Array measurements of the surface pressure beneath a forced axi-symmetric separation bubble

Array measurements of the surface pressure beneath a forced axi-symmetric separation bubble An array of microphones is used to study the space–time characteristics of the wall-pressure field beneath a forced separation bubble downstream of an axi-symmetric backward-facing step. To excite the flow, an externally driven Helmholtz resonator is employed. A unique aspect of the present study is the utilization of an amplitude-modulated forcing scheme in order to avoid contamination of the measured hydrodynamic pressure fluctuations by acoustic radiation from the forcing device. The results lead to the hypothesis that the optimal forcing frequency is achieved when the forced disturbance originates near the center of the unforced separation bubble in the limit of very low levels of forcing. Moreover, a frequency–wavenumber spectrum analysis highlights the possibility for achieving separation control while minimizing potential acoustic radiation due to coupling between the forced disturbance and resonant modes of the underlying surface. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Array measurements of the surface pressure beneath a forced axi-symmetric separation bubble

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Publisher
Springer-Verlag
Copyright
Copyright © 2008 by Springer-Verlag
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-008-0560-y
Publisher site
See Article on Publisher Site

Abstract

An array of microphones is used to study the space–time characteristics of the wall-pressure field beneath a forced separation bubble downstream of an axi-symmetric backward-facing step. To excite the flow, an externally driven Helmholtz resonator is employed. A unique aspect of the present study is the utilization of an amplitude-modulated forcing scheme in order to avoid contamination of the measured hydrodynamic pressure fluctuations by acoustic radiation from the forcing device. The results lead to the hypothesis that the optimal forcing frequency is achieved when the forced disturbance originates near the center of the unforced separation bubble in the limit of very low levels of forcing. Moreover, a frequency–wavenumber spectrum analysis highlights the possibility for achieving separation control while minimizing potential acoustic radiation due to coupling between the forced disturbance and resonant modes of the underlying surface.

Journal

Experiments in FluidsSpringer Journals

Published: Sep 16, 2008

References

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