CFD Online Discussion Forums - Preparing Simulation of a Sphere in a Flow

A warm hello to everyone :),

I want to simulate the flow around a sphere in a tube. Inside the sphere there can be flow as well (electromagnetic forces). It mimics something like a drop, which is steady in a spherical shape. At the interface some reactions and temperature diffusion is going on. But first, I want to look at the flow only.

My first idea was:
1) to make 2 meshes. One for the surrounding flow, one for the flow inside the droplet.
2) Then merging the meshes
3) and stitch them together
4) Afterwards, create a faceSet of the interface
5) create a baffle and applying different boundary conditions for the master and slave patch of the baffle to account for slip boundary inside the droplet and no slip boundary for the outer flow

I started preparing both meshes with snappyHexMesh. The meshes seem good and checkMesh gave me good values. The mergeMesh command worked good, but after stitching (stitchMesh -partial sphereOut sphereIn), I get many nonOrthoFaces at the interface.

On the first picture, you can see both meshes before merging and stitching. The second picture shows the stitched mesh. There you can see the first low quality cells introduced. On the third picture, there are the nonOrthoFaces visible (by foamToVTK -faceSet nonOrthoFaces).

I read about using the stitchMeshTolerancesDict, but I get an error when I do the command:

Code:

stitchMesh -partial -toleranceDict system/stitchMeshTolerancesDict sphereOut sphereIn

Code:

Create time



Create mesh for time = 0



Coupling partially overlapping patches sphereOut and sphereIn

Resulting internal faces will be in faceZone sphereOutsphereInCutFaceZone

Any uncovered faces will remain in their patch





--> FOAM FATAL IO ERROR: 

cannot open file



file: foobar/Case/system/stitchMeshTolerancesDict at line 0.



    From function regIOobject::readStream()

    in file db/regIOobject/regIOobjectRead.C at line 87.



FOAM exiting

So I am stucked.

I read already these threads:
http://www.cfd-online.com/Forums/ope...titchmesh.html
http://www.cfd-online.com/Forums/ope...titchmesh.html
http://www.cfd-online.com/Forums/ope...mesh-used.html

But none of them comes to a final solution in my opinion.

Does anybody can help me to:

1. get the stitchMeshTolerancesDict running?
2. Had this problem before and knows a solution?
3. Has a better idea to tackle this problem? I thought about multiRegionFoam, but I don't know if it can handle different boundary conditions for different flow fields at the interface.

Thanks in advance :),

Christoph

My System:

OpenFOAM Version: OpenFOAM-2.4.x
Operating System: Manjaro Linux 15.09
Hardware: Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz

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