Capabilities of OpenFast

Hello everyone,

I’m new to OpenFast and i was wondering if OpenFast :
1- Can do calculation in frequency domain ? In other words, OpenFast output can be a stress PSD ?
2- Is it possible to replace TMDs built in OpenFast by other types ? Also, is it possible to change the position of the TMD ? If yes, does it require a lot of coding ?

Thank you in advance

Dear @Riad.Elhamoud,

Here are my answers:

  1. OpenFAST functions nonlinearly in the time domain (rather than linearly in the frequency domain) and outputs time-series responses. That said, the time-series responses are often post-processed to calculate power spectral density (PSD). Please note that OpenFAST computs loads at cross sections of members (such as blades, shaft, tower and substructure), not stress directly. To calculate stress requires a separate post-processing step (e.g., cross-sectional analysis).

  2. The Structural Control (StC) submodel of the ServoDyn module of OpenFAST supports multiple types of tuned-mass dampers (TMDs) and tuned liquid-column dampers (TLCDs). These structural controllers can be located most anywhere in the wind turbine system, including the blades, nacelle, tower, and substructure. And their exact position is user-specified. See the online Structural Control documentation on readthedocs for more information: 4.2.11. Structural Control (SrvD) — OpenFAST v3.1.0 documentation.

Best regards,

Dear @Jason.Jonkman ,

Thank you for your reply.
I have input files compatible with OpenFast v2.1 and i’m usin these same files for OpenFast v3.0
Obviously, i’m gettin error.
Is there any solution for updating the file maybe ?

Thank u in advance,

Best Regards

Dear @Riad.Elhamoud,

The online readthedocs documentation describes the changes to the input files between each version of OpenFAST: 4.1.2. API changes between versions — OpenFAST v3.1.0 documentation.

If you use MATLAB, the MATLAB Toolbox have scripts to aid in upgrading input files from old to new versions: matlab-toolbox/ConvertFASTversions at main · OpenFAST/matlab-toolbox · GitHub. I don’t see that these have been updated in a while, but the functionality is generally applicable and may help you get automate the process a bit.

Best regards,

Dear @Jason.Jonkman ,

Thank u for your reply.
I will try this toolbox. Frankly, i took input files for OC3 Hywind for example and i managed to change all parameters.
But i obtained an error. I didn’t know how to fix it. Here is the error i obtained:

Running ElastoDyn.

FAST_InitializeAll:ED_Init:ED_ReadInput:ReadPrimaryFile:Invalid numerical input for file
".\WINDCRETE_GC_IEA-15-240-RWT_ElastoDyn-Copy.dat" occurred while trying to read BldGagNd.

** OpenFAST encountered an error during module initialization.**
** Simulation error level: FATAL ERROR**

** Aborting OpenFAST.**

I tried to put BldGagNd to zero but always i’m gettin the same error.
BldGagNd - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0]

Dear @Riad.Elhamoud,

My guess is that you have formatting error elsewhere in the file. As with any input file formatting issue, I would suggest enabling the Echo option to debug.

Best regards,