Turbulent jet stability increased by ribs inside the nozzle – Stereo PIV measurement one diameter past the nozzle

We observe that decreasing the inner nozzle surface by adding longitudinal ribs increases jet stability in terms of amount turbulent kinetic energy near shear layer. try to explain our observation as a stabilization effect secondary flow vortices emerging corners ribs. These stream-wise damage development larger-scale structures This explanation is supported autocorrelation function velocity component, which displays slightly smaller integral length-scale case with than smooth nozzle. The experiment performed at Reynolds number 2.2 × 10 5 (based on diameter 50 mm); Stereo-PIV (Particle Image Velocimetry) measurement takes place plane perpendicular axis one past exit. Optical 3D scanner controls real geometry. article presents preliminary single position and only; further exploration this problem needed.