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How to impose a flux at the inlet ?

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Old   November 22, 2010, 12:15
Default How to impose a flux at the inlet ?
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Cyp
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Hi !

I want to set up an equation from the knowledge of a flux. My equation has the following form:

Code:
ddt(S)+div(phib)=0
phib is evaluated otherwise.

As inlet boundary condition, I want to impose a constant flux phib0. Moreover with such inlet, I have been told that S do not need any BC. Is there a simple manner to do that ?

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Cyp
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Old   December 2, 2010, 06:28
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Cyp
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Hi everybody!

I am still on this problem : i do not succeed to impose a flux at the inlet without set up a BC fixedValue for my field S...

May be I should try a specific BC ?? which one ?


I hope you can unblock me....


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Old   January 26, 2011, 04:27
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Gert Jan Auwerda
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Hi I have the exact same question. I have a CFD problem where I have a fixed mass flux at the inlet and a fixed pressure at the outlet.
As the pressure at inlet will depend on flow properties, the inlet pressure is not known in advance. As the density depends on this pressure, I do no know the inlet velocity. So is there a velocity BC, which lets me input a fixed (total) flux, from which inlet velocity BC is derived?

I can make a decent guess of course, but I want to be exact. And running the code a few times, adjusting manually my inflow BC seems a really stupid way.
I cannot believe this BC does not exist, it is so common in CFD problems! Please help!
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Old   January 27, 2011, 03:22
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Hello,

do you mean?

boundaryField
{
Inlet
{
type flowRateInletVelocity;
flowRate 2.8; // [kg/s]
value uniform (0 0 0); // only place holder
}



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Ralph
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Old   January 27, 2011, 04:05
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Gert Jan Auwerda
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Ah yes, that is the one I was looking for. Thank you very much!
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