ABSTRACT
Entrainment is the process of drawing ambient fluid into a jet that is discharged into the ambient. It can be described by considering the interaction between two adjacent fluid layers, one going faster than the other. If the discharged fluid is less dense than the ambient, a buoyant jet results. In addition to viscous and turbulent shear, buoyant forces cause the plume to rise relative to the ambient. Diffusion of the discharged fluid into the ambient is caused by molecular diffusion and turbulent mixing. Molecular diffusion results from the random motion of molecules in a fluid. The turbulent velocity and concentration profile in a duct are blunt. The region where the profiles change from "top hat" to bell shaped is known as the zone of flow establishment. Beyond the zone of flow establishment is the zone of established flow where the profiles are all similar changing only in width and centerline magnitude.
