WELKITE UNIVERSITIE
Collage of engineering and technology department of HWRE
NAME: ABUBEKER ABRAR
ID: 0127/13
COURSE NAME: HYDRAULIC STRACTURE 2
DECEMBER 29, 2023
TO D.R BEDDASA
.
1
1) Write what is intake structure, its type and practical applications?
A, An intake structure is basically a structure built to capture water from a
river, lake, or reservoir. Its primary function is to control the flow of water
and to prevent the entry of debris such as branches, leaves, and trash, and
to filter out sediment. It also helps in regulating the amount of water taken
from a water source.
B,Types of intake
1. Submerged Intake Structures
It is the one which is constructed entirely under water.
It is commonly used to obtain supply from a lake.Submerged Intake
Structures
2. Exposed Intake Structures
It is in the form of a well or tower constructed near the bank of a river, or in
some cases even away from the river banks.
Exposed intakes are more common due to ease in operation.
Exposed Intake Structures
3. Wet Intake Structures
It is a type of intake tower in which the water level is practically the same as
the level of the sources of supply.
It is sometimes known as Jack well and is most commonly used.
Wet Intake Structures
4. Dry Intake Structures
In case of dry intake there is no water in the water tower.
Water enters through entry port directly into the conveying pipes.
It is simply used for the operation of valves etc.
2
5. River Intake Structures
It is a type of intake which may either located sufficiently inside the river so
that demands of water are met with in all the seasons of the year, or they
may be located near the river bank where a sufficient depth of water is
available.
Sometimes, an approach channel is constructed and water is led to the
intake tower.
If the water level in the river is low, a weir may be constructed across it to
raise the water level and divert it to the intake tower.
6. Reservoir Intake Structures
When the flow in the river is not guaranteed throughout the year, a dam is
constructed across it to store water in the reservoir so formed.
These are similar to river intake, except that these are located near the
upstream face of the dam where maximum depth of water is available.
Design of intake may vary based on the type of dam.
C, for practical applications, intake structures are widely used in water
treatment plants, irrigation systems, industrial facilities that require water for
their processes, and of course, in hydropower plants where water is used
to generate electricity
2) What is meant by a dam sluice (outlet)? Why are such sluices necessary
in dam construction?
A dam sluice, or outlet, is an opening or a controlled passage in a dam
structure through which water can be released. An outlet works by
regulating the water level in the reservoir created by the dam and
controlling the flow of water downstream. It's like a release valve for the
dam, helping to manage the water level and flow for various purposes.
3
Why are such sluices necessary in dam construction?
1. Flood Control: By allowing controlled release of water, dam sluices help
prevent the reservoir from overfilling and possibly causing downstream
flooding during heavy rainfall or sudden inflows.
2. Sediment Management: Sluices also help in releasing sediment-laden
water from the reservoir. This is important because if the sediment
accumulates in the reservoir, it can reduce water storage capacity and
impact the efficiency of the dam.
3. Environmental Considerations: Releasing water from the reservoir
through the sluices helps maintain the natural flow regime in downstream
river ecosystems, benefitting the ecological balance and aquatic life.
4. Water Regulation: The dam sluices also enable the regulation of water
flow for downstream water users, such as irrigation, water supply, and
industrial needs.
3 Show with neat sketches, the provision of sluiceways in an earth dam
and concrete gravity dam
Sluiceways in an earth dam
4
Sluiceways in concrete gravity dam
4) Write short notes on components of outlet works, trash racks and
different head losses in a conduit pressure flow
1. Intake Structure: This is the entry point for water into the outlet works
system. It is designed to regulate and control the flow of water from the
reservoir.
2. Conduits: These are the channels or pipes through which water is
conveyed from the reservoir to the outlet. They can be pipes, tunnels, or
other hydraulic structures.
3. Gates and Valves: These control mechanisms are used to regulate the
flow of water through the outlet works. They can be operated manually or
automatically.
5
4. Energy Dissipation Devices: These components are designed to reduce
the velocity of the flowing water and dissipate its energy to prevent erosion
downstream.
5. Trash Racks:
Trash racks are installed at the intake of the outlet works to prevent debris,
such as floating logs, branches, and large objects, from entering the
conduits or damaging the components of the outlet works. They help
maintain the efficiency and functionality of the system by screening out
unwanted materials.
Head Losses in Conduit Pressure Flow:
1. Frictional Head Loss: This is caused by the resistance of the conduit
walls to the flow of water. It is influenced by the roughness of the conduit
surface and the velocity of the water.
2. Entrance Head Loss: This occurs at the entry point of the conduit as the
flowing water transitions from a reservoir or open channel into the conduit.
It is related to abrupt changes in flow direction and velocity.
3. Exit Head Loss: Similarly, this occurs at the exit point of the conduit as
the flowing water transitions from the conduit back into a reservoir or open
channel. It is influenced by the design of the outlet structure.
4. Contraction and Expansion Head Losses: These occur when the crosssectional area of the conduit changes, causing variations in flow velocity
and pressure.
5) What are spillways and where they are provided?
Spillways are structures built to safely release excess water from a dam,
reservoir, or other water control structure. They are designed to prevent
flooding and to protect the integrity of the dam or structure by controlling
the flow of water.
6
Spillways are typically provided in areas where there is a risk of flooding
due to excess water accumulation, such as in reservoirs, dams, levees,
and other water control structures. They are also commonly found in areas
where there is a risk of flash flooding, such as in urban areas or near rivers
and streams
A spillway may be located either within the body of the dam or at one end
of the dam or entirely away from the dam as an independent structure.
6) What are the different types of spillways and how they are selected for
individual conditions?
There are several different types of spillways, each with its own unique
design and purpose. The selection of a spillway for specific conditions
depends on various factors, including the amount of water to be
discharged, the topography of the area, environmental considerations, and
cost. Here are some of the common types of spillways and how they are
selected for individual conditions:
1. Free Overflow Spillways: These spillways are designed to allow water to
flow over the top of a dam or structure without any control over the
discharge rate. They are typically used in situations where the flow of water
can be safely allowed to pass over the structure without causing damage.
2. Controlled Spillways: These spillways have gates or other control
mechanisms to regulate the flow of water. They are often used in situations
where it is necessary to manage the release of water to prevent flooding
downstream or to maintain a specific water level in a reservoir.
3. Chute Spillways: Chute spillways are steep, open channels that allow
water to flow rapidly downhill. They are often used in situations where there
is limited space for a traditional spillway and where a high discharge rate is
required.
7
4. Siphon Spillways: Siphon spillways use the siphoning effect to draw
water from a reservoir or dam and discharge it downstream. They are often
used in situations where it is necessary to release water from a reservoir at
a controlled rate.
5. Side Channel Spillways: These spillways divert excess water to a
separate channel or watercourse, allowing it to bypass the main structure.
They are often used in situations where there is limited space for a
traditional spillway or where environmental considerations require the
preservation of natural watercourses.
The selection of a spillway for specific conditions involves a detailed
analysis of factors such as the hydrology of the area, the potential for
flooding, environmental impacts, cost, and safety considerations. Engineers
and hydrologists use various design criteria and modeling techniques to
determine the most appropriate type of spillway for a given situation.
Additionally, local regulations and environmental impact assessments may
also influence the selection of a spillway type for specific conditions.
7) How would you compute the discharge passing over an ogee spillway?
Discuss the various factors affecting coefficient of discharge in the
discharge equation.
Discharge Computation Over Ogee Crest:
The discharge over ogee spillway is computed from the basic equation of
weir given below:
Q = Cd Le H1.5
Where, Q = Discharge in cumecs
Cd = Coefficient of discharge, its value varies from 2.1 to 2.5
H = Head of over flow in meters including velocity of approach head. H =
Hd + Ha Le = Effective length of overflow crest in meters
Le = L-2(N*kp+ka)*H L = Net length of the crest
8
N = Number of piers Kp = Piers contraction coefficient Ka = Abutment
contraction coefficient
The discharge coefficient (Cd) is influenced by a number of factors: 1)
Height of spillway above stream bed or depth of approach
2) Relation of the actual crest shape to the ideal nappe shape
3) Upstream face slope
4) Downstream apron interference, and
5) Downstream submergence
6) Ratio of actual total head to the design head
7) Effect of head due to velocity of approach
8) What is meant by energy dissipator? Discuss the various methods used
for energy dissipation below spillways
Energy dissipator, also known as a hydraulic jump or energy-dissipating
structure, is a hydraulic engineering feature designed to reduce the energy
of flowing water, typically below spillways or other hydraulic structures.
Energy dissipators are used to prevent erosion, scouring, and turbulence
downstream of a spillway or other hydraulic structure by slowing down and
diffusing the energy of the flowing water.
Various methods are used for energy dissipation below spillways, each with
its own advantages and limitations. Some common methods include:
1. Stilling Basins: Stilling basins are large pools of water located
downstream of a spillway. The sudden change in water depth causes the
flowing water to form a hydraulic jump, which dissipates the energy of the
9
flow. Stilling basins are effective at reducing the velocity of the water and
preventing erosion downstream.
2. Hydraulic Jumps: A hydraulic jump occurs when the flow of water
transitions from supercritical (fast-moving) to subcritical (slow-moving). This
abrupt change in flow creates turbulence and energy dissipation. Hydraulic
jumps can occur naturally or can be artificially induced using structures
such as baffle blocks or steps.
3. Riprap and Boulder Aprons: Riprap and boulder aprons consist of layers
of large rocks or boulders placed downstream of a spillway to dissipate the
energy of flowing water. The rough surface of the rocks helps to slow down
the water and reduce erosive forces.
4. Flip Buckets: Flip buckets are curved structures located at the end of a
spillway that redirect the flowing water upward before allowing it to drop
into a plunge pool below. This redirection helps to dissipate the energy of
the flowing water and reduce the potential for erosion downstream.
5. Jet Deflectors: Jet deflectors are angled plates or vanes installed at the
end of a spillway to deflect the flow of water away from the structure and
into a plunge pool. This helps to reduce the velocity and energy of the
flowing water, preventing erosion downstream.
6. Impact Blocks: Impact blocks are solid structures placed in the path of
flowing water to absorb its energy and reduce its velocity. These blocks are
often made of concrete or other durable materials and are designed to
withstand the force of the flowing water.
10
9) Write the differences between tail water curve and hydraulic jump curve,
and discuss their different graphical relationships
The tail water curve and the hydraulic jump curve are both important
concepts in hydraulic engineering and are used to analyze the behavior of
flowing water in different scenarios. Here are the differences between the
two curves and their graphical relationships:
1. Tail water Curve:
- The tail water curve represents the relationship between the
downstream water level (tail water elevation) and the discharge or flow rate
from a hydraulic structure, such as a spillway or a dam.
- It shows how the water level downstream of the structure changes as
the flow rate through the structure is varied.
- The tail water curve is typically plotted with the downstream water level
(y-axis) against the flow rate or discharge from the structure (x-axis).
- The tail water curve is used to determine the potential for flooding or
erosion downstream of a hydraulic structure and to ensure that the
downstream water levels remain within acceptable limits.
2. Hydraulic Jump Curve:
- The hydraulic jump curve represents the relationship between the
upstream and downstream water depths, or energy levels, in a hydraulic
jump.
- It shows how the water depth and energy change as water transitions
from supercritical flow (fast-moving) to subcritical flow (slow-moving) in a
hydraulic jump.
- The hydraulic jump curve is typically plotted with the upstream water
depth (y-axis) against the downstream water depth (x-axis).
11
- The hydraulic jump curve is used to analyze and design energy
dissipators, such as stilling basins, flip buckets, or other structures that
induce hydraulic jumps to dissipate energy and reduce flow velocities.
Graphical Relationships:
The graphical relationships between the tail water curve and the hydraulic
jump curve are different because they represent different aspects of the
behavior of flowing water:
- Tail water Curve: The tail water curve shows how the downstream water
level changes with variations in flow rate from a hydraulic structure. As the
flow rate increases, the downstream water level also increases, and vice
versa. The tail water curve is used to assess the potential impacts on
downstream water levels and to ensure that they remain within acceptable
limits.
- Hydraulic Jump Curve: The hydraulic jump curve shows the relationship
between upstream and downstream water depths or energy levels in a
hydraulic jump. It illustrates how the water depth changes as it transitions
from supercritical to subcritical flow. The shape of the hydraulic jump curve
depends on factors such as flow velocity, channel geometry, and
roughness. The curve helps engineers design energy dissipators to control
flow velocities and reduce erosive forces downstream.
In summary, while both curves are related to the behavior of flowing water
in hydraulic structures, the tail water curve focuses on downstream water
levels in response to changes in flow rate, while the hydraulic jump curve
focuses on the relationship between upstream and downstream water
depths in a hydraulic jump.
12
10) Design a suitable section for ogee spillway of a concrete gravity dam
having the downstream face sloping at 0.8H: 1V. The design discharge for
the spillway is 5000 m3 /s. The height of the spillway crest is kept at a level
of 100 m. The average riverbed level at the site is 130 m. The spillway
crest length consists of 6 spans having a clear width of 9 m each.
Thickness of each pier may be taken as 2.5m
1. Determine the design head (H) for the spillway:
The design head (H) is the difference in elevation between the spillway crest level and
the riverbed level. In this case, H = 100 m - 130 m = -30 m (negative value indicates the
downstream direction).
2. Specific Energy (E) = (Head) + (Velocity Head)
The velocity head can be assumed to be negligible for the design discharge, so E = H.
3. Calculate the effective head (Heff):
Heff is the head available for energy dissipation. It is less than the total head due to
energy losses.
Heff = E - (Head Losses)
The head losses can be estimated based on empirical formulas or historical data for
similar spillways. Let's assume a value of 1.5 m for this example.
Heff = -30 m - 1.5 m = -31.5 m
4. Determine the required discharge capacity:
The design discharge is given as 5000 m3/s.
Determine the crest length:
The total crest length is given as 6 spans, with each span having a clear width of 9 m.
Total Crest Length = 6 spans × 9 m/span = 54 m
5. Determine the ogee curve parameters:
The ogee curve is the shape of the spillway section. It consists of a circular arc followed
by a straight drop. The radius of the circular arc (R) can be determined using the effective
head (Heff) and the design discharge (Q):
13
R = (Heff^2) / (2gQ)
Where g is the acceleration due to gravity (approximately 9.81 m/s^2).
Substituting the values:
R = (-31.5 m)^2 / (2 × 9.81 m/s^2 × 5000 m^3/s)
R ≈ 9.67 m
6. The length of the circular arc (Lc) can be calculated using the formula:
Lc = πR
Lc ≈ 30.43 m
7. Determine the dimensions of the ogee spillway section:
● The height of the ogee spillway section (Hs) is the sum of the design head (H) and the
radius of the circular arc (R):
Hs = |H| + R
Hs ≈ 100 m + 9.67 m
Hs ≈ 109.67 m
● The thickness of each pier is given as 2.5 m.
● The total width of the ogee spillway section (Bs) can be calculated by adding the clear
width of each span and the thickness of each pier:
Bs = 6 × 9 m + 5 × 2.5 m
Bs = 54 m + 12.5 m
Bs = 66.5 m
The resulting ogee spillway section would have a height (Hs) of approximately 109.67 m,
a total width (Bs) of 66.5 m, and a length of the circular arc (Lc) of approximately 30.43
m. The thickness of each pier is 2.5 m.
14