Experimental study of co-annular jet subjected to transverse disturbances

•Flow field of two coaxially aligned jets is presented.•Transverse flow injection bifurcates the co-annular/secondary jet into two lobes.•Manipulated primary jet velocity reduces 30% more compared to primary jet alone case.•Jet manipulation increases mixing and results in faster spreading for the primary jet. The results of an investigation of the flow field of two coaxially aligned jets consisting of an inner primary jet and a co-annular outer jet issuing from a nozzle with convex sidewalls are reported. A transverse flow injection into the co-annular jet was used to shape the co-annular jet flow. In the region between the exits of the two jets, a recirculating toroidal eddy is formed due to opposing pressure gradients. In the presence of transverse injection, the eddy bifurcates into two lobes with radially emanating flow structures that substantially increase the decay of axial velocity and the spread rate to twice the values when compared to the characteristics of the primary jet alone. Measurements of mean velocities and Reynolds stresses were made at the jet Reynolds number of 16,000 with the help of a specially designed two-component Laser-Doppler-Velocimetry system. Topology of the resulting complex flow in view of the measurements is presented and discussed.