Experimental and analytical investigation of multiple jets in a cross-flow

Abstract

Extensive measurements using hot-wire anemometry were carried out for single jet, tandem jets, and side-by-side jets for a velocity ratio of 2, and a jet spacing of 4 for the latter two cases. The measurements yielded axial mean velocity, turbulence intensities, and Reynolds stresses for four downstream stations for the single jet and two downstream stations for the double jet. A preliminary study of the one-dimensional frequency spectra and flow visualization using a tuft wire were also performed. An analytical study using a momentum-integral approach was also carried out in order to predict the gross jet properties such as the jet trajectories, the jet growth, and the mean jet velocity and the mean jet temperature.

The jets showed considerable influence on each other for the jet spacing of four jet diameters. An upward shift of the merged jet trajectory, and a widening of the jet crosssection in both directions for the tandem jets as compared to the single jet, were observed. Good correlation between the mean velocity gradients and Reynolds shear stresses were found to exist. The detailed flow structure was found to be very similar for the single jet and tandem jet cases for the downstream stations. The distribution of the one-dimensional energy spectra showed spatial and/or configurational dependence; however, no discernible variation of the frequency corresponding to the peak energy was observed. The flow visualization study showed the existence of circulatory flow in the cross-planes. The analytical study gave results which agreed very well with experimental data.