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-   -   How to generate internal Baffles with exsisting STL mesh? (http://www.cfd-online.com/Forums/openfoam/121198-how-generate-internal-baffles-exsisting-stl-mesh.html)

keepfit July 23, 2013 13:47

How to generate internal Baffles with exsisting STL mesh?
 
Hi Foamer,

I want to simulate the flow inside a Cyclone. The geometry is shown below:

http://24.media.tumblr.com/f2abf9bf7...saho1_1280.jpg

Part of the air outlet tube is inside the cyclone, so the internal patch (wall) must be created.

I think there are 2 possible ways to do such job:

1) Import the Tetrahedral Mesh generated by GMSH, and then generated the inner walls of air outlet tube with createBaffles, but I didn't find any tutorials about how to generated curved surface (can not find detailed topoSet or setSet guide).

2) Import the Surface Mesh (STL) and utilize the snappyHexMesh to generate the internal cells. But how does snappyHexMesh snap the internal surface and convert it to patches? It's possible in OF 2.2.0 to do this, but could not find the proper examples.

Any advice will be appreciated.

David Long

andre.weiner July 23, 2013 18:50

Quote:

Originally Posted by keepfit (Post 441547)
... createBaffles, but I didn't find any tutorials about how to generated curved surface (can not find detailed topoSet or setSet guide).

Have a look at the "propeller"-tutorial.
tutorials/incompressible/pimpleDyMFoam/propeller

But: you wont get a proper baffle if the surface of the cylinder is not included in your tet-mesh (see the tutorial).

Quote:

Originally Posted by keepfit (Post 441547)
2) Import the Surface Mesh (STL) and utilize the snappyHexMesh to generate the internal cells. But how does snappyHexMesh snap the internal surface and convert it to patches? It's possible in OF 2.2.0 to do this, but could not find the proper examples.

I would do like this:
- generate the stl of your cyclon
- generate a second stl of the part of the cylinder, that is inside your cyclone
- in the snappyHexMeshDict-file the cylinder.stl gets the attribute "inside" in the part of the surface refinement
Code:

        cylinder
        {
            level      (2 2);
            cellZone    cylinder;
            faceZone  cylinder;
            cellZoneInside  inside;
        }

- in version 2.2.0 and higher it is also posible to create baffles (or in your case maybe boundaries) with snappyHexMesh

Code:

            //- Optional specification of what to do with faceZone faces:
            //      internal : keep them as internal faces (default)
            //      baffle  : create baffles from them. This gives more
            //                freedom in mesh motion
            //      boundary : create free-standing boundary faces (baffles
            //                but without the shared points)
            //faceType baffle;

Best regards, Andre

keepfit July 24, 2013 02:19

thanks for the tips, Andre.

I will try it today.


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