Self-aerating spillway flow

The concept upon which most past analyses are based is that a continuum exists in aerated flow from 100 percent water, to air bubbles in water, to a water-air mixture, to an air-water mixture, to water droplets in air, to 100 percent air. Measurements of air concentration would seem to indicate that this is the case inasmuch as the air concentration varies in a continuous fashion over the depth of flow. J.M. Killen however, showed in high-speed photos taken during flume experiments in the mid-fifties, that the water surface remained 'intact but very contorted' with a very small quantity of flying droplets over the surface. Hence, a well-mixed continuum of increasing air and decreasing water over depth does not exist. This paper redefines some of the concepts of self-aerated flow and discusses the impacts of these concepts on the areas of interest.