Manual Page for Command >>> CONSECUTIVE
>>> CONSECUTIVE: max_iter1
By default, TOUGH2 simulations are stopped if 10 consecutive time steps
converge with a single Newton-Raphson iteration because no update of primary
variables occurs. This command allows changing the maximum number of
allowable time steps with ITER=1 to max_iter1.
Consecutive time steps with no update of primary variable occur if:
(1) steady-state is reached;
(2) calibration or printout times are too narrowly spaced;
(3) the maximum time step size (TOUGH2 variable DELTMX) is too small;
(4) the initial time step (TOUGH2 variable DELTEN or DLT(1)) is too small;
(5) a small time step is taken to land on a calibration or printout time.
Only (1) is an acceptable TOUGH2 convergence (see command >>> STEADY-STATE).
All the other reasons may lead to premature termination of a TOUGH2 simulation.
Convergence problems are more often encountered in iTOUGH2 than in a standard
TOUGH2 simulation because many parameter combinations are submitted.
This command makes TOUGH2 more tolerant of this kind of convergence
failure. It is important, however, that max_iter1 is only increased to
overcome temporary convergence problems during the optimization, i.e., the
final parameter set should yield a TOUGH2 simulation without convergence
problems. Calibration points should not be spaced too narrowly in time
(see command >> TIME). Command >>> ADJUST can be used to overcome
problem (4). Note that a special time stepping procedure is incorporated
in iTOUGH2 to avoid problem (5).
>>> accept : 20 CONSECUTIVE time steps that converge on ITER=1
>> TIME |
>>> ADJUST |
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Page updated: July 29, 1997