Revealing the details of vortex core precession in cyclones by means of large-eddy simulation

Lakhbir Singh Brar*, J. J. Derksen

*Corresponding author for this work

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

We investigate the three-dimensional, time-dependent behaviour of coherent flow structures inside two cyclone separator geometries, a Stairmand cyclone and a swirl tube, operating in the turbulent regime. For this, large-eddy simulations (LES) with a standard Smagorinsky subgrid-scale model are carried out on the single-phase flow employing a nonorthogonal curvilinear hexahedral mesh. Reynolds numbers (Re) are in the range 9.104 to 4.105. The simulations successfully capture the quasi-periodic precessing vortex core (PVC) phenomenon. The spectra derived from the temporal signals of different flow variables viz. static pressure, tangential velocity, axial velocity and radial velocity in the Stairmand cyclone exhibit two distinct frequencies at all Re, whereas the spectra for the swirl tube show a single peak. These spectra strongly resemble those reported in the experimental literature. The periodicity pertaining to the inner vortex about its rotational axis is also analysed. Next, the effect of Re on the two distinct spectral peaks have been evaluated for the Stairmand cyclone. Lastly, we present the effect of Re on mean and fluctuating fields and their variations along the geometrical axis of the cyclone.
Original languageEnglish
Pages (from-to)339-352
Number of pages14
JournalChemical Engineering Research & Design
Volume159
Early online date16 May 2020
DOIs
Publication statusE-pub ahead of print - 16 May 2020

Keywords

  • Cyclone separators
  • Large eddy simulation (LES)
  • Precessing vortex core (PVC)
  • Pressure fluctuations
  • Velocity fluctuations

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