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AN AERODYNAMIC STUDY ON MPV SPOILER
RAGUVARAN A/L JAYAHKUDY
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
AN AERODYNAMIC STUDY ON
MPV SPOILER
RAGUVARAN A/L JAYAHKUDY
NAME : RAGUVARAN A/L JAYAHKUDY
MATRIC.NO : B041010046
COURSE : 4 BMCA
SUPERVISOR : NAZRI HUZAIMI BIN ZAKARIA
EVALUVATOR 1 : Mohd Haizal Bin Mohd Husin
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
AN AERODYNAMIC STUDY ON MPV SPOILER
RAGUVARAN A/L JAYAHKUDY
This report is submitted in partial fulfillment
of the requirements for the award of the degree in
Bachelor of Mechanical Engineering (Automotive)
Faculty of Mechanical Engineering
University Teknikal Malaysia Melaka
MAY 2013
i
SUPERVISOR DECLARATION
“I hereby declare that I have read this thesis and in my opinion this report is sufficient in
terms of scope and quality for the award of the degree of
Bachelor of Mechanical Engineering (Automotive)”
Signature: ………………………
Supervisor: ....................................
Date: ....................................
ii
STUDENT’S DECLARATION
“I hereby declare that the work in this report is my own except for summaries and
quotations which have been duly acknowledged.”
Signature : ………………………..
Author : Raguvaran a/l Jayahkudy
Date : 31st
MAY 2012
iii
Dedicated to my beloved Father and Mother
iv
ACKNOWLEDGEMENT
I would like to take this opportunity to thank all who have rendered their full
support towards my “Projek Sarjana Muda” (Final Year Project) report. The pleasure,
the achievement, the glory, the satisfaction, the reward, the appreciation and the
construction of the report cannot be thought without a few or how apart from their
regular schedule, spared a valuable time for me. This acknowledgement is not just a
position of words but also as an account of indictment. They have been a guiding
light and source of inspiration towards the completion of the report. I am very
grateful to my Project Supervisor, Mr.Nazri Huzaimi Bin Zakaria for his kind and
timely help offered to me in execution of this project. Besides that, I would like to
thank my friends, and all my family members who with their valuable suggestions
and support, directly or indirectly helped me in the completion of this project.
v
ABSTRACT
Performance, handling, safety, and comfort of a car are significantly affected
by its aerodynamic properties. Getting high power directly from the engine is just not
enough to judge the performance of the car. Aerodynamic properties must be
considered for the purpose of studying the drag and stability performance of a car. In
order to improve a car’s aerodynamic drag and its stability, an aerodynamic device is
needed to perform such as the rear spoiler. Rear spoiler is an aerodynamic device that
functions to ‘spoil’ the unfavorable air flow across the body or in the scientific
explanation, to spoil the ‘laminar’ flow of the car’s aerodynamic movement in
motion. This rear placing device creates an area of high pressure to replace the usual
low pressure over the trunk resulting in increasing stability of the car. Basically, rear
spoilers are fitted at the trunk of a sedan car for its performance but does it gives the
same results if a rear spoiler were fitted in a Multi Purpose Vehicle (MPV)? Or just
for the sake of styling purpose. Thus, this report is regarding the effect of rear spoiler
on a MPV and the objective of this study is to investigate the aerodynamics on a
MPV vehicle with rear spoiler using CFD software (ANSYS). A simple model of the
MPV had been drawn using CATiA software; import it to ANSYS software and to
run the aerodynamic simulation.
vi
ABSTRAK
Sesebuah kenderaan yang bermutu tinggi bukan sahaja dipengaruhi oleh
keupayaan enjin sahaja, malah rekabentuk aerodinamik kenderaan tersebut juga amat
penting. Aerodinamik sesebuah kenderaan memberi impak kepada prestasi,
keselamatan, kawalan dan juga kestabilan kenderaan tersebut. Setiap kenderaan
mengalami kerugian tenaga disebabkan oleh daya tujah yang bertindak kepadanya
dimana daya tujahan keatas dan daya berlawanan dengan arah pergerakan kenderaan.
Bagi mengurangkan tindakan daya negatif ini, “spoiler” telah dibina oleh para
jurutera dan dipasang pada hampir setiap kereta di atas bonet belakang, dan amat
mudah untuk dilihat pada zaman sekarang. Kebanyakan pengguna tidak tahu tujuan
utama “spoiler” ini dipasang pada kenderaan malah ada yang meletakkan “spoiler”
atas dasar untunk mencantikkan kenderaan mereka sahaja. Secara asasnya, “spoiler”
dipasang bagi mengurangkan daya tujahan serta meningkatkan daya tekanan pada
bahagian belakang kereta agar ia lebih stabil ketika memandu pada kelajuan tinggi. Ia
terbukti pada kereta biasa tetapi adakah “spoiler” yang dipasang pada kenderaan jenis
“Multi Purpose Vehicle” MPV mampu memberi respon yang sama atau sekadar
tujuan kecantikkan ‘sporty’ sahaja. Tujuan projek ini adalah untuk mengkaji sejauh
mana respon “spoiler” ke atas kenderaan MPV dan jikalau ya, bagaimanakah
aerodinamik kenderaan MPV yang dipasang dengan “spoiler” berfungsi. Kajian CFD
pada struktur kenderaan MPV ber’spoiler’ dan tidak ber’spoiler’ akan dikaji
menggunakan perisian komputer (CATiA) dan akan disimulasi dengan menggunakan
perisian komputer (ANSYS).
vii
CONTENTS
CHAPTER CONTENT PAGES
SUPERVISOR’S DECLARATION i
STUDENT’S DECLARATION ii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF SYMBOLS xiii
LIST OF ABBREVIATIONS xiv
CHAPTER 1 INTRODUCTION
1.1 Project Introduction 1
1.2 Problem Statement 2
1.3 Project Objective 3
1.4 Project Scope 3
viii
CHAPTER 2 LITERATURE REVIEW
2.1 General Aerodynamic Concept 4
2.1.1 Definition of Aerodynamics 4
2.1.2 Automotive Aerodynamics 4
2.1.3 Drag & Lift concept 5
2.1.4 Drag Force 7
2.1.5 Lift Force 8
2.1.6 Downforce 9
2.2 Flow Separation Process 10
2.2.1 Laminar & Turbulent Flow 12
2.3 Boundary Layer 13
2.4 Rear Spoiler 15
CHAPTER 3 METHODOLOGY
3.1 Introduction 19
3.2 Modeling in CATiA Software 20
3.3 Analyzing in CFD Software (ANSYS) 23
3.3.1 ANSYS Simulation Process 23
3.3.2 Geometry 24
3.3.3 Meshing Process 25
3.3.4 Problem Setup 27
3.3.5 Solution 31
3.4 Assumptions 33
3.5 Problem Encountered 34
3.6 Overall Methodology of Final Year Project (PSM 1&2) 35
ix
CHAPTER 4 RESULTS & DISCUSSION
4.1 Simulation Results 36
4.1.1 Multi Purpose Vehicle without rear spoiler (MPV) 37
4.1.2 Multi Purpose Vehicle with rear spoiler (MPVs) 39
original full specification
(90degrees + 20cm length, 8cm height)
4.1.3 Multi Purpose Vehicle with rear structured spoiler 41
(MPVss) (100degrees + 50cm length, 8cm height)
4.2 Graphical Analysis 43
4.3 Comparison of MPV, MPVs & MPVss Model 44
CHAPTER 5 CONCLUSION & RECOMMENDATIONS 51
REFERENCES 53
APPENDICES 56
x
LIST OF TABLES
NUM. TITLE PAGE
4.1 Model’s properties at velocity, V=10m/s 44
4.2 Model’s properties at velocity, V=20m/s 44
4.3 Model’s properties at velocity, V=30m/s 45
4.4 Model’s properties at velocity, V=40m/s 45
xi
LIST OF FIGURES
NUM. TITLE PAGE
2.1 Aerodynamic flow of a MPV 5
2.2 Forces acting on an Aerofoil 5
2.3 Shear force and Pressure acting on the surface body 6
2.4 (3D) Modeled bodies 6
2.5 Value of Drag Coefficient of road vehicles 8
2.6 Basic Downforce principles 9
2.7 Pressure & Downforce acting on a vehicle spoiler 10
2.8 Flow Separation Process 12
2.9 Laminar & Turbulent Flow 13
2.10 Boundary Layer 14
2.11 Car Spoiler 15
2.12 Drag due to Pressure Differences 16
2.13 Effect of rear spoiler on lift 17
2.14 Level of pressure increase due to rear spoiler 17
3.1 View of a Porton Exora with Spoiler 20
3.2 Proton Exora’s Technical Specifications & Product Features 21
3.3 CATiA model (Proton Exora) without rear spoiler, named MPV 21
3.4 CATiA model (Proton Exora) with rear spoiler 22
original specification
[90degrees + 20cm length, 8cm height] named MPVs
3.5 CATiA model (Proton Exora) with structured spoiler 22
[100degrees + 50cm length, 8cm height] named MPVss
3.6 Fluid-Flow (FLUENT) system 24
3.7 “Wind-Tunnel” of the MPV model 25
xii
3.8 “Meshing Process” of the MPV model 26
3.9 “General Setup” of the MPV model 27
3.10 “Models & Materials “setup of the MPV model 28
3.11 Boundary Conditions “Velocity-Inlet & Pressure Outlet” 29
for the MPV model
3.12 Reference Values of the MPV model 30
3.13 Solution Methods, Controls & Initialization of the MPV model 31
3.14 Calculation Activities of the MPV model 32
4.1 Contours of Pressure on MPV model 37
4.2 Contours of Total Pressure on MPV model 37
(Maximum Pressure = 1152pa)
4.3 Contours of Velocity Magnitude on MPV model 38
(Maximum Velocity = 61m/s)
4.4 Contours of Turbulence Kinetic Energy on MPV model 38
(Maximum Kinetic Energy = 192.44m2/s2)
4.5 Contours of Pressure on MPVs model 39
4.6 Contours of Total Pressure on MPVs model 39
(Maximum Pressure = 1285pa)
4.7 Contours of Velocity Magnitude on MPVs model 40
(Maximum Velocity = 60.8m/s)
4.8 Contours of Turbulence Kinetic Energy on MPVs model 40
(Maximum Kinetic Energy = 200.65m2/s2)
4.9 Contours of Pressure on MPVss model 41
4.10 Contours of Total Pressure on MPVss model 41
(Maximum Pressure = 1155pa)
4.11 Contours of Velocity Magnitude on MPVss model 42
(Maximum Velocity = 62.8m/s)
4.12 Contours of Turbulence Kinetic Energy on MPVss model 42
(Maximum Kinetic Energy = 187.37m2/s2)
4.13 Graph of model’s Drag Coefficient 47
4.14 Graph of model’s Lift Coefficient 47
4.15 Graph of model’s Drag Force 48
4.16 Graph of model’s Lift Force 48
4.17 Fuel consumption formula 49
xiii
LIST OF SYMBOLS
p = Pressure
ρ = Air density
v = Vehicle’s speed
dFx = Net x-component of force
dFy = Net y-component of force
dA = Small element of surface area
τw = Wall shear stress
D = Drag
L = Lift
DA = Aerodynamic drag force
CD = Drag coefficient
A = Frontal area
LA = Aerodynamic lift force
CL = Lift coefficient
Tr = Air temperature
Pr = Ambient pressure
zs = Height of spoiler
W = Wingspan
H = Height of the wing
AoA = Angle of attack
Re = Reynolds Number
xiv
LIST OF ABBREVIATIONS
MPV = Multi Purpose Vehicle without spoiler
MPVs = Multi Purpose Vehicle with spoiler / original full specification
(90degrees + 20cm length, 8cm height)
MPVss = Multi Purpose Vehicle with structured spoiler
(100degrees + 50cm length, 8cm height)
CFD = Computational Fluid Dynamic
3D = Three Dimensional
SUV = Sport Utility Vehicle
F1 = Formula one
CAD = Computer Aided Design
ANSYS = Simulation Software
Fluent = Simulation System/Process
CATiA = Computer Aided Three-dimensional Interactive Application
1
CHAPTER 1
INTRODUCTION
1.1 PROJECT INTRODUCTION
Nowadays, the everyday cars and even Multi Purpose Vehicle (MPV) are
modified to look sportier and add some ‘looks’ to their ordinary vehicle by the owners
for many reasons. Having tremendous amount of power from the engine leads to higher
speeds for which the aerodynamics properties of the MPV given by the designer are not
enough to offer the required down force and handling. The performance, handling,
safety, and comfort of an automobile are significantly affected by its aerodynamic
properties. Extra parts are added to the body like rear spoilers, lower front and rear
bumpers, air dams and many more aerodynamics aids as to direct the airflow in different
way and offer greater drag reduction to a vehicle and at the same time enhance the
stability. Basically, aerodynamic styling of a vehicle is one of the most crucial aspects of
vehicles design a highly complex phenomenon [1] which encompassing the task of an
artful integration of advanced engineering and stylish aesthetics. A lot of emphasis is
laid on the aerodynamics of a vehicle [2] design as an aerodynamically well designed
vehicle spends the least power in overcoming the drag exerted by air and hence exhibits
higher performance – cruises faster and longer even on less fuel consumption [3]. Apart
from improved fuel economy, an aerodynamically superior vehicle offers better stability
2
and handling at highway speeds and also minimization of harmful interactions [4] with
other vehicles on the roadways.
Rear spoiler is a component to increase down force for vehicle especially
passenger car. It is an aerodynamic device that design to ‘spoil’ unfavorable air
movement across a car body. Main fixing location is at rear portion, depends on shape
of the rear portion either the MPV’s is square back, notchback or fastback because not
all rear spoiler can be fix at any type of rear portion of a MPV. Rear spoiler contributed
some major aerodynamics factor which is lift and drag. The reduction of drag force can
save fuel; moreover spoiler can also be used to control stability at cornering [5]. Besides
that, it even functions to reduce drag and reduce rear-axle lift.
1.2 PROBLEM STATEMENT
Basically, a car spoiler is used to stabilize the performance and get a better
response/control of a sedan car. Rear spoiler are fitted in the rear portion of a sedan car
in order to decrease the lift and drag force acting in the car by providing down force to
the vehicle so that the car gives a better response and control to the driver. Well does it
give the same response if the rear spoiler were fitted on a Multi Purpose Vehicle (MPV),
or act as a cosmetic purpose? Nowadays, we can see a lot of MPV were fitted with rear
spoiler for sportier look and as a “wow factor” in a lame looking MPV and thus, the
main task of this report is to analyze the response of a rear spoiler in a MPV. So, a case
study of the spoiler’s function on a MPV needs to be analyzed in order to gain all the
relevant properties using the Computational Fluid Dynamics (CFD) software (ANSYS).
Besides that, how much does the spoiler effect on an MPV’s performance is also need to
be taken into account.
3
1.3 PROJECT OBJECTIVE
This report is obliged according to the title of the project which is an aerodynamic
study on MPV spoiler. Before preceding this project study, several scopes and
objectives of this study have to be defined clearly and precisely. This is very essential in
order to carry out this study successfully. Therefore the objectives of this study are
mentioned below:-
To study an aerodynamics on MPV vehicle with spoiler using Computational
Fluid Dynamics (CFD) software.
To analyze the aerodynamics of the MPV spoiler using CFD software.
To design a simple MPV spoiler and to run the CFD simulation in order to
observe the flow of the aerodynamics.
1.4 PROJECT SCOPE
This report is conducted on certain limitation which was listed by the supervisor as
follows:-
To study an aerodynamics on a MPV without spoiler.
To study an aerodynamics on a MPV with spoiler.
To differentiate both design in terms of aerodynamic flow using CFD software.
4
CHAPTER 2
LITERATURE REVIEW
2.1 GENERAL AERODYNAMIC CONCEPT
2.1.1 Definition of Aerodynamics
Aerodynamics is a branch of Fluid Mechanics which concern on forces
generated on a body in a flow and thus the aerodynamics usually involves a lot of
calculation in various properties of the flow such as velocity, pressure, temperature,
density and even 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 [6].
2.1.2 Automotive Aerodynamics
Automotive aerodynamics is a type of study/analysis of the aerodynamic
characteristic of road vehicles which involves the related properties such as reducing
drag force, reducing lift force at high speed and preventing the wind noise. It is also
required to produce down force in order to improve traction and cornering abilities on a
road vehicle. Obviously, the shape of a vehicle does give enough response on the
5
aerodynamics characteristic. Figure 2.1 shows the basic view of the aerodynamics of a
Multi Purpose Vehicle (MPV)
Figure 2.1: Aerodynamic flow of a MPV
2.1.3 Drag & Lift concept
There are 2 basic categories of aerodynamics forces acting on a road vehicle
body which described as below and shown in Figure 2.2:-
1) Shear Stress – which acts parallel to the surface body and contributes to drag,
(also known as the component of aerodynamic force parallel to the wind)
2) Pressure – which acts vertically to the surface body and contributes to lift, (also
known as the component of aerodynamic force perpendicular to the wind).[7]
Figure 2.2: Forces acting on an Aerofoil
The resultant force of the shear stress and pressure distribution can be obtained
by integrating the effects of these 2 quantities on the surface body as shown below in
Figure 2.3.
6
Figure 2.3: Shear force and Pressure acting on the surface body
dFx = ( p dA) cos θ + ( τw dA) sin θ [Eq. 1]
dFy = - ( p dA) sin θ + ( τw dA) cos θ [Eq. 2]
Thus, the net x and y component of the force on the object are:
1) Resultant force in the direction of the upstream velocity is termed the drag,D
D= ∫ dFx = ∫ p cos θ dA + ∫ τw sin θ dA [Eq. 3]
2) Resultant force normal to the upstream velocity is termed of lift, L
L = ∫ dFy = - ∫ p sin θ dA + ∫ τw cos θ dA [Eq. 4]
For certain three dimensional (3D) modeled bodies as in Figure 2.4, there might
be also side force acting perpendicular to the plane containing Drag and Lift. The
resultant force can be divided into 3 components which are moment, drag and lift
coefficients but for this study, only drag and lift are to be considered.
Figure 2.4: (3D) Modeled bodies
7
2.1.4 Drag Force
An aerodynamic drag force is the force which opposes the forward motion of the
vehicle while the vehicle is in traveling mode and it acts externally on the body of the
vehicle. The drag force can be measured directly by simply attaching the body subjected
to fluid flow, to a calibrated spring and measuring the displacement in the flow
direction. Drag force is usually an undesirable effect, like friction and mostly engineers
are trying to minimize by creating many devices. Reduction of drag is closely associated
with the reduction of fuel consumption in automobiles, submarines and aircraft,
improved safety and durability of structures subjected to high winds and reduction of
noise and vibration [8]. More sophisticated drag-measuring devices called drag balances
uses flexible beams fitted with strain gauges to measure the drag electronically. Besides
that, it can be calculated using formulas [Equation 5] as shown below:
DA = ½ ρ v^2 CD A [Eq.5]
Where; CD = coefficient of Drag
A = frontal area (m2)
ρ = density of air [kg/m3]
v = velocity of vehicle [m/s]
The drag and lift forces depend on the density of the air, the upstream velocity of
the wind, and the size, shape, and orientation of the body are among other elements
which need to be taken into account. Therefore, it is more convenient to work with
appropriate dimensionless numbers that represent the drag and lift characteristic of the
body which is the drag coefficient. Modern road vehicles such as cars and MPV’s have
the value of coefficient of drag (CD = 0.2 - 0.4) [9]. The smaller the value of CD, the
better the aerodynamic flow of the vehicle. In general, the more blunt the vehicle, the
higher the drag coefficient as shown in Figure 2.5. As a result, the percentage of fuel