EXPERIMENTAL EVALUATION OF VORTEX GENERATOR USAGE TO REDUCE THE COEFFICIENT OF DRAG OF PROTON SAGA CAR

AIZAD AYASYI B AB GHAFAR

A thesis submitted in partial fulfillment

of the requirements for the award of the degree of

Bachelor of Mechanical Engineering

Faculty of Mechanical Engineering

Universiti Malaysia Pahang

UNVERST MALAYSA PAHANG NO. FerOelar,

037921No. Pnogi

- Tarzkh

ABSTRACT

Proton Saga is one of the most successful sedan cars in Malaysia. The

aerodynamics of this car can be defined as bad because the box shape gives a great

value of drag coefficient. The improvement of the aerodynamics of Proton Saga car

can reduce the fuel consumption because the power needed to withstand the drag

force created is decreased. Economical effective wool tufts method is use to analyze

the airflow of Proton Saga car with vortex generator. The increase of pressure

distribution on the rear window surface of the car makes the flow separation to delay.

The aerodynamics improves with the changes of most turbulence flow into laminar

flow. The prediction that can be made that the drag force created decrease

proportionally with the drag coefficient. This paper presents the analysis of the effect

of vortex generator usage on delaying flow separation of Proton Saga car

experimentally.

V

ABSTRAK

Kereta Proton Saga adalah salah satu kenderaan yang banyak digunakan di

Malaysia. Keadaan aerodinamik kereta mi adalah tidak begitu baik kerana bentuknya

yang berupa seakan kotak menyebabkan nilai pemalar heret untuk kereta mi adalah

tinggi. Penambahbaikan aerodinamik dapat mengurangkan kadar penggunaan

minyak kerana kuasa yang dijana oleh enjin yang diperlukan untuk menentang daya

heret yang terhasil dapat dikurangkan. Kaedah analisis yang murah dan berkesan

menggunakan benang kait untuk mengkaji aliran udara keatas permukaan kereta

Proton Saga dengan penambahan allat penjana pusaran angin. Peningkatan tekanan

diatas permukaan cermin belakang kereta mi menyebabkan perubahan aliran udara

ditangguh. Aerodinamik kereta im diperbaiki dengan perubahan aliran udara jems

pusaran kepada aliran udara jenis sekata. Anggapan yang dapat dibuat adalah daya

heret berkurangan secara langsung dengan pemalar heret. Kertas kajian mi ditulis

untuk mengkaji kesan penggunaan alat penjana pusaran angin terhadap penangguhan

aliran udara secara ujikaji.

vi

TABLE OF CONTENT

CHAPTER TITLE PAGE

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

LIST OF CONTENT vii

LIST OF FIGURE x

LIST OF SYMBOLS xii

LIST OF ABBREVIATION xiii

LIST OF APPENDICES xiv

1 INTRODUCTION

1.0 Introduction 1

1.1 Problem Statement 3

1.2 Objectives of the Project 3

1.3 Scope of the Project 4

1.4 Flowchart 5

1.5 Thesis Disposition 6

2 LITERATURE REVIEW

2.0 Introduction 7

2.1 Aerodynamics

2. 1.1 Definition 9

2.1.2 Classes of Aerodynamics Problems 9

2.1.3 Automotive Aerodynamics 10

vii

viii

2.2 Flows Separation through a Road Vehicle

2.2.1 Introduction 11

2.2.2 Boundary Layer Development 11

2.2.3 Laminar & Turbulent Flows 12

2.2.4 Flows around car's body 13

2.2.5 Flows around Sedan 14

2.2.6 Pressure Distribution 15

2.3 Vortex Generator (VG(s))

2.3.1 Introduction 15

2.3.2 Mechanism of VG(s) 16

2.4 Previous Research of VG(s) 18

2.4.1 Research on Aerodynamic Drag

Reduction by VG(s)

2.4.1.lIntroduction 18

2.4.1.2 Experiment Method 18

2.4.1.3 Designing the Evo VG(s) 19

2.4.1.4 Test Results 21

2.4.1.5 Conclusion 24

2.4.2 Blowing the Vortex Part 4

2.4.2.1 Introduction 25

2.4.2.2 Experiment Method 25

2.4.2.3 Test Result 27

2.4.2.4 Conclusion 28

2.5 Airflow Measurement Techniques 29

2.6 Design the VG(s)

2.6.1 Various Designs of VG(s) 30

2.6.2 Factors to be considered 31

2.7 Consequences of using VG(s) 32

2.7 Conclusion 33

3 RESEARCH METHODOLOGY

3.0 Introduction 34

3.1 Wool Tufts Airflow Analysis

lx

3. 1.1 Wool Tufts Preparations 36

3.1.2 Driving and Photographing 37

3.1.3 Method Procedure 37

3.2 Fabricating the VG(s)

3.2.1 Material Selection 38

3.2.2 Design of the VG(s) 38

3.3 Experiment Parameters 39

3.4 Conclusion 40

4

RESULT AND DISCUSSION

4.0 Introduction 41

4.1 Airflow Analysis on Proton Saga Body without VG(s) 41

4.2 Design and Fabricating the VG(s) 44

4.3 Airflow analysis on Proton Saga body with VG(s) 44

4.3.1 Airflow Analysis of 90° VG(s) 45

4.3.2 Airflow Analysis of 15°VG(s) 46

4.3.3 Airflow Analysis on the Designs of the VG(s) 47

4.4 Conclusion 48

5 CONCLUSION

5.1 Overall Conclusion 50

5.2 Recommendations 51

REFERENCES 52

APPENDIX 53

LIST OF FIGURE

NO. TITLE PAGE

1.1 Common shapes with its drag coefficients 2

1.2 Flow around a sedan 2

1.3 Flowchart 5

2.1 Overview diagram for Literature Review 8

2.2 Flow through a plate 11

2.3 Velocity boundary layer development on a flat plate 12

2.4 Patterns of air flows through a Porsche body 13

2.5 Patterns of airflow around rear body observe using tuft-wool 14

2.6 Pressure distribution on sedan car 15

2,7 VG(s) installed on a car 16

2.8 Schematics of velocity profile around rear end 16

2.9 Schematics of flow around VG(s) 17

2.10 Velocity profile on roof 19

2.11 Location of VG(s) 20

2.12 Bump shape VG(s) 20

2.13 Delta wing shape VG(s) 21

2.14 Test result for Bump shape 21

2.15 Test result for Delta wing shape 22

2.16 Velocity distribution by CFD without VG(s) 23

2.17 Velocity distribution by CFD with VG(s) 23

2.18 Pressure distribution by CFD 24

2.19 Wool tufts on Toyota Prius rear window 26

2.20 Airtabs VG(s) 26

2.21 4 VG(s) installed to the car 27

2.22 6 VG(s) installed to the car 28

x

xl

2.23 Single vortex generator designs 31

3.1 Overview diagram for research methodology. 35

3.2 Grid line for wool tufts line up 36

3.3 3D models for 90° angle VG(s) 39

3.4 3D models for 150 edge VG(s) 39

4.1 Wool tufts patents at early acceleration 42

4.2 Wool tufts patterns at 30 km/h 42

4.3 Wool tufts patterns at 50 km/h 43

4.4 The separation point 43

4.5 90°VG(s) 45

4.6 150VG(s) 45

4.7 Comparison of wool tufts patterns with and without VG(s) 46

4.8 Comparison of wool tufts patterns with and without VG(s) 47

4.9 Comparison of wool tufts patterns for both VG(s) designs 48

LIST OF SYMBOLS

Cd = Coefficient of Drag

T = Shear Stress

U = Velocity of Air

FD = Drag Force

P = Density of Air

g = Gravity Acceleration

h = Height

X = Sweep Angle

= Incidence Angle

A = Projected Area

p = Pressure

Re = Reynolds Number

V = Velocity of Car

xii

LIST OF ABBREVIATIONS

VG(s) Vortex Generator/s

CFD Computational Fluid Dynamics

mm Millimeter

m Meter

3D Three Dimensional

kg Kilogram

xlii

xlv

LIST OF APPENDICES

APPENDIX TITLE PAGE

Al 90°VG(s) Design 53

A2 15°VG(s) Design 54

Bl Final Year Project 1 Gantt Chart 55

B2 Final Year Project 2 Gantt Chart 56

CHAPTER 1

INTRODUCTION

4.0 Introduction

The presence of road vehicles is increases each day. This situation forced the

manufactures to improve their vehicle's design. Some of the improving features on

the vehicles are aerodynamic design, ergonomic design and the power of the engine.

Feature such an aerodynamic design need to be improve after concerning to the

attractive looks, fuel consumption and passengers safety regarding to the vehicle's

stability. It is an important feature of aerodynamic design to give safety condition for

the passenger.

The body of a car is design via studies of air flows through the surface. Drag

coefficient of a car is refers to the dimensionless coefficient of drag force of a certain

shape [1]. The reduction of drag is essential to improve driving performance, fuel

consumption and aerodynamics design that can gain attractive.

The body car is design in such ways to allow air flows through the body. The

sedan car like Proton Saga car body's bluffness, when expressed by the drag

coefficient is generally between 0.2 and 0.5, while the more bluff cubic objects is

greater than 1 and least bluff bullets is less than 0.1. Figure 1.1 below shows the

variety shapes and its general drag coefficient:

2

C0 s1.9S Fbtptate

Co = 1.42, Hamisphafe -

_____ C0 039 Harnispw

- Co =0.007 _____ MoH

Figure 11 Common shapes with its drag coefficients

Two elements that have major influence on the drag coefficient of a bluff

object are the roundness of its front corners and the degree of taper at its rear end.

Figure 1.2 Flow around a sedan. [6]

Figure 1.2 above shows the flows around a sedan car. The presence of a trunk at

the rear cause the flow to separates at the roof end and then spreads downwards.

In aeronautical field, it is important to measure the best drag and lift force of

an airplane in order to lower the stall speed of the plane and improve the stability. To

achieve that, vortex generators (VG(s)) increases the mean streamwise momentum of

the boundary layer by drawing in high momentum fluid from the freestream [2].

J

If the same principles applied into the sedan car, theoretically the drag

coefficient can be reduce by the help of VG(s), thus improving the airflow around the

car's body.

4.1 Problem Statement

When a sedan car such as Proton Saga car moving, the airflow separation

above the car's body occur. Because there are different pressure distributions from

the roof of the car down to the window and boot lid, the airflow around these parts is

slightly different. Laminar flow occurs at low pressure region on top of the roof

while the pressure distribution increase as the air flows along the rear window and

the boot lid. The increments of pressure distribution contribute the existence of

turbulent flow at A region as shown in Figure 1.2.

The present of turbulent flow will affected the aerodynamic of the car. The

separation point from laminar flow to turbulent flow occurs at the rear end of the

Proton Saga car roof. The purpose of VG(s) installed are to give additional air and to

control the flow separation at the roof end of Proton Saga car by delaying the flow

separation, thus allowing the laminar air flows along the rear window. As this

happen, the aerodynamic of Proton Saga car will be improved.

1.2 Objective of the Project

i. To study the air flow of Proton Saga car.

ii. To design and fabricate the suitable size of VG(s) that can improve

the aerodynamic of Proton Saga car, thus reduce the drag coefficient.

4

1.3 Scope of the Project

i. Observe and analyze airflow through Proton Saga car body using

wool tufts method.

ii. Fabricate suitable VG(s) using aluminum sheets.

iii. Literature study.

1.4 Flowchart

START

I DEFINE OBJECTIVES AND SCOPE

I LITERATURE STUDY

I RESEARCH METHODOLOGY

OBSERVE AND ANALYZE THE AIRFLOW WITHOUT VG

DESIGN THE VORTEX GENERATOR VG(s)

OBSERVE AND ANALYZE THE

NO I I AIRFLOW WITH VG(s)

AIRFLOW IMPROVE>

YES

RESULT AND DISCUSSION]

T CONCLUSION ]E: FYP FINAL PRESENTATION

4,

FYP FINAL REPORT SUBMISSION

Figure 1.3 Flowchart of the study

LSJ

1.5 Thesis Disposition

Chapter 1 is more towards the introduction of the project. The objectives of

the project, the scope and limitation and the problem statement on why this project is

necessary to be done discussed in this chapter. Chapter 1 also is an overview about

the project in more general view.

Chapter 2 is the Literature Review; discuss about the literature that referring

to the project. The content in this chapter is narrowed from the general description

about aerodynamics to the consequences of VG(s) usage on a car. Also include in

this chapter are the previous studies on VG(s) usage to improve the aerodynamics of

the car with different procedure.

The methodology of the study will be discuss in Chapter 3; Research

Methodology. The procedure for analysis, design and fabrication process will be

discussed in detail and systematic way. The material selection and procedure to be

done for goal achieve will be discuss later on.

Result and Discussion is the title for Chapter 4. All the result data, graphs,

photographic and calculation will be show and discuss in this chapter. the whole

conclusion whether the objective is achieve or not will be stated in Chapter 5 after

concerning all the result and analysis.

CHAPTER 2

LITERATURE REVIEW

5.0 Introduction

The purpose of this chapter is to explain about the principles of aerodynamics

especially on road vehicle which can be understood through fluids dynamics studies.

Chapter Two also discussed about the previous researches on VG(s). In addition, in

order to design the VG(s), the way of the flow through the vehicle must be observed.

This flow can be observed via aero test and using simulation which is will be

explained details in this chapter. From the previous research, the VG(s) was design to

suite a sedan car. A part from that, we can apply the mechanism of VG(s) to

Malaysian sedan car. This mechanism will be discussed details in Chapter Two.

Figure 2.1 shows the overview diagram for Chapter Two.

Aerodynamics of Road Vehicle

Automotive Aerodynamics

Flow separation

Laminar and Turbulence flow

Pressure Distribution on the car surface

Drag Coefficient

Airflow Measurement Techniques

Vortex Generator

Previous Studies of VG(s)

Consequences of VG(s)

Figure 2.1 Overview diagram for Literature Review

2.1 Aerodynamics

2.1.1 Definition

Aerodynamics is a branch of fluids mechanics which study about the forces

generated on a body in a flow 3]. The aerodynamics usually involves calculation in

the properties of the flow such as pressure, velocity, temperature, density as a

function of space and time. In order to calculate or approximate the forces and

moments acting on the bodies in the flow, we must understand the pattern of the

flows.

2.1.4 Classes of Aerodynamics Problems

Aerodynamic problem can occurred in many classes. The studies of flow

around solid objects of various shapes called the External Aerodynamics such as

evaluating the lift and drag on an airplane and the shock waves that form in front of

the nose of a rocket. The Internal Aerodynamic then studies about the flow through

passages in solid objects such as study of the airflow through a jet engine or through

an air conditioning pipe.

The second classification of aerodynamic is the ratio of the characteristic

flow speed to the speed of sound. A problem is called subsonic if all the speeds in the

problem are less than the speed of sound, transonic if speeds both below and above

the speed of sound are present, supersonic when the characteristic flow speed is

greater than the speed of sound, and hypersonic when the flow speed is much greater

than the speed of sound.

The third classification is concerned about the influence of viscosity. Some

problem involve only negligible viscous effects mean that the viscous can be

lv

considered not exist. This problem called inviscid flows meanwhile the flows which

viscosity cannot be neglected called viscous flows

2.1.5 Automotive Aerodynamics

Automotive aerodynamics is the study of the aerodynamics of road vehicles

[4]. This study involves reducing drag, reducing wind noise and preventing undesired

lift forces at high speed. It is also important to produce required downwards

aerodynamics force to improve traction and cornering abilities in some class of

racing car.

To have a small surface, the aerodynamic automotive will integrate the wheel

and lights. To be streamlined, it does not have shape edge crossing the wind stream

and feature a sort tail called fastback. The aerodynamic design will have a flat and

smooth to produce desirable downwards forces. The air rams into the engine bay for

used of cooling, combustion, passengers, reaccelerated by a nozzle and then ejected

under the floor.

Automotive aerodynamic is much different from the aircraft aerodynamic

such as road vehicle shapes is bluff, vehicle operates very close to the ground,

operating speed lower, the ground vehicle has fewer degrees of freedom and its

motion is less affected by aerodynamic forces.

Total Aerodynamic drag = Cd multiplied by the frontal area. The width and

height of curvy cars lead to gross overestimations of frontal area [4].

I

2.2 Flows Separation Through a Road Vehicle

2.2.1 Introduction

In determining and observing the aerodynamic of road vehicles it is important

to know the airflow through the vehicle's body. Basically, airflow around car's body

can be divided into two simple type which are laminar and turbulent flows. Both

layers can be describing in the boundary layer development on car's surface

2.2.2 Boundary Layer Development

In physics and fluid mechanics, the boundary layer is that layer of fluid in the

immediate vicinity of a bounding surface [5]. For flow over any surface, there will

always exist a velocity boundary layer and hence surface friction [6]. On a body of a

car, this surface friction could create drag force that could effect the aerodynamic of

the car. To introduce the concept of boundary layer, consider a flow through a plate

in Figure 2.2.

U. _ Free stream

U00

Velocity Y T ! boundary

I Ia er

bf

pp.x

Figure 2.2 Flow through a plate [1]

Y, v• A

—x, u Turbulent region

Buffer layer Laminar sublayer

12

Boundary layer velocity occurs when a consequence of viscous effects

associated with relative motion between a fluid and a surface. A region of the flow

characterized by shear stresses, t and velocity, u gradients. A region between the

surface and the free stream whose thickness increases in the flow direction. The

surface shear stress, 'rs provides the surface drag force, FD. The surface friction is

strongly depending on the flows condition weather laminar or turbulent flows. On

car's surface, the boundary layer becomes thicker towards the rear of the car. The

thicker the boundary layer, the more easily airflow will separate from the body,

leading to turbulent flow [6].

2.2.5 Laminar & Turbulent Flows

Figure 2.3 shows the laminar and turbulent flows of velocity boundary layer

development on a flat plate.

Streamline

xc

wl-4-1

- Laminar - i• Turbulent Transition

Figure 2.3 Velocity boundary layer development on a flat plate [1]

The laminar flow section preceding the turbulent flow section. Laminar flow

occurs where viscous forces are dominant and characterized by smooth, constant

13

fluid motion. Turbulent flow dominated by inertial forces, producing random eddies,

vortices and other flow fluctuations [6].

2.2.6 Flows Around Car's Body

Figure 2.4 shows the patterns of air flows through a Porsche body on a

common road. Note that the blue arrows represent laminar flow while the red arrows

represent turbulent flow.

Figure 2.4 Patterns of air flows through a Porsche body [7]

The patterns of airflow can be observed by sticking tuft-wool around the car

body and drove the car. Figure 2.5 shows how the tuft-wool sticked to the car body

to observe the airflow patterns.