Questions about Deepcwind natural periods

Dear Jason,

I try to simulate the free decay of OC4 semi model in still water. I have compiled FAST to take quadratic viscous damping into consideration, and the quadratic drag coefficient of surge is 1.25E+6Ns^2/m^2. Unfortunately, the simulation result of surge motion mode is 115.3s, while the model test result is 107s. It seems that something is wrong with the platform mass or mooring system. Would you mind figuring out the errors.
Thanks.

Best regards.
NRELOffshrBsline5MW_Platform_OC4DeepCwind.txt (7.89 KB)

Dear Liang Li,

As we discussed in the forum post found here: http://forums.nrel.gov/t/oc4-deepcwind/692/1, the OC4-DeepCwind semi-submersible model is not currently in the public domain. So, I cannot answer your questions here. But from a quick comparison of your FAST platform input file with ours for the OC4 DeepCwind semi-submersible, there are quite a few differences.

Best regards,

Dear Jason,

Thanks for your prompt reply.

Best regards,