When processing simulations, InfoWorks WS Pro introduces the concept of a run. Runs are created within run groups in the database.
A run is made up of:
A live data configuration may be associated with a run using the Associate Live Data dialog.
See Creating and scheduling a run for detailed information.
In most cases, you will select Normal as the run type when scheduling the run. However, several types of special run are available:
In addition to the run types listed above, further results can be calculated which will indicate potential locations of large transient pressures.
To produce these additional transient advisor results as part of the run, select the Advise on Hydraulic Transients option from the Simulation Options dialog.
See the Transients Advisor topic for further details.
Calculations on the cost of water can be included in a run. Simply add data for the cost of water to the pipe control properties (on the Pipe Control Page). This option is available with any run type. See Price of Water for more information.
InfoWorks WS Pro normally calculates demand without reference to the actual pressure at a node. A pressure related demand run allows demand to vary with changing pressure at nodes. See Pressure Related Demand for more details. This option should be used with care.
It is possible to carry out a run using disconnected networks - a model that contains more than one network segment that are not linked - as long as all the segments contain a means of calculating head. This means that each segment must contain a reservoir or fixed head node. See Modelling a Disconnected System.
It is possible to carry out a run for a selected subset of the network only, by including a selection list when scheduling the run. Only objects in the selection list will be included in the simulation. See Modelling a Subset of the Network.
Optimisation of pumping stations can be carried out for a Normal run type. An optimisation run can be used to determine optimal pumping schedules to reduce electricity costs for a selection of pumping stations. See Cost Management Simulations for further details.
Calculations to express energy losses in the network and energy used at pumping stations as a CO2 equivalent, can be included in a run. This option is available with any run type. See Sustainability Analysis for more information.
A generalised multi run lets you set up a simulation that runs multiple test cases. See Generalised Multi Run Options dialog and Generalised Multi Run Configuration dialog.
The state of a network at times during a simulation can be saved for use as the initial state of a subsequent simulation.
To save the state of a simulation, check the Save state of this simulation option on the Simulation State dialog.
To use the saved state of a previous simulation to provide initial conditions for the current simulation, select an initial state simulation and saved state time in the Schedule Hydraulic Run view.
InfoWorks WS Pro simulates the behaviour of a water supply system by solving several consecutive steady states (timesteps) taking into account all the changes of boundary conditions over time, for example variations of water consumption and water levels in reservoirs and water towers, the on/off state of pumps, valve operation, changes in demands.
The next operation is to check that the model data makes sense. The InfoWorks WS Pro engine checks the data before any computation takes place. Errors may still exist in the model data that have not been trapped by the validation procedures. These procedures do not cover live data, or the relationship between the different types of data that comprise the run.
See Runtime Messages for further information on warning and error messages that might be displayed during runtime validation checks.
After carrying out checks on the validity of the data, InfoWorks WS Pro defines the initial state of the system.
If an initial state simulation has been selected in the Schedule Hydraulic Run view, the initial state of the system will be set from the selected simulation.
If an initial state simulation has not been selected, the initial state of the system will be set from the control data. Any controls for which control data has not been defined will be given defaults:
InfoWorks WS Pro displays these settings in the output window and in the log results. Simulation starts with computation of demand for the start date and time.
InfoWorks WS Prosolves each steady state in the water supply system by applying the improved node-oriented method, perfected and streamlined through long experience.
Each link has an equation relating flow to headloss. The node-oriented method is an iterative scheme that tries to solve these equations for flows into and out of each node, with a flow balance within the tolerance set in the Computational Accuracy field in the Schedule Hydraulic Run view. It is recommended that the tolerance be set to approximately 1% of the average model inflow.
During the process, InfoWorks WS Pro displays output messages . These are also listed in the log results for the simulation. These messages will describe:
It is possible that the engine may fail to converge on a solution. InfoWorks WS Pro stops computation after the maximum number of iterations set in the Schedule Hydraulic Run view. The default value is 99 iterations. If a solution is not reached, InfoWorks WS Pro displays a warning and by default proceeds with the run (the option to stop the run after a failed snapshot can be set in the Simulation Options dialog). This warning is also listed in the log results for the simulation.
InfoWorks WS Pro assumes that the system remains in a steady state throughout the timestep. At the end of each timestep InfoWorks WS Pro does the following:
InfoWorks WS Pro keeps the timestep constant throughout a simulation. The user can decrease the timestep to reduce any inaccuracies that may arise. The advantage of a fixed timestep when dealing with large and complex systems is that it keeps the simulation within reasonable computation time and size limits.
You can carry out simulations using checked out networks if you want to test out modelling scenarios before committing network changes to the database.