Civil Engineering Reference
In-Depth Information
2
V
2
2
V
2
= Velocity head
= Velocity head
g
g
y
= Piezometric height
y
= Water depth
z
= Height above datum
z
= Height above datum
Datum Line
A. Pipe Flow
B. Open Channel Flow
2
V
Total Head:
H
=
z
+
y
+
2
g
Headloss between Point 1 and Point 2,
H
L
V
V
H
L
=
z
+
y
+
1
−
z
+
y
+
1
2
2
1
1
2
g
2
g
Fig. 26-1.
Two types of flow and their components (
Source:
Reference 1)
26-1A. The water levels in the tubes are maintained by pressure exerted by the water
in each section of pipe. The hydraulic grade line in an open channel coincides with
the water surface, provided a uniform velocity distribution is maintained, and is shown
in Figure 26-1B.
The energy grade line, or energy line, represents the total energy in the flow at a
particular section. When referred to an arbitrary datum line as illustrated in Figure
26-1, the energy line is the sum of the pipe centerline height (
z
) (or channel bottom
height), the piezometric height (
y
), and the velocity head (
V
2
/2
g
). The loss of energy
that results when the liquid flows from one point to another is the headloss (
H
L
).
The hydraulic analysis computes the headlosses (
H
L
) of all the separate hydraulic
elements. The total then represents the elevation to which the water must be pumped
in order to allow for gravity flow through the plant. The remainder of this chapter
describes and presents the individual hydraulic elements and the equations that are
used to compute headloss.
Piping Systems
The headloss in piping systems includes the pipe losses and the losses caused by
various hydraulic components in the piping system. The hydraulic components include
the following:
Bends
•
Entrance
•
Increasers and reducers
•
