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Mr. SHIJU JOHN

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Posts posted by Mr. SHIJU JOHN

  2. Posted · Report reply

    I am posting the replies I got and my understanding for general benefit:

     

    The most important thing is to resolve the pressure gradients and the stretching will help to place larger amount of panels close to the leading and trailing edges

    where we expect high pressure gradients. The best way to evaluate the required mesh size is to run several sizes and observe the changes in the pressure.

     

    Michal Orych

     

     

    Hi Michal,

     
    Thankyou. As I understand from your advise and the manuals, the best way to do it should be:
     
    1. To apply stretch function 5 (hyperbolic with both ends specified) so that there are larger amount of panels close to LE and TE.
    2. For a fixed number of panels, vary the starting panel size and end panel size (df, lf) and observe the changes in pressure. Choose an optimum combination for best results.

  7. Posted · Report reply

    Hi,

     

    When you run XPAN for a deep submerged submarine, the resistance should be zero. (D'Alembert's paradox)

    What is this basic resistance coeff that XPAN gives for deep submerged submarine? Is it the pressure coeff or any residual error?

     

    Basic model resistance coefficient (force/0.5*density*Sref*U*U)

    CXPI   -0.000833

    CYPI   0

    CZPI    0.0022034

     

    Pls explain.

    Regards,

    Shiju John

  9. Posted · Report reply

    I have modified the submarine offset file off_sub for my design.
    I am trying to run xpan it through SHIPFLOW GUI using this offset.
     
    First, I imported the offset file. The 3D view shows my sub as ok.
    But, on running i am getting an error message as follows:
     
    ***ERROR (401) - FILE COULD NOT BE OPENED
    SYSTEM DEPENDENT ERROR STATUS NUMBER = 29
    LOGICAL UNIT = 4
    FILENAME = ../off_sub
    xferrm: Error
     
     
    Pls help.
    I am attaching the fdb file for reference.trial1.fdb

     

  11. Posted · Report reply

    Thankyou Maasch,

     
    "3. Most likely not possible! As far as I know shipflow does not offer such code."
     
    I have seen a couple of published papers in which maneuvering of surface ships were carried out using SHIPFLOW. (linear derivatives of velocity and accelerations)
    So I hope there should be a method to extend it to submarines.
     
    "5. In the ExamplesManual which comes with the shipflow software you can find some more detailed descriptions with regard to submarines, such as offset files and command files. If you don't have the ExamplesManual available I can surely upload it here."
     
    Please upload the examples file. It would be very helpful.
     
    And finally, ya it seems very challenging. We also have PARAMARINE here which is a lot easier for submarines.
    But I hope I can crack it with SHIPFLOW as well.
     
    Thanks a lot for your encouraging reply.
    Shiju John
    Scientist, DRDO
    M.Tech Scholar, IIT Madras

  12. Posted · Report reply

    I am trying to design a submarine as part of my Masters project.

     

    My Prof. has suggested me to try using SHIPFLOW.

     

    Basically, I would like to use SHIPFLOW for the following:

     

    1. Resistance estimation of Submarine in deep submerged condition.

    2. Self Propulsion Tests (using Pump-Jet propulsor) in deep submerged condition.

    3. Maneuverability (Straight line tests and Rotating Arm) of Submarine

     

    Please advice if its possible to do such simulations in SHIPFLOW. Is it possible to switch off the free surface effects?

    Is there a separate module for maneuvering?

     

    Regards,

    Shiju John

     

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