Particles in turbulence

We are interested in fundamental understanding of fluid turbulence and how particles behave dynamically in turbulent flow. Current project include the followings, however, projects of similar nature can be suggested and discussed.

On the experimental side, we are foremost interested in the enhancement of water droplet collision-coalescence due to turbulent flow. This problem has strong practical implication on the process of rain formation in atmospheric clouds, which in turn is important for the understanding of earth's climate & its variability. Currently, it is theorized that in order to have rain from warm clouds (where ice particle are limited in number), small water droplets of size 10 to 20 microns must collide and coalesce to form rain droplets of roughly milimeter size. It is hard to imagine that these collision can take place without the help of external forcing from turbulence flow, which common experience as aircraft passenger tells us is plentiful in clouds (e.g. when an aircraft flies within cloud layers). The puzzle of whether this theory is correct and to which extend, requires careful experimental studies. To that end, we will generated turbulent flow and water droplets in laborotary, each requires careful and creative design. We will use Particle Tracking Velocimetry, a modern technique of observing 3-D particle trajectories, to observe droplet behaviour and collisions.

We are also exploring the idea of using super-paramagnetic particles to understand particle dynamics in turbulent flow. This allows us to modulate the physics of particle-flow interaction via external magnetic field. Possibilities are plentiful but the first obvious goal is to study the influence of gravity on particle dynamics by negating or enhancing the net body force on particles.

On the theoretical(computational) side, we are interested to set-up and perform direct numerical simulation (DNS) of turbulent flow with or without particles. DNS is the most accurate theoretical tools for studies of turbulent flow. We hope that this effort will prodive a complemental perspective in our quest of understanding fluid turbulence, which is often described as the last unsolved problem in classical physics.

Contact: Eberhard Bodenschatz