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Pre-Processing
Simcenter STAR-CCM+ solves physics problems on a computational mesh. To provide this mesh, you first define geometry using internal or external tools, and then create a mesh pipeline whose operations generate the mesh in repeatable steps.
Modeling Geometry
This part of the User Guide describes how to use 3D-CAD, the parametric solid modeler available within Simcenter STAR-CCM+. It also describes the features and tools available for further preparation of the geometry model and its surfaces.
Understanding Geometry Parts
You can use the geometry parts manager node to control what parts are meshed and included in the simulation downstream.
Creating and Importing Parts
Geometry parts can be created in the following ways
Extracting Geometry from a Derived Part
The Extract Geometry Part feature allows you to extract a derived part, such as an isosurface, threshold, or vector warp into a geometry part. Extracted parts can be used in mesh controls to refine the volume mesh, and can also be used on their own for simulations. For example, you can extract a closed isosurface from a topology optimization simulation and build a mesh from it.

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Pre-Processing
Simcenter STAR-CCM+ solves physics problems on a computational mesh. To provide this mesh, you first define geometry using internal or external tools, and then create a mesh pipeline whose operations generate the mesh in repeatable steps.
- 3D-CAD
  3D-CAD is a feature-based parametric modeler within Simcenter STAR-CCM+ that allows you to build geometries from scratch. The geometries that you create with 3D-CAD are stored as 3D-CAD models, which you can then convert to geometry parts for integration with the meshing and simulation process.
- Modeling Geometry
  This part of the User Guide describes how to use 3D-CAD, the parametric solid modeler available within Simcenter STAR-CCM+. It also describes the features and tools available for further preparation of the geometry model and its surfaces.
  - Preparing the Geometry
    In general, a Simcenter STAR-CCM+ analysis requires one or more geometry parts from which you define the spatial construction of the regions. Simcenter STAR-CCM+ allows you to create geometry parts directly using the built-in 3D-CAD modeler, or import geometry from a wide range of source formats.
  - Importing Geometry
    One of the possible starting points for the meshing process is to import surface data.
  - Understanding Geometry Parts
    You can use the geometry parts manager node to control what parts are meshed and included in the simulation downstream.
    - Geometry Parts
      A geometry part is a collection of surfaces and curves that you wish to address as one object. Parts surfaces and curves can be defined by CAD data or discrete (surface mesh) data, depending on the type of geometry part. A single object is referred to as a leaf-level part; a collection of geometry parts is referred to as a composite part. A surface can contain one or more sets of faces and a curve can contain one or more sets of edges.
    - What Is Metadata?
      The metadata specifier can be used to associate a key and value with the part.
    - Creating and Importing Parts
      Geometry parts can be created in the following ways
      - Creating and Updating 3D-CAD Parts
        3D-CAD parts are created when a 3D-CAD model is converted to a geometry part.
      - Importing Surfaces as Geometry Parts
        The option to create a geometry part is selected by default when importing surface data.
      - Extracting Geometry from a Derived Part
        The Extract Geometry Part feature allows you to extract a derived part, such as an isosurface, threshold, or vector warp into a geometry part. Extracted parts can be used in mesh controls to refine the volume mesh, and can also be used on their own for simulations. For example, you can extract a closed isosurface from a topology optimization simulation and build a mesh from it.
      - Creating Shape Parts
        Shape parts are simple geometric shapes that you can create quickly. Available shape parts are block, cone, cylinder, and shpere. Typically, shape parts are created after you import a geometry part and are used to create the exterior fluid domain while referencing imported geometry parts.
    - Organizing Assemblies Using Composite Parts
      Composite parts allow other parts to be grouped into assemblies and subassemblies for easier organization.
    - Using Part Contact Data to Create Interfaces
      A geometry part has a Contacts property that provides a list of all other parts with which the part is in contact. This part contact data can be used to generate interfaces for meshing and physics coupling automatically without having to create and assign coincident faces manually.
    - Updating Part Interfaces
      Updating part interfaces between two regions becomes necessary when one or more interfacing parts have been modified or have changed region.
  - Manipulating Parts
    Simcenter STAR-CCM+ allows leaf-level parts to be manipulated in several different ways once they have been imported or created.
  - Part Contacts
    Part contacts define the connection between two part surfaces. The meshers aim to generate a conformal mesh at the contact, which then becomes an interface in the physics region.
  - Repairing CAD Geometry
    The Geometry Repair tool provides diagnostic checks for assessing the validity of geometry and the means to repair the geometry automatically.
  - Displaying the Geometry
- The Surface Repair Tool
  The Surface Repair tool diagnoses errors in, and provides repair tools for, tessellated surfaces and part curves. The same tool allows you to reorganize discretized geometry by searching for face-based features and attributes then assigning the results to new or existing part surfaces or curves.
- Defining the Regions Layout
  An essential part of the process in setting up your simulation is to define the relationship between geometry parts and regions, boundaries, and interfaces.
- Meshing
  A mesh is a discretized representation of a geometric domain. This domain can include real-world geometry, its content, and its surrounding environment.

Extracting Geometry from a Derived Part

The Extract Geometry Part feature allows you to extract a derived part, such as an isosurface, threshold, or vector warp into a geometry part. Extracted parts can be used in mesh controls to refine the volume mesh, and can also be used on their own for simulations. For example, you can extract a closed isosurface from a topology optimization simulation and build a mesh from it.

The surface mesh of the extracted part is extracted from the Volume Representation and is not guaranteed to be closed. If necessary, to obtain a valid mesh from the extracted part you can repair the surface in surface repair or fix the mesh using various mesh operations (such as the surface wrapper, offset, fill holes, or extract volume). For an isosurface derived part, you can activate the Closed option on the part before extracting it. This option is particularly useful in topology optimization studies. See Isosurface Properties.

The extracted part is set out-of-date when the solution changes or when the derived part is modified. You can update the extracted part anytime using the right-click Update action. To apply an automatic update to the part whenever the mesh pipeline is executed, activate Automatic Update on the operation. In manual update mode, you have control over when the part updates.

To extract geometry from a derived part:

Right-click on the Derived Parts node to create either an isosurface, threshold, or vector warp.
See Defining Derived Parts: General Workflow.
Right-click on the derived part node and select Extract Geometry Part.
This action creates a geometry part icon in the Parts node under Geometry.

By default the extracted part does not update automatically when the solution changes the derived part. To automatically update the extracted part when the pipeline is executed:

Right-click Geometry > Parts > [Extracted Geometry Part] node and in the properties window activate Automatic Update.

To manually update the geometry:

Right-click Geometry > Parts > [Extracted Geometry Part] and select Update.

The following screenshot shows how the extracted geometry part appears in Simcenter STAR-CCM+.