Applying a torque at the tower top

Wind & Water Computer-Aided Engineering Software Tools
1

Good afternoon,
I would like to investigate the torsional mode of a tower + monopile (asked in OC6 phase 2). As explained to me, OpenFAST includes a lumped stiffness at the yaw to reproduce the proper behavior. To get the torsional mode shape, one advises me to apply a torque at tower top and look at the rotations along the tower and monopile.
I just don’t know how to apply a torque. Do I have to use the Tower_Top_Loads.dat as explained in the attached pdf file (OpenFAST_Prescribing_Loads_at_Tower_Top.pdf) ?
Then I am not sure of the probe I have to look for.
Finally, is there somewhere a documentation for Elastodyn? I may have missed it or everything needed is explained in the Openfast manual I guess.

Many thanks in advance.
Best regards.
Florence Haudin.
OpenFAST_Prescribing_Loads_at_Tower_Top.pdf (1.01 MB)

2

Dear Florence,

The ability to apply user-defined loads at the tower top (distinct from aerodynamic excitation) was recently added in a version of OpenFAST for use in the OC6 Phase II project; it is not yet included in the dev or master branches of OpenFAST. The feature is described in the report you attached; if something is not clear, I would ask Roger Bergua–who leads OC6 Phase II–for help.

The documentation of OpenFAST is still a work in progress. The ElastoDyn module is currently best described in the old FAST v7 User’s Guide (github.com/OpenFAST/openfast/issues/181) describing the need to update these and migrate them to the OpenFAST documentation.

Best regards,