Lagrangian statistics of light particles in turbulence

We study the Lagrangian velocity and acceleration statistics of light particles (bubbles in water) in homogeneous and isotropic turbulence. Bubbles of size comparable to the Kolmogorov length scale (Stokes numbers $\approx$ O(0.01)) are dispersed in a turbulent water tunnel operated at Taylor Reynolds numbers $Re_{\lambda}$ ranging from 130 to 260. The bubble trajectories are experimentally captured using the three-dimensional Lagrangian Particle Tracking technique. The bubble acceleration PDFs are found to be highly intermittent with flatness values around 23-30. We study the dependence of the velocity and acceleration statistics (PDFs and autocorrelation functions) on $Re_{\lambda}$ and compare our results to those from point-particle DNS and other experiments. We also present our latest results on the Lagrangian statistics of finite-size inertial bubbles (size $\approx$ 2-4 mm and St $\approx$ O(1)).