In COMSOL, parameters are constants, which don't change with results or other variables. Their values are directly assigned by the user. For example, the diameters of a piezoelectric device are parameters. In contrast, variables are defined as a function, which may be different with time, position and/or results.
All definitions are accomplished within Global Definitions node.
Note that the Expressions of some variables will be yellow when input, and show "Unknown variable lambda" when the cursor is placed on those Expressions. Please ignore them, because they will not influence anything.
Note that Expressions include lambda should not be in any Constraints.
There are two methods of including definitions:
Please build a new node for each list of definition, then copy and paste all terms and their expressions. Note that some nodes are Parameters and some nodes are Variables.
Global Variables - Acoustic Field
Global Variables - Internal & External Electromagnetic Fields
Global Variables - Absorbing Boundary Condition
When define a new Parameters or Variables node, the corresponding list of terms can be imported using the following files.
How: Right-click the Global Definitions node and define a Parameters/Variables node. Select Label: in the setting area then input the name of the list. There is a “Load from File” icon below the empty list. Left-click this icon and choose the corresponding “.txt” file.