Additional resistance due to wave of 1.2 m height for a boat with a Froude 0.6

Discussion in 'Hydrodynamics and Aerodynamics' started by Surfer Naval Architect, Nov 11, 2020.

  1. Surfer Naval Architect
    Joined: Feb 2018
    Posts: 46
    Likes: 1, Points: 8
    Location: Amsterdam, The Netherlands

    Surfer Naval Architect Naval Architect

    Hello everyone,

    Do you have a solid approach to calculate additional resistance due to waves height of 1.5 m for a boat with a Fr of 0.6?

    Thank you very much!
     
  2. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    Interesting question. Why specify the wave height and Froude number but nothing about the size of the vessel?
     
  3. Surfer Naval Architect
    Joined: Feb 2018
    Posts: 46
    Likes: 1, Points: 8
    Location: Amsterdam, The Netherlands

    Surfer Naval Architect Naval Architect

    Hi DCockey,

    you are right, vessel size: L 38 m, B 7.5 m, draft 3.2 m
     
  4. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Way too little information to even start. Wave height is meaningless without other period, spectra, and direction information. The answer could be anything from zero to the vessel is lost. Start with a copy of Theory of Seakeeping by Korvin-Kroukovsky or Dynamics of Marine Vehicles by Bhattacharya.

    Edit to add; FWIW, normal sea margin is 20 to 25% See below
    NTNU Open: Rational calculation of sea margin https://ntnuopen.ntnu.no/ntnu-xmlui/handle/11250/2453425#:~:text=The%20sea%20margin%20is%20an,in%20environmental%20and%20deteriorative%20effects.
     

  5. rxcomposite
    Joined: Jan 2005
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    Location: Philippines

    rxcomposite Senior Member

    I usually start with Fn to make sure I am designing at minimum wave resistance. For a given Froude number, I will be guided by ratios and coefficient, including waterlines, shape of hull, entrance angle, ect. There are many published ratios and coeff like Watson and Gilfillian lines. Lindblad and Todd, Saunders, MARIN.

    Right away I can see that you are designing a very fast ship, more than the category of Naval vessels like warships. destroyer, and frigates. Your wavemaking coefficient is downhill but still high.

    Wave height is the area of operation so you start with defining the length and displacement after the Froude number.
     
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