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October 22, 2008, 00:39 |
What is phi in simpleFoam
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#1 |
New Member
ehsan vaghefi
Join Date: Mar 2009
Posts: 9
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Hi there
I have been using simpleFoam to solve my problem, I was wondering the what is the "phi" file that openFoam is calculating ? a more general question , can calculate fluxes (as vectors) on each of nodes ? Cheers. Ehsan |
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October 22, 2008, 08:14 |
As this phi question creeps up
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#2 |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
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As this phi question creeps up every 2 weeks or so, I thought it might be a good candidate for the FAQ: http://openfoamwiki.net/index.php/Main_FAQ#What_is_the_field_phi_that_the_solver _is_writing
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September 7, 2011, 12:31 |
phi Field in Momentum and Eenrgy Equations
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#3 |
Member
,...
Join Date: Apr 2011
Posts: 92
Rep Power: 14 |
Hi Everybody
I have added temperature equation to icoFoam in the manner that has been described in http://openfoamwiki.net/index.php/Ho...ure_to_icoFoam The main part is fvScalarMatrix TEqn ( fvm::ddt(T) + fvm::div(phi, T) - fvm::laplacian(DT, T) );From a mathematical manipulation i founded out that phi should be "ui + vj" here. And this vector form for phi is in complete disagreement with what has been described for the field phi in the following page ----- "http://openfoamwiki.net/index.php/Main_FAQ" in section "3.1.3 What is the field phi that the solver is writing" "3.1.3 What is the field phi that the solver is writing " The answer in this file is the mass flow through the cell faces ( with the area of the face). ----- In Summary: Do you guys know whether phi is different in the vector form of the momentum equation and scalar temperature equation! What I had founded out is that YES, it should be different. But I am NOT sure! I would appreciate if someone helps me!! |
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September 7, 2011, 19:25 |
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#4 | |
Senior Member
Daniel P. Combest
Join Date: Mar 2009
Location: St. Louis, USA
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Quote:
Dan |
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July 22, 2013, 12:10 |
The units do not seem to match
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#5 |
New Member
Sri
Join Date: Nov 2012
Posts: 10
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Hi,
Is Phi just U dotted on to A or rhoU dotted on to A as you have described on the page. The table has units cu.m/s which would fit the first description of Phi (U dotted on to A). Thanks, Sri |
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September 28, 2013, 03:21 |
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#6 |
New Member
eric
Join Date: Nov 2010
Location: Vancouver, Canada
Posts: 16
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I just start learning FOAM and also have the same question about phi.
In the equation of motion UEqn, phi seems to be rho*U. But in the equation of energy TEqn, phi is U. This phi bothers me a lot. Can anyone explain it please. Thanks in advance. |
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September 29, 2013, 07:37 |
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#7 |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
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Greetings to all!
openfoamwiki.net is undergoing some changes on the FAQ section. I've updated the FAQ associated to this thread's topic: http://openfoamwiki.net/index.php/FA..._is_writing.3F @Eric: You didn't mention which solver you were looking at, but the answer should be simple: compressible solvers use the rho field; incompressible solvers do not use the rho field. If look at the user guide, section "2.1.1.3 Physical properties", you'll see that the fluid density is implied when using "kinematic viscosity nu": http://www.openfoam.org/docs/user/cavity.php Best regards, Bruno PS: I also merged the two threads where Eric had posted, because it made sense to keep the two threads in a single discussion.
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September 29, 2013, 12:00 |
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#8 |
New Member
eric
Join Date: Nov 2010
Location: Vancouver, Canada
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Thank you very much for the explanation. I am now much clearer with this little guy phi.
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July 19, 2024, 17:01 |
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#9 | |
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Masoud Rvn
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Quote:
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October 5, 2024, 08:49 |
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#10 |
New Member
Pouya Namakshenas
Join Date: Oct 2024
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If you look at the solver code for instance in $FOAM_SOLVERS/basic/scalarTransportFoam/createFields.H, you can see that it reads createPhi.H, and if you refer to $FOAM_SRC/finiteVolume/cfdTools/incompressible/createPhi.H, you see
surfaceScalarField phi ( IOobject ( "phi", runTime.timeName(), mesh, IOobject::READ_IF_PRESENT, IOobject::AUTO_WRITE ), linearInterpolate(U) & mesh.Sf() ); so for the solvers such as scalarTransport and the ones consider incompressible fluid phi = U*Sf [m³/s] However, for compressible solvers like rhoPimpleFoam it reads compressibleCreatePhi.H instead of createPhi.H and if you refer to that you can see surfaceScalarField phi ( IOobject ( "phi", runTime.timeName(), mesh, IOobject::READ_IF_PRESENT, IOobject::AUTO_WRITE ), linearInterpolate(rho*U) & mesh.Sf() ); hence, phi = rho*U*Sf [kg/s] for compressible solvers. I hope it helps |
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