Experimental and numerical study of the Lagrangian dynamics of high Reynolds turbulence -: art. no. 116

We introduce an original acoustic method to track the motion of tracer particles in high Reynolds number turbulent flows. We present in detail the experimental technique and show that it yields a measurement of the Lagrangian velocity variations of single particles, resolved across the inertial range turbulence. Second-order quantities such as the velocity autocorrelation function and time spectrum are in agreement with Kolmogorov 1941 phenomenology. Higher-order quantities reveal a very strong intermittency in the Lagrangian dynamics. Using both the results of the measurements and of direct numerical simulations, we show that the origin of intermittency can be traced back to the existence of long-time correlations in the dynamics of the Lagrangian acceleration. Finally, we discuss the role played by vortices in the Lagrangian dynamics.