Abstract: Proper orthogonal decomposition can be used to determine the dominant coherent structures present within a turbulent flow. In many flows, these structures are well represented by only a few high-energy modes. However, additional modes with clear spatial structure, but low-energy contribution can often be present in the proper orthogonal decomposition analysis, even for flows with a high degree of periodicity. One such mode has been observed in both free and impinging jets determined from particle image velocimetry. Both experimental and synthetic data are used to investigate the role of this particular mode, linking its existence to the unsteadiness of shear-layer large-scale coherent structures. Graphical abstract: [Figure not available: see fulltext.].
Bibliographical noteFunding Information:
This research was supported by an Australian Research Council Discovery Project (DP160102833). This research was undertaken with the assistance of resources provided at the NCI National Facility systems at the Australian National University through the National Computational Merit Allocation Scheme supported by the Australian Government. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.