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Measurement of Lagrangian velocity in fully developed turbulence

Abstract : We have developed a new experimental technique to measure the Lagrangian velocity of tracer particles in a turbulent flow, based on ultrasonic Doppler tracking. This method yields a direct access to the velocity of a single particule at a turbulent Reynolds number $R_{\lambda} = 740$. Its dynamics is analyzed with two decades of time resolution, below the Lagrangian correlation time. We observe that the Lagrangian velocity spectrum has a Lorentzian form $E^{L}(\omega) = u_{rms}^{2} T_{L} / (1 + (T_{L}\omega)^{2})$, in agreement with a Kolmogorov-like scaling in the inertial range. The probability density function (PDF) of the velocity time increments displays a change of shape from quasi-Gaussian a integral time scale to stretched exponential tails at the smallest time increments. This intermittency, when measured from relative scaling exponents of structure functions, is more pronounced than in the Eulerian framework.
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https://hal.archives-ouvertes.fr/hal-00712206
Contributor : Nicolas Mordant Connect in order to contact the contributor
Submitted on : Tuesday, June 26, 2012 - 4:16:49 PM
Last modification on : Friday, April 23, 2021 - 9:06:03 AM

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N. Mordant, P. Metz, Olivier Michel, J. -F. Pinton. Measurement of Lagrangian velocity in fully developed turbulence. Physical Review Letters, American Physical Society, 2001, pp.214501. ⟨10.1103/PhysRevLett.87.214501⟩. ⟨hal-00712206⟩

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