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.
NRELOffshrBsline5MW_Platform_OC4DeepCwind.txt (7.89 KB)