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-   -   Pressure units in compressible solvers (http://www.cfd-online.com/Forums/openfoam/71694-pressure-units-compressible-solvers.html)

thekay January 12, 2010 08:29

Pressure units in compressible solvers
 
Hi all and happy new year!

I was going through Wolle's thread about the motorbike tutorial: http://www.cfd-online.com/Forums/ope...k-out-box.html
He noticed that:
Quote:

In the 0/p file, the dimensions for p is set to [0 2 -2 0 0 0 0], what would be equivalent to (m*m)/(s*s) which is obviously not a pressure unit... How come?
and he got the reply from askjak that:
Quote:

The incompressible solvers in OpenFOAM solve the density normalized Navier-Stokes equation. The units corresponds to p/rho.
I now see in the tutorial /compressible/sonicFoam/laminar/forwardStep/ that the pressure units have:
dimensions [1 -1 -2 0 0 0 0];
which corresponds to kgr/(m*s^2).
Could somebody explain to me how this is derived?

Thank you very much in advance.

Kay

askjak January 12, 2010 08:45

http://en.wikipedia.org/wiki/Pressure#Units, so kg/(m*s^2) is the SI unit of pressure.

thekay January 12, 2010 08:48

Hmmm... Actually, I found it. My mistake obviously. Read "compressible" instead of incompressible in askjak's reply. Please delete.


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