Flow-3d V12: Crack

If you’re on a tight deadline (e.g., a foundry’s next production run), catching the crack early can save weeks of re‑work.

| Component | Affected Sub‑module | Trigger Condition | |-----------|---------------------|-------------------| | Pressure‑Poisson Solver | Implicit matrix assembly (pre‑conditioner) | Meshes with non‑uniform cell sizes > 4× variation (common in adaptive refinement) | | Surface‑Tension Model | Curvature calculation (height‑function) | Contact‑angle > 150° or triple‑line moving across a grid refinement interface | | GPU‑Accelerated Solver | CUDA kernel for particle‑to‑cell mapping | Thread‑block size > 256 (default on newer RTX 5000‑series cards) | | Post‑Processing Export | VTK/EXODUS writer | Large‑scale (>10 M cells) time‑series with dynamic mesh | Flow-3d V12 Crack

In plain English: V12 introduced a new matrix pre‑conditioner that was supposed to speed up convergence for highly skewed meshes. Unfortunately, the pre‑conditioner’s scaling factor was mis‑calculated for cells whose size ratio crossed a threshold. The result is a singular matrix that crashes the linear solver—a classic “crack” that manifests as a hard abort or a silent divergence. If you’re on a tight deadline (e

Simultaneously, an update to the height‑function curvature routine introduced an off‑by‑one error when the interface crossed a refinement boundary. That bug shows up as spurious “wiggles” or an unphysical pressure spike right at the contact line. | Component | Affected Sub‑module | Trigger Condition

Both issues are independent, but they often appear together in the same simulation because many of the newest use‑cases (e.g., casting with adaptive mesh refinement) trigger both code paths.

Below are the most common tell‑tale signs. Use the table to cross‑reference against your own run logs.

| Symptom | Typical Log Message | How to Verify | |---------|---------------------|---------------| | Solver abort with “Singular matrix” | ERROR: Linear system is singular (matrix id 3) | Check the matrix_stats.txt file: look for a condition number > 1e12. | | Gradual pressure drift (no crash) | WARN: Pressure residual stagnating at 1e‑2 after 2000 iterations | Plot pressure residual vs. iteration; a flat line indicates the hidden singularity. | | Surface‑tension spikes at refinement interfaces | INFO: Curvature at cell (i=145, j=89) = 3.4e+04 (unrealistic) | Visualise curvature field; spikes line up with mesh‑refinement borders. | | GPU kernel timeout on Windows | CUDA driver error: unknown launch failure (code 719) | Run the same case on CPU only (-cpu flag); if it completes, the issue is GPU‑specific. | | VTK export truncates after 5 GB | EXODUS: write failed – file size limit reached | Reduce export frequency or split the time series; the problem is unrelated to the crack but often surfaces together. |