Experiments in Fluids

, Volume 40, Issue 2, pp 267–276

Coherent structures in unsteady swirling jet flow

  • C. E. Cala
  • E. C. Fernandes
  • M. V. Heitor
  • S. I. Shtork
Research Article

DOI: 10.1007/s00348-005-0066-9

Cite this article as:
Cala, C.E., Fernandes, E.C., Heitor, M.V. et al. Exp Fluids (2006) 40: 267. doi:10.1007/s00348-005-0066-9

Abstract

An LDA technique and phase-averaging analysis were used to study unsteady precessing flow in a model vortex burner. Detailed measurements were made for Re=15,000 and S=1.01. On the basis of the analysis of phase-averaged data and vortex detection by the λ2-technique of Joeng and Hussain (1995), three precessing spiral vortex structures were identified: primary vortex (PV), inner secondary vortex (ISV), and outer secondary vortex (OSV). The PV is the primary and most powerful structure as it includes primary vorticity generated by the swirler; the ISV and OSV are considered here as secondary vortical structures. The jet breakdown zone is the conjunction of a pair of co-rotating co-winding spiral vortices, PV and ISV. The interesting new feature described is that the secondary vortices form a three-dimensional vortex dipole with a helical geometry. The effect of coupling of secondary vortices was suggested as a mechanism of enhanced stability reflected in their increased axial extent.

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • C. E. Cala
    • 1
  • E. C. Fernandes
    • 1
  • M. V. Heitor
    • 1
  • S. I. Shtork
    • 1
    • 2
  1. 1.Laboratory of Thermofluids, Combustion and Energy Systems, Center for Innovation, Technology and Policy Research IN+, Department of Mechanical EngineeringInstituto Superior TécnicoLisbonPortugal
  2. 2.Institute of Thermophysics SB RASNovosibirskRussia