Add Geometry

Introduction

In M-Star CFD, the parent-child relationship is a foundational concept used to structure simulations.

Parents define the how and what of a simulation. These properties include what properties are associated with any static boundary conditions, how moving objects are expected to move through a system, what types of particle sets will be included in the simulation, and what types of species will be considered.

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, the location a particle set will be injected into the system, and the location where a species will be introduced into the system. Sometimes the children represent physical geometry, as in static and moving bodies, in other cases the children are simply regions of space where these properties will be applied.

Although not all parents need children geometry, all children geometry must have a parent.

Access

Children geometry are most commonly added to parents via the Add Geometry window. A parent must be created before a child geometry can be added to it. There are two ways to access the window:

1. The Add Geometry window will open automatically when you define a new parent with the Create menu. The child geometry is most often attached to a parent when the parent is first created.

2. Launch the window manually by clicking on Add Geometry in the Context-Specific Toolbar. The toolbar will appear when you select the previously-created parent component you wish to define, and here you will find the Add Geometry command.

Add Geometry Window

The Add Geometry window is where you select your child geometry. There are five options.

Import from file

Import a CAD part file from an external CAD program on a part-by-part basis.

M-Star supports the following geometry formats for import:

• *.stl : STL Mesh files; uses triangles to describe the surface geometry of a three-dimensional object.

• *.obj : OBJ Mesh files; an open 3D graphics format that represents geometry as a list of vertices.

• *.iges, *.igs : IGES Boundary representation files; a vendor-neutral file format used in CAD systems.

• *.step, *.stp : STEP Boundary representation files; an ISO standard exchange format used for 3D modeling.

• *.x_t, *.x_b : Parasolid CAD files

Tip

• Use the Import CAD Assembly Workflow function to import files composed of multiple parts (or sub objects), such as tanks and impellers.

• Be aware of object location in space. Sometimes imported geometry may have an unexpected origin. In general it is suggested to keep the object close to world 0,0,0 when importing the geometry.

• Be aware of the scale of the imported geometry. STL mesh files do not contain any data about units, so you will be prompted at import time to specify what the units are.

Extract Geometry from Assembly

Extract individual parts from an existing CAD assembly file. A CAD assembly file is a file that contains multiple CAD parts. This workflow is useful if you have already integrated your CAD geometry—such as your static and moving bodies—in a single CAD assembly file.

This option launches the Assembly Explorer form which allows you to select and extract individual child geometry from the CAD file. Select the geometry you want to extract from the assembly and click OK.

M-Star supports the following file formats:

• *.iges, *.igs : IGES Boundary representation files; a vendor-neutral file format used in CAD systems.

• *.step, *.stp : STEP Boundary representation files; an ISO standard exchange format used for 3D modeling.

• *.x_t, *.x_b : Parasolid CAD file

User Catalog

The User Catalog allows you to define a path to a local or network directory containing a library of geometry. This functionality allows for quick access to shared geometry databases. The location of this directory can be specified in the Preferences menu.

For an example of how to get started with User Catalogs:

• Getting Started Guide PDF: Review the Getting Started Guide.

• Getting Started Package: Package including PDF guide and example catalog data.

See also User Catalogs.

Tip

• Importing CAD Geometry Tutorial: See for more on importing CAD geometry.

• Explode Geometry Form: Explode an imported geometry after it is imported into multiple sub-objects.

Parametric Catalog

In the Parametric Catalog you find the options for child geometry in which you can fully customize the shape and topology of the geometry. All the parameters used to define the geometry can be edited by the user. These parameters include vessel shapes, head types, impeller blade and angles, and pipe diameters and bends.

For a complete list of the parametric geometry, see the Parametric Catalog.

Non-Parametric Catalog

In the Non-Parametric Catalog you will find non-parametric options for child geometry. Non-parametric geometry parameters are not editable, they can only be scaled uniformly. These include geometries typical of vendor systems.

For a complete list of the non-parametric geometry, see the Non-Parametric Catalog.

Location

The Add Geometry form is found on the following context-specific toolbars (accessed through the Create menu):

Static Body

Moving Body

Massless Tracers

Inertial Particles

Gas Bubbles

Scalar Field