Experimental study of a circular jet under the effect of secondary jets

The present study investigates the interaction between two jets: a primary round jet and secondary jets formed by a manipulated co-annular jet. Secondary jets were formed by a combination of a co-annular jet issuing from a nozzle with convex surfaces and fluid injection into the co-annular jet perpendicular to the primary jet axis. Experiments reported here were carried out using a two-component Laser-Doppler-Velocimetry system to determine the effects of the secondary jet on the primary jet. Mean velocity and Reynolds stress measurements were made along and across the primary jet centerline with and without the presence of the secondary jet. It was observed that fluid injection into the spacing between the inner jet pipe and the outer jet surface highly affects the characteristics of the mixing region. Fluid injection perpendicular to the co-annular jet transforms the co-annular jet into two separate jets positioned at 180 degrees apart from each other. As compared to the primary jet only case, the interaction of the secondary jets with the primary jet results in a planar primary jet showing faster centerline velocity reduction. The spreading of the jet was also seen to be twice the values observed with the primary jet alone at each x/d location. The Reynolds number for the primary jet was about 16000.