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.

The Dirichlet boundary condition for each dependent variable (for example, u2), has a corresponding check box (Prescribed values for 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 button () and select Advanced Physics Options. 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.