A model of flapping motion in a plane jet

Oliver V. Atassi*, Richard M. Lueptow

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Flow visualization near the exit of a plane jet shows a small-amplitude disturbance whose wavelength is large relative to the jet shear layer thickness. Further downstream, in the transition region, concentrated regions of vorticity are observed which drive the flapping motion of the jet. These observations motivate an inviscid, two-dimensional model for the transitional region of the jet. Linear stability analysis of a piecewise-uniform shear layer model indicates that small-amplitude, long wavelength disturbances are unstable. Long wave theory shows that regions of high circulation convect downstream faster than regions of low circulation resulting in nonlinear steepening and that the rate of the steepening is directly proportional to the strength of the local shear. The long wave theory also shows that finite-amplitude sinuous disturbances at the jet centerline will grow linearly as they convect downstream. The results predict the steepening and growth of the jet centerline observed in the flow visualization.

Original languageEnglish (US)
Pages (from-to)171-183
Number of pages13
JournalEuropean Journal of Mechanics, B/Fluids
Issue number2
StatePublished - Mar 2002


  • Long wave theory
  • Plane jet
  • Stability

ASJC Scopus subject areas

  • Mathematical Physics
  • General Physics and Astronomy


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