Fluid Mechanics

DJJ20073 Fluid Mechanics Chapter 5: Energy Loss in Pipelines

Example 5.8

Two reservoirs are connected by a pipeline which is 150 mm in diameter for the first 6 m
and 225 mm in diameter for the remaining 15 m. The entrance and exit are sharp and the
change of section is sudden. The water surface in the upper reservoir is 6 m above that
in the lower. Tabulate the losses of head which occur and calculate the rate of flow in
m3/s. Friction coefficient f is 0.01 for both pipes.

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DJJ20073 Fluid Mechanics Chapter 5: Energy Loss in Pipelines

SELF ASSESSMENT

1. Water is discharged from a reservoir into the atmosphere through a pipe 80 m long.
There is a sharp entrance to the pipe and the diameter is 250 mm for the first 50 m.
The outlet is 35 m below the surface level in the reservoir. The pipe then enlarges
suddenly to 450 mm in diameter for the remainder of its length.

Take f = 0.004 for both pipes. Calculate the discharge.

2. Two reservoirs have a difference in level of 9 m and are connected by a pipe line,
which is 38 mm in diameter for the first 13 m and 23 mm for the remaining 6 m. Take
f = 0.01 for both pipes and CC = 0.66. Calculate the discharge.

3. A pipe carrying 0.056 m3/s of water suddenly changes diameter from;
a) 200 mm to 150 mm
b) 300 mm to 150 mm
c) 450 mm to 150 mm

Find the loss of head and the pressure difference across the contraction in each
case, given CC = 0.62.

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DJJ20073 Fluid Mechanics Chapter 5: Energy Loss in Pipelines

4. Water flows at a rate of 0.02 m3/s from reservoir A to reservoir B through three
concrete pipes that connected in series as shown in Figure below. Find the
difference in water-surface elevations in the reservoirs.

f = 0.01 for all pipes Page 101
Cc = 0.62

ans
1. Q = 0.623 m3/s
2. Q = 0.00345 m3/s
3. (a) 0.19 m, 5299.4 N/m2

(b) 0.19 m, 6574.95 N/m2
(c) 0.19 m, 6826.63 N/m2
4. H = 0.1001 m

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