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-   -   General understanding of postprocessing in paraFoam (https://www.cfd-online.com/Forums/openfoam-post-processing/160902-general-understanding-postprocessing-parafoam.html)

Gerrit October 15, 2015 05:38

General understanding of postprocessing in paraFoam
 
Hi everyone,

I want to get values out of my simulations for a mesh-independence study. No problem:
1. Insert a slice
2. Insert a Filter "Integrate variables"
3. Attribute "Cell Data"

1. As far as I understood, I have to divide the value by the area at that position, is that correct?
2. The pressure, that is defined in 0/p and given in paraFoam in the filter e.g. is the relative static pressure, right?
3. Do I have to multiply that pressure with density to receive the correct pressure?

Sorry for these basic questions, but I do not want to make stupid mistakes!

tomf October 16, 2015 05:10

Hi,

Let me respond to your questions:

Quote:

1. As far as I understood, I have to divide the value by the area at that position, is that correct?
2. The pressure, that is defined in 0/p and given in paraFoam in the filter e.g. is the relative static pressure, right?
3. Do I have to multiply that pressure with density to receive the correct pressure?
1. If you want to have the average over the area: yes. You can actually do this by using the calculator filter after the integrate variables filter (there should be a variable "Area")
2. If you are running an incompressible solver: yes. You can also find it in the dimensions of your 0/p file. If it reads [0 2 -2 0 0 0 0] you have kinematic pressure (pressure divided by density). If it reads [1 -1 -2 0 0 0 0] you have absolute pressure. OpenFOAM uses relative pressure in incompressible cases, but absolute pressure in compressible cases.
3. (Like in 2.): yes if incompressible

Regards,
Tom

Gerrit October 20, 2015 02:08

Hi Tom,

thank you very much for your reply! It's nice to know, that I was on the right path ;)


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