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-   -   Unstructured Grid using InterFoam (http://www.cfd-online.com/Forums/openfoam/84594-unstructured-grid-using-interfoam.html)

Andrea_85 February 3, 2011 07:18

Unstructured Grid using InterFoam
 
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Hello everyone,
I'm trying to simulate a flow around a disk using a fully unstructured grid (all prisms) using interFoam. The mesh is generated with gmsh.
I have several problems on the quality of the solution, concerning the contact angle on the surface of the disc (does not seem to remain constant, probably due to the fact that a lot of cells has only one line, 2D case, on the disc) and also get a very irregular front.
So the question is:
would be better to change the mesh? (even if I do not know how to build a well structured grid around a circle)
Should i change the schemes using by interFoam to get more accurate solution? (now i'm using the default schemes, the same schemes that are in the dambreak tutorial case).

Attached a .jpg of the mesh.

Thanks for any help

andrea

flowris February 3, 2011 14:40

It is not very difficult to construct a structured mesh around a disk using blockMesh.
- Take four points on your cylinder, namely at 45, 135, 225 and 315.
- I suppose you work in a rectangular domain, so you also have four corner points on the outer boundaries.
- Now make 4 blocks, each time using two adjacent points on the disk and two corner points.

If you add grading in the right direction, you will have high resolution on the disk boundary.

Andrea_85 February 4, 2011 04:23

Hi,
thanks for the answer flowris. Surely if I had to simulate the flow around a single disk would be easy with a structured grid (as in the tutorial), unfortunately I have to simulate the flow around 100-200 discs placed randomly and I do not think it is feasible that kind of geometry.

Any suggestions?

andrea

flowris February 4, 2011 05:38

In that case, I suggest you build an unstructured mesh (triagonals) and add boundary layers (rectangles) around the disks. Maybe you can use snappyHexMesh. I haven't done this myself, though.

Andrea_85 February 4, 2011 06:01

So to use a structured grid only around the disc and use an unstructured grid for the rest. might be a good idea!
I want to try


Thanks

andrea


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