Problem: Mooring Line Tension with Dynamics and No Dynamics in AQWA

Discussion in 'Software' started by MattG, Jun 14, 2017.

  1. MattG
    Joined: Jun 2017
    Posts: 1
    Likes: 0, Points: 1
    Location: Malaysia

    MattG New Member

    Hi guys. I am currently using AQWA to analyse the motions and mooring line tensions of an internal turret moored FPSO. Part of my project seeks to compare the line tensions between coupled dynamic analysis and quasi-static analysis. While I am able to obtain the simulation results, I found that the line tensions in the dynamic analysis lower than the quasi-static analysis. This should not be the case, since coupled dynamic analysis includes additional damping due to added mass and drag from the cables. Any idea on why this is happening? I am using ANSYS v16.2.

    On another note, the motion responses seem fine, with the dynamic analysis lower for low frequency motions and similar for wave frequeny motions.
  2. Chiemela Victor
    Joined: Apr 2019
    Posts: 6
    Likes: 0, Points: 1
    Location: London

    Chiemela Victor Junior Member

    You may need to check the coupled system again. Understand the physics of what you are simulating and the equation run by the solver. For instance, is F=Kxx+Mx+C and know how it is coupled. Added mass and damping have some effect on the Turret FPSO, but you should also know how the ANSYS AQWA discretizes the system. Coupling is a bit tricky but first, understand the system dynamics.

    I used ANSYS 18.2 but it should not matter. I have used ANSYS 16.2 and currently using ANSYS 19.0 and ANSYS 19.2 so it should be okay

    Check it again, and let me know how it goes. I used ANSYS AQWA, ANSYS ACP and Orcaflex for my designs and analysis.
    For further reference, you can check out my paper on:
    Strength of submarine hoses in Chinese-lantern configuration from hydrodynamic loads on CALM buoy

    Composite risers for deep waters using a numerical modelling approach

    Particular attention can be seen in my system in the publication, there is a simple description in ANSYS AQWA online

    Attached Files:

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.