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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.
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.
Volumetric Control
Volumetric controls specify alternative mesh sizes and prism layer settings for the surface and volume mesher.

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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.
    - Custom Mesh Control Properties
    - Custom Mesh Control Context Menu
    - Curve Control
      Curve controls specify alternative surface mesh settings for part curves.
    - Surface Control
      Surface controls specify alternative surface mesh and prism layer settings for part surfaces, geometry parts, and composite parts.
    - Part Control
      Part controls specify alternative volume mesh settings for the polyhedral, tetrahedral, and turbomachinery meshers.
    - Volumetric Control
      Volumetric controls specify alternative mesh sizes and prism layer settings for the surface and volume mesher.
      - Volumetric Controls and Values
        Use the volumetric controls and values to define surface and volume mesh sizes within a specified volume.
      - Effect of Volumetric Control on Surface and Volume Meshers
        The volumetric control is activated individually for each meshing model. This functionality can cause unexpected results if the volumetric control is activated on the volume mesher, but not the surface mesher.
    - Query Custom Mesh Controls
      This feature allows you to display – as a list in the Output window – all of the meshing custom control settings that are applied to a selected part, composite part, part surface, or part curve.
  - 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.

Volumetric Control

Volumetric controls specify alternative mesh sizes and prism layer settings for the surface and volume mesher.

Using volumetric controls, you can refine the boundary surface and core cells for any surface or volume mesher. To coarsen the mesh, you can only coarsen core cells for the tetrahedral and polyhedral volume meshers—you cannot coarsen faces on the boundary surface.

Generally, volumetric controls have common properties that specify an alternate face or cell size (see Common Volumetric Control). You can specify the face or cell size as relative or absolute.

However, for the prism layer mesher and trimmed cell mesher, the behavior of volumetric controls is different (see Prism Layer Mesher Volumetric Control and Trimmed Cell Mesher Volumetric Control).

Volumetric controls can overlap and extend outside the parts definition. Volumetric controls can also overlap from one part to another, but the effect is only included if the part belongs to the same mesh operation as the volumetric control. If two or more volumetric controls overlap, the smallest user-defined cell size takes priority.

The relevant growth rate for each core mesh model determines the transition in cell sizes from the volumetric control to the core mesh.

Examples of Volumetric Controls

The following examples show 20% mesh refinement with a cylindrical volumetric control. The image below shows the initial geometry and the cylindrical volumetric control.

Surface Wrapper

Surface Remesher

Polyhedral Mesher

Trimmed Cell Mesher

Tetrahedral Mesher

Prism Layer Mesher

This example is slightly different from the others in that the number of layers, and prism layer thickness, changes within the volumetric control. To make sure that the prism layers are influenced by the volumetric control, use a shape that is larger than the target area of interest.

Advancing Layer Mesher