Sub-skill of cfd-pipeline: Path A: FreeCAD/CAD to Gmsh (+3).
# 1. Export from FreeCAD to STEP/BREP
freecadcmd -c "
import FreeCAD, Part
doc = FreeCAD.openDocument('geometry.FCStd')
Part.export(doc.Objects, 'geometry.step')
"
# 2. Mesh with Gmsh
gmsh geometry.step -3 -format msh2 -o mesh.msh \
-clmin 0.01 -clmax 0.5 \
-algo del3d
# Convert Gmsh mesh to OpenFOAM format
gmshToFoam mesh.msh
# Fix boundary patches (Gmsh exports generic names)
# Edit constant/polyMesh/boundary to set correct patch types
# Automated Gmsh-to-OpenFOAM boundary patch fix
import re
from pathlib import Path
def fix_boundary_patches(case_dir, patch_map):
"""Fix boundary patch types after gmshToFoam conversion.
Args:
case_dir: OpenFOAM case directory
patch_map: dict of {patch_name: patch_type}
e.g. {'inlet': 'patch', 'outlet': 'patch', 'walls': 'wall'}
"""
boundary_file = Path(case_dir) / 'constant' / 'polyMesh' / 'boundary'
content = boundary_file.read_text()
for name, ptype in patch_map.items():
# Replace patch type for named patch
pattern = rf'({name}\s*\{{[^}}]*type\s+)\w+'
content = re.sub(pattern, rf'\g<1>{ptype}', content)
boundary_file.write_text(content)
# 1. Export STL from CAD (FreeCAD or external)
# Ensure STL is watertight and in meters
# 2. Create background mesh with blockMesh
blockMesh
# 3. Run snappyHexMesh
snappyHexMesh -overwrite
# Key files needed:
# - system/blockMeshDict (background mesh)
# - system/snappyHexMeshDict (refinement + snapping)
# - constant/triSurface/geometry.stl
def validate_geometry_to_mesh(stl_path, mesh_dir):
"""Validate the geometry-to-mesh conversion."""
import subprocess
checks = {"passed": True, "issues": []}
# Check STL is readable
import os
if not os.path.exists(stl_path):
checks["issues"].append(f"STL not found: {stl_path}")
checks["passed"] = False
return checks
stl_size = os.path.getsize(stl_path)
if stl_size < 100:
checks["issues"].append(f"STL suspiciously small: {stl_size} bytes")
checks["passed"] = False
# Check OpenFOAM mesh
polymesh = os.path.join(mesh_dir, 'constant', 'polyMesh', 'points')
if not os.path.exists(polymesh):
checks["issues"].append("No polyMesh/points — mesh conversion failed")
checks["passed"] = False
return checks
# Run checkMesh
result = subprocess.run(
['checkMesh', '-case', mesh_dir],
capture_output=True, text=True
)
if 'FAILED' in result.stdout:
checks["issues"].append("checkMesh reports failures")
checks["passed"] = False
# Extract mesh stats
import re
cells_match = re.search(r'cells:\s+(\d+)', result.stdout)
if cells_match:
checks["cells"] = int(cells_match.group(1))
return checks