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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.
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.
Choosing Source and Target Surfaces
Before creating a surface meshes for directed meshing, identify the sources and target surface for each part.

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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.
  - 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.
    - Preparing CAD Parts for Directed Meshing
      This section provides information on preparing CAD parts for directed meshing.
    - Preparing Non-CAD Parts for Directed Meshing
      This section provides information on preparing parts with no underlying CAD for directed meshing.
    - Directed Meshing Workflow
      In Simcenter STAR-CCM+, a directed mesh has its own operation node that identifies the parts in which the mesh belongs, and the sources and target surfaces within those parts.
    - Choosing Source and Target Surfaces
      Before creating a surface meshes for directed meshing, identify the sources and target surface for each part.
      - Selecting Source and Target Surfaces Using the Tree
        This section describes how to select source and target surfaces.
      - Selecting Source and Target Surfaces Interactively
        In the Graphics window, you can select surfaces on the geometry and add them to the source or target surfaces for the mesh.
      - Setting Source and Target Parts as Periodic Interfaces
        It is possible to use boundaries that are specified as periodic interfaces for source and target surfaces in directed meshing.
    - Creating a Source Mesh Using Patches
      For a source mesh using patches, you first define the patches, and then generate quadrilateral faces within the patches. This option is only available as part of the 1-1 meshing strategy.
    - Creating a Source Mesh Using an Existing Mesh
      It is possible to use an existing volume mesh as the source surface mesh.
    - Creating a 2D Source Mesh
      When using Directed Meshing, you can create 2D source surface meshes using the automated 2D mesh operation. This approach allows you to include prism layers on the source surface, which are then swept along the length of the connected parts.
    - Creating Additional Volume Distributions
      After you have specified a patch mesh (1-1 Directed Meshing only) or an existing mesh for the source surfaces, you define the volume mesh distribution to the parts through which Simcenter STAR-CCM+ sweeps the source. If required, you can define different mesh sweeps for specific parts by creating additional distributions.
    - Generating the Directed Volume Mesh
      You can generate the volume mesh for a single part, or for several parts at the same time, in the Directed Mesh panel. This operation can involve single (1-1) or multiple source meshes (M-1) sweeping to a single target surface.
    - Meshing a Stack of Parts
      This section describes how to mesh a stack of parts.
    - Meshing a Single Part in a Closed Loop with a Baffle
      This section describes how to mesh a single part in a closed loop with a baffle. This operation is only possible using one source to one target (1-1).
    - Meshing Around a Rotational Axis
      Simcenter STAR-CCM+ allows you to improve the mesh quality for meshes which are rotationally swept about an axis.
    - Directed Meshing Properties
      This topic describes the Properties of each of the nodes that are available for directed meshing.
  - 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.

Choosing Source and Target Surfaces

Before creating a surface meshes for directed meshing, identify the sources and target surface for each part.

Connected parts must share the source surface(s) and the target surface. The same volume mesh distribution parameters are applied to all of the connected parts. If the connected parts are of different lengths, then Simcenter STAR-CCM+ makes an estimate with regards to the distribution in the sweeping dimension. The directed meshing process transfers the mesh from source(s) onto the target surface. Therefore, target surfaces cannot contain internal part curves.

Note	Naming the faces on either side of the interfaces in a stack of parts makes it easier to identify the source and target surfaces for directed meshing. See Meshing a Stack of Parts for additional information.