Named Selections

Introduction

This section details how to create named selections to reuse throughout the model component when assigning material properties, boundary conditions, and other model settings.

You can create selection nodes under the Component node’s Definitions node to represent various parts of the geometry and simplify the process of assigning materials, model equations, boundary conditions, and other model properties. These user-defined selections can be reused during modeling and named using descriptive titles — for example, Tube, Wall, or Fluid. Changes to the selection (for example, by adding or removing a boundary) updates all nodes in the Component that use that particular selection.

Use the buttons listed in Table 6-2 to create, copy, and paste selections. When there is the possibility of overlapping geometric entities, it is recommended that you use The Selection List Window to ensure the correct part of the geometry is selected.

There are different types of selections: Explicit selections, selections by enclosing part of the geometry by a bounding Ball, Box, or Cylinder, Boolean selections (Union, Intersection, Difference, and Complement), and selections of Adjacent geometric entities. To add selection nodes, right-click a Definitions node and choose from the Selections options as listed in Table 6-6.

You can also right-click the Geometry node and choose from Selections options similar to those in Table 6-6 for defining selections based on the geometry objects in the geometry sequence. See Creating Named Selections in the Geometry Sequence.

Open an Example Model with Defined Explicit Selections

Figure 6-13 uses a COMSOL Multiphysics Applications Libraries example, which includes several user-defined selections.

1	Open The Application Libraries Window.

2	Navigate to the COMSOL Multiphysics>Structural Mechanics>mast_diagonal_mounting model file. Double-click to open it.

3	Expand the Definitions node under Component 1. Several nodes display in the Model Builder. Click the nodes shown in Figure 6-13 to examine the list of geometric entities displayed in the Settings window for Explicit.

In the selection Settings windows, also click the Zoom to Selection () button to zoom in on the selected geometric entities.

Figure 6-13: An example of an Explicit selection window for the Mount, mid level node. The Selection nodes under Definitions are renamed by the user.

The Types of Named Selections

Table 6-6: Named Selections by Type

Icon	Type	Description
	Adjacent	Use the Adjacent node to create the selection as the adjacent geometric entities (boundaries, for example) to one of more selections.
	Ball	Use the Ball node to create the selection by enclosing part of the geometry by a bounding ball (sphere) to select geometric entities that are partially or completely inside the ball.
	Box	Use the Box node to create the selection by enclosing part of the geometry by a bounding box to select geometric entities that are partially or completely inside the box.
	Cylinder	Use the Cylinder node to create the selection by enclosing part of the geometry by a bounding cylinder to select geometric entities that are partially or completely inside the cylinder.
	Explicit	Use an Explicit node to create the selection using the normal selection tools for individual geometric entities (boundaries, for example) on the geometric entity level chosen.
Union, Intersection, Difference, and Complement
	Union	Use the Union node to create the selection as the union (addition) of two or more selections.
	Intersection	Use the Intersection node to create the selection as the intersection of two or more selections.
	Difference	Use the Difference node to create the selection as the difference between a set of one or more selections and another set of one or more selections.
	Complement	Use the Complement node to create the selection as the complement (inverse) of one or more selections.

• Grouping Nodes by Space Dimension and Type • Creating Named Selections in the Geometry Sequence • Working with Geometric Entities