Numerical simulation of strongly swirling turbulent flows through an abrupt expansion

Joongcheol Paik, Fotis Sotiropoulos

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34 Scopus citations


Turbulent swirling flow through an abrupt axisymmetric expansion is investigated numerically using detached-eddy simulation at Reynolds numbers=3.0× 104 and 1.0 × 105. The effects of swirl intensity on the coherent dynamics of the flow are systematically studied by carrying out numerical simulations over a range of swirl numbers from 0.17 to 1.23. Comparison of the computed solutions with the experimental measurements of Dellenback et al. (1988) shows that the numerical simulations resolve both the axial and swirl mean velocity and turbulence intensity profiles with very good accuracy. Our simulations show that, along with moderate mesh refinement, critical prerequisite for accurate predictions of the flow downstream of the expansion is the specification of inlet conditions at a plane sufficiently far upstream of the expansion in order to avoid the spurious suppression of the low-frequency, large-scale precessing of the vortex core. Coherent structure visualizations with the q-criterion, friction lines and Lagrangian particle tracking are used to elucidate the rich dynamics of the flow as a function of the swirl number with emphasis on the onset of the spiral vortex breakdown, the onset and extent of the on-axis recirculation region and the large-scale instabilities along the shear layers and the pipe wall.

Original languageEnglish (US)
Pages (from-to)390-400
Number of pages11
JournalInternational Journal of Heat and Fluid Flow
Issue number3
StatePublished - Jun 2010


  • Hybrid URANS/LES
  • Swirling flow
  • Turbulence
  • Vortex breakdown


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