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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.
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.
Repairing Surfaces
Diagnose and fix surfaces before running the surface remesher.
Merging Vertices
When merging vertices, review and change the tolerance value, if necessary.

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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.
  - The Surface Repair Workflow
    Use the Surface Repair tool to identify and manually repair surface and part curve errors on the discretized geometry.
  - Surface Repair User Interface
    The functions of the Surface Repair tool are contained within the Surface Repair environment. Repair tool modes are presented in the Surface Repair panel; display, selection, and diagnostics/search functions are embedded within the Graphics window.
  - Selecting Entities
    The surface repair tool allows you to select faces based on either individual triangles from the tessellation or underlying patch definitions in the CAD geometry. A number of methods are available for making rapid selections based on continuity and proximity.
  - Repairing Surfaces
    Diagnose and fix surfaces before running the surface remesher.
    - Custom Threshold Options
      Create custom thresholds using the settings in the Create/Modify Thresholds panel.
    - Diagnostics Slide Out Threshold Input Reference
      After running diagnostics, you can control the input for the thresholds in the diagnostics slide out.
    - Understanding Surface Mesh Diagnostics for Multi-Part Cases
      Whether the surface belongs to single or multiple parts affects the diagnosis of non-manifold edges, proximity and self-intersection.
    - Merging Vertices
      When merging vertices, review and change the tolerance value, if necessary.
    - Merging Duplicate Faces
      A duplicate face is a face that shares three vertices with another face.
    - Filling Holes
      This tool fills a hole with new faces using the selected edge loops.
  - Repairing Features
    Diagnose and fix part curves before running the surface remesher.
  - Surface Repair Error Categories
    The Surface Repair tool diagnoses the geometry for surface and feature errors and groups the various errors into color-coded categories.
  - Repair Tools Reference
    Use the repair tools to repair errors on the geometry surface and part curves.
  - Global Tools
    Global tools are designed for work on larger portions of the model as opposed to individual faces, edges, and vertices.
  - Query Tools
    Query tools provide information on selected entities in the Graphics window.
  - Classifying Surfaces
    In many cases, different surfaces of a geometry part require different mesh settings, for example, a different number of prism layers for internal and external surfaces. In Surface Repair, you can Classify faces based on specified criteria and create corresponding part surfaces. This classification process is suitable for regular geometries with well defined angles.
  - Organizing Discretized Geometry
    The search capability of the Surface Repair tool is a powerful feature that helps you organise and prepare discretized geometry for simulation.
  - Tagging Surfaces in Surface Repair
    You can tag selected surfaces in the Surface Repair Tool. You can manually select surfaces for tagging, or tag the surfaces returned by the search filters.
  - Part Controls
    The Organize tab allows you to create or reassign part entities using the Part Edit or Create New Part options.
  - Set Controls
    A set is a collection of faces, edges, or vertices, which you can store, recall and browse, using the Set Controls group box.
  - Query Diagnostic Responses From Java Macros
    This section provides example Java and reference material for accessing information from surface preparation query diagnostics.
  - Surface Repair Hotkeys
    Hotkeys, also known as keyboard shortcuts, execute surface repair operations using the keyboard instead of the user interface.
  - Pop Up Menu of the Surface Repair Tool Graphics Window
    The following pop-up menu items are available when you right-click a part or part surface in the Graphics window, while using the Surface Repair tool.
- 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.

Merging Vertices

When merging vertices, review and change the tolerance value, if necessary.

Set the value to a reasonable value based on the maximum distance that separates the vertices you want to merge, plus a small tolerance (say 1/10th to 1/5th of the measured value). If the tolerance is too high, inadvertent merging of neighboring vertices can occur, especially when choosing to merge based on the active model. The safest way to merge vertices is to select the required vertices, and use the Selected set only option in the merge options.

The following example is a part containing free edges, representing an unmerged portion of the surface:

Select the free edges by clicking the green box in the Diagnostics slide out.
Click (Select Attached Vertices) to select the vertices that are attached to the selected edges.

Alternatively, use the (Select Zone) tool to select the appropriate vertices.
Set the merge options:
1. Click the three dots next to the (Merge adjacent vertices/duplicatet faces) tool to display the options.
2. Enter the tolerance in the Merge Tolerance field.
  You can estimate the required tolerance value by measuring the distance between two vertices on either side of the gap.
3. Deactivate the Merge Duplicate Faces option.
4. Set Operate On to Selected Set Only.
Click (Merge adjacent vertices/duplicatet faces) to merge the selected vertices.

The display updates with the merged result.

The tool has uniformly merged the vertices on one surface with the vertices on the other surface, resulting in a clean merge line. The Output window shows a summary of the number of vertices merged.

If you set the tolerance too low, either no or partial merging would take place. However, any unmerged vertices would remain in the selected set allowing for further merging with a revised tolerance value.

The vertex merging scheme uses a lowest vertex number approach, which means it always merges the highest vertex number (slave vertex) to the lower number (master vertex) within the specified tolerance distance.