An experimental study on the near flow field of a round jet affected by upstream multi-lateral side-jet

Abstract

The application of lateral jets into a confined flow in industry is a common method for mixing of reagents. However, there is limited understanding of the fundamentals surrounding the flow structures, flow evolution and their respective effects on a downstream outflow of a round jet nozzle when there are multiple jets inside the nozzle. To address this, an experimental study of the near-field outflow of a turbulent round water jet affected by multiple side-jet injected laterally into the round flow upstream of the nozzle exit has been conducted. Planar Laser Induced Fluorescence and Particles Image Velocimetry were used to investigate the fluid mixing and velocity in the near-field, respectively. The influence of jet to cross-flow momentum ratio on flow characteristics; including mixing and turbulence intensity, were assessed by varying the primary jet and side injection flow rates. Results indicated that side injection has major effects on the resulting near-field region flow. Flow cases with side-jets show an increase in shear layer roll-ups and spread. Velocity decay rates and turbulence intensity within the jet core increase with increasing jet to cross-flow momentum ratio. However, these effects extend only to the near-field region, as no significant perturbations beyond two primary jet diameters downstream are observed. This indicates that the side injection has significant effect on the flow and mixing in the near-field region, but minor influences further downstream.