Print Email Facebook Twitter Double helix vortex breakdown in a turbulent swirling annular jet flow Title Double helix vortex breakdown in a turbulent swirling annular jet flow Author Vanierschot, M. (TU Delft Aerodynamics; Katholieke Universiteit Leuven) Perçin, M. (TU Delft Aerodynamics) van Oudheusden, B.W. (TU Delft Aerodynamics) Date 2018-03-01 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. To reference this document use: http://resolver.tudelft.nl/uuid:0021ceb8-f947-4bfb-bf54-282a4579eba4 DOI https://doi.org/10.1103/PhysRevFluids.3.034703 ISSN 2469-990X Source Physical Review Fluids, 3 (3) Bibliographical note B.W. van Oudheusden Part of collection Institutional Repository Document type journal article Rights © 2018 M. Vanierschot, M. Perçin, B.W. van Oudheusden Files PDF PhysRevFluids.3.034703.pdf 2.02 MB Close viewer /islandora/object/uuid:0021ceb8-f947-4bfb-bf54-282a4579eba4/datastream/OBJ/view