Turbulence structure and scalar transfer in stratified free–surface flows

Direct numerical simulations were used to investigate turbulence structure and scalar transfer across a shear‐free, nonwavy gas‐liquid interface (free surface) in stably stratified turbulent flows. These simulations solve the Navier–Stokes and thermal‐energy conservation equations, using a finite difference approximation. The relation between the turbulence structure in the stably stratified turbulent boundary layer and organized motion near the free surface are discussed. In addition, scalar transfer across a free surface is investigated by solving a passive scalcr conservation equation after both velocity and temperature fields are fully developed. The effects of stable stratification on the scalar transfer process in a region very close to the free surface are also discussed.