How to plot streamlines

Hello, Sorry, if this is not the right place to post this. I followed the different examples provided by vtkplotter to plot streamlines. Unfortunately I couldn’t make it work. Here is an example of a vtk file cavity.zip that contains the velocity vector field U. Here is my code:

"""
Draw streamlines for the cavity case from OpenFOAM tutorial
"""

from vtkplotter import loadUnStructuredGrid, load, show, interactive, Box, Grid, streamLines, Text

cavity = load('cavity.vtk')

domain = load('cavity.vtk')

comment = Text(__doc__, c='w')
probe = Grid(pos=[0.05,0.1,0.005], normal=[0,1,0], sx=0.01, sy=0.1, resx=30, resy=10)
probe.color('k')

stream = streamLines(domain, probe, direction='forward')
show(domain, stream, probe, comment, axes=8)

when I run the example above, I couldn’t see the streamlines I appreciate your help

[ghost]

Thank you very much. I appreciate your help.

[ghost]

Thank you very much for the detailed answer. Of course you could add it to the examples. You could find many others in the tutorials directory of OpenFOAM, just use foamToVTK to convert the results to vtk files.

I have just another question about how to choose the field to plot if you have more than one. For example if I convert the original OpenFOAM cavity results, the final VTK will contain the field p for pressure and U for velocity. In this case how can I choose which field to plot in vtkplotter?

Thanks