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Special Seminar: Summer 2008

Date: June 20th
Time: 11:00 AM
Location: Latrobe Hall 106
Speaker: Dr. Willem van de Water
Eindhoven Technical University
Title:"Writing in turbulent air"

Abstract

The final stage of mixing in turbulence occurs at the smallest scales. These scales are unreachable in experiments where large numbers of particles are tracked simultaneously, simply because the particle concentrations needed would be prohibitive. Instead, we delineate tiny clouds (with size a few times the Kolmogorov length) in air by selectively tagging molecules with strong lasers. Thus, we write in air. We follow the fate of these clouds using laser induced fluorescence. At these small scales, clouds disperse through turbulence and diffuse through thermal motion. Remarkably, the result of the joint action of these mechanisms is that the spreading rate of clouds does not depend on the Reynolds number. Other experiments reveal the spontaneous clustering of tracers that were painted as lines, and the Batchelor dispersion at inertial-range sca