On the transition to 3D modes for channel flow past a square cylinder

S. Madhavan, Yarub Y. Al-Jahmany, P. D. Minev, K. Nandakumar*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

We consider the case of transient three-dimensional, incompressible and isothermal channel flow of a newtonian fluid past a symmetrically confined obstacle of square cross section at zero incidence. The blockage ratio (ratio of cylinder diameter to channel width) is fixed at 1/4. Results from both Laser Doppler (LDV) experiments and direct simulations upto Reynolds numbers (Re≤250) have been reported. Starting from the onset of instability (Recr≈58), close examination of the apparent region of influence that envelopes the cylinder reveals a clear vortex shedding signature which extends up to about three diameters upstream. While the fundamental vortex shedding frequency displays a fairly steady monotonic increase with Reynolds number, the Strouhal number (St) shows an inflexion point around Re≈115. No signs of hysteresis were detected around this region. Furthermore, incommensurate harmonics observed for Reynolds numbers in the range 127≤Re≤175 suggest a quasi-periodic transition to three-dimensionality. This is shown to be followed by an intermediate periodic window starting around Re≈180. Results from direct simulations performed using OpenFOAM (the Open Source CFD Toolbox) are used not only to enhance confidence in the accuracy of the reported LDV measurements, but also to help explain the observed phenomena through frequency power spectra and spanwise velocity correlations. Finally, it is concluded that only a parametric variation of transverse and spanwise blockage ratios can bring closure to the subject of bluff-body wake transitions.

Original languageEnglish
Pages (from-to)2122-2137
Number of pages16
JournalCanadian Journal of Chemical Engineering
Volume92
Issue number12
DOIs
StatePublished - 1 Dec 2014
Externally publishedYes

Keywords

  • LDV
  • Numerical simulation
  • OpenFOAM
  • Quasiperiodicity
  • Vortex shedding

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