CFD Online Discussion Forums - Cyclic BCs using createPatch in OF 1.6.x

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Cyclic BCs using createPatch in OF 1.6.x

I have been trying to implement cyclic boundary condition for a 22 blade turbomachine using createPatch in OF-1.6.x for simpleSRFFoam.

My createPatchDict is as follows;

Quote:

FoamFile
{
version 2.0;
format ascii;
class dictionary;
object createPatchDict;
}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

matchTolerance 1E-3;
pointSync true;

// Patches to create.
patchInfo
(
{
name PERA;
dictionary
{
type cyclic;
transform rotational;
rotationAxis (0 0 1);
rotationCentre (0 0 0);
}
constructFrom patches;
patches (PER-AA PER-AB);
}

{
name PERB;
dictionary
{
type cyclic;
transform rotational;
rotationAxis (0 0 1);
rotationCentre (0 0 0);
}
constructFrom patches;
patches (PER-BA PER-BB);
}

{
name PERC;
dictionary
{
type cyclic;
transform rotational;
rotationAxis (0 0 1);
rotationCentre (0 0 0);
}
constructFrom patches;
patches (PER-CA PER-CB);
}

);

// ******************************************* //

When I execute createPatch, I get the error;

Quote:

--> FOAM FATAL ERROR:
face 0 area does not match neighbour 84 by 60.4041% -- possible face ordering problem.
patch:PER-AA my area:4.99638e-06 neighbour area:9.32032e-06 matching tolerance:0.001
Mesh face:90500 vertices:4((0.0919444 -0.0172959 -0.01046) (0.0915424 -0.0172218 -0.0128839) (0.0936255 -0.0175195 -0.0126286) (0.0940216 -0.0175922 -0.0101972))
Neighbour face:90584 vertices:4((0.0905044 -0.0170265 -0.0194866) (0.0899021 -0.0169128 -0.0239466) (0.0920072 -0.0172161 -0.0237029) (0.0926016 -0.0173277 -0.0192417))
Rerun with cyclic debug flag set for more information.

From function cyclicPolyPatch::calcTransforms()
in file meshes/polyMesh/polyPatches/constraint/cyclic/cyclicPolyPatch.C at line 180.

FOAM exiting

I have tried:

1. Change patch type from 'cyclic' to 'patch' in the polyMesh/boundary file - found in example file of createPatchDict under $FOAM_UTILITIES/mesh/manipulation/createPatch

Although this succeeds in createPatch, the same error (as above) occurs when checkMesh is executed.

2. loosen match tolerance to get case to load

Same as above, createPack OK but same error remains at checkMesh.

I was wondering if anyone has encountered similar issues and was hoping to gain insight into the above issue.
Any help is greatly appreciated.

I have been able to solve the problem by overwriting the whole <case>/constant/polymesh by <case>/<timestep>/polymesh folder created by running createPatch (where <timestep> directory is named as the timestep configured in controlDict).

Thanks

Hi!

I don't really understand how to use the createPatch utillity. Well it worked, but may anybody explain me please:

I have created a rotational periodic mesh in ICEM. Then I have converted the meshfile with fluent3DMeshToFoam.
The two periodic faces do have the type 'wall' in my file polymesh/boundary. Now I change them into 'patch'.
Then I run my createPatch file:

Code:

matchTolerance 1e-7;



pointSync true;



patches

(

    {

        name periodic;



        dictionary

        {

            type cyclic;



           transform rotational;

           rotationAxis (1 0 0);

              rotationCentre (1 0 0);

        }



        constructFrom patches;



        patches (periodic1 periodic2);



        set f0;

    }

Seems like it works fine. At least I get no error and a new folder in my case file: 1/polymesh. And there are also some other new files in my /case folder named coupled_periodic_half0.obj, coupled_periodic_half1.obj, coupled_periodic_match.obj, final_periodic_half0, final_periodic_half1, final_periodic_match.

Now I dont really understand what to do. I have tried a few things to start a calculation, but without success.

Maybe somebody who has already dealed with this application can give me a quick advice what to do next :) thanks!!!

Sebastian