The axisymmetric and the plane jet in a coflow

The approximate variation of the mean proper-ties in an axisymmetric jet an d a two dimensional jet with an ambient coflow in an infinite duct have bee n determined using the excess momentum equation and an entrainment function . The turbulent velocity flux, consisting of a portion due to the excess je t velocity and a portion due to the turbulent coflow velocity, is carried b y a velocity approximately equal to the top hat velocity. The entrainment i nto this flow is driven by the excess jet velocity and the entrainment func tion varies to allow for the change in entrainment from the strong jet to t he weak jet. The entrainment constant is determined from the data of Nickel s and Perry [14] for the axisymmetric case and the data of Bradbury and Ril ey [6] for the two dimensional case. All coflow experiments are in ducts an d the effect of the duct is explored for the axisymmetric case. This paper is a prelude to the study of a buoyant jet in a coflow and a buoyant jet in a crossflow.