2D Simulations - Switching Between SI and American Units
    • 29 Jul 2022
    • 2 Minutes to read
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    2D Simulations - Switching Between SI and American Units

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    Article Summary

    Along the bottom of the General tab (and all tabs within the 2D simulation tool) is an option for the number of threads to use in the run, alongside Run, Save and Close buttons. The unit system is also shown below these.

    The default number of Threads to use in run will be “Max”. This will use the maximum number of available threads (thus maximising the efficiency and decreasing the run time). The drop-down box allows selection of fewer threads per run as desired.

    The Run button is used to run the 2D simulation. When clicked, the tool will initially validate the XML to ensure all parameters and settings are available for the model to run. If any part of the simulation is not set up properly, a prompt box will appear and the model will not run.

    The Save button saves the 2D simulation. When clicked, this will also validate the XML: checking the setup is correct and all paths are valid. Again, a prompt box will appear if any settings are incorrect. This allows any changes to be made prior to saving the model.

    The Close button closes out of the tool window. You will be prompted to save if any unsaved changes remain.

    By clicking with the right-hand side mouse button in the bottom corner where Unit System is displayed, the following menu can be brought up:

    2DSimulationsimagesusunits.png

    This allows you to switch unit system (between SI and American custom units), to validate the XML prior to running/saving your model (although the Run and Save options perform this validation anyway) and to adjust between relative and absolute file paths as desired.

    Unit settings for boundaries within 2D models

    Boundary data for your 2D models can be set either in the Boundary conditions tab or the Rainfall/Infiltration tab (hydrological inputs only) within the 2D simulation window. Depending on the type of boundary selected the handling of unit settings is slightly different, as described below:

    Boundary Type

    Unit Setting

    Flow or depth boundary using time series csv file, user-entered time series or single constant value

    Entered values have no units specified and will be assumed as default units for the specified setting got the 2D model, i.e. as set in the lower right corner of the 2D simulation window:

    Flows in m3/s or ft3/s

    Depths in m or ft

    Flow boundary using 1D hydrological unit (i.e. rainfall-runoff calculation)

    1D unit will adopt 2D model units setting as described above.

    Rainfall/infiltration boundary using time series csv file or user-entered time series

    A new boundary will initially adopt the units specified for the 2D model, i.e. as set in the lower right corner of the 2D simulation window. However, you can change units for individual boundaries by selecting from the dropdown lists provided. Rainfall and time units can be changed. Options are:

    • mm, in, mm/hr, m/s or in/hr for rainfall depths

    • seconds, minutes, hours or days for times

    Rainfall/infiltration boundary using 1D hydrological unit

    1D unit will adopt 2D model units setting, i.e. as set in the lower right corner of the 2D simulation window (as described above).

    1D linked model (linking to the 1D river or 1D urban solvers)

    Default values for weir discharge coefficient and modular limit will vary depending upon units setting. These parameters are not dimensionless and so are affected by units setting (they include gravity constant, g).


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