stea

    The macro stea is used to manage steady state simulations and is available with all physics modules in FEHM. The macro directs FEHM to monitor changes in variables from timestep to timestep and stop the steady state run when the changes are less than some prescribed tolerance. Alternatively the steady state run is directed to finish when the global “in” and “out” fluxes are less than a prescribed tolerance or the simulated time exceeds the input value.

    After the steady state portion of the simulation is completed, a transient run may be performed. This is accomplished with the boun macro and the key word tran. See the description of the boun macro for details.

    The user should be aware that when the stea macro is used, the parameters associated with the time macro pertain to the transient portion of the simulation if a transient part exists. Values for these parameters may be input using a keyword but if not entered will default to the values specified for the time macro.

    • Group 1 - KEYWORD, VALUE
    Input Variable Format Description
    KEYWORD character
    The following keywords are used with steady to specify the variables to be checked for steady state:
    shea - Head (m)
    spre - Pressure (MPa)
    stem - Temperature (oC)
    ssat - Saturation
    sair - Partial pressure of air/gas (MPa)
    sflu - Mass flux (kg/s)
    sent - Enthalpy (MJ/s)
    stim - Maximum time for steady state simulation (days)
    sday - Initial time step size for steady state simulation (days)
    smul - Time step multiplication factorsmst - Minimum number of time steps to be used for steady state simulation
    snst - Maximum number of time steps to be used for steady state simulation
    shtl - Option to reduce the head_tol factor as the solution approaches steady-state
    stmc - Option to reduce the machine tolerancs factor (tmch) factor as the solution approaches steady-state
    sacc - Maximum change allowed in the accumulation term when flux is being checked
    sper - The tolerance is interpreted as a fractional change in the variable being checked [i.e., (new_value - old_value)/old_value]. Without this keyword it is an absolute change in the variable value.
    endstea - Signifies end of keyword input, a blank line will also work.
    VALUE real Variable tolerance or time control parameter value.

    In the following example a steady state solution is specified. The tolerance for head is specified to be 0.1 m and for flux 0.00001kg/s. The steady state solution will be allowed to run for a maximum of 1.e12 days and the time step multiplier is set to 2.

    stea  
    shead 1.d-1
    stime 1.e12
    smult
    sflux 1.d-5
    end  

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