Transient input files out66 and null


At the end of each simulation, SITRA produces an ASCII file called out66. The first line of the file contains several parameters of the transient calculation. For steady state, they are equal to zero. Additionally, the file contains the last computed potential heads or rather pressure head and the last computed concentrations/temperatures (as long as a transport calculation was performed). This lean (or short) version of the out66-file is automatically generated after each calculation with SITRA. If the user decides to continue the transient calculation and selects in the dialog box “Save for continuing (out66)”), he will get the complete file out66. This file contains all the data required to continue the calculation.

To continue the transient calculation, the user must rename the file out66 into null.

If a file named null exists in the corresponding directory, you have several possibilities for using it:

The potential/pressure heads and concentrations of the null-file can represent the initial values of an iteration (saturated/unsaturated or density dependent flow). Second, they can be used as initial potential heads or rather initial concentrations for a transient calculation. Both procedures require only the short version of the file out66 which has been moved to null.

The continuation of the transient calculation using the data from null (warm start) requires the complete version of the file out66 (renamed into null). In that case the time steps are calculated as follows:

The previous calculation stopped at time step nmax. The parameter nmax is the second last parameter of the first line of the file null. The calculation is continued with time steps nmax+1, nmax+2, ... The transient time steps of the new calculation start with the results of the most recent of the previous time steps.

To continue the transient calculation with another transient input file the parameter nmax (in the first line of the null file) is changed to "-1". Then a new transient input file should be used for the continuation of the transient calculation. The starting time (0.0) of the new calculation is then the last calculated time step of the former calculation, with which the warm start data were generated. The transient time steps of the new calculation start at 0.0. This procedure has the advantage that the data already calculated in former time steps is not carried along in the transient input file

 

 

File with hydrograph data