Further characterization of large-scale coherent structure signatures in a turbulent-plane mixing layer

In order to complement a previous collaborative testing of eddy structure identification methods in free turbulent shear flows, a study about the influence of the transverse location of these large-scale vortical structures on their signatures for the same referenced data base is carried out. Using vorticity-based conditional sampling, events that are located on the same transverse locations are selected and averaged. Results show that a coherent structure has its proper identity contained in its core and keeps it whatever its trajectory. In this way, only its signature in comparison with the surrounding environment changes. The comparison with vorticity-based conditional sampling without this transverse selection brings to the fore a bias on the signature of coherent structures. This result throws back into question previous conclusions about the morphology of structures and related energy transfer scenarios. (Author)