• The auxiliary system's purpose is to allow explicit calculations using nonlinear variables.
  • These values can be used by kernels, BCs and material properties.
    • Just couple to them as if they were a nonlinear variable.
  • They will also come out in the output file. . . useful for viewing things you don't solve for (e.g. velocity).
  • Auxiliary variables currently come in two flavors:
    • Element (constant or higher order monomials)
    • Nodal (linear Lagrange)
  • When using element auxiliary variables:
    • You are computing average values per element (constant) or Cholesky solve.
    • You can couple to nonlinear variables and both element and nodal auxiliary variables.
  • When using nodal auxiliary variables:
    • You are computing values at nodes.
    • You can only couple to nonlinear variables and other nodal auxiliary variables.
  • Auxiliary variables have "old" states just like nonlinear variables.