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  • 1
    Electronic Resource
    Electronic Resource
    Intense vortical structures in grid-generated turbulence (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 2008-2013 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents a set of experiments aimed at investigating the features and the statistical frequency of intense vortical structures (sometimes called "filaments'', or "worms'') as manifested by a migrating bubble technique in a mean shear free, homogeneous, isotropic, stationary turbulence generated by oscillating grids in a water tank for Rλ reaching up to 300. It is found that the nucleation of filaments at the surface of the walls of the tank, where boundary layers are liable to destabilize is much more frequent than in the homogeneous bulk of the tank where one filament is typically detected each hundred large scale turnover time. This distinction between the wall surface and the bulk activity, supplemented with the fact that the size of the filaments and their lifetime compare with the length and time-scales of the largest structures of the flow leads us to formulate an elementary model explaining the origin and the geometrical features of these intense vortical structures in turbulent flows for arbitrary Reynolds numbers. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868512
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  • 2
    Electronic Resource
    Electronic Resource
    Intermittency and Reynolds number (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 910-921 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hot wire measurements of longitudinal and transverse increments are performed in three different types of flows on a large range of Reynolds numbers (100(approximately-less-than)Rλ(approximately-less-than)3000). An improved technique based on cumulant expansion of velocity structure functions is used to estimate the spreading of the pdfs and to study their scaling properties in the inertial range. Thus, the rate of intermittency depth through the scales of flow, called here β(Rλ), is experimentally introduced, and it is shown that β(Rλ) has a universal behavior on a very large Reynolds numbers range. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869613
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  • 3
    Electronic Resource
    Electronic Resource
    On the log-Poisson statistics of the energy dissipation field and related problems of developed turbulence (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 3367-3378 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An energy cascading model of intermittency involving rare localized regions of both large and/or weak energy dissipation (dynamical intermittency) is considered and compared to the case of intermittency arising from a large number of regions with nearly equal dissipation rates (space intermittency). The latter leads to the log-normal statistics of the dissipation rate while the first scenario leads to shifted log-Poisson distributions either for a large or for weak energy dissipation. The only difference between these two cases is that small values of dissipation (with respect to the maximum of PDF) are more probable for intermittency of the regions with weak dissipation than for intermittency of the regions with large values of dissipation. Some consequences are derived which show that Novikov's inequalities are valid for intermittency with rare regions of a weak dissipation only. Different experimental data of probability distributions of dissipation are presented and compared to theoretical predictions. Some experimental evidences of quasi-two-dimensional vortical structures with weak dissipation are discussed. They suggest that the scenario involving dynamical intermittency with holes of dissipation could apply to a real world turbulence. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869123
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  • 4
    Electronic Resource
    Electronic Resource
    Log-similarity for turbulent flows?
    Amsterdam : Elsevier
    Physica D: Nonlinear Phenomena 68 (1993), S. 387-400 
    Details
    ISSN: 0167-2789
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-2789(93)90132-K
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  • 5
    Electronic Resource
    Electronic Resource
    Velocity probability density functions of high Reynolds number turbulence
    Amsterdam : Elsevier
    Physica D: Nonlinear Phenomena 46 (1990), S. 177-200 
    Details
    ISSN: 0167-2789
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-2789(90)90035-N
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  • 6
    Electronic Resource
    Electronic Resource
    Wavelet analysis of turbulence reveals the multifractal nature of the Richardson cascade (1989)
    [s.l.] : Nature Publishing Group
    Nature 338 (1989), S. 51-53 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] FIG. 1 Wavelet analysis of Cantor sets9'15. Coordinates correspond to space (x) and scale (a); both are linear (small scales at the top). The intensity of the wavelet transform is colour-coded according to the natural light spectrum from, black (low intensity) (Tg ^ 0) to red (max (Tg) 〉 0) on each ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/338051a0
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  • 7
    Electronic Resource
    Electronic Resource
    A statistical estimator of turbulence intermittency in physical and numerical experiments (2000)
    Springer
    The European physical journal 16 (2000), S. 549-561 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 47.27.-i Turbulent flows, convection, and heat transfer - 47.27.Gs Isotropic turbulence; homogeneous turbulence - 47.27.Jv High-Reynolds-number turbulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The velocity increments statistic in various turbulent flows is analysed through the hypothesis that different scales are linked by a multiplicative process, of which multiplier is infinitely divisible. This generalisation of the Kolmogorov-Obukhov theory is compatible with the finite Reynolds number value of real flows, thus ensuring safe extrapolation to the infinite Reynolds limit. It exhibits a estimator universally depending on the Reynolds number of the flow, with the same law either for Direct Numerical Simulations or experiments, both for transverse and longitudinal increments. As an application of this result, the inverse dependence is used to define an unbiased value for a Large Eddy Simulation from the resolved scales velocity statistics. However, the exact shape of the multiplicative process, though independent of the Reynolds number for a given experimental setup, is found to depend significantly on this setup and on the nature of the increment, longitudinal or transverse. The asymmetry of longitudinal velocity increments probability density functions exhibits similarly a dependence with the experimental setup, but also systematically depends on the Reynolds number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510070216
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  • 8
    Electronic Resource
    Electronic Resource
    A new representation of energy spectra in fully developed turbulence (1993)
    Springer
    Flow, turbulence and combustion 51 (1993), S. 99-103 
    Details
    ISSN: 1573-1987
    Keywords: turbulence ; scaling ; universality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract It is well known that the Kolmogorov 1941 theory is based on global invariance, in the limit of Reynolds number tending to infinity. Experimentally, it is well verified only for very high Reynolds numbers, namelyR λ≥2000 (Monin and Yaglom 1975). We propose a new experimental representation for energy spectra. Using the Kolmogorov scales, a compilation of dimensionless spectra (E=ε (k)/(εv 5)1/4 andK=k(v 3/ε)1/4) shows that log(0.154E)/log(R λ/R*) is a universal function of log(5.42K)/log(R λ/R*) withR*=75. This new representation is not compatible with neither local nor global scaling invariance. The constant 5.42 takes into account the small scale intermittency. Similar results have been obtained for velocity structure functions of order 2, 3 and 6. In particular the wavenumber constant 5.42 is independent on the order of the moments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01082521
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  • 9
    Electronic Resource
    Electronic Resource
    Self sustained oscillations and collective behaviours in a lattice of jets (1993)
    Springer
    Flow, turbulence and combustion 51 (1993), S. 243-248 
    Details
    ISSN: 1573-1987
    Keywords: interacting jets ; delayed feedback
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Strongly interacting aligned multiple jets are produced behind a perforated plate placed in a uniform flow. The performation patterns investigated experimentally are a square and a triangular lattice of holes with diametersd ranging from 1 mm to 10 mm and of mesh sizeM ranging from 2.54 mm to 25.4 mm. At moderate Reynolds numbers (Re=ud/ν〈3000), each laminar jet develops instabilities causing its effective diameter to increase, thus leading the parallel jets to merge at a distanceL from the plate. The merging distanceL is shown to exhibit a low frequency self sustained oscillation around its mean value with a lateral correlation length much larger than the mesh size. Both the merging distanceL and the oscillation frequency are shown to be functions ofM and of the jet velocity. At larger values ofRe, the merging distance approaches a constant mean value and the amplitude of the oscillations becomes vanishingly small. At the scale of the mesh of the lattice, the oscillating phenomena is shown to result from the local confinement of the jet by its nearby neighbours. This observation is consistent with the fact that when the effect of the nearby jets is simulated by rigid walls, the frequency of the jet's oscillations is found to be of the same order. The influence of the hydrodynamical régime of the individual jets on the oscillations and the role of the lattice pattern on the collective behaviour is discussed on hand of an original model which focuses on the role of the recirculation zone on the delayed non linear saturation of the instabilities of the jet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01082544
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  • 10
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    Superfluid high REynolds von Kármán experiment (2014)
    American Institute of Physics
    Details
    Publication Date: 2014-10-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics
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