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Run-time wall pressure sampling - Nodal / Cell-Centered values

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Old   August 19, 2014, 13:39
Question Run-time wall pressure sampling - Nodal / Cell-Centered values
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Hello, I am using OpenFOAM for an LES case of fluid through a wall-bounded region. I'm outputing the wall pressure at each time-step using sampling function objects in the controlDict (see below). These values are exported at the cell-center of each element along the wall surface. Is there an easy way to export the pressure a nodes instead of cell-centers? This is an option in Fluent,and I was wondering if there is a simple option/way of doing this without having to add in any of my own code or using a post-processing script to do some kind of interpolation. Thank you!


My function in controlDict to export wall pressure:

wallPressure
{
type surfaces;
functionObjectLibs ("libsampling.so");
surfaceFormat raw; // vtk;
outputControl timeStep;
outputInterval 1;
interpolationScheme cellPoint; //cell
enabled true;
timeStart 14.0;

fields
(p);

surfaces
(
Wall
{
type patch;
patches ("Wall");
interpolate false;
triangulate false;
}
);

}
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Old   August 25, 2014, 07:41
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No one has any thoughts? Perhaps I should have posted this in the main OpenFOAM forum instead of the Post-Processing sub-forum.
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Old   August 25, 2014, 22:47
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It appears that you already have cellPoint 'cell-to-point' interpolation activated. Are you sure you aren't already writing out the field you need?
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Old   August 26, 2014, 12:39
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Quote:
Originally Posted by kmooney View Post
It appears that you already have cellPoint 'cell-to-point' interpolation activated. Are you sure you aren't already writing out the field you need?
Hi Kyle, thanks for the reply.

Yes, I have "cellPoint" chosen as an interpolationScheme, but I think this refers to how the pressure is calculated (I could be wrong as the documentation is a little unclear) not where it is written. I have tested this by writing out pressure using both "cellPoint" and "cell" for the interpolationScheme, and both options wrote out data for the cell-center, not at the nodes.
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Old   August 26, 2014, 12:41
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Have you also tried to set

Code:
interpolate true;
for the Wall patch?
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Old   August 26, 2014, 16:08
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Yes, I've tried setting "interpolate true;" for the Wall patch. It affects the values that the sampling function object exports, but not the location. The location is the cell center for either choice.

It appears that this uses the nodal values to calculate the pressure using the "cellPoint" interpolation scheme, but there doesn't seem to be (at least not that I can see ) an option to just export these nodal values themselves? Thanks for your help!
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Old   August 26, 2014, 16:12
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I believe that OF writes node based values when it outputs in VTK format. You could try to write the vtk then check the ascii values within the file perhaps.
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Old   August 28, 2014, 08:35
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Well, I tried changing the "surfaceFormat" to "vtk" instead of "raw", but it is still exporting values at the cell centers. Is this what you were referring to?
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