TIME

Specifies the initial and final simulation time and the time step sizes. Some examples are given below. An example using DATE to define initial and finale times, and a constant maximum time step size is as follows:

TIME
  START_DATE 1 JAN 2005
  FINAL_DATE 31 DEC 2500
  INITIAL_TIMESTEP_SIZE 0.001 d
  MAXIMUM_TIMESTEP_SIZE 50 d
END

An example using a relative time given in days to specify the final time, and a varying maximum time step size is as follows:

TIME
  FINAL_TIME 7300 d
  INITIAL_TIMESTEP_SIZE 1.0d-3 d
  MAXIMUM_TIMESTEP_SIZE 0.5 d at 0 d
  MAXIMUM_TIMESTEP_SIZE 50 d at 20 d
END

In this last example, the start date is defaulted to 1 JAN 2000 for output purposes.

Only the FINAL_TIME keyword is compulsory; however specifying the initial and the maximum time steps, which depend on the problem being model, is advised. Mainly when in presence of strong transient phenomena in the first part of the simulation.

The maximum allowed time step can be varied during the simulation, specifying the new maximum time step and from when it has to start. An example of such instruction is:

MAXIMUM_TIMESTEP_SIZE 50 d at 20 d

This allows a maximum time step of 50 days once the simulation has advanced to 20 days since the start.

DATE can also be used to specify a new maximum time step size, example below:

TIME
  START_DATE 1 JAN 2005
  FINAL_DATE 31 DEC 2500
  INITIAL_TIMESTEP_SIZE 0.001 d
  MAXIMUM_TIMESTEP_SIZE 50 d
  MAXIMUM_TIMESTEP_SIZE 100 d DATE 1 JAN 2030
  MAXIMUM_TIMESTEP_SIZE 250 d DATE 1 JAN 2150
END

The keyword DATE, added after the new maximum time step size, expects a calendar date. Internally the code will account for leap years.

WSTEP

This sets the maximum timestep after there is a change in target for any well or well group. Example:

TIME
  START_DATE 1 JAN 2005
  FINAL_DATE 31 DEC 2500
  INITIAL_TIMESTEP_SIZE 0.001 d
  MAXIMUM_TIMESTEP_SIZE 50 d
  WSTEP 1 d
END

In this case the maximum timestep is one day after a change in well targets.