HydroDyn response generation


I’m currently working on my master thesis, and as a part of this projekt, I need to simulate the response of a TLP FOWT, for this i want to use FAST/HydroDyn. However, since I have never used FAST before, I am currently trying to figure out how the software works.

For now, i’m looking into the HydroDyn sample project NRELOffshrBsline5MW_MIT_NREL_TLP_HydroDyn, just to get a hang on this part of the software.

I have gotten the sample project to run, however, even though i am able to extract the time series for the irregular waves (which looks correct), the displacement of the TLP is not affected by these waves. In the simulation the TLP has a constant displacement, which corresponds to the uWAMITInSteady values, defined in the driver file.

Is it me who has misunderstood how HydroDyn is to be used, or is there a setting somewhere, where i can state that the irregular waves should have an affect on the TLP’ displacement?

Best regards
Thomas Hansen

Dear Thomas,

The HydroDyn driver (and driver file) are only used when running HydroDyn uncoupled from FAST. In this case, the motion of the substructure is specified directly by the user. When HydroDyn is coupled to FAST, the motion of the substructure is calculated by a structural module of FAST (ElastoDyn specifically). ElastoDyn will receive the hydrodynamic loads from HydroDyn at each coupling step and ElastoDyn will calculate the structural response (including motion of the substructure), which in turn, is sent to HydroDyn.

I hope that helps.

Best regards,

Dear Jason

Thank you very much for clearing my confusion, I had the feeling that this was the case. I will start working on developing a FAST project with the relevant coupled modules.

Best regards