Double helix vortex breakdown in a turbulent swirling annular jet flow

M. Vanierschot, M. Percin, and B. W. van Oudheusden
Phys. Rev. Fluids 3, 034703 – Published 28 March 2018

Abstract

In this paper, we report on the structure and dynamics of double helix vortex breakdown in a turbulent annular swirling jet. Double helix breakdown has been reported previously for the laminar flow regime, but this structure has rarely been observed in turbulent flow. The flow field is investigated experimentally by means of time-resolved tomographic particle image velocimetry. Notwithstanding the axisymmetric nature of the time-averaged flow, analysis of the instantaneous three-dimensional (3D) vortical structures shows the existence of a vortex core along the central axis which breaks up into a double helix downstream. The winding sense of this double helix is opposite to the swirl direction (m=2) and it is wrapped around a central vortex breakdown bubble. This structure is quite different from double helix breakdown found in laminar flows where the helix is formed in the wake of the bubble and not upstream. The double helix precesses around the central axis of the jet with a precessing frequency corresponding to a Strouhal number of 0.27.

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  • Received 27 May 2017

DOI:https://doi.org/10.1103/PhysRevFluids.3.034703

©2018 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

M. Vanierschot*

  • Mechanical Engineering Technology Cluster TC, University of Leuven, Campus Group T Leuven, A. Vesaliusstraat 13, B-3000 Leuven, Belgium

M. Percin

  • Department of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft, The Netherlands and Department of Aerospace Engineering, Middle East Technical University, Ankara, Turkey

B. W. van Oudheusden

  • Department of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft, The Netherlands

  • *maarten.vanierschot@kuleuven.be

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Vol. 3, Iss. 3 — March 2018

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