Wind loads on floater body

Hi Jason & others,

I am currently modeling a floating wind concept in which the floater has a non-negligible area above the still water surface. Therefore, it will attract significant wind loads, especially in the cut-out range and above.

It is however unclear to me if there is any option of providing a set of wind coefficients applicable for the floater body to FAST. I couldn’t find such an option. What I also wonder about, is what happens if I define a set of Morison members in HydroDyn in which some members (or part of) are located above the water surface. It’s probably a stretch, but will associated wind induced drag loads be calculated in this case with the density applicable to air and incorporating the instantaneous wind velocity instead of apparent current velocity?

If so, then that would allow me to model the wind loads on the floater body. If not, is there another option available to model floater wind loads that I have missed so far?

Thanks & best regards,


Dear Ebert,

You’ve identified one limitation of the current version of FAST / OpenFAST. FAST / OpenFAST can model the aerodynamic loads and influence of a single tower (in AeroDyn), but FAST / OpenFAST has no way of calculating the aerodynamic loads and influence on a multi-member support structures. This is an area where NREL has not yet been funded to develop the model further (but would like to when the opportunity arises). The source code would need to be modified to consider such loading.

Best regards,

Dear Jason,

Thank you for clearing this up and apologies for my late reply (due to Xmas holiday).

I sincerely hope this feature can be added in a future release, as its an important part of total loading for quite a few of the floating wind concepts out there. The implementation could be quite simple I believe, i.e. taking wind velocity vector at some reference location (neglecting spatial distribution of wind velocities) and combining with a set of wind/current coefficients. If time permits, I will try to see if I can modify the code myself in order to do this.

Best regards,