Repository: Freie Universität Berlin, Math Department

Droplet Collisions and Interaction with the Turbulent Flow within a Two-Phase Wind Tunnel

Bordás, R. and Hagemeier, T. and Wunderlich, B. and Thévenin, D. (2011) Droplet Collisions and Interaction with the Turbulent Flow within a Two-Phase Wind Tunnel. Physics of Fluids, 23 (8). ISSN 1070-6631 (print) 1089-7666 (online)

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Experiments in wind tunnels concerning meteorological issues are not very frequent in the literature. However, such experiments might be essential, for instance for a careful investigation of droplet-droplet interactions in turbulent flows. This issue is crucial for many configurations, in particular to understand warm rain initiation. It is clearly impossible to completely reproduce cloud turbulence within a wind tunnel due to the enormous length scales involved. Nevertheless, it is not necessary to recover the whole spectrum in order to quantify droplet interactions. It is sufficient for this purpose to account correctly for the relevant properties only. In the present paper, these properties and a methodology for setting those in a two-phase wind tunnel are first described. In particular, droplet size and number density, velocities, turbulent kinetic energy, k, and its dissipation rate, ɛ, are suitably reproduced, as demonstrated by non-intrusive measurement techniques. A complete experimental characterization of the air and droplet properties is freely available in a database accessible at Finally, quantifications of droplet collision rates and comparisons with theoretical predictions are presented, showing that measured collision rates are higher, typically by a factor of 2 to 5. These results demonstrate that model modifications are needed to estimate correctly droplet collision probabilities in turbulent flows

Item Type:Article
Subjects:Mathematical and Computer Sciences > Mathematics > Applied Mathematics
ID Code:1014
Deposited By: Ulrike Eickers
Deposited On:14 Jan 2011 08:41
Last Modified:22 Sep 2011 09:41

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