Vorticity and vortex dynamics

CERN Document Server

Wu, Jie-Zhi; Zhou, M-D

2006-01-01

The importance of vorticity and vortex dynamics has now been well rec- nized at both fundamental and applied levels of ?uid dynamics, as already anticipatedbyTruesdellhalfcenturyagowhenhewrotethe?rstmonograph onthesubject, The Kinematics of Vorticity(1954);andasalsoevidencedby the appearance of several books on this ?eld in 1990s. The present book is characterizedbythefollowingfeatures: 1. A basic physical guide throughout the book. The material is directed by a basic observation on the splitting and coupling of two fundamental processes in ?uid motion, i.e., shearing (unique to ?uid) and compre- ing/expanding.Thevorticityplaysakeyroleintheformer,andavortex isnothingbuta?uidbodywithhighconcentrationofvorticitycompared to its surrounding ?uid. Thus, the vorticity and vortex dynamics is - cordinglyde?nedasthetheoryofshearingprocessanditscouplingwith compressing/expandingprocess. 2. A description of the vortex evolution following its entire life.Thisbegins from the generation of vorticity to the formation of thi...

Dynamics of nonstationary dipole vortices

DEFF Research Database (Denmark)

Hesthaven, J.S.; Lynov, Jens-Peter; Nycander, J.

1993-01-01

The dynamics of tilted dipole vortices in the equivalent barotropic vorticity (or Hasegawa-Mima) equation is studied. A recent theory is compared with numerical simulations and found to describe the short time behavior of dipole vortices well. In the long time limit the dipoles are found to eithe...... disintegrate or relax toward a steady eastward propagating dipole vortex. This relaxation is a consequence of nonviscous enstrophy loss by the dipole vortex....

Topological charge algebra of optical vortices in nonlinear interactions.

Science.gov (United States)

Zhdanova, Alexandra A; Shutova, Mariia; Bahari, Aysan; Zhi, Miaochan; Sokolov, Alexei V

2015-12-28

We investigate the transfer of orbital angular momentum among multiple beams involved in a coherent Raman interaction. We use a liquid crystal light modulator to shape pump and Stokes beams into optical vortices with various integer values of topological charge, and cross them in a Raman-active crystal to produce multiple Stokes and anti-Stokes sidebands. We measure the resultant vortex charges using a tilted-lens technique. We verify that in every case the generated beams' topological charges obey a simple relationship, resulting from angular momentum conservation for created and annihilated photons, or equivalently, from phase-matching considerations for multiple interacting beams.

Nonquasineutral electron vortices in nonuniform plasmas

Energy Technology Data Exchange (ETDEWEB)

Angus, J. R.; Richardson, A. S.; Swanekamp, S. B.; Schumer, J. W. [Plasma Physics Division, Naval Research Laboratory, Washington, District of Columbia 20375 (United States); Ottinger, P. F. [Engility Corporation, Chantilly, Virginia 20151 (United States)

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.

Vortices and polynomials: non-uniqueness of the Adler–Moser polynomials for the Tkachenko equation

International Nuclear Information System (INIS)

Demina, Maria V; Kudryashov, Nikolai A

2012-01-01

Stationary and translating relative equilibria of point vortices in the plane are studied. It is shown that stationary equilibria of any system containing point vortices with arbitrary choice of circulations can be described with the help of the Tkachenko equation. It is also obtained that translating relative equilibria of point vortices with arbitrary circulations can be constructed using a generalization of the Tkachenko equation. Roots of any pair of polynomials solving the Tkachenko equation and the generalized Tkachenko equation are proved to give positions of point vortices in stationary and translating relative equilibria accordingly. These results are valid even if the polynomials in a pair have multiple or common roots. It is obtained that the Adler–Moser polynomial provides non-unique polynomial solutions of the Tkachenko equation. It is shown that the generalized Tkachenko equation possesses polynomial solutions with degrees that are not triangular numbers. (paper)

Dynamics of vortices in polariton quantum fluids : From full vortices, to half vortices and vortex pairs

Science.gov (United States)

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.

VORTICAL MODEL OF THE WING COVERED WITH CONTINUOUSLY DISTRIBUTED CIRCULATION OF THE VORTICAL LAYER

Directory of Open Access Journals (Sweden)

B. L. Artamonov

2014-01-01

Full Text Available The linear vortical model ot the final scope of a wing is exsamined. It representis the flat rectangular spatial veil covered with continuously distributed vortical layer. Elements of digitization of a veil are the quadrangular panels laying on its surface. Method, algorithms and the program of calculation of three making vectors of inductive speed from any guided rectangular platform covered with a vortical layer are created. Its intensity linearly changes on the surface of a platform. The decision is received in elementary functions. The numerical way solves the task of a definition of the law of circulation of the attached whirlwinds in scope of a wing and calculation of its aerodynamic characteristics, being based on the accepted vortical model and a hypothesis of flat sections.

Vorticity budget of a tornado-like vortex

Energy Technology Data Exchange (ETDEWEB)

Sassa, Koji; Takemura, Saki, E-mail: sassa@kochi-u.ac.jp [Department of Applied Science, Kochi University (Japan)

2011-12-22

We evaluated the vorticity budget of a tornado-like vortex by measuring vertical and horizontal circulations of it. Though spiral horizontal vortices are clearly observed to converge and tilted into the tornado-like vortex, their circulation is quite small. The conversion of the vertical vorticity concentrated at the side of the spiral horizontal vortices was found to mainly contribute to the maintenance of the tornado-like vortex.

Review of vortices in wildland fire

Science.gov (United States)

Jason M. Forthofer; Scott L. Goodrick

2011-01-01

Vortices are almost always present in the wildland fire environment and can sometimes interact with the fire in unpredictable ways, causing extreme fire behavior and safety concerns. In this paper, the current state of knowledge of the interaction of wildland fire and vortices is examined and reviewed. A basic introduction to vorticity is given, and the two common...

Vortices wiggled and dragged

International Nuclear Information System (INIS)

Reichardt, Charles

2008-01-01

When a sufficiently strong magnetic field is applied to a superconductor, some of the field can pierce it through the generation of magnetic vortices, each of which contains a quantized amount of magnetic flux. Although the superconducting state of the material outside each vortex is maintained (and destroyed within each vortex), the interaction of vortices with a current passing through the material can cause them to move, dissipating energy and thereby generating a source of electrical resistance. The ability to manipulate an individual superconducting vortex represents a powerful tool for studying the dynamics of vortices and the superconductors that support them. It could also lead to the development of a new class of fluxon-based electronics.

A thermodynamically general theory for convective vortices

Science.gov (United States)

Renno, Nilton O.

2008-08-01

Convective vortices are common features of atmospheres that absorb lower-entropy-energy at higher temperatures than they reject higher-entropy-energy to space. These vortices range from small to large-scale and play an important role in the vertical transport of heat, momentum, and tracer species. Thus, the development of theoretical models for convective vortices is important to our understanding of some of the basic features of planetary atmospheres. The heat engine framework is a useful tool for studying convective vortices. However, current theories assume that convective vortices are reversible heat engines. Since there are questions about how reversible real atmospheric heat engines are, their usefulness for studying real atmospheric vortices is somewhat controversial. In order to reduce this problem, a theory for convective vortices that includes irreversible processes is proposed. The paper's main result is that the proposed theory provides an expression for the pressure drop along streamlines that includes the effects of irreversible processes. It is shown that a simplified version of this expression is a generalization of Bernoulli's equation to convective circulations. It is speculated that the proposed theory not only explains the intensity, but also sheds light on other basic features of convective vortices such as their physical appearance.

Near-field multiple traps of paraxial acoustic vortices with strengthened gradient force generated by sector transducer array

Science.gov (United States)

Wang, Qingdong; Li, Yuzhi; Ma, Qingyu; Guo, Gepu; Tu, Juan; Zhang, Dong

2018-01-01

In order to improve the capability of particle trapping close to the source plane, theoretical and experimental studies on near-field multiple traps of paraxial acoustic vortices (AVs) with a strengthened acoustic gradient force (AGF) generated by a sector transducer array were conducted. By applying the integration of point source radiation, numerical simulations for the acoustic fields generated by the sector transducer array were conducted and compared with those produced by the circular transducer array. It was proved that strengthened AGFs of near-field multiple AVs with higher peak pressures and smaller vortex radii could be produced by the sector transducer array with a small topological charge. The axial distributions of the equivalent potential gradient indicated that the AGFs of paraxial AVs in the near field were much higher than those in the far field, and the distances at the near-field vortex antinodes were also proved to be the ideal trapping positions with relatively higher AGFs. With the established 8-channel AV generation system, theoretical studies were also verified by the experimental measurements of pressure and phase for AVs with various topological charges. The formation of near-field multiple paraxial AVs was verified by the cross-sectional circular pressure distributions with perfect phase spirals around central pressure nulls, and was also proved by the vortex nodes and antinodes along the center axis. The favorable results demonstrated the feasibility of generating near-field multiple traps of paraxial AVs with strengthened AGF using the sector transducer array, and suggested the potential applications of close-range particle trapping in biomedical engineering.

Vortices on hyperbolic surfaces

International Nuclear Information System (INIS)

Manton, Nicholas S; Rink, Norman A

2010-01-01

It is shown that Abelian Higgs vortices on a hyperbolic surface M can be constructed geometrically from holomorphic maps f: M → N, where N is also a hyperbolic surface. The fields depend on f and on the metrics of M and N. The vortex centres are the ramification points, where the derivative of f vanishes. The magnitude of the Higgs field measures the extent to which f is locally an isometry. Witten's construction of vortices on the hyperbolic plane is rederived, and new examples of vortices on compact surfaces and on hyperbolic surfaces of revolution are obtained. The interpretation of these solutions as SO(3)-invariant, self-dual SU(2) Yang-Mills fields on R 4 is also given.

Efficient collective swimming by harnessing vortices through deep reinforcement learning.

Science.gov (United States)

Verma, Siddhartha; Novati, Guido; Koumoutsakos, Petros

2018-06-05

Fish in schooling formations navigate complex flow fields replete with mechanical energy in the vortex wakes of their companions. Their schooling behavior has been associated with evolutionary advantages including energy savings, yet the underlying physical mechanisms remain unknown. We show that fish can improve their sustained propulsive efficiency by placing themselves in appropriate locations in the wake of other swimmers and intercepting judiciously their shed vortices. This swimming strategy leads to collective energy savings and is revealed through a combination of high-fidelity flow simulations with a deep reinforcement learning (RL) algorithm. The RL algorithm relies on a policy defined by deep, recurrent neural nets, with long-short-term memory cells, that are essential for capturing the unsteadiness of the two-way interactions between the fish and the vortical flow field. Surprisingly, we find that swimming in-line with a leader is not associated with energetic benefits for the follower. Instead, "smart swimmer(s)" place themselves at off-center positions, with respect to the axis of the leader(s) and deform their body to synchronize with the momentum of the oncoming vortices, thus enhancing their swimming efficiency at no cost to the leader(s). The results confirm that fish may harvest energy deposited in vortices and support the conjecture that swimming in formation is energetically advantageous. Moreover, this study demonstrates that deep RL can produce navigation algorithms for complex unsteady and vortical flow fields, with promising implications for energy savings in autonomous robotic swarms.

Theory of concentrated vortices an introduction

CERN Document Server

Alekseenko, S V; Okulov, V L

2007-01-01

Vortex motion is one of the basic states of a flowing continuum. Intere- ingly, in many cases vorticity is space-localized, generating concentrated vortices. Vortex filaments having extremely diverse dynamics are the most characteristic examples of such vortices. Notable examples, in particular, include such phenomena as self-inducted motion, various instabilities, wave generation, and vortex breakdown. These effects are typically ma- fested as a spiral (or helical) configuration of a vortex axis. Many publications in the field of hydrodynamics are focused on vortex motion and vortex effects. Only a few books are devoted entirely to v- tices, and even fewer to concentrated vortices. This work aims to highlight the key problems of vortex formation and behavior. The experimental - servations of the authors, the impressive visualizations of concentrated vortices (including helical and spiral) and pictures of vortex breakdown primarily motivated the authors to begin this work. Later, the approach based on the hel...

Modeling of oceanic vortices

Science.gov (United States)

Cushman-Roisin, B.

Following on a tradition of biannual meetings, the 5th Colloquium on the Modeling of Oceanic Vortices was held May 21-23, 1990, at the Thayer School of Engineering at Dartmouth College, Hanover, N.H. The colloquium series, sponsored by the Office of Naval Research, is intended to gather oceanographers who contribute to our understanding of oceanic mesoscale vortices via analytical, numerical and experimental modeling techniques.

Global reconnection topology as inferred from plasma observations inside Kelvin-Helmholtz vortices

Directory of Open Access Journals (Sweden)

M. B. Bavassano Cattaneo

2010-04-01

Full Text Available During a long lasting period of northward interplanetary magnetic field and high solar wind speed (above 700 km/s, the Cluster spacecraft go across a number of very large rolled-up Kelvin-Helmholtz (KH vortices at the dusk magnetopause, close to the terminator. The peculiarity of the present event is a particular sequence of ions and electrons distribution functions observed repeatedly inside each vortex. In particular, whenever Cluster crosses the current layer inside the vortices, multiple field-aligned ion populations appear, suggesting the occurrence of reconnection. In addition, the ion data display a clear velocity filter effect both at the leading and at the trailing edge of each vortex. This effect is not present in the simultaneous electron data. Unlike other KH studies reported in the literature in which reconnection occurs within the vortices, in the present event the observations are not compatible with local reconnection, but are accounted for by lobe reconnection occurring along an extended X-line at the terminator in the Southern Hemisphere. The reconnected field lines "sink" across the magnetopause and then convect tailward-duskward where they become embedded in the vortices. Another observational evidence is the detected presence of solar wind plasma on the magnetospheric side of the vortices, which confirms unambiguously the occurrence of mass transport across the magnetopause already reported in the literature. The proposed reconnection scenario accounts for all the observational aspects, regarding both the transport process and the kinetic signatures.

Compact vortices

Energy Technology Data Exchange (ETDEWEB)

Bazeia, D.; Losano, L.; Marques, M.A.; Zafalan, I. [Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, PB (Brazil); Menezes, R. [Universidade Federal da Paraiba, Departamento de Ciencias Exatas, Rio Tinto, PB (Brazil); Universidade Federal de Campina Grande, Departamento de Fisica, Campina Grande, PB (Brazil)

2017-02-15

We study a family of Maxwell-Higgs models, described by the inclusion of a function of the scalar field that represent generalized magnetic permeability. We search for vortex configurations which obey first-order differential equations that solve the equations of motion. We first deal with the asymptotic behavior of the field configurations, and then implement a numerical study of the solutions, the energy density and the magnetic field. We work with the generalized permeability having distinct profiles, giving rise to new models, and we investigate how the vortices behave, compared with the solutions of the corresponding standard models. In particular, we show how to build compact vortices, that is, vortex solutions with the energy density and magnetic field vanishing outside a compact region of the plane. (orig.)

Sources of CAM3 vorticity bias during northern winter from diagnostic study of the vorticity equation

Energy Technology Data Exchange (ETDEWEB)

Grotjahn, Richard [University of California, Department of Land, Air and Water Resources, Davis, CA (United States); Pan, Lin-Lin; Tribbia, Joseph [National Center for Atmospheric Research, Boulder, CO (United States)

2011-06-15

CAM3 (Community Atmosphere Model version 3) simulation bias is diagnosed using the vorticity equation. The study compares CAM3 output with ECMWF (European Centre for Medium-Range Weather Forecasts) 40 year reanalysis (ERA-40) data. A time mean vorticity bias equation is also formulated and the terms are grouped into categories: linear terms, nonlinear terms, transient contributions, and friction (calculated as a residual). Frontal cyclone storms have much weaker band passed kinetic energy and enstrophy in CAM3. The downstream end of the North Atlantic storm track (NAST) has large location error. While the vorticity equation terms have similar amplitude ranking in CAM3 and ERA-40 at upper levels, the ranking differs notably in the lower troposphere. The linear and friction terms dominate the vorticity bias equation. The transient terms contribute along the storm track, but the nonlinear terms are generally much smaller, with the primary exception being over the Iberian peninsula. Friction is much stronger in CAM3. As evidence, nearly all wavelengths (including the longest planetary waves) have smaller amplitude in CAM3 than in ERA-40 vorticity data. Negative near surface vorticity tendency bias on the European side of the Arctic is linked to the NAST track error (evident in the divergence term). CAM3 misses the Beaufort high in sea level pressure (SLP) due to low level warm temperature bias, too little vortex compression, and to too little horizontal advection of negative vorticity compared with ERA-40. Generally lower SLP values in CAM3 over the entire Arctic follow from lower level warm bias in CAM3. (orig.)

Vorticity Dynamics in Single and Multiple Swirling Reacting Jets

Science.gov (United States)

Smith, Travis; Aguilar, Michael; Emerson, Benjamin; Noble, David; Lieuwen, Tim

2015-11-01

This presentation describes an analysis of the unsteady flow structures in two multinozzle swirling jet configurations. This work is motivated by the problem of combustion instabilities in premixed flames, a major concern in the development of modern low NOx combustors. The objective is to compare the unsteady flow structures in these two configurations for two separate geometries and determine how certain parameters, primarily distance between jets, influence the flow dynamics. The analysis aims to differentiate between the flow dynamics of single nozzle and triple nozzle configurations. This study looks at how the vorticity in the shear layers of one reacting swirling jet can affect the dynamics of a nearby similar jet. The distance between the swirling jets is found to have an effect on the flow field in determining where swirling jets merge and on the dynamics upstream of the merging location. Graduate Student, School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA.

Travelling water waves with compactly supported vorticity

International Nuclear Information System (INIS)

Shatah, Jalal; Walsh, Samuel; Zeng, Chongchun

2013-01-01

In this paper, we prove the existence of two-dimensional, travelling, capillary-gravity, water waves with compactly supported vorticity. Specifically, we consider the cases where the vorticity is a δ-function (a point vortex), or has small compact support (a vortex patch). Using a global bifurcation theoretic argument, we construct a continuum of finite-amplitude, finite-vorticity solutions for the periodic point vortex problem. For the non-periodic case, with either a vortex point or patch, we prove the existence of a continuum of small-amplitude, small-vorticity solutions. (paper)

Structure-Preserving Variational Multiscale Modeling of Turbulent Incompressible Flow with Subgrid Vortices

Science.gov (United States)

Evans, John; Coley, Christopher; Aronson, Ryan; Nelson, Corey

2017-11-01

In this talk, a large eddy simulation methodology for turbulent incompressible flow will be presented which combines the best features of divergence-conforming discretizations and the residual-based variational multiscale approach to large eddy simulation. In this method, the resolved motion is represented using a divergence-conforming discretization, that is, a discretization that preserves the incompressibility constraint in a pointwise manner, and the unresolved fluid motion is explicitly modeled by subgrid vortices that lie within individual grid cells. The evolution of the subgrid vortices is governed by dynamical model equations driven by the residual of the resolved motion. Consequently, the subgrid vortices appropriately vanish for laminar flow and fully resolved turbulent flow. As the resolved velocity field and subgrid vortices are both divergence-free, the methodology conserves mass in a pointwise sense and admits discrete balance laws for energy, enstrophy, and helicity. Numerical results demonstrate the methodology yields improved results versus state-of-the-art eddy viscosity models in the context of transitional, wall-bounded, and rotational flow when a divergence-conforming B-spline discretization is utilized to represent the resolved motion.

An Improved Wake Vortex Tracking Algorithm for Multiple Aircraft

Science.gov (United States)

Switzer, George F.; Proctor, Fred H.; Ahmad, Nashat N.; LimonDuparcmeur, Fanny M.

2010-01-01

The accurate tracking of vortex evolution from Large Eddy Simulation (LES) data is a complex and computationally intensive problem. The vortex tracking requires the analysis of very large three-dimensional and time-varying datasets. The complexity of the problem is further compounded by the fact that these vortices are embedded in a background turbulence field, and they may interact with the ground surface. Another level of complication can arise, if vortices from multiple aircrafts are simulated. This paper presents a new technique for post-processing LES data to obtain wake vortex tracks and wake intensities. The new approach isolates vortices by defining "regions of interest" (ROI) around each vortex and has the ability to identify vortex pairs from multiple aircraft. The paper describes the new methodology for tracking wake vortices and presents application of the technique for single and multiple aircraft.

Vorticity and Λ polarization in baryon rich matter

Science.gov (United States)

Baznat, Mircea; Gudima, Konstantin; Prokhorov, George; Sorin, Alexander; Teryaev, Oleg; Zakharov, Valentin

2018-02-01

The polarization of Λ hyperons due to axial chiral vortical effect is discussed. The effect is proportional to (strange) chemical potential and is pronounced at lower energies in baryon-rich matter. The polarization of ¯ has the same sihn and larger magnitude. The emergence of vortical structures is observed in kinetic QGSM models. The hydrodynamical helicity separation receives the contribution of longitudinal velocity and vorticity implying the quadrupole structure of the latter. The transition from the quark vortical effects to baryons in confined phase may be achieved by exploring the axial charge. At the hadronic level the polarization corresponds to the cores of quantized vortices in pionic superfluid. The chiral vortical effects may be also studied in the frmework of Wigner function establishing the relation to the thermodynamical approach to polarization.

Spindles and active vortices in a model of confined filament-motor mixtures.

Science.gov (United States)

Head, David A; Briels, Wj; Gompper, Gerhard

2011-11-16

Robust self-organization of subcellular structures is a key principle governing the dynamics and evolution of cellular life. In fission yeast cells undergoing division, the mitotic spindle spontaneously emerges from the interaction of microtubules, motor proteins and the confining cell walls, and asters and vortices have been observed to self-assemble in quasi-two dimensional microtubule-kinesin assays. There is no clear microscopic picture of the role of the active motors driving this pattern formation, and the relevance of continuum modeling to filament-scale structures remains uncertain. Here we present results of numerical simulations of a discrete filament-motor protein model confined to a pressurised cylindrical box. Stable spindles, nematic configurations, asters and high-density semi-asters spontaneously emerge, the latter pair having also been observed in cytosol confined within emulsion droplets. State diagrams are presented delineating each stationary state as the pressure, motor speed and motor density are varied. We further highlight a parameter regime where vortices form exhibiting collective rotation of all filaments, but have a finite life-time before contracting to a semi-aster. Quantifying the distribution of life-times suggests this contraction is a Poisson process. Equivalent systems with fixed volume exhibit persistent vortices with stochastic switching in the direction of rotation, with switching times obeying similar statistics to contraction times in pressurised systems. Furthermore, we show that increasing the detachment rate of motors from filament plus-ends can both destroy vortices and turn some asters into vortices. We have shown that discrete filament-motor protein models provide new insights into the stationary and dynamical behavior of active gels and subcellular structures, because many phenomena occur on the length-scale of single filaments. Based on our findings, we argue the need for a deeper understanding of the microscopic

High-efficiency single cell encapsulation and size selective capture of cells in picoliter droplets based on hydrodynamic micro-vortices.

Science.gov (United States)

Kamalakshakurup, Gopakumar; Lee, Abraham P

2017-12-05

Single cell analysis has emerged as a paradigm shift in cell biology to understand the heterogeneity of individual cells in a clone for pathological interrogation. Microfluidic droplet technology is a compelling platform to perform single cell analysis by encapsulating single cells inside picoliter-nanoliter (pL-nL) volume droplets. However, one of the primary challenges for droplet based single cell assays is single cell encapsulation in droplets, currently achieved either randomly, dictated by Poisson statistics, or by hydrodynamic techniques. In this paper, we present an interfacial hydrodynamic technique which initially traps the cells in micro-vortices, and later releases them one-to-one into the droplets, controlled by the width of the outer streamline that separates the vortex from the flow through the streaming passage adjacent to the aqueous-oil interface (d gap ). One-to-one encapsulation is achieved at a d gap equal to the radius of the cell, whereas complete trapping of the cells is realized at a d gap smaller than the radius of the cell. The unique feature of this technique is that it can perform 1. high efficiency single cell encapsulations and 2. size-selective capturing of cells, at low cell loading densities. Here we demonstrate these two capabilities with a 50% single cell encapsulation efficiency and size selective separation of platelets, RBCs and WBCs from a 10× diluted blood sample (WBC capture efficiency at 70%). The results suggest a passive, hydrodynamic micro-vortex based technique capable of performing high-efficiency single cell encapsulation for cell based assays.

Effects of outer perturbances on dynamics of wake vortices

International Nuclear Information System (INIS)

Baranov, N.A.; Belotserkovsky, A.S.; Turchak, L.I.

2004-01-01

One of the problems in aircraft flight safety is reduction of the risk related with aircraft encounter with wake vortices generated by other aircraft. An efficient approach to this problem is design of systems providing information on areas of potential danger of wake vortices to pilots in real time. The main components of such a system are a unit for calculations of wake vortices behind aircraft and a unit for calculations of areas of potential danger. A promising way to development of real time algorithms for calculation of wake vortices is the use of vortex methods in CFD based on the hypothesis of quasi-3D flow in the area of wake vorticity. The mathematical model developed by our team calculates positions and intensity of wake vortices past aircraft taking account of such effects as viscous dissipation of vortices, effects of ambient turbulence, wind shear, as well as viscous interaction between wake vortices and the underlying surface. The necessity of including the last factor could be stems from the fact that in the case where wake vortices are in close proximity of the rigid surface, the viscous interaction between the wake vortices and the surface boundary layer results in the boundary layer separation changing the overall intensity and dynamics of the wake vortices. To evaluate the boundaries of the danger areas the authors use an approach based on calculation of additional aerodynamic forces and moments acting on the aircraft encountering wake vortices by means of evaluation of the aircraft additional velocities and angular rates corresponding to distribution of disturbed velocities on the aircraft surface. These criteria could be based on local characteristics of the vorticity areas or on characteristics related to the perturbation effects on the aircraft. The latter characteristics include the actual aerodynamic roll moment, the maximum angular rate or the maximum roll of the aircraft under perturbations in the wake vortices. To estimate the accuracy

Dynamics of vortices in superconductors

International Nuclear Information System (INIS)

Weinan, E.

1992-01-01

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

Dynamics of fractional vortices in long Josephson junctions

International Nuclear Information System (INIS)

Gaber, Tobias

2007-01-01

In this thesis static and dynamic properties of fractional vortices in long Josephson junctions are investigated. Fractional vortices are circulating supercurrents similar to the well-known Josephson fluxons. Yet, they show the distinguishing property of carrying only a fraction of the magnetic flux quantum. Fractional vortices are interesting non-linear objects. They spontaneously appear and are pinned at the phase discontinuity points of so called 0-κ junctions but can be bend or flipped by external forces like bias currents or magnetic fields. 0-κ junctions and fractional vortices are generalizations of the well-known 0-π junctions and semifluxons, where not only phase jumps of pi but arbitrary values denoted by kappa are considered. By using so-called artificial 0-κ junctions that are based on standard Nb-AlO x -Nb technology the classical dynamics of fractional vortices has been investigated experimentally for the very first time. Here, half-integer zero field steps could be observed. These voltage steps on the junction's current-voltage characteristics correspond to the periodic flipping/hopping of fractional vortices. In addition, the oscillatory eigenmodes of fractional vortices were investigated. In contrast to fluxons fractional vortices have an oscillatory eigenmode with a frequency within the plasma gap. Using resonance spectroscopy the dependence of the eigenmode frequency on the flux carried by the vortex and an applied bias current was determined. (orig.)

Theory of Concentrated Vortices

DEFF Research Database (Denmark)

Alekseenko, Sergey; Kuibin, Pavel; Okulov, Valery

This book presents comprehensive and authoritative coverage of the wide field of concentrated vortices observed in nature and technique. The methods for research of their kinematics and dynamics are considered. Special attention is paid to the flows with helical symmetry. The authors have describ...... models of vortex structures used for interpretation of experimental data which serve as a ground for development of theoretical and numerical approaches to vortex investigation. Achievements in the fields of stability analysis, waves on vortices and vortex breakdown are also presented....

Kinematical Compatibility Conditions for Vorticity Across Shock Waves

Science.gov (United States)

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.

Secondary flow vortical structures in a 180∘ elastic curved vessel with torsion under steady and pulsatile inflow conditions

Science.gov (United States)

Najjari, Mohammad Reza; Plesniak, Michael W.

2018-01-01

Secondary flow structures in a 180∘ curved pipe model of an artery are studied using particle image velocimetry. Both steady and pulsatile inflow conditions are investigated. In planar curved pipes with steady flow, multiple (two, four, six) vortices are detected. For pulsatile flow, various pairs of vortices, i.e., Dean, deformed-Dean, Lyne-type, and split-Dean, are present in the cross section of the pipe at 90∘ into the bend. The effects of nonplanar curvature (torsion) and vessel dilatation on these vortical structures are studied. Torsion distorts the symmetric secondary flows (which exist in planar curvatures) and can result in formation of more complex vortical structures. For example, the split-Dean and Lyne-type vortices with same rotation direction originating from opposite sides of the cross section tend to merge together in pulsatile flow. The vortical structures in elastic vessels with dilatation (0.61%-3.23%) are also investigated and the results are compared with rigid model results. It was found that the secondary flow structures in rigid and elastic models are similar, and hence the local compliance of the vessel does not affect the morphology of secondary flow structures.

Gyrofluid potential vorticity equation and turbulent equipartion states

DEFF Research Database (Denmark)

Madsen, Jens; Juul Rasmussen, Jens; Naulin, Volker

2015-01-01

. The equation is relevant for transport barriers in magnetically confined plasmas because particle density, ion temperature and the radial electric field are mutually coupled through the potential vorticity. The potential vorticity equation is derived from an energy conserving, four-field, electrostatic, full......An equation governing potential vorticity in a magnetized plasmas is derived. The equation is analogous to Ertel's theorem. In the long wave-length limit the potential vorticity equals the ratio of the gyro-frequency plus the E × B- and diamagnetic polarization densities to the particle density...

Quantized vortices in superfluids and superconductors

International Nuclear Information System (INIS)

Thoulessi, D.J.; Wexler, C.; Ping Ao, Ping; Niu, Qian; Geller, M.R.

1998-01-01

We give a general review of recent developments in the theory of vortices in superfluids and superconductors, discussing why the dynamics of vortices is important, and why some key results are still controversial. We discuss work that we have done on the dynamics of quantized vortices in a superfluid. Despite the fact that this problem has been recognized as important for forty years, there is still a lot of controversy about the forces on and masses of quantized vortices. We think that one can get unambiguous answers by considering a broken symmetry state that consists of one vortex in an infinite ideal system. We argue for a Magnus force that is proportional to the superfluid density, and we find that the effective mass density of a vortex in a neutral superfluid is divergent at low frequencies. We have generalized some of the results for a neutral superfluid to a charged system. (Copyright (1998) World Scientific Publishing Co. Pte. Ltd)

The Theory of Vortical Gravitational Fields

Directory of Open Access Journals (Sweden)

Rabounski D.

2007-04-01

Full Text Available This paper treats of vortical gravitational fields, a tensor of which is the rotor of the general covariant gravitational inertial force. The field equations for a vortical gravitational field (the Lorentz condition, the Maxwell-like equations, and the continuity equation are deduced in an analogous fashion to electrodynamics. From the equations it is concluded that the main kind of vortical gravitational fields is “electric”, determined by the non-stationarity of the acting gravitational inertial force. Such a field is a medium for traveling waves of the force (they are different to the weak deformation waves of the space metric considered in the theory of gravitational waves. Standing waves of the gravitational inertial force and their medium, a vortical gravitational field of the “magnetic” kind, are exotic, since a non-stationary rotation of a space body (the source of such a field is a very rare phenomenon in the Universe.

Polarization in heavy-ion collisions: magnetic field and vorticity

Science.gov (United States)

Baznat, M.; Gudima, K.; Prokhorov, G.; Sorin, A.; Teryaev, O.; Zakharov, V.

2017-12-01

The polarization of hyperons due to axial chiral vortical effect is discussed. The effect is proportional to (strange) chemical potential and is pronounced at lower energies, contrary to that of magnetic field. The polarization of antihyperons has the same sign and larger magnitude. The emergence of vortical structures is observed in kinetic QGSM models. The hydrodynamical helicity separation receives the contribution of longitudinal velocity and vorticity implying the quadrupole structure of the latter. The transition from the quark vortical effects to baryons in confined phase may be achieved by exploring the axial charge. At the hadronic level the polarization corresponds to the cores of quantized vortices in pionic superfluid. The chiral vortical effects may be also studied in the frmework of Wigner function establishing the relation to the thermodynamical approach to polarization.

On generating counter-rotating streamwise vortices

KAUST Repository

Winoto, S H

2015-09-23

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.

On generating counter-rotating streamwise vortices

KAUST Repository

Winoto, S H; Mitsudharmadi, Hatsari; Budiman, A C; Hasheminejad, S M; Nadesan, T; Tandiono; Low, H T; Lee, T S

2015-01-01

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.

Electrohydrodynamic (EHD) vortices in helical turbulence

International Nuclear Information System (INIS)

Kikuchi, H.

1996-01-01

The study of large-scale coherent hydrodynamic (HD) vortex generation has been extended to electrified charged dusty vortices to be termed as electrohydrodynamic (EHD) vortices, incorporating helical turbulence in electric and magnetic fields into that in fluid velocity, which are all created by an external DC electric field on the background. A new equation of EHD vortices is introduced on the basis of a set of EHD or electromagnetohydrodynamic (EMHD) equations, including equations of state and a full set of Maxwell's equations by using functional techniques for estimating equations for an ensemble average, turbulent background, and additional random field. In fact, EHD vortices for a charged dusty fluid can be more explosive with larger instabilities than HD vortices. In addition, it is inferred that an external DC electric field could provide the origin of additional self-organization to a coalescence of fluid vortex and electric field lines as a manifestation of a new frozen-in field concept for electric fields when the electric Reynolds number is sufficiently high. This is discussed on the basis of a set of general transport equations for fluid vorticity, magnetic and electric fields that are rederived concisely. In particular, a novel concept of electric field line merging-reconnection is developed in close relation to fluid vortex line merging, indicating a coalescence of fluid vortex breakdown or merging point and electric field line reconnection point, X-type or O-type with possible application to tornadic thunderstorms. In fact, a thundercloud charge distribution so as to provide a coalescence of fluid vortex and electric field lines is quite possible without theoretical inconsistency, and is thought most likely to occur from observations available so far. (orig.)

A Family of Vortices to Study Axisymmetric Vortex Breakdown and Reconnection

Science.gov (United States)

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.

Controlled Manipulation of Individual Vortices in a Superconductor

Energy Technology Data Exchange (ETDEWEB)

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.

Vortices and vortex lattices in quantum ferrofluids

International Nuclear Information System (INIS)

Martin, A M; Marchant, N G; Parker, N G; O’Dell, D H J

2017-01-01

The experimental realization of quantum-degenerate Bose gases made of atoms with sizeable magnetic dipole moments has created a new type of fluid, known as a quantum ferrofluid, which combines the extraordinary properties of superfluidity and ferrofluidity. A hallmark of superfluids is that they are constrained to rotate through vortices with quantized circulation. In quantum ferrofluids the long-range dipolar interactions add new ingredients by inducing magnetostriction and instabilities, and also affect the structural properties of vortices and vortex lattices. Here we give a review of the theory of vortices in dipolar Bose–Einstein condensates, exploring the interplay of magnetism with vorticity and contrasting this with the established behaviour in non-dipolar condensates. We cover single vortex solutions, including structure, energy and stability, vortex pairs, including interactions and dynamics, and also vortex lattices. Our discussion is founded on the mean-field theory provided by the dipolar Gross–Pitaevskii equation, ranging from analytic treatments based on the Thomas–Fermi (hydrodynamic) and variational approaches to full numerical simulations. Routes for generating vortices in dipolar condensates are discussed, with particular attention paid to rotating condensates, where surface instabilities drive the nucleation of vortices, and lead to the emergence of rich and varied vortex lattice structures. We also present an outlook, including potential extensions to degenerate Fermi gases, quantum Hall physics, toroidal systems and the Berezinskii–Kosterlitz–Thouless transition. (topical review)

Vortices and vortex lattices in quantum ferrofluids

Science.gov (United States)

Martin, A. M.; Marchant, N. G.; O'Dell, D. H. J.; Parker, N. G.

2017-03-01

The experimental realization of quantum-degenerate Bose gases made of atoms with sizeable magnetic dipole moments has created a new type of fluid, known as a quantum ferrofluid, which combines the extraordinary properties of superfluidity and ferrofluidity. A hallmark of superfluids is that they are constrained to rotate through vortices with quantized circulation. In quantum ferrofluids the long-range dipolar interactions add new ingredients by inducing magnetostriction and instabilities, and also affect the structural properties of vortices and vortex lattices. Here we give a review of the theory of vortices in dipolar Bose-Einstein condensates, exploring the interplay of magnetism with vorticity and contrasting this with the established behaviour in non-dipolar condensates. We cover single vortex solutions, including structure, energy and stability, vortex pairs, including interactions and dynamics, and also vortex lattices. Our discussion is founded on the mean-field theory provided by the dipolar Gross-Pitaevskii equation, ranging from analytic treatments based on the Thomas-Fermi (hydrodynamic) and variational approaches to full numerical simulations. Routes for generating vortices in dipolar condensates are discussed, with particular attention paid to rotating condensates, where surface instabilities drive the nucleation of vortices, and lead to the emergence of rich and varied vortex lattice structures. We also present an outlook, including potential extensions to degenerate Fermi gases, quantum Hall physics, toroidal systems and the Berezinskii-Kosterlitz-Thouless transition.

Tunneling decay of self-gravitating vortices

Directory of Open Access Journals (Sweden)

Dupuis Éric

2018-01-01

Full Text Available We investigate tunneling decay of false vortices in the presence of gravity, in which vortices are trapped in the false vacuum of a theory of scalar electrodynamics in three dimensions. The core of the vortex contains magnetic flux in the true vacuum, while outside the vortex is the appropriate topologically nontrivial false vacuum. We numerically obtain vortex solutions which are classically stable; however, they could decay via tunneling. To show this phenomenon, we construct the proper junction conditions in curved spacetime. We find that the tunneling exponent for the vortices is half that for Coleman-de Luccia bubbles and discuss possible future applications.

Spindles and active vortices in a model of confined filament-motor mixtures

Directory of Open Access Journals (Sweden)

Head David A

2011-11-01

Full Text Available Abstract Background Robust self-organization of subcellular structures is a key principle governing the dynamics and evolution of cellular life. In fission yeast cells undergoing division, the mitotic spindle spontaneously emerges from the interaction of microtubules, motor proteins and the confining cell walls, and asters and vortices have been observed to self-assemble in quasi-two dimensional microtubule-kinesin assays. There is no clear microscopic picture of the role of the active motors driving this pattern formation, and the relevance of continuum modeling to filament-scale structures remains uncertain. Results Here we present results of numerical simulations of a discrete filament-motor protein model confined to a pressurised cylindrical box. Stable spindles, nematic configurations, asters and high-density semi-asters spontaneously emerge, the latter pair having also been observed in cytosol confined within emulsion droplets. State diagrams are presented delineating each stationary state as the pressure, motor speed and motor density are varied. We further highlight a parameter regime where vortices form exhibiting collective rotation of all filaments, but have a finite life-time before contracting to a semi-aster. Quantifying the distribution of life-times suggests this contraction is a Poisson process. Equivalent systems with fixed volume exhibit persistent vortices with stochastic switching in the direction of rotation, with switching times obeying similar statistics to contraction times in pressurised systems. Furthermore, we show that increasing the detachment rate of motors from filament plus-ends can both destroy vortices and turn some asters into vortices. Conclusions We have shown that discrete filament-motor protein models provide new insights into the stationary and dynamical behavior of active gels and subcellular structures, because many phenomena occur on the length-scale of single filaments. Based on our findings, we argue

Core structure and dynamics of non-Abelian vortices in a biaxial nematic spinor Bose-Einstein condensate

Science.gov (United States)

Borgh, Magnus O.; Ruostekoski, Janne

2016-05-01

We demonstrate that multiple interaction-dependent defect core structures as well as dynamics of non-Abelian vortices can be realized in the biaxial nematic (BN) phase of a spin-2 atomic Bose-Einstein condensate (BEC). An experimentally simple protocol may be used to break degeneracy with the uniaxial nematic phase. We show that a discrete spin-space symmetry in the core may be reflected in a breaking of its spatial symmetry. The discrete symmetry of the BN order parameter leads to non-commuting vortex charges. We numerically simulate reconnection of non-Abelian vortices, demonstrating formation of the obligatory rung vortex. In addition to atomic BECs, non-Abelian vortices are theorized in, e.g., liquid crystals and cosmic strings. Our results suggest the BN spin-2 BEC as a prime candidate for their realization. We acknowledge financial support from the EPSRC.

Theory and simulations of electron vortices generated by magnetic pushing

Energy Technology Data Exchange (ETDEWEB)

Richardson, A. S.; Angus, J. R.; Swanekamp, S. B.; Schumer, J. W. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States); Ottinger, P. F. [An Independent Consultant through ENGILITY, Chantilly, Virginia 20151 (United States)

2013-08-15

Vortex formation and propagation are observed in kinetic particle-in-cell (PIC) simulations of magnetic pushing in the plasma opening switch. These vortices are studied here within the electron-magnetohydrodynamic (EMHD) approximation using detailed analytical modeling. PIC simulations of these vortices have also been performed. Strong v×B forces in the vortices give rise to significant charge separation, which necessitates the use of the EMHD approximation in which ions are fixed and the electrons are treated as a fluid. A semi-analytic model of the vortex structure is derived, and then used as an initial condition for PIC simulations. Density-gradient-dependent vortex propagation is then examined using a series of PIC simulations. It is found that the vortex propagation speed is proportional to the Hall speed v{sub Hall}≡cB{sub 0}/4πn{sub e}eL{sub n}. When ions are allowed to move, PIC simulations show that the electric field in the vortex can accelerate plasma ions, which leads to dissipation of the vortex. This electric field contributes to the separation of ion species that has been observed to occur in pulsed-power experiments with a plasma-opening switch.

Calculation of large Reynolds number two-dimensional flow using discrete vortices with random walk

International Nuclear Information System (INIS)

Milinazzo, F.; Saffman, P.G.

1977-01-01

The numerical calculation of two-dimensional rotational flow at large Reynolds number is considered. The method of replacing a continuous distribution of vorticity by a finite number, N, of discrete vortices is examined, where the vortices move under their mutually induced velocities plus a random component to simulate effects of viscosity. The accuracy of the method is studied by comparison with the exact solution for the decay of a circular vortex. It is found, and analytical arguments are produced in support, that the quantitative error is significant unless N is large compared with a characteristic Reynolds number. The mutually induced velocities are calculated by both direct summation and by the ''cloud in cell'' technique. The latter method is found to produce comparable error and to be much faster

Probing dynamics and pinning of single vortices in superconductors at nanometer scales

Science.gov (United States)

Embon, L.; Anahory, Y.; Suhov, A.; Halbertal, D.; Cuppens, J.; Yakovenko, A.; Uri, A.; Myasoedov, Y.; Rappaport, M. L.; Huber, M. E.; Gurevich, A.; Zeldov, E.

2015-01-01

The dynamics of quantized magnetic vortices and their pinning by materials defects determine electromagnetic properties of superconductors, particularly their ability to carry non-dissipative currents. Despite recent advances in the understanding of the complex physics of vortex matter, the behavior of vortices driven by current through a multi-scale potential of the actual materials defects is still not well understood, mostly due to the scarcity of appropriate experimental tools capable of tracing vortex trajectories on nanometer scales. Using a novel scanning superconducting quantum interference microscope we report here an investigation of controlled dynamics of vortices in lead films with sub-Angstrom spatial resolution and unprecedented sensitivity. We measured, for the first time, the fundamental dependence of the elementary pinning force of multiple defects on the vortex displacement, revealing a far more complex behavior than has previously been recognized, including striking spring softening and broken-spring depinning, as well as spontaneous hysteretic switching between cellular vortex trajectories. Our results indicate the importance of thermal fluctuations even at 4.2 K and of the vital role of ripples in the pinning potential, giving new insights into the mechanisms of magnetic relaxation and electromagnetic response of superconductors.

Topological vortices in gauge models of graphene

Science.gov (United States)

Zhang, Xin-Hui; Li, Xueqin; Hao, Jin-Bo

2018-06-01

Graphene-like structure possessing the topological vortices and knots, and the magnetic flux of the vortices configuration quantized, are proposed in this paper. The topological charges of the vortices are characterized by Hopf indices and Brower degrees. The Abelian background field action (BF action) is a topological invariant for the knot family, which is just the total sum of all the self-linking numbers and all the linking numbers. Flux quantization opens the possibility of having Aharonov-Bohm-type effects in graphene without external electromagnetic field.

Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus).

Science.gov (United States)

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

Experimental Observations of Ion Phase-Space Vortices

DEFF Research Database (Denmark)

Pécseli, Hans; Armstrong, R. J.; Trulsen, J.

1981-01-01

Experimental observations of ion phase-space vortices are reported. The ion phase-space vortices form in the region of heated ions behind electrostatic ion acoustic shocks. The results are in qualitative agreement with numerical and analytic studies....

Vorticity imbalance and stability in relation to convection

Science.gov (United States)

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.

Dynamics of Chern-Simons vortices

International Nuclear Information System (INIS)

Collie, Benjamin; Tong, David

2008-01-01

We study vortex dynamics in three-dimensional theories with Chern-Simons interactions. The dynamics is governed by motion on the moduli space M in the presence of a magnetic field. For Abelian vortices, the magnetic field is shown to be the Ricci form over M; for non-Abelian vortices, it is the first Chern character of a suitable index bundle. We derive these results by integrating out massive fermions and following the fate of their zero modes.

Stability of two-dimensional vorticity filaments

International Nuclear Information System (INIS)

Elhmaidi, D.; Provenzale, A.; Lili, T.; Babiano, A.

2004-01-01

We discuss the results of a numerical study on the stability of two-dimensional vorticity filaments around a circular vortex. We illustrate how the stability of the filaments depends on the balance between the strain associated with the far field of the vortex and the local vorticity of the filament, and we discuss an empirical criterion for filament stability

Why does gravitational radiation produce vorticity?

International Nuclear Information System (INIS)

Herrera, L; Barreto, W; Carot, J; Prisco, A Di

2007-01-01

We calculate the vorticity of worldlines of observers at rest in a Bondi-Sachs frame, produced by gravitational radiation, in a general Sachs metric. We claim that such an effect is related to the super-Poynting vector, in a similar way as the existence of the electromagnetic Poynting vector is related to the vorticity in stationary electrovacuum spacetimes

Stability of relative equilibria of three vortices

DEFF Research Database (Denmark)

Aref, Hassan

2009-01-01

Three point vortices on the unbounded plane have relative equilibria wherein the vortices either form an equilateral triangle or are collinear. While the stability analysis of the equilateral triangle configurations is straightforward, that of the collinear relative equilibria is considerably mor...

Collision dynamics of two-dimensional non-Abelian vortices

Science.gov (United States)

Mawson, Thomas; Petersen, Timothy C.; Simula, Tapio

2017-09-01

We study computationally the collision dynamics of vortices in a two-dimensional spin-2 Bose-Einstein condensate. In contrast to Abelian vortex pairs, which annihilate or pass through each other, we observe non-Abelian vortex pairs to undergo rungihilation—an event that converts the colliding vortices into a rung vortex. The resulting rung defect subsequently decays to another pair of non-Abelian vortices of different type, accompanied by a magnetization reversal.

Why superconducting vortices follow to moving hot sport?

Science.gov (United States)

Sergeev, Andrei; Michael, Reizer

Recent experiments reported in Nature Comm. 7, 12801, 2016 show that superconducting vortices follow to the moving hot sport created by a focused laser beam, i.e. vortices move from the cold area to the moving hot area. This behavior is opposite to the vortex motion observed in numerous measurements of the vortex Nernst effect, where vortices always move against the temperature gradient. Taking into account that superconducting magnetization currents do not transfer entropy, we analyze the balance of forces acting on a vortex in stationary and dynamic temperature gradients. We show that the dynamic measurements may be described by a single vortex approximation, while in stationary measurements interaction between vortices is critical. Supported by NRC.

On trailing vortices: A short review

International Nuclear Information System (INIS)

Jacquin, Laurent

2005-01-01

This paper reviews some mechanisms involved in the dynamics of vortices in fluid flows. The topic is first introduced by pointing out its importance in aerodynamics. Several basic notions useful to appraise experimental observations are then surveyed, namely: centrifugal instabilities, inertial waves, cooperative instabilities, vortex merger, vortex breakdown and turbulence in vortices. Each topic is illustrated with experimental or numerical results

Airfoil Drag Reduction using Controlled Trapped Vorticity Concentrations

Science.gov (United States)

Desalvo, Michael; Glezer, Ari

2017-11-01

The aerodynamic performance of a lifting surface at low angles of attack (when the base flow is fully attached) is improved through fluidic modification of its ``apparent'' shape by superposition of near-surface trapped vorticity concentrations. In the present wind tunnel investigations, a controlled trapped vorticity concentration is formed on the pressure surface of an airfoil (NACA 4415) using a hybrid actuator comprising a passive obstruction of scale O(0.01c) and an integral synthetic jet actuator. The jet actuation frequency [Stact O(10)] is selected to be at least an order of magnitude higher than the characteristic unstable frequency of the airfoil wake, thereby decoupling the actuation from the global instabilities of the base flow. Regulation of vorticity accumulation in the vicinity of the actuator by the jet effects changes in the local pressure, leading in turn to changes in the airfoil's drag and lift. Trapped vorticity can lead to a significant reduction in drag and reduced lift (owing to the sense of the vorticity), e.g. at α =4° and Re = 6.7 .105 the drag and lift reductions are 14% and 2%, respectively. PIV measurements show the spatial variation in the distribution of vorticity concentrations and yield estimates of the corresponding changes in circulation.

Thick vortices in SU(2) lattice gauge theory

OpenAIRE

Cheluvaraja, Srinath

2004-01-01

Three dimensional SU(2) lattice gauge theory is studied after eliminating thin monopoles and the smallest thick monopoles. Kinematically this constraint allows the formation of thick vortex loops which produce Z(2) fluctuations at longer length scales. The thick vortex loops are identified in a three dimensional simulation. A condensate of thick vortices persists even after the thin vortices have all disappeared. The thick vortices decouple at a slightly lower temperature (higher beta) than t...

Transitions between Taylor vortices and spirals via wavy Taylor vortices and wavy spirals

International Nuclear Information System (INIS)

Hoffmann, Ch; Altmeyer, S; Pinter, A; Luecke, M

2009-01-01

We present numerical simulations of closed wavy Taylor vortices and of helicoidal wavy spirals in the Taylor-Couette system. These wavy structures appearing via a secondary bifurcation out of Taylor vortex flow and out of spiral vortex flow, respectively, mediate transitions between Taylor and spiral vortices and vice versa. Structure, dynamics, stability and bifurcation behaviour are investigated in quantitative detail as a function of Reynolds numbers and wave numbers for counter-rotating as well as corotating cylinders. These results are obtained by solving the Navier-Stokes equations subject to axial periodicity for a radius ratio η=0.5 with a combination of a finite differences method and a Galerkin method.

Dynamical properties of vortical structures on the beta-plane

DEFF Research Database (Denmark)

Sutyrin, G.G.; Hesthaven, J.S.; Lynov, Jens-Peter

1994-01-01

The long-time evolution of monopolar and dipolar vortices influenced by the large-scale gradient of the ambient potential vorticity (the beta-effect) is studied by direct numerical solutions of the equivalent barotropic quasi-geostrophic equation. Translation and reorganization of vortical...... structures are shown to depend strongly on their intensity. Transport of trapped fluid by vortical structures is illustrated by calculating particle trajectories and by considering closed isolines of potential vorticity and the streamfunction in a co-moving reference frame. The initial behaviour of strong...... monopoles is found to be well described by a recent approximate theory for the evolution of azimuthal mode one, even for times longer than the linear Rossby wave period. In the long-time limit, strong monopoles transport particles mainly westward, although the meridional displacement is several times larger...

Observation of Polarization Vortices in Momentum Space

Science.gov (United States)

Zhang, Yiwen; Chen, Ang; Liu, Wenzhe; Hsu, Chia Wei; Wang, Bo; Guan, Fang; Liu, Xiaohan; Shi, Lei; Lu, Ling; Zi, Jian

2018-05-01

The vortex, a fundamental topological excitation featuring the in-plane winding of a vector field, is important in various areas such as fluid dynamics, liquid crystals, and superconductors. Although commonly existing in nature, vortices were observed exclusively in real space. Here, we experimentally observed momentum-space vortices as the winding of far-field polarization vectors in the first Brillouin zone of periodic plasmonic structures. Using homemade polarization-resolved momentum-space imaging spectroscopy, we mapped out the dispersion, lifetime, and polarization of all radiative states at the visible wavelengths. The momentum-space vortices were experimentally identified by their winding patterns in the polarization-resolved isofrequency contours and their diverging radiative quality factors. Such polarization vortices can exist robustly on any periodic systems of vectorial fields, while they are not captured by the existing topological band theory developed for scalar fields. Our work provides a new way for designing high-Q plasmonic resonances, generating vector beams, and studying topological photonics in the momentum space.

Correlations between Abelian monopoles and center vortices

Energy Technology Data Exchange (ETDEWEB)

Hosseini Nejad, Seyed Mohsen, E-mail: smhosseininejad@ut.ac.ir; Deldar, Sedigheh, E-mail: sdeldar@ut.ac.ir

2017-04-15

We study the correlations between center vortices and Abelian monopoles for SU(3) gauge group. Combining fractional fluxes of monopoles, center vortex fluxes are constructed in the thick center vortex model. Calculating the potentials induced by fractional fluxes constructing the center vortex flux in a thick center vortex-like model and comparing with the potential induced by center vortices, we observe an attraction between fractional fluxes of monopoles constructing the center vortex flux. We conclude that the center vortex flux is stable, as expected. In addition, we show that adding a contribution of the monopole-antimonopole pairs in the potentials induced by center vortices ruins the Casimir scaling at intermediate regime.

Doppler Velocity Signatures of Idealized Elliptical Vortices

Directory of Open Access Journals (Sweden)

Wen-Chau Lee

2006-01-01

Full Text Available Doppler radar observations have revealed a class of atmospheric vortices (tropical cyclones, tornadoes, dust devils that possess elliptical radar reflectivity signatures. One famous example is Typhoon Herb (1996 that maintained its elliptical reflectivity structure over a 40-hour period. Theoretical work and dual-Doppler analyses of observed tropical cyclones have suggested two physical mechanisms that can explain the formation of two types of elliptical vortices observed in nature, namely, the combination of a circular vortex with either a wavenumber two vortex Rossby wave or a deformation field. The characteristics of these two types of elliptical vortices and their corresponding Doppler velocity signatures have not been previously examined.

Statistical balance of vorticity and a new scale for vortical structures in turbulence

International Nuclear Information System (INIS)

Novikov, E.A.

1993-01-01

The balance of one-point and two-point statistical characterics of vorticity, is considered on the basis of the Navier-Stokes equations. It is shown that within the inertial range of scales (L Re -3/4 much-lt r much-lt L, L external scale, Re Reynolds number) there is a physically distinguished scale l s ∼L Re -3/10 . The balance of vortical correlations with scales r≥l s is directly affected by the large-scale motion. l s is a natural length scale for the ''vortex strings,'' observed experimentally and numerically in three-dimensional turbulent flows. The twist of vortex lines in the internal structure of vortex strings is also briefly discussed

Aerodynamics and vortical structures in hovering fruitflies

Science.gov (United States)

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.

A numerical study of vorticity-enhanced heat transfer

Science.gov (United States)

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.

Point vortex description of drift wave vortices: Dynamics and transport

International Nuclear Information System (INIS)

Kono, M.; Horton, W.

1991-05-01

Point-vortex description for drift wave vortices is formulated based on the Hasegawa-Mima equation to study elementary processes for the interactions of vortices as well as statistical properties like vortex diffusion. Dynamical properties of drift wave vortices known by numerical experiments are recovered. Furthermore a vortex diffusion model discussed by Horton based on numerical simulations is shown to be analytically obtained. A variety of phenomena arising from the short-range nature of the interaction force of point vortices are suggested. 12 refs., 10 figs

Dynamics of quantised vortices in superfluids

CERN Document Server

Sonin, Edouard B

2016-01-01

A comprehensive overview of the basic principles of vortex dynamics in superfluids, this book addresses the problems of vortex dynamics in all three superfluids available in laboratories (4He, 3He, and BEC of cold atoms) alongside discussions of the elasticity of vortices, forces on vortices, and vortex mass. Beginning with a summary of classical hydrodynamics, the book guides the reader through examinations of vortex dynamics from large scales to the microscopic scale. Topics such as vortex arrays in rotating superfluids, bound states in vortex cores and interaction of vortices with quasiparticles are discussed. The final chapter of the book considers implications of vortex dynamics to superfluid turbulence using simple scaling and symmetry arguments. Written from a unified point of view that avoids complicated mathematical approaches, this text is ideal for students and researchers working with vortex dynamics in superfluids, superconductors, magnetically ordered materials, neutron stars and cosmological mo...

Potential vorticity field in the Bay of Bengal during southwest monsoon

Digital Repository Service at National Institute of Oceanography (India)

Murty, V.S.N.; Rao, D.P.

theta), potential vorticity distribution is complex due to wind and freshwater forcings. The beta -effect dominates the potential vorticity field on 26.9 sigma theta isopycnal. The field of potential vorticity closely follows that of circulation...

Hairpin vortices in turbulent boundary layers

International Nuclear Information System (INIS)

Eitel-Amor, G; Schlatter, P; Flores, O

2014-01-01

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 Re τ = 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 Re τ < 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.

On the link between martian total ozone and potential vorticity

Science.gov (United States)

Holmes, James A.; Lewis, Stephen R.; Patel, Manish R.

2017-01-01

We demonstrate for the first time that total ozone in the martian atmosphere is highly correlated with the dynamical tracer, potential vorticity, under certain conditions. The degree of correlation is investigated using a Mars global circulation model including a photochemical model. Potential vorticity is the quantity of choice to explore the dynamical nature of polar vortices because it contains information on winds and temperature in a single scalar variable. The correlation is found to display a distinct seasonal variation, with a strong positive correlation in both northern and southern winter at poleward latitudes in the northern and southern hemisphere respectively. The identified strong correlation implies variations in polar total ozone during winter are predominantly controlled by dynamical processes in these spatio-temporal regions. The weak correlation in northern and southern summer is due to the dominance of photochemical reactions resulting from extended exposure to sunlight. The total ozone/potential vorticity correlation is slightly weaker in southern winter due to topographical variations and the preference for ozone to accumulate in Hellas basin. In northern winter, total ozone can be used to track the polar vortex edge. The ozone/potential vorticity ratio is calculated for both northern and southern winter on Mars for the first time. Using the strong correlation in total ozone and potential vorticity in northern winter inside the polar vortex, it is shown that potential vorticity can be used as a proxy to deduce the distribution of total ozone where satellites cannot observe for the majority of northern winter. Where total ozone observations are available on the fringes of northern winter at poleward latitudes, the strong relationship of total ozone and potential vorticity implies that total ozone anomalies in the surf zone of the northern polar vortex can potentially be used to determine the origin of potential vorticity filaments.

Tight focusing properties of linearly polarized Gaussian beam with a pair of vortices

Energy Technology Data Exchange (ETDEWEB)

Chen, Ziyang [Department of Physics, Zhejiang University, Hangzhou 310027 (China); College of Information Science and Engineering, Institute of Optics and Photonics, Huaqiao University, Xiamen, Fujian 361021 (China); Pu, Jixiong [College of Information Science and Engineering, Institute of Optics and Photonics, Huaqiao University, Xiamen, Fujian 361021 (China); Zhao, Daomu, E-mail: zhaodaomu@yahoo.com [Department of Physics, Zhejiang University, Hangzhou 310027 (China)

2011-07-25

The properties of a pair of vortices embedded in a Gaussian beam focused by a high numerical-aperture are studied on the basis of vector Debye integral. The vortices move and rotate in the vicinity of the focal plane for a pair of vortices with equal topological charges. For incident beam with a pair of vortices with opposite topological charges, the vortices move toward each other, annihilate and revive in the vicinity of focal plane. -- Highlights: → The properties of a pair of vortices focused by a high numerical-aperture are studied. → It is shown that the focusing vortices with equal topological charges move toward and rotate. → It is shown that the focusing vortices with opposite topological charges move toward each other, annihilate and revive.

Characteristics of Tornado-Like Vortices Simulated in a Large-Scale Ward-Type Simulator

Science.gov (United States)

Tang, Zhuo; Feng, Changda; Wu, Liang; Zuo, Delong; James, Darryl L.

2018-02-01

Tornado-like vortices are simulated in a large-scale Ward-type simulator to further advance the understanding of such flows, and to facilitate future studies of tornado wind loading on structures. Measurements of the velocity fields near the simulator floor and the resulting floor surface pressures are interpreted to reveal the mean and fluctuating characteristics of the flow as well as the characteristics of the static-pressure deficit. We focus on the manner in which the swirl ratio and the radial Reynolds number affect these characteristics. The transition of the tornado-like flow from a single-celled vortex to a dual-celled vortex with increasing swirl ratio and the impact of this transition on the flow field and the surface-pressure deficit are closely examined. The mean characteristics of the surface-pressure deficit caused by tornado-like vortices simulated at a number of swirl ratios compare well with the corresponding characteristics recorded during full-scale tornadoes.

Growth and wall-transpiration control of nonlinear unsteady Görtler vortices forced by free-stream vortical disturbances

Science.gov (United States)

Marensi, Elena; Ricco, Pierre

2017-11-01

The generation, nonlinear evolution, and wall-transpiration control of unsteady Görtler vortices in an incompressible boundary layer over a concave plate is studied theoretically and numerically. Görtler rolls are initiated and driven by free-stream vortical perturbations of which only the low-frequency components are considered because they penetrate the most into the boundary layer. The formation and development of the disturbances are governed by the nonlinear unsteady boundary-region equations with the centrifugal force included. These equations are subject to appropriate initial and outer boundary conditions, which account for the influence of the upstream and free-stream forcing in a rigorous and mutually consistent manner. Numerical solutions show that the stabilizing effect on nonlinearity, which also occurs in flat-plate boundary layers, is significantly enhanced in the presence of centrifugal forces. Sufficiently downstream, the nonlinear vortices excited at different free-stream turbulence intensities Tu saturate at the same level, proving that the initial amplitude of the forcing becomes unimportant. At low Tu, the disturbance exhibits a quasi-exponential growth with the growth rate being intensified for more curved plates and for lower frequencies. At higher Tu, in the typical range of turbomachinery applications, the Görtler vortices do not undergo a modal stage as nonlinearity saturates rapidly, and the wall curvature does not affect the boundary-layer response. Good quantitative agreement with data from direct numerical simulations and experiments is obtained. Steady spanwise-uniform and spanwise-modulated zero-mass-flow-rate wall transpiration is shown to attenuate the growth of the Görtler vortices significantly. A novel modified version of the Fukagata-Iwamoto-Kasagi identity, used for the first time to study a transitional flow, reveals which terms in the streamwise momentum balance are mostly affected by the wall transpiration, thus

Physical properties corresponding to vortical flow geometry

Energy Technology Data Exchange (ETDEWEB)

Nakayama, K, E-mail: nakayama@aitech.ac.jp [Department of Mechanical Engineering, Aichi Institute of Technology, Toyota, Aichi 470-0392 (Japan)

2014-10-01

We examine a vortical flow geometry specified by the velocity gradient tensor ∇v, and derive properties representing the symmetry (axisymmetry or skewness) of the vortical flow in the swirl plane and a property specifying inflowing (outflowing) motion in all directions around the point. We focus on the radial and azimuthal velocities in a plane nonparallel to the eigenvector corresponding to the real eigenvalue of ∇v and show that these components are expressed as specific quadratic forms. The real and imaginary parts of the complex eigenvalues of ∇v represent averages of these eigenvalues of the quadratic forms, and are inadequate to specify the detailed flow geometry uniquely. The new properties complement specifying the precise flow geometry of the vortical flow.

Towards laboratory detection of topological vortices in superfluid phases of QCD

Science.gov (United States)

Das, Arpan; Dave, Shreyansh S.; de, Somnath; Srivastava, Ajit M.

2017-10-01

Topological defects arise in a variety of systems, e.g. vortices in superfluid helium to cosmic strings in the early universe. There is an indirect evidence of neutron superfluid vortices from the glitches in pulsars. One also expects that the topological defects may arise in various high baryon density phases of quantum chromodynamics (QCD), e.g. superfluid topological vortices in the color flavor locked (CFL) phase. Though vastly different in energy/length scales, there are universal features in the formation of all these defects. Utilizing this universality, we investigate the possibility of detecting these topological superfluid vortices in laboratory experiments, namely heavy-ion collisions (HICs). Using hydrodynamic simulations, we show that vortices can qualitatively affect the power spectrum of flow fluctuations. This can give an unambiguous signal for superfluid transition resulting in vortices, allowing for the check of defect formation theories in a relativistic quantum field theory system, and the detection of superfluid phases of QCD. Detection of nucleonic superfluid vortices in low energy HICs will give opportunity for laboratory controlled study of their properties, providing crucial inputs for the physics of pulsars.

Characteristics and controllability of vortices in ferromagnetics, ferroelectrics, and multiferroics.

Science.gov (United States)

Zheng, Yue; Chen, W J

2017-08-01

Topological defects in condensed matter are attracting e significant attention due to their important role in phase transition and their fascinating characteristics. Among the various types of matter, ferroics which possess a switchable physical characteristic and form domain structure are ideal systems to form topological defects. In particular, a special class of topological defects-vortices-have been found to commonly exist in ferroics. They often manifest themselves as singular regions where domains merge in large systems, or stabilize as novel order states instead of forming domain structures in small enough systems. Understanding the characteristics and controllability of vortices in ferroics can provide us with deeper insight into the phase transition of condensed matter and also exciting opportunities in designing novel functional devices such as nano-memories, sensors, and transducers based on topological defects. In this review, we summarize the recent experimental and theoretical progress in ferroic vortices, with emphasis on those spin/dipole vortices formed in nanoscale ferromagnetics and ferroelectrics, and those structural domain vortices formed in multiferroic hexagonal manganites. We begin with an overview of this field. The fundamental concepts of ferroic vortices, followed by the theoretical simulation and experimental methods to explore ferroic vortices, are then introduced. The various characteristics of vortices (e.g. formation mechanisms, static/dynamic features, and electronic properties) and their controllability (e.g. by size, geometry, external thermal, electrical, magnetic, or mechanical fields) in ferromagnetics, ferroelectrics, and multiferroics are discussed in detail in individual sections. Finally, we conclude this review with an outlook on this rapidly developing field.

Nonautonomous Vortices in (2+1)-Dimensional Graded-Index Waveguide

International Nuclear Information System (INIS)

Lai Xian-Jing; Zhang Jie-Fang; Cai Xiao-Ou

2015-01-01

With the help of self-similarity transformation, we construct and study the nonautonomous vortices with different topological charges inside a planar graded-index nonlinear waveguide, analytically, and numerically. Although these vortices are approximate, they can reflect the real properties of self-similar optical beam during a short-term propagation. Existence of these autonomous vortices require delicate balances between the system parameters such as diffraction, nonlinearity, gain, and external potential. We are concerned with some special but interesting situations, and discussing the changes of the height, width, energy, and central position of the vortices as the increase of propagation distance. Moreover, we are also interested in the azimuthal modulational instability of the system, and comparing our prediction for the modulational instability growth rates to numerical results. (paper)

Driven motion of vortices in superconductors

International Nuclear Information System (INIS)

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 2 CU 3 O 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

Coulomb energy, vortices, and confinement

International Nuclear Information System (INIS)

Greensite, Jeff; Olejnik, Stefan

2003-01-01

We estimate the Coulomb energy of static quarks from a Monte Carlo calculation of the correlator of timelike link variables in the Coulomb gauge. We find, in agreement with Cucchieri and Zwanziger, that this energy grows linearly with distance at large quark separations. The corresponding string tension, however, is several times greater than the accepted asymptotic string tension, indicating that a state containing only static sources, with no constituent gluons, is not the lowest energy flux tube state. The Coulomb energy is also measured on thermalized lattices with center vortices removed by the de Forcrand-D'Elia procedure. We find that when vortices are removed, the Coulomb string tension vanishes

Numerical analysis of propeller induced ground vortices by actuator disk model

NARCIS (Netherlands)

Yang, Y.; Veldhuis, L.L.M.; Eitelberg, G.

2017-01-01

Abstract: During the ground operation of aircraft, the interaction between the propulsor-induced flow field and the ground may lead to the generation of ground vortices. Utilizing numerical approaches, the source of vorticity entering ground vortices is investigated. The results show that the

Potential Vorticity Evolution in the Co-orbital Region of Embedded Protoplanets

International Nuclear Information System (INIS)

Koller, J.

2004-01-01

This thesis presents two-dimensional hydrodynamic disk simulations with embedded protoplanets, emphasizing the non-linear dynamics in the co-orbital region. In particular, it demonstrates how a protoplanetary disk responds to embedded low mass planets at the inviscid limit. Since the potential vorticity (PV) flow is not conserved, due to the spiral shocks and possibly boundary layer effects emanating from the planet, the PV profile develops inflection points which eventually render the flow unstable. Vortices are produced in association with the potential vorticity minima. Born in the separatrix region, these vortices experience close encounters with the planet, consequently exerting strong torques on the planet. The existence of these vortices, if confirmed, have important implications on planetary migration rates. The formation of vortices is discussed in more detail and a key parameter is found which depends solely on planet mass and sound speed. With this key parameter, one can predict the disk evolution, PV growth rates, and threshold conditions for forming vortices in the co-orbital region. An analytical estimate for the change of PV due to shocks is compared to the actual change in PV in the hydrodynamic simulations. They match well except in the inner region where vortices form. In addition, extensive resolution tests were carried out but uncertainties remain about the physics of this particular region

Flow structure and vorticity transport on a plunging wing

Science.gov (United States)

Eslam Panah, Azar

circulation, in magnitude, as the leading-edge shear layer flux. A small but non-negligible vorticity source was also attributed to spanwise flow toward the end of the downstroke. Preliminary measurements of the structure and dynamics of the leading-edge vortex (LEV) are also investigated for plunging finite-aspect-ratio wings at a chord Reynolds number of 10,000 while varying aspect ratio and root boundary condition. Stereoscopic particle image velocimetry (SPIV) measurements are used to characterize LEV dynamics and interactions with the plate in multiple chordwise planes. The relationship between the vorticity field and the spanwise flow field over the wing, and the influence of root boundary conditions on these quantities has been investigated. The viscous symmetry plane is found to influence this flow field, in comparison to other studies YiRo:2010,Vi:2011b,CaWaGuVi:2012, by influencing tilting of the LEV near the symmetry wall, and introducing a corewise root-to-tip flow near the symmetry plane. Modifications in the root boundary conditions are found to significantly affect this. LEV circulations for the different aspect ratio plates are also compared. At the bottom of the downstroke, the maximum circulation is found at the middle of the semi-span in each case. The circulation of the sAR=2 wing is found to significantly exceed that of the sAR=1 wing and, surprisingly, the maximum circulation value is found to be independent of root boundary conditions for thesAR=2 case and also closely matched that of the quasi-2D case. Furthermore, the 3-D flow field of a finite wing ofsAR=2 was characterized using three-dimensional reconstructions of planar PIV data after minimizing the gap between the plunging plate and the top stationary wall. The LEV on the finite wing rapidly evolved into an arch structure centered at approximately the 50% spanwise position, similar to previous observations by Calderon et al., and Yilmaz and Rockwell. At that location, the circulation contribution

A Laboratory Study of Vortical Structures in Rotating Convection Plumes

Science.gov (United States)

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).

Ginzburg-Landau vortices

CERN Document Server

Bethuel, Fabrice; Helein, Frederic

2017-01-01

This book is concerned with the study in two dimensions of stationary solutions of uɛ of a complex valued Ginzburg-Landau equation involving a small parameter ɛ. Such problems are related to questions occurring in physics, e.g., phase transition phenomena in superconductors and superfluids. The parameter ɛ has a dimension of a length which is usually small.  Thus, it is of great interest to study the asymptotics as ɛ tends to zero. One of the main results asserts that the limit u-star of minimizers uɛ exists. Moreover, u-star is smooth except at a finite number of points called defects or vortices in physics. The number of these defects is exactly the Brouwer degree – or winding number – of the boundary condition. Each singularity has degree one – or as physicists would say, vortices are quantized. The singularities have infinite energy, but after removing the core energy we are lead to a concept of finite renormalized energy.  The location of the singularities is completely determined by minimiz...

Error Propagation dynamics: from PIV-based pressure reconstruction to vorticity field calculation

Science.gov (United States)

Pan, Zhao; Whitehead, Jared; Richards, Geordie; Truscott, Tadd; USU Team; BYU Team

2017-11-01

Noninvasive data from velocimetry experiments (e.g., PIV) have been used to calculate vorticity and pressure fields. However, the noise, error, or uncertainties in the PIV measurements would eventually propagate to the calculated pressure or vorticity field through reconstruction schemes. Despite the vast applications of pressure and/or vorticity field calculated from PIV measurements, studies on the error propagation from the velocity field to the reconstructed fields (PIV-pressure and PIV-vorticity are few. In the current study, we break down the inherent connections between PIV-based pressure reconstruction and PIV-based vorticity calculation. The similar error propagation dynamics, which involve competition between physical properties of the flow and numerical errors from reconstruction schemes, are found in both PIV-pressure and PIV-vorticity reconstructions.

On sharp vorticity gradients in elongating baroclinic eddies and their stabilization with a solid-body rotation

Science.gov (United States)

Sutyrin, Georgi G.

2016-06-01

Wide compensated vortices are not able to remain circular in idealized two-layer models unless the ocean depth is assumed to be unrealistically large. Small perturbations on both cyclonic and anticyclonic eddies grow slower if a middle layer with uniform potential vorticity (PV) is added, owing to a weakening of the vertical coupling between the upper and lower layers and a reduction of the PV gradient in the deep layer. Numerical simulations show that the nonlinear development of the most unstable elliptical mode causes self-elongation of the upper vortex core and splitting of the deep PV anomaly into two corotating parts. The emerging tripolar flow pattern in the lower layer results in self-intensification of the fluid rotation in the water column around the vortex center. Further vortex evolution depends on the model parameters and initial conditions, which limits predictability owing to multiple equilibrium attractors existing in the dynamical system. The vortex core strips thin filaments, which roll up into submesoscale vortices to result in substantial mixing at the vortex periphery. Stirring and damping of vorticity by bottom friction are found to be essential for subsequent vortex stabilization. The development of sharp PV gradients leads to nearly solid-body rotation inside the vortex core and formation of transport barriers at the vortex periphery. These processes have important implications for understanding the longevity of real-ocean eddies.

Lattice vortices in the two-dimensional Abelian Higgs model

International Nuclear Information System (INIS)

Grunewald, S.; Ilgenfritz, E.-M.; Mueller-Preussker, M.

1986-01-01

Multi-vortices of the 2D Abelian Higgs model on a finite lattice by relaxation of Monte-Carlo equilibrium configurations are generated and identified. The lattice vortices have action and a uniquely defined topological charge corresponding to the continuum ones. They exhibit the expected exponential decay behaviour and satisfy approximately the classical equations of motion. Vortex-antivortex superpositions are seen as well, supporting the dilute gas picture. Single vortices finally relax into ''dislocations'' and dissapear. A background charge construction turns out nearly insensitive with respect to dislocations

Laboratory experiments on multipolar vortices in a rotating fluid

NARCIS (Netherlands)

Trieling, R.R.; Heijst, van G.J.F.; Kizner, Ziv

2010-01-01

The instability properties of isolated monopolar vortices have been investigated experimentally and the corresponding multipolar quasisteady states have been compared with semianalytical vorticity-distributed solutions to the Euler equations in two dimensions. A novel experimental technique was

Vitality of optical vortices

CSIR Research Space (South Africa)

Roux, FS

2014-02-01

Full Text Available Optical vortices are always created or annihilated in pairs with opposite topological charges. However, the presence of such a vortex dipole does not directly indicate whether they are associated with a creation or an annihilation event. Here we...

Crosswind Shear Gradient Affect on Wake Vortices

Science.gov (United States)

Proctor, Fred H.; Ahmad, Nashat N.

2011-01-01

Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.

Use of acoustic vortices in acoustic levitation

DEFF Research Database (Denmark)

Cutanda Henriquez, Vicente; Santillan, Arturo Orozco; Juhl, Peter Møller

2009-01-01

Acoustic fields are known to exert forces on the surfaces of objects. These forces are noticeable if the sound pressure is sufficiently high. Two phenomena where acoustic forces are relevant are: i) acoustic levitation, where strong standing waves can hold small objects at certain positions......, counterbalancing their weight, and ii) acoustic vortices, spinning sound fields that can impinge angular momentum and cause rotation of objects. In this contribution, both force-creating sound fields are studied by means of numerical simulations. The Boundary Element Method is employed to this end. The simulation...... of acoustical vortices uses an efficient numerical implementation based on the superposition of two orthogonal sound fields with a delay of 90° between them. It is shown that acoustic levitation and the use of acoustic vortices can be combined to manipulate objects in an efficient and controlled manner without...

Visible-Frequency Metasurface for Structuring and Spatially Multiplexing Optical Vortices.

Science.gov (United States)

Mehmood, M Q; Mei, Shengtao; Hussain, Sajid; Huang, Kun; Siew, S Y; Zhang, Lei; Zhang, Tianhang; Ling, Xiaohui; Liu, Hong; Teng, Jinghua; Danner, Aaron; Zhang, Shuang; Qiu, Cheng-Wei

2016-04-06

A multifocus optical vortex metalens, with enhanced signal-to-noise ratio, is presented, which focuses three longitudinal vortices with distinct topological charges at different focal planes. The design largely extends the flexibility of tuning the number of vortices and their focal positions for circularly polarized light in a compact device, which provides the convenience for the nanomanipulation of optical vortices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Role of centre vortices in dynamical mass generation

International Nuclear Information System (INIS)

Leinweber, Derek B.; Bowman, Patrick O.; Heller, Urs M.; Kusterer, Daniel-Jens; Langfeld, Kurt; Williams, Anthony G.

2006-01-01

The mass and renormalization functions of the nonperturbative quark propagator are studied in SU(3) gauge field theory with a Symanzik-improved gluon action and the AsqTad fermion action. Centre vortices in the gauge field are identified by fixing to maximal centre gauge. The role of centre vortices in dynamical mass generation is explored by removing centre vortices from the gauge fields and studying the associated changes in the quark propagator. We find that dynamical mass generation survives in the vortex-removed SU(3) gauge field theory despite the vanishing of the string tension and suppression of the gluon propagator in the infrared suggesting the possibility of decoupling dynamical mass generation from confinement

Vortices and nanostructured superconductors

CERN Document Server

2017-01-01

This book provides expert coverage of modern and novel aspects of the study of vortex matter, dynamics, and pinning in nanostructured and multi-component superconductors. Vortex matter in superconducting materials is a field of enormous beauty and intellectual challenge, which began with the theoretical prediction of vortices by A. Abrikosov (Nobel Laureate). Vortices, vortex dynamics, and pinning are key features in many of today’s human endeavors: from the huge superconducting accelerating magnets and detectors at the Large Hadron Collider at CERN, which opened new windows of knowledge on the universe, to the tiny superconducting transceivers using Rapid Single Flux Quanta, which have opened a revolutionary means of communication. In recent years, two new features have added to the intrinsic beauty and complexity of the subject: nanostructured/nanoengineered superconductors, and the discovery of a range of new materials showing multi-component (multi-gap) superconductivity. In this book, leading researche...

Magnetic monopoles, center vortices, confinement and topology of gauge fields

International Nuclear Information System (INIS)

Reinhardt, H.; Engelhardt, M.; Langfeld, K.; Quandt, M.; Schaefke, A.

2000-01-01

The vortex picture of confinement is studied. The deconfinement phase transition is explained as a transition from a phase in which vortices percolate to a phase of small vortices. Lattice results are presented in support of this scenario. Furthermore the topological properties of magnetic monopoles and center vortices arising, respectively, in Abelian and center gauges are studied in continuum Yang-Mills-theory. For this purpose the continuum analog of the maximum center gauge is constructed

Magnetic Monopoles, Center Vortices, Confinement and Topology of Gauge Fields

OpenAIRE

Reinhardt, H.; Engelhardt, M.; Langfeld, K.; Quandt, M.; Sch"afke, A.

1999-01-01

The vortex picture of confinement is studied. The deconfinement phase transition is explained as a transition from a phase in which vortices percolate to a phase of small vortices. Lattice results are presented in support of this scenario. Furthermore the topological properties of magnetic monopoles and center vortices arising, respectively, in Abelian and center gauges are studied in continuum Yang-Mills-theory. For this purpose the continuum analog of the maximum center gauge is constructed.

Theory of Concentrated Vortices

DEFF Research Database (Denmark)

Alekseenko, Sergey; Kuibin, Pavel; Okulov, Valery

This book presents comprehensive and authoritative coverage of the wide field of concentrated vortices observed in nature and technique. The methods for research of their kinematics and dynamics are considered. Special attention is paid to the flows with helical symmetry. The authors have describ...

Sharp vorticity gradients in two-dimensional turbulence and the energy spectrum

DEFF Research Database (Denmark)

Kuznetsov, E.A.; Naulin, Volker; Nielsen, Anders Henry

2010-01-01

Formation of sharp vorticity gradients in two-dimensional (2D) hydrodynamic turbulence and their influence on the turbulent spectra are considered. The analog of the vortex line representation as a transformation to the curvilinear system of coordinates moving together with the di-vorticity lines...... is developed and compressibility of this mapping appears as the main reason for the formation of the sharp vorticity gradients at high Reynolds numbers. In the case of strong anisotropy the sharp vorticity gradients can generate spectra which fall off as k −3 at large k, which appear to take the same form...

Decay or collapse: Aircraft wake vortices in grid turbulence

NARCIS (Netherlands)

Ren, M.; Elsenaar, A.; van Heijst, G.J.F.; Kuczaj, Arkadiusz K.; Geurts, Bernardus J.

2006-01-01

Trailing vortices are naturally shed by airplanes and they typically evolve into a counter-rotating vortex pair. Downstream of the aircraft, these vortices can persist for a very long time and extend for several kilometers. This poses a potential hazard to following aircraft, particularly during

Influence of artificial tip perturbation on asymmetric vortices flow over a chined fuselage

Directory of Open Access Journals (Sweden)

Shi Wei

2015-08-01

Full Text Available An experimental study was conducted with the aim of understanding behavior of asymmetric vortices flow over a chined fuselage. The tests were carried out in a wind tunnel at Reynolds number of 1.87 × 105 under the conditions of high angles of attack and zero angle of sideslip. The results show that leeward vortices flow becomes asymmetric vortices flow when angle of attack increases over 20°. The asymmetric vortices flow is asymmetry of two forebody vortices owing to the increase of angle of attack but not asymmetry of vortex breakdown which appears when angle of attack is above 35°. Asymmetric vortices flow is sensitive to tip perturbation and is non-deterministic due to randomly distributed natural minute geometrical irregularities on the nose tip within machining tolerance. Deterministic asymmetric vortices flow can be obtained by attaching artificial tip perturbation which can trigger asymmetric vortices flow and decide asymmetric vortices flow pattern. Triggered by artificial tip perturbation, the vortex on the same side with perturbation is in a higher position, and the other vortex on the opposite side is in a lower position. Vortex suction on the lower vortex side is larger, which corresponds to a side force pointing to the lower vortex side.

On hairpin vortices in a transitional boundary layer

Directory of Open Access Journals (Sweden)

Uruba Václav

2012-04-01

Full Text Available In the presented paper the results of experiments on transitional boundary layer are presented. The boundary layer was generated on smooth flat wall with zero pressure gradient forming one side of the channel of rectangular cross section. The hairpin vortices, packets of hairpin vortices, turbulent spots and calmed regions were experimentally investigated using time-resolved PIV technique.

Vortices and domain walls: 'Wormholes' in unconventional superconductors

International Nuclear Information System (INIS)

Bessarab, P F; Radievsky, A V

2010-01-01

In the framework of the 2D and 3D time-dependent Ginzburg-Landau model we study superconductors with multicomponent order parameter (d-pairing). We argue that topological defects inside the sample do affect its thermodynamic properties such as hysteresis loop, susceptibility, etc. Along with earlier known topological defects such as Abrikosov vortices, domain walls (DWs) which separate different magnetic phases and even vortices inside the DW, we found an interesting combination of DWs and vortices. Namely we show that equivalent magnetic phases may be linked together with a vortex going through the other magnetic phase. This configuration may correspond to a stable state even in a zero external magnetic field. We also mention that this configuration is topologically similar to the 'wormholes' in the quantum gravity.

Hard wall - soft wall - vorticity scattering in shear flow

NARCIS (Netherlands)

Rienstra, S.W.; Singh, D.K.

2014-01-01

An analytically exact solution, for the problem of lowMach number incident vorticity scattering at a hard-soft wall transition, is obtained in the form of Fourier integrals by using theWiener-Hopf method. Harmonic vortical perturbations of inviscid linear shear flow are scattered at the wall

Hard wall - soft wall - vorticity scattering in shear flow

NARCIS (Netherlands)

Rienstra, S.W.; Singh, D.K.

2014-01-01

An analytically exact solution, for the problem of low Mach number incident vorticity scattering at a hard-soft wall transition, is obtained in the form of Fourier integrals by using the Wiener-Hopf method. Harmonic vortical perturbations of inviscid linear shear flow are scattered at the wall

LONG-TERM EVOLUTION OF PLANET-INDUCED VORTICES IN PROTOPLANETARY DISKS

International Nuclear Information System (INIS)

Fu, Wen; Li, Hui; Li, Shengtai; Lubow, Stephen

2014-01-01

Recent observations of large-scale asymmetric features in protoplanetary disks suggest that large-scale vortices exist in such disks. Massive planets are known to be able to produce deep gaps in protoplanetary disks. The gap edges could become hydrodynamically unstable to the Rossby wave/vortex instability and form large-scale vortices. In this study we examine the long-term evolution of these vortices by carrying out high-resolution two-dimensional hydrodynamic simulations that last more than 10 4 orbits (measured at the planet's orbit). We find that the disk viscosity has a strong influence on both the emergence and lifetime of vortices. In the outer disk region where asymmetric features are observed, our simulation results suggest that the disk viscous α needs to be low, ∼10 –5 -10 –4 , to sustain vortices to thousands and up to 10 4 orbits in certain cases. The chance of finding a vortex feature in a disk then decreases with smaller planet orbital radius. For α ∼ 10 –3 or larger, even planets with masses of 5 M J will have difficulty either producing or sustaining vortices. We have also studied the effects of different disk temperatures and planet masses. We discuss the implications of our findings on current and future protoplanetary disk observations

Vortices in a rotating dark matter condensate

International Nuclear Information System (INIS)

Yu, Rotha P; Morgan, Michael J

2002-01-01

We examine vortices in a self-gravitating dark matter Bose-Einstein condensate (BEC), consisting of ultra-low mass scalar bosons that arise during a late-time cosmological phase transition. Rotation of the dark matter BEC imprints a background phase gradient on the condensate, which establishes a harmonic trap potential for vortices. A numerical simulation of vortex dynamics shows that the vortex number density, n v ∝ r -1 , resulting in a flat velocity profile for the dark matter condensate. (letter to the editor)

Inward propagating chemical waves in Taylor vortices.

Science.gov (United States)

Thompson, Barnaby W; Novak, Jan; Wilson, Mark C T; Britton, Melanie M; Taylor, Annette F

2010-04-01

Advection-reaction-diffusion (ARD) waves in the Belousov-Zhabotinsky reaction in steady Taylor-Couette vortices have been visualized using magnetic-resonance imaging and simulated using an adapted Oregonator model. We show how propagating wave behavior depends on the ratio of advective, chemical and diffusive time scales. In simulations, inward propagating spiral flamelets are observed at high Damköhler number (Da). At low Da, the reaction distributes itself over several vortices and then propagates inwards as contracting ring pulses--also observed experimentally.

Comparing the dynamics of skyrmions and superconducting vortices

International Nuclear Information System (INIS)

Olson Reichhardt, C.J.; Lin, S.Z.; Ray, D.; Reichhardt, C.

2014-01-01

Highlights: • We describe similarities and differences between skyrmion and vortex dynamics. • The Magnus force can dramatically alter skyrmion transport. • The pinning becomes very weak when the Magnus force is strong. - Abstract: 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

Influence of Initial Vorticity Distribution on Axisymmetric Vortex Breakdown and Reconnection

Science.gov (United States)

Young, Larry A.

2007-01-01

An analytical treatment 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. In particular, the presence of negative vorticity in the inner core of a vortex filament (one example of which is examined in this paper) subsequent to "cutting" by a solid body has a profound influence on the vortex reconnection, leading to analog flow behavior similar to vortex breakdown phenomena described in the literature. Initial vorticity distributions (three specific examples which are examined) without an inner core of negative vorticity do not exhibit vortex breakdown and instead manifest diffusion-like properties while undergoing vortex reconnection. Though this work focuses on laminar vortical flow, this work is anticipated to provide valuable insight into rotary-wing aerodynamics as well as other types of vortical flow phenomena.

4D-flat compactifications with brane vorticities

International Nuclear Information System (INIS)

Randjbar Daemi, S.; Rubakov, V.

2004-07-01

We present solutions in six-dimensional gravity coupled to a sigma model, in the presence of three-brane sources. The space transverse to the branes is a compact non-singular manifold. The example of O(3) sigma model in the presence of two three-branes is worked out in detail. We show that the four-dimensional flatness is obtained with a single condition involving the brane tensions, which are in general different and may be both positive, and another characteristic of the branes, vorticity. We speculate that the adjustment of the effective four- dimensional cosmological constant may occur through the exchange of vorticity between the branes. We then give exact instanton type solutions for sigma models targeted on a general Kaehler manifold, and elaborate in this framework on multi-instantons of the O(3) sigma model. The latter have branes, possibly with vorticities, at the instanton positions, thus generalizing our two-brane solution. (author)

4d-flat compactifications with brane vorticities

International Nuclear Information System (INIS)

Randjbar-Daemi, Seif; Rubakov, Valery

2004-01-01

We present solutions in six-dimensional gravity coupled to a sigma model, in the presence of three-brane sources. The space transverse to the branes is a compact non-singular manifold. The example of O(3) sigma model in the presence of two three-branes is worked out in detail. We show that the four-dimensional flatness is obtained with a single condition involving the brane tensions, which are in general different and may be both positive, and another characteristic of the branes, vorticity. We speculate that the adjustment of the effective four-dimensional cosmological constant may occur through the exchange of vorticity between the branes. We then give exact instanton type solutions for sigma models targeted on a general Kaehler manifold, and elaborate in this framework on multi-instantons of the O(3) sigma model. The latter have branes, possibly with vorticities, at the instanton positions, thus generalizing our two-brane solution. (author)

Compressible dynamic stall vorticity flux control using a dynamic ...

Indian Academy of Sciences (India)

systems, such as a wind turbine, are prevented from ever entering dynamic stall, essentially disregarding potential ... future generations of such systems, an overwhelming need has developed to avail this benefit safely. ... approach must diffuse the vorticity prior to its coalescence, but keep the vorticity over the airfoil up to ...

Continuous control of asymmetric forebody vortices in a bi-stable state

Science.gov (United States)

Wang, Qi-te; Cheng, Ke-ming; Gu, Yun-song; Li, Zhuo-qi

2018-02-01

Aiming at the problem of continuous control of asymmetric forebody vortices at a high angle of attack in a bi-stable regime, a dual synthetic jet actuator embedded in an ogive forebody was designed. Alternating unsteady disturbance with varying degree asymmetrical flow fields near the nozzles is generated by adjusting the duty cycle of the drive signal of the actuator, specifically embodying the asymmetric time-averaged pattern of jet velocity, vorticity, and turbulent kinetic energy. Experimental results show that within the range of relatively high angles of attack, including the angle-of-attack region in a bi-stable state, the lateral force of the ogive forebody is continuously controlled by adjusting the duty cycle of the drive signal; the position of the forebody vortices in space, the vorticity magnitude, the total pressure coefficient near the vortex core, and the vortex breakdown location are continuously changed with the duty cycle increased observed from the time-averaged flow field. Instantaneous flow field results indicate that although the forebody vortices are in an unsteady oscillation state, a continuous change in the forebody vortices' oscillation balance position as the duty cycle increases leads to a continuous change in the model's surface pressure distribution and time-averaged lateral force. Different from the traditional control principle, in this study, other different degree asymmetrical states of the forebody vortices except the bi-stable state are obtained using the dual synthetic jet control technology.

Effects of sharp vorticity gradients in two-dimensional hydrodynamic turbulence

DEFF Research Database (Denmark)

Kuznetsov, E.A.; Naulin, Volker; Nielsen, Anders Henry

2007-01-01

The appearance of sharp vorticity gradients in two-dimensional hydrodynamic turbulence and their influence on the turbulent spectra are considered. We have developed the analog of the vortex line representation as a transformation to the curvilinear system of coordinates moving together with the ......The appearance of sharp vorticity gradients in two-dimensional hydrodynamic turbulence and their influence on the turbulent spectra are considered. We have developed the analog of the vortex line representation as a transformation to the curvilinear system of coordinates moving together...... with the divorticity lines. Compressibility of this mapping can be considered as the main reason for the formation of the sharp vorticity gradients at high Reynolds numbers. For two-dimensional turbulence in the case of strong anisotropy the sharp vorticity gradients can generate spectra which fall off as k−3 at large...

The Born-Infeld vortices induced from a generalized Higgs mechanism.

Science.gov (United States)

Han, Xiaosen

2016-04-01

We construct self-dual Born-Infeld vortices induced from a generalized Higgs mechanism. Two specific models of the theory are of focused interest where the Higgs potential is either of a | ϕ | 4 - or | ϕ | 6 -type. For the | ϕ | 4 -model, we obtain a sharp existence and uniqueness theorem for doubly periodic and planar vortices. For doubly periodic solutions, a necessary and sufficient condition for the existence is explicitly derived in terms of the vortex number, the Born-Infeld parameter, and the size of the periodic lattice domain. For the | ϕ | 6 -model, we show that both topological and non-topological vortices are present. This new phenomenon distinguishes the model from the classical Born-Infeld-Higgs theory studied earlier in the literature. A series of results regarding doubly periodic, topological, and non-topological vortices in the | ϕ | 6 -model are also established.

Modelling of the nonlinear evolution of 2D waves and vortices in plasmas

International Nuclear Information System (INIS)

Taranov, V.B.

1998-01-01

In this report an antisymmetric lattice formed by standing waves of vorticity is considered. For small but finite amplitudes multiple-time-scale analysis is performed, higher harmonics generation and frequency shifts are evaluated analytically and critical amplitude for perturbation theory is determined. For amplitudes bigger than critical numerical simulations are carried out taking into account vortex nonlinearity, drift and dispersion effects. Numerical code is developed which allows to study long-term evolution of two-dimensional spatially periodic waves and vortex structures

Late-Stage Vortical Structures and Eddy Motions in a Transitional Boundary Layer

International Nuclear Information System (INIS)

Xiao-Bing, Liu; Zheng-Qing, Chen; Chao-Qun, Liu

2010-01-01

A high-order direct numerical simulation of flow transition over a flat-plate at a free stream Mach number 0.5 is carried out. Formation and development of three-dimensional vortical structures, typically shown as A-vortices, hairpin vortices and ring-like vortices, are observed. Numerical results show that there is a strong downdraft motion of fluid excited by every ring-like vortex in the late-stage of the transition process. At two sides of the vortical structure centerline, the downdraft motions induced by the ring-like vortex and the rotating legs superimpose. This is responsible for the appearance of a high-speed streak associated with the positive spike observed in a previous investigation and the appearance of a high-shear layer in the near wall region. (fundamental areas of phenomenology(including applications))

Sharp asymptotic estimates for vorticity solutions of the 2D Navier-Stokes equation

Directory of Open Access Journals (Sweden)

Yuncheng You

2008-12-01

Full Text Available The asymptotic dynamics of high-order temporal-spatial derivatives of the two-dimensional vorticity and velocity of an incompressible, viscous fluid flow in $mathbb{R}^2$ are studied, which is equivalent to the 2D Navier-Stokes equation. It is known that for any integrable initial vorticity, the 2D vorticity solution converges to the Oseen vortex. In this paper, sharp exterior decay estimates of the temporal-spatial derivatives of the vorticity solution are established. These estimates are then used and combined with similarity and $L^p$ compactness to show the asymptotical attraction rates of temporal-spatial derivatives of generic 2D vorticity and velocity solutions by the Oseen vortices and velocity solutions respectively. The asymptotic estimates and the asymptotic attraction rates of all the derivatives obtained in this paper are independent of low or high Reynolds numbers.

Longitudinal vortices in a transitioning boundary layer

International Nuclear Information System (INIS)

Anders, J.B.; Backwelder, R.F.

1980-01-01

Naturally occurring spanwise variations of the streamwise velocity component, characteristic of longitudinal vortices embedded in a transitioning boundary layer were explored using hot-wire anemometers. A vibrating ribbon introduced stable or unstable Tollmien-Schlichting waves into the laminar boundary layer. These damped or growing disturbances always developed a strong three-dimensional pattern even though no spanwise perturbations were artificially induced. Changing the radius of the leading edge and other modifications to the flat plate, wind tunnel and boundary layer did not alter the spanwise wavelength of the vortices. (orig.)

Scaling properties of Wilson loops pierced by P-vortices

DEFF Research Database (Denmark)

Dunn, Patrick; Greensite, Jeffrey Paul

2012-01-01

P-vortices, in an SU(N) lattice gauge theory, are excitations on the center-projected Z(N) lattice. We study the ratio of expectation values of SU(2) Wilson loops, on the unprojected lattice, linked to a single P-vortex, to that of Wilson loops which are not linked to any P-vortices. When...

Imparting small vorticity to a Bianchi type-VIh empty spacetime

Science.gov (United States)

Batakis, Nikos A.

1981-04-01

We present and briefly discuss a Bianchi type-VIh empty spacetime. The field equations have been solved after being linearized with respect to a parameter which imparts vorticity to the model. The limit of zero vorticity is an already known solution.

The Interaction of Two Surface Vortices Near a Topographic Slope in a Stratified Ocean

Directory of Open Access Journals (Sweden)

Charly de Marez

2017-10-01

Full Text Available We study the influence of bottom topography on the interaction of two identical vortices in a two-layer, quasi-geostrophic model. The two vortices have piecewise-uniform potential vorticity and are lying in the upper layer of the model. The topography is a smooth bottom slope. For two cyclones, topography modifies the merger critical distance and the merger efficiency: the topographic wave and vortices can advect the two cyclones along the shelf when they are initially far from it or towards the shelf when they are initially closer to it. They can also advect the two cyclones towards each other and thus favour merger. The cyclones deform, and the potential vorticity field undergoes filamentation. Regimes of partial vortex merger or of vortex splitting are then observed. The interaction of the vorticity poles in the two layers are analysed to explain the evolution of the two upper layer cyclones. For taller topography, two new regimes appear: vortex drift and splitting; and filamentation and asymmetric merger. They are due to the hetonic coupling of lower layer vorticity with the upper layer vortices (a heton is a baroclinic vortex dipole, carrying heat and momentum and propagating horizontally in the fluid, or to the strong shear that the former exerts on the latter. The interaction of two anticyclones shows regimes of co-rotation or merger, but specifically, it leads to the drift of the two vortices away from the slope, via a hetonic coupling with oppositely-signed vorticity in the lower layer. This vorticity originates in the breaking of the topographic wave. The analysis of passive tracer evolution confirms the inshore or offshore drift of the fluid, the formation of tracer fronts along filaments and its stirring in regions of vortex merger. The trajectories of particles indicate how the fluid initially in the vortices is finally partitioned.

Internal and vorticity waves in decaying stratified flows

Science.gov (United States)

Matulka, A.; Cano, D.

2009-04-01

Most predictive models fail when forcing at the Rossby deformation Radius is important and a large range of scales have to be taken into account. When mixing of reactants or pollutants has to be accounted, the range of scales spans from hundreds of Kilometers to the Bachelor or Kolmogorov sub milimiter scales. We present some theoretical arguments to describe the flow in terms of the three dimensional vorticity equations, using a lengthscale related to the vorticity (or enstrophy ) transport. Effect of intermittent eddies and non-homogeneity of diffusion are also key issues in the environment because both stratification and rotation body forces are important and cause anisotropy/non-homogeneity. These problems need further theoretical, numerical and observational work and one approach is to try to maximize the relevant geometrical information in order to understand and therefore predict these complex environmental dispersive flows. The importance of the study of turbulence structure and its relevance in diffusion of contaminants in environmental flows is clear when we see the effect of environmental disasters such as the Prestige oil spill or the Chernobil radioactive cloud spread in the atmosphere. A series of Experiments have been performed on a strongly stratified two layer fluid consisting of Brine in the bottom and freshwater above in a 1 square meter tank. The evolution of the vortices after the passage of a grid is video recorded and Particle tracking is applied on small pliolite particles floating at the interface. The combination of internal waves and vertical vorticity produces two separate time scales that may produce resonances. The vorticity is seen to oscilate in a complex way, where the frecuency decreases with time.

Lagrangian investigations of vorticity dynamics in compressible turbulence

Science.gov (United States)

Parashar, Nishant; Sinha, Sawan Suman; Danish, Mohammad; Srinivasan, Balaji

2017-10-01

In this work, we investigate the influence of compressibility on vorticity-strain rate dynamics. Well-resolved direct numerical simulations of compressible homogeneous isotropic turbulence performed over a cubical domain of 10243 are employed for this study. To clearly identify the influence of compressibility on the time-dependent dynamics (rather than on the one-time flow field), we employ a well-validated Lagrangian particle tracker. The tracker is used to obtain time correlations between the instantaneous vorticity vector and the strain-rate eigenvector system of an appropriately chosen reference time. In this work, compressibility is parameterized in terms of both global (turbulent Mach number) and local parameters (normalized dilatation-rate and flow field topology). Our investigations reveal that the local dilatation rate significantly influences these statistics. In turn, this observed influence of the dilatation rate is predominantly associated with rotation dominated topologies (unstable-focus-compressing, stable-focus-stretching). We find that an enhanced dilatation rate (in both contracting and expanding fluid elements) significantly enhances the tendency of the vorticity vector to align with the largest eigenvector of the strain-rate. Further, in fluid particles where the vorticity vector is maximally misaligned (perpendicular) at the reference time, vorticity does show a substantial tendency to align with the intermediate eigenvector as well. The authors make an attempt to provide physical explanations of these observations (in terms of moment of inertia and angular momentum) by performing detailed calculations following tetrads {approach of Chertkov et al. ["Lagrangian tetrad dynamics and the phenomenology of turbulence," Phys. Fluids 11(8), 2394-2410 (1999)] and Xu et al. ["The pirouette effect in turbulent flows," Nat. Phys. 7(9), 709-712 (2011)]} in a compressible flow field.

Adiabatic effective action for vortices in neutral and charged superfluids

International Nuclear Information System (INIS)

Hatsuda, M.; Sato, M.; Yahikozawa, S.; Hatsuda, T.

1996-01-01

Adiabatic effective action for vortices in neutral and charged superfluids at zero temperature are calculated using the topological Landau-Ginzburg theory recently proposed by Hatsuda, Yahikozawa, Ao and Thouless, and vortex dynamics are examined. The Berry phase term arising in the effective action naturally yields the Magnus force in both neutral and charged superfluids. It is shown that in neutral superfluid there is only one degree of freedom, namely the center of vorticities, and the vortex energy is proportional to the sum of all vorticities so that it is finite only for the vanishing total vorticity of the system. On the other hand the effective mass and the vortex energy for a vortex in charged superfluids are defined individually as expected. The effects of the vortex core on these quantities are also estimated. The possible depinning scenario which is governed by the Magnus force and the inertial mass is also discussed

Superconducting vortices in Weinberg - Salam theory

International Nuclear Information System (INIS)

Garaud, J.

2010-09-01

In this dissertation, we analyze in detail the properties of new string-like solutions of the bosonic sector of the electroweak theory. The new solutions are current carrying generalizations of embedded Abrikosov-Nielsen-Olesen vortices. We were also able to reproduce all previously known features of vortices in the electroweak theory. Generically vortices are current carrying. They are made of a compact conducting core of charged W bosons surrounded by a nonlinear superposition of Z and Higgs field. Far away from the core, the solution is described by purely electromagnetic Biot and Savart field. Solutions exist for generic parameter values including experimental values of the coupling constants. We show that the current whose typical scale is the billion of Amperes can be arbitrarily large. In the second part the linear stability with respect to generic perturbations is studied. The fluctuation spectrum is qualitatively investigated. When negative modes are detected, they are explicitly constructed and their dispersion relation is determined. Most of the unstable modes can be eliminated by imposing periodic boundary conditions along the vortex. However there remains a unique negative mode which is homogeneous. This mode can probably be eliminated by curvature effects if a small piece of vortex is bent into a loop, stabilized against contraction by the electric current. (author)

Localized vortices in ηi-modes

International Nuclear Information System (INIS)

Nycander, J.; Lynov, J.P.; Juul Rasmussen, J.

1992-01-01

For a wide variety of nonlinear wave equations necessary conditions for the existence of localized, stationary structures can be found by applying a simple procedure, involving two steps: First the linear dispersion relation is obtained and the regions of the phase velocity of linear waves found. Secondly, assuming that localized solutions exist, their velocities are determined by using integral relations. The obtained velocity takes the form of a ''center of mass velocity''. If this velocity falls outside the regions of phase velocities for linear waves then nonlinear localized vortices may exist. Otherwise, the structure will couple to the linear waves and gradually disperse. Applying this method we have shown that monopole vortex solutions exist for drift waves driven by the ion temperature gradient in a magnetized plasma, the so-called η i -modes. Numerical solutions show that such vortices are steadily propagating and stable and they generally emerge from localized initial conditions. Our study is motivated by recent high resolution simulations of η i -turbulence, where it was observed that coherent vortices developed spontaneously. These had a dominating influence on the evolution of the turbulence, and the associated anomalous transport was found to be significantly reduced as compared with the predictions from quasilinear theory. (author) 8 refs., 3 figs

Electrochemical Analysis of Taylor Vortices.

Czech Academy of Sciences Publication Activity Database

Wouahbi, F.; Allaf, K.; Sobolík, Václav

2007-01-01

Roč. 37, 1 (2007) , s. 57-62 ISSN 0021-891X Institutional research plan: CEZ:AV0Z40720504 Keywords : electrodiffusion method * taylor vortices * three-segment electrode Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.417, year: 2007

Analysis of propeller-induced ground vortices by particle image velocimetry

NARCIS (Netherlands)

Yang, Y.; Sciacchitano, A.; Veldhuis, L.L.M.; Eitelberg, G.

2017-01-01

Abstract: The interaction between a propeller and its self-induced vortices originating on the ground is investigated in a scaled experiment. The velocity distribution in the flow field in two different planes containing the self-induced vortices is measured by particle image velocimetry (PIV).

"Submesoscale Soup" Vorticity and Tracer Statistics During the Lateral Mixing Experiment

Science.gov (United States)

Shcherbina, A.; D'Asaro, E. A.; Lee, C. M.; Molemaker, J.; McWilliams, J. C.

2012-12-01

A detailed view of upper-ocean velocity, vorticity, and tracer statistics was obtained by a unique synchronized two-vessel survey in the North Atlantic in winter 2012. In winter, North Atlantic Mode water region south of the Gulf Stream is filled with an energetic, homogeneous, and well-developed submesoscale turbulence field - the "submesoscale soup". Turbulence in the soup is produced by frontogenesis and the surface layer instability of mesoscale eddy flows in the vicinity of the Gulf Stream. This region is a convenient representation of the inertial range of the geophysical turbulence forward cascade spanning scales of o(1-100km). During the Lateral Mixing Experiment in February-March 2012, R/Vs Atlantis and Knorr were run on parallel tracks 1 km apart for 500 km in the submesoscale soup region. Synchronous ADCP sampling provided the first in-situ estimates of full 3-D vorticity and divergence without the usual mix of spatial and temporal aliasing. Tracer distributions were also simultaneously sampled by both vessels using the underway and towed instrumentation. Observed vorticity distribution in the mixed layer was markedly asymmetric, with sparse strands of strong anticyclonic vorticity embedded in a weak, predominantly cyclonic background. While the mean vorticity was close to zero, distribution skewness exceeded 2. These observations confirm theoretical and numerical model predictions for an active submesoscale turbulence field. Submesoscale vorticity spectra also agreed well with the model prediction.

An efficient and general numerical method to compute steady uniform vortices

Science.gov (United States)

Luzzatto-Fegiz, Paolo; Williamson, Charles H. K.

2011-07-01

Steady uniform vortices are widely used to represent high Reynolds number flows, yet their efficient computation still presents some challenges. Existing Newton iteration methods become inefficient as the vortices develop fine-scale features; in addition, these methods cannot, in general, find solutions with specified Casimir invariants. On the other hand, available relaxation approaches are computationally inexpensive, but can fail to converge to a solution. In this paper, we overcome these limitations by introducing a new discretization, based on an inverse-velocity map, which radically increases the efficiency of Newton iteration methods. In addition, we introduce a procedure to prescribe Casimirs and remove the degeneracies in the steady vorticity equation, thus ensuring convergence for general vortex configurations. We illustrate our methodology by considering several unbounded flows involving one or two vortices. Our method enables the computation, for the first time, of steady vortices that do not exhibit any geometric symmetry. In addition, we discover that, as the limiting vortex state for each flow is approached, each family of solutions traces a clockwise spiral in a bifurcation plot consisting of a velocity-impulse diagram. By the recently introduced "IVI diagram" stability approach [Phys. Rev. Lett. 104 (2010) 044504], each turn of this spiral is associated with a loss of stability for the steady flows. Such spiral structure is suggested to be a universal feature of steady, uniform-vorticity flows.

An experimental investigation of wind pressures on square pillars in tornado-like vortices

International Nuclear Information System (INIS)

Iwatani, Yoshiharu; Maruta, Eizou; Kanda, Makoto; Hattori, Yousuke; Hamano, Naoki; Matsuura, Takeshi

1992-01-01

This report describes a laboratory simulation of tornado-like vortices and laboratory measurements of steady wind loads on model structures in tornado-like vortices. The variations of wind direction and wind speed of tornado-like vortices and ground surface pressure under tornado-like vortices with the swirl ratio, Reynolds number and the surface roughness were investigated. Wind pressure distributions on square pillars were measured in tornado-like vortices. It was observed in the experiment that the negative pressures on the roof faces of square pillars were high and distributed rather uniformly but these on the side faces differed greatly from place to place and locally became high. The high pressure regions on the side faces were close to ground surface in the case where the model structures stood in the center of tornado-like vortex, and became higher as the increase of distance between the model structures and the center of tornado-like vortices. (author)

Effects of wing locations on wing rock induced by forebody vortices

Directory of Open Access Journals (Sweden)

Ma Baofeng

2016-10-01

Full Text Available Previous studies have shown that asymmetric vortex wakes over slender bodies exhibit a multi-vortex structure with an alternate arrangement along a body axis at high angle of attack. In this investigation, the effects of wing locations along a body axis on wing rock induced by forebody vortices was studied experimentally at a subcritical Reynolds number based on a body diameter. An artificial perturbation was added onto the nose tip to fix the orientations of forebody vortices. Particle image velocimetry was used to identify flow patterns of forebody vortices in static situations, and time histories of wing rock were obtained using a free-to-roll rig. The results show that the wing locations can affect significantly the motion patterns of wing rock owing to the variation of multi-vortex patterns of forebody vortices. As the wing locations make the forebody vortices a two-vortex pattern, the wing body exhibits regularly divergence and fixed-point motion with azimuthal variations of the tip perturbation. If a three-vortex pattern exists over the wing, however, the wing-rock patterns depend on the impact of the highest vortex and newborn vortex. As the three vortices together influence the wing flow, wing-rock patterns exhibit regularly fixed-points and limit-cycled oscillations. With the wing moving backwards, the newborn vortex becomes stronger, and wing-rock patterns become fixed-points, chaotic oscillations, and limit-cycled oscillations. With further backward movement of wings, the vortices are far away from the upper surface of wings, and the motions exhibit divergence, limit-cycled oscillations and fixed-points. For the rearmost location of the wing, the wing body exhibits stochastic oscillations and fixed-points.

Cell-based therapeutic strategies for multiple sclerosis.

Science.gov (United States)

Scolding, Neil J; Pasquini, Marcelo; Reingold, Stephen C; Cohen, Jeffrey A

2017-11-01

The availability of multiple disease-modifying medications with regulatory approval to treat multiple sclerosis illustrates the substantial progress made in therapy of the disease. However, all are only partially effective in preventing inflammatory tissue damage in the central nervous system and none directly promotes repair. Cell-based therapies, including immunoablation followed by autologous haematopoietic stem cell transplantation, mesenchymal and related stem cell transplantation, pharmacologic manipulation of endogenous stem cells to enhance their reparative capabilities, and transplantation of oligodendrocyte progenitor cells, have generated substantial interest as novel therapeutic strategies for immune modulation, neuroprotection, or repair of the damaged central nervous system in multiple sclerosis. Each approach has potential advantages but also safety concerns and unresolved questions. Moreover, clinical trials of cell-based therapies present several unique methodological and ethical issues. We summarize here the status of cell-based therapies to treat multiple sclerosis and make consensus recommendations for future research and clinical trials. © The Author (2017). Published by Oxford University Press on behalf of the Guarantors of Brain.

Interaction of plasma vortices with resonant particles

DEFF Research Database (Denmark)

Jovanovic, D.; Pécseli, Hans; Juul Rasmussen, J.

1990-01-01

Kinetic effects associated with the electron motion along magnetic field lines in low‐beta plasmas are studied. Using the gyrokinetic description of electrons, a kinetic analog of the reduced magnetohydrodynamic equations is derived, and it is shown that in the strongly nonlinear regime...... particles. The evolution equations indicate the possibility of excitation of plasma vortices by electron beams....... they possess localized solutions in the form of dipolar vortices, which can efficiently interact with resonant electrons. In the adiabatic limit, evolution equations are derived for the vortex parameters, describing exchange of the energy, enstrophy, and of the Poynting vector between the vortex and resonant...

Agradient velocity, vortical motion and gravity waves in a rotating shallow-water model

Science.gov (United States)

Sutyrin Georgi, G.

2004-07-01

A new approach to modelling slow vortical motion and fast inertia-gravity waves is suggested within the rotating shallow-water primitive equations with arbitrary topography. The velocity is exactly expressed as a sum of the gradient wind, described by the Bernoulli function,B, and the remaining agradient part, proportional to the velocity tendency. Then the equation for inverse potential vorticity,Q, as well as momentum equations for agradient velocity include the same source of intrinsic flow evolution expressed as a single term J (B, Q), where J is the Jacobian operator (for any steady state J (B, Q) = 0). Two components of agradient velocity are responsible for the fast inertia-gravity wave propagation similar to the traditionally used divergence and ageostrophic vorticity. This approach allows for the construction of balance relations for vortical dynamics and potential vorticity inversion schemes even for moderate Rossby and Froude numbers assuming the characteristic value of |J(B, Q)| = to be small. The components of agradient velocity are used as the fast variables slaved to potential vorticity that allows for diagnostic estimates of the velocity tendency, the direct potential vorticity inversion with the accuracy of 2 and the corresponding potential vorticity-conserving agradient velocity balance model (AVBM). The ultimate limitations of constructing the balance are revealed in the form of the ellipticity condition for balanced tendency of the Bernoulli function which incorporates both known criteria of the formal stability: the gradient wind modified by the characteristic vortical Rossby wave phase speed should be subcritical. The accuracy of the AVBM is illustrated by considering the linear normal modes and coastal Kelvin waves in the f-plane channel with topography.

Generation of the vorticity mode by sound in a Bingham plastic

Science.gov (United States)

Perelomova, Anna; Wojda, Pawel

2011-10-01

This study investigates interaction between acoustic and non-acoustic modes, such as vorticity mode, in some class of a non-newtonian fluid called Bingham plastic. The instantaneous equations describing interaction between different modes are derived. The attention is paid to the nonlinear effects in the field of intense sound. The resulting equations which describe dynamics of both sound and the vorticity mode apply to both periodic and aperiodic sound of any waveform. They use only instantaneous quantities and do not imply averaging over the sound period. The theory is illustrated by an example of acoustic force of vorticity induced in the field of a Gaussian sound beam. Some unusual peculiarities in both sound and the vorticity induced in its field as compared to a newtonian fluid, are discovered.

Streaming vorticity flux from oscillating walls with finite amplitude

Science.gov (United States)

Wu, J. Z.; Wu, X. H.; Wu, J. M.

1993-01-01

How to describe vorticity creation from a moving wall is a long standing problem. This paper discusses relevant issues at the fundamental level. First, it is shown that the concept of 'vorticity flux due to wall acceleration' can be best understood by following fluid particles on the wall rather than observing the flow at fixed spatial points. This is of crucial importance when the time-averaged flux is to be considered. The averaged flux has to be estimated in a wall-fixed frame of reference (in which there is no flux due to wall acceleration at all); or, if an inertial frame of reference is used, the generalized Lagrangian mean (GLM) also gives the same result. Then, for some simple but typical configurations, the time-averaged vorticity flux from a harmonically oscillating wall with finite amplitude is analyzed, without appealing to small perturbation. The main conclusion is that the wall oscillation will produce an additional mean vorticity flux (a fully nonlinear streaming effect), which is partially responsible for the mechanism of vortex flow control by waves. The results provide qualitative explanation for some experimentally and/or computationally observed phenomena.

Direct observation of rectified motion of vortices by Lorentz microscopy

Indian Academy of Sciences (India)

We have investigated the vortex dynamics for the `ratchet' operation in a niobium superconductor via a direct imaging of Lorentz microscopy. We directly observe one-directional selective motion of field-gradient-driven vortices along fabricated channels. This results from the rectification of vortices in a spatially asymmetric ...

Propagation and diffraction of optical vortices

International Nuclear Information System (INIS)

Fischer, Pascal; Skelton, Susan E.; Leburn, Christopher G.; Streuber, Casey T.; Wright, Ewan M.; Dholakia, Kishan

2008-01-01

We explore the propagation and diffraction of optical vortices (Laguerre-Gaussian beams) of varying azimuthal index past a circular obstacle and Young's double slits. When the beam and obstacle centers are aligned the famous spot of Arago, which arises for zero azimuthal index, is replaced for non-zero azimuthal indices by a dark spot of Arago, a simple consequence of the conserved phase singularity at the beam center. We explore how for larger azimuthal indices, as the beam and obstacle centers are progressively misaligned, the central dark spot breaks up into several dark spots of Arago. Using Young's double slits we can easily measure the azimuthal index of the vortex beam, even for polychromatic vortices generated by broadband supercontinuum radiation

On the evolution of vortices in massive protoplanetary discs

Science.gov (United States)

Pierens, Arnaud; Lin, Min-Kai

2018-05-01

It is expected that a pressure bump can be formed at the inner edge of a dead-zone, and where vortices can develop through the Rossby Wave Instability (RWI). It has been suggested that self-gravity can significantly affect the evolution of such vortices. We present the results of 2D hydrodynamical simulations of the evolution of vortices forming at a pressure bump in self-gravitating discs with Toomre parameter in the range 4 - 30. We consider isothermal plus non-isothermal disc models that employ either the classical β prescription or a more realistic treatment for cooling. The main aim is to investigate whether the condensating effect of self-gravity can stabilize vortices in sufficiently massive discs. We confirm that in isothermal disc models with Q ≳ 15, vortex decay occurs due to the vortex self-gravitational torque. For discs with 3≲ Q ≲ 7, the vortex develops gravitational instabilities within its core and undergoes gravitational collapse, whereas more massive discs give rise to the formation of global eccentric modes. In non-isothermal discs with β cooling, the vortex maintains a turbulent core prior to undergoing gravitational collapse for β ≲ 0.1, whereas it decays if β ≥ 1. In models that incorpore both self-gravity and a better treatment for cooling, however, a stable vortex is formed with aspect ratio χ ˜ 3 - 4. Our results indicate that self-gravity significantly impacts the evolution of vortices forming in protoplanetary discs, although the thermodynamical structure of the vortex is equally important for determining its long-term dynamics.

Vorticity and particle polarization in heavy ion collisions (experimental perspective

Directory of Open Access Journals (Sweden)

Voloshin Sergei A.

2018-01-01

Full Text Available The recent measurements of the global polarization and vector meson spin alignment along the system orbital momentum in heavy ion collisions are briefly reviewed. A possible connection between the global polarization and the chiral anomalous effects is discussed along with possible experimental checks. Future directions, in particular those aimed on the detailed mapping of the vorticity fields, are outlined. The Blast Wave model is used for an estimate of the anisotropic flow effect on the vorticity component along the beam direction. We also point to a possibility of a circular pattern in the vorticity field in asymmetric, e.g. Cu+Au, central collisions.

The generation of two-dimensional vortices by transverse oscillation of a soap film

International Nuclear Information System (INIS)

Afenchenko, V.O.; Ezersky, A.B.; Kiyashko, S.V.; Rabinovich, M.I.; Weidman, P.D.

1998-01-01

An experimental investigation of the dynamics of horizontal soap films stretched over circular or square boundaries undergoing periodic transverse oscillations at frequencies in the range 20 - 200 Hz is reported. Concomitant with modes of transverse flexural oscillations, it was observed that two-dimensional vortices in the plane of the film are excited. The vortices may be either (i) large, scaling with the size of the cavity or (ii) small, localized at a wavelength or half-wavelength of the membrane modes. In the experiments a stable generation of one, two, hor-ellipsis, ten pairs of counter-rotating vortices were observed in finite regions of amplitude-frequency parameter space. The circulation strength of vortices in a given vortex pattern increases with increasing external forcing and with decreasing soap film thickness. A theoretical model based on the wave-boundary interaction of excited Marangoni waves reveals a vorticity generation mechanism active in vibrating soap films. This model shows that vorticity is generated throughout the entire liquid volume by viscous diffusion, and qualitatively reproduces many steady vortex patterns observed in the experiment. However, the model cannot explain the existence of the sometimes intense vortices observed far from the film boundary that do not appear to be generated by diffusive processes. copyright 1998 American Institute of Physics

Indirect Combustion Noise: Noise Generation by Accelerated Vorticity in a Nozzle Flow

Directory of Open Access Journals (Sweden)

Nancy Kings

2010-09-01

Full Text Available The noise generation by accelerated vorticity waves in a nozzle flow was investigated in a model experiment. This noise generation mechanism belongs, besides entropy noise, to the indirect combustion noise phenomena. Vorticity as well as entropy fluctuations, originating from the highly turbulent combustion zone, are convected with the flow and produce noise during their acceleration in the outlet nozzle of the combustion chamber. In the model experiment, noise generation of accelerated vorticity fluctuations was achieved. The vorticity fluctuations in the tube flow were produced by injecting temporally additional air into the mean flow. As the next step, a parametric study was conducted to determine the major dependencies of the so called vortex noise. A quadratic dependency of the vortex noise on the injected air amount was found. In order to visualise and classify the artificially generated vorticity structures, planar velocity measurements have been conducted applying Particle Image Velocimetry (PIV.

Effect of tip vortices on membrane vibration of flexible wings with different aspect ratios

Directory of Open Access Journals (Sweden)

Genç Mustafa Serdar

2016-01-01

Full Text Available In this study, the effect of the aspect ratio on the aerodynamics characteristic of flexible membrane wings with different aspect ratios (AR = 1 and AR = 3 is experimentally investigated at Reynolds number of 25000. Time accurate measurements of membrane deformation using Digital Image Correlation system (DIC is carried out while normal forces of the wing will be measured by helping a load-cell system and flow on the wing was visualized by means of smoke wire technic. The characteristics of high aspect ratio wings are shown to be affected by leading edge separation bubbles at low Reynolds number. It is concluded that the camber of membrane wing excites the separated shear layer and this situation increases the lift coefficient relatively more as compared to rigid wings. In membrane wings with low aspect ratio, unsteadiness included tip vortices and vortex shedding, and the combination of tip vortices and vortex shedding causes complex unsteady deformations of these membrane wings. The characteristic of high aspect ratio wings was shown to be affected by leading edge separation bubbles at low Reynolds numbers whereas the deformations of flexible wing with low aspect ratio affected by tip vortices and leading edge separation bubbles.

Pair interactions of heavy vortices in quantum fluids

Science.gov (United States)

Pshenichnyuk, Ivan A.

2018-02-01

The dynamics of quantum vortex pairs carrying heavy doping matter trapped inside their cores is studied. The nonlinear classical matter field formalism is used to build a universal mathematical model of a heavy vortex applicable to different types of quantum mixtures. It is shown how the usual vortex dynamics typical for undoped pairs qualitatively changes when heavy dopants are used: heavy vortices with opposite topological charges (chiralities) attract each other, while vortices with the same charge are repelled. The force responsible for such behavior appears as a result of superposition of vortices velocity fields in the presence of doping substance and can be considered as a special realization of the Magnus effect. The force is evaluated quantitatively and its inverse proportionality to the distance is demonstrated. The mechanism described in this paper gives an example of how a light nonlinear classical field may realize repulsive and attractive interactions between embedded heavy impurities.

Decay of MHD-scale Kelvin-Helmholtz vortices mediated by parasitic electron dynamics

International Nuclear Information System (INIS)

Nakamura, T.K.M.; Hayashi, D.; Fujimoto, M.; Shinohara, I.

2004-01-01

We have simulated nonlinear development of MHD-scale Kelvin-Helmholtz (KH) vortices by a two-dimensional two-fluid system including finite electron inertial effects. In the presence of moderate density jump across a shear layer, in striking contrast to MHD results, MHD KH vortices are found to decay by the time one eddy turnover is completed. The decay is mediated by smaller vortices that appear within the parent vortex and stays effective even when the shear layer width is made larger. It is shown that the smaller vortices are basically of MHD nature while the seeding for these is achieved by the electron inertial effect. Application of the results to the magnetotail boundary layer is discussed

Emergence of acoustic waves from vorticity fluctuations: impact of non-normality.

Science.gov (United States)

George, Joseph; Sujith, R I

2009-10-01

Chagelishvili et al. [Phys. Rev. Lett. 79, 3178 (1997)] discovered a linear mechanism of acoustic wave emergence from vorticity fluctuations in shear flows. This paper illustrates how this "nonresonant" phenomenon is related to the non-normality of the operator governing the linear dynamics of disturbances in shear flows. The non-self-adjoint nature of the governing operator causes the emergent acoustic wave to interact strongly with the vorticity disturbance. Analytical expressions are obtained for the nondivergent vorticity perturbation. A discontinuity in the x component of the velocity field corresponding to the vorticity disturbance was originally identified to be the cause of acoustic wave emergence. However, a different mechanism is proposed in this paper. The correct "acoustic source" is identified and the reason for the abrupt nature of wave emergence is explained. The impact of viscous damping is also discussed.

Analysis of vorticity dynamics for hump characteristics of a pump turbine model

Energy Technology Data Exchange (ETDEWEB)

Li, Deyou; Gong, Ruzhi; Wang, Hongjie; Han, Lei; Wei, Xianzhu; Qin, Daqing [School of Energy Science and Engineering, Harbin Institute of Technology, Harbin (China)

2016-08-15

Conventional parameters based on CFD methodology for the investigation on hump characteristics of a pump turbine cannot reflect the dynamic interaction mechanism between the runner and the fluid. This research presents a dynamic interaction mechanism of a pump turbine operating in the hump region. First, vorticity dynamic parameters were obtained based on the theory of vorticity dynamics. Second, 3-D unsteady flow simulations were performed in a full pump turbine model using the SST k-ω turbulence model, and numerical results have a good agreement with the experiments. Then, analysis was carried out to determine the relation between the vorticity dynamic parameters and hump characteristics. The results indicate that the theory of vorticity dynamics has an advantage in evaluating the dynamic performance of a pump turbine. The energy transfer between the runner and the fluid is through vorticity dynamic parameters-pressure and friction terms, in which the pressure term accounts for the most. Furthermore, vortex generation mainly results from the skin friction. Combining vorticity dynamic analysis with the method of Q-criterion indicates that hump characteristics are related to the reduction of the surface normal pressure work and vortex motion on the suction surfaces close to the leading edges in the runner, and the increase of skin friction work in the stay-guide vanes.

Percolating cluster of center vortices and confinement

International Nuclear Information System (INIS)

Gliozzi, Ferdinando; Panero, Marco; Provero, Paolo

2003-01-01

We study the role of percolating clusters of center vortices in configurations of an Ising gauge theory in 3D. It is known that low energy features of gauge theories can be described in terms of an 'effective string picture', and that confinement properties are associated with topologically non-trivial configurations. We focus our attention upon percolating clusters of center vortices, and present numerical evidence for the fact that these objects play a preminent role in confinement phenomenon, since their removal sweeps off confinement altogether. Moreover, numerical simulations show that the string fluctuations, and in particular the Mischer term, are completely encoded in the percolating cluster

A numerical study of the stabilitiy of helical vortices using vortex methods

International Nuclear Information System (INIS)

Walther, J H; Guenot, M; Machefaux, E; Rasmussen, J T; Chatelain, P; Okulov, V L; Soerensen, J N; Bergdorf, M; Koumoutsakos, P

2007-01-01

We present large-scale parallel direct numerical simulations using particle vortex methods of the instability of the helical vortices. We study the instability of a single helical vortex and find good agreement with inviscid theory. We outline equilibrium configurations for three double helical vortices-similar to those produced by three blade wind turbines. The simulations confirm the stability of the inviscid model, but predict a breakdown of the vortical system due to viscosity

A numerical study of the stabilitiy of helical vortices using vortex methods

Energy Technology Data Exchange (ETDEWEB)

Walther, J H [Department of Mechanical Engineering, Technical University of Denmark, DK-2800 Lyngby (Denmark); Guenot, M [Enginering College in Industrial Systems, FR-17041, La Rochelle (France); Machefaux, E [Enginering College in Industrial Systems, FR-17041, La Rochelle (France); Rasmussen, J T [Department of Mechanical Engineering, Technical University of Denmark, DK-2800 Lyngby (Denmark); Chatelain, P [Computational Laboratory, ETH Zurich, CH-8092 Zurich (Switzerland); Okulov, V L [Department of Mechanical Engineering, Technical University of Denmark, DK-2800 Lyngby (Denmark); Soerensen, J N [Department of Mechanical Engineering, Technical University of Denmark, DK-2800 Lyngby (Denmark); Bergdorf, M [Computational Laboratory, ETH Zurich, CH-8092 Zurich (Switzerland); Koumoutsakos, P [Computational Laboratory, ETH Zurich, CH-8092 Zurich (Switzerland)

2007-07-15

We present large-scale parallel direct numerical simulations using particle vortex methods of the instability of the helical vortices. We study the instability of a single helical vortex and find good agreement with inviscid theory. We outline equilibrium configurations for three double helical vortices-similar to those produced by three blade wind turbines. The simulations confirm the stability of the inviscid model, but predict a breakdown of the vortical system due to viscosity.

Motions of quantized vortices attached to a boundary in alternating currents of superfluid 4He

International Nuclear Information System (INIS)

Yano, H.; Hashimoto, N.; Handa, A.; Obara, K.; Ishikawa, O.; Hata, T.; Nakagawa, M.

2007-01-01

The motions of superfluid vortices attached to a boundary are investigated in alternating currents by using a vibrating wire. The attached vortices appear to form a layer on the wire and enhance the mass of the wire, even for low velocity currents. In turbulence, chaotic motions of vortices such as entanglement and reconnection reduce the thickness of the layer in spite of the fact that the vortices unstably expand. When turbulence subsides, the attached vortices appear to shrink, with the degree of shrinking influenced by thermal excitations in the superfluid

Nonlinear Dynamics of Vortices in Different Types of Grain Boundaries

Science.gov (United States)

Sheikhzada, Ahmad K.

As a major component of linear particle accelerators, superconducting radio-frequency (SRF) resonator cavities are required to operate with lowest energy dissipation and highest accelerating gradient. SRF cavities are made of polycrystalline materials in which grain boundaries can limit maximum RF currents and produce additional power dissipation sources due to local penetration of Josephson vortices. The essential physics of vortex penetration and mechanisms of dissipation of vortices driven by strong RF currents along networks of grain boundaries and their contribution to the residual surface resistance have not been well understood. To evaluate how GBs can limit the performance of SRF materials, particularly Nb and Nb3Sn, we performed extensive numerical simulations of nonlinear dynamics of Josephson vortices in grain boundaries under strong dc and RF fields. The RF power due to penetration of vortices both in weakly-coupled and strongly-coupled grain boundaries was calculated as functions of the RF field and frequency. The result of this calculation manifested a quadratic dependence of power to field amplitude at strong RF currents, an illustration of resistive behavior of grain boundaries. Our calculations also showed that the surface resistance is a complicated function of field controlled by penetration and annihilation of vortices and antivortices in strong RF fields which ultimately saturates to normal resistivity of grain boundary. We found that Cherenkov radiation of rapidly moving vortices in grain boundaries can produce a new instability causing generation of expanding vortex-antivortex pair which ultimately drives the entire GB in a resistive state. This effect is more pronounced in polycrystalline thin film and multilayer coating structures in which it can cause significant increase in power dissipation and results in hysteresis effects in I-V characteristics, particularly at low temperatures.

Nonlinear Dynamics of Vortices in Different Types of Grain Boundaries

Energy Technology Data Exchange (ETDEWEB)

Sheikhzada, Ahmad [Old Dominion Univ., Norfolk, VA (United States)

2017-05-01

As a major component of linear particle accelerators, superconducting radio-frequency (SRF) resonator cavities are required to operate with lowest energy dissipation and highest accelerating gradient. SRF cavities are made of polycrystalline materials in which grain boundaries can limit maximum RF currents and produce additional power dissipation sources due to local penetration of Josephson vortices. The essential physics of vortex penetration and mechanisms of dissipation of vortices driven by strong RF currents along networks of grain boundaries and their contribution to the residual surface resistance have not been well understood. To evaluate how GBs can limit the performance of SRF materials, particularly Nb and Nb3Sn, we performed extensive numerical simulations of nonlinear dynamics of Josephson vortices in grain boundaries under strong dc and RF fields. The RF power due to penetration of vortices both in weakly-coupled and strongly-coupled grain boundaries was calculated as functions of the RF field and frequency. The result of this calculation manifested a quadratic dependence of power to field amplitude at strong RF currents, an illustration of resistive behavior of grain boundaries. Our calculations also showed that the surface resistance is a complicated function of field controlled by penetration and annihilation of vortices and antivortices in strong RF fields which ultimately saturates to normal resistivity of grain boundary. We found that Cherenkov radiation of rapidly moving vortices in grain boundaries can produce a new instability causing generation of expanding vortex-antivortex pair which ultimately drives the entire GB in a resistive state. This effect is more pronounced in polycrystalline thin film and multilayer coating structures in which it can cause significant increase in power dissipation and results in hysteresis effects in I-V characteristics, particularly at low temperatures.

Acoustic Virtual Vortices with Tunable Orbital Angular Momentum for Trapping of Mie Particles

Science.gov (United States)

Marzo, Asier; Caleap, Mihai; Drinkwater, Bruce W.

2018-01-01

Acoustic vortices can transfer angular momentum and trap particles. Here, we show that particles trapped in airborne acoustic vortices orbit at high speeds, leading to dynamic instability and ejection. We demonstrate stable trapping inside acoustic vortices by generating sequences of short-pulsed vortices of equal helicity but opposite chirality. This produces a "virtual vortex" with an orbital angular momentum that can be tuned independently of the trapping force. We use this method to adjust the rotational speed of particles inside a vortex beam and, for the first time, create three-dimensional acoustics traps for particles of wavelength order (i.e., Mie particles).

Coherent Vortices in Strongly Coupled Liquids

International Nuclear Information System (INIS)

Ashwin, J.; Ganesh, R.

2011-01-01

Strongly coupled liquids are ubiquitous in both nature and laboratory plasma experiments. They are unique in the sense that their average potential energy per particle dominates over the average kinetic energy. Using ''first principles'' molecular dynamics (MD) simulations, we report for the first time the emergence of isolated coherent tripolar vortices from the evolution of axisymmetric flows in a prototype two-dimensional (2D) strongly coupled liquid, namely, the Yukawa liquid. Linear growth rates directly obtained from MD simulations are compared with a generalized hydrodynamic model. Our MD simulations reveal that the tripolar vortices persist over several turn over times and hence may be observed in strongly coupled liquids such as complex plasma, liquid metals and astrophysical systems such as white dwarfs and giant planetary interiors, thereby making the phenomenon universal.

Coherent Vortices in Strongly Coupled Liquids

Science.gov (United States)

Ashwin, J.; Ganesh, R.

2011-04-01

Strongly coupled liquids are ubiquitous in both nature and laboratory plasma experiments. They are unique in the sense that their average potential energy per particle dominates over the average kinetic energy. Using “first principles” molecular dynamics (MD) simulations, we report for the first time the emergence of isolated coherent tripolar vortices from the evolution of axisymmetric flows in a prototype two-dimensional (2D) strongly coupled liquid, namely, the Yukawa liquid. Linear growth rates directly obtained from MD simulations are compared with a generalized hydrodynamic model. Our MD simulations reveal that the tripolar vortices persist over several turn over times and hence may be observed in strongly coupled liquids such as complex plasma, liquid metals and astrophysical systems such as white dwarfs and giant planetary interiors, thereby making the phenomenon universal.

Spatial-temporal and modal analysis of propeller induced ground vortices by particle image velocimetry

NARCIS (Netherlands)

Yang, Y.; Sciacchitano, A.; Veldhuis, L.L.M.; Eitelberg, G.

2016-01-01

During the ground operation of aircraft, there is potentially a system of vortices generated from the ground toward the propulsor, commonly denoted as ground vortices. Although extensive research has been conducted on ground vortices induced by turbofans which were simplified by suction tubes, these

Dynamics of fractional vortices in long Josephson junctions; Dynamik fraktionaler Flusswirbel in langen Josephsonkontakten

Energy Technology Data Exchange (ETDEWEB)

Gaber, Tobias

2007-07-01

In this thesis static and dynamic properties of fractional vortices in long Josephson junctions are investigated. Fractional vortices are circulating supercurrents similar to the well-known Josephson fluxons. Yet, they show the distinguishing property of carrying only a fraction of the magnetic flux quantum. Fractional vortices are interesting non-linear objects. They spontaneously appear and are pinned at the phase discontinuity points of so called 0-{kappa} junctions but can be bend or flipped by external forces like bias currents or magnetic fields. 0-{kappa} junctions and fractional vortices are generalizations of the well-known 0-{pi} junctions and semifluxons, where not only phase jumps of pi but arbitrary values denoted by kappa are considered. By using so-called artificial 0-{kappa} junctions that are based on standard Nb-AlO{sub x}-Nb technology the classical dynamics of fractional vortices has been investigated experimentally for the very first time. Here, half-integer zero field steps could be observed. These voltage steps on the junction's current-voltage characteristics correspond to the periodic flipping/hopping of fractional vortices. In addition, the oscillatory eigenmodes of fractional vortices were investigated. In contrast to fluxons fractional vortices have an oscillatory eigenmode with a frequency within the plasma gap. Using resonance spectroscopy the dependence of the eigenmode frequency on the flux carried by the vortex and an applied bias current was determined. (orig.)

Phase locking of moving magnetic vortices in bridge-coupled nanodisks

International Nuclear Information System (INIS)

Zhu, Qiyuan; Zheng, Qi; Liu, Xianyin; Liu, Qingfang; Wang, Jianbo

2015-01-01

In this paper, phase locking dynamics of vortices induced by spin transfer torque in bridge-coupled nanodisks are studied by micromagnetic simulations. In the presence of the bridge coupling, the required time for the phase locking is dramatically reduced, and the phase difference between the two vortices keeps at a nonzero value after the phase locking. Moreover, the phase difference is affected significantly by bridge coupling, Oersted field distribution, nanodisk size, as well as in-plane bias magnetic field. In addition, the coupled gyrotropic frequency of vortices depends linearly on the perpendicular magnetic field. This systematic study of phase locking parameters, especially the phase difference, is important for the applications of vortex-based spin-torque nano-oscillators

Phase locking of moving magnetic vortices in bridge-coupled nanodisks

Energy Technology Data Exchange (ETDEWEB)

Zhu, Qiyuan; Zheng, Qi; Liu, Xianyin; Liu, Qingfang, E-mail: liuqf@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Wang, Jianbo [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

2015-05-07

In this paper, phase locking dynamics of vortices induced by spin transfer torque in bridge-coupled nanodisks are studied by micromagnetic simulations. In the presence of the bridge coupling, the required time for the phase locking is dramatically reduced, and the phase difference between the two vortices keeps at a nonzero value after the phase locking. Moreover, the phase difference is affected significantly by bridge coupling, Oersted field distribution, nanodisk size, as well as in-plane bias magnetic field. In addition, the coupled gyrotropic frequency of vortices depends linearly on the perpendicular magnetic field. This systematic study of phase locking parameters, especially the phase difference, is important for the applications of vortex-based spin-torque nano-oscillators.

Propagation dynamics of off-axis symmetrical and asymmetrical vortices embedded in flat-topped beams

Science.gov (United States)

Zhang, Xu; Wang, Haiyan

2017-11-01

In this paper, propagation dynamics of off-axis symmetrical and asymmetrical optical vortices(OVs) embedded in flat-topped beams have been explored numerically based on rigorous scalar diffraction theory. The distribution properties of phase and intensity play an important role in driving the propagation dynamics of OVs. Numerical results show that the single off-axis vortex moves in a straight line. The displacement of the single off-axis vortex becomes smaller, when either the order of flatness N and the beam size ω0are increased or the off-axis displacement d is decreased. In addition, the phase singularities of high order vortex beams can be split after propagating a certain distance. It is also demonstrated that the movement of OVs are closely related with the spatial symmetrical or asymmetrical distribution of vortex singularities field. Multiple symmetrical and asymmetrical optical vortices(OVs) embedded in flat-topped beams can interact and rotate. The investment of the propagation dynamics of OVs may have many applications in optical micro-manipulation and optical tweezers.

Approach and separation of quantum vortices with balanced cores

Science.gov (United States)

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.

Viability in holder of irradiated cells: distinguish between repair and cell multiplication

International Nuclear Information System (INIS)

Araujo, A.C. de.

1980-01-01

In experiments in which liquid holding recovery (LHR) was measured, the majority of cellular population is formed by non-viable cells and cell multiplication may be important for LHR expression. In order to distinguish between recuperation of viability (true LHR) and cell multiplication, it was necessary to employ improved plating techniques and a fluctuation test based on Poisson distribution. Our results are an indication that this fluctuation test, used together with the traditional method, is a good tool to distinguish repair from cell multiplication. (author)

Fast Trailed Vorticity Modeling for Wind Turbine Aerodynamics and its Influence on Aeroelastic Stability

DEFF Research Database (Denmark)

Pirrung, Georg

In this work, an aerodynamic model for the use in aeroelastic wind turbine codes is presented. It consists of a simplified lifting line model covering the induction due to the trailed vorticity in the near wake, a 2D shed vorticity model and a far wake model using the well known blade element...... to earlier implementations, the model has been improved in several ways: Among other things, the need for model-specific user input has been removed, the effect of downwind convection of the trailed vorticity is modeled, the near wake induction is iterated to stabilize the computations and the numerical......-of-plane vibrations agrees much better with high fidelity models. Further, the trailed vorticity effects on the aerodynamic work are found to be of the same order of magnitude as the shed vorticity effects. The trailed vorticity effects are, however, mainly important close to the tip in the investigated cases, which...

Vorticity perturbations and isotropy of the cosmic microwave background

Energy Technology Data Exchange (ETDEWEB)

Anile, A M [Catania Univ. (Italy). Seminario di Matematica; Motta, S

1976-06-01

We investigate the effect of vorticity perturbations of an arbitrary Robertson-Walker universe on the isotropy of the cosmic microwave background. The predicted temperature variations are then compared with the upper limits recently found by Parijskij (1974). In this way we obtain an upper limit on the present vorticity on scales L approximately 10 Mpc which is only marginally consistent with the value suggested by de Vaucouleurs (1971), de Vaucouleurs and Peters (1968).

Pinning, flux diodes and ratchets for vortices interacting with conformal pinning arrays

International Nuclear Information System (INIS)

Olson Reichhardt, C. J.; Wang, Y. L.; Argonne National Laboratory; Xiao, Z. L.; Northern Illinois University, DeKalb, IL

2016-01-01

A conformal pinning array can be created by conformally transforming a uniform triangular pinning lattice to produce a new structure in which the six-fold ordering of the original lattice is conserved but where there is a spatial gradient in the density of pinning sites. Here we examine several aspects of vortices interacting with conformal pinning arrays and how they can be used to create a flux flow diode effect for driving vortices in different directions across the arrays. Under the application of an ac drive, a pronounced vortex ratchet effect occurs where the vortices flow in the easy direction of the array asymmetry. When the ac drive is applied perpendicular to the asymmetry direction of the array, it is possible to realize a transverse vortex ratchet effect where there is a generation of a dc flow of vortices perpendicular to the ac drive due to the creation of a noise correlation ratchet by the plastic motion of the vortices. We also examine vortex transport in experiments and compare the pinning effectiveness of conformal arrays to uniform triangular pinning arrays. In conclusion, we find that a triangular array generally pins the vortices more effectively at the first matching field and below, while the conformal array is more effective at higher fields where interstitial vortex flow occurs.

Multi-dimensional upwinding-based implicit LES for the vorticity transport equations

Science.gov (United States)

Foti, Daniel; Duraisamy, Karthik

2017-11-01

Complex turbulent flows such as rotorcraft and wind turbine wakes are characterized by the presence of strong coherent structures that can be compactly described by vorticity variables. The vorticity-velocity formulation of the incompressible Navier-Stokes equations is employed to increase numerical efficiency. Compared to the traditional velocity-pressure formulation, high order numerical methods and sub-grid scale models for the vorticity transport equation (VTE) have not been fully investigated. Consistent treatment of the convection and stretching terms also needs to be addressed. Our belief is that, by carefully designing sharp gradient-capturing numerical schemes, coherent structures can be more efficiently captured using the vorticity-velocity formulation. In this work, a multidimensional upwind approach for the VTE is developed using the generalized Riemann problem-based scheme devised by Parish et al. (Computers & Fluids, 2016). The algorithm obtains high resolution by augmenting the upwind fluxes with transverse and normal direction corrections. The approach is investigated with several canonical vortex-dominated flows including isolated and interacting vortices and turbulent flows. The capability of the technique to represent sub-grid scale effects is also assessed. Navy contract titled ``Turbulence Modelling Across Disparate Length Scales for Naval Computational Fluid Dynamics Applications,'' through Continuum Dynamics, Inc.

Simulation of Venus polar vortices with the non-hydrostatic general circulation model

Science.gov (United States)

Rodin, Alexander V.; Mingalev, Oleg; Orlov, Konstantin

2012-07-01

The dynamics of Venus atmosphere in the polar regions presents a challenge for general circulation models. Numerous images and hyperspectral data from Venus Express mission shows that above 60 degrees latitude atmospheric motion is substantially different from that of the tropical and extratropical atmosphere. In particular, extended polar hoods composed presumably of fine haze particles, as well as polar vortices revealing mesoscale wave perturbations with variable zonal wavenumbers, imply the significance of vertical motion in these circulation elements. On these scales, however, hydrostatic balance commonly used in the general circulation models is no longer valid, and vertical forces have to be taken into account to obtain correct wind field. We present the first non-hydrostatic general circulation model of the Venus atmosphere based on the full set of gas dynamics equations. The model uses uniform grid with the resolution of 1.2 degrees in horizontal and 200 m in the vertical direction. Thermal forcing is simulated by means of relaxation approximation with specified thermal profile and time scale. The model takes advantage of hybrid calculations on graphical processors using CUDA technology in order to increase performance. Simulations show that vorticity is concentrated at high latitudes within planetary scale, off-axis vortices, precessing with a period of 30 to 40 days. The scale and position of these vortices coincides with polar hoods observed in the UV images. The regions characterized with high vorticity are surrounded by series of small vortices which may be caused by shear instability of the zonal flow. Vertical velocity component implies that in the central part of high vorticity areas atmospheric flow is downwelling and perturbed by mesoscale waves with zonal wavenumbers 1-4, resembling observed wave structures in the polar vortices. Simulations also show the existence of areas with strong vertical flow, concentrated in spiral branches extending

Extreme-Ultraviolet Vortices from a Free-Electron Laser

Directory of Open Access Journals (Sweden)

Primož Rebernik Ribič

2017-08-01

Full Text Available Extreme-ultraviolet vortices may be exploited to steer the magnetic properties of nanoparticles, increase the resolution in microscopy, and gain insight into local symmetry and chirality of a material; they might even be used to increase the bandwidth in long-distance space communications. However, in contrast to the generation of vortex beams in the infrared and visible spectral regions, production of intense, extreme-ultraviolet and x-ray optical vortices still remains a challenge. Here, we present an in-situ and an ex-situ technique for generating intense, femtosecond, coherent optical vortices at a free-electron laser in the extreme ultraviolet. The first method takes advantage of nonlinear harmonic generation in a helical undulator, producing vortex beams at the second harmonic without the need for additional optical elements, while the latter one relies on the use of a spiral zone plate to generate a focused, micron-size optical vortex with a peak intensity approaching 10^{14}  W/cm^{2}, paving the way to nonlinear optical experiments with vortex beams at short wavelengths.

Development of Pre-set Counter-rotating Streamwise Vortices in Wavy Channel

KAUST Repository

Budiman, A.C.

2015-10-23

Development of counter-rotating streamwise vortices in a rectangular channel with one-sided wavy surface has been experimentally quantified using hot-wire anemometry. The wavy surface has fixed amplitude of 3.75 mm. The counter-rotating vortices are pre-set by means of a sawtooth pattern cut at the leading edge of the wavy surface. Variations of the central streamwise velocity Uc with a channel gap H = 35 mm and 50 mm (corresponding to a Reynolds number from 1600 to 4400) change the instability of the flow which can be distinguished from the velocity contours at a certain spanwise plane. The streamwise velocity contours and turbulence intensity for Reynolds number Re = 3100 and H = 35 mm show the disappearance of the mushroom-like vortices prior to turbulence near the second peak of the wavy surface, while for higher Re, this phenomenon occurs earlier. Under certain conditions, for example, for Re = 4400 and H = 50 mm, the splitting of the vortices can also be observed.

Development of Pre-set Counter-rotating Streamwise Vortices in Wavy Channel

KAUST Repository

Budiman, A.C.; Mitsudharmadi, Hatsari; Bouremel, Y.; Winoto, S.H.; Low, H.T.

2015-01-01

Development of counter-rotating streamwise vortices in a rectangular channel with one-sided wavy surface has been experimentally quantified using hot-wire anemometry. The wavy surface has fixed amplitude of 3.75 mm. The counter-rotating vortices are pre-set by means of a sawtooth pattern cut at the leading edge of the wavy surface. Variations of the central streamwise velocity Uc with a channel gap H = 35 mm and 50 mm (corresponding to a Reynolds number from 1600 to 4400) change the instability of the flow which can be distinguished from the velocity contours at a certain spanwise plane. The streamwise velocity contours and turbulence intensity for Reynolds number Re = 3100 and H = 35 mm show the disappearance of the mushroom-like vortices prior to turbulence near the second peak of the wavy surface, while for higher Re, this phenomenon occurs earlier. Under certain conditions, for example, for Re = 4400 and H = 50 mm, the splitting of the vortices can also be observed.

Characterization of counter-rotating streamwise vortices in flat rectangular channel with one-sided wavy wall

KAUST Repository

Bouremel, Yann

2016-11-01

Particle Image Velocimetry (PIV) has been used to characterize the evolution of counter-rotating streamwise vortices in a rectangular channel with one sided wavy surface. The vortices were created by a uniform set of saw-tooth carved over the leading edge of a flat plate at the entrance of a flat rectangular channel with one-sided wavy wall. PIV measurements were taken over the spanwise and streamwise planes at different locations and at Reynolds number of 2500. Two other Reynolds numbers of 2885 and 3333 have also been considered for quantification purpose. Pairs of counter-rotating streamwise vortices have been shown experimentally to be centred along the spanwise direction at the saw-tooth valley where the vorticity ωz=0ωz=0. It has also been found that the vorticity ωzωz of the pairs of counter-rotating vortices decreases along the streamwise direction, and increases with the Reynolds number. Moreover, different quantifications of such counter-rotating vortices have been discussed such as their size, boundary layer, velocity profile and vorticity. The current study shows that the mixing due to the wall shear stress of counter-rotating streamwise vortices as well as their averaged viscous dissipation rate of kinetic energy decrease over flat and adverse pressure gradient surfaces while increasing over favourable pressure gradient surfaces. Finally, it was also demonstrated that the main direction of stretching is orientated at around 45° with the main flow direction.

Characterization of counter-rotating streamwise vortices in flat rectangular channel with one-sided wavy wall

KAUST Repository

Bouremel, Yann; Mitsudharmadi, Hatsari; Budiman, Alexander C.; Winoto, Sonny H.

2016-01-01

Particle Image Velocimetry (PIV) has been used to characterize the evolution of counter-rotating streamwise vortices in a rectangular channel with one sided wavy surface. The vortices were created by a uniform set of saw-tooth carved over the leading edge of a flat plate at the entrance of a flat rectangular channel with one-sided wavy wall. PIV measurements were taken over the spanwise and streamwise planes at different locations and at Reynolds number of 2500. Two other Reynolds numbers of 2885 and 3333 have also been considered for quantification purpose. Pairs of counter-rotating streamwise vortices have been shown experimentally to be centred along the spanwise direction at the saw-tooth valley where the vorticity ωz=0ωz=0. It has also been found that the vorticity ωzωz of the pairs of counter-rotating vortices decreases along the streamwise direction, and increases with the Reynolds number. Moreover, different quantifications of such counter-rotating vortices have been discussed such as their size, boundary layer, velocity profile and vorticity. The current study shows that the mixing due to the wall shear stress of counter-rotating streamwise vortices as well as their averaged viscous dissipation rate of kinetic energy decrease over flat and adverse pressure gradient surfaces while increasing over favourable pressure gradient surfaces. Finally, it was also demonstrated that the main direction of stretching is orientated at around 45° with the main flow direction.

The role of vortices in animal locomotion in fluids

Directory of Open Access Journals (Sweden)

Dvořák R.

2014-12-01

Full Text Available The aim of this paper is to show the significance of vortices in animal locomotion in fluids on two deliberately chosen examples. The first example concerns lift generation by bird and insect wings, the second example briefly mentiones swimming and walking on water. In all the examples, the vortices generated by the moving animal impart the necessary momentum to the surrounding fluid, the reaction to which is the force moving or lifting the animal.

Intrinsic electromagnetic solitary vortices in magnetized plasma

International Nuclear Information System (INIS)

Liu, J.; Horton, W.

1986-01-01

Several Rossby type vortex solutions constructed for electromagnetic perturbations in magnetized plasma encounter the difficulty that the perturbed magnetic field and the parallel current are not continuous on the boundary between two regions. We find that fourth order differential equations must be solved to remove this discontinuity. Special solutions for two types of boundary value problems for the fourth order partial differential equations are presented. By applying these solutions to different nonlinear equations in magnetized plasma, the intrinsic electromagnetic solitary drift-Alfven vortex (along with solitary Alfven vortex) and the intrinsic electromagnetic solitary electron vortex (along with short-wavelength drift vortex) are constructed. While still keeping a localized dipole structure, these new vortices have more complicated radial structures in the inner and outer regions than the usual Rossby wave vortex. The new type of vortices guarantees the continuity of the perturbed magnetic field deltaB/sub perpendicular/ and the parallel current j/sub parallel/ on the boundary between inner and outer regions of the vortex. The allowed regions of propagation speeds for these vortices are analyzed, and we find that the complementary relation between the vortex propagating speeds and the corresponding phase velocities of the linear modes no longer exists

How to distinguish between the annihilation and the creation of optical vortices

CSIR Research Space (South Africa)

Roux, FS

2013-10-01

Full Text Available , the term ‘optical vortex.’ The handedness of the phase circulation around the phase singularities allows optical vortices to be sep- arated into either positive or negative vortices. The sign is associated with the topological charge of the optical vortices... through a turbulent atmosphere. If the resulting scintillation is weak, the distortion can be represented by a single random phase modulation, which can be corrected in an adaptive optics system. On the other hand, if the scintillation is strong, the phase...

Physical modeling of vortical cross-step flow in the American paddlefish, Polyodon spathula

Science.gov (United States)

Brooks, Hannah; Haines, Grant E.; Lin, M. Carly

2018-01-01

Vortical cross-step filtration in suspension-feeding fish has been reported recently as a novel mechanism, distinct from other biological and industrial filtration processes. Although crossflow passing over backward-facing steps generates vortices that can suspend, concentrate, and transport particles, the morphological factors affecting this vortical flow have not been identified previously. In our 3D-printed models of the oral cavity for ram suspension-feeding fish, the angle of the backward-facing step with respect to the model’s dorsal midline affected vortex parameters significantly, including rotational, tangential, and axial speed. These vortices were comparable to those quantified downstream of the backward-facing steps that were formed by the branchial arches of preserved American paddlefish in a recirculating flow tank. Our data indicate that vortices in cross-step filtration have the characteristics of forced vortices, as the flow of water inside the oral cavity provides the external torque required to sustain forced vortices. Additionally, we quantified a new variable for ram suspension feeding termed the fluid exit ratio. This is defined as the ratio of the total open pore area for water leaving the oral cavity via spaces between branchial arches that are not blocked by gill rakers, divided by the total area for water entering through the gape during ram suspension feeding. Our experiments demonstrated that the fluid exit ratio in preserved paddlefish was a significant predictor of the flow speeds that were quantified anterior of the rostrum, at the gape, directly dorsal of the first ceratobranchial, and in the forced vortex generated by the first ceratobranchial. Physical modeling of vortical cross-step filtration offers future opportunities to explore the complex interactions between structural features of the oral cavity, vortex parameters, motile particle behavior, and particle morphology that determine the suspension, concentration, and

Quantitative flow analysis of swimming dynamics with coherent Lagrangian vortices.

Science.gov (United States)

Huhn, F; van Rees, W M; Gazzola, M; Rossinelli, D; Haller, G; Koumoutsakos, P

2015-08-01

Undulatory swimmers flex their bodies to displace water, and in turn, the flow feeds back into the dynamics of the swimmer. At moderate Reynolds number, the resulting flow structures are characterized by unsteady separation and alternating vortices in the wake. We use the flow field from simulations of a two-dimensional, incompressible viscous flow of an undulatory, self-propelled swimmer and detect the coherent Lagrangian vortices in the wake to dissect the driving momentum transfer mechanisms. The detected material vortex boundary encloses a Lagrangian control volume that serves to track back the vortex fluid and record its circulation and momentum history. We consider two swimming modes: the C-start escape and steady anguilliform swimming. The backward advection of the coherent Lagrangian vortices elucidates the geometry of the vorticity field and allows for monitoring the gain and decay of circulation and momentum transfer in the flow field. For steady swimming, momentum oscillations of the fish can largely be attributed to the momentum exchange with the vortex fluid. For the C-start, an additionally defined jet fluid region turns out to balance the high momentum change of the fish during the rapid start.

Quantum Hall effect with small numbers of vortices in Bose-Einstein condensates

Science.gov (United States)

Byrnes, Tim; Dowling, Jonathan P.

2015-08-01

When vortices are displaced in Bose-Einstein condensates (BECs), the Magnus force gives the system a momentum transverse in the direction to the displacement. We show that BECs in long channels with vortices exhibit a quantization of the current response with respect to the spatial vortex distribution. The quantization originates from the well-known topological property of the phase around a vortex; it is an integer multiple of 2 π . In a way similar to that of the integer quantum Hall effect, the current along the channel is related to this topological phase and can be extracted from two experimentally measurable quantities: the total momentum of the BEC and the spatial distribution. The quantization is in units of m /2 h , where m is the mass of the atoms and h is Planck's constant. We derive an exact vortex momentum-displacement relation for BECs in long channels under general circumstances. Our results present the possibility that the configuration described here can be used as a novel way of measuring the mass of the atoms in the BEC using a topological invariant of the system. If an accurate determination of the plateaus are experimentally possible, this gives the possibility of a topological quantum mass standard and precise determination of the fine structure constant.

Layer-Mean Quantities, Local Conservation Laws, and Vorticity

International Nuclear Information System (INIS)

Camassa, R.; Levermore, C.D.

1997-01-01

We derive local conservation laws for layer-mean quantities in two general settings. When applied to Euler flows, the first of these settings yields well-known local conservation laws for quantities averaged between material surfaces. The second, however, leads to new local conservation laws for quantities involving the vorticity that are averaged between arbitrary surfaces. These produce the crucial vorticity conservation laws in shallow water models that admit nonhydrostatic and noncolumnar motion. Moreover, they seem to lie outside the Hamiltonian paradigm of fluid dynamics. The formalism generalizes to skew-symmetric matrix fields; applications to electromagnetism are suggested. copyright 1997 The American Physical Society

First measurements of electron vorticity in the foreshock and solar wind

International Nuclear Information System (INIS)

Gurgiolo, C.; Goldstein, M.L.; Vinas, A.F.; Fazakerley, A.N.

2010-01-01

We describe the methodology used to set up and compute spatial derivatives of the electron moments using data acquired by the Plasma Electron And Current Experiment (PEACE) from the four Cluster spacecraft. The results are used to investigate electron vorticity in the foreshock. We find that much of the measured vorticity, under nominal conditions, appears to be caused by changes in the flow direction of the return (either reflected or leakage from the magnetosheath) and strahl electron populations as they couple to changes in the magnetic field orientation. This in turn results in deflections in the total bulk velocity producing the measured vorticity. (orig.)

First measurements of electron vorticity in the foreshock and solar wind

Energy Technology Data Exchange (ETDEWEB)

Gurgiolo, C. [Bitterroot Basic Research, Hamilton, MT (United States); Goldstein, M.L.; Vinas, A.F. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Geospace Science Lab.; Fazakerley, A.N. [University College London (United Kingdom). Mullard Space Science Lab.

2010-07-01

We describe the methodology used to set up and compute spatial derivatives of the electron moments using data acquired by the Plasma Electron And Current Experiment (PEACE) from the four Cluster spacecraft. The results are used to investigate electron vorticity in the foreshock. We find that much of the measured vorticity, under nominal conditions, appears to be caused by changes in the flow direction of the return (either reflected or leakage from the magnetosheath) and strahl electron populations as they couple to changes in the magnetic field orientation. This in turn results in deflections in the total bulk velocity producing the measured vorticity. (orig.)

First measurements of electron vorticity in the foreshock and solar wind

Directory of Open Access Journals (Sweden)

C. Gurgiolo

2010-12-01

Full Text Available We describe the methodology used to set up and compute spatial derivatives of the electron moments using data acquired by the Plasma Electron And Current Experiment (PEACE from the four Cluster spacecraft. The results are used to investigate electron vorticity in the foreshock. We find that much of the measured vorticity, under nominal conditions, appears to be caused by changes in the flow direction of the return (either reflected or leakage from the magnetosheath and strahl electron populations as they couple to changes in the magnetic field orientation. This in turn results in deflections in the total bulk velocity producing the measured vorticity.

A (Dis)continuous finite element model for generalized 2D vorticity dynamics

NARCIS (Netherlands)

Bernsen, E.; Bokhove, Onno; van der Vegt, Jacobus J.W.

2005-01-01

A mixed continuous and discontinuous Galerkin finite element discretization is constructed for a generalized vorticity streamfunction formulation in two spatial dimensions. This formulation consists of a hyperbolic (potential) vorticity equation and a linear elliptic equation for a (transport)

Effect of electrical field on the quantized vortices in He II

International Nuclear Information System (INIS)

Natsik, V.D.

2007-01-01

Electrical polarization and interaction of quantized vortices with electrical field in superfluid Bose fluid are studied. Two types of the vortices polarization are considered; both of them are caused by action of centrifugal forces upon the fluid atoms at their azimuthal motion around the vortex line. Firstly, atoms obtain dipole moments (internal polarization when external polarization when external field is absent) and a nonuniform symmetrical distribution of the polarization density arises; at that, a vortex has no integral dipole moment but each element of the vortex line bears a quadrupole moment. Secondly, action of the centrifugal forces leads to a nonuniform distribution of the atomic density around the vortex line; therefore, the polarization density of the fluid in the external electrical field is also nonuniform in the vicinity of this line and each isolated element of the vortex line obtains dipole moment proportional to the field magnitude (inductive polarization). Analytical expressions for the polarization density around the straight and circular vortex lines are obtained and the effective dipole and quadrupole moments of the vortices are determined. A distribution of the ponderomotive forces acting on the superfluid fluid with quantized vortices in the external electrical field has been analyzed and the caused by field additives to the energy of the straight and circular vortices are found. Numerical estimations of the effects considered are given for He II

Flux flow of Abrikosov vortices in type-II superconductors

International Nuclear Information System (INIS)

Chen, J.L.; Yang, T.J.

1994-01-01

The theory of flux flow developed by Bardeen and Stephen (BS) is modified and extended to the high-field case. The Clem model and Wigner-Seitz circle-cell approximation for vortices are used in our approach. The distinct boundary of the normal core of a vortex in BS theory is removed and treated naturally. Several interesting results come out as a consequence. The Lorentz force is determined by the normal current rather than the supercurrent. But the supercurrent can sustain the magnetic-field distribution of flux quanta. From energy dissipation considerations, the Lorentz force is equal to viscosity force automatically without assumption as made in BS theory. An expression for the viscosity is also obtained

Vortices and domain walls: 'Wormholes' in unconventional superconductors

Energy Technology Data Exchange (ETDEWEB)

Bessarab, P F [St. Petersburg State University, Universitetskaya nab. 7/9, 199164 St. Petersburg (Russian Federation); Radievsky, A V, E-mail: van_der_paul@yahoo.co.u [Immanuel Kant State University of Russia, Nevskogo str. 14, 236016 Kaliningrad (Russian Federation)

2010-01-15

In the framework of the 2D and 3D time-dependent Ginzburg-Landau model we study superconductors with multicomponent order parameter (d-pairing). We argue that topological defects inside the sample do affect its thermodynamic properties such as hysteresis loop, susceptibility, etc. Along with earlier known topological defects such as Abrikosov vortices, domain walls (DWs) which separate different magnetic phases and even vortices inside the DW, we found an interesting combination of DWs and vortices. Namely we show that equivalent magnetic phases may be linked together with a vortex going through the other magnetic phase. This configuration may correspond to a stable state even in a zero external magnetic field. We also mention that this configuration is topologically similar to the 'wormholes' in the quantum gravity.

Numerical and Experimental Study on Negative Buoyance Induced Vortices in N-Butane Jet Flames

KAUST Repository

Xiong, Yuan

2015-07-26

Near nozzle flow field in flickering n-butane diffusion jet flames was investigated with a special focus on transient flow patterns of negative buoyance induced vortices. The flow structures were obtained through Mie scattering imaging with seed particles in a fuel stream using continuous-wave (CW) Argon-ion laser. Velocity fields were also quantified with particle mage velocimetry (PIV) system having kHz repetition rate. The results showed that the dynamic motion of negative buoyance induced vortices near the nozzle exit was coupled strongly with a flame flickering instability. Typically during the flame flickering, the negative buoyant vortices oscillated at the flickering frequency. The vortices were distorted by the flickering motion and exhibited complicated transient vortical patterns, such as tilting and stretching. Numerical simulations were also implemented based on an open source C++ package, LaminarSMOKE, for further validations.

Vorticity and divergence in the high-latitude upper thermosphere

International Nuclear Information System (INIS)

Thayer, J.P.; Killeen, T.L.

1991-01-01

Measurements made from the Dynamics Explorer-2 satellite in November 1981 through January 1982 and November 1982 through January 1983 have been analyzed to determine the divergence and vertical component of vorticity of the high-latitude neutral wind field in the upper thermosphere for quiet (kp≤6) geomagnetic conditions and for both northern (winter) and southern (summer) hemispheres in the polar thermosphere and provides insight into the relative strengths of the different sources of momentum and energy responsible for driving the winds. The principal findings from this work include the following: The mean neutral wind pattern is dominated by rotational flow rather than by divergent flow, with a typical vorticity: divergence ratio of ∼ 2:1 for active conditions and ∼ 4:1 for quiet conditions. Comparison of the divergence and vorticity patterns for quiet and active conditions indicates that the divergent component of the neutral flow intensifies more significantly with increasing geomagnetic activity than does the rotational component

A Thermodynamically General Theory for Convective Circulations and Vortices

Science.gov (United States)

Renno, N. O.

2007-12-01

Convective circulations and vortices are common features of atmospheres that absorb low-entropy-energy at higher temperatures than they reject high-entropy-energy to space. These circulations range from small to planetary-scale and play an important role in the vertical transport of heat, momentum, and tracer species. Thus, the development of theoretical models for convective phenomena is important to our understanding of many basic features of planetary atmospheres. A thermodynamically general theory for convective circulations and vortices is proposed. The theory includes irreversible processes and quantifies the pressure drop between the environment and any point in a convective updraft. The article's main result is that the proposed theory provides an expression for the pressure drop along streamlines or streamtubes that is a generalization of Bernoulli's equation to convective circulations. We speculate that the proposed theory not only explains the intensity, but also shed light on other basic features of convective circulations and vortices.

Two species of vortices in massive gauged non-linear sigma models

International Nuclear Information System (INIS)

Alonso-Izquierdo, A.; Fuertes, W. García; Guilarte, J. Mateos

2015-01-01

Non-linear sigma models with scalar fields taking values on ℂℙ"n complex manifolds are addressed. In the simplest n=1 case, where the target manifold is the S"2 sphere, we describe the scalar fields by means of stereographic maps. In this case when the U(1) symmetry is gauged and Maxwell and mass terms are allowed, the model accommodates stable self-dual vortices of two kinds with different energies per unit length and where the Higgs field winds at the cores around the two opposite poles of the sphere. Allowing for dielectric functions in the magnetic field, similar and richer self-dual vortices of different species in the south and north charts can be found by slightly modifying the potential. Two different situations are envisaged: either the vacuum orbit lies on a parallel in the sphere, or one pole and the same parallel form the vacuum orbit. Besides the self-dual vortices of two species, there exist BPS domain walls in the second case. Replacing the Maxwell contribution of the gauge field to the action by the second Chern-Simons secondary class, only possible in (2+1)-dimensional Minkowski space-time, new BPS topological defects of two species appear. Namely, both BPS vortices and domain ribbons in the south and the north charts exist because the vacuum orbit consits of the two poles and one parallel. Formulation of the gauged ℂℙ"2 model in a reference chart shows a self-dual structure such that BPS semi-local vortices exist. The transition functions to the second or third charts break the U(1)×SU(2) semi-local symmetry, but there is still room for standard self-dual vortices of the second species. The same structures encompassing N complex scalar fields are easily generalized to gauged ℂℙ"N models.

Two species of vortices in massive gauged non-linear sigma models

Energy Technology Data Exchange (ETDEWEB)

Alonso-Izquierdo, A. [Departamento de Matemática Aplicada, Universidad de Salamanca,Facultad de Ciencias Agrarias y Ambientales, Av. Filiberto Villalobos 119, E-37008 Salamanca (Spain); Fuertes, W. García [Departamento de Física, Universidad de Oviedo, Facultad de Ciencias, Calle Calvo Sotelo s/n, E-33007 Oviedo (Spain); Guilarte, J. Mateos [Departamento de Física Fundamental, Universidad de Salamanca, Facultad de Ciencias, Plaza de la Merced, E-37008 Salamanca (Spain)

2015-02-23

Non-linear sigma models with scalar fields taking values on ℂℙ{sup n} complex manifolds are addressed. In the simplest n=1 case, where the target manifold is the S{sup 2} sphere, we describe the scalar fields by means of stereographic maps. In this case when the U(1) symmetry is gauged and Maxwell and mass terms are allowed, the model accommodates stable self-dual vortices of two kinds with different energies per unit length and where the Higgs field winds at the cores around the two opposite poles of the sphere. Allowing for dielectric functions in the magnetic field, similar and richer self-dual vortices of different species in the south and north charts can be found by slightly modifying the potential. Two different situations are envisaged: either the vacuum orbit lies on a parallel in the sphere, or one pole and the same parallel form the vacuum orbit. Besides the self-dual vortices of two species, there exist BPS domain walls in the second case. Replacing the Maxwell contribution of the gauge field to the action by the second Chern-Simons secondary class, only possible in (2+1)-dimensional Minkowski space-time, new BPS topological defects of two species appear. Namely, both BPS vortices and domain ribbons in the south and the north charts exist because the vacuum orbit consits of the two poles and one parallel. Formulation of the gauged ℂℙ{sup 2} model in a reference chart shows a self-dual structure such that BPS semi-local vortices exist. The transition functions to the second or third charts break the U(1)×SU(2) semi-local symmetry, but there is still room for standard self-dual vortices of the second species. The same structures encompassing N complex scalar fields are easily generalized to gauged ℂℙ{sup N} models.

The characterisation of blood rotation in a human heart chamber based on statistical analysis of vorticity maps

Science.gov (United States)

Wong, Kelvin K. L.; Kelso, Richard M.; Worthley, Stephen G.; Sanders, Prashanthan; Mazumdar, Jagannath; Abbott, Derek

2008-12-01

Modelling of non-stationary cardiac structures is complicated by the complexity of their intrinsic and extrinsic motion. The first known study of haemodynamics due to the beating of heart was made by Leonardo Da Vinci, giving the idea of fluid-solid interaction by describing how vortices develop during cardiac structural interaction with the blood. Heart morphology affects in changes of cardio dynamics during the systolic and diastolic phrases. In a chamber of the heart, vortices are discovered to exist as the result of the unique morphological changes of the cardiac chamber wall by using flow-imaging techniques such as phase contrast magnetic resonance imaging. The first part of this paper attempts to quantify vortex characteristics by means of calculating vorticity numerically and devising two dimensional vortical flow maps. The technique relies on determining the properties of vorticity using a statistical quantification of the flow maps and comparison of these quantities based on different scenarios. As the characteristics of our vorticity maps vary depending on the phase of a cardiac cycle, there is a need for robust quantification method to analyse vorticity. In the second part of the paper, the approach is then utilised for examining vortices within the human right atrium. Our study has shown that a proper quantification of vorticity for the flow field can indicate the strength and number of vortices within a heart chamber.

The generation of sound by vorticity waves in swirling duct flows

Science.gov (United States)

Howe, M. S.; Liu, J. T. C.

1977-01-01

Swirling flow in an axisymmetric duct can support vorticity waves propagating parallel to the axis of the duct. When the cross-sectional area of the duct changes a portion of the wave energy is scattered into secondary vorticity and sound waves. Thus the swirling flow in the jet pipe of an aeroengine provides a mechanism whereby disturbances produced by unsteady combustion or turbine blading can be propagated along the pipe and subsequently scattered into aerodynamic sound. In this paper a linearized model of this process is examined for low Mach number swirling flow in a duct of infinite extent. It is shown that the amplitude of the scattered acoustic pressure waves is proportional to the product of the characteristic swirl velocity and the perturbation velocity of the vorticity wave. The sound produced in this way may therefore be of more significance than that generated by vorticity fluctuations in the absence of swirl, for which the acoustic pressure is proportional to the square of the perturbation velocity. The results of the analysis are discussed in relation to the problem of excess jet noise.

Machine learning vortices at the Kosterlitz-Thouless transition

Science.gov (United States)

Beach, Matthew J. S.; Golubeva, Anna; Melko, Roger G.

2018-01-01

Efficient and automated classification of phases from minimally processed data is one goal of machine learning in condensed-matter and statistical physics. Supervised algorithms trained on raw samples of microstates can successfully detect conventional phase transitions via learning a bulk feature such as an order parameter. In this paper, we investigate whether neural networks can learn to classify phases based on topological defects. We address this question on the two-dimensional classical XY model which exhibits a Kosterlitz-Thouless transition. We find significant feature engineering of the raw spin states is required to convincingly claim that features of the vortex configurations are responsible for learning the transition temperature. We further show a single-layer network does not correctly classify the phases of the XY model, while a convolutional network easily performs classification by learning the global magnetization. Finally, we design a deep network capable of learning vortices without feature engineering. We demonstrate the detection of vortices does not necessarily result in the best classification accuracy, especially for lattices of less than approximately 1000 spins. For larger systems, it remains a difficult task to learn vortices.

Modulation of leading edge vorticity and aerodynamic forces in flexible flapping wings.

Science.gov (United States)

Zhao, Liang; Deng, Xinyan; Sane, Sanjay P

2011-09-01

In diverse biological flight systems, the leading edge vortex has been implicated as a flow feature of key importance in the generation of flight forces. Unlike fixed wings, flapping wings can translate at higher angles of attack without stalling because their leading edge vorticity is more stable than the corresponding fixed wing case. Hence, the leading edge vorticity has often been suggested as the primary determinant of the high forces generated by flapping wings. To test this hypothesis, it is necessary to modulate the size and strength of the leading edge vorticity independently of the gross kinematics while simultaneously monitoring the forces generated by the wing. In a recent study, we observed that forces generated by wings with flexible trailing margins showed a direct dependence on the flexural stiffness of the wing. Based on that study, we hypothesized that trailing edge flexion directly influences leading edge vorticity, and thereby the magnitude of aerodynamic forces on the flexible flapping wings. To test this hypothesis, we visualized the flows on wings of varying flexural stiffness using a custom 2D digital particle image velocimetry system, while simultaneously monitoring the magnitude of the aerodynamic forces. Our data show that as flexion decreases, the magnitude of the leading edge vorticity increases and enhances aerodynamic forces, thus confirming that the leading edge vortex is indeed a key feature for aerodynamic force generation in flapping flight. The data shown here thus support the hypothesis that camber influences instantaneous aerodynamic forces through modulation of the leading edge vorticity.

Lagrangian structures in time-periodic vortical flows

Directory of Open Access Journals (Sweden)

S. V. Kostrykin

2006-01-01

Full Text Available The Lagrangian trajectories of fluid particles are experimentally studied in an oscillating four-vortex velocity field. The oscillations occur due to a loss of stability of a steady flow and result in a regular reclosure of streamlines between the vortices of the same sign. The Eulerian velocity field is visualized by tracer displacements over a short time period. The obtained data on tracer motions during a number of oscillation periods show that the Lagrangian trajectories form quasi-regular structures. The destruction of these structures is determined by two characteristic time scales: the tracers are redistributed sufficiently fast between the vortices of the same sign and much more slowly transported into the vortices of opposite sign. The observed behavior of the Lagrangian trajectories is quantitatively reproduced in a new numerical experiment with two-dimensional model of the velocity field with a small number of spatial harmonics. A qualitative interpretation of phenomena observed on the basis of the theory of adiabatic chaos in the Hamiltonian systems is given. The Lagrangian trajectories are numerically simulated under varying flow parameters. It is shown that the spatial-temporal characteristics of the Lagrangian structures depend on the properties of temporal change in the streamlines topology and on the adiabatic parameter corresponding to the flow. The condition for the occurrence of traps (the regions where the Lagrangian particles reside for a long time is obtained.

Role of vortices in cavitation formation in the flow across a mechanical heart valve.

Science.gov (United States)

Li, Chi-Pei; Lu, Po-Chien; Liu, Jia-Shing; Lo, Chi-Wen; Hwang, Ned H

2008-07-01

Cavitation occurs during mechanical heart valve closure when the local pressure drops below vapor pressure. The formation of stable gas bubbles may result in gaseous emboli, and secondarily cause transient ischemic attacks or strokes. It is noted that instantaneous valve closure, occluder rebound and high-speed leakage flow generate vortices that promote low-pressure regions in favor of stable bubble formation; however, to date no studies have been conducted for the quantitative measurement and analysis of these vortices. A Björk-Shiley Monostrut (BSM) monoleaflet valve was placed in the mitral position of a pulsatile mock circulatory loop. Particle image velocimetry (PIV) and pico coulomb (PCB) pressure measurements were applied. Flow field measurements were carried out at t = -5, -3, -1, -0.5, 0 (valve closure), 0.3, 0.5, 0.75, 1.19, 1.44, 1.69, 1.94, 2, 2.19, 2.54, 2.79, 3.04, 3.29, 3.54, 5 and 10 ms. The vortices were quantitatively analyzed using the Rankine vortex model. A single counter-clockwise vortex was The instantaneous formation of cavitation bubbles at mechanical heart valve (MHV) closure, which subsequently damage blood cells and valve integrity, is a well-known and widely studied phenomenon (1-4). Contributing factors seem to include the water-hammer, squeeze flow and Venturi effects, all of which are short-lived. Both, Dauzat et al. (5) and Sliwka et al. (6) have detected high-intensity transient signals (HITS) with transcranial Doppler ultrasound in the carotid and cerebral arteries of MHV recipients, while Deklunder (7) observed clinical occurrences of cerebral gas emboli that were not seen with bioprosthetic valves. These detected over the major orifice, while a pair of counter-rotating vortices was found over the minor orifice. Velocity profiles were consistent with Rankine vortices. The vortex strength and magnitude of the pressure drop peaked shortly after initial occluder-housing impact and rapidly decreased after 0.5 ms, indicating viscous

A numerical study of the role of the vertical structure of vorticity during tropical cyclone genesis

International Nuclear Information System (INIS)

Venkatesh, T N; Mathew, Joseph

2010-01-01

An eight-level axisymmetric model with simple parameterizations for clouds and the atmospheric boundary layer was developed to examine the evolution of vortices that are precursors to tropical cyclones. The effect of vertical distributions of vorticity, especially that arising from a merger of mid-level vortices, was studied by us to provide support for a new vortex-merger theory of tropical cyclone genesis. The basic model was validated with the analytical results available for the spin-down of axisymmetric vortices. With the inclusion of the cloud and boundary layer parameterizations, the evolution of deep vortices into hurricanes and the subsequent decay are simulated quite well. The effects of several parameters such as the initial vortex strength, radius of maximum winds, sea-surface temperature and latitude (Coriolis parameter) on the evolution were examined. A new finding is the manner in which mid-level vortices of the same strength decay and how, on simulated merger of these mid-level vortices, the resulting vortex amplifies to hurricane strength in a realistic time frame. The importance of sea-surface temperature on the evolution of full vortices was studied and explained. Also it was found that the strength of the surface vortex determines the time taken by the deep vortex to amplify to hurricane strength.

Intrinsic nonadiabatic topological torque in magnetic skyrmions and vortices

KAUST Repository

Akosa, Collins Ashu; Ndiaye, Papa Birame; Manchon, Aurelien

2017-01-01

We propose that topological spin currents flowing in topologically nontrivial magnetic textures, such as magnetic skyrmions and vortices, produce an intrinsic nonadiabatic torque of the form Tt∼[(∂xm×∂ym)·m]∂ym. We show that this torque, which is absent in one-dimensional domain walls and/or nontopological textures, is responsible for the enhanced nonadiabaticity parameter observed in magnetic vortices compared to one-dimensional textures. The impact of this torque on the motion of magnetic skyrmions is expected to be crucial, especially to determine their robustness against defects and pinning centers.

Intrinsic nonadiabatic topological torque in magnetic skyrmions and vortices

KAUST Repository

Akosa, Collins Ashu

2017-03-01

We propose that topological spin currents flowing in topologically nontrivial magnetic textures, such as magnetic skyrmions and vortices, produce an intrinsic nonadiabatic torque of the form Tt∼[(∂xm×∂ym)·m]∂ym. We show that this torque, which is absent in one-dimensional domain walls and/or nontopological textures, is responsible for the enhanced nonadiabaticity parameter observed in magnetic vortices compared to one-dimensional textures. The impact of this torque on the motion of magnetic skyrmions is expected to be crucial, especially to determine their robustness against defects and pinning centers.

Shear and loading in channels: Oscillatory shearing and edge currents of superconducting vortices

Science.gov (United States)

Wambaugh, J. F.; Marchesoni, F.; Nori, Franco

2003-04-01

Via computer simulations we study the motion of quantized magnetic flux-lines, or vortices, confined to a straight pin-free channel in a strong-pinning superconducting sample. We find that, when a constant current is applied across this system, a very unusual oscillatory shearing appears, in which the vortices moving at the edges of the channel periodically trail behind and then suddenly leapfrog past the vortices moving in the inner rows. For small enough driving forces, this oscillatory shearing dynamic phase is replaced by a continuous shearing phase in which the distance between initially-nearby vortices grows in time, quickly destroying the order of the lattice. An animation of this novel “oscillatory leapfrogging shear” effect of the vortex edge currents appears in http://www-personal.engin.umich.edu/˜nori/channel/

Aharonov-Bohm effect with many vortices

International Nuclear Information System (INIS)

Franchini, Fabio; Scharff Goldhaber, Alfred

2008-01-01

The Aharonov-Bohm (A-B) effect is the prime example of a zero-field-strength configuration where a nontrivial vector potential acquires physical significance, a typical quantum mechanical effect. We consider an extension of the traditional A-B problem, by studying a two-dimensional medium filled with many point-like vortices. Systems like this might be present within a type II superconducting layer in the presence of a strong magnetic field perpendicular to the layer, and have been studied in different limits. We construct an explicit solution for the wave function of a scalar particle moving within one such layer when the vortices occupy the sites of a square lattice and have all the same strength, equal to half of the flux quantum. From this construction, we infer some general characteristics of the spectrum, including the conclusion that such a flux array produces a repulsive barrier to an incident low-energy charged particle, so that the penetration probability decays exponentially with distance from the edge.

Aharonov-Bohm effect with many vortices

Science.gov (United States)

Franchini, Fabio; Scharff Goldhaber, Alfred

2008-12-01

The Aharonov-Bohm (A-B) effect is the prime example of a zero-field-strength configuration where a nontrivial vector potential acquires physical significance, a typical quantum mechanical effect. We consider an extension of the traditional A-B problem, by studying a two-dimensional medium filled with many point-like vortices. Systems like this might be present within a type II superconducting layer in the presence of a strong magnetic field perpendicular to the layer, and have been studied in different limits. We construct an explicit solution for the wave function of a scalar particle moving within one such layer when the vortices occupy the sites of a square lattice and have all the same strength, equal to half of the flux quantum. From this construction, we infer some general characteristics of the spectrum, including the conclusion that such a flux array produces a repulsive barrier to an incident low-energy charged particle, so that the penetration probability decays exponentially with distance from the edge.

Trailing vortices from low speed flyers

Science.gov (United States)

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.

Correlation between vortices and wall shear stress in a curved artery model under pulsatile flow conditions

Science.gov (United States)

Cox, Christopher; Plesniak, Michael W.

2017-11-01

One of the most physiologically relevant factors within the cardiovascular system is the wall shear stress. The wall shear stress affects endothelial cells via mechanotransduction and atherosclerotic regions are strongly correlated with curvature and branching in the human vasculature, where the shear stress is both oscillatory and multidirectional. Also, the combined effect of curvature and pulsatility in cardiovascular flows produces unsteady vortices. In this work, our goal is to assess the correlation between multiple vortex pairs and wall shear stress. To accomplish this, we use an in-house high-order flux reconstruction Navier-Stokes solver to simulate pulsatile flow of a Newtonian blood-analog fluid through a rigid 180° curved artery model. We use a physiologically relevant flow rate and generate results using both fully developed and uniform entrance conditions, the latter motivated by the fact that flow upstream to a curved artery may not be fully developed. Under these two inflow conditions, we characterize the evolution of various vortex pairs and their subsequent effect on several wall shear stress metrics. Supported by GW Center for Biomimetics and Bioinspired Engineering.

Origin of chaos near three-dimensional quantum vortices: A general Bohmian theory

Science.gov (United States)

Tzemos, Athanasios C.; Efthymiopoulos, Christos; Contopoulos, George

2018-04-01

We provide a general theory for the structure of the quantum flow near three-dimensional (3D) nodal lines, i.e., one-dimensional loci where the 3D wave function becomes equal to zero. In suitably defined coordinates (comoving with the nodal line) the generic structure of the flow implies the formation of 3D quantum vortices. We show that such vortices are accompanied by nearby invariant lines of the comoving quantum flow, called X lines, which are normally hyperbolic. Furthermore, the stable and unstable manifolds of the X lines produce chaotic scatterings of nearby quantum (Bohmian) trajectories, thus inducing an intricate form of the quantum current in the neighborhood of each 3D quantum vortex. Generic formulas describing the structure around 3D quantum vortices are provided, applicable to an arbitrary choice of 3D wave function. We also give specific numerical examples as well as a discussion of the physical consequences of chaos near 3D quantum vortices.

EFT for vortices with dilaton-dependent localized flux

Energy Technology Data Exchange (ETDEWEB)

Burgess, C.P. [Physics & Astronomy, McMaster University, Hamilton, ON, L8S 4M1 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, ON, N2L 2Y5 (Canada); Division PH -TH, CERN, CH-1211, Genève 23 (Switzerland); Diener, Ross [Physics & Astronomy, McMaster University, Hamilton, ON, L8S 4M1 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, ON, N2L 2Y5 (Canada); Williams, M. [Instituut voor Theoretische Fysica, Katholieke Universiteit Leuven, B-3001 Leuven (Belgium)

2015-11-09

We study how codimension-two objects like vortices back-react gravitationally with their environment in theories (such as 4D or higher-dimensional supergravity) where the bulk is described by a dilaton-Maxwell-Einstein system. We do so both in the full theory, for which the vortex is an explicit classical ‘fat brane’ solution, and in the effective theory of ‘point branes’ appropriate when the vortices are much smaller than the scales of interest for their back-reaction (such as the transverse Kaluza-Klein scale). We extend the standard Nambu-Goto description to include the physics of flux-localization wherein the ambient flux of the external Maxwell field becomes partially localized to the vortex, generalizing the results of a companion paper http://arxiv.org/abs/1506.08095 to include dilaton-dependence for the tension and localized flux. In the effective theory, such flux-localization is described by the next-to-leading effective interaction, and the boundary conditions to which it gives rise are known to play an important role in how (and whether) the vortex causes supersymmetry to break in the bulk. We track how both tension and localized flux determine the curvature of the space-filling dimensions. Our calculations provide the tools required for computing how scale-breaking vortex interactions can stabilize the extra-dimensional size by lifting the dilaton’s flat direction. For small vortices we derive a simple relation between the near-vortex boundary conditions of bulk fields as a function of the tension and localized flux in the vortex action that provides the most efficient means for calculating how physical vortices mutually interact without requiring a complete construction of their internal structure. In passing we show why a common procedure for doing so using a δ-function can lead to incorrect results. Our procedures generalize straightforwardly to general co-dimension objects.

EFT for vortices with dilaton-dependent localized flux

International Nuclear Information System (INIS)

Burgess, C.P.; Diener, Ross; Williams, M.

2015-01-01

We study how codimension-two objects like vortices back-react gravitationally with their environment in theories (such as 4D or higher-dimensional supergravity) where the bulk is described by a dilaton-Maxwell-Einstein system. We do so both in the full theory, for which the vortex is an explicit classical ‘fat brane’ solution, and in the effective theory of ‘point branes’ appropriate when the vortices are much smaller than the scales of interest for their back-reaction (such as the transverse Kaluza-Klein scale). We extend the standard Nambu-Goto description to include the physics of flux-localization wherein the ambient flux of the external Maxwell field becomes partially localized to the vortex, generalizing the results of a companion paper http://arxiv.org/abs/1506.08095 to include dilaton-dependence for the tension and localized flux. In the effective theory, such flux-localization is described by the next-to-leading effective interaction, and the boundary conditions to which it gives rise are known to play an important role in how (and whether) the vortex causes supersymmetry to break in the bulk. We track how both tension and localized flux determine the curvature of the space-filling dimensions. Our calculations provide the tools required for computing how scale-breaking vortex interactions can stabilize the extra-dimensional size by lifting the dilaton’s flat direction. For small vortices we derive a simple relation between the near-vortex boundary conditions of bulk fields as a function of the tension and localized flux in the vortex action that provides the most efficient means for calculating how physical vortices mutually interact without requiring a complete construction of their internal structure. In passing we show why a common procedure for doing so using a δ-function can lead to incorrect results. Our procedures generalize straightforwardly to general co-dimension objects.

Visualization and Quantification of Rotor Tip Vortices in Helicopter Flows

Science.gov (United States)

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.

The impact of intraglottal vortices on vocal fold dynamics

Science.gov (United States)

Erath, Byron; Pirnia, Alireza; Peterson, Sean

2016-11-01

During voiced speech a critical pressure is produced in the lungs that separates the vocal folds and creates a passage (the glottis) for airflow. As air passes through the vocal folds the resulting aerodynamic loading, coupled with the tissue properties of the vocal folds, produces self-sustained oscillations. Throughout each cycle a complex flow field develops, characterized by a plethora of viscous flow phenomena. Air passing through the glottis creates a jet, with periodically-shed vortices developing due to flow separation and the Kelvin-Helmholtz instability in the shear layer. These vortices have been hypothesized to be a crucial mechanism for producing vocal fold vibrations. In this study the effect of vortices on the vocal fold dynamics is investigated experimentally by passing a vortex ring over a flexible beam with the same non-dimensional mechanical properties as the vocal folds. Synchronized particle image velocimetry data are acquired in tandem with the beam dynamics. The resulting impact of the vortex ring loading on vocal fold dynamics is discussed in detail. This work was supported by the National Science Foundation Grant CBET #1511761.

MMS Observations of Vorticity Near Sites of Magnetic Reconnection

Science.gov (United States)

Paterson, W. R.; Giles, B. L.; Avanov, L. A.; Boardsen, S. A.; Dorelli, J.; Gershman, D. J.; Mackler, D. A.; Moore, T. E.; Pollock, C. J.; Schiff, C.; Shuster, J. R.; Viñas, A. F.; Russell, C. T.; Strangeway, R. J.; Burch, J. L.; Torbert, R. B.

2017-12-01

With highly capable plasma instruments on four spacecraft flown in tetrahedral formation, it is possible for MMS investigators to approximate spatial derivatives of the plasma parameters observed. Here, we examine vorticity of the electron and ion components of the plasma computed from the curl of velocity as measured by the Fast Plasma Investigation (FPI). Vorticity of magnetospheric plasma has not previously been studied on scales of tens-of-km to less than 10 km, which are the typical inter-spacecraft separations for MMS. Nor has it been explored on time scales of 30 ms for electrons and 150 ms for ions, which are the burst data rates for the FPI spectrometers. Review of observations from the magnetopause and magnetotail phases of the mission finds increases in vorticity associated with near encounters with the electron diffusion region, with nearby regions of measurable current, and with elevated electron and ion temperatures. These are suggestive of a possible role for turbulence in magnetic reconnection. In this presentation we provide an assessment of the quality of these measurements and discuss their potential significance.

Core sizes and dynamical instabilities of giant vortices in dilute Bose-Einstein condensates

International Nuclear Information System (INIS)

Kuopanportti, Pekko; Lundh, Emil; Huhtamaeki, Jukka A. M.; Pietilae, Ville; Moettoenen, Mikko

2010-01-01

Motivated by a recent demonstration of cyclic addition of quantized vorticity into a Bose-Einstein condensate, the vortex pump, we study dynamical instabilities and core sizes of giant vortices. The core size is found to increase roughly as a square-root function of the quantum number of the vortex, whereas the strength of the dynamical instability either saturates to a fairly low value or increases extremely slowly for large quantum numbers. Our studies suggest that giant vortices of very high angular momenta may be achieved by gradually increasing the operation frequency of the vortex pump.

Nuclear vorticity and the low-energy nuclear response. Towards the neutron drip line

International Nuclear Information System (INIS)

Papakonstantinou, P.; Athens Univ.; Wambach, J.; Ponomarev, V.Y.; Mavrommatis, E.

2004-01-01

The transition density and current provide valuable insight into the nature of nuclear vibrations. Nuclear vorticity is a quantity related to the transverse transition current. In this work, we study the evolution of the strength distribution, related to density fluctuations, and the vorticity strength distribution, as the neutron drip line is approached. Our results on the isoscalar, natural-parity multipole response of Ni isotopes, obtained by using a self-consistent Skyrme-Hartree-Fock+continuum RPA model, indicate that, close to the drip line, the low-energy response is dominated by L > 1 vortical transitions. (orig.)

Four-Spacecraft Magnetic Curvature and Vorticity Analyses on Kelvin-Helmholtz Waves in MHD Simulations

Science.gov (United States)

Kieokaew, Rungployphan; Foullon, Claire; Lavraud, Benoit

2018-01-01

Four-spacecraft missions are probing the Earth's magnetospheric environment with high potential for revealing spatial and temporal scales of a variety of in situ phenomena. The techniques allowed by these four spacecraft include the calculation of vorticity and the magnetic curvature analysis (MCA), both of which have been used in the study of various plasma structures. Motivated by curved magnetic field and vortical structures induced by Kelvin- Helmholtz (KH) waves, we investigate the robustness of the MCA and vorticity techniques when increasing (regular) tetrahedron sizes, to interpret real data. Here for the first time, we test both techniques on a 2.5-D MHD simulation of KH waves at the magnetopause. We investigate, in particular, the curvature and flow vorticity across KH vortices and produce time series for static spacecraft in the boundary layers. The combined results of magnetic curvature and vorticity further help us to understand the development of KH waves. In particular, first, in the trailing edge, the magnetic curvature across the magnetopause points in opposite directions, in the wave propagation direction on the magnetosheath side and against it on the magnetospheric side. Second, the existence of a "turnover layer" in the magnetospheric side, defined by negative vorticity for the duskside magnetopause, which persists in the saturation phase, is reminiscent of roll-up history. We found significant variations in the MCA measures depending on the size of the tetrahedron. This study lends support for cross-scale observations to better understand the nature of curvature and its role in plasma phenomena.

An extended self-organisation principle for modelling and calculating the dissipation of 2D confined vortices

NARCIS (Netherlands)

Eydeland, A.; van Groesen, Embrecht W.C.

1989-01-01

Steady Euler flows in a periodic square that, for positive vorticity distributions, minimise the entropy at given values of the energy and the circulations are non-confined vortices for optimal values of the circulation, and are confined vortices for certain non-optimal values. An extension of the

Near field vorticity distributions from a sharp-edged rectangular jet

International Nuclear Information System (INIS)

Vouros, Alexandros P.; Panidis, Thrassos; Pollard, Andrew; Schwab, Rainer R.

2015-01-01

Highlights: • Axial mean vorticity equation terms are calculated from experimental data. • Appearance of ridges, dumbbell shape and saddleback velocity profiles is highlighted. • Explanations are provided using terms from the vorticity equation. - Abstract: Experimental results on the near field development of a free rectangular jet with aspect ratio 10 are presented. The jet issues from a sharp-edged orifice attached to a rectangular settling chamber at Re h ∼ 23,000, based on slot width, h. Measurements on cross plane grids were obtained with a two-component hot wire anemometry probe, which provided information on the three dimensional characteristics of the flow field. Two key features of this type of jet are mean axial velocity profiles presenting two off axis peaks, commonly mentioned as saddleback profiles, and a predominant dumbbell shape as described by, for example, a contour of the axial mean velocity. The saddleback shape is found to be significantly influenced by the vorticity distribution in the transverse plane of the jet, while the dumbbell is traced to two terms in the axial mean vorticity transport equation that diffuse fluid from the centre of the jet towards its periphery. At the farthest location where measurements were taken, 30 slot widths from the jet exit, the flow field resembles that of an axisymmetric jet

Plasma Cell Neoplasms (Including Multiple Myeloma)—Patient Version

Science.gov (United States)

Plasma cell neoplasms occur when abnormal plasma cells form cancerous tumors. When there is only one tumor, the disease is called a plasmacytoma. When there are multiple tumors, it is called multiple myeloma. Start here to find information on plasma cell neoplasms treatment, research, and statistics.

Transverse ratchet effect and superconducting vortices: simulation and experiment

International Nuclear Information System (INIS)

Dinis, L; Parrondo, J M R; Perez de Lara, D; Gonzalez, E M; Vicent, J L; Anguita, J V

2009-01-01

A transverse ratchet effect has been measured in magnetic/superconducting hybrid films fabricated by electron beam lithography and magnetron sputtering techniques. The samples are Nb films grown on top of an array of Ni nanotriangles. Injecting an ac current parallel to the triangle reflection symmetry axis yields an output dc voltage perpendicular to the current, due to a net motion of flux vortices in the superconductor. The effect is reproduced by numerical simulations of vortices as Langevin particles with realistic parameters. Simulations provide an intuitive picture of the ratchet mechanism, revealing the fundamental role played by the random intrinsic pinning of the superconductor.

Voltage quantization by ballistic vortices in two-dimensional superconductors

International Nuclear Information System (INIS)

Orlando, T.P.; Delin, K.A.

1991-01-01

The voltage generated by moving ballistic vortices with a mass m ν in a two-dimensional superconducting ring is quantized, and this quantization depends on the amount of charge enclosed by the ring. The quantization of the voltage is the dual to flux quantization in a superconductor, and is a manifestation of the Aharonov-Casher effect. The quantization is obtained by applying the Bohr-Sommerfeld criterion to the canonical momentum of the ballistic vortices. The results of this quantization condition can also be used to understand the persistent voltage predicted by van Wees for an array of Josephson junctions

Interaction of ultrasound with vortices in type-II superconductors

International Nuclear Information System (INIS)

Sonin, E.B.

1996-01-01

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 1996 The American Physical Society

Monopoles, vortices, and confinement

International Nuclear Information System (INIS)

Mack, G.; Pietarinen, E.

1981-10-01

An exact relation is established between an SO(3) lattice gauge theory model without monopoles, and a corresponding SU(2) model. Elimination of the monopoles (and their strings) leads to a substantial lowering of the entropy of thin vortices and a corresponding decrease of the string tension for low γ. This is revealed by approximate calculations of the vortex free energy and is confirmed by Monte Carlo data. The value of the physical transition temperature to 'hot gluon soup' is also lowered considerably. (orig.)

Polar vortices on Earth and Mars: A comparative study of the climatology and variability from reanalyses.

Science.gov (United States)

Mitchell, D M; Montabone, L; Thomson, S; Read, P L

2015-01-01

Polar vortices on Mars provide case-studies to aid understanding of geophysical vortex dynamics and may help to resolve long-standing issues regarding polar vortices on Earth. Due to the recent development of the first publicly available Martian reanalysis dataset (MACDA), for the first time we are able to characterise thoroughly the structure and evolution of the Martian polar vortices, and hence perform a systematic comparison with the polar vortices on Earth. The winter atmospheric circulations of the two planets are compared, with a specific focus on the structure and evolution of the polar vortices. The Martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on Earth during winter. While on Earth this residual circulation is very different from the Eulerian circulation, on Mars it is found to be very similar. Unlike on Earth, it is found that the Martian polar vortices are annular, and that the Northern Hemisphere vortex is far stronger than its southern counterpart. While winter hemisphere differences in vortex strength are also reported on Earth, the contrast is not as large. Distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices, in that the Martian polar vortices are observed to decrease in size at higher altitudes, whereas on Earth the opposite is observed. Finally, it is found that the Martian vortices are less variable through the winter than on Earth, especially in terms of the vortex geometry. During one particular major regional dust storm on Mars (Martian year 26), an equatorward displacement of the vortex is observed, sharing some qualitative characteristics of sudden stratospheric warmings on Earth.

Influence of the least-squares phase on optical vortices in strongly scintillated beams

CSIR Research Space (South Africa)

Chen, M

2009-06-01

Full Text Available , the average total number of vortices is reduced further. However, the reduction becomes smaller for each succes- sive step. This indicates that the ability of getting rid of optical vortices by removing the least-squares phase becomes progressively less...

On stability of vortices in three-dimensional self-attractive Bose-Einstein condensates

International Nuclear Information System (INIS)

Malomed, Boris A.; Lederer, Falk; Mazilu, Dumitru; Mihalache, Dumitru

2007-01-01

Results of accurate analysis of stability are reported for localized vortices in the Bose-Einstein condensate (BEC) with the negative scattering length, trapped in an anisotropic potential with the aspect ratio Ω. The cases of Ω-bar 1 and Ω-bar 1 correspond to the 'pancake' (nearly-2D) and 'cigar-shaped' (nearly-1D) configurations, respectively (in the latter limit, the vortices become 'tubular' solitons). The analysis is based on the 3D Gross-Pitaevskii equation. The family of solutions with vorticity S=1 is accurately predicted by the variational approximation. The relative size of the stability area for the vortices with S=1 (which was studied, in a part, before) increases with the decrease of Ω in terms of the number of atoms, but decreases in terms of the chemical potential. All states with S>=2 are unstable, while the stability of the ordinary solitons (S=0) obeys the Vakhitov-Kolokolov criterion. The stability predictions are verified by direct simulations of the full 3D equation

Vortical structures and pressure pulsations in draft tube of a Francis-99 turbine at part load: RANS and hybrid RANS/LES analysis

International Nuclear Information System (INIS)

Gavrilov, A.A.; Sentyabov, A.V.; Dekterev, A.A.; Hanjalić, K.

2017-01-01

Highlights: • Simulations showed the formation of spiralling coherent vortices in the draft tube. • Both hybrid RANS-LES and Re-stress models reproduced well the measured fluctuations. • Re-stress model resolved the precessing vortex core and coherent spiralling vortices. - Abstract: Recognizing the limitations of the conventional linear-eddy-viscosity (LEVM) Reynolds-averaged Navier–Stokes (RANS) models to reproduce complex three-dimensional unsteady flows in hydraulic machinery, we performed a comparative assessment of a second-moment (Re-stress model, RSM) RANS closure and a hybrid RANS/LES method in capturing the flow and vortical structures in the draft tube of a Francis hydroturbine at off-design conditions. Considered is a case of part load (PL) at a flow rate of only 35% of the best efficiency point (BEP) characterised by multiple unsteady vortex systems. Despite some remaining uncertainties in generating the inflow conditions, both approaches reproduced reasonably well the measured mean velocity and the rms of its fluctuations, as well as the pressure spectrum with peaks detecting the precessing vortex core. In contrast to the common LEVMs, the Re-stress closure showed sufficient receptivity to intrinsic unsteadiness and reproduced well the overall flow and vortical patterns as well as the associated pressure pulsations in accord with the experiments. The hybrid RANS/LES method gave similar predictions as the RSM, but resolving a wider range of scales, which however, showed no significant effect on the dynamics of the dominant processing vortex core and the pressure pulsations.

Tripolar vortices of dust-drift waves in dusty plasma with shear flow

International Nuclear Information System (INIS)

Chen Yinhua; Wang Ge

2002-01-01

Nonlinear equations governing dust-drift waves in magnetized dusty plasma with transverse shear flow are derived. For the specific profiles of flow and the plasma equilibrium density, a new type of solution in the form of tripolar vortices is found. The results show that the peak magnitude of tripolar vortices increases with increasing shear intensity and dust content

Vortical structures for nanomagnetic memory induced by dipole-dipole interaction in monolayer disks

Science.gov (United States)

Liu, Zhaosen; Ciftja, Orion; Zhang, Xichao; Zhou, Yan; Ian, Hou

2018-05-01

It is well known that magnetic domains in nanodisks can be used as storage units for computer memory. Using two quantum simulation approaches, we show here that spin vortices on magnetic monolayer nanodisks, which are chirality-free, can be induced by dipole-dipole interaction (DDI) on the disk-plane. When DDI is sufficiently strong, vortical and anti-vortical multi-domain textures can be generated simultaneously. Especially, a spin vortex can be easily created and deleted through either external magnetic or electrical signals, making them ideal to be used in nanomagnetic memory and logical devices. We demonstrate these properties in our simulations.

Ginzburg-Landau vortices driven by the Landau-Lifshitz-Gilbert equation

Energy Technology Data Exchange (ETDEWEB)

Kurzke, Matthias; Melcher, Christof; Moser, Roger; Spirn, Daniel

2009-06-15

A simplified model for the energy of the magnetization of a thin ferromagnetic film gives rise to a version of the theory of Ginzburg-Landau vortices for sphere-valued maps. In particular we have the development of vortices as a certain parameter tends to 0. The dynamics of the magnetization is ruled by the Landau-Lifshitz-Gilbert equation, which combines characteristic properties of a nonlinear Schroedinger equation and a gradient flow. This paper studies the motion of the vortex centers under this evolution equation. (orig.)

Ginzburg-Landau vortices driven by the Landau-Lifshitz-Gilbert equation

International Nuclear Information System (INIS)

Kurzke, Matthias; Melcher, Christof; Moser, Roger; Spirn, Daniel

2009-01-01

A simplified model for the energy of the magnetization of a thin ferromagnetic film gives rise to a version of the theory of Ginzburg-Landau vortices for sphere-valued maps. In particular we have the development of vortices as a certain parameter tends to 0. The dynamics of the magnetization is ruled by the Landau-Lifshitz-Gilbert equation, which combines characteristic properties of a nonlinear Schroedinger equation and a gradient flow. This paper studies the motion of the vortex centers under this evolution equation. (orig.)

Vorticity amplification and its effects on flow separation from simplified landing gear wheels

Science.gov (United States)

McCarthy, Philip; Feltham, Graham; Ekmekci, Alis

2015-11-01

In the presence of weak streams of inbound vorticity, the stagnation region of bluff bodies have been shown to support mechanisms for the collection and amplification of said vorticity into large-scale, discrete vortex structures. For extremely low aspect ratio cylinders, such as those which represent simplified aircraft landing gear wheels, these discrete vortex structures tilt around the sides of the geometry, orientating their axes in the streamwise direction. Once the oncoming vorticity is collected and amplified into discrete vortices, they are shed from the stagnation region and this cycle repeats itself periodically. The present work investigates the effect of the vortex tilting and subsequent shedding on the behaviour of the outboard side flow separation region present on simplified landing gear wheels. Experiments were conducted in a recirculating-type water tunnel on a two-wheel landing gear model, with the upstream vorticity source being a 100 µm platinum wire. Hydrogen bubble visualisations were first used for qualitative understanding of the flow, accompanied by 2D-PIV for vortex identification and tracking of the growth and movement of the observed structures. Finally, the side separation bubble has been characterised using 3D velocity measurements (using V3V). The authors would like to thank Bombardier, Messier-Bugatti-Dowty and NSERC for their support for this project.

Rotating shallow water modeling of planetary,astrophysical and plasma vortical structures (plasma transport across a magnetic field,model of the jupiter's GRS, prediction of existence of giant vortices in spiral galaxies

Directory of Open Access Journals (Sweden)

M. V. Nezlin

1999-01-01

Full Text Available Three kinds of results have been described in this paper. Firstly, an experimental study of the Rossby vortex meridional drift on the rotating shallow water has been carried out. Owing to the stringent physical analogy between the Rossby vortices and drift vortices in the magnetized plasma, the results obtained have allowed one to make a conclusion that the transport rate of the plasma, trapped by the drift vortices, across the magnetic field is equivalent to the “gyro-Bohm” diffusion coefficient. Secondly, a model of big vortices of the type of the Great Red Spot of Jupiter, dominating in the atmospheres of the outer planets, has been produced. Thirdly, the rotating shallow water modeling has been carried out of the hydrodynamical generation mechanism of spiral structures in galaxies. Trailing spiral waves of various azimuthal modes, generated by a shear flow between fast rotating “nucleus” and slow rotating periphery, were produced. The spirals are similar to those existing in the real galaxies. The hydrodynamical concept of the spiral structure formation in galaxies has been substantiated. Strong anticyclonic vortices between the spiral arms of the structures under study have been discovered for the first time. The existence of analogous vortices in real galaxies has been predicted. (This prediction has been reliably confirmed recently in special astronomical observations, carried out on the basis of the mentioned laboratory modeling and the prediction made – see the paper by A. Fridman et al. (Astrophysics and Space Science, 1997, 252, 115.

Generation of optical vortices in an integrated optical circuit

Science.gov (United States)

Tudor, Rebeca; Kusko, Mihai; Kusko, Cristian

2017-09-01

In this work, the generation of optical vortices in an optical integrated circuit is numerically demonstrated. The optical vortices with topological charge m = ±1 are obtained by the coherent superposition of the first order modes present in a waveguide with a rectangular cross section, where the phase delay between these two propagating modes is Δφ = ±π/2. The optical integrated circuit consists of an input waveguide continued with a y-splitter. The left and the right arms of the splitter form two coupling regions K1 and K2 with a multimode output waveguide. In each coupling region, the fundamental modes present in the arms of the splitter are selectively coupled into the output waveguide horizontal and vertical first order modes, respectively. We showed by employing the beam propagation method simulations that the fine tuning of the geometrical parameters of the optical circuit makes possible the generation of optical vortices in both transverse electric (TE) and transverse magnetic (TM) modes. Also, we demonstrated that by placing a thermo-optical element on one of the y-splitter arms, it is possible to switch the topological charge of the generated vortex from m = 1 to m = -1.

Analysis of wake vortices of a medium range twin-propeller military cargo aircraft using statistically designed experiments

Science.gov (United States)

Sahin, Burhan

An experimental study was initiated to analyze the trajectories of the streamwise vortices behind the wing tip and flap of a medium range and propeller driven twin-engine military cargo aircraft. The model used for the experimental study was a generic, high wing and half model of a propeller driven aircraft and mounted within Old Dominion University's Low Speed Wind Tunnel where the wind tunnel flow speed was set to constant value of 9 m/sec. The main purpose of the study was to reach regression models for the motion and vorticity strength of both vortices under varying factors such as angle of attack, flap angle, propeller pitch angle and downstream distance. Velocity measurements of the flow fields were accomplished using both Particle Image Velocimetry (PIV) and Hotwire Anemometry (HWA) to yield average velocities, turbulence levels, vorticity strengths and Reynolds shear stresses in the wake of the model. The results of measurements showed that the vertical motions, horizontal motions, and vorticity strengths of both vortices as well as the shortest distance between both vortices depend on the aforementioned factors and the interactions of some factors. It can be concluded that propeller pitch angle mainly affects the behaviors of the vortices as much as angle of attack to the extent that their second order terms take place in some of the regression models.

Mass deformed world-sheet action of semi local vortices

Energy Technology Data Exchange (ETDEWEB)

Jiang, Yunguo [School of Space Science and Physics, Shandong University at Weihai,264209 Weihai (China); Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment,264209 Weihai (China)

2014-02-10

The mass deformed effective world-sheet theory of semi local vortices was constructed via the field theoretical method. By Euler-Lagrangian equations, the Ansatze for both the gauge field and the adjoint scalar were solved, this ensures that zero modes of vortices are minimal excitations of the system. Up to the 1/g{sup 2} order, all profiles are solved. The mass deformed effective action was obtained by integrating out the transverse plane of the vortex string. The effective theory interpolates between the local vortex and the lump. Respecting certain normalization conditions, the effective theory shows a Seiberg-like duality, which agrees with the result of the Kähler quotient construction.

Vortices and gate-tunable bound states in a topological insulator coupled to superconducting leads

Science.gov (United States)

Finck, Aaron; Kurter, C.; Hor, Y. S.; van Harlingen, D. J.

2014-03-01

It has been predicted that zero energy Majorana bound states can be found in the core of vortices within topological superconductors. Here, we report on Andreev spectroscopy measurements of the topological insulator Bi2Se3 with a normal metal lead and one or more niobium leads. The niobium induces superconductivity in the Bi2Se3 through the proximity effect, leading to both signatures of Andreev reflection and a prominent re-entrant resistance effect. When a large magnetic field is applied perpendicular to the surface of the Bi2Se3, we observe multiple abrupt changes in the subgap conductance that are accompanied by sharp peaks in the dynamical resistance. These peaks are very sensitive to changes in magnetic field and disappear at temperatures associated with the critical temperature of the induced superconductivity. The appearance of the transitions and peaks can be tuned by a top gate. At high magnetic fields, we also find evidence of gate-tunable states, which can lead to stable zero-bias conductance peaks. We interpret our results in terms of a transition occurring within the proximity effect region of the topological insulator, likely due to the formation of vortices. We acknowledge support from Microsoft Project Q.

Vortical flows in technical applications

OpenAIRE

Krause, Egon; Krause, Egon

2006-01-01

Two examples of flows dominated by vortical structures are discussed: In the first interaction and decay of vortex structures in in-cylinder flows of automotive engines are described. Numerical studies revealed clearly identifiable vortex rings, generated during the intake stroke. The influence of compressibility on the vortex formation was studied by using Mach-Zehnder interferometry in a specially designed test stand of a towed one-cylinder engine, and with numerical solutions of the Navier...

Jovian Vortices and Barges: HST observations 1994-1998

Science.gov (United States)

Morales, R.; Sanchez-Lavega, A.; Lecacheux, J.; Colas, F.; Miyazaki, I.

2000-10-01

We have used the HST-WFPC2 archived images of Jupiter in the period 1994-1998 to study the zonal and meridional distributions, long-term motions, lifetimes, interactions and other properties of the vortices larger than 2 degrees. The latitude range covered spans from +75 to -75 degrees. High-resolution images obtained with the 890nm, 410nm and 953nm wavelength filters allowed us to make a morphological classification based on their appearance in each filter. The vortices are anticyclones, and their long-term motions have been completed with ground-based images and are compared to the mean Jovian zonal wind profile. Significant differences are found between the vortex velocities and the mean zonal winds. Some vortices exhibited important drift changes in short period times. We analyze a possible correlation between their size and zonal wind velocity. On the other hand, the "barges" lie in the cyclone domains of the wind-profile and have been identified in several latitudes. Their latitudinal size is similar in all of them (typically 1.6 degrees) but their longitudinal size ranges from 1 to 32 degrees. We discuss the temporal evolution of some of these cyclonic regions. The Spanish team was supported by Gobierno Vasco PI 034/97. The French team was supported by the "Programme National de Planetologie." RM acknowledges a fellowship from Universidad Pais Vasco.

Unfolding of Vortices into Topological Stripes in a Multiferroic Material

Science.gov (United States)

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.

Competitive Stem Cell Recruitment by Multiple Cytotactic Cues

Science.gov (United States)

Mendelson, Avital; Cheung, Yukkee; Paluch, Kamila; Chen, Mo; Kong, Kimi; Tan, Jiali; Dong, Ziming; Sia, Samuel K.; Mao, Jeremy J.

2014-01-01

A multitude of cytotactic cues direct cell migration in development, cancer metastasis and wound healing. However, our understanding of cell motility remains fragmented partially because current migration devices only allow the study of independent factors. We developed a cell motility assay that allows competitive recruitment of a given cell population simultaneously by gradients of multiple cytotactic cues, observable under real-time imaging. Well-defined uniform gradients of cytotactic cues can be independently generated and sustained in each channel. As a case study, bone marrow mesenchymal stem/stromal cells (MSCs) were exposed to 15 cytokines that are commonly present in arthritis. Cytokines that induced robust recruitment of MSCs in multiple groups were selected to ‘compete’ in a final round to yield the most chemotactic factor(s) based on cell migration numbers, distances, migration indices and motility over time. The potency of a given cytokine in competition frequently differed from its individual action, substantiating the need to test multiple cytokines concurrently due to synergistic or antagonistic effects. This new device has the rare capacity to screen molecules that induce cell migration in cancer therapy, drug development and tissue regeneration. PMID:23364311

Vortices in the SU(N) x SU(N) spin systems in two dimensions

International Nuclear Information System (INIS)

Kares, R.J.D.

1982-01-01

The SU(N) x SU(N) or chiral spin systems in two dimensions with spin variables in both the fundamental and the adjoint representations of SU(N) are considered. In the adjoint representation the chiral models are found to possess topologically stable, classical vortex solutions which carry a Z(N) topological charge. A relationship is established between the chiral models and massive Yang-Mills theory in two dimensions. This relationship is exploited to prove the asymptotic freedom of the chiral models and to find their weak coupling mass gap. The connection between the vortices of the chiral models and those of the massive Yang-Mills theory is discussed. The behavior of a gas of vortices in the SU(2) chiral model is considered. This gas is converted to an equivalent field theory and studied using the renormalization group. It is shown that the SU(2) vortex gas does not undergo a Kosterlitz-Thouless phase transition. This behavior probably persists for the higher SU(N) groups as well. Finally, using the massive Yang-Mills theory the effect of the coupling of vortices to spin wave fluctuations is investigated. It is argued that as a result of the vortex-spin wave interaction the vortices acquire a mass scale dynamically. A self consistency condition is derived for the vortex scale and used to compute the mass gap for the chiral models in the presence of vortices. The mass gap obtained in this way is found to be in agreement with the weak coupling result suggesting that vortices may be responsible for generating the mass gap in the chiral models near T = 0

Further determination of the characteristics of magnetospheric plasma vortices with Isee 1 and 2

International Nuclear Information System (INIS)

Hones, E.W. Jr.; Birn, J.; Bame, S.J.; Asbridge, J.R.; Paschmann, G.; Sckopke, N.; Haerendel, G.

1981-01-01

Further studies of the vortices in magnetospheric plasma flow with the Los Alamos Scientific Laboratory/Max-Planck-Institut (LASL/MPI) fast plasma experiment on Isee 1 and 2 have revealed that the pattern of vortical flow has a wavelength of approx.20-40 R/sub E/ and moves tailward through the magnetosphere at speed of several hundred kilometers per second. The tendency toward vorticity pervades the total breadth of the plasma sheet tailward of the dawn-dusk meridian. The sense of rotation of the plasma flow (as viewed from above the ecliptic plane) is clockwise in the morningside of the plasma sheet and counterclockwise in the eveningside. The sense of rotation in the morning and evening boundary layers is reversed from that in the contiguous regions of the plasma sheet. The occurrence of vortical flow is independent of the level of geomagnetic activity but is associated with long-period geomagnetic pulsations. We believe that the source of the vortical motion is a Kelvin-Helmholtz instability of the plasma boundary layer's inner surface (i.e., the interface between the plasma sheet and the boundary layer) that has recently been proposed by Sonnerup [1980

Three-dimensional instability analysis of boundary layers perturbed by streamwise vortices

Science.gov (United States)

Martín, Juan A.; Paredes, Pedro

2017-12-01

A parametric study is presented for the incompressible, zero-pressure-gradient flat-plate boundary layer perturbed by streamwise vortices. The vortices are placed near the leading edge and model the vortices induced by miniature vortex generators (MVGs), which consist in a spanwise-periodic array of small winglet pairs. The introduction of MVGs has been experimentally proved to be a successful passive flow control strategy for delaying laminar-turbulent transition caused by Tollmien-Schlichting (TS) waves. The counter-rotating vortex pairs induce non-modal, transient growth that leads to a streaky boundary layer flow. The initial intensity of the vortices and their wall-normal distances to the plate wall are varied with the aim of finding the most effective location for streak generation and the effect on the instability characteristics of the perturbed flow. The study includes the solution of the three-dimensional, stationary, streaky boundary layer flows by using the boundary region equations, and the three-dimensional instability analysis of the resulting basic flows by using the plane-marching parabolized stability equations. Depending on the initial circulation and positioning of the vortices, planar TS waves are stabilized by the presence of the streaks, resulting in a reduction in the region of instability and shrink of the neutral stability curve. For a fixed maximum streak amplitude below the threshold for secondary instability (SI), the most effective wall-normal distance for the formation of the streaks is found to also offer the most stabilization of TS waves. By setting a maximum streak amplitude above the threshold for SI, sinuous shear layer modes become unstable, as well as another instability mode that is amplified in a narrow region near the vortex inlet position.

A study of vorticity formation in high energy nuclear collisions

Energy Technology Data Exchange (ETDEWEB)

Becattini, F. [Universita di Firenze, Dipartimento di Fisica e Astronomia, Sesto F.no (Firenze) (Italy); INFN, Sezione di Firenze, Sesto F.no (Firenze) (Italy); Inghirami, G. [Universita di Firenze, Dipartimento di Fisica e Astronomia, Sesto F.no (Firenze) (Italy); Johann Wolfgang Goethe University, Frankfurt Institute for Advanced Studies (FIAS), Frankfurt am Main (Germany); Rolando, V.; Pagliara, G. [Universita di Ferrara, Dipartimento di Fisica e Scienze della Terra, Ferrara (Italy); INFN, Sezione di Ferrara, Ferrara (Italy); Beraudo, A.; De Pace, A.; Nardi, M. [INFN, Sezione di Torino, Turin (Italy); Del Zanna, L. [Universita di Firenze, Dipartimento di Fisica e Astronomia, Sesto F.no (Firenze) (Italy); INFN, Sezione di Firenze, Sesto F.no (Firenze) (Italy); INAF, Osservatorio Astrofisico di Arcetri, Florence (Italy); Chandra, V. [Indian Institute of Technology Gandhinagar, Ahmedabad, Gujrat (India)

2015-09-15

We present a quantitative study of vorticity formation in peripheral ultrarelativistic heavy-ion collisions at √(s{sub NN}) = 200 GeV by using the ECHO-QGP numerical code, implementing relativistic dissipative hydrodynamics in the causal Israel-Stewart framework in 3 + 1 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 b = 11.6 fm and with the Bjorken flow profile for a viscous Quark Gluon Plasma with η/s = 0.1 fixed, a vorticity of the order of some 10{sup -2} c/fm can develop at freeze-out. The ensuing polarization of Λ 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. (orig.)

Stationary drift-Rossby vortices in shear flows

International Nuclear Information System (INIS)

Horihata, Satoshi; Irie, Haruyuki; Sato, Masatomo

1990-01-01

Starting from Hasegawa-Mima equation with the generalized vorticity q which describes both electrostatic drift waves in plasmas and Rossby waves in the atmosphere of rotating planets, the stationary solutions of this equation in the (x, y) plane were considered assuming that the equilibrium density no depends on x and the electron temperature T 0 is constant. The arbitrary function F(φ) yielded from integration of transformed Hasegawa-Mima equation was taken either linear or nonlinear in φ, where φ is the stream function. When F is linear, vortex solutions were obtained by dividing the entire plane into internal and external regions by a closed boundary curve. Imposing the boundary conditions at the boundary curve, the constants in the solutions φ ex and φ in were determined. 4 examples are figured. When F is nonlinear, isolated (localized) vortex was considered. Deriving the equation to determine F, the equation for ψ, the internal vortical motion beyond the boundary was given. 2 examples are shown. (M.T.)

Abe homotopy classification of topological excitations under the topological influence of vortices

International Nuclear Information System (INIS)

Kobayashi, Shingo; Kobayashi, Michikazu; Kawaguchi, Yuki; Nitta, Muneto; Ueda, Masahito

2012-01-01

Topological excitations are usually classified by the nth homotopy group π n . However, for topological excitations that coexist with vortices, there are cases in which an element of π n cannot properly describe the charge of a topological excitation due to the influence of the vortices. This is because an element of π n corresponding to the charge of a topological excitation may change when the topological excitation circumnavigates a vortex. This phenomenon is referred to as the action of π 1 on π n . In this paper, we show that topological excitations coexisting with vortices are classified by the Abe homotopy group κ n . The nth Abe homotopy group κ n is defined as a semi-direct product of π 1 and π n . In this framework, the action of π 1 on π n is understood as originating from noncommutativity between π 1 and π n . We show that a physical charge of a topological excitation can be described in terms of the conjugacy class of the Abe homotopy group. Moreover, the Abe homotopy group naturally describes vortex-pair creation and annihilation processes, which also influence topological excitations. We calculate the influence of vortices on topological excitations for the case in which the order parameter manifold is S n /K, where S n is an n-dimensional sphere and K is a discrete subgroup of SO(n+1). We show that the influence of vortices on a topological excitation exists only if n is even and K includes a nontrivial element of O(n)/SO(n).

Streamwise counter-rotating vortices generated by triangular leading edge pattern in flat plate boundary layer

KAUST Repository

Hasheminejad, S. M.

2016-01-05

A series of flow visualizations were conducted to qualitatively study the development of streamwise counter-rotating vortices over a flat plate induced by triangular patterns at the leading edge of a flat plate. The experiments were carried out for a Reynolds number based on the pattern wavelength (λ) of 3080. The results depict the onset, development and breakdown of the vortical structures within the flat plate boundary layer. Moreover, the effect of one spanwise array of holes with diameter of 0.2λ (=3 mm) was examined. This investigation was done on two different flat plates with holes placed at the location x/λ = 2 downstream of the troughs and peaks. The presence of holes after troughs does not show any significant effect on the vortical structures. However, the plate with holes after peaks noticeably delays the vortex breakdown. In this case, the “mushroom-like” vortices move away from the wall and propagate downstream with stable vortical structures. The vortex growth is halted further downstream but start to tilt aside.

Automated platform for designing multiple robot work cells

Science.gov (United States)

Osman, N. S.; Rahman, M. A. A.; Rahman, A. A. Abdul; Kamsani, S. H.; Bali Mohamad, B. M.; Mohamad, E.; Zaini, Z. A.; Rahman, M. F. Ab; Mohamad Hatta, M. N. H.

2017-06-01

Designing the multiple robot work cells is very knowledge-intensive, intricate, and time-consuming process. This paper elaborates the development process of a computer-aided design program for generating the multiple robot work cells which offer a user-friendly interface. The primary purpose of this work is to provide a fast and easy platform for less cost and human involvement with minimum trial and errors adjustments. The automated platform is constructed based on the variant-shaped configuration concept with its mathematical model. A robot work cell layout, system components, and construction procedure of the automated platform are discussed in this paper where integration of these items will be able to automatically provide the optimum robot work cell design according to the information set by the user. This system is implemented on top of CATIA V5 software and utilises its Part Design, Assembly Design, and Macro tool. The current outcomes of this work provide a basis for future investigation in developing a flexible configuration system for the multiple robot work cells.

Grid refinement model in lattice Boltzmann method for stream function-vorticity formulations

Energy Technology Data Exchange (ETDEWEB)

Shin, Myung Seob [Dept. of Mechanical Engineering, Dongyang Mirae University, Seoul (Korea, Republic of)

2015-03-15

In this study, we present a grid refinement model in the lattice Boltzmann method (LBM) for two-dimensional incompressible fluid flow. That is, the model combines the desirable features of the lattice Boltzmann method and stream function-vorticity formulations. In order to obtain an accurate result, very fine grid (or lattice) is required near the solid boundary. Therefore, the grid refinement model is used in the lattice Boltzmann method for stream function-vorticity formulation. This approach is more efficient in that it can obtain the same accurate solution as that in single-block approach even if few lattices are used for computation. In order to validate the grid refinement approach for the stream function-vorticity formulation, the numerical simulations of lid-driven cavity flows were performed and good results were obtained.

Geostrophic tripolar vortices in a two-layer fluid: Linear stability and nonlinear evolution of equilibria

Science.gov (United States)

Reinaud, J. N.; Sokolovskiy, M. A.; Carton, X.

2017-03-01

We investigate equilibrium solutions for tripolar vortices in a two-layer quasi-geostrophic flow. Two of the vortices are like-signed and lie in one layer. An opposite-signed vortex lies in the other layer. The families of equilibria can be spanned by the distance (called separation) between the two like-signed vortices. Two equilibrium configurations are possible when the opposite-signed vortex lies between the two other vortices. In the first configuration (called ordinary roundabout), the opposite signed vortex is equidistant to the two other vortices. In the second configuration (eccentric roundabouts), the distances are unequal. We determine the equilibria numerically and describe their characteristics for various internal deformation radii. The two branches of equilibria can co-exist and intersect for small deformation radii. Then, the eccentric roundabouts are stable while unstable ordinary roundabouts can be found. Indeed, ordinary roundabouts exist at smaller separations than eccentric roundabouts do, thus inducing stronger vortex interactions. However, for larger deformation radii, eccentric roundabouts can also be unstable. Then, the two branches of equilibria do not cross. The branch of eccentric roundabouts only exists for large separations. Near the end of the branch of eccentric roundabouts (at the smallest separation), one of the like-signed vortices exhibits a sharp inner corner where instabilities can be triggered. Finally, we investigate the nonlinear evolution of a few selected cases of tripoles.

Statistical mechanics and correlation properties of a rotating two-dimensional flow of like-sign vortices

International Nuclear Information System (INIS)

Viecelli, J.A.

1993-01-01

The Hamiltonian flow of a set of point vortices of like sign and strength has a low-temperature phase consisting of a rotating triangular lattice of vortices, and a normal temperature turbulent phase consisting of random clusters of vorticity that orbit about a common center along random tracks. The mean-field flow in the normal temperature phase has similarities with turbulent quasi-two-dimensional rotating laboratory and geophysical flows, whereas the low-temperature phase displays effects associated with quantum fluids. In the normal temperature phase the vortices follow power-law clustering distributions, while in the time domain random interval modulation of the vortex orbit radii fluctuations produces singular fractional exponent power-law low-frequency spectra corresponding to time autocorrelation functions with fractional exponent power-law tails. Enhanced diffusion is present in the turbulent state, whereas in the solid-body rotation state vortices thermally diffuse across the lattice. Over the entire temperature range the interaction energy of a single vortex in the field of the rest of the vortices follows positive temperature Fermi--Dirac statistics, with the zero temperature limit corresponding to the rotating crystal phase, and the infinite temperature limit corresponding to a Maxwellian distribution. Analyses of weather records dependent on the large-scale quasi-two-dimensional atmospheric circulation suggest the presence of singular fractional exponent power-law spectra and fractional exponent power-law autocorrelation tails, consistent with the theory

Reconstruction of propagating Kelvin-Helmholtz vortices at Mercury's magnetopause

Science.gov (United States)

Sundberg, Torbjörn; Boardsen, Scott A.; Slavin, James A.; Blomberg, Lars G.; Cumnock, Judy A.; Solomon, Sean C.; Anderson, Brian J.; Korth, Haje

2011-12-01

A series of quasi-periodic magnetopause crossings were recorded by the MESSENGER spacecraft during its third flyby of Mercury on 29 September 2009, likely caused by a train of propagating Kelvin-Helmholtz (KH) vortices. We here revisit the observations to study the internal structure of the waves. Exploiting MESSENGER's rapid traversal of the magnetopause, we show that the observations permit a reconstruction of the structure of a rolled-up KH vortex directly from the spacecraft's magnetic field measurements. The derived geometry is consistent with all large-scale fluctuations in the magnetic field data, establishes the non-linear nature of the waves, and shows their vortex-like structure. In several of the wave passages, a reduction in magnetic field strength is observed in the middle of the wave, which is characteristic of rolled-up vortices and is related to the increase in magnetic pressure required to balance the centrifugal force on the plasma in the outer regions of a vortex, previously reported in computer simulations. As the KH wave starts to roll up, the reconstructed geometry suggests that the vortices develop two gradual transition regions in the magnetic field, possibly related to the mixing of magnetosheath and magnetospheric plasma, situated at the leading edges from the perspectives of both the magnetosphere and the magnetosheath.

Cell-based therapeutic strategies for multiple sclerosis

DEFF Research Database (Denmark)

Scolding, Neil J; Pasquini, Marcelo; Reingold, Stephen C

2017-01-01

and none directly promotes repair. Cell-based therapies, including immunoablation followed by autologous haematopoietic stem cell transplantation, mesenchymal and related stem cell transplantation, pharmacologic manipulation of endogenous stem cells to enhance their reparative capabilities......, and transplantation of oligodendrocyte progenitor cells, have generated substantial interest as novel therapeutic strategies for immune modulation, neuroprotection, or repair of the damaged central nervous system in multiple sclerosis. Each approach has potential advantages but also safety concerns and unresolved...

Stationary Size Distributions of Growing Cells with Binary and Multiple Cell Division

Science.gov (United States)

Rading, M. M.; Engel, T. A.; Lipowsky, R.; Valleriani, A.

2011-10-01

Populations of unicellular organisms that grow under constant environmental conditions are considered theoretically. The size distribution of these cells is calculated analytically, both for the usual process of binary division, in which one mother cell produces always two daughter cells, and for the more complex process of multiple division, in which one mother cell can produce 2 n daughter cells with n=1,2,3,… . The latter mode of division is inspired by the unicellular algae Chlamydomonas reinhardtii. The uniform response of the whole population to different environmental conditions is encoded in the individual rates of growth and division of the cells. The analytical treatment of the problem is based on size-dependent rules for cell growth and stochastic transition processes for cell division. The comparison between binary and multiple division shows that these different division processes lead to qualitatively different results for the size distribution and the population growth rates.

The influence of streamwise vortices on turbulent heat transfer in rectangular ducts with various aspect ratios

International Nuclear Information System (INIS)

Choi, Hang Seok; Park, Tae Seon

2013-01-01

Highlights: ► With changing aspect ratio, the effect of secondary flows on the turbulent heat transfer is scrutinized by a LES. ► The conditional sampling technique of instantaneous near-wall streamwise vortices is developed. ► Clockwise and counter-clockwise rotating streamwise vortices are sampled and discussed with the wall heat transfer. ► The hot-sweep motions of CW and CCW vortices clearly appear with increasing aspect ratio. -- Abstract: The effect of aspect ratio of rectangular duct on the turbulent flow and heat transfer is very important for its engineering applications. But the turbulent thermal fields have not been fundamentally scrutinized in spite of its engineering significance especially for cooling device. Hence, in the present study, large eddy simulation is applied to the turbulent flow and heat transfer in rectangular ducts with varying aspect ratio. The turbulent statistics of the flow and thermal quantities are calculated and the characteristics of wall Nusselt number are investigated for each rectangular duct. Especially, to scrutinize near-wall streamwise vortices, a conditional sampling technique is developed and adopted. Clockwise and counter-clockwise rotating streamwise vortices are sampled and the probability density function of the vortex circulation Reynolds number and wall Nusselt number are calculated. From the results, the time-averaged secondary flow caused by instantaneous vortical motions has a great effect on the heat and momentum transport of the flow in the rectangular ducts. Hence, the wall Nusselt number is enhanced near the downwash flow region of the secondary flow. However, with increasing the aspect ratio, the effects of the hot-sweep flow of the clockwise and counter-clockwise rotating vortices become equally dominant near the wall normal bisector of the ducts. During time averaging process, these two counter-rotating vortices are canceled out each other diminishing a secondary flow but they still enhance the

Microalga propels along vorticity direction in a shear flow

Science.gov (United States)

Chengala, Anwar; Hondzo, Miki; Sheng, Jian

2013-05-01

Using high-speed digital holographic microscopy and microfluidics, we discover that, when encountering fluid flow shear above a threshold, unicellular green alga Dunaliella primolecta migrates unambiguously in the cross-stream direction that is normal to the plane of shear and coincides with the local fluid flow vorticity. The flow shear drives motile microalgae to collectively migrate in a thin two-dimensional horizontal plane and consequently alters the spatial distribution of microalgal cells within a given suspension. This shear-induced algal migration differs substantially from periodic rotational motion of passive ellipsoids, known as Jeffery orbits, as well as gyrotaxis by bottom-heavy swimming microalgae in a shear flow due to the subtle interplay between torques generated by gravity and viscous shear. Our findings could facilitate mechanistic solutions for modeling planktonic thin layers and sustainable cultivation of microalgae for human nutrition and bioenergy feedstock.

Electromagnetic field enhancement and spectrum shaping through plasmonically integrated optical vortices.

Science.gov (United States)

Ahn, Wonmi; Boriskina, Svetlana V; Hong, Yan; Reinhard, Björn M

2012-01-11

We introduce a new design approach for surface-enhanced Raman spectroscopy (SERS) substrates that is based on molding the optical powerflow through a sequence of coupled nanoscale optical vortices "pinned" to rationally designed plasmonic nanostructures, referred to as Vortex Nanogear Transmissions (VNTs). We fabricated VNTs composed of Au nanodiscs by electron beam lithography on quartz substrates and characterized their near- and far-field responses through combination of computational electromagnetism, and elastic and inelastic scattering spectroscopy. Pronounced dips in the far-field scattering spectra of VNTs provide experimental evidence for an efficient light trapping and circulation within the nanostructures. Furthermore, we demonstrate that VNT integration into periodic arrays of Au nanoparticles facilitates the generation of high E-field enhancements in the VNTs at multiple defined wavelengths. We show that spectrum shaping in nested VNT structures is achieved through an electromagnetic feed-mechanism driven by the coherent multiple scattering in the plasmonic arrays and that this process can be rationally controlled by tuning the array period. The ability to generate high E-field enhancements at predefined locations and frequencies makes nested VNTs interesting substrates for challenging SERS applications. © 2011 American Chemical Society

Complex 3D Vortex Lattice Formation by Phase-Engineered Multiple Beam Interference

Directory of Open Access Journals (Sweden)

Jolly Xavier

2012-01-01

Full Text Available We present the computational results on the formation of diverse complex 3D vortex lattices by a designed superposition of multiple plane waves. Special combinations of multiples of three noncoplanar plane waves with a designed relative phase shift between one another are perturbed by a nonsingular beam to generate various complex 3D vortex lattice structures. The formation of complex gyrating lattice structures carrying designed vortices by means of relatively phase-engineered plane waves is also computationally investigated. The generated structures are configured with both periodic as well as transversely quasicrystallographic basis, while these whirling complex lattices possess a long-range order of designed symmetry in a given plane. Various computational analytical tools are used to verify the presence of engineered geometry of vortices in these complex 3D vortex lattices.

Making sound vortices by metasurfaces

Energy Technology Data Exchange (ETDEWEB)

Ye, Liping; Qiu, Chunyin, E-mail: cyqiu@whu.edu.cn; Lu, Jiuyang; Tang, Kun; Ke, Manzhu; Peng, Shasha [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Jia, Han [State Key Laboratory of Acoustics and Key Laboratory of Noise and Vibration Research, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China); Liu, Zhengyou [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Institute for Advanced Studies, Wuhan University, Wuhan 430072 (China)

2016-08-15

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.

RELATIONSHIPS BETWEEN FLUID VORTICITY, KINETIC HELICITY, AND MAGNETIC FIELD ON SMALL-SCALES (QUIET-NETWORK) ON THE SUN

Energy Technology Data Exchange (ETDEWEB)

Sangeetha, C. R.; Rajaguru, S. P., E-mail: crsangeetha@iiap.res.in [Indian Institute of Astrophysics, Bangalore-34 (India)

2016-06-20

We derive horizontal fluid motions on the solar surface over large areas covering the quiet-Sun magnetic network from local correlation tracking of convective granules imaged in continuum intensity and Doppler velocity by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory . From these we calculate the horizontal divergence, the vertical component of vorticity, and the kinetic helicity of fluid motions. We study the correlations between fluid divergence and vorticity, and between vorticity (kinetic helicity) and the magnetic field. We find that the vorticity (kinetic helicity) around small-scale fields exhibits a hemispherical pattern (in sign) similar to that followed by the magnetic helicity of large-scale active regions (containing sunspots). We identify this pattern to be a result of the Coriolis force acting on supergranular-scale flows (both the outflows and inflows), consistent with earlier studies using local helioseismology. Furthermore, we show that the magnetic fields cause transfer of vorticity from supergranular inflow regions to outflow regions, and that they tend to suppress the vortical motions around them when magnetic flux densities exceed about 300 G (from HMI). We also show that such an action of the magnetic fields leads to marked changes in the correlations between fluid divergence and vorticity. These results are speculated to be of importance to local dynamo action (if present) and to the dynamical evolution of magnetic helicity at the small-scale.

The essential role of t cells in multiple sclerosis: A reappraisal

Directory of Open Access Journals (Sweden)

Cris S Constantinescu

2014-04-01

Full Text Available Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system in which destruction of myelin and nerve axons has been shown to be mediated by immune mechanisms. Although the focus of research has been traditionally on T cells as key mediators of the immunopathology, more recent efforts at understanding this complex disorder have been directed increasingly at other cellular and humoral elements of the immune response. This review is a reappraisal of the crucial role of T cells, in particular the CD4+ helper T-cell subset, in multiple sclerosis. Recent evidence is discussed underlining the predominant contribution of T-cell-associated genes to the genome-wide association study results of multiple sclerosis susceptibility, the loss of T-cell quiescence in the conversion from clinically isolated syndrome to clinically definite multiple sclerosis, and the fact that T cells represent the main target of effective immunomodulatory and immunosuppressive treatments in multiple sclerosis.

Self-similar motion of three point vortices

DEFF Research Database (Denmark)

Aref, Hassan

2010-01-01

One of the counter-intuitive results in the three-vortex problem is that the vortices can converge on and meet at a point in a finite time for certain sets of vortex circulations and for certain initial conditions. This result was already included in Groumlbli's thesis of 1877 and has since been ...

Dynamics of vortices in complex wakes: Modeling, analysis, and experiments

Science.gov (United States)

Basu, Saikat

The thesis develops singly-periodic mathematical models for complex laminar wakes which are formed behind vortex-shedding bluff bodies. These wake structures exhibit a variety of patterns as the bodies oscillate or are in close proximity of one another. The most well-known formation comprises two counter-rotating vortices in each shedding cycle and is popularly known as the von Karman vortex street. Of the more complex configurations, as a specific example, this thesis investigates one of the most commonly occurring wake arrangements, which consists of two pairs of vortices in each shedding period. The paired vortices are, in general, counter-rotating and belong to a more general definition of the 2P mode, which involves periodic release of four vortices into the flow. The 2P arrangement can, primarily, be sub-classed into two types: one with a symmetric orientation of the two vortex pairs about the streamwise direction in a periodic domain and the other in which the two vortex pairs per period are placed in a staggered geometry about the wake centerline. The thesis explores the governing dynamics of such wakes and characterizes the corresponding relative vortex motion. In general, for both the symmetric as well as the staggered four vortex periodic arrangements, the thesis develops two-dimensional potential flow models (consisting of an integrable Hamiltonian system of point vortices) that consider spatially periodic arrays of four vortices with their strengths being +/-Gamma1 and +/-Gamma2. Vortex formations observed in the experiments inspire the assumed spatial symmetry. The models demonstrate a number of dynamic modes that are classified using a bifurcation analysis of the phase space topology, consisting of level curves of the Hamiltonian. Despite the vortex strengths in each pair being unequal in magnitude, some initial conditions lead to relative equilibrium when the vortex configuration moves with invariant size and shape. The scaled comparisons of the

Experimental study of coherence vortices: Local properties of phase singularities in a spatial coherence function

DEFF Research Database (Denmark)

Wang, W.; Duan, Z.H.; Hanson, Steen Grüner

2006-01-01

By controlling the irradiance of an extended quasimonochromatic, spatially incoherent source, an optical field is generated that exhibits spatial coherence with phase singularities, called coherence vortices. A simple optical geometry for direct visualization of coherence vortices is proposed, an...

Involvement of multiple cell lineages in atherogenesis | Ogeng'o ...

African Journals Online (AJOL)

Involvement of multiple cell lineages in atherogenesis. ... mast cells, dendritic cells, macrophages and immigrant cells usually found in blood, namely ... which influence inflammation, migration, proliferation and secretory activity of each other in ...

Vitality of optical vortices (Presentation)

CSIR Research Space (South Africa)

Roux, FS

2014-02-01

Full Text Available stream_source_info Roux3_2014.pdf.txt stream_content_type text/plain stream_size 3018 Content-Encoding UTF-8 stream_name Roux3_2014.pdf.txt Content-Type text/plain; charset=UTF-8 Title Vitality of optical vortices F Stef... Roux Presented at Complex Light and Optical Force VIII SPIE Photonics West 2014 Moscone Center, San Francisco, California USA 5 February 2014 CSIR National Laser Centre, Pretoria, South Africa – p. 1/11 Speckle Amplitude Phase – p. 2/11 Vortex...

Vortices on the string and superstring world sheets

International Nuclear Information System (INIS)

Abrikosov, A.A.; Kogan, Ya.I.

1989-01-01

The world-sheet dynamics of the first quantized string propagating in non-simply connected space is considered. Presence of the vortices on the world sheet lead to Berezinsky-Kosterlitz-Thouless(BKT) phase transition. Bosonic and superstring cases are discussed. 20 refs.; 2 figs

Hydrodynamic response of fuel rod with longitudinal fins to upstream generated vortices

International Nuclear Information System (INIS)

Naot, D.; Oron, A.; Technion-Israel Inst. of Tech., Haifa. Dept. of Mechanical Engineering)

1984-01-01

The hydrodynamic response of turbulent channel flow to upstream generated vortices was numerically simulated for fuel element with longitudinal cooling fins. Turbulence is modelled by an algebraic stress model and an energy-dissipation model. The developing flow is solved using a parabolic pressure correction algorithm. The decay of the initial vortices in non-circular sub-channel in the presence of geometry driven secondary currents is described and the uncertainty in the local turbulent shear stresses is discussed. (orig.)

ARE PROTOPLANETARY DISKS BORN WITH VORTICES? ROSSBY WAVE INSTABILITY DRIVEN BY PROTOSTELLAR INFALL

Energy Technology Data Exchange (ETDEWEB)

Bae, Jaehan; Hartmann, Lee [Deptartment of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109 (United States); Zhu, Zhaohuan, E-mail: jaehbae@umich.edu, E-mail: lhartm@umich.edu, E-mail: zhuzh@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Peyton Hall, Princeton, NJ 08544 (United States)

2015-05-20

We carry out two-fluid, two-dimensional global hydrodynamic simulations to test whether protostellar infall can trigger the Rossby wave instability (RWI) in protoplanetry disks. Our results show that infall can trigger the RWI and generate vortices near the outer edge of the mass landing on the disk (i.e., centrifugal radius). We find that the RWI is triggered under a variety of conditions, although the details depend on the disk parameters and the infall pattern. The common key feature of triggering the RWI is the steep radial gradient of the azimuthal velocity induced by the local increase in density at the outer edge of the infall region. Vortices form when the instability enters the nonlinear regime. In our standard model where self-gravity is neglected, vortices merge together to a single vortex within ∼20 local orbital times, and the merged vortex survives for the remaining duration of the calculation (>170 local orbital times). The vortex takes part in outward angular momentum transport, with a Reynolds stress of ≲10{sup −2}. Our two-fluid calculations show that vortices efficiently trap dust particles with stopping times of the order of the orbital time, locally enhancing the dust to gas ratio for particles of the appropriate size by a factor of ∼40 in our standard model. When self-gravity is considered, however, vortices tend to be impeded from merging and may eventually dissipate. We conclude it may well be that protoplanetary disks have favorable conditions for vortex formation during the protostellar infall phase, which might enhance early planetary core formation.

ARE PROTOPLANETARY DISKS BORN WITH VORTICES? ROSSBY WAVE INSTABILITY DRIVEN BY PROTOSTELLAR INFALL

International Nuclear Information System (INIS)

Bae, Jaehan; Hartmann, Lee; Zhu, Zhaohuan

2015-01-01

We carry out two-fluid, two-dimensional global hydrodynamic simulations to test whether protostellar infall can trigger the Rossby wave instability (RWI) in protoplanetry disks. Our results show that infall can trigger the RWI and generate vortices near the outer edge of the mass landing on the disk (i.e., centrifugal radius). We find that the RWI is triggered under a variety of conditions, although the details depend on the disk parameters and the infall pattern. The common key feature of triggering the RWI is the steep radial gradient of the azimuthal velocity induced by the local increase in density at the outer edge of the infall region. Vortices form when the instability enters the nonlinear regime. In our standard model where self-gravity is neglected, vortices merge together to a single vortex within ∼20 local orbital times, and the merged vortex survives for the remaining duration of the calculation (>170 local orbital times). The vortex takes part in outward angular momentum transport, with a Reynolds stress of ≲10 −2 . Our two-fluid calculations show that vortices efficiently trap dust particles with stopping times of the order of the orbital time, locally enhancing the dust to gas ratio for particles of the appropriate size by a factor of ∼40 in our standard model. When self-gravity is considered, however, vortices tend to be impeded from merging and may eventually dissipate. We conclude it may well be that protoplanetary disks have favorable conditions for vortex formation during the protostellar infall phase, which might enhance early planetary core formation

VISUALIZATION METHODS OF VORTICAL FLOWS IN COMPUTATIONAL FLUID DYNAMICS AND THEIR APPLICATIONS

Directory of Open Access Journals (Sweden)

K. N. Volkov

2014-05-01

Full Text Available The paper deals with conceptions and methods for visual representation of research numerical results in the problems of fluid mechanics and gas. The three-dimensional nature of unsteady flow being simulated creates significant difficulties for the visual representation of results. It complicates control and understanding of numerical data, and exchange and processing of obtained information about the flow field. Approaches to vortical flows visualization with the usage of gradients of primary and secondary scalar and vector fields are discussed. An overview of visualization techniques for vortical flows using different definitions of the vortex and its identification criteria is given. Visualization examples for some solutions of gas dynamics problems related to calculations of jets and cavity flows are presented. Ideas of the vortical structure of the free non-isothermal jet and the formation of coherent vortex structures in the mixing layer are developed. Analysis of formation patterns for spatial flows inside large-scale vortical structures within the enclosed space of the cubic lid-driven cavity is performed. The singular points of the vortex flow in a cubic lid-driven cavity are found based on the results of numerical simulation; their type and location are identified depending on the Reynolds number. Calculations are performed with fine meshes and modern approaches to the simulation of vortical flows (direct numerical simulation and large-eddy simulation. Paradigm of graphical programming and COVISE virtual environment are used for the visual representation of computational results. Application that implements the visualization of the problem is represented as a network which links are modules and each of them is designed to solve a case-specific problem. Interaction between modules is carried out by the input and output ports (data receipt and data transfer giving the possibility to use various input and output devices.

Multiple giant cell lesions in a patient with Noonan syndrome with multiple lentigines

NARCIS (Netherlands)

van den Berg, Henk; Schreuder, Willem Hans; Jongmans, Marjolijn; van Bommel-Slee, Danielle; Witsenburg, Bart; de Lange, Jan

2016-01-01

A patient with Noonan syndrome with multiple lentigines (NSML) and multiple giant cell lesions (MGCL) in mandibles and maxillae is described. A mutation p.Thr468Met in the PTPN11-gene was found. This is the second reported NSML patient with MGCL. Our case adds to the assumption that, despite a

Magnus force on quantum Hall skyrmions and vortices

International Nuclear Information System (INIS)

Dhar, S.; Basu, B.; Bandyopadhyay, P.

2003-01-01

We have discussed here the Magnus force acting on the vortices and skyrmions in the quantum Hall systems. We have found that it is generated by the chirality of the system which is associated with the Berry phase and is same for both the cases

Toroidal vortices in resistive magnetohydrodynamic equilibria

International Nuclear Information System (INIS)

Montgomery, D.; Bates, J.W.; Li, S.

1997-01-01

When a time-independent electric current flows toroidally in a uniform ring of electrically conducting fluid, a Lorentz force results, jxB, where j is the local electric current density, and B is the magnetic field it generates. Because of purely geometric effects, the curl of jxB is nonvanishing, and so jxB cannot be balanced by the gradient of any scalar pressure. Taking the curl of the fluid close-quote s equation of motion shows that the net effect of the jxB force is to generate toroidal vorticity. Allowed steady states necessarily contain toroidal vortices, with flows in the poloidal directions. The flow pattern is a characteristic open-quotes double smoke ringclose quotes configuration. The effect seems quite general, although it is analytically simple only in special limits. One limit described here is that of high viscosity (low Reynolds number), with stress-free wall boundary conditions on the velocity field, although it is apparent that similar mechanical motions will result for no-slip boundaries and higher Reynolds numbers. A rather ubiquitous connection between current-carrying toroids and vortex rings seems to be implied, one that disappears in the open-quotes straight cylinderclose quotes limit. copyright 1997 American Institute of Physics

Spatially resolved vertical vorticity in solar supergranulation using helioseismology and local correlation tracking

Science.gov (United States)

Langfellner, J.; Gizon, L.; Birch, A. C.

2015-09-01

Flow vorticity is a fundamental property of turbulent convection in rotating systems. Solar supergranules exhibit a preferred sense of rotation, which depends on the hemisphere. This is due to the Coriolis force acting on the diverging horizontal flows. We aim to spatially resolve the vertical flow vorticity of the average supergranule at different latitudes, both for outflow and inflow regions. To measure the vertical vorticity, we use two independent techniques: time-distance helioseismology (TD) and local correlation tracking of granules in intensity images (LCT) using data from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Both maps are corrected for center-to-limb systematic errors. We find that 8 h TD and LCT maps of vertical vorticity are highly correlated at large spatial scales. Associated with the average supergranule outflow, we find tangential (vortical) flows that reach about 10 m s-1 in the clockwise direction at 40° latitude. In average inflow regions, the tangential flow reaches the same magnitude, but in the anticlockwise direction. These tangential velocities are much smaller than the radial (diverging) flow component (300 m s-1 for the average outflow and 200 m s-1 for the average inflow). The results for TD and LCT as measured from HMI are in excellent agreement for latitudes between -60° and 60°. From HMI LCT, we measure the vorticity peak of the average supergranule to have a full width at half maximum of about 13 Mm for outflows and 8 Mm for inflows. This is larger than the spatial resolution of the LCT measurements (about 3 Mm). On the other hand, the vorticity peak in outflows is about half the value measured at inflows (e.g., 4 × 10-6 s-1 clockwise compared to 8 × 10-6 s-1 anticlockwise at 40° latitude). Results from the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) obtained in 2010 are biased compared to the HMI/SDO results for the same period

Interaction of superconducting vortices: lectures presented at the Canadian Mathematical Society Summer Research Institute on gauge theories

International Nuclear Information System (INIS)

Rebbi, C.

1979-09-01

Results recently obtained on multi-vortex configurations are described. After a brief review of the model, a numerical analysis, performed by variational methods, of the interaction between two vortices is illustrated. The study, done in collaboration with Laurence Jacobs, shows that two vortices attract or repel each other according to whether a dimensionless coupling constant lambda, characterizing the relative strength of the matter self-coupling versus the gauge coupling, takes a value smaller or greater than one. This agrees with results previously obtained for asymptotic separations of the vortices. For lambda = 1, in particular, the vortices appear in equilibrium at any separation, hinting to the existence of a much wider class of solutions to the field equations. In the second lecture, the case lambda = 1 is considered in detail, illustrating analytical results which demonstrate that for this special value of the coupling constant solutions with any number of vortices at arbitrary positions do indeed exist

Dynamics of vortices in planar and tubular microstructured superconductors

International Nuclear Information System (INIS)

Fomin, V. M.

2011-01-01

Full text: Nucleation and denucleation of vortices as well as their guided motion between antidots are key issues to design methods for controlling the vortex manipulation in micro patterned thin films and self-assembled micro tubes. The vortex dynamics in micro structured superconductors is modelled using an adaptive numerical approach on the basis of the time dependent Ginzburg-Landau equations. Evolution of the order parameter and the current density is analyzed for superconducting YBCO films with different patterns of antidots. The resulting picture of the accumulated vortex trajectories clearly reveals a guided motion between the antidots. Dynamics of correlated vortices in superconductor tubes in a magnetic field, which is perpendicular to their axes, is governed by the curvature. I acknowledge fruitful collaboration with R. Woerdenweber and O. G. Schmidt. (author)

Numerical solutions of the linearized Euler equations for unsteady vortical flows around lifting airfoils

Science.gov (United States)

Scott, James R.; Atassi, Hafiz M.

1990-01-01

A linearized unsteady aerodynamic analysis is presented for unsteady, subsonic vortical flows around lifting airfoils. The analysis fully accounts for the distortion effects of the nonuniform mean flow on the imposed vortical disturbances. A frequency domain numerical scheme which implements this linearized approach is described, and numerical results are presented for a large variety of flow configurations. The results demonstrate the effects of airfoil thickness, angle of attack, camber, and Mach number on the unsteady lift and moment of airfoils subjected to periodic vortical gusts. The results show that mean flow distortion can have a very strong effect on the airfoil unsteady response, and that the effect depends strongly upon the reduced frequency, Mach number, and gust wave numbers.

Theoretical confirmation of Feynman's hypothesis on the creation of circular vortices in Bose-Einstein condensates: II

Energy Technology Data Exchange (ETDEWEB)

Senatorski, A; Infeld, E [Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw (Poland)

2004-09-15

In a recent paper (Infeld and Senatorski 2003 J. Phys.: Condens. Matter 15 5865) we confirmed Feynman's hypothesis on how circular vortices can be created from an oppositely polarized linear pair in a Bose-Einstein condensate. This was done by perturbing the original pair numerically, so that a circular vortex (or array of identical circular vortices) was created as a result of reconnection. These circular vortices were then checked against known theoretical relations binding velocities and radii. Agreement to a high degree of accuracy was found. Here in part II, we give examples of the creation of several different vortices from one linear pair. All are checked as above. We also confirm the limit of separation of the line vortices below which mutual attraction, followed by annihilation, prevents the Feynman metamorphosis. Other possible modes of behaviour are illustrated.

A synergetic treatment of the vortices behaviour of a plasma with viscosity

International Nuclear Information System (INIS)

Vo Hong Anh; Nguyen Tien Dung.

1992-09-01

The known system of nonlinear partial differential equations (PDE) describing vortical motions of an ideal electron-ion plasma with viscosity in the presence of a slightly inhomogeneous magnetic field is reduced to a Lorentz type system of 3 ordinary differential equations (ODE) the numerical solution of which with a set of a values for real plasma physical parameters shows the occurrence of a state with strange attractors that means the beginning of the vortices formation as an essential nonlinearity effect. (author)

Nonlinear effects in low-dimensional magnetism: Solitons and vortices

International Nuclear Information System (INIS)

Bishop, A.R.; Kawabata, C.; Mertens, F.G.; Wysin, G.M.

1987-07-01

The report outlines recent results on the dynamics of easy-plane classical ferromagnetic spin in two spatial dimensions emphasising possible signatures of unbound vortices above the Kosterlitz-Thouless topological phase transition. 18 refs, 1 fig

EFT for Vortices with Dilaton-dependent Localized Flux

CERN Document Server

Burgess, C P; Williams, M

2015-01-01

We study how codimension-two objects like vortices back-react gravitationally with their environment in theories (such as 4D or higher-dimensional supergravity) where the bulk is described by a dilaton-Maxwell-Einstein system. We do so both in the full theory, for which the vortex is an explicit classical `fat brane' solution, and in the effective theory of `point branes' appropriate when the vortices are much smaller than the scales of interest for their back-reaction (such as the transverse Kaluza-Klein scale). We extend the standard Nambu-Goto description to include the physics of flux-localization wherein the ambient flux of the external Maxwell field becomes partially localized to the vortex, generalizing the results of a companion paper to include dilaton-dependence for the tension and localized flux. In the effective theory, such flux-localization is described by the next-to-leading effective interaction, and the boundary conditions to which it gives rise are known to play an important role in how (and...

Trichoepithelioma And Multiple Basal Cell Epithelioma

Directory of Open Access Journals (Sweden)

Dey S.K

1996-01-01

Full Text Available A combination of multiple trichoepithelioma and basal cell epithelioma is reported. Although malignant degeneration of trichoepithelioma is debated, clinical and histopathological studies, in our case, hint at that. The case is reported for its rarity.

Thermal chiral vortical and magnetic waves: New excitation modes in chiral fluids

Energy Technology Data Exchange (ETDEWEB)

Kalaydzhyan, Tigran, E-mail: tigran@caltech.edu [Department of Physics, University of Illinois, 845 W Taylor Street, Chicago, IL 60607 (United States); Jet Propulsion Laboratory, 4800 Oak Grove Dr, M/S 298, Pasadena, CA 91109 (United States); Murchikova, Elena [TAPIR, California Institute of Technology, MC 350-17, Pasadena, CA 91125 (United States)

2017-06-15

In certain circumstances, chiral (parity-violating) medium can be described hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible examples of such systems include strongly coupled quark–gluon plasma, liquid helium {sup 3}He-A, neutron stars and the Early Universe. We study first-order hydrodynamics of a chiral fluid on a vortex background and in an external magnetic field. We show that there are two previously undiscovered modes describing heat waves propagating along the vortex and magnetic field. We call them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also identify known gapless excitations of density (chiral vortical and chiral magnetic waves) and transverse velocity (chiral Alfvén wave). We demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the wave is absent and the excitation reduces to the charge diffusion mode. We also comment on the frame-dependent contributions to the obtained propagation velocities.

On simulation of no-slip condition in the method of discrete vortices

Science.gov (United States)

Shmagunov, O. A.

2017-10-01

When modeling flows of an incompressible fluid, it is convenient sometimes to use the method of discrete vortices (MDV), where the continuous vorticity field is approximated by a set of discrete vortex elements moving in the velocity field. The vortex elements have a clear physical interpretation, they do not require the construction of grids and are automatically adaptive, since they concentrate in the regions of greatest interest and successfully describe the flows of a non-viscous fluid. The possibility of using MDV in simulating flows of a viscous fluid was considered in the previous papers using the examples of flows past bodies with sharp edges with the no-penetration condition at solid boundaries. However, the appearance of vorticity on smooth boundaries requires the no-slip condition to be met when MDV is realized, which substantially complicates the initially simple method. In this connection, an approach is considered that allows solving the problem by simple means.

Thermal chiral vortical and magnetic waves: New excitation modes in chiral fluids

International Nuclear Information System (INIS)

Kalaydzhyan, Tigran; Murchikova, Elena

2017-01-01

In certain circumstances, chiral (parity-violating) medium can be described hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible examples of such systems include strongly coupled quark–gluon plasma, liquid helium "3He-A, neutron stars and the Early Universe. We study first-order hydrodynamics of a chiral fluid on a vortex background and in an external magnetic field. We show that there are two previously undiscovered modes describing heat waves propagating along the vortex and magnetic field. We call them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also identify known gapless excitations of density (chiral vortical and chiral magnetic waves) and transverse velocity (chiral Alfvén wave). We demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the wave is absent and the excitation reduces to the charge diffusion mode. We also comment on the frame-dependent contributions to the obtained propagation velocities.

Thermal chiral vortical and magnetic waves: New excitation modes in chiral fluids

Directory of Open Access Journals (Sweden)

Tigran Kalaydzhyan

2017-06-01

Full Text Available In certain circumstances, chiral (parity-violating medium can be described hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible examples of such systems include strongly coupled quark–gluon plasma, liquid helium 3He-A, neutron stars and the Early Universe. We study first-order hydrodynamics of a chiral fluid on a vortex background and in an external magnetic field. We show that there are two previously undiscovered modes describing heat waves propagating along the vortex and magnetic field. We call them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also identify known gapless excitations of density (chiral vortical and chiral magnetic waves and transverse velocity (chiral Alfvén wave. We demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the wave is absent and the excitation reduces to the charge diffusion mode. We also comment on the frame-dependent contributions to the obtained propagation velocities.

Magnetic Monopoles, Center Vortices and Topology of Gauge Fields

OpenAIRE

Reinhardt, H.; Engelhardt, M.; Langfeld, K.; Quandt, M.; Schafke, A.

1999-01-01

The topological properties of magnetic monopoles and center vortices arising, respectively, in Abelian and center gauges are studied in continuum Yang-Mills Theory. For this purpose the continuum analog of the maximum center gauge is constructed.

Magnetic monopoles, center vortices and topology of gauge fields

International Nuclear Information System (INIS)

Reinhardt, H.; Engelhardt, M.; Langfeld, K.; Quandt, M.; Schaefke, A.

2000-01-01

The topological properties of magnetic monopoles and center vortices arising, respectively, in Abelian and center gauges are studied in continuum Yang-Mills Theory. For this purpose the continuum analog of the maximum center gauge is constructed

Multiple cell CPV nickel-hydrogen battery

Science.gov (United States)

Jones, Ken R.; Zagrodnik, Jeffrey P.

1991-01-01

Johnson Controls, Inc. has developed a multiple cell CPV nickel hydrogen battery that offers significant weight, volume, and cost advantages for aerospace applications. The baseline design was successfully demonstrated through the testing of a 26-cell prototype, which completed over 7000 44 percent depth-of-discharge low earth orbit cycles. Prototype designs using both nominal 5 and 10 inch diameter vessels are currently being developed for a variety of customers and applications.

Control of a three-dimensional turbulent shear layer by means of oblique vortices

Science.gov (United States)

Jürgens, Werner; Kaltenbach, Hans-Jakob

2018-04-01

The effect of local forcing on the separated, three-dimensional shear layer downstream of a backward-facing step is investigated by means of large-eddy simulation for a Reynolds number based on the step height of 10,700. The step edge is either oriented normal to the approaching turbulent boundary layer or swept at an angle of 40°. Oblique vortices with different orientation and spacing are generated by wavelike suction and blowing of fluid through an edge parallel slot. The vortices exhibit a complex three-dimensional structure, but they can be characterized by a wavevector in a horizontal section plane. In order to determine the step-normal component of the wavevector, a method is developed based on phase averages. The dependence of the wavevector on the forcing parameters can be described in terms of a dispersion relation, the structure of which indicates that the disturbances are mainly convected through the fluid. The introduced vortices reduce the size of the recirculation region by up to 38%. In both the planar and the swept case, the most efficient of the studied forcings consists of vortices which propagate in a direction that deviates by more than 50° from the step normal. These vortices exhibit a spacing in the order of 2.5 step heights. The upstream shift of the reattachment line can be explained by increased mixing and momentum transport inside the shear layer which is reflected in high levels of the Reynolds shear stress -ρ \\overline{u'v'}. The position of the maximum of the coherent shear stress is found to depend linearly on the wavelength, similar to two-dimensional free shear layers.

New type of cells with multiple chromosome rearrangements

Energy Technology Data Exchange (ETDEWEB)

Aseeva, Elena A. [National Research Centre for Hematology, Russian Academy of Medical Sciences, Novozykovsky proezd 4a, 125167 Moscow (Russian Federation); Snigiryova, Galina P. [Russian Scientific Centre of Roentgenology and Radiology, ul. Profsoyuznaya 86, 117997 Moscow (Russian Federation); Neverova, Anna L. [National Research Centre for Hematology, Russian Academy of Medical Sciences, Novozykovsky proezd 4a, 125167 Moscow (Russian Federation); Bogomazova, Alexandra N.; Novitskaya, Natalia N.; Khazins, Eva D. [Russian Scientific Centre of Roentgenology and Radiology, ul. Profsoyuznaya 86, 117997 Moscow (Russian Federation); Domracheva, Elena V. [National Research Centre for Hematology, Russian Academy of Medical Sciences, Novozykovsky proezd 4a, 125167 Moscow (Russian Federation)], E-mail: dom@blood.ru

2010-04-15

A comparative analysis of the distribution and the frequency of multiaberrant cells (MAC) among lymphocytes in different categories of low dose (up to 0.5 Gy) irradiated people was carried out. The highest MAC frequency was observed in people exposed to {alpha}-radiation (Pu, Rn) and in cosmonauts. This fact allows MAC to be considered as an indicator of a high-energy local exposure. A new type of cells with multiple chromosome rearrangements was discovered in the course of analysis of stable aberrations by the fluorescence in situ hybridization (FISH) method. The biological consequences of MAC formation and possibility of revealing the whole diversity of cells with multiple aberrations by means of modern molecular-cytogenetic methods are discussed.

Eulerian velocity reconstruction in ideal atmospheric dynamics using potential vorticity and potential temperature

Science.gov (United States)

Blender, R.

2009-04-01

An approach for the reconstruction of atmospheric flow is presented which uses space- and time-dependent fields of density ?, potential vorticity Q and potential temperature Î& cedil;[J. Phys. A, 38, 6419 (2005)]. The method is based on the fundamental equations without approximation. The basic idea is to consider the time-dependent continuity equation as a condition for zero divergence of momentum in four dimensions (time and space, with unit velocity in time). This continuity equation is solved by an ansatz for the four-dimensional momentum using three conserved stream functions, the potential vorticity, potential temperature and a third field, denoted as ?-potential. In zonal flows, the ?-potential identifies the initial longitude of particles, whereas potential vorticity and potential temperature identify mainly meridional and vertical positions. Since the Lagrangian tracers Q, Î&,cedil; and ? determine the Eulerian velocity field, the reconstruction combines the Eulerian and the Lagrangian view of hydrodynamics. In stationary flows, the ?-potential is related to the Bernoulli function. The approach requires that the gradients of the potential vorticity and potential temperature do not vanish when the velocity remains finite. This behavior indicates a possible interrelation with stability conditions. Examples with analytical solutions are presented for a Rossby wave and zonal and rotational shear flows.

Goertler vortices in growing boundary layers: The leading edge receptivity problem, linear growth and the nonlinear breakdown stage

Science.gov (United States)

Hall, Philip

1989-01-01

Goertler vortices are thought to be the cause of transition in many fluid flows of practical importance. A review of the different stages of vortex growth is given. In the linear regime, nonparallel effects completely govern this growth, and parallel flow theories do not capture the essential features of the development of the vortices. A detailed comparison between the parallel and nonparallel theories is given and it is shown that at small vortex wavelengths, the parallel flow theories have some validity; otherwise nonparallel effects are dominant. New results for the receptivity problem for Goertler vortices are given; in particular vortices induced by free stream perturbations impinging on the leading edge of the walls are considered. It is found that the most dangerous mode of this type can be isolated and it's neutral curve is determined. This curve agrees very closely with the available experimental data. A discussion of the different regimes of growth of nonlinear vortices is also given. Again it is shown that, unless the vortex wavelength is small, nonparallel effects are dominant. Some new results for nonlinear vortices of 0(1) wavelengths are given and compared to experimental observations.

Aircraft Wake Vortices: An Annotated Bibliography (1923-1990)

Science.gov (United States)

1991-01-01

leading-edge vortex when set at incidence. The engine noise was simulated by a Hartmann whistle mounted above the engine intake. The results are...Tilmann, P., "PROPAGATION OF SOUND RADIATION THROUGH VORTICES: A CONTRIBUTION TO THE THEORY OF FLOW MEASUREMENT WITH ULTRASOUND ," Report 6/1972, 1972, Max

Topologically Allowed Nonsixfold Vortices in a Sixfold Multiferroic Material: Observation and Classification

KAUST Repository

Cheng, Shaobo

2017-04-06

We report structural transformation of sixfold vortex domains into two-, four-, and eightfold vortices via a different type of topological defect in hexagonal manganites. Combining high-resolution electron microscopy and Landau-theory-based numerical simulations, we investigate the remarkable atomic arrangement and the intertwined relationship between the vortex structures and the topological defects. The roles of their displacement field, formation temperature, and nucleation sites are revealed. All conceivable vortices in the system are topologically classified using homotopy group theory, and their origins are identified.

Green's function-stochastic methods framework for probing nonlinear evolution problems: Burger's equation, the nonlinear Schroedinger's equation, and hydrodynamic organization of near-molecular-scale vorticity

International Nuclear Information System (INIS)

Keanini, R.G.

2011-01-01

Research highlights: → Systematic approach for physically probing nonlinear and random evolution problems. → Evolution of vortex sheets corresponds to evolution of an Ornstein-Uhlenbeck process. → Organization of near-molecular scale vorticity mediated by hydrodynamic modes. → Framework allows calculation of vorticity evolution within random strain fields. - Abstract: A framework which combines Green's function (GF) methods and techniques from the theory of stochastic processes is proposed for tackling nonlinear evolution problems. The framework, established by a series of easy-to-derive equivalences between Green's function and stochastic representative solutions of linear drift-diffusion problems, provides a flexible structure within which nonlinear evolution problems can be analyzed and physically probed. As a preliminary test bed, two canonical, nonlinear evolution problems - Burgers' equation and the nonlinear Schroedinger's equation - are first treated. In the first case, the framework provides a rigorous, probabilistic derivation of the well known Cole-Hopf ansatz. Likewise, in the second, the machinery allows systematic recovery of a known soliton solution. The framework is then applied to a fairly extensive exploration of physical features underlying evolution of randomly stretched and advected Burger's vortex sheets. Here, the governing vorticity equation corresponds to the Fokker-Planck equation of an Ornstein-Uhlenbeck process, a correspondence that motivates an investigation of sub-sheet vorticity evolution and organization. Under the assumption that weak hydrodynamic fluctuations organize disordered, near-molecular-scale, sub-sheet vorticity, it is shown that these modes consist of two weakly damped counter-propagating cross-sheet acoustic modes, a diffusive cross-sheet shear mode, and a diffusive cross-sheet entropy mode. Once a consistent picture of in-sheet vorticity evolution is established, a number of analytical results, describing the

Piecewise Potential Vorticity Inversion for Intense Extratropical Cyclones

Science.gov (United States)

Seiler, C.; Zwiers, F. W.

2017-12-01

Global climate models (GCMs) tend to simulate too few intense extratropical cyclones (ETCs) in the Northern Hemisphere (NH) under historic climate conditions. This bias may arise from the interactions of multiple drivers, including surface temperature gradients, latent heating in the lower troposphere, and the upper-level jet stream. Previous attempts to quantify the importance of these drivers include idealized model experiments or statistical approaches. The first method however cannot easily be implemented for a multi-GCM ensemble, and the second approach does not disentangle the interactions among drivers, nor does it prove causality. An alternative method that overcomes these limitations is piecewise potential vorticity inversion (PPVI). PPVI derives the wind and geopotential height fields by inverting potential vorticity (PV) for discrete atmospheric levels. Despite being a powerful diagnostic tool, PPVI has primarily been used to study the dynamics of individual events only. This study presents the first PPVI climatology for the 5% most intense NH ETCs that occurred from 1980 to 2016. Conducting PPVI to 3273 ETC tracks identified in ERA-Interim reanalysis, we quantified the contributions from 3 atmospheric layers to ETC intensity. The respective layers are the surface (1000 hPa), a lower atmospheric level (700-850 hPa) and an upper atmospheric level (100-500 hPa) that are associated with the contributions from surface temperature gradients, latent heating, and the jet stream, respectively. Results show that contributions are dominated by the lower level (40%), followed by the upper level (20%) and the surface (17%), while the remaining 23% are associated with the background flow. Contributions from the surface and the lower level are stronger in the western ocean basins owed to the presence of the warm ocean currents, while contributions from the upper level are stronger in the eastern basins. Vertical cross sections of ETC-centered composites show an

Interlayer vortices and edge dislocations in high-temperature superconductors

International Nuclear Information System (INIS)

Kuklov, A.B.; Krakovsky, A.; Birman, J.L.

1995-01-01

The interaction of an edge dislocation made of half the superconducting plane with a magnetic interlayer vortex is considered within the framework of the Lawrence-Doniach model with negative as well as positive Josephson interlayer coupling. In the first case the binding energy of the vortex and the dislocation has been calculated by employing a variational procedure. The current distribution around the bound vortex turns out to be asymmetric. In the second case the dislocation carries a spontaneous magnetic half vortex, whose binding energy with the dislocation turns out to be infinite. The half-vortex energy has been calculated by the same variational procedure. Implications of the possible presence of such half vortices for the properties of high-temperature sueprconductors are discussed. We suggest employing artificially made superconductor-ferromagnet superlattices with the half plane removed to observe fractional vortices

Generation of optical vortices with an adaptive helical mirror.

Science.gov (United States)

Ghai, Devinder Pal

2011-04-01

Generation of optical vortices using a new design of adaptive helical mirror (AHM) is reported. The new AHM is a reflective device that can generate an optical vortex of any desired topological charge, both positive and negative, within its breakdown limits. The most fascinating feature of the AHM is that the topological charge of the optical vortex generated with it can be changed in real time by varying the excitation voltage. Generation of optical vortices up to topological charge 4 has been demonstrated. The presence of a vortex in the optical field generated with the AHM is confirmed by producing both fork and spiral fringes in an interferometric setup. Various design improvements to further enhance the performance of the reported AHM are discussed. Some of the important applications of AHM are also listed. © 2011 Optical Society of America

The supernova-regulated ISM. III. Generation of vorticity, helicity, and mean flows

Science.gov (United States)

Käpylä, M. J.; Gent, F. A.; Väisälä, M. S.; Sarson, G. R.

2018-03-01

Context. The forcing of interstellar turbulence, driven mainly by supernova (SN) explosions, is irrotational in nature, but the development of significant amounts of vorticity and helicity, accompanied by large-scale dynamo action, has been reported. Aim. Several earlier investigations examined vorticity production in simpler systems; here all the relevant processes can be considered simultaneously. We also investigate the mechanisms for the generation of net helicity and large-scale flow in the system. Methods: We use a three-dimensional, stratified, rotating and shearing local simulation domain of the size 1 × 1 × 2 kpc3, forced with SN explosions occurring at a rate typical of the solar neighbourhood in the Milky Way. In addition to the nominal simulation run with realistic Milky Way parameters, we vary the rotation and shear rates, but keep the absolute value of their ratio fixed. Reversing the sign of shear vs. rotation allows us to separate the rotation- and shear-generated contributions. Results: As in earlier studies, we find the generation of significant amounts of vorticity, the rotational flow comprising on average 65% of the total flow. The vorticity production can be related to the baroclinicity of the flow, especially in the regions of hot, dilute clustered supernova bubbles. In these regions, the vortex stretching acts as a sink of vorticity. In denser, compressed regions, the vortex stretching amplifies vorticity, but remains sub-dominant to baroclinicity. The net helicities produced by rotation and shear are of opposite signs for physically motivated rotation laws, with the solar neighbourhood parameters resulting in the near cancellation of the total net helicity. We also find the excitation of oscillatory mean flows, the strength and oscillation period of which depend on the Coriolis and shear parameters; we interpret these as signatures of the anisotropic-kinetic-α (AKA) effect. We use the method of moments to fit for the turbulent transport

Analysis of optical vortices with suppressed sidelobes using modified Bessel-like function and trapezoid annulus modulation structures.

Science.gov (United States)

Guo, Jian; Wei, Zhongchao; Liu, Yuebo; Huang, Aili

2015-02-01

Two amplitude modulation methods, including modified Bessel-like function modulation structure and trapezoid annulus structure, for suppressing sidelobes of optical vortices are studied. In the former approach, we propose that the order of the Bessel-like function can be an additional parameter to modulate diffraction patterns of optical vortices motivated by the idea of conventional annulus structures. Furthermore, new Bessel-like modulation functions are introduced to solve the problem of low diffraction efficiency of the original one. Trapezoid annulus structure is proposed as a compromise structure between the modified Bessel-like modulation structure and the conventional annulus one, and has advantages of both. It is demonstrated that these two approaches can achieve high-quality optical vortices with suppressed sidelobes effectively, and the relative structures behave as more flexible and applicable structures for producing optical vortices with large coverage of topological charges, which suggests great potential in simplifying the structure designing procedure. These reliable and generalized structures for generating high-quality optical vortices will help to promote the development of future optical communication and optical manipulation significantly.

Dopamine, T cells and multiple sclerosis (MS).

Science.gov (United States)

Levite, Mia; Marino, Franca; Cosentino, Marco

2017-05-01

Dopamine is a key neurotransmitter that induces critical effects in the nervous system and in many peripheral organs, via 5 dopamine receptors (DRs): D1R-D5R. Dopamine also induces many direct and very potent effects on many DR-expressing immune cells, primarily T cells and dendritic cells. In this review, we focus only on dopamine receptors, effects and production in T cells. Dopamine by itself (at an optimal concentration of~0.1 nM) induces multiple function of resting normal human T cells, among them: T cell adhesion, chemotactic migration, homing, cytokine secretion and others. Interestingly, dopamine activates resting effector T cells (Teffs), but suppresses regulatory T cells (Tregs), and both effects lead eventually to Teff activation. Dopamine-induced effects on T cells are dynamic, context-sensitive and determined by the: T cell activation state, T cell type, DR type, and dopamine concentration. Dopamine itself, and also few dopaminergic molecules/ drugs that are in clinical use for cardiac, neurological and other non-immune indications, have direct effects on human T cells (summarized in this review). These dopaminergic drugs include: dopamine = intropin, L-DOPA, bromocriptine, pramipexole, pergolide, haloperidol, pimozide, and amantadine. Other dopaminergic drugs were not yet tested for their direct effects on T cells. Extensive evidence in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) show dopaminergic dysregulations in T cells in these diseases: D1-like DRs are decreased in Teffs of MS patients, and dopamine does not affect these cells. In contrast, D1-like DRs are increased in Tregs of MS patients, possibly causing functional Treg impairment in MS. Treatment of MS patients with interferon β (IFN-β) increases D1-like DRs and decreases D2-like DRs in Teffs, decreases D1-like DRs in Tregs, and most important: restores responsiveness of patient's Teffs to dopamine. DR agonists and antagonists confer some benefits in

Interaction of vortices with ultrasound and the acoustic Faraday effect in type-II superconductors

International Nuclear Information System (INIS)

Dominguez, D.; Bulaevskii, L.; Ivlev, B.; Maley, M.; Bishop, A.R.

1996-01-01

We study the interaction of sound waves with vortices in type-II superconductors, taking into account pinning and electrodynamic forces between vortices and crystal displacements. We propose ultrasound techniques as a method for obtaining information about vortex dynamics. This is particularly appropiate at low temperatures where transport measurements are ineffective. The changes in sound velocity and attenuation due to vortices, can provide information on the elastic constants of the vortex system and on vortex dissipation, respectively. At low temperatures the Magnus force acting on vortices leads to the acoustic Faraday effect: there is a rotation of the polarization plane of tranverse sound waves propagating along the magnetic field. This effect is linear in the Magnus force and magnetic field in crystals with equivalent a and b axes for a field parallel to the c axis. We discuss how this effect can be measured by means of either pulse-echo techniques or standing sound waves. Also, we show that an ac electromagnetic field acting on the vortex system can generate ultrasound. We calculate the amplitude of the generated sound waves in the linear regime and compare with recent experiments. copyright 1996 The American Physical Society

Spatial and Time Dynamics of Non-Linear Vortices in Plasma Lens for High-Current Ion Beam Focusing

Science.gov (United States)

Goncharov, Alexei A.; Maslov, Vasyl I.; Onishchenko, Ivan N.; Tretyakov, Vitalij N.

2002-11-01

It is known from numerical simulation (see, for example, [1]) and from experiments (see, for example, [2]), that an electron density bunches as discrete vortices are long - living structures in vacuum. However, in laboratory experiments [2] it has been shown that the vortices are changed faster, when they are submersed in electrons, distributed around them. The charged plasma lens intended for a focussing of high-current ion beams, has the same crossed configuration of a radial electrical and longitudinal magnetic field [3], as only electron plasma. In this lens the vortical turbulence is excited [3]. The vortex - bunch and vortex - hole are rotated in the inverse directions in system of their rest. The instability development in initially homogeneous plasma causes that the vortices are excited by pairs. Namely, if the vortex - bunch of electrons is generated, near the vortex - hole of electrons is also generated. It is shown, that in nonuniform plasma the vortices behave is various in time. Namely, the vortex - bunch goes to area of larger electron density, and the vortex - hole goes to area of smaller electron density. The speed of the vortex - hole is less than speed of the vortex - bunch. It is shown, that the electron vortices, generated in the plasma lens, can result in to formation of spiral distribution of electron density. The physical mechanism of coalescence of electron vortices - bunches is proposed. 1.Driscoll C.F. et al. Plasma Phys. Contr. Fus. Res. 3 (1989) 507. 2.Kiwamoto Y. et al. Non-neutral plasma physics. Princeton. 1999. P. 99-105. 3.Goncharov A. et al. Plasma Phys. Rep. 20 (1994) 499.

Separation vortices and pattern formation

DEFF Research Database (Denmark)

Andersen, Anders Peter; Bohr, Tomas; Schnipper, Teis

2010-01-01

In this paper examples are given of the importance of flow separation for fluid patterns at moderate Reynolds numbers—both in the stationary and in the time-dependent domain. In the case of circular hydraulic jumps, it has been shown recently that it is possible to generalise the Prandtl–Kármán–P...... results for the vortex patterns behind a flapping foil in a flowing soap film, which shows the interaction and competition between the vortices shed from the round leading edge (like the von Kármán vortex street) and those created at the sharp trailing edge....

Numerical and Experimental Study of Electromagnetically Driven Vortical Flows

NARCIS (Netherlands)

Kenjeres, S.; Verdoold, J.; Tummers, M.J.; Hanjalic, K.; Kleijn, C.R.

2009-01-01

The paper reports on numerical and experimental investigations of electromagnetically driven vortical flows of an electrically conductive fluid in a generic setup. Two different configurations of permanent magnets are considered: a 3-magnet configuration in which the resulting Lorentz force is

Close pairs of relative equilibria for identical point vortices

DEFF Research Database (Denmark)

Dirksen, Tobias; Aref, Hassan

2011-01-01

Numerical solution of the classical problem of relative equilibria for identical point vortices on the unbounded plane reveals configurations that are very close to the analytically known, centered, symmetrically arranged, nested equilateral triangles. New numerical solutions of this kind are fou...

Problems of simulation of large, long-lived vortices in the atmospheres of the giant planets (jupiter, saturn, neptune)

Science.gov (United States)

Nezlin, Michael V.; Sutyrin, Georgi G.

1994-01-01

Large, long-lived vortices are abundant in the atmospheres of the giant planets. Some of them survive a few orders of magnitude longer than the dispersive linear Rossby wave packets, e.g. the Great Red Spot (GRS), Little Red Spot (LRS) and White Ovals (WO) of Jupiter, Big Bertha, Brown Spot and Anne's Spot of Saturn, the Great Dark Spot (GDS) of Neptune, etc. Nonlinear effects which prevent their dispersion spreading are the main subject of our consideration. Particular emphasis is placed on determining the dynamical processes which may explain the remarkable properties of observed vortices such as anticyclonic rotation in preference to cyclonic one and the uniqueness of the GRS, the largest coherent vortex, along the perimeter of Jupiter at corresponding latitude. We review recent experimental and theoretical studies of steadily translating solitary Rossby vortices (anticyclones) in a rotating shallow fluid. Two-dimensional monopolar solitary vortices trap fluid which is transported westward. These dualistic structures appear to be vortices, on the one hand, and solitary “waves”, on the other hand. Owing to the presence of the trapped fluid, such solitary structures collide inelastically and have a memory of the initial disturbance which is responsible for the formation of the structure. As a consequence, they have no definite relationship between the amplitude and characteristic size. Their vortical properties are connected with geostrophic advection of local vorticity. Their solitary properties (nonspreading and stationary translation) are due to a balance between Rossby wave dispersion and nonlinear effects which allow the anticyclones, with an elevation of a free surface, to propagate faster than the linear waves, without a resonance with linear waves, i.e. without wave radiation. On the other hand, cyclones, with a depression of a free surface, are dispersive and nonstationary features. This asymmetry in dispersion-nonlinear properties of cyclones and

Field-Free Nucleation of Antivortices and Giant Vortices in Nonsuperconducting Materials

Science.gov (United States)

Amundsen, Morten; Ouassou, Jabir Ali; Linder, Jacob

2018-05-01

Giant vortices with higher phase winding than 2 π are usually energetically unfavorable, but geometric symmetry constraints on a superconductor in a magnetic field are known to stabilize such objects. Here, we show via microscopic calculations that giant vortices can appear in intrinsically nonsuperconducting materials, even without any applied magnetic field. The enabling mechanism is the proximity effect to a host superconductor where a current flows, and we also demonstrate that antivortices can appear in this setup. Our results open the possibility to study electrically controllable topological defects in unusual environments, which do not have to be exposed to magnetic fields or intrinsically superconducting, but instead display other types of order.

Relativistic quantum vorticity of the quadratic form of the Dirac equation

International Nuclear Information System (INIS)

Asenjo, Felipe A; Mahajan, Swadesh M

2015-01-01

We explore the fluid version of the quadratic form of the Dirac equation, sometimes called the Feynman–Gell-Mann equation. The dynamics of the quantum spinor field is represented by equations of motion for the fluid density, the velocity field, and the spin field. In analogy with classical relativistic and non-relativistic quantum theories, the fully relativistic fluid formulation of this equation allows a vortex dynamics. The vortical form is described by a total tensor field that is the weighted combination of the inertial, electromagnetic and quantum forces. The dynamics contrives the quadratic form of the Dirac equation as a total vorticity free system. (paper)

Fractional Josephson vortices at YBa$_2$Cu$_3$O$_{7-x}$ grain boundaries

OpenAIRE

Mints, R. G.; Papiashvili, Ilya

2001-01-01

We report numerical simulations of magnetic flux patterns in asymmetric 45$^{\\circ}$ [001]-tilt grain boundaries in YBa$_2$Cu$_3$O$_{7-x}$ superconducting films. The grain boundaries are treated as Josephson junctions with the critical current density $j_c(x)$ alternating along the junctions. We demonstrate the existence of Josephson vortices with fractional flux quanta for both periodic and random $j_c(x)$. A method is proposed to extract fractional vortices from experimental flux patterns.

Two dimensional electron transport in disordered and ordered distributions of magnetic flux vortices

International Nuclear Information System (INIS)

Nielsen, M.; Hedegaard, P.

1994-04-01

We have considered the conductivity properties of a two dimensional electron gas (2DEG) in two different kinds of inhomogeneous magnetic fields, i.e. a disordered distribution of magnetic flux vortices, and a periodic array of magnetic flux vortices. The work falls in two parts. In the first part we show how the phase shifts for an electron scattering on an isolated vortex, can be calculated analytically, and related to the transport properties through the differential cross section. In the second part we present numerical results for the Hall conductivity of the 2DEG in a periodic array of flux vortices found by exact diagonalization. We find characteristic spikes in the Hall conductance, when it is plotted against the filling fraction. It is argued that the spikes can be interpreted in terms of ''topological charge'' piling up across local and global gaps in the energy spectrum. (au) (23 refs.)

Can symmetry transitions of complex fields enable 3-d control of fluid vorticity?

Energy Technology Data Exchange (ETDEWEB)

Martin, James E. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Solis, Kyle Jameson [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

2015-08-01

Methods of inducing vigorous noncontact fluid flow are important to technologies involving heat and mass transfer and fluid mixing, since they eliminate the need for moving parts, pipes and seals, all of which compromise system reliability. Unfortunately, traditional noncontact flow methods are few, and have limitations of their own. We have discovered two classes of fields that can induce fluid vorticity without requiring either gravity or a thermal gradient. The first class we call Symmetry-Breaking Rational Fields. These are triaxial fields comprised of three orthogonal components, two ac and one dc. The second class is Rational Triad Fields, which differ in that all three components are alternating. In this report we quantify the induced vorticity for a wide variety of fields and consider symmetry transitions between these field types. These transitions give rise to orbiting vorticity vectors, a technology for non-contact, non-stationary fluid mixing.

Numerical simulation using vorticity-vector potential formulation

Science.gov (United States)

Tokunaga, Hiroshi

1993-01-01

An accurate and efficient computational method is needed for three-dimensional incompressible viscous flows in engineering applications. On solving the turbulent shear flows directly or using the subgrid scale model, it is indispensable to resolve the small scale fluid motions as well as the large scale motions. From this point of view, the pseudo-spectral method is used so far as the computational method. However, the finite difference or the finite element methods are widely applied for computing the flow with practical importance since these methods are easily applied to the flows with complex geometric configurations. However, there exist several problems in applying the finite difference method to direct and large eddy simulations. Accuracy is one of most important problems. This point was already addressed by the present author on the direct simulations on the instability of the plane Poiseuille flow and also on the transition to turbulence. In order to obtain high efficiency, the multi-grid Poisson solver is combined with the higher-order, accurate finite difference method. The formulation method is also one of the most important problems in applying the finite difference method to the incompressible turbulent flows. The three-dimensional Navier-Stokes equations have been solved so far in the primitive variables formulation. One of the major difficulties of this method is the rigorous satisfaction of the equation of continuity. In general, the staggered grid is used for the satisfaction of the solenoidal condition for the velocity field at the wall boundary. However, the velocity field satisfies the equation of continuity automatically in the vorticity-vector potential formulation. From this point of view, the vorticity-vector potential method was extended to the generalized coordinate system. In the present article, we adopt the vorticity-vector potential formulation, the generalized coordinate system, and the 4th-order accurate difference method as the

Body-induced vortical flows: a common mechanism for self-corrective trimming control in boxfishes.

Science.gov (United States)

Bartol, Ian K; Gharib, Morteza; Webb, Paul W; Weihs, Daniel; Gordon, Malcolm S

2005-01-01

Boxfishes (Teleostei: Ostraciidae) are marine fishes having rigid carapaces that vary significantly among taxa in their shapes and structural ornamentation. We showed previously that the keels of the carapace of one species of tropical boxfish, the smooth trunkfish, produce leading edge vortices (LEVs) capable of generating self-correcting trimming forces during swimming. In this paper we show that other tropical boxfishes with different carapace shapes have similar capabilities. We conducted a quantitative study of flows around the carapaces of three morphologically distinct boxfishes (spotted boxfish, scrawled cowfish and buffalo trunkfish) using stereolithographic models and three separate but interrelated analytical approaches: digital particle image velocimetry (DPIV), pressure distribution measurements, and force balance measurements. The ventral keels of all three forms produced LEVs that grew in circulation along the bodies, resembling the LEVs produced around delta-winged aircraft. These spiral vortices formed above the keels and increased in circulation as pitch angle became more positive, and formed below the keels and increased in circulation as pitch angle became more negative. Vortices also formed along the eye ridges of all boxfishes. In the spotted boxfish, which is largely trapezoidal in cross section, consistent dorsal vortex growth posterior to the eye ridge was also present. When all three boxfishes were positioned at various yaw angles, regions of strongest concentrated vorticity formed in far-field locations of the carapace compared with near-field areas, and vortex circulation was greatest posterior to the center of mass. In general, regions of localized low pressure correlated well with regions of attached, concentrated vorticity, especially around the ventral keels. Although other features of the carapace also affect flow patterns and pressure distributions in different ways, the integrated effects of the flows were consistent for all forms

Evolution of the vorticity-area density during the formation of coherent structures in two-dimensional flows

NARCIS (Netherlands)

Capel, H.W.; Pasmanter, R.A.

2000-01-01

It is shown: (1) that in two-dimensional, incompressible, viscous flows the vorticity-area distribution evolves according to an advection-diffusion equation with a negative, time dependent diffusion coefficient and (2) how to use the vorticity-stream function relations, i.e., the so-called

Multiple exciton generation in quantum dot-based solar cells

Science.gov (United States)

Goodwin, Heather; Jellicoe, Tom C.; Davis, Nathaniel J. L. K.; Böhm, Marcus L.

2018-01-01

Multiple exciton generation (MEG) in quantum-confined semiconductors is the process by which multiple bound charge-carrier pairs are generated after absorption of a single high-energy photon. Such charge-carrier multiplication effects have been highlighted as particularly beneficial for solar cells where they have the potential to increase the photocurrent significantly. Indeed, recent research efforts have proved that more than one charge-carrier pair per incident solar photon can be extracted in photovoltaic devices incorporating quantum-confined semiconductors. While these proof-of-concept applications underline the potential of MEG in solar cells, the impact of the carrier multiplication effect on the device performance remains rather low. This review covers recent advancements in the understanding and application of MEG as a photocurrent-enhancing mechanism in quantum dot-based photovoltaics.

Robust Prediction of High Lift Using Surface Vorticity, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — FlightStream has been developed a fast, accurate, aerodynamic prediction code based on vorticity computations on the surface of an aircraft. The code, though still a...

The dynamics of magnetic vortices in type II superconductors with pinning sites studied by the time dependent Ginzburg–Landau model

Energy Technology Data Exchange (ETDEWEB)

Sørensen, Mads Peter, E-mail: mpso@dtu.dk [Department of Applied Mathematics and Computer Science, Richard Petersens Plads, Bldg. 324, Technical University of Denmark, Kongens Lyngby DK-2800 (Denmark); Pedersen, Niels Falsig [Department of Applied Mathematics and Computer Science, Richard Petersens Plads, Bldg. 324, Technical University of Denmark, Kongens Lyngby DK-2800 (Denmark); Ögren, Magnus [School of Science and Technology, Örebro University, Örebro SE-70182 (Sweden)

2017-02-15

We investigate the dynamics of magnetic vortices in type II superconductors with normal state pinning sites using the Ginzburg–Landau equations. Simulation results demonstrate hopping of vortices between pinning sites, influenced by external magnetic fields and external currents. The system is highly nonlinear and the vortices show complex nonlinear dynamical behaviour.

STRUCTURES OF TURBULENT VORTICES AND THEIR INFLUENCE ON FLOW PROPERTIES

Directory of Open Access Journals (Sweden)

Alfonsas Rimkus

2015-03-01

Full Text Available In spite of the many investigations that have been conducted on turbulent flows, the generation and development of turbulent vortices has not been investigated sufficiently yet. This prevents to understand well the processes involved in the flow. That is unfavorable for the further investigations. The developing vortex structures are interacting, and this needs to be estimated. Physical summing of velocities, formed by all structures, can be unfavorable for investigations, therefore they must be separated; otherwise bias errors can occur. The difficulty for investigations is that the widely employed Particle Image Velocity (PIV method, when a detailed picture of velocity field picture is necessary, can provide photos covering only a short interval of flow, which can’t include the largest flow structures, i.e. macro whirlpools. Consequently, action of these structures could not be investigated. Therefore, in this study it is tried to obtain the necessary data about the flow structure by analyzing the instantaneous velocity measurements by 3D means, which lasts for several minutes, therefore the existence and interaction of these structures become visible in measurement data. The investigations conducted in this way have been already discussed in the article, published earlier. Mostly the generation and development of bottom vortices was analyzed. In this article, the analysis of these turbulent velocity measurements is continued and the additional data about the structure of turbulent vortices is obtained.

Neutrino induced vorticity, Alfven waves and the normal modes

Energy Technology Data Exchange (ETDEWEB)

Bhatt, Jitesh R. [Theory Division, Physical Research Laboratory, Ahmedabad (India); George, Manu [Theory Division, Physical Research Laboratory, Ahmedabad (India); Indian Institute of Technology, Department of Physics, Ahmedabad (India)

2017-08-15

We consider a plasma consisting of electrons and ions in the presence of a background neutrino gas and develop the magnetohydrodynamic equations for the system. We show that the electron neutrino interaction can induce vorticity in the plasma even in the absence of any electromagnetic perturbations if the background neutrino density is left-right asymmetric. This induced vorticity supports a new kind of Alfven wave whose velocity depends on both the external magnetic field and on the neutrino asymmetry. The normal mode analysis show that in the presence of neutrino background the Alfven waves can have different velocities. We also discuss our results in the context of dense astrophysical plasma such as magnetars and show that the difference in the Alfven velocities can be used to explain the observed pulsar kick. We discuss also the relativistic generalisation of the electron fluid in presence of an asymmetric neutrino background. (orig.)

Novel human multiple myeloma cell line UHKT-893

Czech Academy of Sciences Publication Activity Database

Uherková, L.; Vančurová, I.; Vyhlídalová, I.; Pleschnerová, M.; Špička, I.; Mihalová, R.; Březinová, J.; Hodný, Zdeněk; Čermáková, K.; Polanská, V.; Marinov, I.; Jedelský, P.L.; Kuželová, K.; Stöckbauer, P.

2013-01-01

Roč. 37, č. 3 (2013), s. 320-326 ISSN 0145-2126 Institutional support: RVO:68378050 Keywords : human myeloma cell line * human multiple myeloma * plasma cell * IL-6 dependence * immunoglobulin * free light chain Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.692, year: 2013

Automatic tracking of wake vortices using ground-wind sensor data

Science.gov (United States)

1977-01-03

Algorithms for automatic tracking of wake vortices using ground-wind anemometer : data are developed. Methods of bad-data suppression, track initiation, and : track termination are included. An effective sensor-failure detection-and identification : ...

Estimation of perspective errors in 2D2C-PIV measurements for 3D concentrated vortices

Science.gov (United States)

Ma, Bao-Feng; Jiang, Hong-Gang

2018-06-01

Two-dimensional planar PIV (2D2C) is still extensively employed in flow measurement owing to its availability and reliability, although more advanced PIVs have been developed. It has long been recognized that there exist perspective errors in velocity fields when employing the 2D2C PIV to measure three-dimensional (3D) flows, the magnitude of which depends on out-of-plane velocity and geometric layouts of the PIV. For a variety of vortex flows, however, the results are commonly represented by vorticity fields, instead of velocity fields. The present study indicates that the perspective error in vorticity fields relies on gradients of the out-of-plane velocity along a measurement plane, instead of the out-of-plane velocity itself. More importantly, an estimation approach to the perspective error in 3D vortex measurements was proposed based on a theoretical vortex model and an analysis on physical characteristics of the vortices, in which the gradient of out-of-plane velocity is uniquely determined by the ratio of the maximum out-of-plane velocity to maximum swirling velocity of the vortex; meanwhile, the ratio has upper limits for naturally formed vortices. Therefore, if the ratio is imposed with the upper limits, the perspective error will only rely on the geometric layouts of PIV that are known in practical measurements. Using this approach, the upper limits of perspective errors of a concentrated vortex can be estimated for vorticity and other characteristic quantities of the vortex. In addition, the study indicates that the perspective errors in vortex location, vortex strength, and vortex radius can be all zero for axisymmetric vortices if they are calculated by proper methods. The dynamic mode decomposition on an oscillatory vortex indicates that the perspective errors of each DMD mode are also only dependent on the gradient of out-of-plane velocity if the modes are represented by vorticity.

Blowup with vorticity control for a 2D model of the Boussinesq equations

Science.gov (United States)

Hoang, V.; Orcan-Ekmekci, B.; Radosz, M.; Yang, H.

2018-06-01

We propose a system of equations with nonlocal flux in two space dimensions which is closely modeled after the 2D Boussinesq equations in a hyperbolic flow scenario. Our equations involve a vorticity stretching term and a non-local Biot-Savart law and provide insight into the underlying intrinsic mechanisms of singularity formation. We prove stable, controlled finite time blowup involving upper and lower bounds on the vorticity up to the time of blowup for a wide class of initial data.

Dissecting zero modes and bound states on BPS vortices in Ginzburg-Landau superconductors

Energy Technology Data Exchange (ETDEWEB)

Izquierdo, A. Alonso [Departamento de Matematica Aplicada, Universidad de Salamanca,Facultad de Ciencias Agrarias y Ambientales,Av. Filiberto Villalobos 119, E-37008 Salamanca (Spain); Fuertes, W. Garcia [Departamento de Fisica, Universidad de Oviedo, Facultad de Ciencias,Calle Calvo Sotelo s/n, E-33007 Oviedo (Spain); Guilarte, J. Mateos [Departamento de Fisica Fundamental, Universidad de Salamanca, Facultad de Ciencias,Plaza de la Merced, E-37008 Salamanca (Spain)

2016-05-12

In this paper the zero modes of fluctuation of cylindrically symmetric self-dual vortices are analyzed and described in full detail. These BPS topological defects arise at the critical point between Type II and Type I superconductors, or, equivalently, when the masses of the Higgs particle and the vector boson in the Abelian Higgs model are equal. In addition, novel bound states of Higss and vector bosons trapped by the self-dual vortices at their core are found and investigated.

Twist effects in quantum vortices and phase defects

Science.gov (United States)

Zuccher, Simone; Ricca, Renzo L.

2018-02-01

In this paper we show that twist, defined in terms of rotation of the phase associated with quantum vortices and other physical defects effectively deprived of internal structure, is a property that has observable effects in terms of induced axial flow. For this we consider quantum vortices governed by the Gross-Pitaevskii equation (GPE) and perform a number of test cases to investigate and compare the effects of twist in two different contexts: (i) when this is artificially superimposed on an initially untwisted vortex ring; (ii) when it is naturally produced on the ring by the simultaneous presence of a central straight vortex. In the first case large amplitude perturbations quickly develop, generated by the unnatural setting of the initial condition that is not an analytical solution of the GPE. In the second case much milder perturbations emerge, signature of a genuine physical process. This scenario is confirmed by other test cases performed at higher twist values. Since the second setting corresponds to essential linking, these results provide new evidence of the influence of topology on physics.

New type of cells with multiple chromosome rearrangements

International Nuclear Information System (INIS)

Aseeva, E.A.; Domracheva, E.V.; Neverova, A.L; Bogomazova, A.N.; Snigiryova, G.P.; Novitskaya, N.N.; Khazins, E.D.

2008-01-01

Full text: A comparative analysis of the distribution and the frequency of multiaberrant cells (MAC) among lymphocytes in different categories of low dose (up to 0.5 Gy) irradiated people was carried out. MAC were found in most of the examined groups and they were absent in the control population. A highest MAC frequency was observed in people exposed to alpha radiation (Pu, Ra). This fact allows MAC to be considered as an indicator of a high-energy local exposure. A new type of cells with multiple chromosome rearrangements was discovered in the course of analysis of stable aberrations by the FISH method. The biological consequences of MAC formation and possibility of revealing the whole diversity of cells with multiple aberrations by means of modern molecular-cytogenetic methods is discussed

Natural killer cell lines preferentially kill clonogenic multiple myeloma cells and decrease myeloma engraftment in a bioluminescent xenograft mouse model.

Science.gov (United States)

Swift, Brenna E; Williams, Brent A; Kosaka, Yoko; Wang, Xing-Hua; Medin, Jeffrey A; Viswanathan, Sowmya; Martinez-Lopez, Joaquin; Keating, Armand

2012-07-01

Novel therapies capable of targeting drug resistant clonogenic MM cells are required for more effective treatment of multiple myeloma. This study investigates the cytotoxicity of natural killer cell lines against bulk and clonogenic multiple myeloma and evaluates the tumor burden after NK cell therapy in a bioluminescent xenograft mouse model. The cytotoxicity of natural killer cell lines was evaluated against bulk multiple myeloma cell lines using chromium release and flow cytometry cytotoxicity assays. Selected activating receptors on natural killer cells were blocked to determine their role in multiple myeloma recognition. Growth inhibition of clonogenic multiple myeloma cells was assessed in a methylcellulose clonogenic assay in combination with secondary replating to evaluate the self-renewal of residual progenitors after natural killer cell treatment. A bioluminescent mouse model was developed using the human U266 cell line transduced to express green fluorescent protein and luciferase (U266eGFPluc) to monitor disease progression in vivo and assess bone marrow engraftment after intravenous NK-92 cell therapy. Three multiple myeloma cell lines were sensitive to NK-92 and KHYG-1 cytotoxicity mediated by NKp30, NKp46, NKG2D and DNAM-1 activating receptors. NK-92 and KHYG-1 demonstrated 2- to 3-fold greater inhibition of clonogenic multiple myeloma growth, compared with killing of the bulk tumor population. In addition, the residual colonies after treatment formed significantly fewer colonies compared to the control in a secondary replating for a cumulative clonogenic inhibition of 89-99% at the 20:1 effector to target ratio. Multiple myeloma tumor burden was reduced by NK-92 in a xenograft mouse model as measured by bioluminescence imaging and reduction in bone marrow engraftment of U266eGFPluc cells by flow cytometry. This study demonstrates that NK-92 and KHYG-1 are capable of killing clonogenic and bulk multiple myeloma cells. In addition, multiple myeloma

Self-focusing instability of two-dimensional solitons and vortices

DEFF Research Database (Denmark)

Kuznetsov, E.A.; Juul Rasmussen, J.

1995-01-01

The instability of two-dimensional solitons and vortices is demonstrated in the framework of the three-dimensional nonlinear Schrodinger equation (NLSE). The instability can be regarded as the analog of the Kadomtsev-Petviashvili instability [B. B. Kadomtsev and V. I. Petviashvili, Sov. Phys. Dokl...

Quantification of topological changes of vorticity contours in two-dimensional Navier-Stokes flow.

Science.gov (United States)

Ohkitani, Koji; Al Sulti, Fayeza

2010-06-01

A characterization of reconnection of vorticity contours is made by direct numerical simulations of the two-dimensional Navier-Stokes flow at a relatively low Reynolds number. We identify all the critical points of the vorticity field and classify them by solving an eigenvalue problem of its Hessian matrix on the basis of critical-point theory. The numbers of hyperbolic (saddles) and elliptic (minima and maxima) points are confirmed to satisfy Euler's index theorem numerically. Time evolution of these indices is studied for a simple initial condition. Generally speaking, we have found that the indices are found to decrease in number with time. This result is discussed in connection with related works on streamline topology, in particular, the relationship between stagnation points and the dissipation. Associated elementary procedures in physical space, the merging of vortices, are studied in detail for a number of snapshots. A similar analysis is also done using the stream function.

Mechanism for multiplicity of steady states with distinct cell concentration in continuous culture of mammalian cells.

Science.gov (United States)

Yongky, Andrew; Lee, Jongchan; Le, Tung; Mulukutla, Bhanu Chandra; Daoutidis, Prodromos; Hu, Wei-Shou

2015-07-01

Continuous culture for the production of biopharmaceutical proteins offers the possibility of steady state operations and thus more consistent product quality and increased productivity. Under some conditions, multiplicity of steady states has been observed in continuous cultures of mammalian cells, wherein with the same dilution rate and feed nutrient composition, steady states with very different cell and product concentrations may be reached. At those different steady states, cells may exhibit a high glycolysis flux with high lactate production and low cell concentration, or a low glycolysis flux with low lactate and high cell concentration. These different steady states, with different cell concentration, also have different productivity. Developing a mechanistic understanding of the occurrence of steady state multiplicity and devising a strategy to steer the culture toward the desired steady state is critical. We establish a multi-scale kinetic model that integrates a mechanistic intracellular metabolic model and cell growth model in a continuous bioreactor. We show that steady state multiplicity exists in a range of dilution rate in continuous culture as a result of the bistable behavior in glycolysis. The insights from the model were used to devise strategies to guide the culture to the desired steady state in the multiple steady state region. The model provides a guideline principle in the design of continuous culture processes of mammalian cells. © 2015 Wiley Periodicals, Inc.

Maxwell-Higgs vortices with internal structure

Science.gov (United States)

Bazeia, D.; Marques, M. A.; Menezes, R.

2018-05-01

Vortices are considered in relativistic Maxwell-Higgs systems in interaction with a neutral scalar field. The gauge field interacts with the neutral field via the presence of generalized permeability, and the charged and neutral scalar fields interact in a way dictated by the presence of first order differential equations that solve the equations of motion. The neutral field may be seen as the source field of the vortex, and we study some possibilities, which modify the standard Maxwell-Higgs solution and include internal structure to the vortex.

Vortical flows over delta wings and numerical prediction of vortex breakdown

Science.gov (United States)

Ekaterinaris, J. A.; Schiff, Lewis B.

1990-01-01

Navier-Stokes solutions of subsonic vortical flow over a 75 deg sweep delta wing with a sharp leading edge are presented. The sensitivity of the solution to the numerical scheme is examined using both a partially upwind scheme and a scheme with central differencing in all directions. At moderate angles of attack, no vortex breakdown is observed, whereas the higher angle-of-attack cases exhibit breakdown. The effect of numerical grid density is investigated, and solutions that are obtained with various grid densities are compared with experimental data. An embedded grid approach is implemented to enable higher resolution in selected isolated flow regions, such as the leeward-side surface, the leading-edge vortical flow, and the vortex breakdown region.

Composite optical vortices in noncollinear Laguerre–Gaussian beams and their propagation in free space

International Nuclear Information System (INIS)

Chen Ke; Liu Pusheng; Lü Baida

2008-01-01

Taking two Laguerre—Gaussian beams with topological charge l = ± 1 as an example, this paper studies the composite optical vortices formed by two noncollinear Laguerre—Gaussian beams with different phases, amplitudes, waist widths, off-axis distances, and their propagation in free space. It is shown by detailed numerical illustrative examples that the number and location of composite vortices at the waist plane are variable by varying the relative phase β, amplitude ratio η, waist width ratio ζ, or off-axis distance ratio μ. The net topological charge l net is not always equal to the sum l sum of charges of the two component beams. The motion, creation and annihilation of composite vortices take place in the free-space propagation, and the net charge during the propagation remains unchanged and equals to the net charge at the waist plane

On the appearance of vorticity and gradient shear bands in wormlike micellar solutions of different CPCl/salt systems

Energy Technology Data Exchange (ETDEWEB)

Mütze, Annekathrin, E-mail: muetzea@ethz.ch; Heunemann, Peggy; Fischer, Peter [ETH Zürich, Institute of Food, Nutrition and Health, Schmelzbergstrasse 9, 8092 Zürich (Switzerland)

2014-11-01

Wormlike micellar salt/surfactant solutions (X-salicylate, cetylpyridinium chloride) are studied with respect to the applied shear stress, concentration, temperature, and composition of the counterions (X = lithium, sodium, potassium, magnesium, and calcium) of the salicylate salt solute to determine vorticity and gradient shear bands. A combination of rheological measurements, laser technique, video analysis, and rheo-small-angle neutron scattering allow for a detailed exploration of number and types of shear bands. Typical flow curves of the solutions show Newtonian, shear-thinning, and shear-thickening flow behavior. In the shear-thickening regime, the solutions show vorticity and gradient shear bands simultaneously, in which vorticity shear bands dominate the visual effect, while gradient shear bands always coexist and predominate the rheological response. It is shown that gradient shear bands change their phases (turbid, clear) with the same frequency as the shear rate oscillates, whereas vorticity shear bands change their phases with half the frequency of the shear rate. Furthermore, we show that with increasing molecular mass of the counterions the number of gradient shear bands increases, while the number of vorticity shear bands remains constant. The variation of temperature, shear stress, concentration, and counterions results in a predictable change in the rheological behavior and therefore allows adjustment of the number of vorticity shear bands in the shear band regime.

Stream function-vorticity finite elements and the resolution of the Navier-Stokes equations

International Nuclear Information System (INIS)

Almeida, R.C.C. de.

1987-07-01

A stream function-vorticity finite element formulation for the solution of the Navier-Stokes equations is proposed. The present work shows a procedure to solve the problem posed by the no-slip conditions on solid frontiers which can also be applied to flow problems in a multi-connected domain. Moreover, a methodology to solve the pressure is developed using the stream function-vorticity approximate solution. Numerical experiments were conducted for some steady and unsteady problems and the performance of the proposed methods is discussed. (author) [pt

Combined effect of viscosity and vorticity on single mode Rayleigh-Taylor instability bubble growth

International Nuclear Information System (INIS)

Banerjee, Rahul; Mandal, Labakanta; Roy, S.; Khan, M.; Gupta, M. R.

2011-01-01

The combined effect of viscosity and vorticity on the growth rate of the bubble associated with single mode Rayleigh-Taylor instability is investigated. It is shown that the effect of viscosity on the motion of the lighter fluid associated with vorticity accumulated inside the bubble due to mass ablation may be such as to reduce the net viscous drag on the bubble exerted by the upper heavier fluid as the former rises through it.

Vorticity dynamics after the shock-turbulence interaction

Science.gov (United States)

Livescu, D.; Ryu, J.

2016-05-01

The interaction of a shock wave with quasi-vortical isotropic turbulence (IT) represents a basic problem for studying some of the phenomena associated with high speed flows, such as hypersonic flight, supersonic combustion and Inertial Confinement Fusion (ICF). In general, in practical applications, the shock width is much smaller than the turbulence scales and the upstream turbulent Mach number is modest. In this case, recent high resolution shock-resolved Direct Numerical Simulations (DNS) (Ryu and Livescu, J Fluid Mech 756:R1, 2014) show that the interaction can be described by the Linear Interaction Approximation (LIA). Using LIA to alleviate the need to resolve the shock, DNS post-shock data can be generated at much higher Reynolds numbers than previously possible. Here, such results with Taylor Reynolds number approximately 180 are used to investigate the changes in the vortical structure as a function of the shock Mach number, Ms, up to Ms=10. It is shown that, as Ms increases, the shock interaction induces a tendency towards a local axisymmetric state perpendicular to the shock front, which has a profound influence on the vortex-stretching mechanism and divergence of the Lamb vector and, ultimately, on the flow evolution away from the shock.

Analysis of Wind Vorticity and Divergence in the High-latitude Lower Thermosphere: Dependence on the Interplanetary Magnetic Field (IMF

Directory of Open Access Journals (Sweden)

Young-Sil Kwak

2008-12-01

Full Text Available To better understand the physical processes that control the high-latitude lower thermospheric dynamics, we analyze the divergence and vorticity of the high-latitude neutral wind field in the lower thermosphere during the southern summertime for different IMF conditions. For this study the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEG CM is used. The analysis of the large-scale vorticity and divergence provides basic understanding flow configurations to help elucidate the momentum sources that ultimately determine the total wind field in the lower polar thermosphere and provides insight into the relative strengths of the different sources of momentum responsible for driving winds. The mean neutral wind pattern in the high-latitude lower thermosphere is dominated by rotational flow, imparted primarily through the ion drag force, rather than by divergent flow, imparted primarily through Joule and solar heating. The difference vorticity, obtained by subtracting values with zero IMF from those with non-zero IMF, in the high-latitude lower thermosphere is much larger than the difference divergence for all IMF conditions, indicating that a larger response of the thermospheric wind system to enhancement in the momentum input generating the rotational motion with elevated IMF than the corresponding energy input generating the divergent motion. the difference vorticity in the high-latitude lower thermosphere depends on the direction of the IMF. The difference vorticity for negative and positive B_y shows positive and negative, respectively, at higher magnetic latitudes than -70°. For negative B_z, the difference vorticities have positive in the dusk sector and negative in the dawn sector. The difference vorticities for positive B_z have opposite sign. Negative IMF B_z has a stronger effect on the vorticity than does positive B_z.

Helicity conservation and twisted Seifert surfaces for superfluid vortices.

Science.gov (United States)

Salman, Hayder

2017-04-01

Starting from the continuum definition of helicity, we derive from first principles its different contributions for superfluid vortices. Our analysis shows that an internal twist contribution emerges naturally from the mathematical derivation. This reveals that the spanwise vector that is used to characterize the twist contribution must point in the direction of a surface of constant velocity potential. An immediate consequence of the Seifert framing is that the continuum definition of helicity for a superfluid is trivially zero at all times. It follows that the Gauss-linking number is a more appropriate definition of helicity for superfluids. Despite this, we explain how a quasi-classical limit can arise in a superfluid in which the continuum definition for helicity can be used. This provides a clear connection between a microscopic and a macroscopic description of a superfluid as provided by the Hall-Vinen-Bekarevich-Khalatnikov equations. This leads to consistency with the definition of helicity used for classical vortices.

Vortices and quark confinement in non-Abelian gauge theories

International Nuclear Information System (INIS)

Mandelstam, S.

1976-01-01

Non-Abelian vortices of the type proposed by Nielsen and Olesen are discussed. It is shown that the vortices must contain a single unit of quantized flux absorbed by a Dirac monopole at each end. The monopoles satisfy a confinement condition; if quark numbers are assigned to the monopoles, is is found that the model contains a natural explanation of quark confinement. The I-spin variables associated with the non-Abelian gauge field correspond to the colour degree freedom. An alternative model in which (colour) charges and monopoles are interchanged is also suggested. The Higgs field which breaks the degeneracy of the vacuum is replaced by an operator which creates monopoles of the type suggested by 't Hooft. In such a model colour might be confined. The investigations are at a very preliminary stage, but the model appears to offer a natural explanation of confinement without the explicit introduction of monopole fields. (Auth.)

Visualization of pre-set vortices in boundary layer flow over wavy surface in rectangular channel

KAUST Repository

Budiman, Alexander Christantho

2014-12-04

Abstract: Smoke-wire flow visualization is used to study the development of pre-set counter-rotating streamwise vortices in boundary layer flow over a wavy surface in a rectangular channel. The formation of the vortices is indicated by the vortical structures on the cross-sectional plane normal to the wavy surface. To obtain uniform spanwise vortex wavelength which will result in uniform vortex size, two types of spanwise disturbances were used: a series of perturbation wires placed prior and normal to the leading edge of the wavy surface, and a jagged pattern in the form of uniform triangles cut at the leading edge. These perturbation wires and jagged pattern induce low-velocity streaks that result in the formation of counter-rotating streamwise vortices that evolve downstream to form the mushroom-like structures on the cross-sectional plane of the flow. The evolution of the most amplified disturbances can be attributed to the formation of these mushroom-like structures. It is also shown that the size of the mushroom-like structures depends on the channel entrance geometry, Reynolds number, and the channel gap.Graphical Abstract: [Figure not available: see fulltext.

Studies of the relationship between environmental forcing and the structure and dynamics of tornado-like vortices; TOPICAL

International Nuclear Information System (INIS)

Nolan, David S.; Almgren, Ann S.; Bell, John B.

2000-01-01

Axisymmetric numerical simulations continue to provide insight into how the structure, dynamics, and maximum wind speeds of tornadoes, and other convectively-maintained vortices, are influenced by the surrounding environment. This work is continued with a new numerical model of axisymmetric incompressible flow that incorporates adaptive mesh refinement. The model dynamically increases or decreases the resolution in regions of interest as determined by a specified refinement criterion. Here, the criterion used is based on the cell Reynolds number dx dv / nu, so that the flow is guaranteed to be laminar on the scale of the local grid spacing. The model is used to investigate how the altitude and shape of the convective forcing, the size of the domain, and the effective Reynolds number (based on the choice of the eddy viscosity nu) influence the structure and dynamics of the vortex. Over a wide variety of domain and forcing geometries,the vortex Reynolds number Gamma / nu (the ratio of the far-field circulation to the eddy viscosity) is shown to be the most important parameter for determining vortex structure and behavior. Furthermore,it is found that the vertical scale of the convective forcing only affects the vortex inasmuch as this vertical scale contributes to the total strength of the convective forcing. The horizontal scale of the convective forcing, however, is found to be the fundamental length scale in the problem, in that it can determine both the circulation of the fluid that is drawn into the vortex core, and also influences the depth of the swirling boundary layer. Higher mean wind speeds are sustained as the eddy viscosity is decreased; however, it is observed that the highest wind speeds are found in the high-swirl, two-celled vortex regime rather than in the low-swirl, one-celled regime, which is in contrast with some previous results. The conclusions drawn from these results are applied to dimensional simulations with scales similar to the

Magneto-optical observation of twisted vortices in type-II superconductors

Science.gov (United States)

Indenbom, M. V.; van der Beek, C. J.; Berseth, V.; Benoit, W.; D'Anna, G.; Erb, A.; Walker, E.; Flükiger, R.

1997-02-01

When magnetic flux penetrates a type-II superconductor, it does so as quantized flux lines or vortex lines, so called because each is surrounded by a supercurrent vortex. Interactions between such vortices lead to a very rich and well characterized phenomenology for this 'mixed state'. But an outstanding question remains: are individual vortex lines 'strong', or can they easily be cut and made to pass through one another? The concept of vortex cutting was originally proposed to account for dissipation observed in superconducting wires oriented parallel to an applied magnetic field, where the vortex lines and transport current should be in a force-free configuration1-6. Previous experiments, however, have been unable to establish the vortex topology in the force-free configuration or the size of the energy barrier for vortex cutting. Here we report magneto-optical images of YBa2Cu3O7-δ samples in the force-free configuration which show that thousands of vortex lines can twist together to form highly stable structures. In some cases, these 'vortex twisters' interact with one another to produce wave-like dynamics. Our measurements also determine directly the current required to initiate vortex cutting, and show that it is much higher than that needed to overcome the pinning of vortices by material defects. This implies that thermodynamic phases of entangled vortices7-10 are intrinsically stable and may occupy a significant portion of the mixed-state phase diagram for type-II superconductors.

Helicity and potential vorticity in the surface boundary layer turbulence

Science.gov (United States)

Chkhetiani, Otto; Kurgansky, Michael; Koprov, Boris; Koprov, Victor

2016-04-01

An experimental measurement of all three components of the velocity and vorticity vectors, as well as the temperature and its gradient, and potential vorticity, has been developed using four acoustic anemometers. Anemometers were placed at vertices of a tetrahedron, the horizontal base of which was a rectangular triangle with equal legs, and the upper point was exactly above the top of the right angle. The distance from the surface to the tetrahedron its base was 5.5 m, and the lengths of legs and a vertical edge were 5 m. The measurements were carried out of total duration near 100 hours both in stable and unstable stratification conditions (at the Tsimlyansk Scientific Station in a uniform area of virgin steppe 700 x 650 m, August 2012). A covariance-correlation matrix for turbulent variations in all measured values has been calculated. In the daytime horizontal and vertical components of the helicity are of the order of -0.03 and +0.01 m s-2, respectively. The nighttime signs remain unchanged, but the absolute values are several times smaller. It is confirmed also by statistics of a relative helicity. The cospectra and spectral correlation coefficients have been calculated for all helicity components. The time variations in the components of "instantaneous" relative helicity and potential vorticity are considered. Connections of helicity with Monin-Obukhov length and the wind vertical profile structure are discussed. This work was supported by the Russian Science Foundation (Project No 14-27-00134).

Application of kinematic vorticity techniques for mylonitized Rocks in Al Amar suture, eastern Arabian Shield, Saudi Arabia

Science.gov (United States)

Hamimi, Z.; Kassem, O. M. K.; El-Sabrouty, M. N.

2015-09-01

The rotation of rigid objects within a flowing viscous medium is a function of several factors including the degree of non-coaxiality. The relationship between the orientation of such objects and their aspect ratio can be used in vorticity analyses in a variety of geological settings. Method for estimation of vorticity analysis to quantitative of kinematic vorticity number (Wm) has been applied using rotated rigid objects, such as quartz and feldspar objects. The kinematic vorticity number determined for high temperature mylonitic Abt schist in Al Amar area, extreme eastern Arabian Shield, ranges from ˜0.8 to 0.9. Obtained results from vorticity and strain analyses indicate that deformation in the area deviated from simple shear. It is concluded that nappe stacking occurred early during an earlier thrusting event, probably by brittle imbrications. Ductile strain was superimposed on the nappe structure at high-pressure as revealed by a penetrative subhorizontal foliation that is developed subparallel to tectonic contacts versus the underlying and overlying nappes. Accumulation of ductile strain during underplating was not by simple shear but involved a component of vertical shortening, which caused the subhorizontal foliation in the Al Amar area. In most cases, this foliation was formed concurrently with thrust sheets imbrications, indicating that nappe stacking was associated with vertical shortening.

Capping Ligand Vortices as "Atomic Orbitals" in Nanocrystal Self-Assembly.

Science.gov (United States)

Waltmann, Curt; Horst, Nathan; Travesset, Alex

2017-11-28

We present a detailed analysis of the interaction between two nanocrystals capped with ligands consisting of hydrocarbon chains by united atom molecular dynamics simulations. We show that the bonding of two nanocrystals is characterized by ligand textures in the form of vortices. These results are generalized to nanocrystals of different types (differing core and ligand sizes) where the structure of the vortices depends on the softness asymmetry. We provide rigorous calculations for the binding free energy, show that these energies are independent of the chemical composition of the cores, and derive analytical formulas for the equilibrium separation. We discuss the implications of our results for the self-assembly of single-component and binary nanoparticle superlattices. Overall, our results show that the structure of the ligands completely determines the bonding of nanocrystals, fully supporting the predictions of the recently proposed Orbifold topological model.

Direct observation of rectified motion of vortices by Lorentz microscopy

Indian Academy of Sciences (India)

one-directional selective motion of field-gradient-driven vortices along fabricated channels. This results from ... was irradiated around etched holes to fabricate the asymmetric potential [19]. Fig- ures 1a .... The dotted line is a guide to the eye.

Taylor vortices in the flow between two coaxial cylinders one of which has a step change in radius

International Nuclear Information System (INIS)

Raju, V R K

2014-01-01

A numerical study of the flow between two coaxial cylinders, where one of the cylinders has a step change in radius, is carried out. The inner cylinder rotates and the outer cylinder is stationary. Computation is restricted to axisymmetric motion since instability in flow between coaxial cylinders is found to first occur in the form of axisymmetric Taylor vortices. In the presence of a step, Taylor vortices are found to appear first in the region where the gap between the cylinders is larger and approximately when the local Taylor number in this region reaches the critical Taylor number for onset of instability. Subsequently, Taylor vortices appear in the region where the gap is narrower, and when the local Taylor number in that region exceeds the critical Taylor number. The Taylor vortices have inward flow at a stationary end plate, and outward flow at an end plate which rotates with the same angular velocity as the inner cylinder. Similar results were obtained by Sprague et al (2008 Phys. Fluids 20 014102) for a step on inner cylinder configuration. The step functions as another end plate, if the step size is large. Whereas, it has no effect, if the step size is small. In most situations, these determine whether the number of Taylor vortices in the wide and narrow gap regions is even or odd. When the end plates rotate synchronously, but at a different speed from the inner cylinder, a change from even to odd or odd to even number of vortices in each region occurs at certain rotation rates of the end plates by sudden appearance or disappearance of a vortex at the end of the column. For a certain range of rotation rates of the end plates, the total number of vortices in the entire fluid column is odd, although the end conditions are symmetrical. (paper)

Coherent structures amidst chaos: Solitons, fronts, and vortices

International Nuclear Information System (INIS)

Campbell, D.K.

1996-01-01

I introduce the concept of open-quote open-quote coherent structures close-quote close-quote emdash localized, persistent, propagating nonlinear waves emdash and argue that they are ubiquitous in spatially extended nonlinear systems. I discuss various specific forms of coherent structures emdash solitons, wave fronts, vortices emdash and illustrate how they arise in physics, chemistry, biology, and physiology. copyright 1996 American Institute of Physics

Imaging the Statics and Dynamics of Superconducting Vortices and Antivortices Induced by Magnetic Microdisks

Directory of Open Access Journals (Sweden)

R. B. G. Kramer

2011-10-01

Full Text Available If a magnet of microscopic dimensions is brought in close proximity to a superconductor, the quantized nature of their interaction due to the creation of flux quanta in the superconducting system becomes noticeable. Herein, we directly image, via scanning Hall microscopy, the vortex-antivortex pairs in a superconducting film created by micromagnets. The number of antivortices at equilibrium conditions can be changed either by tuning the magnetic moment of the magnets or by annihilation with externally induced vortices. We demonstrate that small ac field excitations shake the antivortices sitting next to the micromagnets whereas no sizable motion is observed for the vortices sitting on top of the magnets, clearly revealing the different mobility of these two vortex species. A metastable state, which is obtained by applying a field after the system has been cooled down below the superconducting transition, shows a complex graded distribution of coexisting vortices and antivortices forming an intertwined critical state.

Ionospheric travelling convection vortices observed by the Greenland magnetometer chain

DEFF Research Database (Denmark)

Kotsiaros, Stavros; Stolle, Claudia; Friis-Christensen, Eigil

2013-01-01

The Greenland magnetometer array continuously provides geomagnetic variometer data since the early eighties. With the polar cusp passing over it almost every day, the array is suitable to detect ionospheric traveling convection vortices (TCVs), which were rst detected by Friis-Christensen et al...

Hematopoietic stem cell transplantation in multiple sclerosis

DEFF Research Database (Denmark)

Rogojan, C; Frederiksen, J L

2009-01-01

Intensive immunosuppresion followed by hematopoietic stem cell transplantation (HSCT) has been suggested as potential treatment in severe forms of multiple sclerosis (MS). Since 1995 ca. 400 patients have been treated with HSCT. Stabilization or improvement occurred in almost 70% of cases at least...

Conformal invariance of the Lungren-Monin-Novikov equations for vorticity fields in 2D turbulence

Science.gov (United States)

Grebenev, V. N.; Wacławczyk, M.; Oberlack, M.

2017-10-01

We study the statistical properties of the vorticity field in two-dimensional turbulence. The field is described in terms of the infinite Lundgren-Monin-Novikov (LMN) chain of equations for multi-point probability density functions (pdf’s) of vorticity. We perform a Lie group analysis of the first equation in this chain using the direct method based on the canonical Lie-Bäcklund transformations devised for integro-differential equations. We analytically show that the conformal group is broken for the first LMN equation i.e. for the 1-point pdf at least for the inviscid case but the equation is still conformally invariant on the associated characteristic with zero-vorticity. Then, we demonstrate that this characteristic is conformally transformed. We find this outcome coincides with the numerical results about the conformal invariance of the statistics of zero-vorticity isolines, see e.g. Falkovich (2007 Russian Math. Surv. 63 497-510). The conformal symmetry can be understood as a ‘local scaling’ and its traces in two-dimensional turbulence were already discussed in the literature, i.e. it was conjectured more than twenty years ago in Polyakov (1993 Nucl. Phys. B 396 367-85) and clearly validated experimentally in Bernard et al (2006 Nat. Phys. 2 124-8).

Vorticity generation and wake transition for a translating circular cylinder: Wall proximity and rotation effects

DEFF Research Database (Denmark)

Hourigan, K.; Rao, A.; Brøns, Morten

2013-01-01

The wake transitions of generic bluff bodies, such as a circular cylinder, near a wall are important because they provide understanding of different transition paths towards turbulence, and give some insight into the effect of surface modifications on the flow past larger downstream structures......-annihilate with opposite-signed vorticity, and can be stored at a free surface, thus conserving the total vorticity, or circulation. Vorticity generation, diffusion and storage are demonstrated for a cylinder translating and rotating near a wall. The wake characteristics and the wake transitions are shown to change...... dramatically under the influence of cylinder rotation and wall proximity. At gaps between the cylinder and the wall of less than approximately 0.25 cylinder diameter, the wake becomes three dimensional prior to becoming unsteady, while for larger gaps the initial transition is to an unsteady two...

Generation of large-scale vorticity in rotating stratified turbulence with inhomogeneous helicity: mean-field theory

Science.gov (United States)

Kleeorin, N.

2018-06-01

We discuss a mean-field theory of the generation of large-scale vorticity in a rotating density stratified developed turbulence with inhomogeneous kinetic helicity. We show that the large-scale non-uniform flow is produced due to either a combined action of a density stratified rotating turbulence and uniform kinetic helicity or a combined effect of a rotating incompressible turbulence and inhomogeneous kinetic helicity. These effects result in the formation of a large-scale shear, and in turn its interaction with the small-scale turbulence causes an excitation of the large-scale instability (known as a vorticity dynamo) due to a combined effect of the large-scale shear and Reynolds stress-induced generation of the mean vorticity. The latter is due to the effect of large-scale shear on the Reynolds stress. A fast rotation suppresses this large-scale instability.

Energy conserving numerical methods for the computation of complex vortical flows

Science.gov (United States)

Allaneau, Yves

One of the original goals of this thesis was to develop numerical tools to help with the design of micro air vehicles. Micro Air Vehicles (MAVs) are small flying devices of only a few inches in wing span. Some people consider that as their size becomes smaller and smaller, it would be increasingly more difficult to keep all the classical control surfaces such as the rudders, the ailerons and the usual propellers. Over the years, scientists took inspiration from nature. Birds, by flapping and deforming their wings, are capable of accurate attitude control and are able to generate propulsion. However, the biomimicry design has its own limitations and it is difficult to place a hummingbird in a wind tunnel to study precisely the motion of its wings. Our approach was to use numerical methods to tackle this challenging problem. In order to precisely evaluate the lift and drag generated by the wings, one needs to be able to capture with high fidelity the extremely complex vortical flow produced in the wake. This requires a numerical method that is stable yet not too dissipative, so that the vortices do not get diffused in an unphysical way. We solved this problem by developing a new Discontinuous Galerkin scheme that, in addition to conserving mass, momentum and total energy locally, also preserves kinetic energy globally. This property greatly improves the stability of the simulations, especially in the special case p=0 when the approximation polynomials are taken to be piecewise constant (we recover a finite volume scheme). In addition to needing an adequate numerical scheme, a high fidelity solution requires many degrees of freedom in the computations to represent the flow field. The size of the smallest eddies in the flow is given by the Kolmogoroff scale. Capturing these eddies requires a mesh counting in the order of Re³ cells, where Re is the Reynolds number of the flow. We show that under-resolving the system, to a certain extent, is acceptable. However our

High throughput single-cell and multiple-cell micro-encapsulation.

Science.gov (United States)

Lagus, Todd P; Edd, Jon F

2012-06-15

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement from a bulk fluid environment with applications in high throughput screening, cytometry, and mass spectrometry. We describe a method to not only encapsulate single cells, but to repeatedly capture a set number of cells (here we demonstrate one- and two-cell encapsulation) to study both isolation and the interactions between cells in groups of controlled sizes. By combining drop generation techniques with cell and particle ordering, we demonstrate controlled encapsulation of cell-sized particles for efficient, continuous encapsulation. Using an aqueous particle suspension and immiscible fluorocarbon oil, we generate aqueous drops in oil with a flow focusing nozzle. The aqueous flow rate is sufficiently high to create ordering of particles which reach the nozzle at integer multiple frequencies of the drop generation frequency, encapsulating a controlled number of cells in each drop. For representative results, 9.9 μm polystyrene particles are used as cell surrogates. This study shows a single-particle encapsulation efficiency P(k=1) of 83.7% and a double-particle encapsulation efficiency P(k=2) of 79.5% as compared to their respective Poisson efficiencies of 39.3% and 33.3%, respectively. The effect of consistent cell and particle concentration is demonstrated to be of major importance for efficient encapsulation, and dripping to jetting transitions are also addressed. Continuous media aqueous cell suspensions share a common fluid environment which allows cells to interact in parallel and also homogenizes the effects of specific cells in measurements from the media. High-throughput encapsulation of cells into picoliter-scale drops confines the samples to protect drops from cross-contamination, enable a measure of cellular diversity within samples, prevent dilution of reagents and expressed biomarkers, and amplify

Kinematic vorticity number – a tool for estimating vortex sizes and circulations

Directory of Open Access Journals (Sweden)

Lisa Schielicke

2016-02-01

Full Text Available The influence of extratropical vortices on a global scale is mainly characterised by their size and by the magnitude of their circulation. However, the determination of these properties is still a great challenge since a vortex has no clear delimitations but is part of the flow field itself. In this work, we introduce a kinematic vortex size determination method based on the kinematic vorticity number Wk to atmospheric flows. Wk relates the local rate-of-rotation to the local rate-of-deformation at every point in the field and a vortex core is identified as a simply connected region where the rotation prevails over the deformation. Additionally, considering the sign of vorticity in the extended Wk-method allows to identify highs and lows in different vertical layers of the atmosphere and to study vertical as well as horizontal vortex interactions. We will test the Wk-method in different idealised -D (superposition of two lows/low and jet and real -D flow situations (winter storm affecting Europe and compare the results with traditional methods based on the pressure and the vorticity fields. In comparison to these traditional methods, the Wk-method is able to extract vortex core sizes even in shear-dominated regions that occur frequently in the upper troposphere. Furthermore, statistics of the size and circulation distributions of cyclones will be given. Since the Wk-method identifies vortex cores, the identified radii are subsynoptic with a broad peak around 300–500 km at the 1000 hPa level. However, the total circulating area is not only restricted to the core. In general, circulations are in the order of 107 m2/s with only a few cyclones in the order of 108 m2/s.

B Cells and Autoantibodies in Multiple Sclerosis

Directory of Open Access Journals (Sweden)

Anne-Katrin Pröbstel

2015-07-01

Full Text Available While over the past decades T cells have been considered key players in the pathogenesis of multiple sclerosis (MS, it has only recently become evident that B cells have a major contributing role. Our understanding of the role of B cells has evolved substantially following the clinical success of B cell-targeting therapies and increasing experimental evidence for significant B cell involvement. Rather than mere antibody-producing cells, it is becoming clear that they are team players with the capacity to prime and regulate T cells, and function both as pro- and anti-inflammatory mediators. However, despite tremendous efforts, the target antigen(s of B cells in MS have yet to be identified. The first part of this review summarizes the clinical evidence and results from animal studies pointing to the relevance of B cells in the pathogenesis of MS. The second part gives an overview of the currently known potential autoantigen targets. The third part recapitulates and critically appraises the currently available B cell-directed therapies.

Vorticity and symplecticity in multi-symplectic, Lagrangian gas dynamics

Science.gov (United States)

Webb, G. M.; Anco, S. C.

2016-02-01

The Lagrangian, multi-dimensional, ideal, compressible gas dynamic equations are written in a multi-symplectic form, in which the Lagrangian fluid labels, m i (the Lagrangian mass coordinates) and time t are the independent variables, and in which the Eulerian position of the fluid element {x}={x}({m},t) and the entropy S=S({m},t) are the dependent variables. Constraints in the variational principle are incorporated by means of Lagrange multipliers. The constraints are: the entropy advection equation S t = 0, the Lagrangian map equation {{x}}t={u} where {u} is the fluid velocity, and the mass continuity equation which has the form J=τ where J={det}({x}{ij}) is the Jacobian of the Lagrangian map in which {x}{ij}=\\partial {x}i/\\partial {m}j and τ =1/ρ is the specific volume of the gas. The internal energy per unit volume of the gas \\varepsilon =\\varepsilon (ρ ,S) corresponds to a non-barotropic gas. The Lagrangian is used to define multi-momenta, and to develop de Donder-Weyl Hamiltonian equations. The de Donder-Weyl equations are cast in a multi-symplectic form. The pullback conservation laws and the symplecticity conservation laws are obtained. One class of symplecticity conservation laws give rise to vorticity and potential vorticity type conservation laws, and another class of symplecticity laws are related to derivatives of the Lagrangian energy conservation law with respect to the Lagrangian mass coordinates m i . We show that the vorticity-symplecticity laws can be derived by a Lie dragging method, and also by using Noether’s second theorem and a fluid relabelling symmetry which is a divergence symmetry of the action. We obtain the Cartan-Poincaré form describing the equations and we discuss a set of differential forms representing the equation system.

Maxwell-Chern-Simons vortices in a CPT-odd Lorentz-violating Higgs electrodynamics

International Nuclear Information System (INIS)

Casana, R.; Ferreira, M.M.; Hora, E. da; Neves, A.B.F.

2014-01-01

We study BPS vortices in a CPT-odd and Lorentz-violating Maxwell-Chern-Simons-Higgs (MCSH) electrodynamics attained from the dimensional reduction of the Carroll-Field-Jackiw-Higgs model. The Lorentz-violating parameter induces a pronounced behavior at origin (for the magnetic/electric fields and energy density) which is absent in the MCSH vortices. For some combination of the Lorentz-violating coefficients there always exists a sufficiently large winding number n 0 such that for all vertical stroke n vertical stroke ≥ vertical stroke n 0 vertical stroke the magnetic field flips sign, yielding two well-defined regions with opposite magnetic flux. However, the total magnetic flux remains quantized and proportional to the winding number. (orig.)

Alpha-particles induce autophagy in multiple myeloma cells

Directory of Open Access Journals (Sweden)

Joelle Marcelle Gaschet

2015-10-01

Full Text Available Objectives: Radiations emitted by the radionuclides in radioimmunotherapy (RIT approaches induce direct killing of the targeted cells as well as indirect killing through bystander effect. Our research group is dedicated to the development of α-RIT, i.e RIT using α-particles especially for the treatment of multiple myeloma (MM. γ-irradiation and β-irradiation have been shown to trigger apoptosis in tumor cells. Cell death mode induced by 213Bi α-irradiation appears more controversial. We therefore decided to investigate the effects of 213Bi on MM cell radiobiology, notably cell death mechanisms as well as tumor cell immunogenicity after irradiation.Methods: Murine 5T33 and human LP-1 multiple myeloma (MM cell lines were used to study the effects of such α-particles. We first examined the effects of 213Bi on proliferation rate, double strand DNA breaks, cell cycle and cell death. Then, we investigated autophagy after 213Bi irradiation. Finally, a co-culture of dendritic cells (DC with irradiated tumour cells or their culture media was performed to test whether it would induce DC activation.Results: We showed that 213Bi induces DNA double strand breaks, cell cycle arrest and autophagy in both cell lines but we detected only slight levels of early apoptosis within the 120 hours following irradiation in 5T33 and LP-1. Inhibition of autophagy prevented 213Bi induced inhibition of proliferation in LP-1 suggesting that this mechanism is involved in cell death after irradiation. We then assessed the immunogenicity of irradiated cells and found that irradiated LP-1 can activate DC through the secretion of soluble factor(s, however no increase in membrane or extracellular expression of danger associated molecular patterns (DAMPs was observed after irradiation.Conclusion: This study demonstrates that 213Bi induces mainly necrosis in MM cells, low levels of apoptosis and also autophagy that might be involved in tumor cell death.

T–CELL VACCINE PREPARATION FOR MULTIPLE SCLEROSIS TREATMENT

Directory of Open Access Journals (Sweden)

I. P. Ivanova

2005-01-01

Full Text Available Abstract. A two–stage technology of preparation of T–cell vaccine designated for multiple sclerosis treatment is described. At the first stage myelin–specific lymphocytes undergoe antigen–dependent cultural selection, whereas at the second stage they are grown by means of non–specific stimulation. The vaccine prepared in this way was found to induce specific anti–idiotypic immune response, directed against myelin–reactive T–lymphocytes. The results of 1–year follow–up of 18 vaccinated patients with a cerebral–spinal type of multiple sclerosis indicated the absence of side effects of T–cell vaccination, and suggest the possibility of effective application of this treatment within early stages of disease. (Med. Immunol., 2005, vol.7, № 1, pp 27532

Classification of hemispheric monthly mean stratospheric potential vorticity fields

Directory of Open Access Journals (Sweden)

R. Huth

Full Text Available Monthly mean NCEP reanalysis potential vorticity fields at the 650 K isentropic level over the Northern and Southern Hemispheres between 1979 and 1997 were studied using multivariate analysis tools. Principal component analysis in the T-mode was applied to demonstrate the validity of such statistical techniques for the study of stratospheric dynamics and climatology. The method, complementarily applied to both the raw and anomaly fields, was useful in determining and classifying the characteristics of winter and summer PV fields on both hemispheres, in particular, the well-known differences in the behaviour and persistence of the polar vortices. It was possible to identify such features as sudden warming events in the Northern Hemisphere and final warming dates in both hemispheres. The stratospheric impact of other atmospheric processes, such as volcanic eruptions, also identified though the results, must be viewed at this stage as tentative. An interesting change in behaviour around 1990 was detected over both hemispheres.

Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; general circulation; climatology

Spin motive forces due to magnetic vortices and domain walls

NARCIS (Netherlands)

Lucassen, M.E.; Kruis, G.C.F.L.; Lavrijsen, R.; Swagten, H.J.M.; Koopmans, B.; Duine, R.A.

2011-01-01

We study spin motive forces, that is, spin-dependent forces and voltages induced by time-dependent magnetization textures, for moving magnetic vortices and domain walls. First, we consider the voltage generated by a one-dimensional field-driven domain wall. Next, we perform detailed calculations on

Control of secondary instability of the crossflow and Görtler-like vortices (Success and problems)

Science.gov (United States)

Kozlov, Viktor V.; Grek, Genrich R.

The secondary instability on a group of crossflow vortices developing in a swept wing boundary layer is described. It is shown that, for travelling waves, there is a region of linear development, and the growth rate of disturbances appreciably depends on the separation between the vortices. Methods of controlling the secondary instability of the vortices by a controlled wave and local suction are proposed and substantiated. The stability of a flat plate boundary layer modulated by G&ou ml;rtler-like stationary vortices is described. Vortices were generated inside the boundary layer by means of roughness elements arranged in a regular array along the spanwise (z) direction. Transition is not caused directly by these structures, but by the growth of small amplitude travelling waves riding on top of the steady vortices. This situation is analogous to the transition process in Görtler and cross-flows. The waves were found to amplify up to a stage where higher harmonics are gener ated, leading to turbulent breakdown and disintegration of the spanwise boundary layer structure. For strong modulations, the observed instability is quite powerful, and can be excited "naturally" by small uncontrollable background disturbances. Controlled oscillations were then introduced by means of a vibrating ribbon, allowing a detailed investigation of the wave characteristics. The instability seems to be associated with the spanwise gradients of the mean flow, , and at all z-positions, the maximum wave amplitude was found at a wall-normal position where the mean velocity is equal to the phase velocity of the wave, U(y)=c, i.e., at the local critical layer. Unstable waves were observed at frequency well above those for which Tollmien-Schlichting (TS) waves amplify in the Blasius boundary layer. Excitation at lower frequencies and milder basic flow modulation showed that TS-type waves may a lso develop. Study of the transition control in that flow by means of riblets shows that the effect

Concept of multiple-cell cavity for axion dark matter search

Science.gov (United States)

Jeong, Junu; Youn, SungWoo; Ahn, Saebyeok; Kim, Jihn E.; Semertzidis, Yannis K.

2018-02-01

In cavity-based axion dark matter search experiments exploring high mass regions, multiple-cavity design is under consideration as a method to increase the detection volume within a given magnet bore. We introduce a new idea, referred to as a multiple-cell cavity, which provides various benefits including a larger detection volume, simpler experimental setup, and easier phase-matching mechanism. We present the characteristics of this concept and demonstrate the experimental feasibility with an example of a double-cell cavity.

On the theory of superfluid liquid rotation in pulsars taking into account relativistic effects in vortices

International Nuclear Information System (INIS)

Chernobaj, V.A.; Andronik, V.V.

1978-01-01

The necessity of taking into account the relativistic effects in quantized vortices of pulsar superfluid nuclei is shown. The full energy of a single vortex for special relativity theory approximation is determined. The single vortex full energy asymptotics for quantized numbers n, which are much greater than the ratio of vortex exterior radius to Compton's length of the nucleon, wave is linear with respect to n while in the nonrelativistic case the kinetic energy is proportional to n 2 . This suggests the possibility of existence of quasistable vortices with great quantized numbers n. It is revealed that for small quantized numbers the taking into account of the relativistic effects in the vortices does not lead to qualitative changes of the general condition of superfluid liquid rotation as compared to non-relativistic theory

Fish mouths as engineering structures for vortical cross-step filtration

Science.gov (United States)

Sanderson, S. Laurie; Roberts, Erin; Lineburg, Jillian; Brooks, Hannah

2016-03-01

Suspension-feeding fishes such as goldfish and whale sharks retain prey without clogging their oral filters, whereas clogging is a major expense in industrial crossflow filtration of beer, dairy foods and biotechnology products. Fishes' abilities to retain particles that are smaller than the pore size of the gill-raker filter, including extraction of particles despite large holes in the filter, also remain unexplained. Here we show that unexplored combinations of engineering structures (backward-facing steps forming d-type ribs on the porous surface of a cone) cause fluid dynamic phenomena distinct from current biological and industrial filter operations. This vortical cross-step filtration model prevents clogging and explains the transport of tiny concentrated particles to the oesophagus using a hydrodynamic tongue. Mass transfer caused by vortices along d-type ribs in crossflow is applicable to filter-feeding duck beak lamellae and whale baleen plates, as well as the fluid mechanics of ventilation at fish gill filaments.

Vortices in superconducting films: Statistics and fractional quantum Hall effect

International Nuclear Information System (INIS)

Dziarmaga, J.

1996-01-01

We present a derivation of the Berry phase picked up during exchange of parallel vortices. This derivation is based on the Bogolubov endash de Gennes formalism. The origin of the Magnus force is also critically reanalyzed. The Magnus force can be interpreted as an interaction with the effective magnetic field. The effective magnetic field may be even of the order 10 6 T/A. We discuss a possibility of the fractional quantum Hall effect (FQHE) in vortex systems. As the real magnetic field is varied to drive changes in vortex density, the vortex density will prefer to stay at some quantized values. The mere existence of the FQHE does not depend on vortex quantum statistics, although the pattern of the plateaux does. We also discuss how the density of anyonic vortices can lower the effective strengh of the Magnus force, what might be observable in measurements of Hall resistivity. copyright 1996 The American Physical Society

Three-dimensional quantification of vorticity and helicity from 3D cine PC-MRI using finite-element interpolations.

Science.gov (United States)

Sotelo, Julio; Urbina, Jesús; Valverde, Israel; Mura, Joaquín; Tejos, Cristián; Irarrazaval, Pablo; Andia, Marcelo E; Hurtado, Daniel E; Uribe, Sergio

2018-01-01

We propose a 3D finite-element method for the quantification of vorticity and helicity density from 3D cine phase-contrast (PC) MRI. By using a 3D finite-element method, we seamlessly estimate velocity gradients in 3D. The robustness and convergence were analyzed using a combined Poiseuille and Lamb-Ossen equation. A computational fluid dynamics simulation was used to compared our method with others available in the literature. Additionally, we computed 3D maps for different 3D cine PC-MRI data sets: phantom without and with coarctation (18 healthy volunteers and 3 patients). We found a good agreement between our method and both the analytical solution of the combined Poiseuille and Lamb-Ossen. The computational fluid dynamics results showed that our method outperforms current approaches to estimate vorticity and helicity values. In the in silico model, we observed that for a tetrahedral element of 2 mm of characteristic length, we underestimated the vorticity in less than 5% with respect to the analytical solution. In patients, we found higher values of helicity density in comparison to healthy volunteers, associated with vortices in the lumen of the vessels. We proposed a novel method that provides entire 3D vorticity and helicity density maps, avoiding the used of reformatted 2D planes from 3D cine PC-MRI. Magn Reson Med 79:541-553, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Understanding dynamics of large-scale atmospheric vortices with moist-convective shallow water model

International Nuclear Information System (INIS)

Rostami, M.; Zeitlin, V.

2016-01-01

Atmospheric jets and vortices which, together with inertia-gravity waves, constitute the principal dynamical entities of large-scale atmospheric motions, are well described in the framework of one- or multi-layer rotating shallow water models, which are obtained by vertically averaging of full “primitive” equations. There is a simple and physically consistent way to include moist convection in these models by adding a relaxational parameterization of precipitation and coupling precipitation with convective fluxes with the help of moist enthalpy conservation. We recall the construction of moist-convective rotating shallow water model (mcRSW) model and give an example of application to upper-layer atmospheric vortices. (paper)

Feasibility of mesenchymal stem cell culture expansion for a phase I clinical trial in multiple sclerosis.

Science.gov (United States)

Planchon, Sarah M; Lingas, Karen T; Reese Koç, Jane; Hooper, Brittney M; Maitra, Basabi; Fox, Robert M; Imrey, Peter B; Drake, Kylie M; Aldred, Micheala A; Lazarus, Hillard M; Cohen, Jeffrey A

2018-01-01

Multiple sclerosis is an inflammatory, neurodegenerative disease of the central nervous system for which therapeutic mesenchymal stem cell transplantation is under study. Published experience of culture-expanding multiple sclerosis patients' mesenchymal stem cells for clinical trials is limited. To determine the feasibility of culture-expanding multiple sclerosis patients' mesenchymal stem cells for clinical use. In a phase I trial, autologous, bone marrow-derived mesenchymal stem cells were isolated from 25 trial participants with multiple sclerosis and eight matched controls, and culture-expanded to a target single dose of 1-2 × 10 6 cells/kg. Viability, cell product identity and sterility were assessed prior to infusion. Cytogenetic stability was assessed by single nucleotide polymorphism analysis of mesenchymal stem cells from 18 multiple sclerosis patients and five controls. One patient failed screening. Mesenchymal stem cell culture expansion was successful for 24 of 25 multiple sclerosis patients and six of eight controls. The target dose was achieved in 16-62 days, requiring two to three cell passages. Growth rate and culture success did not correlate with demographic or multiple sclerosis disease characteristics. Cytogenetic studies identified changes on one chromosome of one control (4.3%) after extended time in culture. Culture expansion of mesenchymal stem cells from multiple sclerosis patients as donors is feasible. However, culture time should be minimized for cell products designated for therapeutic administration.

A vorticity based approach to handle the fluid-structure interaction problems

Energy Technology Data Exchange (ETDEWEB)

Farahbakhsh, Iman; Ghassemi, Hassan [Department of Ocean Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Sabetghadam, Fereidoun, E-mail: i.farahbakhsh@aut.ac.ir [Mechanical and Aerospace Engineering Department, Science and Research Branch, Islamic Azad University (IAU), Tehran (Iran, Islamic Republic of)

2016-02-15

A vorticity based approach for the numerical solution of the fluid-structure interaction problems is introduced in which the fluid and structure(s) can be viewed as a continuum. Retrieving the vorticity field and recalculating a solenoidal velocity field, specially at the fluid-structure interface, are the kernel of the proposed algorithm. In the suggested method, a variety of constitutive equations as a function of left Cauchy–Green deformation tensor can be applied for modeling the structure domain. A nonlinear Mooney–Rivlin and Saint Venant–Kirchhoff model are expressed in terms of the left Cauchy–Green deformation tensor and the presented method is able to model the behavior of a visco-hyperelastic structure in the incompressible flow. Some numerical experiments, with considering the neo-Hookean model for structure domain, are executed and the results are validated via the available results from literature. (paper)

Pinning of superconducting vortices in MoGe/Au Thin nano–squares

Energy Technology Data Exchange (ETDEWEB)

Serrier-Garcia, Lise, E-mail: serriergarcia.lise@fys.kuleuven.be; Timmermans, Matias; Van de Vondel, Joris; Moshchalkov, Victor V.

2017-02-15

Highlights: • A scanning tunneling spectroscopy study of vortex patterns in mesoscopic superconducting squares is reported. • The impact of defects and corrugations inherently present in nanofabricated structures is explored. • Hillocks at the edge can attract and repulse vortices. • The small surface corrugation creates metastable states. • Vortex rotations during dynamical vortex penetrations are visualized. - Abstract: In this work, we report a scanning tunneling spectroscopy study of vortex patterns in mesoscopic superconducting squares and explore the impact of defects and corrugations inherently present in nanofabricated structures. We find that a hillock at the edge can function as an attractive or repulsive pinning center for vortices deforming the, theoretically predicted, symmetry-induced vortex configurations. In addition, we exploit the inherently present imperfections, creating metastable states, to visualize the dynamics of vortex penetration during magnetic field sweeps.

Process development of starch hydrolysis using mixing characteristics of Taylor vortices.

Science.gov (United States)

Masuda, Hayato; Horie, Takafumi; Hubacz, Robert; Ohmura, Naoto; Shimoyamada, Makoto

2017-04-01

In food industries, enzymatic starch hydrolysis is an important process that consists of two steps: gelatinization and saccharification. One of the major difficulties in designing the starch hydrolysis process is the sharp change in its rheological properties. In this study, Taylor-Couette flow reactor was applied to continuous starch hydrolysis process. The concentration of reducing sugar produced via enzymatic hydrolysis was evaluated by varying operational variables: rotational speed of the inner cylinder, axial velocity (reaction time), amount of enzyme, and initial starch content in the slurry. When Taylor vortices were formed in the annular space, efficient hydrolysis occurred because Taylor vortices improved the mixing of gelatinized starch with enzyme. Furthermore, a modified inner cylinder was proposed, and its mixing performance was numerically investigated. The modified inner cylinder showed higher potential for enhanced mixing of gelatinized starch and the enzyme than the conventional cylinder.

Multiple passage cells theory

International Nuclear Information System (INIS)

Riva, R.

1983-01-01

A review of the main concepts envolved in non astigmatic multiple passes cells is presented. It is shown that these concepts can be extended to ring cavities in which the analysis of the ray propagation (in the paraxial approaching) in two separated plans is accomplished. The concepts developed are applyed to a simple ring cavity (one curve mirror and two plane ones) showing that the acquired pattern of the rays on the mirrors is the one of a Lissajours figure which allows a better use of the mirror's area and consequently a larger number of passes. The cavity has applications in optical delay lines, measurements of mirrors reflectivities and possibly in passive optical gyroscopes. (Author) [pt

Vortices in dam reservoir: A case study of Karun III dam

Indian Academy of Sciences (India)

Formation of vortices at power intakes is a challenging problem for hydraulic engineers. ... at a distance equal to the radius of the intake from the axis of rotation. ... demand for irrigation and drinking purposes and also power generation, Karun.

Numerical simulation of cavitation surge and vortical flows in a diffuser with swirling flow

Energy Technology Data Exchange (ETDEWEB)

Ji, Bin; Wang, Jiong; Xiao, L. Z.; Long, X. [Wuhan University, Hubei (China); Luo, X. [Tsinghua University, Beijing (China); Miyagawa, K. [Waseda University, Tokyo (Japan); Tsujimoto, Yoshinobu [Osaka University, Osaka (Japan)

2016-06-15

The strong swirling flow at the exit of the runner of a Francis turbine at part load causes flow instabilities and cavitation surges in the draft tube, deteriorating the performance of the hydraulic power system. The unsteady cavitating turbulent flow in the draft tube is simplified and modeled by a diffuser with swirling flow using the Scale-adaptive simulation method. Unsteady characteristics of the vortex rope structure and the underlying mechanisms for the interactions between the cavitation and the vortices are both revealed. The generation and evolution of the vortex rope structures are demonstrated with the help of the iso-surfaces of the vapor volume fraction and the Qcriterion. Analysis based on the vorticity transport equation suggests that the vortex dilatation term is much larger along the cavity interface in the diffuser inlet and modifies the vorticity field in regions with high density and pressure gradients. The present work is validated by comparing two types of cavitation surges observed experimentally in the literature with further interpretations based on simulations.

Assessment of intracardiac flow and vorticity in the right heart of patients after repair of tetralogy of Fallot by flow-sensitive 4D MRI

Energy Technology Data Exchange (ETDEWEB)

Hirtler, Daniel [University Hospital Freiburg, Department of Congenital Heart Defects and Pediatric Cardiology (Heart Center, University of Freiburg), Freiburg (Germany); Garcia, Julio; Barker, Alex J. [Northwestern University Feinberg School of Medicine, Department of Radiology, Chicago, IL (United States); Geiger, Julia [University Childrens' Hospital Zurich, Department of Radiology, Zurich (Switzerland)

2016-10-15

To comprehensively and quantitatively analyse flow and vorticity in the right heart of patients after repair of tetralogy of Fallot (rTOF) compared with healthy volunteers. Time-resolved flow-sensitive 4D MRI was acquired in 24 rTOF patients and 12 volunteers. Qualitative flow evaluation was based on consensus reading of two observers. Quantitative analysis included segmentation of the right atrium (RA) and ventricle (RV) in a four-chamber view to extract volumes and regional haemodynamic information for computation of regional mean and peak vorticity. Right heart intra-atrial, intraventricular and outflow tract flow patterns differed considerably between rTOF patients and volunteers. Peak RA and mean RV vorticity was significantly higher in patients (p = 0.02/0.05). Significant negative correlations were found between patients' maximum and mean RV and RA vorticity and ventricular volumes (p < 0.05). The main pulmonary artery (MPA) regurgitant flow was associated with higher RA and RV vorticity, which was significant for RA maximum and RV mean vorticity (p = 0.01/0.03). The calculation of vorticity based on 4D flow data is an alternative approach to assess intracardiac flow changes in rTOF patients compared with qualitative flow visualization. Alterations in intracardiac vorticity could be relevant with regard to the development of RV dilation and impaired function. (orig.)

Assessment of intracardiac flow and vorticity in the right heart of patients after repair of tetralogy of Fallot by flow-sensitive 4D MRI

International Nuclear Information System (INIS)

Hirtler, Daniel; Garcia, Julio; Barker, Alex J.; Geiger, Julia

2016-01-01

To comprehensively and quantitatively analyse flow and vorticity in the right heart of patients after repair of tetralogy of Fallot (rTOF) compared with healthy volunteers. Time-resolved flow-sensitive 4D MRI was acquired in 24 rTOF patients and 12 volunteers. Qualitative flow evaluation was based on consensus reading of two observers. Quantitative analysis included segmentation of the right atrium (RA) and ventricle (RV) in a four-chamber view to extract volumes and regional haemodynamic information for computation of regional mean and peak vorticity. Right heart intra-atrial, intraventricular and outflow tract flow patterns differed considerably between rTOF patients and volunteers. Peak RA and mean RV vorticity was significantly higher in patients (p = 0.02/0.05). Significant negative correlations were found between patients' maximum and mean RV and RA vorticity and ventricular volumes (p < 0.05). The main pulmonary artery (MPA) regurgitant flow was associated with higher RA and RV vorticity, which was significant for RA maximum and RV mean vorticity (p = 0.01/0.03). The calculation of vorticity based on 4D flow data is an alternative approach to assess intracardiac flow changes in rTOF patients compared with qualitative flow visualization. Alterations in intracardiac vorticity could be relevant with regard to the development of RV dilation and impaired function. (orig.)

Topologically Allowed Nonsixfold Vortices in a Sixfold Multiferroic Material: Observation and Classification

KAUST Repository

Cheng, Shaobo; Li, Jun; Han, Myung-Geun; Deng, Shiqing; Tan, Guotai; Zhang, Xixiang; Zhu, Jing; Zhu, Yimei

2017-01-01

We report structural transformation of sixfold vortex domains into two-, four-, and eightfold vortices via a different type of topological defect in hexagonal manganites. Combining high-resolution electron microscopy and Landau

Plasma Cell Neoplasms (Including Multiple Myeloma)—Health Professional Version

Science.gov (United States)

There are several types of plasma cell neoplasms, including monoclonal gammopathy of undetermined significance (MGUS), isolated plasmacytoma of the bone, extramedullary plasmacytoma, and multiple myeloma. Find evidence-based information on plasma cell neoplasms treatment, research, and statistics.

Numerical investigation of Dean vortices in a curved pipe

Science.gov (United States)

Bernad, S. I.; Totorean, A.; Bosioc, A.; Stanciu, R.; Bernad, E. S.

2013-10-01

This study is devoted to the three-dimensional numerical simulation of developing secondary flows of Newtonian fluid through a curved circular duct. The numerical simulations produced for different Dean numbers show clearly the presence of two steady Dean vortices. Therefore, results confirm that helical flow constitutes an important flow signature in vessels, and its strength as a fluid dynamic index.

Chiral vortical effect from the compactified D4-branes with smeared D0-brane charge

Energy Technology Data Exchange (ETDEWEB)

Wu, Chao; Chen, Yidian [Institute of High Energy Physics, Chinese Academy of Sciences,Beijing 100049 (China); Huang, Mei [Institute of High Energy Physics, Chinese Academy of Sciences,Beijing 100049 (China); University of Chinese Academy of Sciences,Beijing 100049 (China); Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences,Beijing 100049 (China)

2017-03-15

By using the boundary derivative expansion formalism of fluid/gravity correspondence, we study the chiral vortical effect from the compactified D4-branes with smeared D0-brane charge. This background corresponds to a strongly coupled, nonconformal relativistic fluid with a conserved vector current. The presence of the chiral vortical effect is induced by the addition of a Chern-Simons term in the bulk action. Except that the non-dissipative anomalous viscous coefficient and the sound speed rely only on the chemical potential, most of the other thermal and hydrodynamical quantities of the first order depend both on the temperature and the chemical potential. According to our result, the way that the chiral vortical effect coefficient depends on the chemical potential seems irrelevant with whether the relativistic fluid is conformal or not. Stability analysis shows that this anomalous relativistic fluid is stable and the doping of the smeared D0-brane charge will slow down the sound speed.

Secondary Instability of Stationary Crossflow Vortices in Mach 6 Boundary Layer Over a Circular Cone

Science.gov (United States)

Li, Fei; Choudhari, Meelan M.; Paredes-Gonzalez, Pedro; Duan, Lian

2015-01-01

Hypersonic boundary layer flows over a circular cone at moderate incidence can support strong crossflow instability. Due to more efficient excitation of stationary crossflow vortices by surface roughness, such boundary layer flows may transition to turbulence via rapid amplification of the high-frequency secondary instabilities of finite amplitude stationary crossflow vortices. The amplification characteristics of these secondary instabilities are investigated for crossflow vortices generated by an azimuthally periodic array of roughness elements over a 7-degree half-angle circular cone in a Mach 6 free stream. Depending on the local amplitude of the stationary crossflow mode, the most unstable secondary disturbances either originate from the second (i.e., Mack) mode instabilities of the unperturbed boundary layer or correspond to genuine secondary instabilities that reduce to stable disturbances at sufficiently small amplitudes of the stationary crossflow vortex. The predicted frequencies of dominant secondary disturbances are similar to those measured during wind tunnel experiments at Purdue University and the Technical University of Braunschweig, Germany.

Identify multiple myeloma stem cells: Utopia?

Science.gov (United States)

Saltarella, Ilaria; Lamanuzzi, Aurelia; Reale, Antonia; Vacca, Angelo; Ria, Roberto

2015-01-26

Multiple myeloma (MM) is a hematologic malignancy of monoclonal plasma cells which remains incurable despite recent advances in therapies. The presence of cancer stem cells (CSCs) has been demonstrated in many solid and hematologic tumors, so the idea of CSCs has been proposed for MM, even if MM CSCs have not been define yet. The existence of myeloma CSCs with clonotypic B and clonotypic non B cells was postulated by many groups. This review aims to focus on these distinct clonotypic subpopulations and on their ability to develop and sustain MM. The bone marrow microenvironment provides to MM CSCs self-renewal, survival and drug resistance thanks to the presence of normal and cancer stem cell niches. The niches and CSCs interact each other through adhesion molecules and the interplay between ligands and receptors activates stemness signaling (Hedgehog, Wnt and Notch pathways). MM CSCs are also supposed to be responsible for drug resistance that happens in three steps from the initial cancer cell homing microenvironment-mediated to development of microenvironment-independent drug resistance. In this review, we will underline all these aspects of MM CSCs.

Mean Characteristics of Conical Vortices Above Roof Eaves of Low–Rise Cubic Buildings Using Particle Image Velocimetry

Directory of Open Access Journals (Sweden)

M. Gamboa–Marrufo

2009-04-01

Full Text Available Fluctuating low pressures near the edges of flat roofs are often caused when the wind impinges on one corner of the building so that conical vortices form above the diagonal roof edges. In turbulent flow, these vortices vary in position and strength and the underlying surface pressures fluctuate accordingly. A preliminary approach to the study of the mechanism linking instantaneous roof edge pressures with the wind vortical structures involves the evaluation of mean characteristics and positions of the latter. However the flow examination has so far been severely limited by the restriction of available anemometers to single–point sampling. In this experimental study, a 200mm cube has been used to model a building with a flat square roof set at an angle of 45° to the oncoming flow direction, and a Particle Image Velocimetry system was used to capture instantaneous two–dimensional velocity vector images of entire flow cross–sections, both normal to the vortex axis and in planes parallel to that axis. The se vector maps were used to estimate the mean characteristics of the vortices and appropriate observation–plane directions to measure wind velocities in the study of the instantaneous problem.

Turbulent flow over craters on Mars: Vorticity dynamics reveal aeolian excavation mechanism

Science.gov (United States)

Anderson, William; Day, Mackenzie

2017-10-01

Impact craters are scattered across Mars. These craters exhibit geometric self-similarity over a spectrum of diameters, ranging from tens to thousands of kilometers. The late Noachian-early Hesperian boundary marks a dramatic shift in the role of mid-latitude craters, from depocenter sedimentary basins to aeolian source areas. At present day, many craters contain prominent layered sedimentary mounds with maximum elevations comparable to the rim height. The mounds are remnants of Noachian deposition and are surrounded by a radial moat. Large-eddy simulation has been used to model turbulent flows over synthetic craterlike geometries. Geometric attributes of the craters and the aloft flow have been carefully matched to resemble ambient conditions in the atmospheric boundary layer of Mars. Vorticity dynamics analysis within the crater basin reveals the presence of counterrotating helical vortices, verifying the efficacy of deflationary models put forth recently by Bennett and Bell [K. Bennett and J. Bell, Icarus 264, 331 (2016)], 10.1016/j.icarus.2015.09.041 and Day et al. [M. Day et al., Geophys. Res. Lett. 43, 2473 (2016)], 10.1002/2016GL068011. We show how these helical counterrotating vortices spiral around the outer rim, gradually deflating the moat and carving the mound; excavation occurs faster on the upwind side, explaining the radial eccentricity of the mounds relative to the surrounding crater basin.

Turbulent flow over craters on Mars: Vorticity dynamics reveal aeolian excavation mechanism.

Science.gov (United States)

Anderson, William; Day, Mackenzie

2017-10-01

Impact craters are scattered across Mars. These craters exhibit geometric self-similarity over a spectrum of diameters, ranging from tens to thousands of kilometers. The late Noachian-early Hesperian boundary marks a dramatic shift in the role of mid-latitude craters, from depocenter sedimentary basins to aeolian source areas. At present day, many craters contain prominent layered sedimentary mounds with maximum elevations comparable to the rim height. The mounds are remnants of Noachian deposition and are surrounded by a radial moat. Large-eddy simulation has been used to model turbulent flows over synthetic craterlike geometries. Geometric attributes of the craters and the aloft flow have been carefully matched to resemble ambient conditions in the atmospheric boundary layer of Mars. Vorticity dynamics analysis within the crater basin reveals the presence of counterrotating helical vortices, verifying the efficacy of deflationary models put forth recently by Bennett and Bell [K. Bennett and J. Bell, Icarus 264, 331 (2016)]ICRSA50019-103510.1016/j.icarus.2015.09.041 and Day et al. [M. Day et al., Geophys. Res. Lett. 43, 2473 (2016)]GPRLAJ0094-827610.1002/2016GL068011. We show how these helical counterrotating vortices spiral around the outer rim, gradually deflating the moat and carving the mound; excavation occurs faster on the upwind side, explaining the radial eccentricity of the mounds relative to the surrounding crater basin.

Prognostic impact of circulating plasma cells in patients with multiple myeloma: implications for plasma cell leukemia definition.

Science.gov (United States)

Granell, Miquel; Calvo, Xavier; Garcia-Guiñón, Antoni; Escoda, Lourdes; Abella, Eugènia; Martínez, Clara Mª; Teixidó, Montserrat; Gimenez, Mª Teresa; Senín, Alicia; Sanz, Patricia; Campoy, Desirée; Vicent, Ana; Arenillas, Leonor; Rosiñol, Laura; Sierra, Jorge; Bladé, Joan; de Larrea, Carlos Fernández

2017-06-01

The presence of circulating plasma cells in patients with multiple myeloma is considered a marker for highly proliferative disease. In the study herein, the impact of circulating plasma cells assessed by cytology on survival of patients with multiple myeloma was analyzed. Wright-Giemsa stained peripheral blood smears of 482 patients with newly diagnosed myeloma or plasma cell leukemia were reviewed and patients were classified into 4 categories according to the percentage of circulating plasma cells: 0%, 1-4%, 5-20%, and plasma cell leukemia with the following frequencies: 382 (79.2%), 83 (17.2%), 12 (2.5%) and 5 (1.0%), respectively. Median overall survival according to the circulating plasma cells group was 47, 50, 6 and 14 months, respectively. At multivariate analysis, the presence of 5 to 20% circulating plasma cells was associated with a worse overall survival (relative risk 4.9, 95% CI 2.6-9.3) independently of age, creatinine, the Durie-Salmon system stage and the International Staging System (ISS) stage. Patients with ≥5% circulating plasma cells had lower platelet counts (median 86×10 9 /L vs 214×10 9 /L, P <0.0001) and higher bone marrow plasma cells (median 53% vs 36%, P =0.004). The presence of ≥5% circulating plasma cells in patients with multiple myeloma has a similar adverse prognostic impact as plasma cell leukemia. Copyright© Ferrata Storti Foundation.

Matter-wave vortices in cigar-shaped and toroidal waveguides

International Nuclear Information System (INIS)

Salasnich, L.; Toigo, F.; Malomed, B. A.

2007-01-01

We study vortical states in a Bose-Einstein condensate (BEC) filling a cigar-shaped trap. An effective one-dimensional (1D) nonpolynomial Schroedinger equation (NPSE) is derived in this setting, for the models with both repulsive and attractive interatomic interactions. Analytical formulas for the density profiles are obtained from the NPSE in the case of self-repulsion within the Thomas-Fermi approximation, and in the case of the self-attraction as exact solutions (bright solitons). A crucially important ingredient of the analysis is the comparison of these predictions with direct numerical solutions for the vortex states in the underlying 3D Gross-Pitaevskii equation. The comparison demonstrates that the NPSE provides for a very accurate approximation, in all the cases, including the prediction of the stability of the bright solitons and collapse threshold for them. In addition to the straight cigar-shaped trap, we also consider a torus-shaped configuration. In that case, we find a threshold for the transition from the axially uniform state, with the transverse intrinsic vorticity, to a symmetry-breaking pattern, due to the instability in the self-attractive BEC filling the circular trap

Manipulating Josephson junctions in thin-films by nearby vortices

International Nuclear Information System (INIS)

Kogan, V.G.; Mints, R.G.

2014-01-01

Highlights: • Vortex located in a bank of a planar Josephson junction changes its character. • Vortex located at some discreet positions in thin strip bank suppresses to zero the zero-field current. • The number of these positions is equal to the number of vortices trapped. • Critical current-field patterns are strongly affected by the vortex position. - Abstract: It is shown that a vortex trapped in one of the banks of a planar edge-type Josephson junction in a narrow thin-film superconducting strip can change drastically the dependence of the junction critical current on the applied field, I c (H). When the vortex is placed at certain discrete positions in the strip middle, the pattern I c (H) has zero at H=0 instead of the traditional maximum of ‘0-type’ junctions. The number of these positions is equal to the number of vortices trapped at the same location. When the junction–vortex separation exceeds ∼W, the strip width, I c (H) is no longer sensitive to the vortex presence. The same is true for any separation if the vortex approaches the strip edges

Statistical solutions of the Navier endash Stokes equations on the phase space of vorticity and the inviscid limits

International Nuclear Information System (INIS)

Constantin, P.; Wu, J.

1997-01-01

Using the methods of Foias [Sem. Math. Univ. Padova 48, 219 endash 343 (1972); 49, 9 endash 123 (1973)] and Vishik endash Fursikov [Mathematical Problems of Statistical Hydromechanics (Kluwer, Dordrecht, 1988)], we prove the existence and uniqueness of both spatial and space endash time statistical solutions of the Navier endash Stokes equations on the phase space of vorticity. Here the initial vorticity is in Yudovich space and the initial measure has finite mean enstrophy. We show under further assumptions on the initial vorticity that the statistical solutions of the Navier endash Stokes equations converge weakly and the inviscid limits are the corresponding statistical solutions of the Euler equations. copyright 1997 American Institute of Physics

Measurements of Tip Vortices from a Full-Scale UH-60A Rotor by Retro- Reflective Background Oriented Schlieren and Stereo Photogrammetry

Science.gov (United States)

Schairer, Edward; Kushner, Laura K.; Heineck, James T.

2013-01-01

Positions of vortices shed by a full-scale UH-60A rotor in forward flight were measured during a test in the National Full- Scale Aerodynamics Complex at NASA Ames Research Center. Vortices in a region near the tip of the advancing blade were visualized from two directions by Retro-Reflective Background-Oriented Schlieren (RBOS). Correspondence of points on the vortex in the RBOS images from both cameras was established using epipolar geometry. The object-space coordinates of the vortices were then calculated from the image-plane coordinates using stereo photogrammetry. One vortex from the tip of the blade that had most recently passed was visible in most of the data. The visibility of the vortices was greatest at high thrust and low advance ratios. At these favorable conditions, vortices from the most recent passages of all four blades were detected. The vortex positions were in good agreement with PIV data for a case where PIV measurements were also made. RBOS and photogrammetry provided measurements of the angle at which each vortex passed through the PIV plane.

Nonlinear magnetic electron tripolar vortices in streaming plasmas.

Science.gov (United States)

Vranjes, J; Marić, G; Shukla, P K

2000-06-01

Magnetic electron modes in nonuniform magnetized and unmagnetized streaming plasmas, with characteristic frequencies between the ion and electron plasma frequencies and at spatial scales of the order of the collisionless skin depth, are studied. Two coupled equations, for the perturbed (in the case of magnetized plasma) or self-generated (for the unmagnetized plasma case) magnetic field, and the temperature, are solved in the strongly nonlinear regime and stationary traveling solutions in the form of tripolar vortices are found.

Efficient cascade multiple heterojunction organic solar cells with inverted structure

Science.gov (United States)

Guo, Tingting; Li, Mingtao; Qiao, Zhenfang; Yu, Leiming; Zhao, Jianhong; Feng, Nianjun; Shi, Peiguang; Wang, Xiaoyan; Pu, Xiaoyun; Wang, Hai

2018-05-01

In this work, we demonstrate an efficient cascade multiple heterojunction organic solar cell with inverted structure. By using two donor materials, poly(3-hexylthiosphene) (P3HT) and titanyl phthalocyanine (TiOPc), as well as two acceptor materials, [6,6]-phenyl C61 butyric acid methyl ester (PCBM) and C60, the cascade multiple heterojunctions of P3HT:PCBM/TiOPc:C60/C60 have been constructed. Applying the optimized inverted configuration of FTO/Zinc Tin Oxide (ZTO)/C60 (30 nm)/TiOPc:C60 (1:1.5, 25 nm)/P3HT:PCBM (1:0.8, 100 nm)/MoO3 (4 nm)/Ag, the considerably enhanced open circuit voltage (VOC) and short circuit current (JSC) can be harvested together, and the power conversion efficiency (PCE) is three times higher than that of the control cell with conventional structure. The significant improvements of the inverted cell are mostly due to the broadened spectral absorption and high efficient multi-interface exciton dissociation in the cascade multiple heterojunctions, indicating that the optimized cascade heterojunctions match the inverted structure well.

Effect of single Abrikosov vortices on the properties of Josephson tunnel junctions

International Nuclear Information System (INIS)

Golubov, A.A.; Kupriyanov, M.Yu.

1987-01-01

The effect of single Abrikosov vortices, trapped in the electrodes of a Josephson tunnel junction perpendicularly to the junction surface, on the tunnel current through the junction is studied within the framework of the microscopic theory. The current-voltage characteristic and the critical junction current I c are calculated for temperatures 0 c . It is shown that if the vortices at the junction are misaligned, singularities on the current-voltage characteristic appear at eV Δ (T), and in some cases the magnitude of suppression of I c may be of the order of magnitude of I c itself. The temperature dependence of the critical current is calculated for the case of one of the electrodes being a two-dimensional superconducting film in which the creation of opposite sign vortex pairs is significant

A Coherent vorticity preserving eddy-viscosity correction for Large-Eddy Simulation

Science.gov (United States)

Chapelier, J.-B.; Wasistho, B.; Scalo, C.

2018-04-01

This paper introduces a new approach to Large-Eddy Simulation (LES) where subgrid-scale (SGS) dissipation is applied proportionally to the degree of local spectral broadening, hence mitigated or deactivated in regions dominated by large-scale and/or laminar vortical motion. The proposed coherent-vorticity preserving (CvP) LES methodology is based on the evaluation of the ratio of the test-filtered to resolved (or grid-filtered) enstrophy, σ. Values of σ close to 1 indicate low sub-test-filter turbulent activity, justifying local deactivation of the SGS dissipation. The intensity of the SGS dissipation is progressively increased for σ activated in developed turbulence characterized by σ ≤σeq, where the value σeq is derived assuming a Kolmogorov spectrum. The proposed approach can be applied to any eddy-viscosity model, is algorithmically simple and computationally inexpensive. LES of Taylor-Green vortex breakdown demonstrates that the CvP methodology improves the performance of traditional, non-dynamic dissipative SGS models, capturing the peak of total turbulent kinetic energy dissipation during transition. Similar accuracy is obtained by adopting Germano's dynamic procedure albeit at more than twice the computational overhead. A CvP-LES of a pair of unstable periodic helical vortices is shown to predict accurately the experimentally observed growth rate using coarse resolutions. The ability of the CvP methodology to dynamically sort the coherent, large-scale motion from the smaller, broadband scales during transition is demonstrated via flow visualizations. LES of compressible channel are carried out and show a good match with a reference DNS.

Plume rise from multiple sources

International Nuclear Information System (INIS)

Briggs, G.A.

1975-01-01

A simple enhancement factor for plume rise from multiple sources is proposed and tested against plume-rise observations. For bent-over buoyant plumes, this results in the recommendation that multiple-source rise be calculated as [(N + S)/(1 + S)]/sup 1/3/ times the single-source rise, Δh 1 , where N is the number of sources and S = 6 (total width of source configuration/N/sup 1/3/ Δh 1 )/sup 3/2/. For calm conditions a crude but simple method is suggested for predicting the height of plume merger and subsequent behavior which is based on the geometry and velocity variations of a single buoyant plume. Finally, it is suggested that large clusters of buoyant sources might occasionally give rise to concentrated vortices either within the source configuration or just downwind of it

Development and Breakdown of Goertler Vortices in High Speed Boundary Layers

Science.gov (United States)

Li, Fei; Choudhari, Meelan; Chang, Chau-Lyan; Wu, Minwei; Greene, Ptrick T.

2010-01-01

The nonlinear development of G rtler instability over a concave surface gives rise to a highly distorted stationary flow in the boundary layer that has strong velocity gradients in both spanwise and wall-normal directions. This distorted flow is susceptible to strong, high frequency secondary instability that leads to the onset of transition. For high Mach number flows, the boundary layer is also subject to the second mode instability. The nonlinear development of G rtler vortices and the ensuing growth and breakdown of secondary instability, the G rtler vortex interactions with second mode instabilities as well as oblique second mode interactions are examined in the context of both internal and external hypersonic configurations using nonlinear parabolized stability equations, 2-D eigenvalue analysis and direct numerical simulation. For G rtler vortex development inside the Purdue Mach 6 Ludwieg tube wind tunnel, multiple families of unstable secondary eigenmodes are identified and their linear and nonlinear evolution is examined. The computation of secondary instability is continued past the onset of transition to elucidate the physical mechanisms underlying the laminar breakdown process. Nonlinear breakdown scenarios associated with transition over a Mach 6 compression cone configuration are also explored.

Compressible flows with periodic vortical disturbances around lifting airfoils. Ph.D. Thesis - Notre Dame Univ.

Science.gov (United States)

Scott, James R.

1991-01-01

A numerical method is developed for solving periodic, three-dimensional, vortical flows around lifting airfoils in subsonic flow. The first-order method that is presented fully accounts for the distortion effects of the nonuniform mean flow on the convected upstream vortical disturbances. The unsteady velocity is split into a vortical component which is a known function of the upstream flow conditions and the Lagrangian coordinates of the mean flow, and an irrotational field whose potential satisfies a nonconstant-coefficient, inhomogeneous, convective wave equation. Using an elliptic coordinate transformation, the unsteady boundary value problem is solved in the frequency domain on grids which are determined as a function of the Mach number and reduced frequency. The numerical scheme is validated through extensive comparisons with known solutions to unsteady vortical flow problems. In general, it is seen that the agreement between the numerical and analytical results is very good for reduced frequencies ranging from 0 to 4, and for Mach numbers ranging from .1 to .8. Numerical results are also presented for a wide variety of flow configurations for the purpose of determining the effects of airfoil thickness, angle of attack, camber, and Mach number on the unsteady lift and moment of airfoils subjected to periodic vortical gusts. It is seen that each of these parameters can have a significant effect on the unsteady airfoil response to the incident disturbances, and that the effect depends strongly upon the reduced frequency and the dimensionality of the gust. For a one-dimensional (transverse) or two-dimensional (transverse and longitudinal) gust, the results indicate that airfoil thickness increases the unsteady lift and moment at the low reduced frequencies but decreases it at the high reduced frequencies. The results show that an increase in airfoil Mach number leads to a significant increase in the unsteady lift and moment for the low reduced frequencies, but a

Vorticity generation and evolution in shock-accelerated density-stratified interfaces

International Nuclear Information System (INIS)

Yang, X.; Chern, I.; Zabusky, N.J.; Samtaney, R.; Hawley, J.F.

1992-01-01

The results of direct numerical simulations of inviscid planar shock-accelerated density-stratified interfaces in two dimensions are presented and compared with shock tube experiments of Haas [(private communication, 1988)] and Sturtevant [in Shock Tubes and Waves, edited by H. Gronig (VCH, Berlin, 1987), p. 89] . Heavy-to-light (''slow/fast or s/f) and light-to-heavy (''fast/slow,'' or f/s) gas interfaces are examined and early-time impulsive vorticity deposition and the evolution of coherent vortex structures are emphasized and quantified. The present second-order Godunov scheme yields excellent agreement with shock-polar analyses at early time. A more physical vortex interpretation explains the commonly used (i.e., linear paradigm) designations of ''unstable'' and ''stable'' for the f/s and s/f interfaces, respectively. The later time events are Rayleigh--Taylor like and can be described in terms of the evolution of a vortex layer (large-scale translation and rotation): asymmetric tip vortex ''roll-up'' and ''binding;'' layer ''instability;'' convective mixing; and baroclinic vorticity generation from secondary shock--interface interactions

Multiple eigenmodes of the Rayleigh-Taylor instability observed for a fluid interface with smoothly varying density

Science.gov (United States)

Yu, C. X.; Xue, C.; Liu, J.; Hu, X. Y.; Liu, Y. Y.; Ye, W. H.; Wang, L. F.; Wu, J. F.; Fan, Z. F.

2018-01-01

In this article, multiple eigen-systems including linear growth rates and eigen-functions have been discovered for the Rayleigh-Taylor instability (RTI) by numerically solving the Sturm-Liouville eigen-value problem in the case of two-dimensional plane geometry. The system called the first mode has the maximal linear growth rate and is just extensively studied in literature. Higher modes have smaller eigen-values, but possess multi-peak eigen-functions which bring on multiple pairs of vortices in the vorticity field. A general fitting expression for the first four eigen-modes is presented. Direct numerical simulations show that high modes lead to appearances of multi-layered spike-bubble pairs, and lots of secondary spikes and bubbles are also generated due to the interactions between internal spikes and bubbles. The present work has potential applications in many research and engineering areas, e.g., in reducing the RTI growth during capsule implosions in inertial confinement fusion.

Vortices in nonuniform upper-hybrid field

International Nuclear Information System (INIS)

Davydova, T.A.; Vranjes, J.

1992-01-01

The equations describing the interaction of an upper-hybrid pump wave with small low-frequency density perturbations are discussed under assumption that the pump is spatially nonuniform. The conditions for the modulational instability are investigated. Instead of a dispersion relation, describing the growth of perturbations in the case of an uniform pump, in our case of nonuniform pump a differential equation is obtained and from its eigenvalues are found the instability criteria. Taking into account the slow-frequency self-interaction terms some localized solutions similar to dipole vortices are found, but described by analytic functions in all space. It is shown that their characteristic size and speed are determined by the pump intensity and its spatial structure. (au)

Formation of intrathermocline eddies at ocean fronts by wind-driven destruction of potential vorticity

Science.gov (United States)

Thomas, Leif N.

2008-08-01

A mechanism for the generation of intrathermocline eddies (ITEs) at wind-forced fronts is examined using a high resolution numerical simulation. Favorable conditions for ITE formation result at fronts forced by "down-front" winds, i.e. winds blowing in the direction of the frontal jet. Down-front winds exert frictional forces that reduce the potential vorticity (PV) within the surface boundary in the frontal outcrop, providing a source for the low-PV water that is the materia prima of ITEs. Meandering of the front drives vertical motions that subduct the low-PV water into the pycnocline, pooling it into the coherent anticyclonic vortex of a submesoscale ITE. As the fluid is subducted along the outcropping frontal isopycnal, the low-PV water, which at the surface is associated with strongly baroclinic flow, re-expresses itself as water with nearly zero absolute vorticity. This generation of strong anticyclonic vorticity results from the tilting of the horizontal vorticity of the frontal jet, not from vortex squashing. During the formation of the ITE, high-PV water from the pycnocline is upwelled alongside the subducting low-PV surface water. The positive correlation between the ITE's velocity and PV fields results in an upward, along-isopycnal eddy PV flux that scales with the surface frictional PV flux driven by the wind. The relationship between the eddy and wind-induced frictional PV flux is nonlocal in time, as the eddy PV flux persists long after the wind forcing is shut off. The ITE's PV flux affects the large-scale flow by driving an eddy-induced transport or bolus velocity down the outcropping isopycnal layer with a magnitude that scales with the Ekman velocity.

Plasma Cell Neoplasms (Including Multiple Myeloma) Treatment (PDQ®)—Patient Version

Science.gov (United States)

Plasma cell neoplasms occur when abnormal plasma cells or myeloma cells form tumors in the bones or soft tissues of the body. Multiple myeloma, plasmacytoma, lymphoplasmacytic lymphoma, and monoclonal gammopathy of undetermined significance (MGUS) are different types of plasma cell neoplasms. Find out about risk factors, symptoms, diagnostic tests, prognosis, and treatment for these diseases.

Fragmentation of Fast Josephson Vortices and Breakdown of Ordered States by Moving Topological Defects.

Science.gov (United States)

Sheikhzada, Ahmad; Gurevich, Alex

2015-12-07

Topological defects such as vortices, dislocations or domain walls define many important effects in superconductivity, superfluidity, magnetism, liquid crystals, and plasticity of solids. Here we address the breakdown of the topologically-protected stability of such defects driven by strong external forces. We focus on Josephson vortices that appear at planar weak links of suppressed superconductivity which have attracted much attention for electronic applications, new sources of THz radiation, and low-dissipative computing. Our numerical simulations show that a rapidly moving vortex driven by a constant current becomes unstable with respect to generation of vortex-antivortex pairs caused by Cherenkov radiation. As a result, vortices and antivortices become spatially separated and accumulate continuously on the opposite sides of an expanding dissipative domain. This effect is most pronounced in thin film edge Josephson junctions at low temperatures where a single vortex can switch the whole junction into a resistive state at currents well below the Josephson critical current. Our work gives a new insight into instability of a moving topological defect which destroys global long-range order in a way that is remarkably similar to the crack propagation in solids.

EEN regulates the proliferation and survival of multiple myeloma cells by potentiating IGF-1 secretion

International Nuclear Information System (INIS)

Huang, Er-Wen; Xue, Sheng-Jiang; Li, Xiao-Yan; Xu, Suo-Wen; Cheng, Jian-Ding; Zheng, Jin-Xiang; Shi, He; Lv, Guo-Li; Li, Zhi-Gang; Li, Yue; Liu, Chang-Hui; Chen, Xiao-Hui; Liu, Hong; Li, Jie; Liu, Chao

2014-01-01

Highlights: • Levels of EEN expression paralleled with the rate of cell proliferation. • EEN was involved in the proliferation and survival of multiple myeloma (MM) cells. • EEN regulated the activity of IGF-1-Akt/mTOR pathway. • EEN regulated proliferation and survival of MM cells by enhancing IGF-1 secretion. - Abstract: The molecular mechanisms of multiple myeloma are not well defined. EEN is an endocytosis-regulating molecule. Here we report that EEN regulates the proliferation and survival of multiple myeloma cells, by regulating IGF-1 secretion. In the present study, we observed that EEN expression paralleled with cell proliferation, EEN accelerated cell proliferation, facilitated cell cycle transition from G1 to S phase by regulating cyclin-dependent kinases (CDKs) pathway, and delayed cell apoptosis via Bcl2/Bax-mitochondrial pathway. Mechanistically, we found that EEN was indispensable for insulin-like growth factor-1 (IGF-1) secretion and the activation of protein kinase B-mammalian target of rapamycin (Akt-mTOR) pathway. Exogenous IGF-1 overcame the phenotype of EEN depletion, while IGF-1 neutralization overcame that of EEN over-expression. Collectively, these data suggest that EEN may play a pivotal role in excessive cell proliferation and insufficient cell apoptosis of bone marrow plasma cells in multiple myeloma. Therefore, EEN may represent a potential diagnostic marker or therapeutic target for multiple myeloma

EEN regulates the proliferation and survival of multiple myeloma cells by potentiating IGF-1 secretion

Energy Technology Data Exchange (ETDEWEB)

Huang, Er-Wen [Guangzhou Institute of Forensic Science, Guangzhou (China); Department of Forensic Pathology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou (China); Xue, Sheng-Jiang [Department of Forensic Pathology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou (China); Li, Xiao-Yan [Department of Pharmacy, The Third Affiliated Hospital, Sun Yat-Sen University, Guangzhou (China); Xu, Suo-Wen [Department of Pharmacology and Toxicology, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou (China); Cheng, Jian-Ding; Zheng, Jin-Xiang [Department of Forensic Pathology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou (China); Shi, He; Lv, Guo-Li; Li, Zhi-Gang; Li, Yue; Liu, Chang-Hui; Chen, Xiao-Hui; Liu, Hong [Guangzhou Institute of Forensic Science, Guangzhou (China); Li, Jie, E-mail: mdlijie@sina.com [Department of Anaesthesiology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou (China); Liu, Chao, E-mail: liuchaogaj@21cn.com [Guangzhou Institute of Forensic Science, Guangzhou (China)

2014-05-02

Highlights: • Levels of EEN expression paralleled with the rate of cell proliferation. • EEN was involved in the proliferation and survival of multiple myeloma (MM) cells. • EEN regulated the activity of IGF-1-Akt/mTOR pathway. • EEN regulated proliferation and survival of MM cells by enhancing IGF-1 secretion. - Abstract: The molecular mechanisms of multiple myeloma are not well defined. EEN is an endocytosis-regulating molecule. Here we report that EEN regulates the proliferation and survival of multiple myeloma cells, by regulating IGF-1 secretion. In the present study, we observed that EEN expression paralleled with cell proliferation, EEN accelerated cell proliferation, facilitated cell cycle transition from G1 to S phase by regulating cyclin-dependent kinases (CDKs) pathway, and delayed cell apoptosis via Bcl2/Bax-mitochondrial pathway. Mechanistically, we found that EEN was indispensable for insulin-like growth factor-1 (IGF-1) secretion and the activation of protein kinase B-mammalian target of rapamycin (Akt-mTOR) pathway. Exogenous IGF-1 overcame the phenotype of EEN depletion, while IGF-1 neutralization overcame that of EEN over-expression. Collectively, these data suggest that EEN may play a pivotal role in excessive cell proliferation and insufficient cell apoptosis of bone marrow plasma cells in multiple myeloma. Therefore, EEN may represent a potential diagnostic marker or therapeutic target for multiple myeloma.

Quantum fluctuations of vortices in Josephson-coupled superconductors

International Nuclear Information System (INIS)

Bulaevskii, L.N.; Maley, M.P.

1994-01-01

The effect of quantum fluctuations of vortices on the low temperature specific heat and reversible magnetization in the mixed state in highly anisotropic layered superconductors is discussed. For reversible magnetization, M, the change of slope in the dependence of M vs ln B, observed in Bi(2:2:1:2), is explained. In the mean, field approach this slope should be almost B independent. The specific heat due to the vortex fluctuation contribution is predicted to be linear in T at low T

A note on the energy of relative equilibria of point vortices

DEFF Research Database (Denmark)

Aref, Hassan

2007-01-01

Analytical formulas are derived for the energy of simple relative equilibria of identical point vortices such as the regular polygons, both open and centered, and the various known configurations consisting of nested regular polygons with or without a vortex at the center. ©2007 American Institute...

Dipole vortices in the Great Australian Bight

DEFF Research Database (Denmark)

Cresswell, George R.; Lund-Hansen, Lars C.; Nielsen, Morten Holtegaard

2015-01-01

Shipboard measurements from late 2006 made by the Danish Galathea 3 Expedition and satellite sea surface temperature images revealed a chain of cool and warm mushroom' dipole vortices that mixed warm, salty, oxygen-poor waters on and near the continental shelf of the Great Australian Bight (GAB...... denser than the cooler offshore waters. The field of dipoles evolved and distorted, but appeared to drift westwards at 5km day-1 over two weeks, and one new mushroom carried GAB water southwards at 7km day(-1). Other features encountered between Cape Leeuwin and Tasmania included the Leeuwin Current...

Dynamics of Two Point Vortices in an External Compressible Shear Flow

Science.gov (United States)

Vetchanin, Evgeny V.; Mamaev, Ivan S.

2017-12-01

This paper is concerned with a system of equations that describes the motion of two point vortices in a flow possessing constant uniform vorticity and perturbed by an acoustic wave. The system is shown to have both regular and chaotic regimes of motion. In addition, simple and chaotic attractors are found in the system. Attention is given to bifurcations of fixed points of a Poincaré map which lead to the appearance of these regimes. It is shown that, in the case where the total vortex strength changes, the "reversible pitch-fork" bifurcation is a typical scenario of emergence of asymptotically stable fixed and periodic points. As a result of this bifurcation, a saddle point, a stable and an unstable point of the same period emerge from an elliptic point of some period. By constructing and analyzing charts of dynamical regimes and bifurcation diagrams we show that a cascade of period-doubling bifurcations is a typical scenario of transition to chaos in the system under consideration.

Vorticity generation and jetting caused by a laser-induced optical breakdown

Science.gov (United States)

Wang, Jonathan; Buchta, David; Freund, Jonathan

2017-11-01

A focused laser can cause optical breakdown of a gas that absorbs energy and can seed ignition. The local hydrodynamics are complex. The breakdown is observed to produce vorticity that subsequently collects into a jetting flow towards the laser source. The strength and the very direction of the jet is observed to be sensitive to the plasma kernel geometry. We use detailed numerical simulations to examine the short-time (inverse Bremsstrahlung, and 11 charged and neutral species for air. We quantify the early-time contributions of different thermodynamic and gas-dynamic effects to the baroclinic torque. It is found that the breakdown produces compression waves within the plasma kernel, and that the mismatch in their strengths precipitates the involution of the plasma remnants and yields the net vorticity that ultimately develops into the jet. We also quantify the temperature distribution and local strain rates and demonstrate their importance in seeding ignition in non-homogeneous hydrogen/air mixtures.

Electron acoustic vortices in the presence of inhomogeneous current

Energy Technology Data Exchange (ETDEWEB)

Haque, Q; Masood, W; Saleem, H [Theoretical Plasma Physics Division, PINSTECH, P O Nilore, Islamabad (Pakistan)], E-mail: qamar@pinstech.org.pk

2008-03-15

Linear and nonlinear dynamics of an electron acoustic wave in an inhomogeneous magnetized plasma are studied in the presence of non-uniform background current. The modified Rayleigh instability condition is found due to shear in the magnetic field and the current. A nonlinear stationary solution is also obtained in the form of tripolar vortices. The relevance of the present study to auroral and magnetotail plasmas is pointed out.

Increased T cell expression of CD154 (CD40-ligand) in multiple sclerosis

DEFF Research Database (Denmark)

Jensen, J; Krakauer, M; Sellebjerg, F

2001-01-01

CD154 (CD40-ligand, gp39), expressed on activated T cells, is crucial in T cell-dependent immune responses and may be involved in the pathogenesis of multiple sclerosis (MS). We studied cerebro-spinal fluid and peripheral blood T cell expression of CD154 in MS by flow cytometry. Patients with sec......CD154 (CD40-ligand, gp39), expressed on activated T cells, is crucial in T cell-dependent immune responses and may be involved in the pathogenesis of multiple sclerosis (MS). We studied cerebro-spinal fluid and peripheral blood T cell expression of CD154 in MS by flow cytometry. Patients...

Intracranial Tumor Cell Migration and the Development of Multiple Brain Metastases in Malignant Melanoma

Directory of Open Access Journals (Sweden)

Trude G. Simonsen

2016-06-01

Full Text Available INTRODUCTION: A majority of patients with melanoma brain metastases develop multiple lesions, and these patients show particularly poor prognosis. To develop improved treatment strategies, detailed insights into the biology of melanoma brain metastases, and particularly the development of multiple lesions, are needed. The purpose of this preclinical investigation was to study melanoma cell migration within the brain after cell injection into a well-defined intracerebral site. METHODS: A-07, D-12, R-18, and U-25 human melanoma cells transfected with green fluorescent protein were injected stereotactically into the right cerebral hemisphere of nude mice. Moribund mice were killed and autopsied, and the brain was evaluated by fluorescence imaging or histological examination. RESULTS: Intracerebral inoculation of melanoma cells produced multiple lesions involving all regions of the brain, suggesting that the cells were able to migrate over substantial distances within the brain. Multiple modes of transport were identified, and all transport modes were observed in all four melanoma lines. Thus, the melanoma cells were passively transported via the flow of cerebrospinal fluid in the meninges and ventricles, they migrated actively along leptomeningeal and brain parenchymal blood vessels, and they migrated actively along the surfaces separating different brain compartments. CONCLUSION: Migration of melanoma cells after initial arrest, extravasation, and growth at a single location within the brain may contribute significantly to the development of multiple melanoma brain metastases.

A critical examination of the numerology of antigen-binding cells: evidence for multiple receptor specificities on single cells.

Science.gov (United States)

Miller, A

1977-01-01

The data available from other laboratories as well as our own on the frequency of cells recognizing major histocompatibility antigens or conventional protein and hapten antigens is critically evaluated. The frequency of specific binding for a large number of antigens is sufficiently high to support the idea that at least part of the antigen-binding cell population must have multiple specificities. Our results suggest that these multiple specific cells result from single cells synthesizing and displaying as many as 50-100 species of receptor, each at a frequency of 10(4) per cell. A model involving gene expansion of constant-region genes is suggested and some auxilliary evidence consistent with such C-gene expansion is presented.

Study of ultrasonic propagation through vortices for acoustic monitoring of high-temperature and turbulent fluid

International Nuclear Information System (INIS)

Massacret, Nicolas; Moysan, Joseph; Ploix, Marie-Aude; Chaouch, Naim; Jeannot, Jean-Philippe

2016-01-01

Ultrasonic monitoring in high temperature fluids with turbulences requires the knowledge of wave propagation in such media and the development of simulation tools. Applications could be the monitoring of sodium-cooled fast reactors. The objectives are mainly acoustic telemetry and thermometry, which involve the propagation of ultrasounds in turbulent and heated sodium flows. We developed a ray-tracing model to simulate the wave propagation and to determine wave deviations and delays due to an inhomogeneous medium. In previous work we demonstrated the sensitivity of ultrasounds to temperature gradients in liquid sodium. To complete that study, we need to investigate the sensitivity of ultrasounds to vortices created in a moving fluid. We designed a specific experimental setup called IKHAR (Instabilities of Kelvin-Helmholtz for Acoustic Research) in order to assess the validity of the ray-tracing model and the potential of ultrasounds for monitoring such fluid. In this experiment, Von Karman instabilities were created in a flow of water. Fluid temperature was homogeneous in our experimental setup. Through a careful choice of the parameters, periodic vortices were generated. The experiment was also simulated using Comsol registered to allow discussion about repeatability. The throughtransmission method was used to measure wave delays due to the vortices. Arrays of transducers were used to measure time of flight variations of several nanoseconds with a high spatial resolution. Results were similar to simulation results. They demonstrate that beam delays due to vortices can be measured and confirm the potential of ultrasounds in monitoring very inhomogeneous fluid media such as liquid sodium used as coolant fluid in nuclear fast reactors.

Cyclic AMP induces apoptosis in multiple myeloma cells and inhibits tumor development in a mouse myeloma model

International Nuclear Information System (INIS)

Follin-Arbelet, Virginie; Hofgaard, Peter O; Hauglin, Harald; Naderi, Soheil; Sundan, Anders; Blomhoff, Rune; Bogen, Bjarne; Blomhoff, Heidi K

2011-01-01

Multiple myeloma is an incurable disease requiring the development of effective therapies which can be used clinically. We have elucidated the potential for manipulating the cAMP signaling pathway as a target for inhibiting the growth of multiple myeloma cells. As a model system, we primarily used the murine multiple myeloma cell line MOPC315 which can be grown both in vivo and in vitro. Human multiple myeloma cell lines U266, INA-6 and the B-cell precursor acute lymphoblastic leukemia cell line Reh were used only for in vitro studies. Cell death was assessed by flow cytometry and western blot analysis after treatment with cAMP elevating agents (forskolin, prostaglandin E2 and rolipram) and cAMP analogs. We followed tumor growth in vivo after forskolin treatment by imaging DsRed-labelled MOPC315 cells transplanted subcutaneously in BALB/c nude mice. In contrast to the effect on Reh cells, 50 μM forskolin more than tripled the death of MOPC315 cells after 24 h in vitro. Forskolin induced cell death to a similar extent in the human myeloma cell lines U266 and INA-6. cAMP-mediated cell death had all the typical hallmarks of apoptosis, including changes in the mitochondrial membrane potential and cleavage of caspase 3, caspase 9 and PARP. Forskolin also inhibited the growth of multiple myeloma cells in a mouse model in vivo. Elevation of intracellular levels of cAMP kills multiple myeloma cells in vitro and inhibits development of multiple myeloma in vivo. This strongly suggests that compounds activating the cAMP signaling pathway may be useful in the field of multiple myeloma

Management of Vortices Trailing Flapped Wings via Separation Control

Science.gov (United States)

Greenblatt, David

2005-01-01

A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management via separation control. Passive control was achieved by means of a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressure ports, was used to predict vortex characteristics by means of inviscid rollup relations. Furthermore, 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 both outboard and inboard edge vortices while producing negligible lift excursions. Dynamic separation and attachment control was found to be an effective means for dynamically perturbing the vortex from arbitrarily long wavelengths down to wavelengths less 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.

Smart Energy Management of Multiple Full Cell Powered Applications

Energy Technology Data Exchange (ETDEWEB)

Mohammad S. Alam

2007-04-23

In this research project the University of South Alabama research team has been investigating smart energy management and control of multiple fuel cell power sources when subjected to varying demands of electrical and thermal loads together with demands of hydrogen production. This research has focused on finding the optimal schedule of the multiple fuel cell power plants in terms of electric, thermal and hydrogen energy. The optimal schedule is expected to yield the lowest operating cost. Our team is also investigating the possibility of generating hydrogen using photoelectrochemical (PEC) solar cells through finding materials for efficient light harvesting photoanodes. The goal is to develop an efficient and cost effective PEC solar cell system for direct electrolysis of water. In addition, models for hydrogen production, purification, and storage will be developed. The results obtained and the data collected will be then used to develop a smart energy management algorithm whose function is to maximize energy conservation within a managed set of appliances, thereby lowering O/M costs of the Fuel Cell power plant (FCPP), and allowing more hydrogen generation opportunities. The Smart Energy Management and Control (SEMaC) software, developed earlier, controls electrical loads in an individual home to achieve load management objectives such that the total power consumption of a typical residential home remains below the available power generated from a fuel cell. In this project, the research team will leverage the SEMaC algorithm developed earlier to create a neighborhood level control system.

Steady state drift vortices in plasmas with shear flow in equilibrium

DEFF Research Database (Denmark)

Chakrabarti, N.

1999-01-01

The Hasegawa-Mima equation in the presence of sheared poloidal flow is solved for two-dimensional steady state vortex. It is shown that when the phase velocity of the vortex is the same as the diamagnetic drift velocity, an exact solution in the form of counter-rotating vortices may appear...

Raman spectroscopy differentiates between sensitive and resistant multiple myeloma cell lines

Science.gov (United States)

Franco, Domenico; Trusso, Sebastiano; Fazio, Enza; Allegra, Alessandro; Musolino, Caterina; Speciale, Antonio; Cimino, Francesco; Saija, Antonella; Neri, Fortunato; Nicolò, Marco S.; Guglielmino, Salvatore P. P.

2017-12-01

Current methods for identifying neoplastic cells and discerning them from their normal counterparts are often nonspecific and biologically perturbing. Here, we show that single-cell micro-Raman spectroscopy can be used to discriminate between resistant and sensitive multiple myeloma cell lines based on their highly reproducible biomolecular spectral signatures. In order to demonstrate robustness of the proposed approach, we used two different cell lines of multiple myeloma, namely MM.1S and U266B1, and their counterparts MM.1R and U266/BTZ-R subtypes, resistant to dexamethasone and bortezomib, respectively. Then, micro-Raman spectroscopy provides an easily accurate and noninvasive method for cancer detection for both research and clinical environments. Characteristic peaks, mostly due to different DNA/RNA ratio, nucleic acids, lipids and protein concentrations, allow for discerning the sensitive and resistant subtypes. We also explored principal component analysis (PCA) for resistant cell identification and classification. Sensitive and resistant cells form distinct clusters that can be defined using just two principal components. The identification of drug-resistant cells by confocal micro-Raman spectroscopy is thus proposed as a clinical tool to assess the development of resistance to glucocorticoids and proteasome inhibitors in myeloma cells.

Matter in the form of toroidal electromagnetic vortices

Science.gov (United States)

Hagen, Wilhelm F.

2015-09-01

The creation of charged elementary particles from neutral photons is explained as a conversion process of electromagnetic (EM) energy from linear to circular motion at the speed of light into two localized, toroidal shaped vortices of trapped EM energy that resist change of motion, perceptible as particles with inertia and hence mass. The photon can be represented as a superposition of left and right circular polarized transverse electric fields of opposite polarity originating from a common zero potential axis, the optical axis of the photon. If these components are separated by interaction with a strong field (nucleon) they would curl up into two electromagnetic vortices (EMV) due to longitudinal magnetic field components forming toroids. These vortices are perceptible as opposite charged elementary particles e+/- . These spinning toroids generate extended oscillating fields that interact with stationary field oscillations. The velocity-dependent frequency differences cause beat signals equivalent to matter waves, leading to interference. The extended fields entangled with every particle explain wave particle duality issues. Spin and magnetic moment are the natural outcome of these gyrating particles. As the energy and hence mass of the electron increases with acceleration so does its size shrink proportional to its reduced wavelength. The artificial weak and strong nuclear forces can be easily explained as different manifestations of the intermediate EM forces. The unstable neutron consists of a proton surrounded by a contracted and captured electron. The associated radial EM forces represent the weak nuclear force. The deuteron consists of two axially separated protons held together by a centrally captured electron. The axial EM forces represent the strong nuclear force, providing stability for "neutrons" only within nucleons. The same principles were applied to determine the geometries of force-balanced nuclei. The alpha-particle emerges as a very compact

Dynamics of two-dimensional solitary vortices in a low-β plasma with convective motion

International Nuclear Information System (INIS)

Makino, Mitsuhiro; Kamimura, Tetsuo; Taniuti, Tosiya.

1980-12-01

Numerical studies of the Hasegawa-Mima equation, derived in the context of drift waves but equivalent to the quasigeostrophic vortex potential equation for Rossby waves, show the stable properties of solitary vortices which are two dimensional, localized, steady and translating solutions of this same equation. A solitary vortex can propagate only in the direction (x-direction) perpendicular to the density gradient. When this solitary vortex solution is inclined at some angle with respect to the x-axis, its propagation direction oscillates in the x and y plane. In two dimensional collisions, i.e. head-on collision and overtaking, solitary vortices interact two-dimensionally and recover their initial shapes at the end of both types of collisions. (author)

Fundamental vortices, wall-crossing, and particle-vortex duality

Energy Technology Data Exchange (ETDEWEB)

Hwang, Chiung; Yi, Piljin [School of Physics, Korea Institute for Advanced Study,Seoul 02455 (Korea, Republic of); Yoshida, Yutaka [Research Institute for Mathematical Sciences, Kyoto University,Kyoto 606-8502 (Japan)

2017-05-18

We explore 1d vortex dynamics of 3d supersymmetric Yang-Mills theories, as inferred from factorization of exact partition functions. Under Seiberg-like dualities, the 3d partition function must remain invariant, yet it is not a priori clear what should happen to the vortex dynamics. We observe that the 1d quivers for the vortices remain the same, and the net effect of the 3d duality map manifests as 1d Wall-Crossing phenomenon; although the vortex number can shift along such duality maps, the ranks of the 1d quiver theory are unaffected, leading to a notion of fundamental vortices as basic building blocks for topological sectors. For Aharony-type duality, in particular, where one must supply extra chiral fields to couple with monopole operators on the dual side, 1d wall-crossings of an infinite number of vortex quiver theories are neatly and collectively encoded by 3d determinant of such extra chiral fields. As such, 1d wall-crossing of the vortex theory encodes the particle-vortex duality embedded in the 3d Seiberg-like duality. For N=4, the D-brane picture is used to motivate this 3d/1d connection, while, for N=2, this 3d/1d connection is used to fine-tune otherwise ambiguous vortex dynamics. We also prove some identities of 3d supersymmetric partition functions for the Aharony duality using this vortex wall-crossing interpretation.

Adult T-cell leukemia/lymphoma presenting multiple lymphomatous polyposis

Institute of Scientific and Technical Information of China (English)

Akira Hokama; Nobuyuki Takasu; Jiro Fujita; Takeaki Tomoyose; Yu-ichi Yamamoto; Takako Watanabe; Tetsuo Hirata; Fukunori Kinjo; Seiya Kato; Koichi Ohshima; Hiroshi Uezato

2008-01-01

Multiple lymphomatous polyposis (HLP) is an unusual form of non-Hodgkin's lymphoma characterized by polyps throughout the gastrointestinal tract. It has been reported that most MLP are observed in cases with mantle cell lymphoma of B-cell type. We herein present a case of a 66-year-old man with adult T-cell leukemia/lymphoma (ATLL). Colonoscopy revealed MLP throughout the colon and histopathological findings of ATLL cell infiltration. The patient died despite combination of chemotherapy. The literature of manifestations of colonic involvement of ATLL is reviewed and the importance of endoscopic evaluation to differentiate ATLL intestinal lesions from opportunistic infectious enterocolitis is discussed.

Global solubility of the three-dimensional Navier-Stokes equations with uniformly large initial vorticity

International Nuclear Information System (INIS)

Makhalov, A S; Nikolaenko, V P

2003-01-01

This paper is a survey of results concerning the three-dimensional Navier-Stokes and Euler equations with initial data characterized by uniformly large vorticity. The existence of regular solutions of the three-dimensional Navier-Stokes equations on an unbounded time interval is proved for large initial data both in R 3 and in bounded cylindrical domains. Moreover, the existence of smooth solutions on large finite time intervals is established for the three-dimensional Euler equations. These results are obtained without additional assumptions on the behaviour of solutions for t>0. Any smooth solution is not close to any two-dimensional manifold. Our approach is based on the computation of singular limits of rapidly oscillating operators, non-linear averaging, and a consideration of the mutual absorption of non-linear oscillations of the vorticity field. The use of resonance conditions, methods from the theory of small divisors, and non-linear averaging of almost periodic functions leads to the limit resonant Navier-Stokes equations. Global solubility of these equations is proved without any conditions on the three-dimensional initial data. The global regularity of weak solutions of three-dimensional Navier-Stokes equations with uniformly large vorticity at t=0 is proved by using the regularity of weak solutions and the strong convergence

Breaking down the delta wing vortex: The role of vorticity in the breakdown process

Science.gov (United States)

Nelson, R. C.; Visser, Kenneth Dale

1991-01-01

Experimental x-wire measurements of the flowfield above a 70 degree and 75 degree flat plate delta wing were performed at a Reynolds number of 250,000. Grids were taken normal to the wing at various chordwise locations for angles of attack of 20 degrees and 30 degrees. Axial and azimuthal vorticity distributions were derived from the velocity fields. The dependence of circulation on distance from the vortex core and on chordwise location was also examined. The effects of nondimensionalization in comparison with other experimental data is made. The results indicate that the circulation distribution scales with the local semispan and grows in a nearly linear fashion in the chordwise direction. The spanwise distribution of axial vorticity is severely altered through the breakdown region and the amount of vorticity present appears to reach a maximum immediately preceding breakdown. The axial velocity components with a negative sense, such as that found in the secondary vortex, seem to remain unaffected by changes in wing sweep or angle of attack, in direct contrast to the visible components. In addition, the inclusion of the local wing geometry into a previously derived correlation parameter allows the circulation of growing leading edge vortex flows to be reduced to a single curve.

Multiple cell common pressure vessel nickel hydrogen battery

Science.gov (United States)

Zagrodnik, Jeffrey P.; Jones, Kenneth R.

1991-01-01

A multiple cell common pressure vessel (CPV) nickel hydrogen battery was developed that offers significant weight, volume, cost, and interfacing advantages over the conventional individual pressure vessel (IPV) nickel hydrogen configuration that is currently used for aerospace applications. The baseline CPV design was successfully demonstrated though the testing of a 26 cell prototype, which completed over 7,000 44 percent depth of discharge LEO cycles. Two-cell boilerplate batteries have now exceeded 12,500 LEO cycles in ongoing laboratory tests. CPV batteries using both nominal 5 and 10 inch diameter vessels are currently available. The flexibility of the design allows these diameters to provide a broad capability for a variety of space applications.

Large-scale vortices in compressible turbulent medium with the magnetic field

Science.gov (United States)

Gvaramadze, V. V.; Dimitrov, B. G.

1990-08-01

An averaged equation which describes the large scale vortices and Alfven waves generation in a compressible helical turbulent medium with a constant magnetic field is presented. The presence of the magnetic field leads to anisotropization of the vortex generation. Possible applications of the anisotropic vortex dynamo effect are accretion disks of compact objects.

Borneo Vortices: A case study and its relation to climatology

Science.gov (United States)

Braesicke, P.; Ooi, S. H.; Samah, A. A.

2012-04-01

Borneo vortices (BVs) develop over the South China Sea and are main drivers for the formation of deep convection and heavy rainfall in East Malaysia. We present a case study of a cold-surge-induced BV during January 2010 in which the export of potential energy lead to a strengthening of the subtropical jet. Potential vorticity (PV) and water vapour analyses confirm a significant impact of the BV on upper tropospheric composition. Dry, high PV air is found far below 100 hPa in the vicinty of the vortex. Using a PV threshold analysis of ERA-Interim data we construct a climatological composite of similar events and characterise the thermal, dynamical and composition structure of a 'typical' BV. We note the preferential formation of BVs during ENSO cold conditions and show that two effects contribute to the formation of the dry upper layer above a BV: Air is vertically transported upwards in the BV whilst precipitating and the large scale flow in which the BV is embedded advect dry, ozone rich air from the equatorial TTL over the BV. Thus the occurence frequency of BVs is important for the regional variability of upper tropospheric/lower stratospheric composition.

Imaging of multiple myeloma and related monoclonal plasma cell diseases. An update

International Nuclear Information System (INIS)

Weber, Marc-Andre; Delorme, Stefan; Hillengass, Jens

2014-01-01

Multiple myeloma is a hematologic disorder characterized by the infiltration and proliferation of monoclonal plasma cells mainly in the bone marrow. The main symptoms are hypercalcemia, renal impairment, cytopenia/anemia and bone disease - summarized as CRAB-criteria. Symptomatic multiple myeloma is consistently preceded by asymptomatic premalignant stages called monoclonal gammopathy of undetermined significance and smoldering multiple myeloma. Staging of multiple myeloma is based on the measurement of the monoclonal protein in serum and urine as well as the assessment of impairment of hematopoiesis, renal function and mineralized bone. In the last decade the development of novel therapeutic agents has led to an increase in response rates and survival time of patients with multiple myeloma, which further stresses the value of response assessment by imaging. Cross sectional imaging like MRI and CT is currently replacing conventional radiological surveys in the initial work-up and follow-up of patients with monoclonal plasma cell diseases. The added value of MRI is to improve initial staging by unraveling a diffuse infiltration of bone marrow by plasma cells, a focal pattern or a combination of both. Furthermore, a complete remission of myeloma confirmed by MRI and CT goes along with a better prognosis compared to a complete response based only on serological parameters.

A hydrodynamic model for superfluid helium with vortices

International Nuclear Information System (INIS)

Lhuillier, D.; Francois, M.

1975-01-01

Although their existence is experimentally well verified, the so-called mutual friction force Fsub(sn) and superfluid friction force Fsub(s) cannot emerge from the Landau irrotational model of superfluidity. Up to now these forces have merely been added to the Landau equations but this is untenable since, as a consequence, one destroys the irrotationality condition with which the equations have expressly been built. It is shown that these friction forces appear in a natural way in a model where superfluid helium with vortices is compared to a fluid with a conserved intrinsic momentum. (Auth.)

Assessment of intracardiac flow and vorticity in the right heart of patients after repair of tetralogy of Fallot by flow-sensitive 4D MRI.

Science.gov (United States)

Hirtler, Daniel; Garcia, Julio; Barker, Alex J; Geiger, Julia

2016-10-01

To comprehensively and quantitatively analyse flow and vorticity in the right heart of patients after repair of tetralogy of Fallot (rTOF) compared with healthy volunteers. Time-resolved flow-sensitive 4D MRI was acquired in 24 rTOF patients and 12 volunteers. Qualitative flow evaluation was based on consensus reading of two observers. Quantitative analysis included segmentation of the right atrium (RA) and ventricle (RV) in a four-chamber view to extract volumes and regional haemodynamic information for computation of regional mean and peak vorticity. Right heart intra-atrial, intraventricular and outflow tract flow patterns differed considerably between rTOF patients and volunteers. Peak RA and mean RV vorticity was significantly higher in patients (p = 0.02/0.05). Significant negative correlations were found between patients' maximum and mean RV and RA vorticity and ventricular volumes (p tetralogy of Fallot. • Regurgitant flow in the main pulmonary artery is associated with higher right heart vorticity.

Multiple jaw cysts not associated with basal cell nevus syndrome

International Nuclear Information System (INIS)

Yoon, Suk Ja; Kang, Byung Cheol

2003-01-01

We present two cases of multiple jaw cysts not associated with basal cell nevus syndrome. Case 1 : a nine year-old boy visited CNU Hospital for orthodontic treatment and his radiographs showed cystic lesions surrounding the crowns of teeth 13 and 17 respectively, which were diagnosed as dentigerous cysts. Subsequently, two more cysts were found on his follow-up radiographs in 12 and 15 months. The two cysts were determined to be odontogenic keratocysts. The boy had no skeletal abnormalities and no skin lesions associated with basal cell nevus syndrome. Case 2: a fifty-eight year old man had three impacted third molars with pericoronal radiolucencies, which were diagnosed as dentigerous cysts. He had no additional abnormalities associated with basal cell nevus syndrome. Multiple jaw cysts can occur at any age, and periodic radiographic surveillance may be needed for any cases of impacted tooth.

Multiple jaw cysts not associated with basal cell nevus syndrome

Energy Technology Data Exchange (ETDEWEB)

Yoon, Suk Ja; Kang, Byung Cheol [Chonnam National University College of Medicine, Kwangju (Korea, Republic of)

2003-09-15

We present two cases of multiple jaw cysts not associated with basal cell nevus syndrome. Case 1 : a nine year-old boy visited CNU Hospital for orthodontic treatment and his radiographs showed cystic lesions surrounding the crowns of teeth 13 and 17 respectively, which were diagnosed as dentigerous cysts. Subsequently, two more cysts were found on his follow-up radiographs in 12 and 15 months. The two cysts were determined to be odontogenic keratocysts. The boy had no skeletal abnormalities and no skin lesions associated with basal cell nevus syndrome. Case 2: a fifty-eight year old man had three impacted third molars with pericoronal radiolucencies, which were diagnosed as dentigerous cysts. He had no additional abnormalities associated with basal cell nevus syndrome. Multiple jaw cysts can occur at any age, and periodic radiographic surveillance may be needed for any cases of impacted tooth.

Transplantation of Human Embryonic Stem Cells in Patients with Multiple Sclerosis and Lyme Disease

OpenAIRE

Shroff, Geeta

2016-01-01

Case series Patient: Male, 42 ? Female, 30 Final Diagnosis: Human embryonic stem cells showed good therapeutic potential for treatment of multiple sclerosis with lyme disease Symptoms: Fatigue ? weakness in limbs Medication: ? Clinical Procedure: Human embryonic stem cells transplantation Specialty: Transplantology Objective: Rare disease Background: Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease in which the myelin sheath of nerve cells is damaged. It can cause dela...

Vortical Structures and Turbulent Bursts Behind Magnetic Obstacles in Transitional Flow Regimes

NARCIS (Netherlands)

Kenjeres, S.; Ten Cate, S.; Voesenek, C.J.

2011-01-01

The present paper reports on numerical investigations of vortical structures in transient flow regimes generated by the local action of the Lorentz force on an electrically conductive fluid. The locally imposed non-uniform magnetic field generates similar effects as observed for flows over submerged

Images of interlayer Josephson vortices in single-layer cuprates

International Nuclear Information System (INIS)

Moler, K. A.; Kirtley, J. R.; Liang, R.; Bonn, D. A.; Hardy, W. N.; Williams, J. M.; Schlueter, J. A.; Hinks, D.; Villard, G.; Maignan, A.; Nohara, M.; Takagi, H.

2000-01-01

The interlayer penetration depth in layered superconductors may be determined from scanning Superconducting QUantum Interference Device (SQUID) microscope images of interlayer Josephson vortices. The authors compare their findings at 4 K for single crystals of the organic superconductor κ-(BEDT-TTF) 2 Cu(NCS) 2 and three near-optimally doped cuprate superconductors: La 2-x Sr x CuO 4 , (Hg, Cu)Ba 2 CuO 4+δ , and Tl 2 Ba 2 CuO 6+δ

Investigation of the Unsteady Total Pressure Profile Corresponding to Counter-Rotating Vortices in an Internal Flow Application

Science.gov (United States)

Gordon, Kathryn; Morris, Scott; Jemcov, Aleksandar; Cameron, Joshua

2013-11-01

The interaction of components in a compressible, internal flow often results in unsteady interactions between the wakes and moving blades. A prime example in which this flow feature is of interest is the interaction between the downstream rotor blades in a transonic axial compressor with the wake vortices shed from the upstream inlet guide vane (IGV). Previous work shows that a double row of counter-rotating vortices convects downstream into the rotor passage as a result of the rotor blade bow shock impinging on the IGV. The rotor-relative time-mean total pressure distribution has a region of high total pressure corresponding to the pathline of the vortices. The present work focuses on the relationship between the magnitude of the time-mean rotor-relative total pressure profile and the axial spacing between the IGV and the rotor. A survey of different axial gap sizes is performed in a two-dimensional computational study to obtain the sensitivity of the pressure profile amplitude to IGV-rotor axial spacing.

Selective particle and cell capture in a continuous flow using micro-vortex acoustic streaming.

Science.gov (United States)

Collins, David J; Khoo, Bee Luan; Ma, Zhichao; Winkler, Andreas; Weser, Robert; Schmidt, Hagen; Han, Jongyoon; Ai, Ye

2017-05-16

Acoustic streaming has emerged as a promising technique for refined microscale manipulation, where strong rotational flow can give rise to particle and cell capture. In contrast to hydrodynamically generated vortices, acoustic streaming is rapidly tunable, highly scalable and requires no external pressure source. Though streaming is typically ignored or minimized in most acoustofluidic systems that utilize other acoustofluidic effects, we maximize the effect of acoustic streaming in a continuous flow using a high-frequency (381 MHz), narrow-beam focused surface acoustic wave. This results in rapid fluid streaming, with velocities orders of magnitude greater than that of the lateral flow, to generate fluid vortices that extend the entire width of a 400 μm wide microfluidic channel. We characterize the forces relevant for vortex formation in a combined streaming/lateral flow system, and use these acoustic streaming vortices to selectively capture 2 μm from a mixed suspension with 1 μm particles and human breast adenocarcinoma cells (MDA-231) from red blood cells.

Experimental research on free-surface vortices as transport mechanism in wastewater sumps

NARCIS (Netherlands)

Clemens, F.H.L.R.; Duinmeijer, S.P.A.

2016-01-01

Sumps of wastewater pumping station can experience problems due the formation of (solid) floating layers of fat and scum as a result of insufficient current guidelines for sump design with respect to transport of floating debris. To complimentary the guidelines, the use of free-surface vortices is

Chiral heat wave and mixing of magnetic, vortical and heat waves in chiral media

International Nuclear Information System (INIS)

Chernodub, M.N.

2016-01-01

We show that a hot rotating fluid of relativistic chiral fermions possesses a new gapless collective mode associated with coherent propagation of energy density and chiral density waves along the axis of rotation. This mode, which we call the Chiral Heat Wave, emerges due to a mixed gauge-gravitational anomaly. At finite density the Chiral Heat Wave couples to the Chiral Vortical Wave while in the presence of an external magnetic field it mixes with the Chiral Magnetic Wave. The coupling of the Chiral Magnetic and Chiral Vortical Waves is also demonstrated. We find that the coupled waves — which are coherent fluctuations of the vector, axial and energy currents — have generally different velocities compared to the velocities of the individual waves.

Assessing atmospheric bias correction for dynamical consistency using potential vorticity

International Nuclear Information System (INIS)

Rocheta, Eytan; Sharma, Ashish; Evans, Jason P

2014-01-01

Correcting biases in atmospheric variables prior to impact studies or dynamical downscaling can lead to new biases as dynamical consistency between the ‘corrected’ fields is not maintained. Use of these bias corrected fields for subsequent impact studies and dynamical downscaling provides input conditions that do not appropriately represent intervariable relationships in atmospheric fields. Here we investigate the consequences of the lack of dynamical consistency in bias correction using a measure of model consistency—the potential vorticity (PV). This paper presents an assessment of the biases present in PV using two alternative correction techniques—an approach where bias correction is performed individually on each atmospheric variable, thereby ignoring the physical relationships that exists between the multiple variables that are corrected, and a second approach where bias correction is performed directly on the PV field, thereby keeping the system dynamically coherent throughout the correction process. In this paper we show that bias correcting variables independently results in increased errors above the tropopause in the mean and standard deviation of the PV field, which are improved when using the alternative proposed. Furthermore, patterns of spatial variability are improved over nearly all vertical levels when applying the alternative approach. Results point to a need for a dynamically consistent atmospheric bias correction technique which results in fields that can be used as dynamically consistent lateral boundaries in follow-up downscaling applications. (letter)

Conservation properties and potential systems of vorticity-type equations

International Nuclear Information System (INIS)

Cheviakov, Alexei F.

2014-01-01

Partial differential equations of the form divN=0, N t +curl M=0 involving two vector functions in R 3 depending on t, x, y, z appear in different physical contexts, including the vorticity formulation of fluid dynamics, magnetohydrodynamics (MHD) equations, and Maxwell's equations. It is shown that these equations possess an infinite family of local divergence-type conservation laws involving arbitrary functions of space and time. Moreover, it is demonstrated that the equations of interest have a rather special structure of a lower-degree (degree two) conservation law in R 4 (t,x,y,z). The corresponding potential system has a clear physical meaning. For the Maxwell's equations, it gives rise to the scalar electric and the vector magnetic potentials; for the vorticity equations of fluid dynamics, the potentialization inverts the curl operator to yield the fluid dynamics equations in primitive variables; for MHD equations, the potential equations yield a generalization of the Galas-Bogoyavlenskij potential that describes magnetic surfaces of ideal MHD equilibria. The lower-degree conservation law is further shown to yield curl-type conservation laws and determined potential equations in certain lower-dimensional settings. Examples of new nonlocal conservation laws, including an infinite family of nonlocal material conservation laws of ideal time-dependent MHD equations in 2+1 dimensions, are presented

The influence of trailed vorticity on flutter speed estimations

International Nuclear Information System (INIS)

Pirrung, Georg R; Madsen, Helge Aa; Kim, Taeseong

2014-01-01

This paper briefly describes the implementation of a coupled near and far wake model for wind turbine rotor induction in the aeroelastic code HAWC2 and its application for flutter analysis of the NREL 5 MW wind turbine. The model consists of a far wake part based on Blade Element Momentum (BEM) theory, which is coupled with Beddoes' near wake model for trailed vorticity. The first part of this work outlines the implementation in HAWC2, with a focus on the interaction of the induction from the blade based near wake model with the induction from the polar grid based BEM model in HAWC2. The influence of the near wake model on the aeroelastic stability of the blades of the NREL 5 MW turbine in overspeed conditions is investigated in the second part of the paper. The analysis is based on a runaway case in which the turbine is free to speed up without generator torque and vibrations start building up at a critical rotor speed. Blades with modified torsional and flapwise stiffness are also investigated. A flutter analysis is often part of the stability investigations for new blades but is normally carried out with engineering models that do not include the influence of unsteady trailed vorticity. Including this influence results in a slightly increased safety margin against classical flutter in all simulated cases

Experiments with a Regional Vector-Vorticity Model, and Comparison with Other Models

Science.gov (United States)

Konor, C. S.; Dazlich, D. A.; Jung, J.; Randall, D. A.

2017-12-01

The Vector-Vorticity Model (VVM) is an anelastic model with a unique dynamical core that predicts the three-dimensional vorticity instead of the three-dimensional momentum. The VVM is used in the CRMs of the Global Quasi-3D Multiscale Modeling Framework, which is discussed by Joon-Hee Jung and collaborators elsewhere in this session. We are updating the physics package of the VVM, replacing it with the physics package of the System for Atmosphere Modeling (SAM). The new physics package includes a double-moment microphysics, Mellor-Yamada turbulence, Monin-Obukov surface fluxes, and the RRTMG radiation parameterization. We briefly describe the VVM and show results from standard test cases, including TWP-ICE. We compare the results with those obtained using the earlier physics. We also show results from experiments on convection aggregation in radiative-convective equilibrium, and compare with those obtained using both SAM and the Regional Atmospheric Modeling System (RAMS).

Analytical BPS Maxwell-Higgs Vortices

International Nuclear Information System (INIS)

Hora, E. da; Ferreira, M. M. Jr.; Santos, C. dos; Casana, R.

2014-01-01

We have established a prescription for the calculation of analytical vortex solutions in the context of generalized Maxwell-Higgs models whose overall dynamics is controlled by two positive functions of the scalar field, namely, f(|ϕ|) and w(|ϕ|). We have also determined a natural constraint between these functions and the Higgs potential U(|ϕ|), allowing the existence of axially symmetric Bogomol'nyi-Prasad-Sommerfield (BPS) solutions possessing finite energy. Furthermore, when the generalizing functions are chosen suitably, the nonstandard BPS equations can be solved exactly. We have studied some examples, comparing them with the usual Abrikosov-Nielsen-Olesen (ANO) solution. The overall conclusion is that the analytical self-dual vortices are well-behaved in all relevant sectors, strongly supporting the consistency of the respective generalized models. In particular, our results mimic well-known properties of the usual (numerical) configurations, as localized energy density, while contributing to the understanding of topological solitons and their description by means of analytical methods.

Nonlinear effects and vortical structures in homogeneous rotating turbulence under stable density stratification; Antei seisoka ni aru kaiten ichiyo ranryu no hisenkei koka to uzu kozo

Energy Technology Data Exchange (ETDEWEB)

Tsujimura, S.; Iida, O.; Nagano, Y. [Nagoya Institute of Technology, Nagoya (Japan)

2000-02-25

The generation mechanism of the vertical vortices associated with the baroclinic instability and the effects of nonlinear term on the vortices are investigated by using both direct numerical simulation (DNS) and rapid distortion theory (RDT). Two kinds of the anisotropic flow fields are used as initial conditions. As a result, the initial anisotropy of Reynolds stresses is found to affect asymmetry of the vertical vortices. In the cases where the initial vertical velocity is set to be zero, the p. d. f. of the vertical vorticity tends to incline toward the anticyclonic side. When the vertical component of initial velocity is larger than the horizontal one, the cyclonic vortices are more enhanced. By comparing DNS and RDT, it is found that in both cases of the initial conditions the enhanced vortices of DNS are stretched in the vertical direction, which is not observed in the RDT results. This should be because the nonlinear vortex-stretching term intensifies and elongates vertical vortices in the vertical direction. The anticyclones are markedly augmented in low Prandtl number fluids, while the cyclones become dominant in the high Prandtl number case. In particular, the flow field becomes almost two-dimensionalized and Taylor columns are formed in the vertical direction in the low Prandtl number case. However, neither two-dimensionalization nor Taylor column is observed in the RDT analysis which neglects the nonlinear terms. (author)

CUTLASS HF radar observations of high-latitude azimuthally propagating vortical currents in the nightside ionosphere during magnetospheric substorms

Directory of Open Access Journals (Sweden)

J. A. Wild

Full Text Available High-time resolution CUTLASS observations and ground-based magnetometers have been employed to study the occurrence of vortical flow structures propagating through the high-latitude ionosphere during magnetospheric substorms. Fast-moving flow vortices (~800 m s^-1 associated with Hall currents flowing around upward directed field-aligned currents are frequently observed propagating at high speed (~1 km s^-1 azimuthally away from the region of the ionosphere associated with the location of the substorm expansion phase onset. Furthermore, a statistical analysis drawn from over 1000 h of high-time resolution, nightside radar data has enabled the characterisation of the bulk properties of these vortical flow systems. Their occurrence with respect to substorm phase has been investigated and a possible generation mechanism has been suggested.

Key words: Ionosphere (auroral ionosphere; electric fields and currents · Magnetospheric physics (storms and substorms

Time Accurate Euler Calculations of Vortical Flow over a Delta Wing in Rolling Motion

National Research Council Canada - National Science Library

Fritz, W

2003-01-01

.... An important component of the program were the Common Exercises (CE), which promoted the exchange of knowledge between the participating nations and aided the development of computational methods to predict vortical flows...

Reducing the Drag and Damage of a High-Speed Train by Analyzing and Optimizing its Boundary Layer Separation and Roll-up into Wake Vortices

Science.gov (United States)

Jiang, Chung-Hsiang; Marcus, Philip

2012-11-01

We present numerical calculations of the boundary layers and shed wake vortices behind several aerodynamic bodies and generic models of high-speed trains. Our calculations illustrate new visual diagnostics that we developed that clearly show where the separation of a boundary layer occurs and where, how, and with what angles (with respect to the stream-wise direction) the wake vortices form. The calculations also illustrate novel 3D morphing and mesh ``pushing and pulling'' techniques that allow us to change the shapes of aerodynamic bodies and models in a controlled and automated manner without spurious features appearing. Using these tools we have examined the patterns of the shed vortices behind generic bodies and trains and correlated them with the changes in the drag as well as with the effects of the shed vortices on the environment. In particular, we have applied these techniques to the end car of a next-generation, high-speed train in order to minimize the drag and to minimize the adverse effects of the shed vortices on the track ballast.

T helper 17.1 cells associate with multiple sclerosis disease activity: perspectives for early intervention.

Science.gov (United States)

van Langelaar, Jamie; van der Vuurst de Vries, Roos M; Janssen, Malou; Wierenga-Wolf, Annet F; Spilt, Isis M; Siepman, Theodora A; Dankers, Wendy; Verjans, Georges M G M; de Vries, Helga E; Lubberts, Erik; Hintzen, Rogier Q; van Luijn, Marvin M

2018-05-01

Interleukin-17-expressing CD4+ T helper 17 (Th17) cells are considered as critical regulators of multiple sclerosis disease activity. However, depending on the species and pro-inflammatory milieu, Th17 cells are functionally heterogeneous, consisting of subpopulations that differentially produce interleukin-17, interferon-gamma and granulocyte macrophage colony-stimulating factor. In the current study, we studied distinct effector phenotypes of human Th17 cells and their correlation with disease activity in multiple sclerosis patients. T helper memory populations single- and double-positive for C-C chemokine receptor 6 (CCR6) and CXC chemokine receptor 3 (CXCR3) were functionally assessed in blood and/or cerebrospinal fluid from a total of 59 patients with clinically isolated syndrome, 35 untreated patients and 24 natalizumab-treated patients with relapsing-remitting multiple sclerosis, and nine patients with end-stage multiple sclerosis. Within the clinically isolated syndrome group, 23 patients had a second attack within 1 year and 26 patients did not experience subsequent attacks during a follow-up of >5 years. Low frequencies of T helper 1 (Th1)-like Th17 (CCR6+CXCR3+), and not Th17 (CCR6+CXCR3-) effector memory populations in blood strongly associated with a rapid diagnosis of clinically definite multiple sclerosis. In cerebrospinal fluid of clinically isolated syndrome and relapsing-remitting multiple sclerosis patients, Th1-like Th17 effector memory cells were abundant and showed increased production of interferon-gamma and granulocyte macrophage colony-stimulating factor compared to paired CCR6+ and CCR6-CD8+ T cell populations and their blood equivalents after short-term culturing. Their local enrichment was confirmed ex vivo using cerebrospinal fluid and brain single-cell suspensions. Across all pro-inflammatory T helper cells analysed in relapsing-remitting multiple sclerosis blood, Th1-like Th17 subpopulation T helper 17.1 (Th17.1; CCR6+CXCR3+CCR4

Activation energy of fractional vortices and spectroscopy of a vortex molecule in long Josephson junction

International Nuclear Information System (INIS)

Buckenmaier, Kai

2010-01-01

This thesis is divided into two parts, the measurement of the activation energy of a fractional vortex and the spectroscopy of a vortex-molecule. Fractional vortices can be studied in long 0-κ Josephson junctions, where a jump of the Josephson phase is created artificially with a pair of tiny current injectors. To compensate for this phase discontinuity, a ρ vortex is formed. Here, ρ describes the vortex's so called topological charge. The ρ vortices are pinned at the discontinuity and they carry the fraction (ρ/2).Φ 0 of magnetic flux, with the magnetic flux quantum Φ 0 2.07.10 -15 . Two stable vortex configurations are possible, a direct Vortex and a complementary one. ρ depends on the injector current. When the bias current of the junction exceeds a characteristic threshold, which dependents on ρ, the Lorentz force is bigger than the pinning force of the vortex and a fluxon is pulled away. In this case a complementary (ρ-2π) vortex is left behind. This switching of the ρ vortex and the resulting emission of a fluxon can be described as a Kramers like escape of a particle out of a tilted washboard potential. The washboard potential is tilted to the point where the barrier is small enough, so that the particle can escape via thermal or quantum fluctuations. In the case of thermal fluctuations the barrier height is called activation energy. The activation energy can be determined by measuring the junction's switching current statistics. In this thesis, the activation energy, necessary for the vortex escape, was measured as a function of ρ and a homogenous external magnetic field perpendicular to the junction. The main focus was the investigation of 0-π junctions. The temperature dependence of the activation energy was investigated, too. It turns out, that the transition-state-theory is convenient to describe the switching probability of the standard Nb-AlO x -Nb junctions at 4.2 K. For the measurements at 0.5 K a model of low to intermediate damping

Coordinated learning of grid cell and place cell spatial and temporal properties: multiple scales, attention and oscillations.

Science.gov (United States)

Grossberg, Stephen; Pilly, Praveen K

2014-02-05

A neural model proposes how entorhinal grid cells and hippocampal place cells may develop as spatial categories in a hierarchy of self-organizing maps (SOMs). The model responds to realistic rat navigational trajectories by learning both grid cells with hexagonal grid firing fields of multiple spatial scales, and place cells with one or more firing fields, that match neurophysiological data about their development in juvenile rats. Both grid and place cells can develop by detecting, learning and remembering the most frequent and energetic co-occurrences of their inputs. The model's parsimonious properties include: similar ring attractor mechanisms process linear and angular path integration inputs that drive map learning; the same SOM mechanisms can learn grid cell and place cell receptive fields; and the learning of the dorsoventral organization of multiple spatial scale modules through medial entorhinal cortex to hippocampus (HC) may use mechanisms homologous to those for temporal learning through lateral entorhinal cortex to HC ('neural relativity'). The model clarifies how top-down HC-to-entorhinal attentional mechanisms may stabilize map learning, simulates how hippocampal inactivation may disrupt grid cells, and explains data about theta, beta and gamma oscillations. The article also compares the three main types of grid cell models in the light of recent data.

Center vortices at strong couplings and all couplings

International Nuclear Information System (INIS)

Greensite, J.

2001-01-01

Motivations for the center vortex theory of confinement are discussed. In particular, it is noted that the abelian dual Meissner effect, which is the signature of dual superconductivity, cannot adequately describe the confining force at large distance scales. A long-range effective action is derived from strong-coupling lattice gauge theory in D=3 dimensions, and it is shown that center vortices emerge as the stable saddlepoints of this action. Thus, in the case of strong couplings, the vortex picture is arrived at analytically. I also respond briefly to a recent criticism regarding maximal center gauge. (author)

Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

International Nuclear Information System (INIS)

Sugimoto, Norihiko

2015-01-01

Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone–anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone–anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (∼2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone–anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves

Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

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