How to convert from WAMIT file to FAST input file (.1.dat)

Wind & Water Computer-Aided Engineering Software Tools
1

Hello,

Thank you for your attention.
I’m studying a coupled response of TLP floating wind turbine. While doing a calculation in FAST, I found my WAMIT file from SESAM HydroD should be changed to the proper input file for FAST. Could you explain how to convert from WAMIT(1.dat and 3.dat) file to FAST input file?
Herein the files are attached.

Thanks.
Hailey.Seo
WAMIT_5S.3.txt (349 KB)
WAMIT_5S.1.txt (53.2 KB)

2

In addition to above questions, could you please check some error messages like below;
It didn’t work although I have not changed any function in your sample files (Test23.fst) except time range from 60s to 1000s. I checked Test24 and Test25 for semi and spar works very well.

Timestep: 65 of 1000 seconds. Estimated final compleation at 16:17:32.

FAST_Solution : CalcOutputs_And_SolveForInputs:SolveOption2:InflowWind_CalcOutput : CalcOutput:IfW_TSF
FWind_CalcOutput [position=(-8.523, -19.844, 50.377) in wind-file coordinates]:Error: FF wind
array was exhausted at 65.35 seconds (trying to access data at 72.102 seconds).

FAST encountered an error at simulation time 65.338 of 1000 seconds.
Simulation error level : FATAL ERROR

Aborting FAST.

3

Dear Hailey,

I haven’t looked at your files in detail, but the format of the WAMIT-generated output files (*.1, *.3, and *.hst for first order, etc.) needed by HydroDyn can be found in Chapter 4 of the WAMIT User’s Manual, available online: wind.nrel.gov/nwtc/docs/HydroDyn_Manual.pdf.

An error regarding the “FF wind array was exhausted” has been discussed many times on this forum e.g.: Error: FF wind array was exhausted - #6 by Jason.Jonkman.

I hope that helps.

Best regards,

4

@Jason.Jonkman Dear Jason,

I want to convert the wind output of fast.farm in vtk format into bts format file, or output the wind data in bts format by fast.farm directly. Is there any way? Thank you in advance.

Best regards,
Liye

5

Dear @Liye.Zhao,

I’m not aware of a script that will do exactly what you want. But there are scripts in the MATLAB Toolbox (matlab-toolbox/Utilities at main · OpenFAST/matlab-toolbox · GitHub) and Python Toolbox (python-toolbox/pyFAST/input_output at main · OpenFAST/python-toolbox · GitHub) that will get you part way there.

Please note that the FAST.Farm output in VTK format can be 4D, with 3 spatial and 1 time dimensions . However, the TurbSim BTS format is only 3D, with 2 spatial and 1 time dimensions. So, what you propose likely only makes sense if you output a plane of data from FAST.Farm, e.g., through NOutDisWindYZ and OutDisWindX.

Best regards,

6

Dear Jonkman,
Excuse me, are all the data in the. 1 file dimensionless? The first column is frequency or period, the second and third columns are matrix indices, the fourth column is additional mass matrix data, and the fifth column is radiation damping coefficient matrix data.
And how is nondimensionalization done in Waimit?
Best regards,

7

Dear @Cuizhi.Zhu,

The hydrodynamic added mass and radiation damping matrices in the WAMIT .1 output file are nondimensional. This nondimensionalization is documented in Chapter 4 of the WAMIT User’s Manual, available online: https://www.wamit.com/manual6.4/Chap4.pdf.

Best regards,

8

Dear Jason, Im trying to make a WAMIT.1 using WADAM for the IEA-15-240-RWT-UMaineSemi. My WADAM file contains values for hydrodynamic added mass and radiation damping matrices for all matrix indices. For example I have values for 1 1, 1 2, 1 3, 1 4, 1 5, 1 6 but in the WAMIT.1 file i found in hydrodata folder for the IEA-15-240-RWT-UMaineSemi there are only values for 1 1, 1 3 and 1 5. Do I need only those values because my results are different when i use my WAMIT.1 file with all of these values?

best regards

9

Dear @Georgia.Tsoukleri,

In the WAMIT .1 and .3 output file formats, values that are zero are not included in the file.

Due to the XZ plane of symmetry, I would expect the (1,2), (1,4), and (1,6) values to be zero or near zero.

Best regards,

10

Dear Jason, thank you for your help.
I alsol want to test the IEA-15-240-RWT-UMaineSemi for different WaveDir values so I have values for (1,2), (1,4), and (1,6) etc. I want to ask you if openFAST can read these values

Best regards

11

Dear @Georgia.Tsoukleri,

In what matrices are you referring to? The wave direction (WaveDir) should only impact the wave-excitation loads in the potential-flow solution, i.e., the wave-excitation vector, not the added mass, radiation damping, or hydrostatic matrices from WAMIT.

Best regards

12

Dear Jason
I read that the WAMIT data for the UMaine semisubmersible are generated for zero-degrees wave heading. So, I run WADAM for my range of wave headings and for example I have some values for (1,2), (1,4), and (1,6) etc. Can openFAST read those values or I need only (1 1), (1 3) and (1 5)?

13

Dear @Georgia.Tsoukleri

I read that the WAMIT data for the UMaine semisubmersible are generated for zero-degrees wave heading

This statement applies to the first-order wave-excitation load vector, as well as the second-order quadratic transfer functions (QTFs).

I have some values for (1,2), (1,4), and (1,6) etc.

Again, what matrices are you referring to, which I would not expect would depend on WaveDir.

Best regards,

14

Dear Jason, Im referring to the .1 and .3 files. I have some extra values.
For example I have values for (1 1), (1 2), (1 3),( 1 4), (1 5), (1 6) but in the WAMIT.1 and WAMIT.3 file ,i found in hydrodata folder there are only values for 1 1, 1 3 and 1 5. I want to know if OpenFAST can take into consideration these values even if they are near zero due to symmetry.

Best regards

15

Dear @Georgia.Tsoukleri,

HydroDyn will use these values from the .1 and .3 files, but I would not expect them to result from WaveDir and I would question if they are actually nonzero, or only small nonzero values resulting from numerical approximations in WADAM, which you could filter out before inputting into HydroDyn.

Best regards