The head-one interaction of a supersonic streamwise vortex with
a circular cylinder
reveals a vortex breakdown similar in many ways to that of incompressible
vortex
breakdown. In particular, the dramatic flow reorganization observed during
the
interaction resembles the conical vortex breakdown reported by Sarpkaya
(1995) at
high Reynolds number. In the present study, vortex breakdown is brought
about when
moderate and strong streamwise vortices encounter the bow shock in front
of a circular
cylinder at Mach 2.49. The main features of the vortex/cylinder interaction
are the
formation of a blunt-nosed conical shock with apex far upstream of the
undisturbed
shock stand-off distance, and a vortex core which responds to passage through
the apex
of the conical shock by expanding into a turbulent conical flow structure.
The
geometry of the expanding vortex core as well as the location of the conical
shock apex
are seen to be strong functions of the incoming vortex strength and the
cylinder
diameter. A salient feature of the supersonic vortex breakdown is the formation
of an
entropy-shear layer, which separates an interior subsonic zone
containing the burst
vortex from the surrounding supersonic flow. In keeping with the well-established
characteristics of the low-speed vortex breakdown, a region of reversed
flow is
observed inside the turbulent subsonic zone. The steady vortex/cylinder
interaction
flow fields generated in the current study exhibit many characteristics
of the unsteady
vortex distortion patterns previously observed during normal shock wave/vortex
interactions. This similarity of the instantaneous flow structure indicates
that the
phenomenon previously called vortex distortion
by Kalkhoran et al. (1996) is a form of
supersonic vortex breakdown.
Experimental investigation of vortex breakdown in a coaxial swirling jet with a density difference