Flow Lines

Flow lines are used to keep track of the total flow passing through a line.

Flow lines are read from shape files. 2D Solver will use the first attribute of the shape file as a label for the flow line hydrograph in result files. The first attribute in a flow line shape file should be of string type.

The following code snippet shows two flow line shape files being read in the model XML file.

<output_results>

<output output_id="" format="SMS9">

<variables>

Depth

ELevation

Flow

Velocity

Froude

</variables>

<frequency>300</frequency>

</output>

<flowline frequency="100">flow_lines\southern_area.shp</flowline>

<flowline>flow_lines\northern_area.shp</flowline>

<massfile frequency="10">Dam_ADI_MB.csv</massfile>

<check>true</check>

</output_results>

The frequency attribute is optional and dictates how often flow values will be written. If no frequency is specified, flows will be written at every time step. From version 4.0 onwards, the flow is calculated as an average of calculated flow values over all timesteps between two output steps, as opposed to a snapshot at the time of output.

As ASCII grid is written along with the other check files to allow the user to see which cells will be used to determine the flow crossing the flow line. The values of each cell in the check file indicate the positive direction of flow across the line as seen by 2D Solver. The values represent an angle, clockwise from east.

If, for example, a cell in the check file had the value of 90, then flow will be recorded in the y-direction only for that cell, with positive flow moving from north to south. If a cell in the check file had the value of 225, then flow will be recorded in the x and y directions for that cell, with positive flow moving from south-east to north-west.