mphkit

Helpers on top of MPh for building COMSOL geometries and geometry-based selections in Python. Select boundaries by location instead of by entity number, so selections keep working when the geometry changes.

Not affiliated with COMSOL AB.

Example

import mph
import mphkit as mk

client = mph.start()
model = client.create('demo')
geom = mk.geometry(model, 3, length_unit='mm')

plate = mk.block(geom, (100, 100, 10), name='plate')
hole = mk.cylinder(geom, 5, 10, (50, 50, 0))
mk.difference(geom, plate, [hole])
model.build(geom)

bottom = mk.sel.box(geom, 'boundary', z=0)     # faces on the plane z = 0

# plain MPh from here on
physics = (model/'physics').create('HeatTransfer', geom)
physics.create('TemperatureBoundary', 2).select(bottom)
model.save('demo.mph')

Every helper takes MPh Nodes, and those that create something return one, so mphkit and MPh mix freely. Physics, mesh, study and results stay plain MPh (or the COMSOL Java API through node.java).

Requirements

• COMSOL Multiphysics with a license, installed where MPh can find it (see the MPh documentation).
• Python 3.10 or newer, MPh 1.4 or newer.
• Importing CAD files (mk.import_ with STEP, IGES, ...) needs a license for CAD import (CAD Import Module, Design Module or a LiveLink). Everything else needs COMSOL only.

Tested with COMSOL 6.4 and MPh 1.4.0, on macOS (Apple silicon) with Python 3.10 and 3.13 and on Windows with Python 3.13. Linux is not tested yet; since mphkit only goes through MPh, it is expected to work the same way.

Installation

pip install mphkit

or uv add mphkit in a uv project.

What changed between versions is listed in CHANGELOG.md.

What it covers

Geometry, in 3D, 2D and in work planes:

mk.block(geom, (10, 10, 5)); mk.cylinder(geom, r, h, pos); mk.sphere(geom, r)
mk.union(geom, [a, b]); mk.difference(geom, a, [b]); mk.intersection(geom, [a, b])
mk.move(geom, part, (10, 0, 0)); mk.rotate(geom, part, 90, axis='z')
mk.mirror(geom, part, (1, 0, 0)); mk.array(geom, part, size=(5, 5, 1), displ=(10, 10, 0))
mk.fillet(geom, block, 0.5); mk.chamfer(geom, block, 0.5)   # all edges, or a selection
mk.partition(geom, part, tool); mk.delete(geom, part)
plane = mk.workplane(geom, quickz=0)
mk.circle(plane, 2); mk.extrude(geom, plane, 5); mk.revolve(geom, plane)
mk.import_(geom, 'part.step')
mk.feature(geom, 'AnyType', ...)   # any other geometry feature

Selections by location (mk.sel), usable in physics, materials and mesh:

mk.sel.box(geom, 'boundary', z=0)                 # a range per axis, or a value
mk.sel.ball(geom, 'domain', center, r); mk.sel.cylinder(...); mk.sel.disk(...)
mk.sel.union(geom, 'boundary', [a, b])            # also intersection, difference, complement
mk.sel.adjacent(geom, domains)                    # boundaries around a domain selection
mk.sel.result(geom, feature, 'domain')            # what a feature produced
holes = mk.sel.cumulative(geom, 'holes', 'domain', create=True)
mk.cylinder(geom, 1, 5, pos, contributeto=holes)  # collect from several features

where='geometry' makes a selection inside the geometry sequence instead, for use as input of a later operation, e.g. mk.sel.box(geom, 'object', x=(20, 40), where='geometry') to pick whole objects for mk.delete. In a work plane, selections pick single corners or edges: mk.fillet(plane, mk.sel.box(plane, 'point', x=1, y=1), 0.3).

Queries return plain Python values and leave nothing in the model:

mk.sel.entities(geom, bottom)            # [3]
mk.sel.find(geom, 'domain', x=(0, 10))   # entity numbers inside a box
mk.measure(geom, 'domain')               # volume (area, length for other levels)
mk.bounding_box(geom, 'boundary', 3)     # {'x': (0, 10), 'y': ..., 'z': ...}

And a few helpers outside geometry:

mk.coordinate_system(geom, 'PML', selection=layer)   # e.g. perfectly matched layers
mk.set(mesh_size, hmax=0.5, hgrad=2)   # any node or Java object; converts ints and lists

Arguments are COMSOL property names, so the COMSOL documentation of each feature applies. The docstrings describe each helper in detail.

examples/plate_with_holes.py is a complete script, from geometry to solved results: heat conduction in a plate with a row of cooling holes, for any number of holes.

Limitations

• mphkit covers geometry and selections only. Physics, mesh, studies and results are left to MPh.
• No named helpers yet for geometry parts (PartInstance), sweeps, cones and the other remaining primitives, virtual operations or repair. They work through mk.feature(geom, 'Sweep', ...) with the same conversions and input handling.

Development

uv run pytest

The tests start COMSOL and build real models. Without a CAD import license, the CAD import test is skipped.

License

MIT, see LICENSE.