[eaglemckenna]

Hi

I have been having this issue for quite sometime now - my solution blows up after 0.3 seconds where delta t is 0.025 seconds - it is clear as the simulation tends towards 0.3seconds the time step continuity error grows drastically - could this be a problem with the mesh:


Time = 0.3

DILUPBiCG: Solving for Ux, Initial residual = 0.204415, Final residual = 5.54525e-18, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.640813, Final residual = 2.86092e-47, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.0423122, Final residual = 1.83948e-18, No Iterations 1
DILUPBiCG: Solving for T, Initial residual = 0.00825384, Final residual = 7.90288e-19, No Iterations 1
DICPCG: Solving for p_rgh, Initial residual = 1.68731e-13, Final residual = 1.68731e-13, No Iterations 0
DICPCG: Solving for p_rgh, Initial residual = 1.68731e-13, Final residual = 1.68731e-13, No Iterations 0
time step continuity errors : sum local = 4.47156e+27, global = 3.90964e+12, cumulative = 2.94328e+12
#0 Foam::error:rintStack(Foam::Ostream&) at ??:?
#1 Foam::sigFpe::sigHandler(int) at ??:?
#2 in "/lib/x86_64-linux-gnu/libc.so.6"
#3 double Foam::sumProd<double>(Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4 Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?

checkMesh:


Mesh stats
points: 549839
faces: 3109936
internal faces: 3014960
cells: 1298904
faces per cell: 4.71543
boundary patches: 9
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 0
prisms: 929280
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 369624
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
back 1725 917 ok (non-closed singly connected)
body 84480 42242 ok (closed singly connected)
bottom 1719 913 ok (non-closed singly connected)
front 1771 945 ok (non-closed singly connected)
inlet 96 51 ok (non-closed singly connected)
left 1595 855 ok (non-closed singly connected)
outlet 100 53 ok (non-closed singly connected)
right 1831 966 ok (non-closed singly connected)
top 1659 882 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-1 -1 -1.75) (1 1 0.25)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-1.29639e-16 -5.51539e-17 -2.6796e-17) OK.
***High aspect ratio cells found, Max aspect ratio: 1.23469e+06, number of cells 68
<<Writing 68 cells with high aspect ratio to set highAspectRatioCells
Minimum face area = 1.00917e-10. Maximum face area = 0.0160897. Face area magnitudes OK.
Min volume = 1.86084e-16. Max volume = 0.000268742. Total volume = 7.92765. Cell volumes OK.
Mesh non-orthogonality Max: 89.9483 average: 28.8914
*Number of severely non-orthogonal (> 70 degrees) faces: 56830.
Non-orthogonality check OK.
<<Writing 56830 non-orthogonal faces to set nonOrthoFaces
Face pyramids OK.
***Max skewness = 4.30872, 1 highly skew faces detected which may impair the quality of the results
<<Writing 1 skew faces to set skewFaces
Coupled point location match (average 0) OK.

Failed 2 mesh checks.

[tomf]

Hi,

I think it can be blamed on the mesh, both high aspect ratio and non-orthogonality would suggest some very distorted cells.

Regards,
Tom