Added mass in Hydrodyn

Dear NERL members,

As for offshore floating wind turbine, I am interested in the issue about added mass of floater. I have one question, I will appreciate for your kind help.
1.In free decay test.
It is indicated we should always use the added mass at infinite wave frequency from WAMIT results, is it also same for free decay test?
Thanks a lot.

 Best regards,
 Shining. Zhang

Dear Shining,

The short answer is, “yes.”

The frequency-dependence of hydrodynamic added mass and damping is captured in the time domain by applying a constant added mass and damping expressed via a convolution integral. The approach taken in HydroDyn is to take the infinite-frequency limit as the constant added mass and the Kernel of the convolution integral based on the cosine-transform of the frequency-dependent damping matrix. That is, the use of the infinite-frequency limit of added mass is compatible with the approach used to calculate the Kernel of the convolution integral. See section 2.4.2.1 of my PhD thesis-turned NREL report for more information: nrel.gov/docs/fy08osti/41958.pdf.

Best regards,