To improve productivity, and the range and sophistication of work that can be carried out, the cavitation tunnel is being upgraded to be one of the most modern internationally for modeling of cavitation phenomena. 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 upgraded tunnel is to be 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 degaser, 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 nuclei injectors penetrate the honeycomb from which generated nuclei are convected through the contraction and into the test section. Typical nuclei sizes are 100 µm 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 the ability 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 viscous flows a system for controlling the test section ceiling boundary layer is also being included in the upgrade. The boundary layer is controlled using injection of an array of transverse jets to not only control the boundary layer profile but also the turbulence profile. Considerable efforts are also being made to achieve low a background noise level via 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 the to diversity of specialisations involved. The cavitation tunnel hydraulic design is being carried out by AMC and UTas with collaboration from YLec Consultants. Extensive use has been made of CFD 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. Structural and Mechanical design has been carried out by Towers Technical and AMC. Vibration and Acoustic Studies by VIPAC Engineers and Scientists and civil and structural design by Pitt and Sherry Consulting Engineers. Construction of the tunnel circuit by The Engineering Company and precision equipment manufacture by a range of specialist machining and fabrication contractors.

Three Dimensional View of the Upgraded Cavitation Tunnel