Inception and Entrainment in Self-Aerated Flows

Abstract

Inception and entrainment of air in self-aerated open channel flows are studied. For inception to occur surface eddies should leave the free surface and the whole fluid should be turbulent. A criterion for the surface eddy to leave the free surface is formulated using the energy concept. A method to locate the zone of boundary layer emergence to the free surface which causes the whole fluid to be turbulent in the case of flow over free overfall spillways is developed. Using the concept of entrainment, the basic equations for aerated flow down prismatic channels are formulated. Using these equations, several flow characteristics of the uniform aerated flow are studied. The investigations help in computing uniform aerated flow characteristics knowing the non-aerated flow data.