Water Circulation in Non-Isothermal Droplet-laden Turbulent Channel Flow

We propose a point-particle model for two-way coupling of water droplets dispersed in turbulent flow of a carrier gas consisting of air and water vapor. An incompressible flow formulation is applied for direct numerical simulation (DNS) of turbulent channel flow with a warm and a cold wall. Compared to simulations without droplets or with solid particles a significant increase in Nusselt number is found, arising from the additional phase changes. In the statistically steady state, which is reached after a long time, the flow exhibits a mean motion of water vapor from the warm wall to the cold wall. Vapor condenses on average on drops near the cold wall and evaporates from drops near the warm wall. This transport is balanced by a net mean mass transfer of droplets from the cold wall to the warm wall.