Europhys. Lett.
Volume 66, Number 2, April 2004
Page(s) 219 - 225
Section Electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics
Published online 01 April 2004
Europhys. Lett., 66 (2) , pp. 219-225 (2004)
DOI: 10.1209/epl/i2003-10187-x

Dispersion of tracer particles in a compressible flow

J. R. Cressman1, W. I. Goldburg1 and J. Schumacher2

1  Department of Physics and Astronomy, University of Pittsburgh Pittsburgh, PA 15260, USA
2  Fachbereich Physik, Philipps-Universität - D-35032 Marburg, Germany

(Received 12 November 2003; accepted in final form 5 February 2004)

The turbulent diffusion of Lagrangian tracer particles has been studied in a flow on the surface of a large tank of water and in computer simulations. The effect of flow compressibility is captured in images of particle fields. The velocity field of floating particles has a divergence, whose probability density function shows exponential tails. Also studied is the motion of pairs and triplets of particles. The mean-square separation $\langle \Delta(t)^2 \rangle$ is fitted to the scaling form $\langle \Delta(t)^2 \rangle \propto t^{\alpha}$, and in contrast with the Richardson-Kolmogorov prediction, an extended range with a reduced scaling exponent of $\alpha=1.65\pm 0.1$ is found. Clustering is also manifest in strongly deformed triangles spanned within triplets of tracers.

47.27.Gs - Isotropic turbulence; homogeneous turbulence.
47.27.Qb - Turbulent diffusion.
06.30.Gv - Velocity, acceleration, and rotation.

© EDP Sciences 2004