Inquiry Regarding Free Decay Calculation of Floating Foundation Without Upper Structure in OpenFAST

[cx330-xxr]

Dear Professor Jonkman,

I hope this email finds you well.

I am currently working on a project involving the dynamic response of a floating foundation. Specifically, I am interested in calculating the free decay motion of the foundation without considering the upper structure (e.g., tower, nacelle, and rotor). However, I am uncertain about the best approach to achieve this using OpenFAST.

Could you kindly provide guidance on how to set up the simulation in OpenFAST to calculate the free decay motion of the floating foundation alone? I would appreciate any suggestions on how to configure the relevant parameters and which modules should be considered or excluded in this context.

Thank you in advance for your assistance.

[jjonkman]

Dear @cx330-xxr,

Yes, OpenFAST can be used to simulate a floater without a wind turbine on top. Basically, you should disable BeamDyn, InflowWind, AeroDyn, and ServoDyn; disable all degrees of freedom (DOFs) in ElastoDyn other than the six platform DOFs, and set the geometry, mass, and inertias of the tower, nacelle, drivetrain, and blades to zero (or very small numbers for inputs that ElastoDyn does not allow to be exactly zero).

Best regards,