where βh is the coefficient of hygroscopic swelling,
Mm is the molar mass,
cmo is the moisture concentration, and
cmo,ref is the strain-free reference concentration.
The Hygroscopic Swelling subnode is only available with some COMSOL products (see
http://www.comsol.com/products/specifications/).
From the Concentration c list, select an existing concentration variable from another physics interface, if any concentration variables exist. For
User defined enter a value or expression for the concentration. The unit for the input depends on the setting of
Concentration type in the
Hygroscopic Swelling Properties section. Only concentration variables having the chosen physical dimension are available in the
Concentration list.
In the Concentration type list, select
Molar concentration or
Mass concentration, depending on the units used for the concentration.
Enter a Strain reference concentration cref . This is the concentration at which there are no strains due to hygroscopic swelling.
If Molar concentration is selected as the
Concentration type, enter also the
Molar mass of the fluid,
Mm. The default value is 0.018 kg/mol, which is the molar mass of water.
The default Coefficient of hygroscopic swelling βh uses values
From material. For
User defined, select
Isotropic,
Diagonal, or
Symmetric from the list to enter one or more components for a general coefficient of hygroscopic swelling tensor
βh. The default value for the
User defined case is
1.5e-4 m
3/kg. When a nonisotropic coefficient of hygroscopic swelling is used, the axis orientations are given by the coordinate system selection in the parent node.
The Include moisture as added mass check box is selected by default. When selected, the mass of the fluid is included in a dynamic analysis, and when using mass proportional loads. It will also contribute when computing mass properties.
Physics tab with Linear Elastic Material,
Nonlinear Elastic Material, or
Hyperelastic Material node selected in the model tree:
