13  Mesh

Formats, multiple zones, scope namespaces, and scale_factor

13.1 What this setting is

A mesh is the computational model that divides the analysis space into finite cells. In Wake CFD, the mesh file provides names called zones and markers; domains use zones as physical regions and boundary conditions use markers as boundary faces. The required resolution and naming for geometry, boundary layers, and wakes are therefore the starting point for analysis setup.

13.2 Configure in the GUI

Figure 13.1: An imported mesh in the project outline, with its zone and boundary markers expanded, and the mesh properties below. Format, Scale factor, and Scope are editable; File, Dimension, and the element counts are read from the file.

Use Home → Import Mesh or right-click the Meshes tree node to add a CGNS, SU2, or Gmsh file. Import as link to keep the source file read-only, or as editable to save a project-owned CGNS copy when the project is saved. Select an imported mesh in the tree to inspect its zones and boundary markers; select the mesh entry to edit its properties. Zone and marker names are then assigned in Domains, not in the mesh block.

GUI location / control	Input key	What it does
Import Mesh → selected file	mesh[].file_name	Adds a mesh file; the File property is read-only after import.
Mesh Properties → Format	mesh[].format	Sets the reader format for the imported file.
Mesh Properties → Scale factor	mesh[].scale_factor	Converts mesh coordinates to metres; use 0.001 for millimetres.
Mesh Properties → Scope	mesh[].scope	Names a mesh file when a case uses multiple files.
Mesh tree → zones / markers	—	Shows imported names for later domain and boundary assignment; these names are not keys in mesh[].

The GUI import picker lists CGNS, SU2, and Gmsh. UGRID can be supplied in JSONC; it is not listed in that picker. The mesh block is an array, even for one file.

13.3 Input keys

Key	Required	Meaning
file_name	✓	Path to the mesh file
format		cgns (default), su2, gmsh, or ugrid; set it explicitly for non-CGNS files
scale_factor		Coordinate scale factor (e.g. mm→m = 0.001); see scale_factor below
scope		File-level namespace for zone paths across multiple files; see Multiple zones below

The array must contain at least one file, except when initialization.type: "restart" loads a full mesh from the restart file.

13.4 Supported formats

Format	format value	Notes
CGNS	cgns	Recognizes boundaries by BC_t node name
SU2	su2	Recognizes boundaries by MARKER_TAG
Gmsh	gmsh	Uses msh2 and physical-group names
AFLR UGRID	ugrid	Available to the solver through JSONC; Desktop import currently lists CGNS, SU2, and Gmsh

format accepts these four values. When it is omitted, the solver uses cgns; it does not select a format from the filename extension. Set it explicitly for SU2, Gmsh, or UGRID input. Desktop import recognizes supported extensions and writes the detected format into the case.

13.5 Multiple zones (multiple files)

With more than one mesh file, every entry needs a distinct, nonempty scope, and a scope cannot contain /. A zone is then addressed as scope/zone (or by the file’s scope when selecting the whole file). Boundary markers keep their names and are resolved within the bound domain’s zone; do not add the scope prefix to mesh_markers.

13.6 Boundary-name matching

domains[].boundaries[].mesh_markers in JSONC and mesh-file marker names are matched without regard to ASCII letter case, within the domain’s bound zone. The spelling otherwise needs to match. To inspect zone, section, and marker names before authoring a case, run wake_grid <mesh_file> --bc. On mismatch:

Mesh location has no matching config boundary

Format	Boundary-name source	Notes
CGNS	BC_t node name	Not Family name (currently unsupported)
SU2	MARKER_TAG	In the .su2 file
Gmsh	Physical-group name	Physical Surface("inlet") in .geo

Warning

CGNS notes

• Wake CFD reads ZoneBC_t/BC_t node names (cg_boco_info).
• FamilyName_t is unsupported.
• ICEM CFD: Part names are automatically converted to BC_t names.
• Pointwise: Set BC names directly.
• Names can be lost during Gmsh-to-CGNS conversion; use Gmsh directly when possible.

13.7 scale_factor

Use this for coordinate-unit conversion. All coordinates are internally converted to SI units (m) before processing.

13.8 JSONC examples

For a single CGNS mesh, keep the required array shape. The default format can be omitted:

{ "mesh": [{ "file_name": "naca0012.cgns" }] }

Convert millimetre coordinates to metres with scale_factor:

{
  "mesh": [
    { "file_name": "model_mm.cgns", "format": "cgns", "scale_factor": 0.001 }
  ]
}

Use distinct scopes for multiple files:

{
  "mesh": [
    { "file_name": "rotor.cgns", "format": "cgns", "scope": "rotor" },
    { "file_name": "stator.su2", "format": "su2", "scope": "stator" }
  ]
}