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Confused with '==' in UEqn

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Old   June 9, 2014, 11:50
Default Confused with '==' in UEqn
  #1
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David Long
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Hi Foamers,

I have few questions on the UEqn in OpenFoam:

e.g.

1. understandable UEqn in pisoFoam

Quote:
fvVectorMatrix UEqn
(
fvm::ddt(U)
+ fvm::div(phi, U)
+ turbulence->divDevReff(U)
);
and

Quote:
if (momentumPredictor)
{
solve(UEqn == -fvc::grad(p));
}
so the full equation for U is:

Quote:
fvm::ddt(U)+ fvm::div(phi, U) + turbulence->divDevReff(U) == -fvc::grad(p)
2. confused with this UEqn in pimpleFoam (OF 2.2.2), namely the ' ==':

Quote:
tmp<fvVectorMatrix> UEqn
(
fvm::ddt(U)
+ fvm::div(phi, U)
+ turbulence->divDevReff(U)
==
fvOptions(U)
);
and

Quote:
if (pimple.momentumPredictor())
{
solve(UEqn() == -fvc::grad(p));
fvOptions.correct(U);
}
So in this case the full equation is ??

Quote:
fvm::ddt(U)+ fvm::div(phi, U) + turbulence->divDevReff(U)
== fvOptions(U)
== -fvc::grad(p)
but this seems not logical, should it be like this?

Quote:
fvm::ddt(U)+ fvm::div(phi, U) + turbulence->divDevReff(U) - fvOptions(U)
== -fvc::grad(p)
Why is there a '==' in the UEqn ?


Cheers,

Daivd

Last edited by keepfit; June 9, 2014 at 14:00.
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Old   June 9, 2014, 22:22
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  #2
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xuhe-openfoam
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hi,
you could watch this .
HTML Code:
http://www.cfd-online.com/Forums/openfoam-programming-development/85013-operator.html
it is a little long to read , but you could understand the "==" well after reading!


best wish
xuhe
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Old   June 10, 2014, 09:11
Default
  #3
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David Long
Join Date: May 2012
Location: Germany
Posts: 64
Rep Power: 6
keepfit is on a distinguished road
Quote:
Originally Posted by bieshuxuhe View Post
hi,
you could watch this .
HTML Code:
http://www.cfd-online.com/Forums/openfoam-programming-development/85013-operator.html
it is a little long to read , but you could understand the "==" well after reading!


best wish
xuhe
thanks xuhe, I will look to that post.
keepfit is offline   Reply With Quote

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