DNS of aerosol evolution in a turbulent mixing layer

The complex interaction of turbulent mixing and aerosol growth processes in a canonical turbulent flow configuration is investigated by means of direct numerical simulation. A cold gaseous stream mixes with a hot stream of vapor in a developing mixing layer. Nanometer sized particles (droplets) nucleate as vapor becomes supersaturated and subsequently grow as more vapor condenses on their surface. Aerosol dynamics are solved with the Quadrature Method of Moments. Aerosol moments advection is solved with a Lagrangian particles scheme. The results show that the highest nucleation rate region is located on the cold, lean vapor region, while particles experience a high growth rate on the hot, rich vapor region. The effect of differential diffusion of aerosol particles and the gas is investigated. Small nucleated particles tend to drift towards the hot, rich vapor region, while bigger particles drift towards the cold, lean vapor region, and the particle volume fraction peaks in the middle region of the mixture fraction space. Monte Carlo simulation of aerosol evolution is perfomred along a selected Lagrangian trajectory to analyze the particle size distribution, which is found to exhibits complex modality due to the synergistic effect of nucleation and condensation.