xii
TABLE OF CONTENTS
CHAPTER
TITLE
DEDICATION
PAGE
viii
ACKNOWLEDGEMENT
ix
ABSTRACT
x
ABSTRAK
xi
TABLE OF CONTENTS
xii
LIST OF FIGURES
xv
LIST OF TABLES
NOMENCLATURE
1.
2.
INTRODUCTION
xviii
xix
1
1.1
Introduction
1
1.2
Problem Statement
2
1.3
Research Objective
3
1.4
Scope of Work
3
1.5
Research Methodology
4
1.6
Organization of The Thesis
5
LITERATURE REVIEW
7
2.1
Introduction
7
2.2
Aerodynamic Characteristic
9
2.2.1
Forces and Moments
9
2.2.2
Aerodynamic Derivative
11
2.2.3
Pressure Distribution
11
2.2.4
Crosswind Sensitivity
12
2.2.5
The Angle of Side Slip for Crosswind
12
xiii
2.2.6
Vehicle’s Crosswind Stability
14
2.4
Bluff Body Type
14
2.5
Computational Fluid Dynamic Simulation
15
Review of Previous Related CFD Study
COMPUTATIONAL FLUID DYNAMICS
18
23
3.1
Introduction
23
3.2
Pre-processing
24
3.2.1
Selection Grid
25
3.2.2
Size Function
25
3.2.3
Computational Domain
27
3.2.4
Grid Generation Using GAMBIT
28
3.2.5
Three Dimensional (3D) Modeling Mesh
28
3.2.6
Independent Meshing
30
3.3
4.
13
2.3
2.5.1
3.
Center of Pressure
Solver Setup for Simulation
31
3.3.1
CFD Simulations Using FLUENT 6.3
31
3.3.2
Solver Setup
36
3.3.3
Boundary Conditions
37
3.3.4
Fluid Properties
40
3.3.5
Solution Control
40
3.4
Post-Processing
42
3.5
Assumption of The Simulation
43
WIND TUNNEL TEST
44
4.1
Introduction
44
4.2
Wind Tunnel Specification
44
4.3
Model specification
45
4.4
Measurement Method
46
4.5
Solid Blockage
47
4.6
Experiment Setup
48
4.6.1
4.7
Comparison with Loughborough Wind Tunnel Test Results
0
Results from 20 Rear Slant Angle
4.7.1
Side Force and Yaw Moment Derivatives of 200 Slant
48
50
51
4.8
The Effect Rear Slant Angle
52
4.9
Side Force and Yaw Moment Derivatives of Various Slant
55
xiv
5.
6.
RESULTS AND DISCUSSION
58
5.1
Introduction
58
5.2
Detailed Simulation Results
58
5.3
Drag Force
59
5.4
Side Force Coefficient and Derivative
65
5.5
Yawing Moment Coefficient and Derivative
70
CONCLUSION AND RECOMMENDATION
77
6.1
Conclusion
77
6.2
Recommendations
78
REFERENCES
80
APPENDIX A
84
APPENDIX B
93
xv
LIST OF FIGURES
FIGURE NO.
FIGURE
PAGE
1.1
Flow chart for research methodology
5
2.1
SAE vehicle body axes
8
2.2
Pressure distribution on a horizontal vehicle
11
2.3
The angle of side slip for crosswind
12
2.4
The center of gravity and center of pressure
13
2.5
Computed and experimental drag coefficients for various rear
slants angle of Ahmed model after Gillieron and Chometon
2.6
Instantaneous streamwise velocity fields in the symmetry plane, for
different time of simulation. Hinterberger et.al. (2004)
2.7
20
Surface mesh of Ahmed model with 30° rear slant angle, after
Francis T. Makowski and Sung-Eun Kim (2000)
2.8
19
21
Time-study of CD (DES) Figure (a) and Time -Study of CD
(RANS) Figure (b) after Sagar Kapadia et.al. 2003
22
3.1
(a) & (b). Grid generation using size functions
26
3.2
Computational domain size
27
3.3
Davis model configuration
29
3.4
Computational meshing model
30
3.5
Drag coefficient versus number of meshing element (Mesh
independent study)
3.6
31
Graph drag coefficient versus yaw angle for different turbulence
model for 200 rear slant angle
35
4.1
Universiti Teknologi Malaysia Low Speed Tunnel (UTM-LST)
45
4.2
General dimensions of baseline shape (rear slant angle 200) of
Davis model. All edge radii 10 mm.
46
4.3
Model with different rear slant angles. All edge radii 10 mm.
46
4.4
Aerodynamic coefficient against yaw angle at wind speeds 40 m/s
of 200 slant. (a) drag force, (b) side force ,(c) yaw moment
49
xvi
4.5
Model slant angle 200 setup for static test
4.6
Aerodynamic coefficients against yaw angle at different wind
50
speeds of rear slant angle 200. (a) side force, (b) yaw moment
4.7
Aerodynamic coefficient versus yaw angle for different rear slant
angles at 40 m/s. (a) drag, (b) side force, (c) yaw moment
4.8
53
Side force, yaw moment coefficient and centre of pressure for
various rear slant angles for 100 yaw and drag
4.9
54
Static aerodynamic derivatives of different slant angles at 30 to
50 m/s. (a) side force, (b) yaw moment
4.10
56
Static side force derivatives versus Reynolds number for
different rear slant angles.
4.11
51
57
Static yaw moment derivatives versus Reynolds number for
different rear slant angles.
57
5.1
(a) and (b): Velocity vector and contours in the wake of 00 slant
60
5.2
(a) and (b): Velocity vector and contours in the wake of 100slant
61
5.3
(a) and (b): Velocity vector and contours in the wake of 200 slant 62
5.4
(a) and (b): Velocity vector and contours in the wake of 300 slant 63
5.5
(a) and (b): Velocity vector and contours in the wake of 400 slant 64
5.6
Graph side force coefficients versus yaw angle for slant 00
65
5.7
Graph side force coefficients versus yaw angle for slant 100
65
5.8
Graph side force coefficients versus yaw angle for slant 200
66
5.9
Graph side force coefficients versus yaw angle for slant 300
66
0
66
5.10
Graph side force coefficients versus yaw angle for slant 40
5.11
Graph side force coefficients versus yaw angle at different slant
angle
5.12
Graph side force coefficients versus rear slant angle at yaw
angle 100
5.13
68
Comparison experimental and CFD static side force derivatives
versus rear slant angles for 40 m/s.
5.15
68
Static side force derivatives versus Reynolds number for
different rear slant angles.
5.14
67
69
Graph yawing moment coefficients versus yaw angle for rear
slant 00
70
xvii
5.16
Graph yawing moment coefficients versus yaw angle for
rear slant 100
5.17
Graph yawing moment coefficients versus yaw angle for
rear slant 200
5.18
5.24
73
Static yawing moment derivatives versus Reynolds number for
different rear slant angles.
5.23
72
Graph yawing moment coefficients versus rear slant angle at
yaw angle 100
5.22
71
Graph yaw moment coefficients versus yaw angle at different
rear slant angle
5.21
71
Graph yawing moment coefficients versus yaw angle for
rear slant 400
5.20
71
Graph yawing moment coefficients versus yaw angle for
rear slant 300
5.19
70
73
Comparison experimental and CFD static yaw moment force
derivatives versus rear slant angles for 40 m/s.
73
Velocity vector at plane behind the model
75
xviii
LIST OF TABLES
TABLE NO.
TABLE
PAGE
2.1
Forces and moment.
8
3.1
Default values of in FLUENT
41
4.1
Balance load range and accuracy.
47
4.2
Comparison aerodynamic derivative UTM-LST and
Loughborough University wind tunnel test
50
4.3
Static measured derivatives of Cy and Cn for 200 slant.
52
4.4
Side force and moment derivative at different rear slant angle
56
5.1
The drag force and the coefficient of drag for the Fluent and wind
tunnel test result.
5.2
Tabulated data experimental and CFD static yaw moment force
derivatives versus rear slant angles for 40 m/s.
5.3
59
69
Tabulated data experimental and CFD static yaw moment force
derivatives versus rear slant angles for 40 m/s.
74
xix
NOMENCLATURE
m2
m2
Cy E
- model frontal area
- model side area
- aerodynamic drag coefficient
- centre of gravity
- aerodynamic yaw moment coefficient
- centre of pressure
- distance center of aerodynamic to center wheel base
- distance center of aerodynamic to center wheel base
- aerodynamic side force derivative
Cn E
- aerodynamic yaw moment derivative
rad-1
Cy
- aerodynamic side force coefficient
- dissipation rate
- model rig yaw moment of inertia
- kinetic energy
- model characteristic length
- distance between cp and cg
- wheel base length
- distance between front axle to cg
A
As
Cd
cg
Cn
cp
e0
es
I zz
k
"
"cp
"wb
lF
"r
m
Na
Re
Nf
- distance between rear axle to cg
- mass of the model
- aerodynamic yaw moment
- Reynolds Number
- yaw moment fluctuation
m
m
rad-1
kg.m2
m
m
m
m
m
kg
Nm
Nm
Vy
- wind tunnel lateral velocity
m.s-1
m.s-1
m.s-1
m.s-1
Vz
- wind tunnel vertical velocity
- lateral velocity fluctuation
m.s-1
m.s-1
- crosswind velocity
- model yaw angle
- relative crosswind angle
- air density
- model angle of rotation
- phase angle
- crosswind angle with respect to vehicle forward speed
m.s-1
deg
deg
kg.m-3
deg
deg
deg
u, v, w - forward, lateral and vertical speed
V
- wind tunnel velocity
Vx
- wind tunnel axial velocity
Vf
Vw
E
Ew
U
T
I
\