Cavitation Research Laboratory

AMC Cavitation Research
AMC Cavitation Research
AMC Cavitation Research
AMC Cavitation Tunnel
AMC Cavitation Research
AMC Cavitation Research
AMC Cavitation Research
AMC Cavitation Research
AMC Cavitation Research
AMC Cavitation Research
If you want to be at the cutting edge of research then as an AMC engineering student you will have access to the recently upgraded AMC Cavitation Research Laboratory.

It is unique in Australia and one of the few experimental laboratories in the world used to test hydrodynamic behaviour of submerged structures such as submarines and ship hulls.

Working closely with the (DSTO) Defence Science and Technology Organisation the facility plays a key role when providing research and advice on the future development of submarines, destroyers, patrol boats and other maritime vessels.

Interest in cavitation has traditionally been in hydraulic and hydrodynamic applications such as in hydro-electric machinery, nuclear plant and rocket propulsion. Modern research is more diverse and often focused on fluid dynamics with potential applications in medicine, biomedical engineering and biology.

CLICK HERE TO VIEW THE SEGMENT AIRED ON ABC'S CATALYST PROGRAM ABOUT THE RESEARCH TAKING PLACE IN AMC'S CAVITATION TUNNEL (BUBBLE BEHAVIOUR) MARCH 2012.
 

Cavitation Research and its Applications

Cavitation may strictly be defined as the change of phase, from liquid to vapour, that occurs when the static pressure in the liquid on or about a body is reduced below the vapour pressure. It is similar to boiling but the driving mechanism is pressure rather than heat. It is a complex phenomenon and places limitations on the performance of submerged machinery. It may cause thrust breakdown in propulsors and hydrofoils, loss of efficiency, metal erosion, noise, vibration and ultimately destruction of machinery.

Interest in cavitation has traditionally been in hydraulic and hydrodynamic applications such as in naval hydrodynamics, hydro-electric machinery, nuclear plant and rocket propulsion. Modern research is more diverse and often focused on basic fluid dynamic phenomena with applications additionally in medicine, biomedical engineering and biology. Cavitation in this context is more appropriately defined as encompassing all phenomena involving the interaction between vaporous or gaseous volumes (or cavities) with flowing or non flowing liquid volumes.

Cavitation research at the AMC, University of Tasmania, involves classical work such as cavitation about marine propulsors and control surfaces but also more novel problems. Typical of these includes mechanisms for air entrainment about ship hulls, the effects of propellers and control surfaces in mixing and bubble breakup and subsequent dispersion and dissipation of bubbles in the ship wake. Other relevant problems in hydrodynamics include the effects of bubble populations present in the ocean that provide seeding for cavitation inception and hence control its dynamic behaviour. Dissolved (incondensable) gases, invariably present in practical liquid volumes, may also play a role in cavitation behaviour via diffusion across the liquid-vapour interface. Finally, turbulence and surface tension also play an important role in cavitation physics.

To study such problems new laboratory facilities have been developed funded by national competitive grant schemes and the Defense Science and Technology Organisation. These include a variable pressure water tunnel with the capability for control of free (as bubbles) and dissolved gas content and a pressurisable chamber for the study of small-scale bubble and related phenomena.


Cavitation occurrence below the lip of a flush water-jet inlet duct (left) and unsteady cavitation about a sphere showing coherent vortices, due to Kelvin-Helmholtz instability, in the overlying interfacial layer (right).

Cavitation Tunnel

The cavitation tunnel is a variable pressure water tunnel for the study of cavitating and bubbly viscous flows. Funded principally under the AusIndustry Major National Research Facilities Program it has been conceived as the most sophisticated medium-sized variable-pressure water tunnel internationally for experimental modeling of cavitation physics. It has been developed to support basic and applied research into the performance of naval platforms and high-speed craft, and fluid mechanics research generally. Its principal capabilities include precise control of dissolved and free gas in the test flow critical for modeling of nucleation and diffusion processes.

Fundamental investigation of cavitation has shown that, in addition to turbulence, the presence of non-condensable gases, both dissolved and free as bubbles, play a critical role in particularly dynamic cavitation situations. The new tunnel is fitted with several systems to control both the dissolved gas content and the bubble or nuclei spectra. To control the dissolved gas content the tunnel is equipped with a rapid degasser, utilising microbubble injection, to enable the dissolved gas content to be reduced to 20% of saturation at atmospheric pressure within 2 hours. For control of the nuclei spectra an array of injectors penetrate the honeycomb from which generated nuclei are convected through the contraction and into the test section. Typical nuclei sizes are in the order of 10 to 100 um and concentrations may be varied from 0.1 to 10/cm3 via a system of direct injection or external one or two stage dilution followed by injection. After injection nuclei are removed online via a process of coalescence and gravity separation in a downstream tank and dissolution in a resorber. The downstream tank not only has the ability for nuclei separation but also for removal of large quantities of non-condensable gases (up to 200ℓ/s) produced from diffusion of dissolved gas or from ventilated flows. To enhance investigation of flows involving boundary layers a system for controlling the thickness of the test section ceiling boundary layer has also been included in the new facility. The boundary layer may be thinned or thickened via suction or injection respectively of fluid through a full-width perforated plate at entrance to the test section. Considerable efforts have also been made to achieve a low background noise level by isolation of machinery and the tunnel circuit and minimisation of flow noise and sources of vibration.

A range of consultants and contractors have been involved with the design and construction of the tunnel owing to the diversity of specialisations involved. The cavitation tunnel hydraulic design was carried out by AMC, University of Tasmania, with collaboration from YLec Consultants. Extensive use has been made of Computational Fluid Dynamics in addition to ¼ and full scale physical models of the tunnel circuit and particular components. The design of systems for degassing and nuclei injection have been carried out by YLec Consultants and AMC, University of Tasmania. Structural and Mechanical design was by Towers Technical and AMC, University of Tasmania. Vibration and acoustic studies were carried out by VIPAC Engineers and Scientists and civil and structural design by Pitt and Sherry Consulting Engineers. Construction of the tunnel circuit is by The Engineering Company and precision equipment manufacture by a range of specialist machining and fabrication contractors.

Principal capabilities sought in development of the new facility include:

  • high uniformity, low turbulence test section flow
  • fine control of test section velocity and pressure
  • low test section cavitation number
  • independent control of free and dissolved gas content
  • continuous injection and separation of high volumes of incondensable gases
  • boundary layer control on one wall of the test section
  • low background noise and vibration levels

 


Three dimensional view of cavitation tunnel and ancillaries.

Cavitation Tunnel Specifications

  • Test section 0.6 m square x 2.6 m long
  • Max flow speed 12 m/s
  • Pressure range from 4 to 400 kPa absolute
  • Test section velocity uniformity at mid section 0.25%
  • Test section turbulence intensity at mid section 0.3%
  • Test section temporal stability of velocity 0.01%
  • Test section temporal stability of pressure 0.01%
  • Cavitation number from 0.07 to 200
  • Tunnel volume 365 m3
  • Minimum bubble residence 85 s
  • Main pump motor power 200 kW


Schematic of cavitation tunnel ancillary systems and control equipment.

Cavitation Tunnel Instrumentation and ancillaries:

  • High speed microbubble degasser – 20% saturation at atmospheric pressure in 2 hours
  • Waterjet propulsor test loop – maximum flow 150 ℓ/s
  • Test section ceiling boundary layer control using injection/suction at maximum of 50 ℓ/s (0 to 0.1 m total thickness)
  • Continuous nuclei injection and removal – 0.1 to 10/cm3 in sizes ranging from 10 to 100um
  • 200 ℓ/s continuous removal of non-condensable gases
  • 2 Propeller dynamometers
  • 4 six-component force balances
  • High-speed camera, time-resolved particle imaging velocimetry (PIV), stereo PIV and shadowgraphy system
  • Scanning laser vibrometer
  • 3D automatic traverse and 1D/3D fast response pressure probes

Bubble Dynamics Chamber

The bubble dynamics chamber developed in collaboration with and funded by the Defence Science and Technology Organisation is used for basic studies of bubble behaviour in stationary or small scale flows. Similar test conditions, in terms of pressure range, dissolved gas content, nuclei and microbubble injection and available measurements can be achieved in the chamber to those in the cavitation tunnel. This enables a range of experiments to be carried out in parallel with those in the tunnel and indeed this chamber has been used for development of some of the systems used in the main facility.

Bubble Dynamics Chamber Specfications:

  • Chamber dimensions 0.5 m square by 1.2m long
  • Pressure range from 4 to 400 kPa absolute
  • Optical access equivalent to cavitation tunnel
  • Parallel or compatible instrumentation with cavitation tunnel


Bubble dynamics chamber.


Vortex formation from Rayleigh-Taylor instability and bubble dispersion in a stream of micron-sized bubbles

References

Brandner, P.A., Dawson E.C. and Walker G.J., An Experimental Investigation into the Influence of Ramp-Mounted Vortex Generators on the Performance of a Flush Water-jet Inlet, Accepted for publication, Journal of Ship Research, SNAME, 2009.

Brandner, P.A., Roberts, J.L. and Walker G.J., The Influence of Viscous Effects and Physical Scale on Cavitation Tunnel Contraction Performance, Journal of Fluids Engineering, ASME, Vol 130, No. 1, October, 2008.

Clarke, D.B., Brandner, P.A., and Walker, G.J., Computational and Experimental Investigation of Flow Around a 3-1 Prolate Spheroid, WSEAS Transactions on Fluid Mechanics, Issue 3, Volume 3, July 2008, pp 207-217.

Seil, G., Widjaja, R., Anderson, B., Brandner, P.A., Computational Analysis of Submarine Propeller Hydrodynamics and Validation against Experimental Measurement, Undersea Defence Technology Pacific Conference, Sydney, Australia, Nov 2008.

Brandner, P.A., Walker G.J., Niekamp, P.N. and Anderson, B., Cloud Cavitation About a Sphere, Sixteenth Australasian Fluid Mechanics Conference, Gold Coast, Queensland, Dec, 2007.

Brandner, P.A., Lecoffre Y., and Walker G.J., Design Considerations in the Development of a Modern Cavitation Tunnel, Sixteenth Australasian Fluid Mechanics Conference, Gold Coast, Queensland, Dec, 2007.

Pearce, B.W., and Brandner, P.A., Limitations on 2D Super-cavitating Hydrofoil Performance, Sixteenth Australasian Fluid Mechanics Conference, Gold Coast, Queensland, Dec, 2007.

Clarke, D.B., Brandner, P.A., and Walker G.J., Computational and Experimental Investigation of Flow Around a 3-1 Prolate Spheroid, Sixteenth Australasian Fluid Mechanics Conference, Gold Coast, Queensland, Dec, 2007.

Brandner, P.A. and Walker G.J., An Experimental Investigation into the Performance of a Flush Water-jet Inlet, Journal of Ship Research, SNAME, Vol 51, No. 1, March 2007.

Brandner, P.A., Walker G.J., Niekamp, P. N. and Anderson, B., Cloud Cavitation About a Sphere, Sixteenth Australasian Fluid Mechanics Conference, Gold Coast, Queensland, Dec, 2007.

Brandner, P.A., Lecoffre Y., and Walker G.J., Design Considerations in the Development of a Modern Cavitation Tunnel, Sixteenth Australasian Fluid Mechanics Conference, Gold Coast, Queensland, Dec, 2007.

Brandner, P.A., Lecoffre, Y. and Walker, G.J., Development of an Australian National Facility for Cavitation Research, Sixth International Symposium on Cavitation – CAV2006, Wageningen, The Netherlands, September, 2006.

Clarke, D.B. Anderson, B., Brandner, P.A., Kidd, B. and Kanev, S., A Preliminary Investigation into the Hydroelastic Behaviour of a Non-Rigidly Mounted Hydrofoil, UDT Pacific 2006.

Brandner, P.A., Clarke, D. B. and Walker G.J., Development of a Fast Response Pressure Probe for Use in a Cavitation Tunnel, Proceedings of the Fifteenth Australasian Fluid Mechanics Conference, Sydney, New South Wales, Dec, 2004.

Brandner, P.A. and Walker G.J., Hydrodynamic Performance of a Surfboard Fin, Proceedings of the Fifteenth Australasian Fluid Mechanics Conference, Sydney, New South Wales, Dec, 2004.

Brandner, P.A., Clarke, D. B. and Walker G.J., Development of a Fast Response Pressure Probe for Use in a Cavitation Tunnel, Proceedings of the Fifteenth Australasian Fluid Mechanics Conference, Sydney, New South Wales, Dec, 2004.

 

For further information contact:

Associate Professor Paul Brandner
Australian Maritime College's Cavitation Research Laboratory 
Locked Bag 1395
Launceston, Tasmania, 7250

Phone: +61 (0)3 6324 9832
Fax: +61 (0)3 6324 9337 
Email: p.brandner@amc.edu.au

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