VAYU EDUCATION OF INDIA

Hydraulics and Hydraulic Machines ( Including Lab Manual) Second Edition

Saiful Islam

SAIFUL ISLAM M. TECH. (I.I.T., ROORKEE),

Member of Indian Society of Technical Education (MISTE) Assistant Professor Department of Civil Engineering, GCET, Greater Noida (U.P.)

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Copyright ©VAYU EDUCATION OF INDIA ISBN: 978-93-83758-24-1 First Edition: 2011 Second Edition: 2014

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At present there are some excellent books written on the subject. However, all of them presume a reasonably high level of knowledge of HYDRAULICS AND HYDRAULIC MACHINES. Consequently, the student with only an elementary knowledge of Hydraulics and Hydraulic Machines find these books beyond their comprehension. Besides, the majority of these books deals with the entire course of the Hydraulics and Hydraulic Machines in the Indian Universities. No one cover the syllabus according to recent UPTU syllabus. This books has been written keeping in mind the recent syllabus of UPTU and other Indian Universities. An attempt has been made to enrich the book with simple language, lucid expression, and make it available at the low price. The author would feel obliged if any error in this book are brought to their notice. Constructive suggestions from the readers to further improve the book are always welcome. SAIFUL ISLAM

I express my sincere gratitude to my father Dr. Fakhrul Islam Azmi, Reader, Department of Arabic, Shibli National PG College, Azamgarh, for his constant inspiration and encouragement. I have the benefits of valuable advice and suggestions from Mr. Kunal Rai and Mr. Ashish Kashyap. I express my indebtedness to books, references, journals, which have been referred to during the preparation of this book. Dr. Rajiv Kumar Jain, Managing Director, Vayu Publication, deserves special thanks, who has taken special pains in bringing out this book in this form. I wish to thanks the production team member of Vayu Education of India, Darya Ganj, New Delhi-110002, especially Mr. Vijay Kumar (Production Manager), Mr. Mohamad Asif (Sales Executive) and Ayaz Khan (DTP Operator) for their unfailing cooperation they executed during the course of publication of this book January, 2011 SAIFUL ISLAM

Preface Acknowledgement Unit 1: Flow in Open Channels 1.1 Introduction 1.2 Applications of Open Channel Flow 1.3 Difference between Open Channel Flow and Pipe Flow 1.4 Types of Channels 1.5 Classification of Open Channel Flows 1.6 Geometrical Parameters of a Channel 1.7 Equation of Continuity 1.8 Momentum Correction Factor () 1.9 Specific Energy and Specific Energy Curve 1.11 Critical Depth 1.12 Critical Velocity 1.13 Critical Flow 1.14 Calculation of Critical Depth 1.15 First Hydraulic Exponent ‘M’ 1.16 Concept of Specific Force 1.13 Minimum Size of Hump for Critical Flow Solved Problems Review Questions Unit 2: Uniform Flow 2.1 Introduction 2.2 Chezy’s Equation for Uniform Flow 2.3 Manning’s Formula for Uniform Flow 2.4 Compound Channel 2.5 Conveyance of Channel

v vii 1 1 1 2 4 4 8 9 12 12 17 18 19 19 25 25 32

71 71 71 74 77 78

(x) / Hydraulics and Hydraulic Machines 2.6 2.7 2.8 2.9 2.10 2.11

Channels of First Kind Channels of Second Kind Second Hydraulic Exponent N Velocity Distribution in Open Channel Flow Shear Stress Distribution Most Efficient Channel Section Solved Problems Review Questions Unit 3: Non-Uniform Flow–I 3.1 Introduction 3.2 Equation of Gradually Varied Flow 3.3 Differential Equation of GVF 3.4 Limitation of Gradually Varied Flow 3.5 Flow Classification and Surface Profiles 3.6 Back Water Curve and Afflux 3.7 Computations for Gradually Varied Flow Profile 3.8 Direct Integration or Analytical Method for Circular Channel 3.9 Flow in Channels of Non-linear Alignment Solved Problems Review Questions Unit 4: Non-Uniform Flow–II 4.1 Introduction 4.2 Classical Hydraulic Jump 4.3 Application of Hydraulic Jump 4.4 Momentum Equation for the Jump 4.5 Hydralic Jump in Horizontal Rectangular Channel 4.6 Jumps in Horizontal Non-Rectangular Channel 4.7 Jumps on a Sloping Floor 4.8 Classification of Jumps 4.9 Use of Jump at Energy Dissipater 4.10 Open Channel Surge 4.11 Deep and Shallow Water Wave 4.12 Celerity of the surge 4.13 Elementary Negative Surge Solved Numericals Review Questions

78 79 79 80 83 84

121 121 121 122 126 126 140 142 145 153

177 177 177 178 179 180 183 185 188 191 192 196 199 199

Hydraulics and Hydraulic Machines / (xi) Unit 5: Rotodynamic Pumps & Turbines 5.1 Introduction 5.2 Pumps 5.3 Rotodynamic Pump 5.4 Basic Equations 5.5 Velocity Traingle 5.6 Head of Pump 5.7 Efficiencies of Centrifugal Pump 5.8 Minimum Speed of Starting Centrifugal pump 5.9 Multistage Centrifugal Pump 5.10 Specific Speed of Centrifugal Pump (NS) 5.11 Model Testing of Centrifugal Pump 5.12 Characteristics Curves of Centrifugal Pump 5.13 Cavitation in Pump 5.14 Priming of Centrifugal Pump 5.15 Selection of Pump 5.16 Operational Difficulties in Centrifugal Pumps 5.17 Rotodynamic Machine 5.18 Heads of Turbine 5.19 Efficiencies of turbine 5.20 Impulse turbine 5.21 Radial Flow reaction Turbine 5.22 Francis Turbine 5.23 Axial Flow Reaction Turbine 5.24 Specific Speed of Turbine 5.25 Similarity Law in Turbine 5.26 Unit Quantities 5.27 Draft Tube 5.28 Characteristic Curves of Hydraulic 5.29 Cavitation in Turbine 5.30 Selection of Hydraulic Turbines Solved Problems Review Questions Model Test Papers Lab-Experiments and Lab Manual Index

219 219 219 220 224 225 229 230 231 232 233 235 236 238 239 239 240 240 242 243 245 252 256 257 259 261 263 265 267 270 271

393 405 453

Unit

1

Flow in Open Channels

1.1 INTRODUCTION The term open channel flow represents flows through channels that are open to the atmosphere and liquid flows with a free surface. The free surface is the interface between the moving liquid and an overlying fluid medium and will have constant pressure. For example, water is the most common liquid with air at atmospheric pressure as the overlying fluid. The most important force behind open channel flow is gravity. Examples of open channel flow include flow in rivers, canals, laboratory flumes, flow over weirs and spillways and overland runoff. It is necessary to remember that Froude number is the prime non-dimensional number governing the flow in open channels.

1.2 APPLICATIONS OF OPEN CHANNEL FLOW Some of the important applications of the principles of open channel flow are as follows: 1. Measuring the discharge in a river or canal. 2. Developing a relationship between the depth of flow and discharge in a channel. 3. Designing a canal to carry given amount of water. 4. Estimating the area of submergence due to construction of a dam on a river.

2 / Hydraulics and Hydraulic Machines

5. Preventing very high velocity flows from damaging the channel. 6. Estimating the change in the flow condition due to a change in the bed width or bed elevation. 7. Estimating change in the flow depth due to the over-land runoff. 8. Estimating the time taken by the flood wave to pass through a given length of a river. 9. Estimating the amount of sediment carried by a channel. 10. Studying the spread of pollutants in a river.

1.3 DIFFERENCE AND PIPE FLOW

(V12/2g)

E n erg Hy

y G ra

dr a ul i cG

(p/w) 1

de L i

rad e

BETWEEN

V22/2g

Energ y Gra

ne

L in

Wa ter

(V22/2g)

Sur face

V22/2g

v1

X1 (p/w) 2

v2 z2

Chan nel B ot

tom

v2

v2

z1 z2

Datum

Datum

1

h1

de Li ne

e

v1

z1

OPEN CHANNEL FLOW

2

1

2

Fig. 1.1: Comparison between pipe flow and channel flow

Points

Cause of Flow

Geometry of cross-section

Surface roughness

Piezometric head

Velocity distribution

S.No.

1.

2.

3.

4.

5.

The maximum velocity occurs at a little distance below the water surface. The shape of velocity profile is dependent on channel roughness.

(Z + y), where y is the depth of flow. Hydraulic gradient line concides with water surface.

The hydraulic roughness varies with depth of flow.

Open channels may have any shape Rectangular, Triangular, Trapezoidal, Circular, etc.

Gravity force (provided by slope)

Open Channel Flow

The velocity distribution is symmetrical about the pipe axis, maximum velocity occurs at pipe centre and the velocity at the wall is zero.

(Z+p/w), where p is the pressure in pipe. Hydraulic gradient line (HGL) does not concide with water surface.

Roughness coefficient depends upon the material of pipe.

Pipes are generally round in cross-section.

Pipe flow take place at the expense of hydraulic pressure.

Pipe Flow

Flow in Open Channels / 3

4 / Hydraulics and Hydraulic Machines

1.4 TYPES OF CHANNELS The various types of channels are as follows: 1. Prismatic and Non-prismatic Channels: A channel in which cross-sectional shape and size and also bottom slope are constant is termed as a prismatic channel. Most of man made channels are prismatic channels. The rectangular, circular, trapezoidal, traiangular are the examples of man made channel. All natural channels generally have varying cross-section are non-prismatic channels. 2. Rigid and Mobile Boundry Channels: Rigid channels are those in which boundry is not deformable, therefore the shape and roughness are not the functions of flow parameters e.g., lined canal, sewer etc. No scour and erosion take place in such a channel. All unlined channels and natural rivers in which boundary undergo deformation due to continuous process of erosion, in such a case flows carries sediments. Such channels are classified as mobile boundary channel. 3. Natural and Artificial Channels: Natural Channels are those channels which have irregular sections of varying shapes, developed in a natural way. Examples: Rivers, Streams, etc. Artificial channels are those channels which are build artificially for carrying water. They have regular geometrical shapes. Examples: Rectangular, Trapezoidal, Parabolic Channels, etc.

1.5 CLASSIFICATION OF OPEN CHANNEL FLOWS Open channel flows are classified for purposes of Identification and analysis as follows:

HYDRAULICS AND HYDRAULIC MACHINES ( Including Lab Manual) Second Edition

THE BOOK Hydraulics and Hydraulic Machines is a compulsory paper in Civil Engineering, student of UPTU, Lucknow and other Indian Universities. This book is Flow in Open Channels primarily designed as an Introductory Text Book for the student pursuing undergraduate Degree Uniform Flow (B. Tech. /B.E.) in Civil Engineering. In includes topics such as: Flow in Non-Uniform Flow–I Open Channels, Uniform flow, Non Uniform Flow (Gradually varied flow, Hydraulic Jump and Non-Uniform Flow –II Surge), Pumps and Turbines. The silent features of the five units dealt within the book Rotodynamic Pumps are: Exhaustive coverage; and Turbines clear concise itemized presentation styled for relaxed understanding to Lab Experiments and Lab Manual. grades readers; illustrative figures; solved and unsolved numerical, review questions; model papers. THE AUTHOR Saiful lslam is presently as an Assistant Professor in the Department of Civil Engineering, GCET, Greater Noida, UP. He did his B.Tech degree from Zakir Hussein College of Enineering, A.M.U. He has completed his M.Tech degree from Indian Institute of Technology, Roorkee. He is the life member of Indian Society of Technical Education. He is also the author of Engineering Geology, Building Material and Construction (Vayu Education of India). He has attended several Conferences /Workshops in National and International level.

CONTENTS

VAYU EDUCATION OF INDIA

ISBN: 978-93-83758-24-1

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