Vortex Breakdown: A Two-Stage Transition
Abstract
It is demonstrated that a large-scale isentropic transition between conjugate swirling flow states can occur with no change in the flow force and that both flow states are supercritical. It is argued that such a transition represents the first stage of vortex breakdown in a tube, the second stage being a non-isentropic transition in the nature of a hydraulic jump to the downstream subcritical state. The intermediate (supercritical) state consists of a zone of stagnant fluid surrounded by a region of potential flow. These two zones are separated by a layer of rotational fluid originating in the upstream vortex core. An outline is given of the analysis for an upstream flow modelled as a Rankine vortex. It is found that for any ratio of core-to-tube radii, breakdown (i.e. the first transition) occurs for a unique value of the swirl number Gamma/ pi r sub c U. In the limiting case of an infitesimally small core, the value is square root of 2, compared with the critical value 2.405. It is argued that this limit cannot represent free breakdown, which in consequence must have a different character from the tube-flow breakdown generally observed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1983
- Accession Number
- ADP002263
Entities
People
- J. J. Keller
- M. P. Escudier