back to article Hot bodies get super-slippery when wet

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 …

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  1. Anonymous Coward
    Paris Hilton

    Hot Slippery Bodies

    Why do we need a professor to tell us hot bodies get slippery and wet? It's common knowledge.

    Paris, because she also gets slippery and wet easily.

    1. Rodrigo Valenzuela

      mmm

      May be this is news for the professor?

      R

  2. Adam Cooper
    WTF?

    Haha.

    Heat up the hull of a container ship to "significantly more" then 100 degrees Celsius whilst it's submerged in ocean water.

    They thinking of including Nuclear reactors on them now? I'm pretty certain that they're the only things that could even come close to the necessary power output.

    1. Anonymous Coward
      Anonymous Coward

      Maybe not the whole hull

      How about if it was coated with a film which could be heated quickly but was itself a good insulator? I'm sure trickier materials problems have been solved getting vessels into space in the past.

      1. Anonymous Coward
        Anonymous Coward

        If only nanotubes weren't prohibitively expensive...

        see title

    2. Anonymous Coward
      Joke

      Think green

      Scratch the nuke and make it tide-powered.

      Anyway, I'm off to get a bucket of nitrogen and a lawyer...

    3. Havin_it
      FAIL

      ^This

      I'll take some convincing that this idea (which only applies in open seas where thrust is worth more than manoeuvrability, I suspect) can actually reduce overall emissions.

    4. Captain TickTock
      Alert

      Boiling the ocean

      Literally too

      1. G2

        firefly

        Burn the land and boil the sea,

        you can’t take the sky from me...

    5. ennui

      Heating the boat's hulk.

      We do not need any other heating system,. These boatscarry coal to Japan. All what they have to do set fire to it. The Ship will go so fast that there will be at least 10% left for Japan.

  3. beerandbiscuits

    torpedo

    I'm sure there are some naval ordnance techno boffins out there who can put me right on this, but I would have thought the cavitation from all the escaping vapour would make for a hell of a noisy torpedo, which I would expect to cancel out at least some of the speed advantage.

    Also how would the necessary temperature be maintained? Onboard equipment would take up space and fuel, which would presumably limit range and warhead size.

    Over to the people who claim to know what they're talking about.

    1. Anonymous Coward
      Boffin

      It can go

      at 250 mph, and there are (classified, but in principle workable with some degree-level physics) some ways to reduce the noise.

      But do you seriously think that at this speed, the noise matters?

      Typical range over which you want to use torpedo is at most 5 miles - do you really think a big ship can do much in around 2 minutes it takes supercavitating torpedo to reach it? Especially if it's got some sort of guiding system?

    2. Anonymous Coward
      Anonymous Coward

      Oh,

      and of course I was talking about "normal" supercavitating torpedo, which doesn't need all that heating.

    3. PT
      Black Helicopters

      @ torpedo

      As a former junior naval ordnance techno boffin, I can assure you that the intended victim of a torpedo generally - and in the case of a submarine, certainly - knows it's coming the moment it's launched and immediately takes evasive action. No amount of additional noise makes a difference to the target once the fish is on the way, but a few seconds less time to evade or distract it certainly does. The noise may affect the torpedo's ability to identify a target by its acoustic signature, but that feature is most important for devices that sit quietly and spring into action when they spot a target - self propelled mines, in other words - and there are clear practical problems with keeping a loitering torpedo hot.

    4. Gordon 10

      Stealth torpedo

      Afaik torpedoes generally swap stealth for high speed.

      Stealth torpedoes are normally called mines and are fairly stationary.

    5. SkippyBing

      Speed is life

      The Russian rocket powered torpedo thing basically goes in a straight line very fast, the idea is it's so fast that the target vessel would be unable to alter its velocity enough to avoid a collision. The videos I've seen of them (they're on youtube) show a massive wake on the surface so it's by no means a stealth weapon however you look at it . I don't think the range isn't that great either and they're designed to be launched by surface vessels rather than submarines who'd just end up with a trail of bubbles pointing to them.

      Of course the other problem they have is there's no real way of guiding them as they generate too much self noise for sonar to work, although wire guidance might be an option, in which case the counter measure is to take out the launch platform.

      1. Anonymous Coward
        Anonymous Coward

        Not on submarines?

        Remember the "Kursk affair" a few years ago?

  4. Mike Moyle

    Just don't use...

    ...heat-sensitive payload or fuzing on your torpedoes!

  5. Bucky 2
    Pint

    A La Cartman

    It's my hot body. I do what I won't.

  6. WonkoTheSane
    Mushroom

    He's been watching Mythbusters

    http://www.youtube.com/watch?v=UZio0f7fP04

    Skip ahead to 6 minutes in.

    (Explosion because... well.... Mythbusters!)

  7. Anonymous Coward
    Anonymous Coward

    You are kidding.

    "The same effect can also allow a person to put their hand into a bucket of liquid nitrogen without harm."

    You go first and then maybe I'll believe you.

    1. Robert Hill

      WRONG

      I have spent a lot of time playing with liquid nitrogen in the lab, and I can tell you the one thing you DO NOT want to do is "dip your hand" into it. You will lose it, quickly, because the pressure of the liquid rapidly displaces that thin boundary layer.

      What you can do quite safely is pour it all over you - as long as it has a path to run. You can take a Dewar flask of it and pour it all over your hands, arms and legs...as long as you are not wearing gloves or shoes that will trap it, and thus allow it to burn-through the vapour barrier.

    2. Anonymous Coward
      Boffin

      A bit wide of the mark

      I'm reasonably sure I saw a professor pour it over his hand, and briefly cup some in his palm, giving the same explanation. I suspect that he'd have stuck his hand into it if it had been safe to do so. This was ~20 years ago when 'safe' had a slightly different meaning.

    3. This post has been deleted by its author

    4. Abremms
      Headmaster

      In Which I Fully Submerge My Hand in Liquid Nitrogen

      Popular Science did a cool (get it?) article about this some time back, complete with video, heres the link: http://www.popsci.com/diy/article/2010-08/cool-hand-theo

      he wussed out on the molten lead experiment that Mythbusters did though.

      Naturaly it ends with "ACHTUNG! Do not try this. If liquid nitrogen soaks into your clothes, you will not be protected by the Leidenfrost effect, and you can get frostbite very quickly."

    5. Anonymous Coward
      Anonymous Coward

      I didn't believe it

      Until i saw it done, it's the same effect that enables someone to gargle liquid nitrogen.

    6. PT

      Yes he's kidding

      I was sitting on the floor half under a machine once, when someone knocked over a liter beaker of liquid nitrogen. I can confirm that the "Leidenfrost effect" works very well for LN on a tiled floor, causing it to speed about and rapidly cover the entire room, but fails utterly when the LN encounters the seat of a person's pants.

      1. Old Handle
        Coat

        Pants

        Your pants ruined the effect. Had you been naked, it would probably have worked fine. Cloth is just about the worst thing in this situation, since it actually soaks up the LN2 and holds it close to your body.

        Icon: Liquid Nitrogen Work Area - Undress For Safety

    7. OrsonX
      Alert

      hand into a bucket of liquid nitrogen without harm(!)

      like AC above I have serious dobts about this also!

  8. TakeTheSkyRoad
    Joke

    Title too long...

    "The same effect can also allow a person to put their hand into a bucket of liquid nitrogen without harm."

    You first :)

    1. Anonymous Coward
      Boffin

      Mythbusters went first so I don't have to

      Actually, they dipped their fingers and hand in molten lead - perhaps an even more frightening prospect (though they didn't keep it in long). Skip forward to about the 2 minute mark.

      http://www.youtube.com/watch?v=UZio0f7fP04

    2. Gannon (J.) Dick

      A typo, I suspect

      It allows a person to leave their hand in the bucket without arm.

  9. Jacqui
    Happy

    ultrasonics

    I thought that correct frequency vibrations would create the same effect at a much lower energy cost than the 400+C required.

    I like the idea of the russian gas injection design.

  10. Kevin McMurtrie Silver badge
    FAIL

    Fish'n'Chips

    This is a great idea. We should start removing salt from the ocean immediately so it stops clogging up the Leidenfrost effect on ship hulls.

  11. Anonymous Coward
    Anonymous Coward

    Corrosion unlikely to be a problem

    in torpedoes at least, given their hoped-for lifetime once activated.

    On the other hand it would possibly provide a solution to any that fail to hit their intended target, rather than just bobbing around they could neatly degrade so that no passing children (kids snorkelling) will pick them up and think "shiny toy!" and find they've entered a sudden weight loss program.

  12. ElReg!comments!Pierre
    Facepalm

    Mwahahahaha

    "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."

    Is that supposed to be a joke? If not I have another great idea: to reduce costs and greenhouse gas emission, Australia could ship it's ore and grain using Endeavour instead.

    1. Anonymous Coward
      Anonymous Coward

      Why?

      Coal doesn't go off and the life of wheat stored under proper conditions is months or even years. Why do these freighters need to go faster?

      I think he's also forgetting the realities of the shipping market which is to reduce costs as far as possible by only ever using very old, single hulled bulkers manned by third world crews sailing under flags of convenience. Only a few years ago, one of these monsters was sinking every month and no one in power gave a toss until the MV Derbyshire vanished, but since then, nothing's changed.

  13. Ian Ferguson
    Boffin

    Safety first

    I would suggest amending this sentence:

    "The same effect can also allow a person to put their hand into a bucket of liquid nitrogen without harm"

    True, but only if they dip their hand in and out VERY QUICKLY. I would highly recommend not casually sticking your hand in a bowl of liquid nitrogen and saying to your mates "Look! This won't harm me!"

    The same trick can be done with hot oil - IF you wet your hand with water first. Dip it in quick enough and the steam will allow the oil to run off before you get burnt. Still - not to be tried at home - you need to do it VERY QUICKLY, and this is NOT enough time to grab a dropped ring from the bottom of a hot deep fat fryer!

  14. Jess--

    Corrosion?!?

    " the effect of increased heat on corrosion."

    I wouldn't worry too much about the effects of faster corrosion on a torpedo since I would think that their expected working life is measured in single digits of minutes

  15. NoneSuch Silver badge
    Meh

    Global warming?

    Nawwwww..... Lets just heat up the oceans so we can get our cheap Singapore hatchbacks quicker...

  16. Anonymous Coward
    Anonymous Coward

    Not so brilliant idea...

    Question... What happen when a ship gets on top of air bubbles? The answer, it lose it's buoyancy and sink right away! This is a true fact, and it did occur in the past.

    1. The First Dave
      Boffin

      @AC

      That only happens if the ship is above an area where the water itself _contains_ a lot of bubbles, the whole point of this piece is that you are only dealing with a boundary layer, so the density of the water is _not_ affected.

      1. Red Bren
        Pint

        The SodaStream (tm) Defence

        So you could divert the hot torpedo beneath you if you fired something fizzy in it's direction?

  17. Anonymous Coward
    Anonymous Coward

    Don't try this at home kids!

    "The same effect can also allow a person to put their hand into a bucket of liquid nitrogen without harm."

    1. IainS
      Go

      It is possible

      I have done this many times. Being a PhD chemist I had plenty of access to liquid nitrogen when in the lab and it is useful for lots of capers. I should add that I was never brave enough to hold my hand under for more than a second - but a dip in and out is perfectly fine.

  18. brainwrong
    Childcatcher

    It won't work

    Pushing a ship either through or over the sea is vastly different to watching a drop of water dance about on a spoon heated over the gas cooker (I done that as a child, fire is great!).

    If they're planning to ease the ship through the water, as ships move currently, then surely most of the resistance is due to moving the large bulk of water out of the way of the ship, and putting it back after the ship has passed. This won't change that.

    If they're planning to ride the ship over the top of the water, then surely the waves will scupper that one.

    Either way, sea salt will be deposited on the ship's hull, which won't help.

    Even if the vapour layer does insulate well, warming the ship's hull up in the first place will require insane amounts of power.

    This whole thing is just about as stupid as an article I once read in new scientist about supercavitation. The suggestion was to reduce the drag on an underwater passenger craft by going fast enough using rockets to cause deliberate cavitation at the rear of the craft. Not crashing into things like whales and other submarines would be difficult at several hundred mph, even if it did reduce drag.

    1. Red Bren
      Joke

      Maybe at launch?

      Heat the hull up in dry dock before each voyage?

  19. Dave 32
    Happy

    You go first

    The Leidenfrost effect is real. I happened to demonstrate it a few months ago while doing some plumbing work. I'd heated a leaky value to a temperature, high enough to melt solder (not the Lead-Tin variety, but the new and improved variety that has to be used on Copper pipes now, which requires even more heat to melt). I removed the value with a pair of pliers, and laid it aside. Then, in a bout of forgetfulness, I reached over and grabbed it with my bare hand. There was an incredible amount of sizzling, as the water on my fingers evaporated, but, quite surprisingly, I didn't get burned (although I did drop it pretty quickly, when the sizzling reminded me that it was probably 200 degrees C!).

    As for making torpedoes move through water faster/more easily, why don't they coat them with teflon? Or, maybe they should add a soap dispenser to the front of them to give them a coating of soap? Or, maybe add an air bubbler to the front of them? What other slippery things are there out there that could be used? Those might be cheaper than trying to heat them well above 100C.

    Dave

  20. Donn Bly
    Boffin

    Would it really work for a floating vessel?

    Not that this is my area of expertise, but wouldn't creating a gas layer under a floating vessel cause the vessel to fall into that void, eliminating its buoyancy?

  21. NoneSuch Silver badge

    Lets see...

    You want the British Navy to fill a metal tube with 650 pounds of Torpex high explosive, then heat that cylinder to 800F. Riiiiiiight...

    Please step through this door Sir. Some large lads from the Security Service would like to have a chat with you.

  22. Anonymous Coward
    Boffin

    I remain highly skeptical

    A) Superheating the hull of the ship in question would take far more power than would be saved in moving the ship.

    B) I can only imagine the workplace risks involved for the sailors on said ship

    C) Pushing a ship through the water creates a tremendous amount of pressure at the bow and along the sides of the ship. That pressure would tend to overwhelm the vapor barrier unless you made the ship's hull even hotter.

    D) How long until this starts affecting ocean surface temperatures, especially in shipping lanes?

    E) how would the heated hull work in storms/high seas? Would it tend to exaggerate listing or the risk of capsizing because the vapor barrier presents less "good" friction that keeps the ship stable?

  23. Oldfogey
    Boffin

    Stingray

    I presume Stingray used the cavitation effect to let it travel at several hundred mph? And maybe used red-hot Sting Missiles so they could go even faster, thus giving the Terrorfish no time to escape.

    "Anything can happen in the next half hour."

  24. Anonymous Coward
    Anonymous Coward

    What would happen if ...

    ... you tried this on a hydrofoil?

    1. Sandy106
      Mushroom

      Title

      Division by zero D:

  25. Mikel
    Thumb Up

    Just blow bubbles

    No need for fancy heating.

  26. John Smith 19 Gold badge
    Boffin

    Bottom line is power saved on engines > power used to create vapour layer ?

    Because this is a *dead* failure if it's not as essentially power = money.

    Water has both a high specific heat capacity and a *very* high heat of vaporisation. Getting this much water *to* boiling point is *nothing* compared to the energy needed to boil it.

    The torpedo situation might be a bit different. The benefits of speed might outweigh the cost of doing it. You might make life a bit easier by using a film heater (a metal foil pattern like a high power strain gauge) backed by an efficient insulator to dump nearly all the heat into the water.

    Strange to say it but the Russian torpedo with the rocket exhaust in the nose does seem to be the *simplest* way to do this. Anything that involves changes of state (solid->liquid->gas and vice versa) *always* involve large amounts of energy. They might be better off trying to build a porus torpedo casing and bubbling high pressure gas (at 100m the gas has to be > 10atm to escape and that rises 1atm for every 10m of water depth)

    Feasible in theory, but worthwhile IRL?

  27. Anonymous Coward
    Anonymous Coward

    Imagine the order to sailor...

    Ok Expert Seaman Bones heat up your torpedo and shoot it in the direction of the incoming weapon.

  28. Mike Flugennock
    Paris Hilton

    Sizzling speedy torpedoes?

    Congrats, El Reg; you've outdone yourselves again.

    So, hot bodies get super-slippery when wet? Who'da thunk it? Ooooh la la, baby.

    Paris, because she knows a thing or two about sizzling speedy torpedoes.

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