Aerodynamic Drag Reduction for Ground Vehicles using Lateral Guide Vanes

American University of Sharjah
Department of Mechanical Engineering
MCE491: Design Project II
FINAL REPORT
Project title: Aerodynamic Drag Reduction for Sport Utility Vehicles Using Side Guide-
Vanes
Team members
Name ID
Humaid Al Marzooqi 26245
Majd Shaath 31736
Mohamed Shahin 33060
Tarek El Dhmashawy 30959
Advisor(s): Dr. Essam Wahba
Approved by: Dr. Essam Wahba Date: May 21, 2012

MCE491: Design Project II Final Report
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DISCLAIMER
This report was written by student(s) at the Mechanical Engineering Department, College of
Engineering, The American University of Sharjah, Sharjah, UAE. It has not been altered or
corrected (other than editorial corrections) as a result of assessment and it may contain errors.
The views expressed in it together with any recommendations are those of the student(s). The
American University of Sharjah accepts no responsibility or liability for the consequences of
this report being used for a purpose other than the purpose for which it was commissioned.

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Declaration and Statement of Authorship:
1. We hold a copy of this document which can be produced if the original is lost/ damaged.
2. This proposal is our original work and no part of it has been copied from any other
student’s work or from any other source except where due acknowledgement is made.
3. No part of this document has been written for us by any other person except where such
collaboration has been authorized by the advisor concerned.
4. We have not previously submitted this work for this or any other course.
5. We give permission for this work to be reproduced, communicated, compared and archived
for the purpose of detecting plagiarism.
6. We give permission for a copy of our marked work to be retained by the Department for
review and comparison, including review by external examiners.
We understand that:
7. Plagiarism is the presentation of the work, idea or creation of another person as though it is
your own. It is a form of cheating and is a very serious academic offence that may lead to
expulsion from the University. Plagiarized material can be drawn from, and presented in,
written, graphic and visual form, including electronic data, and oral presentations. Plagiarism
occurs when the origin of the material used is not appropriately cited.
8. Plagiarism includes the act of assisting or allowing another person to plagiarize or to copy
our work.
Student Name Signature Date
Humaid Al Marzooqi May 21,2012
Majd Shaath May 21,2012
Mohamed Shahin May 21,2012
Tarek El Dhmashawy May 21,2012

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Executive Summary
Using side guide vanes mounted on the rear end of the vehicle is a new concept that leads to a
reduction in the aerodynamic drag force on car by increasing the pressure at the separation
region or the wake area, thus leading to a reduction in the pressure difference across the
vehicle. The aim of this project is to design then manufacture a set side guide vanes to reduce
aerodynamic drag across SUVs, thus achieving lower fuel consumption, lower harmful
emissions and conservation of energy.
In the first phase of the design, which was MCE 490, four different parameters were chosen
to varied, which are the type of air foil, the angle of the airfoil, the chord length of the air foil
and finally the position of the airfoil with respect to the car. HUMMER H2 was chosen as the
car to be simulated and experimented on, and a total of thirty six simulations were carried out
using ANSYS CFX resulting in a total reduction in the coefficient of drag by 17.90%
compared to the original one. Also the material selection for the manufacturing of the lateral
guide vanes was tackled, and the preliminary choice of the optimum material was fiberglass.
The second phase of design (MCE 491), included going over the material selection in details,
designing the connectors, buying scaled models of the HUMMER H2, manufacturing the side
guide vanes and attaching it to the model, and finally testing the prototype in a wind tunnel
and comparing the results obtained numerically and experimentally. Two 1:16 HUMMER
H2’s were bought for the testing as well as one model that is 1:8 for presentation purposed,
the side guide vanes were manufactured using Plexiglas and attached to the vehicles using a
two plate connector mechanism. Numerically the simulation yielded a 15% reduction in drag
coefficient with the connectors on ANSYS CFX, while experimentally a reduction of around
9% was obtained, which is around 4% error when compared to the numerical value.

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Table of Contents
Executive Summary...................................................................................................................... 4
Table of Contents.......................................................................................................................... 5
List of Tables ................................................................................................................................. 7
List of Figures................................................................................................................................ 8
Introduction................................................................................................................................. 10
Alternative Designs..............................................................................................................12
Optimum Design ..................................................................................................................12
Main objective of second phase the project .........................................................................12
Work done in second phase of the project ...........................................................................13
Deviation from the proposal.................................................................................................13
Structure of the report.......................................................................................................13
Simulation and Experiment ....................................................................................................... 15
Simulation ............................................................................................................................15
Outline of computational Fluid Dynamics .......................................................................15
Meshing and Pre-Processing ............................................................................................15
Numerical Solver..............................................................................................................16
Post Processor...................................................................................................................16
Approach..............................................................................................................................17
Experiment ...........................................................................................................................24
Design of experiment........................................................................................................24
Experimental detail...........................................................................................................25
Design, Manufacturing, and Prototype Testing....................................................................... 27
Design...................................................................................................................................27
First alternative design......................................................................................................28
Second alternative design.................................................................................................28
Third alternative design....................................................................................................29
Evaluating of conceptual designs .....................................................................................30
Optimum design ...............................................................................................................31
Connecting Plates drawn by ANSYS ...............................................................................32
Manufacturing......................................................................................................................33
Material selection .............................................................................................................33
Comparison between the materials of our choice.............................................................33
Plexiglass..........................................................................................................................36

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CNC Machine...................................................................................................................38
Computer Numerical Control.................................................................................................... 38
1. Motion control...........................................................................................................40
2. Programmable accessories: .......................................................................................40
The CNC program ............................................................................................................41
The CNC control ..............................................................................................................42
CAM system.....................................................................................................................42
DNC system......................................................................................................................43
Mastercam ........................................................................................................................44
G Code..............................................................................................................................44
Manufacturing Procedure .................................................................................................46
Assembly..............................................................................................................................49
Prototype testing...................................................................................................................50
Prototype...........................................................................................................................50
Scale Car (Model).............................................................................................................51
Wind Tunnel.....................................................................................................................54
Test Procedure..................................................................................................................57
Results..................................................................................................................................60
Results & Discussion................................................................................................................... 63
Experimental & Theoretical Results ....................................................................................63
Data Interpretation & Error Analysis...................................................................................64
Drag force reading (Force Balance) .................................................................................65
Velocity reading (Pitot Static Tube).................................................................................66
Other sources of error.......................................................................................................67
Cost Analysis........................................................................................................................67
Impact on Safety & Environment.........................................................................................68
Conclusion & Future Work ....................................................................................................... 69
Recommendation..................................................................................................................70
References.................................................................................................................................... 72
Appendix...................................................................................................................................... 75
G-Codes generated...............................................................................................................75

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List of Tables
Table 1: Results........................................................................................................................24
Table 2: Advantages and disadvantages of first alternative.....................................................28
Table 3: Advantages and disadvantages of second alternative................................................29
Table 4: Advantages and disadvantages of third alternative ...................................................30
Table 5: Evaluating of conceptual designs of the bearings......................................................31
Table 6: Material selection criteria ..........................................................................................35
Table 7: Material Evaluation ...................................................................................................35
Table 8: Properties of Plexiglass..............................................................................................37
Table 9: Codes and explanation...............................................................................................45
Table 10: Price list ...................................................................................................................53
Table 11: Experimental value of Cd for Hummer H2 .............................................................60
Table 12: Experimental value of Cd for Hummer H2 with side guide vanes..........................62
Table 13: Final results..............................................................................................................62
Table 14: Numerical results obtained from ANSYS ...............................................................63
Table 15: Experimental results obtained from wind tunnel testing.........................................64
Table 16: Cost Analysis...........................................................................................................67

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List of Figures
Figure 1: Frontal Region..........................................................................................................10
Figure 2: Rear Vacuum............................................................................................................10
Figure 3: Hummer H2..............................................................................................................18
Figure 4: Duct with vehicle......................................................................................................18
Figure 5: Mesh around duct.....................................................................................................19
Figure 6: Mesh around the vehicle...........................................................................................19
Figure 7: Pressure over vehicle without side guide vanes .......................................................20
Figure 8: Side Vane orientation by varying the angle of attack ..............................................21
Figure 9: Orientation of Side Guide Vane ...............................................................................22
Figure 10: Pressure over vehicle with side guide vanes ..........................................................22
Figure 11: Hummer H2 with side guide vanes and connecting plates.....................................23
Figure 12: Cylindrical connecting element..............................................................................28
Figure 13: Two side plates connecting element.......................................................................29
Figure 14: Single plate connecting element.............................................................................30
Figure 15: Side guide vanes with connecting plates................................................................32
Figure 16: Side guide vanes assembled with the vehicle.........................................................32
Figure 17: CNC machine .........................................................................................................39
Figure 18: Side guide vanes with connecting plates................................................................46
Figure 19: Transfer the drawing into MasterCam....................................................................47
Figure 20: Front view of vane..................................................................................................48
Figure 21: Top view of vane....................................................................................................48
Figure 22: Top view of vanes after painting and assembling..................................................49
Figure 23: Side view of vanes after painting and assembling .................................................49

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Figure 24: Overview look after painting and assembling vanes..............................................50
Figure 25: H2 scale model 1....................................................................................................51
Figure 26: H2 scale model 2....................................................................................................52
Figure 27: 1/32 H2 scale model...............................................................................................52
Figure 30: 1:16 hummer H2 scale model.................................................................................54
Figure 31 Sub-Sonic Wind tunnel C-2.....................................................................................55
Figure 32: C-2 Wind tunnel.....................................................................................................56
Figure 33: Force balance (Lift & Drag)...................................................................................56
Figure 34: Manometer..............................................................................................................57
Figure 35: Motor and Controller..............................................................................................57
Figure 36: Rear view of models...............................................................................................59
Figure 37: Side view of models ...............................................................................................59
Figure 38: Model without side guide vanes in the wind tunnel...............................................60
Figure 39: Model with side guide vanes in the wind tunnel....................................................61
Figure 40: Measuring the Drag forces on the model with side guide vanes in the wind tunnel
..................................................................................................................................................61
Figure 41: Force Balance (Wind Tunnel)................................................................................65
Figure 42: Pitot Static Tube (Prandtl Tube).............................................................................66

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Introduction
Nowadays, the aerodynamics of cars is becoming a rich topic and a vital issue, since it’s a
concern to enhance the drag coefficient of road vehicles which can be considered as the heart
of cars aerodynamics. The concept behind the Vehicle aerodynamic is that when it is in
motion, there is a high pressure (frontal Pressure) in its frontal region which is caused by the
air attempting to flow around the vehicle while in its rear region there is a low pressure (Rear
Vacuum), and this difference in pressure is the driving force for the drag force.
Figure 1: Frontal Region
Figure 2: Rear Vacuum
Basically, on a moving vehicle there are two types of friction forces that act on it, the
drag force and the rolling resistance forces. At high speeds, the drag force becomes the
dominant force acting on a moving vehicle and the rolling forces are negligible. Thus, in our

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senior design project, the analysis, design, and simulation of utilizing side guided vanes that
will be installed on the rear side of Sport Utility Vehicles (SUV’s) in order to improve the
SUV’s aerodynamic by reducing its drag coefficient is accomplished.
The main objectives in this project are to design, analyze, simulate, and then
manufacture the external side guide-vanes that will cause a significant reduction in the
aerodynamic drag force on a body of an SUV and so on the drag coefficient. In addition to
that, the secondary objectives of the project are the investigation of economic aspects and
savings and its impact on the environment due to the reduction in the fuel consumption, the
enhancement of the car performance (acceleration), performing simulation using ANSYS
software, the Comparison of the alternative designs of the guide-vanes and optimization, the
selection of the construction material for the side guided vanes, and manufacturing a
prototype side guide-vane and installing it on an SUV prototype.
As for the scope of our project, the design team decided to limit the concept of the
usage of the side guided vanes on bluff big bodies such as sport utility vehicles rather than
sedan vehicles since SUV’s have a higher drag coefficient and so the percentage reduction
can be showed clearly. Also, in this phase of the project, the testing is done using ANSYS
CFX software only while in the next phase it will be tested in a wind tunnel.
According to the predefined purpose and objectives of the project, the design team’s
method of approach to deal with the project is to define the criteria and the standard of codes
and ethics in order to design, analyze, and manufacture the side guided vanes in a
professional engineering manner. After that, the conceptual design stage is simulated and
then various alternative parameters are varied in order to get the optimum design that will
generate the best value for the drag coefficient. Then, the side guided vanes construction
material is selected based on the predefined criteria and standards. Finally, after completing

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each single phase of the project, the last step is to perform detailed cost analysis on the
project to check its feasibility and applicability.
Alternative Designs
In the first phase of the project, several alternative designs were obtained and
evaluated in order to get the best optimum design that will provide the largest reduction on
the forces acting on the body of the SUV and so the maximum reduction in the drag
coefficient is obtained also. Actually, four parameters are used to form thirty six alternative
solutions. In the first parameter which is the type of airfoil; three different airfoils which are
NACA 2412, NACA 0015, and NACA 64(3)218 are used. For the second parameter which is
the angle of attack; three different angles which are 5, 10, and 15 degrees are simulated. Also,
two different positions with respect to the x-axis and z-axis are evaluated. Finally, two cord
length of 1/8 and 1/12 are used as the forth parameter in the alternative design process.
Optimum Design
After evaluating thirty-six alternative designs based on the predefined criteria, the
optimum design is chosen to be the one which have the highest CD reduction, less drag
forces, low CL for airfoil and the easiest to manufacture. The Optimum design is NACA
0015 at an angle of attack of 10 degrees, with position of L1= 57mm and L2= 1522mm, and a
cord length of 1/8.
Main objective of second phase the project
In addition to the objectives that were previously mentioned in the first phase of the
project, a new goal was set to be met as the project progressed and the specifications are
solidified, in order to ensure the validity of our theory; which is to experimentally test the
final assembled scaled model of the side guided vanes and the HUMMER H2 in wind tunnel

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to measure the drag forces and the drag coefficient. By moving toward this goal, the
deviation from the theoretical drag forces is measured and our assumptions are validated.
Work done in second phase of the project
After completing the first phase which is the design, analysis, and simulation phase of
the project, the second phase which is selecting a scale car, manufacturing a prototype of the
vanes, assembling the side guided vanes to the prototype, and experimentally testing it, is
initiated. Initially, the first step is to find a HUMMER H2 scale model to apply our concept
on it. Then, the manufacturing stage of the side guided vanes using the desired material and
dimensions are done. Moving forward, the assembling process of the scaled side guided
vanes to the HUMMER H2 scale model is performed based on the optimum position and
angle that were previously obtained in the first phase from the simulation using the ANSYS
CFD software. After that, in order to validate our theory, the final assembled prototype will
be experimentally tested in a wind tunnel so that a comparison between the theoretical and
experimental reduction in the drag coefficient is obtained.
Deviation from the proposal
In fact, after completing the first phase and the second phase of the project, there were
no deviations from the scope of the project which was primarily defined before initiating with
the project.
Structure of the report
This report has five main sections and several sub-sections for each section in
addition to the executive summary. Initially, in the executive summary, the problem
statement and the objectives of the project are defined clearly and the results from the two
phases are stated properly. Then, in the first section which is the introduction, the work done

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in the two phases are showed and the main objective of MCE 491 is stated. Moving forward,
in the second section which the simulation and experimental one, theoretical results obtained
from the software during the second phase of the project are included. After that, in the third
section which is manufacturing, assembly and prototype testing the achievements in this
section are explained in details and technical specification and drawings are provided.
Furthermore, in the fourth section which is the results and discussion of the results, the results
are analyzed and checked if they meet the predefined objectives. Also, in this section, error
analysis for the measured data and cost analysis (estimated vs. actual) are performed. Finally,
in the last section, which is the conclusion, a brief summary of the project is stated, the
lessons learned from this project are listed, and final recommendations and future work are
defined.

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Simulation and Experiment
Simulation
The software used to solve the formulated problem is called ANSYS. ANSYS is a
fluid solver package which analyzes flow over any body and provides any results wanted. It
contains many packages like Design Modeler, CFX, etc. used to fully investigate fluid flow.
The software basically uses the concept of Computational Fluid Dynamics (CFD) to solve the
required problem at hand using finite element/volume analysis.
Outline of computational Fluid Dynamics
Computational Fluid Dynamic codes are structured around the numerical algorithms that
can tackle fluid flow problems. All the CFD codes available in the market have four basic
elements which divide the complete analysis of the numerical experiment to be performed on
the specific domain or geometry. The four basic elements are:
i. Design Modeler
ii. Pre-processor
iii. Numerical Solver
iv. Post-Processor
Meshing and Pre-Processing
The pre-processor is the link between the user and the solver. The user can alter or
generate any geometry in the design modeler as follows:
1. Definition of Geometry or region of interest: This process involves several computer
aided design (CAD) software like CATIA, Solidworks, etc.
2. Meshing: Since the CFD process is a numerical approximation method using finite
volume method, the given domain or region of interest needs to be divided into

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several structured elements. This stage is the key element in the CFD finite volume
numerical simulation and it also contributes to the accuracy of the final results.
3. Definition of Fluid properties: Every fluid domain or surface has its own distinct
property. The properties of the fluid used in the CFD domain or region of interest are
defined at this stage of the CFD Process.
4. Boundary Conditions: Every different setup of the CFD domain needs to have an
initialization, which is fulfilled by the boundary conditions input.
Numerical Solver
The numerical solver is the key element of the CFD process as it covers the major part of
the process. The finite element method is used to solve the flow over the specified body. The
finite element method is usually suitable for stress and structure analysis and does not suite
the requirements of the CFD process. The finite volume method is also for the CFD process.
As the name implies, finite volume method is a numerical algorithm calculation process
involving the use of finite volume cells. The steps involved in this solving process are usually
carried out in the following sequence:
i. Integration of the governing equations over all the control volumes.
ii. The conversion of the integral forms of the equations into a system of algebraic
equations.
iii. Calculations of the algebraic equations by an iterative method.
Post Processor
Data visualization and results analysis of the CFD process is carried in this section. The
results can be in the following forms:
i. Domain geometry and Grid display
ii. Vector plots
iii. Function calculator
iv. Line and shaded contour plots
v. 2D and 3D surface plots
vi. Particle tracking
vii. XY plots and graphs of results

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Approach
HUMMER H2, similar to box model, is used to find out the drag coefficient experimentally
and analytically. The vehicle has length of 25.8 cm, width of 10.3 cm, height of 9.885 cm and
ground clearance of 1.3 cm. The Vehicle experimentally has a drag coefficient of 0.57.
However; the analytical value is obtained using simulation via ANSYS CFX. The analysis
starts on ANSYS Workbench by creating an empty project. The first step was to create the
CAD with the desired dimensions mentioned previously. Then, construct a duct with
dimensions equal to 10 times the box dimensions in order to avoid any errors. In order to
create a fine mesh that will generate good results, the team started with course mesh as initial
guess and then keep refining it by trial and error until the desired value of drag coefficient
converges. After several trails, the desired value of the drag coefficient is achieved closely by
using refining options in the mesh window. Under the Spacing option, the maximum spacing
of the body spacing was defined to be 23mm. Nevertheless below the control option, the
point spacing was defined to be 4 mm, and 14 triangular controls were used on the box
surfaces. The achieved number of elements (nodes) is approximately 900,000 elements. As
the simulation is performed, the drag force is calculated to be 3.18 N. Drag coefficient can be
calculated by the equation below:
Cd: Drag coefficient
Fd: Drag force
ρ: Density = 1.184 m^3 /Kg
v: Velocity of the object = 120 Km/h = 33.333 m/s
A: Frontal area of the body= 9 /1000 m^2
The drag coefficient is calculated to be 0.54.

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Figure 3: Hummer H2
Figure 4: Duct with vehicle

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Figure 5: Mesh around duct
Figure 6: Mesh around the vehicle

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Figure 7: Pressure over vehicle without side guide vanes
The second simulation was performed of the vehicle with the side guide vanes. The
first step was to create the CAD with the desired dimensions mentioned previously. Then,
construct a duct with dimensions equal to 10 times the box dimensions in order to avoid any
errors. In order to create a fine mesh that will generate good results, the team started with
course mesh as initial guess and then keep refining it by trial and error until the desired value
of drag coefficient converges. After several trails, the desired value of the drag coefficient is
achieved closely by using refining options in the mesh window. Under the Spacing option,
the maximum spacing of the body spacing was defined to be 23mm. Nevertheless below the
control option, the point spacing was defined to be 4 mm, and 16 triangular controls were
used on the box surfaces. The achieved number of elements (nodes) is approximately

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1,200,000 elements. As the simulation is performed, the drag force is calculated to be
2.81567 N. Drag coefficient can be calculated by the equation below:
Fd: Drag force
A: Frontal area of the body= 9.654 /1000 m^2
Figure 8: Side Vane orientation by varying the angle of attack

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Figure 9: Orientation of Side Guide Vane
Figure 10: Pressure over vehicle with side guide vanes
The second simulation was performed of the vehicle with the side guide vanes and
connecting plates. The first step was to create the CAD with the desired dimensions
mentioned previously. Then, construct a duct with dimensions equal to 10 times the box
dimensions in order to avoid any errors. In order to create a fine mesh that will generate good
results, the team started with course mesh as initial guess and then keep refining it by trial

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and error until the desired value of drag coefficient converges. After several trails, the desired
value of the drag coefficient is achieved closely by using refining options in the mesh
window. Under the Spacing option, the maximum spacing of the body spacing was defined to
be 23mm. Nevertheless below the control option, the point spacing was defined to be 4 mm,
and 18 triangular controls were used on the box surfaces. The achieved number of elements
(nodes) is approximately 1400,000 elements. As the simulation is performed, the drag force is
calculated to be 2.9210 N. Drag coefficient can be calculated by the equation below:
Fd: Drag force
A: Frontal area of the body= 9.654 /1000 m^2
Figure 11: Hummer H2 with side guide vanes and connecting plates

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Simulation at various speed have been also performed as shown in the table below.
Table 1: Results
Velocity
(km/h)
Fd
single
(N)
Fd
vanes
(N)
Area
single
(m^2)
Area
vanes
(m^2)
Cd
single
Cd
vanes
Reduction
in Fd (%)
Reduction
in Cd (%)
54.00
52.20
50.40
48.60
43.20
39.60
0.6418
0.5996
0.5588
0.5194
0.4104
0.3449
0.6066
0.5669
0.5283
0.4908
0.3878
0.3259
0.009
0.009
0.009
0.009
0.009
0.009
0.009645
0.009645
0.009645
0.009645
0.009645
0.009645
0.54
0.54
0.54
0.54
0.54
0.54
0.47
0.47
0.47
0.47
0.47
0.47
5.5
5.5
5.5
5.5
5.5
5.5
13
13
14
13
13
13
Experiment
Design of experiment
An experiment is a methodical trial and error procedure carried out with the goal of
verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in
their goal and scale, but always rely on repeatable procedure and logical analysis of the
results. Experimental design is a planned interference in the natural order of events by the
researcher. This emphasis on experiment reflects the higher regard generally given to
information so derived. There is good rationale for this. Much of the substantial gain in
knowledge in all sciences has come from actively manipulating or interfering with the stream
of events. There is more than just observation or measurement of a natural event. A selected
condition or a change (treatment) is introduced. Observations or measurements are planned to
illuminate the effect of any change in conditions. The importance of experimental design also
stems from the quest for inference about causes or relationships as opposed to simply

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description. Researchers are rarely satisfied to simply describe the events they observe. They
want to make inferences about what produced, contributed to, or caused events. To gain such
information without ambiguity, some form of experimental design is ordinarily required. As a
consequence, the need for using rather elaborate designs ensues from the possibility of
alternative relationships, consequences or causes. The purpose of the design is to rule out
these alternative causes, leaving only the actual factor that is the real cause. Our main
objective of the experiment in this project is to verify the results obtained by simulation. In
order to do so, we have to use wend tunnel testing of a real model.
Experimental detail
A wind tunnel is a research tool or a testing laboratory with a controlled environment
used to understand aerodynamically what is happening to a particular shape or object. It is
used to quantify and validate what is going on aerodynamically to the vehicle by measuring
forces exerted on the body through a 6 component balance underneath the floor that the
vehicle is fixed to by use of adjustable wheel pads.
Adding a rear wing to your car might gain you down force, but a wind tunnel will tell
you in fact if it is, how much, and how it affected the overall front to rear balance of your
car. Each test will output the drag, down force (front & rear), and side force (front & rear),
yaw/pitch/roll moments, in order to see the big picture of what is really happening for any
given configuration. Even though we test at 85mph we can scale the force data to virtually
any speed you would see with your vehicle to see what the aero forces would be at that speed.
It is hard to imagine that something you cannot see could have such a significant
influence on the performance of a vehicle. More and more racers are catching on to the
importance of aerodynamic testing and the value it can bring to just about any application.

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Whether you have a specific handling issue, or you just looking for more top speed, a wind
tunnel is a good place to make some measurable differences.

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Design, Manufacturing, and Prototype Testing
Design
In the first phase of the project, design of side guide vanes has been done. However,
the group has designed the connecting plates in the second phase of the project.
Since the side guide vane is design to have the same concept of spoiler, it is designed
to be removable. A connecting element is used to connect the side guide vanes with the body
of the vehicle. This connecting element should be designed so that the installation is easy and
fast. To achieve this objective, car spoiler has been taken as benchmark; it has simple and
short procedure of instillation. An example of installation procedure is shown in the
following steps:
Step 1: Place the spoiler on top of the trunk in the proper position.
Step 2: Place the drill guide from the spoiler kit onto the trunk lid. Use a marker to indicate
on the trunk lid the positions of the holes for the spoiler attachment legs.
Step 3: Drill small pilot holes at the markings on the trunk lid from the top.
Step 4: Place the sealing gasket over the holes and bolt the spoiler down onto the trunk lid,
but do not over-tighten, which may cause dimpling on the surface.
In order to have similar procedure, three different alternative types of connecting
elements are proposed, compared and evaluated to have the optimum type which will be used
to calculate the forces and stress acting on it.

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First alternative design
The first alternative design is the cylindrical connecting element. This design is
simply has cylindrical shape as shown in the figure below.
Figure 12: Cylindrical connecting element
Table 2: Advantages and disadvantages of first alternative
Advantages Disadvantages
1. Occupies small space
2. Number of cylindrical connecters
equal to number of bolts needed
1. Causes bad air layer separation
2. Does not fit the optimum design
of side guide vanes
Second alternative design
The second alternative design is the two side plates connecting element. This design is
simply has rectangular shape as shown in the figure below.

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Figure 13: Two side plates connecting element
Table 3: Advantages and disadvantages of second alternative
1. Cause good air layer separation
2. Bolts can be added as much as
possible along each connecter
3. can be positioned anywhere
4. Does fit the optimum design of
side guide vanes
1. Occupies large space
Third alternative design
The third alternative design is the single plate connecting element. This design is
simply has rectangular shape as shown in the figure below.

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Figure 14: Single plate connecting element
Table 4: Advantages and disadvantages of third alternative
1. Cause good air layer separation
2. Bolts can be added as much as
possible along connecter
3. Occupies small space
4. Less material is used
1. Has fixed position
2. Does not fit the optimum design of
side guide vanes
Evaluating of conceptual designs
Basically, three conceptual designs of the connecting element that will be used in
connecting the side guide vanes with the body of the vehicle were studied and they are: The
cylindrical connecting element, The two side plates connecting element and The single plate
connecting element. These three conceptual designs are evaluated as the following:

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Table 5: Evaluating of conceptual designs of the bearings
Cylindrical Two side plates Single plate
Most important
advantages
 Number of
cylindrical
connecters equal
to number of
bolts needed
 Cause good air
layer
separation
 Does fit
optimum
design of side
guide vanes
 Cause good air
layer
separation
 Less material
is used
Most important
disadvantages
 Causes bad air
layer separation
 Does not fit
optimum design
of side guide
vanes
 Takes large
space
 Has fixed
position
 Does not fit
optimum
design of side
guide vanes
Optimum design
Optimal designs are a class of experimental designs that are optimal with respect to some
statistical criterion. Optimal designs offer three advantages:
1. Optimal designs reduce the costs of experimentation by allowing statistical models to
be estimated with fewer experimental runs.
2. Optimal designs can accommodate multiple types of factors, such as process, mixture,
and discrete factors.
3. Designs can be optimized when the design-space is constrained.

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These conceptual designs were evaluated using certain criteria depending on the features and
the characteristics of each element meant to be designed. Taking the separation of air layer
and matching with optimum design of side guide vanes as the most important criteria, the
optimum design is chosen to be the double plate connecting element.
Connecting Plates drawn by ANSYS
Figure 15: Side guide vanes with connecting plates
Figure 16: Side guide vanes assembled with the vehicle

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Manufacturing
The manufacturing of the side guide vanes can be broken down into three parts.
1. Material Selection
2. Manufacturing the parts
3. Assembly
Material selection
To begin with, the material selection part was done in the previous semester as part of MCE
490 which is Senior Design Project I and it included the following:
Comparison between the materials of our choice
Manufacturability
In terms of manufacturability, all 4 materials are easily manufactured through
different processes such as casting and molding. For ABS plastic there are absolutely no
restrictions in terms of manufacturability as it can be easily handled and its shape can be
altered by heating it or cooling it, as for fiber glass and carbon fiber there are restrictions
regarding some colors, shapes and sizes that it can be manufactured for. As for silicone
polymers they are also easily manufactured although a trial and error process could be
necessary since silicone- polymers tend to be unpredictable sometimes.

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Reliability/durability
Carbon fiber poses the greatest strength to weight ratio that is due to the millions of
fibers bundled together; this is the same for fiber glass with the only difference in the use of
carbon element in carbon fiber as compared to glass (silicone oxide). Silicone polymers and
ABS plastics are also high on the strength scale but still lower that carbon fiber and
fiberglass, with ABS trailing the 4 materials.
Lifetime
Silicone-organic polymers lead the lifetime charts between these materials followed
by, fiberglass, then carbon fiber and then ABS plastics. This is because carbon fiber is
somewhat not very resistant to abrasion and the fact that ABS plastics are easily affected by
temperatures.
Weight
In terms of weight they are all pretty similar since spoilers, side skirts and similar
parts that enhance the performance of cars by adding it are supposed to be light. Carbon fiber
has the edge due to its strength to weight ratio, followed by fiberglass, then ABS plastics,
then silicone polymers.
Cost
The most expensive out of these materials is carbon fiber, followed by silicone
polymers, fiber glass and lastly ABS plastics.

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Table 6: Material selection criteria
Criteria Assigned
Weights
Material Used
Carbon
Fiber
ABS
Plastic
Silicon-organic
polymers
Fiberglass
Cost 10 5 10 6 9
Reliability(Strength) 7 7 4 5 6
Manufacturability 9 7 8 5 7
Weight 6 6 4 4 5
Lifetime 7 6 2 6 7
Table 7: Material Evaluation
Material Cost Reliability Manufacturability Weight Lifetime Calculated
Total
Carbon
Fiber
10*5 7*7 9*7 6*6 7*6 240
Fiberglass 10*9 7*6 9*7 6*5 7*7 274
ABS Plastic 10*10 7*4 9*8 6*4 7*2 238
Silicone-
Organic
polymers
10*6 7*5 9*5 6*4 7*6 206

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The conclusion of this process was fiberglass is the most suitable material to use in
our application as it weighed good in all the aspects that were needed in the material of our
choice, thus scoring the highest in the weight calculation table that is shown above.
The objective in MCE 491 was to purchase the fiberglass and start manufacturing it
according to the optimum design and install it on the prototype, both for testing and for
presenting to the committee. Fiberglass proved to be somewhat difficult to obtain since there
are no readymade fiberglass sheets or cubes, etc. that could be bought and then cut and
manufactured according to what is needed, instead the designs of the object had to emailed to
one of the many fiberglass manufacturers available in the country and let them finish up the
product, this meant that the group wasn’t going to be involved in the manufacturing of the
side guide vanes as initially planned. Therefore, since this part involves working with models
and prototypes, the group opted for plexiglass as a substitute material for fiberglass in this
intermediate stage. Plexiglass (explained in more details in the following section) has very
similar properties to fiberglass, and in addition to that it’s already available in the
Manufacturing Laboratory which will reduce our manufacturing costs to zero Dirhams since
no external agents or products are bought.
Plexiglass
Plexiglass, also known as acrylic glass and Perspex, is a transparent thermoplastic that
is made of poly(methyl methacrylate), it’s produced by emulsion polymerization, bulk
polymerization and solution polymerization and it can be processed using injection molding,
compression molding, extrusion and cell casting which is molding and polymerization
simultaneously. Although plexiglass can be cut my most cutting techniques available,
whether it’s done using a CNC machine, a conventional saw or even laser cutting, surface

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finishing techniques such as filing will immediately scratch its surface since the material is
already very smooth on the surface.
Properties of Plexiglass:
Table 8: Properties of Plexiglass
Mechanical Properties
Young’s Modulus 1800 – 3100 (MPa)
Shear Modulus 1700 (MPa)
Tensile Strength 48 - 76 (MPa)
Elongation 2 – 10 (%)
Compressive Strength 83 – 124 (MPa)
In addition to this, Plexiglass has very good dimension stability, chemical resistance and
weather resistance. In the safety properties, when Plexiglass breaks it doesn’t shatter like
glass, instead it breaks into bulky pieces that can be easily spotted and taken away to avoid
injury. Plexiglass has many uses such as:
1. Transparent glass substitute, such as in aquariums and car wind shields.
2. New technologies in medicine and implants such as the ones in plastic surgery.
3. Artistic models and aesthetics such as car models, furniture and sculptors.
4. Other uses include optic fibers, semi-conductors research in the nanotechnology area.

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CNC Machine
Computer Numerical Control
CNC stands for Computer Numerical Control and has been around since the early
1970's. Prior to this, it was called NC, for Numerical Control (In the early 1970's computers
were introduced to these controls, hence the name change).While people in most walks of life
have never heard of this term, CNC has touched almost every form of manufacturing process
in one way or another. If you'll be working in manufacturing, it's likely that you'll be dealing
with CNC on a regular basis.
While there are exceptions to this statement, CNC machines typically replace (or
work in conjunction with) some existing manufacturing process/es. Take one of the simplest
manufacturing processes, drilling holes, for example.
A drill press can of course be used to machine holes. (It's likely that almost everyone
has seen some form of drill press, even if you don't work in manufacturing.) A person can
place a drill in the drill chuck that is secured in the spindle of the drill press. They can then
(manually) select the desired speed for rotation (commonly by switching belt pulleys), and
activate the spindle. Then they manually pull on the quill lever to drive the drill into the work
piece being machined.
As you can easily see, there is a lot of manual intervention required to use a drill press
to drill holes. A person is required to do something almost every step along the way! While
this manual intervention may be acceptable for manufacturing companies if but a small
number of holes or work pieces must be machined, as quantities grow, so does the likelihood
for fatigue due to the tediousness of the operation. And do note that we've used one of the
simplest machining operations (drilling) for our example. There are more complicated

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machining operations that would require a much higher skill level (and increase the potential
for mistakes resulting in scrap work pieces) of the person running the conventional machine
tool. (We commonly refer to the style of machine that CNC is replacing as the conventional
machine.)
Figure 17: CNC machine
By comparison, the CNC equivalent for a drill press (possibly a CNC machining
center or CNC drilling & tapping center) can be programmed to perform this operation in a
much more automatic fashion. Everything that the drill press operator was doing manually
will now be done by the CNC machine, including: placing the drill in the spindle, activating
the spindle, positioning the work piece under the drill, machining the hole, and turning off the
spindle.
Regarding the CNC work principle, everything that an operator would be required to do
with conventional machine tools is programmable with CNC machines. Once the machine is
setup and running, a CNC machine is quite simple to keep running. In fact CNC operators
tend to get quite bored during lengthy production runs because there is so little to do. With
some CNC machines, even the workpiece loading process has been automated. (We don't

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mean to over-simplify here. CNC operators are commonly required to do other things related
to the CNC operation like measuring work pieces and making adjustments to keep the CNC
machine running good work pieces. Furthermore, here are some of the specific programmable
functions:
1. Motion control
All CNC machine types share this commonality: They all have two or more
programmable directions of motion called axes. An axis of motion can be linear (along a
straight line) or rotary (along a circular path). One of the first specifications that implies a
CNC machine's complexity is how many axes it has. Generally speaking, the more axes, the
more complex the machine.
The axes of any CNC machine are required for the purpose of causing the motions needed
for the manufacturing process. In the drilling example, these (3) axis would position the tool
over the hole to be machined (in two axes) and machine the hole (with the third axis). Axes
are named with letters. Common linear axis names are X, Y, and Z. Common rotary axis
names are A, B, and C.
2. Programmable accessories:
A CNC machine wouldn't be very helpful if all it could only move the workpiece in two
or more axes. Almost all CNC machines are programmable in several other ways. The
specific CNC machine type has a lot to do with its appropriate programmable accessories.
Again, any required function will be programmable on full-blown CNC machine tools. Here
are some examples for one machine type.

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3. Machining centers
Automatic tool changer
Most machining centers can hold many tools in a tool magazine. When required, the
required tool can be automatically placed in the spindle for machining.
Spindle speed and activation
The spindle speed (in revolutions per minute) can be easily specified and the spindle
can be turned on in a forward or reverse direction. It can also, of course, be turned off.
Coolant
Many machining operations require coolant for lubrication and cooling purposes.
Coolant can be turned on and off from within the machine cycle.
The CNC program
Think of giving any series of step-by-step instructions. A CNC program is nothing
more than another kind of instruction set. It's written in sentence-like format and the control
will execute it in sequential order, step by step.
A special series of CNC words are used to communicate what the machine is intended
to do. CNC words begin with letter addresses (like F for feed rate, S for spindle speed, and X,
Y & Z for axis motion). When placed together in a logical method, a group of CNC words
make up a command that resemble a sentence.

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For any given CNC machine type, there will only be about 40-50 words used on a
regular basis. So if you compare learning to write CNC programs to learning a foreign
language having only 50 words, it shouldn't seem overly difficult to learn CNC programming.
The CNC control
The CNC control will interpret a CNC program and activate the series of commands
in sequential order. As it reads the program, the CNC control will activate the appropriate
machine functions, cause axis motion, and in general, follow the instructions given in the
program.
Along with interpreting the CNC program, the CNC control has several other
purposes. All current model CNC controls allow programs to be modified (edited) if mistakes
are found. The CNC control allows special verification functions (like dry run) to confirm the
correctness of the CNC program. The CNC control allows certain important operator inputs
to be specified separate from the program, like tool length values. In general, the CNC
control allows all functions of the machine to be manipulated.
CAM system
For simple applications such as drilling a single hole the CNC program can be
developed manually. That is, a programmer will sit down to write the program armed only
with pencil, paper, and calculator. Again, for simple applications, this may be the very best
way to develop CNC programs.
As applications get more complicated, writing programs manually becomes much
more difficult. To simplify the programming process, a computer aided manufacturing
(CAM) system can be used. A CAM system is a software program that runs on a computer

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(commonly a PC) that helps the CNC programmer with the programming process. Generally
speaking, a CAM system will take the tediousness and drudgery out of programming.
In many companies the CAM system will work with the computer aided design
(CAD) drawing developed by the company's design engineering department. This eliminates
the need for redefining the work piece configuration to the CAM system. The CNC
programmer will simply specify the machining operations to be performed and the CAM
system will create the CNC program (much like the manual programmer would have written)
automatically.
DNC system
Once the program is developed (either manually or with a CAM system) it must be
loaded into the CNC control. Though the setup person could type the program right into the
control, this would be like using the CNC machine as a very expensive typewriter. If the
CNC program is developed with the help of a CAM system, then it is already in the form of a
text file. If the program is written manually, it can be typed into any computer using a
common word processor (most companies use a special CNC text editor for this purpose).
Either way, the program is in the form of a text file that can be transferred right into the CNC
machine. A distributive numerical control (DNC) system is used for this purpose.
A DNC system is nothing more than a computer that is networked with one or more
CNC machines. Until only recently, rather crude serial communications protocol (RS-232c)
had to be used for transferring programs. Newer controls have more current communications
capabilities and can be networked in more conventional ways (Ethernet, etc.). Regardless of
methods, the CNC program must of course be loaded into the CNC machine before it can be
run.

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Mastercam
As mentioned above CAD and CAM were later integrated with the CNC machines,
Mastercam is a software that was developed for that exact purpose. Instead of the user
actually writing the G-Codes him/herself, Mastercam enables the user to draw the object and
choose everything related to the machining performed, from the dimensions of the drawings
to the dimensions of the tool used and the starting point of the machining. The software
already has some predefined tool paths whether it’s contouring, drilling, the surface speed,
and many more, thus allowing a much more accurate and efficient machining. It also allows
the use of 3rd
party applications with it, for example one might draw the object on any other
drawing software such as AutoCAD or 3D Max and then import the drawing to Mastercam
and it will be able to interpret it directly and generate the G-Codes that will tell the machine
what to do. Below is a picture of the connecting parts and the side guide vanes as seen on
Mastercam followed by the G-Codes for both parts.
G Code
G-codes are the most common codes used when programming the CNC tools. It is
called preparatory functions codes that involve actual tool movement. The following table
(table 1) describes the function of some of the codes:

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Table 9: Codes and explanation
The code What is it for?
G01 Linear interpolation (Straight line movement)
G02 Circular interpolation (clockwise)
G03 Circular interpolation (counterclockwise)
Here are three different examples of how to use these three codes in block and the
explanation of them:
N10 T05 M06
 Changing the tool by using the tool function (M06), tool number 5 (T05) is chosen
from the set of tools available.
N20 S500 M3
 The spindle rotates clockwise rotation (M03) at a spindle speed of (500 rpm).
N30 G00 X0 Y0 Z10
 Rapid movement (G00) to the reference point (0,0) (X0 Y0) and moving 10 units
towards the positive direction of the Z axis.
N40 F100 G01 Z-10 M08
 Turning the coolant on (M08). linear tool movement (G01) to the point with
coordinates -10 on the Z-axis at a feed rate of 100 mm/min (F100).

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N50 G02 X20 Y20
 Circular interpolation (G02) in the clockwise direction till the point (20,20) on the
X-Y axis.
N60 G00 Z10 M09
 Rapid movement (G00) to the point with Z coordinates of 10 (Z10) turning of the
coolant (M09)
Manufacturing Procedure
1. Draw side guide vanes using any software
Figure 18: Side guide vanes with connecting plates

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2. Transfer the drawing into MasterCam
Figure 19: Transfer the drawing into MasterCam
3. Produce a G-code.
4. Transfer the G-code produced to software of the CNC machine.
5. Operate the CNC machine in order to produce the part.

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Figure 20: Front view of vane
Figure 21: Top view of vane

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Assembly
Figure 22: Top view of vanes after painting and assembling
Figure 23: Side view of vanes after painting and assembling

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Figure 24: Overview look after painting and assembling vanes
Prototype testing
Prototype
After completing the design, analysis, and simulation process in the first phase of the project,
a prototype and scale models of the side guided vanes with the HUMMER H2 should be
provided in order to experimentally test the concept of drag reduction and validate our theory.
In fact, there is uncertainty as to whether the new concept of using the side guide vanes on
SUV’s will actually do what is desired as new designs often have unexpected problems. A
prototype is often used as part of the product design process to allow the design team to test
the theory and confirm performance prior to starting production of the new product. There are
several advantages of prototyping such as:
1- May provide the proof of concept necessary to attract funding.
2- Encourages active participation among users and producer.

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3- Cost effective (Development costs reduced).
4- Assists to identify any problems with the efficacy of earlier design, requirements
analysis and coding activities.
In this project, scale models of the HUMMER H2 with the required dimensions and the side
guide vanes scaled and attached will serve as the prototype which will be provided in the
final presentation to visualize the concept of the project. Also, another scale model of the
HUMMER H2 will be tested experimentally in wind tunnel to validate the obtained results.
Scale Car (Model)
In the process of searching for the HUMMER H2 scale models, several approaches were
used. The first approach was to search in stores located in Dubai and Sharjah for the models,
which results in finding somehow appropriate scale models of the H2 in the Dragon (China)
Mall as observed in the following figures.
Figure 25: H2 scale model 1

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Figure 26: H2 scale model 2
The other approach was to search online for the H2 scale models. From Souq.com which is a
popular website in UAE for selling and buying online, a model was obtained from a supplier
in Dubai, and it has the following details:
1/32 Scale Ninco Slot Car. Ninco HUMMER H2 is number one in the ever popular Gulf live.
This car will give you some Fantastic off road track action, Fully loaded with Strong Magna
traction, Sprung pivoting guide, 4 wheel drive with independent Pro shock Suspension, Ninco
NC-7 Raider motor rated at 19.3K RPM with 265 g/cm of torque based on a 14.8 volt
supply, displayed in a clear crystal case for your collection.
Figure 27: 1/32 H2 scale model

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Also, from the Ebay.com which is the most popular online buying and selling website all
over the world several scale models were found, but, the following two models were chosen
since they can be shipped to UAE with a reasonable time. The two models are:
Table 10: Price list
Location of
the Supplier
Scale Price Shipment
cost
Total cost
Dragon mall
(Dubai)
- 120 AED - 120 AED
Souq.com
(Dubai)
1/32 130 AED - 130 AED

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Ebay.com
(China)
1/24 42 USD 70 USD 412 AED
1/27 11 USD 50 USD 225 AED
All in all, the needed scale of the HUMMER H2, the price, and the availability will decide
which of the previous models will be chosen, and this cannot be obtained unless the exact
dimensions of the wind tunnel is provided.
After the detailed searching process of the HUMMER H2 scale mode in the market, the
design team decided to choose the following models which fits our criteria the best in terms
of price, appearance, dimensions since it costs only 80 AED and it is scaled to 1:16 of the
real HUMMER H2.
Figure 30: 1:16 hummer H2 scale model
Wind Tunnel
Moving forward, the experimental testing of the concept was performed on a sub-sonic wind
tunnel testing C-2 which is shown below.

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Figure 31 Sub-Sonic Wind tunnel C-2
The previously showed wind tunnel has the following specifications:
 Self-contained wind tunnel for the study of subsonic aerodynamics, complete with
two- component balance system and air speed indicator
 Special features:
 Contraction and Diffuser: precision glass fibre mouldings
 Test Section: clear acrylic, which retracts to permit access to the models.
 Adjustment of models can be made with the tunnel in operation.
Fan: Variable speed motor driven unit downstream of the working section permitting stepless
control of airspeed between 0 and 26ms-1
Balance: Lift and drag : Lift - 7.0N, Drag - 2.5N, Sensitivity ±0.01N
Air speed: Indicated on inclined manometer directly calibrated in m/s
Support structure: A strong steel frame including working surface and fitted with castors for
easy movement
 Suitable for undergraduate and simple research work.

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 Working section: 304mm wide x 304mm high x 457mmlong (octagonal cross-
section)
 Contraction area ratio: 3:1
 Motor rating: 1.5kW
Also, here are some specified figures that illustrate the features that are previously described:
Figure 32: C-2 Wind tunnel
Figure 33: Force balance (Lift & Drag)

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Figure 34: Manometer
Figure 35: Motor and Controller
Test Procedure
The test is performed at different wind speeds, with the test object on the optimum position
and angle with respect to the wind direction based on the analysis from the first phase of the
project. The test procedure is listed below.
1. Place the structure on which the test object will be mounted in the wind tunnel and run a
complete set of tests. The structure must interfere with the test object as little as possible
and cause a minimum amount of turbulence. At the same time, it must hold the test object
securely and not let it move.

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2. Analyze the supporting structure test data. The results of the test object test will have to be
corrected for the influence of the supporting structure but the values obtained from the
supporting structure test must be small in comparison to those expected for the test object.
If that is not the case, modify the supporting structure.
3. Attach the test object to the supporting structure and run sample tests to check that the
results are reasonable and consistent. Run a full set of tests with the test object static in its
initial position. Check the results for consistency with the sample results. If at any time the
test gives inconsistent or unreasonable results, check the sensors, the recording equipment
and the mounting of the test object.
4. Run a full set of tests with the test object at the different angles to be tested and turned at
different orientations to the wind direction. If the object can change shape with time, as in
a propeller which changes the angle of its blades or for a bicyclist who is pedaling, test the
different shapes statically and individually or test the object dynamically as it moves. In
the latter case, many readings must be taken rapidly to get good results.
5. Analyze all the results for consistency before proceeding to conclusions. Some results will
have to be discarded if there is too much variation. This is especially true of the results
from dynamic tests. The remaining results can be analyzed to determine whether the test
object has the required smoothness to minimize drag, whether it will withstand high wind
speeds without damage or whether it will produce the anticipated thrust or power.
Basically, in order to perform the experiment in right conditions, two models were provided,
one with the side guided vanes and the other without anything.

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Figure 36: Rear view of models
Figure 37: Side view of models
As a results, the experiment were divided into two parts, the first part was to obtain the drag
forces and so the drag coefficient acting on the body of the H2 model without the side guided
vanes as shown below.

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Figure 38: Model without side guide vanes in the wind tunnel
Results
The obtained results from the first part of the experiment can be summarized in the table
below.
Table 11: Experimental value of Cd for HUMMER H2
Velocity (km/h) Cd
54.00
52.20
50.40
48.60
43.20
39.60
0.61
0.58
0.59
0.56
0.54
0.50
Average value of Cd 0.56
On the other hand, for the second part, the scaled HUMMER H2 model with the scaled side
guide vanes installed on its rear side were tested as below.

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Figure 39: Model with side guide vanes in the wind tunnel
Figure 40: Measuring the Drag forces on the model with side guide vanes in the wind tunnel

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The obtained results for the second part of the experiment are summarized as in the following
table:
Table 12: Experimental value of Cd for HUMMER H2 with side guide vanes
Velocity (km/h) Cd
54.00
52.20
50.40
48.60
43.20
39.60
0.50
0.52
0.51
0.54
0.53
0.48
Average value of Cd 0.52
Table 13: Final results
Velocity
(km/h)
Fd
single
(N)
Fd
vanes
(N)
Area
single
(m^2)
Area
vanes
(m^2)
Cd
single
Cd
vanes
Reduction
in Fd (%)
Reduction
in Cd (%)
54.00
52.20
50.40
48.60
43.20
39.60
1.01
0.89
0.85
0.75
0.57
0.44
0.86
0.83
0.77
0.75
0.59
0.44
0.0125
0.0125
0.0125
0.0125
0.0125
0.0125
0.013
0.013
0.013
0.013
0.013
0.013
0.61
0.58
0.59
0.56
0.54
0.50
0.50
0.52
0.51
0.54
0.53
0.48
14.8
6.7
9.4
0.0
- 3.5
0.0
18
10.3
13.5
3.5
1.9
4.0

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Results & Discussion
In this chapter, an overview of the results obtained (Theoretically and experimentally) will be
shown and discussed in details to provide a clear view of the completed objectives of MCE
490/491.
Experimental & Theoretical Results
The results obtained in MCE 490 using ANSYS software are summarized in the table below
in order to compare those results with the experimental results. Also, the results obtained
from the wind tunnel section as previously viewed in the Testing section are summarized in
the table below with extra information about the drag force, area with and without vanes, and
the total reduction in both drag force and drag alone.
Table 14: Numerical results obtained from ANSYS
Velocity
(km/h)
Fd
single
(N)
Fd
vanes
(N)
Area
single
(m^2)
Area
vanes
(m^2)
Cd
single
Cd
vanes
Reduction
in Fd (%)
Reduction
in Cd (%)
54.00
52.20
50.40
48.60
43.20
39.60
0.6418
0.5996
0.5588
0.5194
0.4104
0.3449
0.6066
0.5669
0.5283
0.4908
0.3878
0.3259
0.009
0.009
0.009
0.009
0.009
0.009
0.009645
0.009645
0.009645
0.009645
0.009645
0.009645
0.54
0.54
0.54
0.54
0.54
0.54
0.47
0.47
0.47
0.47
0.47
0.47
5.5
5.5
5.5
5.5
5.5
5.5
13
13
14
13
13
13

Page 64 of 78
Table 15: Experimental results obtained from wind tunnel testing
Velocity
(km/h)
Fd
single
(N)
Fd
vanes
(N)
Area
single
(m^2)
Area
vanes
(m^2)
Cd
single
Cd
vanes
Reduction
in Fd (%)
Reduction
in Cd (%)
54.00
52.20
50.40
48.60
43.20
39.60
1.01
0.89
0.85
0.75
0.57
0.44
0.86
0.83
0.77
0.75
0.59
0.44
0.0125
0.0125
0.0125
0.0125
0.0125
0.0125
0.013
0.013
0.013
0.013
0.013
0.013
0.61
0.58
0.59
0.56
0.54
0.50
0.50
0.52
0.51
0.54
0.53
0.48
14.8
6.7
9.4
0.0
- 3.5
0.0
18
10.3
13.5
3.5
1.9
4.0
Data Interpretation & Error Analysis
From the tables above, it is clear that there is a reduction in the drag coefficient of the
car using the side guided vanes, which clearly meet the primary objectives of the project. In
total, the average amount of drag reduction obtained experimentally is around 9%, as shown
in the table. Compared to the numerical value obtained which was around 17%, this is
considered a good achievement considering the sources of errors. Also, the average 9%
reduction was obtained at an average speed of 48 km/hr, while the 17% reduction
(Numerical) was obtained at 120 km/hr. Therefore, the team prepared another simulation at a
speed of 54 km/hr and found a total drag reduction of about 13 %.
Therefore, it is concluded that using these lateral vanes can achieve an average drag
reduction of about 9% on a moving SUV at a speed of 54 km/hr, which is the primary
objective of this senior design project.
The difference between the percentage reduction between the experimental and
theoretical (Numerical) is due to the sources of error that is discussed below.

Page 65 of 78
 Drag force reading from the force balance
 Velocity reading from the Pitot static tube
The two sources above will be discussed in detail in the following paragraph. Furthermore,
other sources of error include the perfect alignment of the car with the directed flow, errors
reading the total pressure from the Pitot static tube since the resolution of the device is small,
and errors occurring from the external pressures acting on the flow and affecting the Pitot
static tube reading.
Drag force reading (Force Balance)
The force balance is a method used inside wind tunnels to measure the drag force
experienced by the test body inside the tunnel. A schematic drawing of the force balance
inside the wind tunnel is shown below with the labels. As implied from the name, the force
balance works with the principle of balancing weights on the strut and the balanced weight is
the amount of drag force exerted on the body.
Figure 41: Force Balance (Wind Tunnel)
The sources of error in the force reading occurred in the difficulty of misbalancing the
weights to determine the force as the flow is always disturbed and had non-constant reading
of the force.

Page 66 of 78
Velocity reading (Pitot Static Tube)
The Pitot static tube (Prandtl Tube) is a pressure transducer used to read the total
pressure in a flow. The total pressure is composed of the static pressure and the dynamic
pressure, and from the dynamic pressure, the velocity of the flow is determined.
Figure 42: Pitot Static Tube (Prandtl Tube)
The equation governing the total pressure is shown below, and from it the corresponding
velocity of the flow is determined as follows.
The errors that occurred from this section are when reading the total pressure from the Pitot
static tube which affects the velocity calculation of the flow and in turn affects the value of
the drag coefficient which depends on the velocity value.

Page 67 of 78
Other sources of error
Other sources of error include the imperfect assembly of the vanes to the car. Since it
is manually, the position along with the angle of attack were not fit perfectly to the needed
values and thus introduced error in the experiment. Furthermore, the connecting rods that are
used to assemble the side guided vanes to the vehicle were not aerodynamically shaped.
Having a rectangular cross-section and extrusion, the flow around these plates will be
disturbed and will cause a lot of turbulence affecting the results.
Cost Analysis
Regarding this particular project, there weren’t many parts bought except for 2
HUMMER H2 scaled cars and a bigger scaled one. The table below shows the cost for each
item.
Table 16: Cost Analysis
Item Quantity Description Cost
HUMMER H2
scaled car (1:16)
2
One is used to assemble the vanes on, and
other is free. Both to be used in the wind
tunnel testing
80 Dhs
HUMMER H2
scaled car (1:8)
1
Used to visualize the position of the side
guide vanes to the audience in the
presentation
215 Dhs
- - - 375 Dhs
Compared to the budget given by the department, which is 2,000 Dhs, the items bought were
enough and didn’t exceed the budget given.

Page 68 of 78
Impact on Safety & Environment
This proposed solution, that is proven to reduce the drag effectively, has no or little
impact on the safety and environment.
In terms of safety, the side guided vanes are installed on the sides of the car, which
makes them safe in terms of stability of the vehicle. Since the vanes are installed on both
sides, the lift force generated by each airfoil will cancel each other as they are in the same
line of action and will have no effect on the stability of the car. Furthermore, the vanes are
very close to the sides of the car (i.e. 14 cm), and this does not affect the mirror view for the
drives for the car and hence they’re safe to install. Finally, the connecting element chosen to
assemble the vanes to the car are safely designed taking into account the extra forces and
stresses acting on the vane in the worst conditions, therefore, it is safe to use these vanes.
In term of environment, the main cause of air pollution all over the world is car
exhaust emissions that have a negative impact on the environment such as Local effects by
polluting the air, Regional effects and Global effects which are changing the relations
between the atmosphere, sun and the oceans. As for the environmental effects that depends
on the performance of the side guide vanes, by introducing more than 3.58% reduction in the
average fuel consumption of an SUV, the car exhaust emissions such as Carbon dioxide,
Carbon monoxide, Nox, etc. will be reduced tremendously and it is assumed a great
achievement towards a healthier environment.

Page 69 of 78
Conclusion & Future Work
In conclusion, the main objective of this project is met which was the aerodynamic drag
reduction on SUV’s using the side guided vanes. The team started with searching literature to
find the existing solutions regarding the drag reduction aerodynamically. Then, an
optimization study was done to find the best airfoil cross-section, best chord length, best
angle of attack, position, and the best material. Using the ANSYS software, the best solution
was found to be the following:
 NACA 0015 airfoil
 Chord length 1/8 of the car length
 Angle of attack of 10˚
 A position of 57 mm from the center of the car
 A position of 252 mm from the front region of the car
 Plexiglass as the material selected
Afterwards, in MCE 491, additional studies were done to find the best connecting
element to assemble the side guide vane and testing the model car in a wind tunnel to prove
the theoretical results. Finally, the main objective of the project was achieved and the model
car containing the assembled side guide-vanes is made available.
By doing this project, the team achieved several positive points to make a good and
everyday practice in the upcoming career. Teamwork is an essential and crucial point when it
comes to the success of any project. This project content and work made it essential that the
team meet on regular basis, trust each other, rely on each other’s work, and know each other
better and better. Experiencing real life problems is another positive point learnt from this
project, as theoretical assumptions don’t always resembles real life problems. For this project,

Page 70 of 78
drag reduction is a real problem faced by automotive industries and the tackle of this problem
comes from a project like this. Also, applying the theoretical and practical experience learnt
in the courses taken in Mechanical Engineering is made possible in this project as it combines
many aspects in mechanical engineering such as fluid mechanics, mechanical design,
manufacturing, material selection, and simulation software.
Drag reduction has become one of the important aspects for any automotive industry. In
fact, it is very crucial to the safety and welfare of the society along with the environmental
impact that can be reduced by achieving reduction in drag. Several solutions are discovered
to reduce the drag on any moving vehicle and this project is one of them. The body shapes of
cars became more aerodynamic than before as a result of the importance of this topic, and
many companies trade off car performance for the benefit of drag reduction. This broad area
of drag reduction is yet to evolve into more mature manner that to be taken care off in any
automotive industry.
Recommendation
If the team is to continue on this project, there are several aspects that are to be studied
and experimented to expand the use of this product. But due to the time limit, these aspects
will be left to be further experimented by any other team. These recommendations are:
 Advanced design for the connecting element to minimize the extra effect of drag due
to its presence.
 An automated opening/closing of the side guide vane can be done in order to ensure
the effect at high speed, since these vanes take effect at high flow speeds. This idea is
inspired by the automated spoiler of the Audi R8 car that opens at a speed of 100
km/hr and above.

Page 71 of 78
 Further parametric study can be done on the angle of attack and vanes positions to see
where the maximum drag reduction occurs. The team only considered three angles of
attacks and three positions from the center and front of the car.
 Experiment the model car with the side guide-vanes attached in a larger wind tunnel
having a speed of 120 km/hr. The wind tunnel testing was done at the maximum
speed of the wind tunnel which was 54 km/hr.

Page 72 of 78
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Page 75 of 78
Appendix
G-Codes generated
N110 T240 M06 ; 6. BALL ENDMILL
N120 ;MAX : Z50.
N130 ;MIN : Z-.756
N140 ;TOOLPATH - FINISHPARL
N150 ;STOCK LEFT ON DRIVE SURFS = 0.
N160 G00 G90 X10.031 Y127.61 S3500 M03
N170 G43 D0
N180 Z50. M08
N190 Z1.244
N200 G01 Z-.756 F75.
N210 X324.969 F700.
N220 Z.093
N230 X324.987 Y128.207
N240 X10.013
N250 Z.741
N260 X10. Y128.805
N270 X325.
N280 Z1.241
N290 X324.973 Y129.402
N300 X10.027
N310 Z1.612
N320 X10.08 Y130.
N330 X324.92
N340 Z1.934
N350 X325. Y130.598
N360 X10.
N370 Z2.229
N380 X10.009 Y131.195
N390 X324.991
N400 Z2.491
N410 X325. Y131.793
N420 X10.
N430 Z2.726
N440 Y132.39
N450 X325.
N460 Z2.916
N470 Y132.988
N480 X10.
N490 Z3.103
N500 Y133.586
N510 X325.
N520 Z3.268
N530 Y134.183
N540 X10.

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N550 Z3.429
N560 Y134.781
N570 X325.
N580 Z3.568
N590 Y135.378
N600 X10.
N610 Z3.695
N620 Y135.976
N630 X325.
N640 Z3.812
N650 Y136.574
N660 X10.
N670 Z3.912
N680 Y137.171
N690 X325.
N700 Z4.011
N710 Y137.769
N720 X10.
N730 Z4.106
N740 Y138.367
N750 X325.
N760 Z4.183
N770 Y138.964
N780 X10.
N790 Z4.259
N800 Y139.562
N810 X325.
N820 Z4.336
N830 Y140.159
N840 X10.
N850 Z4.39
N860 Y140.757
N870 X325.
N880 Z4.442
N890 Y141.355
N900 X10.
N910 Z4.495
N920 Y141.952
N930 X325.
N940 Z4.543
N950 Y142.55
N960 X10.
N970 Z4.58
N980 Y143.147
N990 X325.
N1000 Z4.618
N1010 Y143.745
N1020 X10.
N1030 Z4.656
N1040 Y144.343

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N1050 X325.
N1060 Z4.679
N1070 Y144.94
N1080 X10.
N1090 Z4.699
N1100 Y145.538
N1110 X325.
N1120 Z4.718
N1130 Y146.135
N1140 X10.
N1150 Z4.737
N1160 Y146.733
N1170 X325.
N1180 Z4.752
N1190 Y147.331
N1200 X10.
N1210 Z4.754
N1220 Y147.928
N1230 X325.
N1240 Z4.756
N1250 Y148.526
N1260 X10.
N1270 Z4.758
N1280 Y149.123
N1290 X325.
N1300 Z4.76
N1310 Y149.721
N1320 X10.
N1330 Z4.761
N1340 Y150.319
N1350 Z4.755
N1360 X325.
N1370 Y150.916
N1380 Z4.747
N1390 X10.
N1400 Y151.514
N1410 Z4.74
N1420 X325.
N1430 Y152.111
N1440 Z4.732
N1450 X10.
N1460 Y152.709
N1470 Z4.72
N1480 X325.
N1490 Y153.307
N1500 Z4.701
N1510 X10.
N1520 Y153.904
N1530 Z4.682
N1540 X325.

Page 78 of 78
N1550 Y154.502
N1560 Z4.662
N1570 X10.
N1580 Y155.1
N1590 Z4.641
N1600 X325.
N1610 Y155.697
N1620 Z4.609
N1630 X10.
N1640 Y156.295
N1650 Z4.577
N1660 X325.
N1670 Y156.892
N1680 Z4.545
N1690 X10.
N1700 Y157.49
N1710 Z4.513
N1720 X325.
N1730 Y158.088
N1740 Z4.476
N1750 X10.
N1760 Y158.685
N1770 Z4.439
N1780 X325.
N1790 Y159.283
N1800 Z4.403
N1810 X10.
N1820 Y159.88
N1830 Z4.366
N1840 X325.
N1850 Y160.478
N1860 Z4.321
N1870 X10.
N1880 Y161.076
N1890 Z4.275
N1900 X325.
N1910 Y161.673
N1920 Z4.229
N1930 X10.
N1940 Y162.271
N1950 Z4.183
N1960 X325.
N1970 Y162.868
N1980 Z4.137
N1990 X10.
N2000 Y163.466
N2010 Z4.091
N2020 X325.
N2030 Y164.064
N2040 Z4.038

Page 79 of 78
N2050 X10.
N2060 Y164.661
N2070 Z3.983
N2080 X325.
N2090 Y165.259
N2100 Z3.928
N2110 X10.
N2120 Y165.856
N2130 Z3.873
N2140 X325.
N2150 Y166.454
N2160 Z3.818
N2170 X10.
N2180 Y167.052
N2190 Z3.763
N2200 X325.
N2210 Y167.649
N2220 Z3.703
N2230 X10.
N2240 Y168.247
N2250 Z3.641
N2260 X325.
N2270 Y168.845
N2280 Z3.579
N2290 X10.
N2300 Y169.442
N2310 Z3.517
N2320 X325.
N2330 Y170.04
N2340 Z3.455
N2350 X10.
N2360 Y170.637
N2370 Z3.393
N2380 X325.
N2390 Y171.235
N2400 Z3.328
N2410 X10.
N2420 Y171.833
N2430 Z3.259
N2440 X325.
N2450 Y172.43
N2460 Z3.19
N2470 X10.
N2480 Y173.028
N2490 Z3.122
N2500 X325.
N2510 Y173.625
N2520 Z3.053
N2530 X10.
N2540 Y174.223

Page 80 of 78
N2550 Z2.984
N2560 X325.
N2570 Y174.821
N2580 Z2.913
N2590 X10.
N2600 Y175.418
N2610 Z2.839
N2620 X325.
N2630 Y176.016
N2640 Z2.765
N2650 X10.
N2660 Y176.613
N2670 Z2.69
N2680 X325.
N2690 Y177.211
N2700 Z2.616
N2710 X10.
N2720 Y177.809
N2730 Z2.54
N2740 X325.
N2750 Y178.406
N2760 Z2.461
N2770 X10.
N2780 Y179.004
N2790 Z2.381
N2800 X325.
N2810 Y179.601
N2820 Z2.301
N2830 X10.
N2840 Y180.199
N2850 Z2.222
N2860 X325.
N2870 Y180.797
N2880 Z2.142
N2890 X10.
N2900 Y181.394
N2910 Z2.058
N2920 X325.
N2930 Y181.992
N2940 Z1.973
N2950 X10.
N2960 Y182.589
N2970 Z1.889
N2980 X325.
N2990 Y183.187
N3000 Z1.804
N3010 X10.
N3020 Y183.785
N3030 Z1.72
N3040 X325.

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N3050 Y184.382
N3060 Z1.634
N3070 X10.
N3080 Y184.98
N3090 Z1.545
N3100 X325.
N3110 Y185.578
N3120 Z1.455
N3130 X10.
N3140 Y186.175
N3150 Z1.366
N3160 X325.
N3170 Y186.773
N3180 Z1.276
N3190 X10.
N3200 Y187.37
N3210 Z1.187
N3220 X325.
N3230 Y187.968
N3240 Z1.094
N3250 X10.
N3260 Y188.566
N3270 Z1.
N3280 X325.
N3290 Y189.163
N3300 Z.906
N3310 X10.
N3320 Y189.761
N3330 Z.812
N3340 X325.
N3350 Y190.358
N3360 Z.717
N3370 X10.
N3380 Y190.956
N3390 Z.617
N3400 X325.
N3410 Y191.554
N3420 Z.516
N3430 X10.
N3440 Y192.151
N3450 Z.415
N3460 X325.
N3470 Y192.749
N3480 Z.313
N3490 X10.
N3500 G00 Z2.313
N3510 Z50. M09
N3520 M05
N3530 G44 G53 Z0.
N3540 G53 Y0.

Page 82 of 78
N3550 G90
N3560 M30

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