Ansys Aqwa Strange Problem :confused:

Discussion in 'Software' started by digijtal, Mar 27, 2012.

  1. digijtal
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    digijtal Junior Member

    Hi all! I am also using ansys AQWA to model a simple vertical cylindrical pile in regular waves in order to extract the morison drag forces on the pile. The results seem to make sense, howver, when I change the water level, the results do not change. This is strange since the results are very dependant on the water level, and at the extreme if the water level is below the whole structure the results should be 0 force all the time. But this is not the case. What could be the problem here?
    Thanks in advance!
     
  2. CWTeebs
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    CWTeebs AnomalyGenerator

    From AQWA TSB:

    You're going to need to find and use their workaround.

    -CWTeebs
     
  3. digijtal
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    digijtal Junior Member

    sorry... I'm even more confused now!!:p
     
  4. CWTeebs
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    CWTeebs AnomalyGenerator

    It's okay, the problem is a bug in AQWA that doesn't get corrected until version 14.5, so, until later this year you will not be able to use STUB (Slender TUBe) elements and get the proper wave forces (e.g. Froude+Krylov). So, try chaning the type of tube element you are using, and see if that works. Alternatively you can post your workspace and if I find time I might be able to look at it (but I'm pretty busy lately).

    - CWTeebs
     
  5. CWTeebs
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    CWTeebs AnomalyGenerator

    Here's the actual error report from the ANSYS website.
     

    Attached Files:

  6. digijtal
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    digijtal Junior Member

    wow

    Wow thats surpising!! however i'm not sure if I am using stub elements. I have modelled the pile on ansys design modeller by creating two points and drawing a line between them. After that I selected a tube cross section. So I guess I am working with tube elements not stub elements. What do you think? How can I double check what kind of element I am using?
    Thanks a lot!
    Alan
     
  7. CWTeebs
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    CWTeebs AnomalyGenerator

    Find the generated .dat file that is created by ansys workbench. This is typically located in something like:

    SimulationDirectory\dp0\AQW\AQW\AQ\Analysis\Analysis.dat

    Then search for "TUB" in the job file, I believe you'll either find the word "TUBE" or "STUB" depending on what elements you're using. Be very careful doing this, you can corrupt your Workbench workspace. I suggest you copy the .dat file to the "User Files" directory, which is typically found at :

    SimulationDirectory\user_filse


    Otherwise I'd need to personally inspect your project, it seems there may be other factors going on that's screwing things up. I've got a jacket launch tutorial somewhere, IIRC that's similar to what you're simulating.

    - CWTeebs
     
  8. digijtal
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    digijtal Junior Member

    I opened the .dat file and it says I've got Tube elements. The following is what's in the .dat file (part of it).

    How do you suggest I go about this problem?
    Thanks

    ********************************************************************************
    *********************************** DECK 2 ************************************
    ********************************************************************************
    ********************************************************************************
    ELM1
    *This structure is not the last one in an interacting group
    SEAG ( 81, 51, 0., 0., 0., 0.)
    ZLWL ( 0.75)
    1FIXD
    * Group ID 36 is body named Line Body
    1TUBE 36(1)(90000)(90001)(90000)(90000)
    END
     
  9. CWTeebs
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    CWTeebs AnomalyGenerator

    Hmm, I'm not immediately sure from the bit of information you've provided how the Froude-Krylov wave forces could possibly remain invariant for that element.
     
  10. digijtal
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    digijtal Junior Member

    May I send you the project archive maybe you can have a look if you've got some time on your hands?
     
  11. CWTeebs
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    CWTeebs AnomalyGenerator

    Sure, post your workspace and I'll take a look at it. I warn you, I am pretty busy with some projects but I might have some time this weekend.

    - CWTeebs
     
  12. digijtal
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    digijtal Junior Member

    Great! How can I post my workspace? this forum doesnt allow me to upload an aqwa archive
    cheers
     
  13. digijtal
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    digijtal Junior Member

    Ok I managed to upload as zip. Thanks in advance.
    -Digijtal
     

    Attached Files:

  14. iD_Dre
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    iD_Dre New Member

    Strangely I've got the same problem. Did you find a solution?
     

  15. digijtal
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    digijtal Junior Member

    No, I am still looking into it. CWTeebs suggested it is a bug from the same software, but it is awkward that they did not fix this simple analysis procedure. :/
     
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