Hi everyone, i have three doubts and i would really be grateful if you could help me with this:

-Is it valid to do a simulation of 200 seconds with a DT of 0,05? I would like to put 0,005 but since i have to copy the table of the output file, i want to make it condense. However, is there a problem with these numbers i said?

-About linearizing, what things could we obtain with it?

-I am doing a final thesis for the upscaling from 15 MW WT to a 20 MW, focusing only on the RNA and tower (not on the floating or fixed platform). Apart from running simulations for both turbines with steady wind (from 3 m/s to 25 m/s) and turbulent wind, would you recommend adding more interesting things to my final thesis which can be done with openfast? I know there are many thought-provoking things i could get with openfast , but what ones would you say it is a must in openfast?

Thanks

Dear @Alberto.Utrera,

Regarding your first question, as has been discussed before in several forum topics, the required time step (`DT`

) of an OpenFAST simulation is dictated by the natural frequencies and excitation frequencies inherent in a model. You can always coarsen the OpenFAST output (via input `DTOut`

) if you wish to have less output data than youâ€™d get if you output every time step. The required length of a given simulation (`TMax`

) is typically chosen to cover the core dynamic response of the transient or to capture statistical significance (when accounting for turbulence). 10 minute simulations are typical for wind turbine simulations for a given turbulent condition.

Regarding linearization of OpenFAST, it is mainly useful for full-system eigenanalysis (to obtain full-system natural frequencies, damping, and mode shapes), controls design, stability analysis, and for generally â€śunderstandingâ€ť the system response.

Best regards,

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Thanks for the reply @Jason.Jonkman.

In which file, could I be able to see the highest natural frequency in Hz of coupling between modules?

In my simulation, I am using steady conditions and not turbulent. I am setting the Tmax to 200s. Although the trends of the majority of some parameters can be seen perfectly (because of the convergence), there are others that I do not know if the response will be damped or amplified. In this case, it is better for me to broaden the Tmax, right?

br

Dear @Alberto.Utrera,

You can find the highest natural frequency (as well as any full-system natural frequency) through an OpenFAST linearization analysis, followed by Eigenanalysis. For the purposes of computed the highest frequency for identifying DT, you can choose simple conditions such as `CompAero`

= 0 (in the OpenFAST primary input file) and `RotSpeed`

= 0 (in ElastoDyn).

When using steady inflow, presumably your objective is to find the steady-state condition. If the steady-state condition is not obvious after 200 s, you could increase `TMax`

.

Best regards,

Hi @Jason.Jonkman,

I am basing part of my final thesis on the methodology stated in the following thesis:(https://oaktrust.library.tamu.edu/bitstream/handle/1969.1/193162/WU-THESIS-2021.pdf?sequence=1&isAllowed=y)

Since i am doing an upscaling from the 15 MW IEA Wind turbine fixed in a monopile, could it be possible to use the aforementioned thesis (link attached) to upscale the 15 MW iEA? I am asking this question because the thesis is for floating platforms and the 15 MW IEA is fixed on a monopile.

Thank u . ALbert

Dear @Alberto.Utrera,

Iâ€™m not familiar with the paper you reference. I recall reviewing the following the paper about scaling at one point: https://www.researchgate.net/publication/258724726_Upscaling_wind_turbines_Theoretical_and_practical_aspects_and_their_impact_on_the_cost_of_energy, but that was a while ago. Iâ€™m sure there are other wind turbine scaling-related papers in the literature as well.

Best regards,

Dear @Jason.Jonkman

I also Saw that paper but unfortunately It does not apply to my specific case since i am dealing with AN upscaling from 15 MW to 20 MW. It would be comfortable if i had only to interpolate, but It is not the case.

I have been reading papers such as Turaj Ashuri one , applying MDO.

Anyway, the question IS wether i can make use of floating wind turbine parameters and apply them to monopile supported wind turbine parameters.

Thank u. Albert

Dear @Alberto.Utrera,

If you are referring to simple geometry scaling of a wind turbine, I would not think the scaling relationships would depend on the support structure.

FYI: There is a new IEA Wind 22-MW RWT that has been developed in case you are interested: GitHub - IEAWindTask37/IEA-22-280-RWT: Repository for 22MW offshore reference wind turbine developed by the IEA Wind Task 37.

Best regards,