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-   -   directMappedPatch and directMappedFixedInternalValue for fluid-fluid BC (http://www.cfd-online.com/Forums/openfoam/102978-directmappedpatch-directmappedfixedinternalvalue-fluid-fluid-bc.html)

anon_a June 7, 2012 13:49

directMappedPatch and directMappedFixedInternalValue for fluid-fluid BC
 
4 Attachment(s)
In the spirit of experimentation (but also as a possibility for my work), I decided to test the directMapped BC as a way to exchange data in two different regions of the same fluid.

For this reason, I modified the multiRegionHeater tutorial of chtMultiRegionFoam in the following way:
- Only two regions, both of them fluid (topAir, bottomAir)
- Walls all around
- topAir @ 6x10^4 Pa, bottomAir @ 10^5 Pa
- Communication between the two regions is done with directMappedPatch and directMappedFixedInternalValue for all fields
- Gravity, radiation, turbulence, etc all turned off

I need to stress that this is just for testing purposes and I do not have the ambition or desire to take accurate results for this problem. This was meant to be a rough run. I just want to make sure that the BC does what I think, i.e. provide a correct exchange of data and a smooth interface between the two fluid regions.

The problem is that, even though the field data seem to be correctly transmitted, the value exactly at the boundary does not change. It is actually the one that I give in the "value" field at the beginning (if I don't give anything, I get an error related to the thermophysical properties). The result is that the pressure field looks ok with cell data, but when I plot the interpolated field, there is a fine line of different color (see attached files). The situation is much worse when I plot the distribution in one dimension (also see the awful 1D plot attached here).

Does anyone know how to fix this?
The case is attached here, be my guest and play with it.
I am using OF Version 2.0.1, compiled from sources.

manderson010 July 6, 2012 09:29

Just one of those "Is it plugged in?" sort of things: using ParaView, if the boundaries are included in the rendered image, that could possibly throw things off in just the way you describe.

2.1.5.7 in user guide:
Quote:

Also, data is interpolated incorrectly at boundaries if the boundary regions are selected in the Mesh Parts panel. Therefore the user should deselect the patches in the Mesh Parts panel ... and apply the changes.
Also, I am new to openfoam, and I am trying to do the very thing you are doing. Would a cyclic boundary work for this purpose just as well?

anon_a July 6, 2012 10:17

No, the boundaries are deselected :-(
And also unfortunately no, the cyclic BC would not work because we are talking about two different meshes while cyclic BC is applicable for one mesh and two different patches (I think).

But if you find something, please let me know about it.


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