Mooring Dynamic Response for various Damage Scenarios

Dear NREL team and users.

I am using FAST v8.16 to Simulate a semi-submersible offshore wind turbine (The DTU 10MW Wind Turbine with the OO-Star Wind Floater), for the purpose of developing a Structural Health Monitoring method for in-operation wind turbines and under varying Environmental and Operational Conditions (EOCs). The methods that are being developed are using acceleration signals in various positions of the wind turbine. Τo ascertain that there is change in the dynamic response of the structure, estimations of the Power Spectral Densities from the output data of different EOCs and damage scenarios are being compared.

Some of the Damage scenarios that are under consideration are on the mooring system and to simulate those, the axial stiffness of the lines is being reduced to several levels. To do so, using the MoorDyn v1.01 module, I have changed the Line Property “EA” in the “LINE TYPE” section and to compare the results I am using the same Random Seeds in the HydroDyn module and the same Full Field files from TurbSim.

Despite the change of the Line Properties the results are identical which to my understanding shouldn’t be the case. So, the question is:

why is the dynamic response of the platform not influenced by the line properties of the mooring system?

I also tried to output the Node acceleration (Using L#N@ax in the output section of Moordyn) but I wasn’t able to.

I am attaching some of the results of the simulation along with a Link for the input files i am using.

If someone could help, I would appreciate it.

Best regards
Nikolas Anastasiadis