Scale-free topology of vortical networks in a turbulent thermoacoustic system

We use complex network analysis to investigate the vortical interactions in a bluffbody stabilized combustion system containing a turbulent lean premixed swirling flame. Using time-resolved vorticity measurements, we construct time-varying weighted spatial networks whose node strength distribution is derived from the Biot-Savart law. We find widespread evidence of scale-free topology in the vortical networks, with the most coherent flow structures acting as the primary network hubs. Crucially, we find that even after the onset of thermoacoustic instability, the scale-free topology can persist continuously in time, contrary to some suggestions from the literature. This discovery could have important implications for the design of flow controllers that rely on destroying the primary hubs of vortical networks.