ANALYSIS OF THE WATER FLOW IN RECTANGULAR OPEN CHANNEL FLUME WITH RECTANGULAR SHARP CRESTED WEIR MUHAMMAD NORKHUZAIRI BIN SHAHARIN A report submitted in partial fulfillment of the requirements for award of the degree of Bachelor of Mechanical Engineering Faculty of Mechanical Engineering UNIVERSITY MALAYSIA PAHANG JUNE 2013
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ANALYSIS OF THE WATER FLOW IN RECTANGULAR OPEN CHANNEL FLUME
WITH RECTANGULAR SHARP CRESTED WEIR
MUHAMMAD NORKHUZAIRI BIN SHAHARIN
A report submitted in partial fulfillment of the requirements for award of the degree
of
Bachelor of Mechanical Engineering
Faculty of Mechanical Engineering
UNIVERSITY MALAYSIA PAHANG
JUNE 2013
vii
ABSTRACT
The sharp-crested weir is the most commonly used device in channels for flow
measurement and flow regulation due to its simplicity. Several attempts have been made
to study in detail the flow over different shapes of normal conventional weirs including
those with sharp crest, side weirs and oblique weirs, mainly based on experimental
work. On the contrary, little efforts have been done to use numerical models in
investigating flow characteristic and pressure distributing over these types of weirs. The
concern of this paper is to study flow over a rectangular sharp crested weir and to
provide a means to estimate the discharge coefficient. A CFD Software which is
ANSYS CFx-14 has been used for evolving a relationship to estimate the discharge
coefficient for rectangular sharp crested weirs. Several combinations of discharge and
weir height have been used to develop a best fit curve for estimating the discharge
coefficient. The discharge coefficient estimate by the develop model has been found to
be in good agreement with those listed in the literature within %4 error. The study
showed that the important variable governing discharge over sharp crested weir was the
water head over weir per weir divide by weir height, h/P. Furthermore, the advantages
of an ANSYS CFX-14 as a tool for examining velocity vectors and pressure pattern
over rectangular sharp crested weirs have been highlighted.
viii
ABSTRAK
Empangan limpah berpuncak tajam adalah salah satu alatan yang biasa digunakan untuk
mengukur pergerakan bendalir dan pengawalan sifat bendalir kerana ianya mudah untuk
dikendalikan. Beberapa kajian telah dilakukan dalam usaha untuk menkaji dan
mendapatkan maklumat penting yang berkaitan dengan alatan ini melalui kaedah
eksperimen. Sebaliknya terdapat juga beberapa kajian yang menggunakan kaedah
numerikal model untuk mengkaji sifat dan bentuk pengaliran bendalir serta tekanan
yang terlibat terhadap empangan limpah tersebut. Perkara utama dalam tesis ini adalah
untuk mengkaji pergerakan bendalir yang terjadi apabila melalui empangan berpuncak
tajam yang berbentuk segi empat tepat. Selain itu, kajian ini juga adalah untuk
mendapatkan nilai coefficient kadar air yang dilepaskan. Dalam kajian ini, satu software
CFD digunakan pakai iaitu ANYSY CFx-14. Software ini digunakan untuk mengkaji
perhubunghan antara nilai coefficient kadar air yang dilepaskan apabila melalui
empangan limpah berpuncak tajam yang berbentuk segi empat tepat. Beberapa
gabungan nilai coefficient kadar air yang dilepaskan dan ketinggian empang limpah
telah digunakan dalam usaha untuk mendapatkan kadar terbaik lengkungan.
ix
TABLE OF CONTENTS
Page
EXAMINER DECLARATION
SUPERVISOR’S DECLARATION
ii
iii
STUDENT’S DECLARATION iv
DEDICATION v
ACKNOWLEDGEMENTS vi
ABSTRACT vii
ABSTRAK viii
TABLE OF CONTENTS ix
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 Project Background 3
1.3 Problem Statements 3
1.4 Project Objectives 3
1.5 Project Scope 3
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 5
2.2 Sharp Crested Weir 5
2.3 Rectangular Sharp Crested Weir 7
2.4 Experimental and Computational Analysis of the Rectangular
Sharp Crested Weir
10
2.4.1 Sisman H. Cigdem Experiment 10
2.4.2 Sara Bagheri Experiment
2.4.3 Reda M. Abd Computational Analysis
15
16
x
2.5 Theoretical Consideration 19
2.5.1 Discharge Equation 19
CHAPTER 3 METHODOLOGY
3.1 Methodology Flow Chart 21
3.2 Simulation Flow Chart 22
3.3 Design of the Rectangular Open Channel Flume and Weir 23
3.3.1 Design of Rectangular Open Channel Flume 23
3.3.2 Design of Rectangular Sharp Crested Weir 24
3.4 Analysis Using ANSYS CFX-14 26
3.5 Analysis with the Different Weir Height 33
3.6 Flow Pattern or Water Surface Analysis 33
CHAPTER 4 RESULT AND DISCUSSION
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Introduction 50
5.2 Conclusion 50
5.3 Recommendation 51
References 52
Appendix A 53
4.1 Introduction 34
4.2 Flow Pattern over the Weir 34
4.3 Analysis of Flow over Weir with the Different Weir Height 38
4.4 Calculation of Discharge Coefficient 46
4.5 Comparison with the previous study 49
xi
LIST OF TABLES
4.1 Water depth of different discharge over 0.5m weir height 38
4.2 Water depth of different discharge over 0.75m weir height 40
4.3 Water depth of different discharge over 1m weir height 42
4.4 Total deep of stream, hT of different weir height with different
discharge
44
4.5 Water head data collection of different weir height with different
discharge.
44
4.6 Discharge coefficient calculation of 0.5m weir height 46
4.7 Discharge coefficient calculation of 0.75m weir height 46
4.8 Discharge coefficient calculation of 1m weir height 47