Spray Evolution of a Coflowing Round Liquid Jet in High Speed Air Flow

Instantaneous flow visualization was used to study spray evolution in high-speed flow. At very low air velocities, the observed instability of the liquid column agreed qualitatively with numerical simulation of other workers using model eddies. Downstream, a supersonic region with helical instability displaying treelike branches, and a more familiar subsonic region with transverse instability waves, were observed. Apparently, most of the liquid jet was atomized in the upstream, supersonic regions, followed by entrainment of the surrounding air and mixing with it in the subsonic regions.