Dear Jason,
Sorry to bother you again.
I recently have done some free-decay tests for 5MW+OC4 with linearized mooring model in a lab CFD code based on Actuator Line Method, and the natural periods of Heave and Pitch are fine. However, my surge period (~125s) is significantly overestimated comparing to the experimental result (107s) with an initial surge amplitude of 22m.
I find it may due to the strong non-linear effects of the surge force-displacement relation when surge_dis > 15m in the Fig. 5-2 in the OC4 definition report as shown below:
So, I would like to use to the nonlinear mooring model of the mooring system described in section 5.3 of the OC4 definition report. However, I cannot find the MooringSystemFD.txt file mentioned in the report or in this Forum (The file for OC3-Spar was mentioned in a previous post: Fairlead tensions of Test24 not matching with hand calculation in still conditions - Wind & Water / General - NREL Forum). Could you share me some information where I can find the MooringSystemFD.txt for OC4 mooring system?
Best regards,
Lin Yang.