Wave piercers

Discussion in 'Hydrodynamics and Aerodynamics' started by ShaneK, Feb 21, 2018.

  1. TANSL
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    TANSL Senior Member

    "then" or "than" or ...?
     
  2. BlueBell
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    BlueBell Ahhhhh...

    As it is printed.
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    But,…I’m referring to ‘displacement’ hulls, thus the CB will naturally be high! This is pertinent to the ‘basic’ explanation too, without getting too in-depth for someone whom requires/needs just a basic understanding.

    As far as I can tell, he’s not looking at changing his hull, just what it all means and how boats can go faster than the prismatic hump of a typical displacement hulls. Thus, keeping it 'simple'...
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    It is ineed...just don't use an auto spell checker when trying.... :D
     
  5. Mani Kandasa
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    Mani Kandasa Junior Member

    Yes, extending the hull aft with a platform would definitely help. They have done that for many navy ships with good results - they call them stern flaps. Also, I'd check out stern wedges too - they'll help with trim reduction.
     
  6. fastsailing
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    fastsailing Junior Member

    When a submarine climbs up while remaining submerged, there is no energy needed from the sub to do that. It's the force of buoyancy doing all the work. All the potential energy for the sub comes from the potential energy of the dispaced water going down at the same time. An aircraft using lift instead of buoyancy can not do the same while climbing, as the potential energy of the air it is displacing is far less the that of the plane. An airship or a hot air balloon can do so.
    If a boat loses energy while jumping up and due to that, it must be a planing boat thereby using lift just like the plane, and not buoyancy like the sub or hot air balloon.
    Otherwise it's not climbing higher that consumes energy, but added drag. In that case it all depends on size of the wave being pierced compared to the boat, and the cross sectional area of the whole boat compared to the normal under water cross sectional area of the same boat. If the former is much bigger, the drag is substantially increased while piercing the wave due to increasing cross sectional area and wetted area. In case of a small wave piercing can be beneficial, as cross sectional area is hardly increased as attitude of the boat can remain the same. Not so if pitching heavily while climbing over the wave.
     
  7. TANSL
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    TANSL Senior Member

    Hi @fastsailing, what do you have to say against my assertion : "A submerged submarine does not consume energy due to wave formation". I will gladly study, and try to learn, any theory against.
     
  8. fastsailing
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    fastsailing Junior Member

    Nothing against it, since it's valid as long as the sub is not too close to the surface.
     
  9. BlueBell
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    BlueBell Ahhhhh...

    So long as it's more than 3 diameters below the surface.
     
  10. TANSL
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    TANSL Senior Member

    That is very true, intelligent observation ;) . From what depth do you think I am beginning to be right?
     
  11. BlueBell
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    BlueBell Ahhhhh...

    I just told you, 3X the sub diameter, minimum.
     
  12. TANSL
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    TANSL Senior Member

    I have doubts about it, it is likely that the speed of the submarine and the depth of the seabed will also influence. But, for venturing a number, without any scientific rigor, I would say that when the submarine sails more than 5 meters deep
     
  13. BlueBell
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    BlueBell Ahhhhh...

    All one needs to do is watch the surface as it passes...
     
  14. TANSL
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    TANSL Senior Member


  15. BlueBell
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    BlueBell Ahhhhh...

    If you doubt it, look it up.
    It's common knowledge, that's why I'm repeating it.

    Yes, I would agree, let the thread follow it's normal course.

    I would also agree that a minimum of 5 meters would be adequate
    depth for a 1.5 meter diameter sub.

    Cheers
     
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