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

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;
}
);

}

No one has any thoughts? Perhaps I should have posted this in the main OpenFOAM forum instead of the Post-Processing sub-forum. :o

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.

Have you also tried to set

for the Wall patch?

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 :o ) an option to just export these nodal values themselves? Thanks for your help!

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.

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?