How to obtain aerodynamic added mass and damping？

[benwys957]

Hello,
I would like to compare the aerodynamic added mass and damping between RAFT and OpenFAST. How can I obtain the aerodynamic added mass and aerodynamic damping simulated by OpenFAST? Is it only possible to obtain frequency-dependent aerodynamic added mass and damping like RAFT by performing forced harmonic motion at different frequencies?
Thank you in advance,
Ben

[jjonkman]

Dear @benwys957,

I assume by aerodynamic added mass you mean the aerodynamic forces dependent on structural acceleration, and likewise by aerodynamic damping you mean the aerodynamic forces dependent on structural velocity.

Just a few comments:

• While the unsteady airfoil aerodynamic models (if enabled) may have a small nonzero contribution to added mass, AeroDyn does not support other aerodynamic added mass effects.
• AeroDyn certainly supports aerodynamic damping.
• While the aerodynamic damping deriveable through an OpenFAST linearization analysis will depend on the linearization operating point, it is not directly frequency dependent.
• To obtain frequency-dependent terms, you'd like have to derive these using custom scripts, e.g., post-processing aerodynamic forces from the standalone AeroDyn driver under prescribed floater motion.

Best regards,

[benwys957]

Dear @jjonkman ,
Thank you for your guidance.
I truly appreciate getting a direct reply from the main developer.

Have a nice day!

Best regards, Ben.