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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.
Meshing
A mesh is a discretized representation of a geometric domain. This domain can include real-world geometry, its content, and its surrounding environment.
The Meshing Workflow
This section contains the recommended workflow for setting up and generating the volume mesh at the parts level.
Surface Wrapping the Geometry
The Surface Wrapper generates a closed and manifold surface mesh from poor quality or complex CAD geometry.
Setting the Volume of Interest and Wrap Properties
The volume of interest control determines the volume that the surface wrapper extracts from the input parts. The wrapper properties control the wrap.

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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.
- 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.
  - Mesh Construction
    Within a bounding volume defined by geometrical surfaces, Simcenter STAR-CCM+ can construct meshes for finite volume and finite element solvers.
  - Meshers in Simcenter STAR-CCM+
    The meshers in Simcenter STAR-CCM+ generate surface and volume meshes for geometry parts that are assigned to regions and make them ready for analysis.
  - Parts-Based Meshing
    Parts-based meshing (PBM) is a meshing strategy in which you create one or more mesh operations that define workflows for preparing, fixing, and processing geometry. A major benefit of PBM is that every mesh operation you create forms part of a linear and repeatable process.
  - The Meshing Workflow
    This section contains the recommended workflow for setting up and generating the volume mesh at the parts level.
    - Preparing Geometry for Meshing
    - Surface Wrapping the Geometry
      The Surface Wrapper generates a closed and manifold surface mesh from poor quality or complex CAD geometry.
      - Creating the Surface Wrap Operation and Selecting the Parts to Wrap
        Create a Surface Wrapper operation and select the parts to wrap.
      - Closing Gaps and Checking for Leaks
        Identify and close any obvious gaps in the geometry. Run the leak detection tool to identify less obvious gaps and holes.
      - Preventing Surface Contact
        Contact prevention ensures that selected close surfaces do not touch each other in the wrapped surface.
      - Setting the Volume of Interest and Wrap Properties
        The volume of interest control determines the volume that the surface wrapper extracts from the input parts. The wrapper properties control the wrap.
      - Generating a Basic Wrap and Checking the Fidelity
        Generate a basic wrap and check the fidelity.
      - Refining the Wrap
        Typically you wrap geometry using coarse settings before refining the wrap. Local wrapping speeds up the re-execution of the surface wrapper after local changes are made to the input geometry or wrapper settings. With this feature, Simcenter STAR-CCM+ only wraps surfaces within a defined location and leaves other surfaces unchanged. Surfaces that are excluded by the partial wrapping option are not wrapped by local wrapping.
      - Assigning Wrapped Parts to Regions
        There are three different procedures to assign wrapped parts to regions, depending on what you want to achieve.
    - Generating the Surface and Volume Mesh
      Meshing parts generates the surface and volume discretization of the imported CAD geometry. The solvers use this discretization to obtain a physical solution.
    - Local Meshing
      Local meshing speeds up the re-execution of mesh generation after changes are made to the geometry or mesh settings (and you already have an initial completed mesh). With this feature, Simcenter STAR-CCM+ remeshes surfaces or volume within a defined location without regenerating a complete mesh.
    - Creating a Parts-Based Mesh with Baffles
    - Creating Shells from Parts
      Simcenter STAR-CCM+ provides support for thin-walled structures that are best represented by a two-dimensional cell layer during simulation. These single-cell layers are known as shells.
    - Anisotropic Meshing for Lifting Surfaces
      Anisotropic meshing allows you to generate a surface mesh that contains stretched quad elements aligned with features (anisotropic faces). By using stretched elements, you can reduce the number of faces in the mesh while retaining geometrical and solution accuracy.
    - Extruding Surfaces from a Parts-Based Volume Mesh
      Use the extruder to extend the existing volume mesh beyond the original dimensions of the starting surface, normal to the existing volume mesh, or in a specified direction.
    - Replacing a Part in a Parts-Based Volume Mesh
      Simcenter STAR-CCM+ provides a Replace Part operation that allows you to repeat the meshing pipeline with one or more different parts. When the replacement part is defined by a file input from a global parameter, you can use Design Manager to supply the list of filenames during a design study.
    - Replacing a Mesh
      A region associated with a volume mesh in Simcenter STAR-CCM+ can be replaced by another topologically identical volume mesh at any point during the analysis.
    - Extracting Surface Mesh
      The Extract Surface Mesh feature allows you to retrieve the surface mesh after the volume mesh has morphed. This feature allows the volume mesh to be reconstructed with the new shape.
  - Mesh Operations
    Mesh operations perform actions on geometry parts that you can easily repeat whenever their input parts or properties are changed.
  - Mesh Descriptions
    A mesh description is a version of a surface or volume mesh belonging to a geometry part. Geometry parts can have more than one surface mesh description associated with them. You create and change descriptions by importing surfaces or executing operations.
  - Custom Mesh Controls
    Custom controls override any default controls for the surface and volume meshers. This facility allows you to refine or coarsen the mesh for part curves, part surfaces, geometry parts, and specified volumes.
  - Surface Meshers
    Simcenter STAR-CCM+ contains meshing tools which can be used to help prepare a high-quality surface mesh before a volume mesh can be generated.
  - Volume Meshers
    Simcenter STAR-CCM+ contains different types of meshers that can be used to generate a volume mesh starting from a suitably prepared surface mesh.
  - Mesh Refinement
    Simcenter STAR-CCM+ can refine the mesh by approximating the wake region or using solution-based approach. These features allow you to achieve efficient refinement by reducing the cell size in areas of interest.
  - Directed Meshing
    Directed meshing is a method for generating high quality swept meshes on geometries in Simcenter STAR-CCM+. The method operates by sweeping a mesh from the surfaces of a geometry through its volume onto a facing target surface.
  - Two Dimensional and Axisymmetric Meshes
    The use of a one-cell-thick three-dimensional mesh is much less efficient than using a real two-dimensional mesh for two-dimensional and axisymmetric simulations. When circumstances allow, use real two-dimensional meshes.
  - Turbomachinery Mesh
    Turbomachinery applications with axial blades typically require a flow-aligned, structured mesh. This type of mesh has implicit connectivity and a fixed number of vertex or face neighbors, leading to a more accurate solution.
  - Mesh Visualization
    You can visualize any mesh representation in Simcenter STAR-CCM+. After you have imported or generated a mesh, you visualize it to check the cell quality and mesh validity.
  - Checking the Surface Mesh
    The volume mesh quality is directly dependent on the surface mesh quality. Therefore, it is crucial to make sure that all surface meshes are of good quality.
  - Checking the Volume Mesh
    This section describes the tools available for checking the validity and quality of the volume mesh, and for diagnosing problem areas. Such problems can then be fixed, either inside Simcenter STAR-CCM+ or in the originating mesh generator.
  - Meshing Field Functions Reference
    This section contains a list of field functions that are related to meshing.
  - Working With Representations
    This section provides information on representations as a useful part of the meshing process.
  - Scaling the Entire Mesh
    Scaling the mesh is important as the units of the model must be in meters before running an analysis.
  - Working with Baffles
  - Exporting Mesh and Solution Data
    This section outlines the steps for exporting Simcenter STAR-CCM+ mesh and solution data to formats that can be used in other CAE packages.
  - Multi-Region Meshing
    This section outlines the surface requirements for performing multi-region meshing, as well as step-by-step instructions when starting from surface imports that result in single region and multiple regions definitions. Additionally, guidelines are provided on what the best approaches are for exporting surface data from CAD packages when multiple regions are required.

Setting the Volume of Interest and Wrap Properties

The volume of interest control determines the volume that the surface wrapper extracts from the input parts. The wrapper properties control the wrap.

Set the volume of interest:
1. Select the Surface Wrapper > Default Controls > Volume of Interest node and set Method to one of the following properties:
  - Largest Internal — Specifies that the wrapper extracts the largest internal, self-contained volume from the input geometry surfaces.
  - External — Specifies that the surface wrapper extracts the outer surfaces of all parts, that is, the external surfaces.
  - Seed Point — Specifies that a user-defined location determines the surface that the wrapper extracts. The resultant mesh is the surface that surrounds this location. See Step 2.
  - Nth Largest — Specifies that the wrapper extracts a particular surface according to volume size. The surfaces are ranked from largest to smallest, and the user-defined Volume Number determines the output surface. See Step 3.
If you set Method to Seed Point, create a seed point:
Seed points define a location within the volume of interest for the seed point volume extraction method.
1. Make sure that you have a scene open.
  If you do not have a scene open, you can only define the seed point using its properties.
2. Right-click the Surface Wrapper > Volume of Interest > Seed Points node and select New.
3. Define the position of the seed point:
  - Use the X, Y, and Z positions to specify an exact position.
  - Activate the Display Point Tool checkbox to define the position interactively in the Graphics window.
4. Click Create and then Close.
5. Select the Seed Point 1 node, and specify the Coordinate System.
If you set Method to Nth Largest, define the volume number:
The volume number property defines the volume of interest, ranked from largest to smallest, for the nth largest volume extraction method.
1. Select Surface Wrapper > Default Controls > Volume of Interest > Volume Number node, and then set Volume Number to define the volume of interest.
  For example, setting Volume Number to 1 extracts the largest volume and 2 extracts the second largest volume.
Select the Operations > Surface Wrapper node and set the properties in the Properties window. See Surface Wrapper Properties.