General Junction Information

The different types of junctions on the Toolbox offer a great degree of freedom in assembling a pipe network model. While there is some redundancy in capabilities between the junctions, each of the types of junctions offers specialized features to allow you to prepare a good conceptual model of the physical system of interest. Table 1 compares the features of the junction types.

There is a junction Properties window for each junction type. Each junction Properties window falls into one of two basic window formats, depending on the number of connecting pipes allowed for that junction type.

Note: AFT Impulse does not prevent negative flow through junctions. Should this occur, AFT Impulse will use the same loss factor or pressure drop data referenced to the defined upstream pipe, just as in forward flow. Because it is possible that the loss factor or pressure drop data would not be the same for both flow directions, the flow solution could be misleading. For this reason it is important that you either properly define the pipe flow directions for junctions or pay close attention to the flow directions that result. AFT Impulse will not always give a warning for this, though it will for certain junctions.

Table 1: Comparison of junction capabilities

Junction Type Connecting Pipes Special Conditions Custom Library Window Format
Air Valve 1-2 Yes Yes 1
Area Change 2   Yes 1
Assigned Flow 1 Yes Yes 1
Assigned Pressure* 1/1-25   Yes 1
Bend/Elbow 2   Yes 1
Branch 2-25 Yes Yes 2
Check Valve 2 Yes Yes 1
Control Valve 2 Yes Yes 1
Dead End 1     1
Gas Accumulator 1-25 Yes Yes 2
General Component 2 Yes Yes 1
Liquid Accumulator 1-25 Yes Yes 2
Orifice 2   Yes 1
Pump 2 Yes Yes 1
Relief Valve 1-2 Yes Yes 1
Reservoir 1-25   Yes 2
Screen 2   Yes 1
Spray Discharge 1-4 Yes Yes 2
Surge Tank 1-25 Yes Yes 2
Tee/Wye** 3     2
Turbine 2 Yes Yes 1
Valve 1-2 Yes Yes 1
Venturi 2   Yes 1
Volume Balance 2     1
Weir 2 Yes Yes 1

*Assigned Pressure junction connects to only one pipe for static pressure, and up to 25 for stagnation

**Tee/Wye junctions have a unique format closer to Format #2 than Format #1