Dear Jason,
Really appreciate you again for your quick and complete answer.
Highly regards,
Arsalan
Good day Dr. Jason and everyone,
Recently, I just started using FAST v8 coupled with OrcaFlex for my research study, focused on OC4 DeepCwind FOWT.
I’m trying to validate the results from paper entitled “Validation of a FAST semi-submersible floating wind turbine numerical model with DeepCwind test data”, before implement both methods for experimental model soon.
In that paper, one of cases that have been consider is dynamic wind-only case. The wind input is based on temporally dynamic NPD wind, which possessed a mean wind speed at hub height of 20.6m/s, a standard deviation of 2.04m/s, a maximum wind speed of 28.7m/s, and a minimum wind speed of 12.9m/s. For FAST simulation a dynamic wind file was created, by multiplying the recorded hub height wind velocity time history by 0.952 and utilizing a wind shear exponent of 0.0912.
My first question is, how to setup the NPD wind spectrum? Since NPD was not listed in InflowWind module (only have 5 wind types).
Secondly, I noticed that some of InflowWind module is for 12 m/s turbulent winds. Is it consider as dynamic wind flow? If yes, then how we want to generate NPD wind file for uniform wind type?
Meanwhile in OrcaFlex, there is NPD spectrum been indicated, unfortunately, there is no input for min/max wind speed (only min/max frequency).
After made adjustment of the few FAST modules as following below, and the simulation run time is set to 1 hr (3600s), instead of 3 hr (10800) because there is an error stated that “FAST_Init:ValidateInputData:TMax is too large for a 10-character time column in text tabular (time-marching) output files. Postprocessors with this limitation may not work.”, the simulation for dynamic wind-only case run smoothly.
- InflowWind: Steady wind type has been used, and the wind input follow as indicated in TABLE VI. Wind turbine operating parameters.
- ElastoDyn: Blade (1~3) initial pitch angle also follow as indicated in TABLE VI.
The result from OrcaFlex Interphase shows that the gap difference between TABLE XIV in that paper is not so big. However, I’m still thinking the result is not good enough since the wind input and the procedure was not firm.
So, my last question, does the setup procedure above is correct or not? If not, kindly advise the exact method to analyse the dynamic wind only case, before I’m proceeding to analyse the combined dynamic wind-irregular waves.
Attached herewith is the comparison dynamic wind-only case result for your review.
Thanks and regards,
Hanis
Dear Mhanis,
While I was a coauthor on the paper you reference, I did not run the simulations and don’t have access to them. So, I’ll try to answer your questions, but not based on the actual simulations that were ran.
The NPD spectrum is known as the API or Frøya model and is implemented in TurbSim (TurbModel = “API”). See the TurbSim v2 for more information: nwtc.nrel.gov/alphas. TurbSim can generate wind data files for use by FAST’s InflowWind module–including either full-field turbulence wind data files (WindType = 3 or 4 in InflowWind) or uniform wind data files (WindType = 2 in InflowWind). This will enable you to run dynamic wind flow simulations.
Despite the warning, you should still be able to run 3-hr long simulations.
Best regards,
Dear Jason,
I use a turbulent wind file when the input program can run successfully, but when I change to a uniform wind file program, an error is reported, can you help me explain it?
Related documents.zip (32.7 KB)
Dear Zhe.Zhang,
The error is reporting that an aerodynamic analysis node is below the ground, or in this case of a floating offshore wind turbine, below the still water level (SWL). You haven’t sent me enough information to know, but I would guess that the platform heaved downward a bit and an aerodynamic analysis node of the tower is now below the SWL. To eliminate the error, you could try increasing the lowest-most tower aerodynamic analysis node, TwrElev(1), a bit in the AeroDyn v15 input file.
Best regards,
Hi Mr Jonkman
Perl scripts seem to be missing in the link posted, is it possible for you to send it to me?
thanks
Dear @Ali.Rouhbakhsh,
Presumably you are referring to the old scripts such as RunIEC and RunNTM, which are no longer supported by NREL.
Many users of FAST / OpenFAST who need to run many simulations have written there own scripts for their own purposes. For example, the scripts in the MATLAB Toolbox (GitHub - OpenFAST/matlab-toolbox: Collection of Matlab tools developed for use with OpenFAST) or Python toolbox (GitHub - OpenFAST/python-toolbox) can be used to read and write FAST input files, so–using these scripts–it would not be difficult to write your own MATLAB- or Python-based scripts to generate OpenFAST input files for a large set of cases based on a master set of OpenFAST input files. This topic was discussed a bit here: #573.
The Systems Engineering team at NREL also developed the AeroelasticSE module of WISDEM to automate the running of many of the IEC DLCs. These scripts are in the process of being overhauled and migrated into the new WEIS framework to support integrated loads analysis, design, and optimization of wind turbines–see: GitHub - WISDEM/WEIS: Wind Energy with Integrated Servo-controls Toolset.
Best regards,