# Dimensions in ScalarTransportFoam

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 November 26, 2017, 09:15 Dimensions in ScalarTransportFoam #1 New Member   Dan Join Date: Sep 2016 Posts: 20 Rep Power: 7 Hi, I have an simple question. I'm referring to OF 4.1. There is the definition of the equation: fvScalarMatrix TEqn ( fvm::ddt(T) + fvm::div(phi, T) - fvm::laplacian(DT, T) == fvOptions(T) ); So, this means: . For incompressible fluids phi means: . I don't get the dimensions right here. For the first term it's obviously . But for the second term phi has to be U, to get the right dimension. I looked up phi and it says: surfaceScalarField phi ( IOobject ( "phi", runTime.timeName(), mesh, IOobject::READ_IF_PRESENT, IOobject::AUTO_WRITE ), fvc::flux(U) ); So what exactly is meant with flux(U), is this without the area? I couldn't find the code definition of flux(U). I hope someone can help me to clarify this topic. Best regards Gesetzt

November 27, 2017, 03:55
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Join Date: Mar 2014
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Quote:
 Originally Posted by Gesetzt So what exactly is meant with flux(U), is this without the area? I couldn't find the code definition of flux(U).
Hi,
please have a look at src/finiteVolume/finiteVolume/fvc/fvcFlux.C where the volVectorField is U in your case! Makes things clearer ?

 December 3, 2017, 05:48 #3 New Member   Dan Join Date: Sep 2016 Posts: 20 Rep Power: 7 Hey, Thanks. I think it's clear now. Part of the problem was, that I didn't thought about the fact we are using FVM, so for the discretisation over all faces we need the area. Best Regards, Gesetzt

February 16, 2018, 02:27
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Ramana
Join Date: Jul 2017
Location: India
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Quote:
 Originally Posted by Gesetzt Hi, I have an simple question. I'm referring to OF 4.1. There is the definition of the equation: fvScalarMatrix TEqn ( fvm::ddt(T) + fvm::div(phi, T) - fvm::laplacian(DT, T) == fvOptions(T) ); So, this means: . For incompressible fluids phi means: . I don't get the dimensions right here. For the first term it's obviously . But for the second term phi has to be U, to get the right dimension. I looked up phi and it says: surfaceScalarField phi ( IOobject ( "phi", runTime.timeName(), mesh, IOobject::READ_IF_PRESENT, IOobject::AUTO_WRITE ), fvc::flux(U) ); So what exactly is meant with flux(U), is this without the area? I couldn't find the code definition of flux(U). I hope someone can help me to clarify this topic. Best regards Gesetzt
HI,
i have question about TEqn. can this be valid for porous simple foam also.

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