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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.
Working With Representations
This section provides information on representations as a useful part of the meshing process.
Using Cell Sets
The purpose of a cell set is to allow you to identify collections of cells that are useful for visualizing the model, such as during post processing or mesh checking.
Modifying an Existing Cell Set
Once a cell set has been created, it can be easily modified using a range of global and/or Boolean operations in order to manipulate the cell collection further.
Using the Replace Option
The replace option allows you to replace the existing cell set with a new one based on the cells in the entire model. Cells that are contained in the original set can be reselected if desired.

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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.
  - 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.
    - What Are Representations?
      Representations help you keep track of the surface and volume meshes that Simcenter STAR-CCM+ uses as part of the meshing and simulation setup process. Several different representations are available.
    - Displaying Representations
      The new surface or volume mesh representations that are generated using the meshing tools are not automatically displayed in the plot window once the meshing process is complete.
    - Using Proxy Representations
      A proxy representation acts as a placeholder and allows you to control the representation of multiple objects (scenes, reports, and plots) from a single location.
    - Replacing a Surface Mesh
      Any of the five types of surface mesh representations, namely import and remeshed surface, can be replaced at any given time by a new surface read in from an external file.
    - Preparing a Surface Mesh
    - Exporting a Surface Mesh
      Any of the five types of surface mesh representations, namely import and extracted surface can be exported from Simcenter STAR-CCM+ for further manipulation.
    - Extracting a Surface Mesh
      This facility extracts a surface mesh from a volume mesh representation so that you can generate a new volume mesh using the Simcenter STAR-CCM+ meshing tools.
    - Using Cell Sets
      The purpose of a cell set is to allow you to identify collections of cells that are useful for visualizing the model, such as during post processing or mesh checking.
      - Creating a New Cell Set
        Generate a new cell set before any further manipulation can be done on the set or the set contents displayed.
      - Modifying an Existing Cell Set
        Once a cell set has been created, it can be easily modified using a range of global and/or Boolean operations in order to manipulate the cell collection further.
        Using the Fill Option
        The fill option replaces a previous collection of cells with all the cells that currently exist in the model.
        Using the Clear Option
        The clear option can be used to clear all the cells from the cell set. The previous collection of cells is removed leaving the cell set empty.
        Using the Invert Option
        The invert option deletes the existing cells from the set and replaces them with all other cells in the model, that is, those cells that were previously outside the set.
        Using the Grow Option
        The grow option can be used to expand the current cell set by a single layer of cells in all directions.
        Using the Grow Across Interfaces Option
        The Grow Across Interfaces option can be used with the grow option to expand the current cell set by one layer across an interface.
        Using the Shrink Option
        The shrink option can be used to reduce the current cell set by one layer, removing cells that have a face exposed in the interior of the model. Cells with faces that are on a boundary are ignored.
        Using the Shrink All Option
        The shrink all option can be used to reduce the current cell set by one layer, removing cells that have a face exposed in the interior of the model or on a boundary.
        Using the Subset Option
        The subset option allows you to create a set of cells based on the existing cell set only, rather than the entire model. Cells that are not contained in the original cell set are ignored.
        Using the Add Option
        The add option allows you to add cells to the existing cell set based on all the cells in the model.
        Using the Remove Option
        The remove option allows you to remove cells from the existing cell set.
        Using the Replace Option
        The replace option allows you to replace the existing cell set with a new one based on the cells in the entire model. Cells that are contained in the original set can be reselected if desired.
        Editing a Cell Set in the Current Scene
        In order to allow multiple set operations to be performed without the dialog closing each time, a cell set can be edited using an in-place dialog as part of the current scene. The same global and Boolean operations as described above are allowed.
      - Copying and Pasting Cell Sets
        Boolean operations between two cell sets can be performed by copying and pasting from one cell set to another.
  - 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.

Using the Replace Option

The replace option allows you to replace the existing cell set with a new one based on the cells in the entire model. Cells that are contained in the original set can be reselected if desired.

To access the cell set replace option, right-click on the desired cell set node and select Replace from the pop-up menu:

Four different replace options are allowed:

cell list - Replace cells based on cell index ID’s or offsets.
threshold - Replace cells based on a scalar threshold.
zone - Replace cells based on a zone.
geometric range - Replaced cells based on a geometric range.

An example before and after snapshot of a replace operation using a zone is shown below:

In this example, the original cell set contained a portion of the model cells. The replace operation using a zone was used to select a new set containing some cells below the original set, as well as the right half portion of the original set.