wake distribution

Discussion in 'Software' started by pavel915, Mar 22, 2008.

  1. pavel915
    Joined: Nov 2006
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    pavel915 Senior Member

    There are quite some software for estimating average wake in the propeller plane. I wonder if any software is available to estimate the wake distribution in the propeller plane as well.

    Can anyone suggest me if Michlet can do this estimation?
     
  2. Leo Lazauskas
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    Leo Lazauskas Senior Member

    No, Michlet doesn't include near-field calculations. I have other code such as SWPE and Flotilla to do those calculations, but they are not free.

    All the best,
    Leo.
     
  3. pavel915
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    pavel915 Senior Member

    thanx Leo for your fast reply.
    actually i need to calculate the effect of a long transom stern on wake; can swpe or Flotilla can calculate the speed of advance ?
    How can i buy flotilla and swpe? how much they cost?

    Regards!
     
  4. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Flotilla and SWPE can calculate the fluid velocity vectors at the prop plane, but they don't calculate the speed of advance. That is a propeller issue.

    SWPE enquires can be sent to david.scullen@adelaide.edu.au

    Flotilla is way out of your price range. I might sell it one day when I don't make as much out of contract work as I do now. I'd have to finish a manual for other users and that sort of work bores me to tears.

    The effect of transom sterns on wakes is a difficult problem and I'm doing a bit on that in my PhD. Michlet might help you a bit, but you should remember that large transom sterns can violate the thin-ship assumption. It really depends on the way the hollow behind the transom is modelled.

    Good luck!
    Leo.
     
  5. pavel915
    Joined: Nov 2006
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    pavel915 Senior Member

    Thanx Leo; for you detailed answer.
    If i can calculate the effect of the transom stern on the hull efficeincy that will be enough for me.
    somedays befor; i started a thread regarding this kind of problem; here is the link
    http://boatdesign.net/forums/showthread.php?t=18646&highlight=pavel915

    in this thread; it was discussed about the effect of long transom stern of my ship; michlet was giving a large value of resistance so i started this thered.
    but now i need the mathematical value of the effect of that stern shape.

    How much help michlet can provide me regarding the mathematical value of the effect of stern shape?

    thanx.
     
  6. Leo Lazauskas
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    Leo Lazauskas Senior Member

    The equations required to predict the additional effect of the transom stern on wave-making in thin-ship theory are described in SWPE Report 4:
    http://www.cyberiad.net/library/pdf/tsl00b.pdf

    You will also need to include in your equations the hydrostatic component of resistance if the transom is running partly or fully dry.

    When the transom is fully wet, there is a (hydrostatic) pressure acting in a direction opposite to the direction of travel.
    When the transom is dry, that pressure is absent, and needs to be accounted for.

    It's not a difficult calculation: just integrate the hydrostatic pressure over the transom, i.e. from the bottom of the transom up to the waterline at the undisturbed free surface. (In actual calculations, Simpson's rule is good enough.)

    All the best,
    Leo.
     
  7. Leo Lazauskas
    Joined: Jan 2002
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    Leo Lazauskas Senior Member

    Sorry, I meant...
    When the transom is fully wet, there is a (hydrostatic) pressure acting in the direction of travel.

    Leo.
     

  8. pavel915
    Joined: Nov 2006
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    pavel915 Senior Member

    thanx leo; i am trying your sugession
     
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