What type of tests available/viable?

Discussion in 'Boat Design' started by YXY, Oct 23, 2013.

  1. YXY
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    YXY Junior Member

    What type of tests can I do with a towing tank, dimensions of 30m x 3m x 3m (Length x Width x Height).

    I know of a few tests like resistance, open water etc but am not sure of the standards of each test.

    Also, is it possible to do a propulsion test with such a small tank?

    Need some kind advice. :confused:
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    Depends on the type of testing, the scale and the speed of testing you wish to do.

    But yes, that size tank is acceptable, for many forms of testing, providing the model scale/speed is within the limits of the tank size.
     
  3. YXY
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    YXY Junior Member

    My maximum speed of model is 1.5m/s but I am supposed to come out with the maximum scale model that I can do and what type of testing is suitable.
    I have a budget of 500K USD (excluding the model costing) but am not sure what test I can do which can provide a decent accuracy of measurements.

    I am a mechanical engineer student with zero knowledge on hydrodynamic, I know what terms are involved in setting up tests but am uncertain on how they will affect the tests.
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    With a model speed of 1.5m/s that should be fine. Since the max for you tank depth is circa 4.0m/s.

    Max scale depends on what it is you wish to get from a model testing, and hence the accuracy and thus how it fits into the tank and not being affected by tank effects. One i mentioned above the speed, your speed of 1.5m/s is fine.

    Thus other than resistance/speed, what else will you do with the model?
     
  5. YXY
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    YXY Junior Member

    I am contemplating if I can do propulsion open water, propulsion cavitation tests and seakeeping tests as well. Will it cost more to do propulsion tests or seakeeping tests?

    My model scale is 1-2m (Maximum). What type of waterborne vessels can it represent?
    I am also unsure of the difference between Planar Motion Mechanism, Vertical Motion Mechanism, Rotating Arm Test and Yawed model test? Which one of them is feasible for such towing tank? :/
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    That means open water..i.e. NOT in a tank. So on a lake/river/estuary of some kind.

    That's done in a cavitation tunnel. But simple calculation and correct selection of prop size will tell you whether you have a problem or not.

    You can if the tank has a wave generator. You also need to check what wave spectrums it can produce.

    Of course, nothing is free :)

    But you should get a full range of resistance/seakeeping and open water test easily for the sums of money you are quoting. With a lot of spare too...If you are tied to 1 tank facility, they may over charge you. But many will be able to do this range of testing for circa $50k at a 2m model size.
     
  7. rwatson
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    rwatson Senior Member

    This is very interesting to me, being in he middle of model testing myself.

    1:5 scale seems to be the minimum recommended for scale testing.

    I investigated tank testing, and got this reply from a local testing facility
    "I have spoken with the person at AMC who runs the tank there. The cost of testing will depend on exactly what you want, but if the model that you provide is suitable, the cost will be somewhere in the range of $7,000 - $10,000 + GST"

    Dont forget, as well as a tank, you need the pumps, flow meters, measurement gantries, etc.

    I went for a self powered model, with a GPS camera - as a start. I even discussed the techniques for measuring power input on one thread

    http://www.boatdesign.net/forums/on...ls/measuring-pressure-diffferences-47511.html

    I guess the priority I have is the ability to achieve a design speed with a maximum power.
    http://schoolroad.weebly.com/rpgmodel_11.html

    The model building is a big investment in time in itself - and finding gear to go in it.

    I look forward to hearing about your project, and see how you get on
     
  8. YXY
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    YXY Junior Member

    Thanks Ad Hoc and rwatson.
    My current project revolves around building towing tank for waterborne vessels, meaning I have to build the tank with the "necessary" testing equipments but I had insufficient specifications required for the project;
    only KNOWN specifications are
    1)Dimension of tank: 30m X 3m X 3m (May need to shrink the width to 2m)
    2)Maximum model speed: 1.5m/s
    3)Budget of 500K USD
    4)No space constraints other than the tank size itself

    My main focus is more on the towing tank's testing capabilities rather than the model itself.
     
  9. rwatson
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    rwatson Senior Member


    ah, I see - and the budget is an academic exercise too.

    I guess we need to consider wave making ability for seakeeping, measuring propulsion power required at different speeds (maybe at varying inclination angles for sailing vessels), at different displacements ( fully loaded, ballast only ).

    Could we add aerodynamic capabilities testing ( simulating storm behaviour ) with fans etc. Stability testing with load conditions and wind conditions,

    Pumping water is expensive and complex. Maybe use a reservoir like a couple of water tanks, to provide a head of water big enough for say an hours testing. Either that or a circular return system with pumps.

    Some good info at
    http://en.wikipedia.org/wiki/Ship_model_basin
     
  10. YXY
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    YXY Junior Member

    There are plans of building a towing tank facility with the budget of 500K but currently my team needs to know more on hydrodynamics knowledge relating to that, the various testing options available in the market and reliable suppliers of such testing equipments.

    I guess the few testing options we are limited to are only resistance tests, perhap simple propulsion and seakeeping tests. Thanks for providing your insights on other sorts of tests.
     
  11. Ad Hoc
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    Ad Hoc Naval Architect

    Then you should ideally aim to be accepted as an ITTC Towing Tank Testing facility, to demonstrate quality.

    For eqpt, try the Wolfson Unit at Southampton University, they specialise in such eqpt like dynamometers:
    http://www.wumtia.soton.ac.uk/
     
  12. YXY
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    YXY Junior Member

    Hmm...the international towing tank conference website changed into a China webpage.
    http://ittc.sname.org/
    Any idea where can I get the standards (latest) from?
     

  13. Ad Hoc
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    Ad Hoc Naval Architect

    I get the same. It appears their website is being upgraded.
     
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