vamseeachanta 4.1 Error Message Format (+2)
4.1 Error Message Format
--> FOAM FATAL ERROR:
<description>
From function <Class>::<method>
in file <source.C> at line <N>.
FOAM exiting
4.2 Common Failures and Fixes
1. Floating Point Exception (exit code 136)
| Cause | Diagnosis | Fix |
|---|---|---|
| Courant number too high | Check Courant Number max: in log |
Enable adjustTimeStep yes; maxCo 1; or reduce deltaT |
| Poor mesh quality | Run checkMesh -allTopology -allGeometry |
Fix cells with non-orthogonality > 70, negative volumes |
| Zero/negative k or epsilon | Check 0/ initial values | Set k > 0 and epsilon > 0 everywhere |
| Bad turbulence initialization | Residuals blow up immediately | Start laminar, then switch to turbulent |
2. GAMG Solver Divergence
Symptoms: p residuals stuck near 1.0, or oscillating without decreasing.
| Cause | Fix |
|---|---|
| Mesh too coarse | Refine mesh at critical regions |
| Bad relaxation factors | Reduce: p from 0.3 to 0.2, U from 0.7 to 0.5 |
| Non-orthogonal mesh | Increase nNonOrthogonalCorrectors to 1-3 |
| GAMG agglomeration failure | Switch to solver PCG; preconditioner DIC; for p |
3. Missing Field/File
FOAM FATAL IO ERROR: cannot find file ... /0/k
Fix: ensure all fields required by the turbulence model exist in 0/. See table in Section 1.6.
4. Boundary Condition Mismatch
FOAM FATAL ERROR: patch type 'xxx' not constraint type ... for patch yyy
Fix: patch types in 0/ files must match boundary types in constant/polyMesh/boundary. If mesh defines empty, all field files must use empty for that patch.
5. Courant Number Blowup (transient)
Courant Number mean: 0.5 max: 150.3
| Solver | Acceptable maxCo |
|---|---|
| icoFoam (PISO) | < 1 (strict) |
| interFoam (VOF) | maxCo < 1, maxAlphaCo < 1 |
| pimpleFoam (nOuterCorrectors > 1) | up to 5-10 |
6. Convergence Stall (simpleFoam)
Residuals plateau or oscillate without decreasing.
| Action | How |
|---|---|
| Reduce relaxation | U: 0.5-0.7, p: 0.2-0.3 |
| Enable consistent SIMPLE | consistent yes; in SIMPLE dict |
| Initialize with potentialFoam | potentialFoam -writephi before simpleFoam |
| Check BCs | Ensure mass balance (inlet flux = outlet flux) |
7. Out of Memory (exit code 137)
| Action | How |
|---|---|
| Reduce mesh | Coarsen or reduce refinement levels |
| Use parallel | decomposePar + mpirun -np N distributes memory |
| Use binary write | writeFormat binary; in controlDict |
| Increase swap | System-level: sudo fallocate -l 8G /swapfile |
8. Parallel Decomposition Errors (exit code 255)
| Symptom | Fix |
|---|---|
numberOfSubdomains mismatch |
Must match -np N in mpirun |
| Missing processor directories | Run decomposePar first |
| Inconsistent mesh across processors | Re-run decomposePar |
9. snappyHexMesh Failures
| Symptom | Fix |
|---|---|
| Empty mesh after castellated step | Check locationInMesh is inside domain, not inside geometry |
| Feature edge artifacts | Increase nFeatureSnapIter to 10-20 |
| Layer addition failure | Reduce nSurfaceLayers, increase minThickness |
| STL not found | Check path in geometry {} block, use triSurfaceMesh type |
10. Dimension Mismatch
FOAM FATAL ERROR: dimensions not compatible
Fix: check dimensions line in 0/ field files against the reference table (Section 1.8). Common mistake: using absolute pressure dimensions [1 -1 -2 0 0 0 0] instead of kinematic [0 2 -2 0 0 0 0] for incompressible solvers.
4.3 Mesh Quality Thresholds
| Metric | OK | Warning | Fail |
|---|---|---|---|
| Non-orthogonality max | < 65 | 65-80 | > 80 |
| Skewness | < 4 | 4-10 | > 10 |
| Aspect ratio | < 100 | 100-1000 | > 1000 |
| Min volume | > 0 | near 0 | < 0 (inverted) |
| Min determinant | > 0.001 | 0.0001-0.001 | < 0 |