Abstract
A circular turbulent jet issued along a plane wall is visualized by means of laser-induced fluorescence to investigate the large-scale structure in the fully devloped region of jet.The fluorescence dye was premixed to jet fluid, and a cross section normal to jet axis was illuminated by a thin laser sheet. To observe the evolution of jet fluid pattern, the laser sheet was moved to follow the flow strucure. And a surrounding fluid was marked by deeper fluorescence dye and process of the entrainment and the mixing with jet fluid were observed. The results indicate that the structure of the jet is characterized by three-dimensional large-scale vortices and that the flow is filled with numerous streamwise vortices. A pair of large-scale secondary flow which entrain the fluid from upper region and push to lateralward is found to exert an important effect on the entrainment of surrounding fluid and appear to play a dominant role on the greater lateral rate of spread.
