Lagrangian investigation of turbulence : experimental techniques and statistical results

Christophe Baudet, Laboratoire des Ecoulements Géophysiques et Industriels (LEGI), Grenoble, France

The availability of experimental Lagrangian statistics in fully developped turbulence is of prime interest for a better understanding and modelling of turbulent flows. Reliable Lagrangian statistics impose several demanding constraints on the measurement techniques : size and density of the seeded particles, tracking procedures, spatial resolution and extension of the detection systems. In the past few years, several experiments have been conducted on various kinds of flows, using either optical devices or acoustic ultrasonic waves. I will review, the pros and cons of these experimental approaches. Then, I will present some of the most salient statistical results obtained with these techniques, focusing on Lagrangian intermittency and Lagrangian correlations of the turbulent velocity field.