PERPUSTAKAAN UMP I VU III ll IV 111 VII 11111 0000092511 EXPERIMENTAL STUDY ON FLOW AROUND IMMERSED OBJECTS LAILATUL JALILAII BIINTI KAHARUDIN Thesis submitted in partial fulfillment of the requirements for the award of the degree of B. ENG (lIONS.) CIVIL ENGINEERING Faculty of Civil Engineering & Earth Resources UN1VERSITI MALAYSIA PAHANG JUNE 2014
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PERPUSTAKAAN UMP
I VU III ll IV 111 VII 11111 0000092511
EXPERIMENTAL STUDY ON FLOW AROUND
IMMERSED OBJECTS
LAILATUL JALILAII BIINTI KAHARUDIN
Thesis submitted in partial fulfillment of the requirements
for the award of the degree of
B. ENG (lIONS.) CIVIL ENGINEERING
Faculty of Civil Engineering & Earth Resources
UN1VERSITI MALAYSIA PAHANG
JUNE 2014
ABSTRACT
It is well known that when fluid flows around an object, the object will experience a force due to the interaction between the object and the fluid surrounding it. This study was conducted in an open channel using three different types of immersed objects (circular-shaped, rectangular-shaped, square-shaped) and was divided into two parts. The first part was on the investigation of wake length that results due to different immersed object shapes and fluid flow velocities. The experiments were carried out at different flow rates ranging from 2 L/s to 14 L/s and the corresponding wake lengths were measured. The results show that the wake length increases as the velocity increases. The second part of the study was on the investigation of the resultant drag force on the immersed objects during different combinations of object shapes and fluid flow velocities. Based on the experimental data, the Reynolds number for each immersed object was calculated and the drag coefficient of each immersed object was obtained from graphs and tables in established publications. It was found that the Reynolds numbers for both square and circular shape of the immersed objects were similar due to the frontal area of the objects that were taken into account in the calculations. The resultant drag force was calculated based on the drag coefficient obtained. From the results, the flowing water exerted the highest drag force on the immersed object that was rectangular-shaped compared to the other two shapes that was investigated. This is the effect of different drag coefficient values that are in turn based on the respective Reynolds number and object shape. Another finding was that when the velocity and drag coefficient were increased, the drag force values also increased.
Vi
ABSTRAK
Seperti yang diketahui bahawa apabila aliran mengalir di sekeliling objek, objek akan mengalami daya yang disebabkan oleh interaksi di antara objek clan cecair sekitamya. Kajian mi dijalankan. dalam saluran terbuka dengan menggunakan tiga jenis objek tenggelam (bentuk bulat, bentuk segi empat tepat, bentuk segi empat sama) dan dibahagikan kepada dua bahagian. Bahagian pertama adalah mengenai penyiasatan panjang 'wake' akibat kerana bentuk objek tenggelam berbeza dan halaju aliran bendalir. Kajian mi telah dijalankan pada kadar aliran yang berbeza dari 2 L / s 14 L I s dan panjang 'wake' sepadan telah diukur. Keputusan menunjukkan bahawa panjang 'wake' bertambah apabila halaju bertambah. Bahagian kedua kajian mi adalah berkenaan dengan penyiasatan daya seretan yang terhasil pada objek tenggelam dalam kombinasi yang berbeza bentuk objek dan halaju aliran bendalir. Berdasarkan data eksperimen, nombor Reynolds bagi setiap objek tenggelam dikira dan pekali seretan setiap objek tenggelarn telah diperolehi danipada graf dan jadual dalam penerbitan ditubuhkan. la telah mendapati bahawa nombor Reynolds bagi kedua-dua bentuk persegi dan bulat objek tenggelam adalah sama kerana kawasan hadapan objek yang telah diambil kira dalam pengiraan. Daya seretan terhasil dikira berdasarkan pekali seretan yang diperolehi. Daripada keputusan, air yang mengalir dikenakan daya seretan yang paling tinggi pada objek yang terendam yang segi empat tepat berbentuk berbanding dua bentuk yang lain yang telah dikaji. mi adalah kesan danipada nilai-nilai pekali seret yang berbeza yang seterusnya berdasarkan bilangan Reynolds masing-masing dan bentuk objek. Penemuan lain adalah bahawa apabila halaju dan pekali seretan telah meningkat, nilai daya seretan juga meningkat.
VII
TABLE OF CONTENTS
Page
SUPERVISOR'S DECLARATION
STUDENT'S DECLARATION
DEDICATION iv
ACKNOWLEDGEMENT v
ABSTRACT vi
ABSTRAK vii
TABLE OF CONTENTS viii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF SYMBOLS xiv
LIST OF ABBREVIATIONS xv
CHAPTER 1 INTRODUCTION
1.1 Introduction 1
1.2 Problem Statement 4
1.3 Objective of the Research 4
1.4 Scope of Study 5
CHAPTER 2 LITERATURE REVIEW
2.1 Characteristics of Flow past an Object 6
2.2 Boundary Layer 9
2.3 Drag Force 10
2.3.1 Friction Drag 12 2.3.2 Pressure Drag 12
VIII
ix
2.4 Drag Coefficient 13
2.4.1 Object Shape 13 2.4.2 Reynolds Number 14
2.5 Wake Control
15
2.6 Past Experiment on Flow Immersed Object 1R
CHAPTER 3 METHODOLOGY
3.1 Introduction 19
3.2 Flowchart of the Study 20
3.3 Location of Experiment 21
3.4 Research Parameter Selection 21
3.5 Materials and Tools 23
3.6 Experimental Setup 26
3.7 Laboratory Experiment Procedure 27
CHAPTER 4 RESULTS AND DISCUSSIONS
4.1 Introduction 31
4.2 Data Collection 32
4.3 Wake behind Immersed Objects 33
4.4 Analysis of Wake 37
4.5 Drag Coefficient and Reynolds Number 39
4.5.1 Calculation of Reynolds Number 39 4.5.2 Analysis of Drag Coefficient and Reynolds Number 42 4.5.2.1 Circular Object Shape 43 4.5.2.2 Square Object Shape 44 4.5.2.3 Rectangle Object Shape 45 4.5.2.4 Drag Coefficient versus Reynolds Number 46
4.6 Drag Force 47
4.6.1 Calculation of Drag Force 47 4.6.2 Analysis of Drag Force 51
x
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Conclusion 53
5.2 Recommendations 55
REFERENCES 56
APPENDICES
A Graph Drag Coefficient, Cd for Circular Shape 58
B Table Drag Coefficient, Cd for Square Shape 59
C Table Drag Coefficient, Cd for Rectangle Shape 60
D Table of Physical Properties of Water 61
E Laboratory Experiment 62
LIST OF TABLES
Table No. Title Page
3.1 Experiments parameter values 23
4.1 Experiments data recorded 33
4.2 Wake behind Circular Objects 35
4.3 Wake behind Square Objects 35
4.4 Wake behind Rectangle Objects 36
4.5 Reynolds number for Circular shape 40
4.6 Reynolds number for Square shape 41
4.7 Reynolds number for Rectangle shape 41
4.8 Re and CD for each objects 42
4.9 Data calculated for circular shape 48
4.10 Data calculated for square shape 49
4.11 Data calculated for rectangle shape 50
4.12 Drag force, FD for three objects 51
A
LIST OF FIGURES
Figure No. Title Page
1.1 Flow pattern past a cylinder 2
1.2 Water flowing around the object 3
2.1 Categories of bodies 7
2.2 Flows past flat plate 8
2.3 Boundary layer profile over a flat plate 9
2.4 Flows within the boundary layer along flat plate 10
2.5 Lift and drag concepts 11
2.6 Drag coefficient for an ellipse 14
2.7 Drag coefficient as a function of Reynolds number 15
2.8 Experiment using splitter plate 17
3.1 Flowchart of the Study 20
3.2 Hydraulic Laboratory, UMP 21
3.3 Size of open channel 22
3.4 Shapes of the objects 22
3.5 Object shapes 24
3.6 Flow meter 25
3.7 Meter Tape 25
3.8 Experimental setup 26
3.9 Water admits into the channel 27
3.10 Object place in the center 28
3.11 Measure using the flow meter 28
3.12 Height of water 29
3.13 Measure using meter tape 29
XII
XIII
3.14 Rectangle and square shapes 30
3.15 Control valve 30
4.1 Wake length vs. velocity for circular 37
4.2 Wake length vs. velocity for square 37
4.3 Wake length vs. velocity for rectangle 38
4.4 Wake length vs. velocity for different objects shapes 38
4.5 Drag coefficient vs. Reynolds number for circular 43
4.6 Drag coefficient vs. Reynolds number for square 44
4.7 Drag coefficient vs. Reynolds number for rectangle 45
4.8 Drag coefficient vs. Reynolds number 46
4.9 Drag force versus Velocity 52
LIST OF SYMBOLS
CD Drag coefficient
Re Reynolds number
Ma Mach number
Fr Froude number
L Lift
FD Drag force
V Velocity
P Density
D Diameter
A Area of the body
1 Length
V Kinematic viscosity
T Temperature
xiv
LIST OF ABBREVIATIONS
FKASA Faculty of Civil Engineering & Earth Resources
LDV Laser Doppler Velocimetry
LES Large Eddy Simulations
UMP Universiti Malaysia Pahang
Vs. Versus
xv
CHAPTER 1
INTRODUCTION
1.1 Introduction
Whenever fluid moves past the body of an object, an interaction between the
body of an object and the fluid happens. This study deliberates on the flow over bodies
that are immersed in water. This situation includes flow past objects. When an object is
immersed in moving water, it experiences a force due to the interaction between the
object and the water surrounding it. The forces are namely drag force, lift force, shear
force and pressure force. Besides that, flow past an object such as a circular cylinder
will produce a wake or vorticity due to shear present in the boundary layer. This
vorticity in the flow field combines into areas of concentrated vorticity recognized as
vortices on either side of the cylinder (Stappenbelt, 2010).
There are various phenomena related to flow around bodies. One of the most
important of these is the force acting on the body due to the fluid. They happen in many
engineering circumstances, such as bridges, stacks, transmission lines, aircraft control