Compound (Parallel) Pipes

h_{f 1} = h_{f 2}, Q = Q_{1} + Q_{2}, h_{f} = f \frac{L}{D} \frac{V ^{2}}{2 g}

Pipes in parallel between two junctions share the same head loss. Total discharge splits so that hf1 = hf2 = … . Equivalent pipe methods (or Hardy Cross for loops) are in the Handbook. Series pipes: same Q, heads add.

$h_{f}$ (m): Friction head loss
$Q$ (m³/s): Total discharge

Step-by-step solved example

Two parallel pipes, identical f, L, D. Total Q = 0.20 m³/s. Flow in each?

Parallel pipes: equal head loss, Q total splits.

1. Equal loss
Identical pipes ⇒ identical Q split.
2. Each
Q1 = Q2 = 0.10 m³/s.

Answer: 0.10 m³/s each

10 practice questions

0/10 correct

1.Parallel pipes have equal

2.Series pipes have equal

3.The larger of two parallel pipes carries

4.Darcy hf ∝ V² L / D. For fixed hf, Q ∝

5.Hardy Cross is used for

6.Equivalent pipe has the same

7.A closed valve on one parallel branch

8.Minor losses can be lumped as

9.Two series pipes: 2 m + 3 m loss. Total hf =

10.Hazen–Williams can replace Darcy when