DEDICATION

To Almighty God, family, and my beloved friends

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ACKNOWLEDGEMENT

Many thank to my project supervisor, Dr.Carol Eastwick for her verbally helps and guidance throughout the entire project. She demonstrates a good model to me with her passion and knowledge sharing to motivate and assist me to establish the skills I required. Also, I am very appreciate the warm advises from my personal tutor, Dr. Wei, Sun.

I have no doubt to express my gratitude to family and friends in my homeland for their spiritually support. Of course, I would like to give thanks to my soul mates who unceasingly keep me into their prayers in strengthening my soul. Without Him, I am nothing.

Lastly, thank you very much to all my dearest professors and course mates in University of Nottingham for their teaching, guidance, advises, and helping either directly or indirectly throughout the academic year.

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ABSTRACT

A two-dimensional Luton tractor-trailer based van is used as baseline model to investigate the drag force exerted on the vehicle using CFD at urban speed. The results verification and justification has been carried by applying different size of element in the critical zones nearby the vehicle to avoid diffusion of solution. Investigation of drag force reduction is achievable by having aerodynamic devices installed on the vehicle. They are two configurations for cab roof design and three different angles for inward flap at rear end trailer. The simulated results have reflected that the cab roof feature enable to reduce significant amount of drag. It becomes a connecting bridge to enclose the exposed region on top of the tractor where flow separation starts immediately after it passes the front end trailer. However, the results of features combination are not equal to the sum of their individual result. Each feature has their distinction function only in the particular location. When the combination is considered, the features will work distinctively to improve the upstream flow condition before they reach to downstream feature and consequently, flow separation point may delay further to downstream. Therefore, combination of features work more effectively than the single aerodynamic feature in drag reduction.

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Contents

Acknowledgement………………………………………………………………………..…...ii

Abstract……………………………………………………………………………………...…….iii

Chapter One: Introduction and Background1.1 Background and Context………………………………………………………………...……..1

1.1.1 Effects of Viscosity………………………………………………………………….11.1.2 Principle of Bernoulli……………………………………………………..…………31.1.3Principle of Aerodynamic……………………………………………………………4

1.2 Problem Statement……………………………………………………………………………..61.3 Objectives……………………………………………………………………………..……….7

Chapter Two: Literature Review2.1 Introduction………………………………………………………………..…………………..82.2 Bluff Bodies Design……………………………………………………..…………………….82.3 Front End of the Tractor……………………………………………………..…….…………102.4 Underbody Flaps……………………………………………………………..…………….…112.5 Vortex Strake Device (VDS) ………………………………………………………………...122.6 Flow Vane s and Rounded Corners of Trailer………………………………………………..13

Chapter Three: Methodology3.1 Introduction………………………………………………………………………...…………153.2 CAD Model and Testing Domain Preparation………………………………………………..153.3 Meshing……………………………………………………………………………………….183.4 Computational Fluid Dynamics (CFD) Simulation…………………………………………..19

Chapter Four: Discussion4.1 Verification on Baseline Model Result……………………………………………………….224.2 Results of Cab Roof Options…………………………………………………………………254.3 Results of Rear Flaps……………………………………..…………….…………………….264.4 Result of Optimal Combination…………………………...………………………………….274.5 Transient Simulation………………………………………………...………………………..30

Chapter Five: Conclusion and Reccommendation.......…………………..……………………….34

References…………………………………………………………………….…………………..36

Appendix A: Work Schedule……………………………………………………………………..39Appendix B: Design configurations and its results………………………………………………40Appendix C: Figures of baseline model for transient solver……………………………………..50Appendix D: Figures of optimal model for transient solver……………………………………...61Appendix E: Project supervision forms…………………………………………………………..70

List of figures and tablesFigure 1.1 Character of flow, viscous flow past a flat plate parallel to upstream velocity………...2

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Figure 1.2 Effect of pressure gradient on boundary layer profile; PI = point of inflection………..2Figure 1.3 Flow field and pressure distribution for a vehicle-shaped body in

two-dimensional flow………………………………………………………………….3Figure 1.4 Forces on a body…………………………………………………………………..........4Figure 1.5 Change of the rear wheel load of a notchback car through lift,

depending on speed…………………………………………………………………………………...5

Figure 1.6 Drag coefficients of two-dimensional bodies at ℜ>104.............................................6Figure 1.7 Licensed vehicles by body type: Great Britain, 1994 to 2011…………….......…….…6Figure 2.1 Typical airflow pattern around a bluff body vehicle………………………….......……9Figure 2.2 Bluff body with sharp edges………………………………………………….......….…9Figure 2.3 Relationship between shapes of vehicle front and drag coefficient…………......……10Figure 2.4 Effect of streamlined front ends on the drag coefficient of rectangular

bodies in ground proximity…………………………………………………….......…11Figure 2.5 Effectiveness of tractor and trailer side skirts…………………………….…......……12Figure 2.6 Vortex strake devices……………………………………………………..…......……12Figure 2.7 Effect of vortex strake device behind the trailer……………………….……......……13Figure 2.8 Flow vane device……………………………………………………………......……14Figure 2.9 Flow vane device………………………………………………………......…………14Figure 2.10 Flow vane device…………………………………………………..……......………14Figure 3.1 Luton box van…………………………………………………………......….………15Figure 3.2 The virtual testing…………………………………………………...……......………17Figure 3.3 Meshing Zone……………………………………………………………......….……18Figure 3.4 Inflation layers……………………………………………………………......………19Figure 4.1 Velocity field around the baseline model………………………………......…...……24Figure 4.2 Velocity field behind the vehicle………………………………………......…………24Figure 4.3 Pressure contour of baseline model……………………………………......…………24Figure 4.4 Optimal model…………………………………………………………......…………27Figure 4.5 Velocity field at optimal model…………………………………………......……..…28Figure 4.6 Wake at rear end trailer……………………………………………...…......…………28Figure 4.7 Pressure contour at optimal model……………………………………........…………29Figure 4.8 Analysis of wake region at rear end trailer…………………………….......…….……29Figure 4.9 Forces for baseline model over the time………………………………….......…….…30Figure 4.10 Forces for baseline model from 4s to 6s……………………………….......…...……30Figure 4.11 Forces for optimal model over time…………………………………......………..…31Figure 4.12 Average forces for optimal model from 4s to 6s…………………..…......…………32

Table 3.1 Mesh Sizes……………………………………………………………......……………19Table 3.2 Solver type…………………………………………………………......………………20Table 3.3 Simulation model……………………………………………………….......…….……20Table 3.4 Types of material……………………………………………………….......…….……20Table 3.5 Reference values………………………………………………………......…...………20Table 3.6 Boundary conditions…………………………………………………......….…………20Table 3.7 Solution methods………………………………………………………......……..……21Table 4.1 Forces by first order upwind scheme solution…………………………........…………22Table 4.2 Forces by second order upwind scheme solution……………………….......…………22Table 4.3 Standard deviation for both solution methods………………………….......…….……23Table 4.4 Standard deviation at each part……………………………………….......……………23Table 4.5 Results obtained by both cab roof designs………………………….….......………..…25Table 4.6 Results obtained by three geometry flaps……………………………….......…………26

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Table 4.7 Results of combination features………………………………………...…….......……27Table 4.8 Comparison of result………………………………………………………….......……28Table 4.9 Comparison results of baseline model by two different solvers……….……….......….31Table 4.10 Comparison results of optimal model by two different solvers……...……….......…..32

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A – Projected Area

CD – Coefficient of Drag

CL – Coefficient of Lift

CP – Coefficient of Pressure

D – Drag Force

Df – Skin Drag

DP – Pressure Drag

L – Life Force

M – Pitching Moment

P – Pressure

P∞ - Free Stream Pressure

Re – Reynold Number

T – Thrust Force

U – Velocity

U∞ - Free Stream Velocity

W – Gravity Force

x – Distance in horizontal direction

y – Distance in vertical direction

ρ – Density of air

τw – Wall shear stress

H – Height of vehicle

CFD – Computational fluid dynamics

HGVs – Heavy goods vehicles

LGVs – Light goods vehicles

VSD – Vortex strake device

W – Width of vehicle

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NOMENCLATURE