Feeds

Hot bodies get super-slippery when wet

Steamy balls could lead to sizzling speedy torpedoes

Beginner's guide to SSL certificates

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. ®

Beginner's guide to SSL certificates

More from The Register

next story
Antarctic ice THICKER than first feared – penguin-bot boffins
Robo-sub scans freezing waters, rocks warming models
I'll be back (and forward): Hollywood's time travel tribulations
Quick, call the Time Cops to sort out this paradox!
Your PHONE is slowly KILLING YOU
Doctors find new Digitillnesses - 'text neck' and 'telepressure'
Reuse the Force, Luke: SpaceX's Elon Musk reveals X-WING designs
And a floating carrier for recyclable rockets
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
Bond villains lament as Wicked Lasers withdraw death ray
Want to arm that shark? Better get in there quick
prev story

Whitepapers

Free virtual appliance for wire data analytics
The ExtraHop Discovery Edition is a free virtual appliance will help you to discover the performance of your applications across the network, web, VDI, database, and storage tiers.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
5 critical considerations for enterprise cloud backup
Key considerations when evaluating cloud backup solutions to ensure adequate protection security and availability of enterprise data.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Security and trust: The backbone of doing business over the internet
Explores the current state of website security and the contributions Symantec is making to help organizations protect critical data and build trust with customers.