The turbulent radial jet

A hot-film anemometer has been used to investigate the mean velocity and turbulence intensity distributions in turbulent radial jets. A geometric parameter termed the constraint ratio, defined as the ratio of nozzle diameter to separation distance, is shown to characterize radial-jet behaviour. Large values of the constraint ratio typify ‘constrained’ radial jets, for which the nozzle walls constrain the flow leaving the orifice to be parallel; a small constraint ratio is representative of two opposing free axisymmetric jets, the collision of which produces an ‘impinged’ radial jet. It is found that the well-behaved constrained radial jet spreads at the same rate as does the familiar plane jet, whereas the impinged radial jet spreads at a rate more than three times as fast. Neither type of radial jet is amenable to a self-similar analytic solution; however, while the impinged jet is shown to require numerical solution techniques, an empirical solution for the constrained jet is demonstrated.