Child Geometry

The parent-child relationship is a foundational concept used to structure simulations. Children define the extent and shape of the parents. These properties include the extent of the static boundary geometry, the shape of the moving impeller, and the location of species insertion. Sometimes the children represent physical geometry, as in static and moving bodies; in other cases, the children are simply regions of space where properties will be applied.

Child geometry provided as either Surface files or Mesh files, depending on how it was originally created. The pre-processor can import and manipulate either type, but all child geometry is ultimately converted to a mesh before being used in the simulation. Surface files are automatically tessellated into mesh form at runtime, with mesh density and aspect ratio adjustable via the Edit Mesh command. Mesh files are imported in their existing tessellated form and passed directly to the solver without modification. Each child geometry has a unique Child Geometry Toolbar.

Adding Geometry

Child geometry can be added to the pre-processor through two workflows, each suited to different geometry sources and formats.

  • Add Geometry Form: The Add Geometry form is the most common workflow. It opens automatically when you select a parent component from the Create menu. Additionally, when you select an already-existing parent component, you can add children via the Add Geometry command.

  • CAD Assembly Explorer: The CAD Assembly Explorer is used to open CAD assembly files and extract relevant part geometry. The CAD Assembly Explorer can be accessed on the File menu under Import CAD Assembly.

Geometry File Types

Child geometry is categorized as surface, mesh, or moving parametric, based on the file type loaded into the pre-processor. This classification determines how the geometry is prepared for simulation and what editing options are available.

  • Surface: Defines geometry using curves and surfaces (e.g., IGES, STEP, OCC Brep, Parasolid). Requires tessellation before simulation. The resulting mesh can be previewed and adjusted using Edit Mesh commands.

  • Mesh: Represents geometry as flat facets (e.g., STL, OBJ). Used directly in simulation without remeshing. Meshes can be previewed but not directly edited.

  • Moving Parametric: A subset of parametric geometry that follows a user-defined path over time. Limited to shapes like spheres and cylinders, whose boundaries are calculated with analytical equations. Can only be assigned to particle, scalar and global variable parents.

  • Child Geometry Toolbars: Selections for the various child geometry context-specific toolbars.

Geometry Catalogs

Within the Add Geometry form, predefined geometry catalogs are built into the software, with the option to link to external catalogs.

  • Parametric Geometry Catalogue: Contains geometry where all defining parameters are exposed and editable. Parametric geometries include objects such as mixing vessels, mixing impellers, piping system, primitive geometries, storage tanks, etc.

  • Non-Parametric Geometry Catalogue: Contains geometry with fixed parameters. These include geometries typical of vendor systems, including glass-lined vessel internals, wave bags, glass lined impellers, etc.

  • User Catalog: Contains geometry from a local or network directory, allowing custom libraries. This functionality allows for quick access to shared geometry databases.