Learning Forum

[kingdsystems]

Hi,

I am not very conversant with ANSYS AQWA but i am working on FPSO mooring line analysis. The following errors were encountered while running the Hydrodynamic response:

1. The structure keeps sinking completely into the fluid domain.
2. Aqwa-librium iteration failed to coverge after the 500 requested steps (as shown in the last screenshot).
3. The selected structure no longer exists. Please update your selection.

I can try to fix the last one but in the sinking of the fpso completely into the fluid domain is what i cannot understand. I have tried reducing the mass of the structure, the mass/length of the mooring lines and even the area but still cannot solve the challenge.

 

Please, if there is any way you can help me resolve this, i will be grateful.

 

Thanks.

This is the mooring line configuration used in this analysis.

Mooring line details

[Shuangxing Du]

Aqwa requires the external hull surface normal direction points outwards.  Please check the hydrostatic properties in the Hydrodynamic Diffraction: (1) Displacement, (2) Hydrostatic restoring stiffness, K33. The buoynancy force should be the same of the structure gravity force, and K33 should be positive.

In Static Stability analysis, please check (1) the lengths of the cables and (2) the total cable force in z direction, and the gravity force, hydrostatic force.