Turbulent Jet Approach to Predict Expansion Head Loss at Submerged Outlets

Abstract

As the flow expands at expansions, generation of turbulence by shear layers results in the dissipation of energy of the mean flow. Based on simplified momentum equations, this head loss was previously estimated to be comparable to the velocity head of the incoming flow. In this paper, an approach based on turbulent jet theories is used to more accurately evaluate head loss at outlets. This approach is based on the similarity between the generation of a shear layer at an outlet to that of a turbulent jet at its origin. A general equation is derived for the variation of the kinetic energy of the flow from outlets of any geometry and the corresponding head loss coefficient. The equation is simplified for rectangular outlets, which are more common in practice.