Hydrostatic Stiffness Matrix in ANSYS AQWA

Discussion in 'Software' started by mekchu, Sep 12, 2013.

  1. mekchu
    Joined: Jul 2013
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Korea

    mekchu Junior Member

    HI all,

    I was wondering about hydrostatic stiffness matrix in ANSYS AQWA. According to hydrostatic stiffness matrix formulation described in Section 3.1.3 of AQWA Line Manual, the pitch and roll restoring components (RXX, RYY) is not affected by center of gravity (CG) location. However, I tested simply cylinder model considering different CG position. I realized that there is different value for the pitch and roll restoring components. What's wrong?
    Please give me some advise for this situation.

    Thanks.
     
  2. jehardiman
    Joined: Aug 2004
    Posts: 2,528
    Likes: 222, Points: 63, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Cylinder on end or on edge? Cylinders are not good hydrostatic test cases, they have a lot of interesting singularities.
     
  3. mekchu
    Joined: Jul 2013
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Korea

    mekchu Junior Member

    Hi Jehardiman,

    Thank you for your responses.
    Actually, I also tested semi-submersible platform model which seem to be complex geometry. I realized that the hydrostatic stiffness matrix depends on CG location. That's why I used simply cylinder model to test my analysis.
    Can you give me some advises?

    Cheers.
     
  4. UTKARSH RAMAYAN
    Joined: Oct 2012
    Posts: 9
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: IIT MADRAS

    UTKARSH RAMAYAN Junior Member

  5. CWTeebs
    Joined: Apr 2011
    Posts: 232
    Likes: 15, Points: 0, Legacy Rep: 171
    Location: Maine

    CWTeebs AnomalyGenerator

    Did you add an internal lid?
     
  6. mekchu
    Joined: Jul 2013
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Korea

    mekchu Junior Member

    Hi CWTeebs,

    I did not use internal lid option.

    Cheers
     

  7. CWTeebs
    Joined: Apr 2011
    Posts: 232
    Likes: 15, Points: 0, Legacy Rep: 171
    Location: Maine

    CWTeebs AnomalyGenerator

    Add one, it'll stop those fictitious waves inside the spar.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.