Discontinuity printout

Discontinuity printout Simulation results are sampled at a constant rate. The rate is defined by the “print interval” in the Run Parameter settings. It is quite rare that a discontinuity point occurs at the same time as a predefined print point. As discontinuity points represent particular and interesting events, it can be useful to record these specific points. This is the role of the “discontinuity printout” option.

Note

The discontinuity printout option does not change the behavior of the simulation. Users often think that disabling the discontinuity printout will disable the whole discontinuity handling mechanism, which is wrong. Simcenter Amesim standard solver always handles discontinuities.

The discontinuity printout simply orders the simulation to record discontinuity points in the results file. For each discontinuity, 2 supplementary points are recorded in the results file: the first point “just before” the discontinuity corresponds to the end of simulation using current equations. The second point “just after” the discontinuity corresponds to the solver restart using up to date submodel equations.

On rare occasions, a discontinuity point can occur at the same time as a normal print point. In this case, the results file will contain 3 values corresponding to the same time (2 points corresponding to discontinuity records, and one normal print point).

The discontinuity printout option is available in the “Standard Options” tab of the Run Parameters settings.

Figure 7: discontinuities printout option

When the discontinuity printout option is enabled, the Simulation Log of the Run Monitor pane displays one message for each discontinuity. This message indicates the name of the submodel source of discontinuity and the precise time at which discontinuity appeared.

If 2 or more submodels register a discontinuity exactly at the same time, only one message will be displayed, containing the name of one of these submodels. This does not mean that other submodels have been ignored. Showing a single message helps keeping the log window lighter.

Figure 8: discontinuity messages

Selecting the discontinuity printout is necessary to visualize steps in signals. This is especially true in case of sampled signal as in the following example.

Figure 9: sampler curve with and without discontinuity printout

This example of discrete signal is generated by a simple sampler ZOH00 (sampling period = 0.7s, print interval = 0.1s). The default results (bottom plot) are poor because the sampling events are not precisely recorded. The blue curve on the top plot looks more precise since each change of sampling interval produces 2 points: one point just before the sample change, one point just after.