Basic Modelling Concepts

Introduction

In the workflow of 3Di we distinguish a schematisation and a simulation template.

Fig. 77 The modelling concepts of 3Di

In general, the schematisation contains all information that 3Di needs for preprocessing, e.g. to create a calculation grid, and subgrid tables.

Fig. 78 The modelling concepts of 3Di

The converted schematisation we call a 3Di model.

When building a schematisation, a user has more than one version. Online we support different versions of the same schematisation. For every version, or revision, a 3Di model can be created

This 3Di model needs information to run, which are initial conditions or events (e.g. rain).

To run a simulation, a user can use a simulation template or select a 3Di model and add all information required to run a simulation.

We provide all models of a simulation template based on the sqlite.

Together the ThreeDiModel, Scenario Information or Simulation Template form a Simulation

The simulation template can either be used as is, or can be run with changes and stored as a new simulation template.

Schematisation

A detailed overview of a schematisation is given in this paragraph. It consists of:

General rasters:

• dem_file

• frict_coef_file

• interception_file

Simple infiltration rasters:

• infiltration_rate_file

• max_infiltration_capacity_file

Interflow rasters:

• hydraulic_conductivity_file

• porosity_file

Ground water rasters

• equilibrium_infiltration_rate_file

• groundwater_hydro_connectivity_file

• groundwater_impervious_layer_level_file

• infiltration_decay_period_file

• initial_infiltration_rate_file

• leakage_file

• phreatic_storage_capacity_file

1D elements:

• channels

• pipes

• manholes

• connection nodes

• structures: o weirs o culverts o orifices o pumps

• location (node id) & type (e.g. water level / discharge / etc) of boundary conditions

• dem averaging

• impervious surfaces & mapping

• surfaces

• dem refinement

• cross section locations

• levees & obstacles

GridSettings

• use_2d: bool

• use_1d_flow: bool

• use_2d_flow: bool

• grid_space: float

• dist_calc_points: float

• kmax: int

• embedded_cutoff_threshold: float = 0.05

• max_angle_1d_advection: float = 90.0

TableSettings

• table_step_size: float

• frict_coef: float

• frict_coef_type: InitializationType

• frict_type: int = 4

• interception_global: Optional[float] = None

• interception_type: Optional[InitializationType] = None

• table_step_size_1d: float = None # actual default is set in __post_init__

• table_step_size_volume_2d: float = None # actual default is set in __post_init__

Simulation template

A simulation template consists of:

Simulation settings:

aggregation settings ()

numerical settings

• pump_implicit_ratio: 0,

• cfl_strictness_factor_1d: 0,

• cfl_strictness_factor_2d: 0,

• convergence_cg: 0,

• flow_direction_threshold: 0,

• friction_shallow_water_depth_correction: 0,

• general_numerical_threshold: 0,

• time_integration_method: 0,

• limiter_waterlevel_gradient_1d: 0,

• limiter_waterlevel_gradient_2d: 0,

• limiter_slope_crossectional_area_2d: 0,

• limiter_slope_friction_2d: 0,

• max_non_linear_newton_iterations: 0,

• max_degree_gauss_seidel: 0,

• min_friction_velocity: 0,

• min_surface_area: 0,

• use_preconditioner_cg: 0,

• preissmann_slot: 0,

• limiter_slope_thin_water_layer: 0,

• use_of_cg: 0,

• use_nested_newton: true,

• flooding_threshold: 0

physical settings

• use_advection_1d: 0,

• use_advection_2d: 0

time step settings

• time_step: 0,

• min_time_step: 0,

• max_time_step: 0,

• use_time_step_stretch: true,

• output_time_step: 0

Initial Water in the simulation:

• initial_groundwater (file / global setting)

• initial_waterlevels (file / global setting)

• saved state

Events:

• Dem edit

• Breach

• Laterals

• DWF

• structure controls:

  • table

  • time

  • memory

Forcings:

• Rain

• Wind

• Inflow 0D (impervious surfaces & surfaces)

Workflow

In the 3Di workflow a user creates a schematisation. This schematisation consists of sqlite & rasters. The simulation template is extracted from the spatialite. The name of the simulation template is the same as the name in global settings.

Database overview

Download the database overview including the global settings section here.