water velocities (point data) are all zero

sophie_l · April 19, 2013, 11:24

Hi there,

I ran a case using interFoam. The mesh is 2D (only one cell in the z direction). Y-axis is 4 m high, 0-2m is water and 2-4 m is air. The free surface (using alpha1) looks good in paraview. But when I choose U-magnitude (point data) for animation, only the inlet patch and the top of air have non-zero velocities. When using U-magnitude (cell data), the water velocities are non-zero and look normal.

However, I need to extract the water velocity at sampling points or over a line to do some comparison. I cannot save the cell data via 'plot over line', only point data are saved, ie., water velocites are all zero. It is really strange to me. I am thinking maybe there is something wrong with the settings in paraview as the output U files are of non-zero values. Could someone shed some light on this please?

Thanks a lot in advance.
Sophie

ngj · April 20, 2013, 03:50

Hi Sophie,

Maybe you could use the OpenFoam utility "sample" instead. This allows you to sample along a given line.

You can find more information and an example of the needed dictionary here:

OpenFOAM/OpenFOAM-2.2.0/applications/utilities/postProcessing/sampling/sample

Kind regards

Niels

sophie_l · April 20, 2013, 06:08

Hi Niels,

Many thanks for your guidance! I'll try it.

Best wishes,
Sophie

April 19, 2013, 11:24	water velocities (point data) are all zero	#1
sophie_l Member Join Date: Nov 2012 Location: Liverpool, UK Posts: 51 Rep Power: 13	Hi there, I ran a case using interFoam. The mesh is 2D (only one cell in the z direction). Y-axis is 4 m high, 0-2m is water and 2-4 m is air. The free surface (using alpha1) looks good in paraview. But when I choose U-magnitude (point data) for animation, only the inlet patch and the top of air have non-zero velocities. When using U-magnitude (cell data), the water velocities are non-zero and look normal. However, I need to extract the water velocity at sampling points or over a line to do some comparison. I cannot save the cell data via 'plot over line', only point data are saved, ie., water velocites are all zero. It is really strange to me. I am thinking maybe there is something wrong with the settings in paraview as the output U files are of non-zero values. Could someone shed some light on this please? Thanks a lot in advance. Sophie

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April 20, 2013, 03:50		#2
ngj Senior Member Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Copenhagen, Denmark Posts: 1,900 Rep Power: 37	Hi Sophie, Maybe you could use the OpenFoam utility "sample" instead. This allows you to sample along a given line. You can find more information and an example of the needed dictionary here: OpenFOAM/OpenFOAM-2.2.0/applications/utilities/postProcessing/sampling/sample Kind regards Niels

April 20, 2013, 06:08		#3
sophie_l Member Join Date: Nov 2012 Location: Liverpool, UK Posts: 51 Rep Power: 13	Hi Niels, Many thanks for your guidance! I'll try it. Best wishes, Sophie