Controls are statements that determine how the network is operated over time. They specify the status of selected links as a function of time,
tank water levels, and pressures at select points within the network. There are two categories of controls that can be used:
- Simple controls
- Rule-Based Controls
Simple controls depend on only a single condition in the network (e.g., a water level in a certain tank) while rule-based controls depend on a number of conditions occurring simultaneously.
Simple controls change the status or setting of a link based on
- the water level in a tank,
- the pressure at a junction,
- the time into the simulation,
- or the time of day.
1) LINK linkID status IF NODE NodeID ABOVE/BELOW value
2) LINK linkID status AT TIME time
3) LINK linkID status AT CLOCKTIME clocktime AM/PM
where
| linkID | = | link ID label |
| status | = | OPEN or CLOSED, a pump speed setting, or a control valve setting |
| nodeID | = | node ID label |
| value | = | pressure for a junction or water level for a tank |
| time | = | time since the start of the simulation in decimal hours or hours:minutes |
| clocktime | = | 24-hour clock time |
Some examples of simple controls are:
Link 12 CLOSED IF NODE 23 ABOVE 20
(Link 12 will be closed when the level in Tank 23 exceeds 20 ft.)
Link 12 OPEN IF NODE 130 BELOW 30
(Link 12 will be opened if the pressure at Node 130 drops below 30 psi)
Link PUMP02 1.5 AT TIME 16
(The relative speed of pump PUMP02 is set to 1.5 at 16 hours into the simulation)
Link 12 CLOSED AT CLOCKTIME 10 AM
Link 12 OPEN AT CLOCKTIME 8 PM
(Link 12 is repeatedly closed at 10 am and opened at 8 pm throughout the simulation)
There is no limit on the number of simple control statements that can be used.
Note: Using a pair of pressure controls to open and close a link can cause the system to become unstable if the pressure settings are too close to one another. In this case using a pair of Rule-Based controls might provide more stability.