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Department of Mechanical, Aerospace and Manufacturing Engineering
Polytechnic University
Brooklyn, New York, 11201, USA
Abstract-
Supersonic vortex breakdown, when sufficiently strong
streamwise vortices encounter otherwise planar, normal and oblique shock
fronts as well as solid surfaces placed in their passages, will be
discussed. The dramatic destruction of a streamwise vortex during
supersonic vortical interactions reveals a vortex breakdown similar in
many ways to the well-documented incompressible vortex bursting. The
main features of supersonic vortex breakdown include formation of a
spherically blunt-nosed conical shock, and a vortex core, which upon
crossing the apex of the conical shock expands into a subsonic turbulent
conical region. A notable characteristic of the supersonic vortex
breakdown is the formation of an entropy-shear layer separating an inner
subsonic zone containing the burst structure from the surrounding
supersonic flow. Numerical, experimental, and analytical studies of
shock wave/vortex interactions are discussed and results from wind
tunnel studies involving head-on collision of supersonic vortices with
solid surfaces are presented.
The head-on 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 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 flowfields generated in the current study exhibit many characteristics of the unsteady vortex distortion patterns previously observed during normal shock wave/vortex interactions.
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