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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.
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.
Surface Wrapper
The Surface Wrapper can be used to provide a closed, manifold, non-intersecting surface when starting from poor quality CAD data.
Surface Wrapper Defeature Control
Use the defeature controls of the surface wrapper to choose which features are removed, or more precisely, which features are not retained when wrapping geometry parts.

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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.
  - 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.
    - Surface Meshers Overview
      This section provides a comparison of the Surface Remesher and Surface Wrapper
    - Surface Wrapper
      The Surface Wrapper can be used to provide a closed, manifold, non-intersecting surface when starting from poor quality CAD data.
      - Gap Closure
        The surface wrapper can close holes in the input geometry which would otherwise prevent distinct separation of volumes within the mesh.
      - Leak Detection
        The surface wrapper leak detection tool is useful for determining whether “leaks” exist in the resultant wrapped surface that is created from an imported surface.
      - Contact Prevention
        Contact Prevention avoids the merging of two or more part surfaces that are close to one another during surface wrapping.
      - Surface Wrapper Defeature Control
        Use the defeature controls of the surface wrapper to choose which features are removed, or more precisely, which features are not retained when wrapping geometry parts.
      - Surface Wrapper with Internal Baffles
        The surface wrapping process automatically detects and inflates internal surfaces representing baffles.
      - Surface Wrapper Properties
        This section describes the properties that you can set for the Surface Wrapper.
    - Surface Remesher
      In order to improve the overall quality of an existing surface and optimize it for the volume mesh models, the surface remesher can be used to retriangulate the surface.
    - Geometric Sensitivity
      The Geometric Sensitivity mesher allows you to calculate and visualize how sensitive a 3D-CAD model or CAD Client model is to the adjustment of specific shape parameters. The mesher applies an offset to the specified parameters and calculates how sensitive the surface is to changes in the parameter for each face on the surface, using a finite difference approximation.
    - Automatic Surface Repair
      The Automatic Surface Repair operation provides an automatic procedure for correcting a range of geometric type problems that can exist in the remeshed surface once the surface remeshing process is complete.
    - Surface Mesher Controls and Values
      This section details the controls and values for all surface meshers.
  - 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.

Surface Wrapper Defeature Control

Use the defeature controls of the surface wrapper to choose which features are removed, or more precisely, which features are not retained when wrapping geometry parts.

Without the defeature control capability of the wrapper, you would have to adjust the surface size to control feature retention, reducing the size where you want to capture features and increasing the size where geometric accuracy is not important. Due to many factors, such as contact prevention, geometric versus topological distance, etc., it is not always possible to increase the surface size in a specific portion of the model, which can lead to undesired results.

Using the defeature control, you can control what features are retained by creating control sets of part surfaces, between which feature retention does not occur. By defining the control sets, you are essentially choosing the location where the features are not retained.

There are two types of control sets:

One Group Wrapper Defeature Control — Contains a single group of surfaces. Feature retention does not occur between these surfaces.
Two Group Wrapper Defeature Control — Contains two groups of surfaces. Feature retention does not occur between the two groups.

The control sets in the defeature control are similar to contact prevention sets. See Contact Prevention.

To control which features are not retained during the wrap:

Create a defeature control:
- For a single set of surfaces, right-click the Surface Wrapper > Wrapper Defeature node and select New > One Group Wrapper Defeature Control.
- For two groups of surfaces, right-click the Surface Wrapper > Wrapper Defeature node and select New > Two Group Wrapper Defeature Control
Select the surfaces that define the defeature control set:
- For a one group control, in the Surfaces property, select the surfaces between which you want to stop feature retention.
- For a two group control, select a group of surfaces for the Surface set 1 property, and a group of surfaces for the Surface set 2 property. Feature retention is prevented between the two sets.