Large-Eddy Simulation of a Droplet-Laden Air Flow over a Waved Water Surface

Large-eddy simulation of the dynamics of a turbulent, droplet-laden air flow over a waved water surface has been carried out. Sufficiently small droplets (with a diameter of up to 300 µm) are considered, which allows us to neglect their deformation. Collisions between the droplets, as well as their evaporation and heat exchange with the air, are also not taken into account. The mass fraction of the droplets is prescribed to be sufficiently small, which allows one to neglect their impact on the air flow; the surface wave is prescribed and not affected by either droplets or wind. The numerical model is based on the solution of three-dimensional, filtered over subgrid-scale fluctuations, Eulerian equations of air-phase motion, and Lagrangian equations of the motion of individual droplets. A turbulent-viscosity concept is employed for the closure of the subgrid stresses in the air velocity equations where the kinetic energy of the pulsations unresolved by the grid is determined by the solution of a prognostic equation. The model is verified by a comparison with the results of direct numerical integration of the full equations of the dynamics of the air and dispersed phases. Phase-averaged profiles of the air velocity and momentum flux and droplet concentration are obtained for different Reynolds numbers of the carrier flow (up to 10⁵) and scenarios of droplet injection into the flow.