gmsh-sim

name	gmsh-sim
description	Use when driving Gmsh (finite-element mesh generator) via .geo DSL scripts or Python scripts using the gmsh API — 2D/3D meshing, CAD import, boundary layers, export to downstream solvers (CalculiX, OpenFOAM, FEniCS, SU2) through sim runtime one-shot execution.

gmsh-sim

You are connected to Gmsh via sim-cli. This file is the index — see the sections below for content.

Gmsh is an open-source finite-element mesh generator. It is a pre-processor (not a solver). Its "result" is a mesh file (.msh) that feeds downstream solvers like CalculiX, OpenFOAM, FEniCS, SU2.

Two input forms:

• .geo — Gmsh native DSL (SetFactory, Point, Sphere, Physical Volume, ...)
• .py — Python scripts that import gmsh and call the API

Both are run by sim via subprocess. .geo goes through Gmsh's CLI wrapper; .py runs as plain Python (the script itself does gmsh.initialize() / .finalize()).

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base/ — always relevant

Path	What's there
base/reference/geo_scripting.md	GEO kernel DSL basics: Point/Line/Circle/Surface/Volume, Physical groups, OpenCASCADE.
base/reference/python_api.md	gmsh Python API patterns (initialize/add/occ/synchronize/mesh.generate/write).
base/reference/mesh_formats.md	.msh v2 vs v4 format, export targets for downstream solvers.
base/snippets/01_sphere_mesh.geo	Verified unit-sphere mesh snippet.
base/known_issues.md	Shebang on PATH, pip wheel vs system binary, msh2 vs msh4.

solver/4.15/ — Gmsh 4.15 specifics

• solver/4.15/notes.md — provenance, capabilities, format defaults.

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Hard constraints

1. Gmsh is a mesher, not a solver. Acceptance = mesh topology (node/element count, bbox, physical-group tags), NOT physical state.
2. Always define Physical groups when the mesh feeds a downstream solver — untagged entities are NOT exported by default.
3. OpenCASCADE kernel requires synchronize() before meshing or querying entities, after any boolean/create operation.
4. Default output format is MSH 4.1; many downstream solvers need MSH 2.2 (-format msh22 flag).
5. Never confuse Mesh.<option> = ... (config) with geometry commands — a .geo containing only options has no geometry to mesh.

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Required protocol

After sim check gmsh confirms availability: gather Category A inputs from user (geometry intent, target mesh size, physical group semantics, downstream solver format). Write .geo or .py. Lint with sim lint. Run with sim run --solver gmsh. Validate via JSON output from script (node/element counts, bbox). Hand off .msh to downstream solver driver.