Measurement of Lagrangian velocity in fully developed turbulence.
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 particle at a turbulent Reynolds number R(lambda) = 740, 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(2)(rms)T(L)/[1+(T(L)omega)(2)], in agreement with a Kolmogorov-like scaling in the inertial range. The probability density functions of the velocity time increments display an intermittency which is more pronounced than that of the corresponding Eulerian spatial increments.
Mordant
N
N
CNRS & Laboratoire de Physique, Ecole Normale Supérieure, 46 allée d'Italie, F-69007 Lyon, France.
Metz
P
P
Michel
O
O
Pinton
J F
JF