The near-field structure of free jets from a contoured nozzle, a long pipe and an orifice plate

Abstract

Azimuthal vorticity fields generated from particle image velocimetry suggest that vortex pairs shed within 2 exit diameters from a contraction nozzle tend towards instantaneous axi-symmetry, while those shed from a sharp-edge orifice plate tend toward an asymmetric near-field structure. Relatively smaller scale and somewhat less organised structures are evident in the flow produced by a long upstream pipe.