Mooring in AQWA

[CWTeebs]

If you use the quasi-static solution for composite catenary lines (as
opposed to cable dynamics) this defines the upper bound for motions above
the initial position of the connection point on the vessel. See section
2.4.1 of the ANSYS Help for AQWA.

I circumvent this problem by never having cables attached directly to the sea bed. I create a fictitious body near the sea bed that has no diffracting panels and is not allowed to move. I create the connection point in design modeler by creating a primitive->cone as a surface body.

It's sometimes difficult to get the initial cable properties just right. You need to have realistic values for stiffness, maximum tension and weight per unit length of the cable.

[omid]

Hi Mikhail,

you can send crane barge moored aqwa file to:

fazli.srbiau@gmail.com

Thanks

[omid]

hi
you can send crane barge aqwa file to:
fazli.srbiau@gmail.com
thanks

[Jaqen]

Hi everybody,
i'm an Italian engineer. and I've got a question about the mooring problem in AQWA. I'm trying to simulate the behaving of a small hull, anchored with a steel chain with a buoy. I've run many simulations with standard sea characteristics, but every time te hull starts to rotate along its z-axis, in an uncontrollable (and I think irrealistic) yaw that invalidate any other result of the simulation. I've tried many combination of mooring line (even the simple elastic line) and even with double lines on oth sides of the hull, but the problem persist.
So I'm asking if there is a way to insert a certain yaw stiffness in the model trough the mooring line, as it happens in reality.

Thank you in advance

Andrea

[CWTeebs]

If the yaw motions are truly unimportant you can either deactivate that degree of freedom using the DACF keyword, passing 6 as an argument indicating yaw is to be deactivated. Alternatively you can use a type of hinge constraint.

[Jaqen]

Hi, thanks for your reply.
I need to specify that I'm using AQWA through Ansys Workbench, so I don't know where to insert keywors like DACF.
My problem is that I want to know if the yaw is really unimportant with my mooring line, since now I have an unstable behaving of the hull with the yaw, that in my opinion it's not realistic. I would like to give a pre-tension to the cable, or something that may limitate the yaw and stabilize my hull movement. I was looking for someone that may have encountered the same problem and maybe knows how to solve it.

Andrea

[CWTeebs]

I just downloaded and tested Ansys WB v14, and it allows you to insert articulations for use in a time domain simulation from workbench. So, if you have access to v14 you could try inserting a hinge articulation. Otherwise, I strongly suggest learning the native AQWA keywords as a ton of AQWA functionality isn't even possible from Workbench.

[onaindi]

Hi aqwa users! I am a begginer in aqwa.
I am usin aqua 12. An I am making a project of a catamaran with 3 suction anchors to reduce de roll and the pitch motions. I would like to obtain the graphs of tension in each mooring line. But unfortunately the tension is 0 in the three lines.
First I created an AL....dat file and define the nodes for the mooring lines in the bottom of the sea with jonhswap spectrum, then I created an AF....DAT file for the mooring lines and after run aqwa line again with the AF...DAT. When I open aqwa gs to see the graphs there is no tension in the mooring lines.
You can have a look at the attachment AF...dat file to see if is something wrong/missing in this message
Thank you very much
Alex

AQWA LINE BARGE.txt

AQWA FER BARGE.txt