InfoWorks TS Options dialog

This dialog allows parameters to be set up for an InfoWorks TS simulation.

The dialog is displayed from the Schedule Hydraulic Run view when:

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Field Description
Transient simulation start

Date-time of start of Transient simulation.

A transient hydraulic snapshot will be run at this time to identify non-convergence caused by switching to the transient hydraulic conditions. If the transient hydraulic snapshot fails validation, the transient simulation will not be carried out.


Duration of Transient simulation in seconds

Only perform hydraulic simulation

Check this option to run the base hydraulic simulation and transient hydraulic snapshot only

Pipe segment length tolerance

Allowable error for pipe segmentation by surge engine.

Pipe lengths in the model may be adjusted up to the value specified in this field to allow a simplified system analysis.

Cavitation pressure

Local pressure resulting in vaporisation (default -10.122 m)

NRV response time

The amount of time it takes for non-return valve network objects in the system to go from fully opened to fully closed.

PID control time

PID sample time.

See InfoWorks TS (Transient System) Simulations for details.

Dynamic Friction Factors

If checked, InfoWorks converts resistance (headloss/flow2) values for changes in value of flow in each pipe. The conversion is re-evaluated at each iteration of the simulation.

If unchecked, InfoWorks converts the resistance value once for each pipe using resistance values determined from the pre-surge hydraulic run.

Pressure related demand

Check this option to model demand at nodes during the transient simulation as pressure related demand based on standard orifice behaviour.

PRD Exit pressure

Enabled when Pressure related demand option is checked.

Assumed pressure at exit region for pressure related transient demand.

This pressure is compared to pressure at the node to determine variance in demand.

Default value = 0 (atmospheric pressure)

Intrusion calculation type

Enabled when Pressure related demand option is checked.

Select the option to be used to calculate intrusion of liquid back into the system when PRD Exit pressure exceeds pipe pressure:

  • None - do not calculate intrusion volume
  • Demand fraction - calculate intrusion volume using Demand fraction specified
  • Leakage flow - calculate intrusion volume using Leakage flow specified for a reference pipe of 100 mm diameter at 50 m pressure
Demand fraction

Enabled when Intrusion calculation type is set to Demand Fraction.

Fraction of demand in the network, e.g. a value of 0.1 represents 10% of network demand.

From this value, a leakage constant is calculated for each demand node, which will discharge this fraction of flow at the initial pressure.

For example, at a node where the demand is 10 l/s at 64 m pressure difference, assume that 1 l/s (10% of the demand) is leaking through an orifice.

The Leakage Constant is calculated using the relationship:

Q(leak) = Lc*(pressure difference)0.5

For this example Lc = 1/(64)^0.5 = 0.125

Leakage rate at 50m pressure

Enabled when Intrusion calculation type is set to Leakage Flow.

Leakage rate for a reference pipe at 50 m pressure.

The Leakage Constant is calculated using the relationship:

Q(leak) = Lc*(pressure difference)0.5

For a leakage flow Q, equivalent value for Lc = Q/(50)^0.5

NRV Opening for Inertial Effects

Value between 0 and 1, used to model inertial effects of valve disc or flap, where 0 represents no inertial effects.

When the NRV is in closing mode (due to reverse flow through the valve) and the NRV open ratio is greater than the value entered here, the NRV will continue to close even if the flow direction changes to the forward direction.

Use of this setting may reduce pressure spiking.

Time Steps to Cavity Collapse

Integer value representing number of time increments for complete collapse of a vapour cavity.

If a value is not specified, a time increment of 1 will be used.

Used to 'soften' the effects of cavity collapse and avoid excessive pressure spiking.

Time Step Divider

Integer value used to divide calculated surge timesteps into smaller increments.

May be required where high frequency periodic disturbances occur.

InfoWorks TS (Transient System) Simulations

Creating and Scheduling a Run

Schedule Hydraulic Run View