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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.
Importing Geometry
One of the possible starting points for the meshing process is to import surface data.
Importing Surface Data into Simcenter STAR-CCM+
All surface data (except for XML-based imports) for use in the meshing pipeline is imported into Simcenter STAR-CCM+ using the Import Surface Mesh... menu item:
Sewing Tolerance
For IGES files, it is possible for gaps to exist in the sheet bodies during translation. The sewing tolerance is used to create solid bodies after the translation process.

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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.
    - Surface Mesh Formats
      A surface mesh is a discrete representation of the geometry of individual regions that are used for the volume mesh generation.
    - Neutral Formats
      Neutral format data files allow CAD model data to be exchanged between different programs while still maintaining the model integrity.
    - Native CAD Formats
      Native CAD data files are created with parametric based CAD programs and contain all the relevant solid model information for that program.
    - XML Formats
      XML files are top-level data files that typically describe the assembly structure and components of a product.
    - CAD Package Support
      This section contains a list of supported CAD Clients, the CAD import versions, and the CAD export versions.
    - Importing Surface Data into Simcenter STAR-CCM+
      All surface data (except for XML-based imports) for use in the meshing pipeline is imported into Simcenter STAR-CCM+ using the Import Surface Mesh... menu item:
      - Import Mode
        The Import Mode option determines whether the surface data file or files are imported as regions or as geometry parts.
      - Boundary Mode
      - Region Mode
        The region mode determines how the regions are created based on the input data.
      - Part Mode
        The Part Mode option is available when importing surface mesh files and determines the way geometry parts are created based on the underlying surface description.
      - Surface Mode
        The Surface Mode option is available when importing surface mesh files and determines the way individual part surface nodes are created for a geometry part.
      - Units
        A choice of centimeters (cm), feet, (ft), inches, (in), kilometers, (km), meters (m) (default), miles (mi), millimeters (mm), micrometers (um), and yards (yd) is allowed.
      - Merge Vertices
        When importing either STL or JTOpen files, this option allows the vertices for each surface element to be automatically merged or not.
      - Database ID
        When a pro-STAR database file is imported, the database ID option allows specific surface geometries to be selected, when the file contains more than one.
      - Import Type
        This option appears when importing geometry from file types that support both CAD and tessellated imports--such as CATIA V5 and SolidWorks formats.
      - Using the CAD Client Translators to Import Geometry
        You can import geometry into Simcenter STAR-CCM+ using the CAD client translators. These translators can provide a better result when importing your geometry compared to other translators.
      - Mark Feature Edges
        This option allows you to specify which of the mesh edges that lie along CAD edges are marked as feature edges.
      - Sharp Edge Angle
        Creates feature edges from edges of attached faces that make an angle sharper than the Sharp Edge Angle value.
      - Merge Parts by Name
        This option is available when the Import Mode is set to create new geometry parts.
      - Create One Part Surface Per Part
        When activated, ignores the different surface names in each part and instead adopts the name of the parent part.
      - Create Part Contacts from Coincident Entities
        This option is available when the Import Mode is set to create new geometry parts.
      - Create Shells
        This option is available when the Import Mode is set to create new geometry parts.
      - Coincident Face Tolerance
        When the Create Part Contacts from Coincident Entities option is activated, the option to specify the Coincident Face Tolerance becomes available.
      - Check Parts' Validity
        The Check Parts' Validity option is available when importing any surface mesh file type. When this option is activated, the validity of the surface mesh import is examined.
      - Repair Invalid Bodies
        Imported CAD models can contain geometry that is not suitable for use in a Simcenter STAR-CCM+ analysis. This type of geometry is considered invalid, and typically contains errors in the Parasolid geometry. When this happens, you can instruct Simcenter STAR-CCM+ to attempt repairs on the geometry.
      - Tessellation Density
        The Tessellation Density determines the level of surface refinement that Simcenter STAR-CCM+ uses when importing geometry.
      - Sewing Tolerance
        For IGES files, it is possible for gaps to exist in the sheet bodies during translation. The sewing tolerance is used to create solid bodies after the translation process.
      - Show Detailed Tessellation Parameters
        Activating the Show Detailed Tessellation Parameters option displays detailed tessellation parameters within the Import Surface Options dialog. You can then edit these parameters as required.
      - Multi-Pass Sewing
        For IGES files, it is possible for gaps to exist in the sheet bodies during translation.
      - Open Geometry Scene After Import
        A new geometry scene can be created automatically containing the imported surfaces.
      - Run Diagnostics After Import
        The surface quality mesh diagnostics report for the imported surface is produced in the Output window when this option is turned on for the import of surface meshes.
      - JT Import Options
        This property becomes available in the Import Surface Options dialog when importing a JT Open file which contains tessellation data and B-rep data.
    - Importing Surfaces Using an XML File
      XML-based data files can be used to import many parts with a given hierarchy, such as a CAD assembly.
    - Importing Multiple Surface Data Files
      STAR-CCM+ allows multiple surface input files of the same format to be imported simultaneously using the File > Import Surface option.
    - Reviewing the Surface Data Import Report
      A summary of the surface statistics for the imported file is reported in the Output window.
    - Using Surface Data Import Representations
      When importing surfaces as regions, an Import representation is created under the Representations node in the simulation tree.
    - Checking the Surface Validity
      The validity of the surface can be checked using one of two different methods:
  - Understanding Geometry Parts
    You can use the geometry parts manager node to control what parts are meshed and included in the simulation downstream.
  - 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.

Sewing Tolerance

For IGES files, it is possible for gaps to exist in the sheet bodies during translation. The sewing tolerance is used to create solid bodies after the translation process.

Gaps that exist between each sheet are sewn together based on the supplied sewing tolerance value (1e-5 m by default). If the sheet bodies are not sewn together properly, then each sheet is treated as a separate body. If the Region mode is set to One region per body, multiple regions are produced. Additionally, if the translated surface is used as the starting point for the surface wrapper, then the surface quality at edges and corners where sheets meet is not as good as when the surfaces are closed to form a solid body.