Parent Command
>> OPTION
Subcommand

Description
This command allows TOUGH2 to reach steady state prior to or after a transient simulation.
This option can be used to calibrate against steadystate data (only or in combination with
transient data), or to reach an equilibrium as initial conditions for a subsequent transient simulation.
Note that a transient TOUGH2 simulation must be performed to reach steady state which is
usually indicated by one of the following convergence failures:
 too many time steps converged on a single NewtonRaphson iteration (see command
 convergence failure followed by two time steps converging on a single Newton Raphson iteration;
 too many time step reductions (see command
 maximum number of time steps reached (TOUGH2 variable MCYC);
 maximum simulation time reached (TOUGH2 variable TIMAX);
 maximum time step size reached (use a colon on the command line followed by
max_time_step to select a maximum time step size. The time_step must be
smaller than TOUGH2 variable DELTMX)
minimum time step size reached (use a colon on the command line followed by a negative time_step to select a minimum time step size, suggesting convergence problems that are assumed to indicate steadystate conditions are reached).
iTOUGH2 usually stops if a TOUGH2 run terminates due to one of the above mentioned
convergence failures (see command
The second application of the steadystate option is the following.
If a steadystate regime is to precede a transient regime within a single simulation
(e.g., to assure initial conditions are at equilibrium, a state that depends on the parameters to be
estimated), a negative starting time tINF (TOUGH2 variable TSTART) must be specified. Ensure that tINF is
larger than the duration required to reach steady state, e.g., tINF = 1.0E20. The TOUGH2
simulation proceeds until a convergence failure occurs at an unknown point in time tCF creating the steadystate regime.
The primary variables at that point are written to file SAVE to be used as initial conditions for the
subsequent TOUGH2 run (only if keyword SAVE is present). The simulation time is then set to zero, and
the transient regime of the simulation is initiated. This requires that boundary
conditions are changed at time zero, e.g., by starting injection or withdrawal, or by changing
Dirichlettype boundary conditions (see command
Example
> OBSERVATION
>> steadystate point in TIME: 1 (= t_inf)
1.0E20
>> PRESSURE
>>> ELEMENT: FDF76
>>>> DATA
1.0E20 1.354E5
>>>> DEVIATION: 0.05E5
<<<<
<<<
<<
> COMPUTATION
>> OPTION
>>> allow STEADYSTATE, use SAVE file for restart
<<<
>> CONVERGEnce criteria
>>> Presume steadystate if : 5 CONSECUTIVE time steps converge on ITER=1
>>> number of ITERATIONS: 5
<<<
<<
<
See Also