Wave Making Resistance

Discussion in 'Hydrodynamics and Aerodynamics' started by AAbercrombie, Oct 24, 2016.

  1. AAbercrombie
    Joined: Oct 2016
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    AAbercrombie New Member

    I am a Mechanical Engineering student and I have just started a project which requires me to look at friction on rowing boats and how that varies with the boat's width.

    I have done a bit of background reading, and due to the very thin design of rowing boats the largest factor of drag seems to be 'wave making resistance'. As I have no history of looking at this sort of thing, are there any good resources you can recommend that would help me investigate the relationship between drag and hull breadth.

    Many thanks,
    Alfie
     
  2. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    Actually, you seem to have mixed up the types of resistance at play and hence got your conclusion wrong.
    The biggest part of resistance on very slender hulls is made of friction resistance, which is mostly related to the amount of wetted surface and its roughness.

    Considering that, I would suggest you to dedicate some time to studying elements of ship resistance and propulsion before proceeding further into your research. Some good starting points could be:
    - "Basic Ship Theory" by Tupper & Rawson
    - "Principles of Yacht Design" by Larsson and Eliasson
    - "Aero-hydrodynamics and the Performance of Sailing Yachts" by Fossati

    Cheers
     
  3. Petros
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    Petros Senior Member

    there are three elements of drag of hulls in water, skin friction, wave making, and form drag. A square box has more form drag than a long slender hull of the same size. but the long slender hull as more surface area, so more skin friction. the drag of wave making goes down with length, but again the longer and smoother the shape, the more skin area. So it is a trade off between length, shape, and surface area. Usually low speed boats will not benefit from a lot of length because the skin friction goes up. OTOH, a fast hull must have the length so you do not get a lot of wave drag, which would be higher than the skin drag.

    the text books listed above should explain it for you.

    Another one is "The Nature of Boats" by Gurr. it starts with basics and is a good overveiw with enough techical information to get you started.
     
  4. mydauphin
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    mydauphin Senior Member

    Absolutely true above....and in general the less wake, the more efficient it is, which is what he may be stating as wave making resistance.
     
  5. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Don't know... If one says that "the largest factor of drag seems to be wave-making resistance", my first guess is that he meant exactly what he said.
    If you put the word "wake" instead of "wave making", you get a tautology. :)
     
  6. philSweet
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    philSweet Senior Member

    Is this a senior design project? Is the theoretical math a crucial part of what you are doing, or would your goals be better served with practical engineering data and some good nondimentionalized charts?

    In the PDF below, notice the way beam appears in the nondimensionalized resistance data on page 15.

    http://www.maths.adelaide.edu.au/yvonne.stokes/Tuck/pdfiles/t8701.pdf
     

  7. tspeer
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    tspeer Senior Member

    I think you should download Leo Lazauskas' program, Michlet, and experiment with different hull shapes and sizes. It is ideal for the slender hulls of rowing shells. Leo used to have a paper on the web on low drag rowing shells, but I don't think the site is active any more.

    This paper on The Physics of Rowing may be helpful.

    You may also want to check out this bibliography.
     
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