Effects of periodic excitation on turbulent flow separation from a flap

B. Nishri, I. Wygnanski

Research output: Contribution to journalArticlepeer-review

164 Scopus citations


The effects of periodic perturbations on delaying separation or promoting reattachment of initially separated flow were experimentally investigated. The leading parameters affecting the flow are the flap deflection, the input momentum, and its reduced frequency. The sensitivity of the flow to the imposed oscillations depends on its initial state, and this leads to hysteresis with respect to changes in any of the aforementioned parameters. For example, the most effective frequency required to attach the flow to the surface is much lower than the one required to prevent its separation. The amplitude needed to force reattachment may be an order of magnitude larger than the amplitude required to prevent separation at a given inclination of the flap. Nevertheless, periodic forcing is much more effective than steady blowing for boundary-layer control.

Original languageEnglish (US)
Pages (from-to)547-556
Number of pages10
JournalAIAA journal
Issue number4
StatePublished - Apr 1998

ASJC Scopus subject areas

  • Aerospace Engineering


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