Universiti Malaysia Sarawak 2000

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LAMINAR TRANSITION TO TURBULENT IN DESIGN OF OPEN CHANNEL FLOW

MURNI BT MOHD MOKHTAR

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Universiti Malaysia Sarawak

2000

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LAMINAR TRANSITION TO TURBULENT IN DESIGN OF OPEN CHANNEL FLOW

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MURNI BINTI MOHD MOKHTAR

A Thesis Paper is Submitted to

Faculty of Engineering, University Malaysia Sarawak As a Fulfillment of the Requirement for the Award of A Bachelor's Degree With Honours in

Mechanical and Manufacturing System

April 2000

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Borang Penyerahan Tesis Universiti Malaysia Sarawak

R13a BORANG PENYERAHAN TESIS

Judul: LAMINAR TRANSITION TO TURBULENT IN DESIGN OF OPEN CHANNEL FLOW

SESI PENGAJIAN: 1997/2000

Saya MURNI BT MOHD MOKHTAR

mengaku membenarkan tesis ini disimpan di Pusat Khidmat Maklumat, Universiti Malaysia Sarawak dengan syarat-syarat kegunaan seperti berikut:

I. Hakmilik kertas projek adalah di bawah nama penulis melainkan penulisan sebagai projek bersama dan di biayai oleh UNIMAS, hakmiliknya adalah kepunyaan UNIMAS.

2. Naskah salinan di dalam bentuk kertas atau mikro hanya boleh dibuat dengan kebenaran bertulis daripada penulis.

3. Pusat Khidmat Maklumat Akademik, UNIMAS dibenarkan membuat salinan untuk pengajian mereka.

4. Kertas projek hanya boleh diterbitkan dengan kebenaran penulis. Bayaran royalti adalah mengikut kadar yang dipersetujui kelak.

5. * Saya fferi4emwcae/tidak membenarkan Perpustakaan membuat salinan kertas projek ini sebagai bahan pertukaran di antara institusi pengajian tinggi.

6. ** Sila tandakan ( )

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SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972).

TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan).

TIDAK TERHAD

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Alamat Tetap: IA-2-4 Lebuhraya Thean Teik, 11500 Bandar Baru Air Itam, Pulau Pinang

Tarikh: 4 April 2000

CATATAN ⁱ

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(TA)(gATANGAN PENYELIA) Nama Penyelia: En. Nazeri Abdul Rahman

Tarikh: ýf

Potong yang tidak berkenaan

Jika Kertas Projek ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyertakan sekali tempoh kertas projek.

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Disahkan oleh

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This project report entitled "LAMINAR TRANSITION TO TURBULENT IN DESIGN OF OPEN CHANNEL FLOW" was prepared by Murni Bt Mohd Mokhtar as a partial fulfillment of the requirement for the degree of Bachelor of Engineering with honours (Mechanical and Manufacturing System) is hereby read and approved by:

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ri Abd Rahmar Date

(Supervisor)

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Special Thanks to my beloved family and

my friend Hayaty

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ACKNOWLEDGEMENTS

This special acknowledgement goes to all those who have helped the author greatly for all these years. This includes her undergraduate thesis advisor at UNIMAS, Mr. Nazeri who supervise and "always there" when needed.

To Dr Ha How Ung, the head program of Mechanical and Manufacturing System, Dr Kadim, Dean of Faculty Engineering and not forgotten to all the technicians; Mr. Rhyier, Mr. Masri, and Mr. Affendi for theirs help which the author will never forget. To author friends who has given academical sources and support, directly or indirectly. This acknowledgement also goes especially to the author family and her friend Hayaty Binti Mahdini for their support and love.

Special thanks to all the author's lecturers and tutors. To author ex teacher, in primary and secondary school for their guidance. Lastly to all persons that the author does not mentioned here and may Allah bless all of you.

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ABSTRACT

The laminar transition to turbulent flow is usually occurred at any flow of liquid but what make it difference are their velocity and other condition. The main objective of this study was to understand how laminar flow transition to turbulent occurred in open channel flow and designed an open channel model. Their effect is studied and thoroughly the Reynolds number that suitable for each laminar, transition and turbulent flow condition are determined. The method of study was discussed and the data will be plotted in the form of Pressure against Velocity by using a simple program, which has been made using Visual Basic language. The results obtained from this study of open channel could not achieved laminar flow because of inadequate equipment and parts.

Besides, errors on the design have only been realized after the design has been produced.

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ABSTRAK

Aliran laminar yang mengalami pertukaran kepada aliran bergelora biasanya berlaku dalam semua jenis aliran cecair, tetapi apa yang membezakan aliran-aliran ini adalah nilai halaju dan faktor-faktor lain. Objektif utama kajian ini dibuat adalah untuk memahami arus laminar yang bertukar kepada arus gelora dalam salur aliran terbuka yang dibuat dan direka dalam bentuk model. Kajian ini juga dijalankan untuk mengkaji dengan lebih mendalam mengenai kesan dan nilai nombor Reynolds yang bersesuaian dengan kajian ini. Data yang diperolehi dari kedalaman aliran air akan dimasukkan dalam suatu program kiraan yang dibuat menggunakan Visual Basic, di mana dalam program ini graf tekanan air melawan halaju aliran air akan diperolehi. Keputusan eksperimen yang diperolehi daripada kajian mengenai salu aliran terbuka ini tidak dapat menghasilkan arus laminar disebabkan oleh penggunaan alat yang tidak memenuhi spesifikasi. Selain daripada itu, kesilapan dalam merekabentuk model hanya disedari apabila model tersebut telah dihasilkan.

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... 10 2.2 Design of Channel ... 11

2.2.1 The Law of Water Flow in Open Channel

... 11 2.2.2 Flow Velocities in Open Channel Flow

... 12 2.2.3 An Equation for Open Channel

... 12 2.3 Manning Summary

... 13

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CHAPTER 3

- DESIGN OF OPEN CHANNEL ... 14 3.1 Introduction

... 15 3.2 Part of Design ... 14

3.2.1 Test Sectional

... 15 3.2.2 Coloring Holder

... 16 3.2.3 Flow Rate Meter

... 17 3.2.4 Valve

... 18 3.2.5 Honeycomb

... 19 3.2.6 Water Pump

... 21 3.3 Entire Design

... 21

CHAPTER 4 - EXPERIMENTAL METHODOLOGY ... 26 4.1 Introduction

. . . 26

4.2 Description of Laminar Transition to Turbulent Flow Test ... 26

4.2.1 Pump

... 27 4.2.2 Velocity

... 29 4.2.3 Water Pressure

... 29 4.2.4 Visual Basic Program

... 29

4.3 Open Channel Flow Theory

... 31 4.4 Experimental Procedure

... 34

CHAPTER 5 - CALCULATION PROGRAM ... 36 5.1 Introduction

... 36 5.2 The user Interface ... 36

5.2.1 Splash Screen

... 37

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5.2.2 Optional Screen

... 38

5.2.3 Experiment Calculation Screen ... 39

5.2.4 About Screen ... 41

CHAPTER 6 - RESULT AND DISCUSSION ... 43

6.1 Introduction ... 43

6.2 Transition to Turbulent Flow ... 44

6.3 Problem Facing ... 47

6.3.1 Effect From Pump ... 48

6.3.2 Effect From Gate Valve ... 48

6.3.3 Effect From Table ... 49

6.3.4 Effect From Coloring Injector ... 49

6.3.5 Effect From Small Outlet Flow ... 49

6.3.6 Effect From Pipe ... 50

6.3.7 Effect From Volume of Water ... 50

6.3.8 Effect From Type of Coloring ... 50

CHAPTER 7 - CONCLUSIONS AND RECOMMENDATION ... 51

7.1 Conclusions ... 51

7.2 Recommendation for Further Work ... 52

7.2.1 Using Other System ... 52

7.2.2 Use Advance Measurement ... 52

7.2.3 Using More Concentrate Coloring ... 52

7.2.4 Change Open Channel Flow Design Concept ... 53

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BIBLIOGRAPHY

... 54

APPENDIXES APPENDIX A - DESIGN REFERENCES ... 57

APPENDIX B - CONVERTER GRAPH ... 61

APPENDIX C - CALCULATION PROGRAM ... 63

APPENDIX D - EXPERIMENTAL DATA ... 69

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INDEX OF FIGURES

Figure 1.1 Figure 1.2 Figure 1.3 Figure 1.4 Figure 1.5 Figure 1.6 Figure 3.1 Figure 3.2 Figure 3.3 Figure 3.4 Figure 3.5 Figure 3.6 Figure 3.7 Figure 3.8 Figure 3.9 Figure 4.1 Figure 4.2 Figure 4.3 Figure 4.4 Figure 4.5

Uniform and Non-uniform Flow

... 2 Uniform and Non-Uniform Flow Effect in Channel

... 3 Laminar Flow

... 4 Turbulent Flow

... 4 laminar flow around basic shape of submarine ... 5 Waves in Rectangular Channel

... 6 Glass Box for Test Sectional

... 15 Process of Installer Coloring Holder

... 16 Gate Valve

... ... ... 19

Flow Moves in Straight Line

... 19 Flow Straightened with Using Honeycomb ... 20 Honeycomb with a Circle Shape

... 20 Water Tank

... 23 Entire Design with Measurement

... 24 Entire Design

... 25 Open Channel Flow Design

... 27 Connection of Pipe ... 28 Set of Instrument ... 30 Wetted Perimeter

... 32 The Different Position to Read The Data

... 35

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Figure 5.1 Splash Screen for OCFC Program

... 37 Figure 5.2 The Optional Screen

... 39 Figure 5.3 Experiment 1 Calculation Screen

... 40 Figure 5.4 Experiment 2 Calculation Screen

... 41 Figure 5.5 The About Screen

... 42 Figure 6.1 Transition Flow

... 45 Figure 6.2 Turbulent Flow

... 45

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INDEX OF TABLE

Table 4.1 Centrifugal Pump General Description

... 28 Table 6.1 Transitional Flow in Open Channel

... 46 Table 6.2 Turbulent Flow in Open Channel

... 47

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NOMENCLATURE

A Cross Sectional

b Width of Open Channel

Dh Hydraulic Diameter

h Channel Length

P Wetted Perimeter

P Water Pressure

Pa Atmospheric Pressure

Re Reynolds Number

Rh Hydraulic Radius

V Velocity

v Water viscosity

z Depth of Flow in Open Channel

yw Specific weight of water

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CHAPTER 1

INTRODUCTION

1.1 Introduction to Open Channel Flow

The open channel means the liquid, which are bounded by side walls while their upper boundary is a free surface. Water at room temperature is practically used for experiment in open channel. Since there was free surface in open channel, it was subjected to atmosphere pressure and at the bottom layer friction. This is because the flow in the upper part of the channel is effected by gravity while lower part of the channel is effected by friction of channel surface.

The examples of open channels are frequently encountered at natural streams, rivers, canals and also for pipe-lines or tunnels which are not completely fill with liquid.

The open channel has several shapes such as rectangular, circle and irregular. Different in shape gives the different value effect of friction and ambient pressure. Usually the channel with irregular width such as river is suitable for the research in finding the hydraulic jump and friction loss. This is due to the channel roughness, which will have more difficulties to have the laminar flow. It will also directly produce turbulent when the flow collide with the roughness surface. [Robert, 1994]

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Chapter 1 Introduction

1.2 Flows in Open Channel

The flow in open channel may be uniform or non-uniform, steady or unsteady. It is said to be uniform if the velocity of the liquid does not change either in magnitude or direction. This condition is achieved only if the cross-section of the flow does not change along the length of the channel and thus the depth of the liquid must be unchanged. Consequently, uniform flow is characterized by the liquid surface being parallel to the base of the channel.

Flow in which the liquid surface is not parallel to the base of the channel is said to be non-uniform or also known as varied, since the depth of the liquid continuously varies from one section to another. Figure 1.1 shows the uniform and non-uniform flow in open channel flow. The change in depth may be rapid or gradual and it is commonly called rapidly varied flow and gradually varied flow. Sometime uniform flow exists in one part of a channel while varied flow exists in another part. This phenomenon is showed by Figure 1.2. [Walter, 1990]

Figure 1.1 Uniform and Non-uniform Flow [Massey, 1983]

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Figure 1.2 Uniform and Non-Uniform Flow Effect in Channel [Massey, 1983]

The flow is classified as steady or laminar and unsteady or turbulent in accordance to the velocity and depth of channel. These two main types of flows in open channel have differences in their flow properties. Laminar flow is a fluid that moving in straight line and is also known as steady flow. Laminar usually occur at very low flow rates and it is difficult to be achieved in open channel because of the effect from the ambient pressure. It is also occurred at shorter length. Laminar flow is longer in length if it is flowing in the closed duct such as piping system. Figure 1.3 shows the laminar flow out from pipe, which the liquid is not completely filled the pipe.

Meanwhile, Turbulent flows generally take place when the flow rate is high.

Turbulent is a flow, which is no longer smooth and not straight. Usually open channel produce turbulent flow due to effect from surrounding. With the free surface, the flows of open channel can be easily transformed to turbulent whenever it receives any

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Chapter I Introduction

disturbance. In addition the transition is very fast and short, sometime could not be seen by naked eyes. Figure 1.4 shows the turbulent flow out from pipe as the liquid is not completely full. [White. 1994]

Figure 1.3 Laminar Flow [White. 1994]

Figure 1.4 Turbulent Flow [White. 19941

1.2.1 Reynolds number

Co measure ý hether the flow is in laminar or turbulent flow. it is needed to calculate their Reynolds number. To find Reynolds number the hydraulic diameter, it is

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Chapter 1 Introdnctron

required to determine the velocity and viscosity of the liquid. Usually in open channel, laminar flow occurs when the Reynolds number is 600. If the Reynolds number is over than 600, the flow is no longer laminar and will be in transition to turbulent flow.

Meanwhile for turbulent to happen in open channel flow, the Reynolds number should be bigger than 1 x 10' . I f the Reynolds number is between 600 and l x 10' the flow is called as transition flow. The Reynolds number is different for different shape of channel. Thus, to find the Reynolds number the wetted perimeter for the channel will be considered. Besides. the velocity also affects the Reynolds number. [Massey. 1983]

Reynolds number has a lot advantages in fluid mechanics, because it gives information to the flow condition. For example, the submarine has been designed in cylindrical shape and sharp at its front because it gives smooth movement and it can reduce the turbulent flow. Therefore, the speed of submarine will increase because of less resistance to the flow. Figure 1.5 shows the laminar flow around the basic shape of submarine.

Figure 1.5 laminar flow around basic shape of submarine. [Merzkirch, 1987]

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Chapter I Introduction

1.3 Simple Waves and Surges in Open Channel

Waves and surges of various kinds, which produce unsteady condition, may disturb the flow in open channel. Open channel was a free surface, therefore any disturbances will produce wave in their flow and this will cause turbulent flow in open channel. For example, a stone dropped into a pond causes a series of small surface waves or the effect from opening water gate produce, surged waves and the laminar flow is difficult to be achieved. Figure 1.6 shows the waves in the simple rectangular channel that always occurs in open channel flow.

Waves f-

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Figure 1.6 Waves in Rectangular Channel [Massey, 1983]

1.4 Objective of This Study

The objective of this study is to design an experiment for open channel flow and to define at what condition, laminar flow will change to turbulence.

This study will also find the suitable Reynolds number or each condition of flow by using the experiment data obtained.

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A simple program to calculate and compare the data from experiment will be created. With the data that have been calculated, by the program, graphs of pressure against velocity will be plotted. In order to determine at the relationship between the pressure and velocity in open channel flow.

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CHAPTER 2 LITERATURE

REVIEW

2.1 Open Channel Flow

The study of open channel flow is started by Greeks scientists, particularly Aristotle and Archimedes.

Aristotle (384-322 B. C. ) believed that the motion exhibited by all elements, including water, was related to their tendency to return to their natural level. He discussed the movement of bodies through air and water, and found out that "when the moving thing impedes, it will cause a difference in the medium. In a secondary degree, even if it is at rest, most of all it is moving in the opposite direction. " He was then thought about drag. Drag occurred when the body moved through a medium (air, water) or fluid resistance if the fluid flowed over a stationary streambed.