Learning Forum

[Hilal Çelik]

hi, I try to linear elastic cables but I meet the error text. The floating pontoon models and mooring lines can be seen in the first picture. The joint types are hinged but I change the second joint as ball and socket joint to get rid of the errors but it didn't help. What is the solution for this error?

 

 

 

[Shuangxing Du]

For a hydrodynamic interaction group of structures, the hydrodynamic properties are sensitive to the relative positions of the structures. In Aqwa time domain analysis the relative positions of some selected pairs of diffraction elements between adjacent structures are checked and compared to the relative positions defined in the Hydrodynamic Diffraction analysis. If the changes are too big in the time domain simulation, error message will be issued.

In your model, are the gaps between the structures  too narrow?  If yes, can you set the surfaces of structures of which they face to each other as non-diffraction surface before meshing?  

The socket joint (which allows the relative yaw and roll motions) may make the situation even worse.

[Hilal Çelik]

Thanks for your help. The gaps between the pontoons are 40 mm, yes they are too small. How can I set the faces as non-diffraction surfaces? 

[Shuangxing Du]

In Geometry, make the adjacent surfaces as a Body among a Part. Then in Aqwa Editor, select the surface and set its surface type to be Non-Diffracting.

[Hilal Çelik]

I set those surfaces as non-diffracting surfaces but still I encountered the same error.

 

[abubakarumar1097]

 

Hi! It sounds like you're facing issues with your floating pontoon models and mooring lines. Here are a few suggestions to troubleshoot the error:

1. Check Constraints: Ensure all joints are properly defined and compatible with the linear elastic cables you're using.

2. Review Connections: Confirm that all connections between the pontoon and mooring lines are correctly set up.

3. Joint Settings: Double-check the settings for the ball and socket joint. Make sure it’s configured to allow the necessary degrees of freedom.

4. Model Scale: Ensure the scale of your model is appropriate; sometimes, very small or large scales can lead to unexpected behavior.

5. Software Documentation: Refer to the software’s documentation or forums for specific guidance on the error message you’re receiving.

If the problem persists, providing the specific error text could help diagnose the issue further. Good luck!

[Hilal Çelik]

actually, I changed the joint type, to hinged connections.

 

[fakhrafakhrifakhru]

It might be with how the mooring lines or cable connections are modeled. Changing the joint type to a ball and socket could be a good step, but you may also need to check if the cable properties, boundary conditions, or loading setup are properly defined. Ensure that the cables are correctly assigned as "linear elastic" and that all constraints are compatible with the floating pontoon's movement. Additionally, try reviewing the error message details, as they can provide specific clues about what is causing the problem.