Cavitation induced flow instabilities are of interest in numerous applications. Experimental and numerical investigations of this phenomenon are taking place at several institutions around the world. Although there is qualitative agreement among the numerous recent papers on the subject, there is a lack of agreement with regard to important details, such as the spectral content of unsteady lift oscillations. This paper summarizes observations of a cavitating NACA0015 foil in three different tunnels that revealed remarkably different cavity shedding appearances and behaviors. Some of the differences were attributed to system instabilities. However, in addition to a different cavitation behavior attributed to system instabilities, it was found that differences in gas content could significantly alter the lift spectrum of a cavitating foil. For a certain range of the composite parameter $σ∕2α$ near 4, the dominant frequency appears to double when the gas content is reduced by a half. It is also argued that surface effects can have a significant influence on fully wetted time during cavity shedding. Normally, surface effects are assumed to play an important role in the initial inception of a fully wetted hydrofoil with gas content being the primary factor governing developed cavitation behavior. However, the repetitive nature of the process implies that each shedding cycle is an individual inception process. Hence, the unexpected role of surface effects in partially cavitating hydrofoils. The conclusions reached have important ramifications concerning numerical code verification that is a topic of major concern.

1.
Kjeldsen
,
M.
,
Arndt
,
R. E. A.
, and
Effertz
,
M.
, 2000, “
Spectral Characteristics of Sheet∕Cloud Cavitation
,”
ASME J. Fluids Eng.
0098-2202,
122
, pp.
481
487
.
2.
Reisman
,
G. E.
,
Wang
,
Y.-C.
, and
Brennen
,
C. E.
, 1997, “
Observation of Shockwaves in Cloud Cavitation
,”
J. Fluid Mech.
0022-1120,
355
, pp.
255
283
.
3.
Arndt
,
R. E. A.
,
Song
,
C. S. S.
,
Kjeldsen
,
M.
,
He
,
J.
, and
Keller
,
A.
, 2001, “
Instability of Partial Cavitation: A Numerical∕Experimental Approach
,”
Proceedings of the Twenty-Third Symposium on Naval Hydrodynamics
,
Val de Reul, France
, Office of Naval Research, Naval Studies Board, National Research Council, National Academies Press.
4.
Pham
,
T. M.
,
Larrarte
,
F.
,
Fruman
, and
D. H.
, 1999, “
Investigation of Unsteady Sheet Cavitation and Cloud Cavitation Mechanisms
,”
ASME J. Fluids Eng.
0098-2202,
121
, pp.
289
296
.
5.
Kawanami
,
Y.
,
Kato
,
H.
,
Yamaguchi
,
H.
,
Tagaya
,
Y.
, and
Tanimura
,
M.
, 1996, “
Mechanism and Control of Cloud Cavitation
,”
Proceedings ASME Symposium on Cavitation and Gas-Liquid Flows in Fluid Machinery and Devices
, Paper No. FED-236,
29
336
.
6.
Arndt
,
R. E. A.
,
Ellis
,
C. R.
, and
Paul
,
S.
, 1995, “
Preliminary Investigation of the Use of Air Injection to Mitigate Cavitation Erosion
,”
ASME J. Fluids Eng.
0098-2202,
117
, pp.
498
504
.
7.
Amromin
,
E.
,
Arndt
,
R. E. A.
,
Kopriva
,
J.
, and
Wosnik
,
M.
, 2006, “
Hydrofoil Drag Reduction by Partial Cavitation
,”
ASME J. Fluids Eng.
0098-2202,
128
(
5
), pp.
931
936
.
8.
Kopriva
,
J.
,
Arndt
,
R. E. A.
,
Wosnik
,
M.
, and
Amromin
,
E.
, 2005, “
Comparison of Hydrofoil Drag Reduction by Natural and Ventilated Partial Cavitation
,”
Proceedings of 2005 ASME Fluids Engineering Division Summer Meeting and Exhibition
,
Houston, TX
, Jun. 19-23, FEDSM2005-77131.
9.
Watanabe
,
S.
,
Tsujimoto
,
Y.
, and
Furukawa
,
A.
, 2001, “
Theoretical Analysis of Transitional and Partial Cavity Instabilities
,”
ASME J. Fluids Eng.
0098-2202,
123
, pp.
692
697
.
10.
Callenaere
,
M.
,
Franc
,
J. P.
,
Michel
,
J. M.
, and
Riondet
,
M.
, 2001, “
The Cavitation Instability Induced by the Development of a Re-Entrant Jet
,”
J. Fluid Mech.
0022-1120,
444
, pp.
223
256
.
11.
Franc
,
J. P.
, 2003, “
Partial Cavity Instabilites and Re-Entrant Jet
,”
Proceedings of the Fourth International Symposium on Cavitation
,
Pasedena, CA
.
12.
Sato
,
K.
,
,
M.
,
Monden
,
S.
, and
Tsujimoto
,
Y.
, 1999, “
Observations of Oscillating cavitation on a Flat Plate Hydrofoil
,”
JSME Int. J., Ser. B
1340-8054,
65
(
639
), pp.
3659
3667
.
13.
Arndt
,
R. E. A.
, and
Keller
,
A. P.
, 2003, “
A Case Study of International Cooperation: 30 Years of Collaboration in Cavitation Research
,”
Proceedings of Fourth ASME̱JSME Joint Fluids Engineering Conference
,
Honolulu, HI
, Jul. 6–10, Keynote Paper.
14.
Sakoda
,
M.
,
Yakushiji
,
R.
,
Maeda
,
M.
, and
Yamaguchi
,
H.
, 2001, “
Mechanism of Cloud Cavitation Generation on a 2-D Hydrofoil
,”
Proceedings of the Fourth International Symposium on Cavitation
,
.
15.
Kawakami
,
D. T.
,
Qin
,
Q.
, and
Arndt
,
R. E. A.
, 2003, “
Can Water Quality affect the Lift Dynamics of Cavitating Hydrofoils?
,”
Proceedings of the Fifth International Symposium on Cavitation
,
Osaka, Japan
.
16.
Arndt
,
R. E. A.
,
Paul
,
S.
, and
Ellis
,
C. R.
, 1997, “
Application of Piezoelectric Film in Cavitation Research
,”
J. Hydraul. Eng.
0733-9429,
123
(
6
),
539
548
.
17.
Fujii
,
A.
,
Kawakami
,
D. T.
,
Tsujimoto
,
Y.
, and
Arndt
,
R. E. A.
, 2007, “
Effect of Hydrofoil Shape on Cavity Oscillation
,”
ASME J. Fluids Eng.
0098-2202,
129
(
6
), pp.
669
674
.
18.
Guennoun
,
F.
,
Farhat
,
M.
,
,
Y.
, and
Avellan
,
F.
, 2003, “
Experimental Investigation of a Particular Traveling Bubble Cavitation
,”
Proceedings of the Fifth International Symposium on Cavitation
,
Osaka, Japan
.