Topology of the Counter Rotating Vortex Pairs in Parallel Jets in Crossflow

The formation and evolution of the Counter Rotating Vortex Pairs (CVP) are among the critical phenomena associated with the Jet in Crossflow (JICF) flowfield. These time-averaged vortical structures are the dominant structure in the far field of the JICF flow field. They are associated with enhanced overall mixing efficiency for the JICF flow field compared to a free jet or mixing layer. In this work, we experimentally characterize the topological changes associated with the evolution of the CVPs when the flowfield consists of 2 or 3 jets arranged in a parallel/ inline configuration. 5 kHz Stereo Particle Image Velocimetry (SPIV) measurements of the transverse plane were performed at distinct locations from the jet exit as the momentum flux ratio (J) of the jets and the spacing between the jets (L) were systematically varied. Using these measurements, we characterize the change in strength of the CVPs of the coupled jets and characterize the modifications to the flowfield induced by the coupled CVPs. This work reports the combination of J and L where different CVP topologies (merged vs distorted vs distinct) are observed.