Bonjean curve formula

Discussion in 'Software' started by Dr34m3r, Jun 15, 2016.

  1. Dr34m3r
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    Dr34m3r Senior Member

    any one can tell the formula for calculating the moment of area above BL , which is also included in bonjean curve table beside the area of each section ?


    basically want to know the formula being used to calculate the MOM BL coloumn,

    [​IMG]
     
  2. NavalSArtichoke
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    NavalSArtichoke Senior Member

    Any standard text on naval architecture should show you the procedure. Some of these texts can even be found online.
     
  3. Dr34m3r
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    Dr34m3r Senior Member

    i did not find the formula exactly , so i ask here.
     
  4. TANSL
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    TANSL Senior Member

    I'm not sure what "MOM BL" means but in general, hydrostatic values are not calculated by a formula. Overall it is a calculation procedure in which they are involved several formulas. With certain values obtained by this method, we then calculate some coefficients for which, indeed, one can talk of a formula.
     
  5. NavalSArtichoke
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    NavalSArtichoke Senior Member

    I think "MOM BL" indicates that the moment of area is referred to the baseline.
     
  6. NavalSArtichoke
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    NavalSArtichoke Senior Member

    Well, there are a couple of ways it can be done. If you have a table of offsets for each station, you can set up a Simpson's integration to obtain the area and first moment of area about the BL. If you have only a table of Bonjean areas, you can still set up a Simpson's integration using that data. In both cases, it's best if the offsets or the areas are tabulated at regular intervals; this makes the Simpson's integration much easier.

    That's also why I recommended that you find a suitable textbook for naval architecture. These calculation procedures are often well-illustrated in such texts to show you how to set up your own calculation.

    Like TANSL said, it's not a formula, it's a procedure which uses a tabular form.
     
  7. b1ck0
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    b1ck0 Senior Member

    Things become much easier once you know what you want to calculate ...
     
  8. jehardiman
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    jehardiman Senior Member

    Formula = Summation from 0 to x of (B|x+B|x+dx)/2*dx*(x+dx/2)
     
  9. Dr34m3r
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    Dr34m3r Senior Member

    @Jehardiman:

    for the third value , T =1
    so you mean,
    B = 1 m , x = 2.9 , dx = 0.5 ?
     

  10. jehardiman
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    jehardiman Senior Member

    If you want it in terms of that table you posted

    T is the vertical distance from the baseline
    B would be the beam of the body at T.

    B is not necessarily continuous over T

    Area X at T would be
    Summation from 0 to T of (B|T + B|T+dT)/2 * dT

    MOM BL at T would be
    Summation from 0 to T of (B|T + B|T+dT)/2 * dT * (T + dT/2)
     
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