Oscillations of flow past perforated and slotted plates: attenuation via a leading-edge ramp
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The present investigation aims to attenuate purely hydrodynamic, long-wavelength, self-excited oscillations of flow past a perforated or slotted plate by deflection of the inflow with a small ramp located at the leading-edge of the plate. Digital particle image velocimetry is complemented by unsteady pressure measurements to determine the underlying physics associated with attenuation of the oscillations. Irrespective of whether a perforated or slotted plate is employed, complete attenuation of the pressure fluctuations associated with the oscillation can be achieved for dimensionless deflection ratios of h/L ≥ 0.035, in which h is the height of the ramp and L is the effective plate length. The attenuation of the self-excited oscillation involves: a steady jet at the trailing-edge of the plate directed into the cavity; a lower magnitude upstream-oriented counterflow along the backside of the plate; and jet-like flows through the plate openings to satisfy the entrainment demands of the separating shear layer.
KeywordsParticle Image Velocimetry Shear Layer Perforated Plate Separate Shear Layer Plate Length
The authors gratefully acknowledge the financial support of the Office of Naval Research under Grant N00014-01 1-0606, monitored by Drs. Pat Purtell and Ron Joslin. Supplemental support, in the form of facilities and instrumentation, was from the Air Force of Scientific Research under Grant F49620-02-1-0061. The continuing advice of Dr. Ted Farabee of the Naval Surface Warfare Center, Carderock, is appreciated.
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