My nephew asked me a Hydrodynamics question about sub-surface hull speed.

Discussion in 'Hydrodynamics and Aerodynamics' started by mydauphin, Jul 26, 2016.

  1. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    He says that tear drop submarine hull running just below the surface is not restricted by the same concept of hull speed vs hull length like a surface displacement boat. I keep thinking it is far easier to plane over the water than drive a hull with all that surface resistance all around it. This whole conversation started because he is making a RC model of the Jules Verne/Disney 20,000 League under the Sea - Nautilus submarine, which if you remember would do a high-speed torpedo like pass to attack ships. Some torpedos go pretty fast. Any thoughts?
  2. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    If the hull is within 3 diameters of the surface or bottom boundary (including large density boundaries), there is a wake and/or suction effect caused by the boundary reflection and flow blockage. It is still present at greater distances, but generally negligible (a distance squared effect). Google "submerged body wake" for info. Edit: also see "dead water".
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