Coherent structures and mixing enhancement in a confined impinging-jet mixer

This study attempted to apply improved delayed detached-eddy simulation (IDDES) method to the pre-diction of the turbulent mixing in a confined impinging-jet mixer (a simplified model of a side-dump combustor). It was found that the time-averaged velocity and second-order statistics were in good agree-ment with available experimental data, demonstrating the reliability of IDDES for the numerical study of impinging jets. We visualized all discovered coherent structures and revealed the existence of two arrays of quasi-two-dimensional spanwise vortices in the jet shear layers and the continuous rolling-up of large-scale counter-rotating spanwise vortices in the downstream region with the aid of conditional sampling method. We provided insights on the generation and evolution mechanisms of both discovered and newly-discovered coherent structures. Furthermore, the effects of coherent structures on phase -averaged turbulence statistics were evaluated. The improvements of mixing efficiency associated with coherent structures were elaborated through the phase-averaging analysis on heat flux components.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

This study applied the improved delayed detached-eddy simulation (IDDES) method to predict turbulent mixing in a confined impinging-jet mixer. The results showed good agreement with experimental data and provided insights on the coherent structures and their effects on turbulence statistics and mixing efficiency.