Discovery can double submarine speeds

Drag resistance on hot bodies moving through liquid can be drastically reduced by up to 85%.

Sydney: A discovery by Australian scientists could potentially open up ways for sea vessels like submarines to go much faster under water. A team led by a Swinburne University professor showed that drag (resistance) on hot bodies moving through liquid can be drastically reduced by up to 85 percent, potentially doubling their speed.

In practical terms, this finding could help a submarine and other vessels to virtually double their speed while moving under the sea, the journal Physical Review Letters report.

Swinburne researchers Ivan Vakarelski and Professor Derek Chan observed that a heated ball can fall through liquid more than twice as fast as a colder, `control` ball, according to a Swinburne statement.

The discovery exploits the drag-reducing properties of a vapour layer formed between a hot body and surrounding liquid, known as the Leidenfrost effect.

This is a novel application of the familiar phenomenon where water drops are observed to dance or `levitate` around when splashed onto a very hot plate -- known for over 200 years.

"A very hot body - hot enough to vapourise the thin layer of liquid in contact with it - can drastically reduce energy-sapping drag forces when such bodies travel at high speed through the liquid," Chan said.


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