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Lookup NU author(s): Dr Jonathan McDonough, Professor Anh Phan, Professor Adam Harvey
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).
© 2019 Elsevier B.V. When a liquid is oscillated in a tube containing a helical coil, there are two key flow phenomena: vortex-shedding and “swirl”. Together, they cause plug flow to be achievable over a wide range of conditions in this design. When an additional small cylindrical rod is placed in the centre of the helical coil, a new dual vortex regime is realised. This new flow regime was studied via CFD and PIV. It was demonstrated that a significant swirling velocity was generated by the helical coils, inducing an outward centrifugal force and inward pressure gradient, creating an instability resulting in the formation of a pair of counter-rotating vortices. The oscillatory amplitudes and frequencies necessary for the formation of these dual vortices at this scale (5 mm diameter) were centre-to-peak amplitude of 2–4 mm and frequency ≥ 3 Hz. The vortex pairs were also visualised in 3D, and exhibited a double-helix shape. Additionally, the transition of this flow to a more turbulent-like state was investigated. It was found to occur in the range Reo = 600–630. Through analysis of the swirl and radial numbers, it is clear that swirling dominates the flow structures at amplitudes of xo ≥ 4 mm.
Author(s): McDonough JR, Ahmed SMR, Phan AN, Harvey AP
Publication type: Article
Publication status: Published
Journal: Chemical Engineering and Processing - Process Intensification
Year: 2019
Volume: 143
Print publication date: 01/09/2019
Online publication date: 06/07/2019
Acceptance date: 01/07/2019
Date deposited: 11/09/2019
ISSN (print): 0255-2701
ISSN (electronic): 1873-3204
Publisher: Elsevier BV
URL: https://doi.org/10.1016/j.cep.2019.107588
DOI: 10.1016/j.cep.2019.107588
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