For dummies: acceleration, simulation duration, wind speed

Hello, I’m a FAST newbie.

I’m using the 5MW_Baseline with the Test18.fst input file.
In the output file only loads are computed. I would like to have accelerations or displacements in the nacelle and tower: is it possible to have them?

I would like to change the duration of the simulation but I get a fatal error if I put more than 60 seconds: how is it possible to simulate e.g. 10 minutes? I edited the usable time in 90m_12mps_twr.inp, but no luck.

I would like to change the (average) speed of the wind. I modify the URef speed value in the file 90m_12mps_twr.inp, for example from 12 to 14. However, after I run the simulation, the values of Wind1VelX in the output file remain the same and if you do the average of the vector the value is always 12.9361 m/s. How can the wind speed be changed?

Thanx!
Emanuele

Dear Emanuele,

You can add accelerations of the nacelle and tower or other motion-related outputs to a FAST model by adding output parameters to the OutList section of the ElastoDyn primary input file. The “ElastoDyn” worksheet of the OutListParameters.xlsx spreadsheet available in the FAST v8 archive provides a complete list of available ElastoDyn outputs.

To run FAST simulations with turbulent wind inflow, you must first use TurbSim to generate turbulent wind data file(s) of suitable length. After editing 90m_12mps_twr.inp, you must run TurbSim to generate the (binary) turbulent wind data file before running FAST.

Best regards,

Hello all, thanks Jason so much for the reply.

I was able to ask FAST the variables I wanted in output.

About turbsim: how do we do that? To run FAST we go in the folder with the executable and .fst file, and type “FAST_Win32 input.fst”. What is the procedure to run turbsim? I don’t see an executable called turbsim in the downloaded bundle… I’m a little lost on the practical side…

Thank you!
Emanuele

Dear Emanuele,

TurbSim is a separate download, available from: nwtc.nrel.gov/TurbSim.

Best regards,

Hello, thanks for the useful replies.

I run TurbSim to generate the binary input data. I set 600 seconds as analysis time and usable time.
I get: “Error allocating 1315 MB for velocity array.” and TurbSim gets aborted.
What does this error refer to? Hard disk? RAM? (There’s enough space on the hard disk and 8 gb RAM…)
If I lower analysis time to 60 seconds TurbSim runs ok.
What would the machine requirements be to run a ten minutes simulation with turbulent wind?

Cheers!
Emanuele

Emanuele,

I posted a spreadsheet to help people estimate the memory requirements for a TurbSim simulation. The link is in this post: http://forums.nrel.gov/t/memory-requirements-for-full-field-wind-arrays/545/3, but earlier in that topic is a summary of what that spreadsheet calculates.

If you are using a 32-bit TurbSim executable on Windows, you will be limited to a total of 2 GB (of RAM) in your simulation. If you need to simulate something larger than that, use a 64-bit executable.