Droplet condensation in two-dimensional Bolgiano turbulence

Abstract

The evolution of microdroplets transported by a turbulent flow is considered. Droplets surrounded by moist air are able to grow by diffusion of water vapour on their surface. A two-dimensional model of dry Boussinesq thermal convection is considered in which the turbulent velocity field is driven by a temperature gradient. The evolution of the velocity, temperature, vapour fields and of droplet trajectories and radii is analysed by means of high-resolution direct numerical simulations. Despite the fact that the environment becomes drier and drier, a mean growth of droplets is obtained. The mechanism identified is based on the presence of correlations between the vapour field and droplet trajectories. Besides, a spreading of size distribution is observed, with the formation of droplets with very different sizes. Improvements with respect to previous models are discussed.

Keywords:

• Atmospheric turbulence
• Turbulent convection
• Direct numerical simulation
• Two-dimensional turbulence

Acknowledgements

This work has been supported by the EU under the contract HPRN–CT–2002–00300, by the Italian MIUR COFIN 2005 project no. 2005027808 and by the Italian consortium CINFAI; AS has been partially supported by L'ORÉAL Italia Per le Donne e la Scienza.