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An experimental investigation of cloud cavitation about a sphere

Published online by Cambridge University Press:  21 May 2010

P. A. BRANDNER ,
G. J. WALKER ,
P. N. NIEKAMP  and
B. ANDERSON
P. A. BRANDNER*
Affiliation:
Australian Maritime College, University of Tasmania, Launceston, Tasmania 7248, Australia
G. J. WALKER
Affiliation:
School of Engineering, University of Tasmania, Hobart, Tasmania 7001, Australia
P. N. NIEKAMP
Affiliation:
Australian Maritime College, University of Tasmania, Launceston, Tasmania 7248, Australia
B. ANDERSON
Affiliation:
Maritime Platforms Division, Defence Science and Technology Organisation, Fishermans Bend, Victoria 3032, Australia
*
†Email address for correspondence: P.Brandner@amc.edu.au
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Abstract

Cloud cavitation occurrence about a sphere is investigated in a variable-pressure water tunnel using low- and high-speed photography. The model sphere, 0.15 m in diameter, was sting-mounted within a 0.6 m square test section and tested at a constant Reynolds number of 1.5 × 106 with cavitation numbers varying between 0.36 and 1.0. High-speed photographic recordings were made at 6 kHz for several cavitation numbers providing insight into cavity shedding and nucleation physics. Shedding phenomena and frequency content were investigated by means of pixel intensity time series data using wavelet analysis. Instantaneous cavity leading edge location was investigated using image processing and edge detection.

The boundary layer at cavity separation is shown to be laminar for all cavitation numbers, with Kelvin–Helmholtz instability and transition to turbulence in the separated shear layer the main mechanism for cavity breakup and cloud formation at high cavitation numbers. At intermediate cavitation numbers, cavity lengths allow the development of re-entrant jet phenomena, providing a mechanism for shedding of large-scale Kármán-type vortices similar to those for low-mode shedding in single-phase subcritical flow. This shedding mode, which exists at supercritical Reynolds numbers for single-phase flow, is eliminated at low cavitation numbers with the onset of supercavitation.

Complex interactions between the separating laminar boundary layer and the cavity were observed. In all cases the cavity leading edge was structured in laminar cells separated by well-known ‘divots’. The initial laminar length and divot density were modulated by the unsteady cavity shedding process. At cavitation numbers where shedding was most energetic, with large portions of leading edge extinction, re-nucleation was seen to be circumferentially periodic and to consist of stretched streak-like bubbles that subsequently became fleck-like. This process appeared to be associated with laminar–turbulent transition of the attached boundary layer. Nucleation occurred periodically in time at these preferred sites and formed the characteristic cavity leading edge structure after sufficient accumulation of vapour had occurred. These observations suggest that three-dimensional instability of the decelerating boundary layer flow may have significantly influenced the developing structure of the cavity leading edge.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 656 , 10 August 2010 , pp. 147 - 176
Copyright
Copyright © Cambridge University Press 2010

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References

REFERENCES

Achenbach, E. 1972 Experiments on the flow past spheres at very high Reynolds numbers. J. Fluid Mech. 54 (3), 565–575.CrossRefGoogle Scholar
Achenbach, E. 1974 Vortex shedding from spheres. J. Fluid Mech. 62 (2), 209–221.CrossRefGoogle Scholar
Addison, P. S. 2002 The Illustrated Wavelet Transform Handbook. Taylor and Francis.CrossRefGoogle Scholar
Arakeri, V. H. 1975 Viscous effects on the position of cavitation separation from smooth bodies. J. Fluid Mech. 68 (4), 779–799.CrossRefGoogle Scholar
Arakeri, V. H. & Acosta, A. J. 1973 Viscous effects in the inception of cavitation on axisymmetric bodies. J. Fluids Engng 95 (4), 519–527.CrossRefGoogle Scholar
Arakeri, V. H. & Acosta, A. J. 1976 Cavitation inception observations on axisymmetric bodies at supercritical Reynolds numbers. J. Ship Res. 20 (1), 40–50.CrossRefGoogle Scholar
Arndt, R. E. A. 1976 Semi-empirical analysis of cavitation in the wake of a sharp-edged disk. J. Fluids Engng 98, 560–562.CrossRefGoogle Scholar
Bakić, V. & Perić, M. 2005 Visualization of flow around sphere for Reynolds numbers between 22 000 and 400 000. Thermophys. Aeromech. 12 (3), 307–315.Google Scholar
Belahadji, B., Franc, J. P. & Michel, J. M. 1995 Cavitation in the rotational structures of a turbulent wake. J. Fluid Mech. 287, 383–403.CrossRefGoogle Scholar
Brandner, P. A., Clarke, D. B. & Walker, G. J. 2004 Development of a fast response probe for use in a cavitation tunnel. In 15th Australasian Fluid Mechanics Conference, p. 4. The University of Sydney, Sydney.Google Scholar
Brandner, P. A., Walker, G. J., Niekamp, P. N. & Anderson, B. 2007 An investigation of cloud cavitation about a sphere. In 16th Australasian Fluid Mechanics Conference, pp. 1392–1998. Crown Plaza, Gold Coast.Google Scholar
Brennen, C. E. 1970 a Cavity surface wave patterns and general appearance. J. Fluid Mech. 44 (1), 33–49.CrossRefGoogle Scholar
Brennen, C. E. 1970 b Some cavitation experiments with dilute polymer solutions. J. Fluid Mech. 44 (1), 51–63.CrossRefGoogle Scholar
Brennen, C. E. 1995 Cavitation and Bubble Dynamics. Oxford University Press.CrossRefGoogle Scholar
Briançon-Marjollet, L., Franc, J. P. & Michel, J. M. 1990 Transient bubbles interacting with an attached cavity and the boundary layer. J. Fluid Mech. 218, 355–376.CrossRefGoogle Scholar
Ceccio, S. L. & Brennen, C. E. 1992 Dynamics of attached cavities on bodies of revolution. J. Fluids Engng 114 (1), 93–99.CrossRefGoogle Scholar
Fage, A. 1936 Experiments on a sphere at critical Reynolds numbers. Reports and Memoranda 1766. Aeronautical Research Council.Google Scholar
Farge, M. 1992 Wavelet transforms and their applications to turbulence. Annu. Rev. Fluid Mech. 24, 395–457.CrossRefGoogle Scholar
Franc, J. P. 2001 Partial cavity instabilities and re-entrant jet. In Fourth International Symposium on Cavitation. California Institute of Technology, Pasadena, CA.Google Scholar
Franc, J. P. & Michel, J. M. 2004 Fundamentals of Cavitation. Kluwer.Google Scholar
Hinze, J. O. 1955 Fundamentals of the hydrodynamic mechanism of splitting in dispersion processes. AIChE J. 1 (3), 289–295.CrossRefGoogle Scholar
Ho, C.-M. & Huerre, P. 1984 Perturbed free shear layers. Annu. Rev. Fluid Mech. 16, 365–422.CrossRefGoogle Scholar
Jaffard, S., Meyer, Y. & Ryan, R. D. 2001 Wavelets: Tools for Science and Technology. SIAM.CrossRefGoogle Scholar
Joseph, D. D. 1998 Cavitation and the state of stress in a flowing liquid. J. Fluid Mech. 366, 367–378.CrossRefGoogle Scholar
Kjeldsen, M. & Arndt, R. E. A. 2001 Joint time frequency analysis techniques: a study of transitional dynamics in sheet/cloud cavitation. In Fourth International Symposium on Cavitation (ed. Brennen, C. E., Arndt, R. E. A. & Ceccio, S. L.). California Institute of Technology, Pasadena, CA.Google Scholar
Li, C.-Y. & Ceccio, S. L. 1996 Interaction of single travelling bubbles with the boundary layer and attached cavitation. J. Fluid Mech. 322, 329–353.CrossRefGoogle Scholar
Mørch, K. A., Bark, G., Grekula, M., Jøenck, K., Nielsen, P. L. & Stendys, P. 2003 The formation of cavity clusters at sheet cavity/re-entrant jet contact. In Fifth International Symposium on Cavitation, pp. GS–4–005. Osaka, Japan.Google Scholar
Padrino, J. C., Joseph, D. D., Funada, T., Wang, J. & Sirignano, W.A. 2007 Stress-induced cavitation for the streaming motion of a viscous liquid past a sphere. J. Fluid Mech. 578, 381–411.CrossRefGoogle Scholar
Reisman, G. E., Wang, Y. C. & Brennen, C. E. 1998 Observations of shock waves in cloud cavitation. J. Fluid Mech. 355, 255–283.CrossRefGoogle Scholar
Schmidt, S. J., Sezal, I. H., Schnerr, G. H. & Thalhamer, M. 2008 Numerical analysis of shock dynamics for detection of erosion sensitive areas in complex 3-D flows. In WIMRC Cavitation Forum 2008, pp. 107–120. Warwick, UK.Google Scholar
Schnerr, G. H., Schmidt, S., Sezal, I. & Thalhamer, M. 2006 Shock and wave dynamics of compressible liquid flows with special emphasis on unsteady load on hydrofoils and on cavitation in injection nozzles. In Sixth International Symposium on Cavitation. Maritime Research Institute, Wageningen, The Netherlands.Google Scholar
Tassin Leger, A., Bernal, L. P. & Ceccio, S. L. 1998 Examination of the flow near the leading edge of attached cavitation. Part 2. Incipient breakdown of two-dimensional and axisymmetric cavities. J. Fluid Mech. 376, 91–113.CrossRefGoogle Scholar
TassinLeger, A. Leger, A. & Ceccio, S. L. 1998 Examination of the flow near the leading edge of attached cavitation. Part 1. Detachment of two-dimensional and axisymmetric cavities. J. Fluid Mech. 376, 61–90.Google Scholar
Torrence, C. & Compo, G. P. 1998 A practical guide to wavelet analysis. Bull. Am. Met. Soc. 79 (1), 61–78.2.0.CO;2>CrossRefGoogle Scholar
Van den Braembussche, R., (Ed.) 2002 Lecture Series on Supercavitation, RTO-EN-010 AC/323(AVT-058)TP/45. Von Karman Institute for Fluid Dynamics, Sint-Genesius-Rode, Belgium.Google Scholar