Effect of evaporation and condensation on droplet size distribution in turbulence

Abstract

The interaction of droplets that undergo phase transition with a turbulent flow is encountered in many areas of engineering and atmospheric science as described in (Lanotte et al., 2008). In the context of cloud physics the evaporation and condensation of water vapor from and to the droplets is the governing process for the growth of the droplets from sub micron size up to a size of around 20 μm, after which they grow mostly by coalescence until they become large enough to fall as rain drops under gravity. Much pioneering work has been done in (Luo et al., 2008; Lanotte et al., 2008; Sidin et al., 2009) on the theoretical and numerical investigation of the influence of turbulence on evaporation and condensation associated with aerosol droplets. In this paper we consider the situation of water droplets undergoing phase change and moving in air. Air also advects the vapor concentration field. We compute the natural size distribution of the droplets that arises as a result of the interaction between the droplets and the transporting turbulent flow. We assume the turbulent flow to be homogeneous and isotropic. We will perform DNS of the velocity field and the passively advected vapor and temperature field. The droplet trajectories are computed time-accurately in a domain with periodic boundary conditions.