Simulate OpenFAST with only subset (time) of turbulent wind file

Dear all,

after simulating a 600 seconds simulation of a full field turbulent wind OpenFAST simulation and obtaining loads, is it possible to resimulate OpenFAST with lets say only 200 seconds of the exact same wind file?

Of course the simulation length can just be shortened, but if let say the turbulent wind of interest is in the range of 300 to 500 seconds of the wind timeseries, how can the OpenFAST start be shifted?

The reason why I am asking is, that for instance BeamDyn requires often still a very small timestep. Thus, it would mostly be more practically in load simulation to just resimulate for each sensor the related turbulent timeseries around the highest occurrances of load for this sensor, which has been obtained before with less fidelity simulation with ElastoDyn. The drawback is that this does not work for fatigue loads.

The only promising parameter to do this, which I have found, is the XOffset parameter in InfloWind input file. It describes the initial offset in +x direction (shift of wind box) using the HAWC-format binary files.

Please let me know if it is possible via the XOffset or any other parameter.

Kind regards,

Hi @Max.Becker,

I agree that adding support for an input like XOffset for WindType = 5 (HAWC format) in InflowWind would be useful to add for other turbulent wind file formats including Bladed and TurbSim. This is not a feature currently available, but I would suggest adding it as a feature request on OpenFAST issues: Issues · OpenFAST/openfast · GitHub.

FYI: We are working on addressing the speed of OpenFAST when BeamDyn (or SubDyn) are enabled by introducing a tight coupling algorithm in OpenFAST around the structural modules (ElastoDyn, BeamDyn, SubDyn). I presented the status of this development last month at WESC and plan to present the final results at the NAWEA / WindTech 2023 conference in October.

Best regards,

Hi Jason Jonkman,

I was able to apply an offset of about 200 seconds for 10 m/s mean wind turbulent HAWC format wind file with the Xoffset parameter set to 2000 m in the InflowWind file.

However, the resulting time series in OpenFAST does show that there is a minimal variation in the maxima and minima, see attached plot and related statistics below:

Is there a specific source for this deviation? We would have expected it to be exactly the same if the turbulent wind time series are just shifted with the Xoffset.

Thank you for the update regarding the speed of OpenFAST if coupled with BeamDyn or SubDyn. This is indeed a very much appreciated development.

Kind regards,

Dear @Max.Becker,

I would expect that you’d see exactly the time shift you’ve specified if you look at ambient wind-speed related outputs. But turbine-related outputs will also be impacted by the turbine operation, specifically different orientations of the rotor azimuth angle, which will impact how the rotor interacts with the wind.

Best regards,