Michlet 9.20 Released

Discussion in 'Software' started by Leo Lazauskas, Apr 28, 2011.

  1. Remmlinger
    Joined: Jan 2011
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    Location: Germany

    Remmlinger engineer

    Thank you for the helpful links.
    It seems that mentioning CFD is like touching your red button, but I guess I get your point.
    I am not very keen to spend many months to get a CFD software running, only to find out that my computer is too slow and the results are unreliable. I wish there were an alternative.
    For mathematicians the world is easy. They develop a calculation method and then they look for an application that suits this method. No doubt the applause for Michlet is well deserved, it is the ideal tool for thin ships.
    In contrast engineers are first confronted with a problem and this starts the search for a suitable tool. This is my situation. All VPPs that I know are lacking a realistic estimate of the additional wave resistance caused by the keel. Adding a lift producing keel will surely change the wave resistance of the yacht compared to the bare hull (you mentioned the AMECRC paper by Binns). To develop an estimate for this additional drag one needs the drag force of a yacht with and without keel at heel and leeway. The yacht in this case is not a thin ship. Which tool would you use? I tried to solve it experimentally in a circulating water channel, but the experimental error was larger than the drag differences I was looking for.
    Uli
     
  2. Leo Lazauskas
    Joined: Jan 2002
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    Leo Lazauskas Senior Member

    I have no problem with CFD if it is the appropriate tool for the job. And I do like the work of Prof. Fred Stern and his group because they are very much committed to proper validation and verification.

    Openfoam requires a lot of programming, so it is not an easy CFD code for beginners. I do like the fact that it is open source though.

    I'm not sure what you could try instead of CFD. Potential codes using Neumann-Kelvin type boundary conditions should be better than thin-ship theory, but then there are still problems with consistency. Satisfying one boundary condition better, but still linearising another is not consistent and will improve estimates in many cases, but not in many others. Fully non-linear codes (like RAPID, Shipflow etc) are not guaranteed to find a solution in all cases, especially for vessels with large transoms. Some just use linear theory when they fail, which is not much better than using thin-ship theory in many cases.

    My late colleague Ernie Tuck used to say that ship hydrodynamics was about 50 years behind aerodynamics. I don't think that situation has changed much in the last 15 years.

    Good luck!
    Leo.
     
  3. thudpucker
    Joined: Jul 2007
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    Location: Al.

    thudpucker Senior Member

    Me (the software inept) downloaded Micolet from the link in the first post.
    I thought since it was free, I'd try my hand at drawing a boat. I still cannot get it to work.

    Suddenly I feel like I'm trying to do Neurosurgery from a DIY sketch.
    After I downloaded it, what was I supposed to do next?
    Who knows what I'm supposed to do now?
     
  4. FMS
    Joined: Jul 2011
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    Location: united states

    FMS Senior Member

  5. thudpucker
    Joined: Jul 2007
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    Location: Al.

    thudpucker Senior Member

    Thanks FMS, I did not realize it was an eval program. I'll delete it. I was looking for an easy boat drawing program.
     
  6. patrik111
    Joined: Sep 2003
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    Location: Sweden

    patrik111 Junior Member

    Running Michlet under windows 7 64

    Hello,

    Is there a way to run Michlet and Godzilla under 64 bit windows 7?
    (or any other, linux?, 64 bit OS)

    I have tried compatibility mode and running as administrator, but with little success. (the program runs, but quite is not very responsive to keystrokes)



    Kind regards

    Patrik Elfving
     
  7. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    Michlet/GODZILLA works fine under Windows 7 on several machines I have tried. I didn't need to use "compatibility mode".

    It is not available for other OS at present.

    Good luck!
    Leo.
     
  8. The Scuttlebut
    Joined: Sep 2011
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    Location: New York

    The Scuttlebut Junior Member

    Low Froude Number resistance question

    Hi all,

    I've been using Michlet and trying to compare it to other methods we use for resistance estimation, to see if we can add it to our stable of methods. I am finding that at froude numbers from 0.05 to around 0.3, there is a sharp increase in resistance predicted from Michlet, then a plateau. This doesn't appear in the other methods (Holtrop, Feng-Leibman, etc.). I compared it to my thesis model test data for a long slender hull (268m long 25m beam, 9m draft) and found the same issue with real data (full scale using the ITTC 57 method). Anyone have any insight as to this? On displacement and semi-planing/semi-displacement hulls I see the same character to the resistance curve.

    Attached find a graph of the comparison of my thesis data to various methods.
     

    Attached Files:

  9. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Have you run the examples which are included in the download? Do the results from them look reasonable?
     
  10. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    Sorry, but I can't help much without seeing the input file.
    Does this hull have a large transom stern?

    I haven't seen that sort of behaviour except for small models of hulls with large transom sterns.
    Or when people have not produced a correct input file of offsets (e.g. putting the ship back to front, or upside down).

    Is the pointy end at the front in the offset section? :)

    Good luck!
    Leo.
     
  11. The Scuttlebut
    Joined: Sep 2011
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    Location: New York

    The Scuttlebut Junior Member

    The lines plan in Michlet looks right.

    The boats in question do have large transom sterns. I would love to provide the input file, but although it was my thesis, I am unsure of my ability to share the hullform due to the people who created it. I am assuming from your question that the transom stern could be the reason for the hump in resistance?

    I ran another design we have with a small transom and got better results, I assumed at the time it was because of the displacement hull type, as opposed to the semi-displacement hulls I am currently working on.

    Any ideas how to counter act this or is it just a limitation of the theory used in the program?

    Thanks.
     
  12. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    It is a limitation of the thin-ship theory implemented in Michlet.
    Flotilla might give better results, but I'd need the offsets to run that.

    Experiments with large transoms at low Froude numbers can also be very prone to uncertainty.
    This is something that the ITTC is trying to address because Prohaska's method for determining
    form factors requires accurate experimental values of resistance at low Fr,
    but this is exactly where the greatest experimental uncertainties occur.

    On the other hand, judging by your graph, Michlet gives reasonable results for Fr > 0.3.
    Should anyone be seriously concerned with the performance of ships with large transoms at low Fr? :)

    Good luck!
    Leo.
     
    1 person likes this.
  13. patrik111
    Joined: Sep 2003
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    patrik111 Junior Member

    Hi Leo,

    Donation made!

    I have now tried this on several machines and I am getting the same symptoms. i.e. the programs runs but extremely slowly.

    Today I have a vista sp2 32 bit computer, but this is going to be a cnc router controller in a, hopefully, not to distant future. If there is one piece of software I would like to transfer to more up to date computers, it is michlet/godzilla. I have been a fan since I discovered it around v8,07. But now I am having no success as of late.

    Would you have any idea on what might be causing this?
    Anyone else have had simalar issues ?
    is possible to re-compile the program under win7 64?

    Kind regards

    Patrik Elfving


    Kind regards
    Patrik Elfving
     
  14. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    Thanks Patrick!

    I tried Michlet on two different i7 computers using the Godzilla example input file gpenta58.mlt

    This should be a very severe test for any machine because it tries to "optimise" the dimensions, shapes and placement of 5 independent hulls.

    It took 30 seconds to evaluate 4706 combinations and I got identical results under Windows 7 and XP.

    Could someone else please try the same input file for comparison?

    Good luck,
    Leo.
     

  15. aki123
    Joined: Dec 2011
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    Location: Austria

    aki123 New Member

    Michlet and Linux

    First: Michlet is great! Thanks for sharing!

    For running Michlet in Linux (Ubuntu) do the following:

    .) Install 'wine' - the windows emulator
    .) Extract the mlt920.zip to some directory
    .) Run Michlet via doubleclick or terminal command ./mlt920.exe

    So Michlet is running in wine. It is running fine unless you try to move the window. Then wine crashes. So keep the window positioned, where it pops up.

    Scripting Michlet:
    I tried to feed Michlet via a command-file that contains all the keyboard operations I need to get the desired analysis output: ./mlt920.exe < input.txt
    With input.txt containing the letters for controlling Michlet. Unfortunately this seems not to work. I will continue on this.

    All the best
    Aki
     
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