$\newcommand{\Dev}{\operatorname{Dev}}$ $\newcommand{\dev}{\operatorname{dev}}$ $\newcommand{\grad}{\operatorname{grad}}$ $\newcommand{\divg}{\operatorname{div}}$ $\newcommand{\Ei}{\operatorname{Ei}}$ $\newcommand{\tr}{\operatorname{tr}}$

Nodal degrees of freedom (dof) can be prescribed using the prescribe boundary condition. This element has two required attributes: the type is set to “prescribe” and the node set to which this boundary condition applies is defined vua node_set. The optional name attribute can be used to give the boundary condition a name. The value is defined via the scale parameter. (If omitted the default value is 1.0). The degree of freedom is defined via the dof parameter. A loadcurve can be associated with the scale parameter. The relative parameter defines wheter the values are absolute or relative to the current displacement.

<bc type="prescribe" node_set="nodeset1">
  <dof>x</dof>
  <scale lc="1">2.0</scale>
  <relative>0</relative>
</bc>

Here, nodeset1 is the name of a node set defined in the Mesh section. See Section 3.6.3↑ for more information on how to define node sets. Node sets can also be defined via surfaces or element sets. To define a node set via a surface, use the following syntax.

node_set="@surface:surface1"

Here, surface1 is a surface defined in the Mesh section. Similarly, defining a node set via an element set is done using @elem_set:.

For solutes, replace “$n$ ” with the solute id from the global solute table (Section 3.4.2↑); for example, “c2”.

<Boundary>
  <bc type="prescribe" node_set="set1">
    <dof>x</dof>
    <scale lc="1">2.0</scale>
    <relative>0</relative>
  </bc>
</Boundary>
<MeshData>
  <mesh_data param="fem.bc_prescribed[0]">
    <node lid="1">1.0</node>
    <node lid="2">2.0</node>
    <node lid="3">3.0</node>
  </mesh_data>
</MeshData>

Keep in mind that the scale parameter of the prescribed bc will scale the values defined in the mesh data section.