Active control of a circular cylinder flow at transitional reynolds numbers

A. Naim, D. Greenblatt, A. Seifert, I. Wygnanski

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

Active and passive control of flow around a circular cylinder, at transitional Reynolds numbers was investigated experimentally by measuring cylinder surface pressures and wake velocity profiles. Two- and three-dimensional passive boundary layer tripping was considered and periodic active control using piezo-fluidic actuators was introduced from a two-dimensional slot that was nearly tangential to the cylinder surface. The slot location was varied circumferentially by rotating the cylinder and this facilitated either upstream- or downstream-directed actuation using sinusoidal or modulated wave-forms. Separation was controlled by two distinct methods, namely: by forcing laminar-turbulent transition when applied at relatively small angles (30-60°) from the forward stagnation point; and by directly forcing the separated shear-layer at larger angles. In the latter case, actuation produced the largest load changes when it was introduced at approximately 90° from the forward stagnation point. When the forcing frequency was close to the natural vortex-shedding frequency, the two frequencies "locked-in" creating clear and persistent structures. These were examined and categorized. The "lock-in" effect lowered the base pressure and increased the form-drag whereas delaying separation from the cylinder did the opposite.

Original languageEnglish (US)
Pages (from-to)383-407
Number of pages25
JournalFlow, Turbulence and Combustion
Volume78
Issue number3-4
DOIs
StatePublished - Jun 1 2007
Externally publishedYes

Keywords

  • Boundary layer
  • Cylinder
  • Flow control
  • Separation
  • Shedding
  • Transition

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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