Convergence blues
 

Hi,


Im running a simpleFoam case with k-e. After approximately 570 iterations the simulation crashes. Any general ideas on what might cause this? Attached the residuals and the instability - the velocity goes through the roof..


regards

Does checkMesh complain about the mesh quality?

Hi jherb,


I think the mesh is ok.. see below:


Mesh stats
points: 171587
faces: 1781432
internal faces: 1682136
cells: 865892
faces per cell: 4
boundary patches: 7
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 0
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 865892
polyhedra: 0

Checking topology...
Boundary definition OK.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
Patch Faces Points Surface topology
inlet1 238 141 ok (non-closed singly connected)
inlet2 232 138 ok (non-closed singly connected)
outlet1 232 138 ok (non-closed singly connected)
outlet2 234 139 ok (non-closed singly connected)
sym 36380 18443 ok (non-closed singly connected)
wall1 48840 24753 ok (non-closed singly connected)
pipes 13140 6738 ok (non-closed singly connected)

Checking faceZone topology for multiply connected surfaces...
No faceZones found.

Checking basic cellZone addressing...
No cellZones found.

Checking geometry...
Overall domain bounding box (0 0 0) (194 189 13)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (-1.05596e-16 6.78774e-18 3.33865e-15) OK.
Max cell openness = 2.51381e-16 OK.
Max aspect ratio = 6.12287 OK.
Minimum face area = 0.00594874. Maximum face area = 4.18215. Face area magnitudes OK.
Min volume = 0.000219401. Max volume = 2.55495. Total volume = 464436. Cell volumes OK.
Mesh non-orthogonality Max: 52.7944 average: 14.6586
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.688954 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End

Ok. Step by step. What are the settings in fvSchemes and fvSolutions?

Hi jherb...thanks for the reply.. attached the settings:

Ok, just guesses: You could try to increase the nNonOrthogonalCorrectors to something like 2 or 3 and reduce the relaxation factors.

It works when I reduce the k,e & U relaxation to 0.2 at the start of the simulation then gradually increase to 0.5. The 0.2 seems a bit low but the results are looking ok I think.