Mesure acoustique de vitesse lagrangienne dans un jet d'air turbulent

Abstract : The aim of this work is the experimental study of turbulence in an air jet from the lagrangian viewpoint. Fluid particle tracking is achieved by injection of small helium-filled soap bubbles, density-matched with air. The three components of the bubble velocity vector have been measured by a new method, based on the acoustical Doppler effect. A substantial part of the inertial range is resolved. Velocity components have gaussian density probability function, and are statistically independent with one another. Velocity autocorrelation are well fitted by an exponential function. Transverse components are indistinguishable, but differ from the longitudinal one. As a jet has a mean velocity, simultaneous hot-wire measurement were possible. Lagrangian and Eulerian velocity probability density functions are very close to each other. Integral time scale is shorter for the eulerian case, for a given location in the flow. Intermittency is more pronounced in the Lagrangian case, with a smaller inertial range. A significant cross-correlation between Lagrangian and Eulerian longitudinal velocities has been found. No correlation exists between transverse Lagrangian and Longitudinal Eulerian components. This suggests that a proper modeling of this phenomenon is likely to be non purely scalar.
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Contributor : Philippe Gervais <>
Submitted on : Wednesday, January 11, 2006 - 9:57:44 AM
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Philippe Gervais. Mesure acoustique de vitesse lagrangienne dans un jet d'air turbulent. Dynamique des Fluides [physics.flu-dyn]. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00011343⟩

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