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-   -   Boundary conditions on a wake cut (http://www.cfd-online.com/Forums/openfoam-solving/58665-boundary-conditions-wake-cut.html)

sjs August 4, 2008 20:18

I am modeling a 2D airfoil in
 
I am modeling a 2D airfoil in constant flow. My c-grid mesh (generated by an outside mesher) has a wake cut in it. By wake cut, I mean that there is a small gap along the chord direction behind the airfoil; this results from the way the C-grid is generated and OpenFoam's requirement of not having 2 overlapping points. Physically there should be no cut.
I want boundary conditions that specify that what flows out of one side of the cut flows in the other. Should this be cyclic boundary conditions (even though there is no cyclic symmetry, physically)?

Thank you.
Sylvia

mattijs August 5, 2008 17:11

1. merge the points (they are
 
1. merge the points (they are coincident I hope) then merge the two boundary faces into an internal face (using e.g. mergeOrSplitBaffles)

2. You could try cyclic. This requires strict conformity of point locations and face areas though - your mesher should output the cyclic faces ordered according to the OpenFOAM rules (see http://openfoamwiki.net/index.php/Write_OpenFOAM_meshes)

sjs August 6, 2008 14:30

Thank you for suggestions. I g
 
Thank you for suggestions. I got the cyclic conditions right but the solution is funny. So I am trying to merge. I see lots of postings about faceSetDict, etc but I can't seem to get this quite right. Can you give me step-by-step instructions how to do this so I can use mergeOrSplitBaffles? I am not using blockmesh. So once I have faces and patches set, how to I name the face set for the dictionary and then merge?

Thank you.
Sylvia

sjs August 6, 2008 21:56

Ok, I was going down a wrong p
 
Ok, I was going down a wrong path with the faceSetDict -- turns out I didn't need that all. And then what was holding me up on the merging is that I needed to have faces defined by points of the same number (instead of points with different numbers but in the same location) to be recognized as duplicate. Thank you for the pointer.

Sylvia


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