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Flow diode boundary condition

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Old   July 12, 2013, 10:13
Default Flow diode boundary condition
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Oliver Lauer
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I am looking for something which is at least available in OpenFOAM and probably also in FLUENT.
I would like to have sort of a modified pressure boundary condition which suppresses inflow, that means
if flow is going out of the domain => normal pressure boundary
if flow is going into the domain => set boundary normal velocity to zero

Is there any possibility to create such a boundary condition in CCM+? Could this somehow be realized by a user boundary condition?

Any help appreciated.

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Old   July 14, 2013, 02:28
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siamak rahimi ardkapan
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There is the option of pressure outlet boundary condition.
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Old   July 15, 2013, 03:20
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Quote:
Originally Posted by siara817 View Post
There is the option of pressure outlet boundary condition.
Yes sure, but this pressure outlet boundary condition allows inflow.

I am looking for a modification that prevents inflow and only allows outflow.
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Old   July 15, 2013, 07:51
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There are some reasons for this inflow.
Sometimes because in the outlet the mesh is not enough fine. It is also a good idea to extrude the outlet, it helps removing the reversed flow. Because the software tries to reduce the pressure difference to zero, and this itself causes some reversed flows. If you extrude the outlet then you let enough length to reduce the pressure gradually.
However, in reality reversed flow may happen .
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Old   July 15, 2013, 10:06
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I know why inflow could occur and I also know how to work around it.
Nevertheless I am looking for a "Flow diode" boundary condition like it is available in OpenFOAM with a possibility of setting boundary normal velocitiy component to zero if creating inflow.
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Old   July 16, 2013, 10:05
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You might be able to do this using field functions. I'm thinking something like this:

1) Create a new field function which modifies the field function reporting the boundary face normal velocity. This new field function is a conditional which sets all reverse flow to zero.
2) Use the new field function as the boundary condition.
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