On the Influence of Array Size and Jet Spacing on Jet Interactions and Confluence in Round Jet Arrays

This work uses computational models to study the effects of confluence and jet-to-jet interactions for inline matrices of confluent round jets. In total, 12 different confluent jet arrangements, having various jet array sizes and dimensionless jet spacing, $S/d0$⁠, have been investigated. The array size varies from 6 × 6 to 10 × 10 jets, while $S/d0$ varies between $1.75≤S/d0≤4.0$⁠. The Reynolds number, based on the nozzle exit diameter, is between 2200 and 6600. The results show that both jet spacing and jet array size largely influence the jet-to-jet interactions and flow field development in confluent jet arrays. The jet interactions in the investigated setups result in regions of negative static pressure between jets, jet deformation, high spanwise velocity, and jet displacement. Generally, smaller jet spacing and larger array size result in stronger influence of jet interactions. After the jets have combined, the confluent jets form a zone with constant maximum streamwise velocity and decay of turbulence intensity, called a confluent core zone (CCZ). During the CCZ, the combined jet will have asymmetric spreading rates leading to axis-switching. The entrainment rate of the CCZ is constant, but the volumetric flow rate of the combined jet is substantially affected by the degree of entrainment before the jets have combined.