The system parameters are accessed in the Network Panel window by editing the General item. These parameters have default values, some of which should only be altered after advice from expert users.
General Information
| Parameter | Description | |
|---|---|---|
Title | Optional model title of up to 40 characters. If more than 40 characters are used then only the first 40 will be transferred to tabular and graphical results | n/a |
Node Count | Number of nodes in the model. This is automatically generated by the program and cannot be overwritten | n/a |
File name | Name of the ASCII data file for the model. This cannot be overwritten - to change the name of the file, use File | Save As from the main menu | n/a |
Roughness file name | (Optional) Enter the name of the Roughness Advisor (*.rad) file here if using CES River sections, or the roughness factors (*.rff) file if using these. Use the check box if the file name is specified as an absolute path, e.g. c:\..., else leave unchecked if spwecified relative to the model folder. |
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Units
Use this to select the units of measurement for the current model: SI (Metric) or US. If left as DEFAULT, the global Flood Modeller default units will be used, as chosen when you first launched Flood Modeller, or accessed via Home > 1D Options > General
Froude Numbers for Supercritical Flow
| Parameter | Description | |
|---|---|---|
Lower | Value of Froude number below which there is no simplification of the St Venant momentum equation | 0.75 |
Upper | Value of Froude number above which part of the convective acceleration term is removed so that supercritical flow can be modelled. If no value or zero is assigned in this field, no simplification is performed | 0.9 |
Numerical Solution Parameters
| Parameter | Description | |
|---|---|---|
Under-relaxation (a) | Under relaxation factor used to accelerate or smooth convergence between iterations during timestepping | 0.7 |
Mathematical damping (q) | Preissmann Box weighing parameter which should lie between 0.5 and 1. The default value is 0.7 but for tidal problems, a value closer to 0.5 should be used e.g. 0.55 or less | 0.7 |
Pivotal choice | Pivotal choice parameter. This should not be altered by the non-expert user | 0.1 |
Matrix dummy (h) | A dummy coefficient to maintain the matrix structure. This should not be changed by the non-expert user | 0 |
Convergence Parameters
| Parameter | Description | |
|---|---|---|
Direct method | Tolerance parameter for the direct steady state solver. A single tolerance value is used for both stage and flow. For stage the tolerance refers to the difference (m) between water levels computed at network junctions between iterations. For flow the tolerances refers to the ratio of computed and specified flows between iterations | 0.001 |
Flow (Qtol) | Flow convergence parameter per timestep | 0.01 |
Head (Htol) | Water level convergence parameter per timestep | 0.01 |
Miscellaneous
| Parameter | Description | |
|---|---|---|
Average water temperature | Temperature of the water (°C). A value must be input for this parameter which should lie between 0 and 60°C. Results are insensitive to water temperature | 10 |
Minimum depth of water | Minimum water depth permitted in channels or culverts (m). If a value of zero is used then a minimum water depth is not imposed and water levels may drop below the channel bed in iterating to a solution | 0.1 |
The following parameters may be overridden by selecting values for them in the Advanced Parameters tab of the 1D Scenario Data window of the 1D simulation:
- a (alpha)
- q (theta)
- Qtol
- Htol