Hi everybody,

I was plotting the damping coefficients calculated by WAMIT for the OC4 semi-submersible that are provided in the github repository. All coefficients seem to be ok but Heave. I would say that as frequency goes to zero, so should the damping coefficient. Is this correct? But what’s happening is that there’s a steep slope in the range [0Hz-0.7Hz] that I wouldn’t be expecting…

I’ve uploaded an image with the coefficients in function of frequency, for Heave. Any idea?

Thanks for in advance,

Tomás

Dear Tomás,

Are you sure you are plotting the WAMIT data correctly? (To dimensionalize the nondimensional WAMIT data, you must multiply by the angular frequency in addition to the water density and length scales.) The WAMIT data for the OC4-DeepCwind semi for the first-order radiation solution is plotted in Figure 4-3 of the specifications report: nrel.gov/docs/fy14osti/60601.pdf, which clearly shows that the damping tends toward zero at low frequency.

Best regards,

Dear Jason,

I was missing that part. It now looks exactly as the graphs in the report. Thank you for the help!

Best regards,

Tomás