COMSOL 6.4 - Settings for the Layered Darcy’s Law Interface

The is the default physics interface name.

The is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the field. The first character must be a letter.

The default (for the first physics interface in the model) is ldl.

Here you select specific layers in a layered material on which the physics interface should be active. By default, the checkbox is selected. This means that all layers in all layered materials on the selected boundaries are used.

If you clear the checkbox, you can select individual layers within a single layered material. This means that the physics interface is restricted to the boundaries on which a specific layered material is defined.

	For a general description of layer selections, see The Shell Properties and Interface Selection Sections in the Structural Mechanics Module User’s Guide.

There are physics symbols available with some physics features to help you to graphically indicate boundary conditions, boundary normal orientation, loads, and other features. To display them select the checkbox under in the Settings window. You can click the button, which displays all symbols in that physics interface by selecting all checkboxes in the Settings windows for the physics features that include symbols. Similarly, the button clears all checkboxes in the individual physics features.

	For a more detailed description of Physics Symbols, see Physics Symbols in the COMSOL Multiphysics Reference Manual.

Enter a pref (SI unit: Pa). The default value is 1[atm].

Enter a value for the acceleration of gravity. The default value g_const is the predefined standard acceleration of gravity on Earth.

Note that by default there are no gravity effects added to the Layered Darcy’s Law interface. To activate the acceleration of gravity, add the feature node from the toolbar or right-click to select it from the context menu.

To display all settings available in this section, click the button (

) and select in the dialog.

You can choose the order of the shape functions used for the pressure variable solved by the Layered Darcy’s Law interface. The default shape functions are Lagrange.

The checkbox is not activated by default. When this option is selected, the solver computes variables storing accurate boundary fluxes from each boundary into the adjacent domain.

If the checkbox is cleared, the COMSOL Multiphysics software instead computes the flux variables from the dependent variables using extrapolation, which is less accurate in postprocessing results, but does not create extra dependent variables on the boundaries for the fluxes.

Also the checkbox is available if the previous checkbox is selected. The smoothing can provide a better behaved flux value close to singularities.

The setting should in most pure mass transport problems be set to , which is the default. It makes sure that the dependent variable does not get affected by small imaginary contributions, which can occur, for example, when combining a Time Dependent or Stationary study with a frequency-domain study.

The dependent variable (field variable) is the p. The name can be changed but the names of fields and dependent variables must be unique within a model.