Initial Conditions
  • 23 Aug 2022
  • 3 Minutes to read
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Initial Conditions

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Initial conditions are specified in the CONCENTRATION INITIAL CONDITIONS section which must be the last data block in the datafile.

Initial conditions are required at each node for all for the water quality variables being simulated by 1D Water Quality Solver.  The easiest means of setting up the initial conditions is to use WQGENERAL editor (from the Network Property window) to set default values (Figure 6). However it is possible to use values from a previous run of 1D Water Quality Solver (a warm start).

If possible the initial conditions should be based on observed concentrations of the water quality variables. This should reduce the length of time it takes for the model to reach dynamic equilibrium, particularly in the case of salinity and the bed sediment variables. The concentrations of the variables should vary smoothly along river reaches and where possible some account should be taken of changes in concentration due to pollutant loadings at sources. If these precautions are taken, the establishment of dynamic equilibrium in the model will be accelerated.

To extract initial conditions from a previous simulation of 1D Water Quality Solver you will need to understand the format of the ASCII 'filename.con' file. First use TabularCSV output (Accessing and Viewing Results) and select the option to extract information at all nodes for a selected timestep (Figure 1 - Figure 2).

Figure 1. Node Selection tab, TabularCSV tool

Figure 2. Timestep Selection for initial conditions extraction, TabularCSV.

TabularCSV will produce a file with extension 'iic' which will look like in Figure 3.

Figure 3. TabularCSV initial conditions output file 'filename.iic'.

Next use a text editor to replace the initial conditions in the bottom of the 'filename.con' file with the results from the tabular output processor (section within the red area in Figure 22). You should check when using extracted results in this manner that they match up with the boundary conditions which have been specified in the boundary section of the 1D Water Quality datafile. The use of a warm start enables the model to start up smoothly without the need for an initial settling down period.

An example of the structure of the initial conditions section of the datafile is shown in Figure 4.

Figure 4. Example of the initial conditions Data section of the 1D Water Quality datafile.

Datafile Format (initial data block)

Line 1                                       CONCENTRATION INITIAL CONDITIONS

Line 2                                       ndat (i10)

Line 3 to Line 2+ndat              sorpol (a)

Line 4 to Line 2+ndat              label, conold (1 to 'ndat')

Where:

CONCENTRATION INITIAL CONDITIONS = keywords

ndat (i10) = Number of water quality variables specified in initial conditions.

sorpol (a) = Variable names of water quality variables listed in the same order as they are specified in the following initial conditions block (Line 4a etc). This line is repeated 'ndat' times.

label = Node label. The node labels must be specified in the same order as they are specified in Flood Modeller 1D Solver 'dat' file

conold = Initial concentration of different water quality variables. If more than 7 water quality variables are being set in the initial conditions, the line is repeated until the correct number of variables has been set (Figure 5).

Figure 5. Example of the initial conditions Data section for more than 7 variables.

The initial conditions module checks that all of the water quality variables that are being simulated are specified as initial conditions. If the user has extracted 'warm start' conditions from a previous 1D Water Quality simulation which used more water quality variables than are needed for the current run, 1D Water Quality Solver will ignore this redundant information.


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