This document provides information on spillway and energy dissipator design. It begins with an introduction to spillways, their classification, and factors considered in design. It then focuses on the design of ogee or overflow spillways. It discusses spillway crest profiles, discharge characteristics including effects of approach depth, upstream slope, and submergence. It provides example designs for overflow spillways and calculations for determining spillway length. The key aspects covered are types of spillways, design considerations, standard crest profiles, discharge equations, and worked examples for spillway sizing.
Energy dissipaters are needed when water is released over a spillway to prevent scouring downstream. Various devices can be used, including baffle walls, deflectors, and staggered blocks, which reduce kinetic energy by converting it to turbulence and heat. Hydraulic jumps also dissipate energy by maintaining a high water level downstream. The type of dissipater used depends on the tailwater rating curve in relation to the jump height curve and the flow conditions. Stilling basins, sloping aprons, and roller buckets are suitable for different tailwater classifications.
050218 chapter 7 spillways and energy dissipatorsBinu Karki
The document discusses different types of spillways and energy dissipaters used in dams. It describes overflow or ogee spillways, chute spillways, and other spillway types. The main purposes of spillways are to safely release surplus water from the reservoir and regulate floods. Energy dissipaters, like stilling basins, are structures that reduce the high kinetic energy of water flowing from spillways to prevent erosion. Hydraulic jumps, baffle blocks, and deflector buckets are common dissipater types discussed in the document. Design considerations like discharge calculations, basin length, and tailwater conditions are also covered.
Cross drainage works are structures constructed where canals cross natural drainages like rivers or streams. There are several types of cross drainage works depending on the relative bed levels of the canal and drainage. The document discusses determining the maximum flood discharge of a drainage using various empirical formulas and methods. It also covers topics like fluming of canals, which involves contracting the canal width to reduce the size of cross drainage structures.
This document provides an overview of the hydraulic design considerations for barrages. It discusses key aspects of barrage design including sub-surface flow calculations to determine seepage pressure, force, and exit gradients. It also covers surface flow hydraulics to determine the waterway length. Critical design elements like cut-offs, scour depth, block protections are explained. Emphasis is given to ensuring safety against piping failure and sand boilling. The document concludes that model studies are necessary before prototype construction due to uncertainties in soil properties.
Cross section of the canal, balancing depth and canal fslAditya Mistry
1) The document discusses the cross section of irrigation canals, including configurations for cutting, filling, and partial cutting/filling. It describes the main components of a canal cross section such as side slopes, berms, and banks.
2) Balancing depth is defined as the depth of cutting where the quantity of excavated earth equals the amount required to form the canal banks, resulting in the most economical cross section.
3) Canal FSL (Full Supply Level) refers to the normal maximum operating water level of a canal when not affected by floods, corresponding to 100% capacity.
Khosla modified Bligh's theory for designing irrigation structures on permeable foundations. Khosla accounted for actual flow patterns below impermeable bases, unlike Bligh. Khosla derived equations to calculate uplift pressures and exit gradients at key points for structures with single or multiple piles. He also defined safe exit gradients and developed a method of independent variables to solve complex profiles by breaking them into simple components and applying corrections. Khosla's theory is now used for designing hydraulic structures on permeable foundations.
Energy dissipaters are needed when water is released over a spillway to prevent scouring downstream. Various devices can be used, including baffle walls, deflectors, and staggered blocks, which reduce kinetic energy by converting it to turbulence and heat. Hydraulic jumps also dissipate energy by maintaining a high water level downstream. The type of dissipater used depends on the tailwater rating curve in relation to the jump height curve and the flow conditions. Stilling basins, sloping aprons, and roller buckets are suitable for different tailwater classifications.
050218 chapter 7 spillways and energy dissipatorsBinu Karki
The document discusses different types of spillways and energy dissipaters used in dams. It describes overflow or ogee spillways, chute spillways, and other spillway types. The main purposes of spillways are to safely release surplus water from the reservoir and regulate floods. Energy dissipaters, like stilling basins, are structures that reduce the high kinetic energy of water flowing from spillways to prevent erosion. Hydraulic jumps, baffle blocks, and deflector buckets are common dissipater types discussed in the document. Design considerations like discharge calculations, basin length, and tailwater conditions are also covered.
Cross drainage works are structures constructed where canals cross natural drainages like rivers or streams. There are several types of cross drainage works depending on the relative bed levels of the canal and drainage. The document discusses determining the maximum flood discharge of a drainage using various empirical formulas and methods. It also covers topics like fluming of canals, which involves contracting the canal width to reduce the size of cross drainage structures.
This document provides an overview of the hydraulic design considerations for barrages. It discusses key aspects of barrage design including sub-surface flow calculations to determine seepage pressure, force, and exit gradients. It also covers surface flow hydraulics to determine the waterway length. Critical design elements like cut-offs, scour depth, block protections are explained. Emphasis is given to ensuring safety against piping failure and sand boilling. The document concludes that model studies are necessary before prototype construction due to uncertainties in soil properties.
Cross section of the canal, balancing depth and canal fslAditya Mistry
1) The document discusses the cross section of irrigation canals, including configurations for cutting, filling, and partial cutting/filling. It describes the main components of a canal cross section such as side slopes, berms, and banks.
2) Balancing depth is defined as the depth of cutting where the quantity of excavated earth equals the amount required to form the canal banks, resulting in the most economical cross section.
3) Canal FSL (Full Supply Level) refers to the normal maximum operating water level of a canal when not affected by floods, corresponding to 100% capacity.
Khosla modified Bligh's theory for designing irrigation structures on permeable foundations. Khosla accounted for actual flow patterns below impermeable bases, unlike Bligh. Khosla derived equations to calculate uplift pressures and exit gradients at key points for structures with single or multiple piles. He also defined safe exit gradients and developed a method of independent variables to solve complex profiles by breaking them into simple components and applying corrections. Khosla's theory is now used for designing hydraulic structures on permeable foundations.
Spillways are structures used to release surplus flood waters from a reservoir in a controlled manner. The main types of spillways include ogee or overflow spillways, chute spillways, morning glory spillways, and siphon spillways. To determine spillway capacity, engineers study past flood data and rainfall records to calculate the maximum probable flood, then add a margin of safety like 25%. This establishes the required discharge capacity. Energy dissipators like stilling basins are also important to safely discharge flood waters downstream.
The document discusses the design of gravity dams. It begins with basic definitions related to gravity dam geometry and forces that act on gravity dams, such as water pressure, weight of the dam, uplift pressure, and pressure due to earthquakes. It then covers stability analyses to prevent overturning, sliding, crushing, and tension. Finally, it addresses designing the dam section to be economical while satisfying stability requirements, and categorizing dams as low or high based on height.
This document discusses different types of canal outlets used to release water from distributing channels into watercourses. It describes non-modular, semi-modular, and modular outlets. Non-modular outlets discharge based on water level differences, while modular outlets discharge independently of water levels. Semi-modular outlets discharge depending on the channel water level but not the watercourse level. Specific outlet types are also defined, such as pipe outlets, open sluice, and Gibbs, Khanna, and Foote rigid modules. Discharge equations for different outlet types are provided.
The document discusses the design of an ogee spillway for a concrete gravity dam. It describes how shifting the curve of the nappe spillway profile can save concrete by becoming tangential to the downstream dam face. It then provides sample calculations for designing an ogee spillway based on given parameters like discharge rate, dam dimensions, and river levels. These include calculating the design head, developing the upstream and downstream spillway profiles, and considering factors that affect spillway design.
A weir is a solid structure built across a river to raise the water level and divert water into canals. There are different types of weirs including masonry weirs with vertical drops, rock fill weirs with sloping aprons, and concrete weirs with downstream slopes. Weirs can fail due to subsurface piping, uplift pressure, surface water suction or scouring. Remedies include installing sheet piles and ensuring sufficient floor thickness and length. A barrage is similar to a weir but uses gates rather than a solid structure to control water levels. Barrages are more expensive than weirs but allow better control of water levels and less silting during floods by raising the gates.
The document provides information on diversion head works and their components. It can be summarized as:
1) Diversion head works are structures constructed at the head of a canal to divert river water into the canal and ensure a regulated supply of silt-free water with a minimum head.
2) Key components of diversion head works include under sluices, divide walls, fish ladders, silt exclusion devices, guide banks, and head regulators. Under sluices control silt entry and water levels. Divide walls separate flows. Fish ladders allow fish passage.
3) Site selection factors for diversion head works include suitable foundations, positioning the weir at a right angle to river flow, space for
Spillway crest gates are adjustable gates used to control water flow in reservoir and river systems. They act as barriers to store additional water, allowing the height of dams to be increased and requiring more land acquisition. The main types of spillway gates are dripping shutters, stop logs, radial/tainter gates, drum gates, and vertical lift/rectangle gates. Vertical lift gates are rectangular gates that spin horizontally between grooved piers and can be raised or lowered by a hoisting mechanism to control water flow.
Canal fall- necessity and location- types of falls- Cross regulator and
distributory head regulator- their functions, Silt control devices, Canal
escapes- types of escapes.
The document discusses different types of canals including contour canals, ridge canals, and side slope canals. It describes how canals are classified based on alignment and position. The key parts of a canal system are described including main canals, branch canals, distributaries, and water courses. Methods for fixing canal alignment and designing canal cross-sections are outlined. Different types of canal lining materials and their purposes are also summarized.
WEIRS VERSUS BERRAGE
TYPES OF WEIRS
COMPONENT PARTS OF A WEIR
CAUSES OF FAILURE OF WEIRS & THEIR REMEDIES
DESIGN CONSIDERATIONS
DESIGN FOR SURFACE FLOW
DESIGN OF BARRAGE OR WEIR
The document discusses the hydraulic jump, which is the rise in water level caused by the transformation from unstable supercritical flow to stable subcritical flow. It causes energy loss due to turbulence and eddies. Applications include mixing chemicals, maintaining downstream water levels for irrigation, and removing air from pipes. The hydraulic jump typically occurs below structures like weirs, due to obstructions, or changes in channel slope. It dissipates surplus energy and creates disturbances like eddies and reverse flow that can remove pollution. The problem finds the depth of flow after a hydraulic jump in a 4m wide channel with a discharge of 16 m3/s, given an upstream depth of 0.5m.
Chapter 8:Hydraulic Jump and its charactersticsBinu Khadka
The document discusses hydraulic jumps, which occur when flow transitions from supercritical to subcritical. Hydraulic jumps are characterized by an abrupt rise in water surface with turbulence and eddies, dissipating energy. The depths before and after are called conjugate depths. Classification of jumps include undular, weak, oscillating and steady based on Froude number, and free, repelled and submerged based on tailwater depth. Key variables discussed are conjugate depths, jump height and length, and efficiency. Equations are presented for calculating conjugate depths based on conservation of specific force and energy.
This document discusses spillways and energy dissipators for dams. It defines spillways as structures used to safely release surplus water from reservoirs. The main types of spillways are main, auxiliary, and emergency spillways. Spillways can also be classified based on their prominent features, such as free overflow, overflow, side channel, open channel, tunnel, shaft, and siphon spillways. Energy dissipators, such as stilling basins and bucket types, are also discussed to reduce the energy of water flowing from spillways. Common energy dissipator types include horizontal and sloping apron stilling basins, and solid roller, slotted roller, and ski jump bucket dissipators.
A canal is an artificial channel constructed to carry water from a river or reservoir to fields. Canals are classified based on their source of water supply, financial purpose, function, boundary type, water discharge level, and alignment. Canal alignment should aim to irrigate the maximum area with minimum length and cost. The balancing depth is the depth of cutting where the amount of cut material equals the amount of fill. Canal lining reduces water seepage and includes hard surface materials like concrete and softer materials like compacted earth.
Types- selection of the suitable site for the diversion headwork components
of diversion headwork- Causes of failure of structure on pervious foundation- Khosla’s theory- Design of concrete sloping
glacis weir.
Gravity dams are structures designed so that their own weight resists external forces. Concrete is the preferred material. Forces acting on the dam include water pressure, uplift pressure, earthquake forces, silt pressure, wave pressure, and ice pressure. The dam's weight counters these forces. Dams are checked when full and empty, accounting for load combinations. Gravity dams can fail due to overturning, crushing, tension cracks, or sliding along foundation planes. Design aims to prevent failure from these modes.
Lacey's regime theory states that the dimensions and slope of a channel are uniquely determined by the discharge, silt load, and erodibility of the soil material. A channel is in regime if there is no scouring or silting. Lacey proposed equations to calculate parameters like velocity, slope, and dimensions based on variables like discharge, silt factor, and side slopes. The theory has limitations as the conditions of true regime cannot be achieved and parameters like silt grade/load are not clearly defined. Lacey also developed shock theory accounting for form resistance due to bed irregularities.
OPEN CHANNEL FLOW AND HYDRAULIC MACHINERY
Open channel flow: Types of flows – Type of channels – Velocity distribution – Energy and momentum correction factors – Chezy’s, Manning’s; and Bazin formula for uniform flow – Most Economical sections. Critical flow: Specific energy-critical depth – computation of critical depth – critical sub-critical – super critical flows
Non-uniform flows –Dynamic equation for G.V.F., Mild, Critical, Steep, horizontal and adverse slopes-surface profiles-direct step method- Rapidly varied flow, hydraulic jump, energy dissipation
Regulation works are structures constructed to regulate water flow in canals. The main types are head regulators, cross regulators, canal escapes, and canal outlets. Head regulators control water entry into off-taking channels from parent channels. Cross regulators are located downstream of off-takes and help control water levels and closures for repairs. Canal outlets connect distribution channels to field channels and supply water to irrigation fields at regulated discharges.
(1) Drop structures are used in canals to lower the water level along its course. There are several types of drop structures including vertical drops, inclined drops, piped drops, and farm drops.
(2) The main types of vertical drops discussed are the common straight drop, Sarda-type fall, and YMGT-type drop. Inclined drops include common chutes, rapid fall drops, and stepped cascades. Piped drops can be well drops or pipe falls.
(3) Each type has specific design considerations like crest shape and length, basin/stilling pool dimensions, upstream and downstream protections works, and guidelines for selection based on discharge and design head.
This document discusses the hydraulic design of the main diversion structure of a barrage. It covers sub-surface flow considerations like seepage pressure, exit gradient, and uplift forces. It also discusses surface flow conditions during floods when barrage gates are open. Analytical solutions and graphs are provided to calculate seepage pressures and exit gradient. Corrections are also described to account for factors like floor thickness, slope, and interference between sheet piles. Surface flow hydraulics involve operating barrage gates to pass floods while maintaining the pool water level.
Spillways are structures used to release surplus flood waters from a reservoir in a controlled manner. The main types of spillways include ogee or overflow spillways, chute spillways, morning glory spillways, and siphon spillways. To determine spillway capacity, engineers study past flood data and rainfall records to calculate the maximum probable flood, then add a margin of safety like 25%. This establishes the required discharge capacity. Energy dissipators like stilling basins are also important to safely discharge flood waters downstream.
The document discusses the design of gravity dams. It begins with basic definitions related to gravity dam geometry and forces that act on gravity dams, such as water pressure, weight of the dam, uplift pressure, and pressure due to earthquakes. It then covers stability analyses to prevent overturning, sliding, crushing, and tension. Finally, it addresses designing the dam section to be economical while satisfying stability requirements, and categorizing dams as low or high based on height.
This document discusses different types of canal outlets used to release water from distributing channels into watercourses. It describes non-modular, semi-modular, and modular outlets. Non-modular outlets discharge based on water level differences, while modular outlets discharge independently of water levels. Semi-modular outlets discharge depending on the channel water level but not the watercourse level. Specific outlet types are also defined, such as pipe outlets, open sluice, and Gibbs, Khanna, and Foote rigid modules. Discharge equations for different outlet types are provided.
The document discusses the design of an ogee spillway for a concrete gravity dam. It describes how shifting the curve of the nappe spillway profile can save concrete by becoming tangential to the downstream dam face. It then provides sample calculations for designing an ogee spillway based on given parameters like discharge rate, dam dimensions, and river levels. These include calculating the design head, developing the upstream and downstream spillway profiles, and considering factors that affect spillway design.
A weir is a solid structure built across a river to raise the water level and divert water into canals. There are different types of weirs including masonry weirs with vertical drops, rock fill weirs with sloping aprons, and concrete weirs with downstream slopes. Weirs can fail due to subsurface piping, uplift pressure, surface water suction or scouring. Remedies include installing sheet piles and ensuring sufficient floor thickness and length. A barrage is similar to a weir but uses gates rather than a solid structure to control water levels. Barrages are more expensive than weirs but allow better control of water levels and less silting during floods by raising the gates.
The document provides information on diversion head works and their components. It can be summarized as:
1) Diversion head works are structures constructed at the head of a canal to divert river water into the canal and ensure a regulated supply of silt-free water with a minimum head.
2) Key components of diversion head works include under sluices, divide walls, fish ladders, silt exclusion devices, guide banks, and head regulators. Under sluices control silt entry and water levels. Divide walls separate flows. Fish ladders allow fish passage.
3) Site selection factors for diversion head works include suitable foundations, positioning the weir at a right angle to river flow, space for
Spillway crest gates are adjustable gates used to control water flow in reservoir and river systems. They act as barriers to store additional water, allowing the height of dams to be increased and requiring more land acquisition. The main types of spillway gates are dripping shutters, stop logs, radial/tainter gates, drum gates, and vertical lift/rectangle gates. Vertical lift gates are rectangular gates that spin horizontally between grooved piers and can be raised or lowered by a hoisting mechanism to control water flow.
Canal fall- necessity and location- types of falls- Cross regulator and
distributory head regulator- their functions, Silt control devices, Canal
escapes- types of escapes.
The document discusses different types of canals including contour canals, ridge canals, and side slope canals. It describes how canals are classified based on alignment and position. The key parts of a canal system are described including main canals, branch canals, distributaries, and water courses. Methods for fixing canal alignment and designing canal cross-sections are outlined. Different types of canal lining materials and their purposes are also summarized.
WEIRS VERSUS BERRAGE
TYPES OF WEIRS
COMPONENT PARTS OF A WEIR
CAUSES OF FAILURE OF WEIRS & THEIR REMEDIES
DESIGN CONSIDERATIONS
DESIGN FOR SURFACE FLOW
DESIGN OF BARRAGE OR WEIR
The document discusses the hydraulic jump, which is the rise in water level caused by the transformation from unstable supercritical flow to stable subcritical flow. It causes energy loss due to turbulence and eddies. Applications include mixing chemicals, maintaining downstream water levels for irrigation, and removing air from pipes. The hydraulic jump typically occurs below structures like weirs, due to obstructions, or changes in channel slope. It dissipates surplus energy and creates disturbances like eddies and reverse flow that can remove pollution. The problem finds the depth of flow after a hydraulic jump in a 4m wide channel with a discharge of 16 m3/s, given an upstream depth of 0.5m.
Chapter 8:Hydraulic Jump and its charactersticsBinu Khadka
The document discusses hydraulic jumps, which occur when flow transitions from supercritical to subcritical. Hydraulic jumps are characterized by an abrupt rise in water surface with turbulence and eddies, dissipating energy. The depths before and after are called conjugate depths. Classification of jumps include undular, weak, oscillating and steady based on Froude number, and free, repelled and submerged based on tailwater depth. Key variables discussed are conjugate depths, jump height and length, and efficiency. Equations are presented for calculating conjugate depths based on conservation of specific force and energy.
This document discusses spillways and energy dissipators for dams. It defines spillways as structures used to safely release surplus water from reservoirs. The main types of spillways are main, auxiliary, and emergency spillways. Spillways can also be classified based on their prominent features, such as free overflow, overflow, side channel, open channel, tunnel, shaft, and siphon spillways. Energy dissipators, such as stilling basins and bucket types, are also discussed to reduce the energy of water flowing from spillways. Common energy dissipator types include horizontal and sloping apron stilling basins, and solid roller, slotted roller, and ski jump bucket dissipators.
A canal is an artificial channel constructed to carry water from a river or reservoir to fields. Canals are classified based on their source of water supply, financial purpose, function, boundary type, water discharge level, and alignment. Canal alignment should aim to irrigate the maximum area with minimum length and cost. The balancing depth is the depth of cutting where the amount of cut material equals the amount of fill. Canal lining reduces water seepage and includes hard surface materials like concrete and softer materials like compacted earth.
Types- selection of the suitable site for the diversion headwork components
of diversion headwork- Causes of failure of structure on pervious foundation- Khosla’s theory- Design of concrete sloping
glacis weir.
Gravity dams are structures designed so that their own weight resists external forces. Concrete is the preferred material. Forces acting on the dam include water pressure, uplift pressure, earthquake forces, silt pressure, wave pressure, and ice pressure. The dam's weight counters these forces. Dams are checked when full and empty, accounting for load combinations. Gravity dams can fail due to overturning, crushing, tension cracks, or sliding along foundation planes. Design aims to prevent failure from these modes.
Lacey's regime theory states that the dimensions and slope of a channel are uniquely determined by the discharge, silt load, and erodibility of the soil material. A channel is in regime if there is no scouring or silting. Lacey proposed equations to calculate parameters like velocity, slope, and dimensions based on variables like discharge, silt factor, and side slopes. The theory has limitations as the conditions of true regime cannot be achieved and parameters like silt grade/load are not clearly defined. Lacey also developed shock theory accounting for form resistance due to bed irregularities.
OPEN CHANNEL FLOW AND HYDRAULIC MACHINERY
Open channel flow: Types of flows – Type of channels – Velocity distribution – Energy and momentum correction factors – Chezy’s, Manning’s; and Bazin formula for uniform flow – Most Economical sections. Critical flow: Specific energy-critical depth – computation of critical depth – critical sub-critical – super critical flows
Non-uniform flows –Dynamic equation for G.V.F., Mild, Critical, Steep, horizontal and adverse slopes-surface profiles-direct step method- Rapidly varied flow, hydraulic jump, energy dissipation
Regulation works are structures constructed to regulate water flow in canals. The main types are head regulators, cross regulators, canal escapes, and canal outlets. Head regulators control water entry into off-taking channels from parent channels. Cross regulators are located downstream of off-takes and help control water levels and closures for repairs. Canal outlets connect distribution channels to field channels and supply water to irrigation fields at regulated discharges.
(1) Drop structures are used in canals to lower the water level along its course. There are several types of drop structures including vertical drops, inclined drops, piped drops, and farm drops.
(2) The main types of vertical drops discussed are the common straight drop, Sarda-type fall, and YMGT-type drop. Inclined drops include common chutes, rapid fall drops, and stepped cascades. Piped drops can be well drops or pipe falls.
(3) Each type has specific design considerations like crest shape and length, basin/stilling pool dimensions, upstream and downstream protections works, and guidelines for selection based on discharge and design head.
This document discusses the hydraulic design of the main diversion structure of a barrage. It covers sub-surface flow considerations like seepage pressure, exit gradient, and uplift forces. It also discusses surface flow conditions during floods when barrage gates are open. Analytical solutions and graphs are provided to calculate seepage pressures and exit gradient. Corrections are also described to account for factors like floor thickness, slope, and interference between sheet piles. Surface flow hydraulics involve operating barrage gates to pass floods while maintaining the pool water level.
Hydraulic characteristics of flow and energy dissipation over stepped spillwayIAEME Publication
This document summarizes an experimental study on the hydraulic characteristics of flow over stepped spillways. Seventy-two experiments were conducted using three types of stepped spillway models with varying downstream slopes and numbers of steps. Water surface profiles, energy dissipation, and pressure distributions were measured. The results showed that increases in relative step height and step length led to higher energy dissipation. Increasing the number of steps and roughness Froude number resulted in lower energy dissipation. An empirical equation was developed to calculate energy dissipation over stepped spillways based on affecting factors.
Hydraulic characteristics of flow and energy dissipation over stepped spillwayIAEME Publication
This document summarizes an experimental study on the hydraulic characteristics of flow over stepped spillways. Seventy-two experiments were conducted using three types of stepped spillway models with varying downstream slopes and numbers of steps. Water surface profiles, energy dissipation, and pressure distributions were measured. The results showed that increases in relative step height and step length led to higher energy dissipation. Increasing the number of steps and roughness Froude number resulted in lower energy dissipation. An empirical equation was developed to calculate energy dissipation over stepped spillways based on affecting factors.
1) The document discusses groundwater flow to wells and pumping tests. It covers basic well hydraulics, assumptions of groundwater flow, and equations for confined, unconfined, and leaky aquifers.
2) The Theis and Jacob methods are presented for analyzing pumping test data from confined aquifers, while the Hantush and Walton methods are used for leaky aquifers.
3) Pumping tests are important to determine an aquifer's hydraulic properties and long-term well yield.
The document discusses flow characteristics over broad crested weirs and stepped weirs. It begins with definitions of broad crested weirs and their advantages. Previous studies on broad crested weirs are summarized that examined factors like rounded edges, discharge coefficients, and separation zones. The document then describes a physical model experiment conducted in a laboratory flume to study a broad crested weir and stepped weir. Numerical modeling using FLUENT software is also discussed to simulate flow over the weirs using the volume of fluid method. The objectives are to examine laboratory data and 2D numerical modeling results to compare free surface profiles.
This document discusses the hydraulic design of culverts and bridges. It begins by defining culverts and bridges, noting that culverts are designed to allow submergence while bridges are not. It then covers culvert shapes, materials, end treatments, and key terminology. The remainder of the document discusses culvert hydraulic design considerations and approaches, including inlet control, outlet control, and formulas for calculating flow under various conditions. Design procedures are outlined, noting the iterative nature of selecting a culvert size that meets design constraints.
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- A spillway is a structure used to provide controlled release of water from a dam to prevent overtopping and potential dam failure.
- There are several common types of spillways including free overfall, ogee overflow, chute, and saddle spillways.
- The required spillway capacity should be equal to the maximum outflow determined from flood routing calculations considering reservoir inflow and storage capacity.
1. Shaft spillways are conduits that rapidly transfer flood flows from high to low elevations. They have axial flow in the shaft and downstream leg.
2. Shaft spillways are classified based on hydraulic action in the shaft and leg, including axial, vortex, or swirling flows.
3. Design considerations for free shaft spillways include the crest profile, transition from crest to shaft, discharge characteristics, and air entrainment. The crest profile depends on parameters like head and radius. Transitions are designed using continuity equations.
This document provides a 3-paragraph summary of a course on hydraulics:
The course is titled "Hydraulics II" with course number CEng2152. It is a 5 ECTS credit degree program course focusing on open channel flow. Open channel flow occurs when water flows with a free surface exposed to the atmosphere, such as in rivers, culverts and spillways. Engineering structures for open channel flow are designed and analyzed using open channel hydraulics.
The document covers different types of open channel flow including steady and unsteady, uniform and non-uniform flow. It also discusses the geometric elements of open channel cross-sections including depth, width, area and hydraulic radius. Uniform flow
This document provides an overview of spillways, including:
- Spillways are important structural components of dams that evacuate flood waters from reservoirs.
- The main types of spillways discussed are straight drop, overflow, chute, side channel, shaft, siphon, labyrinth, baffled chute, and cascade spillways.
- Overflow spillways are the most common type and allow flood waters to flow over an ogee-shaped crest. Design considerations for overflow spillways include crest profile, gates, discharge equations, and preventing cavitation.
This document contains 31 questions regarding boundary layer concepts and fluid mechanics. It covers topics such as the range of Reynolds numbers for laminar and turbulent flow, Hagen-Poiseuille formula, velocity distribution formulas, boundary layer thickness definitions, and equations for major and minor head losses in pipes. The document also provides definitions for terms like boundary layer, laminar sublayer, displacement thickness, and momentum thickness.
1) The document discusses water flow in pipes, including descriptions of laminar and turbulent flow, the Reynolds number, energy in pipe flow, and head loss from pipe friction.
2) Key concepts covered include the Darcy-Weisbach equation for calculating head loss from pipe friction and empirical equations like the Hazen-Williams equation.
3) Friction factors are discussed for both laminar and turbulent flow and their relationship to parameters like the Reynolds number and pipe roughness.
Effect of Height and Surface Roughness of a Broad Crested Weir on the Dischar...RafidAlboresha
Weir is usually incorporated as control or regulation devices in hydraulic systems,
with flow measurement as their secondary. It is normally intended for use in the field and thus
to regulate broad discharges. Broad-Crested weir is among the oldest common weir types. In this
paper, the effect of height and surface roughness for different Board Crested weirs models were
studied on discharge coefficient (Cd) in a horizontal open channel. In the crest of the weir,
certain materials may be combined with concrete (e.g., boulders) or may be used as cladding to
minimize the effect of water overflow (e.g. stone). The weir surface should not be considered
smooth in this case, and the discharge coefficient (Cd) must be re-estimated. For these purposes, laboratory flume was used to study the effect of height and surface roughness on the discharge coefficients with four of the different weir models dimensions of the concrete blocks. In this study, the flow conditions were considered to be free water flow and the viscosity effect was neglected. In all cases, the weir height effect was directly proportional to the discharge coefficient while the surface roughness effect was found to be inversely proportional to the coefficient Cd of the case study.
Flow over a rectangular side weir under subcritical conditionsIJARIIT
A side weir is set into the side of the main channel it is an overflow weir have been extensively used in hydraulic and
environmental engineering application. They typically are used for water level control in canal system, diverting excess water
into relief channels during floods. An example of a situation of spatially varied flow is the flow over a side weir.
This document discusses hydraulic modeling and flood inundation mapping using HEC-RAS. It defines hydraulic models as mathematical representations of water systems used to analyze system behavior under different scenarios. It describes one-dimensional hydraulic models, like HEC-RAS, which assume unidirectional flow, and outlines the governing equations and calculations involved in HEC-RAS modeling, including conveyance, friction slope, energy balance, and iterative profile computations. Finally, it discusses data requirements and the steps to set up and run a HEC-RAS model and generate flood inundation maps.
Use of downstream facing aerofoil shaped bridge piers to reduce local scourIAEME Publication
This document discusses research on using downstream-facing aerofoil-shaped bridge piers to reduce local scour compared to traditional upstream-facing designs. It provides background on how scour occurs due to horseshoe vortices forming in front of piers. An experiment tested scour for circular, upstream-facing aerofoil, and downstream-facing aerofoil piers. Results showed the downstream-facing design reduced maximum scour depth by 59% versus the upstream aerofoil and 68% versus circular, and reduced the scour hole volume by 87% versus circular. Orienting the aerofoil shape to face downstream effectively weakened vortices causing scour.
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TENDERS and Contracts basic syllabus for engineering
Chapter 7 spillway and energy dissipators
1. CHAPTER 7: SPILLWAY AND ENERGY
DISSIPATORS
1
0401544 - HYDRAULIC STRUCTURES
University of Sharjah
Dept. of Civil and Env. Engg.
DR. MOHSIN SIDDIQUE
ASSISTANT PROFESSOR
3. LEARNING OUTCOME
After taking this lecture, students should be able to:
(1). Obtain in-depth knowledge on various types of spillways
used in dams and their design guide lines
(2). Apply the design guide lines for the design of selected
Spillway
3
References:
Khatsuria, R. M., Hydraulics of Spillways and Energy Dissipators,
Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan, Hydraulic Structures, 4th Ed. CRC Press
Santosh, K. G., Irrigation Engineering and Hydraulic Structures, Khanna Publishers
BULU, A., Lecture noted of water resources, Istanbul Technical University
4. SPILLWAY
A spillway is a structure
designed to 'spill' flood waters
under controlled (i.e. safe)
conditions.
The Spillways can be
Uncontrolled (Normally)
Controlled
Note: Concrete dams
normally incorporate an over-fall
or crest spillway, but
embankment dams generally
require a separate side-channel
or shaft spillway structure
located adjacent to the dam.
Sketch of conventional weir/spillway
4
5. CLASSIFICATION OF SPILLWAYS
I. According to the most
prominent feature
• A. Ogee spillway
• B. Chute spillway
• C. Side channel spillway
• D. Shaft spillway
• E. Siphon spillway
• F. Straight drop or overfall
spillway
• G. Tunnel spillway/Culvert
spillway
• H. Labyrinth spillway
• I. Stepped spillway
II. According to Function
• A. Service spillway
• B. Auxiliary spillway
• C. Fuse plug or emergency
spillway
III. According to Control
Structure
• A. Gated spillway
• B. Ungated spillway
• C. Orifice of sluice spillway
5
7. ANALYSIS OF EXISTING STRUCTURES
Semenkov (1979) analyzed more than 400 projects in terms of
parameters L/H and N for the three main types of spillways: gravity
spillways, chute spillways, and tunnel spillways for concrete and
earth-fill dams.
Where, L and H are the length and height of the dam crest respectively, and
N is the power of the flow
Types of spillways for concrete and earth-fill dams. T: Tunnel spillways, C:
Chute spillways, G: Gravity spillways (Semenkov, 1979).
7
8. VARIOUS ASPECTS INVOLVED IN A
SPILLWAY DESIGN
The following aspects are involved in the design of spillways:
1. Hydrology
• Estimation of inflow design flood
• Selection of spillway design flood
• Determination of spillway outflow discharge
• Determination of frequency of spillway use
2. Topography and geology
• Type and location of spillway
3. Utility and operational aspects
• Serviceability
4. Constructional and structural aspects
• Cost-effectiveness
8
10. SPILLWAY DESIGN FLOOD
Probable Maximum Flood (PMF)
This is the flood that may be expected from the most severe
combination of critical meteorological and hydrological conditions that
are reasonably possible in the region. This is computed by using the
Probable Maximum Storm.
Standard Project Flood (SPF)
This is the flood that may be expected from the most severe
combination of hydrological and meteorological factors that are
considered reasonably characteristic of the region and is computed by
using the Standard Project Storm (SPS).
In US, generally, large dams are designed for PMF, intermediate for
SPF/PMF, and small dams for floods of return period of 100 years to
SPF.
10
11. ESTIMATION OF SPILLWAY DESIGN FLOOD
The estimation of spillway design flood or the inflow design flood is an
exercise involving diverse disciplines of hydrology, meteorology,
statistics and probability.
There is a great variety of methods used around the world to determine
exceptional floods and their characteristics. ICOLD (1992) groups all
these methods under the two main categories:
1. Methods based mainly on flow data.
2. Methods based mainly on rainfall data.
(discussion on the methods is not scope of this course)
11
13. OGEE OR OVERFLOW SPILLWAYS
The ogee or overflow spillway is the most common type of spillway. It
has a control weir that is Ogee or S-shaped. It is a gravity structure
requiring sound foundation and is preferably located in the main river
channel.
13
14. OGEE OR OVERFLOW SPILLWAYS
The basic shape of the overfall (ogee) spillway is derived from the
lower envelope of the overall nappe flowing over a high vertical
rectangular notch with an approach velocity, Vo,=0 and a fully aerated
space beneath the nappe (p=po)
14
15. OGEE OR OVERFLOW SPILLWAYS
DISCHARGE CHARACTERISTICS
Similar to the crest profile, the discharge characteristics of the standard
spillway can also be derived from the characteristics of the sharp
crested weir. The weir equation in the form:
If the discharge, Q, is used as the design discharge in above Eq, then the term
He will be the corresponding design head (Hd) plus the velocity head (Ha). i.e.,
He= Hd +Ha
For high ogee spillways, the velocity head is very small, and He≅ Hd.
2/3
2 eLHgCQ =
He
15
16. OGEE OR OVERFLOW SPILLWAYS
Overflow spillways are named as high-overflow, and low-overflow
depending upon to the relative upstream depth P/HD.
In high-overflow spillways, this ratio is (P/HD>1.33) and the approach
velocity is generally negligible.
Low spillways have appreciable approach velocity, which affects both
the shape of the crest and the discharge coefficients.
17. OGEE OR OVERFLOW SPILLWAYS
Definition sketch of overflow spillway cross-section
19. OGEE OR OVERFLOW SPILLWAYS
Figure gives variation of CD, the value of C when H equals the design
head HD, with the relative upstream depth P/HD. Here P is the height of
the spillway crest with respect to the channel bed.
20. OGEE OR OVERFLOW SPILLWAYS
Overflow spillways
frequently use undershot
radial gates for releases
over the dam. The
governing equation for
gated flows:
Where C is a coefficient of
discharge, and H1 and H2
are total heads to the
bottom and top of the gate
opening. The coefficient C
is a function of geometry
and the ratio d/H1, where d
is the gate aperture.
21. OGEE OR OVERFLOW SPILLWAYS
THE SPILLWAY CREST PROFILE
On the crest shape based on a design head, HD, when the actual head
is less than HD, the trajectory of the nappe falls below the crest profile,
creating positive pressures on the crest, thereby reducing the
discharge. On the other hand, with a higher than design head, the
nappe-trajectory is higher than crest, which creates negative pressure
pockets and results in increased discharge.
H=HD
H>HD
H<HD
23. OGEE OR OVERFLOW SPILLWAYS
THE SPILLWAY CREST PROFILE
Accordingly, it is considered desirable to under design the crest shape
of a high overflow spillway for a design head, HD, less than the head on
the crest corresponding to the maximum reservoir level, He (~Hmax).
However, with too much negative pressure, cavitation may occur. The
U.S. Bureau of Reclamation (1988) recommendation has been that
He/HD should not exceed 1.33.
The Corps of Engineers (COE) has accordingly recommended that a
spillway crest be designed so that the maximum expected head will
result in an average pressure on the crest no lower than (-4.50m) of
water head (U.S. Department of Army, 1986). Pressures of (-4.50m)
can be approximated by the following equations (Reese and Maynord,
1987).
24. OGEE OR OVERFLOW SPILLWAYS
THE SPILLWAY CREST PROFILE
He/HD <=1.33
25. OGEE OR OVERFLOW SPILLWAYS
THE SPILLWAY CREST PROFILE
Crest shapes have been studied extensively in the USBR hydraulic
laboratories with various approach depths. On the basis of the USBR
data, the US Army Corps of Engineers, WES (1952)** has developed
several standard shapes, designated as WES standard spillway
shapes, represented on the downstream of the crest axis by the
equation:
**WES Spillway for Genegantslet dam,. New York, Tech Memo 2–351, 1952.
27. OGEE OR OVERFLOW SPILLWAYS
THE SPILLWAY CREST PROFILE (typical values)
28. OGEE OR OVERFLOW SPILLWAYS
In the revised procedure developed by Murphy (1973), using the same
basic data of USBR, the upstream quadrant was shaped as an ellipse
with the equation
and the downstream profile conformed to the equation
Where K is a parameter depending on the ratio approach depth and
design head
For vertical u/s face
origin at the base of apex
29. OGEE OR OVERFLOW SPILLWAYS
Figure. Coordinate coefficients for spillway crest (USACE, 1986)
31. OGEE OR OVERFLOW SPILLWAYS
In a high-overflow section, the crest profile merges with the straight
downstream section of slope α, as shown in Fig. (i.e., dy/dx = α).
Differentiation and expressing that in terms of x
yield the distance to the position of downstream tangent as follows:
where
xDT = Horizontal distance from
the apex to the downstream
tangent point
α = Slope of the downstream
face.
32. OGEE OR OVERFLOW SPILLWAYS
With respect to origin at the apex, the equation of the elliptical shape
for upstream quadrant is expressed as,
where
x = Horizontal coordinate, positive to the right
y = Vertical coordinate, positive downward
A, B = One-half of the ellipse axes, as given in Fig. above for various
values of approach depth and design head.
33. OGEE OR OVERFLOW SPILLWAYS
For a inclined upstream face of slope
FS, the point of tangency with elliptical
shape can be determined by the
following equation.
34. OGEE OR OVERFLOW SPILLWAYS
The coefficient of discharge (or say discharge) is influenced by a
number of factors such as
(1) the relation of the actual crest shape to the ideal nappe shape,
(2) the depth of approach,
(3) the inclination of the upstream face,
(4) the contraction caused by the crest piers and abutment,
(5) the interference due to downstream apron, and
(6) the submergence of the crest due to downstream water level.
35. OGEE OR OVERFLOW SPILLWAYS
(1). The relation of the
actual crest shape to the
ideal nappe shape,
R. M. Khatsuria, Hydraulics of Spillways and Energy Dissipators,
36. OGEE OR OVERFLOW SPILLWAYS
(2) the depth of approach
R. M. Khatsuria, Hydraulics of Spillways and Energy Dissipators,
37. OGEE OR OVERFLOW SPILLWAYS
(3) the inclination of the upstream face
R. M. Khatsuria, Hydraulics of Spillways and Energy Dissipators,
38. OGEE OR OVERFLOW SPILLWAYS
(4) The effective length (L’) of Ogee spillway
Crest piers and abutments cause contraction of the flow, reduction in
the effective length of the crest, and cause reduction in the discharge
as compared to that of an otherwise uncontrolled crest. The following
relationship applies:
The values of KP and Ka depend mainly upon the shape of the piers
and that of the abutments.
R. M. Khatsuria, Hydraulics of Spillways and Energy Dissipators,
41. OGEE OR OVERFLOW SPILLWAYS
(5 & 6): Submerged Discharge on Overflow Spillways
The coefficient of discharge decreases under the condition of
submergence. Submergence can result from either excessive tailwater
depth or changed crest profile.
The effect of tailwater submergence on the coefficient of discharge
depends upon the degree of submergence defined by hd/He and the
downstream apron position, (hd+d)/He shown in Fig. (7.5).
For a value of (hd+d)/He up to approximately 2, the reduction in the
coefficient depends on the factor (hd+d)/He and is independent of hd/He
as shown in Fig. (7.5.a), i.e., it is subject to apron effects only.
42. OGEE OR OVERFLOW SPILLWAYS
(5 & 6): Submerged Discharge on Overflow Spillways
Atıl BULU, Lecture noted of water resources, Istanbul Technical University
43. OGEE OR OVERFLOW SPILLWAYS
When (hd+d)/He is above 5,
the reduction depends only
on hd/He as shown in Fig.
(7.4.b), i.e., tailwater effects
control.
For (hd+d)/He between 2 and
5, the reduction of the
coefficient depends on both
factors, given in Fig. (7.5.c).
44. OGEE OR OVERFLOW SPILLWAYS
SPILLWAY TOE
The spillway toe is the junction between the discharge channel and the
energy dissipator. Its function is to guide the flow passing down the
spillway and smoothly in the energy dissipator
A minimum radius of 3 times the depth of flow entering the toe is
recommended.
45. OGEE OR OVERFLOW SPILLWAYS
EXAMPLE 7.1: Design an overflow spillway section for a design
discharge of 1500 m3/sec. The upstream water surface level is at
elevation 240m and the upstream channel floor is at 200 m. The
spillway, having a vertical face, is 50 m long.
46. OGEE OR OVERFLOW SPILLWAYS
Solution:
1. Assuming a high overflow spillway section, for P/HD ≥ 3, discharge
coefficient CD =0.49 from Fig.
2. From the discharge equation
47. OGEE OR OVERFLOW SPILLWAYS
5. Calculate height of the crest,
P = 40.00 − 5.73 = 34.27m
6. Calculate design head
Since He=5.76 m<10m
Design head=HD=0.7He=0.7*5.76=4.03m
7. Calculate P/HD
P/HD=34.27/4.03=8.5 >1.33 high overflow
48. OGEE OR OVERFLOW SPILLWAYS
8. Shape of downstream quadrant
for P/HD=8.5 K= 2 (from Fig)
Therefore,
49. OGEE OR OVERFLOW SPILLWAYS
Coordinates of the downstream shape computed by the equation
are as follows:
9. Calculate point of tangency: Assume a downstream slope of (2/1).
From Eq.
50. OGEE OR OVERFLOW SPILLWAYS
10. Shape of upstream quadrant:
Eq.
Therefore ,
51. OGEE OR OVERFLOW SPILLWAYS
Coordinates of the downstream shape computed by
the equation are as follows:
52. OGEE OR OVERFLOW SPILLWAYS
sketch of overflow spillway cross-section
53. OGEE OR OVERFLOW SPILLWAYS
EXAMPLE 7.2: A spillway has been designed for a head of 2.80 m with
a length 200 m. The discharge coefficient is C = 0.49. Calculate the
discharge for this head.
What will the discharge be for heads of 0.20 m and 1.50 m?
What is the maximum discharge that can be passed over this spillway
without cavitation?
57. OGEE OR OVERFLOW SPILLWAYS
EXAMPLE 7.3: Determine the length of an overflow spillway to pass 60
m3/s with a depth of flow upstream not to exceed 1.50 m above the
crest. The spillway is 2.50 m high. The upstream face is sloped 1/1. For
60 m3/s, the tailwater rises 1.00 m above the crest. The spillway is
designed for the maximum head.
58. OGEE OR OVERFLOW SPILLWAYS
1. Since the spillway is designed for maximum head,
HD= He = 1.50 (without the approach velocity head)
2. From the given figure,
>2 but <5
62. OGEE OR OVERFLOW SPILLWAYS
Problem 1:
Design a suitable section for the overflow portion of a concrete gravity
dam having the downstream face sloping at a slope of 0.7H: 1V. The
design discharge for the spillway is 8,000 m3/s. The height of the
spillway crest is kept at RL 204.0 m. The average river bed level at the
site is 100.0 m. Thickness of each pier may be taken to be 2.5 m.
(Take He=HD)
63. OGEE OR OVERFLOW SPILLWAYS
Problem 2:
Design a suitable section for the overflow portion of a concrete gravity
dam having the downstream face sloping at a slope of 0.7H: 1V. The
design discharge for the spillway is 8,000 m3/s. The height of the
spillway crest is kept at RL 204.0 m. The average river bed level at the
site is 100.0 m. The spillway length consists of 6 spans having a clear
width of 10 m each. Thickness of each pier may be taken to be 2.5 m.
(Take He=HD)
64. THANK YOU
Slides are prepared from various sources(References). It may have
discrepancies/ inconsistency. If you find any, kindly rechecked with
sources list in “references” .
64
66. LEARNING OUTCOME
After taking this lecture, students should be able to:
(1). Obtain knowledge on energy dissipators (stilling basin)
used in hydraulic structures and their design guide lines
(2). Apply the design guide lines for the design of selected
energy dissipators
66
References:
Khatsuria , R. M., Hydraulics of Spillways and Energy Dissipators,
Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan, Hydraulic Structures, 4th Ed. CRC Press
Santosh, K. G., Irrigation Engineering and Hydraulic Structures, Khanna Publishers
Mays, L. W., Hydraulic design handbook (CHAPTER 18), Mcgraw hills
67. ENERGY DISSIPATION
Dissipation of the kinetic energy generated at the base of a spillway is
essential for bringing the flow into the downstream river to the normal—
almost pre-dam— condition in as short of a distance as possible.
This is necessary, not only to protect the riverbed and banks from
erosion, but also to ensure that the dam itself and adjoining structures
like powerhouse, canal, etc. are not undermined by the high velocity
turbulent flow.
Low velocity
Very high velocity
V1=(2gH1)0.5
y1=q/V1
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68. ENERGY DISSIPATION
CLASSIFICATION
1. Based on hydraulic action: Turbulence and internal friction as in
hydraulic jump stilling basins, roller buckets, and impact and pool
diffusion as with ski jump buckets and plunge pools.
2. Based on the mode of dissipation: Horizontal as in the hydraulic
jump, vertical as with ski jump buckets/free jets, and oblique as with
spatial and cross flows. The vertical dissipation may be in the downward
direction as with free jets and plunge pools and in upward direction as
with roller buckets.
3. Based on geometry or form of the main flow: Situations involving
sudden expansion, contraction, counter acting flows, impact, etc.
4. Based on the geometry or form of the structure: Stilling basin
employs hydraulic jump with or without appurtenances like chute blocks,
baffle piers, etc. Buckets (ski jump or flip buckets) include special
shapes like serrated, dentated buckets, and roller buckets that are either
solid roller bucket or slotted buckets.
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69. ENERGY DISSIPATION
PRINICIPAL TYPES OF ENERGY DISSIPATORS
The energy dissipators for spillways can be grouped under the following
five categories:
1. Hydraulic jump stilling basins
2. Free jets and trajectory buckets
3. Roller buckets
4. Dissipation by spatial hydraulic jump
5. Impact type energy dissipators
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70. ENERGY DISSIPATION
ANALYSIS OF PARAMETERS
E
g
V
y
g
V
y
g
V
y o
o ∆++=+=+
222
2
2
2
2
2
1
2
∆E= Energy dissipation between
u/s and d/s
Energy equation:
Mass conservation:
Q1=Q2=Q3
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71. ENERGY DISSIPATION
In case of hydraulic jump at the d/s
V1=(2gH1)0.5
y1=q/V1
Thus, q/y1=(2gH1])0.5
+−
+==∆
g
V
y
g
V
yE
22
2
2
1
2
2
2
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Energy dissipation
Assumption of Horizontal bed !!!
72. ENERGY DISSIPATION
Hence, for a given discharge intensity and given height of spillway, y1 is
fixed and thus y2 (required for the formation of hydraulic jump) is also
fixed.
But the availability of a depth equal to y2 in the channel on the d/s cannot
be guaranteed as it depends upon the tail water level, which depends
upon the hydraulic dimensions and slope of the river channel at d/s.
The problem should, therefore, be analyzed before any solution can be
found by plotting the following curves:
Tail Water Curve (TW Curve): A graph plotted between q and tail water
depth,
Jump Height Curve (JH Curve) also called y2 curve: A curve plotted on
the same graph, between q and y2,
72
75. ENERGY DISSIPATION
(1). When TW curve coincides with y2 curve
This is the most ideaI condition for jump formation. The hydraulic
jump will form at the toe of the spillway at all discharges. In such a case,
a simple concrete apron of length equivalent to length of jump (e.g.,5 [y2
- y1]) is generally sufficient to provide protection
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76. ENERGY DISSIPATION
(A). When TW curve is above the y2 curve
When y2 is always below the tail water, the jump forming at toe will be
drowned out by the· tail water, and little energy will be dissipated.
The problem can be solved by:
(i). constructing a sloping apron above the river bed level
(ii). providing a roller bucket type of energy dissipator
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78. ENERGY DISSIPATION
(B). When TW curve is below the y2 curve
When the tail water depth is insufficient or low at all discharges, the
following solution can be applied:
(i). Ski jump bucket type: This type of energy dissipator requires
sound and rocky river bed, because a part of the energy dissipation
takes place by impact, although some of the energy is dissipated in air
by diffusion and aeration
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82. ENERGY DISSIPATION
(D). When TW curve is above the y2 curve at low discharges and
below the y2 curve at high discharges: In this case, at low
discharges, the jump will be drowned and at high discharges, tail water
depth is insufficient. The following solutions can be applied by:
(i). Providing a sloping apron partly above and partly below the river bed
(ii). A combination of energy dissipator performing as a hydraulic jump
apron for low discharges and flip bucket for high discharges
At low discharges, the jump
will form on the apron above
the river bed.
Similarly, at high discharges,
the jump will form on the
apron below the river bed
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83. ENERGY DISSIPATION
(C). When TW curve is below the y2 curve at low discharges and
above the y2 curve at high discharges (inverse of case D)
83
The following solutions can be applied:
(i). Sloping-cum-horizontal apron such that the
jump forms on the horizontal portion for low
discharges and on the sloping portion for high
discharges
84. ENERGY DISSIPATION IN HYDRAULIC JUMP
Hydraulic jump can be used as Energy Dissipator
+−
+=∆
g
V
y
g
V
yE
22
2
2
1
2
2
2
yqV /=
However, the real problem in the design of stilling basins, is not the absolute
dissipation of energy, but is the dissipation of this energy in as short a length
as possible.
−
=∆
21
12
4 yy
yy
E
=
gy
V
F
84
V1=(2gH1)0.5
y1=q/V1
Thus, q/y1=(2gH1])0.5
85. STILLING BASIN
• In general, a stilling basin may be defined, as a structure in which the
energy dissipating action is confined.
• If the phenomenon of hydraulic jump is basically used for dissipating
this energy; it may be called a hydraulic jump type of stilling basin.
• The auxiliary devices may be used as additional measures for
controlling the jump, etc.
• Stilling basins are placed at the ends of dam spillways and at the
ends of steep-sloped canal sections where elevation change has
generated high kinetic energy.
• Stilling basin come in a variety of types and can either contain a
straight drop to a lower elevation or an inclined chute
• Inclined chutes are the most common design for stilling basins
and the most used inclined chutes are: USBR Stilling Basins
Type II-IV, SAF Stilling Basins
85
86. STILLING BASIN
In practice, the following types are highly recommended:
• USBR Type II basin for large structures and Fr > 4.5;
• USBR Type III basin and the SAF basin for small structures;
• USBR Type IV basin for oscillating jump flow conditions
The designs are selected based on the Froude Number of the flow and
the flow velocity:
1
1
1
1
1
y
q
V
gy
V
Fr
=
=
86
88. STANDARD STILLING BASINS
• Chute blocks -concrete blocks built into the inclined sections of the
spillway. These features are commonly placed at the head of the
stilling basin to create turbulence prior to the hydraulic jump
• Baffle blocks -freestanding concrete blocks built in the main basin.
These blocks are only used for flows <20m/s due to the high force
they are subjected to and the potential for cavitation
• End sills -a built-up lip at the tail of the basin, with or without blocks.
The sill height has the most significant impact on energy dissipation
and taller sills are used to reduce the overall length of the stilling
basin
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94. ENERGY DISSIPATION
DEFLECTOR BUCKETS
Sometimes it is convenient to direct spillway into the river without
passing through a stilling basin. This is accomplished with a deflector
bucket designed so that the jet strikes the riverbed a safe distance from
the spillway and dam. This type of spillway is often called a flip bucket
or ski jump spillway.
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95. ENERGY DISSIPATION
The trajectory of the jump
Where,
hv = Velocity head
d = Thickness of the jump
When the free jet discharging from the deflection bucket falls into an
erodible riverbed, a plunge pool is eroded to a depth, D, given by:
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96. THANK YOU
Slides are prepared from various sources(References). It may have
discrepancies/ inconsistency. If you find any, kindly rechecked with
sources list in “references” .
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