Mixing Process in the Jet Flow of Lobed Nozzle

The vortical and turbulent structure changes in the near field (X/D<3.0) of the jet mixing flow caused by a lobed nozzle had been investigated experimentally in the present study. The techniques of planar Laser Induced Fluoresce (LIF) and Particle Image Velocimetry (PIV) were used to accomplish the flow visualization and velocity field measurements. The experimental results showed that, compared with a circular jet flow, lobed jet mixing flow was found to have shorter laminar region, smaller scale of the spanwise Kelvin-Helmholtz vortices, earlier appearance of small scale turbulent structures and larger intensive mixing region in the near field of the jet mixing flow. The central line velocity decay of the lobed jet mixing flow was also found to be much faster than that in a conventional circular jet. All these indicted the better mixing enhancement performance of a lobed nozzle over a conventional circular nozzle.