Flotilla 6.2 Released

Discussion in 'Software' started by Leo Lazauskas, Apr 8, 2014.

  1. Leo Lazauskas
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    Leo Lazauskas Senior Member

    This free (64-bit Windows) version of Flotilla is an enhanced thin-ship
    code that estimates the total resistance, squat and wave patterns of
    monohulls.

    Version 6.2 fixes some minor bugs described in the thread for the
    previous version. Other changes include better estimates of wave
    patterns very close to the hull (e.g. within one beam), some additional
    output (e.g. hydrostatics and metacentric heights) and several new
    examples.

    Latest features, tips, and updated reports can be found at:
    www.cyberiad.net/flotilla/flotilla.htm
    and
    www.cyberiad.net/flotilla/flotilla_mono.htm

    INSTRUCTIONS
    To install the program, uncompress the zip file into a suitable
    directory. To uninstall, just delete the entire sub-directory.

    The manual is in the "doc" sub-directory.
     

    Attached Files:

  2. Remmlinger
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    Remmlinger engineer

    Pure enjoyment!

    Leo, may be you are willing to unveil the source of the spline offsets for the Delft 372. van't Veer's thesis shows only a rough sketch. One would need a lot of creativity to turn this into an offset-table.
    Thanks for your gift to the world
    Uli
     
  3. Leo Lazauskas
    Joined: Jan 2002
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    Leo Lazauskas Senior Member

    Uli:
    I took the lines from very much enlarged graphics in some of the
    papers I referenced. They are not deadly accurate, but they are
    good enough for comparisons. I stress in the manual that the users
    primary task is to capture as well as they can the displacement,
    wetted area, waterline length etc. I suggest that they should be
    within about 1% of the published values to get reasonable results.

    Flotilla can produce a table of offsets from the spline files, much
    like Michlet does. I left that out of the public release, but I
    might include that capability later.

    Attached are a spline file for Flotilla and a table of offsets.
    I will add these to the catamaran version as an example. There are
    many recent experimental results and CFD calculations I can use as
    comparisons, so it is an important test case.

    Note the "stepped" appearance of the lines near the stern. These are
    ugly, but they have a negligible effect on calculations of resistance,
    squat and wave elevations. Flotilla (and Michlet) use clever
    integrations which smooth out those steps and small bumps. Those
    steps in the lines would be very bad news for codes that use
    derivatives of hull offsets, for example in surface pressure
    calculations, or in the original Michell's integral which was
    presented in terms of hull slopes. (For those who care: a "simple"
    integration by parts was used to express the various equations
    in terms of actual offsets.)

    If you can produce smoother lines, then I'll be happy to use them
    instead of my rough effort.

    Leo.
     

    Attached Files:

  4. Remmlinger
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    Remmlinger engineer

    the file _offsets.zip was already included in the flotilla_mono_....._globals_offsets.flo folder.
    I converted this file into an excel-file und created a diagram for each station. These sections are very smooth, without any "stepped" appearance. That was the reason why I asked in my previous post for the source of your linesplan, I was impressed by the quality. You seemed to be a good Loftsman!

    It is strange that these good splines result in such stepped lines in the on-screen display.
     

    Attached Files:

  5. Leo Lazauskas
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    Leo Lazauskas Senior Member

    It depends on the number of stations and waterlines that you choose at the
    top of the offsets.flo file. Some combinations will look smooth, others will give those ugly steps.
     
  6. Remmlinger
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    Remmlinger engineer

    irritating....
    Is it just a display-issue and the internal calculation is using the correct spline, or does it actually affect the basic curve of sectional areas?
     
  7. Leo Lazauskas
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    Leo Lazauskas Senior Member

    The program first fits splines through each section, and then fits waterline
    splines through interpolated points on the section splines. It's just an
    inadequacy of using cubic splines that pass exactly through the supplied
    points. I guess that's why NURBS and other splines are used in actual hull
    design programs (which Flotilla is not!).

    As I said, it makes very little difference in calculations, as long as you have
    captured the displacement, wetted area, and BWL reasonably accurately.

    When Delftship gets back online properly, I will see if they will modify the
    Michlet output option to include a couple of lines that will make creating
    offsets easier for some users. Freeship has made a start to that effect, but I
    haven't checked if they work properly yet. I know I joke about "Russian
    brides", but every time I visit Freeship sites or Ukrainian marine sites I end
    up getting spam and weird requests.

    Added later: Of course, it is unreasonable to expect simple cubic splines to
    approximate rectangular sections very well. That can cause some unusual
    oscillations in the lines.
     
  8. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Has anyone tried Flotilla with Windows 8.1?
    I just got an email from someone who got a "compatibility error" on a laptop running 8.1.
    Any advice?
     
  9. johnhazel
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    Location: Michigan

    johnhazel Senior Member

    Toshiba P75-A7200 laptop with updates to Windows 8.1 (14APR14)
    i7-4700 CPU, 8Gig RAM, SSD

    Batch file "monoexwp" ran with no errors 0.31718E+02 seconds (wall clock).

    Michlet does run oddly in windows 8. The window redraws slowly (e.g. control-V to show sections) and when a calculate drag command (control-R then t) is executed there is no Rt graph, only Rw and Rv but the graph box is scaled for the Rt line. If you issue a "c" instead of a "t" in the second step the total resistance graph is visible.

    Windows 8.0 and 8.1 really, really, suck. I am so frustrated with it that I tried to install Windows 7 on this laptop and was ready to pay the 170 us dollars to do it. Unfortunately this laptop did not cooperate.
     
  10. johnhazel
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    Location: Michigan

    johnhazel Senior Member

    Just some more runs of "monoexwp"

    from the test of flotilla 6.1:

    0.51780E+02 seconds (wall clock)
    i3-2310M 2.1Ghz 4Gb Windows 7 Home Premium
    Windows experience index Processor: 6.4, Memory 7.3

    and from another run on my desktop computer:

    0.64254E+02 seconds (wall clock).
    AMD A10-5800k (3.8Ghz - 4.2Ghz turbo), 16Gb 1600Mhz RAM, ssd
    Windows experience index 7.3 processor and also 7.3 for memory


    Seems almost any reasonable Intel processor beats AMD in single thread math intensive computing. (but watch out and dont get quagmired in that damn Windows 8!)
     
  11. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Very much appreciated, John.
    I agree that 8.1 is a beast, but maybe the graphics problems in Michlet are unique to your laptop.

    Leo.
     
  12. Remmlinger
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    Remmlinger engineer

    Delft 372

    I modeled the hull in Rhino and used the smoothing function to get sections with a continuous curvature. Unfortunately this does not work for the waterlines, they are still slightly wavy. The result is the attached IGES-file. For those people without Rhino I have attached the corresponding file for Delftship. Offset-files for Michlet and Flotilla (.flo is not a valid extension in this forum) are also added.
    Hope you have fun
    Uli
     

    Attached Files:

    1 person likes this.
  13. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Great work, Uli.
    Which version of Delftship did you use? I couldn't load it into version 5.06.186.
     
  14. Remmlinger
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    Remmlinger engineer

    The free version 6.27.259
    The updates come automatically
     

  15. Remmlinger
    Joined: Jan 2011
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    Location: Germany

    Remmlinger engineer

    Delft 372

    I compared the residuary resistance coefficient to the predicted wave resistance. There is a 33% difference at Fn=0.45.
    Did I make a mistake?
    Uli
     

    Attached Files:

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