NEWTON_SOLVER FLOW

Specifies nonlinear solver parameters associated with the simulation. An example is as follows:

NEWTON_SOLVER FLOW
  ATOL 1D-8
  RTOL 1D-8
  STOL 1D-30
END

An example showing all possible options is:

NEWTON_SOLVER FLOW
  NO_INFINITY_NORM
  NO_FORCE_ITERATION
  NO_PRINT_CONVERGENCE
  PRINT_DETAILED_CONVERGENCE
  ATOL 1D-8
  RTOL 1D-8
  STOL 1D-30
  ITOL 1D-6
  ITOL_S 1D-6
  ITOL_UPDATE 1D-6
  MAXIT 10
  MAXF 50
  MATRIX_TYPE AIJ
  PRECONDITIONER_MATRIX_TYPE AIJ
END

The variables in the keywords above have the following meanings:

NEWTON_SOLVER Type

Can be FLOW or TRANSPORT. For TOIL_IMS, GAS_WATER, BLACK_OIL, TODD_LONGSTAFF and SOLVENT_TL, this must be FLOW.

NO_INFINITY_NORM

If included, toggles off calculation of infinity norm on residual and update vectors. The default is to calculate infinity norm.

NO_FORCE_ITERATION

If included toggles off the forcing of at least 1 linear iteration. The default is to force at least 1 linear iteration.

NO_PRINT_CONVERGENCE

If included, prints convergence information.

ATOL

Absolute tolerance. Absolute size of 2-norm of residual.

RTOL

Relative tolerance. Relative decrease in size of 2-norm of residual.

STOL

Relative update tolerance. Relative decrease in size of 2-norm of solution

Note: STOL needs to be treated with great caution, as it simply accepts the step when then solution updates fall below the specified criteria, and this may allow badly unconverged steps to be accepted. It is recommended that STOL be set very low (e.g. 1.0D-30, as in the examples above) so that this cannot happen

ITOL

Infinity tolerance. Size of infinity norm of residual.

ITOL_S

Infinity tolerance. Size of infinity norm of scaled residual.

ITOL_UPDATE

Infinity tolerance. Size of infinity norm of update

MAXIT

Maximum number of Newton iterations before reporting failed convergence.

MAXF

Maximum number of function evaluations before reporting failed convergence.

MATRIX_TYPE

Format of main solver matrix. PETSc Mat (i.e. AIJ, BAIJ, or HYPRESTRUCT).

PRECONDITIONER_MATRIX_TYPE

Format of preconditioning matrix. Default is same as solver.