Problem simulating a reactor inlet area using rhoReactingFoam
 

Hello OpenFoamers,

I'm having difficulties with rhoReactingFoam. I try to simulate a reactor but due to problems with the inlet area I created a smaller model, which just contains the inlet area (pipes) and is discussed below. I tried to make it work for weeks but I can't find my mistake.

=== geometry and mesh ===

This is what it looks like:
https://dl.dropboxusercontent.com/s/...9jfa6/mesh.jpg
The inlet area contains an abrupt cross section enlargement from 4.57 mm to 23.5 mm.
I'm using an unstructured mesh, since I use Salome to create my mesh. Later on the geometry will get more complex so I will use an unstructured mesh anyway.
All mesh checks are okay.
http://dl.dropboxusercontent.com/s/l.../checkmesh.log
Could the mesh be a problem? The max non-orthogonality is 50. Is that too high? I don't have much experience to evaluate this value correctly.

=== initial and boundary conditions ===

These are my files in 0/:
p: https://www.dropbox.com/s/337xqn2iimxd50o/p?dl=0
I have a fixed pressure of 9.5 Pa at the outlet. During my research I found the waveTransmissive boundary condition which should work for my problem. I used fixedValue at first, but then the flow got "bounced back" from the outlet area.
U: https://www.dropbox.com/s/nmkkfzz745z8t27/U?dl=0
The inlet velocity for this test case is 10 m/s, max(Co) is 0.12. In the actual reactor I have velocities up to 70 m/s.
T: https://www.dropbox.com/s/uo4viafdps08kng/T?dl=0
Uniform temperature of 293 K in the whole domain and all boundaries.

I used no mixture, only Argon. Reactions are turned off, but combustion is still on.

=== simulation setup ===

My fvSolution and fvSchemes-file:
https://www.dropbox.com/s/7v6l7iuhl7...vSolution?dl=0
https://www.dropbox.com/s/4phkmjhy8v...fvSchemes?dl=0

=== problem ===

The temperature rises up to 300 K altough it should remain constant at 293 K.
After a while the simulation crashes with a sigFpe.
I included the log- file and the errror message.
https://www.dropbox.com/s/zhyvl7ly7dti2zp/log?dl=0
https://www.dropbox.com/s/st37blb2l2fzw9i/error?dl=0

I checked the BC and I think they're okay. Could the mesh be the problem? Or did I miss something?

Any help, comment or hint is greatly appreciated!
Thank you in advance.

hester

PS: Does anyone know how to actually show pictures in a post like it was done here: http://www.cfd-online.com/Forums/openfoam/98988-how-give-enough-info-get-help.html? I couldn't figure it out myself. And the include image doesn't seem to work with dropbox-urls...