Experimental observation of a swirling flow with a double precessing vortex

This paper describes a new phenomenon of generating a stable double precessing vortex in a highly swirling turbulent flow. It also identifies the range of flow conditions providing the clearest observation of this effect. It also identifies key features of the internal flow structure and the kinematic scheme of the double vortex precessional motion. The geometric parameters of the helical vortex are measured depending on the flow regime. The obtained results are important not only from a practical standpoint for the possibilities of controlling the flow structure in industrial apparatuses, but also from the standpoint of fundamental problems in vortex dynamics. Precession of a helical structure represents a canonical case of self-induced motion of a vortex filament with a helical axis of rotation.