Regensburg 2002 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 11: Fluiddynamik

DY 11.3: Hauptvortrag

Montag, 11. März 2002, 10:30–11:00, H3

Why would a mosquito care about turbulence and why should you? — •Eberhard Bodenschatz — Laboratory of Atomic and Solid State Physics, Cornell University, USA

The motion of fluid particles as they are pushed along erratic trajectories by fluctuating pressure gradients is fundamental to transport and mixing in turbulence. It is essential in cloud formation, the formation of nanoparticles in aerosol reactors; the formation, transport, and removal of particulate air pollutants; and multi-phase processes used in the chemical industry for heat and mass transfer, and catalytic chemical reactions. However, many fundamental issues of particle transport in turbulence are unresolved. One such issue is the Heisenberg-Yaglom prediction of fluid particle accelerations, based on the 1941 scaling theory of Kolmogorov.

Here we report acceleration measurements using a detector adapted from high-energy physics to track particles in a high Reynolds number laboratory water flow with a very high spatial and temporal resolution . We find that universal K41 scaling of the acceleration variance is approximately attained at high Reynolds numbers. Our data show very strong intermittency—particles are observed with accelerations of up to 1,500 times the acceleration of gravity (40 times the root mean square value). We find that the anisotrpy of the flow is present at the smallest scales even at very high Reynolds numbers.

We also study turbulence in very dilute polymer solutions. We find a huge effect at the dissipation scales of turbulence, i.e., the acceleration variance decreases and the acceleration correlation time increseases.