Command Qualifier

Some commands require a qualifier. The qualifier is used to distinguish one use of the command from another.

For example, two different material models are distinguished by their qualifiers:
MATERIAL_MODEL( "air" ) {
density_model = "air at standard atmosphere"
viscosity_model = "air"
}
MATERIAL_MODEL( "aluminum" ) {
density_model = "aluminum"
conductivity_model = "aluminum"
}
The specification of the qualifier is mandatory for commands that accommodate it and is an error for those commands that do not accommodate one. There are two types of qualifiers: user-given name and enumerated. The user-given name qualifier is any user-specified name, as in the above MATERIAL_MODEL examples. The user-given name of a command may be referenced by another command. For example:
ELEMENT_SET( "channel" ) {
material_model = "air"
}
The enumerated type is for selecting a specific value from a predefined set of options. For example, consider:
NODAL_INITIAL_CONDITION( velocity ) {
default_values = { 1, 0, 0 }
}
and
NODAL_INITIAL_CONDITION( pressure ) {
default_value = 0
}

In the first command, the initial conditions are applied to velocity and in the second command they are applied to pressure. NODAL_INITIAL_CONDITION is currently the only command that uses the enumerated type of qualifier.