Hydrodynamic sewer calculation

BaSYS supports full structural engineering data collection for the planned and/or existing sewer network. In general drainage planning, the recorded data are used for hydraulic predimensioning of the planned network versions. The hydraulic capacity of the realised and/or rehabilitated sewer network is verified by the integrated hydrodynamic simulation process. Detailed views and tables for data collection, planning and administration of the source data and hydraulics data for the sewer network are provided in the intuitive BaSYS technical data forms.

Hydraulic variants support the design of different execution versions without changing the source data. The catchment area data, important hydraulic pipe parameters and details of special structures such as the basin volume, weir sill height and pump capacity for example can be varied for each version. After the preferred version is approved by the client, it can be reconciled with the source data.

Through the views in the technical data forms and interactive graphics, the results of the hydrodynamic calculation can be clearly presented and examined in a variety of ways. General default data are available across projects in libraries that can be expanded with user-defined interfaces. These include sewer profiles with curves, actual/modelled precipitation, catchment area characteristics, and volume and pump curves.

Fields of application

The BaSYS modules that can be used within the scope of sewer hydraulics support numerous possible applications. These include:

  • Statistical analysis of precipitation data according to DWA-A 118/121
  • General drainage plans for sewer networks
  • Detailed and execution planning for sewer networks
  • Expanding/redesigning existing sewer networks; also hydrodynamically
  • Hydrodynamic backup verification of existing sewer networks according to DIN EN 752
  • Modelling and hydrodynamic simulation of special structures
  • Hydrodynamic backup verification within the scope of sewer rehabilitation planning
  • Hydraulic condition assessment within the scope of a sewer rehabilitation concept Input data for sewer network flooding simulation

Time coefficient method for sewer network dimensioning

General drainage planning for sewer networks requires an efficient method for fast sewer network dimensioning within the scope of the network variants being examined. The proven time coefficient method is integrated into the BaSYS applications for this purpose. It has the following advantages:

  • Direct use of the existing source data without additional modelling
  • KOSTRA rain library with standard rain and user-defined interface
  • Library of the sewer profiles and profile scales compiled from them
  • Library of the possible dry weather loads
  • Definition of the partial networks to be calculated
  • Direct dimensioning of the entire sewer network with possibilities for subsequent adaptations in the longitudinal planning section
  • User-defined default settings for the relevant dimensioning parameters
  • Overviews and detailed reports on the dimensioning results

Automatic dimensioning can be carried out for the overall network, or alternatively just for the planned or hydraulically overloaded sewer segments. Hydraulically complex sections of the sewer network, such as sewer segments with a reverse slope, pumping stations or special structures for rainwater treatment, are dimensioned by means of hydrodynamic sewer network simulation with MIKE1D and used further for the time coefficient procedure when needed.

Hydrodynamic sewer network simulation with MIKE1D

The hydrodynamic calculation program uses the nationally and internationally recognised MIKE1D calculation engine from DHI for the simulation. After careful calibration with measurement data, the integrated precipitationdrainage model realistically represents the flow processes from drainage development in the catchment area to the transfer points from the sewer network to the sewage works and/or receiving waters. The Saint-Venant equations underlying the hydrodynamic sewer network simulation are normally solved without major instabilities, also for the following boundary conditions:

  • Lowering curves at drops and for slope changes
  • Losses of momentum due to cross-section and direction changes
  • Retention including hydraulic losses in structures and manholes, especially in water rings and for discharge under sluices
  • Storage in structures and manholes, also based on volume curves
  • Pump operating ranges, respectively between two characteristic curves

The curve library supports the standardised specification of volume, seepage, pump, flow and throttle curves. Since they have relative elevations, they can be used independently of the elevation of the referenced sewer objects.

Rain Manager

Mass data from the German weather service are imported into Rain Manager by default. There the data are administered in a Firebird database. The import of other mass data formats is also possible with corresponding configuration of the definition file.

Date-specific and single precipitation events, model rain groups, series rain and/or a continuum are generated using the integrated statistics functions according to DWA-A 121 depending on the task. Standard views with various levels of detail and additional display of the extreme values as well as individually configurable views can be used for the advance analysis of the precipitation data. The configurations for generating the model rain groups and series rain are generated automatically using the defaults according to DWA-A 118. The chosen result of the statistical analysis is written to a standardised XML file – which can be imported directly into the hydrodynamic sewer network stimulation or another application.

Hydraulic modelling

The sewer network section being calculated is automatically generated as what is known as a hydraulic network once the ending sewer segments are selected. Starting sewer segments are defined in addition when needed. The sewer objects of the hydraulic network can be calculated directly from the database without changing the source data through hydraulic standby systems. For each calculation run, the hydrodynamic sewer network simulation takes into account all calculation elements such as pipes, open ditches, retaining basins, junctions, special structures, weirs, pumps and slide valves/throttles.

Sewer network dimensioning with the time coefficient method automatically interprets the hydraulic network as a manhole-sewer segment model that does not take the details of special structures into account. Global default settings enable the parallel formulation and administration of different boundary conditions for the hydraulic dimensioning and/or hydrodynamic simulation of the sewer network. The desired global default settings are chosen before each calculation run. Individual hydraulic conditions that deviate from the default settings can also be defined per sewer object. Rain from the rain type library is assigned to each calculation run.

Visualisation of the results

Predefined database queries and reports are available for visualising the results of sewer network dimensioning and the hydrodynamic sewer network simulation. The resulting data output can be exported as Office documents of any form, such as MS Excel files, for subsequent use. A statistical analysis of the results is performed with the BaSYS Dashboard. Important characteristics are output dynamically in diagrams with a modular layout. The statistics integrated into the modular system can be filtered interactively. Thus the current project status is interactively presented to decision makers.

Hydrographs are generated for the relevant sewer object and stored in the database by the calculation runs of the hydrodynamic sewer network simulation. The hydrograph values are displayed graphically and as tables in the forms, the extreme values as tables and in fields. In BaSYS-Plan the data are visualised with theme plans, for example regarding the water level and hydraulic utilisation.

An overview of results for the sewer network simulation also shows the hydrographs for the active sewer object and the adjacent objects. Drainage hydrographs of the connected catchment areas are also shown for sewer segments, the hydrographs of the sub-elements for special structures. The view can be switched between water depth and flow. The dynamic longitudinal section is described in a separate section. Standardised XML documents define the database queries and reports, the dashboard and theme plans. These can be duplicated, edited in the multifunction editor and imported or exported as desired.

Dynamic longitudinal section

The dynamic longitudinal section is integrated into the hydrodynamic sewer network simulation and corresponds to a video animation of the development of the water level situation over time in a chosen sequence of sewer segments. Thus the simulation results for critical sections of the sewer network can be realistically visualised for the decision makers. The sewer segment sequences of the dynamic longitudinal section are defined intuitively and administered in a database. For each sewer segment sequence that is loaded, the data of any calculation run can be called up. The animation is carried out automatically and/or with a manual slider. Interrupting the animation, stopping the slider or navigating directly to a time step produces a freeze frame that can be printed and/or exported.

Value creation through sewer network simulation

Focused on the key parameters, sewer network simulation with the MIKE1D calculation engine integrated in BaSYS has the following main benefits for the user:

  • Simplified numeric solving of the Saint-Venant equations for short pipe lengths and automated optimisation of the iteration intervals to avoid instabilities.
  • Consideration of backup, the compound effect of interconnected networks, retention, complex hydraulic boundary conditions and possible flow direction changes.
  • Direct simulation of all network elements (pipes, pressure pipes, ditches, retaining capacities, junctions, special structures, slide valves/throttles) without changing the source data through hydraulic standby systems.
  • Straightforward hydraulic detailing of special structures for rainwater treatment without changing the source data. Planning the connections, weirs, pumps and slide valves/throttles using the building block principle with a virtually unlimited number of those elements.
  • Use of the BaSYS Arena architecture with numerous possibilities for fast searching, comparison, verification of plausibility, structured adaptation and output of the relevant data.
  • Definition of the catchment area attributes via the surface type library. Its intelligent use significantly reduces the data collection time for catchment areas and therefore the calibration of drainage development.
  • Graphical output of the precipitation data, profile cross-sections, hydrographs and curves. Comparative hydrograph output for adjacent sewer segments and for structures with all sub-elements. Complete user-defined variable theme plans and dynamic longitudinal section of the calculation results.
  • CSV interface for all library data and interface to import the precipitation data from Rain Manager.

Rainwater management projects with MIKE1D therefore quickly add solid value for contractors and clients.