Active control of a circular cylinder flow at transitional reynolds numbers

A. Naim, D. Greenblatt, A. Seifert, Israel J Wygnanski

Research output: Contribution to journalArticle

34 Citations (Scopus)

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 2007
Externally publishedYes

Fingerprint

active control
circular cylinders
Circular cylinders
Reynolds number
stagnation point
Vortex shedding
Fluidics
actuation
slots
Drag
Boundary layers
Actuators
base pressure
vortex shedding
fluidics
shear layers
wakes
upstream
drag
boundary layers

Keywords

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

ASJC Scopus subject areas

  • Mechanics of Materials
  • Computational Mechanics
  • Physical and Theoretical Chemistry
  • Fluid Flow and Transfer Processes

Cite this

Active control of a circular cylinder flow at transitional reynolds numbers. / Naim, A.; Greenblatt, D.; Seifert, A.; Wygnanski, Israel J.

In: Flow, Turbulence and Combustion, Vol. 78, No. 3-4, 06.2007, p. 383-407.

Research output: Contribution to journalArticle

Naim, A. ; Greenblatt, D. ; Seifert, A. ; Wygnanski, Israel J. / Active control of a circular cylinder flow at transitional reynolds numbers. In: Flow, Turbulence and Combustion. 2007 ; Vol. 78, No. 3-4. pp. 383-407.
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