Learning Forum

[NavalArch]

In Hydrodynamic Response analysis in AQWA I got this error above that the hydrodynamically interacting structures have moved too far! my model is moored to the ground and it does not make sense to get such an error! I have tried several stiffness values both for cables and hinges but none of them solve the issue.

I would really appreciate if you could help me in this matter.

 

With regards,

[Mike Pettit]

Hello,

When we include hydrodynamic interaction in the Hydrodynamic Diffraction analysis, the radiation damping and added mass matrices are calculated for the structures in their relative analysis positions. However, when the structures move relative to one another in the time domain, these damping/added mass terms due to hydrodynamic interaction are not updated. Therefore the Aqwa solver will stop if it thinks that results are becoming inaccurate due to the relative structure motion.

Is it possible that your joint connections have changed the order of the structures? Judging by the part colours, from left to right, the structure order seems to be

Body 6 - Body 4 - Body 2 - Body 1 - Body 3 - Body 5

Does this match the arrangement in the Hydrodynamic Diffraction analysis? Is there any other difference between the structure analysis positions in the Hydrodynamic Diffraction analysis, and their positions at the start of the time domain Hydrodynamic Response analysis?

Mike

[NavalArch]

Hello,

I changed the order of the structure (body 1 - ... - body 6) and it is the same arrangement in Hydrodynamic Diffraction analysis (see picture below). I did run the Hydrodynamic Response and again the same error occurred!

I also noticed that the initial attachment point separation of cables in both ends are quite different (cabels that are attached to body 1 have different values than the cables that are attached to body 6 almost 10m). I have no clue of why this is like this!

Many thanks in advance for your valuable assistance.