Hi,
I want to get wake deficits at different heights, but when I set up the radial nodes, I found that the first radial node starts at the hub center and then gradually takes values upwards, so that the final output is N01-N20, as shown in the figure below.
My question is how should I set the radial nodes to a position below the hub center, the point I marked in red. Or how should I get velocity deficits at different heights starting from the ground instead of starting from the hub center.
The image you show is from the FAST.Farm documentation for the original polar wake model (as apposed to the recently introduced curled wake model), so, presumably you are using that option of FAST.Farm. This wake model is axisymmetric, so, the wake deficit will be the same at red dots that are opposite the black dots (at consistent radial locations).
When I am using the polar wake model, because the inflow wind speed I give is not axisymmetric, but the polar wake model is axisymmetric, so the wake deficit will be the same. After I have considered it, I am going to use the curled wake model, and now the problem I encounter is that when I use the output of the radial node method, it shows invalid results. I would like to ask how I should get the wake deficit results of different heights , and which output should I look at.
I’m not sure I fully understand your question about axisymmetry. Indeed the polar wake solution is axiymmetric regardless of the inflow. The curled wake solution is not axisymmetric only when the skew angle is nonzero.
Regarding outputting the wake deficit when the wake is not axisymmetric for the curled wake model, I agree that the typical FAST.Farm outputs involving NOutRadii and OutRadii are not useful. There are two other outputs that are useful for the curled wake model, however. The first is the visualization outputs in the XY, YZ, XZ or full domain. The second is the OutAllPlanes option. Both generate a lot of data, and so, should be used sparingly, but should help you assess the wake deficit results for specific simulations of interest.
The wake model I chose was "2:Curl, 3:Cartesian"and the fast.farm worked fine, but the following error occurred when visualizing the flow field with paraview:
"Generic Warning: In C:\glr\builds\paraview\paraview-ci\build\superbuild\paraview\src\VTK\IO\Legacy\vtkDataReader.cxx, line 1506
Error reading ascii data. Possible mismatch of datasize with declaration.
ERROR: In C:\glr\builds\paraview\paraview-ci\build\superbuild\paraview\src\VTK\IO\Legacy\vtkDataReader.cxx, line 1007
vtkStructuredPointsReader (000002CFB4CE4320): Unsupported point attribute type: ********** for file: G:\3.5.0\r-test-main\glue-codes\openfast\5MW_OC4Semi_WSt_WavesWN\vtk_ff\FAST.Farm_30.Low.DisYZ09.0046.vtk"
Please tell me what to do. Thank you in advance.
Best regards,
Can you open the VTK file using your text editor and check whether the values are correct? Do you see NaN or ******** values? If this is the case, there could be something wrong in your simulation (something not physical).
It could also potentially be an implementation bug with some variable not initialized correctly. Can you try and generate the same outputs using the two FAST.Farm test cases present in the r-test repository? Do you see the same “NaN” values? If you do, feel free to report a bug.
