In this investigation, flow mixing between turbulent jets injecting to a channel containing a rod bundle and the channel flows is studied using Particle Image Velocimetry (PIV) and Matched Index of Refraction (MIR) techniques. A specific case of a single impinging jet with a Reynolds number of 13,400 is considered for this analysis. The time-averaged vorticity fields for three different planes within the measurement volume verify the presence of coherent structures within all three fields, specifically in areas close to the jet impingement area and in the shear layer of the jet within the impingement plane. The cumulative effect of the vorticity patterns observed within all measurement planes is believed to have a significant role in the enhancement of mixing within the test section.
To further analyze the behavior of the large-scale coherent structures observed in the time-averaged vorticity fields, Proper Orthogonal Decomposition (POD) technique was applied to the PIV velocity fields. The results confirm that the jet flow is the most energetic and the dominant feature of the flow field. Therefore, to further analyze the behavior of some of the relatively smaller-scale coherent structures which could play a significant role in the mixing process, a higher number of modes or a different approach needs to be considered.