A laboratory investigation into the influence of a localized region of turbulence on the evolution of a round turbulent jet

Results are described from a series of laboratory experiments in which the effects of a localized two-dimensional region of turbulence on the spatial development of a round, turbulent jet have been investigated. The evolution of the jet has been studied for respective cases with and without background turbulence in the receiving environment. For the former flow configuration, the breakdown of the jet by the presence of background turbulence (generated by an oscillating grid) has been investigated parametrically for a range of values of the source specific momentum flux J0 of the jet and the grid action K. Measurements of the location of the breakdown point of the jet, as detected by (i) a significant local increase in the jet spreading angle and (ii) the simultaneous decrease and increase in the magnitude of the axial and horizontal velocity components, respectively, of the flow field, confirm scaling predictions showing that the jet is destroyed significantly by the background turbulence when the background turbulence intensity is of the same order as the local turbulence intensity of the jet.