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Formation and evolution of vortex rings with weak to moderate swirl

Ortega Chavez, Rigoberto; Gan, Lian; Gaskell, Philip



The formation of swirling vortex rings and their early time evolution, resulting from the controlled discharge of an incompressible, Newtonian fluid into a stationary equivalent fluid bulk, is explored for weak to moderate swirl number S∈[0,1]. Two practically realisable inlet conditions are investigated with swirl simultaneously superposed onto a linear momentum discharge; the corresponding circulation based Reynolds number is 7500. The results obtained reveal that for S>1/2, the addition of swirl promotes the breakdown of the leading primary vortex ring structure, giving rise to the striking feature of significant negative azimuthal vorticity generation in the region surrounding the primary vortex ring core, whose strength scales with S2. Through a nonlinear interaction with the vortex breakdown, the radius of the primary toroidal vortex core is rapidly increased; consequently, the self-induced propagation velocity of the leading ring decreases with S and vortex stretching along the circular primary vortex core increases counteracting viscous diffusion effects. The latter governs the evolution of the peak vorticity intensity and the swirl velocity magnitude in the primary ring core, the circulation growth rate of the primary ring, as well as the vorticity intensity of the trailing jet and hence its stability. This combination of effects leads to an increased dimensionless kinetic energy for the primary ring with increasing S and results in an almost linearly decreasing circulation based formation number, F.


Ortega Chavez, R., Gan, L., & Gaskell, P. (2023). Formation and evolution of vortex rings with weak to moderate swirl. Journal of Fluid Mechanics, 967, Article A16

Journal Article Type Article
Acceptance Date Jun 5, 2023
Online Publication Date Jul 17, 2023
Publication Date Jul 25, 2023
Deposit Date Jun 6, 2023
Publicly Available Date Aug 18, 2023
Journal Journal of Fluid Mechanics
Print ISSN 0022-1120
Electronic ISSN 1469-7645
Publisher Cambridge University Press
Peer Reviewed Peer Reviewed
Volume 967
Article Number A16
Public URL
Publisher URL


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