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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.
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.
Creating Part Contacts from Coincident Entities
Simcenter STAR-CCM+ can automatically create part contacts from pairs of coincident faces when importing CAD models, provided the Create Part Contacts from Coincident Entities option is selected on the Import Surface Options dialog.

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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
    - 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.
      - Creating Part Contacts from Coincident Entities
        Simcenter STAR-CCM+ can automatically create part contacts from pairs of coincident faces when importing CAD models, provided the Create Part Contacts from Coincident Entities option is selected on the Import Surface Options dialog.
      - Imprinting Parts on Their Neighbors
        In some cases, the imported data results in multiple geometry parts that have multiple part surface per part, but the parts have not been imprinted on their neighbors. For these cases, it is possible to use the single or multi-part imprint mode of the surface preparation tool to generate separate part surfaces at the point of contact.
      - Finding Part Contacts Automatically
        Part contacts can be found automatically between two or more parts that are based on a user supplied tolerance value. This feature is useful in circumstances where several parts exist, some of which can be touching two or more other parts.
      - Creating Part Contacts Manually
        This section describes how to create part contact data manually.
      - Browsing Part Contact Data
        The Part/Part Contact Browser allows you to scan through the part contact data and see the contacting parts in the Graphics window.
    - 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.

Creating Part Contacts from Coincident Entities

Simcenter STAR-CCM+ can automatically create part contacts from pairs of coincident faces when importing CAD models, provided the Create Part Contacts from Coincident Entities option is selected on the Import Surface Options dialog.

This option is exposed when the import mode is set to create geometry parts.

The operation searches all of the imported CAD bodies for pairs of coincident faces that are within the specified Coincident Face Tolerance. For each pair found, part contact data is created and stored in the Contacts property of each part. A strict definition of coincidence is adhered to, in that the faces belonging to each pair must have an identical surface definition and identical trimming loops. They must overlap exactly without any offset unless they are imprinted.

This same operation is applied when converting 3D-CAD models to geometry parts, and when faces are imprinted using the single or multi-part imprint tool.

The example below shows a 3D-CAD model where the cylinder has been imprinted on the surface of the block. As the imprint operation results in a pair of coincident faces, Simcenter STAR-CCM+ creates part contact data when the 3D-CAD model is converted to a geometry part.

The advantage in using this method to generate the part contact data is that each part surface can be mapped to its own boundary during region assignment. A separate boundary is created for the interface. The One boundary per part surface option gives this result.