Some junctions in AFT Impulse use a pipe as a connector for some elements, although it is not a complete element by itself. Such an element may also include an orifice as shown in Figure 1. These connector pipes are modeled as pipes with lumped inertia (Wylie, 1993Wylie, E.B., V.L. Streeter & L. Suo, Fluid Transients in Systems, Prentice Hall, Englewood Hills, New Jersey, 1993.), such that their losses are included with the junction calculations.

Summing forces acting on the lumped section, 2,

or,

Now,

Substituting terms and dividing by area A2

Taking average values over time, and denoting current time by a prime,

Collecting terms and simplifying

where

(1)

(2)

If a connector pipe exists but no orifice then

If an orifice exists but no connector pipe

If neither exist then