HeshamFS/mesh-generation

Mesh Generation

Goal

Provide a consistent workflow for selecting mesh resolution and checking mesh quality for PDE simulations.

Requirements

• Python 3.10+
• No external dependencies (uses stdlib)

Inputs to Gather

| Input | Description | Example | |-------|-------------|---------| | Domain size | Physical dimensions | 1.0 × 1.0 m | | Feature size | Smallest feature to resolve | 0.01 m | | Points per feature | Resolution requirement | 10 points | | Aspect ratio limit | Maximum dx/dy ratio | 5:1 | | Quality threshold | Skewness limit | < 0.8 |

Decision Guidance

Resolution Selection

What is the smallest feature size?
├── Interface width → dx ≤ width / 5
├── Boundary layer → dx ≤ layer_thickness / 10
├── Wave length → dx ≤ lambda / 20
└── Diffusion length → dx ≤ sqrt(D × dt) / 2

Mesh Type Selection

| Problem | Recommended Mesh | |---------|------------------| | Simple geometry, uniform | Structured Cartesian | | Complex geometry | Unstructured triangular/tetrahedral | | Boundary layers | Hybrid (structured near walls) | | Adaptive refinement | Quadtree/Octree or AMR |

Script Outputs (JSON Fields)

| Script | Key Outputs | |--------|-------------| | scripts/grid_sizing.py | dx, nx, ny, nz, notes | | scripts/mesh_quality.py | aspect_ratio, skewness, quality_flags |

Workflow

1. Estimate resolution - From physics scales
2. Compute grid sizing - Run scripts/grid_sizing.py
3. Check quality metrics - Run scripts/mesh_quality.py
4. Adjust if needed - Fix aspect ratios, reduce skewness
5. Validate - Mesh convergence study

Conversational Workflow Example

User: I need to mesh a 1mm × 1mm domain for a phase-field simulation with interface width of 10 μm.

Agent workflow:

1. Compute grid sizing:

   python3 scripts/grid_sizing.py --length 0.001 --resolution 200 --json
   

2. Verify interface is resolved: dx = 5 μm, interface width = 10 μm → 2 points per interface width.
3. Recommend: Increase to 500 points (dx = 2 μm) for 5 points across interface.

Pre-Mesh Checklist

• [ ] Define target resolution per feature/interface
• [ ] Ensure dx meets stability constraints (see numerical-stability)
• [ ] Check aspect ratio < limit (typically 5:1)
• [ ] Check skewness < threshold (typically 0.8)
• [ ] Validate mesh convergence with refinement study

CLI Examples

# Compute grid sizing for 1D domain
python3 scripts/grid_sizing.py --length 1.0 --resolution 200 --json

# Check mesh quality
python3 scripts/mesh_quality.py --dx 1.0 --dy 0.5 --dz 0.5 --json

# High aspect ratio check
python3 scripts/mesh_quality.py --dx 1.0 --dy 0.1 --json

Error Handling

| Error | Cause | Resolution | |-------|-------|------------| | length must be positive | Invalid domain size | Use positive value | | resolution must be > 1 | Insufficient points | Use at least 2 | | dx, dy must be positive | Invalid spacing | Use positive values |

Interpretation Guidance

Aspect Ratio

| Aspect Ratio | Quality | Impact | |--------------|---------|--------| | 1:1 | Excellent | Optimal accuracy | | 1:1 - 3:1 | Good | Acceptable | | 3:1 - 5:1 | Fair | May affect accuracy | | > 5:1 | Poor | Solver issues likely |

Skewness

| Skewness | Quality | Impact | |----------|---------|--------| | 0 - 0.25 | Excellent | Optimal | | 0.25 - 0.50 | Good | Acceptable | | 0.50 - 0.80 | Fair | May affect accuracy | | > 0.80 | Poor | Likely problems |

Resolution Guidelines

| Application | Points per Feature | |-------------|-------------------| | Phase-field interface | 5-10 | | Boundary layer | 10-20 | | Shock | 3-5 (with capturing) | | Wave propagation | 10-20 per wavelength | | Smooth gradients | 5-10 |

Security

Input Validation

• All inputs (length, resolution, dx, dy, dz) are validated as finite positive numbers with upper bounds to prevent resource exhaustion
• dims is restricted to {1, 2, 3}
• argparse type parameters reject non-numeric input at the CLI boundary before any processing occurs

File Access

• Scripts read no external files; all inputs are provided via CLI arguments
• Scripts write only to stdout (JSON output); no files are created unless the agent explicitly uses the Write tool

Tool Restrictions

• Read: Used to inspect script source, references, and user configuration files
• Write: Used to save grid sizing results or mesh quality reports; writes are scoped to the user's working directory
• Grep/Glob: Used to locate relevant files and search references
• The skill's allowed-tools excludes Bash to prevent the agent from executing arbitrary commands when processing user-provided inputs

Safety Measures

• No eval(), exec(), or dynamic code generation
• All subprocess calls use explicit argument lists (no shell=True)
• Reduced tool surface (no Bash) means the agent should use Read and Write to prepare inputs and capture outputs rather than constructing shell commands from user text
• All output is deterministic JSON with no shell-interpretable content

Limitations

• 2D/3D only: No unstructured mesh generation
• Quality metrics: Basic aspect ratio and skewness only
• No mesh generation: Sizing recommendations only

References

• references/mesh_types.md - Structured vs unstructured
• references/quality_metrics.md - Aspect ratio/skewness thresholds

Version History

• v1.1.0 (2024-12-24): Enhanced documentation, decision guidance, examples
• v1.0.0: Initial release with 2 mesh quality scripts