Particles in turbulence
High-tech wind tunnel experiments, particularly those under conditions of extreme turbulence, hold much promise in advancing climate research such as that related to the formation of rain and clouds. The EU-funded project 'Particles in turbulence: from tracers to rain formation' (PTURB) conducted novel laser measurements called 3D-LPT in the Goettingen wind tunnel in Germany to further cutting-edge research on the topic. The team aimed to overcome optical problems arising from the change of index of refraction related to pressure changes in the wind tunnel, effectively manipulating camera optics and laser projection. Other challenges studied include seeding the flow and establishing an acoustic probe to measure vorticity. In addition, the team built what is known as a Von Kármán flow device in water involving two coaxial counter-rotating disks to conduct even more sophisticated experiments under fully developed turbulence. Another important achievement has been the dynamic coupling between a turbulent flow and inertial particles (i.e. those heavier than the fluid in which they evolve). Through these experiments the team gained insight into a variety of aspects related to climate change from the spread of pollution to industrial mixing processes. The work has also shed light on fluid mechanics measurement techniques and deepened our understanding in this respect. Project scientists also conducted tests on measuring the full motion of particles, including translation and rotation, together with the fluid velocity around it. PTURB successfully accomplished its objectives, bringing researchers closer to understanding many intricate aspects of weather and climate change.
