At low flow Mach numbers, fluid-elastic lock-in may occur when a shear layer instability interacts with an adjoining or nearby structure and the resulting vibration of the structure reinforces the shear layer instability. Despite the significant amount of study of lock-in with acoustic resonators, fluid-elastic lock-in of a shear layer fluctuation over a cavity and a structural resonator is not well understood and has not been thoroughly studied. Design of an experimental system is described and preliminary diagnostics are addressed as a basis for a platform for developing a fundamental understanding of the feedback mechanism, analytical models for predicting and describing fluid-elastic lock-in conditions, and the roles of the fluid and structural dynamics in the process. Features of the system investigated here include design for characterization of modal excitation of a beam-like structure from the shear layer fluctuation, isolation of the predominant instability source to the shear layer fluctuation over the cavity, variation of the cavity size to identify critical parameters that govern fluid-elastic lock-in, and alteration of the inflow boundary layer momentum thickness. So far, lock-in between the cavity and the distributed elastic resonator has not been achieved. Further investigations to determine the role of the source and resonator attributes are underway.

1.
Davis
M. R
., “
Design of Flat Plate Leading Edges to Avoid Flow Separation
,”
AIAA Journal
(Technical Note), Vol.
18
, No.
1
,
1979
, pp.
598
600
.
2.
Dunham, W. H., “Flow-Induced Cavity Resonance in Viscous Compressible and Incompressible Fluids,” Report ARC-73, Fourth Symposium on Naval Hydrodynamics, Vol. 3, ONR 1962, 1057–1081.
3.
Harrington
M. C.
, and
Dunham
W. H.
, “
Studies of the Mechanism For Flow-Induced Cavity Resonances
,”
J. Acoustical Society of America
, Vol.
32
, July
1960
, p.
921
921
.
4.
Khalak
A.
and
Williamson
C. H. K.
, “
Motions, Forces, and Mode Transitions in Vortex-Induced Vibrations at Low Mass-Damping
,”
Journal of Fluids and Structures
, Vol.
13
,
1999
, pp.
813
851
.
5.
Knisely
C.
and
Rockwell
D.
, “
Self-Sustaining Low-Frequency Components in an Impinging Shear Layer
,”
Journal of Fluid Mechanics
, Vol.
116
,
1982
, pp.
157
186
.
6.
Lucas, M. J., Noreen, R. A., Sutherland, L. C., Cole, J. E., and Junger, M. C., Handbook of the Acoustic Characteristics of Turbomachinery Cavities. New York: ASME Press, 1997.
7.
Nelson
P. A.
,
Halliwell
N. A.
, and
Doak
P. E.
, “
Fluid Dynamics of a Flow Excited Resonance, Part I: Experiment
,”
Journal of Sound and Vibration
, Vol.
78
,
1981
, pp.
15
38
.
8.
Nelson
P. A.
,
Halliwell
N. A.
, and
Doak
P. E.
, “
Fluid Dynamics of a Flow Excited Resonance, Part II: Flow Acoustic Interaction
,”
Journal of Sound and Vibration
, Vol.
91
,
1983
, pp.
375
402
.
9.
Rockwell
D.
,
Lin
J.-C.
,
Oshkai
P.
,
Reiss
M.
and
Pollack
M.
, “
Shallow Cavity Flow Tone Experiments: Onset of Locked-On States
,”
Journal of Fluids and Structures
, Vol.
17
, No.
3
, March
2003
, pp.
381
414
.
10.
Rockwell
D.
and
Naudascher
E.
, “
Review - Self-Sustaining Oscillations of Flow past Cavities
,”
ASME Journal of Fluids Engineering
, Vol.
100
,
1978
, pp.
152
165
.
11.
Saelim, N., Self-Excited Oscillations of a Horizontal Cylinder Adjacent to a Free-Surface, MS Thesis, Lehigh University, 1999.
12.
Ziada
S.
and
Rockwell
D.
, “
Generation of Higher Harmonics in a Self-Oscillating Mixing Layer-Wedge System
,”
AIAA Journal
, Vol.
20
, No.
2
,
1982
, pp.
196
202
.
13.
Zoccola, P. J., Experimental Investigation of Flow Induced Cavity Resonance, Ph.D. Thesis, The Catholic University of America, 2000.
14.
Ziada
S.
,
Ng
H.
, and
Blake
C.
, “
Flow Excited Resonance of a Confined Shallow Cavity in Low Mach Number Flow and Its Control
,”
ASME, Applied Mechanics Division
, Vol.
263
, No.
2
,
2002
, pp.
889
898
.
This content is only available via PDF.
You do not currently have access to this content.