Entrainment velocity in an axisymmetric turbulent jet

Mean radial and turbulent radial velocity profiles were measured in a circular jet at up to 40 jet diameters downstream of the jet exit using an LDA. The, mean radial velocity in the ambient reservoir (the entrainment velocity) is found to be inversely proportional to the radial distance from the jet centerline. The coefficient of proportionality, c, increases in the zone of flow establishment and reaches a constant after the transition zone. It is suggested that the traditional definition of entrainment velocity, which maintains direct proportionality to the local jet velocity by the entrainment coefficient, should be augmented by this inverse function.