Vertical Turbulent Diffusion in Air-Driven Water Flows

Turbulence intensities and Reynolds stresses produced in a water channel by an air flow over the surface have been measured. An expression for the vertical eddy diffusion coefficient is derived from these results. The drag necessary for the creation of waves and the development of a boundary layer, including the acceleration of the water mass, have been taken into account and are shown to be significant. A linear shear stress distribution has been measured within the boundary layer, and the Prandtl mixing length theory and Boussinesq hypothesis are shown to provide a good basis for describing the diffusion process.