Learning Forum

[S.S.S.ShankaVasuki]

Hi,

I am working on a floating problem with 15 connected bodies as shown in the figure. The dimensions of the structure is 1.88x1.88x0.14m and the draft is 0.096m. The mesh size was set to 0.08m with 20,000 panels. 

Kxx = 0.48m, Kyy = 0.48m, Kxx = 0.62m, CoG = 0.03m

Hydrodynamic diffraction analysis: To run the diffraction analysis, I specified the connection stiffness matrix between each body (a total of 21 matrices) as shown in the figure below. I have not included the mooring stiffness matrix in this calculation and the simulation runs without errors BUT the results dont match the reference results as shown below for the pitch RAO for all the middle blocks. I dont know where I am going wrong here. As even if I include the mooring line stiffness, the RAOs will reduce even further which still does not match the reference values. Also, I have not included any additional damping matrices as well. So can you please let me know where the mistake is?

Hydrodynamic Response: For the time domain analysis, I replaced all double hinges (as shown in the first image) with a ball and socket joint as shown in the figure below to avoid the closed loop error along with a soft mooring line with the properties as shown below. I used an irregular wave spectrum with a JONSWAP spectrum with properties as shown in the last image.  With all these definitions, the time domain solution tends to diverge about RZ-Yaw (as shown in the last image), I also tried to reduce the time step to 0.001s, but no luck. Hence could you please let me know on how to resolve this issue as I have been asking this question from a month, but have not received any response from the Ansys team.

 

[Ashish Khemka]

Hi,

It looks that your query is already answered here: AQWA: Hydrodynamic response error

Regards,

Ashish Khemka