About Hydrodyn output format

---------------------- OUTPUT --------------------------------------------------
True HDSum - Output a summary file [flag]
False OutAll - Output all user-specified member and joint loads (only at each member end, not interior locations) [flag]
2 OutSwtch - Output requested channels to: [1=Hydrodyn.out, 2=GlueCode.out, 3=both files]
“ES11.4e2” OutFmt - Output format for numerical results (quoted string) [not checked for validity!]
“A11” OutSFmt - Output format for header strings (quoted string) [not checked for validity!]
I have fast version 8.16.0. And running this program, I wanted to see numerical results about floating platform so I changed word ‘False’ to True but Computer said That is under on developing. So What I want to say, Is this function(numerical results) not available?
Thank you for reading it.

Dear HongBhin.Kim,

The OutAll option of HydroDyn has never been implemented, hence the error. For now, you can select which HydroDyn-level outputs you want through by specifying them in the Output Channels section of the HydroDyn input file.

Best regards,

Hello, I am an research student at Inha University’s Applied Marine Hydrodynamics Lab. and I am researching the topic of aerodynamic and hydrodynamic coupled analysis to use NREL FAST. And In the situation where only the Aerodyn module and the hydrodynamic module are used, I wondered how the aerodynamic force(aerodynamic thrust force in hub coordinate system) could be converted into the force acting on the center of gravity of the floating platform(like oc4,nrel-tlp). In my opinion, it is possible to use a transformation matrix. But it is difficult to understand precisely.
So, I want to ask how you implemented these parts in the FAST.
Thank you for reading my question.
Best Regards

Dear HongBhin.Kim,

I’m not sure I understand your question. In FAST / OpenFAST, it is not possible to disable ElastoDyn, although you can disable all structural DOFs.

If the structure is rigid with all DOFs disabled, the force due to thrust at any point in the system is the same, and the moment associated with the thrust force will depend on the moment arm.

Best regards,

Hello, I am an research student at INHA University’s Applied Marine Hydrodynamics Lab. First of all, thank you for answering the last question.
It was a small question but it helped a lot.
What I want to ask is the part about the elastic module. I think FAST seems to consider tower as an elastic body… So, is it correct that the elastic body of the tower is affected by aerodynamics and the applied force due to the movement of the tower affects the mass point of the floating body? If so, I would like to ask, where is the program source code for calculating the Tower Applied force, and if you can receive the data that is the basis for this calculation?

Thank you for reading my question.
Best Regards

Dear HongBhin.Kim,

Yes, applying forces to the elastic tower will induce motion of the floating body (through the platform DOFs, when enabled). The only loads applied to the tower in OpenFAST are those from the tower aerodynamic load calculation of AeroDyn v15. You can output the aerodynamic loads calculated by AeroDyn v15 from that module, as documented here: openfast.readthedocs.io/en/main … t-channels.

Of course, the aerodynamic loads applied to the tower are generally much less than the aerodynamic loads applied to the rotor, unless the rotor is parked/idling with all blades feathered. So, in most cases, the aerodynamic loads applied to the rotor have a much larger effect on the floater motion than the aerodynamic loads applied to the tower.

Best regards,

Hello, I am an research student at INHA University’s Applied Marine Hydrodynamics Lab. First of all, thank you for answering the last question(about aerodyn).
To be honest, I was curious about exactly how the Tower dynamics program in the ELASTODYN MODULE affects the floating platform, so I asked a question. But I was understood that the effect of tower dynamics on the platform was not great from the last question.
Then I want to ask, from a platform point of view what is the biggest difference between when the tower is rigid and when it is elastic

researchgate.net/profile/De … P_W640.jpg

Also I have one more question, I would like to ask if the mass property in the link above is the weight that contains the 5mw wind turbine.

Thank you for reading my question.
Best Regards

Dear HongBhin.Kim,

The tower is what couples the rotor dynamics with the floater dynamics, and so, is often quite important to the response of a floating offshore wind turbine (but not typically because of tower aerodynamic loads). The tower typically has the lowest natural frequency of the supported wind turbine (other than the floater modes of motion), and so, can get resonated from rotor rotation (if not controlled or designed properly) and wave-excitation. And for TLP floaters, the tower-bending modes can directly impact the TLP-pitch mode natural frequencies.

Regarding the MIT/NREL TLP discussed in the report you linked to, this table shows the properties only of the TLP floater, not including the supported wind turbine or tendons.

Best regards,