Some errors about the addition of dampers to 15MW monopile wind turbines

[3sdb]

I am getting the following error during the simulation, can you give me some suggestions?

[jjonkman]

Dear @3sdb ,

A similar set of error messages was reported in the following issue where the problem was incorrect initialization of the rotor speed: https://github.com/OpenFAST/openfast/issues/1718.

Best regards,

[3sdb]

Dear： I've changed the rotor velocity, as you prompted, but I've got some other errors in the analog (gendof is turned off)

[jjonkman]

Dear @3sdb,

It appears your model is numerically unstable, but it is not clear to me why. With GenDOF = FALSE, the ROSCO controller will have no effect on the response, even when enabled.

What else have you changed in the IEA Wind 15-MW baseline wind turbine atop monopile model relative to the original OpenFAST model provided in its repository: https://github.com/IEAWindTask37/IEA-15-240-RWT/tree/master/OpenFAST/IEA-15-240-RWT-Monopile?

Best regards,

[3sdb]

Dear @jjonkman ： I tried to revert it back to the original model, but I just added the damping file to the servo file, but something happened during the simulation, and I was a bit helpless IEA-15-240-RWT-Monopile_TMDInput.txt

[jjonkman]

Dear @3sdb,

Are you saying that your simulation runs as expected except when you add a nacelle-based TMD that causes your model to go unstable?

In our Structural Controller (StC) input file, I see that StC_P_Z is likely specified incorrectly because for a nacelle-based TMD, this input should be specified relative to the yaw bearing. Also, I've not personally used StC_CMODE = 1; does the simulation if your TMD is passive with StC_CMODE = 0?

Best regards,

[3sdb]

Dear @jjonkman , Thank you for the answer, it's really a question, and now I don't make a mistake when simulating, but I still want to ask where I can find the yaw bearing and the location of the center (I'm doing research on damper damping) Best regards,

[jjonkman]

Dear @3sdb,

In OpenFAST, the center of the yaw bearing is user-specified via ElastoDyn input TowerHt.

Best regards,

[3sdb]

Hello@jjonkman , Thank you, I also found your parameters, I have a new doubt: what is the size of the damper in OpenFast and is there a manual for designing the damper, at the moment I am using the data that comes with the downloaded 5MW, the shock absorption effect is not very good, almost similar to the effect without the damper, so I think the parameters of the damper (stiffness, damping) are set incorrectly. Best regards,

[jjonkman]

Dear @3sdb,

The OpenFAST r-test cases with the Structural Controller (StC) submodel of ServoDyn enabled are set up more to test that StC is working as expected rather than as examples of optimal StC configurations.

NREL has not provided guidance on how to design TMDs, but the NREL-provided documentation does describe how the StC submodel is implemented in OpenFAST and how to use it: https://openfast.readthedocs.io/en/main/source/user/servodyn-stc/StC_index.html. I'm sure you can find relevant literature on how to design optimal TMDs.

Best regards,