Turbulent mixing in a free jet issuing from a low aspect ratio contoured rectangular nozzle

The flow field of a turbulent free jet issuing from a contoured rectangular nozzle of aspect ratio 2 has been studied experimentally, using hot-wire anemometry. The study was undertaken to gain some understanding of the mixing process within the jet. Results of the measured and derived mean flow and turbulence quantities are presented. The three components of the mean velocity vector, the three Reynolds normal stresses, the two Reynolds primary shear stresses, and the flatness factor of the streamwise fluctuating velocity were measured. Mass entrainment, turbulence kinetic energy, and the intermittency factor were derived from the mean streamwise velocity data, the Reynolds normal stress data, and the flatness factor data, respectively. The derived results and the Reynolds primary shear stress data indicate enhanced near-field mixing of the present rectangular jet compared to a round turbulent free jet. The mean streamwise velocity field changes from a rectangular to an oval and then to an approximately circular shape at about twenty equivalent nozzle diameters downstream of the nozzle exit plane.