Plenty of liquid has passed under the bridge since Leonardo da Vinci drew his famous sketches of moving water, but scientific interest in water dynamics is as relevant today as it was 500 years ago.
Fluid dynamics research provides essential information in a multitude of areas such as the understanding of how heat is transferred by the water coolant flowing though nuclear reactor cores.
ANSTO engineer David Wassink says that we can still learn a lot about water behaviour.
"Small differences in the roughness of objects can make big differences in the fluid drag on the object," David said. "The dimples on a golf ball are designed to reduce drag, and the very rough skins of sharks have the same effect, which allows them to be very efficient swimmers. Research continues so we can design surfaces to our advantage, using examples that nature provides." ANSTO operates a specially designed water tunnel which has been used recently by universities for this type of research.
David says that water testing can also be useful for people looking to model the movement of air flowing at high velocities. "Because of the density difference, water flow can simulate air flowing at velocities which can't readily be reached in a laboratory."
ANSTO’s Water Tunnel consists of a closed loop of pipes with a capacity of 3,000 litres of water, which is circulated around the loop at speeds up to 230 litres per second.
David Wassink and Year-in-Industry student Mark Ho have also used ANSTO’s Water Tunnel to perform tests on new irradiation cans being trialed to increase efficiency for the production of Molybdenum-99 - the parent of the most widely used agent in diagnostic nuclear medicine, Technetium-99m. Irradiation cans are used for the production of Molybdenum-99 in ANSTO’s HIFAR research reactor.
Flow characteristics around the irradiation cans are determined by Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) methods. The PIV system provides a two dimensional picture of the flow velocity around the model using tiny reflective additives as flow tracers illuminated by the blue/green light from an Argon laser. The resulting flow patterns are recorded with digital images, videotape or by conventional photography. Images are then analysed to provide flow velocity and direction information.
The LDV system, which also uses an Argon laser, obtains three dimensional point velocity measurements and turbulence information from the flow. Both systems combine to provide a complete flow analysis.
Another example of the use of the water tunnel is for performance tests on hydraulic fittings, which can be conducted to Australian Standards. These tests include flow/pressure loss tests and endurance testing and can be certified by the National Association of Testing Authorities through ANSTO’s Quality Control Section.
Published: 21/01/2002