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Applied: Fine-tune a PMDB export with PMDBExportOptions

PMDB (Persistent Model Database) is the recommended format for transferring geometry to Ansys Mechanical, Fluent Meshing, DesignModeler, and other Ansys solvers. By default export_to_pmdb() exports everything — solid bodies, surface bodies, line bodies, named selections, coordinate systems, planes, and more.

PMDBExportOptions lets you tailor exactly what ends up in the file. This is useful when, for example:

• You want to send only solid bodies to a structural solver and ignore the surface and line bodies that live in the same design.

• You need a CFD-ready mesh file that targets Fluent Meshing instead of PartMgr.

• You want to strip named selections so that the receiving tool starts with a clean slate.

This example builds a simple mixed-body assembly (a solid box and a surface panel), attaches named selections, and then exports it three ways to illustrate the most commonly used options.

Build the assembly

The design contains two body types so that the body-filter options have something visible to work with:

Body	Type	Description
Solid_Box	Solid	50 × 30 × 20 mm extruded box
Surface_Panel	Surface	60 × 40 mm thin planar panel

from ansys.geometry.core import launch_modeler
from ansys.geometry.core.math import (
    UNITVECTOR3D_X,
    UNITVECTOR3D_Z,
    Point2D,
    Point3D,
)
from ansys.geometry.core.shapes.box_uv import BoxUV
from ansys.geometry.core.shapes.parameterization import Interval
from ansys.geometry.core.shapes.surfaces import PlaneSurface
from ansys.geometry.core.sketch import Sketch

# ── Launch the Geometry service ────────────────────────────────────────────
modeler = launch_modeler()
design = modeler.create_design("MixedBodyAssembly")

Add a solid body

# Sketch a 50 × 30 mm rectangle and extrude it 20 mm
sketch = Sketch()
sketch.box(Point2D([0, 0]), 0.05, 0.03)  # width=50 mm, height=30 mm (metres)
solid_box = design.extrude_sketch("Solid_Box", sketch, 0.02)  # depth=20 mm
print(f"Solid body created  : '{solid_box.name}'  is_surface={solid_box.is_surface}")

Solid body created  : 'Solid_Box'  is_surface=False

Add a surface (shell) body

Surface bodies — sometimes called sheet bodies or midsurfaces — have zero thickness. They are common in thin-walled structural models.

# Build a planar surface offset in Z so it does not overlap the solid box.
# A Plane surface with a BoxUV trim gives a finite rectangular patch.
plane_geom = PlaneSurface(
    origin=Point3D([0, 0, 0.04]),  # 40 mm above the bottom face of the box
    reference=UNITVECTOR3D_X,
    axis=UNITVECTOR3D_Z,
)

# Trim to a 60 × 40 mm rectangle (±0.03 m in X, ±0.02 m in Y)
trimmed = plane_geom.trim(
    BoxUV(range_u=Interval(-0.03, 0.03), range_v=Interval(-0.02, 0.02))
)

surface_panel = design.create_body_from_surface("Surface_Panel", trimmed)
print(f"Surface body created: '{surface_panel.name}'  is_surface={surface_panel.is_surface}")

Surface body created: 'Surface_Panel'  is_surface=True

Visualise the assembly

design.plot()

Create named selections

Named selections are labels that group bodies (or faces/edges/vertices). They pass through PMDB into Mechanical as Named Selections, where they can scope boundary conditions and mesh controls.

design.create_named_selection("NS_Solid",   bodies=[solid_box])
design.create_named_selection("NS_Surface", bodies=[surface_panel])
design.create_named_selection("NS_All",     bodies=[solid_box, surface_panel])

print("Named selections in design:")
for ns in design.named_selections:
    print(f"  '{ns.name}'")

Named selections in design:
  'NS_Solid'
  'NS_Surface'
  'NS_All'

Export scenarios

The table below summarises the four exports performed in this section.

Scenario	Key options changed	Purpose
Default	(none)	Baseline — everything exported
Solids only	process_surface_bodies=False	Strip shells
No named selections	named_selection=False	Clean-slate transfer
CFD target	target_application=PMDBTargetApplication.FLUENTMESHING	Prepare for Fluent Meshing

from pathlib import Path

from ansys.geometry.core.misc.options import (
    AnalysisType,
    PMDBExportOptions,
    PMDBTargetApplication,
)

output_dir = Path.cwd() / "pmdb_exports"
output_dir.mkdir(exist_ok=True)

Scenario 1 — Default export

No options are passed, so export_to_pmdb() uses the PMDBExportOptions defaults, which include all body types and named selections.

path_default = design.export_to_pmdb(output_dir)
print(path_default)
print(f"Default export  → {path_default.name}  ({path_default.stat().st_size:,} bytes)")

/home/runner/work/pyansys-geometry/pyansys-geometry/doc/source/examples/04_applied/pmdb_exports/MixedBodyAssembly.pmdb
Default export  → MixedBodyAssembly.pmdb  (530,152 bytes)

Scenario 2 — Solid bodies only

Setting process_surface_bodies=False tells the exporter to discard surface bodies. Only the solid box (and its named selection) will be present in the resulting PMDB file.

opts_solids_only = PMDBExportOptions(
    process_surface_bodies=False,
)

path_solids = design.export_to_pmdb(
    output_dir / "assembly_solids_only.pmdb",
    options=opts_solids_only,
)
print(f"Solids-only export → {path_solids.name}  ({path_solids.stat().st_size:,} bytes)")

Solids-only export → MixedBodyAssembly.pmdb  (530,152 bytes)

Scenario 3 — All body types, but no named selections

Here named_selection=False strips the named selection data from the export. This is useful when the downstream tool should not inherit the groupings defined in CAD.

opts_no_ns = PMDBExportOptions(
    named_selection=False,
)

path_no_ns = design.export_to_pmdb(
    output_dir / "assembly_no_named_selections.pmdb",
    options=opts_no_ns,
)
print(f"No-NS export       → {path_no_ns.name}  ({path_no_ns.stat().st_size:,} bytes)")

No-NS export       → MixedBodyAssembly.pmdb  (530,152 bytes)

Scenario 4 — CFD-ready: target Fluent Meshing

Changing target_application to FLUENTMESHING configures the PMDB for import into Ansys Fluent Meshing.

opts_cfd = PMDBExportOptions(
    target_application=PMDBTargetApplication.FLUENTMESHING,
)

path_cfd = design.export_to_pmdb(
    output_dir / "assembly_fluent_meshing.pmdb",
    options=opts_cfd,
)
print(f"CFD export         → {path_cfd.name}  ({path_cfd.stat().st_size:,} bytes)")

CFD export         → MixedBodyAssembly.pmdb  (530,152 bytes)

Compare the exported files

A quick size comparison gives a rough indication of how much data each option set includes. In a real project the differences in body counts are more meaningful — here the assembly is intentionally small.

exports = {
    "Default (all bodies + NS)": path_default,
    "Solids only":               path_solids,
    "No named selections":       path_no_ns,
    "CFD / Fluent Meshing":      path_cfd,
}

col_w = max(len(k) for k in exports) + 2
print(f"{'Scenario':<{col_w}} {'File':<45} {'Size (bytes)':>14}")
print("-" * (col_w + 45 + 16))
for label, path in exports.items():
    size = path.stat().st_size
    print(f"{label:<{col_w}} {path.name:<45} {size:>14,}")

Scenario                    File                                            Size (bytes)
----------------------------------------------------------------------------------------
Default (all bodies + NS)   MixedBodyAssembly.pmdb                               530,152
Solids only                 MixedBodyAssembly.pmdb                               530,152
No named selections         MixedBodyAssembly.pmdb                               530,152
CFD / Fluent Meshing        MixedBodyAssembly.pmdb                               530,152

Key takeaways

• PMDBExportOptions is a plain Python dataclass — every field has a sensible default, so you only need to override what matters.

• Use process_solid_bodies and process_surface_bodies to filter which body types reach the solver.

• Use named_selection=False if the receiving tool should start without pre-defined named selections.

• Use target_application to tailor the PMDB for a specific Ansys product (PARTMGR, DESIGNMODELER, FLUENTMESHING, AIM, or SPACECLAIM).

Close the Geometry service

modeler.close()

References

• PMDBExportOptions API reference

• Design.export_to_pmdb API reference

• PyAnsys Geometry examples gallery

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Download this example

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