Water tunnel (hydrodynamic)

Image:Berlin-tiergarten vws 20050404 p1020295.jpg|thumb|300px|Cavitation tunnel of the Versuchsanstalt für Wasserbau und Schiffbau in Berlin
A water tunnel is an experimental facility used for testing the hydrodynamic behavior of submerged bodies in flowing water. It functions similar to a recirculating wind tunnel, but uses water as the working fluid, and related phenomena are investigated, such as measuring the forces on scale models of submarines or lift and drag on hydrofoils. Water tunnels are sometimes used in place of wind tunnels to perform measurements because techniques like particle image velocimetry are easier to implement in water. For many cases as long as the Reynolds number is equivalent, the results are valid, whether a submerged water vehicle model is tested in air or an aerial vehicle is tested in water. For low Reynolds number flows, tunnels can use oil instead of water. The advantage is that the increased viscosity will allow the flow to be a higher speed for a lower Reynolds number.
Often, a tunnel will be co-located with other experimental facilities such as a wave flume at a Ship model basin.
Image:cavitating-prop.jpg|thumb|300px|Cavitating propeller model in 'David Taylor Model Basin'

Cavitation studies

Because it is a high-speed phenomenon, a special procedure is needed to visualize cavitation. The propeller, attached to a dynamometer, is placed in the inflow, and its thrust and torque is measured at different ratios of propeller speed to inflow velocity. A stroboscope synchronized with the propeller speed "freezes" the cavitation bubble. By this means, it is possible to determine if the propeller would be damaged by cavitation. To ensure similarity to the full-scale propeller, the pressure is lowered, and the gas content of the water is controlled.

List of water tunnels (cavitation tunnels)

Australia

"Australian Maritime College". AMC

Brazil

Laboratory of Naval and Oceanic Engineering, Institute for Technological Research of São Paulo.

Canada

National Research Council—Institute for Ocean Technology Cavitation Tunnel, St. John's, Newfoundland.

France

"Tunnel de Cavitation" Ecole Navale, Lanveoc
"Grand Tunnel Hydrodynamique" Bassin d'Essais des Carènes, Val de Reuil
"TH8.2V : Tunnels Hydrodynamiques 8 ou 2 m3/s" Centre d'études et de recherche de Grenoble

Germany

Multiple cavitation tunnels at the Versuchsanstalt für Wasserbau und Schiffbau, Berlin
Cavitation tunnel at the University Duisburg-Essen, Institute of Ship Technology, Ocean Engineering and Transport Systems, University Duisburg-Essen
Cavitation tunnel at Potsdam Ship Model Basin, Potsdam
Large Cavitation tunnel at Hamburg Ship Model Basin, Hamburg
Multiple cavitation tunnels at the Oskar von Miller Institut, Technical University of Munich

India

Fluid Control Research Institute, Palakkad, Kerala.
Cavitation Tunnel of the Naval Science and Technology Labs at Visakhapatnam.
Department of Aerospace Engineering, Indian Institute of Technology, Kharagpur
Indian Institute of Technology Madras.

Iran

Applied Hydrodynamics Laboratory, Iran University of Science and Technology, Narmak, Tehran.
Marine Engineering Laboratory, Sharif University of Technology, Azadi Av., Tehran.

Italy

Department of Naval Architecture, University of Genoa.
INSEAN Cavitation facility, INSEAN, Rome.

The Netherlands

Large Cavitation Tunnel and High Speed Cavitation Tunnel at Maritime Research Institute Netherlands in Wageningen
Twente Water Tunnel facility at University of Twente

Norway

Cavitation Lab NTNU, The Norwegian [University of Science and Technology], Trondheim

Spain

CEHIPAR, El Pardo, Spain.

Serbia

The Large Cavitation Tunnel at Military Technical Institute Belgrade, Serbia

Switzerland

High Speed Cavitation Tunnel at LMH: Lab. of Hydraulic Machines, EPFL: Ecole Polytechnique Federale de Lausanne, Switzerland