Attenuation of cavity internal pressure oscillations by shear layer forcing with pulsed micro-jets

Experimental results concerning the pressure oscillations induced by a grazing flow over a deep cavity like a Helmholtz resonator are presented. The study deals with the forcing of the neck shear layer instability in an opened-loop control scheme by means of pulsed micro-jets. The effects of the fre...

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Bibliographic Details
Published in:European journal of mechanics, B, Fluids B, Fluids, 2006-11, Vol.25 (6), p.939-947
Main Authors: Hémon, P., Wojciechowski, J.
Format: Article
Language:English
Subjects:
Acoustics
Aeroacoustics
Aeroacoustics and atmospheric sound
Aeroacoustics, atmospheric sound
Cavity
Control
Engineering Sciences
Exact sciences and technology
Fluid mechanics
Fluids mechanics
Fundamental areas of phenomenology (including applications)
Mechanics
Physics
Shear layer
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Summary:Experimental results concerning the pressure oscillations induced by a grazing flow over a deep cavity like a Helmholtz resonator are presented. The study deals with the forcing of the neck shear layer instability in an opened-loop control scheme by means of pulsed micro-jets. The effects of the frequency and amplitude are investigated. It is found that efficient attenuation of the pressure oscillations can be reached when the forcing frequency is larger than the cavity resonance frequency. Then the shear layer is locked with the forcing and resonance with the cavity is lost, inducing a significant decrease of the acoustic pressure level in the cavity. Effects of the jet amplitude are weak, a very small amplitude being capable of forcing the shear layer. By contrast, when the forcing frequency is lower than the cavity resonance frequency (the forcing wave length is greater than twice the neck length) the forcing is ineffective.
ISSN:0997-7546
1873-7390
DOI:10.1016/j.euromechflu.2006.03.001