Experimental study on the flow interaction of two parallel rectangular jets through exits with sudden contraction

The flow characteristics of two parallel jets ejecting from the nozzles with sudden contraction exits were studied using particle imaging velocimetry (PIV) technique. The measured mean velocity components, velocity vector contours, turbulence characteristics and Reynolds shear stresses showed that the flow fields adjacent to the exits are significantly different from those of the dual flows ejecting from the nozzles with constant cross section area. The sudden contraction at the exits strongly promotes the merging of the two parallel jets and enhances the turbulence intensity in the merging region. The location of the combined point locates much closer to the exits when the contraction ratio in area varies from 1 to 1.5 and thereafter changes slowly when the contraction ratio further increases. The measured results also showed that the parallel jets ejecting from the nozzles with sudden contraction exits creates much stronger turbulence in the inner and outer shear layers of the two parallel jets than the jets ejecting from the nozzles with constant cross-section area.