Affiliations: Experimental Aerodynamics Division, National Aerospace
Laboratories, Bangalore, Inda | Indian Institute of Science, Bangalore, India
Abstract: The near flow field of small aspect ratio elliptic turbulent free
jets (issuing from nozzle and orifice) was experimentally studied using a 2D
PIV. Two point velocity correlations in these jets revealed the extent and
orientation of the large scale structures in the major and minor planes. The
spatial filtering of the instantaneous velocity field using Gaussian
convolution kernel shows that while a single large vortex ring circumscribing
the jet seems to be present at the exit of nozzle, the orifice jet exhibited a
number of smaller vortex ring pairs close to jet exit. The smaller length scale
observed in the case of the orifice jet is representative of the smaller
azimuthal vortex rings that generate exial vortex field as they are convected.
This results in the axis switching in the case of orifice jet and may have a
mechanism different from the self induction process as observed in the case of
contoured nozzle jet flow.
Keywords: PIV, Elliptic jet, Axis switching, Spatial filtering, Two point correlation