Extrapolation of towing tank results

Discussion in 'Hydrodynamics and Aerodynamics' started by Remmlinger, Oct 15, 2012.

  1. Remmlinger
    Joined: Jan 2011
    Posts: 242
    Likes: 20, Points: 18, Legacy Rep: 172
    Location: Germany

    Remmlinger engineer

    We discussed in this forum several times the usage of towing tank results for the full scale performance prediction. I questioned the applicability of the ITTC 57 friction line and Leo shared a paper by the ITTC, showing the large scatter of resistance results between different towing tank facilities (perhaps caused by scale effects). I found a comprehensive paper on this subject that might be of interest to some of you.

    http://www.marin.nl/upload_mm/d/7/f...0_2008-RINA-MarineCFD-RavenPloegStarkeEca.pdf

    Have fun
    Uli
     
  2. Mikko Brummer
    Joined: May 2006
    Posts: 514
    Likes: 50, Points: 28, Legacy Rep: 258
    Location: Finland

    Mikko Brummer Senior Member

    Great paper, thank you.
     
  3. Leo Lazauskas
    Joined: Jan 2002
    Posts: 2,696
    Likes: 148, Points: 63, Legacy Rep: 2229
    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    Thanks Uli.
    They add weight to one of Grigson's observations about several large ships
    built in the 1980-1990s being under-powered by about 5%. (Raven et al
    show that resistance could be under-estimated by about 7%.)

    Grigson put the blame for the under-prediction on the ITTC line and the form
    factors back in about 1996, and he fought for a long time to have the issue
    of a new standard friction line opened up for debate. He died a few years
    ago and the issue is still not resolved.
    Hydrodynamics sometimes moves through a very viscous medium! :)
     
  4. BMcF
    Joined: Mar 2007
    Posts: 1,001
    Likes: 51, Points: 48, Legacy Rep: 361
    Location: Maryland

    BMcF Senior Member

    *groan*


    Thanks for the paper, Uli.
     
  5. Remmlinger
    Joined: Jan 2011
    Posts: 242
    Likes: 20, Points: 18, Legacy Rep: 172
    Location: Germany

    Remmlinger engineer

    The Reynolds number of this process is too low > no boundary layer exists > the entire global mass has to be moved, not just the neighborhood > that takes generations.
    If anything can make the learning process more turbulent, then it's the internet.
     
  6. Ad Hoc
    Joined: Oct 2008
    Posts: 6,609
    Likes: 617, Points: 113, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Thanks Uli, I'll have a read.

    I think this is being "serialised" in the Maritime Reporter magazine. As MARIN have written a few short article on this very subject recently.
     
  7. J Feenstra
    Joined: Jan 2012
    Posts: 79
    Likes: 6, Points: 0, Legacy Rep: 100
    Location: The Netherlands

    J Feenstra Junior Member


    That's why MARIN has constructed a new tank, that operates under a lower atmospheric pressure, therefore reducing viscosity.
     

  8. DCockey
    Joined: Oct 2009
    Posts: 4,703
    Likes: 315, Points: 83, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Changing atmospheric pressure has negligable effect on the viscosity of the water. It does have a major effect on cavitation though which is not related to viscosity.

    Page on the new MARIN tank: http://www.marin.nl/web/Facilities-Tools/Basins/Depressurised-Wave-Basin.htm
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.