Velocity Field of Submerged Multiple Non-buoyant Jet Groups in Crossflow

This paper presents the results of a laboratory study on the three-dimensional velocity field of circular non-buoyant multiple jets discharged into a perpendicular crossflow. Two to four momentum jets were taken in a group with spacings five times the jet diameters and the three-dimensional velocity field was measured using an Acoustic Doppler Velocimetry (ADV) system to investigate the interaction of jets with crossflow. The rear jets were found to be less deflected than the front one due to the reduction of effective crossflow velocity because of the sheltering effect as well as the entrainment demand. For a jet spacing of 5 times of jet diameter, the effective crossflow to upstream approach velocity ratios were found to vary between 0.4 and 0.6 regardless of the momentum length scale and the number of jets in a group. The rates of velocity reduction in between jets observed in this study, were favorably compared with previous results, where velocity was inferred from Laser Induced Fluorescence (LIF) measurements. The findings of this study can be used to predict the jet trajectories and dilutions of multiple jets in crossflow as well as modeling of discharges from multiport diffusers. This work will be helpful for the engineers and other scientists dealing with the disposal of wastewater, thermal effluents, or air pollutants into flowing environments.