Feeds

Hot bodies get super-slippery when wet

Steamy balls could lead to sizzling speedy torpedoes

High performance access to file storage

An Australian boffin says he has come up with a novel method for making things such as ship's hulls or torpedoes slip through water more easily.

Professor Derek Chan of Melbourne uni suggests that it would be practical for ships to exploit the "Leidenfrost effect", named after its discoverer in 1756. This refers to the behaviour of liquids when they encounter a surface significantly hotter than their boiling point: the portion of the liquid in contact turns into a cushion of vapour, keeping the remainder of the liquid away from the hot surface.

An everyday example of the Leidenfrost effect in play is that of a drop of water hitting a hot skillet and skittering about. As the vapour cushion is poorer at transmitting heat than direct contact, the droplet will then actually take longer to boil away than it would have if the pan were cooler. The same effect can also allow a person to put their hand into a bucket of liquid nitrogen without harm.

The Leidenfrost effect is poorly understood, however: it's quite hard to predict at just what temperature it will set in. But Professor Chan has carried out detailed experiments which involved dropping hot, polished balls into various liquids and viewing their interactions on high-speed video. The prof believes he's gained enough of a handle on the effect that it could be used in practical applications.

"An obvious area of application is shipping," he says. "Australia transports a large amount of products such as iron ore and grain around the world. The ship's hot body could substantially minimise the amount of drag as it passes through water, therefore potentially reducing transportation costs and greenhouse gas emissions."

In effect, the situation would be the same as that of the water droplet on the hot skillet but reversed: the hot ship would skitter frictionlessly on the sea's surface just as the drop does on the pan. However the prospect of massive bulk carriers with their hulls heated up well past boiling point seems a trifle unrealistic.

Where the idea might find an application is in torpedos, whose speed is seriously limited by water drag. There is already an advanced Russian rocket torpedo – the famous "Shkval" – which operates on similar lines, though the Shkval generates its slippery surrounding gas layer internally rather than by evaporating water. Leidenfrost-effect hot projectiles might offer similar high speeds.

That said, "there are still a number of issues that need to be addressed before this drag reduction method can be applied commercially," warns Chan, "such as the effect of increased heat on corrosion.”

The research is laid out in a paper by Chan and his colleagues, published in the journal Physical Review Letters. ®

High performance access to file storage

More from The Register

next story
Elon Musk's LEAKY THRUSTER gas stalls Space Station supply run
Helium seeps from Falcon 9 first stage, delays new legs for NASA robonaut
Russian deputy PM: 'We are coming to the Moon FOREVER'
Plans to annex Earth's satellite with permanent base by 2030
KILLER SPONGES menacing California coastline
Surfers are safe, crustaceans less so
LOHAN's Punch and Judy show relaunches Thursday
Weather looking good for second pop at test flights
New FEMTO-MOON sighted BIRTHING from Saturn's RING
Icy 'Peggy' looks to be leaving the outer rings
Discovery time for 200m WONDER MATERIALS shaved from 4 MILLENNIA... to 4 years
Alloy, Alloy: Boffins in speed-classification breakthrough
Curiosity finds not-very-Australian-shaped rock on Mars
File under 'messianic pastries' and move on, people
Top Secret US payload launched into space successfully
Clandestine NRO spacecraft sets off on its unknown mission
Get your MOON GEAR: Auction to feature Space Race memorabilia
Keepsakes from early NASA, Soviet programs up for bids
prev story

Whitepapers

Securing web applications made simple and scalable
In this whitepaper learn how automated security testing can provide a simple and scalable way to protect your web applications.
Five 3D headsets to be won!
We were so impressed by the Durovis Dive headset we’ve asked the company to give some away to Reg readers.
HP ArcSight ESM solution helps Finansbank
Based on their experience using HP ArcSight Enterprise Security Manager for IT security operations, Finansbank moved to HP ArcSight ESM for fraud management.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Mobile application security study
Download this report to see the alarming realities regarding the sheer number of applications vulnerable to attack, as well as the most common and easily addressable vulnerability errors.