Boundary Layer Texture?

Discussion in 'Boat Design' started by Bill PKS, Apr 20, 2010.

  1. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    You could also think of the stern "surfing" the wave created at the bow, and thereby getting a bit of a free "ride".

    Without mathematics you are stuck with fairly sloppy descriptions like that from me. I hope someone else here can describe it better than I can.

    Good luck!
    Leo.
     

  2. ancient kayaker
    Joined: Aug 2006
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    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    Random thoughts on air injection:

    I assume it works by modifying the effective viscosity of the water. I'd expect it to be less effective on a slow moving displacement hull because the bubbles take the shortest route to the surface. If a displacement hull is moving very quickly then wave effect has more effect than viscosity so there is little benefit to be had.

    It would be reasonable to expect that a planing boat would do better. However, designers of really fast hydroplanes might not want it - I suspect they employ suction to achieve gees on tight turns and the last thing they want is air under the hull.

    Air injection is not the same as the introduction of air to aid "unsticking" which requires larger quantities of air not little bubbles. It is also not related to the surface texture of a golf ball which, I understand, creates lift from the ball's spin and makes the "slice" predictable rather than random for improved range and accuracy.

    Those are random thoughts which seem reasonable but may not be correct.

    Small bubbles are going to persist longer than larger ones, which should be helpful. Rather than experimenting with direct air injection, I wonder if a foam can be used which is first created within the boat and then injected under it. An additive would probably help which would be environmentally undesirable, but perhaps acceptable in the context of a speed record or a military vessel at combat speed.
     
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