The Dirichlet Boundary Condition specifies a value of u on the boundary of the domain: u = r. By default, it is a unidirectional condition, applying reaction terms on u but not on any variables appearing in r. You can also add Dirichlet Boundary Condition nodes for edges in 3D components and for points in 2D and 3D components by right-clicking the main PDE interface node and choosing Constraint from the Edges and Points submenus.

The Dirichlet boundary condition for each dependent variable (for example, u2), has a corresponding check box (Prescribed value of u2), which is selected by default. Enter a value or expression for the prescribed value in the associated text field or clear the check box as needed. If cleared, no Dirichlet constraint is added for that dependent variable, and, for example, a flux condition on the same boundary then remains as the active boundary condition.

To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box. This section contains settings for specifying the type of constraint and whether to use a pointwise or weak constraint. See Constraint Settings for more information.