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  • 1
    Electronic Resource
    Electronic Resource
    Study of the von Kármán flow between coaxial corotating disks (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 914-922 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report an experimental study of the swirling flow generated in the gap between two coaxial corotating disks. We use a free geometry, i.e., unshrouded disks in air, with moderate to high Reynolds numbers. When the relative rotation rate is varied, transitions in the flow can be observed by global power measurement and are related to the geometry of the external recirculating flow. The mean flow is studied in details with hot-wire measurements using a boxcar-type averaging technique. It involves a single turbulent vortex undergoing a slow precession motion. We show that statistical properties of the turbulent fluctuations are affected by the dynamics of the mean flow, which also displays a correlation with the global power fluctuations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868871
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  • 2
    Electronic Resource
    Electronic Resource
    Universality of rare fluctuations in turbulence and critical phenomena (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 396 (1998), S. 552-554 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A statistical treatment of three-dimensional turbulent flow continues to pose a challenge to theorists,. One suggestion invokes an analogy with equilibrium phase transitions. Here we approach this idea experimentally, presenting evidence of a strong analogy between the statistical behaviour of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/25083
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  • 3
    Electronic Resource
    Electronic Resource
    Velocity measurement of a settling sphere (2000)
    Springer
    The European physical journal 18 (2000), S. 343-352 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 06.30.Gv Velocity, acceleration, and rotation - 43.60.+d Acoustic signal processing - 47.27.Vf Wakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study experimentally the motion of a solid sphere settling under gravity in a fluid at rest. The particle velocity is measured with a new acoustic method. Variations of the sphere size and density allow measurements at Reynolds numbers, based on limit velocity, between 40 and 7 000. At all Reynolds numbers, our observations are consistent with the presence of a memory-dependent force acting on the particle. At short times it has a t -1/2 behaviour as predicted by the unsteady Stokes equations and as observed in numerical simulations. At long times, the decay of the memory (Basset) force is better fitted by an exponential behaviour. Comparison of the dynamics of spheres of different densities for the same Reynolds number show that the density is an important control parameter. Light spheres show transitory oscillations at Re∼ 400, but reach a constant limit speed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011074
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic permeability of a diphasic flow, made of liquid gallium and iron beads (2000)
    Springer
    The European physical journal 18 (2000), S. 337-341 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 47.65.+a Magnetohydrodynamics and electrohydrodynamics - 75.50.Mm Magnetic liquids - 47.55.Kf Multiphase and particle-laden flows
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Magnetohydrodynamics studies in laboratory experiments have long been restricted to low magnetic Reynolds number flows, mainly as a result of the very high magnetic diffusivity λ = 1/μσ of common conducting fluids (μ is the fluid's magnetic permeability and σ its electrical conductivity). The best conductivities are found in liquid metals which have a unit magnetic permeability, relative to vacuum. We show experimentally that a suspension of solid particles with a high magnetic permeability in a liquid metal yields an effective medium that has a high electrical conductivity and an enhanced magnetic permeability. The dispersion of the beads results from the turbulent fluid motion. The range of accessible magnetic Reynolds number can be increased by a factor of as much as 4 in our experimental setup.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510070066
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic induction by coherent vortex motion (2000)
    Springer
    The European physical journal 16 (2000), S. 373-378 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 47.27.-i Turbulent flows, convection, and heat transfer - 47.65.+a Magnetohydrodynamics and electrohyrodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We investigate experimentally the advection of a magnetic field by a flow of conducting fluid, at moderate magnetic Reynolds numbers. More specifically, we study the influence of a large scale intense vortex on an externally applied field. We show that at large scales the magnetic field lines are distorted in a way that is consistent with a scenario of magnetic field expulsion by vorticity. Measurements at small scales show that the magnetic fluctuations are also quite sensitive to the large scale vortex motion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510070239
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  • 6
    Electronic Resource
    Electronic Resource
    Effective magnetic permeability of a turbulent fluid with macroferroparticles (2002)
    Springer
    The European physical journal 25 (2002), S. 399-402 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 47.65Magnetohydrodynamic fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A fully developed turbulent flow is capable to mix and homogenize a suspension of heavy macroscopic particles even at a high concentration of particles. If the particles are ferromagnetic, a kind of “turbulent ferrofluid" can be obtained. In the present work, we present a direct measurements of the effective magnetic permeability in a turbulent fluid with suspended ferromagnetic particles of typical size 0.01-0.1 mm and volume fraction c up to 25%. We show that the effective permeability can be fitted by the linear law = 1 + 5.3c for c? 10%. For higher volume fractions the permeability exceeds this linear relation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020044
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  • 7
    Electronic Resource
    Electronic Resource
    Transmission of sound through a single vortex (2003)
    Springer
    The European physical journal 37 (2003), S. 229-239 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We investigate experimentally the deformation of acoustic wavefronts after crossing of a single, isolated vortex in free space. The incident sound wavelength can be varied in a large domain. We study the wavefronts at variable distance after transmission through the vortex, when the wavelength and the vortex strength are varied. For small wavelength ( $\lambda \ll a$ , the vortex core size) our results are in very good agreement with predictions and simulations based on geometrical acoustics principles. However, as the sound wavelength increases to value comparable with the vortex diameter, the deformation of the wavefronts show the development of scattering contributions, with characteristics in agreement with recent theoretical and numerical studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00051-y
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  • 8
    Electronic Resource
    Electronic Resource
    Global fluctuations in decaying Burgers turbulence (2002)
    Springer
    The European physical journal 28 (2002), S. 231-241 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 47.27.Eq Turbulence simulation and modeling – 52.25.Gj Fluctuation and chaos phenomena – 02.50.-r Probability theory, stochastic processes, and statistics – 05.70.Ln Nonequilibrium and irreversible thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We consider the statistics of the total energy and the global dissipation in numerical simulations of decaying Burgers turbulence. We observe that at large times these global quantities develop strongly non-Gaussian statistics with asymmetric probability density functions characterized by an exponential tail for values above the mean. Although χ2 distributions would be expected in the description of such definite positive quantities as the energy or the dissipation, we observe that the generalized Gumbel Ga functions provide a better functional form. These distributions have an exponential tail which correctly represents the large fluctuations of the energy or dissipation at large times. We find that the value of the control parameter a(t) of the fitting Gumbel distribution Ga at time t is set by the ratio of the system size to the velocity correlation length, which thus plays the role of an effective number of degrees of freedom. We show that in this problem, the development of exponential tails for the global variables is linked to extreme statistics properties for the largest local events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00225-7
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  • 9
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    Propagation of Sound through a Turbulent Vortex (1998)
    American Physical Society
    Details
    Publication Date: 1998-08-17
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 10
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    Generation of a Magnetic Field by Dynamo Action in a Turbulent Flow of Liquid Sodium (2007)
    American Physical Society
    Details
    Publication Date: 2007-01-25
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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