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Reversal in Spreading of a Tabbed Circular Jet Under Controlled ExcitationDetailed flow field measurements have been carried out for a turbulent circular jet perturbed by tabs and artificial excitation. Two "delta tabs" were placed at the nozzle exit at diametrically opposite locations. The excitation condition involved subharmonic resonance that manifested in a periodic vortex pairing in the near flow field. While the excitation and the tabs independently increased jet spreading, a combination of the two diminished the effect. The jet spreading was most pronounced with the tabs but was reduced when excitation was applied to the tabbed jet. The tabs generated streamwise vortex pairs that caused a lateral spreading of the jet in a direction perpendicular to the plane containing the tabs. The excitation, on the other band, organized the azimuthal vorticity into coherent ring structures whose evolution and pairing also increased entrainment by the jet. In the tabbed case, the excitation produced coherent azimuthal structures that were distorted and asymmetric in shape. The self-induction of these structures produced an effect that opposed the tendency for the lateral spreading of the streamwise vortex pairs. The passage of the distorted vortices, and their pairing, also had a cancellation effect on the time-averaged streamwise vorticity field. These led to the reduction in jet spreading.
Document ID
19990027602
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Zaman, K. B. M. Q.
(NASA Lewis Research Center Cleveland, OH United States)
Raman, G.
(NYMA, Inc. Brook Park, OH United States)
Date Acquired
August 19, 2013
Publication Date
December 1, 1997
Publication Information
Publication: Physics of Fluids
Volume: 9
Issue: 12
Subject Category
Fluid Mechanics And Heat Transfer
Distribution Limits
Public
Copyright
Other

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