Experimental investigation of turbulent transport of material particles
Résumé
We report measurements of Lagrangian velocity and acceleration statistics of particles transported in a turbulent flow obtained with an acoustic Doppler velocimelly technique. We consider a homogeneous isotropic grid turbulence generated in a wind tunnel. As a first step we study isolated particles dynamics with a particular focus on the influence of particles finite size on their response to the turbulence forcing. As particles we use neutrally buoyant soap bubbles inflated with helium. The size of the particles can be adjusted from 1.5 mm to 6 mm, corresponding to inertial range scales. We show that the response time of the particles to the turbulence forcing increases with their size. We analyze our data in the frame of two times stochastic models, and show that the cut-of! time scale in the Lagrangian energy spectrum of the particles dynamics has a dependence on their diameter consistent with a lowpass .filtering of the turbulent cascade by the particles finite size.
