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totalPressureIncompressible Default Rho value = 1.2 |
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March 28, 2018, 07:34 |
totalPressureIncompressible Default Rho value = 1.2
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#1 |
Member
Scott
Join Date: Sep 2009
Posts: 44
Rep Power: 16 |
Hi there,
I'm running the following command after a simulation to get the total pressure field around my geometry. Code:
postProcess -func "totalPressureIncompressible(p,U)" I've tested with different velocities and the corresponding total pressure in the freestream always comes back to 1.2, once you recalculate density based on the new total pressure value. I've also tested with random values of nu, and it does not affect the freestream total pressure, again, we always get 1.2, but the total pressure value doesn't change, so it is not actually dependent on nu. It appears that it is using the following equation fro freestream total pressure 0.5 *density*velocity^2 = 0.5*1.2*U^2. My problem is, I don't want it to use 1.2 as a default, I just can't work out how to change it! Can anyone confirm that this is the intent? I've tried setting rho an rhoInf to 1.184 in many places so far with no apparent change to the result. For completeness, I am running this command in OpenFOAM v1706 Windows10. Once this command is executed, the freestream pressure can be seen in /0/total(p) based on initial conditions. It also is apparent in paraview. Thanks for your time! Note: I am using simpleFoam, and I know that the density is not used in the solve calculations, and that to get the correct pressure values I need to multiply by density due to the way OpenFOAM calculates. As part of the type of work we do, we typically use Total Pressure as an output hence I'm trying to work out how to get the correct output. I guess I could scale the field as I know how far out it is, but there has to be somewhere that this 1.2 value is being pulled from, and I'd like to modify it if anyone can help. |
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July 23, 2018, 19:29 |
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#2 |
New Member
Carlitre
Join Date: Jun 2013
Posts: 1
Rep Power: 0 |
Hi,
According to https://github.com/OpenFOAM/OpenFOAM...Incompressible the value is 1.2 try to change in totalPressureIncompressible.cfg /*--------------------------------*- C++ -*----------------------------------*\ ========= | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox \\ / O peration | \\ / A nd | Web: www.OpenFOAM.org \\/ M anipulation | ------------------------------------------------------------------------------- Description Calculates the total pressure field for a case where the solver is incompressible (pressure is kinematic, e.g. m^2/s^2). \*---------------------------------------------------------------------------*/ #includeEtc "caseDicts/postProcessing/pressure/totalPressureIncompressible.cfg" pRef 0.0; rhoInf 1.2; // ************************************************** *********************** // |
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October 19, 2018, 05:34 |
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#3 |
Member
Martin
Join Date: Aug 2018
Posts: 33
Rep Power: 7 |
I cannot change value 1.2 in file /etc/caseDicts/postProcessing/pressure/staticPressure because I don't have permission to change this file.
Is there a way to set custom rho value that will be used by postProcess tool staticPressure instead of reading dafault value 1.2? |
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October 26, 2018, 04:52 |
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#4 |
Member
Anna Feichtner
Join Date: Dec 2016
Location: Cornwall (UK)
Posts: 36
Rep Power: 9 |
Hi artymk4
I think you would create your own copies of the totalPressureIncompressible and the totalPressureIncompressible.cfg files, in wich you can modify the values of pref and rhoInf - with adapting the "#include..."-path accordingly. Does that help? Regards, Anna |
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October 28, 2018, 19:44 |
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#5 |
Member
Scott
Join Date: Sep 2009
Posts: 44
Rep Power: 16 |
Hi everyone,
I've tried all combinations of adding a config file and having the #include in the controlDict. Does anyone have this working? I've been tring with rho of 6 as an example but still get a rho equivalent to 1.2 when I run: postProcess -func "totalPressureIncompressible(p,U)" Hoping someone can save me further hours... Thanks, Scott |
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October 29, 2018, 03:40 |
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#6 |
Member
Anna Feichtner
Join Date: Dec 2016
Location: Cornwall (UK)
Posts: 36
Rep Power: 9 |
Hi Scott,
have you tried it with Code:
<solvername> -postProcess -fields "(p U)" -func totalPressureIncompressible Anna |
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October 29, 2018, 18:11 |
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#7 |
Member
Scott
Join Date: Sep 2009
Posts: 44
Rep Power: 16 |
Hi Anna,
Yes I've tried with both: Code:
postProcess -func "totalPressureIncompressible(p,U)" Code:
simpleFoam -postProcess -fields "(p U)" -func totalPressureIncompressible Code:
/*--------------------------------*- C++ -*----------------------------------*\ ========= | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox \\ / O peration | \\ / A nd | Web: www.OpenFOAM.org \\/ M anipulation | ------------------------------------------------------------------------------- Description Calculates the total pressure field for a case where the solver is incompressible (pressure is kinematic, e.g. m^2/s^2). \*---------------------------------------------------------------------------*/ #includeEtc "caseDicts/postProcessing/pressure/totalPressureIncompressible.cfg" pRef 0.0; rho rhoInf; rhoInf 6; // ************************************************************************* // It doesn't seem as straightforward as it should be. Oh, I also have this in my controlDict: Code:
functions { #includeEtc "/mnt/c/OpenFOAM/Total_Pressure_Value_Test/system/totalPressureIncompressible.cfg" } Thanks! Scott |
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October 30, 2018, 04:58 |
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#8 |
Member
Anna Feichtner
Join Date: Dec 2016
Location: Cornwall (UK)
Posts: 36
Rep Power: 9 |
Hi Scott
it works for me with: I have a "totalPressureIncompressible1" file in the system folder: Code:
#includeEtc "caseDicts/postProcessing/pressure/totalPressureIncompressible.cfg" pRef 0.0; rhoInf 6; //1.2; Code:
functions { #includeFunc totalPressureIncompressible1 } Code:
simpleFoam -postProcess -fields "(p U)" -func totalPressureIncompressible1 Anna |
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