Fluid turbulence occurs whenever the inertial forces overwhelm the viscous damping in the flow. Most natural and industrial flows are turbulent due to the large scales and/or high flow speeds. Turbulence per se is mostly of academic interest. Turbulent transport, however, is fundamental to natural and technological flows. The transport properties are the more important when turbulent flows carry particulate matter or "particles’’. Examples can be found in technological flows ranging from fuel sprays in combustion engines and oil burners, to powder and slurry processing in chemical engineering and waste removal in water. In natural flows examples reach from water droplets in warm clouds, and plankton biology in the ocean, to dust in the earth’s atmosphere or the formation of proto-planets in proto-planetary disks. Rarely these particles are sufficiently small or density matched to the fluid to be considered tracers. Usually they are heavier (i.e. sand in water or air, or cloud droplets in air) or lighter (air or oil droplets in water) and due to inertia do not follow the flow. As a result particles cluster and/or collide. Understanding the dynamics of the dispersed particles in turbulent flows is therefore of paramount importance to engineers and natural scientists alike. Understanding particle in turbulence is linked to many economical and ecological challenges.

 

Research in this field is very challenging, but important progress has been achieved during the last decade. For the first time, new experimental techniques allow to trackthousands of particles in 3D; numerical simulation has advanced to the point where model assumptions can be compared quantitatively with experiment; and analytical calculation has given important new insights. In this talk, I will present the work at the Max Planck Institute for Dynamics and Self-Organization (MPIDS), Goettingen, Germany. Our research relies on highly advanced experimental investigations with state-of-the-art measurement techniques. I will also cover other related numerical and theoretical work.