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-   -   Quarter Burner mesh with periosic condition (http://www.cfd-online.com/Forums/fluent/80065-quarter-burner-mesh-periosic-condition.html)

SamCanuck September 14, 2010 05:18

Quarter Burner mesh with periosic condition
 
Hi,

I have a 90deg periodic wedge with small holes for air inlets surrounding a burner set to species transport of carbon-monoxide mixture. I created the mesh in ICEMCFD. This is the error:

> iter continuity x-velocity y-velocity z-velocity energy k epsilon o2 co2 co h2o time/iter
# Divergence detected in AMG solver: pressure correction -> Turning off correction scaling!
# Divergence detected in AMG solver: pressure correction -> Increasing relaxation sweeps!

turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 376 cells

Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: k
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: species-2
Divergence detected in AMG solver: species-3
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: k
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: species-2
Divergence detected in AMG solver: species-3
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: k
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: species-2
Divergence detected in AMG solver: species-3
Divergence detected in AMG solver: temperature
Primitive Error at Node 0: floating point exception

Primitive Error at Node 1: floating point exception

Primitive Error at Node 2: floating point exception

Error: floating point exception
Error Object: #f

I tried going to 1st order discretization and even switching to just air, but no dice. Could I please get some sort of suggestion on what may help?

Sam

Shamoon Jamshed August 31, 2011 10:00

Preesure correction sweep
 
I am simulating a twin rotor turbine blade with 180 degree periodic BC. I am simulating at velocities of 7, 10, 15, 20 and 25 m/s. The mesh diverges at 20 and 25 m/s saying divergence detected in AMG solver --> increasing pressure sweep correction,
primtive error at node 0
primtive error at node 1
primtive error at node 2
primtive error at node 3
primtive error at node 4
primtive error at node 5
primtive error at node 6
primtive error at node 7

Initially this error appeared in first few iteration of 20 and 25 m/s but later appeared in other velocity cases as well. I am using default UR factors with Standard pressure and SIMPLE schemes. I also tried with lowering UR factors but didn't work. (However, the mesh was a little bit coarse that time). I have also seen that lowering the UR factors from scratch also diverges the solution.

Any solutions in this regard are welcomed.

SamCanuck August 31, 2011 11:34

Everytime I had a similar error, it was a mesh quality issue. Either there are overlapping nodes (quick and easy) or the mesh density isn't optimal. I am no longer working on CFD so my advice may be rusty.

Good luck,

Sam


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