Selection Input
A Selection Input node () adds an extra selection of geometrical entities to the parent feature. Use such extra selections to show a selection in the graphics rendering or to select entities on different domains when coupling them to this feature, for example.
To add a Selection Input, first add a feature node or property node (for example, a Generic Feature, Domain Condition, or Device Model Feature), then right-click the feature node (in this example, Generic Feature, Domain Condition, or Device Model Feature) and select it from the Inputs submenu.
The Settings window of a selection input has the following sections:
Declaration
In the Declaration section you specify the name and a description of the selection input in the Input name and Description fields.
You also specify the entity level from the Geometric entity level list. The default is the same level as the parent feature. The choices Same as top level (Domain condition) and One level below top level (Boundary condition) are relative to the top level of the interface. If the top level of the interface is Domain, choosing One level below top level (Boundary Condition) means that the selection input applies to boundaries. If the top level is Boundary, choosing One level below top level (Boundary Condition), the selections are for lines (edges) in 3D and points in 2D. The choices Same as parent level and One level below parent level make the selections apply to entities of the same geometric entity level or one level below (boundaries, if the parent level is domains, for example), respectively.
Initially, the selection can be cleared or include all entities for the selected geometric entity level. Choose Cleared (the default) or All entities from the Initial selection list.
Restrictions
In the Allowed space dimensions list you can define what space dimensions this particular selection input can be used in. The option Same as parent (the default option) means that the selection input supports the same space dimensions as the parent feature or property. If you want to control the space dimensions manually, choose Customized from the list. You can then select the allowed space dimensions from a list of all space dimensions.
Selection Settings
Applicable Entities
It is possible to limit the types of entities where the selection can be active. For example, a boundary selection can be limited to only interior boundaries. All other selected boundaries then get marked as not applicable. For more complex situations, you can use conditions on domain types to decide if a specific boundary is applicable or not.
Select a form of Applicable entities from the list: From entity types (the default) or From sequence.
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If From entity types is selected, select one or more of the options available when you click the Add button () add them to the list of applicable entities. Exterior and Interior boundaries are selected by default. Use the buttons under the list to organize as needed.
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If From sequence is selected, select a Selection filter sequence: Locally defined (the default), From built-in quantities, or Imported from external resource. Select a sequence to link to from the Link list. Click the Add button () to display a quick menu where you can select a source to add in to the list and use it as the current reference. A Confirm Operation dialog box will appear and ask for confirmation if there is already a reference exist in the Link list. Click the Go to Source button to move to the referenced node in the Link list. I the sequence is Imported from external resource also select an Imported file.
For more details on entity types, see Selection Terminology.
Override Rule
Some features cannot exist on the same selection (for example a boundary), and COMSOL Multiphysics uses override rules to decide how the selection of one feature overrides another feature’s selection.
Select an Override rule: Built in (the default), Locally defined, Imported from external resource, or None.
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If Built in is selected there are four options in the Override type list: Exclusive, Contributing, Override features of same type, and Never overridden:
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Exclusive means that the feature should override all other features except those that are of the type Never overridden. An exclusive feature is overridden by other exclusive features.
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Contributing means that the feature should not override other features. The exception is for entity levels below the top entity level of the physics, where features of any type override the default features.
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Override features of same type means that the feature only overrides other features of the same feature type.
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Never overridden ensures that a feature is never overridden and does not override any other feature.
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If Locally defined is selected, also select a Link from the list. Click the Go to Source button as needed.
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If Imported from external resource is selected, select an Imported file from the list. Click the Go to Source button as needed. Then select a Link from the list.
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In None is selected, no override rule is used.
Override Type
The Override type list specifies if the feature is Exclusive or Contributing to other features. In the Model Builder, an exclusive feature (such as constraints and fixed values) replaces all previous feature instances for intersecting selections, whereas a contributing feature (such as loads and sources) adds to other contributing features sharing the same selection. You also select to only Override features of the same type or to let the feature be Never overridden.
GUI Options
In this section you can specify some options for the user interface.
To lock the selection so that it cannot be modified, select the Lock selection check box.
By default, the section is initially expanded. Select the Section is initially collapsed check box if it should be collapsed when first displaying the Settings window.
To hide the selection in the Settings window, select the Hide in GUI check box. Even if the selection is hidden from the Settings window, you can choose to still show the rendering of the selected entities in the user interface by selecting the Show rendering when hidden check box. You can hide the feature in different categories in the Category for hiding feature list, which has the options Always hidden, Advanced physics options, Technology preview, and Develop. Select Always hidden (the default) to hide it permanently, or select Advanced physics options to make it possible for users to show it by selecting Advanced Physics Options in the Show More Options dialog box.