Hydraulics IIT

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IntroductionUnit 1

Free Surface Flows - Introduction

Historical Development of Hydraulics

History of Hydraulics in India

Classification of Flow

Unit 2

Channels and their Geometric PropertiesExamples

Pipe Flow and Free Surface Flow

Basic EquationsUnit 3

Continuity Equation

Energy in Free Surface Flow

Basic Momentum Equation

Velocity DistributionUnit 4

Velocity Measurement and Distribution

Discharge Measurement by Velocity-area Method

Radio-active tracer technique for Measurement of RiverDischarges

Measurement of Flow of Water and the Limitations of Velocity-

area Method

Errors in Depth Measurement in High Velocity Flows

Unit 5

Secondary Current and Spiral Flow

Unit 6

Energy and Momentum Coefficients-Derivation

Energy and Momentum Coefficients for Different Velocity

Distributions

Comparison between Momentum and Energy Equation

Unit 7Pressure Distribution

Specific EnergyUnit 8

Specific Energy Equations for Rectangular Channels

Application of Specific Energy

Problems

Unit 9

Specific Force

Transition-Problems

Application of Specific Force and Specific Energy

Transition in Field

Critical FlowUnit 10

Characteristics of Critical Flow

Occurrence of Critical Flow

Unit 11

Critical Depth in Trapezoidal & Circular Channels

Hydraulic Exponent for Critical Flow

Problem

Unit 12


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Critical Flow Depth Computations

Problems

Flow MeasurementUnit 13

Measuring Flumes

Critical Depth Flumes

Unit 14

Weris-IntroductionTypes of Control Structures

Proportional weirs

Flow Over weirs

Polygonal weirs

Special types of weirs

Broad Crested weirs

Different types of Broad Crested weirs

Bear Trap weir

Unit 15

Flow below a Sluice Gate

Brink Depth

Modern Measurements of Flow MeasurementsOutlets & Modules

Errors in Measurements

International Standards for Flow Measurement in Open Channel

Uniform FlowUnit 16

Concept of Uniform Flow

Derivation of Uniform Flow Equations

Resistance in Open Channel Hydraulics

History of Uniform Flow Velocity and Resistance Factor

Unit 17

Friction

Ganguillet and Kutter FormulaConveyance

Section Factor for Uniform Flow Computation

Unit 18

Hydraulic Exponent for Uniform Flow Computation

Maximum Discharge

Classification of bed Slope

Computations

Unit 19

Problems-Maximum Discharge

Problem-Irregular Channel

Solution of algebraic or Transcendental Equation by Bisection

Method

Solution of Manning Equation by Newton Raphson Method

Unit 20

Slope-area Method

Normal & Critical Slopes

Design of CanalsUnit 21

Design of Canals

Typical Canal Cross Sections


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Unit 22

Lining the Canals

Seepage Prevention with Impermeable membranes

Failure of Canal Lining

Most Efficient Hydraulic Section

Design of Unlined Channels

Examples & Problems

Gradually Varied FlowUnit 23

Introduction

Dynamic Equation for Steady Gradually Varied Flow

Classification of Gradually Varied Flow Profiles

Unit 24

Real Life Cases of Water Surface Profiles

Sketching of Composite Water Surface Profiles

Examples

Unit 25

Computation of Gradually Varied Flow

Example

Unit 26Standard Step Method

Example

Unit 27

Integration of Differential Equation

Improved Euler Method

Fourth-order Runga-Kutta Method

HEC-2

Hydraulic JumpUnit 28

Normal Hydraulic Jumps

Classification of Jumps

Momentum EquationGeneral Hydraulic Jump Equation

Unit 29

Energy loss in the Jump

Turbulent Characteristics of the Jump

Pressure Distribution in the Jump

Velocity Distribution in Hydraulic Jump

Length of the Jump

Unit 30

Air Entrainment Characteristics of the Jump

Pre Entrained Hydraulic Jump

Air Concentration Distribution along the Jump

Decay of Turbulence Downstream from a Stilling Basin

Unit 31

Hydraulic Jumps in Sloping Channels

Unit 32

Sequent Depth Tail Water Relationship Stilling Basin

Baffle Stilling Basin

Bhavani Type Stilling Basin

Stilling Basin in Sudden Expansion

Slotted Bucket Stilling Basin


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SpillwaysUnit 33

Spillways - Introduction

Unit 34

Siphon Spillway

Unit 35

Chute Spillway

Stepped SpillwayFlow in Bends

Unit 36

Introduction

Classification of River Bends

Transverse Water Surface Slope in Bends

Superelevation

Velocity Distribution in Bends

Unsteady FlowUnit 37

Introduction

Basic TerminologyClassification of waves

Ocean Waves

Tides

Nature of waves

Unit 38

Surge Computation

Example-1

Example-2Unit 39

Gradually Varied unsteady Flow

Celerity

Unit 40Method of Characteristics

Method of Specified Intervals

Unit 41

Dam break Problem-Introduction

History of Dam Failures

Causes of Dam Failures

Routing

Case Study-Dam Break Analysis for Kali River

Self Aerated FlowsUnit 42

Self Aerated Flow-Definition of Terms and Instrumentation

Characteristics of Self Aerated FlowsUnit 43

Measurement in Self Aerated Flows

Experimental Investigation

Bhakra Dam SpillwayA Case Study


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HYDRAULICS - FREE SURFACE FLOWS

1.1 Introduction

A fluid is any substance that deforms continuously when subjected to shear stress, no

matter how small the shear stress is.

Shear force is the force component tangent to the surface. Average shear stress is the

shear force per unit area.

Fluids can be classified as ideal fluids and real fluids.

Ideal fluids are those which are incompressible with zero viscosity and, shear stress is

always zero. Ideal fluid is hypothetical.

Fluids with viscosity are known as real fluids.

Example: Water, Milk, and Honey etc.,Then real fluids are classified as Newtonian and

non-Newtonian. Box 1.1.

Examples of non-Newtonian fluids are

Thixotrophic substance (thixotrophic jelly paints), ideal plastic, Bingham plastic (sewage

sludge), pseudo plastic (clay, milk, cement), dilatant substance(quick sand) etc. Fig 1.1.


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Yield stress Shear stress

Figure 1.1 Rheological diagram

Box 1.1 Newtonian flu ids fo llow the law of viscosi ty

du

= dy 1.1

in which , is the Shear stress, is the viscosity co-efficient anddu

dy is the

velocity gradient in y direction.

Viscosity is a fluid property and is known as dynamic viscosity. The equation

1.1 is known as Newton's law of viscosity.

The kinematic viscosity is given by the ratio of dynamic viscosity to mass

density of fluid .

= 1.2


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Dimensions and units

Coefficient of Dynamic viscos ity

-2 -1 -1-1 -1M L T Nsm kg m s Poise

-1 -110 poise = 1 kg m s , Pa s (Pascal seconds)

-3 -1 -1Example: Water: 1.14 x 10 kg m s ;

-5 -1 -1Air : 1.78 x 10 kg m s

2 -1 2 -1 4 = L T m s , 10 Stokes =1

or or

=

=

2 -1m s

-6 2 -1 -5 2 -1Example: water 1.14 x 10 m s at 15 C , air 1.46 x 10 m s

However viscosity depends on temperature.

Physical properties of water at atmospheric pressure and S.I units are given

Mass Density of water : Mass per unit Volume.

-3 -3 -3=[ML ]; kg m , =1000kg m

-3Mass density of air = 1.23 kg m

5 -2at atmospheric pressure of 1.013 x 10 N m and temperature 288.15 K.

weight per unit volume

is known as specific weight

-3N m

3 -39.81 x 10 N mof water

-3= 12.07 N mof air

g

=

=

In free surface flows water is the dominating fluid. Water is a basic element and

supports the life system.

Proper control and management of water is required for sustaining the life on earth.

Hydraulics forms a part of water resources engineering. The free surface flows deals

with the movement of surface water in rivers, stream, canals etc. In order to understand

the mechanism of free surface flows, the different classification of them is to be

understood.


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1.2 HISTORICAL DEVELOPMENT OF HYDRAULICS

Hydraulic Engineering has served the mankind althrough the ages by providing drinking

water as well as protective measures against floods and storms. In the course of history

it has made the water resource available for human uses of many kinds. Management

of the world's water is a complex task and both its scope and its importance continue to

grow.

In course of time mankind has not only diverted and used the waters of the world for its

purposes, but by engaging nature into its service has turned deserts into fertile land

(e.g. Rajasthan Indira Gandhi Canal Project). Natural habitat is threatened in more and

more parts of the world by an ever-growing human population. Time has come for

formulation of the new value system. Thus long term needs are not only food, water and

shelter but also for an aesthetically pleasing, healthy, nurturing environment.

Sustainable development is "mantra" of the future.Method of teaching Hydraulic Engineering has undergone several changes considering

the availability of computers, GPS, GIS, Remote sensing data, and web based tools.

1.2.1 The stages of Development

1950s Experimental hydraulics - empirical Hydraulics - Development of Engineering

hydraulics.1960s Fundamental Research in unsteady flows, Open channel and ground water.

1970s Gathering of large data - hydrologic engineering - Flood control.

1980sInitial awareness on the Environmental aspects. Large scale water Resourcesplanning, stochastic hydrology, System Analysis, distributed rainfall runoffmodeling.

Early1990s

Modeling, urban hydrology, disaster management including floods,computational engineering, CAD in hydraulics, Environmental hydraulics,water quality - quantity integration, GIS based distributed modeling inhydrology, Decision support systems.

Late1990s

Integrating of hydraulics with water resources engineering for sustainable

development using GIS, GPS, Remote sensing - Hydro 2004 informatics,Enviro informatics, Physical hydrology , space and Time scales, Climatechange and its impact on river basin, planning and management. Softcomputing (ANN, GA etc.,) IT impact on Water Data base and knowledge,Integrated River basin Development. Reliability and Risk tools. WEB - WaterEarth Biota. Alternate sources of energy.


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1.2.2 Future

Broad scope for specialisation in aggregation of many integrated aspects of the water

system.

To design integrated systems and integration of numerical modeling into information

systems.

Globalisation of water research and exchange through Internet and its impact on

sustainable development.

Integrating sociology, economics, biology, environment - Hydro bio modeling.

Global water markets, participatory approach.


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1.3 HISTORY OF HYDRAULICS IN INDIA

"ONE WHO SOLVES THE PROBLEM OF WATER IS WORTH OF TWO NOBEL

PRIZES,ONE FOR PEACE AND ONE FOR SCIENCE" -JOHN.F. KENNEDY.

1.3.1 Growth of Hydraulics and Irrigation Research In India-

Introduction (CBI&P 1979)

During the nineteenth and early part of twentieth century, hydraulic and irrigation

problems were being tackled mostly by engineering judgement based on experience.

However, many engineers, with intuitive insight and initiative gave deep thought to

various problems and arrived at valuable conclusions. They were the pioneers of of

individual research exploring virgin ground in advance of the era of organised research

with the aid of models and other experimental facilities and techniques. Roorkee

professional papers on Indian Engineering (1863-1886) contain many original and

useful ideas on the theory of flow in artificial earthen channels, measures for efficient

distribution of irrigation waters and the design of hydraulic structures justifying high

tribute to these pioneer researchers. In 1864, fundamental ideas on the causes of silting

and scouring were initiated. At about the same time, tables of mean velocities and

depths were evolved for North Indian Canals. The Ogee type fall was originated on the

Ganga Canal (by 1870). Between 1874-79, Cunningham made a valuable contribution

in the techniques of the measurements of discharges and determination of velocities. By

about 1880, training of rivers with embankments combined with a system of groynes

was experimented in the field. During 1881 - 82, Kennedy made important estimations

of the losses by evaporation and absorption in the Bari Doab Canal. Cotton in the south

and Cauteley in the north produced some of the most imaginative river conservation

schemes over a hundred years ahead of the time they were realized to be essential and

taken up for implementation.


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Cottonreddypalem, Andhra Pradesh, several other villages rooted in the Cotton name

and several generations of males with variations of Cotton name, all celebrated Sir

Arthur Cotton's bicentenary in the Godavari District, David Abbott of the British Deputy

High Commission, was present at the Rajahmundry celebrations. Cottons contribution

to making the Krishna- Godavari area the granary of South India.

"Father of Irrigation", "Sculptor of Deltas". It is to be noted that the 3.685 km long

Dowleswaram Barrage across the Godavari, built at a cost of 120,000 over five years,

turned a flood and drought prone area into million acres of flourishing paddy and

sugarcane, where the rent of an acre of paddy land today is Rs.1 lakh. "When the

farmer tills his land (here) or receives the money for his produce, he thinks one man

Sir Arthur Cotton".

A Sir Arthur Cotton Museum is to be set up at the dam site at a cost of Rs. 1 crore and,

more significantly, a Sir Arthur Cotton Memorial Agricultural Service Centre is being set

up over 15 acres, at Bobbarlanka, 20 km from Rajahmundry and near Dowleswaram, at

a cost of Rs. 1 1/4 crore.

He was the beloved of the Ryots (farmers).

General Sir Arthur Cotton: His life and work, is described as "a classic on India's

development". "India had taken hold of him. Not the India of Romance, but the India of

need". The 500 page book was reprinted by the Institution of Engineers (India, in 1964).

Cotton had spent two years in Vishakhapatnam before moving on to Rajahmundry and

his greatest work. While at Vizag, he had built the St. John's Church in Waltair, and

groynes to protect the beach. He also predicted that Vizag would one day be a great

port. Truly was he a farsighted engineer.

The reports of the select committee admitted the success of all the irrigation works in

the Madras delta with which Sir Arthur Cotton's name is so honourably associated,

namely the Cauvery, Kistna and Godavari, and indicated that if there was any financial


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failure in other case in the past, the main cause appears to be the want of ability or

energy on the part of the officers of the Public Works Department and their reliance on

hasty generalisation.

Cotton use to use to tell his daughter, "Do something, my girl, do something. Never be

idle for a single moment. Remember Time is short, Eternity is near."

He was 96 and had not suffered any major illness. On the night of July 14th, 1899 he

became feverish and restless and began slowly sinking. The end when it came was

'perfect peace'.

"His life, judged by any test was one of the true greatness, such as is only given to vary

few to attain in the world. He has left behind him a fame and a name which must

endure to all times". Sir Richard Sankey, R.E., K.C.B., wrote in a letter to Lady Arthur

on hearing of her husband's death.

Reference

Madras Musings, October 1 - 15, 1999.

During 18th and 19th centuries, the irrigation works in India were neglected by East

India Company so much so that Arthur Cotton, Royal Engineer working with Madras

Presidency complained bitterly in 1821 against the policy of apathy of the government.

In the history of India, 18th and 19th centuries saw some of the worst famines in the

north as well as south. As a result, efforts were made for saving agriculture. In the field

of irrigation, these included reopening of Western and Eastern Yamuna canals,

renovating Hissar branch canal and repairing Grand Anicut on Kaveri during 1810 -

1836 period.

Col. Proby T. Cautley of the Royal Artillery (1802 - 1871), was the superintendent of the

canals in the North-Western Province and director of the proposed Ganga Canal. In

1838, Cautley submitted to the government the first proposal to take a canal from


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Ganga at Haridwar.

Governor General Lord Hardinge visited the site personally and authorized the

construction of canal in 1842.

James Thomason (1804 - 1853) who was then Lt. Governor of Northern Province fully

supported the proposal of Ganga canal.

The excavation of the canal was started in 1842 and water entered the canal in 1854. It

is interesting to note that when the canal was designed, the only hydraulic principles

known were continuity equation and resistance law. And yet the unlined canal designed

to carry discharge of approximately 300 cumecs as well as the cross drainage works

such as Solani aqueduct, siphons and level crossings which are still intact and

functioning well and have stood the test of time.

It is worth mentioning that Cautley became involved in public controversy over the

design of Ganga canal against Arthur Cotton in 1863 - 65 and was publicly censured in

the columns of the Times. However, he was officially exonerated by the Governor

General in 1865.

LOOKING BACK

If we have done our duty at least to this part of India, and have founded a system which

will be a source of strength and wealth and credit to us as a nation, it is due to ONE

MASTER MIND Which, with admirable industry and perseverance, inspite of every

discouragement, has worked out this great result. Other able and devoted officers have

caught Colonel Cot-tons spirit and have rendered invaluable aid under his advice and

direction, but for this first creation of genius we are indebted to him alone.

Colonel Cottons name will be venerated by millions yet unborn, when many, who now

occupy a much larger place in the public view, will be forgotten; but, although it

concerns not him, it would be, for our own sake, a matter of regret if Colonel Cotton

were not to receive due acknowledgement during his lifetime. - Minute by the


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Government of Madras. Sir Charles Trevelyan, Governor, in his review of the Public

Works Department on May 15th, 1858.

General Sir Arthur Cotton, R.E., K.C.S.I., was born in Cheshire, England on May 15,

1803, the tenth son of Henry Calveley Cotton. Lt. Arthur Cotton arrived in Madras in

September 1821 and was attached to the office of the Chief Engineer for the

presidency. In May 1822, he was posted as an Assistant to the Superintending

Engineer of the Tank department, Southern Division.

Survey of the Pamban Pass to propose an enlargement of the pass for the passage of

oceangoing steamers from the West Coast to the East Coast ports. This was the

beginning of the Sethusamudram Project we have been talking of for a century ! .

In 1829, he was promoted as Captain and given separate charge of the Cauvery

irrigation. He soon saw the need for saving the district from the ruin that was staring it

with barely any flow in the cauvery due to heavy silting at the Grand Anicut. He soon

evolved the scheme for erecting a control structure on the Coleroon at the Upper Anicut

and the opening up of scour vents in the old Grand Anicut. On January 1, 1830 the

great work of seven sluices was started. In 1832, got the project reports both for Upper

Anicut and the Lower Coleroon Anicut on the Coleroon ready. They were sanctioned by

the Government in time to get the preliminary work started before the freshes arrived in

June.The first bold step taken by Cotton was the construction of the Upper Coleroom

Dam at Mukkombu.

Mr. W.N. Kindersley, the Collector of the district, wrote there was not one individual in

the province who did not consider the Upper Anicut the greatest blessings that had ever

been conferred upon it. The name of the projector would, in Tanjore, survive those of

all the Europeans who had ever been connected with it.

At this distant date we fail to realize the great truth in these statements made and the

valuable contributions of this pioneer, Sir, Arthur Cotton. He always insisted on saying


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that the value of irrigation works was not to be measured simply by the additional

revenue yielded to the Government treasury, but that a much truer criterion would be

found in the enhancement of the income of the people and in the consequent saleable

value of the land itself. Irrigation brings with it prosperity to the region, some perceptible

and much more imperceptible and intangible.

The work that made a magical change in the hinterland of the delta of the River

Godavari, the masterpiece of the great thinker, the planner, the designer and the maker,

Major Arthur Cotton, was to come soon after.

Cotton, after a careful study of the sufferings of the people in the delta, while huge

volumes of floodwaters were being carried out to the sea day in and day out by the

mighty Godavari, reported to the Board of Revenue in May 1844 that the only way to

turn the Godavari district from being the poorest to nearly the richest in the presidency

was bringing in irrigation-cum-navigation facilities in the Delta by building an anicut

across the wide river.

Reference

Madras Musings-September 16-30, 1999.

Outstanding contributions to sub-surface and surface flow research came from Col.

Clibborn and Kennedy during 1890's. Col. Clibborn carried out the historic experiments

(1895-97) with Khanki sand to investigate the laws of flow of water through sand in

relation to weir design. Col.Clibborn's other contribution was on investigations on the

replenishment and velocity of flow of ground water in the Gangetic plains. In 1895, after

field experiments on the Upper Bari Doab Canal, Kennedy propounded his classical

relations between the critical velocity and channel depth as influencing channel design.

The early twentieth century has been notable for the rapid extension of irrigation in the

country and with it for the rigorous efforts on the investigations on the economic and


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reliable design of hydraulic structures, design of stable channels, efficient distribution

devices, weed control, anti-water logging measures and land reclamation.

Kennedy's classical equations for the design of channels were followed by Lindley's

relations in 1919 indeed the very concept of the regime theory itself. Between 1929-39,

Lacey's sustained and pioneering work led to the development of comprehensive

formulae for designing stable channels in alluvium. The thread was picked up by various

workers- principally, Inglis, Bose, Malhotra, Blench, et al. and this subject has continued

to be a subject of sustained interest in India.

Investigations for the control of sand entering channels attracted the attention of many

engineers also, Inglis, the father of hydraulic model research in India, demonstrated that

curvature of flow- or nature's way- was the dominant factor affecting surface and bed

flow and, therefore, the most effective way of controlling sand. In 1922, Eldsen initiated

the idea of the tunnel type of excluders, and in 1934 Nicholson built the first excluder at

the head of the Lower Chenab Canal at Khanki. King's investigations for exclusion of

heavy silt from canal by vaned pitching (1918) and with silt vanes (1920) were earlier

notable investigations in the same field.

India's contribution of the development of subsoil flow hydraulics in relation to the

design of weirs has indeed been unsurpassed. After Col. Clibborn's historic experiments

(1895-97) with Khanki sand, Khosla propounded (1929-36) the very valuable theory of

subsoil flow in relation to the design of weirs on permeable foundations. The first full

size experiments in the world was conducted during 1929-36 on the Panjnad Weir. This

was followed by laboratory research on models of Rasul Weir (1930-34) and Panjnad

Weir (1934-35) by Taylor and Uppal, and on electrical analogy models by Vaidyanathan

(1936) and others.

Efficient distribution of water from canals was another subject which attracted the

attention of engineers from early times. Up to the end of the nineteenth century,

ordinary canal outlets in the form of open cuts, pipe or barrel outlets were in vogue. In


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1882, Beresford introduced a general type of outlet with a 15.2 cm pipe with flap and

face walls. Since the beginning of this century, a number of investigators have studied

the various aspects of canal outlets and several types have been developed. The

earliest semi-modular type was in 1902 by Kennedy-the sill outlet. Kennedy's gauge

outlet was introduced in 1906which was further improved in 1915. By 1922 Kirkpatrick

on the Jamras (Sind) and Crump in Punjab developed semi-modules of the open flume

and the orifice types. Among the modules with moving parts, Visvesvarya's self acting

module (1904), Kennedy's outlet module (1906), Wilkins type (1913), Joshi's module

(1919) and Kenti's 'O' type module (1923) were the important developments. A module

without any moving parts had been developed by Gibb as far back as 1906 and it was

greatly improved later by experiments in Poona. Many silt extracting outlets were also

developed, the outstanding one being the Haigh's type in 1937. Valuable experiments

conducted on broad-crested weirs were utilised by Burkitt in developing the 'Head-less

meter.

Bharat Rathna Dr. Sir. Dr. Mokshagundam Visvesvaraya (1861 - 1962)

September 15 is a memorable day in the annals of the engineering community in

particular in this country. On this day 135 years ago, one of the greatest sons of India,

Dr. Sir. Mokshagundam Visvesvaraya, the towering personality in the history of Indian

engineering - was born at Muddenhalli in the Kolar district of Karnataka. Graduated from

the college of science, Poona in 1883, Visvesvaraya joined the Bombay PWD and rose

to the position of Chief Engineer. He worked ceaselessly throughout his life to bring

fruits of advanced science and technology to the doorsteps of the common man. On

retirement, his services were requisitioned by the Maharaja of the erstwhile Mysore

State, who appointed him as Dewan. The following years witnessed an era of planned

development and all-round growth. A visionary who could think ahead of his time,

Visvesvaraya realised that there could be no salvation for the people of the country

except judicious use of the results of technological innovations. In recognition of his

services to national development and for the cause of engineering, he was honoured by


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presentation of the country's highest award - Bharat Ratna - in 1955.

To perpetuate the memory of this great engineer-statesman, the Council of Institution of

Engineers India decided to observe September 15 each year as Engineer's Day and

evolved guidelines for celebrating the Day.

The State of Mysore has been well known for its engineers. Modern research as such in

engineering started about 1870's. The first claimant for leadership in engineering

research was Sri Adil Shah Dabe who constructed in the first decade of the 20 th

Century the Mari Kanave Dam with masonry in Surki mortar. It was easily the highest

dam at that time in the world constructed with a matrix other than cement.

The second decade of the 20th Century started with the advent of the world famous

Engineer Bharat Ratna Dr. Sir. M. Visvesvaraya at the helm of affairs in Engineering

and Administration. His pioneering works in the block system of Irrigation, Invention of

the automatic gates are well known. Under his leadership considerable progress in

research in the use of surki mortar for construction of hydraulic structures, gauging of

rivers, evaporation and seepage losses, etc,.

Ganesh Iyer during 1930's initiated research and experimentation on Volute siphons.

In the development of canal falls, the Ogee type was in use as early as 1870. The

trapezoidal notch fall was developed by 1894. With the mechanism of the energy of

flowing water and the formation of the standing wave becoming known better, the

standing wave flume type of fall was developed by Inglis by 1930.

Numerous investigators worked on the theory of the hydraulic jump which has helped

immensely in tackling various hydraulic problems. Important investigators on this

problem were Inglis and Joglekar (1924 - 1940), Coyler (1926), Lindley (1927), Montagu

(1929) and Crump (1930). Energy dissipation works below river and canal structures by

means of a cistern with baffles, deflectors and blocks were evolved with the help of


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model experiments by Bhandari and Uppal (1938) in the Punjab and by Inglis in Poona

(1935).

The control of rivers flowing through bridges and other structures by a system of guide

banks, first introduced by Bell in 1888, has subsequently been investigated extensively,

both on the model and in the field, and the system is now widely in use.

Losses by evaporation and percolation in canals were investigated by Kennedy on the

Bari Doab Canal as early as 1882 and further work was carried out by various

engineers.

The special Irrigation Research Division, created in the Bombay P.W.D. in 1916,

through efforts of Inglis, contributed a great deal in the field of organised irrigation

research. During 1916-1928, valuable investigations were made on the problems of

land drainage and reclamation, canal losses, canal lining, weed growth and improved

irrigation methods. In the field of hydrodynamic research with the aid of hydraulic

models, experiments on standing wave flumes, energy dissipation devices below falls,

cutwater and ease-water experiments for the best design of Sukkur Barrage piers are

few examples of early organised research.

With the realisation of the importance of model investigations, research centres at

Poona and Lahore were developed and new Research station started in United

Provinces (1938) and some other states. The attainment of Independence and

formulation of plans for a number of River valley Projects posed a multiplicity of

problems and it became necessary to expand the facilities at the existing research

centres and to open new centres of research, today, laboratories equipped for dealing

with the problems connected with River Valley Projects, including reservoir surveys,

testing of soils, concrete and other construction materials have been set up in most of

the states.


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1.3.2 CO-ORDINATION OF RESEARCH

The creation of the Central Board of Irrigation in 1927 was a sequel to the realisation of

the need for coordinating research activities at various centres. After Independence,

with growing realisation of the need for development of power the Board was

redesignated as the Central Board of Irrigation and Power. In addition, it co-ordinates

the national activities and functions as Indian National Committee for the International

Commission on Large Dams (ICOLD), International Commission on Irrigation and

Drainage (ICID), International Association for Hydraulic Research (IAHR), International

Water Resources Association (IWRA) and International Conference on Large High

Voltage Electric System (CIGRE). The board also actively collaborates with the Bureau

of Indian Standards, the Central Road Research Institute, the Council of Scientific and

Industrial Research, the Indian Council of Agricultural Research, the Department of

Science and Technology, the Seven Indian Institutes of Technology, the council of

Technology Education, Indian Institute of Science.

On the recommendations of an expert committee appointed by the board in 1958, a

scheme of research on fundamental and basic problems, relating to river valley projects

and flood control works was sanctioned. To start with 12 main topics were included for

study under the scheme. Till 1980's, the work under the scheme has increased to the

extent that there are 44 main topics presently under study at 16 State and Central

Research Stations and 12 technical institutions under the supervisory control of the

Board. The Board publishes every year the Annual Review Summaries of the work done

on these problems. A quarterly journal 'Irrigation and Power' brought out by the Board

contains papers on both basic and applied research in water and power engineering.

The papers contributed and discussed at Annual Research Sessions are brought out as

proceedings of these sessions.

Besides the journal and proceedings, publication of important researches relating to

specific subjects carried out by individuals or institutions are compiled as Board's

publications and these form useful authentic reference manuals with the irrigation and


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power engineers of the country. As part of the Research Studies the research stations

have prepared Reviews with Bibliographies as well as status reports on a number of

topics. These are also issued as publications of the Board. In late 70's a new periodical

'Irrigation and Power Research Digest' has been started to furnish the latest research

work done at various research stations to the research community.

1.3.3 RESEARCH ACTIVITY IN INDIA TODAY

There were sixteen major research stations in India (in 1980's) which were undertaking

research studies on various aspects of river valley developments and which usually

participated in the Research Scheme applied to River Valley Projects. A number of

technical institutions are also associated with this programme and they are mostly

tackling the problems with a great academic bias. The background and the special

features of some of the State and Central Government research stations are given

below.

(1) Andhra Pradesh Engineering Research Laboratory, Hyderabad

The Engineering Research Department, established by then Hyderabad State

Government in the year 1945 became the Research Laboratories of Andhra Pradesh

when the new state was formed in November 1956.

(2) Central Soil and Materials Research Station, New Delhi

To meet the need for research wing, for soils and material testing on the pattern of the

central water and Power Research Station, Pune, (Described subsequently) the Central

Soil and Materials Research Station came into existence at New Delhi during the year

1953-54. The research station undertakes field and laboratory investigations for river

valley and other projects in the disciplines of soil mechanics, rock mechanics, concrete

technology, sediment investigation, pre-irrigation soil surveys and chemical analysis of

construction materials. The station has extended its service of consultancy to a number

of foreign countries including Bhutan, Nepal and Afghanistan. Highly sophisticated


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testing facilities such as 1,000 tonne testing machine, have been installed and it is one

of the best equipped laboratory of the country in its field.

(3) Central Water and Power Research Station, Pune

As a sequel to the need for organised research, a special Irrigation Research Division

was created under the auspices of Bombay P.W.D. in 1916, by the efforts of Sir C.C.

Inglis, who did pioneering work on various aspects of the irrigation problems and laid

the foundation of organised research in the country. Problems concerning laid drainage

and reclamation, canal losses, canal lining and improved irrigation works were taken for

investigation. Soon the Research Division expanded its activities in new branches and

this centre was subsequently taken over by Government of India in 1937. Irrigation and

river training research were added to its scope and was renamed as 'Indian Waterways

Experiment Station'. In 1946-47, the expansion and reorganisation of the station was

sanctioned with seven new branches for dealing with navigation, soils, materials of

construction, statistics, physics, mathematics, hydraulic machinery research problems.

The station was redesignated the 'Central Water and Power Research Station' and

brought under the administrative control of Central Water Commission. The quality of

research work turned out by the Research Station won it acclaim not only within the

country but abroad as well. In recognition of the tremendous progress made, it has been

chosen as Regional Laboratory for the United Nations Economic Commission for Asia

and Far east. CWPRS has extreme built up expertise in many fields during its life span

of more than 85 years. Some of the notables are: hydraulic structures, earth sciences,

ship model testing, coastal engineering and the application of methods from the

different disciplines of physics, chemistry, mathematics, statistics, botany, geology,

instrumentation and computer science.

The station extends its activities to prototype testing, digital data acquisition, field

investigations, testing of turbine and pump models in cavitation tanks and developing

techniques for the use of radioactive and fluorescent tracers in tidal as well as fluvial

flow conditions for various purposes.


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The station has been offering technical assistance and consultancy services to other

countries also, which include Burma, Afghanistan, Tanzania, Iraq, Philippines,

Singapore, Libya, Nepal, Sri Lanka, Egypt and Zambia. Notable engineers from these

stations are Sir C.C. Inglis and Dr. D.V. Joglekar.

(4) Gujarat Engineering Research Institute, Vadodara

On the bifurication of the Bombay State, the development and Research Division at

Vadodara, which was a branch of the Central Research Institute, Nasik was transferred

to the Gujarat State in 1960 and was renamed as Gujarat Engineering Research

Institute, with head-quarters at Vadodara. The institute's major contribution related to

the study of ground water flow and its recharge, river training, sediment studies in canal

and reservoirs, canal lining, soil mechanics and materials testing specially pozzolana.

(5) Hirakud Research Station, Hirakud, Orissa

During the planning of the Hirakud Dam Project in 1947, this research station was

started at the dam site for observations of data on the silt load of the Mahanadi and for

testing construction materials for the project. Subsequently, this station was expanded

to take up the quality control work during the construction and for the fixing and

observations of the instruments provided both in the earth dam and the masonry and

concrete dams. With the transfer of this station, along with the Hirakud Dam Project to

the Government of Orissa in April 1960, the activity of the Research Station has been

extended to cover the whole of the Orissa State.

A Masonry Testing Unit for testing large size masonry and concrete blocks, has been

set up about 11.3 Km away and it is one of the few such units in the country.

The Station also undertakes the sedimentation survey of the Hirakud Reservoir by

echo-sounding.


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(6) Insti tute of Hydraulics and Hydrology, Poondi (Tamil Nadu)

Abundant water and land becoming available with completion of the Poondi Reservoir

Irrigation Research Station came into being at Poondi, 60 Km from Chennai, in April

1944.

This Research Station deals with all hydraulic problems of the river valley and flood

control projects. T-shaped blocks have been evolved for effective and economic

dissipation of energy below spillways. Implemented in Bhavani Sagar project. Similarly,

lined canal chutes have been developed and considerable savings have been effected

in the cost of the Lower Bhavani Project Canal System by work at this Station. A special

mention may be made of the studies conducted for the improvement of the coefficient of

discharge of tank weirs, which has enabled the irrigation of additional areas from the

remodeling of a large number of tanks in the Tamil Nadu State.

The Irrigation Research Station was functioning as a part of the State Public Works

Department and as such it concentrated on applied research having relevance to the

immediate functional needs of the department. Observing the switchover from hydraulic

to hydrologic research all over the world urgent need was felt to bring about a change in

the outlook of this statement also.

The station was upgraded into a full fledged Institute of Hydraulics and Hydrology in the

year 1973 making it possible to deal with problems in ground water and coastal

hydrology and surface water management using computer simulation methods, system

analysis and the like.

The need for instrumentation, especially on the electronics side had also been realised

fully. As a result an electronic laboratory has been established.

The activities of the Institute are spread over area of Ground Water Hydrology,

Hydrology of River Basins including Flood Prediction, Hydrological Modeling,

Instrumentation and Water shed Management Schemes.


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(7) Irrigation Research Directorate, Bhopal

The research station has been started in 1964. It is mainly dealing with hydraulics, soils,

and concrete and model prototype conformity problems.

(8) Irrigation Research, Jaipur

With the advent of irrigation projects in the State of Rajasthan and use of local materials

for the constructional purposes, the Irrigation Research has been conceived.

(9) Irrigation Research Institute, Khagaul, Patna

The research station was opened in 1956 at Khagaul, 10 km from Patna. The Institute

has done considerable work on soil, use of micaceous sand in mortar and concrete, and

other construction material problems. It has recently taken up studies regarding

sedimentation survey of reservoirs and ground water problems including optimum

spacing of tubewells in various regions of Bihar State.

(10) Kerala Engineering Research Inst itute, Peechi (Kerala)

On the formation of the Kerala State on 1 November 1956, the systematic and intensive

development of the water resources of the state assumed great importance.

The State Government sanctioned a Research Institute in Kerala which started

functioning on June 1960.

The main Research Institute is located at the foot of the Peechi Dam, about 22.5 km

from Trichur.

Being a coastal State the Institute has mainly concentrated on the problem of coastal

erosion and has evolved cheaper designs of sea walls which have been constructed to

protect the land against sea erosion successfully. Other studies being carried out are

use of laterite as pozzolana, water requirement for rice, etc.


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(11) Karnataka Engineering Research Station, Krishnarajasagar

Though it started as a small section attached to Gauging Sub-Division dealing with

hydraulic investigations only, with the increase in demand for the testing of soils and

various engineering materials, the Soil Mechanics Branch and the Material testing

Branch were added during 1940.

The Hydraulic Research Station was later strengthened in 1945 and made a seperate

wing of Public Works Department under the direct administrative control of the chief

Engineer and redesignated 'Mysore Engineering Research Station'. During 1974 due to

the redesignation of Mysore State to Karnataka State, the station was also redesignated

'Karnataka Engineering Research Station'.

The outdoor hydraulic laboratory and the indoor laboratories (material testing, soil

mechanics, chemical, road research, etc.) are all located at Krishnarajasagar, just below

the Krishanarajasagar Dam overlooking the famous Brindavan Gardens.

One of the important contributions from this Research Station has been the

development of the volute siphons, initially designed and promoted by Ganesh Iyer, an

eminent engineer of the Mysore State. One of the important studies carried out by this

Research Station in collaboration, with other research stations was to determine the

prototype behaviour of the siphons when running full under likely cavitation conditions

under excessive head.

Other notable studies carried out by this Research Station are the twin surge tanks, the

approach channel to the Vodenbyle twin tunnel, and the surplussing arrangements of

the Linganamakki Talakalale, Kali Complex and other projects of the state. Experiments

for restriction of evaporation, cheaper canal lining, model prototype conformity,

sedimentation survey of reservoirs, problems of soil mechanics, materials testing and

rock mechanics are some other important achievements of the station.


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During 1971, an Engineering Staff Training College has been started under aegis of

Karnataka Engineering Research Station, to impart training to in service engineers of

P.W.D. by running short-term and long-term refresher courses.

(12) Land Reclamation, Irrigation and Power Research Institute,

Punjab, Amritsar

Around the year 1925, the Government of Punjab constituted a Water logging Enquiry

Committee to study and report on the extent and causes of water logging in irrigated

areas and the preventive measures which should be adopted. A small farm at

Chakanwali for field experiments regarding the reclamation of waterlogged areas and a

laboratory at Lahore for the analysis of soil and water samples-later designated as the

'Scientifc Research Laboratory' was set up in this connection.

In 1931, the Hydraulic Section was started and, by 1932, under the redesignated name

'Irrigation Research Institute, Lahore' there were six independent Sections: Hydraulics,

Physics, Chemical, Statistical, Mathematical and Land Reclamation. During the next 15

years, the Institute was able to carry out a great deal of work which gained recognition

in the scientific and engineering circles.

The Hydraulic Section initiated (1932) small-scale model experiments for tracing subsoil

flow under structures on permeable foundations, by treating the sand in the model with

a chemical and allowing another chemical to flow from one side of the work to the other

through the sand. Arrangements were made to measure the pressures under the work

at different points. The comparisons of the results with theoretical expectations pointed

to the need for a mathematical technique to give more exact results and standard cases

were successfully tackled from 1936 to 1940 to obtain the effects of various

components of a structure on the pressure distribution under it. The physics section

developed, at the same time, the electric analogy model for a rapid determination of the

pressure distribution comparable with those given by theory and the hydraulic model.


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In 1936, Khosla put forward his 'method of independent variables' for determining the

pressure distribution based on the concept that each component had an individual effect

and the superposing of these individual effects have the overall effect. The theoretical

results and the laboratory experiments were used to verify and, where necessary,

modify Khosla's method, which ultimately became the standard method, which

ultimately became the standard method for the design of works on permeable

foundations. This was indeed a signal contribution by a co-operative group of Indian

workers to a difficult engineering problem.

Dr. A.N. Khosla made a name in the the field of Research through his work on seepage

theory and design of weirs on permeable foundations. He was appointed the first

chairmen of the newly constituted Central Waterways, Irrigation and Navigation

Commission in 1945 and developed it into a front rank organisation. When Bhakra

control of board was set up in 1950, Dr Khosla was appointed its Vice Chairman and

Chairman of the board of Consultants. He remained associated with the project till its

commissioning in 1963.He served as the Vice Chancellor of the Roorkee University

from 1954 to 1959 and virtually transformed it from a small though reputed college to a

leading technical university. In 1962 he was appointed as Governor of Orissa, the first

and so far the only professional engineer to have been given such a responsibility.

Another name worth noting is that of Dr Kanwar Sain. He was responsible for planning

of the gigantic planning of the gigantic Rajasthan Canal project still under completion.

For nine years he worked on the planning of the complex Mekong River project under

the auspices of the United Nations.

Another important contribution of those years was in regard to the design of stable

channels in alluvium. The Institute developed, for the first time, appropriate scientific

instruments capable of collecting and analysing samples of silt from irrigation channels.

The results of analysis were processed to obtain the mean size of the silt and to

correlate it with the other hydraulic elements of the channel.


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Another field of study related to the engineering works connected with the control and

training of rivers. This required comparatively large-scale methods and a field research

station was opened at Malakpur in Gurdaspur District where the requisite facilities were

available. This station, which was started around 1934, subsequently grew into one of

the most advanced station in India and handled the model work for most of the

important projects in the Punjab.

Yet another development was the large-scale work on land reclamation undertaken by

Punjab Government in 1940. This ultimately led to a seperate department of Land

Reclamation being formed under a 'Director, Land Reclamation'.

Immediately after partition in 1947, East Punjab set up a new Institute at Amritsar and

work at the Malakpur Station was continued. Since then, the institute has grown

considerably and has now been made a zonal institute for the North Zone, consisting of

Himachal Pradesh, Jammu and Kashmir, Punjab and Rajasthan.

In the field of hydraulics, a substantial contribution was made in regard to the design of

spillway and outlets for Bhakra and Nangal Dams and of the flood control, drainage and

reclamation problems of Kashmir Valley.

The Hydraulic Research Station, Malakpur has been recognised to help and solve many

complicated problems in connection with Beas Dam at Pong, Beas Sutlej Link-Part II,

Sirhind, Ferozpur and Rajasthan Feeders and recently for Shah Nahar Project,

Anandpur Hydel Project, Mukerian Hydel Project and the prestigious Thein Dam and its

appurtenant works. The station specializes in developing sediment excluding devices

from rivers and channels.

A Field Lining Research Station has been set up at Doburji (Near Amritsar) for

Investigations relating to the economical specifications of lining material for reducing

seepage from the earthen channels and water courses. Research for development of

pressure release values behind canal lining is also being undertaken at this station.

Excellent work regarding vortex suppressors in the intake has been carried out.


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(13) Maharashtra Engineering Research Institute, Nasik

Considering the importance of achieving efficiency, economy and progress of large

development works undertaken in the Bombay State, the State Government approved

the creation of a Central Engineering Research Institute, and it was set up with

headquarters at Nasik in 1959. On the creation of Maharashtra State and bifurcation of

research station it has been redesignated 'Maharashtra Engineering Research Institute'.

The Institute carries out investigations on soil mechanics, materials testing, hydro-

dynamic problems and public health and rural engineering. The Institute specializes in

Environmental Engineering with special reference to water quality and its measurement

throughout Maharashtra State. Recently field studies have been conducted on

breaching and dismantling of Old Waghad Dam.

The Soil Survey Division at Poona does systematic soil surveys of the areas under the

command of various irrigation projects in the state.

(14) River Research Inst itute, West Bengal, Kolkata

Due principally to the abandonment of the Bhagirathi-Hoogly course by the Ganga,

many of the rivers of West Bengal have decayed and the drainage of West Bengal

during the flood Season has been seriously affected. A Research Station to study the

various river problems and to evolve measures for controlling the destructive causes of

the dying rivers was set up in the State in the year 1943.

Investigations for foundations of hydraulic structures for borrow materials for

construction of dams and soil surveys for irrigation projects have also been taken up.

Facilities are also available for conducting aggregate and concrete tests. With the

passage of time the institute has acquired specialization in a number of fields such as

River training for the purpose of conservancy of the river, prevention of erosion and

flooding, Navigation and irrigation, Design of channels, Meandering of streams and

conservation of tidal rivers, Tidal computation, closure of estuaries, tidal channel and

reclamation and Engineering properties of soils.


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(15) Soil Mechanics and Research Division, Chennai

The Research Station was initially formed as Physics and Soil Mechanics Office in

1946. The Concrete Laboratory was established in 1947. In 1953 the two were merged

to function as "Soil Mechanics and Research Division" of the Tamil Nadu Public Works

Department. The Research Station had the benefit of guidance of K.L. Rao, the noted

engineer statesman in the early stages.

The laboratory has successfully evolved Ennore sand as the Indian standard sand. This

sand is now supplied to engineering research institutions and cement factories all over

India and has resulted in considerable saving of foreign exchange.

The laboratory, in its thirty years of useful service has made significant contributions in

the various fields of engineering research. Intensive soil investigation work has been

carried out for all the irrigation projects executed in the state, regular quality control

work has been organised. For building works, regular foundation analysis by load tests

has been carried out for almost all major buildings. The station has done notable work

on Design of Weirs on permeable Foundations of Finite Depth.

(16) Uttaranchal Irrigation Research Institute, Roorkee

A small Hydraulic station was established at Lucknow in 1938 to study the problems of

scour and erosion below falls and bridges on irrigation channels. To meet the needs of

an increasing number of problems, an Irrigation Research Station at Bahadrabad, about

20 km from Roorkee, started functioning in 1947. This Station was further expanded in

1955. Earlier it was known as Uttar Pradesh Irrigation Research Institute, Roorkee.

The activities of this Institute cover both basic and applied problems in hydraulics, soil

mechanics, ground water, mathematics, physics, instrumentation, hydrology and

measurement of discharges of rivers and canals. Specific problems concerning the

development projects, such as river training and protection works, soils and construction

material problems, etc., constitute its main activities, but the station has been also doing

remarkable basic research work in a number of fields.


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Few of the important contributions of the Institute relates to the design of the 1.8 m high

dentated sill for dissipating energy below Sarda Barrage sluices, which had collapsed

during the floods of 1956. This was the first kind successfully tested and adopted in

India under boulder river conditions.

Hydraulic design of Surge tanks for all major projects constructed / under construction in

Himalayan region and its computer simulation, design of gravel pack and prepacked

filter for tube wells, design of stilling basin for low Froude Number, design of stilling

basin for low Froude Number, design of guide bunds at bridges and barrages, intake

structures, stilling basins, design of bifurcations and trifurcations for tunnels, assortment

of river training problems, prototype load test, design of channels and evolving formula

for design of channels, design of structures founded on stratified soils, design of

barrages and canal regulators on three-dimensional flow consideration, etc., are a few

of the fields of the specialization of the Institute. The Institute offers technical assistance

not only to State Irrigation Department but to other States and departments. The

Institute also takes up the foundation investigations for dams, power houses and other

hydraulic structures, Instrumentation in dams, in situ testing of rocks and model

prototype conformity studies. Recently due to reorganisation of states, this is now in

Uttraranchal.

Reference

Water Resources Research in India, Publication No. 78 (Revised) CBI&P, New Delhi,

1979.


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1.4 CLASSIFICATION OF FLOW

Uniform flow Non-uniform flow

Subcritical

Critical

Supercritical

Steady Unsteady

Gradually varied flow

Rapidly varied flow

Spatially varied flow

Fluid flow

Froude number

Reynolds number

Spatial

Temporal

Compressible / incompressible

Pressure Flow

Free Surface Flow

Single phase

Two phase

Multi phaseReciprocating upstream flowUnidirectional upstream flow

Highly irregular

Highly variable upstream flow

Fluid flow

One dimensional

Two dimensional

Three dimensional

Classification of flow is done based on different criteria. A brief description of the

classification is given in the following paragraphs.

CLICK ON THE TITLE FOR FURTHER DETAILS

(a) Based on Ideal and Real fluid flows

(b) Pressure flow and Gravity flow

(c) Based on ratio of Inertial and Gravitational forces

(d) Based on Inertial and Viscous force ratio

(e) Compressible and Incompressible flow

(f) Based on Spatial variations

(g) Based on dimensions

(h) Based on Time

(i) Based on Rotational and Irrotational flows

(j) Based on Mono phase and Multi phase flows

(k) Based on Stratification

Examples of some combination of flows
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2. CHANNELS AND THEIR GEOMETRIC PROPERTIES

2.1 INTRODUCTION

An open channel is a physical system in which water flows with a free surface at the

atmospheric pressure. In other words the pressure is impressed on free surface. A

channel can be classified as either natural or artificial channel according to its origin.

Natural channels include all watercourses of varying sizes from tiny hillside rivulets,

streams, small and large rivers to tidal estuaries that exist naturally on the earth.

Subsurface streams carrying water with a free surface are also treated as natural open

channels.

The cross sections of natural channel are irregular and hence hydraulic properties may

vary from section to section, and reach to reach. A comprehensive study of the behavior

of flow in natural channels (the mobile boundaries) requires knowledge of other fields,

such as hydrology, geomorphology and sediment transportation. Generally, these

aspects are dealt in detail in river mechanics (fluvial hydraulics).

Artificial channels are those constructed or developed by human effort such as gutters,

drainage, ditches, floodways, tunnels, log chutes, navigation channels, power canals

and trough, spillways including model channels that are built in the laboratory for

experimental investigation studies. Long distance canals have been constructed to

achieve the interbasin transfer of water at Nationaland International levels.

The artificial channel is known by different names, such as " canal "," chute", "culvert",

"drop","flumes"and"open - flow tunnel",Aqueduct.

However, these names, are used rather loosely and can be defined only in very general

manner.

The canal is usually a long and mild-sloped channel built in the ground, which may be

lined or unlined with stone masonry, concrete, cement, wood or bituminous materials

etc.

Eg: Ganga Canal,Indira Gandhi Canal,Narmada Canal.
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The chutes are a channel having steep slopes. The culvert, flowing partly full, is a

covered channel of comparatively short length provided for draining water across

roadways and through railway embankments.

The drop is similar to chute, but the change in elevation is effected with in a short

distance.

The flume is a channel of wood, metal, fiber reinforced plastic, concrete, or masonry,

usually supported on or above the surface of the ground to carry water across a

depression.

The open -flow tunnel,fall,is a comparatively long covered channel used for carry water

through a hill or any obstruction on the ground. Normally these artificial canals are with

rigid boundaries.

The channels can be classified as prismatic and nonprismatic. A channel built with

constant cross section and constant bottom slope and fixed alignment is named as

prismaticchannel. Otherwise, the channel isnonprismatic.

Example:spillwayhaving variable width and canals curved alignment. (Meandering).

The term channel section refers to the cross section of channel taken normal to the

direction of the flow.

A vertical channel section, however, is the vertical section passing through the lowest or

bottom point of the channel section. For horizontal channels, therefore, the channel

section is always a vertical channel section.

Natural sections are in general very irregular, usually varying from an approximate

parabola to an approximate trapezoid shapes and for streams subject to frequent

floods, the channel may consist of a main channel section carrying normal discharges

and one or more side channel sections for accommodating overflows. These are called

compound channel.

Artificial channels are usually designed with sections of regular geometrical shapes.

Table gives the geometric properties for the cases of rectangular, trapezoidal,

triangular, circular, parabolic channels. In addition the details of Round bottomed

triangular and round bottom rectangular are also given.
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2.1.2 Geometrical Properties

Unlined trapezoidal section is the most common channel section used in the field for it

provides side slopes for stability. The rectangular channel with an angle 90 and

triangular channel with a bed width equal to zero are special cases of the trapezoidal

channel. Since the rectangular channel has vertical sides, it is commonly used for

channels built of materials, such as lined masonry, rocks, metal, or timber. Precast

concrete sections are also used for small size canals. The triangular section is used

only for small ditches, roadside gutters, and for experimental investigations in the

laboratory. The circular shape is the popular section for sewers and culverts of small

and medium sizes. The parabola is used as an approximation for section of small and

medium- size natural channels. Practical sections are also used as shown in figure (as

recommended by Central Board of Irrigation and Power).

b

1

m

1

m

Lined channel section for Q > 55 m3/s

y

1 1y

y y1 1 A = by + y2( 1+ Cot1)

P = b + 2y( 1+ Cot1)

R = by + y2( 1+ Cot1)

b + 2y ( 1+ Cot1)__________________

1

mm

1

0

Lined channel section

for Q < 55 m3

/ s

y y1 1

21 A = 2(1+y2Cot1) + y22112

__

= y2(1+Cot1)

P=2yCot1+2y1 = 2y(1+Cot1)

R=AP

__ y2(1+Cot1)

2y(1+Cot1)____________=

y2

__=

y

Closed geometric sections other than circular section are frequently used in sewer

system, particularly for sewers large enough for a person to enter. These sections are

given various names according to their form, they may be egg-shaped, ovoid,

Semi-elliptical,U-shaped,catenary,horseshoe,basket-handle,etc. The complete

rectangular and square are also common for large sewers.
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A special geometric section known as hydrostatic catenary or lintearia is the shape of

the cross section of trough, formed of flexible sheets of negligible weight, filled with

water upto the top of the section, and firmly supported at the upper edges of the sides

but with no effects of fixation. The hydrostatic catenary has been used for the design of

the section of some elevated irrigation flumes in UK (United Kingdom). These flumes

are constructed of metal plates so thin that their weight is negligible, and are firmly fixed

to beams at the upper edges.

Hydrostatic Catenary

Cartesian equation: y = a cosh(x/a)

Click here for Geometric elements of channel sections

Geometric elements are properties of a channel section that may be defined entirely by

the geometry of the section and the depth of flow. These elements are extensively used

in computations of flows.

The geometric elements for simple regular channel sections can be expressed

mathematically in terms of the depth of flow and other dimensions of the section. For

complicated sections and sections of natural streams, however, no simple formula can

be written to express these elements, but graphs representing the relation between

these elements and the depth of flow can be prepared for use in hydraulic

computations.
http://2_26.pdf/http://2_26.pdf/


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2.1.3 Definitions of several geometric elements of basic importance

are given below

Depth of flow

The depth of flow y is the vertical distance from the lowest point of channel cross

section to the free surface. This term is often used interchangeably with the depth of

flow section. Strictly speaking, the depth of flow section is the depth of flow normal to

the direction of flow, or the height of the channel section containing the water. For a

channel with a longitudinal slope angle , it can be seen that the depth of flow is equal

to the depth of flow section divided by. In the case of steep channels, therefore, the two

terms should be used discriminately.

x

y

900

horizontal

Normal and vertical depths

Box

10 , cos = 0.9848,thus there would be an error of 1.51%.y = d cos

=

If x is measured along the horizontal direction instead of the sloping bed, then the

2% error occurs at about 11 S 0.20or

= = . On the other hand if x is measured

along the sloping bed instead of the horizontal 2% error occurs at

about 16 or S 0.29

= = , which is an extremely steep slope in open channels.

However, there is exception in cases such as spill ways, falls, chutes.


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11

m = 2m = 2

T

P

A Channel cross section

b

A = Area of flowT = free surface width (m)m = side slope defined in horizontal to 1 vertical; m:1m = cot

lm

0

P = Wetted perimeter is the boundary which is in

contact with the flow (m)

b = bed width in (m)y = depth of flow

y

Stage

Datum

0

Water surface

Bed

Definition of stage

H (M.S.L)(Above Mean Sea Level)

Datum

EL 210.00 m

EL 205.00 m

EL 200.00 m

The stage H is the elevation or vertical distance of the free surface above the datum. If

the lowest point of the section is chosen as the datum, the stage is identical with the


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depth of flow. Free surface width T is the width of channel section at the free surface.

dAT

dy

The water flow area A is the cross-sectional area of the normal to the direction of flow.

The wetted perimeter P is the length of the line of intersection of the channel wetted

surface with a cross sectional plane normal to the direction of flow.

The hydraulic mean radius R is the ratio of the water flow area to its wetted perimeter,A

R =P

When a shallow channel of b is used andb

y then R 2

.

b

b__2

y

R

Hydraulic mean radius

Wide Rectangular

y

y

R

dR

dy__

Trapezoidal

y then Rb__2

b R y R


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The hydraulic mean depth D is the ratio of the water area to the free surface

width, A

D =T

. The section factor for critical- flow computation m is the product of the

water area and the square root of the hydraulic depth, A

Z = A D = AT

. The section

factor S.F for uniform-flow computation in case of Manning formula is the product of the

water area and the two-thirds power of the hydraulic radius

2

3S.F = AR other wise for

chezy's formula it is i.e.,

2

3AR . The details of circular channel are given in OPEN -

CHANNEL HYDRAULICS by VEN TE CHOW - pp 632 - 639(1959).

Earlier the nomographs for trapezoidal and parabolic sections were used for specific

side slopes see reference. The geometrical characteristic of the irregular cross section

can be obtained using a set of co - ordinates describing the cross section, with the help

of interpolation between any inter mediate depth. The typical programme is given in the

appendix.The computations can be done either by from top or from the bottom most

point.

Actual area up to depth y =Total area A - dA

Area up to (y + dy) = Area up to y +dA

y

distance

dy

River bed elevation as a fuction of distance from

the river bank
http://2_27.pdf/http://2_27.pdf/http://2_27.pdf/


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2.1.4 Circular channel

Normalised geometric characteristics are shown in figure. When the flow is full the

hydraulic mean radius is (i.e)

2d

d1 A 4d = =

4 P d 4

which is less than the maximum

hydraulic mean radius which occurs at 0.81d when relative velocity of the flow is

considered for constant Manning roughness coefficient. similarly it is (click)0.938d

for

maximum value of

2

3AR when the discharge is maximum.

do

y

T___

do

Z

do2.5

___

D___

do

A___

Ao

P___Po

R

Ro

___

Po = do A0=do

2

___4

R0=do___4

Normalized geometric elements for a circular section

Subscript zero indicates full flow condtion

0 0.1 0.2 0.3 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.30.4

0.1

0.2

0.3

0.5

0.6

0.7

0.8

0.9

1.0

0.4

y__d0

Problem: Write a computer program to obtain the geometrical elements of a circular

shape channel and obtain the2/ 3

2/ 30 0 0

y ARVs

d A R

Compute the geometric elements, area, hydraulic mean radius, hydraulic mean depth

for the following cases:
http://problem_2.pdf/http://problem_2.pdf/http://problem_2.pdf/http://problem_2.pdf/


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Rectangular channel: Bed width is 10 m, Depth of embankment is 15.15 m, Depth of

flow is 8.870 m.

Trapezoidal channel: Bed width is 10 m, Depth of embankment is 15.15 m, Depth of

flow is 7.77 m, side slope m:1 = 2:1.

Triangular channel: Depth of embankment is 15.15 m, Depth of flow is 9.75 m, side

slope m:1 = 2:1.

Circular channel: Diameter is 15.15 m, Depth of flow is 6.47 m.

2.1.5 Natural channel

The depth of flow 7.567 m.

The program could be developed using spread sheet.

The INPUT for the natural channel is as follows

Distance of the embankments form referenceStage of flow (m)

Left embankment Right embankment (m)

2.000 10.000 10.000

3.000 9.000 11.000

4.000 8.500 12.500

5.000 8.000 13.600

6.000 7.000 15.000

7.000 6.300 16.900

8.000 5.400 18.000

9.000 5.000 19.500

10.000 4.300 21.000

11.000 3.900 22.000

12.000 3.000 23.300

13.000 2.700 25.000

14.000 2.200 26.300

15.000 1.900 27.000

16.000 1.300 28.200

17.000 1.000 29.000

18.150 0.700 30.000

The depth of flow = 7.567 m


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Solution:

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

**

*

*

*

Distance from reference (m)

Natural channel

0.0 12.0 18.0 24.0 30.06.0

4

8

12

16

20


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**

* *

*

*

*

*

*

*

*

*

*

*

*

Variation of area with depth of flowDepth of flow (m)

0.0 3.0 6.0 9.0 12.0 15.0

100.0

200.0

300.0

400.0

500.0

600.0

Natural

Triangular

*

*

* *********

* * ** *

***** ***

*

***

*

***

*

****

************

Variation of hydraulic mean depth with depth of flowDepth of flow (m)

0.0 3.0 6.0 9.0 12.0 15.0

10.0

20.0

30.0

40.0

50.0

60.0


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3.0 6.0 9.0 12.0 15.0

2.0

4.0

6.0

8.0

*

*

*

*

*

**

*

*

*

*

*

*

Depth of flow (m)

Variation of Hydraulic radius with the depth of flow

Table showing the geometrical elements for the above channels (metric units)

Section y A P T R D Z A D=

Trapezoidal 7.77 198.800 44.748 41.080 4.434 4.830 437.665Rectangular 8.870 88.700 27.740 10.000 3.196 8.870 264.316

Triangular 9.750 190.500 43.603 39.000 4.360 4.875 421.324

Circular 6.470 73.488 21.575 14.954 3.397 4.910 163.428

Natural 7.567 58.895 39.0007 15.747 1.504 3.724 114.067

Problem: Compute the geometric elements for the horse shoe tunnel shown in figure

below. Plot the normalised graphs representing the geometrical elements.


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Horse shoe tunnel

d0

If d0is 10 m and the depth of flow 7.5 m, what would be the area of flow, wetted

perimeter, hydraulic mean radius, section factor for uniform flow.


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2.2 Verify the geometrical elements for Circular channel

2

2 2

4

=

=

22

222

0

2 22

Top width of water T

dT y - = r

2 2

dT r y -

4 2

d d T = 2 y -

2 2

d d d T = 2 y + - 2y

4 2

or

2d = 2

4 2

2 dy4

( ) ( )

1802 2

+

=

=

2yd

2

T = 2 y -y +d T = 2 y d yT

sin ( 180 - ) r2 2

or T = d sin d sin

Area of flow = Area of circle - Area above the chord

or

180

2

180 1802 2 2

4 2

=

= = =

= =

2

dTArea of triangle = x y -

2 2

d d

sin y -2 2d

y -d d d2cos( ) or y - cos( ) cos

r 2 2 2

Area of full circleArea for = x

2

d d

.

( )

8

8 8

8

2

2 2

2

d d sin

d Area of flow = sin


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( )

( )

2

2

22

1

8

4

2

1

2

2

2

1

8

= =

= = =

=

=

=

2

d d1P x

2 2A

sinsin

d sin R = 4

AZ =A D A T

1sin d

A 8D = =T d sin

dA sinD =

T 8 sin

d sinD =

8 sin

ddA

RdP

Z ( )

( )1 5

0 5

2

2

32

2

=

2

. 5/20.

d sinsin d

8 sin

sin d

sin

Z


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2.3 Difference between Pipe Flow and Free Surface Flow

OPEN CHANNEL FLOW PIPE FLOW

Defines as a passage in which liquidflows with its upper surface exposed toatmosphere.The flow is due to gravityFlow conditions are greatly influenced

by slope of the channel.Hydraulic grade line coincides with thewater surfaceThe maximum velocity occurs at a littledistance below the water surface.The shape of the velocity profile isdependent on the channel roughness.

A pipe is a closed conduit which isused for carrying fluids under pressure.The flow in a pipe is termed as pipeflow only when the fluid completely fillsthe cross section & there is no free

surface of fluid.Hydraulic grade line does not coincideswith the water surface.The maximum velocity occurring at thepipe centre.Velocity Distribution is symmetricalabout the pipe axis.

Horizontal

TEL

HGL

Datum

PIPE AXIS

Velocity

head

Piezometric

head

(2)

Piezometer

Z1

Z2

hfV12

____

2gV2

2

____

2gP1____

P2____

V(1)

2.3.1 Hydraul ic Grade Line (HGL)

Definition: A curve drawn above the datum which has ordinates equal to the piezometric

head at every point is called HGL or Hydraulic gradient.

The vertical intercept between the datum and pipe axis is the elevation head.

the datum and pressure gradient (HGL) is the peizometric head.

the pipe axis and the HGL is the pressure head.

HGL and TEL is the velocity head. Datum and TEL is the total head.

The TEL always falls on the direction of flow because of loss of head. The HGL may

rise or falls depending on the pressure variation in the pipe.


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In a pipe of uniform section the velocity head remains the same, if the rate of flow is

constant. hence TEL and HGL are parallel if the pipe axis is horizontal.

HGL is always below the TEL. At point where pressure is equal to the atmospheric

pressure, HGL meets the pipe axis.

Shear stress distribution in pipe flow

Velocity distribution Shear stress distribution


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3.1 Continuity equation

Continuity equation represents the law of conservation of mass.

In general for unsteady flow the continuity equation is

(Mass flow rate into the system) - (Mass flow rate out of the system) = Rate of change

of storage.

For steady state condition

(Mass flow rate into the system) - (Mass flow rate out of the system) = 0.

Example: Inflow: The flow that is coming into a system or an elemental volume such as

rainfall in y direction, flow entering into the river or a channel.

Outflow: The flow escaping from the system such as evaporation, seepage, water

released from a system.

Elemental volume

Inflow

Inflow

Outflow

Outflow

x

y

Generally, the mass balance is written in all the three directions namely x, y and z.


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u v w0

x x x

in which

u, v and w are the velocity components in x, y, z directions respectively,

is the mass density of the fluid. If the mass density is cons tan t the above

equation can be rewritte

+ + =

n as

u v w 0x x x

If for one dimensional flow it reduces to

u0

x

MassMassdensity

Volume

u*elemental area = constant

x

Integrating one gets

UA = constant

Volume rate could be express

v=0, w=0 i.e.,

+ + =

=

=

( )

3

3

ed as m / s. This is generally known as

flow rate or discharge and expressed as cubic meter / second and is

abbreviated as cumec (m / s).

Q Area *Velocity AV

Q

= =


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3.2 ENERGY IN FREE SURFACE FLOW

It is known in basic fluid mechanics that the total energy in ( Newton-meter per Newton )

of water along any streamline passing through a channel section may be expressed as

the total head in meter of water, which is equal to the sum of the elevation (above a

datum), the pressure head, and the velocity head. For example, with respect to the

datum plane, the total head H at a section containing point X on a streamline of flow in a

channel of large slope may be written as

2V

H cos z2g xx

dx x

= + +

o

y = d cos

z

900

v2g

Datum

Energy in gradually varied open channel flow

yx z

_

Total Energy Line

1

v2g

__

11

y1 =d1cos

v__

1

z1

z2

y2 =d2cos

v2g

__

1 2

hf

__

Streamlines

Y

Y

Section YY

H

H = z + y +v2g

__2

2

2

2

in which z is the elevation of point Y above the datum plane, d is the depth of flow

normal to the bed, y is the vertical depth below the water surface measured at the

channel section, is the angle of the channel bottom with horizontal and

2V

2g is the

mean velocity head of the flow in the streamline passing through point X. In view of the

variation in velocity over the depth, the velocity head would be differing. The mean

velocity obtained by integrating the velocity distribution is considered for the entire

sectionA

V = v dA

0 . In order to account for the variation of the velocity due to non uniform

pattern of velocity distribution, an energy correction factor is used.


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Theoretical uniform flowvelocity distribution

(Ideal)

Linearvelocity

distribution

depth

of flow

y

y

Logarithmic

velocitydistribution

PowerLaw

Typica

Hydraulics IIT

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