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Outlet boundary setup for interFoam

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Old   July 7, 2010, 19:29
Question Outlet boundary setup for interFoam
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Kushagra Mittal
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Hi,

I am new to OpenFoam. I want to set up a simulation for a problem that I used to run using Fluent earlier.

The case involves water and air as two continuous phases. To track the interface, I will be using interFoam (LES turbulence modeling) solver for this purpose.

I need some help/guidance to setup boundary conditions properly. Your input will highly be appreciated.

Geometry has one 'inlet' and one 'outlet' and rest 'wall'. At inlet, volume fraction of water is 1 and it is velocity specified inlet. The outlet is open to atmosphere (hence gauge p =0) and if the backflow occurs, only air can enter in.

I have searched in this forum and as I understand I will need to use BCs similar to 'inletOutlet' for my outlet. I am wondering what does 'value' mean in the bc? (highlighted in red below)

************************ alpha1 ************************

dimensions [0 0 0 0 0 0 0];
internalField uniform 0;

boundaryField
{
inlet
{
type fixedValue;
value uniform 1;
}

outlet
{
type inletOutlet;
inletValue uniform 0;
value ??????? (what to put here and what does it mean?)
}

wall
{
type zeroGradient;
}
}

**************************************************

Similar to that, how should I treat the U and pressure at the 'outlet'? Basically I am having problems in understanding 'outlet' boundary setup.

Thank you very much for your help.

With very kind regards
Mittal
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Old   July 14, 2010, 06:49
Default Outlet boundary setup for interFoam
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ata
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ata kamyabi
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Hi Kushagra Mittal
May be you can use zero gradient for pressure and velocity at outlet.
good luck
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Old   July 14, 2010, 08:59
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Stefan Herbert
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Quote:
Originally Posted by mittal View Post
I will need to use BCs similar to 'inletOutlet' for my outlet. I am wondering what does 'value' mean in the bc?
...
outlet
{
type inletOutlet;
inletValue uniform 0;
value ??????? (what to put here and what does it mean?)
}
Hi mittal,

this value is re-evaluated in every time step. It is simply showing the actual value on patch derived from zeroGradient or inletValue respectivley depending on flow direction. But it is not used as a bc or something similar. To my understanding the value entry is there to give some values to paraFoam in postprocessing.

Therefore you can input any value you want to, e.g. uniform 0. It should have no influence on the solution.

Regards,
Stefan
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