Abstract
Based on a double triggering criterion, the axisymmetric and azimuthal structures within the initial region of an unexcited coaxial jet of mean velocity ratio of 0.3 (inner to outer) were recovered. Outer vortices, two trains of inner vortices and their amalgamation are found in the outer and inner mixing regions. Bifurcation of the amalgamated inner vortices occurs within the first two diameters of the jet and is responsible for the occurrence of the azimuthal structures in the inner jet region further downstream. Co-dominance of the symmetrical and azimuthal structures having different convection velocities is observed in the fully merged zone. Spatial separation between vortical structures and their relative vorticities are important parameters in affecting their convection velocities, growth and decay.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Au H; Ko NWM (1987) Coaxial jets of different mean velocity ratios, Part 2. J Sound Vib 116: 427–443
Batchelor GK (1967) An introduction to fluid dynamics. London: Cambridge University Press
Brunn HH (1971) Interpretation of a hot wire signal using a universal calibration law. J Phys E: Sci Instrum 4: 225–231
Champagne FH; Wygnanski IJ (1971) An experimental investigation of coaxial jet. Int J Heat Mass Trans 14: 1445–1461
Dahm WJA; Frieler CE; Tryggvason G (1992) Vortex structure and dynamics in the near field of a coaxial jet. J Fluid Mech 241: 371–402
Fuchs HV; Mercker E; Michel U (1979) Large-scale coherent structures in the wake of axisymmetric bodies. J Fluid Mech 93: 185–207
Hussain AKMF (1986) Coherent structures and turbulence. J Fluid Mech 173: 303–356
Hussain AKMF; Zaman KBMQ (1980) Vortex pairing in a circular jet under controlled excitation. Part 2. Coherent structure dynamics. J Fluid Mech 101: 493–544
Ko NWM; Au H (1985) Coaxial jets of different mean velocity ratios. J Sound Vib 100: 203–219
Ko NWM; Chan WT (1979) The inner region of annular jet. J Fluid Mech 93: 549–584
Ko NWM; Davies POAL (1971) The near field within the potential core of subsonic cold jets. J Fluid Mech 50: 49–78
Lamb H (1932) Hydrodynamics. New York: Dover
Milne-Thomson LM (1983) Theoretical hydrodynamics. New York: Maxmillan
Petersen RA (1978) Influence of wave dispersion on vortex pairing in a jet. J Fluid Mech 89: 469–495
Perry AE; Lim TT (1978) Coherent structures in coflowing jets and wakes. J Fluid Mech 88: 451–463
Ribeiro MM; Whitelaw JH (1980) Coaxial jets with and without swirl. J Fluid Mech 96: 769–795
Tang SK (1992) The aeroacoustics of free shear layers and vortex interactions. PhD Thesis. The University of Hong Kong, Hong Kong
Tang SK; Ko NWM (1992) Vortex interaction in unexcited coaxial jet of mean velocity ratio of 0.3. Proc. 5th Asian Cong. Fluid Mech Taejon, 583–586
Williams TJ; Ali MRMH; Anderson JS (1969) Noise and flow characteristics of coaxial jets. J Mech Eng Sci 11: 133–142
Yamada H; Matsui T (1979) Mutual slip-through of a pair of vortex rings. Phys Fluids 22: 1245–1249
Zaman KBMQ; Hussain AKMF (1984) Natural large-scale structures in the axisymmetric mixing layer. J Fluid Mech 138: 325–351
Author information
Authors and Affiliations
Additional information
The work was partly supported by a donation from Dr. Haking Wong and by a grant from the Hong Kong Research Grants Council.
Rights and permissions
About this article
Cite this article
Tang, S.K., Ko, N.W.M. Coherent structure interactions in an unexcited coaxial jet. Experiments in Fluids 17, 147–157 (1994). https://doi.org/10.1007/BF00190911
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00190911