AERODYNAMIC STUDY OF HEAVY TRUCK USING CFD FLUENT
HILMI SAFUAN BIN JAPAR
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
“I hereby verify that I have read this report and I find it sufficient in term of quality and
scope to be awarded with the Bachelor Degree in Mechanical Engineering “
Signature : …………………………………
Supervisor Name : …………………………………
Date : …………………………………
AERODYNAMIC STUDY OF HEAVY TRUCK USING CFD-FLUENT
HILMI SAFUAN BIN JAPAR
This report is submitted to Faculty of Mechanical Engineering in partial fulfill of the
requirement of the award of Bachelor’s Degree of Mechanical Engineering
(Thermal-Fluid)
Faculty of Mechanical Engineering
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
May 2010
i
“I hereby to declare that the work is my own except for summaries and quotations which
have been duly acknowledge”
Signature : ………………………………….
Author : HILMI SAFUAN BIN JAPAR
Date : 17TH MAY 2010
ii
DEDICATION
To him who is our source of grace, our source of commitment, and our source of knowledge,
And, To him, whose love is a source of joy.
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ACKNOWLEDGMENT
All praises to the Almighty Allah, for giving me the strength, patience and
guidance throughout the process of completing this investigation. I am grateful to have
the morally and physically support from many people throughout completing this study.
For this opportunity, I would love to thank whose are either directly or indirectly
involved during the process of this research is conducted.
Most immediately, I would like to express my very special gratitude and
appreciations to my supervisor, Mr. Mohd Afzanizam bin Mohd Rosli for his valuable
suggestion, comments and advice in every stage of this project. All the discussion makes
me understand every detailed in this road vehicle aerodynamic analysis.
Special Thanks should also be forwarded to my all my beloved family members,
especially my father, Mr Japar @ Wan Jaafar Lasim, and my mother, Pn. Herlizah
Abdullah @ Mailih Sugari, who never failed to be there for their support, prayer and
love. Last but not least, I would like to thank all my friends, especially Mohd Faiz bin
Mat Zaid, Nur Izrin bte Mahyon and all my classmates. Not to forget to all Universiti
Teknikal Malaysia Melaka staff that gives cooperation on this project. Thanks you very
much.
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ABSTRACT
Aerodynamic is a study about air flow around an object. In land vehicle
application, aerodynamic is one of land vehicle important design after engine and
suspension. A smooth design is needed to reduce air resistance to the vehicle at high
speed, because air resistance will increase as the velocity increase. The Computational
Fluid Dynamic (CFD) is another method to study about the air flow around the vehicle.
This method was used to give the users an overview of the air flow and expected result
in the aerodynamic simulation. Hence, after the experiment in the wind tunnel, the users
may verify they experimental result with CFD. In this project, analysis of aerodynamic
will be done on a heavy truck by using CFD-FLUENT method and wind tunnel testing.
In this first part of the project, the progress was done until meshing the truck model
using GAMBIT. The research is done by experimenting 2 types of model which is tri-
cab design and square-cab design with 3 different angles. It is found that the tri-cab
design at 30° angle give the lowest drag coefficient which is 0.55.
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ABSTRAK
Aerodinamik adalah satu kajian tentang aliran udara sekitar sesuatu objek. Di
dalam aplikasi terhadap kenderaan darat, aerodinamik merupakan salah satu aspek
penting terhadap kenderaan tanah selain enjin dan suspensi. Rekaan yang halus
diperlukan bagi mengurangkan rintangan udara terhadap kenderaan pada kelajuan tinggi,
kerana rintangan udara akan meningkat seiring dengan peningkatan halaju.
Computational Fluid Dynamic adalah satu lagi kaedah untuk mengkaji aliran udara
sekitar kenderaan. Kaedah ini biasa memberi pengguna CFD satu gambaran keseluruhan
aliran udara dan jangkaan keputusan eksperimen yang akan di lakukan kelak. Oleh itu,
selepas eksperimen dalam terowong angin, pengguna CFD boleh mengesahkan hasil
eksperimen mereka dengan CFD. Dalam projek ini, analisis aerodinamik akan dibuat ke
atas kenderaan berat dengan menggunakan kaedah CFD-FLUENT dan ujian terowong
angin. Bahagian pertama di dalam projeck ini, kaedah telah dibuat sehingga penghasilan
jaringan model trak menggunakan GAMBIT. Kajian ini dilakukan dengan percubaan 2
jenis model yang berbeza bentuk iaitu tri-cab dan square-cab dengan 3 sudut yang
berbeza. Setelah kajian dilakukan, didapati bahawa bentuk tri-cab pada sudut 30°
memberikan pekali seretan yang terendah iaitu 0.55.
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TABLE OF CONTENT
CHAPTER CONTENT PAGE
DECLARATION i
DEDICATION ii
ACKNOWLEDGEMENT iii
ABSTRACT iv
TABLE OF CONTENT vi
LIST OF TABLES ix
LIST OF FIGURES x
LIST OF GRAPH xii
CHAPTER 1 INTRODUCTION
1.1 Research Background 1
1.2 Objective 4
1.3 Research Scope 4
1.4 Problem Statements 5
1.5 Project Discussion 6
1.6 Significant of Research 6
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 7
2.2 Relationship between Aerodynamic and Fuel
Consumption 7
2.3 Cab Shape 9
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2.4 Fundamental of Aerodynamic in Vehicle 13
2.4.1 Boundary Layer 15
2.4.2 Coefficient of Drag 16
2.4.3 Coefficient of Lift 17
2.4.4 Pressure Distribution 19
2.4.5 Reynolds Number 21
2.5 Wind Tunnel 22
2.6 Summary 22
CHAPTER 3 METHADOLOGY
3.1 Introduction 23
3.2 Process Flow 24
3.2.1 Literature Review Process 25
3.2.2 Model Development Process using Solid
Work 25
3.2.3 GAMBIT Meshing and Defining Overview 26
3.2.4 Wind Tunnel Study and Scaled Analysis 27
3.3 Step of Model Designing using Solid work 28
3.3.1 Solid Work Design 28
3.3.2 Hand-made Model Truck 32
3.4 GAMBIT and FLUENT analysis 35
3.5 Wind Tunnel Testing 39
CHAPTER 4 DATA AND RESULT ANALYSIS
4.1 Introduction 41
4.2 Wind Tunnel Result 41
4.3 CFD-Fluent Result 45
4.4 Sample of Calculation 49
4.4.1 Wind Tunnel Force Calculation 49
4.4.2 Coefficient of Drag Calculation 49
4.4.3 Dynamic Similarity 50
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CHAPTER 5 RESULT AND DATA DISCUSSION
5.1 Introduction 51
5.2 Wind Tunnel and CFD Simulation Comparison 51
5.3 Square-cab Design and Tri-cab Design
Comparison 52
5.4 Cab Angle 54
5.4.1 Square-cab Design 54
5.4.2 Tri-cab Design 56
5.5 Fuel Consumption Effect 58
5.5.1 Fuel Consumption on Square-cab Truck 59
5.5.2 Fuel Consumption on Tri-cab Truck 60
5.5.3 Fuel Consumption on Truck without
Roof-cab 62
5.5.4 Comparison of Truck with Roof-cab and
without Roof-cab 63
CHAPTER 6 CONCLUSION AND RECOMMENDATION
6.1 Conclusion 64
6.2 Recommendation 65
REFERENCE 69
APENDICE A: Simple and Low-Cost Aerodynamic Drag Reduction Devices for Tractor-Trailer Trucks 71 APENDICE B: Progress in Reducing Aerodynamic Drag for Higher Efficiency of Heavy Duty Trucks (Class 7-8) 72
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LIST OF TABLES
NUMBER TITLE PAGE
1.1 Range of coefficient of drag for various type of vehicle 3
2.1 Standard force and moment of vehicle. 14
3.0 Boundary Types Identification 38
4.0 Truck Identification 42
4.1 Model Wind Tunnel Results 42
4.2 CFD Simulation Results 43
4.3 Square-cab Truck Coefficient of Drag 44
4.4 Tri-cab Truck Coefficient of Drag 46
4.5 Drag Coefficient of Truck without Roof-cab 46
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LIST OF FIGURES
NUMBER TITLE PAGE
1.1 1980 Chevrolet Corvette T-Top 2
1.2 P-130 SCANIA Truck 5
2.0 Influence of drag on fuel consumption for a 40 tons trailer 8
2.1 Tractor semi-trailer configuration 9
2.2 Air flow on Truck without CVTD 10
2.3 Air flow on Truck without USD and VSD 11
2.4 Cross Flow Vortex Trap Device 11
2.5 Vortex Strake Trailer Device 12
2.6 Undercarriage Flow Device 12
2.7 Road vehicle axis system 15
2.8 Boundary Layers 15
2.9 Boundary layer occurs on the roof of a bus 16
2.10 Coefficient of drag for heavy vehicle 17
2.11 Effects of underfloor to ground clearance on air speed,
pressure and lift force 18
2.12 Pressure distribution above and below the body structure 19
2.13 Trailer floe body pressure distribution with and
without roof deflector 20
3.1 Model Development by Solidwork 26
3.2 Diagram of Wind tunnel testing 28
3.3 30° Square-cab Truck 29
xi
3.4 45° Square-cab Truck 29
3.5 60° Square-cab Truck 30
3.6 30° Tri-cab Truck 30
3.7 45° Tri-cab Truck 31
3.8 60° Tri-cab Truck 31
3.9 Sand Paper 32
3.10 Nexa Auto Color 32
3.11 1.2” Screw 32
3.12 Wind Tunnel Testing 40
3.13 Fan Controller 40
3.14 Force Indicator 40
5.0 Square-cab Truck Pressure Distribution 53
5.1 Tri-cab Truck Pressure Distribution 53
5.2 Square-cab Truck at 45° 55
5.3 Square-cab Truck at 60° 55
5.4 Turbulence Occur On the Truck 55
5.5 Pressure Distribution Contour for Tri-cab 30° 56
5.6 Pressure Distribution Contour for Tri-cab 45° 57
5.7 Pressure Distribution Contour for Tri-cab 60° 57
5.8 Drag Coefficient Properties 58
5.9 Rate of Fuel Consumption for 30° Square-cab Truck 59
5.10 Rate of Fuel Consumption for 30° Tri-cab Truck 61
5.11 Rate of Fuel Consumption for Truck without Roof-cab 62
6.0 Research on truck with different container height 65
6.1 Position of the overhead cab at lower container height 66
6.2 Position of the overhead cab at higher container height but still
maintain 30° angle 67
6.3 Research on truck side skirt to improve aerodynamic 68
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LIST OF GRAPH
NUMBER TITLE PAGE
4.0 [Truck 1/52 scale] Coefficient of Drag versus Velocity (m/s) 44
4.1 [Truck 1/1 scale] Coefficient of Drag versus Velocity (m/s) 44
4.2 Square-cab Truck, Drag Coefficient versus Velocity (m/s) 47
4.3 Tri-cab Truck, Drag Coefficient versus Velocity (m/s) 47
4.4 Truck Drag Coefficient without Roof-cab 48
1
CHAPTER 1
INTRODUCTION
1.1 Research Background
Aerodynamics is a branch of fluid dynamics concerned with the study of gas
flows. The solution of an aerodynamic problem normally involves calculating for
various properties of the flow, such as velocity, pressure, density, and temperature, as a
function of space and time. Understanding the flow pattern makes it possible to calculate
or approximate the forces acting on bodies in the flow.
In this recent century, vehicles were becoming faster and better. New types of
research were introduced in transportation industry which is vehicle aerodynamic. Since
1914 vehicle have transform from square design into smoother design, where it improve
the aerodynamic of the vehicles. The aerodynamic of road vehicle research is very
important due to reduction of fuel consumption, optimize performance also to improve
stability and handling in term of safety. The constant air flow are needed for better fuel
economy, greater vehicle performance, reduction in wind noise level and improved road
holding and stability for a vehicle on the move.
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Figure 1.1: 1980 Chevrolet Corvette T-Top
(Source: www.automagazineonline.com)
The road vehicle aerodynamic is important for increasing the performance of the
vehicle with less fuel consumption; furthermore, it also will improve stability of the
vehicle. A smooth airflow around the vehicle will reduce drag on the vehicle itself,
which will also reduce the engine load, as the engine load reduce, fuel consumption may
reduce as well, hence giving the user the opportunity for financial saving. Other then
increasing engine performance, air flow will also increase the stability of the vehicle at
high speed, as the vehicle is stable at high speed the safety of the passengers were
assured and the passenger may arrive at they destination in a short time.
Heavy truck is a common vehicle that people see in a highway for goods
transportation. However not all people realizes that heavy truck is a blood line of
economic grows where it transport goods from one point to the others. Hence by saving
the maintenance cost of the truck may reduce the transportation cost, one way of
reducing maintenance cost is improve the aerodynamic of the truck since truck is large
and fast moving vehicle it is essential to have a good air flow around the truck to reduce
engine load.
3
Aerodynamic characteristic is not obvious at low speed, but as the speed increase
the air resistances are also increase. At this occasion more energy is needed form the
engine to overcome the air resistance. The common highway speed today is at 110 km/h,
to overcoming aerodynamic drag represents about 65% of the total energy expenditure
for a typical heavy truck vehicle. Reduced fuel consumption for heavy vehicles can be
achieved by altering truck shapes to decrease the aerodynamic resistance (drag). It is
conceivable that present day truck drag coefficients might be reduced by as much as
50%.
A modern Class 7-8 tractor-trailer can weigh up to 8 tons and has a wind-
averaged drag coefficient around CD=0.55 to 0.80. The drag coefficient is defined as the
drag/ (dynamic pressure x projected area).
Table 1.1: Range of coefficient of drag for various type of vehicle
(Source: Barnard, R.H. [2001])
Expected Result
4
1.2 Objective
The objective of this research is:
i. To study the existing heavy truck aerodynamics.
ii. To compare two roof-cap design, and study the effect to the truck.
iii. To propose a better design of roof-cap complies with good aerodynamics
features.
1.3 Research Scope
i. Study an existing heavy truck aerodynamics specifically in Malaysia.
ii. Comparing two design of roof cab and propose the best aerodynamic features.
iii. Develop a CFD model and perform the airflow study of the heavy truck
aerodynamic.
iv. Conduct a wind tunnel testing to validate the CFD simulation.
In this research, SCANIA P380 was chosen as a model for study because it is
one of Malaysia most popular heavy truck. This research will focus on Computational
Fluid Dynamic (CFD). Nevertheless, the validation of the CFD result will be done in the
wind tunnel experiment where in this experiment further aerodynamic characteristic will
be understood by the researcher. The research will be conducted using Solid work,
GAMBIT and FLUENT software, where Solid work as a model builder, GAMBIT as a
modeler and FLUENT as a simulator. As for experiment, wind tunnel facility will be
used to investigate the aerodynamic of the truck model. The tunnel that will be used is
MP 130D subsonic tunnels (Essom Company Limited).
5
1.4 Problem Statements
Initially, the author has a problem in choosing type of truck that would be the
most suitable truck to be analyzed. It is found that SCANIA is the favorite heavy duty
vehicle manufacturer in Malaysia not only that because it’s have been here since 1971
but also the technology behind the wheel were competitive with other truck
manufacturer. As we can see, SCANIA have been used for container transportation, fire
fighting, cargo transport and buses.
P-130 model have been choose because it is the latest model of class 8 truck in
SCANIA manufacturing industry. The model that the author will develop from solid
work will not be the exact dimension with the real model; some of the truck
specification will not be inserted in the truck drawing model. Specifications of the truck
model that will be neglected in the solid work model is:
• Side mirror.
• Truck side doors.
• Details of the truck such as bolt nut, tires detail etc.
Figure 1.2: P-130 SCANIA Truck.
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1.5 Project Discussion
In starting the project, expecting the worst case scenario would be the best step
of doing the project, hence, several limitation have been expected to interrupt the project
or change the method of the project. Limitation is problems that occur during
completing this investigation and we cannot avoid it. There are a few limitations during
the wind tunnel experimental test and listed as follows:
1. The maximum speed can be used of the wind tunnel approximately
30m/s or 108km/h because it is a subsonic downstream fan type.
2. Since the wind tunnel test section is a 1ft x 1ft, the wind tunnel size is
not suitable for scale model within the range 1:1 to 1:10 due to
blockage factor. The maximum scale model can be used for road
vehicle is 1:20.
1.6 Significant Of The Research
The significant of this project is important for those who read this report
especially for researcher in aerodynamic vehicle or people in transportation industry.
This report may be useful as one of the reference for individual that working in this
particular area or individual that continuing the research in heavy truck. This paper
emphasizes more on how to implement an aerodynamic experiment and gathered
qualitative and quantitative values. If the result of this project is better and shows some
good improvement, it is better to implement the design of the roof cab to all the truck in
Malaysia which will reduce operating cost or fuel consumption to generate economy
development.
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CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
Literature review is about understanding the theory of the research that being
done, it is considered as the most important part of research where at this part the
researcher will understand the theory, then proceed with the project by referring to the
theory as a guide. The information about the research theory can be found through
internet thesis, journal and reference book. In this research case, all the theory or
information about fundamentals of aerodynamic, vehicle aerodynamic and heavy truck
aerodynamic are needed as a reference.
2.2 Relation between Aerodynamic and Fuel Consumption
The purpose of truck aerodynamic improvements is to minimize fuel
consumption. The effect of drag reduction and fuel consumption in operation can be
shown with typical vehicle in typical driving condition as in Figure 2.0.
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Figure 2.0: Influence of drag on fuel consumption for a tractor-trailer.
(Source: H.Gǘtz, 1982.)
From the graph we can see that more fuel can save if coefficient of drag reduces.
In other words, by improving the truck aerodynamic will reduce the drag coefficient
which also reduce the engine load and save fuel. In the century where fuel source are
depleting, it is essential that we reduce the usage of fuel. Since truck were use to
transport goods, by reducing the fuel consumption will reduce the operating cost of the
truck, hence directly will reduce the goods cost. This occasion is good for economy
purposes especially for the developing country such as Malaysia.
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2.3 Cab Shape
In truck aerodynamic improvement, cab shape plays the most important roles in
reducing drag. By referring to Richard, M.W. (2003), at low speed, the mass of the truck
will influence the engine load of the truck, but as the truck speeding more then 80
KM/H, aerodynamic of the truck will influence the engine load. Since in highway,
trucks were speeding until approximately 100KM/H it is essential that aerodynamic
improvement need to be done to reduce operating cost.
A research title Reassessment of Heavy-Duty Truck Aerodynamic Design
Features done by Edwin J.S. and Robert R. Meyer, Jr, (1999) under NASA. The report
describe that the aerodynamic of the truck need to be done because of the fuel crisis that
hunted the transportation industry. The goal of the research is to prove that the
combination of tractor-semitrailer (as shown in figure 2.1) aerodynamic configuration
will reduce conventional truck coefficient of drag.
Figure 2.1: Tractor semi-trailer configuration.
(Source: Saltzman, E.J.,1999)