An equation is a structuring object which aggregates operators into a scalar partial differential equation. Equations are used both for operators applied to the interior of a structure as well as for the aggregation of operators applied to a boundary or interface to enforce a boundary contition.
equation -name equationName -solvesFor fieldName
-operators operatorList [ -parabolic ]
The name of the equation is for debugging purposes. Any string may be used.
The fieldName being solved for specifies to which field nonlinear updates are applied. For parabolic systems of differential equations, this should be the field in the time derivative term.
Parabolic indicates that the PDE is of the form
where C is the fieldName being solved for. All equations in a region should either be parabolic or not. Instantaneous flux constraints, such as the segregation operator are not parabolic.