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Dimension of pressure: M/LT2 or L2/T2?

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Old   August 7, 2013, 13:57
Question Dimension of pressure: M/LT2 or L2/T2?
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Sometimes the dimension of pressure is specified differently in 0/p file for different problems:

tutorials/basic/potentialFoam/cylinder
dimensions [0 2 -2 0 0 0 0];

tutorials/compressible/rhoSimpleFoam/angledDuctExplicitFixedCoeff
dimensions [1 -1 -2 0 0 0 0];

What tips me off to the correct dimension to use for a particular problem?

Is there a general rule for the correct dimension of pressure in 0/p file? Is it simply a matter of whether the problem is 2D or 3D? Compressible or incompressible?

I see that (M/LT2)/(M/L3) = L2/T2.

Thanks.

Last edited by gcengineer; August 7, 2013 at 13:59. Reason: Courtesy
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Old   August 7, 2013, 15:37
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one is pressure and the other one is pressure divide on density
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Old   August 7, 2013, 15:44
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Thank you, nimasam, for responding.

As I wrote, "I see that (M/LT2)/(M/L3) = L2/T2."

What I want to know is why does one case require M/LT2, but another requires L2/T2?

Is it 2D v 3D? Compressible v incompressible? Choice of solver?

Last edited by gcengineer; August 7, 2013 at 15:45. Reason: Correction
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Old   August 7, 2013, 15:59
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you should check each solver , but its pressure on density in some incompressible solvers
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Old   August 7, 2013, 16:24
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It appears that the dimension of pressure is M/LT2 for compressible solvers and L2/T2 for incompressible solvers. Here, Boussinesq solvers are incompressible (e.g., buoyantBoussinesqSimpleFoam, buoyantBoussinesqPimpleFoam).

If there is an exception to this rule, I would appreciate knowing about it.

Thanks.
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Old   August 7, 2013, 16:29
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forexample interFoam which is two-phase incompressible solver
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Old   August 7, 2013, 16:41
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Yes. However, for the cases in /tutorials/multiphase/interFoam, there is no 0/p, but 0/p_rgh has dimension M/LT2.

Thanks again.
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