Dear Jason,
I now want to obtain the horizontal stiffness curve of a floating wind turbine mooring system, and I need to conduct a horizontal stiffness curve test. After searching, the method is shown in the following figure. The floating structure and its mooring are subjected to a horizontal force under no wind, no waves, and no flow conditions, and the resulting model displacement is measured. But now the problem I am facing is how to apply a large horizontal force to floating structures and mooring systems in Openfast?
Best regards
Dear @Cuizhi.Zhu,
You can specify user-defined time series 6-component loads (3 forces, 3 moments) at arbitrary locations in the blades, nacelle, tower, or substructure of OpenFAST through the StC_DOF_MODE = 4 option in the structural control submodel of ServoDyn. For the use case you propose, I would define one 6-component load located in the substructure at (StC_P_X, StC_P_Y, StC_P_Z) = (0, 0, 0) m.
That said, you could also define static offsets of the platform directly via the initial conditions in ElastoDyn (by setting a nonzero PtfmSurge, etc.)
Best regards,
Dear Jason,
I couldn’t find StP_DOF-MODE=4 option in the Servodyn file of Openfast. I wonder if I misunderstood it? Also, is there a template file that defines a 6-component load in a substructure located at (StCP_X, StCP_Y, StCP_Z)=(0, 0, 0) m?
Best regards
Dear @Cuizhi.Zhu,
The structural control (StC) related inputs are specified in the StC input file. To define an StC in the substructure, in ServoDyn, set NumSStC = 1 and then SStCfiles is the name and path to the StC input file. You can find an OpenFAST r-test example that makes use of StC with user-defined 6-component load time series (applied to the blade) here: r-test/glue-codes/openfast/StC_test_OC4Semi at main · OpenFAST/r-test · GitHub.
Best regards,
