An experimental investigation has been made with the objective of studying the mixing mechanism near the nozzle exit of a laminar nonreacting and reacting jet under axial forcing. The evolution of the three dimensional vortex structure was visualized with Mie scattering technique and direct photography and phase-averaged Laser Velocimeter measurement of fluctuating velocity was carried out. The jet was forced with the resonant frequency of the experimental apparatus for the strong fluctuating velocity ranging from 0.1 to 1.0 of the centerline velocity. A loudspeaker is used to force the jet.
From the velocity measurement and flow visualization results, it was found that the surrounding air was introduced into the nozzle and three-dimensional vortex structure was developed from the interaction between a jet and the surrounding air. The lobe structure which enhances the entrainment and mixing rate was found in the nozzle exit.
In the reacting jet mixing was very important parameter thus improving the mixing results in increasing the combustion efficiency. The structure of the forced diffusion flame depends heavily on the internal flow structure. The internal azimuthal vortex was counter-rotating and induced the surrounding air inside the jet and enlarged the surface at which reacting was occurred.