TABLE OF CONTENTS The model used for the underlying single phase liquid requires closures for the turbulent terms in the averaged equations of motion. For present purposes we presume that some closure has been chosen for the underlying liquid with sufficient complexity to give those properties of the base of the surface layer indicated with subscript b, that are needed here. As indicated in Part 1, we suppose that primary properties of the free surface depend on turbulent kinetic energy k, or q, and a turbulent length scale L. This ( k, L) assumption also serves to polarise this discussion into consideration of two extreme cases, although many intermediate examples occur.
The first of these cases, and the simplest is where the structure of the free surface depends entirely on turbulence reaching it from below. That is, the surface layer is roughly horizontal and we assume that its properties are just due to the turbulence at its base. In which case all the layer terms needed for closure might be estimated from a knowledge of the flow's location in the ( q, L) plane, as in figure 10 of Part 1, and the major effect at the surface is due to gradients of the turbulent properties along the surface.
For flows driven by turbulence from below, we assume that some of the mean and turbulent flow properties have a uniform profile across the surface layer. This is...
