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69 results on '"Gagne, Y"'

53. Using Third-Order Moments of Fluctuations in V and B to Determine Turbulent Heating Rates in the Solar Wind.

Author

Forman, M. A., Smith, C. W., Vasquez, B. J., MacBride, B. T., Stawarz, J. E., Podesta, J. J., Elton, D. C., Malecot, U. Y., and Gagne, Y.

Subjects
SOLAR wind, SOLAR activity, STELLAR winds, ENERGY dissipation, SOLAR magnetic fields
Abstract

The inertial range scaling of certain mixed third-order moments of velocity and magnetic field fluctuations in a turbulent MHD plasma such as the solar wind is related to the energy dissipation rate of the turbulence. We have used this relation to measure energy dissipation rates in the solar wind and other statistical methods to estimate the accuracy of these measurements. This paper reviews results we and others have recently published, and some new results. [ABSTRACT FROM AUTHOR]

Published
2010
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54. 3D acoustic Lagrangian velocimetry.

Author

Oliemans, R. V. A., Rodi, W., Geurts, Bernard J., Clercx, Herman, Uijttewaal, Wim, Bourgoin, M., Gervais, P., Cartellier, A., Gagne, Y., and Baudet, C.

Abstract

We report Lagrangian measurements obtained with an acoustic Doppler velocimetry technique. From the Doppler frequency shift of acoustic waves scattered by tracer particles in a turbulent flow, we are able to measure the full three-component velocity of the particles. As a first application, we have studied velocity statistics of Lagrangian tracers in a turbulent air jet at Rλ ∼ 320 and at various distances from the nozzle. The choice of an air jet is motivated by the fact that jets produce a well characterized high level turbulence and open air flows are well suited to simultaneously achieve classical hot wire Eulerian measurements. Therefore, we are also able to explicitly address the question of the differences between Eulerian and Lagrangian statistics. As Lagrangian tracers we use soap bubbles inflated with Helium which are neutrally buoyant in air and can be assimilated to fluid particles. Velocity statistics are analyzed. We show that the Lagrangian autocorrelation decays faster in time than its Eulerian counterpart. [ABSTRACT FROM AUTHOR]

Published
2007
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55. A cryogenic high-Reynolds turbulence experiment at CERN.

Author

Be´zaguet, A., Dauvergne, J.-P., Knoops, S., Lebrun, P., Pezzetti, M., Pirotte, O., Bret, J.-L., Chabaud, B., Garde, G., Guttin, C., He´bral, B., Pietropinto, S., Roche, P., Barbier-Neyret, J.-P., Baudet, C., Gagne, Y., Poulain, C., Castaing, B., Ladam, Y., and Vittoz, F.

Subjects
LOW temperature engineering, TURBULENCE, MEASUREMENT
Abstract

The potential of cryogenic helium flows for studying high-Reynolds number turbulence in the laboratory has been recognised for a long time and implemented in several small-scale hydrodynamic experiments. With its large superconducting particle accelerators and detector magnets, CERN, the European Laboratory for Particle Physics, has become a major world center in helium cryogenics, with several large helium refrigerators having capacities up to 18 kW @ 4.5 K. Combining a small fraction of these resources with the expertise of three laboratories at the forefront of turbulence research, has led to the design, swift implementation, and successful operation of GReC (Grands Reynolds Cryogéniques) a large axisymmetric turbulent-jet experiment. With flow-rates up to 260 g/s of gaseous helium at ≈5 K and atmospheric pressure, Reynolds numbers up to 10[sup 7] have been achieved in a 4.6 m high, 1.4 m diameter cryostat. This paper presents the results of the first runs and describes the experimental set-up comprehensively equipped with "hot" wire micro-anemometers, acoustic scattering vorticity measurements and a large-bandwidth data acquisition system. [ABSTRACT FROM AUTHOR]

Published
2002

59. Structure functions in turbulence, in various flow configurations, at Reynolds number between 30 and 5000, using extended self-similarity

Author

Arneodo, A, primary, Baudet, C, additional, Belin, F, additional, Benzi, R, additional, Castaing, B, additional, Chabaud, B, additional, Chavarria, R, additional, Ciliberto, S, additional, Camussi, R, additional, Chillà, F, additional, Dubrulle, B, additional, Gagne, Y, additional, Hebral, B, additional, Herweijer, J, additional, Marchand, M, additional, Maurer, J, additional, Muzy, J. F, additional, Naert, A, additional, Noullez, A, additional, Peinke, J, additional, Roux, F, additional, Tabeling, P, additional, Water, W. van de, additional, and Willaime, H, additional

Published
1996
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68. Turbulent transport of material particles: an experimental study of finite size effects.

Author

Qureshi NM, Bourgoin M, Baudet C, Cartellier A, and Gagne Y

Abstract

We present experimental Lagrangian statistics of finite sized, neutrally bouyant, particles transported in an isotropic turbulent flow. The particle's diameter is varied over turbulent inertial scales. Finite size effects are shown not to be trivially related to velocity intermittency. The global shape of the particle's acceleration probability density functions is not found to depend significantly on its size while the particle's acceleration variance decreases as it becomes larger in quantitative agreement with the classical k(-7/3) scaling for the spectrum of Eulerian pressure fluctuations in the carrier flow.

Published
2007
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