When setting up your simulation, you can use selections to represent different parts of your geometry. This can be helpful in many instances, such as when you are specifying materials, applying boundary conditions, customizing the mesh, and more.
In COMSOL Multiphysics®, using Boolean and adjacent selections, you can create customized groups of geometric entities that update automatically when you change your model geometry. All of the following selection types use previously defined selections as input.
Boolean selections include:
Complement selections — create selections that are the inverse of one or more selections
Difference selections — create selections of entities that are in one selection, but not another
Union selections — combine two or more selections into a single one
Intersection selections — create selections of entities contained in all input selections
If you want to create selections of geometric entities that are touching other selections, use adjacent selections. You also have the option to select exterior or interior entities with this selection type.