CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   BlockMesh versus gmsh2ToFoam (http://www.cfd-online.com/Forums/openfoam-solving/59071-blockmesh-versus-gmsh2tofoam.html)

bretttully March 6, 2008 09:50

Hi guys, I am relatively ne
 
Hi guys,

I am relatively new to OpenFOAM and am trying to assess if it is a suitable tool to use for my DPhil.

I have started by trying to design a simple case to test features that I will need to use.
I have a 1/4 circle extruded to make a "wedge" cylinder. The flat surfaces are symmetry conditions, and the circular face is a wall (essentially forming an pipe), the ends are inlet (fixed velocity) and outlet (fixed pressure).

I can run this with a blockMesh generated mesh with no problems, however, it will be important for me eventually to be able to use unstructured tet meshes. For this, I have written a *.geo file and fed it to gmsh2ToFoam and as far as I can tell the generated mesh is decent (viewed in paraFoam, and run checkMesh). Yet, if I pass the same control/initial conditions from the blockMesh case to this one, the first few iterations _converge_ but it eventually blows up. Looking at the results from the first few iterations with paraFoam shows that these solutions are not at all correct.

Can anyone suggest where I can look to see what is causing the trouble. It is important to be able to use unstructured grids, as my project will require some very complex meshes.

Cheers,
Brett.

wese March 6, 2008 10:36

Hi Brett, I've also just star
 
Hi Brett,
I've also just started using openFOAM.
So I also tried to simulate the flow through a circular pipe.
First I've tried icoFoam, but my results also were divergent.
So I've switched to simpleFoam for the steady state solution but even now I received strange results.
After a while I figured out, that the "double used" points (as described on p. 148 of the users manual) in the middle of the tube were the problem (but untill now I have no idea why).
An image of the calculated velocity profile is in the attached case (t1_u.jpg).
After I've put then on one of the sides everything worked fine (see images the attached case):
http://www.cfd-online.com/OpenFOAM_D...hment_icon.gif tube.tar.gz

Greetings
Christian


All times are GMT -4. The time now is 09:32.