Bulb interference

Discussion in 'Hydrodynamics and Aerodynamics' started by idkfa, Aug 11, 2013.

  1. idkfa
    Joined: Sep 2005
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    Location: Windward islands, Caribbean

    idkfa Senior Member

    Wondering what's the drag like due to interference between the bulb and the hull.

    ie. A hull is slower in shallower water, my guess is, due to some sort of pressure gradient the hull projects downwards, and at some min depth the increased drag is minimal.

    Well may the bulb project such a gradient upwards, towards the hull? And what's the effect on each other? Maybe a squashed bulb (lower centre of gravity) is not such a great idea?

    Or is it due to wave drag, and the bulb has none?
     
  2. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    Start your research here:
    http://en.wikipedia.org/wiki/Bulbous_bow
    http://www.dieselduck.ca/library/01 articles/bulbous_bows.htm
     
  3. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    A bulb accelerates the water flow over the bulbs surface and thus generates a low pressure region and may extend up to the waters free surface. The water passing the bow generates a high pressure region. Thus when designed correctly the objective is to cancel each other out or at the very least a reduced amplitude wave. Studies by Inui in the 60s clearly show that optimum BB shape is Fn dependent.
     
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