2. Introduction
Any water conveying system may include the following
elements:
Pipes (pipes in series, pipes in parallel,
Elbows,
Valves, and
Other devices
If all elements are connected are connected in series, the
arrangement is known as a pipeline
Otherwise, it is known as pipe network.
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8. Turbulent: The behavior of fluid articles within a flow stream
characterized by the rapid movement of particles in many directions as
well as the general direction of the overall fluid flow..
Vacuum: pressure less than atmospheric pressure.
Turbulent
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9. pressure is high and
velocity is low, in the
small part, pressure is
low and velocity high.
The Venturi Effect
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10. The general form of the law (neglecting friction) is:
𝑃
𝜌 𝑔
+
𝑉2
2 𝑔 1
=
𝑃
𝜌 𝑔
+
𝑉2
2 𝑔 2
where p1 is the pressure, v1 the velocity and h1 the elevation at point “1” and the
same parameters are used at point “2”. Gamma is the fluid density and g the
acceleration due to gravity.
In the case of the cyclist there is no pressure and only the velocity and elevation
can vary, so that Bernoulli's law becomes:
as the cyclist (
راكب
الدراجة
) goes down the hill h2 becomes smaller than h1 and to
balance the equation then V2 must be larger than V1.
In the case of the Venturi tube there is no elevation change and only the velocity
and pressure can vary, so that Bernoulli's law becomes:
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11. Specific speed: a number that provides an indication what type of
pump (for example radial, mixed flow or axial) is suitable for the
application. The figure below is know as the Balje diagram.
Specific speed is calculated with this formula:
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12. 9/21/2022 12
How to Solve Flow Problems
Calculate the total head loss (major and
minor) using the method of chapter 2.
Apply the energy loss (Bernoulli’s equation)
This technique can be applied for different
systems.
17. A pipeline including all the steel
fittings for pipe connections,
manholes, valve, connection
with the old pipeline and
backfilling above the pipes
A natural gas pipeline.
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20. Pipe Line with Negative Pressure “Syphon Phenomena”
Long pipelines laid to transport water from one reservoir to
another over a large distance usually follow the natural
contour of the land.
A section of the pipeline may be raised to an elevation
that is above the local hydraulic gradient line (siphon
phenomena) as shown:
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22. Definition:
It is a long bent pipe which is used to transfer liquid from a
reservoir at a higher elevation to another reservoir at a lower level
when the two reservoirsare separatedby a hill or highground
Occasionally, a section of the pipeline may be raised
to an elevation that is above the local HGL.
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Pipe Line with Negative Pressure “Syphon Phenomena”
23. 9/21/2022 23
To carry water from one reservoir to another
reservoir separated by a hill or high ground
level.
To take out the liquid from a tank which is not
having outlet
To empty a channel not provided with any
outlet sluice.
Syphon happened in the following cases:
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A
-ve value Must be -ve value ( below the atmospheric pressure)
Neg
ative pressureexists in thepipelines wherever the pipe line is raised above thehydraulic
gradient line (between P & Q)
𝑍𝑝 +
𝑃𝑝
𝜌 𝑔
+
𝑉𝑝
2
2𝑔
= 𝑍𝑠 +
𝑃𝑠
𝜌 𝑔
+
𝑉𝑠
2
2𝑔
+ ℎ𝐿
𝑍𝑝 − 𝑍𝑠 =
𝑃𝑠
𝜌 𝑔
+
𝑉𝑠
2
2𝑔
+ ℎ𝐿
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The negative pressure at the summit point can reach
theoretically -10.33 m water head (gauge pressure) and zero
(absolute pressure)
But in the practice water contains dissolved gasses that will
vaporize before -10.33 m water head which reduces the
pipe flow cross section.
Generally
, this pressure reach to -7.6 m water head (gauge
pressure) and 2.7m (absolute pressure)
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Siphon pipe between two pipe has diameter of 20cm and
length 500m as shown. The difference between reservoir
levels is 20m. The distance between reservoir A and summit
point S is 100m. Calculate the flow in the system and the
pressure head at summit. f = 0.02
Worked Example
28. 28
Pumps may be needed in a pipeline to lift water
from a lower elevation or simply to boost the rate
of flow. Pump operation adds energy to water in
the pipeline by boosting the pressure head.
The computation of pump installation in a
pipeline is usually carried out by separating the
pipeline system into two sequential parts, the
suction side and discharge side.
Pumps
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29. 29
H P H R H s hL
Pumps design has been
discussed in details last
semester
30. Branching in pipes occur when water is brought by pipes to a
junction when more than two pipes meet.
This system must simultaneously satisfy twobasic conditions:
The total amount of water brought by pipes to a junction must
equal to that carried away from the junction by other pipes Q = 0.
All pipes that meet at the junction must share the same pressure
at the junction (Pressureat point J = P)
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Branching Pipe Systems
