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.

iii

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

vii

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

viii

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

ix

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

x

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

xii

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.

2

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.

6

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.

7

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.

8

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.

9

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)