can arise in which turbulence comes into play, with the eddy turn-over time becoming comparable to the wave period, and for which isotropy recovers for sufficiently high Reynolds numbers. One may decompose the flow-- observational, experimental or numerical, in terms of the normal modes that it supports, i.e. the inertia-gravity waves and the (slow, zero frequency) vortical modes carrying the potential vorticity, thanks to the existence of a small parameter, as for example the fluctuation around a mean flow or the ratio of the wave period to the eddy turn-over time. In this context an ensemble of data sets of rotating stratified turbulence will be analyzed, stemming from accurate direct numerical simulations of the Boussinesq equations at high resolution, up to 40963 grid points, using high-performance computing. These flows all support a constant-flux bi-directional cascade of energy towards both the large scales and the small scales. The parameter space includes the Reynolds number, the Prandtl number(s), and the Rossby and Froude numbers, and a universal response to a variety
Surfzone vorticity in the presence of extreme bathymetric variability
NASA Astrophysics Data System (ADS)
Clark, D.; Elgar, S.; Raubenheimer, B.
2014-12-01
Surfzone vorticity was measured at Duck, NC using a novel 5-m diameter vorticity sensor deployed in 1.75 m water depth. During the 4-week deployment the initially alongshore uniform bathymetry developed 200-m long mega-cusps with alongshore vertical changes of 1.5 m or more. When waves were small and the vorticity sensor was seaward of the surfzone, vorticity variance and mean vorticity varied with the tidally modulated water depth, consistent with a net seaward flux of surfzone-generated vorticity. Vorticity variance increased with incident wave heights up to 2-m. However, vorticity variance remained relatively constant for incident wave heights above 2-m, and suggests that eddy energy may become saturated in the inner surfzone during large wave events. In the presence of mega-cusps the mean vorticity (shear) is often large and generated by bathymetrically controlled rip currents, while vorticity variance remains strongly correlated with the incident wave height. Funded by NSF, ASD(R&E), and WHOI Coastal Ocean Institute.
Large Deviation Statistics of Vorticity Stretching in Isotropic Turbulence
NASA Astrophysics Data System (ADS)
Johnson, Perry; Meneveau, Charles
2015-11-01
A key feature of 3D fluid turbulence is the stretching/re-alignment of vorticity by the action of the strain-rate. It is shown using the cumulant-generating function that cumulative vorticity stretching along a Lagrangian path in isotropic turbulence behaves statistically like a sum of i.i.d. variables. The Cramer function for vorticity stretching is computed from the JHTDB isotropic DNS (Reλ = 430) and compared to those of the finite-time Lyapunov exponents (FTLE) for material deformation. As expected the mean cumulative vorticity stretching is slightly less than that of the most-stretched material line (largest FTLE), due to the vorticity's preferential alignment with the second-largest eigenvalue of strain-rate and the material line's preferential alignment with the largest eigenvalue. However, the vorticity stretching tends to be significantly larger than the second-largest FTLE, and the Cramer functions reveal that the statistics of vorticity stretching fluctuations are more similar to those of largest FTLE. A model Fokker-Planck equation is constructed by approximating the viscous destruction of vorticity with a deterministic non-linear relaxation law matching conditional statistics, while the fluctuations in vorticity stretching are modelled by stochastic noise matching the statistics encoded in the Cramer function. The model predicts a stretched-exponential tail for the vorticity magnitude PDF, with good agreement for the exponent but significant error (30-40%) in the pre-factor. Supported by NSF Graduate Fellowship (DGE-1232825) and NSF Grant CMMI-0941530.
Non-Abelian vortices on a cylinder: Duality between vortices and walls
Eto, Minoru; Fujimori, Toshiaki; Isozumi, Youichi; Nitta, Muneto; Ohashi, Keisuke; Sakai, Norisuke; Ohta, Kazutoshi
2006-04-15
We investigate vortices on a cylinder in supersymmetric non-Abelian gauge theory with hypermultiplets in the fundamental representation. We identify moduli space of periodic vortices and find that a pair of wall-like objects appears as the vortex moduli is varied. Usual domain walls also can be obtained from the single vortex on the cylinder by introducing a twisted boundary condition. We can understand these phenomena as a T duality among D-brane configurations in type II superstring theories. Using this T-duality picture, we find a one-to-one correspondence between the moduli space of non-Abelian vortices and that of kinky D-brane configurations for domain walls.
Low-momentum ghost dressing function and the gluon mass
Boucaud, Ph.; Leroy, J. P.; Le Yaouanc, A.; Micheli, J.; Pene, O.; Gomez, M. E.; Rodriguez-Quintero, J.
2010-09-01
We study the low-momentum ghost propagator Dyson-Schwinger equation in the Landau gauge, assuming for the truncation a constant ghost-gluon vertex, as it is extensively done, and a simple model for a massive gluon propagator. Then, regular Dyson-Schwinger equation solutions (the zero-momentum ghost dressing function not diverging) appear to emerge, and we show the ghost propagator to be described by an asymptotic expression reliable up to the order O(q{sup 2}). That expression, depending on the gluon mass and the zero-momentum Taylor-scheme effective charge, is proven to fit pretty well some low-momentum ghost propagator data [I. L. Bogolubsky, E. M. Ilgenfritz, M. Muller-Preussker, and A. Sternbeck, Phys. Lett. B 676, 69 (2009); Proc. Sci., LAT2007 (2007) 290] from big-volume lattice simulations where the so-called ''simulated annealing algorithm'' is applied to fix the Landau gauge.
Antiangular Ordering of Gluon Radiation in QCD Media
Mehtar-Tani, Yacine; Salgado, Carlos A.; Tywoniuk, Konrad
2011-03-25
We investigate angular and energy distributions of medium-induced gluon emission off a quark-antiquark antenna in the framework of perturbative QCD as an attempt toward understanding, from first principles, jet evolution inside the quark-gluon plasma. In-medium color coherence between emitters, neglected in all previous calculations, leads to a novel mechanism of soft-gluon radiation. The structure of the corresponding spectrum, in contrast with known medium-induced radiation, i.e., off a single emitter, retains some properties of the vacuum case; in particular, it exhibits a soft divergence. However, as opposed to the vacuum, the collinear singularity is regulated by the pair opening angle, leading to a strict angular separation between vacuum and medium-induced radiation, denoted as antiangular ordering. We comment on the possible consequences of this new contribution for jet observables in heavy-ion collisions.
Transverse Flow of Gluon Fields in Heavy Ion Collision
NASA Astrophysics Data System (ADS)
Chen, Guangyao; Fries, Rainer J.
2014-09-01
We describe the dynamics of initial gluon fields in heavy ion collision using a formal recursive solution of the Yang Mills equations and solving for the energy momentum tensor analytically in a boost-invariant setup. We generalize the original McLerran-Venugopalan (MV) model in order to allow for realistic nuclear profiles. This leads to a transverse flow of gluon fields. This flow pattern is inherited by the quark gluon plasma fluid after thermalization. Its most interesting aspect is a rapidity-odd flow component. We show that this rapidity-odd flow does not break boost invariance and that it emerges naturally from the Yang Mills equations. It leads to directed flow of particles and introduces angular momentum to the system.
A study of coherence of soft gluons in hadron jets
NASA Astrophysics Data System (ADS)
Akrawy, M. Z.; Alexander, G.; Allison, J.; Allport, P. P.; Anderson, K. J.; Armitage, J. C.; Arnison, G. T. J.; Ashton, P.; Azuelos, G.; Baines, J. T. M.; Ball, A. H.; Banks, J.; Barker, G. J.; Barlow, R. J.; Batley, J. R.; Becker, J.; Behnke, T.; Bell, K. W.; Bella, G.; Bethke, S.; Biebel, O.; Binder, U.; Bloodworth, I. J.; Bock, P.; Breuker, H.; Brown, R. M.; Brun, R.; Buijs, A.; Burckhart, H. J.; Capiluppi, P.; Carnegie, R. K.; Carter, A. A.; Carter, J. R.; Chang, C. Y.; Charlton, D. G.; Chrin, J. T. M.; Clarke, P. E. L.; Cohen, I.; Collins, W. J.; Conboy, J. E.; Couch, M.; Coupland, M.; Cuffiani, M.; Dado, S.; Dallavalle, G. M.; Debu, P.; Deninno, M. M.; Dieckmann, A.; Dittmar, M.; Dixit, M. S.; Duchovni, E.; Duerdoth, I. P.; Dumas, D. J. P.; El Mamouni, H.; Elcombe, P. A.; Estabrooks, P. G.; Etzion, E.; Fabbri, F.; Farthouat, P.; Fischer, H. M.; Fong, D. G.; French, M. T.; Fukunaga, C.; Gaidot, A.; Ganel, O.; Gary, J. W.; Gascon, J.; Geddes, N. I.; Gee, C. N. P.; Geich-Gimbel, C.; Gensler, S. W.; Gentit, F. X.; Giacomelli, G.; Gibson, V.; Gibson, W. R.; Gillies, J. D.; Goldberg, J.; Goodrick, M. J.; Gorn, W.; Granite, D.; Gross, E.; Grunhaus, J.; Hagedorn, H.; Hagemann, J.; Hansroul, M.; Hargrove, C. K.; Harrus, I.; Hart, J.; Hattersley, P. M.; Hauschild, M.; Hawkes, C. M.; Heflin, E.; Hemingway, R. J.; Heuer, R. D.; Hill, J. C.; Hillier, S. J.; Ho, C.; Hobbs, J. D.; Hobson, P. R.; Hochman, D.; Holl, B.; Homer, R. J.; Hou, S. R.; Howarth, C. P.; Hughes-Jones, R. E.; Humbert, R.; Igo-Kemenes, P.; Ihssen, H.; Imrie, D. C.; Jawahery, A.; Jeffreys, P. W.; Jeremie, H.; Jimack, M.; Jobes, M.; Jones, R. W. L.; Jovanovic, P.; Karlen, D.; Kawagoe, K.; Kawamoto, T.; Kellogg, R. G.; Kennedy, B. W.; Kleinwort, C.; Klem, D. E.; Knop, G.; Kobayashi, T.; Kokott, T. P.; Köpke, L.; Kowalewski, R.; Kreutzmann, H.; Kroll, J.; Kuwano, M.; Kyberd, P.; Lafferty, G. D.; Lamarche, F.; Larson, W. J.; Layter, J. G.; Le Du, P.; Leblanc, P.; Lee, A. M.; Lehto, M. H.; Lellouch, D.; Lennert, P.; Lessard, L.; Levinson, L.; Lloyd, S. L.; Loebinger, F. K.; Lorah, J. M.; Lorazo, B.; Losty, M. J.; Ludwig, J.; Ma, J.; Macbeth, A. A.; Mannelli, M.; Marcellini, S.; Maringer, G.; Martin, A. J.; Martin, J. P.; Mashimo, T.; Mättig, P.; Maur, U.; McMahon, T. J.; McNutt, J. R.; McPherson, A. C.; Meijers, F.; Menszner, D.; Merritt, F. S.; Mes, H.; Michelini, A.; Middleton, R. P.; Mikenberg, G.; Miller, D. J.; Milstene, C.; Minowa, M.; Mohr, W.; Montanari, A.; Mori, T.; Moss, M. W.; Murphy, P. G.; Murray, W. J.; Nellen, B.; Nguyen, H. H.; Nozaki, M.; O'Dowd, A. J. P.; O'Neale, S. W.; O'Neill, B. P.; Oakham, F. G.; Odorici, F.; Ogg, M.; Oh, H.; Oreglia, M. J.; Orito, S.; Pansart, J. P.; Patrick, G. N.; Pawley, S. J.; Pfister, P.; Pilcher, J. E.; Pinfold, J. L.; Plane, D. E.; Poli, B.; Pouladdej, A.; Pritchard, T. W.; Quast, G.; Raab, J.; Redmond, M. W.; Rees, D. L.; Regimbald, M.; Riles, K.; Roach, C. M.; Robins, S. A.; Rollnik, A.; Roney, J. M.; Rossberg, S.; Rossi, A. M.; Routenburg, P.; Runge, K.; Runolfsson, O.; Sanghera, S.; Sansum, R. A.; Sasaki, M.; Saunders, B. J.; Schaile, A. D.; Schaile, O.; Schappert, W.; Scharff-Hansen, P.; Schreiber, S.; Schwarz, J.; Shapira, A.; Shen, B. C.; Sherwood, P.; Simon, A.; Singh, P.; Siroli, G. P.; Skuia, A.; Smith, A. M.; Smith, T. J.; Snow, G. A.; Springer, R. W.; Sproston, M.; Stephens, K.; Stier, H. E.; Ströhmer, R.; Strom, D.; Takeda, H.; Takeshita, T.; Tsukamoto, T.; Turner, M. F.; Tysarczyk-Niemeyer, G.; Van den plas, D.; VanDalen, G. J.; Vasseur, G.; Virtue, C. J.; von der Schmitt, H.; von Krogh, J.; Wagner, A.; Wahl, C.; Ward, C. P.; Ward, D. R.; Waterhouse, J.; Watkins, P. M.; Watson, A. T.; Watson, N. K.; Weber, M.; Weisz, S.; Wells, P. S.; Wermes, N.; Weymann, M.; Wilson, G. W.; Wilson, J. A.; Wingerter, I.; Winterer, V.-H.; Wood, N. C.; Wotton, S.; Wuensch, B.; Wyatt, T. R.; Yaari, R.; Yang, Y.; Yekutieli, G.; Yoshida, T.; Zeuner, W.; Zorn, G. T.; OPAL Collaboration
1990-09-01
We study the inclusive momentum distribution of charged particles in multihadronic events produced in e +e - annihilations at ECM∼ M(Z 0). We find agreement with the analytical formulae for gluon production that include the phenomena of soft gluon interference. Using data from CM energies between 14 and 91 GeV, we study the dependence of the inclusive momentum distribution on the centre of momentum energy. We find that the analytical formulae describe the data over the entire energy range. Both the momentum distribution at a fixed energy and the change with energy are described by QCD shower Monte Carlo's which include either coherent gluon branchings or string fragmentation. Simple incoherent models with independent fragmentation fail to reproduce the energy dependence and momentum spectra.
On effects of multiple gluons in J/ψ hadroproduction
Motyka, Leszek; Sadzikowski, Mariusz
2015-04-10
The three-gluon contribution to J/ψ hadroproduction is calculated within perturbative QCD in the k{sub T}-factorization framework. This mechanism involves double gluon density and enters at a non-leading twist, but it is enhanced at large energies due to large double gluon density at small x. We obtain results for differential p{sub T}-dependent cross-sections for all J/ψ polarisations. The rescattering contribution is found to provide a significant correction to the standard leading twist cross-section at the energies of the Tevatron or the LHC at moderate p{sub T}. We also discuss a possible contribution of the rescattering correction to the anti-shadowing effect for J/ψ production in proton - nucleus collisions.
Worldline calculation of the three-gluon vertex
Ahmadiniaz, N.; Schubert, C.
2012-10-23
The three-gluon vertex is a basic object of interest in nonabelian gauge theory. At the one-loop level, it has been calculated and analyzed by a number of authors. Here we use the worldline formalism to unify the calculations of the scalar, spinor and gluon loop contributions to the one-loop vertex, leading to an extremely compact representation in terms of field strength tensors. We verify its equivalence with previously obtained representations, and explain the relation of its structure to the low-energy effective action. The sum rule found by Binger and Brodsky for the scalar, spinor and gluon loop contributions in the present approach relates to worldline supersymmetry.
Polyakov loop and gluon quasiparticles in Yang-Mills thermodynamics
NASA Astrophysics Data System (ADS)
Ruggieri, M.; Alba, P.; Castorina, P.; Plumari, S.; Ratti, C.; Greco, V.
2012-09-01
We study the interpretation of lattice data about the thermodynamics of the deconfinement phase of SU(3) Yang-Mills theory, in terms of gluon quasiparticles propagating in a background of a Polyakov loop. A potential for the Polyakov loop, inspired by the strong coupling expansion of the QCD action, is introduced; the Polyakov loop is coupled to transverse gluon quasiparticles by means of a gaslike effective potential. This study is useful to identify the effective degrees of freedom propagating in the gluon medium above the critical temperature. A main general finding is that a dominant part of the phase transition dynamics is accounted for by the Polyakov loop dynamics; hence, the thermodynamics can be described without the need for diverging or exponentially increasing quasiparticle masses as T→Tc, at variance respect to standard quasiparticle models.
Zombie Vortices: Angular Momentum Transport and Planetesimal Formation
NASA Astrophysics Data System (ADS)
Barranco, Joseph; Marcus, Philip; Pei, Suyang; Jiang, Chung-Hsiang; Hassanzadeh, Pedram; Lecoanet, Daniel
2014-11-01
Zombie vortices may fill the dead zones of protoplanetary disks, where they may play important roles in star and planet formation. We will investigate this new, purely hydrodynamic instability and explore the conditions necessary to resurrect the dead zone and fill it with large amplitude vortices that may transport angular momentum and allow mass to accrete onto the protostar. One unresolved issue is whether angular momentum transport is mediated via asymmetries in the vortices, vortex-vortex interactions, or acoustic waves launched by the vortices. Vortices may also play a crucial role in the formation of planetesimals, the building blocks of planets. It is still an open question how grains grow to kilometer-size. We will investigate the interactions of dust with vortices generated via our new hydrodynamic instability, and bridge the gap between micron-sized grains and kilometer-sized planetesimals. Supported by NSF AST-1010052.
Numerical studies of the margin of vortices with decaying cores
NASA Technical Reports Server (NTRS)
Liu, G. C.; Ting, L.
1986-01-01
The merging of vortices to a single one is a canonical incompressible viscous flow problem. The merging process begins when the core sizes or the vortices are comparable to their distances and ends when the contour lines of constant vorticity lines are circularized around one center. Approximate solutions to this problem are constructed by adapting the asymptotic solutions for distinct vortices. For the early stage of merging, the next-order terms in the asymptotic solutions are added to the leading term. For the later stage of merging, the vorticity distribution is reinitialized by vortices with overlapping core structures guided by the 'rule of merging' and the velocity of the 'vortex centers' are then defined by a minimum principle. To show the accuracy of the approximate solution, it is compared with the finite-difference solution.
On streamwise vortices in turbulent wakes of cylinders
NASA Astrophysics Data System (ADS)
Bays-Muchmore, B.; Ahmed, A.
1993-02-01
Flow-visualization methods were used to explore the structure of streamwise vortices and their interactions with the von Kármán vortices in the immediate wakes of cylinders. The experiments were conducted in a water tunnel at Reynolds numbers from 330-21 000 based on cylinder diameter. Over this entire range of Reynolds number, pairs of counter-rotating streamwise vortices were observed immediately behind the cylinders, with a mean spanwise spacing of approximately one pair per diameter. The streamwise vortices significantly distorted the von Kármán vortices, but only on their upstream-facing sides. The cylinder near-surface-flow topology was found to include a secondary separation line containing ``dominant-foci structures'' whose spanwise locations correlated with those of the streamwise vortices.
On streamwise vortices in turbulent wakes of cylinders
NASA Astrophysics Data System (ADS)
Bays-Muchmore, B.; Ahmed, A.
1993-02-01
Flow-visualization methods were used to explore the structure of streamwise vortices and their interactions with the von Karman vortices in the immediate wakes of cylinders. The experiments were conducted in a water tunnel at Reynolds numbers from 330-21,000 based on cylinder diameter. Over this entire range of Reynolds number, pairs of counter-rotating streamwise vortices were observed immediately behind the cylinders, with a mean spanwise spacing of approximately one pair per diameter. The streamwise vortices significantly distorted the von Karman vortices, but only on their upstream-facing sides. The cylinder near-surface-flow topology was found to include a secondary separation line containing 'dominant-foci structures' whose spanwise locations correlated with those of the streamwise vortices.
Analysis of LIMS data by potential vorticity inversion
NASA Technical Reports Server (NTRS)
Robinson, Walter A.
1988-01-01
This paper analyzes LIMS data for a minor warming of January 1979 by potential vorticity inversion, to investigate how flows in the middle atmosphere were determined. The inversion problem of calculating the flow from the potential vorticity is solved repeatedly, including and excluding different portions of the potential vorticity, thus revealing which bits of potential vorticity were important in determining the flow at a time and location of interest. The results of the analysis of LIMS data indicate that the middle stratospheric flow is dominated by potential vorticity that is local in height and in latitude, while planetary-scale mesospheric flows are primarily induced by potential vorticity in the stratosphere. A possible explanation for this difference is proposed.
NASA Astrophysics Data System (ADS)
Hassanzadeh, Pedram
Large coherent vortices are abundant in geophysical and astrophysical flows. They play significant roles in the Earth's oceans and atmosphere, the atmosphere of gas giants, such as Jupiter, and the protoplanetary disks around forming stars. These vortices are essentially three-dimensional (3D) and baroclinic, and their dynamics are strongly influenced by the rotation and density stratification of their environments. This work focuses on improving our understanding of the physics of 3D baroclinic vortices in rotating and continuously stratified flows using 3D spectral simulations of the Boussinesq equations, as well as simplified mathematical models. The first chapter discusses the big picture and summarizes the results of this work. In Chapter 2, we derive a relationship for the aspect ratio (i.e., vertical half-thickness over horizontal length scale) of steady and slowly-evolving baroclinic vortices in rotating stratified fluids. We show that the aspect ratio is a function of the Brunt-Vaisala frequencies within the vortex and outside the vortex, the Coriolis parameter, and the Rossby number of the vortex. This equation is basically the gradient-wind equation integrated over the vortex, and is significantly different from the previously proposed scaling laws that find the aspect ratio to be only a function of the properties of the background flow, and independent of the dynamics of the vortex. Our relation is valid for cyclones and anticyclones in either the cyclostrophic or geostrophic regimes; it works with vortices in Boussinesq fluids or ideal gases, and non-uniform background density gradient. The relation for the aspect ratio has many consequences for quasi-equilibrium vortices in rotating stratified flows. For example, cyclones must have interiors more stratified than the background flow (i.e., super-stratified), and weak anticyclones must have interiors less stratified than the background (i.e., sub-stratified). In addition, this equation is useful to
Potential Vorticity as a Diagnostic for the Mars Polar Vortex
NASA Astrophysics Data System (ADS)
McConnochie, T. H.; Conrath, B. J.; Gierasch, P. J.; Banfield, D.; Smith, M. D.
2009-05-01
Polar vortices dominate the dynamics of the winter mid- and polar latitudes in the martian atmosphere as well as in the terrestrial stratosphere. Polar vortices have also been observed on Venus (Taylor, 2002), Jupiter (Orton, 2002), Saturn (Fletcher, 2008), and Titan (Teanby, 2008). Potential vorticity is the analysis quantity of choice for the terrestrial polar vortices because its vertical component distills the most important features of the wind and temperature fields into a single scalar variable; because it is a conserved tracer under adiabatic conditions; because it serves as the medium for Rossby waves; and because steep potential vorticity gradients are observed to be correlated with steep gradients in the concentrations of chemical species. Using potential vorticity derived from Mars Global Surveyor Thermal Emission Spectrometer (TES) temperature soundings, we compare the structure of the martian polar vortices to those of the earth. We find that the northern martian winter polar vortex, just like its terrestrial conterpart, is bounded by a region of very steep potential vorticity gradients and is surrounded by a "surf zone", a region of low potential vorticity and very low potential vorticity gradients. The surf zone concept, as first described for the terrestrial stratosphere by McIntyre and Palmer (1983), implies persistent Rossby wave breaking. In the vicinity of the northern polar vortex, the TES data set provides some examples of local gradient reversals that are suggestive of wave breaking. There is also one case of possible large-scale wave breaking accompanied by an abrupt polar warming. The martian southern polar vortex, unlike its terrestrial counterpart and unlike the northern martian polar vortex, lacks a distinct boundary between the polar vortex and a surf zone. Instead, the potential vorticity field is highly disorganized with local gradient reversals throughout the middle and polar latitudes. In the zonal mean, the southern winter
Vortical superlattices in a gold nanorods' self-assembled monolayer
NASA Astrophysics Data System (ADS)
Xie, Yong; Liang, Yujia; Chen, Dongxue; Wu, Xiaochun; Dai, Luru; Liu, Qian
2014-02-01
This paper describes the novel vortical self-assembly of CTAB-capped gold nanorods. Representative left-hand, radial, and right-hand vortices are shown. Micelles formed by CTAB molecules enhance the organized self-assembly process. The drag force of solvent flow and dynamic vortex flow in the thin solvent layer are thought to be responsible for the final vortical superlattices. FDTD simulation suggests these structures have potential applications in nanofocusing and polarized light response.
Resource Article: Experiments with Vortices in Superfluid Atomic Gases
NASA Astrophysics Data System (ADS)
Anderson, Brian P.
2010-12-01
Observations of quantized vortices in dilute-gas Bose-Einstein condensates were first reported in 1999. Over the next 10 years, more than 70 papers describing experiments involving vortices in superfluid atomic gases were published in scientific journals. This resource article provides a guide to the published experimental studies related to quantized vortices in atomic Bose-Einstein condensates and superfluid Fermi gases. A BibTex-formatted bibliography document listing these published studies is also available electronically.
Quark-Gluon Plasma Model and Origin of Magic Numbers
Ghahramany, N.; Ghanaatian, M.; Hooshmand, M.
2008-04-21
Using Boltzman distribution in a quark-gluon plasma sample it is possible to obtain all existing magic numbers and their extensions without applying the spin and spin-orbit couplings. In this model it is assumed that in a quark-gluon thermodynamic plasma, quarks have no interactions and they are trying to form nucleons. Considering a lattice for a central quark and the surrounding quarks, using a statistical approach to find the maximum number of microstates, the origin of magic numbers is explained and a new magic number is obtained.
Gluon saturation and inclusive production at low transverse momenta
NASA Astrophysics Data System (ADS)
Levin, Eugene
2010-11-01
In this paper we suggest the generalization of kT factorization formula for inclusive gluon production for the dense-dense parton system scattering. It turns out that the soft gluon production with transverse momentum pT is suppressed by an additional Sudakov-like factor that depends on the pT2/Qs2 ratio in good agreement with the first numerical calculation in the color glass condensate approach by J. P. Blaizot, T. Lappi, and Y. Mehtar-Tan.
Quarkonium in a weakly-coupled quark-gluon plasma
Vairo, Antonio
2010-12-22
We report about a recent calculation of the heavy quarkonium mass and decay width in a quark-gluon plasma, whose temperature T and screening mass m{sub D} satisfy the hierarchy m{alpha}{sub s}>>T>>m{alpha}{sub s}{sup 2}>>m{sub D}, m being the heavy-quark mass, up to order m{alpha}{sub s}{sup 5}. The calculation may be relevant to understand the behavior of the {Upsilon}(1S) in a quark-gluon plasma at present-day colliders.
T-Odd Gluon TMDs Inside a Transversely Polarized Hadron
NASA Astrophysics Data System (ADS)
Echevarria, Miguel G.
2016-03-01
We consider the relevant gluon transverse momentum dependent distributions (TMDs) in the spin asymmetries generated by the scattering off transversely polarized hadrons. At large transverse momentum they can be expressed in terms of different collinear distributions, via perturbatively calculable Wilson coefficients. We calculate these coefficients at next-to-leading order, and show that when the small-x limit is taken only one independent function remains for dipole-type gluon TMDs: the so-called spin-dependent odderon. This universal origin for the spin asymmetries is of importance to better understand hadron substructure.
Probing the quark-gluon interaction with hadrons
NASA Astrophysics Data System (ADS)
Sanchis-Alepuz, Hèlios; Williams, Richard
2015-10-01
We present a unified picture of mesons and baryons in the Dyson-Schwinger/Bethe-Salpeter approach, wherein the quark-gluon and quark-(anti)quark interactions follow from a systematic truncation of the QCD effective action and include all its tensor structures. The masses of some of the ground-state mesons and baryons are found to be in reasonable agreement with the expectations of a 'quark-core calculation', suggesting a partial insensitivity to the details of the quark-gluon interaction. However, discrepancies remain in the meson sector, and for excited baryons, that suggest higher order corrections are relevant and should be investigated following the methods outlined herein.
Gluon saturation and inclusive production at low transverse momenta
Levin, Eugene
2010-11-15
In this paper we suggest the generalization of k{sub T} factorization formula for inclusive gluon production for the dense-dense parton system scattering. It turns out that the soft gluon production with transverse momentum p{sub T} is suppressed by an additional Sudakov-like factor that depends on the p{sub T}{sup 2}/Q{sub s}{sup 2} ratio in good agreement with the first numerical calculation in the color glass condensate approach by J. P. Blaizot, T. Lappi, and Y. Mehtar-Tan.
The hard gluon component of the QCD Pomeron
White, A.R.
1996-10-20
The authors argue that deep-inelastic diffractive scaling provides fundamental insight into the QCD Pomeron. The logarithmic scaling violations seen experimentally are in conflict with the scale-invariance of the BFKL Pomeron and with phenomenological two-gluon models. Instead the Pomeron appears as a single gluon at short-distances, indicating the appearance of a Super-Critical phase of Reggeon Field Theory. That the color compensation takes place at a longer distance is consistent with the Pomeron carrying odd color charge parity.
Viscous quark-gluon plasma model through fluid QCD approach
Djun, T. P.; Soegijono, B.; Mart, T.; Handoko, L. T. E-mail: Laksana.tri.handoko@lipi.go.id
2014-09-25
A Lagrangian density for viscous quark-gluon plasma has been constructed within the fluid-like QCD framework. Gauge symmetry is preserved for all terms inside the Lagrangian, except for the viscous term. The transition mechanism from point particle field to fluid field, and vice versa, are discussed. The energy momentum tensor that is relevant to the gluonic plasma having the nature of fluid bulk of gluon sea is derived within the model. By imposing conservation law in the energy momentum tensor, shear viscosity appears as extractable from the equation.
The evolution of the small x gluon TMD
NASA Astrophysics Data System (ADS)
Zhou, Jian
2016-06-01
We study the evolution of the small x gluon transverse momentum dependent (TMD) distribution in the dilute limit. The calculation has been carried out in the Ji-Ma-Yuan scheme using a simple quark target model. As expected, we find that the resulting small x gluon TMD simultaneously satisfies both the Collins-Soper (CS) evolution equation and the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution equation. We thus confirmed the earlier finding that the high energy factorization (HEF) and the TMD factorization should be jointly employed to resum the different type large logarithms in a process where three relevant scales are well separated.
Inviscid to turbulent transition of trailing vortices
NASA Technical Reports Server (NTRS)
Iversen, J. D.
1974-01-01
The characteristics of the plateau region in the vortex system which trails from a lifting wing are discussed. The decay of the vortex due to viscous or turbulent shear is very slow in the plateau so that the maximum tangential speed in the vortices remains nearly constant for some distance downstream of roll-up and then begins to decrease, becoming inversely proportional to the square root of the distance downstream. Mathematical models are developed to analyze the structure of the plateau area. Solutions are obtained for both constant and variable eddy viscosity models.
Nonlinear Generation of Vorticity by Surface Waves.
Filatov, S V; Parfenyev, V M; Vergeles, S S; Brazhnikov, M Yu; Levchenko, A A; Lebedev, V V
2016-02-01
We demonstrate that waves excited on a fluid surface produce local surface rotation owing to hydrodynamic nonlinearity. We examine theoretically the effect and obtain an explicit formula for the vertical vorticity in terms of the surface elevation. Our theoretical predictions are confirmed by measurements of surface motion in a cell with water where surface waves are excited by vertical and harmonic shaking the cell. The experimental data are in good agreement with the theoretical predictions. We discuss physical consequences of the effect. PMID:26894714
On the dynamical influence of ocean eddy potential vorticity fluxes
NASA Astrophysics Data System (ADS)
Maddison, J. R.; Marshall, D. P.; Shipton, J.
2015-08-01
The impact of eddy potential vorticity fluxes on the dynamical evolution of the flow is obscured by the presence of large and dynamically-inert rotational fluxes. However, the decomposition of eddy potential vorticity fluxes into rotational and divergent components is non-unique in a bounded domain and requires the imposition of an additional boundary condition. Here it is proposed to invoke a one-to-one correspondence between divergent eddy potential vorticity fluxes and non-divergent eddy momentum tendencies in the quasi-geostrophic residual-mean equations in order to select a unique divergent eddy potential vorticity flux. The divergent eddy potential vorticity flux satisfies a zero tangential component boundary condition. In a simply connected domain, the resulting divergent eddy potential vorticity flux satisfies a powerful optimality condition: it is the horizontally oriented divergent flux with minimum L2 norm. Hence there is a well-defined sense in which this approach removes as much of the dynamically inactive eddy potential vorticity flux as possible, and extracts an underlying dynamically active divergent eddy potential vorticity flux. It is shown that this approach leads to a divergent eddy potential vorticity flux which has an intuitive physical interpretation, via a direct relationship to the resulting forcing of the mean circulation.
Characteristics of internal vortical structures in a merged turbulent spot†
NASA Astrophysics Data System (ADS)
Makita, Hideharu; Nishizawa, Akira
2001-07-01
Interaction phenomena between two turbulent spots were investigated in a zero pressure-gradient laminar boundary layer. Two types of hotwire rakes, a 16-channel I- and a 30-channel X-probe gave clear instantaneous vortical motion inside the spots, showing that the single spot was an aggregation of many small-scale hairpin vortices accompanied by upwashes and downwashes around their legs. The legs, a pair of counter-rotating longitudinal vortices, were identified by the existence of streaky velocity-defect and -excess regions at the bottom of the spot. As the spot grew downstream, the number of longitudinal vortices increased, though its wingtips were always accompanied by upwashes. When two spots were produced in parallel and merged with each other, the upwash of the low-speed fluid was strongly enhanced in their merged part through the mutual interaction between the longitudinal vortices at their inside wingtips. Resultant unstable inflectional velocity profile gave birth to several spanwise vortices around the top of the merged part. These intensified spanwise vortices conformed the heads of horseshoe vortices and grew larger than those around the head of non-interacting isolated spots. Such strengthened horseshoe vortices possibly maintain their geometric identity to the turbulent boundary layer further downstream and initiate the turbulent bulges in it.
Dynamics of vortices and drift waves: a point vortex model
NASA Astrophysics Data System (ADS)
Leoncini, Xavier; Verga, Alberto
2013-03-01
The complex interactions of localized vortices with waves are investigated using a model of point vortices in the presence of a transverse or longitudinal wave. This simple model shows a rich dynamical behavior including oscillations of a dipole, splitting and merging of two like-circulation vortices, and chaos. The analytical and numerical results of this model have been found to predict under certain conditions, the behavior of more complex systems, such as the vortices of the Charney-Hasegawa-Mima equation, where the presence of waves strongly affects the evolution of large coherent structures.
Drift waves and vortices: a dynamical point vortex model
NASA Astrophysics Data System (ADS)
Leoncini, Xavier; Verga, Alberto
2013-10-01
Interactions of localized vortices with drift waves are investigated using a model of point vortices in the presence of a transverse or longitudinal wave. This simple model shows a rich dynamical behavior including oscillations of a dipole, splitting and merging of two like-circulation vortices, and chaos. The analytical and numerical results of this model have been found to predict under certain conditions, the behavior of more complex systems, such as the vortices of the Charney-Hasegawa-Mima equation, where the presence of waves strongly affects the evolution of large coherent structures.
On the stability of shear-Alfven vortices
Jovanovic, D.; Horton, W.
1993-08-01
Linear stability of shear-Alfven vortices is studied analytically using the Lyapunov method. Instability is demonstrated for vortices belonging to the drift mode, which is a generalization of the standard Hasegawa-Mima vortex to the case of large parallel phase velocities. In the case of the convective-cell mode, short perpendicular-wavelength perturbations are stable for a broad class of vortices. Eventually, instability of convective-cell vortices may occur on the perpendicular scale comparable with the vortex size, but it is followed by a simultaneous excitation of coherent structures with better localization than the original vortex.
On relation between scalar interfaces and vorticity in inviscid flows
NASA Astrophysics Data System (ADS)
Ramesh, O. N.; Patwardhan, Saurabh
2013-11-01
A great variety of applications like pollutant mixing in the atmosphere, mixing of reactants in combustion highlight the importance of passive scalar dynamics in fluid flows. The other dynamically important variable in the study of fluid flow is the vorticity. Vorticity though, unlike a passive scalar, does affect the fluid motion. The dynamics of scalar (linear) and vorticity (non-linear) are governed by the equations which inherently have different characteristics. This paper addresses the question of the faithfulness of representation of vorticity by scalar marker and the motivation for this comes from the experiment of Head and Bandyopadhyay (1981) which showed the existence of coherent vortices by using smoke flow visualization in a turbulent boundary layer. We will show analytically in regions where the molecular diffusion effects are negligible, the vorticity and scalar gradients are orthogonal to each other. The iso- surface of scalar follows the vorticity in an inviscid situation. Also, we will demonstrate that in the case of unsteady burgers vortex and vortex shedding behind a finite circular cylinder, the scalar gradient is orthogonal to vorticity and inner product of vorticity and scalar gradients is zero in regions away from the wall.
Non-Abelian vortices and non-Abelian statistics
Lo, H.; Preskill, J. )
1993-11-15
We study the interactions of non-Abelian vortices in two spatial dimensions. These interactions have novel features, because the Aharonov-Bohm effect enables a pair of vortices to exchange quantum numbers. The cross section for vortex-vortex scattering is typically a multivalued function of the scattering angle. There can be an exchange contribution to the vortex-vortex scattering amplitude that adds coherently with the direct amplitude, even if the two vortices have distinct quantum numbers. Thus two vortices can be indistinguishable'' even though they are not the same.
Observations of Electron Vorticity in the Inner Plasma Sheet
NASA Technical Reports Server (NTRS)
Gurgiolo, C.; Goldstein, M. L.; Vinas, A. F.; Matthaeus, W. H.; Fazakerley, A. N.
2011-01-01
From a limited number of observations it appears that vorticity is a common feature in the inner plasma sheet. With the four Cluster spacecraft and the four PEACE instruments positioned in a tetrahedral configuration, for the first time it is possible to directly estimate the electron fluid vorticity in a space plasma. We show examples of electron fluid vorticity from multiple plasma sheet crossings. These include three time periods when Cluster passed through a reconnection ion diffusion region. Enhancements in vorticity are seen in association with each crossing of the ion diffusion region.
Superconducting resonators with trapped vortices under direct injection of quasiparticles
NASA Astrophysics Data System (ADS)
Nsanzineza, Ibrahim; Patel, Umesh; Dodge, K. R.; McDermott, R. F.; Plourde, B. L. T.
Nonequilibrium quasiparticles and trapped magnetic flux vortices can significantly impact the performance of superconducting microwave resonant circuits and qubits at millikelvin temperatures. Quasiparticles result in excess loss, reducing resonator quality factors and qubit lifetimes. Vortices trapped near regions of large microwave currents also contribute excess loss. However, vortices located in current-free areas in the resonator or in the ground plane of a device can actually trap quasiparticles and lead to a reduction in the quasiparticle loss. We will describe experiments involving the controlled trapping of vortices in superconducting resonators with direct injection of quasiparticles using Normal metal-Insulator-Superconductor (NIS)-tunnel junctions.
Enhancing critical current density of cuprate superconductors
Chaudhari, Praveen
2015-06-16
The present invention concerns the enhancement of critical current densities in cuprate superconductors. Such enhancement of critical current densities include using wave function symmetry and restricting movement of Abrikosov (A) vortices, Josephson (J) vortices, or Abrikosov-Josephson (A-J) vortices by using the half integer vortices associated with d-wave symmetry present in the grain boundary.
Acoustical vortices on a Chip for 3D single particle manipulation and vorticity control
NASA Astrophysics Data System (ADS)
Riaud, Antoine; Thomas, Jean-Louis; Bou Matar, Olivier; Baudoin, Michael
Surface acoustic waves offer most of the basic functions required for on-chip actuation of fluids at small scales: efficient flow mixing, integrated pumping, particles separation, droplet displacement, atomization, division and fusion. Nevertheless some more advanced functions such as 3D particles manipulation and vorticity control require the introduction of some specific kind of waves called acoustic vortices. These helical waves propagate spinning around a phase singularity called the dark core. On the one hand, the beam angular momentum can be transferred to the fluid and create point-wise vorticity for confined mixing, and on the other the dark core can trap individual particles in an acoustic well for single object manipulation. In this presentation, I will show how acoustical vortices on-a-chip can be synthesized with a programmable electronics and an array of transducers. I will then highlight how some of their specificities can be used for acoustical tweezing and twisting. This work is supported by ANR Project No. ANR-12-BS09-0021-01 and ANR-12- BS09-0021-02, and Rgion Nord Pas de Calais.
Multiplicity and transverse energy of produced gluon in relativistic heavy ion collision
Xiao Bowen
2005-09-01
We present a simple gluon production picture that is based on the McLerran-Venugopalan model and gluon BFKL evolution in relativistic heavy-ion collision. Results for the multiplicity and transverse energy distribution in both the central and forward rapidity regions for gluon production in early stages of heavy-ion collisions at the LHC are given. Finally, we provide a general qualitative discussion of the consequences of the forward rapidity behavior of produced gluons.
The Weighted GMD Model for multiplicity distributions. Probing gluon production at LHC energies
NASA Astrophysics Data System (ADS)
Wang, W. Y.; Seah, S.; Setianegara, J.; Chan, A. H.; Oh, C. H.
2016-07-01
A new distribution, the Weighted GMD (WGMD) is obtained from the Generalised Multiplicity Distribution (GMD), describing charged-particle multiplicity distributions as the hadronisation products of quark and gluon branching with fluctuations in the initial gluon numbers produced from the collision. The WGMD is shown to describe charged-particle multiplicity distributions in pp collisions at the Large Hadron Collider (LHC), and the average initial gluon number is obtained for Poisson distributed gluon multiplicities.
NASA Astrophysics Data System (ADS)
Gu, Mingyao; Feltham, Graham; Ekmekci, Alis
2014-11-01
When oncoming streams of weak vorticity aligned with the axle axis of a two-wheel landing gear impinge near the forward stagnation point of the wheels, a mechanism for vorticity collection, growth, amplification into discrete large-scale vortices, and shedding was formerly shown to exist. In the current study, the impinging vorticity streams are perpendicular to the axle axis, i.e. in a vertical orientation as opposed to the horizontal orientation before. Experiments are conducted in a recirculating water channel using hydrogen bubble visualization and particle image velocimetry at a Reynolds number of 32,500 (based on the wheel diameter). As with the horizontal orientation, vorticity collection and amplification are observed, but the large-scale vortices thus formed are stretched around the wheel circumference in contrast to being stretched around the wheel sides, as observed for the horizontal orientation. This flow behavior varies with the impingement location of the vorticity streams across the wheel width. Maximum vorticity amplification occurs at a critical impingement location and drastically alters the flow separation along the wheel circumference. In addition, the instantaneous vortical structures are identified and tracked using a Galilean-invariant criterion.
The effect of entrainment on starting vortices
NASA Astrophysics Data System (ADS)
Rosi, Giuseppe; Rival, David
2015-11-01
Recent work shows that vortex detachment behind accelerating plates coincides with when streamlines enclosing the starting vortex (SV) form a full saddle. In the case of a linearly accelerating plate, it can be shown that vorticity-containing mass, and thus the SV's development scale with only dimensionless towed distance, while the SV's circulation scales with the acceleration rate. This results in shear-layer instabilities whose structure is Reynold-number independent, but whose strength scale with Reynolds number. It is hypothesized that the increased strength of the instabilities promotes entrainment, which causes the formation of the full saddle and thereby detachment to occur at an earlier dimensionless towed distance. To test this hypothesis, a circular plate is linearly accelerated from rest to pinch-off with chord-based Reynolds numbers of 103, 104, and 105 at the midpoint of the motion. Planar PIV data is acquired, from which FTLE and enstrophy fields are calculated. Vortex detachment is identified from the dynamics of the FTLE saddles, while the enstrophy fields are used to calculate both the vorticity-containing mass entering from the shear layer and the mass entrained from the quiescent surroundings.
Tomographic PIV Study of Hairpin Vortices
NASA Astrophysics Data System (ADS)
Sabatino, Daniel; Rossmann, Tobias
2014-11-01
Tomographic PIV is used in a free surface water channel to quantify the flow behavior of hairpin vortices that are artificially generated in a laminar boundary layer. Direct injection from a 32:1 aspect ratio slot at low blowing ratios (0 . 1 < BR < 0 . 2) is used to generate an isolated hairpin vortex in a thick laminar boundary layer (485 < Reδ* < 600). Due to the large dynamic range of length and velocity scales (the resulting vortices have advection velocities 5X greater than their tangential velocities), a tailored optical arrangement and specialized post processing techniques are required to fully capture the small-scale behavior and long-time development of the flow field. Hairpin generation and evolution are presented using the λ2 criterion derived from the instantaneous, three-dimensional velocity field. The insight provided by the tomographic data is also compared to the conclusions drawn from 2D PIV and passive scalar visualizations. Finally, the three-dimensional behavior of the measured velocity field is correlated with that of a simultaneously imaged, passive scalar dye that marks the boundary of the injected fluid, allowing the examination of the entrainment behavior of the hairpin. Supported by the National Science Foundation under Grant CBET-1040236.
Large eddy simulation of longitudinal stationary vortices
NASA Astrophysics Data System (ADS)
Sreedhar, Madhu; Ragab, Saad
1994-07-01
The response of longitudinal stationary vortices when subjected to random perturbations is investigated using temporal large-eddy simulation. Simulations are obtained for high Reynolds numbers and at a low subsonic Mach number. The subgrid-scale stress tensor is modeled using the dynamic eddy-viscosity model. The generation of large-scale structures due to centrifugal instability and their subsequent breakdown to turbulence is studied. The following events are observed. Initially, ring-shaped structures appear around the vortex core. These structures are counter-rotating vortices similar to the donut-shaped structures observed in a Taylor-Couette flow between rotating cylinders. These structures subsequently interact with the vortex core resulting in a rapid decay of the vortex. The turbulent kinetic energy increases rapidly until saturation, and then a period of slow decay prevails. During the period of maximum turbulent kinetic energy, the normalized mean circulation profile exhibits a logarithmic region, in agreement with the universal inner profile of Hoffman and Joubert [J. Fluid Mech. 16, 395 (1963)].
Reconnection of vorticity lines and magnetic lines
NASA Technical Reports Server (NTRS)
Greene, John M.
1993-01-01
Magnetic field and fluid vorticity share many features. First, as divergence-free vector fields they are conveniently visualized in terms of their field lines, curves that are everywhere tangent to the field. The lines indicate direction and their density indicates field strength. The question arises of the extent to which the evolution of the fields can be treated in terms of the evolution of their field lines. Newcomb (1958) derived the general conditions on the evolution of vector fields that permit the identification of field lines from one instant to the next. The equations of evolution of the vorticity field and the magnetic field fall within Newcomb's analysis. The dynamics of the flows differ between these two systems, so that geometrically similar phenomena happen in different ways in the two systems. In this paper the geometrical similarities are emphasized. Reconnection will be defined here as evolution in which it is not possible to preserve the global identification of some field lines. There is a close relation between reconnection and the topology of the vector field lines. Nontrivial topology occurs where the field has null points or there are field lines that are closed loops.
Vortices and flux tubes: The crossover
NASA Astrophysics Data System (ADS)
Bracco, A.; Spiegel, E. A.
2012-12-01
The sun has magnetic flux tubes that cause sunspots by locally inhibiting convection near its surface. Jupiter has vortices that make the great red spot and other such blemishes. Why are there no similar vortices on the sun? How is the difference in the two kinds of system controlled by the magnetic Prandtl number? What happens at the crossover between the two behaviors? The transition between velocity and magnetically dominated regimes is the driving question of this work. It should occur somewhere in the enormous range in Prandtl number between the sun and planets like Jupiter. Objects that lie in between these vastly different extremes are Brown Dwarfs that have such low mass that they do not burn hydrogen in their cores. These objects are now being actively observed though there is as yet no direct evidence bearing on the present calculations. Other possibly interesting conditions may arise in certain disks around newborn stars where planetary systems are thought to be forming. These may be cool enough to place them in an interesting parameter range for the competition we describe. Using 2D calculations, we seek a quantitative measure of the relative importance of the two vector fields seen in the calculations, statistical or spectral, topological or structural.
Close relative equilibria of identical point vortices
NASA Astrophysics Data System (ADS)
Dirksen, Tobias; Aref, Hassan
2011-11-01
Via numerical solution of the classical problem of relative equilibria for identical point vortices on the unbounded plane we have found configurations that are very close to the analytically known, centered, symmetrically arranged, nested equilateral triangles. Numerical solutions of this kind were found for 3 n + 1 vortices, where n = 2 , 3 , ... , 30 . A sufficient, although apparently not necessary, condition for this phenomenon of close solutions is that the ``core'' of the configuration is marginally stable, as occurs for a central vortex surrounded by an equilateral triangle. The open, regular heptagon also has this property, and new relative equilibria close to the nested, symmetrically arranged, regular heptagons have been found. The centered regular nonagon is also marginally stable. Again, a new family of close relative equilibria has been found. The closest relative equilibrium pairs occur, however, for symmetrically nested equilateral triangles. The numerical evidence is surveyed and related recent work mentioned. A Letter in Physics of Fluids 23 (2011) 051706 is available. Supported in part by the Danish National Research Foundation through a Niels Bohr visiting professorship.
Dynamics of Quantized Vortices Before Reconnection
NASA Astrophysics Data System (ADS)
Andryushchenko, V. A.; Kondaurova, L. P.; Nemirovskii, S. K.
2016-04-01
The main goal of this paper is to investigate numerically the dynamics of quantized vortex loops, just before the reconnection at finite temperature, when mutual friction essentially changes the evolution of lines. Modeling is performed on the base of vortex filament method using the full Biot-Savart equation. It was discovered that the initial position of vortices and the temperature strongly affect the dependence on time of the minimum distance δ (t) between tips of two vortex loops. In particular, in some cases, the shrinking and collapse of vortex loops due to mutual friction occur earlier than the reconnection, thereby canceling the latter. However, this relationship takes a universal square-root form δ ( t) =√{( κ/2π ) ( t_{*}-t) } at distances smaller than the distances, satisfying the Schwarz reconnection criterion, when the nonlocal contribution to the Biot-Savart equation becomes about equal to the local contribution. In the "universal" stage, the nearest parts of vortices form a pyramid-like structure with angles which neither depend on the initial configuration nor on temperature.
Four vortices on doubly periodic paths
NASA Astrophysics Data System (ADS)
Rott, Nicholas
1994-02-01
Plane vortex configurations in ideal flow are considered for which the total ``mass'' of the vortex strengths, their ``moments,'' and their ``polar moments of inertia'' all vanish. These properties are conserved for all times. The simplest nontrivial realization of such a configuration requires four vortices. For this case, which belongs to the more extended family of four-vortex problems that are known to be integrable [Phys. Fluids 31, 2796 (1989); Phys. Fluids A 2, 1477 (1990)], some simple closed-form results are given. The analysis shows that the paths are periodic in a ``configuration plane'' moving with the vortices as well as in the absolute fluid plane. A ``winding number'' is determined from the analysis, which gives the ratio of the two periods. Patterns of the vortex paths are determined by a program based on the step-by-step integration of the equations of motion, which is—beyond a certain level of the analysis—still the more practical method of solution. Results showing the typical behavior of the motion paths for different winding numbers are presented.
Vortices in superconducting MoGe pentagon
NASA Astrophysics Data System (ADS)
Ishida, Takekazu; Thanh Huy, Ho; Kato, Masaru; Hayashhi, Masahiko
2013-03-01
Vortices in bulk prefer to form a triangular lattice while a mesoscopic superconductor with a size comparable to coherence length ξ or the magnetic penetration depth λ is quite different so as to create particular configuration of vortices. The behavior of such structures in an external magnetic field is strongly influenced by the boundary conditions. Vortex states in superconducting disk, triangle and square pattern have been extensively studied both theoretically and experimentally [B. J. Baelus et al., Phys. Rev. B 69, 064506 (2004)]. We present vortex structures in MoGe pentagon disks imaged by means of a scanning quantum interference device (SQUID) microscopy [Ho Thanh Huy et al., Physica C, in press; DOI 10.1016/j.physc.2012.03.037.] Systematic measurements allow us to reveal how vortex arrangement evolves with the applied magnetic field. Moreover, we found that shell filling rule is subjected to change when a pinning center is introduced. Numerical calculations of vortex structure in pentagon disks on the basis of the nonlinear Ginzburg-Landau theory reveal that there are good agreement between experimental data and theoretical calculations.
Optimal Free-Stream Vortical Disturbances
NASA Astrophysics Data System (ADS)
Hack, M. J. Philipp
2015-11-01
In boundary layers exposed to moderate levels of free-stream disturbances, natural transition via the exponential amplification of Tollmien-Schlichting waves is bypassed by a more rapid breakdown process. The external disturbances interact with the mean shear and induce the growth of highly energetic streaks, which cause transition to turbulence by virtue of the growth of inviscid secondary instabilities. The relationship between external vortices and boundary-layer perturbations is, however, not entirely understood. The present study provides a rigorous link between the dynamics in the free-stream and inside the boundary layer by computing the optimal free-stream vortical disturbances, i.e. the external disturbances which maximize the energy content of the resulting boundary-layer perturbations. The mathematical framework is based on a semi-norm formulation of the adjoint linearized compressible Navier-Stokes equations in curvilinear coordinates and enables the global analysis of disturbance sensitivity as well as the computation of optimal disturbances in flows with variable density and miscellaneous geometries.
Gluon condensate in a pion superfluid beyond the mean-field approximation
Jiang Yin; Zhuang Pengfei
2011-03-15
We study gluon condensate in a pion superfluid by calculating the equation of state of the system in the Nambu-Jona-Lasinio model. While in mean-field approximation the growing pion condensate leads to an increasing gluon condensate, meson fluctuations reduce the gluon condensate, and the broken scalar symmetry can be smoothly restored at finite isospin density.
Z -peaked excess from heavy gluon decays to vectorlike quarks
NASA Astrophysics Data System (ADS)
Vignaroli, Natascia
2015-06-01
A 3 sigma excess has been recently announced by ATLAS in events with Z -peaked dilepton pairs, jets, and large transverse missing energy. We interpret this finding in the context of composite Higgs/Randall-Sundrum theories. We find that composite Higgs theories with custodial symmetry protection to the Z b b ¯ coupling predict a significant contribution to Z Z b b (and to h h b b ) final states coming from heavy gluon decays to pairs of bottom partner vectorlike quarks. The heavy gluon to vectorlike quark signal is largely accepted by the ATLAS selection if one of the Z bosons in the Z Z b b final state decays leptonically and the other to neutrinos. For a bottom partner of ˜900 GeV , we find that the ATLAS excess can be reproduced by composite Higgs models, in an experimentally allowed parameter space, for heavy gluon masses roughly in a range 1.87-2.15 TeV and for heavy gluon couplings to light quarks within ˜(0.3 - 0.65 )gS . We briefly discuss the implication of this result for future experimental tests.
From classical to quantum saturationin the nuclear gluon distribution
NASA Astrophysics Data System (ADS)
Triantafyllopoulos, D. N.
2005-08-01
We study the gluon content of a large nucleus (i) in the semi-classical McLerran-Venugopalan model and (ii) in the high-energy limit as given by the quantum evolution of the color glass condensate. We give a simple and qualitative description of the Cronin effect and high- pT suppression in proton-nucleus collisions.
Quark and Gluon Orbital Angular Momentum: Where Are We?
NASA Astrophysics Data System (ADS)
Lorcé, Cédric; Liu, Keh-Fei
2016-06-01
The orbital angular momentum of quarks and gluons contributes significantly to the proton spin budget and attracted a lot of attention in the recent years, both theoretically and experimentally. We summarize the various definitions of parton orbital angular momentum together with their relations with parton distributions functions. In particular, we highlight current theoretical puzzles and give some prospects.
Synchrotron contribution to photon emission from quark-gluon plasma
NASA Astrophysics Data System (ADS)
Zakharov, B. G.
2016-08-01
We study the inuence of the magnetic field on the photon emission from the quark-gluon plasma created in AA collisions. We find that even for very optimistic assumption on the magnitude of the magnetic field for noncentral AA collisions the effect of magnetic field is very small.
The gluon mass generation mechanism: A concise primer
NASA Astrophysics Data System (ADS)
Aguilar, A. C.; Binosi, D.; Papavassiliou, J.
2016-04-01
We present a pedagogical overview of the nonperturbative mechanism that endows gluons with a dynamical mass. This analysis is performed based on pure Yang-Mills theories in the Landau gauge, within the theoretical framework that emerges from the combination of the pinch technique with the background field method. In particular, we concentrate on the Schwinger-Dyson equation satisfied by the gluon propagator and examine the necessary conditions for obtaining finite solutions within the infrared region. The role of seagull diagrams receives particular attention, as do the identities that enforce the cancellation of all potential quadratic divergences.We stress the necessity of introducing nonperturbative massless poles in the fully dressed vertices of the theory in order to trigger the Schwinger mechanism, and explain in detail the instrumental role of these poles in maintaining the Becchi-Rouet-Stora-Tyutin symmetry at every step of the mass-generating procedure. The dynamical equation governing the evolution of the gluon mass is derived, and its solutions are determined numerically following implementation of a set of simplifying assumptions. The obtained mass function is positive definite, and exhibits a power law running that is consistent with general arguments based on the operator product expansion in the ultraviolet region. A possible connection between confinement and the presence of an inflection point in the gluon propagator is briefly discussed.
Gluon transport equations with condensate in the small angle approximation
NASA Astrophysics Data System (ADS)
Blaizot, Jean-Paul; Liao, Jinfeng
2016-05-01
We derive the set of kinetic equations that control the evolution of gluons in the presence of a condensate. We show that the dominant singularities remain logarithmic when the scattering involves particles in the condensate. This allows us to define a consistent small angle approximation.
Exploring dynamical gluon mass generation in three dimensions
NASA Astrophysics Data System (ADS)
Cornwall, John M.
2016-01-01
We reexamine the d =3 dynamical gluon mass problem in pure-glue non-Abelian S U (N ) gauge theories, paying particular attention to the observed (in Landau gauge) violation of positivity for the spectral function of the gluon propagator. This is expressed as a large bulge in the propagator at small momentum, due to the d =3 avatar of asymptotic freedom. Mass is defined through m-2=Δ (p =0 ) , where Δ (p ) is the scalar function for the gluon propagator in some chosen gauge; it is not a pole mass and is generally gauge dependent, except in the gauge-invariant pinch technique (PT). We truncate the PT equations with a recently proposed method called the vertex paradigm that automatically satisfies the QED-like Ward identity relating the three-gluon PT vertex function with the PT propagator. The mass is determined by a homogeneous Bethe-Salpeter equation involving this vertex and propagator. This gap equation also encapsulates the Bethe-Salpeter equation for the massless scalar excitations, essentially Nambu-Goldstone fields, that necessarily accompany gauge-invariant gluon mass. The problem is to find a good approximate value for m and at the same time explain the bulge, which by itself leads, in the gap equation for the gluon mass, to excessively large values for the mass. Our point is not to give a high-accuracy determination of m but to clarify the way in which the propagator bulge and a fairly accurate estimate of m can coexist, and we use various approximations that illustrate the underlying mechanisms. The most critical point is to satisfy the Ward identity. In the PT we estimate a gauge-invariant dynamical gluon mass of m ≈N g2/(2.48 π ) . We translate these results to the Landau gauge using a background-quantum identity involving a dynamical quantity κ such that m =κ mL , where mL-2≡ΔL(p =0 ) . Given our estimates for m , κ , the relation is fortuitously well satisfied for S U (2 ) lattice data.
NASA Astrophysics Data System (ADS)
Hassanzadeh, Pedram
Large coherent vortices are abundant in geophysical and astrophysical flows. They play significant roles in the Earth's oceans and atmosphere, the atmosphere of gas giants, such as Jupiter, and the protoplanetary disks around forming stars. These vortices are essentially three-dimensional (3D) and baroclinic, and their dynamics are strongly influenced by the rotation and density stratification of their environments. This work focuses on improving our understanding of the physics of 3D baroclinic vortices in rotating and continuously stratified flows using 3D spectral simulations of the Boussinesq equations, as well as simplified mathematical models. The first chapter discusses the big picture and summarizes the results of this work. In Chapter 2, we derive a relationship for the aspect ratio (i.e., vertical half-thickness over horizontal length scale) of steady and slowly-evolving baroclinic vortices in rotating stratified fluids. We show that the aspect ratio is a function of the Brunt-Vaisala frequencies within the vortex and outside the vortex, the Coriolis parameter, and the Rossby number of the vortex. This equation is basically the gradient-wind equation integrated over the vortex, and is significantly different from the previously proposed scaling laws that find the aspect ratio to be only a function of the properties of the background flow, and independent of the dynamics of the vortex. Our relation is valid for cyclones and anticyclones in either the cyclostrophic or geostrophic regimes; it works with vortices in Boussinesq fluids or ideal gases, and non-uniform background density gradient. The relation for the aspect ratio has many consequences for quasi-equilibrium vortices in rotating stratified flows. For example, cyclones must have interiors more stratified than the background flow (i.e., super-stratified), and weak anticyclones must have interiors less stratified than the background (i.e., sub-stratified). In addition, this equation is useful to
Towards a theory of stochastic vorticity-augmentation. [tornado model
NASA Technical Reports Server (NTRS)
Liu, V. C.
1977-01-01
A new hypothesis to account for the formation of tornadoes is presented. An elementary one-dimensional theory is formulated for vorticity transfer between an ambient sheared wind and a transverse penetrating jet. The theory points out the relevant quantities to be determined in describing the present stochastic mode of vorticity augmentation.
The vortices in the latticed model of the planar nematic
Khvechshenko, D.V.; Kogan, Y.I.; Nechaev, S.K.
1990-06-01
The vortices in the planar nematic are considered using the field-theoretical description in terms of the Rp{sup 2} {sigma}-model. In the strong-coupling expansion the vortices interactions are considered and the new type of phase transition is obtained in the mean-field approximation.
Separating Internal Waves and Vortical Structure in the Open Ocean
NASA Astrophysics Data System (ADS)
Lauffenburger, N. E.; Sanford, T. B.; Lien, R.
2012-12-01
Deviating from past oceanographic surveys, a new, powerful array of profiling floats has been deployed for three weeks in the Sargasso Sea to monitor the evolving sub-mesoscale field. Using 18-20 EM-APEX floats, profiling to 100 m depth simultaneously, velocity (U and V), temperature, salinity and microstructure measurements (χ) were made on horizontal scales between 100 m and 10 km. This strategy provided a 3-D snapshot of the physical properties every half hour, which significantly reduces temporal aliasing. Area-averaged relative vorticity, vortex stretching, non-linear twisting, horizontal divergence and Ertel's potential vorticity have been computed and projected onto isopycnal surfaces. Since vortical modes carry Ertel's potential vorticity (and internal waves do not), this is a useful step in understanding the energetic contribution of vortical motions to the background internal wave field on small scales. In addition, the temporal material conservation law of Ertel's potential vorticity will be tested for the first time by determining the advection of the floats' measurements relative to the motion of the water parcels and by computing the horizontal gradients of the potential vorticity signal. The three deployments provide data to analyze the interaction of inertial waves, vortical processes and barotropic tides in and out of active frontogenesis.
Vorticity amplification near the stagnation point of landing gear wheels
NASA Astrophysics Data System (ADS)
Feltham, G.; Ekmekci, A.
2014-04-01
The vicinity near the forward stagnation point of landing-gear wheels has been found to support a mechanism for oncoming streams of weak vorticity to collect, grow, and amplify into discrete large-scale vortical structures that then shed with a distinct periodicity. To the authors' knowledge, such a flow phenomenon has never been reported before for landing gear wheels, which are in essence finite (three-dimensional) cylinders. To gain further insight into this phenomenon, a detailed experimental study has been undertaken employing the hydrogen bubble visualization and Particle Image Velocimetry techniques. A very thin platinum wire, similar to those used in hydrogen bubble visualization applications, was placed upstream of the wheel model to produce two streams of weak vorticity (with opposite sign) that convected toward the model. As the vorticity streams enter the stagnation region of the wheels, significant flow deceleration and vorticity stretching act to collect, grow, and amplify the incoming vorticity streams into large-scale vortical structures. Experiments were performed at a fixed Reynolds number, with a value of 32 500 when defined based on the diameter of the wheel and a value of 21 based on the diameter of the vorticity-generating upstream wire. First, to establish a baseline, the natural flow field (without the presence of an upstream wire) was characterized, where experimentally determined values for the stagnation boundary-layer thickness and the velocity profile along the stagnation streamline were both found to agree with the values provided in the literature for two-dimensional cylinders. Subsequently, the dynamics of vorticity collection, growth, amplification, and shedding were studied. The size, stand-off distance and the shedding frequency of the vortical structures forming near the stagnation region were all found to strongly depend on the impingement location of the inbound vorticity on the wheel. A simple relationship between the non
Numerical study of vorticity-enhanced heat transfer
NASA Astrophysics Data System (ADS)
Wang, Xiaolin; Alben, Silas
2013-11-01
Vortices produced by vibrated reeds and flapping foils can improve heat transfer efficiency in electronic hardware. Vortices enhance forced convection by boundary layer separation and thermal mixing in the bulk flow. In this work, we modeled and simulated the fluid flow and temperature in a 2-D channel flow with vortices injected at the upstream boundary. We classified four types of vortex streets depending on the Reynolds number and vortices' strengths and spacings, and studied the different vortex dynamics in each situation. We then used Lagrangian coherent structures (LCS) to study the effect of the vortices on mixing and determined how the Nusselt number and Coefficients of performance vary with flow parameters and Peclet numbers.
Vorticity imbalance and stability in relation to convection
NASA Technical Reports Server (NTRS)
Read, W. L.; Scoggins, J. R.
1977-01-01
A complete synoptic-scale vorticity budget was related to convection storm development in the eastern two-thirds of the United States. The 3-h sounding interval permitted a study of time changes of the vorticity budget in areas of convective storms. Results of analyses revealed significant changes in values of terms in the vorticity equation at different stages of squall line development. Average budgets for all areas of convection indicate systematic imbalance in the terms in the vorticity equation. This imbalance resulted primarily from sub-grid scale processes. Potential instability in the lower troposphere was analyzed in relation to the development of convective activity. Instability was related to areas of convection; however, instability alone was inadequate for forecast purposes. Combinations of stability and terms in the vorticity equation in the form of indices succeeded in depicting areas of convection better than any one item separately.
Kinematical Compatibility Conditions for Vorticity Across Shock Waves
NASA Astrophysics Data System (ADS)
Baty, Roy
2015-11-01
This work develops the general kinematical compatibility conditions for vorticity across arbitrary shock waves in compressible, inviscid fluids. The vorticity compatibility conditions are derived from the curl of the momentum equation using singular distributions defined on two-dimensional shock wave surfaces embedded in three-dimensional flow fields. The singular distributions are represented as generalized differential operators concentrated on moving shock wave surfaces. The derivation of the compatibility conditions for vorticity requires the application of second-order generalized derivatives and elementary tensor algebra. The well-known vorticity jump conditions across a shock wave are then shown to follow from the general kinematical compatibility conditions for vorticity by expressing the flow field velocity in vectorial components normal and tangential to a shock surface.
Vorticity is a marker of right ventricular diastolic dysfunction.
Fenster, Brett E; Browning, James; Schroeder, Joyce D; Schafer, Michal; Podgorski, Chris A; Smyser, Jamie; Silveira, Lori J; Buckner, J Kern; Hertzberg, Jean R
2015-09-15
Right ventricular diastolic dysfunction (RVDD) is an important prognostic indicator in pulmonary arterial hypertension (PAH). RV vortex rings have been observed in healthy subjects, but their significance in RVDD is unknown. Vorticity, the local spinning motion of an element of fluid, may be a sensitive measure of RV vortex dynamics. Using four-dimensional (4D) flow cardiac magnetic resonance imaging (CMR), we investigated the relationship between right heart vorticity with echocardiographic indexes of RVDD. Thirteen (13) PAH subjects and 10 controls underwent same-day 4D flow CMR and echocardiography. RV diastolic function was assessed using trans-tricuspid valve (TV) early (E) and late (A) velocities, E/A ratio, and e' and a' tissue Doppler velocities. RV and right atrial (RA) integrated mean vorticity was calculated for E and A-wave filling periods using 4D datasets. Compared with controls, A-wave vorticity was significantly increased in RVDD subjects in both the RV [2343 (1,559-3,295) vs. 492 (267-2,649) 1/s, P = 0.028] and RA [30 (27-44) vs. 9 (5-27) 1/s, P = 0.005]. RA E vorticity was significantly decreased [13 (7-22) vs. 28 (15-31) 1/s, P = 0.038] in RVDD. E-wave vorticity correlated TV e', E-,and TV E/A (P < 0.05), and A-wave vorticity associated with both TV A and E/A (P < 0.02). RVDD is associated with alterations in E- and A-wave vorticity, and vorticity correlates with multiple echocardiographic markers of RVDD. Vorticity may be a robust noninvasive research tool for the investigation of RV fluid and tissue mechanical interactions in PAH. PMID:26254331
Large-deviation statistics of vorticity stretching in isotropic turbulence
NASA Astrophysics Data System (ADS)
Johnson, Perry L.; Meneveau, Charles
2016-03-01
A key feature of three-dimensional fluid turbulence is the stretching and realignment of vorticity by the action of the strain rate. It is shown in this paper, using the cumulant-generating function, that the cumulative vorticity stretching along a Lagrangian path in isotropic turbulence obeys a large deviation principle. As a result, the relevant statistics can be described by the vorticity stretching Cramér function. This function is computed from a direct numerical simulation data set at a Taylor-scale Reynolds number of Reλ=433 and compared to those of the finite-time Lyapunov exponents (FTLE) for material deformation. As expected, the mean cumulative vorticity stretching is slightly less than that of the most-stretched material line (largest FTLE), due to the vorticity's preferential alignment with the second-largest eigenvalue of strain rate and the material line's preferential alignment with the largest eigenvalue. However, the vorticity stretching tends to be significantly larger than the second-largest FTLE, and the Cramér functions reveal that the statistics of vorticity stretching fluctuations are more similar to those of the largest FTLE. In an attempt to relate the vorticity stretching statistics to the vorticity magnitude probability density function in statistically stationary conditions, a model Kramers-Moyal equation is constructed using the statistics encoded in the Cramér function. The model predicts a stretched-exponential tail for the vorticity magnitude probability density function, with good agreement for the exponent but significant difference (35%) in the prefactor.
Vortices within vortices: Hierarchical vortex structures in experimental, two-dimensional flow
NASA Astrophysics Data System (ADS)
Kelley, Douglas H.; Ouellette, Nicholas T.
2010-03-01
The topology of a fluid flow is concisely described by its critical points (locations of zero flow) and the manifolds (streamlines) that connect them. Streamlines that carry fluid away from a critical point and then return it to the same critical point from another direction are known as homoclinic manifolds. Rare in three-dimensional flow, homoclinic manifolds are common in two-dimensional flow and form unambiguous topological boundaries useful for defining vortex edges. Approximating two-dimensional flow with an electromagnetically driven, stably stratified solution in a 90 cm x 90 cm pan, we use particle tracking to measure the velocity field and locate its critical points and their manifolds. Strikingly, homoclinic manifolds are often nested --- the flow contains vortices within vortices. Its regions can thus be classified by an embedding number, an integer defined as the depth of vortex nesting. We will discuss the dynamics of this hierarchical vortex embedding number, particularly as a function of flow speed (Reynolds number).
Dynamics of coupled vortices in perpendicular field
Jain, Shikha; Novosad, Valentyn Fradin, Frank Y.; Pearson, John E.; Bader, Samuel D.
2014-02-24
We explore the coupling mechanism of two magnetic vortices in the presence of a perpendicular bias field by pre-selecting the polarity combinations using the resonant-spin-ordering approach. First, out of the four vortex polarity combinations (two of which are degenerate), three stable core polarity states are achieved by lifting the degeneracy of one of the states. Second, the response of the stiffness constant for the vortex pair (similar polarity) in perpendicular bias is found to be asymmetric around the zero field, in contrast to the response obtained from a single vortex core. Finally, the collective response of the system for antiparallel core polarities is symmetric around zero bias. The vortex core whose polarization is opposite to the bias field dominates the response.
Dynamic Assembly of Magnetic Colloidal Vortices.
Mohorič, Tomaž; Kokot, Gašper; Osterman, Natan; Snezhko, Alexey; Vilfan, Andrej; Babič, Dušan; Dobnikar, Jure
2016-05-24
Magnetic colloids in external time-dependent fields are subject to complex induced many-body interactions governing their self-assembly into a variety of equilibrium and out-of-equilibrium structures such as chains, networks, suspended membranes, and colloidal foams. Here, we report experiments, simulations, and theory probing the dynamic assembly of superparamagnetic colloids in precessing external magnetic fields. Within a range of field frequencies, we observe dynamic large-scale structures such as ordered phases composed of precessing chains, ribbons, and rotating fluidic vortices. We show that the structure formation is inherently coupled to the buildup of torque, which originates from internal relaxation of induced dipoles and from transient correlations among the particles as a result of short-lived chain formation. We discuss in detail the physical properties of the vortex phase and demonstrate its potential in particle-coating applications. PMID:27128501
Rotation Invariant Vortices for Flow Visualization.
Günther, Tobias; Schulze, Maik; Theisel, Holger
2016-01-01
We propose a new class of vortex definitions for flows that are induced by rotating mechanical parts, such as stirring devices, helicopters, hydrocyclones, centrifugal pumps, or ventilators. Instead of a Galilean invariance, we enforce a rotation invariance, i.e., the invariance of a vortex under a uniform-speed rotation of the underlying coordinate system around a fixed axis. We provide a general approach to transform a Galilean invariant vortex concept to a rotation invariant one by simply adding a closed form matrix to the Jacobian. In particular, we present rotation invariant versions of the well-known Sujudi-Haimes, Lambda-2, and Q vortex criteria. We apply them to a number of artificial and real rotating flows, showing that for these cases rotation invariant vortices give better results than their Galilean invariant counterparts. PMID:26390472
Vortices and strings in a model ecosystem
NASA Astrophysics Data System (ADS)
Tainaka, Kei-Ichi
1994-11-01
We study the spatial pattern formation in a model ecosystem by the position-fixed reaction method. This ecosystem contains three biospecies whose competing powers are cyclic. It is well known that this system is self-organized into a quasistationary state, and that the mean-field approximation (MFA) never predicts such a pattern formation. Recently, several authors applied the pair approximation (PA), and obtained considerable improvements. However, applying PA to our ecosystem fails to yield such an improvement as revealed by computer simulations. The failures of MFA and PA may be attributed to the fact that both approximations neglect a long-range correlation. Thus we introduce the concept of topological defects, such as ``vortices'' or ``strings,'' and demonstrate that the dynamics of these defects can at least qualitatively account for the observed pattern formation dynamics.
Eddies and vortices in ocean basin dynamics
NASA Astrophysics Data System (ADS)
Siegel, A.; Weiss, Jeffrey B.; Toomre, Juri; McWilliams, James C.; Berloff, Pavel S.; Yavneh, Irad
A wind-driven, closed-basin quasi-geostrophic ocean model is computed at very high horizontal resolution to study the effect of increasing Reynolds number (Re) on eddy variability. Five numerical simulations are performed with identical configurations, varying only in horizontal resolution and viscosity coefficient (and therefore Re). Qualitative changes in the structure of eddy variability are evident in the dramatic increase of isolated vortex structures at the highest Re. While the time-mean kinetic energy is relatively independent of Re, the vortex emergence contributes to a continual increase with Re of eddy kinetic energy and meridional vorticity flux. The rate of increase slows somewhat at the highest Re, indicating the possibility of a regime where eddy variability becomes insensitive to further increases in Re.
Computational simulations of vorticity enhanced diffusion
NASA Astrophysics Data System (ADS)
Vold, Erik L.
1999-11-01
Computer simulations are used to investigate a phenomenon of vorticity enhanced diffusion (VED), a net transport and mixing of a passive scalar across a prescribed vortex flow field driven by a background gradient in the scalar quantity. The central issue under study here is the increase in scalar flux down the gradient and across the vortex field. The numerical scheme uses cylindrical coordinates centered with the vortex flow which allows an exact advective solution and 1D or 2D diffusion using simple numerical methods. In the results, the ratio of transport across a localized vortex region in the presence of the vortex flow over that expected for diffusion alone is evaluated as a measure of VED. This ratio is seen to increase dramatically while the absolute flux across the vortex decreases slowly as the diffusion coefficient is decreased. Similar results are found and compared for varying diffusion coefficient, D, or vortex rotation time, τv, for a constant background gradient in the transported scalar vs an interface in the transported quantity, and for vortex flow fields constant in time vs flow which evolves in time from an initial state and with a Schmidt number of order unity. A simple analysis shows that for a small diffusion coefficient, the flux ratio measure of VED scales as the vortex radius over the thickness for mass diffusion in a viscous shear layer within the vortex characterized by (Dτv)1/2. The phenomenon is linear as investigated here and suggests that a significant enhancement of mixing in fluids may be a relatively simple linear process. Discussion touches on how this vorticity enhanced diffusion may be related to mixing in nonlinear turbulent flows.
Persistence of the Lower Stratospheric Polar Vortices
NASA Technical Reports Server (NTRS)
Waugh, Darryn W.; Randel, William J.; Pawson, Steven; Newman, Paul A.; Nash, Eric R.
1999-01-01
The persistence of the Arctic and Antarctic lower stratospheric vortices is examined over the period 1958 to 1998. Three different vortex-following diagnostics (two using potential vorticity and one based solely on the zonal winds) are compared, and shown to give very similar results for the break up date. The variability in the timing of the breakup of each vortex is qualitatively the same: there are large interannual variations together with smaller decadal-scale variations and there is a significant increase in the persistence since the mid-1980s (all variations are larger for the Arctic vortex). Also, in both hemispheres there is a high correlation between the persistence and the strength and coldness of the spring vortex, with all quantities having the same interannual and decadal variability. However, there is no such correlation between the persistence and the characteristics of the mid-winter vortex. In the northern hemisphere there is also a high correlation between the vortex persistence and the upper tropospheric/lower stratospheric eddy heat flux averaged over the two months prior to the breakup. This indicates that the variability in the wave activity entering the stratosphere over late-winter to early-spring plays a key role in the variability of the vortex persistence (and spring polar temperatures) on both interannual and decadal time scales. However, the decadal variation in the Arctic vortex coldness and persistence for the 1990's falls outside the range of natural variability, while this is not the case for the eddy heat flux. This suggests that the recent increase in vortex persistence is not due solely to changes in the wave activity entering the stratosphere.
Fast solver for systems of axisymmetric ring vortices
NASA Astrophysics Data System (ADS)
Strickland, James H.; Amos, Donald E.
1992-03-01
A method that is capable of efficient calculation of the axisymmetric flowfield produced by a large system of ring vortices is presented in this paper. The system of ring vortices can, in turn, be used to model body surfaces and wakes in incompressible unsteady axisymmetric flowfields. This method takes advantage of source-point and field-point series expansion, which enables one to make calculations for interactions between groups of vortices that are in well-separated spatial domains rather than having to consider interactions between every pair of vortices. A FORTRAN computer code, RSOLV, has been written to execute the fast solution technique. For 100 vortices in the field, there is virtually no CPU time savings with the fast solver. For 10,000 vortices in the flow, the fast solver obtains solutions in about 1-3 percent of the time required for the direct solution technique. Formulas for the self-induced velocity of discretized regions of the flowfield have been developed. Use of these formulas allows correct convection of discretized patches of vorticity in the flowfiled.
Structures of the vorticity tube segment in turbulence
NASA Astrophysics Data System (ADS)
Wang, Lipo
2012-04-01
To address the geometrical properties of the turbulent velocity vector field, a new concept named streamtube segment has been developed recently [L. Wang, "On properties of fluid turbulence along streamlines," J. Fluid Mech. 648, 183-203 (2010), 10.1017/S0022112009993041]. According to the vectorial topology, the entire velocity field can be partitioned into the so-called streamtube segments, which are organized in a non-overlapping and space-filling manner. In principle, properties of turbulent fields can be reproduced from those of the decomposed geometrical units with relatively simple structures. A similar idea is implemented to study the turbulent vorticity vector field using the vorticity tube segment structure. Differently from the conventional vortex tubes, vorticity tube segments are space-filling and can be characterized by non-arbitrary parameters, which enables a more quantitative description rather than just an illustrative explanation of turbulence behaviors. From analyzing the direct numerical simulation data, the topological and dynamical properties of vorticity tube segments are explored. The characteristic parameters have strong influence on some conditional statistics, such as the enstrophy production and the probability density function of vorticity stretching. Consequently the common knowledge in turbulence dynamics that vorticity are more stretched than compressed need to be rectified in the vorticity tube segment context.
The motion of point vortices on closed surfaces
Dritschel, D. G.; Boatto, S.
2015-01-01
We develop a mathematical framework for the dynamics of a set of point vortices on a class of differentiable surfaces conformal to the unit sphere. When the sum of the vortex circulations is non-zero, a compensating uniform vorticity field is required to satisfy the Gauss condition (that the integral of the Laplace–Beltrami operator must vanish). On variable Gaussian curvature surfaces, this results in self-induced vortex motion, a feature entirely absent on the plane, the sphere or the hyperboloid. We derive explicit equations of motion for vortices on surfaces of revolution and compute their solutions for a variety of surfaces. We also apply these equations to study the linear stability of a ring of vortices on any surface of revolution. On an ellipsoid of revolution, as few as two vortices can be unstable on oblate surfaces or sufficiently prolate ones. This extends known results for the plane, where seven vortices are marginally unstable (Thomson 1883 A treatise on the motion of vortex rings, pp. 94–108; Dritschel 1985 J. Fluid Mech. 157, 95–134 (doi:10.1017/S0022112088003088)), and the sphere, where four vortices may be unstable if sufficiently close to the equator (Polvani & Dritschel 1993 J. Fluid Mech. 255, 35–64 (doi:10.1017/S0022112093002381)).
Lifetime and layering of vortices in rotating stratified fluids
NASA Astrophysics Data System (ADS)
Aubert, Oriane; Le Bars, Michaël; Le Gal, Patrice
2012-11-01
Ocean and atmosphere are natural stratified fluid layers influenced by the rotation of the planet through the Coriolis force, where it is common to observe long-lived anticyclonic vortices sometimes surrounded by layers of constant density as the ocean Meddies. In the continuity of the experiments of Griffiths & Linden (1981) and Hedstrom & Armi (1988), we reproduce a rotating and linearly stratified layer in a tank where freely-decaying or sustained laboratory anticyclonic vortices are created via a short or continuous injection of isodense fluid. We quantify their long term evolution using PIV measurements. The Rossby number Ro of the freely-decaying vortices decreases in time, which is theoretically described by the energy conservation equations applied to a gaussian model that fits both laboratory and oceanic vortices. Using this theory and numerical simulations, we investigate the respective roles of rotation and stratification to explain the longevity of the vortices. Ro for the sustained vortices remains large and allows for the formation of layers above and below the vortices, following the double-diffusive instability of McIntyre (1970). Typical length and time scales of the instability are well described by a linear stability analysis based on our gaussian model.
Trailing vortices in the wakes of surface-mounted obstacles
NASA Astrophysics Data System (ADS)
Mason, P. J.; Morton, B. R.
1987-02-01
The generation of trailing vortices in the wakes of surface-mounted obstacles at moderate Reynolds numbers is examined by channel-flow experiments and numerical simulation. A skew-mounted obstacle generates a single concentrated trailing vortex, together with weak streamwise vorticity of opposite sense extending to considerable distances on either side and zero gross circulation across the whole stream. Cross-streamed-symmetrical obstacles (having a streamwise plane of symmetry normal to the plane surface) generate one or more nested vortex pairs, usually of alternate sense, of which one pair is normally dominant. The sense of rotation of the dominant vortex pair depends on both the shape of the obstacle and its depth relative to that of the boundary layer. Obstacles that divide the stream laterally produce dominant vortex pairs with a central downwash, whereas those lifting the flow predominantly over their crests produce dominant vortex pairs with a central upwash. It is argued that the vorticity of the dominant trailing vortices is generated largely as a component of cross-stream vorticity at the boundary, shed as a shear layer from the body, and turned inertially by the flow to form trailing vortices. It should also be emphasized that the dominant trailing vortex or vortex pair is generally embedded in a weak distribution of trailing vorticity of opposite signs, but with net circulation comparable with that of the dominant core.
Lifetime and layering of vortices in rotating stratified fluids
NASA Astrophysics Data System (ADS)
Aubert, O.; Le Bars, M.; Le Gal, P.
2012-12-01
Oceans, atmospheres, accretion disks are natural stratified fluid layers that are influenced by the rotation of the planet or the disk through the Coriolis force. There, it is common to observe long-lived anticyclonic vortices such as Jupiter's Great Red Spot, sometimes surrounded by layers of constant density as the ocean Meddies. In the continuity of the experiments of Griffiths & Linden (1981) and Hedstrom & Armi (1988), we reproduce a rotating and linearly stratified environment where freely-decaying or sustained laboratory anticyclonic vortices are created via a short or continuous injection of isodense fluid at mid-depth of the stratified layer. We quantify their long term evolution using PIV measurements to determine their Rossby number Ro at all times. Ro of the freely-decaying vortices decreases in time as seen in Fig. 1. This is theoretically described by the energy conservation equations applied to a gaussian model that fits both laboratory and oceanic vortices. Using this theoretical derivation as well as numerical simulations, we investigate the respective roles of rotation and stratification to explain the longevity of the vortices. Ro of the sustained vortices remains large and allows for the formation of layers above and below the vortices as in Fig. 2, following the double-diffusive instability of McIntyre (1970). Typical length and time scales of the instability are well described by a linear stability analysis based on our gaussian model. Some of these results are applied to natural vortices such as the Meddies or vortices in accretion disks and help to understand their characterictics.; Temporal evolution of Ro for a laboratory freely-decaying vortex (triangle) compared to the theoretical evolution obtained with the gaussian model (solid line). ; Visualization by synthetic Schlieren of layers of constant density above and below a sustained laboratory vortex.
Quark-Gluon Soup -- The Perfectly Liquid Phase of QCD
NASA Astrophysics Data System (ADS)
Heinz, Ulrich
2015-03-01
At temperatures above about 150 MeV and energy densities exceeding 500 MeV/fm3, quarks and gluons exist in the form of a plasma of free color charges that is about 1000 times hotter and a billion times denser than any other plasma ever created in the laboratory. This quark-gluon plasma (QGP) turns out to be strongly coupled, flowing like a liquid. About 35 years ago, the nuclear physics community started a program of relativistic heavy-ion collisions with the goal of producing and studying QGP under controlled laboratory conditions. This article recounts the story of its successful creation in collider experiments at Brookhaven National Laboratory and CERN and the subsequent discovery of its almost perfectly liquid nature, and reports on the recent quantitatively precise determination of its thermodynamic and transport properties.
The physics of hot and dense quark-gluon matter
Kharzeev, Dmitri E
2012-05-10
This technical report describes the work done under the DOE grant DE-FG-88ER41723 (final award number DE-SC0005645), "The physics of hot and dense quark-gluon matter", during the year of 12/01/2010 through 11/30/2011. As planned in the proposal, the performed research focused along two main thrusts: 1) topological effects in hot quark-gluon matter and 2) phenomenology of relativistic heavy ion collisions. The results of research are presented in 12 papers published in reputable refereed journals (Physical Review Letters, Physical Review, Physics Letters and Nuclear Physics). All of the performed research is directly related to the experimental programs of DOE, especially at the Relativistic Heavy Ion Collider. Much of it also has broader interdisciplinary implications - for example, the work on the non-dissipative chiral magnetic current is directly relevant for quantum computing. The attached report describes the performed work in detail.
From quarks and gluons to baryon form factors
Eichmann, Gernot
2012-01-01
I briefly summarize recent results for nucleon and Δ(1232) electromagnetic, axial and transition form factors in the Dyson–Schwinger approach. The calculation of the current diagrams from the quark–gluon level enables a transparent discussion of common features such as: the implications of dynamical chiral symmetry breaking and quark orbital angular momentum, the timelike structure of the form factors, and their interpretation in terms of missing pion-cloud effects. PMID:26766879
Analytic structure of Landau gauge ghost and gluon propagators
NASA Astrophysics Data System (ADS)
Strauss, Stefan; Fischer, Christian S.; Kellermann, Christian
2012-04-01
We summarize first explicit results for the analytic structure of the ghost and gluon propagators in the complex momentum plane. To this end we work in Landau gauge and use a truncation of the Dyson-Schwinger equations for the propagators which is close to lattice results at real spacelike Euclidean momenta. Our results indicate the absence of singularities in the complex part of the momentum plane contrary to expectations from Gribov-Zwanziger-like effective theories.
RHIC AND THE PURSUIT OF THE QUARK-GLUON PLASMA.
MITCHELL,J.T.
2001-07-25
There is a fugitive on the loose. Its name is Quark-Gluon Plasma, alias the QGP. The QGP is a known informant with knowledge about the fundamental building blocks of nature that we wish to extract. This briefing will outline the status of the pursuit of the elusive QGP. We will cover what makes the QGP tick, its modus operandi, details on how we plan to hunt the fugitive down, and our level of success thus far.
Angular correlations in gluon production at high energy
Kovner, Alex; Lublinsky, Michael
2011-02-01
We present a general, model independent argument demonstrating that gluons produced in high energy hadronic collision are necessarily correlated in rapidity and also in the emission angle. The strength of the correlation depends on the process and on the structure/model of the colliding particles. In particular we argue that it is strongly affected (and underestimated) by factorized approximations frequently used to quantify the effect.
Tests of QCD at HERA: determination of the gluon density
Repond, J.
1996-12-31
An overview is given of the various methods available to the colliding beam experiments at HERA to determine the gluon density of the proton. The article includes a description of fits to the structure function F{sub 2}, of studies of dijet and open charm production in deep inelastic scattering, of elastic and inelastic {psi} photoproduction, and of inclusive diffractive scattering. 13 refs., 8 figs.
Observation of "True" Optical Vortices in a Laser System
NASA Astrophysics Data System (ADS)
Barland, S.; Caboche, E.; Genevet, P.; Hachair, X.; Giudici, M.; Pedaci, F.; Tredicce, J. R.
We briefly review a series of experiments performed at the Institut Nonlineaire de Nice on localized structures in semiconductor optical devices. We concentrate our attention on the observation of localized single addressable optical vortices. This type of optical vortices, predicted theoretically more than 30 years ago, have been only observed recently in a system formed by two vertical cavity surface emitter lasers (VCSELs) in a face-to-face configuration. We describe the experimental setup and we discuss the results and the reasons for which such a system is able to display "true" optical vortices.
Kinetic study of ion-acoustic plasma vortices
Khan, S. A.; Aman-ur-Rehman; Mendonca, J. T.
2014-09-15
The kinetic theory of electron plasma waves with finite orbital angular momentum has recently been introduced by Mendonca. This model shows possibility of new kind of plasma waves and instabilities. We have extended the theory to ion-acoustic plasma vortices carrying orbital angular momentum. The dispersion equation is derived under paraxial approximation which exhibits a kind of linear vortices and their Landau damping. The numerical solutions are obtained and compared with analytical results which are in good agreement. The physical interpretation of the ion-acoustic plasma vortices and their Landau resonance conditions are given for typical case of Maxwellian plasmas.
Dynamics of circular arrangements of vorticity in two dimensions
NASA Astrophysics Data System (ADS)
Swaminathan, Rohith V.; Ravichandran, S.; Perlekar, Prasad; Govindarajan, Rama
2016-07-01
The merger of two like-signed vortices is a well-studied problem, but in a turbulent flow, we may often have more than two like-signed vortices interacting. We study the merger of three or more identical corotating vortices initially arranged on the vertices of a regular polygon. At low to moderate Reynolds numbers, we find an additional stage in the merger process, absent in the merger of two vortices, where an annular vortical structure is formed and is long lived. Vortex merger is slowed down significantly due to this. Such annular vortices are known at far higher Reynolds numbers in studies of tropical cyclones, which have been noticed to a break down into individual vortices. In the preannular stage, vortical structures in a viscous flow are found here to tilt and realign in a manner similar to the inviscid case, but the pronounced filaments visible in the latter are practically absent in the former. Five or fewer vortices initially elongate radially, and then reorient their long axis closer to the azimuthal direction so as to form an annulus. With six or more vortices, the initial alignment is already azimuthal. Interestingly at higher Reynolds numbers, the merger of an odd number of vortices is found to proceed very differently from that of an even number. The former process is rapid and chaotic whereas the latter proceeds more slowly via pairing events. The annular vortex takes the form of a generalized Lamb-Oseen vortex (GLO), and diffuses inward until it forms a standard Lamb-Oseen vortex. For lower Reynolds number, the numerical (fully nonlinear) evolution of the GLO vortex follows exactly the analytical evolution until merger. At higher Reynolds numbers, the annulus goes through instabilities whose nonlinear stages show a pronounced difference between even and odd mode disturbances. Here again, the odd mode causes an early collapse of the annulus via decaying turbulence into a single central vortex, whereas the even mode disturbance causes a more
Dynamics of circular arrangements of vorticity in two dimensions.
Swaminathan, Rohith V; Ravichandran, S; Perlekar, Prasad; Govindarajan, Rama
2016-07-01
The merger of two like-signed vortices is a well-studied problem, but in a turbulent flow, we may often have more than two like-signed vortices interacting. We study the merger of three or more identical corotating vortices initially arranged on the vertices of a regular polygon. At low to moderate Reynolds numbers, we find an additional stage in the merger process, absent in the merger of two vortices, where an annular vortical structure is formed and is long lived. Vortex merger is slowed down significantly due to this. Such annular vortices are known at far higher Reynolds numbers in studies of tropical cyclones, which have been noticed to a break down into individual vortices. In the preannular stage, vortical structures in a viscous flow are found here to tilt and realign in a manner similar to the inviscid case, but the pronounced filaments visible in the latter are practically absent in the former. Five or fewer vortices initially elongate radially, and then reorient their long axis closer to the azimuthal direction so as to form an annulus. With six or more vortices, the initial alignment is already azimuthal. Interestingly at higher Reynolds numbers, the merger of an odd number of vortices is found to proceed very differently from that of an even number. The former process is rapid and chaotic whereas the latter proceeds more slowly via pairing events. The annular vortex takes the form of a generalized Lamb-Oseen vortex (GLO), and diffuses inward until it forms a standard Lamb-Oseen vortex. For lower Reynolds number, the numerical (fully nonlinear) evolution of the GLO vortex follows exactly the analytical evolution until merger. At higher Reynolds numbers, the annulus goes through instabilities whose nonlinear stages show a pronounced difference between even and odd mode disturbances. Here again, the odd mode causes an early collapse of the annulus via decaying turbulence into a single central vortex, whereas the even mode disturbance causes a more
Manifestations of vortices during ultracold-atom propagation through waveguides
Bromley, M.W.J.; Esry, B.D.
2004-07-01
The possibility of generating vortices during matter-wave propagation through microstructures is examined. Vortices can arise solely due to wave interference in low-density ultracold atom clouds, and do not require any atom-atom (nonlinear) interactions. The properties of these 'interference vortices' are understood from a simple two-mode model in a straight waveguide. This model is then applied to vortex creation in a circular bend since a circular waveguide bend is one of the simplest atom optical elements that can induce mode excitations. Time-independent and time-dependent analyses are used to investigate vortex creation and dynamics in these systems.
Experiments to Study Photoemission of Electron Bubbles from Quantized Vortices
Konstantinov, Denis; Hirsch, Matthew; Maris, Humphrey J.
2006-09-07
At sufficiently low temperatures, electron bubbles (negative ions) can become trapped on quantized vortices in superfluid helium. Previously, the escape of electron bubbles from vortices by thermal excitation and through quantum tunneling has been studied. In this paper, we report on an experiment in which light is used to release bubbles from quantized vortices (photoemission). A CO2 laser is used to excite the electron from the 1S to the 1P state, and it is found that each time a photon is absorbed there is a small probability that the bubble containing the electron escapes from the vortex.
Gyration eigenfrequencies of vertically coupled vortices in layered magnetic disks
NASA Astrophysics Data System (ADS)
Luo, Y. M.; Zhou, C.; Won, C.; Wu, Y. Z.
2014-12-01
The dynamic properties of vertically coupled vortices in two magnetic nanodisks were studied using numerical simulations and analytical calculations. If the core polarizations of the two vortices are parallel, there exist two distinct normal modes with two distinct eigenfrequencies corresponding to the apparent complex motions of two vortices. Conversely, only a degenerate mode with a single eigenfrequency exists when the cores have opposite polarization. We show that the gyration eigenfrequencies can be tuned by changing the coupling strength, i.e., the separation between the disks. The dependence of the normal modes and the eigenfrequencies on the relative vortex-state configuration can be well understood based on the analytic model.
Stability and nesting of dissipative vortex solitons with high vorticity
NASA Astrophysics Data System (ADS)
Aleksić, B. N.; Aleksić, N. B.; Skarka, V.; Belić, M.
2015-04-01
Using the variational method extended to dissipative systems and numerical simulations, an analytical stability criterion is established allowing the determination of stability domains of parameters for vortices with high topological charge S. Parameters from these domains are used as inputs for numerical self-generation of previously unexplored coexisting stable vortex solitons with topological charge ranging from S =3 to S =20 . The nesting of low-vorticity solitons within those of higher vorticity is discovered. Such a self-organized structuring of light allows for selective dynamic nanophotonic tweezing.
The Gluon Contribution to the Sivers Effect COMPASS results
NASA Astrophysics Data System (ADS)
Kurek, Krzysztof; Szabelski, Adam
2016-02-01
The Sivers effect describes the correlation between the spin of the nucleon and the orbital motion of partons. It can be measured via Semi-Inclusive Deep Inelastic Scattering of lepton on a transversely polarised proton and deuteron targets by determining the azimuthal asymmetry related to the modulation in the Sivers angle ϕSiv. In the paper a method of obtaining the Sivers asymmetry for gluons is presented. It is based on the model of lepton nucleon interactions via three single-photon-exchange processes: photon-gluon fusion (PGF), QCD Compton (QCDC) and leading process (LP). A method of simultaneous extraction of the Sivers asymmetries of the three processes with the use of Monte Carlo (MC) and neural networks (NN) approach is presented. The method has been applied to COMPASS data taken with 160GeV/c muon beam scattered off transversely polarised deuteron and transversely polarised proton target. For each target a data sample of events containing at least two hadrons with large transverse momentum has been selected. Finally the results for gluon Sivers asymmetry were obtained to be: Adg = -0.14 ± 0.15(stat.) ± 0.06(syst.) at
Initial Gluon Multiplicity in Heavy-Ion Collisions
Krasnitz, Alex; Venugopalan, Raju
2001-02-26
The initial gluon multiplicity per unit area per unit rapidity, dN/L{sup 2}/d{eta} , in high energy nuclear collisions, is equal to f{sub N}(g{sup 2}{mu}L) (g{sup 2}{mu}){sup 2}/g{sup 2 } , with {mu}{sup 2} proportional to the gluon density per unit area of the colliding nuclei. For an SU(2) gauge theory, we compute f{sub N}(g{sup 2}{mu}L)=0.14{+-} 0.01 for a wide range in g{sup 2}{mu}L . Extrapolating to SU(3), we predict dN/L{sup 2}/d{eta} for values of g{sup 2}{mu}L relevant to the Relativistic Heavy Ion Collider and the Large Hadron Collider. We compute the initial gluon transverse momentum distribution, dN/L{sup 2}/d{sup 2}k{sub {perpendicular}} , and show it to be well behaved at low k{sub {perpendicular}} .
Bulk Properties and Collective Flow of Quark Gluon Plasma
NASA Astrophysics Data System (ADS)
Kapusta, Joseph
2007-10-01
Quantum Chromodynamics predicts a transition from a hadronic phase at temperatures less than 150-200 MeV to a quark gluon plasma phase at higher temperatures. Lattice calculations show a big increase in the entropy density in this vicinity. Whether the transition is first or second order or a smooth rapid crossover depends upon the values of the up, down and strange quark masses. The goal of the heavy ion experimental program at RHIC is to observe this transition and to study the nature of the quark gluon plasma quantitatively. Two big surprises arose from these experiments: Substantial collective flow has been observed, as evidenced by single-particle transverse momentum distributions and by azimuthal correlations among the produced particles, and the degree to which high energy jets are attenuated in the produced matter. A variety of theoretical models of these collisions require initial energy densities more than a factor of 10 greater than in neutron star cores and more than a factor of 100 greater than within atomic nuclei. Taken together this body of work implies a strongly interacting phase of quarks and gluons beyond the capabilities of perturbation theory. This has motivated approaches based on gauge theories with gravity duals where physical observables may be calculated in a strong coupling limit. This in turn has stimulated interest from members of the string theory community who are currently bringing their expertise to bear on the problem.
Quark and gluon decay functions in QCD and recombination model
Change, V.; Hwa, R.C.
1980-04-01
Inclusive longitudinal-momentum distributions of pions in jets initiated by quarks and gluons are determined in perturbative QCD and recombination model. The quark and antiquark joint distributions in jets are first calculated in the leading-order approximation at high Q/sup 2/. Gluons in the jets are completely converted to quark pairs. From the overall distribution q anti q pairs with definite quantum numbers then recombine to form pions. The recombination function for the process is well determined in the valon model. No adjustable parameters are involved in these calculations, and no data at low Q/sup 2/ are used as phenomenological input. The result for the quark decay functions can be compared with data on e/sup +/e/sup -/ annihilation, and the agreement is very good in both shape and normalization. Predictions for the gluon decay functions are presented, but they cannot yet be checked by experiments. The x and Q/sup 2/ dependences of both types of decay functions have been parametrized in simple form suitable for use in theoretical and experimental applications. 17 figures, 1 table.
Exact kinematics in the small-x evolution of the color dipole and gluon cascade
Motyka, Leszek; Stasto, Anna M.
2009-04-15
The problem of kinematic effects in gluon and color dipole cascades is addressed in the large N{sub c} limit of SU(N{sub c}) Yang-Mills theory. We investigate the tree-level multigluon components of the gluon light-cone wave functions in the light-cone gauge keeping the exact kinematics of the gluon emissions. We focus on the components with all helicities identical to the helicity of the incoming gluon. The recurrence relations for the gluon wave functions are derived. In the case when the virtuality of the incoming gluon is neglected the exact form of the multigluon wave function is obtained. Furthermore, we propose an approximate scheme to treat the kinematic effects in the color dipole evolution kernel. The new kernel entangles longitudinal and transverse degrees of freedom and leads to a reduced diffusion in the impact parameter. When evaluated in the next-to-leading logarithmic (NLL) accuracy, the kernel reproduces the correct form of the double logarithmic terms of the dipole size ratios present in the exact NLL dipole kernel. Finally, we analyze the scattering of the incoming gluon light-cone components off a gluon target and the fragmentation of the scattered state into the final state. The equivalence of the resulting amplitudes and the maximally helicity-violating amplitudes is demonstrated in the special case when the target gluon is far in rapidity from the evolved gluon wave function.
Control of vortical separation on conical bodies
NASA Technical Reports Server (NTRS)
Mourtos, Nikos J.; Roberts, Leonard
1987-01-01
In a variety of aeronautical applications, the flow around conical bodies at incidence is of interest. Such applications include, but are not limited to, highly maneuverable aircraft with delta wings, the aerospace plane and nose portions of spike inlets. The theoretical model used has three parts. First, the single line vortex model is used within the framework of slender body theory, to compute the outer inviscid field for specified separation lines. Next, the three dimensional boundary layer is represented by a momentum equation for the cross flow, analogous to that for a plane boundary layer; a von Karman Pohlhausen approximation is applied to solve this equation. The cross flow separation for both laminar and turbulent layers is determined by matching the pressure at the upper and lower separation points. This iterative procedure yields a unique solution for the separation lines and consequently for the position of the vortices and the vortex lift on the body. Lastly, control of separation is achieved by blowing tangentially from a slot located along a cone generator. It is found that for very small blowing coefficients, the separation can be postponed or suppressedy completely.
Ertel's Potential Vorticity in Unstratified Turbulence.
NASA Astrophysics Data System (ADS)
Herring, J. R.; Kerr, R. M.; Rotunno, R.
1994-01-01
The evolution of Ertel's potential vorticity (PV) is examined in direct numerical simulations (DNS) of decaying turbulence advecting passive scalars and in a generalized Taylor-Green vortex (TGV). It is noted that although PV itself is advected as a passive scalar, its dissipation occurs over all scales and is not concentrated in the velocity or scalar dissipations range. Thus, attempts to invoke cascade arguments to infer an inertial range for PV variance are vitiated. Moreover, for the TGV it is noted that molecular dissipation can create PV from an initial state for which it is everywhere zero. For the random initial value problem, the DNS results suggest a simple characterization of PV dissipation, which implies that for isotropic turbulence (and small Prandtl numbers) PV decays roughly exponentially on a lime scale (L/Urms)R 1/2 , L being the integral scale, urms the large rms velocity, and Rrms, the microscale Reynolds number. The statistics of PV are also examined, and it is noted that it is far from Gaussian, even at modest values of Reynolds number R.
The fate of stratospheric potential vorticity cutoffs
NASA Astrophysics Data System (ADS)
Portmann, Raphael; Crezee, Bas; Quinting, Julian; Wernli, Heini
2016-04-01
Stratospheric cutoffs of potential vorticity (PV) frequently form through non-linear breaking of Rossby waves in mid-latitudes. Through destabilisation of the tropospheric layers beneath, they can trigger convection. Alternatively, through their induced horizontal advection they can produce intense precipitation events near topography and in regions with a background baroclinicity. PV cutoff lifecycles show high variability: their lifetime ranges between 1 and more than 10 days and the end of the lifecycle can occur through diabatic decay - leading to stratosphere-troposphere exchange - or re-absorption by the polar stratospheric reservoir. The relative frequency of these two processes is however unclear, as is the quantitative link between cutoffs and convective and large-scale precipitation. Two case studies are performed by using ECMWF analysis data, backward trajectories and radio soundings to look in detail at the processes involved in the diabatic decay. It is found that latent heating in convective updrafts - and the associated cross-isentropic transport of low PV air - largely explains the diabatic decay of the cutoffs. Using a tracking algorithm we produce an ERA-Interim cutoff climatology that provides information about the statistics of the cutoff lifetime and the relative frequency of stratospheric re-absorption versus diabatic decay. In addition, we track atmospheric stability and total column water beneath the cutoffs in order to investigate why certain cutoffs decay faster than others. The results contribute to a better understanding of the lifecycle of PV cutoffs and a particular process of stratosphere-troposphere exchange.
Potential vorticity patterns in Mediterranean hurricanes
NASA Astrophysics Data System (ADS)
Laviola, Sante; Marcello Miglietta, M.; Cerrai, Diego; Cattani, Elsa; Levizzani, Vincenzo
2016-04-01
Two new variables have been introduced to better identify the potential vorticity (PV) anomalies due to the intrusion of dry stratospheric air from those induced by the diabatic latent heating. This new approach has been applied to the analysis of three Mediterranean tropical-like cyclones characterized by heavy precipitation patterns. Model simulations show that the interaction between an upper level PV streamer, located on the left exit of a jet stream and a middle-low level PV anomaly, induced by the convection development around the low level vortex, plays a key role in the intensification of cyclones in all cases. These anomalies, despite their strong mutual interaction, do not form a fully developed PV tower. In the mature stage, the shape of the upper level PV anomaly around the cyclone is different for each case and appears somehow dependent on the lifetime of the vortex. A first comparison with satellite-derived products seems to confirm the initial results from model simulations.
Spiral inertial waves emitted from geophysical vortices
NASA Astrophysics Data System (ADS)
Wang, Peng; Özgökmen, Tamay M.
2016-03-01
By numerically simulating an initially unstable geophysical vortex, we discover for the first time a special kind of inertial waves, which are emitted in a spiral manner from the vortices; we refer to these waves as spiral inertial waves (SIWs). SIWs appear at small Rossby numbers (0.01 ≤ Ro ≤ 1) according to our parameter sweep experiments; the amplitude, wavelength and frequency of SIWs are sensitive to Rossby numbers. We extend the Lighthill-Ford radiation into inertial waves, and propose an indicator for the emission of inertial waves; this indicator may be adopted into general circulation models to parameterize inertial waves. Additionally, in our tracer releasing experiments, SIWs organize tracers into spirals, and modify the tracer's local rate of change by advecting tracers vertically. Further, the spirals of SIWs resembles some spiral features observed in the ocean and atmosphere, such as spiral ocean eddies and spiral hurricane rainbands; thus, SIWs may offer another mechanism to form spiral eddies and rainbands. Since no density anomaly is required to generate the spirals of SIWs, we infer that the density anomaly, hence the baroclinic or frontal instability, is unlikely to be the key factor in the formation of these spiral features.
Nonparaxial optical vortices and Kummer laser beams
NASA Astrophysics Data System (ADS)
Kovalev, Alexey A.; Kotlyar, Victor V.; Nalimov, Anton G.
2013-09-01
Two approaches to describe nonparaxial optical vortices were considered. One approach is to use a revised Kirchhoff integral, which does not neglect the relief of an optical element. Using this integral and the finite-difference time-domain method it is shown that an optical vortex generated by a refractive spiral plate with a relief step has an asymmetric profile. The annular diffraction pattern in the vortex beam cross-section is found to be disturbed not only for the near-field diffraction but also for the middle-field diffraction, at a distance of several Fresnel lengths. Another approach is to solve the Helmholtz equation without any approximations. An analytical solution to describe propagation of a light beam in the positive direction of the optical axis was found. The complex amplitude of such a beam is found to be in direct proportion to the product of two linearly independent solutions of Kummer's differential equation. Relationships for a particular case of such beams-namely, the Hankel-Bessel (HB) beams-are deduced. The autofocusing of the HB beams is studied.
Magnetic imaging of interlayer Josephson vortices.
Kirtley, J. A.
1999-01-15
The authors have magnetically imaged interlayer Josephson vortices emerging parallel to the planes of single crystals of the organic superconductor {kappa}-(BEDT-TTF){sub 2} Cu(NCS){sub 2}, and the single layer cuprate high-T{sub c} superconductors Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} (Tl-2201) and (Hg,Cu)Ba{sub 2}CuO{sub 6+{delta}} (Hg-1201), using a scanning Superconducting Quantum Interference Device (SQUID) microscope. These images provide a direct measurement of the interlayer penetration depth, which is approximately 63 {micro}m for {kappa}-(BEDT-TTF){sub 2} Cu(NCS){sub 2}, 18 {micro}m for Tl-2201 and 8 {micro}m for Hg-1201. The lengths for the cuprates are about a factor of 10 larger than originally predicted by the interlayer tunneling model for the mechanism of superconductivity in layered compounds, indicating that this mechanism alone cannot account for the high critical temperatures in these materials.
Chirp-driven giant phase space vortices
NASA Astrophysics Data System (ADS)
Trivedi, Pallavi; Ganesh, Rajaraman
2016-06-01
In a collisionless, unbounded, one-dimensional plasma, modelled using periodic boundary conditions, formation of steady state phase space coherent structures or phase space vortices (PSV) is investigated. Using a high resolution one-dimensional Vlasov-Poisson solver based on piecewise-parabolic advection scheme, the formation of giant PSV is addressed numerically. For an infinitesimal external drive amplitude and wavenumber k, we demonstrate the existence of a window of chirped external drive frequency that leads to the formation of giant PSV. The linear, small amplitude, external drive, when chirped, is shown to couple effectively to the plasma and increase both streaming of "untrapped" and "trapped" particle fraction. The steady state attained after the external drive is turned off and is shown to lead to a giant PSV with multiple extrema and phase velocities, with excess density fraction, defined as the deviation from the Maxwellian background, Δ n / n 0 ≃ 20 % - 25 % . It is shown that the process depends on the chirp time duration Δt. The excess density fraction Δn/n0, which contains both trapped and untrapped particle contribution, is also seen to scale with Δt, only inhibited by the gradient of the distribution in velocity space. Both single step drive and multistep chirp processes are shown to lead to steady state giant PSV, with multiple extrema due to embedded holes and clumps, long after the external drive is turned off.
Regularity for steady periodic capillary water waves with vorticity.
Henry, David
2012-04-13
In the following, we prove new regularity results for two-dimensional steady periodic capillary water waves with vorticity, in the absence of stagnation points. Firstly, we prove that if the vorticity function has a Hölder-continuous first derivative, then the free surface is a smooth curve and the streamlines beneath the surface will be real analytic. Furthermore, once we assume that the vorticity function is real analytic, it will follow that the wave surface profile is itself also analytic. A particular case of this result includes irrotational fluid flow where the vorticity is zero. The property of the streamlines being analytic allows us to gain physical insight into small-amplitude waves by justifying a power-series approach. PMID:22393112
Creation and doubling of vortices in intracavity second harmonic generation
NASA Astrophysics Data System (ADS)
Lim, Oo-Kaw; Boland, Brian; Saffman, Mark; Krolikowski, Wieslaw
2004-05-01
Optical vortices are topological objects whose transformation properties under propagation in linear and nonlinear optical media have been the subject of much recent interest. In this work we demonstrate generation and frequency doubling of unit charge vortices in a linear astigmatic resonator. By appropriate alignment of a near confocal cavity we couple a fundamental laser beam at 860nm to a vortical resonator mode. With a nonlinear crystal in the resonator a doubly charged vortex at the second harmonic frequency is generated. Topological instability of the double charge harmonic vortices leads to well separated vortex cores that are shown to rotate and become anisotropic, as the resonator is tuned across resonance. A simple theory that accounts for crystal induced astigmatism agrees well with the experimental measurements.
A numerical study of vorticity-enhanced heat transfer
NASA Astrophysics Data System (ADS)
Wang, Xiaolin; Alben, Silas
2012-11-01
The Glezer lab at Georgia Tech has found that vorticity produced by vibrated reeds can improve heat transfer in electronic hardware. Vortices enhance forced convection by boundary layer separation and thermal mixing in the bulk flow. In this work, we simulate the heat transfer process in a 3-dimensional plate-fin heat sink. We propose a simplified model by considering flow and temperature in a 2-D channel, and extend the model to the third dimension using a 1-D heat fin model. We simulate periodically steady-state solutions. We determine how the global Nusselt number is increased, depending on the vortices' strengths and spacings, in the parameter space of Reynolds and Peclet numbers. We find a surprising spatial oscillation of the local Nusselt number due to the vortices. Support from NSF-DMS grant 1022619 is acknowledged.
Simulations and observations of vortices near Saturn's dayside magnetopause
NASA Astrophysics Data System (ADS)
Walker, Raymond; Fukazawa, Keiichiro; Ogino, Tatsuki; Morozoff, Daniel
We have used a global magnetohydrodynamic simulation of the interaction of the solar wind with Saturn's magnetosphere and Cassini observations to investigate vorticity in the dayside magnetosphere when the interplanetary magnetic field (IMF) is northward. Following the northward turning of the IMF, vortices form on the morning magnetopause in the region of large velocity shear. Later vortices form on the afternoon magnetopause near dusk. In the simulations the boundary vortices cause magnetic field oscillations in the Kronian magnetosphere. The oscillations have a period of about three hours. We have examined Cassini magnetic field observations1 in the morning magnetosphere and find similar oscillations. We will present a comparison between the observations and the simulation results. 1 Daugherty, M. K., S. Kellock, A. P. Slootweg, N. Achilles, S. P. Joy and J. N. Mafi, CASSINI MAG CALIBRATED SUMMARY AVERAGED , CO-E/SWS/J/S-MAG-4-SUMM-AVERAGED-V1.0, NASA Planetary Data System, 2007.
The decay of longitudinal vortices shed from airfoil vortex generators
NASA Technical Reports Server (NTRS)
Wendt, Bruce J.; Reichert, Bruce A.; Foster, Jeffry D.
1995-01-01
An experimental study is conducted to examine the crossplane structure and streamwise decay of vortices shed from airfoil-type vortex generators. The vortex generators are set in a counter-rotating array spanning the full circumference of a straight pipe. The span of the vortex generators above the duct surface, h, is approximately equal to the local turbulent boundary layer thickness, delta. Measurement of three-component mean flow velocity in downstream crossplanes are used to characterize the structure of the shed vortices. Measurements in adjacent crossplanes (closely spaced along the streamwise coordinate) characterize the interaction and decay of the embedded vortices. A model constructed by the superposition of Oseen vortices is compared to the data for one test case.
Comparing the dynamics of skyrmions and superconducting vortices
NASA Astrophysics Data System (ADS)
Olson Reichhardt, C. J.; Lin, S. Z.; Ray, D.; Reichhardt, C.
2014-08-01
Vortices in type-II superconductors have attracted enormous attention as ideal systems in which to study nonequilibrium collective phenomena, since the self-ordering of the vortices competes with quenched disorder and thermal effects. Dynamic effects found in vortex systems include depinning, nonequilibrium phase transitions, creep, structural order-disorder transitions, and melting. Understanding vortex dynamics is also important for applications of superconductors which require the vortices either to remain pinned or to move in a controlled fashion. Recently, topological defects called skyrmions have been realized experimentally in chiral magnets. Here we highlight similarities and differences between skyrmion dynamics and vortex dynamics. Many of the previous ideas and experimental setups that have been applied to superconducting vortices can also be used to study skyrmions. We also discuss some of the differences between the two systems, such as the potentially large contribution of the Magnus force in the skyrmion system that can dramatically alter the dynamics and transport properties.
EFFECTS OF DUST FEEDBACK ON VORTICES IN PROTOPLANETARY DISKS
Fu, Wen; Liang, Edison; Li, Hui; Li, Shengtai; Lubow, Stephen
2014-11-10
We carried out two-dimensional, high-resolution simulations to study the effect of dust feedback on the evolution of vortices induced by massive planets in protoplanetary disks. Various initial dust to gas disk surface density ratios (0.001-0.01) and dust particle sizes (Stokes number 4 × 10{sup –4}-0.16) are considered. We found that while dust particles migrate inward, vortices are very effective at collecting them. When dust density becomes comparable to gas density within the vortex, a dynamical instability is excited and it alters the coherent vorticity pattern and destroys the vortex. This dust feedback effect is stronger with a higher initial dust/gas density ratio and larger dust grain. Consequently, we found that the disk vortex lifetime can be reduced up to a factor of 10. We discuss the implications of our findings on the survivability of vortices in protoplanetary disks and planet formation.
Effects of jets, wakes, and vortices on lifting surfaces
NASA Technical Reports Server (NTRS)
Margason, R. J.
1976-01-01
The interaction of jets, wakes, and vortices on lifting bodies represents a broad spectrum of aerodynamic flow phenomena. A literature survey is presented of 79 research activities in related aerodynamic situations.
Stability of superfluid vortices in dense quark matter
NASA Astrophysics Data System (ADS)
Alford, Mark G.; Mallavarapu, S. Kumar; Vachaspati, Tanmay; Windisch, Andreas
2016-04-01
Superfluid vortices in the color-flavor-locked (CFL) phase of dense quark matter are known to be energetically disfavored relative to well-separated triplets of so-called semi-superfluid color flux tubes. However, the short-range interaction (metastable versus unstable) has not been established. In this paper we perform numerical calculations using the effective theory of the condensate field, mapping the regions in the parameter space of coupling constants where the vortices are metastable versus unstable. For the case of zero-gauge coupling we analytically identify a candidate for the unstable mode and show that it agrees well with the results of the numerical calculations. We find that in the region of the parameter space that seems likely to correspond to real-world CFL quark matter the vortices are unstable, indicating that if such matter exists in neutron star cores it is very likely to contain semi-superfluid color flux tubes rather than superfluid vortices.
A fast solver for systems of axisymmetric ring vortices
NASA Astrophysics Data System (ADS)
Strickland, James H.; Amos, Donald E.
1990-09-01
A method which is capable of efficient calculation of the axisymmetric flow field produced by a large system of ring vortices is presented in this report. The system of ring vortices can, in turn, be used to model body surfaces and wakes in incompressible unsteady axisymmetric flow fields. This method takes advantage of source point and field point series expansions which enables one to make calculations for interactions between groups of vortices which are in well separated spatial domains rather than having to consider interactions between every pair of vortices. In this work, series expansions for the stream function of the ring vortex system are obtained. Such expansions explicitly contain the radial and axial velocity components. A FORTRAN computer code RSOLV has been written to execute the fast solution technique to calculate the stream function and the axial and radial velocity components at points in the flow field. Test cases have been run to optimize the code and to benchmark the truncation errors and CPU time savings associated with the method. Non-dimensional truncation errors for the stream function and total velocity field are on the order of 5 times 10(exp -5) and 3 times 10(exp -3) respectively. Single precision accuracy produces errors in these quantities up to about 1 times 10(exp -5). For 100 vortices in the field, there is virtually no CPU time savings with the fast solver. For 10,000 vortices in the flow, the fast solver obtains solutions in about 1 to 3 percent of the time required for the direct solution technique. Simulations of vortices with square and circular cores were run in order to obtain expressions for the self-induced velocities of such vortices.
NASA Astrophysics Data System (ADS)
Onishchenko, O. G.; Pokhotelov, O. A.; Horton, W.; Scullion, E.; Fedun, V.
2015-12-01
The new type of large-scale vortex structures of dispersionless Alfvén waves in collisionless plasma is investigated. It is shown that Alfvén waves can propagate in the form of Alfvén vortices of finite characteristic radius and characterised by magnetic flux ropes carrying orbital angular momentum. The structure of the toroidal and radial velocity, fluid and magnetic field vorticity, the longitudinal electric current in the plane orthogonal to the external magnetic field are discussed.
Population trends of spanwise vortices in wall turbulence
NASA Astrophysics Data System (ADS)
Wu, Y.; Christensen, K. T.
2006-12-01
The present effort documents the population trends of prograde and retrograde spanwise vortex cores in wall turbulence outside the buffer layer. Large ensembles of instantaneous velocity fields are acquired by particle-image velocimetry in the streamwise wall-normal plane of both turbulent channel flow at Re_tauequiv u_*delta/nu=570, 1185 and 1760 and a zero-pressure-gradient turbulent boundary layer at Re_tau=1400, 2350 and 3450. Substantial numbers of prograde spanwise vortices are found to populate the inner boundary of the log layer of both flows and most of these vortices have structural signatures consistent with the heads of hairpin vortices. In contrast, retrograde vortices are most prominent at the outer edge of the log layer, often nesting near clusters of prograde vortices. Appropriate Reynolds-number scalings for outer- and inner-scaled population densities of prograde and retrograde vortices are determined. However, the Re_tau=570 channel-flow case deviates from these scalings, indicating that it suffers from low-Re effects. When the population densities are recast in terms of fractions of resolved prograde and retrograde spanwise vortices, similarity is observed for 100 {<} y(+ {<} 0.8delta^+) in channel flow and in both flows for 100 {<} y(+ {<} 0.3delta^+) over the Re_tau range studied. The fraction of retrograde vortices increases slightly with Re_tau beyond the log layer in both flows, suggesting that they may play an increasingly important role at higher Reynolds numbers. Finally, while the overall prograde and retrograde population trends of channel flow and the boundary layer show little difference for y {<} 0.45delta, the retrograde populations differ considerably beyond this point, highlighting the influence of the opposing wall in channel flow.
Onishchenko, O. G.; Horton, W.; Scullion, E.; Fedun, V.
2015-12-15
The new type of large-scale vortex structures of dispersionless Alfvén waves in collisionless plasma is investigated. It is shown that Alfvén waves can propagate in the form of Alfvén vortices of finite characteristic radius and characterised by magnetic flux ropes carrying orbital angular momentum. The structure of the toroidal and radial velocity, fluid and magnetic field vorticity, the longitudinal electric current in the plane orthogonal to the external magnetic field are discussed.
Effect of vorticity distribution on the blades on fan noise
NASA Astrophysics Data System (ADS)
Koscso, Gabor
Tests have been performed to determine the connection between noise emission of radial flow fans, impellers, with different inlet design, and vorticity distribution on the blades. An inlet cone protruding into the impeller was found to reduce significantly the radiated sound power level. Measurements showed that for the tested impellers about the duty point corresponding to maximum efficiency, vorticity distribution on the blades has little effect on the sound power level.
Simulating living organisms with populations of point vortices
Schmieder, R.W.
1995-07-01
The author has found that time-averaged images of small populations of point vortices can exhibit motions suggestive of the behavior of individual organisms. As an example, the author shows that collections of point vortices confined in a box and subjected to heating can generate patterns that are broadly similar to interspecies defense in certain sea anemones. It is speculated that other simple dynamical systems can be found to produce similar complex organism-like behavior.
Visualization and Quantification of Rotor Tip Vortices in Helicopter Flows
NASA Technical Reports Server (NTRS)
Kao, David L.; Ahmad, Jasim U.; Holst, Terry L.
2015-01-01
This paper presents an automated approach for effective extraction, visualization, and quantification of vortex core radii from the Navier-Stokes simulations of a UH-60A rotor in forward flight. We adopt a scaled Q-criterion to determine vortex regions and then perform vortex core profiling in these regions to calculate vortex core radii. This method provides an efficient way of visualizing and quantifying the blade tip vortices. Moreover, the vortices radii are displayed graphically in a plane.
Water wave model with accurate dispersion and vertical vorticity
NASA Astrophysics Data System (ADS)
Bokhove, Onno
2010-05-01
Cotter and Bokhove (Journal of Engineering Mathematics 2010) derived a variational water wave model with accurate dispersion and vertical vorticity. In one limit, it leads to Luke's variational principle for potential flow water waves. In the another limit it leads to the depth-averaged shallow water equations including vertical vorticity. Presently, focus will be put on the Hamiltonian formulation of the variational model and its boundary conditions.
3D Zombie Vortices in Rotating Stratified Shear
NASA Astrophysics Data System (ADS)
Marcus, Philip; Pei, Suyang; Jiang, Chung-Hsiang; Hassanzadeh, Pedram; Barranco, Joseph; Lecoanet, Daniel
2013-11-01
We have shown that there is a finite-amplitude instability in linearly-stable, rotating, vertically-stratified, horizontally-shearing flows. The instability is due to excitations of baroclinic critical layers in which the vertical velocity of a neutrally-stable eigenmode is singular in the inviscid limit. This singularity coupled with the Coriolis and stretching terms in the vertical vorticity equation create intense vortex layers. Those layers roll-up into 3D vortices, which then de-stabilize other critical layers. These vortices, which we call zombie vortices, can fill the dead zone of a protoplanetary disk around a forming star. The vortices, either by themselves or by exciting inertio-gravity waves or acoustic waves, can transport angular momentum in a protoplanetary disk and thereby allow a protostar to form into a star. We find that the zombie vortices are similar in flows with Boussinesq, anelastic, and fully compressible equations of state. However, the rates of angular momentum transport and the mechanisms by which it is transported vary significantly in flows with different equations of state.
Orientation and circulation of vortices in a turbulent boundary layer
NASA Astrophysics Data System (ADS)
Gao, Qi; Ortiz-Dueñas, Cecilia; Longmire, Ellen
2007-11-01
The strengths of individual vortices are important in determining the generation and development of surrounding vortices in turbulent boundary layers. The dual-plane PIV data at z^+ = 110 and z/δ = 0.53 in a turbulent boundary layer at Reτ=1160 obtained by Ganapathisubramani et al. (2006) were investigated. 3D swirl strength was used to identify vortex cores. The eigenvector of the velocity gradient tensor was used to determine the orientation of each core, and the resulting eigenvector direction was compared with the average vorticity direction. Circulation of the cores was calculated using the vorticity vector only and using the vorticity vector projected onto the eigenvector. The probability distribution of the angle between the eigenvector and the vorticity vector indicated a peak at 15-20 degrees. The eigenvector angle distributions indicate that at z^+=110, more hairpin legs cross the measurement plane while at z/δ = 0.53, more heads are evident. Details of the orientation and circulation distributions will be discussed in the presentation.
Objective detection of vortices in massively-separated flow
NASA Astrophysics Data System (ADS)
Huang, Yangzi; Hadjighasem, Alireza; Green, Melissa; Haller, George
2015-11-01
We study the formation and shedding of vortices in two vortex-dominated flows around a pitching panel in order to detect coherent structures objectively (i.e., in a frame invariant fashion) in massively-separated flow. We employ a recently developed objective definition and extraction technique for rotationally coherent Lagrangian vortices. This methods renders material vortex boundaries as outermost convex level surfaces of the Lagrangian-Averaged Vorticity Deviation (LAVD), i.e., the trajectory integral of the normed deviation of the vorticity from its spatial mean. We also employ the derivative of the LAVD, the Instantaneous Vorticity Deviation (IVD), to uncover instantaneous Eulerian vortex boundaries in an objective fashion. These Eulerian vortex boundaries, therefore, remain the same in all possible rotating and translating unsteady frames. The multiple methods we use identify and track both leading edge and trailing edge vortices as they form and shed. This helps in describing the relationship between the vortex dynamics and the loss of lift during dynamic stall on a 2D flat plate undergoing a 45 degree pitch-up maneuver. Dr. Jeff Eldredge and his research group at UCLA are gratefully acknowledged for sharing the database of simulation results for the current research. This work was supported by the Air Force Office of Scientific Research under AFOSR Award No. FA9550-14-1.
A Laboratory Study of Vortical Structures in Rotating Convection Plumes
NASA Astrophysics Data System (ADS)
Fu, Hao; Sun, Shiwei; Wang, Yuan; Zhou, Bowen; Thermal Turbulence Research Team
2015-11-01
A laboratory study of the columnar vortex structure in rotating Rayleigh-Bénard convection is conducted. A rectangular water tank is uniformly heated from below and cooled from above, with Ra = (6 . 35 +/- 0 . 77) ×107 , Ta = 9 . 84 ×107 , Pr = 7 . 34 . The columnar vortices are vertically aligned and quasi steady. Two 2D PIV systems were used to measure velocity field. One system performs horizontal scans at 9 different heights every 13.6s, covering 62% of the total depth. The other system scans vertically to obtain the vertical velocity profile. The measured vertical vorticity profiles of most vortices are quasi-linear with height while the vertical velocities are nearly uniform with only a small curvature. A simple model to deduce vertical velocity profile from vertical vorticity profile is proposed. Under quasi-steady and axisymmetric conditions, a ``vortex core'' assumption is introduced to simplify vertical vorticity equation. A linear ODE about vertical velocity is obtained whenever a vertical vorticity profile is given and solved with experimental data as input. The result is approximately in agreement with the measurement. This work was supported by Undergraduates Training Project (J1103410).
The treatment of convected vortices in compressible potential flow
NASA Technical Reports Server (NTRS)
Steinhoff, J.; Ramachandran, K.; Suryanarayanan, K.
1983-01-01
A method is described for incorporating line vortices into the three dimensional compressible potential flow equation. A modified Biot-Savart law is used to compute a vortical velocity field, which is added to the gradient of the potential to form a total velocity. A rapidly converging approximate factorization (AFZ) scheme is then used to compute a potential such that the modified potential flow equation as well as the appropriate boundary conditions, based on total velocity, are satisfied. As part of a coupled iteration procedure, the positions of the line vortices are computed so that they convect with the total flow. The method is used to compute the field due to a single line vortex convecting past a wing. This represents an approximation of the effect of a canard or other lifting surface ahead of the wing, which sheds a tip vortex. It is seen that the flow field is substantially modified by the passage of the vortex. Unlike Euler equation schemes, which are also used to compute these flows, the solutions exhibit no numerical diffusion: The convected vortices retain their initial upstream width. Euler solutions, on the other hand, involve a vorticity which is numerically convected in an Eulerian frame and, unless extensive adaptive grid refinement is used they result in vortices with spread as they convect. Also, the potential flow method requires approximately two orders of magnitude less computing time and much less computer storage than the Euler methods.
Stationary Vortices in Karman Grooves. I.Vortex Growth Rate
NASA Astrophysics Data System (ADS)
Balle, Gregory J.; Kier, Thiemo M.; Breidenthal, Robert E.
1999-11-01
The effect of a stationary vortex on wall fluxes in turbulent flow is predicted by the vortex persistence theory of turbulence. As a first step to test the theory, the feasibility of holding a vortex sufficiently stationary whilst embedded in a turbulent boundary layer is investi gated. Exploiting the stationarity of von Karman vortices in a wake, the dividing stream line is replaced by a wavy wall. Vortex generators are accurately positioned in the valleys (the "Karman grooves") so that the resulting streamwise vortices correspond to those in the vortex street. Complex potential theory predicts stationary points for such vortices, while there are no such points near a flat wall. Flow visualization experiments explore the basic properties of these vortices. In comparison to vortices near a flat plate, the growth rate of the stationary vortex in a Karman groove is reduced dramatically, i.e. by about an order of magnitude. This is consistent with the idea that the stationarity, persistence and growth rate of a turbulent vortex are intimately linked. Passive control of near-wall stream wise vortices is demonstrated, a foundation for the next step, measurement of a wall flux.
A study of the temporal stability of multiple cell vortices
NASA Technical Reports Server (NTRS)
Khorrami, Mehdi R.
1989-01-01
The effect of initial mean velocity field on the stability characteristics of longitudinal vortices is documented in detail. The temporal stability of isolated multiple cell vortices is considered. The types of vortices studied include single cell as well as two and three cell vortices. It is shown that cell multiplicity in the vortex core has drastic effects on the stability characteristics. On the basis of numerical calculations, it is concluded that the growth rates of instabilities in multiple cell vortices are substantially larger (two to threefold increases are observed) than those of a single cell vortex. It is also determined that there is a substantial increase in the effective range of axial and azimuthal wavenumbers where instabilities are present. But most importantly, there is the appearance of a variety of viscous modes of instability. In the case of vortices, these latter instabilities which highlight the importance of viscous forces have never been reported before. These effects are discussed in detail for the case of a two cell vortex.
Quasi-steady linked vortices with chaotic streamlines
NASA Astrophysics Data System (ADS)
Velasco Fuentes, Oscar; Romero Arteaga, Angelica
2010-11-01
We study the dynamics of two or more toroidal filamentary vortices ---i.e. thin tubular vortices coiled on an immaterial torus--- in an otherwise quiescent, ideal fluid. Assuming that the vortices are identical and equally spaced on a meridional section of the torus, the flow evolution depends on the torus aspect ratio (R), the number of vortices (N), and the vortex topology (Vp,q, where p and q are coprime integers such that the Vp,q vortex winds p times round the torus symmetry axis and q times round the torus centerline). The evolution of sets of V1,1 and V1,2 vortices was computed using the Rosenhead--Moore approximation to evaluate the velocity field and a fourth-order Runge-Kutta scheme to advance in time. It was found that vortex sets with N<6 and R<0.15 progressed along and rotated around the torus symmetry axis in an almost steady manner while each vortex in the set approximately preserved its shape. The velocity field, observed in the comoving frame, has two stagnation points. The stream tube starting at the forward stagnation point and the stream tube ending at the backward stagnation point transversely intersect along a finite number of streamlines. The three-dimensional chaotic tangle that arises has a geometry which depends primarily on the number of vortices N.
The structure of intense vorticity in homogeneous isotropic turbulence
NASA Technical Reports Server (NTRS)
Jimenez, J.; Wray, A. A.; Saffman, P. G.; Rogallo, R. S.
1992-01-01
The structure of the intense vorticity regions is studied in numerically simulated homogeneous, isotropic, equilibrium turbulent flow fields at four different Reynolds numbers in the range Re(sub lambda) = 36-171. In accordance with previous investigators, this vorticity is found to be organized in coherent, cylindrical or ribbon-like, vortices ('worms'). A statistical study suggests that they are just especially intense features of the background, O(omega'), vorticity. Their radii scale with the Kolmogorov microscale and their lengths with the integral scale of the flow. An interesting observation is that the Reynolds number based on the circulation of the intense vortices, gamma/nu, increases monotonically with Re(sub lambda), raising the question of the stability of the structures in the limit of Re(sub lambda) approaching infinity. One and two-dimensional statistics of vorticity and strain are presented; they are non-gaussian, and the behavior of their tails depends strongly on the Reynolds number. There is no evidence of convergence to a limiting distribution in our range of Re(sub lambda), even though the energy spectra and the energy dissipation rate show good asymptotic properties in the higher Reynolds number cases. Evidence is presented to show that worms are natural features of the flow and that they do not depend on the particular forcing scheme.
Hidden vortices in a Bose-Einstein condensate in a rotating double-well potential
Wen Linghua; Xiong Hongwei; Wu Biao
2010-11-15
We study vortex formation in a Bose-Einstein condensate in a rotating double-well potential. In addition to the ordinary quantized vortices and elusive ghost vortices, 'hidden' vortices are found distributed along the central barrier. These hidden vortices are invisible like ghost vortices but carry angular momentum. Moreover, their core size is not given by the healing length, but is strongly influenced by the external potential. We find that the Feynman rule can be well satisfied only after including the hidden vortices. There is no critical rotation frequency for the formation of hidden vortices while there is one for the formation of ordinary visible vortices. Hidden vortices can be revealed in the free expansion of Bose-Einstein condensates. In addition, the hidden vortices in a Bose-Einstein condensate can appear in other external potentials, such as a rotating anisotropic toroidal trap.
Evidence for the Absence of Gluon Orbital Angular Momentum in the Nucleon
Brodsky, S.J.; Gardner, S.
2006-08-23
The Sivers mechanism for the single-spin asymmetry in unpolarized lepton scattering from a transversely polarized nucleon is driven by the orbital angular momentum carried by its quark and gluon constituents, combined with QCD final-state interactions. Both quark and gluon mechanisms can generate such a single-spin asymmetry, though only the quark mechanism can explain the small single-spin asymmetry measured by the COMPASS collaboration on the deuteron, suggesting the gluon mechanism is small relative to the quark mechanism. We detail empirical studies through which the gluon and quark orbital angular momentum contributions, quark-flavor by quark-flavor, can be elucidated.
On calculating the potential vorticity flux
Hsu, Pei-Chun; Diamond, P. H.
2015-03-15
We discuss and compare different approaches to calculating the dynamics of anisotropic flow structure formation in quasi two-dimensional turbulence based on potential vorticity (PV) transport in real space. The general structure of the PV flux in the relaxation processes is deduced non-perturbatively. The transport coefficients of the PV flux are then systematically calculated using perturbation theory. We develop two non-perturbative relaxation models: the first is a mean field theory for the dynamics of minimum enstrophy relaxation based on the requirement that the mean flux of PV dissipates total potential enstrophy but conserves total fluid kinetic energy. The results show that the structure of PV flux has the form of a sum of a positive definite hyper-viscous and a negative or positive viscous flux of PV. Turbulence spreading is shown to be related to PV mixing via the link of turbulence energy flux to PV flux. In the relaxed state, the ratio of the PV gradient to zonal flow velocity is homogenized. This homogenized quantity sets a constraint on the amplitudes of PV and zonal flow in the relaxed state. The second relaxation model is derived from symmetry principles alone. The form of PV flux contains a nonlinear convective term in addition to viscous and hyper-viscous terms. For both cases, the transport coefficients are calculated using perturbation theory. For a broad turbulence spectrum, a modulational calculation of the PV flux gives both a negative viscosity and a positive hyper-viscosity. For a narrow turbulence spectrum, the result of a parametric instability analysis shows that PV transport is also convective. In both relaxation and perturbative analyses, it is shown that turbulent PV transport is sensitive to flow structure, and the transport coefficients are nonlinear functions of flow shear.
Complex Convective Thermal Fluxes and Vorticity Structure
NASA Astrophysics Data System (ADS)
Redondo, Jose M.; Tellez, Jackson; Sotillos, Laura; Lopez Gonzalez-Nieto, Pilar; Sanchez, Jesus M.; Furmanek, Petr; Diez, Margarita
2015-04-01
Local Diffusion and the topological structure of vorticity and velocity fields is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of convective cooling and/or heating[1,2]. Patterns arise by setting up a convective flow generated by an array of Thermoelectric devices (Peltier/Seebeck cells) these are controlled by thermal PID generating a buoyant heat flux [2]. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form density interfaces and low Prandtl number mixing with temperature gradients. The set of dimensionless parameters define conditions of numeric and small scale laboratory modeling of environmental flows. Fields of velocity, density and their gradients were computed and visualized [3,4]. When convective heating and cooling takes place the combination of internal waves and buoyant turbulence is much more complicated if the Rayleigh and Reynolds numbers are high in order to study entrainment and mixing. Using ESS and selfsimilarity structures in the velocity and vorticity fieds and intermittency [3,5] that forms in the non-homogeneous flow is related to mixing and stiring. The evolution of the mixing fronts are compared and the topological characteristics of the merging of plumes and jets in different configurations presenting detailed comparison of the evolution of RM and RT, Jets and Plumes in overall mixing. The relation between structure functions, fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the advance of a mixing or nonmixing front occurring at a density interface due to body forces [6]and gravitational acceleration are analyzed considering the fractal and spectral structure of the fronts like in removable plate experiments for Rayleigh-Taylor flows. The evolution of the turbulent mixing layer and its complex configuration is studied
Complex Convective Thermal Fluxes and Vorticity Structure
NASA Astrophysics Data System (ADS)
Redondo, Jose M.; Tellez, Jackson; Sotillos, Laura; Lopez Gonzalez-Nieto, Pilar; Sanchez, Jesus M.; Furmanek, Petr; Diez, Margarita
2015-04-01
Local Diffusion and the topological structure of vorticity and velocity fields is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of convective cooling and/or heating[1,2]. Patterns arise by setting up a convective flow generated by an array of Thermoelectric devices (Peltier/Seebeck cells) these are controlled by thermal PID generating a buoyant heat flux [2]. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form density interfaces and low Prandtl number mixing with temperature gradients. The set of dimensionless parameters define conditions of numeric and small scale laboratory modeling of environmental flows. Fields of velocity, density and their gradients were computed and visualized [3,4]. When convective heating and cooling takes place the combination of internal waves and buoyant turbulence is much more complicated if the Rayleigh and Reynolds numbers are high in order to study entrainment and mixing. Using ESS and selfsimilarity structures in the velocity and vorticity fieds and intermittency [3,5] that forms in the non-homogeneous flow is related to mixing and stiring. The evolution of the mixing fronts are compared and the topological characteristics of the merging of plumes and jets in different configurations presenting detailed comparison of the evolution of RM and RT, Jets and Plumes in overall mixing. The relation between structure functions, fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the advance of a mixing or nonmixing front occurring at a density interface due to body forces [6]and gravitational acceleration are analyzed considering the fractal and spectral structure of the fronts like in removable plate experiments for Rayleigh-Taylor flows. The evolution of the turbulent mixing layer and its complex configuration is studied
Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus).
Maia, Anabela; Sheltzer, Alex P; Tytell, Eric D
2015-03-01
In their natural environment, fish must swim stably through unsteady flows and vortices, including vertical vortices, typically shed by posts in a flow, horizontal cross-flow vortices, often produced by a step or a waterfall in a stream, and streamwise vortices, where the axis of rotation is aligned with the direction of the flow. Streamwise vortices are commonly shed by bluff bodies in streams and by ships' propellers and axial turbines, but we know little about their effects on fish. Here, we describe how bluegill sunfish use more energy and are destabilized more often in flow with strong streamwise vorticity. The vortices were created inside a sealed flow tank by an array of four turbines with similar diameter to the experimental fish. We measured oxygen consumption for seven sunfish swimming at 1.5 body lengths (BL) s(-1) with the turbines rotating at 2 Hz and with the turbines off (control). Simultaneously, we filmed the fish ventrally and recorded the fraction of time spent maneuvering side-to-side and accelerating forward. Separately, we also recorded lateral and ventral video for a combination of swimming speeds (0.5, 1.5 and 2.5 BL s(-1)) and turbine speeds (0, 1, 2 and 3 Hz), immediately after turning the turbines on and 10 min later to test for accommodation. Bluegill sunfish are negatively affected by streamwise vorticity. Spills (loss of heading), maneuvers and accelerations were more frequent when the turbines were on than in the control treatment. These unsteady behaviors, particularly acceleration, correlated with an increase in oxygen consumption in the vortex flow. Bluegill sunfish are generally fast to recover from roll perturbations and do so by moving their pectoral fins. The frequency of spills decreased after the turbines had run for 10 min, but was still markedly higher than in the control, showing that fish partially adapt to streamwise vorticity, but not completely. Coping with streamwise vorticity may be an important energetic
Eikonal gluon bremsstrahlung at finite Nc beyond two loops
NASA Astrophysics Data System (ADS)
Delenda, Yazid; Khelifa-Kerfa, Kamel
2016-03-01
We present a general formalism for computing the matrix-element squared for the emission of soft energy-ordered gluons beyond two loops in QCD perturbation theory at finite Nc. Our formalism is valid in the eikonal approximation. A Mathematica program has been developed for the automated calculation of all real/virtual eikonal squared amplitudes needed at a given loop order. For the purpose of illustration, we show the explicit forms of the eikonal squared amplitudes up to the fifth-loop order. In the large-Nc limit, our results coincide with those previously reported in literature.
Attractive Casimir effect in an infrared modified gluon bag model
Oxman, L.E.; Amaral, R.L.P.G.
2005-12-15
In this work, we are motivated by previous attempts to derive the vacuum contribution to the bag energy in terms of familiar Casimir energy calculations for spherical geometries. A simple infrared modified model is introduced which allows studying the effects of the analytic structure as well as the geometry in a clear manner. In this context, we show that if a class of infrared vanishing effective gluon propagators is considered, then the renormalized vacuum energy for a spherical bag is attractive, as required by the bag model to adjust hadron spectroscopy.
Interactions of quarks and gluons with nuclei at intermediate energies
Mueller, A.H.
1994-04-01
Some processes involving the interaction of medium energy quarks and gluons with nuclear matter are described. Possible mechanisms for the A-dependence of the energy loss of leading protons produced in proton-nucleus collisions are given, and an experiment which may help to distinguish these mechanisms is described. A possible color transparency experiment at CEBAF is described. Experiments to measure energy loss of quarks in nuclear matter and the formation time of hadrons are discussed along with the possibilities of measuring {sigma}{sub J}/{psi} and {sigma}{sub {psi}{prime}} at CEBAF.
Photon gluon fusion cross sections at HERA energy
NASA Astrophysics Data System (ADS)
Engelen, J. J.; Dejong, S. J.; Poletiek, M.; Vermaseren, J. A. M.
1988-01-01
Cross sections for heavy flavor production through photon gluon fusion in electron proton collisions are presented. The electron photon vertex is taken into account explicitly, and the Q sq of the exchanged photon ranges from nearly zero (almost real photon) to the kinematically allowed maximum. The QCD scale is set by the mass of the produced quarks. The formalism is also applicable to the production of light quarks as long as the invariant mass of the pair is sufficiently high, so cross sections for u anti-u, d anti-d, and s anti-s production are also given.
Quark-gluon plasma in an external magnetic field.
Levkova, L; DeTar, C
2014-01-10
Using numerical simulations of lattice QCD we calculate the effect of an external magnetic field on the equation of state of the quark-gluon plasma. The results are obtained using a Taylor expansion of the pressure with respect to the magnetic field for the first time. The coefficients of the expansion are computed to second order in the magnetic field. Our setup for the external magnetic field avoids complications arising from toroidal boundary conditions, making a Taylor series expansion straightforward. This study is exploratory and is meant to serve as a proof of principle. PMID:24483888
Polarized Quarks, Gluons and Sea in Nucleon Structure Functions
NASA Astrophysics Data System (ADS)
Bourrely, C.; Buccella, F.; Pisanti, O.; Santorelli, P.; Soffer, J.
1998-06-01
We perform a NLO analysis of polarized deep inelastic scattering data to test two different solutions to the so-called spin crisis, one of them based on the axial gluon anomaly and consistent with the Bjorken sum rule, and another in which the defects in the spin sum rules and in the Gottfried sum rule are related. In this case a defect is also expected for the Bjorken sum rule. The first solution is slightly favoured by the SLAC E154 results, but both options seem to be consistent with the CERN SMC data.
Heavy quarks, gluons and the confinement potential in Coulomb gauge
NASA Astrophysics Data System (ADS)
Popovici, Carina; Watson, Peter; Reinhardt, Hugo
2011-05-01
We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.
Heavy quarks, gluons and the confinement potential in Coulomb gauge
Popovici, Carina; Watson, Peter; Reinhardt, Hugo
2011-05-23
We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.
Imaging of quantum vortices in superfluid helium droplets
NASA Astrophysics Data System (ADS)
Vilesov, Andrey
Helium nanodroplets are especially promising for exploring quantum hydrodynamics in self-contained, isolated superfluids. However, until very recently, the dynamic properties of individual droplets, such as vorticity, could not be assessed experimentally. Here we investigate the rotation of single superfluid 4-He droplets ranging from 200 to 2000 nm in diameter at T = 0.4 K via single-shot femtosecond X-ray coherent diffractive imaging. The droplets were produced by free jet expansion of liquid helium into vacuum. The angular velocities of the droplets were estimated from the centrifugal distortion and span a range from vanishing to those close to the disintegration limit. For visualization of vortices, Xe atoms were added to the droplets where they gather in cores forming nm-thin filaments. A newly developed phase retrieval technique enables the reconstruction of the instantaneous positions and shapes of the vortices from the diffraction images with about 20 nm resolution. The vorticity attainable in the nano-droplets was found to be about six orders of magnitude larger than achieved in previous experiments in the bulk. Stationary configurations of vortices are represented by triangular lattice in large (2 μm) droplets and symmetric arrangements of few vortices in smaller (200 nm) droplets. Evidence for non-stationary vortex dynamics comes from observation of asymmetric formations of vortices in some droplets. This collaborative work was performed at Linac Coherent Light Source, the free electron laser within SLAC National Accelerator Laboratory. The experiments and the full list of collaborators are reported in: L. F. Gomez et. al. Science, 345 (2014) 906.
A Family of Vortices to Study Axisymmetric Vortex Breakdown and Reconnection
NASA Technical Reports Server (NTRS)
Young, Larry A.
2007-01-01
A new analytic model describing a family of vortices has been developed to study some of the axisymmetric vortex breakdown and reconnection fluid dynamic processes underlying body-vortex interactions that are frequently manifested in rotorcraft and propeller-driven fixed-wing aircraft wakes. The family of vortices incorporates a wide range of prescribed initial vorticity distributions -- including single or dual-core vorticity distributions. The result is analytical solutions for the vorticity and velocities for each member of the family of vortices. This model is of sufficient generality to further illustrate the dependence of vortex reconnection and breakdown on initial vorticity distribution as was suggested by earlier analytical work. This family of vortices, though laminar in nature, is anticipated to provide valuable insight into the vortical evolution of large-scale rotor and propeller wakes.
Bacterial aggregation and biofilm formation in a vortical flow
Yazdi, Shahrzad; Ardekani, Arezoo M.
2012-01-01
Bacterial aggregation and patchiness play an important role in a variety of ecological processes such as competition, adaptation, epidemics, and succession. Here, we demonstrate that hydrodynamics of their environment can lead to their aggregation. This is specially important since microbial habitats are rarely at rest (e.g., ocean, blood stream, flow in porous media, and flow through membrane filtration processes). In order to study the dynamics of bacterial collection in a vortical flow, we utilize a microfluidic system to mimic some of the important microbial conditions at ecologically relevant spatiotemporal scales. We experimentally demonstrate the formation of “ring”-shaped bacterial collection patterns and subsequently the formation of biofilm streamers in a microfluidic system. Acoustic streaming of a microbubble is used to generate a vortical flow in a microchannel. Due to bacteria's finite-size, the microorganisms are directed to closed streamlines and trapped in the vortical flow. The collection of bacteria in the vortices occurs in a matter of seconds, and unexpectedly, triggers the formation of biofilm streamers within minutes. Swimming bacteria have a competitive advantage to respond to their environmental conditions. In order to investigate the role of bacterial motility on the rate of collection, two strains of Escherichia coli bacteria with different motilities are used. We show that the bacterial collection in a vortical flow is strongly pronounced for high motile bacteria. PMID:24339847
Simulations and Observations of Vortices Near Saturn's Dawn Magnetopause
NASA Astrophysics Data System (ADS)
Walker, R. J.; Fukazawa, K.; Ogino, T.; Morozoff-Abezgauz, D.
2008-12-01
We have used a global magnetohydrodynamic simulation of the interaction of the solar wind with Saturn's magnetosphere and Cassini observations to investigate vorticity in the morning magnetosphere. We find that large vortices form for northward IMF in a region near the morning magnetopause with large velocity shear. The vortices are associated with strong field aligned currents. The vortices do not form in simulations with southward IMF or low velocity shear. For our initial simulations we assumed a source of plasma from the moon Enceladus of 2X1029 AMU/s. This is near the upper limit on the Enceladus plasma source. In this study we will present results from simulations which span the entire range of estimated Enceladus sources. In the simulations the boundary vortices cause magnetic field oscillations in the Kronian magnetosphere. The oscillations have periods of one to three hours. We have examined Cassini magnetic field observations1 in the morning and find similar oscillations. In this talk we will present the results from a statistical study of the observed oscillations and a comparison of their properties with the simulation results. 1 Daugherty, M. K., S. Kellock, A. P. Slootweg, N. Achilles, S. P. Joy and J. N. Mafi, CASSINI MAG CALIBRATED SUMMARY AVERAGED, C-E/SWS/J/S-MAG-4-SUMM-AVERAGED-V1.0, NASA Planetary Data System, 2007.
Numerical simulation of dust devil-scale vortices
NASA Astrophysics Data System (ADS)
Kanak, Katharine M.
2005-04-01
A high-resolution (2 m grid) large-eddy simulation of the convective boundary layer is performed for the purpose of comparing physical characteristics of simulated convective vertical vortices to those of observed dust devils. This study is a necessary part of a larger effort to examine the possible formation and maintenance mechanisms for vertical vortices in the convective boundary layer. The case of convective vertical vortex formation in environments without imposed mean winds or wind shears is considered in this paper. Simulated vertical vortices and observations of dust devils compare favourably overall. Other findings include the detection of 'bookend' vortex patterns embedded within the convergence branches of the simulated cellular convective pattern, which is different from prior results in which vortices were found only at cell vertices. Lastly, the theoretical Rankine and Burgers-Rott vortex models are compared to the simulated vortices. It is found that the Burgers-Rott model matches the high-resolution simulated vortex data better than the often used Rankine model.
ON THE STABILITY OF DUST-LADEN PROTOPLANETARY VORTICES
Chang, Philip; Oishi, Jeffrey S. E-mail: jsoishi@astro.berkeley.ed
2010-10-01
The formation of planetesimals via gravitational instability of the dust layer in a protoplanetary disks demands that there be local patches where dust is concentrated by a factor of a few x10{sup 3} over the background value. Vortices in protoplanetary disks may concentrate dust to these values, allowing them to be the nurseries of planetesimals. The concentration of dust in the cores of vortices increases the dust-gas ratio of the core compared to the background disk, creating a 'heavy vortex'. In this work, we show that these vortices are subject to an instability which we have called the heavy-core instability. Using Floquet theory, we show that this instability occurs in elliptical protoplanetary vortices when the gas-dust density of the core of the vortex is heavier than the ambient gas-dust density by a few tens of percent. The heavy-core instability grows very rapidly, with a growth timescale of a few vortex rotation periods. While the nonlinear evolution of this instability remains unknown, it will likely increase the velocity dispersion of the dust layer in the vortex because instability sets in well before sufficient dust can gather to form a protoplanetary seed. This instability may thus preclude vortices from being sites of planetesimal formation.
Vorticity Transport on a Flexible Wing in Stall Flutter
NASA Astrophysics Data System (ADS)
Akkala, James; Buchholz, James; Farnsworth, John; McLaughlin, Thomas
2014-11-01
The circulation budget within dynamic stall vortices was investigated on a flexible NACA 0018 wing model of aspect ratio 6 undergoing stall flutter. The wing had an initial angle of attack of 6 degrees, Reynolds number of 1 . 5 ×105 and large-amplitude, primarily torsional, limit cycle oscillations were observed at a reduced frequency of k = πfc / U = 0 . 1 . Phase-locked stereo PIV measurements were obtained at multiple chordwise planes around the 62.5% and 75% spanwise locations to characterize the flow field within thin volumetric regions over the suction surface. Transient surface pressure measurements were used to estimate boundary vorticity flux. Recent analyses on plunging and rotating wings indicates that the magnitude of the pressure-gradient-driven boundary flux of secondary vorticity is a significant fraction of the magnitude of the convective flux from the separated leading-edge shear layer, suggesting that the secondary vorticity plays a significant role in regulating the strength of the primary vortex. This phenomenon is examined in the present case, and the physical mechanisms governing the growth and evolution of the dynamic stall vortices are explored. This work was supported by the Air Force Office of Scientific Research through the Flow Interactions and Control Program monitored by Dr. Douglas Smith, and through the 2014 AFOSR/ASEE Summer Faculty Fellowship Program (JA and JB).
Inviscid Interactions Between Wake Vortices and Shear Layers
NASA Technical Reports Server (NTRS)
Zheng, Z. C.; Baek, K.
1998-01-01
Aircraft trailing vortices can be influenced significantly by atmospheric conditions such as crosswind, turbulence, and stratification. According to the NASA 1994 and 1995 field measurement program in Memphis, Tennessee, the descending aircraft wake vortices could stall or be deflected at the top of low-level temperature inversions that usually produce pronounced shear zones. Numerical simulations of vortex/shear interactions with ground effects have been performed by several groups. Burnham used a series of evenly spaced line vortices at a particular altitude to model the ground shear layer of the cross- wind. He found that the wind shear was swept up around the downwind vortex and caused the downwind vortex to move upward, and claimed that the effect was actually produced by the vertical gradient in the wind shear rather than by the wind shear directly, because uniformly distributed wind-shear vortices would have no effect on the trailing vortex vertical motion. Recently, Proctor et al. numerically tested the effects of narrow shear zones on the behavior of the vortex pair, motivated by the observation of the Memphis field data. The shear-layer sensitivity tests indicated that the downwind vortex was more sensitive and deflected to a higher altitude than its upwind counterpart. The downstream vortex contained vorticity of opposite sign to that of the shear. There was no detectable preference for the downwind vortex (or upwind vortex) to weaken (or strengthen) at a greater rate.
Vortical Flow Prediction Using an Adaptive Unstructured Grid Method
NASA Technical Reports Server (NTRS)
Pirzadeh, Shahyar Z.
2003-01-01
A computational fluid dynamics (CFD) method has been employed to compute vortical flows around slender wing/body configurations. The emphasis of the paper is on the effectiveness of an adaptive grid procedure in "capturing" concentrated vortices generated at sharp edges or flow separation lines of lifting surfaces flying at high angles of attack. The method is based on a tetrahedral unstructured grid technology developed at the NASA Langley Research Center. Two steady-state, subsonic, inviscid and Navier-Stokes flow test cases are presented to demonstrate the applicability of the method for solving practical vortical flow problems. The first test case concerns vortex flow over a simple 65 delta wing with different values of leading-edge radius. Although the geometry is quite simple, it poses a challenging problem for computing vortices originating from blunt leading edges. The second case is that of a more complex fighter configuration. The superiority of the adapted solutions in capturing the vortex flow structure over the conventional unadapted results is demonstrated by comparisons with the wind-tunnel experimental data. The study shows that numerical prediction of vortical flows is highly sensitive to the local grid resolution and that the implementation of grid adaptation is essential when applying CFD methods to such complicated flow problems.
On the Stability of Dust-laden Protoplanetary Vortices
NASA Astrophysics Data System (ADS)
Chang, Philip; Oishi, Jeffrey S.
2010-10-01
The formation of planetesimals via gravitational instability of the dust layer in a protoplanetary disks demands that there be local patches where dust is concentrated by a factor of a few ×103 over the background value. Vortices in protoplanetary disks may concentrate dust to these values, allowing them to be the nurseries of planetesimals. The concentration of dust in the cores of vortices increases the dust-gas ratio of the core compared to the background disk, creating a "heavy vortex." In this work, we show that these vortices are subject to an instability which we have called the heavy-core instability. Using Floquet theory, we show that this instability occurs in elliptical protoplanetary vortices when the gas-dust density of the core of the vortex is heavier than the ambient gas-dust density by a few tens of percent. The heavy-core instability grows very rapidly, with a growth timescale of a few vortex rotation periods. While the nonlinear evolution of this instability remains unknown, it will likely increase the velocity dispersion of the dust layer in the vortex because instability sets in well before sufficient dust can gather to form a protoplanetary seed. This instability may thus preclude vortices from being sites of planetesimal formation.
Pressure distribution based optimization of phase-coded acoustical vortices
Zheng, Haixiang; Gao, Lu; Dai, Yafei; Ma, Qingyu; Zhang, Dong
2014-02-28
Based on the acoustic radiation of point source, the physical mechanism of phase-coded acoustical vortices is investigated with formulae derivations of acoustic pressure and vibration velocity. Various factors that affect the optimization of acoustical vortices are analyzed. Numerical simulations of the axial, radial, and circular pressure distributions are performed with different source numbers, frequencies, and axial distances. The results prove that the acoustic pressure of acoustical vortices is linearly proportional to the source number, and lower fluctuations of circular pressure distributions can be produced for more sources. With the increase of source frequency, the acoustic pressure of acoustical vortices increases accordingly with decreased vortex radius. Meanwhile, increased vortex radius with reduced acoustic pressure is also achieved for longer axial distance. With the 6-source experimental system, circular and radial pressure distributions at various frequencies and axial distances have been measured, which have good agreements with the results of numerical simulations. The favorable results of acoustic pressure distributions provide theoretical basis for further studies of acoustical vortices.
On the local stability of vortices in differentially rotating discs
NASA Astrophysics Data System (ADS)
Railton, A. D.; Papaloizou, J. C. B.
2014-12-01
In order to circumvent the loss of solid material through radial drift towards the central star, the trapping of dust inside persistent vortices in protoplanetary discs has often been suggested as a process that can eventually lead to planetesimal formation. Although a few special cases have been discussed, exhaustive studies of possible quasi-steady configurations available for dust-laden vortices and their stability are yet to be undertaken, thus their viability or otherwise as locations for the gravitational instability to take hold and seed planet formation is unclear. In this paper we generalize and extend the well-known Kida solution to obtain a series of steady-state solutions with varying vorticity and dust density distributions in their cores, in the limit of perfectly coupled dust and gas. We then present a local stability analysis of these configurations, considering perturbations localized on streamlines. Typical parametric instabilities found have growth rates of 0.05ΩP, where ΩP is the angular velocity at the centre of the vortex. Models with density excess can exhibit many narrow parametric instability bands while those with a concentrated vorticity source display internal shear which significantly affects their stability. However, the existence of these parametric instabilities may not necessarily prevent the possibility of dust accumulation in vortices.
The influence of convective activity on the vorticity budget
NASA Technical Reports Server (NTRS)
Townsend, T. L.; Scoggins, J. R.
1983-01-01
The influence of convective activity on the vorticity budget was determined during the AVE VII and AVE-SESAME I periods. This was accomplished by evaluating each term in the expanded vorticity equation with twisting and tilting and friction representing the residual of all other terms. Convective areas were delineated by use of radar summary charts. The influence of convective activity was established by analyzing contoured fields of each term as well as numerical values and profiles of the various terms in convective and nonconvective areas. Vertical motion was computed by the kinematic method, and all computations were performed over the central United States using a grid spacing of 158 km. The results show that, in convective areas in particular, the residual is of comparable magnitude to the horizontal advection and divergence terms, and therefore, cannot be neglected. In convective areas, the residual term represents a sink of vorticity below 500 mb and a strong source near 300 mb. In nonconvective areas, the residual was small in magnitude at all levels, but tended to be negative (vorticity sink) at 300 mb. The local change term, over convective areas, tended to be balanced by the residual term, and appeared to be a good indicator of development (vorticity becoming more cyclonic). Finally, the shape of the vertical profiles of the term in the budget equation agreed with those found by other investigators for easterly waves, but the terms were one order of magnitude larger than those for easterly waves.
Gluon saturation and Feynman scaling in leading neutron production
NASA Astrophysics Data System (ADS)
Carvalho, F.; Gonçalves, V. P.; Spiering, D.; Navarra, F. S.
2016-01-01
In this paper we extend the color dipole formalism for the study of leading neutron production in e + p → e + n + X collisions at high energies and estimate the related observables which were measured at HERA and could be analyzed in future electron-proton (ep) colliders. In particular, we calculate the Feynman xF distribution of leading neutrons, which is expressed in terms of the pion flux and the photon-pion total cross section. In the color dipole formalism, the photon-pion cross section is described in terms of the dipole-pion scattering amplitude, which contains information about the QCD dynamics at high energies and gluon saturation effects. We consider different models for the scattering amplitude, which have been used to describe the inclusive and diffractive ep HERA data. Moreover, the model dependence of our predictions with the description of the pion flux is analyzed in detail. We demonstrate the recently released H1 leading neutron spectra can be described using the color dipole formalism and that these spectra could help us to observe more clearly gluon saturation effects in future ep colliders.
The Fluid Nature of Quark-Gluon Plasma
NASA Astrophysics Data System (ADS)
Zajc, W. A.
2008-06-01
Collisions of heavy nuclei at very high energies offer the exciting possibility of experimentally exploring the phase transformation from hadronic to partonic degrees of freedom which is predicted to occur at several times normal nuclear density and/or for temperatures in excess of ˜170MeV. Such a state, often referred to as a quark-gluon plasma, is thought to have been the dominant form of matter in the universe in the first few microseconds after the Big Bang. Data from the first five years of heavy ion collisions of Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) clearly demonstrate that these very high temperatures and densities have been achieved. While there are strong suggestions of the role of quark degrees of freedom in determining the final-state distributions of the produced matter, there is also compelling evidence that the matter does not behave as a quasi-ideal state of free quarks and gluons. Rather, its behavior is that of a dense fluid with very low kinematic viscosity exhibiting strong hydrodynamic flow and nearly complete absorption of high momentum probes. The current status of the RHIC experimental studies is presented, with a special emphasis on the fluid properties of the created matter, which may in fact be the most perfect fluid ever studied in the laboratory.
Study of the subjet structure of quark and gluon jets
NASA Astrophysics Data System (ADS)
Buskulic, D.; Casper, D.; de Bonis, I.; Decamp, D.; Ghez, P.; Goy, C.; Lees, J.-P.; Minard, M.-N.; Odier, P.; Pietrzyk, B.; Ariztizabal, F.; Chmeissani, M.; Crespo, J. M.; Efthymiopoulos, I.; Fernandez, E.; Fernandez-Bosman, M.; Gaitan, V.; Garrido, Ll.; Martinez, M.; Orteu, S.; Pacheco, A.; Padilla, C.; Palla, F.; Pascual, A.; Perlas, J. A.; Sanchez, F.; Teubert, F.; Creanza, D.; de Palma, M.; Farilla, A.; Iaselli, G.; Maggi, G.; Marinelli, N.; Natali, S.; Nuzzo, S.; Ranieri, A.; Raso, G.; Romano, F.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Bonvicini, G.; Cattaneo, M.; Comas, P.; Coyle, P.; Drevermann, H.; Engelhardt, A.; Forty, R. W.; Frank, M.; Ganis, G.; Girone, M.; Hagelberg, R.; Harvey, J.; Jacobsen, R.; Jost, B.; Knobloch, J.; Lehraus, I.; Maggi, M.; Markou, C.; Martin, E. B.; Mato, P.; Meinhard, H.; Minten, A.; Miquel, R.; Palazzi, P.; Pater, J. R.; Perrodo, P.; Pusztaszeri, J.-F.; Ranjard, F.; Rolandi, L.; Schlatter, D.; Schmelling, M.; Tejessy, W.; Tomalin, I. R.; Veenhof, R.; Venturi, A.; Wachsmuth, H.; Wiedenmann, W.; Wildish, T.; Witzeling, W.; Wotschack, J.; Ajaltouni, Z.; Bardadin-Otwinowska, M.; Barres, A.; Boyer, C.; Falvard, A.; Gay, P.; Guicheney, C.; Henrard, P.; Jousset, J.; Michel, B.; Monteil, S.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Proriol, J.; Rossignol, J.-M.; Saadi, F.; Fearnley, T.; Hansen, J. B.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Johnson, S. D.; Nilsson, B. S.; Kyriakis, A.; Simopoulou, E.; Siotis, I.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Bonneaud, G.; Brient, J. C.; Bourdon, P.; Passalacqua, L.; Rougé, A.; Rumpf, M.; Tanaka, R.; Valassi, A.; Verderi, M.; Videau, H.; Candlin, D. J.; Parsons, M. I.; Veitch, E.; Focardi, E.; Parrini, G.; Corden, M.; Delfino, M.; Georgiopoulos, C.; Jaffe, D. E.; Antonelli, A.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Cerutti, F.; Chiarella, V.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Pepe-Altarelli, M.; Salomone, S.; Colrain, P.; Ten Have, I.; Knowles, I. G.; Lynch, J. G.; Maitland, W.; Morton, W. T.; Raine, C.; Reeves, P.; Scarr, J. M.; Smith, K.; Smith, M. G.; Thompson, A. S.; Thorn, S.; Turnbull, R. M.; Becker, U.; Braun, O.; Geweniger, C.; Graefe, G.; Hanke, P.; Hepp, V.; Kluge, E. E.; Putzer, A.; Rensch, B.; Schmidt, M.; Sommer, J.; Stenzel, H.; Tittel, K.; Wunsch, M.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Colling, D. J.; Dornan, P. J.; Konstantinidis, N.; Moneta, L.; Moutoussi, A.; Nash, J.; San Martin, G.; Sedgbeer, J. K.; Stacey, A. M.; Dissertori, G.; Girtler, P.; Kneringer, E.; Kuhn, D.; Rudolph, G.; Bowdery, C. K.; Brodbeck, T. J.; Finch, A. J.; Foster, F.; Hughes, G.; Jackson, D.; Keemer, N. R.; Nuttall, M.; Patel, A.; Sloan, T.; Snow, S. W.; Whelan, E. P.; Galla, A.; Greene, A. M.; Kleinknecht, K.; Raab, J.; Renk, B.; Sander, H.-G.; Schmidt, H.; Walther, S. M.; Wanke, R.; Wolf, B.; Aubert, J. J.; Bencheikh, A. M.; Benchouk, C.; Bonissent, A.; Bujosa, G.; Calvet, D.; Carr, J.; Diaconu, C.; Etienne, F.; Thulasidas, M.; Nicod, D.; Payre, P.; Rousseau, D.; Talby, M.; Abt, I.; Assmann, R.; Bauer, C.; Blum, W.; Brown, D.; Dietl, H.; Dydak, F.; Gotzhein, C.; Halley, A. W.; Jakobs, K.; Kroha, H.; Lütjens, G.; Lutz, G.; Männer, W.; Moser, H.-G.; Richter, R.; Rosado-Schlosser, A.; Schwarz, A. S.; Settles, R.; Seywerd, H.; Stierlin, U.; Denis, R. St.; Wolf, G.; Alemany, R.; Boucrot, J.; Callot, O.; Cordier, A.; Courault, F.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jacquet, M.; Janot, P.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Musolino, G.; Nikolic, I.; Park, H. J.; Park, I. C.; Schune, M.-H.; Simion, S.; Veillet, J.-J.; Videau, I.; Abbaneo, D.; Bagliesi, G.; Batignani, G.; Bettarini, S.; Bottigli, U.; Bozzi, C.; Calderini, G.; Carpinelli, M.; Ciocci, M. A.; Ciulli, V.; Dell'Orso, R.; Ferrante, I.; Fidecaro, F.; Foà, L.; Forti, F.; Giassi, A.; Giorgi, M. A.; Gregorio, A.; Ligabue, F.; Lusiani, A.; Marrocchesi, P. S.; Messineo, A.; Rizzo, G.; Sanguinetti, G.; Sciabà, A.; Spagnolo, P.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Triggiani, G.; Vannini, C.; Verdini, P. G.; Walsh, J.; Betteridge, A. P.; Blair, G. A.; Bryant, L. M.; Gao, Y.; Green, M. G.; Johnson, D. L.; Medcalf, T.; Mir, Ll. M.; Strong, J. A.; Bertin, V.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Haywood, S.; Edwards, M.; Maley, P.; Norton, P. R.; Thompson, J. C.; Bloch-Devaux, B.; Colas, P.; Duarte, H.; Emery, S.; Kozanecki, W.; Lançon, E.; Lemaire, M. C.; Locci, E.; Marx, B.; Perez, P.; Rander, J.; Renardy, J.-F.; Rosowsky, A.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Si Mohand, D.; Trabelsi, A.; Vallage, B.; Johnson, R. P.; Litke, A. M.; Taylor, G.; Wear, J.; Beddall, A.; Booth, C. N.; Boswell, R.; Cartwright, S.; Combley, F.; Dawson, I.; Koksal, A.; Letho, M.; Newton, W. M.; Rankin, C.; Thompson, L. F.; Böhrer, A.; Brandt, S.; Cowan, G.; Feigl, E.; Grupen, C.; Lutters, G.; Minguet-Rodriguez, J.; Rivera, F.; Saraiva, P.; Schäfer, U.; Smolik, L.; Bosisio, L.; Della Marina, R.; Giannini, G.; Gobbo, B.; Pitis, L.; Ragusa, F.; Kim, H.; Rothberg, J.; Wasserbaech, S.; Armstrong, S. R.; Bellantoni, L.; Elmer, P.; Feng, Z.; Ferguson, D. P. S.; Gao, Y. S.; González, S.; Grahl, J.; Harton, J. L.; Hayes, O. J.; Hu, H.; McNamara, P. A.; Nachtman, J. M.; Orejudos, W.; Pan, Y. B.; Saadi, Y.; Schmitt, M.; Scott, I. J.; Sharma, V.; Turk, J. D.; Walsh, A. M.; Weber, F. V.; Wu, Sau Lan; Wu, X.; Yamartino, J. M.; Zheng, M.; Zobernig, G.; Aleph Collaboration
1995-02-01
Measurements of the subjet structure of quark and gluon jets in hadronic Z decays are presented. The analysis is based on one million hadronic events recorded by the ALEPH detector. Roughly symmetric three-jet events are selected with a coarse jet-resolution cut-off, y1. Gluon jets are identified with a purity of 94.6% in those events where evidence of long-lived heavy-flavour hadrons in the other two jets is found. The jets are then analyzed using a smaller cut-off y0 (< y1) so that subjets are resolved. The properties of the jets (subjet multiplicities ( Nq), ( Ng) and rates Rng( q) for n = 1, 2, 3, 4) are determined and are found to be in good agreement with the expectations of perturbative QCD as long as the subjet resolution parameter y0 is sufficiently large to keep non-perturbative effects small. In particular, the ratio {(N g - 1) }/{(N q - 1) }, which to leading order in QCD is given by the ratio of colour factors {C A}/{C F} = {9}/{4}, is measured to be 1.96 ± 0.15 for y0 = 2 · 10 -3, but falls to 1.29 ± 0.03 for y0 = 1.6 · 10 -5.
NASA Astrophysics Data System (ADS)
Tuchin, Kirill
2016-05-01
A quark propagating through the quark gluon plasma and scattering off the thermal gluons can radiate photons in states with definite angular momentum and magnetic helicity. These states, known as the Chandrasekhar-Kendall states, are eigenstates of the curl operator and have a nontrivial topology. I compute the spectrum of these states in the ultrarelativistic limit and study its properties.
NASA Astrophysics Data System (ADS)
Grinyuk, A. A.; Lipatov, A. V.; Lykasov, G. I.; Zotov, N. P.
2016-01-01
We study the role of the nonperturbative input to the transverse momentum dependent (TMD) gluon density in hard processes at the LHC. We derive the input TMD gluon distribution at a low scale μ02˜1 GeV2 from a fit of inclusive hadron spectra measured at low transverse momenta in p p collisions at the LHC and demonstrate that the best description of these spectra for larger hadron transverse momenta can be achieved by matching the derived TMD gluon distribution with the exact solution of the Balitsky-Fadin-Kuraev-Lipatov equation obtained at low x and small gluon transverse momenta outside the saturation region. Then, we extend the input TMD gluon density to higher μ2 numerically using the Catani-Ciafoloni-Fiorani-Marchesini gluon evolution equation. Special attention is paid to phenomenological applications of the obtained TMD gluon density to some LHC processes, which are sensitive to the gluon content of a proton.
Superadiabatic evolution of acoustic and vorticity perturbations in Couette flow
NASA Astrophysics Data System (ADS)
Favraud, Gael; Pagneux, Vincent
2014-03-01
Nonadiabatic transitions between the acoustic and the vorticity modes perturbing a plane Couette flow are examined in the context of higher-order WKB asymptotics. In the case of the Schrödinger equation, it is known that looking at the solution expressed in the superadiabatic base, composed of higher-order asymptotic solutions, smoothes quantum state transitions. Then, increasing the order of the superadiabatic base causes these transitions to tend to the Gauss error function, and, once an optimal order is reached, the asymptotic process starts to diverge. We show that for perturbations in Couette flow, similar results can be applied on the amplitudes of the vorticity and acoustic modes. This allows us to more closely track the emergence of the acoustic modes in the presence of the vorticity mode.
Approach and separation of quantum vortices with balanced cores
NASA Astrophysics Data System (ADS)
Kerr, Robert M.; Rorai, C.; Skipper, J.; Sreenivasan, K. R.
2014-11-01
Using two innovations, smooth but different, scaling laws for the reconnection of pairs of initially orthogonal and anti-parallel quantum vortices are obtained using the three-dimensional Gross-Pitaevskii equations. For the anti-parallel case, the scaling laws just before and after reconnection obey the dimensional δ ~ | t - tr| 1 / 2 prediction with temporal symmetry about the reconnection time tr and physical space symmetry about xr, the mid-point between the vortices, with extensions forming the edges of an equilateral pyramid. For all of the orthogonal cases, before reconnection δin ~(t -tr) 1 / 3 and after reconnection δout ~(tr - t) 2 / 3 , which are respectively slower and faster than the dimensional prediction. In these cases, the reconnection takes place in a plane defined by the directions of the curvature and vorticity. Robert.Kerr@warwick.ac.uk.
Drift and ion acoustic wave driven vortices with superthermal electrons
Ali Shan, S.; Haque, Q.
2012-08-15
Linear and nonlinear analysis of coupled drift and acoustic mode is presented in an inhomogeneous electron-ion plasma with {kappa}-distributed electrons. A linear dispersion relation is found which shows that the phase speed of both the drift wave and the ion acoustic wave decreases in the presence of superthermal electrons. Several limiting cases are also discussed. In the nonlinear regime, stationary solutions in the form of dipolar and monopolar vortices are obtained. It is shown that the condition for the boundedness of the solution implies that the speed of drift wave driven vortices reduces with increase in superthermality effect. Ignoring density inhomogeniety, it is investigated that the lower and upper limits on the speed of the ion acoustic driven vortices spread with the inclusion of high energy electrons. The importance of results with reference to space plasmas is also pointed out.
Stability of model flocks in a vortical flow
NASA Astrophysics Data System (ADS)
Baggaley, A. W.
2016-06-01
We investigate the stability of self-propelled particle flocks in the Taylor-Green vortex, a steady vortical flow. We consider a model in which particles align themselves to a combination of the orientation and the acceleration of particles within a critical radius. We identify two distinct regimes: If alignment with orientation is dominant, the particles tend to be expelled from regions of high vorticity. In contrast, if anticipation is dominant, the particles accumulate in areas of large vorticity. In both regimes, the relative order of the flock is reduced. However, we show that there can be a critical balance of the two effects that stabilizes the flock in the presence of external fluid forcing. This strategy could provide a mechanism for animal flocks to remain globally ordered in the presence of fluid forcing, and it may also have applications in the design of flocking autonomous drones and artificial microswimmers.
Stability of model flocks in a vortical flow.
Baggaley, A W
2016-06-01
We investigate the stability of self-propelled particle flocks in the Taylor-Green vortex, a steady vortical flow. We consider a model in which particles align themselves to a combination of the orientation and the acceleration of particles within a critical radius. We identify two distinct regimes: If alignment with orientation is dominant, the particles tend to be expelled from regions of high vorticity. In contrast, if anticipation is dominant, the particles accumulate in areas of large vorticity. In both regimes, the relative order of the flock is reduced. However, we show that there can be a critical balance of the two effects that stabilizes the flock in the presence of external fluid forcing. This strategy could provide a mechanism for animal flocks to remain globally ordered in the presence of fluid forcing, and it may also have applications in the design of flocking autonomous drones and artificial microswimmers. PMID:27415360
Characterization of a vortical gust generator using PIV
NASA Astrophysics Data System (ADS)
Hufstedler, Esteban; McKeon, Beverley
2015-11-01
A heaving plate has been used to generate aperiodic vortical gusts in a free-surface water tunnel as part of an effort to experimentally investigate the interaction between a wing and an incoming parallel vortex. Particle image velocimetry measurements provided information about the growth and evolution of the vortices over a range of heaving and freestream speeds. Vortex tracking methods were used to examine the circulation and movement paths of the vortices. Preliminary results of vortex-airfoil interactions will also be presented, with a view to identifying the gust response and tolerance. This work was supported by the Gordon and Betty Moore Foundation through grant GBMF #2645 to the California Institute of Technology.
Vorticity scaling and intermittency in drift-interchange plasma turbulence
Dura, P. D.; Hnat, B.; Robinson, J.; Dendy, R. O.
2012-09-15
The effects of spatially varying magnetic field strength on the scaling properties of plasma turbulence, modelled by an extended form of Hasegawa-Wakatani model, are investigated. We study changes in the intermittency of the velocity, density, and vorticity fields, as functions of the magnetic field inhomogeneity C=-{partial_derivative} ln B/{partial_derivative}x. While the velocity fluctuations are always self-similar and their scaling is unaffected by the value of C, the intermittency levels in density and vorticity change with parameter C, reflecting morphological changes in the coherent structures due to the interchange mechanism. Given the centrality of vorticity in conditioning plasma transport, this result is of interest in scaling the results of transport measurements and simulations in tokamak edge plasmas, where drift-interchange turbulence in the presence of a magnetic field gradient is likely to occur.
Vorticity equation for MHD fast waves in geospace environment
NASA Technical Reports Server (NTRS)
Yamauchi, M.; Lundin, R.; Lui, A. T. Y.
1993-01-01
The MHD vorticity equation is modified in order to apply it to nonlinear MHD fast waves or shocks when their extent along the magnetic field is limited. Field-aligned current (FAC) generation is also discussed on the basis of this modified vorticity equation. When the wave normal is not aligned to the finite velocity convection and the source region is spatially limited, a longitudinal polarization causes a pair of plus and minus charges inside the compressional plane waves or shocks, generating a pair of FACs. This polarization is not related to the separation between the electrons and ions caused by their difference in mass, a separation which is inherent to compressional waves. The resultant double field-aligned current structure exists both with and without the contributions from curvature drift, which is questionable in terms of its contribution to vorticity change from the viewpoint of single-particle motion.
Decay of Far-Flowfield in Trailing Vortices
NASA Technical Reports Server (NTRS)
Baldwin, B. S.; Chigier, N. A.; Sheaffer, Y. S.
1973-01-01
Methods for reduction of velocities in trailing vortices of large aircraft are of current interest for the purpose of shortening the waiting time between landings at central airports. We have made finite-difference calculations of the flow in turbulent wake vortices as an aid to interpretation of wind-tunnel and flight experiments directed toward that end. Finite-difference solutions are capable of adding flexibility to such investigations if they are based on an adequate model of turbulence. Interesting developments have been taking place in the knowledge of turbulence that may lead to a complete theory in the future. In the meantime, approximate methods that yield reasonable agreement with experiment are appropriate. The simplified turbulence model we have selected contains features that account for the major effects disclosed by more sophisticated models in which the parameters are not yet established. Several puzzles are thereby resolved that arose in previous theoretical investigations of wake vortices.
Coherent vorticity extraction in turbulent channel flow using anisotropic wavelets
NASA Astrophysics Data System (ADS)
Yoshimatsu, Katsunori; Sakurai, Teluo; Schneider, Kai; Farge, Marie; Morishita, Koji; Ishihara, Takashi
2014-11-01
We examine the role of coherent vorticity in a turbulent channel flow. DNS data computed at friction-velocity based Reynolds number 320 is analyzed. The vorticity is decomposed using three-dimensional anisotropic orthogonal wavelets. Thresholding of the wavelet coefficients allows to extract the coherent vorticity, corresponding to few strong wavelet coefficients. It retains the vortex tubes of the turbulent flow. Turbulent statistics, e.g., energy, enstrophy and energy spectra, are close to those of the total flow. The nonlinear energy budgets are also found to be well preserved. The remaining incoherent part, represented by the large majority of the weak coefficients, corresponds to a structureless, i.e., a noise-like background flow.
Large Eddy Simulation of Aircraft Wake Vortices: Atmospheric Turbulence Effects
NASA Technical Reports Server (NTRS)
Han, Jongil; Lin, Yuh-Lang; Arya, S. Pal; Kao, C.-T.
1997-01-01
Crow instability can develop in most atmospheric turbulence levels, however, the ring vortices may not form in extremely strong turbulence cases due to strong dissipation of the vortices. It appears that strong turbulence tends to accelerate the occurrences of Crow instability. The wavelength of the most unstable mode is estimated to be about 5b(sub 0), which is less than the theoretical value of 8.6b(sub 0) (Crow, 1970) and may be due to limited domain size and highly nonlinear turbulent flow characteristics. Three-dimensional turbulence can decay wake vortices more rapidly. Axial velocity may be developed by vertical distortion of a vortex pair due to Crow instability or large turbulent eddy motion. More experiments with various non-dimensional turbulence levels are necessary to get useful statistics of wake vortex behavior due to turbulence. Need to investigate larger turbulence length scale effects by enlarging domain size or using grid nesting.
Kinematics of velocity and vorticity correlations in turbulent flow
NASA Technical Reports Server (NTRS)
Bernard, P. S.
1983-01-01
The kinematic problem of calculating second-order velocity moments from given values of the vorticity covariance is examined. Integral representation formulas for second-order velocity moments in terms of the two-point vorticity correlation tensor are derived. The special relationships existing between velocity moments in isotropic turbulence are expressed in terms of the integral formulas yielding several kinematic constraints on the two-point vorticity correlation tensor in isotropic turbulence. Numerical evaluation of these constraints suggests that a Gaussian curve may be the only form of the longitudinal velocity correlation coefficient which is consistent with the requirement of isotropy. It is shown that if this is the case, then a family of exact solutions to the decay of isotropic turbulence may be obtained which contains Batchelor's final period solution as a special case. In addition, the computed results suggest a method of approximating the integral representation formulas in general turbulent shear flows.
Warping and interactions of vortices in exciton-polariton condensates
NASA Astrophysics Data System (ADS)
Toledo-Solano, M.; Mora-Ramos, M. E.; Figueroa, A.; Rubo, Y. G.
2014-01-01
We investigate the properties of the vortex singularities in two-component exciton-polariton condensates in semiconductor microcavities in the presence of transverse-electric-transverse-magnetic (TE-TM) splitting of the lower polariton branch. This splitting does not change qualitatively the basic (lemon and star) geometry of half-quantum vortices (HQVs), but results in warping of both the polarization field and the supercurrent streamlines around these entities. The TE-TM splitting has a pronounced effect on the HQV energies and interactions, as well as on the properties of integer vortices, especially on the energy of the hedgehog polarization vortex. The energy of this vortex can become smaller than the energies of HQVs. This leads to modification of the Berezinskii-Kosterlitz-Thouless transition from the proliferation of half-vortices to the proliferation of hedgehog-based vortex molecules.
Vorticity Preserving Flux Corrected Transport Scheme for the Acoustic Equations
Lung, Tyler B.; Roe, Phil; Morgan, Nathaniel R.
2012-08-15
Long term research goals are to develop an improved cell-centered Lagrangian Hydro algorithm with the following qualities: 1. Utilizes Flux Corrected Transport (FCT) to achieve second order accuracy with multidimensional physics; 2. Does not rely on the one-dimensional Riemann problem; and 3. Implements a form of vorticity control. Short term research goals are to devise and implement a 2D vorticity preserving FCT solver for the acoustic equations on an Eulerian mesh: 1. Develop a flux limiting mechanism for systems of governing equations with symmetric wave speeds; 2. Verify the vorticity preserving properties of the scheme; and 3. Compare the performance of the scheme to traditional MUSCL-Hancock and other algorithms.
Vortical structure in a forced plane mixing layer
NASA Technical Reports Server (NTRS)
Leboeuf, Richard L.
1993-01-01
The objective of this phase of an ongoing study is to obtain detailed three dimensional phase-averaged measurements of forced mixing layer vorticity development and evolution. Acoustic forcing is being used to phase-lock the initial development and subsequent pairing of the span wise vortical structures. Phase averaged measurements of the three velocity components will permit the study of three dimensional vorticity distributions without invoking Taylor's hypothesis which is known to introduce uncertainty. Currently two sine waves, one at the fundamental roll-up frequency and the second, its subharmonic, are being used to force the initial roll-up and first pairing of the span wise rollers. The two dimensional measurements described in this report were obtained in order to determine the best operating conditions for the detailed three dimensional study of the mixing layer undergoing pairing via various pairing mechanisms.
Rapid expulsion of microswimmers by a vortical flow
Sokolov, Andrey; Aranson, Igor S.
2016-01-01
Interactions of microswimmers with their fluid environment are exceptionally complex. Macroscopic shear flow alters swimming trajectories in a highly nontrivial way and results in dramatic reduction of viscosity and heterogeneous bacterial distributions. Here we report on experimental and theoretical studies of rapid expulsion of microswimmers, such as motile bacteria, by a vortical flow created by a rotating microparticle. We observe a formation of a macroscopic depletion area in a high-shear region, in the vicinity of a microparticle. The rapid migration of bacteria from the shear-rich area is caused by a vortical structure of the flow rather than intrinsic random fluctuations of bacteria orientations, in stark contrast to planar shear flow. Our mathematical model reveals that expulsion is a combined effect of motility and alignment by a vortical flow. Our findings offer a novel approach for manipulation of motile microorganisms and shed light on bacteria–flow interactions. PMID:27005581
Numerical Modeling Studies of Wake Vortices: Real Case Simulations
NASA Technical Reports Server (NTRS)
Shen, Shao-Hua; Ding, Feng; Han, Jongil; Lin, Yuh-Lang; Arya, S. Pal; Proctor, Fred H.
1999-01-01
A three-dimensional large-eddy simulation model, TASS, is used to simulate the behavior of aircraft wake vortices in a real atmosphere. The purpose for this study is to validate the use of TASS for simulating the decay and transport of wake vortices. Three simulations are performed and the results are compared with the observed data from the 1994-1995 Memphis field experiments. The selected cases have an atmospheric environment of weak turbulence and stable stratification. The model simulations are initialized with appropriate meteorological conditions and a post roll-up vortex system. The behavior of wake vortices as they descend within the atmospheric boundary layer and interact with the ground is discussed.
Rapid expulsion of microswimmers by a vortical flow
NASA Astrophysics Data System (ADS)
Sokolov, Andrey; Aranson, Igor S.
2016-03-01
Interactions of microswimmers with their fluid environment are exceptionally complex. Macroscopic shear flow alters swimming trajectories in a highly nontrivial way and results in dramatic reduction of viscosity and heterogeneous bacterial distributions. Here we report on experimental and theoretical studies of rapid expulsion of microswimmers, such as motile bacteria, by a vortical flow created by a rotating microparticle. We observe a formation of a macroscopic depletion area in a high-shear region, in the vicinity of a microparticle. The rapid migration of bacteria from the shear-rich area is caused by a vortical structure of the flow rather than intrinsic random fluctuations of bacteria orientations, in stark contrast to planar shear flow. Our mathematical model reveals that expulsion is a combined effect of motility and alignment by a vortical flow. Our findings offer a novel approach for manipulation of motile microorganisms and shed light on bacteria-flow interactions.
Visualizing the elongated vortices in γ -Ga nanostrips
NASA Astrophysics Data System (ADS)
Zhang, Hui-Min; Li, Zi-Xiang; Peng, Jun-Ping; Song, Can-Li; Guan, Jia-Qi; Li, Zhi; Wang, Lili; He, Ke; Ji, Shuai-Hua; Chen, Xi; Yao, Hong; Ma, Xu-Cun; Xue, Qi-Kun
2016-01-01
We study the magnetic response of superconducting γ -Ga via low temperature scanning tunneling microscopy and spectroscopy. The magnetic vortex cores rely substantially on the Ga geometry, and exhibit an unexpectedly large axial elongation with aspect ratio up to 40 in rectangular Ga nanostrips (width l <100 nm). This is in stark contrast with the isotropic circular vortex core in a larger round-shaped Ga island. We suggest that the unusual elongated vortices in Ga nanostrips originate from geometric confinement effect probably via the strong repulsive interaction between the vortices and Meissner screening currents at the sample edge. Our finding provides novel conceptual insights into the geometrical confinement effect on magnetic vortices and forms the basis for the technological applications of superconductors.
Vorticity scaling and intermittency in drift-interchange plasma turbulence
NASA Astrophysics Data System (ADS)
Dura, P. D.; Hnat, B.; Robinson, J.; Dendy, R. O.
2012-09-01
The effects of spatially varying magnetic field strength on the scaling properties of plasma turbulence, modelled by an extended form of Hasegawa-Wakatani model, are investigated. We study changes in the intermittency of the velocity, density, and vorticity fields, as functions of the magnetic field inhomogeneity C =-∂ ln B/∂x. While the velocity fluctuations are always self-similar and their scaling is unaffected by the value of C, the intermittency levels in density and vorticity change with parameter C, reflecting morphological changes in the coherent structures due to the interchange mechanism. Given the centrality of vorticity in conditioning plasma transport, this result is of interest in scaling the results of transport measurements and simulations in tokamak edge plasmas, where drift-interchange turbulence in the presence of a magnetic field gradient is likely to occur.
Interaction between x-ray and magnetic vortices
NASA Astrophysics Data System (ADS)
van Veenendaal, Michel
2015-12-01
The interaction between two topological objects, an x-ray beam carrying orbital angular momentum (OAM) and a magnetic vortex, is studied theoretically. The resonant x-ray scattering intensity is calculated as a function of the relative position of the magnetic and x-ray vortices. For a homogeneous system, the charge scattering is zero. For magnetic scattering, the intensity profile strongly depends on the relative topological indices of the x-ray and magnetic singularities. A strong enhancement in the intensity profile is observed for equal winding factors. Additionally, the profile displays edge effects, which depend on the scattering conditions, the radial dependence of the magnetic vortex, and the Laguerre-Gaussian mode of the OAM x-ray beam. The potential of resonant OAM x-ray scattering from magnetic vortices opens the door to study the dynamics and switching of magnetic vortices.
A measurement of quark and gluon jet differences at the Z{sup 0} resonance
Iwasaki, Yoshihito
1994-08-01
The authors have studied differences between quark and gluon jets using 3-jet events in hadronic decays of Z{sup 0} bosons collected by the SLD experiment at SLAC. Gluon jets were identified in symmetric 3-jet events containing one jet tagged as a heavy quark jet and compared with a mixed sample of quark and gluon jets and also with a mixed sample of light quark (u, d and s) and gluon jets. Their preliminary results show that the particle multiplicity in gluon jets is higher than that in light quark jets. These results are in qualitative agreement with QCD expectations. Differences are also observed in particle energy spectra and the jet widths, consistent with QCD expectations.
LPM Interference and Cherenkov-like Gluon Bremsstrahlung in DenseMatter
Majumder, Abhijit; Wang, Xin-Nian
2005-07-26
Gluon bremsstrahlung induced by multiple parton scattering in a finite dense medium has a unique angular distribution with respect to the initial parton direction. A dead-cone structure with an opening angle; theta2{sub 0}; approx 2(1-z)/(zLE) for gluons with fractional energy z arises from the Landau-Pomeran chuck-Migdal (LPM) interference. In a medium where the gluon's dielectric constant is; epsilon>1, the LPM interference pattern is shown to become Cherenkov-like with an increased opening angle determined by the dielectric constant$/cos2/theta{sub c}=z+(1-z)//epsilon$. For a large dielectric constant/epsilon; gg 1+2/z2LE, the corresponding total radiative parton energy loss is about twice that from normal gluon bremsstrahlung. Implications of this Cherenkov-like gluon bremsstrahlung to the jet correlation pattern in high-energy heavy-ion collisions is discussed.
Quark and gluon jet properties in symmetric three-jet events
NASA Astrophysics Data System (ADS)
Buskulic, D.; Casper, D.; de Bonis, I.; Decamp, D.; Ghez, P.; Goy, C.; Lees, J.-P.; Lucotte, A.; Minard, M.-N.; Odier, P.; Pietrzyk, B.; Chmeissani, M.; Crespo, J. M.; Efthymiopoulos, I.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll.; Juste, A.; Martinez, M.; Orteu, S.; Pacheco, A.; Padilla, C.; Palla, F.; Pascual, A.; Perlas, J. A.; Riu, I.; Sanchez, F.; Teubert, F.; Colaleo, A.; Creanza, D.; de Palma, M.; Farilla, A.; Gelao, G.; Girone, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Marinelli, N.; Natali, S.; Nuzzo, S.; Ranieri, A.; Raso, G.; Romano, F.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Alemany, R.; Bazarko, A. O.; Bonvicini, G.; Cattaneo, M.; Comas, P.; Coyle, P.; Drevermann, H.; Forty, R. W.; Frank, M.; Hagelberg, R.; Harvey, J.; Jacobsen, R.; Janot, P.; Jost, B.; Kneringer, E.; Knobloch, J.; Lehraus, I.; Martin, E. B.; Mato, P.; Minten, A.; Miquel, R.; Mir, Ll. M.; Moneta, L.; Oest, T.; Palazzi, P.; Pater, J. R.; Pusztaszeri, J.-F.; Ranjard, F.; Rensing, P.; Rolandi, L.; Schlatter, D.; Schmelling, M.; Schneider, O.; Tejessy, W.; Tomalin, I. R.; Venturi, A.; Wachsmuth, H.; Wildish, T.; Witzeling, W.; Wotschack, J.; Ajaltouni, Z.; Barrès, A.; Boyer, C.; Falvard, A.; Gay, P.; Guicheney, C.; Henrard, P.; Jousset, J.; Michel, B.; Monteil, S.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Proriol, J.; Rossignol, J.-M.; Fearnley, T.; Hansen, J. B.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Nilsson, B. S.; Wäänänen, A.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Siotis, I.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Bonneaud, G.; Brient, J. C.; Bourdon, P.; Rougé, A.; Rumpf, M.; Tanaka, R.; Valassi, A.; Verderi, M.; Videau, H.; Candlin, D. J.; Parsons, M. I.; Focardi, E.; Parrini, G.; Corden, M.; Delfino, M.; Georgiopoulos, C.; Jaffe, D. E.; Antonelli, A.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Chiarella, V.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Curtis, L.; Dorris, S. J.; Halley, A. W.; Knowles, I. G.; Lynch, J. G.; O'Shea, V.; Raine, C.; Reeves, P.; Scarr, J. M.; Smith, K.; Thompson, A. S.; Thomson, F.; Thorn, S.; Turnbull, R. M.; Becker, U.; Braun, O.; Geweniger, C.; Graefe, G.; Hanke, P.; Hepp, V.; Kluge, E. E.; Putzer, A.; Rensch, B.; Schmidt, M.; Sommer, J.; Stenzel, H.; Tittel, K.; Werner, S.; Wunsch, M.; Abbaneo, D.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Colling, D. J.; Dornan, P. J.; Moutoussi, A.; Nash, J.; San Martin, G.; Sedgbeer, J. K.; Stacey, A. M.; Dissertori, G.; Girtler, P.; Kuhn, D.; Rudolph, G.; Bowdery, C. K.; Brodbeck, T. J.; Colrain, P.; Crawford, G.; Finch, A. J.; Foster, F.; Hughes, G.; Sloan, T.; Whelan, E. P.; Williams, M. I.; Galla, A.; Greene, A. M.; Kleinknecht, K.; Quast, G.; Renk, B.; Rohne, E.; Sander, H.-G.; van Gemmeren, P.; Zeitnitz, C.; Aubert, J. J.; Bencheikh, A. M.; Benchouk, C.; Bonissent, A.; Bujosa, G.; Calvet, D.; Carr, J.; Diaconu, C.; Etienne, F.; Konstantinidis, N.; Nicod, D.; Payre, P.; Rousseau, D.; Talby, M.; Sadouki, A.; Thulasidas, M.; Trabelsi, K.; Abt, I.; Assmann, R.; Bauer, C.; Blum, W.; Brown, D.; Dietl, H.; Dydak, F.; Ganis, G.; Gotzhein, C.; Jakobs, K.; Kroha, H.; Lütjens, G.; Lutz, G.; Männer, W.; Moser, H.-G.; Richter, R.; Rosado-Schlosser, A.; Schael, S.; Settles, R.; Seywerd, H.; Denis, R. St.; Wiedenmann, W.; Wolf, G.; Boucrot, J.; Callot, O.; Cordier, A.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jacquet, M.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Nikolic, I.; Park, H. J.; Park, I. C.; Schune, M.-H.; Simion, S.; Veillet, J.-J.; Videau, I.; Azzurri, P.; Bagliesi, G.; Batignani, G.; Bettarini, S.; Bozzi, C.; Calderini, G.; Carpinelli, M.; Ciocci, M. A.; Ciulli, V.; Dell'Orso, R.; Fantechi, R.; Ferrante, I.; Foà, L.; Forti, F.; Giassi, A.; Giorgi, M. A.; Gregorio, A.; Ligabue, F.; Lusiani, A.; Marrocchesi, P. S.; Messineo, A.; Rizzo, G.; Sanguinetti, G.; Sciabà, A.; Spagnolo, P.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Vannini, C.; Verdini, P. G.; Walsh, J.; Betteridge, A. P.; Blair, G. A.; Bryant, L. M.; Cerutti, F.; Chambers, J. T.; Gao, Y.; Green, M. G.; Johnson, D. L.; Medcalf, T.; Perrodo, P.; Strong, J. A.; von Wimmersperg-Toeller, J. H.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Haywood, S.; Edwards, M.; Maley, P.; Norton, P. R.; Thompson, J. C.; Bloch-Devaux, B.; Colas, P.; Emery, S.; Kozanecki, W.; Lançon, E.; Lemaire, M. C.; Locci, E.; Marx, B.; Perez, P.; Rander, J.; Renardy, J.-F.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Trabelsi, A.; Vallage, B.; Johnson, R. P.; Kim, H. Y.; Litke, A. M.; McNeil, M. A.; Taylor, G.; Beddall, A.; Booth, C. N.; Boswell, R.; Brew, C. A. J.; Cartwright, S.; Combley, F.; Koksal, A.; Letho, M.; Newton, W. M.; Rankin, C.; Reeve, J.; Thompson, L. F.; Böhrer, A.; Brandt, S.; Cowan, G.; Feigl, E.; Grupen, C.; Lutters, G.; Minguet-Rodriguez, J.; Rivera, F.; Saraiva, P.; Smolik, L.; Stephan, F.; Apollonio, M.; Bosisio, L.; Della Marina, R.; Giannini, G.; Gobbo, B.; Musolino, G.; Ragusa, F.; Rothberg, J.; Wasserbaech, S.; Armstrong, S. R.; Bellantoni, L.; Elmer, P.; Feng, Z.; Ferguson, D. P. S.; Gao, Y. S.; González, S.; Grahl, J.; Greening, T. C.; Harton, J. L.; Hayes, O. J.; Hu, H.; McNamara, P. A.; Nachtman, J. M.; Orejudos, W.; Pan, Y. B.; Saadi, Y.; Schmitt, M.; Scott, I. J.; Sharma, V.; Turk, J. D.; Walsh, A. M.; Wu, Sau Lan; Wu, X.; Yamartino, J. M.; Zheng, M.; Zobernig, G.; Aleph Collaboration
1996-02-01
Quark and gluon jets with the same energy, 24 GeV, are compared in symmetric three-jet configurations from hadronic Z decays observed by the ALEPH detector. Jets are defined using the Durham algorithm. Gluon jets are identified using an anti-tag on b jets, based on a track impact parameter method. The comparison of gluon and mixed flavour quark jets shows that gluon jets have a softer fragmentation function, a larger angular width and a higher particle multiplicity, Evidence is presented which shows that the corresponding differences between gluon and b jets are significantly smaller. In a statistically limited comparison the multiplicity in c jets was found to be comparable with that observed for the jets of mixed quark flavour.
Behaviors of Early Time Gluon Fields in High Energy Nuclear Collisions
NASA Astrophysics Data System (ADS)
Chen, Guangyao; Fries, Rainer
2010-11-01
We discuss the properties of the early time gluon fields in ultra-relativistic heavy ion collisions in a quasi-classical approximation. Using recursive solutions of the Yang-Mills equations for two intersecting color currents on the light cone, we describe the classical gluon field and its energy momentum tensor at small proper times τ after the collision of two nuclei. We explicitly check energy momentum conservation up to forth order. We compute multi-gluon correlation functions in the McLerran-Venugopalan model which are necessary to calculate the expectation value of the energy momentum tensor. An interpolation with linear gluon fields at large times provides a good approximation of the full time evolution. Our results can also be used to create an event-by- event sample of early time gluon fields.
Gluon distribution functions and Higgs boson production at moderate transverse momentum
Sun Peng; Xiao Bowen; Yuan Feng
2011-11-01
We investigate the gluon distribution functions and their contributions to the Higgs boson production in pp collisions in the transverse momentum-dependent factorization formalism. In addition to the usual azimuthal symmetric transverse momentum-dependent gluon distribution, we find that the azimuthal correlated gluon distribution also contributes to the Higgs boson production. This explains recent findings on the additional contribution in the transverse momentum resummation for the Higgs boson production as compared to that for electroweak boson production processes. We further examine the small-x naive k{sub t}-factorization in the dilute region and find that the azimuthal correlated gluon distribution contribution is consistently taken into account. The result agrees with the transverse momentum-dependent factorization formalism. We comment on the possible breakdown of the naive k{sub t}-factorization in the dense medium region, due to the unique behaviors for the gluon distributions.
Gluon distribution functions and Higgs boson production at moderate transverse momentum
Sun P.; Yuan F.; Xiao, B.W.
2011-11-04
We investigate the gluon distribution functions and their contributions to the Higgs boson production in pp collisions in the transverse momentum-dependent factorization formalism. In addition to the usual azimuthal symmetric transverse momentum-dependent gluon distribution, we find that the azimuthal correlated gluon distribution also contributes to the Higgs boson production. This explains recent findings on the additional contribution in the transverse momentum resummation for the Higgs boson production as compared to that for electroweak boson production processes. We further examine the small-x naive kt-factorization in the dilute region and find that the azimuthal correlated gluon distribution contribution is consistently taken into account. The result agrees with the transverse momentum-dependent factorization formalism. We comment on the possible breakdown of the naive kt-factorization in the dense medium region, due to the unique behaviors for the gluon distributions.
Shadowing of gluons in perturbative QCD: A comparison of different models
Jalilian-Marian, Jamal; Wang, Xin-Nian
2001-05-01
We investigate the different perturbative QCD-based models for nuclear shadowing of gluons. We show that, in the kinematic region appropriate to the BNL relativistic heavy ion collider experiment, all models give similar estimates for the magnitude of gluon shadowing. At scales relevant to CERN large hadron collider (LHC), there is a sizable difference between the predictions of the different models. However, the uncertainties in gluon shadowing coming from a different parametrization of the gluon distribution in nucleons, are larger than those due to different perturbative QCD models of gluon shadowing. We also investigate the effect of initial nonperturbative shadowing on the magnitude of perturbative shadowing and show that the magnitudes of perturbative and nonperturbative shadowing are comparable at RHIC but perturbative shadowing dominates over nonperturbative shadowing at smaller values of x reached at LHC.
Observation of Solitonic Vortices in Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Donadello, Simone; Serafini, Simone; Tylutki, Marek; Pitaevskii, Lev P.; Dalfovo, Franco; Lamporesi, Giacomo; Ferrari, Gabriele
2014-08-01
We observe solitonic vortices in an atomic Bose-Einstein condensate (BEC) after free expansion. Clear signatures of the nature of such defects are the twisted planar density depletion around the vortex line, observed in absorption images, and the double dislocation in the interference pattern obtained through homodyne techniques. Both methods allow us to determine the sign of the quantized circulation. Experimental observations agree with numerical simulations. These solitonic vortices are the decay product of phase defects of the BEC order parameter spontaneously created after a rapid quench across the BEC transition in a cigar-shaped harmonic trap and are shown to have a very long lifetime.
Local stability of the Abrashkin Yakubovich family of vortices
NASA Astrophysics Data System (ADS)
Guimbard, D.; Leblanc, S.
2006-11-01
The three-dimensional stability of the family of two-dimensional inviscid vortex patches discovered by Abrashkin & Yakubovich (Sov. Phys. Dokl. vol. 29, 1984, p. 370) is explored. Generally unsteady and non-uniform, these bounded regions of vorticity evolve freely in a surrounding irrotational flow. This family of solutions includes the Rankine circular vortex, Kirchhoff's ellipse, and freely rotating polygonal vortices as special cases. Taking advantage of their Lagrangian description, the stability analysis is carried out with the theory of local instabilities. It is shown that, apart from the Rankine vortex, these flows are three-dimensionally unstable. Background rotation or density stratification may however be stabilizing.
Vortical flow aerodynamics - Physical aspects and numerical simulation
NASA Technical Reports Server (NTRS)
Newsome, Richard W.; Kandil, Osama A.
1987-01-01
Progress in the numerical simulation of vortical flow due to three-dimensional flow separation about flight vehicles at high angles of attack and quasi-steady flight conditions is surveyed. Primary emphasis is placed on Euler and Reynolds-averaged Navier-Stokes methods where the vortices are 'captured' as a solution to the governing equations. A discussion of the relevant flow physics provides a perspective from which to assess numerical solutions. Current numerical prediction capabilities and their evolutionary development are surveyed. Future trends and challenges are identified and discussed.
Numerical solutions for unsteady subsonic vortical flows around loaded cascades
NASA Technical Reports Server (NTRS)
Fang, J.; Atassi, H. M.
1992-01-01
A frequency domain linearized unsteady aerodynamic analysis is presented for three-dimensional unsteady vortical flows around a cascade of loaded airfoils. The analysis fully accounts for the distortion of the impinging vortical disturbances by the mean flow. The entire unsteady flow field is calculated in response to upstream three-dimensional harmonic disturbances. Numerical results are presented for two standard cascade configurations representing turbine and compressor bladings for a reduced frequency range from 0.1 to 5. Results show that the upstream gust conditions and blade sweep strongly affect the unsteady blade response.
TOMS total ozone trends in potential vorticity coordinates
NASA Technical Reports Server (NTRS)
Randel, William J.; Wu, Fei
1995-01-01
Global total ozone measurements from the Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) are analyzed using potential vorticity (PV) as an approximate vortex-following coordinate. We analyze the time period November 1978-May 1991, prior to the volcanic eruption of Mt. Pinatubo. The TOMS data are remapped into PV coordinates and trends are calculated, thereby characterizing ozone losses inside and outside the winter polar vortices. These analyses show large regions of ozone loss outside of the vortex in both hemispheres. Furthermore, these data suggest that midlatitude losses in the NH during winter-spring do not result solely from the transport of ozone depleted air from inside to outside the vortex.
Z2 x Z3 Symmetry of Multferroic Vortices
NASA Astrophysics Data System (ADS)
Cheong, Sang-Wook
2014-03-01
Hexagonal REMnO3 (RE = rare earths) with RE =Ho-Lu, Y, and Sc, is an improper ferroelectric where the size mismatch between RE and Mn induces a trimerization-type structural phase transition, and this structural transition leads to three structural domains, each of which can support two directions of ferroelectric polarization. We reported that domains in h-REMnO3 meet in cloverleaf arrangements that cycle through all six domain configurations, Occurring in pairs, the cloverleafs can be viewed as vortices and antivortices, in which the cycle of domain configurations is reversed. Vortices and antivortices are topological defects: even in a strong electric field they won't annihilate. These ferroelectric vortices/antivortices are found to be associated with intriguing collective magnetism at domain walls, reflecting the multiferroic nature of vortices. We have found that an intriguing, but seemingly irregular network of a zoo of multiferroic vortices and antivortices in h-REMnO3 can be neatly analyzed in terms of graph theory, and this graph theoretical analysis reveals the emergence of Z2 × Z3 symmetry in the vortices/antivortices network. In addition, poling or self-poling due to a surface charge boundary condition induces global topological condensation of the network through breaking of the Z2 part of the Z2 × Z3 symmetry. The opposite process of restoring the Z2 symmetry can be considered as topological evaporation. It turns out that these Z2xZ3 vortices are, in fact, three-dimensional vortex loops, which result from the emergent continuous U(1) symmetry near the critical temperature. This spontaneous trapping of topological defects in the process of undergoing a continuous phase transition is important to understand numerous novel phenomena such as the early stage of universe after big bang. The so-called Kibble-Zurek mechanism was proposed for the trapping process of topological defects right after big bang. It appears that the Kibble-Zurek mechanism is also
Interaction of ultrasound with vortices in type-II superconductors
Sonin, E.B.
1996-04-01
The theory of ultrasound in the mixed state of type-II superconductors is suggested which takes into account the Magnus force on vortices, the anti-Magnus force on ions, and diamagnetism of the mixed state. The acoustic Faraday effect (rotation of polarization of the transverse ultrasonic wave propagating along vortices) is linear in the Magnus force in any regime of the flux flow for wavelengths now used in the ultrasound experiments. Therefore, in contrast to previous predictions, the Faraday effect should be looked for only in clean superconductors with a strong Magnus force. {copyright} {ital 1996 The American Physical Society.}
Unfolding of Vortices into Topological Stripes in a Multiferroic Material
NASA Astrophysics Data System (ADS)
Wang, X.; Mostovoy, M.; Han, M. G.; Horibe, Y.; Aoki, T.; Zhu, Y.; Cheong, S.-W.
2014-06-01
Multiferroic hexagonal RMnO3 (R =rare earths) crystals exhibit dense networks of vortex lines at which six domain walls merge. While the domain walls can be readily moved with an applied electric field, the vortex cores so far have been impossible to control. Our experiments demonstrate that shear strain induces a Magnus-type force pulling vortices and antivortices in opposite directions and unfolding them into a topological stripe domain state. We discuss the analogy between this effect and the current-driven dynamics of vortices in superconductors and superfluids.
Rectilinear lattices of polarization vortices with various spatial polarization distributions.
Fu, Shiyao; Zhang, Shikun; Wang, Tonglu; Gao, Chunqing
2016-08-01
In this paper, we propose a type of rectilinear lattices of polarization vortices, each spot in which has mutually independent, and controllable spatial polarization distributions. The lattices are generated by two holograms under special design. In the experiment, the holograms are encoded on two spatial light modulators, and the results fit very well with theory. Our scheme makes it possible to generate multiple polarization vortices with various polarization distributions simultaneously, for instance, radially and azimuthally polarized beams, and can be used in the domains as polarization-based data transmission system, optical manufacture, polarization detection and so on. PMID:27505812
Probing the Dynamics of Spontaneous Quantum Vortices in Polariton Superfluids
Lagoudakis, K. G.; Manni, F.; Pietka, B.; Deveaud-Pledran, B.; Wouters, M.; Liew, T. C. H.; Savona, V.; Kavokin, A. V.; Andre, R.
2011-03-18
The experimental investigation of spontaneously created vortices is of utmost importance for the understanding of quantum phase transitions towards a superfluid phase, especially for two-dimensional systems that are expected to be governed by the Berezinski-Kosterlitz-Thouless physics. By means of time-resolved near-field interferometry we track the path of such vortices, created at random locations in an exciton-polariton condensate under pulsed nonresonant excitation, to their final pinning positions imposed by the stationary disorder. We formulate a theoretical model that successfully reproduces the experimental observations.
Phase singularity of surface plasmon polaritons generated by optical vortices.
Tan, P S; Yuan, G H; Wang, Q; Zhang, N; Zhang, D H; Yuan, X-C
2011-08-15
We demonstrate an experimental result that shows the phase singularity of surface plasmon waves generated by the direct transform of optical vortices at normal incidence focused on a structureless metal surface. The near-field two-dimensional intensity distribution near the focal plane is experimentally examined by using near-field scanning optical microscopy and shows a good agreement with the finite-difference time-domain simulation result. The experimental realization demonstrates a potential of the proposed excitation scheme to be reconfigured locally with advantages over structures milled into optically thick metallic films for plasmonics applications involving plasmonic vortices. PMID:21847236
Turbulence in Flowing Soap Films: Velocity, Vorticity, and Thickness Fields
Rivera, M.; Vorobieff, P.; Ecke, R.E.
1998-08-01
We report experimental measurements of the velocity, vorticity, and thickness fields of turbulent flowing soap films using a modified particle-image velocimetry technique. These data yield the turbulent energy and enstrophy of the two-dimensional flows with microscale Reynolds numbers of about 100 and demonstrate the effects of compressibility arising from variations in film thickness. Despite the compressibility of the flow, real-space correlations of velocity, vorticity, and enstrophy flux are consistent with theoretical predictions for two-dimensional turbulence. {copyright} {ital 1998} {ital The American Physical Society }
Observation of solitonic vortices in Bose-Einstein condensates.
Donadello, Simone; Serafini, Simone; Tylutki, Marek; Pitaevskii, Lev P; Dalfovo, Franco; Lamporesi, Giacomo; Ferrari, Gabriele
2014-08-01
We observe solitonic vortices in an atomic Bose-Einstein condensate (BEC) after free expansion. Clear signatures of the nature of such defects are the twisted planar density depletion around the vortex line, observed in absorption images, and the double dislocation in the interference pattern obtained through homodyne techniques. Both methods allow us to determine the sign of the quantized circulation. Experimental observations agree with numerical simulations. These solitonic vortices are the decay product of phase defects of the BEC order parameter spontaneously created after a rapid quench across the BEC transition in a cigar-shaped harmonic trap and are shown to have a very long lifetime. PMID:25148333
Experimental Studies of Quark Gluon Plasma at RHIC
Esumi, ShinIchi
2010-05-12
A new state of matter, Quark Gluon Plasma (QGP) is supposed to exist under extreme temperature and/or density conditions just as a beginning of this early universe after the Big Bang. High energy nucleus-nucleus collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) has been used to form the QGP and to study the properties of QGP. The recent progress on the experimental research of QGP at RHIC experiments and the understanding of the properties are discussed. Major discoveries at RHIC experiments are very strong energy loss of high energy partons in central Au+Au collisions and very large elliptic and collective expansion given by the initial almond geometry in non-central Au+Au collisions. Those two finding and related physics explanations as well as future plans are presented.
Nonfactorizable soft gluons in nonleptonic heavy meson decays
Li, H.; Tseng, B.
1998-01-01
We include nonfactorizable soft gluon corrections to the perturbative QCD formalism for exclusive nonleptonic heavy meson decays, which combines factorization theorems and effective field theory. These corrections are classified according to their color structures, and exponentiated separately to complete the Sudakov resummation up to next-to-leading logarithms. The nonfactorizable contributions in nonleptonic decays are clearly identified in our formalism, and found to be positive for bottom decays and negative for charm decays. Our analysis confirms that the large-N{sub c} approximaton is applicable to charm decays, but not to bottom decays, consistent with the phenomenological implications of experimental data. The comparision of our predictions with those from QCD sum rules is also made. {copyright} {ital 1997} {ital The American Physical Society}
Experimental Studies of Quark Gluon Plasma at RHIC
NASA Astrophysics Data System (ADS)
Esumi, ShinIchi
2010-05-01
A new state of matter, Quark Gluon Plasma (QGP) is supposed to exist under extreme temperature and/or density conditions just as a beginning of this early universe after the Big Bang. High energy nucleus-nucleus collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) has been used to form the QGP and to study the properties of QGP. The recent progress on the experimental research of QGP at RHIC experiments and the understanding of the properties are discussed. Major discoveries at RHIC experiments are very strong energy loss of high energy partons in central Au+Au collisions and very large elliptic and collective expansion given by the initial almond geometry in non-central Au+Au collisions. Those two finding and related physics explanations as well as future plans are presented.
Gluon-fusion contributions to {Phi}+2 jet production
Campanario, F.; Zeppenfeld, D.; Kubocz, M.
2011-11-01
In high energy hadronic collisions, a scalar or pseudoscalar Higgs boson, {Phi}=H, A, can be efficiently produced via gluon fusion, which is mediated by heavy quark loops. In this paper, we consider double real emission corrections to {Phi}=A production, which lead to a Higgs plus two-jet final state, at order {alpha}{sub s}{sup 4}. Full quark mass effects are considered in the calculation of scattering amplitudes for the CP-odd Higgs boson A, as induced by quark triangle-, box-, and pentagon-diagrams. They complement the analogous results for a CP-even Higgs boson H in Ref. [1]. Interference effects between loops with top and bottom quarks as well as between CP-even and CP-odd couplings of the heavy quarks are fully taken into account.
Gluon fragmentation into quarkonium at next-to-leading order
NASA Astrophysics Data System (ADS)
Artoisenet, Pierre; Braaten, Eric
2015-04-01
We present the first calculation at next-to-leading order (NLO) in α s of a fragmentation function into quarkonium whose form at leading order is a nontrivial function of z, namely the fragmentation function for a gluon into a spin-singlet S-wave state at leading order in the relative velocity. To calculate the real NLO corrections, we introduce a new subtraction scheme that allows the phase-space integrals to be evaluated in 4 dimensions. We extract all ultraviolet and infrared divergences in the real NLO corrections analytically by calculating the phase-space integrals of the subtraction terms in 4 - 2 ɛ dimensions. We also extract the divergences in the virtual NLO corrections analytically, and detail the cancellation of all divergences after renormalization. The NLO corrections have a dramatic effect on the shape of the fragmentation function, and they significantly increase the fragmentation probability.
Quantum simulations of strongly coupled quark-gluon plasma
Filinov, V. S.; Ivanov, Yu. B.; Bonitz, M.; Levashov, P. R.; Fortov, V. E.
2011-09-15
A strongly coupled quark-gluon plasma (QGP) of heavy constituent quasiparticles is studied by a path-integral Monte-Carlo method. This approach is a quantum generalization of the model developed by B.A. Gelman, E.V. Shuryak, and I. Zahed. It is shown that this method is able to reproduce the QCD lattice equation of state and also yields valuable insight into the internal structure of the QGP. The results indicate that the QGP reveals liquid-like rather than gas-like properties. At temperatures just above the critical one it was found that bound quark-antiquark states still survive. These states are bound by effective string-like forces and turn out to be colorless. At the temperature as large as twice the critical one no bound states are observed. Quantum effects turned out to be of prime importance in these simulations.
Renormalization group analysis of the gluon mass equation
NASA Astrophysics Data System (ADS)
Aguilar, A. C.; Binosi, D.; Papavassiliou, J.
2014-04-01
We carry out a systematic study of the renormalization properties of the integral equation that determines the momentum evolution of the effective gluon mass in pure Yang-Mills theory, without quark effects taken into account. A detailed, all-order analysis of the complete kernel appearing in this particular equation, derived in the Landau gauge, reveals that the renormalization procedure may be accomplished through the sole use of ingredients known from the standard perturbative treatment of the theory, with no additional assumptions. However, the subtle interplay of terms operating at the level of the exact equation gets distorted by the approximations usually employed when evaluating the aforementioned kernel. This fact is reflected in the form of the obtained solutions, for which the deviations from the correct behavior are best quantified by resorting to appropriately defined renormalization-group invariant quantities. This analysis, in turn, provides a solid guiding principle for improving the form of the kernel, and furnishes a well-defined criterion for discriminating between various possibilities. Certain renormalization-group inspired Ansätze for the kernel are then proposed, and their numerical implications are explored in detail. One of the solutions obtained fulfills the theoretical expectations to a high degree of accuracy, yielding a gluon mass that is positive definite throughout the entire range of physical momenta, and displays in the ultraviolet the so-called "power-law" running, in agreement with standard arguments based on the operator product expansion. Some of the technical difficulties thwarting a more rigorous determination of the kernel are discussed, and possible future directions are briefly mentioned.
The Berry Connection of the Ginzburg-Landau Vortices
NASA Astrophysics Data System (ADS)
Nagy, Ákos
2016-06-01
We analyze 2-dimensional Ginzburg-Landau vortices at critical coupling, and establish asymptotic formulas for the tangent vectors of the vortex moduli space using theorems of Taubes and Bradlow. We then compute the corresponding Berry curvature and holonomy in the large area limit.
Propagation of magnetic vortices using nanocontacts as tunable attractors
NASA Astrophysics Data System (ADS)
Manfrini, M.; Kim, Joo-Von; Petit-Watelot, S.; van Roy, W.; Lagae, L.; Chappert, C.; Devolder, T.
2014-02-01
Magnetic vortices in thin films are in-plane spiral spin configurations with a core in which the magnetization twists out of the film plane. Vortices result from the competition between atomic-scale exchange forces and long-range dipolar interactions. They are often the ground state of magnetic dots, and have applications in medicine, microwave generation and information storage. The compact nature of the vortex core, which is 10-20 nm wide, makes it a suitable probe of magnetism at the nanoscale. However, thus far the positioning of a vortex has been possible only in confined structures, which prevents its transport over large distances. Here we show that vortices can be propagated in an unconstrained system that comprises electrical nanocontacts (NCs). The NCs are used as tunable vortex attractors in a manner that resembles the propelling of space craft with gravitational slingshots. By passing current from the NCs to a ferromagnetic film, circulating magnetic fields are generated, which nucleate the vortex and create a potential well for it. The current becomes spin polarized in the film, and thereby drives the vortex into gyration through spin-transfer torques. The vortex can be guided from one NC to another by tuning attractive strengths of the NCs. We anticipate that NC networks may be used as multiterminal sources of vortices and spin waves (as well as heat, spin and charge flows) to sense the fundamental interactions between physical objects and fluxes of the next-generation spintronic devices.
Swirls and splashes: air vortices created by drop impact
NASA Astrophysics Data System (ADS)
Bischofberger, Irmgard; Mauser, Kelly W.; Latka, Andrzej; Nagel, Sidney R.
2013-03-01
A drop impacting a solid surface with sufficient velocity will splash and emit many small droplets. While liquid and substrate properties are clearly important for determining the splashing threshold, it has been shown that removing the ambient air suppresses splashing completely. However, the mechanism underlying how the surrounding gas affects splashing remains unknown. As has been recently shown, there is no air beneath the liquid that could cause the splash - thus where does the air matter? We use modified Schlieren optics combined with high-speed video imaging to visualize the air vortices created by the rapid spreading of the drop after it hit the substrate. In the first moments after impact, these vortices remain bound to the spreading drop, creating a low-pressure zone that travels with the advancing lamella. At a later time, after the occurrence of the splash, the vortices detach from the drop. We discuss possible connections between the forces generated by the vortices on the liquid lamella and the initiation of a splash.
3D visualization of unsteady 2D airplane wake vortices
NASA Technical Reports Server (NTRS)
Ma, Kwan-Liu; Zheng, Z. C.
1994-01-01
Air flowing around the wing tips of an airplane forms horizontal tornado-like vortices that can be dangerous to following aircraft. The dynamics of such vortices, including ground and atmospheric effects, can be predicted by numerical simulation, allowing the safety and capacity of airports to be improved. In this paper, we introduce three-dimensional techniques for visualizing time-dependent, two-dimensional wake vortex computations, and the hazard strength of such vortices near the ground. We describe a vortex core tracing algorithm and a local tiling method to visualize the vortex evolution. The tiling method converts time-dependent, two-dimensional vortex cores into three-dimensional vortex tubes. Finally, a novel approach calculates the induced rolling moment on the following airplane at each grid point within a region near the vortex tubes and thus allows three-dimensional visualization of the hazard strength of the vortices. We also suggest ways of combining multiple visualization methods to present more information simultaneously.
Vortical Flow Prediction Using an Adaptive Unstructured Grid Method
NASA Technical Reports Server (NTRS)
Pirzadeh, Shahyar Z.
2001-01-01
A computational fluid dynamics (CFD) method has been employed to compute vortical flows around slender wing/body configurations. The emphasis of the paper is on the effectiveness of an adaptive grid procedure in "capturing" concentrated vortices generated at sharp edges or flow separation lines of lifting surfaces flying at high angles of attack. The method is based on a tetrahedral unstructured grid technology developed at the NASA Langley Research Center. Two steady-state, subsonic, inviscid and Navier-Stokes flow test cases are presented to demonstrate the applicability of the method for solving practical vortical flow problems. The first test case concerns vortex flow over a simple 65deg delta wing with different values of leading-edge bluntness, and the second case is that of a more complex fighter configuration. The superiority of the adapted solutions in capturing the vortex flow structure over the conventional unadapted results is demonstrated by comparisons with the windtunnel experimental data. The study shows that numerical prediction of vortical flows is highly sensitive to the local grid resolution and that the implementation of grid adaptation is essential when applying CFD methods to such complicated flow problems.
The Vortices Trapped above Low-aspect-ratio Wings
NASA Astrophysics Data System (ADS)
Tang, Jian
2007-11-01
A stationary vortex trapped above the nondelta, low-aspect-ratio wings was first obtained in 3D unsteady numerical simulation. Flow visualization was conducted in water-channel using hydrogen bubble. The results verify that there is a vortex trapped above the low-aspect-ratio wings and the stationary vortex is consisted of two semi-ball, anti-rotation vortices which are different from the leading edge vortices on the delta wing. This stationary vortex trapped above the nondelta, low-aspect-ratio wings is a new phenomenon, which is different from the leading edge vortex on the delta wing. The numerical results show that lift coefficient increase to 0.8 when incidence increases form 0^o to 30^o, the lift coefficient keeps this value up to 45^o--a very high stall angle. The numerical results indicate that the trapped vortex might be the source of the high stall angle of attack and nonlinear lift at high incidence. Accompanied with the low-aspect-ratio wing, the existence of the stationary vortex is thought to be related to the strong effects of tip vortices. Further experimental and numerical works have been undertaken, the results show that trapped vortices have variant shapes and different critical angels of attack.
Analysis of vortical flow with axial swirl and toroidal circulation
NASA Astrophysics Data System (ADS)
Bhattacharya, Sukalyan
2006-11-01
Vortical flows with an axial swirl and a toroidal circulation can be observed in a wide range of fluid mechanical phenomena such as flow around rotary machines or natural vortices like tornadoes and hurricanes. These flows can be described by a general scalar equation if incompressible fluid and negligible viscous dissipation are assumed. We consider one of the simpler cases of this general formulation where the involved equation has a resemblance with the governing equation of the hydrogen problem. As a result, we obtain a quantization relation similar to the expression of quantized energies in an hydrogen atom. We solve the equation for two systems. First, we consider three- dimensional vortices confined between two parallel walls. Our examples include flows between two infinite plates, inside and outside of a vertical cylinder bounded at the ends by walls, and in an axially confined annular region. Then we also use our formulation to compute highly chaotic velocity fields with three-dimensional vortical structures which qualitatively mimic the features of physical flows. Hence, these solutions may be used in modeling of complicated flow systems.