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-   -   incompressible, The exact meaning of P in case/0/p ? (http://www.cfd-online.com/Forums/openfoam/70660-incompressible-exact-meaning-p-case-0-p.html)

panda60 December 1, 2009 23:27

incompressible, The exact meaning of P in case/0/p ?
 
Dear all:
For simpleFoam solver, what is the exzct meaning of P in case/0/P file ?
It is refference value or the actual value ?
for initial field and outlet condition , we should set 0 or 101325/rho ?
Because I saw many imcompressible case set it to 0, but I set 101325/rho .
Thank you very much.

Ohbuchi December 2, 2009 00:44

There is no meaning for the value of p in incompressible flow. Only the gradient term of p is appeared in Navier-Stokes eq.
You can start both from p=0 or p=101324/rho, then simulated result may be translate by constant value.

panda60 December 2, 2009 01:09

Quote:

Originally Posted by Ohbuchi (Post 238411)
There is no meaning for the value of p in incompressible flow. Only the gradient term of p is appeared in Navier-Stokes eq.
You can start both from p=0 or p=101324/rho, then simulated result may be translate by constant value.

Thanks Ohbuchi,
I am l little understand, I saw the solver of simpleFoam ,in creatfields,H

# include "createPhi.H"

label pRefCell = 0;
scalar pRefValue = 0.0;
setRefCell(p, mesh.solutionDict().subDict("SIMPLE"), pRefCell, pRefValue);

The solver will select the pressure reference possition and reference value itself, so I just set the actual value in P file, is it right ?

Ohbuchi December 2, 2009 05:41

Yes, specified value for p in 0 directory means difference from reference value. So if you set the reference value of p=0, values in 0/p means absolute value.


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