Setting up a 1D river simulation - the max/min/mean (.mmm) file

Processing of a large results file in order to calculate the maximum of a particular variable can take a long time as it searches through the results in their entirety. Therefore, in Flood Modeller, the maxima of all the main output variables, as well as the minima and mean value, are tracked and calculated during a simulation and output to a much smaller file (extension .mmm). This makes post-processing to obtain a maximum or minimum value a quick and easy process and provides a mechanism to calculate a mean value directly.

The mmm file contains, in binary format, the maximum, minimum and mean values at each node for stage and flow, and, where calculated, the Froude number, velocity and unit state. The results are then able to be processed quickly by the graphical processors in the Flood Modeller User Interface, and TabularCSV.

Outputting of the mmm file is on by default when running a simulation. You can disable the outputting of this file from the Options tab in the 1D Simulation window.

By default, the mmm calculations will occur from the start of the simulation until the end of the simulation. This time-band can be adjusted if required. This feature is particularly useful to restrict the time horizon for a particular tidal cycle, or to ignore the results from an initial run-in/warm-up period, for instance.

To specify mmm calculation times that differ from the start and end time of your simulation, check the box provided on the Times tab of the 1D Simulation window. Click in the Calculation start time and Calculation end time fields and enter the values required. These should be in hours from time zero of the simulation.

Please note, this means if your simulation Start Time is 8hrs and you want the mmm calculation to start 1 hour later, the Calculation start time should be set to 9hrs. This is the case regardless of whether you have specified a Time Zero in your simulation.

Using the mmm with TabularCSV

When selecting Maxima and Minima output in TabularCSV, the use max/min/mean file option will become available if the relevant mmm file is present. In this case, the mmm file will be selected by default.

Additional information about the mmm file

Unit mode is not output to the mmm file as the concept of a maximum, minimum or mean unit mode is of no specific relevance.

If a simulation fails, but is trapped gracefully, the mmm file will still be output (if selected). However, the user should be aware that the cause or effect of a failure may be an unrealistically large (positive or negative) value, which is then captured in the mmm output. On the other hand, this could be useful in diagnosing the location of the problem.

Note: The maxima, minima and mean are captured on a model timestep by timestep basis, as opposed to the traditional methods which use the full results (*.zzn) file and therefore only capture the values each output timestep. Thus there may be minor discrepancies between the different methods; the mmm file will therefore be the more accurate.

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