Configure Simulation Parameter
Usage Instructions
The simulation parameter configuration function is used to set parameters that affect the water movement process, such as evaporation rate, rainfall rate, participating layers, initial water depth, infiltration parameters, Manning's roughness coefficient, and time step.
Function Entry
- Flood Simulation Tab -> Configure Simulation Layers Group -> Simulation Parameter Configuration Button
Operating Steps
- Click the Flood Simulation Tab -> Configure Simulation Layers Group -> Simulation Parameter Configuration Button to pop up the "Simulation Parameter Configuration" dialog.
- Target Datasource Setting: Select the target datasource for the operation. Simulation parameters will be saved in this datasource.
- Evaporation Rate Setting: Set the water evaporation rate in mm/h. The default value is 0.
- The Study Area is a Closed Region: Check this box if water cannot flow in or out of the study area. Commonly used for simulating waterlogging or closed depressions.
- Rainfall Rate Setting: Configure the rainfall amount and its temporal distribution during the simulation. Complete the settings through the following operations:
- Add Row: Click the "Add Row" button on the toolbar. A new row will be added to the list where you can set the rainfall start time (format: hh:mm:ss) and rainfall rate.
- Delete: Select any row in the list and click the "Delete" button on the toolbar to remove it.
- Import Table: Click the "Import Table" button on the toolbar to open the "Import CSV" dialog. Select the target CSV file, then choose the columns corresponding to "Start Time", "Rate", and "Unit" in the file to complete the import.
- Export Table: Click the "Export Table" button on the toolbar to open the "Export CSV" dialog. After setting the file name and storage path, the currently configured rainfall rate data can be saved as a CSV file.
- Parameter Layers: Check the layers in the target datasource (such as waterways, water areas, water sources, obstacles, etc.) to participate in the simulation analysis. All layers are checked by default.
- Initial Water Depth: Set the initial water depth by selecting a raster dataset..After selection, the initial water depth for each cell will be the cell value at the corresponding location in the selected raster dataset.
- Infiltration Parameter Settings: Set the following parameters via the dropdown lists:
- Initial Infiltration Rate (mm/h): The infiltration rate of the soil at the initial moment. A larger value indicates stronger infiltration capacity of the soil in a dry state.
- Saturated Infiltration Rate (mm/h): The steady infiltration rate when the soil is near saturation, which is less than the initial infiltration rate.
- Infiltration Decay Coefficient (h): Indicates how quickly the infiltration rate decays from the initial value to the saturated value.A larger value means faster decay, and the soil approaches saturation quickly; a smaller value means a slower decrease in infiltration rate.
- Manning's Roughness Coefficient: Reflects the resistance of the ground surface or riverbed to water flow. A larger value indicates greater resistance and slower flow velocity. Different surface types (e.g., grassland, forest, built-up areas) correspond to different Manning's roughness coefficient values.
- Simulation Parameter Settings:
- Time Step (seconds): The time interval corresponding to each computational step in the model calculation process. A smaller time step results in finer calculation results but also longer computation time.
- CFL Number: A stability condition in numerical computation, used to automatically adjust the actual computational step size, with a value range of [0.0,10]. A smaller CFL number means more stable calculation but lower efficiency. It is typically set between 0.5 and 1 to ensure calculation stability.
- Total Simulation Time (seconds): The total simulated duration from start to end of the model, i.e., the duration of the flood process to be simulated.
- Output Interval (steps): The number of computational steps between each output of simulation results. For example, if the output interval is 10, result data is saved every 10 time steps.
- Wet/Dry Boundary Depth (m): The critical water depth used to determine whether a cell is "dry" or "wet". When the water depth is below this value, the cell is considered a non-water area and does not participate in flow calculations, which can improve computational efficiency.
- Minimum Water Depth (m): The allowed minimum water depth threshold. When a cell's water depth falls below this value, it may be ignored or specially handled to avoid numerical calculation anomalies.
- After completing the settings, click OK. The simulation parameters will be saved in the parameter table dataset.
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