I checked my model and tried to implement ebveryhting you suggested but no luck in getting the same results as the reference article. I tried to manually change some values of the connection stiffness matrix to negative and I did get a better match with the reference but I dont think this is the right approach to validate the results. Hence, I am now also trying to run the hydrodynamic response analysis with physical definitions of the connections and mooring lines to see if get a better match with respect to the RAOs.
Connections: In order to replicate the connection sequence between each body as the reference article as shown in the first post, and to also avoid the closed loop error in the aqwa simulation, I replaced double connections with single hinge (circled in blue) and ball&socket (circled in red) connections as shown in the figure below. The stiffness of the each connection is given as twice the value mentioned in the connection stiffness matrix in the reference article along Rx-Rx, Ry-Ry, Rz-Rz as I am technically replacing two connection joints with one. The details of the connections are shown below.
Mooring line cables: I have included two linear mooring line cables as shown in the figure below:
Waves: I have used an irregular wave with the jonswap spectrum with the following paramters:
time domain results: With these parameters as mentioned, I get an error as shown in the figure below. But when I change the Hs from 1m to 0.15m, the simulation run without any errors but when Hs>0.15m, the simulation results in this error. So I am guessing the system is unstable at high wave heights which could be due to mooring line cables or connections between the bodies. So is there any recommendations to run the simulation without this error at Hs = 1m?
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