Physical Quantity
Add a Physical Quantity node () to a Physics Builder file to define variable declarations and definitions of material properties. These are in addition to the predefined physical quantities available.
To add an Physical Quantity node:
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On the Home toolbar, click Physical Quantity (), or
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Right-click the Auxiliary Definitions node () and select it from the context menu.
To use this customized physical quantity when defining a Variable Declaration, Dependent Variable Definition, Dependent Variable Declaration, Material Property (Auxiliary Definitions), or Material Property node (or any node with the Physical quantity list), select Locally defined from the Physical quantity list (the top item in the list), and then select the added physical quantity from the Link list.
The Settings window has the following sections:
Physical Quantity
Enter a Name for the physical quantity (seebeck_coefficient, for example). Enter a Variable name to be used to define a common model input variable. The variable name can be the same as the name.
Enter a Description for the physical quantity (Seebeck coefficient, for example).
Enter a symbol for the property in the Symbol (LaTeX encoded) field (S, for example). You can use LaTeX syntax for Greek letters, subscripts, superscripts, and mathematical symbols if desired. See Mathematical Symbols and Special Characters in the COMSOL Multiphysics Reference Manual.
Define the dimension of the physical quantity by typing the corresponding SI unit (V/K, for example).
From the Category list, choose the category. The default category is General.
The Dimension list determines the dimension of the physical quantity: Use the default value, Scalar, for a scalar quantity or select Vector (3x1) for a vector-valued quantity, Matrix (3x3) for a tensor quantity, or Custom to type a dimension in the NxM format.
In the Default value field (or fields, depending on the selection in the Dimension list above), enter a default value for this quantity.
Preferences
To specify that the physical quantity also is a material property, select the Is material property check box.
To specify that the physical quantity can be used as a common model input, select the Is model input property check box. This setting requires that the variable name is not empty and that it has not been used by the other physical quantities.