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Journal of Mechanical Science and Technology

, Volume 20, Issue 11, pp 1993–2001 | Cite as

Active control of flow noise sources in turbulent boundary layer on a flat-plate using piezoelectric bimorph film

  • Woo-Seog Song
  • Seungbae Lee
  • Dong-Shin Shin
  • Yang Na
Article

Abstract

The piezoelectric bimorph film, which, as an actuator, can generate more effective displacement than the usual PVDF film, is used to control the turbulent boundary-layer flow. The change of wall pressures inside the turbulent boundary layer is observed by using the multi-channel microphone array flush-mounted on the surface when actuation at the non-dimensional frequency f b + =0.008 and 0.028 is applied to the turbulent boundary layer. The wall pressure characteristics by the actuation to produce local displacement are more dominantly influenced by the size of the actuator module than the actuation frequency. The movement of large-scale turbulent structures to the upper layer is found to be the main mechanism of the reduction in the wallpressure energy spectrum when the 700v/uτ-long bimorph film is periodically actuated at the non-dimensional frequency f b + =0.008 and 0.028. The biomorph actuator is triggered with the time delay for the active forcing at a single frequency when a 1/8″ pressuretype, pin-holed microphone sensor detects the large-amplitude pressure event by the turbulent spot. The wall-pressure energy in the late-transitional boundary layer is partially reduced near the convection wavenumber by the open-loop control based on the large amplitude event.

Key Words

Flow Control Piezoelectric Bimorph Wavenumber-Frequency Spectrum 

Nomenclature

Δx+

Normalized streamwise length (≡ uτΔx/v)

Δz+

Normalized spanwise length (≡ uτΔz/v)

fb+

Mean bursting frequency (≡ fv/u τ 2

U0

Flow velocity

Uc

Convective velocity

Uτ

Friction velocity

v

Viscosity

d+

Non-dimensional pin-hole diameter (≡ uτd/v)

Reθ

Reynolds number based on momentum thickness

kx

Streamwise wavenumber (rad/m)

τω

Mean wall shear-stress

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Copyright information

© The Korean Society of Mechanical Engineers (KSME) 2006

Authors and Affiliations

  • Woo-Seog Song
    • 1
  • Seungbae Lee
    • 1
  • Dong-Shin Shin
    • 2
  • Yang Na
    • 3
  1. 1.Department of Mechanical Engineering, College of EngineeringInha UniversityIncheonKorea
  2. 2.Department of Mechanical System Design Engineering, College of EngineeringHongik UniversitySeoulKorea
  3. 3.CAESIT, Department of Mechanical EngineeringKonkuk UniversitySeoulKorea

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