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. You can also use a named selection to create a certain parts of the geometry that you want to hide from the view (see Hide for Physics).

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.

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