A Digital Particle Image Velocimetry Study on Jets Issuing from Hybrid Inclined Nozzles

Abstract

Digital particle image velocimetry was used to study hybrid inclined nozzles formed by combining flat- and inclined-sections, where the latter are designed based on the aspect-ratios (AR = 2 and 4) of half-ellipses. Results show that AR2 nozzle exhibits flow behaviour largely similar to inclined nozzles with inclined vortex roll-ups moving away from the nozzle centerline. In contrast, AR4 nozzle leads to significantly more intense near-field flow behaviour caused by the sharper junctions, which prevent similar movement of the vortex roll-ups. Streamwise vortices are also observed to form off the peaks of inclined-sections which produce wider jets-spreads along the inclined-sections due to associated lateral jet fluid ejection, though there is a limit to the jet-spread increment. Lastly, both nozzles produce higher turbulent stress levels over those of the conventional circular nozzle, and vortex roll-up vectoring leads to higher turbulent stresses for the AR2 nozzle along certain measurement planes.