Merging Vertices by Collapsing Edges

This example of virtual geometry operations illustrates how you can use the Collapse Edges operation (or the Merge Vertices operation) to prepare the geometry for efficient meshing.

Geometry 1

1	Add a 3D Component, either when Creating a New Model or adding The Component Node.

2	On the Home toolbar click Import ().

3	On the Settings window for Import under the Import section, click Browse.

4	In the COMSOL installation directory navigate to the folder applications/COMSOL_Multiphysics/Tutorials and double-click virtualgeom_demo_2.mphbin.

The location of the file varies based on the installation. For example, if the installation is on your hard drive, the file path might be similar to C:\Program Files\COMSOL\COMSOL52a\Multiphysics\applications (in Windows).

5	Click Import.

The imported geometry displays in the Graphics window.

Geometry 1

In the Model Builder click Mesh 1. On the Settings window, click Build All ().

The resulting mesh displays in the Graphics window.

The figure shows that the mesh is very fine in the region marked by the red box. To zoom into this region, click the Geometry 1 node in the Model Builder. In the Graphics window, click the Zoom In button () and zoom into this region. You then can see the reason for the fine mesh. There is a very short edge at the junction of the four curved faces.

Remove this short edge by collapsing it into a vertex.

Collapse Edges 1

1	On the Geometry toolbar, from the Virtual Operations menu, select Collapse Edges ().

2	Select Edge 4.

3	Click the Build Selected button ().

You can also remove this short edge with an Ignore Edges operation forming a composite face of the two adjacent faces. However, then the small distance between the vertices of the ignored edge remains.

Mesh 1

In the Model Builder click Mesh 1. On the Settings window, click Build All (). The mesh displays in the Graphics window. Click the Go to View button () on the Graphics window.

You can achieve the same virtual geometry using a Merge Vertices operation.

Geometry 1

Right-click Collapse Edges 1 and choose Disable ().

Merge Vertices 1

1	On the Geometry toolbar, from the Virtual Operations menu, select Merge Vertices ().

2	Select Point 2.

3	Go to the Settings window for Merge Vertices. Locate the Vertex to Remove section and select Point 3.

4	Click the Build Selected button ().

Mesh 1

In the Model Builder click Mesh 1. On the Settings window, click Build All ().