COMSOL Multiphysics™

femnlin
components fixed, the augmentation components are assumed to fulfill a linear
equation. The property Augtol control the tolerance for the augmentation
components and the property Ntol the tolerance for the main components in the
convergence criteria for the combined iteration (two substeps each). The
convergence criteria is that the relative increment, from one iteration to the next,
for the augmented components and the main components must not be larger than
their tolerances. The maximum number of combined iterations is controlled by the
property Augmaxiter. The linear system solver used for the solution of the
augmentation components can be controlled by the property Augsolver. For a
more detailed description of this solution procedure, see the “Nonlinear Solver
Settings” on page 381 in the User’s guide.
Setting Hnlin to on causes the solver to treat the problem as being highly nonlinear.
This option can be tried if there is no convergence with Hnlin set to off.
Depending on this parameter, certain standard values are selected for the Initstep
and Minstep properties. Moreover, certain internal control structures are adapted.
Especially, the error control is biased from a more absolute norm towards a relative
norm. So this parameter is also useful if a solution with components of highly
varying orders of magnitudes are present. In the context of parameter stepping, you
can also try this option if the step sizes in the parameter seem to be too small.
Initstep is the initial damping factor for the step length. The default is 1 if Hnlin
is off and 1e-4 if Hnlin is on.
Maxiter and Minstep are safeguards against infinite Newton iterations. They
bound the number of iterations and the damping factor used in each iteration.
Minstep defaults to 1e-4 if Hnlin is off and 1e-8 if Hnlin is on.
The tolerance Ntol gives the criterion for convergence, see “Nonlinear Solver
Settings” on page 381 in User’s Guide.
The property Out explicitly sets output variables and their order. The output
variable fem means the FEM structure with the solution object fem.sol added. The
solution object sol has a field sol.u, which is the solution vector for the FEM
formulation of the PDE problem. The solution vector u is a column vector with one
component for each degree of freedom of the discretized problem. If the parameter
variation feature is used, then sol.u is a matrix, and there are additional fields
sol.pname and sol.plist. The field sol.pname is the name of the parameter, and
sol.plist is a row vector with parameter values for which a solution was
computed. The corresponding solution vectors are stored as columns in the matrix
sol.u. The output variable Stop is 0 if a complete solution was returned, 1 if a
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