Transition from a turbulent jet into a turbulent plume

Flow visualization and temperature measurements were made in an axisymmetrical turbulent hot jet with a high exit densimetric Froude number. The experimental results obtained in the region of transition from a jet-like to a plume-like flow were correlated successfully by a set of scales and dimensionless parameters that were derived from the momentum flux, buoyancy flux, and heat flux of the exit. Turbulent and intermittency levels in the plume region were found to be much higher than those in the jet region near the exit. This had led to different transition behaviors for the mean and for the fluctuating quantities. As far as the mean quantities are concerned, plume behavior is established beyond a distance of approximately 4 L(s) from the exit, L(s) being the length scale derived from the momentum and buoyancy fluxes of the exit. Turbulent fluctuations take significantly longer distances to establish. The distance necessary for turbulent fluctuations to reach the level of a plume is about 10 L(s) from the exit.