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The formation and evolution of turbulent swirling vortex rings generated by axial swirlers

He, Chuangxin; Gan, Lian; Liu, Yingzheng

The formation and evolution of turbulent swirling vortex rings generated by axial swirlers Thumbnail


Chuangxin He

Yingzheng Liu


The present work investigates the formation process and early stage evolution of turbulent swirling vortex rings, by using planar Particle Image Velocimetry (PIV) and Large Eddy Simulation (LES). Vortex rings are produced in a piston-nozzle arrangement with swirl generated by 3D-printed axial swirlers in experiments. Idealised solid-body rotation is applied in LES to evaluate the effect of nozzle exit velocity profile in experiments. The Reynolds number (Re) based on the nozzle diameter D and the slug velocity U0 in the nozzle is 20,000. The swirl number S generated ranges from 0 (zero-swirl vortex ring) and 1.1, covering the two critical swirl numbers previously identified in a swirling jet. Both PIV and LES results show that the formation number F decreases linearly as S increases, with the maximum F ≈ 2.6 at S = 0 (produced by the swirler with straight vanes) and minimum F = 1.9 at S = 1.1. The corresponding maximum attainable circulation in the nozzle axis parallel plane also diminishes with increasing S. Evolution of compact rings produced by a stroke ratio L/D = 1.5 reveals that circulation decay rate is largely proportional to S. The trajectory of the vortex core in the axial direction, hence the ring axial propagation velocity, decreases as S, while that in the radial direction and the radial propagation velocity, increase with S. An empirical scaling function is proposed to scale these variables.


He, C., Gan, L., & Liu, Y. (2020). The formation and evolution of turbulent swirling vortex rings generated by axial swirlers. Flow, Turbulence and Combustion, 104(4), 795-816.

Journal Article Type Article
Acceptance Date Sep 13, 2019
Online Publication Date Nov 25, 2019
Publication Date Apr 30, 2020
Deposit Date Sep 17, 2019
Publicly Available Date Nov 27, 2019
Journal Flow, Turbulence and Combustion
Print ISSN 1386-6184
Electronic ISSN 1573-1987
Publisher Springer
Peer Reviewed Peer Reviewed
Volume 104
Issue 4
Pages 795-816


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Advance online version This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution,<br /> and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source,<br /> provide a link to the Creative Commons license, and indicate if changes were made.

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