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Old   April 6, 2010, 13:47
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Axel Söhngen
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Hello, can anybody say me what output of pressure OpenFoam delivers? For example when I simulate a flow in side a pipe is the pressure in the pipe only the change of pressure or the change of pressure + atmospheric pressure or something else?

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Old   April 6, 2010, 17:15
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Vesselin Krastev
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It depends of what kind of solver are you using. If it is an incompressible flow solver, the pressure output is the kinematic (p/rho) relative pressure, measured from an initial arbitrary reference value (which is not relevant for the flow solution). If it is a compressible one, the pressure output is the absolute effective pressure (p) in your domain, which has much more importance for your solution.
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Old   April 7, 2010, 04:21
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Axel Söhngen
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Ok thank you that helps me!
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Old   April 7, 2010, 09:06
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Cean
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Quote:
Originally Posted by vkrastev View Post
If it is an incompressible flow solver, the pressure output is the kinematic (p/rho) relative pressure, measured from an initial arbitrary reference value (which is not relevant for the flow solution).
I am trying to understand the p/rho output for potentialFoam cylinder sample. How could I get the relevent pressure field?

Thanks

Cean
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Old   April 7, 2010, 13:43
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Axel Söhngen
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So is the pressure = p(reference) - p ?
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Old   April 8, 2010, 04:53
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Vesselin Krastev
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For the incompressible solvers the p/rho output is a difference between the calculated and the reference value: so, if the reference value is set to zero, an output of 10 means +10 m^2/s^2 measured from the reference and so on (for example, you can imagine that the zero value corresponds to the atmospheric p/rho value in standard conditions and then evaluate the effective pressure in your domain at the end of the calculations).
For the incompressible solvers you are forced to set realistic initial values of effective absolute pressure and temperature, because both of them influence the initial density (rho) value of the species contained in your domain. At the end of the calculation, the pressure output is exactly the absolute pressure (p, measured in Pa) in your domain.

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