Research on the vortical and turbulent structures in the lobed jet flowusing laser induced fluorescence and particle image velocimetrytechniques

Abstract

The changes in vortical and turbulent structure in the near field(X / D < 3.0) of jet mixing flow caused by a lobed nozzle were investigatedexperimentally in the present study. The techniques of planar laser inducedfluorescence and particle image velocimetry were used to accomplishflow visualization and velocity field measurements. The experimental resultsshowed that, compared with a circular jet flow, lobed jet mixing flow wasfound to have a shorter laminar region, a smaller scale of the spanwiseKelvin-Helmholtz vortices, earlier appearance of small scale turbulentstructures and a larger region of intensive mixing in the near field of the jetmixing flow. The central line velocity decay of the lobed jet mixing flow wasalso found to be much faster than that in a conventional circular jet. Allthese indicated that the lobed nozzle provides better mixing performance thandoes a conventional circular nozzle.