MECH 3810 Level 3 Individual Project

Efficiency of a front wing on a FSAE car

Tarass Gorevoi 200566920

Dr Peter Walker

Date 30/04/2013

Proforma Statement

SCHOOL OF MECHANICAL

ENGINEERING

TITLE OF PROJECT PRESENTED BY IF THE PROJECT IS INDUSTRIALLY LINKED TICK THIS BOX AND PROVIDE DETAILS BELOW THIS PROJECT REPORT PRESENTS OUR OWN WORK AND DOES NOT CONTAIN ANY UNACKNOWLEDGED WORK FROM ANY OTHER SOURCES. SIGNED DATE 30/04/2013

Efficiency of a front wing on a FSAE car

Tarass Gorevoi

COMPANY NAME AND ADDRESS:

N/A

INDUSTRIAL MENTOR:

Mech3810 INDIVIDUAL PROJECT 30 credits

1 | P A G E

Abstract

The aerodynamic performance of a racing car is greatly influenced by the front and rear wings,

producing the downforce which is responsible for overall car performance. This project delivers

the computational study of a front wing on a FSAE race car, where University of Leeds F14

prototype was used as a baseline model. The study focuses on the efficiency of a front wing

expressed in lift to drag coefficients ratio.

A single element wing of NACA 23012 aerofoil profile was firstly analysed in a two-dimensional

space of CFD package ANSYS 14.0 to find the ground clearance and angle of attack variation

effect on wing performance. Observation showed that best operational settings are 50mm

above the ground with an angle of attack of 4 degrees - drag coefficient of 0.008582217 and lift

coefficient of -0.130266475. This was followed by a 3D CFD analysis of the baseline model with

and without a front wing, specified as the real problem analysis using turbulent flow of

Reynolds number equal to 2.7 x 106, therefore the SST k-omega model of turbulence was used

in CFD FLUENT software. Further positional and design modifications obtained through a

detailed review of the literature were inspected which resulted in an overall increase of F14

prototype race car performance by 241%, thus compared to a race car without a wing.

Based on this research it is suggested to implement the front wing on a FSAE race car. However,

in order to do so, further investigation of the efficiency of different front wing designs on the

overall performance of a race car should be undertaken.

2 | P A G E

Contents

TABLE OF SYMBOLS ............................................................................................................................................... 4

ACKNOWLEDGEMENTS .......................................................................................................................................... 5

1. INTRODUCTION .................................................................................................................................................. 6

1.1 AIMS AND OBJECTIVES ............................................................................................................................................... 7

2. LITERATURE REVIEW .......................................................................................................................................... 8

2.1 RACE CAR WINGS ..................................................................................................................................................... 9

2.2 FORMULA SAE ...................................................................................................................................................... 10

2.3 WING SELECTION .................................................................................................................................................... 11

2.4 AEROFOIL THEORY .................................................................................................................................................. 12

2.5 LIFT AND DRAG FORCES ............................................................................................................................................ 14

2.6 CFD AND ANALYSIS ................................................................................................................................................. 15

3. METHODOLOGY ............................................................................................................................................... 17

3.1 AEROFOIL SELECTION ............................................................................................................................................... 17

3.2 INTRODUCTION TO ANSYS FLUENT.......................................................................................................................... 17

3.3 2D ANALYSIS OF NACA 23012 AEROFOIL ................................................................................................................... 19

3.4 3D ANALYSIS OF F14 WINGLESS RACE CAR PROTOTYPE (BASELINE) ................................................................................... 22

3.5 3D ANALYSIS OF F14 RACE CAR PROTOTYPE WITH A SIMPLE FRONT WING .......................................................................... 26

3.6 MODIFICATIONS OF A FRONT WING ........................................................................................................................... 27

4. RESULTS ........................................................................................................................................................... 29

4.1 NACA 23012 2D ANALYSIS .................................................................................................................................... 29

4.1.2 Angle of Attack Validation ......................................................................................................................... 29

4.1.3 Ground Clearance ...................................................................................................................................... 30

4.2 BASELINE F14 PROTOTYPE 3D ANALYSIS .................................................................................................................... 31

4.3 F14 PROTOTYPE WITH A SIMPLE WING 3D ANALYSIS ..................................................................................................... 32

4.3.1 Back/forward position of a front wing ....................................................................................................... 32

4.3.2 1st

Design – Endplate .................................................................................................................................. 33

4.3.3 2nd

Design – Gurney Flap ............................................................................................................................ 33

4.4 F14 PROTOTYPE WITH A FINAL WING DESIGN 3D ANALYSIS ............................................................................................ 33

5. DISCUSSION ..................................................................................................................................................... 35

6. CONCLUSIONS .................................................................................................................................................. 37

APPENDIX I: MEETING LOG .................................................................................................................................. 38

APPENDIX II: NACA 23012 COORDINATES ............................................................................................................ 39

APPENDIX III: COMPARISON OF DIFFERENT NACA AEROFOIL DESIGNS (14, 18, 23, 34) ........................................ 42

APPENDIX IV: DETAILED DRAWING OF F14 MODIFIED PROTOTYPE RACE CAR ..................................................... 43

APPENDIX V: 3D DOMAIN GEOMETRY DIMENSIONS ........................................................................................... 44

APPENDIX VI: ANGLE OF ATTACK 2D RESULTS ..................................................................................................... 45

3 | P A G E

APPENDIX VII: GROUND EFFECT 2D RESULTS ....................................................................................................... 46

APPENDIX VIII: 3D RESULTS VISUALISATION - PRESSURE ..................................................................................... 47

APPENDIX IX: 3D RESULTS VISUALISATION - STREAMLINES ................................................................................. 48

APPENDIX X: GURNEY FLAP HEIGHT VARIATION 3D RESULTS .............................................................................. 48

7. REFERENCES ..................................................................................................................................................... 50

PROJECT DVD ....................................................................................................................................................... 53

4 | P A G E

Table of Symbols

Cd - Drag Coefficient

Cl - Lift Coefficient

CP - centre of pressure

CG - centre of gravity

2D - two-dimensional

3D - three-dimensional

RNG - renormalization group

CFD - Computational Fluid Dynamics

CPU - central processing unit

NACA - National Advisory Committee for Aeronautics

SAE - Society of Automotive Engineers

FSAE - Formula Society of Automotive Engineers

5 | P A G E

Acknowledgements

I would never have been able to finish my individual project without the counselling of

my supervisor, help from friends, and support from my family and girlfriend.

I would like to thank Dr. Peter G. Walker for giving an opportunity to do a research in

favourite area of mine, and providing excellent feedback and valuable guidance during the

project.

I am obliged to many of my course colleagues who supported me: Calum Mathen,

Haider Zaidi, Ian Mbote and Steven Marsh. They were always willing to help and gave very

useful suggestions, as well as support during whole project thus increasing my enthusiasm.

I would also like to thank my parents and my elder sister. They all encouraged me to do

my best during the research and supported on a psychological level.

I am truly indebted and thankful to my girlfriend, who was always cheering me up and

waited for me after long hours spent at University.

6 | P A G E

1. Introduction

Aerodynamics of racing cars became very important in the beginning of 1900’s when engineers

tried to minimize the air drag thus increasing the maximum speed. First of all, the “tear-drop”

shaped car was introduced, and only 20 years later inverted aerofoil profiled wings were

mounted to increase downforce, in order to increase the stability of cars on high speeds (1).

There are several tools used by race car designers in order to generate downforce. The

downforce allows the race car to withstand corners at high speeds and to have better traction

during acceleration. One of the most important tools for producing this downforce would be

the wings. However, there is still a substantial lack of knowledge and evidence on the true

effect that race car wings have on the car’s overall downforce, more so on car racing at low

speeds such as Formula SAE. The design of the Formula Student car according to SAE rules

should meet certain requirements and when concentrating on the aerodynamics of a FSAE car,

relatively low speeds (average maximum is 100km/h) and good manoeuvrability must be taken

into account. This report is considering only one aerodynamics element - the design and

efficiency of the front wing on a FSAE car. In order to complete the analysis of the effect of a

front wing on FSAE car, the University of Leeds F14 race car prototype of the year 2012, was

used.

However, even though the wings are an essential element when analysing the car’s downforce,

they are not the only things which should be taken into account, bearing in mind that a front

wing on a car does not have the same leading affect that a wing has on a plane. According to

Katz (2), this is because there is a strong ground effect and also because when analysing the

aerodynamics of the open wheel race car, the wings and other vehicle components undergo

strong interaction which explains why it is important to take into account every single body part

of the car.

This report mainly focuses on the best possible ratio in which to achieve low drag and to

generate high downforce on the entire F14 prototype racing car, using 3 different front wing

designs. According to the task, the Computational Fluid Dynamics (CFD) of the front wing is to

7 | P A G E

be built first in 2D and then in 3D which is further used to investigate the drag and lift

coefficients. ANSYS FLUENT 14.0 is used in this project as a CFD software.

Moving from 2D analysis in CFD Software FLUENT 14.0 to 3D, firstly aerofoil NACA 23012 was

studied to get the angle at which the best drag/lift ratio is received. The ground effect study

was also undertaken to find the ground clearance value between the wing and the road.

Following that, the analysis was made more complex by moving to 3D, where half of the

symmetric University of Leeds F14 formula student car prototype is used. Back-front positions

of the wing were analysed in 3D in order to achieve the highest possible downforce with the

lowest drag. The results obtained from the CFD were analysed in order to record the effects of

a front wing on the aerodynamics of the University of Leeds FSAE car.

1.1 Aims and objectives

The aim of this project is to find how efficient the front wing on a Formula SAE car is, according

to lift and drag coefficients, thus giving an opinion on the necessity of implementation of a

front wing onto University of Leeds FSAE car.

Project objectives are as followed:

1. Design front wing of the Formula Student FSAE car based on the 2013 SAE regulations.

2. Produce a detailed Computational Fluid Dynamics model of a designed front wing and

analyse drag/lift coefficients on it.

3. Find the effect of the ride height on a chosen aerofoil.

4. Quantify the outcome of changing the angle of attack for a given front wing.

5. Define the horizontal position of the front wing on University of Leeds Formula Student

FSAE F14 car of year 2012.

6. Give results and analyse three different front wing designs, clearly stating the difference

between them.

7. Document all the work undertaken to create the CFD model used and give a clear

verdict on efficiency of front wing. Should it be implemented or not.

8 | P A G E

2. Literature Review

All components of a moving vehicle are in some way affected by the motion of air surrounding

them. This creates a drag force which has a negative impact on the vehicle. In fact, tire

adhesion can be improved by aerodynamic forces, which consequently have a positive impact

on the overall vehicle performance. When making a race car, it is almost always desired to

create the fastest within a certain category. The effects of external aerodynamics are

encapsulated within the terms of drag, lift and stability.

When it was considered that vehicle

stability could be improved by balancing

the downforce on the tires, the three

aerodynamics came to attention (3). On

Figure 1, all forces acting on a race car are

shown, except the friction forces between

the tires and road, because they have no

direct connection to aerodynamics of a

race car.

Modifying or adding lifting surfaces onto the vehicle’s body can generate this aerodynamic

downforce. From the driver’s point of view, lateral instability could become somewhat of a

discomfort when the vehicle is moving at a high speed and it was not until the mid-1960s that

this was uncovered. It was also realized that dramatic improvement could be obtained when

taking corners, when breaking at a high speed and in lateral stability, by utilizing the aero-

assisted tire performance.

It quickly becomes evident that vehicle drag reduction alone is not the sole focus of

aerodynamic aspects of a race car design.

Studies which were carried out show that tire-to-road adhesion can be increased without

increasing the vehicle mass, allowing the control of vehicle stability characteristics as well as

improving both breaking and cornering, which is highly important when considering the FSAE

Figure 1: Forces acting on a race car.

9 | P A G E

competition. Adding inverted wings to the existing race cars proved to be the simplest and

most efficient way to increase downforce without affecting the overall mass.

2.1 Race Car Wings

The importance of the front wing is to provide a substantial amount of downforce, focusing on

the front tires in order to give the vehicle greater traction for balancing and turning. However,

it does create more drag; therefore engineers find it in their best interest to create a

drag/downforce medium. On the other hand, it is often speculated whether the increased drag

is enough in order to outweigh the advantage of the downforce in the car’s performance. In the

example of FSAE, the drag is less important than the need to generate downforce when

cornering. This can differ on the track and race conditions.

The front wing (Figure 2) is designed to give the

vehicle downforce directed at the front tires as

well as to direct the airflow over the body, as it

is the first thing that comes to contact with

oncoming airflow. It directs air towards the

under-body of the chassis, the intakes, turbos

and most importantly over and around the

tires. Any changes in airflow over the front wing can affect the overall airflow over the entire

body of the vehicle. As a consequence, it is highly important for engineers to consider how the

front wing could impact the overall performance of the race car.

As shown by research of Seljak, the front wing creates

about 1/3 of the car’s downforce (1) and it has

experienced more modifications than the rear wing. It is

the first part of the car to meet the air mass; therefore,

besides creating downforce, its main task is to efficiently

guide the air towards the body and rear of the car, as the

turbulent flow impacts the efficiency of the rear wing.

Figure 2: Front wing of a race car (20).

Figure 3: Detailed design of the front wing of a race car (21).

10 | P A G E

As shown on Figure 3, the front wings of a race car usually consist of a combination of multiple

elements and components designed to control the flow. These include endplates [1, Figure 3],

endplate feet [2, Figure 3] and Gurney flaps [3, Figure 3]. In order to generate the downforce,

the suction surfaces of the elements are directed downwards.

2.2 Formula SAE

With more than 30 years of history behind Formula SAE racing, the competition has become an

international event hosted by the Society of Automotive engineers, (SAE). The competition

consists of experienced and professional engineering contestants who are required to design

and build their own open wheel, formula-style race car.

The competition has rapidly spread throughout

Europe, Asia, South Africa and Australasia. As

oppose to conventional motorsport races,

teams are awarded points for eight different

events; the team with the highest cumulative

total is pronounced the winner. The

competition consists of three ‘static events’ (Cost analysis, Presentation, Engineering Design)

and here teams are judged on their presentation, costing skills, and their design justification. It

also consists of five ‘dynamic events’ (acceleration, skid pan, autocross, efficiency, endurance)

where the performance of the car is tested as well as the student drivers (4).

This type of points system highlights that success varies on the quality and accuracy of all

aspects of the car designing and development process.

The peak of the competition occurs when each team attends the regional event, where they are

up against other local and international teams in a series of both static and dynamic events (5).

The Formula SAE 2013 rules state that front wing should be placed no further than 762mm

forward of the front wheels, and that it is no wider than the outside of the front tires and it

must have a minimum radius of 1.5mm.

Figure 4: Leeds FSAE car of Year 2010 (22)

11 | P A G E

2.3 Wing selection

According to the rules of the Formula SAE, the geometry constraints for the wings, (if they are

used for a car) are loosely prescribed.

There is a broad range of shapes and sizes of the wings, as a consequence of a lack of design

constraints. Reviewing several different aerofoil designs which may be found in a tool created

by Penn State University students (6) marks the beginning of the selection process. Studies

have shown that the best aerofoil profile for racing applications is with high lift to drag

coefficient. There are several parameters which are generally required in order to identify the

wing’s positions and orientations even after the selection of aerofoil, and these are as follow:

- The attack angles and chord lengths of both elements (for multi-element wing).

- The horizontal distance between the noses of each element.

- The vertical distance between the tail of the main element and the lower surface of the flap.

- The vertical distance between the nose of the main element and the top surface of the rear

cowling (7).

There are several approaches which can be taken at this point of the design process and the

first is to identify the main parameters and find their near-optimal values. It is done in a more

methodical way using the design from experiments which are later analysed in CFD in order to

produce clearer and more accurate results. Another approach would be an inverse design

process in which the desired aerodynamic characteristics are set on the aerofoil and the

outcome of the process will be produced by the resulting shape of the aerofoil. A more

common approach is one in which an experienced guess is used, which is followed by a CFD

analysis to verify the selection.

As previously mentioned in the Formula SAE section, there are certain rules on the size and

shape of the wing. More so, in order to maintain good handling qualities there is a strict

constraint on the for-and-aft location of the aerodynamic centre of pressure (CP), which should

usually be located within a certain distance in front or behind the car centre of gravity (CG). The

12 | P A G E

constraint on the location of the CP for a car with front rear wings identifies the front-to-rear

aerodynamic balance for the downforce.

Wings can be divided into two different aerodynamics packages; the single wing configuration

and the dual wing configuration.

The single wing configuration consists of just a rear wing attached to the rear with any other

aerodynamic body components. They are not usually used in high-speed as the wing would

hold the risk of generating lift in the front, affecting the traction at the front tires; this can have

a drastic effect on steering braking. Dual wing configuration consists of a rear and front wing,

thus providing a complex aerodynamics system, because rear wing configurations are now

dependent on the front wing construction. In FSAE both configurations are considered as the

speed of the cars remain low.

There are ways in which to model a wing in ground effect, although only the use of a moving

ground installation will provide accurate results. Other options of using the reflection method

using mirrored models or using a fixed ground with or without suction all carry their faults. A

much higher downforce can be produced by a wing in ground effect as oppose to when it has

been placed in free stream conditions. Reducing ground clearance will increase the downforce.

Once it reaches a maximum value, a flow separation occurs (2).

2.4 Aerofoil theory

The wing is an aerodynamic structure which is

generating lift, when it is in direct contact with moving

air particles. The lift is generated due to the wing’s

unique shape with a flat surface and a curved top

allowing air to pass over it. This releases a difference in

pressure between the top and the bottom of the wing

forcing an upward net force which is referred to as the lift. The shape of the wings aerofoil and

its angle of incidence will determine the amount of lift obtained. There is most commonly a

correlation between the amount of lift generated and the angle at which the wing is

Figure 5: Angle of attack vs. Lift Coefficient (19)

13 | P A G E

permanently inclined to the free stream of the air. At small angles, as the angle of attack is

increased the lift increases (8); however, at some point, the lift on the wing is going to be

overpowered by the drag, so that the best angle can be obtained to produce the highest

lift/drag ratio. Aerofoils carry different aerodynamic properties, because they are used in

various areas. In the history of aerodynamics engineers targeted mainly on minimizing drag,

therefore producing a drastic change in the choice of race car element shapes.

Aerofoils can be designed upon many different objectives; to minimize

drag, to have high lift/drag ratio, or to obtain maximum lift force.

Generating lift can be as simple as placing a flat plate at an angle with its

movement direction. However, more lift (and less drag) would be

generated by a curved plate, which is caused by the downward deflection

which is created in the air stream. This is due to the viscosity of the air,

which prevents it from curving back around the edges, much like those on

a plate or of an aerofoil. As a result, there is the creation of the so called

Kutta condition where the air viscosity is tightly connected to both the lift

and drag forces.

Other than to provide lift at different speeds and flying conditions, wing

aerofoils also need to allow internal space for structures, landing gears and

fuel tanks (9).

3D studies on aerofoil have not usually been made other than Mahon’s study which was never

published, showing a substantial lack of information on 3D wing in ground effect stimulations.

However, studies of a wing on a 3D plain will be undertaken in this report, which closely

analyses the efficiency of the front wing on a FSAE race car (10).

Figure 6: Different aerofoil sections and their evolution (23).

14 | P A G E

2.5 Lift and drag forces

Lift and drag forces are generated perpendicularly to

the direction of travel of the moving object through

a fluid. Identical impact is taking place when a

stationary object like aerofoil is fixed in a wing

tunnel, which is a moving fluid. Researches showed

that the most efficient model for generating high lift

and at the same time minimizing drag is aerofoil

(11).

In aerodynamics drag is one of the most important resistive forces which influences the moving

of an object in a fluid. There are two types of drag forces:

1. Surface drag: depends on the type of the surface of the object moving through a fluid. It

is basically viscous friction between the surface and a fluid, determined from the wall

shear stress.

2. Form Drag: depends on the shape, precisely on a cross-sectional area of the object

moving in a fluid.

Drag force could be found using formulae (13):

Where CD is the drag coefficient, ρ is the density of a fluid, A is a cross-sectional area of an

object perpendicular to the direction of the motion, v is velocity of the object relatively to a

fluid.

Lift force is net force acting on the object perpendicular to the motion of a fluid, which is

created by different pressure on converse sides (16). This is clearly seen in an aerofoil where

the low pressure is created on the top side of an aerofoil and the high pressure underneath it,

those creating lift.

Figure 7: Lift and Drag force acting on an aerofoil. (12)

15 | P A G E

Lift force is calculated by (16):

Where CL is the lift coefficient, ρ is the density of a fluid, A is a cross-sectional area of an object

perpendicular to the direction of the motion, v is velocity of the object relatively to a fluid.

As it can be seen both forces are dependent on the density of a fluid, velocity, size and shape of

an object. So when analysing the real model, all assumptions have to be made with for

example, finding best suitable velocity for the described problem, knowing the density of the

fluid in which the object is moving and some parameters of the object, like cross-sectional area

and specific coefficients.

2.6 CFD and analysis

Computational Fluid Dynamics (CFD) is essentially numerical simulation which using algorithms

to solve any aerodynamical problems involving fluid flow. Nowadays, to perform millions of

operations in order to reproduce the real model of interaction between an object and a fluid,

computers are used. CFD itself involves three processes: pre-processing, solving partial

differential equations and the last part is post-processing. Both, first and last steps are much

simple and are basically just parameters which are inputted into graphical interface of any CFD

software.

CFD consists of a wide range of automotive design applications, more so when aerodynamics

play an important role, allowing the designer to make computational estimates of the effects. It

consequently allows the designer to make changes and alterations at this earlier point of the

design stage, instead of altering the prototype after the wind tunnel tests. This is highlighted as

one of its leading advantages. The ability to obtain results without the actual construction of

the required prototype can reduce the cost of producing the F1 cars. It is therefore no surprise

that CFD is chosen and used by many racing teams around the world. However, using it comes

at a cost and investment would have to be included due to the necessity of extensive resources

for the CFD analysis of the complex separated flows associated with a race car.

16 | P A G E

However, when covering all aspects and advantages of the CFD, the accuracy and validity of the

results must be taken into account as one of the most important aspects when using the

software stimulation. This is controlled as obtained results are compared to experimental

outcomes from the wind tunnel tests. This comparison has shown the results of the CFD

analysis to predict fairly accurate results, within 10% of the experimental value.

Namely, CFD is the best and least expensive way to analyse the flow past the object. Some of

the examples of producing aerodynamic packages of components used in FSAE showed, that

even basic 2D analysis of the flow past the different parts of the race car completely helps to

make an accurate decision whilst building FSAE race car. Cornell University in American FSAE

competition was one of those who managed to build their front wing by investing into research

on increasing the efficiency of aerodynamics of their race car. This process involved choosing

aerofoil with a high lift/drag ration, and putting it into a basic 2D analysis in software called

FLUENT. After the end of analysis in 2D, the results clearly showed the maximum downforce

created by the specific aerofoil; therefore, small optimizations and decisions were made before

building the actual model. This showed the importance of CFD, compared to Formula 1 racing

competition (10).

17 | P A G E

3. Methodology

3.1 Aerofoil selection

Aerofoil selection is one of the most important processes before proceeding to building the

actual front wing. The choice of the aerofoil to be used in this particular project was based on

the review of different designs stated in the database of the National Advisory Committee for

Aeronautics and the summary of aerofoil data by Ira H. Abbott. The main parameters which are

considered when choosing an aerofoil are dependant from the operation condition, which is

represented in the Reynolds number. As far as FSAE speed limitations are low, so that along this

project a maximum speed of 100km/h or 27.78m/s is used. For analysis of effectiveness of a

front wing Reynolds number was calculated to be 2.7 x 106, using a formula:

, where V is velocity, l is a chord length of a wing, which is 1.525m (full width of a car)

and is kinematic viscosity (

) (24).

Knowing the Reynolds number, the Cd and Cl have to be compared to different aerofoils given

in the databases. Focusing on getting the lowest drag to lift ratio at different angles of attack,

the 5-digit NACA aerofoil series provided the lowest drag at a given Reynolds number (25),

compared to 4 and 6-digit NACA aerofoils and by further investigation NACA 23012 was chosen

as the best suitable cambered aerofoil. Comparison figures are available at Appendix III.

Numbering in NACA aerofoils database shows that, for example 23012 represents an aerofoil

with designed Cl of 0.3, thickness ratio of 12% and shows that the maximum camber is at 15%

of the chord.

3.2 Introduction to ANSYS FLUENT

All calculations and analysis of the efficiency of a front wing of a FSAE race car can be done in

ANSYS FLUENT CFD package, which was first introduced with a tutorial from the University of

Leeds Engineering department. As far as this project was directly connected with the flow

18 | P A G E

around the aerofoil, the corresponding tutorial was chosen: “ANSYS Workbench Tutorial – Flow

Over an Aerofoil” by S. Richards, K. Martin and J. M. Cimbala.

First, the coordinates of aerofoil

NACA 23012 were imported from the

University of Illinois at Urbana-

Champaign Aerofoil Coordinates

database (26) into an Excel

spreadsheet which is available in

Appendix II. Using the provided 118

coordinate points, the 2D surface of

NACA 23012 aerofoil geometry was

created in ANSYS Design Modeller. Secondly, fluid volume domain rounded at the beginning

was built around an aerofoil profile, as shown in Figure 8. Moving to the meshing, patch

independent tetrahedrons with an automatic method were selected, with a further selection of

edges of an aerofoil and usage of mesh sizing module, to create a finer mesh around an

aerofoil. In this particular case a bias factor of 50 was applied and the minimum size of an

element was decreased to 0.00001 m. The final mesh is shown in Figure 8.

Once the meshing was done, the solver was set as stated in tutorial to a Spalart-Almaras

turbulence model, the fluid was defined to be air with a density of 1.225 kg/m3. Boundary

conditions were set as followed: velocity inlet with an X magnitude of 27.78 m/s, outlet

boundary was changed to pressure outlet with a gauge pressure equal to 0 and all other walls

were left as default (symmetry). Finally, the problem was initialized to the values at the velocity

inlet and then solved using 1000 iterations to get more precise results. When the calculation

was complete, a velocity profile was plotted to see the visualisation of the solution.

Figure 8: NACA 23012 aerofoil mesh profile.

Figure 9: Velocity vectors along the aerofoil profile.

19 | P A G E

0

0.005

0.01

0.015

0.02

0 50000 100000 150000 200000 250000 300000 350000 400000

Dra

g C

oe

ffic

ien

t

Number of nodes

2D Mesh Dependency Study

It could be clearly seen that there is a stagnation point at the leading edge and flow separation

behind the aerofoil. The analysis conducted above served as a basis of more complex 2D and 3D

front wing simulations in FLUENT.

3.3 2D analysis of NACA 23012 aerofoil

In order to analyse the correlation between the drag/lift coefficients, ride height and impact of

changing the angle of attack, more complex 2D CFD simulations of NACA 23012 aerofoil were

run in FLUENT 14.0. Compared to the tutorial and analysis done in Chapter 3.2, with the

objective to reduce the errors and interaction between the volume domain and solid body

(aerofoil), as well as to simulate the problem closely to the wind-tunnel testing for further

validation of results, the bigger air domain was introduced.

Following the successful application and input of initial geometry, the mesh setup was then

determined. In numerical studies it is very important to validate the size of the mesh of the

object prior to running the actual simulation. As a result mesh dependency study was

performed. It allowed to find the most suitable mesh size range in order to save computational

time and at the same time reduce error. Each time, a different number of nodes in the mesh of

the 2D aerofoil was used, and the Drag Coefficient was taken as a reference value, as it was

known to be 0.008 from past papers (17). As it can be seen clearly from Figure 10 the ideal

mesh size range lies in between 200,000 and 350,000 nodes. Therefore all the 2D simulations

involving NACA 23012 in CFD analysis had a mesh size close to average i.e. 250,000 nodes.

Figure 10: Mesh Dependency results for 2D NACA 23012 simulation.

20 | P A G E

A working mesh was made using the Advanced

Size Function in the meshing module, which helps

to control mesh size distribution better than

Automatic settings. For boundary walls, element

sizes varying from 0.4m to 1m were used and the

bottom wall representing road needed finer mesh for future references when ground effect will

be considered, so an element size of 0.1m was introduced. As part of an Element Sizing module,

edge sizing of 0.5m was applied for an aerofoil body. Refinement control of a 3rd level selected

for a whole fluid domain provided a maximum refinement of the mesh, making it faultless.

Finally, smooth transition default settings for an aerofoil and bottom wall were selected to get

an inflation layer (Figure 11), which represents the boundary layer around the object and the

road, providing much more accurate results (28). A detailed picture of the mesh is given below.

In setup of this 2D simulation, realizable k-epsilon turbulence model was set. The standard k-

epsilon turbulence model assumes that in particular simulation the flow is completely turbulent

and viscosity on a molecular level is not taken into account. There are altogether three different

models of k-epsilon: Standard, RNG and realizable. Fully modified realizable k-epsilon is the best

in this case, because it allows an alternative option of turbulence viscosity and it is the only

model which works perfectly when strong streamline curvatures, vortices and rotations occur.

It can be seen from above explanation that for this simulation, where separation/recirculation

Figure 12: Detailed mesh of a full domain for 2D simulation of an aerofoil NACA 23012, with presented boundary conditions.

Figure 11: Showing aerofoil and road inflation layers.

21 | P A G E

may occur and where boundary layer is presented, that it is most beneficial to use realizable k-

epsilon model (27).

Furthermore, the boundary condition of the bottom wall was changed to a moving wall with a

constant velocity of 27.78 m/s. Velocity inlet was specified to an absolute constant velocity of

magnitude 27.78 m/s in X direction. In addition, boundary conditions for pressure outlet and

top wall were left as default. Solution method was held as default as well and prior running the

simulation hybrid initialization was applied.

According to several papers (17) (18), drag coefficient obtained either from CFD software or in a

wind tunnel for this particular aerofoil, NACA 23012, at the angle of attack 0 degrees, has to be

in the range between 0.0078 and 0.0085. This means that drag coefficient of 0.008 obtained in

this simulation is correct and the set up model could be used in further studies.

Mentioned in researches of Katz (2), in racing competitions inverted aerofoils are more

favourable in order to provide downforce (negative lift). Hence, further research of

effectiveness of a front wing based on the NACA 23012 profile will be made on an inverted

aerofoil.

Figure 14: Ground clearance of a front wing explained.

Figure 13: Anatomy of NACA 23012 aerofoil.

22 | P A G E

Since aerofoil is going to be implemented onto an FSAE racing car, the ride height and an angle

of attack analysis must be considered prior to moving to 3D simulation. In order to quantify the

best suitable angle of attack of NACA 23012, which produces the highest lift to drag ratio, an

inverted aerofoil under different angles of attack from 0-12 degrees was tested in 2D setup

examined at the beginning of Chapter 3.3. For a ground clearance analysis (Figure 14) the

height between an aerofoil leading edge and a moving wall was changed from 12.5 to 1.25 cm,

which is respectively equal to the height/thickness of aerofoil ratios from 5 to 0.5.

3.4 3D analysis of F14 wingless race car prototype (Baseline)

In the next approach the actual three-dimensional CAD model of the University of Leeds FSAE

race car F14 prototype was used. Due to the fact that the prototype of the F14 race car was

previously modelled by Kaushal Gokhale, who performed an analysis of the effectiveness of the

rear wing on FSAE car performance at the University of Leeds in 2012, the existing model was

used with slight modifications in the front part of the car as well as more sleeked wheels

suggested by 3rd Year Automotive Engineering Student of University of Leeds, Haider Zaidi,

making the model closer to reality when using the front wing. Also, a more tapered nose is used

nowadays in the University of Leeds FSAE race car, which gave even more impetus to redesign

the front end. A comparison between the old F14 and the modified designs is shown below in

Figure 15.

The modified version of the F14 race car prototype served as a baseline (Figure 16) for 3D

simulation, providing the necessary settings and compatible mesh for further analysis of the

Figure 15: F14 Prototype before and after modifications of a front end.

23 | P A G E

front wing effect on a FSAE type race car. The detailed CAD drawing with all dimensions is

provided in Appendix IV.

An identical approach to the one in 2D for setting up a model in 3D was performed. The

modified F14 prototype Solidworks part file was imported into ANSYS Geometry module, where

further manipulations took place: building a fluid domain, using symmetry to simplify the model

(half of the car), merging some parts of the car body and constructing a smaller box domain

around a car.

Those modifications were performed in order to save computational time of the stated CFD

problem, as well as to reduce risks of errors related to bad geometry. This step is very

important, because a higher complexity of geometry model is increasing CPU time and awaited

solution time, which in some cases makes the numerical model more intricate, thus influencing

the accuracy of the results (29).

The computational domain size, as stated by Lanfrit, should be at least 3 car lengths at the front

and 5 lengths behind (29), thus allowing more accurate results, and at the same time saving

CPU time by limiting the domain dimensions. For this project the car prototype length is equal

to 2.42m, therefore the total length of the computational domain was set to 24.2m. All other

dimensions are clearly stated in Appendix V as well as named selections which help to setup the

boundary conditions in FLUENT 14.0. Moreover, a smaller box around a car was used as a

Figure 16: Modified Full 3D model of F14 race car prototype, served as a baseline in this project.

24 | P A G E

0

0.2

0.4

0.6

0.8

1

0 1000000 2000000 3000000 4000000 5000000

Cd

an

d C

l co

eff

cie

int

Number of elements

3D Mesh Dependency Study

Cd

Cl

Figure 17: Mesh dependency study results for F14 prototype race car.

control volume for a better mesh setup. In this study only half of the car prototype with vertical

symmetry plane through the middle is used to save computational time.

After successfully finishing the geometry input and building necessary control volume with

simplifications of a car body design, the meshing procedure must be considered. As with 2D

meshing, first of all the mesh sensitivity analysis must be completed in order to understand

how fine the mesh should be in order to provide the most accurate results as well as to save

computational time. In the mesh setup, in the sizing option, the mesh on proximity and

curvature with a medium smoothing and slow transition as well as a fine span angle centre due

to the quite sharp nose of the car, were used. In the next step, in order to create an inflation

layer around the car, the program controlled first aspect ratio inflation options were applied

with the smoothing iterations of 10, which created very fine mesh with inflation around the

curved parts of the model. All other settings were left as default. In addition, body sizing with a

body of influence was added with the element size of 75mm. Finally, to refine the mesh on the

race car model itself face, a sizing was created of 7.5mm, thus keeping the ratio of 1:10 to the

size of the mesh of a control volume created in the geometry step. Most of the mesh settings

were adopted from Lanfrit researches in Automotive External Aerodynamics area (29).

In the mesh dependency study only the size of a smaller box (shown in red in Figure 19) and the

actual car body mesh size were changed, whilst keeping the ratio of 1:10 between the sizes of

those two meshes. The analytical graph representing the number of elements used in the

model to Drag and absolute Lift Coefficients are shown below.

25 | P A G E

An established 3D mesh dependency study showed that after around 2,200,000 elements the

resulting value is not changing, therefore, any number between 2,200,000 and 4,100,000

elements could be used in this project, knowing that the result is going to have a minimum risk

of error. Nevertheless, the closer the value of elements to 2,200,000 used in a mesh the less

amount of time is needed to complete an analysis of the problem in FLUENT 14.0. The decision

was made to use a mesh size of 2,500,000 elements, to receive the most accurate results for

future simulations. The final mesh of a baseline is demonstated in Figure 18. As a result of the

baseline mesh being used in further studies, a more detaile dmesh is shown in Figure 19 but

with the added front wing, eventhough the overall mesh is the same.

Once the mesh setup is finished, the actual problem method could be specified in FLUENT

module. The main difficulty that needs to be prioritised is precise prediction of flow separation

in simulation with smooth surfaces. Shear stress transport (SST) k-omega turbulence model is

known as best for the problems involving separating flows and giving extremely accurate

results comparing to other turbulence models available in FLUENT. Due to the fact that this

project is highly based on the flow near the walls involving boundary layers, it is recommended

by several studies to use SST k-omega turbulence model (27)(30). In addition, by ANSYS FLUENT

14.0 User’s Guide it is recommended to change turbulence intensity for velocity inlet and

pressure outlet boundary conditions to 1% and 5% respectively (27). To approximate the

problem to a more real operational condition the rotating wheels were brought in. It was done

by simply changing boundary conditions of both wheels to a moving wall with the angular

Figure 18: Baseline mesh visualisation.

26 | P A G E

velocity of 115.75 rad/s, which is equal to 27.78 m/s for a wheel with radius of 240mm. For the

solution method pressure-based coupled solver (PBCS) was selected, which makes a reduction

on convergence time by five times, but slightly increasing the computational time. Coupled

solution allows solving two different equations: pressure-based and momentum, at the same

time, meaning the simulation is going to converge must faster (31). The negative side of using a

coupled solver is only a slight problem, because for this project access to the high performance

computer was given, so that a small increase to CPU time could be neglected on

supercomputers. All other settings in FLUENT were left as default.

3.5 3D analysis of F14 race car prototype with a simple front wing

For the analysis of influence of a simple front wing on a F14 race car prototype baseline model

described in Chapter 3.4 was used. Furthermore, a front wing of NACA 23012 aerofoil shape

was built as shown on Figure 13 with a span of 1526mm, which is the full width of the car from

one wheel to another. Following the geometry input, mesh settings according to previous

dependency study and baseline model were applied, using 2,500,000 elements. In addition,

inflation layer was added to the front wing. The final mesh domain for F14 race car prototype

with a front wing and clearly highlighted inflation layers is represented in Figure 19.

Figure 19: Detailed mesh of 2,500,000 elements of F14 prototype race car with a front wing (side view).

27 | P A G E

Results from 2D analysis were used to determine the optimal vertical position of the front wing

as well as the angle of attack. Further studies in 3D space involved defining the horizontal

position of the front wing and then changing the design. Positional settings are shown on

Figure 20.

Varying the design of a front wing by adding a gurney flap and modified endplates will show the

complete picture of efficiency of a front wing in FSAE racing competition based on the F14

prototype race car. All modifications of a front wing are presented in the chapter 3.6. For each

modification a simulation was ran and comparison of the results gave transparent answer to all

the objectives of this project.

3.6 Modifications of a Front Wing

Based on the research, and pointed out

by Katz (2), gurney flaps and endplates

were the best modifications both for

front and rear wings for a race car. As

known from the design of the Formula 1

front wing, shown in Figures 2 and 3, there are no limitations for creativeness of the design.

Considering that FSAE competition race cars are running on low speeds, main attention should

be given to the stability of the car on the corners, rather than straight line performance,

complicated modifications are not going to pay off. In respect to that, by new designs of a front

wing for a F14 prototype race car it was attempted to lead the flow around the front wheels by

adding the endplates and by using the gurney flaps, thus creating a wake of vortices and

therefore, gaining more load on a wing (32).

The first design was represented by adding simple-shaped

endplates to the front wing (Figure 21). Endplates are mostly

always used in an open-wheel race car wings, because endplates

are helping to reduce the intensity of vortices created at the

wing tip (33). The particular design of the endplate presented in

Figure 20: Positional settings of the front wing.

Figure 21: Simple endplate design.

28 | P A G E

this report used a half-chord height as well as more curved shape on the top, mainly used in

Indy type series race cars.

The second design consisted of additional gurney flap of the height H shown on Figure 22, equal

to 13% of the chord length (32), which in this case is equal to 3mm. Also, 4mm and 2mm height

Gurney flaps were tested. The main purpose of using a Gurney flap is increasing the downforce

by moving a separation point and creating an anti-clockwise vortex when flow reaches the rear

end of a wing. A sketch representing a front wing with a Gurney flap is shown below.

Third design is the final design of a single element front wing, which based on a research of

visualization and results gave the best overall performance for the front wing used on a F14

prototype race car in FSAE competition. It consisted of both Gurney Flap and Endplate and

overall small modifications of a shape. Final design is clearly shown in Figure 23.

Figure 23: Final front wing design.

Figure 22: Front wing profile with a Gurney flap.

29 | P A G E

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 1 2 3 4 5 6 7 8 9 10 11 12

Cd

Angle of attack

Cd vs. Angle of Attack

CFD

Theoretical

4. Results

The main purpose of the CFD analysis was firstly to validate settings and simulation of NACA

23012 to the theoretical values and secondly to find the positional settings of a front wing on

F14 University of Leeds FSAE race car prototype with the Cl to Cd ratio results, giving the

efficiency of a front wing on a given race car. Results obtained below were configured using

methods described in Chapter 3 and the main 2D tabulated values are given in Appendixes VI

and VII.

4.1 NACA 23012 2D Analysis

2D analysis made it possible to validate the results of performance of NACA 23012 aerofoil with

the theoretical values. In addition, further investigations were performed: angle of attack giving

best Cl to Cd ratio, ground effect study.

4.1.2 Angle of Attack Validation

Theoretical values for the angle of attack comparison were taken from Eastman and William

research in wind tunnels (34). Figure 23 and 24 represent computational data obtained from

the 2D CFD Analysis of non-inverted NACA 23012 aerofoil, where angle of attack between 0 to

12 degrees was compared to Cd and Cl respectively.

Figure 24: Drag Coefficient vs. Angle of Attack CFD and theoretical results.

30 | P A G E

-1.40

-1.20

-1.00

-0.80

-0.60

-0.40

-0.20

0.00

0 1 2 3 4 5 6 7 8 9 10 11 12

Cl

Angle of attack

Cl

CFD

Theoretical

-30

-20

-10

0

0 1 2 3 4 5 6 7 8 9 10 11 12

Cl/

Cd

Angle of attack

Cl/Cd vs. Angle of Attack

In order to find the angle of attack which is the giving the best possible performance for the

tested aerofoil, Figure 26 was plotted to show the Cl to Cd ratio obtained from computational

analysis.

4.1.3 Ground Clearance

Inverted aerofoil NACA 23012 was used in a research of the ground clearance effect on Drag

and Lift forces. From Figure 26 it can be clearly seen that the best performance is received for

the aerofoils with the angle of attack from 4 to 7 degrees, therefore ground clearance study

was limited to that range. For a comparison Cl to Cd ratio was used and the ground effect is

represented in Figure 27. The smaller the ground clearance, the greater performance of a front

wing, but due to limitations of FSAE 2013 rules, inverted aerofoil at 4 degrees with 5cm ground

clearance showed best results: Cd of 0.008582217 and Cl of -0.130266475 (Appendix VII).

Figure 25: Lift Coefficient vs. Angle of Attack CFD and theoretical results.

Figure 26: Lift to Drag Coefficient ratio vs. Angle of Attack obtained from CFD analysis.

31 | P A G E

0

2

4

6

8

10

12

14

16

18

20

22

24

0 2.5 5 7.5 10 12.5

Cl/

Cd

rat

io

Ground Clearance (cm)

Cl/Cd vs. Ground Clearance

0 degrees

3 degrees

4 degrees

5 degrees

6 degrees

7 degrees

Velocity of the streamlines around the body is for both in free air condition and close to the

ground is represented in Figure 28.

4.2 Baseline F14 Prototype 3D Analysis

For the baseline F14 race car prototype 3D model without a front wing, both Drag and Lift

forces were analysed, as well as drag and lift coefficients, which provided an aerodynamic

efficiency of the body represented in Lift to Drag ratio. Both data with wheels included and

without are shown in a table below:

Type Drag Force Drag Coefficient Lift Force Lift Coefficient Lift/Drag Ratio

With wheels 132.53286 0.48196958 -31.699369 -0.11527807 -0.239181216

Without wheels 99.620104 0.36227892 -58.771662 -0.21372929 -0.589957842 Table 1: Baseline results for 3D analysis of a FSAE race car prototype.

Figure 27: Cl/Cd ratio vs. Ground Clearance for an inverted aerofoil under different angle of attacks (0, 3-7 degrees).

Figure 28: NACA 23012 velocity streamlines visualisation, first in a free air condition and second is close to the ground condition.

32 | P A G E

60.00%

65.00%

70.00%

75.00%

80.00%

484 mm 584 mm 684 mm 762 mm

Pe

rce

nta

ge D

iffe

ren

ce

Distance from the front wheel

Positional Performance Study

Figure 29: Positional variation results of a front wing comparison with the baseline model.

For further analysis and visualisation of improving flow around a race car due to addition of the

front wing, velocity as well as behaviour of the streamlines can be observed in Appendix VIII.

4.3 F14 Prototype with a simple wing 3D Analysis

As described in Chapter 3.6, two modifications of a front wing were used to give the best

possible results on efficiency of a front wing on aerodynamic performance of FSAE car, as well

as final position of a front wing was found in 3D analysis.

4.3.1 Back/forward position of a front wing

Front wing was moved along X axis, to find the final position, which provided the best

performance in the form of Lift/Drag Ratio.

Distance from the front wheel

Drag Force

Drag Coefficient Lift Force

Lift Coefficient

Lift/Drag Ratio

484 mm 131.6261 0.47876377 -53.54435 -0.19475679 -0.406791

584 mm 134.4675 0.48909846 -53.68346 -0.19526279 -0.399230

684 mm 133.8340 0.48679447 -56.71381 -0.20628508 -0.423762

762 mm (FSAE limit) 133.8340 0.48679447 -56.71381 -0.20628508 -0.423762 Table 2: Results of a back/forward position variation for a simple front wing.

For a clearer representation, Figure 29 was plotted, comparing the percentage difference

between positional modifications and baseline model results, given in Chapter 4.2.

33 | P A G E

4.3.2 1st Design – Endplate

The simple endplate shown in Figure 21 was analysed as a 1st modification of a front wing, the

data received from the analysis is represented in Table 3.

Drag Force

Drag Coefficient

Lift Force

Lift Coefficient

Lift/Drag Ratio

Wing Lift Force

Wing lift coefficient

132.6512 0.4817 -84.2824 -0.3061 -0.6354 -54.5452 -0.1981 Table 3: Simple endplate design results.

The second modification of a front wing is shown in Figure 30. A curved end of 10mm was

added to the simple endplate. Results for this modification are shown below:

4.3.3 2nd Design – Gurney Flap

For 2nd and final analysis simulation, the gurney flap (Figure 21) was added without any

endplates or any other modifications, to clearly see the effect of the gurney flap on a front wing

performance. Gurney flap height was specified to be 3mm, but 2mm and 4mm height gurney

flaps were also tested – results are available in Appendix X. Results for 3mm gurney flap are

given in Table 5.

Drag Force

Drag Coefficient

Lift Force

Lift Coefficient

Lift/Drag Ratio

Wing Lift Force

Wing lift coefficient

134.9264 0.4900 -109.908 -0.3991 -0.8146 -76.0596 -0.2762 Table 5: Results of a gurney flap addition to the front wing.

4.4 F14 Prototype with a final wing design 3D Analysis

The final design (Figure 23) consisted of combining modifications analysed in previous steps

(Gurney flap, endplate), expecting to see even better results.

Drag Force Drag Coefficient Lift Force

Lift Coefficient

Lift/Drag Ratio

Wing Lift Force

Wing lift coefficient

135.0473 0.4904 -106.6987 -0.3875 -0.7901 -75.8906 -0.2756

Table 4: Modified endplate results.

Figure 30: Modified endplate design.

34 | P A G E

Results for the final design model are as followed:

Drag Force

Drag Coefficient

Lift Force

Lift Coefficient

Lift/Drag Ratio

Wing Lift Force

Wing lift coefficient

133.032 0.4833 -97.0811 -0.3527 -0.7298 -69.6138 -0.2529 Table 6: Performance results of a final design front wing which consisted of endplate and gurney flap combination.

Figures of a streamlines around the front wheel of a race car with and without a front wing are

presented below:

Other visualisation comparison figures of total pressure and streamlines around the race car

body are presented in Appendices VIII-IX.

Visualisation type

Baseline Baseline + final wing design

Streamlines around the

wheel (Front)

Streamlines around the wheel (Top)

Table 7: Visualisation of a streamlines around the front wheel with and without a front wing.

35 | P A G E

5. Discussion

The results confirm that the front wing increased the overall performance of the tested FSAE

race car F14 prototype. Without further aerodynamic changes on a body itself, addition of a

front wing and implementation of slight changes onto its design resulted in increasing the lift to

drag ratio, when finding the efficiency of a front wing.

Optimizations used in this report, for example, positional performance as well as design

modifications showed further increase in the Lift to Drag ratio and increase in the downforce.

Considering the theory behind the front wing of an open wheel race car (2), results have proven

the fact, that with the increase of the angle of attack, downforce and drag are increasing, but

after a certain level a stall condition is achieved, which decreases the performance of a front

wing compared to 0 degree position. The best performance for NACA 23012 aerofoil was

achieved at an angle of attack equal to 4 degrees, same as in the experimental report presented

by Eastman and William (34).

For the further positional settings, ground clearance analysis presented the prognosticated

results by experiments of Mokhtar (33): with the decrease of a distance between the leading

edge of a front wing and a ground, drag on a surface increased with a downforce. The best lift

coefficient was achieved for an inverted aerofoil with an angle of attack of 4 degrees at a

ground clearance of 50mm, as this is the minimum gap between the road and race car

components in order to compile with FSAE 2013 regulations (4).

The back/front position investigation demonstrated a slight increase of a performance (Figure

30), as well as no improvement of front wing characteristics after the distance of 684mm

further of a front wheel. The addition of a front wing at a position of 684mm further than the

front wheel showed a 77.17% increase in the overall performance compared to a baseline

model.

Modifications of a design of a front wing presented a high improvement of efficiency

represented in Cl to Cd ratio in Figure 31.

36 | P A G E

0.00%

50.00%

100.00%

150.00%

200.00%

250.00%

300.00%

Pe

rce

nta

ge c

han

ge

Efficiency

Endplate 1 Endplate 2 Gurney Flap Final Design

Change of a Drag and Lift Coefficients were analysed furthermore in Figures 32a and 32b.

The final front wing design showed no higher increase in efficiency than the models with single

modification. This could be explained with the complexity of the geometry and the lack of

literature about the interaction between gurney flap and endplates. At this point of the

research the best performance was achieved by the additional gurney flap to the front wing of

NACA 23012 inverted aerofoil profile at an angle of attack at 4 degrees, with 50mm ground

clearance and 684mm further of the front wheel. Namely, the F14 prototype race car could

have an increase in 241% of efficiency by adding a single element front wing with the 3mm

height gurney flap, where drag coefficient is equal to 0.49 and lift coefficient is -0.40.

Figure 31: Efficiency (Cl/Cd ratio) of a modified variations of a front wing, compared to a baseline model.

0.475

0.48

0.485

0.49

0.495

Dra

g C

oe

ffic

ien

t

Drag Coefficient for different models

Baseline Endplate 1 Endplate 2 Gurney Flap

Figure 32a: Drag coefficient of different models.

-0.5

-0.4

-0.3

-0.2

-0.1

0

Lift

Co

eff

icie

nt

Lift Coefficient for different models

Baseline Endplate 1 Endplate 2 Gurney Flap

Figure 32b: Lift coefficient of different models.

37 | P A G E

6. Conclusions

The effect of a front wing on the performance of a FSAE race car is studied based on the

University of Leeds F14 prototype race car with and without a wing moving at maximum speed

achieved at competition, which is 100km/h or 27.78m/s representing the turbulent flow with

the Reynolds number of 2.7 x 106. The study was performed on selection of the aerofoil,

construction of the front wing 3D CAD model based on FSAE 2013 rules, adjustment of the front

wing design established by research in literature and further analysis in CFD package ANSYS

14.0. The judgement on the efficiency of the front wing was limited to Lift/Drag ratio, as this is

the main characteristic describing the overall aerodynamic performance, which could also be

backed up by the experimental results.

The analysis involved both 2D and 3D analysis in ANSYS CFD system, which involved a lot of

effort in order to first import needed geometry from CAD software Solidworks, with further

addition of a fluid domain around the object, choosing the right mesh settings to reduce the

possibility of an error and improving the speed of simulation, selection of a right turbulence

model, specification of relevant settings for boundary conditions, sending the setup to a high

performance computer and finally analysing the data received from the output.

During the studies positional settings as well as implementations to the design of a front wing

were found and validated by relevant literature.

Although, conducted research on a single element front wing showed great results in improving

the lift to drag ratio, further studies are needed to investigate the stability and manoeuvrability

change with addition of a front wing. This report must be used as a base for the further

research on efficiency of a front wing in FSAE racing, for example, the study of a multi-element

wing, further investigation of a different endplate design, complex aerodynamics research with

front/rear wings and wind tunnel or track testing could be done in order to come to a clear and

precise conclusion on the efficiency of the front wing on a FSAE race car.

38 | P A G E

Appendix I: Meeting Log Date of Meeting Summary of Discussion Objectives for next meeting Supervisors Initials

15/10/2012 - Project allocation - Brief introduction about possible projects and main aspects of it

- Buy logbook - Do further reading - Speak to Formula Student Leader

PW

22/10/2012 - Further allocation - Objectives/Tasks - Mind map

- Aims and objectives - Come up with 1st simple front wing model

PW

30/10/2012 - Objectives - How to find a simple aerofoil coordinates

- FLUENT tutorial - 2D of aerofoil

PW

06/11/2012 - Turbulence modeling - Meshing - Boundary Layer

- Mesh dependency (Reading) - Boundary layer mesh 2D

PW

13/11/2012 - Meshing of 2D aerofoil - Aims and Objectives - List of Tasks - Gantt Chart

PW

20/11/2012 - Check of Objectives and Tasks - Comments on Gantt Chart

- Risk Assessment - Mesh Dependency (Excel plots) - Rewrite Objectives and improve Gantt Chart

PW

27/11/2012 - Gantt Chart (2nd check) - Aerofoil mesh check - Results discussion of Cd vs Cl

- Check boundary conditions - Angle of Attack - Size of a domain - Bring CD of MSc student

PW

04/12/2012 - Showing working model of 2D aerofoil on level 5

- Redo 2D PW

23/01/2013 - Review of “where we are” - 2D results discussion

- Validate results of AoA - Size of the wing (scaling)

PW

30/01/2013 - Angle of attack results check - Cl/Cd validation check

- Wall roughness - Accuracy of results validation

PW

13/02/2013 - 2D NACA23012 validation - Check turbulence model parameters - Calculate Cd & Cl

PW

20/02/2013 - 2D Results check - Change angle of attack (3-4) to get “real” lift

PW

27/02/2013 - Inverted aerofoil angle of attack

- Validate ground effect - Move to 3D

PW

06/03/2013 - Solidworks car model check - 3D baseline FLUENT PW

13/03/2013 - Mesh check - Finish baseline - Position of the wing (front-back) - 3 new front wing designs - Validation of all results

PW

39 | P A G E

Appendix II: NACA 23012 coordinates #NACA23012

#Group Point X_cord Y_cord Z_cord

1 1 0,45399 0,891007 0

1 2 0,451245 0,889372 0

1 3 0,449207 0,886587 0

1 4 0,446364 0,882699 0

1 5 0,442727 0,877714 0

1 6 0,43831 0,871646 0

1 7 0,433129 0,864508 0

1 8 0,427202 0,856318 0

1 9 0,420552 0,847096 0

1 10 0,413201 0,836863 0

1 11 0,405176 0,825645 0

1 12 0,396504 0,81347 0

1 13 0,387215 0,800366 0

1 14 0,377341 0,786369 0

1 15 0,366914 0,771512 0

1 16 0,355968 0,755833 0

1 17 0,34454 0,739372 0

1 18 0,332667 0,722171 0

1 19 0,320387 0,704274 0

1 20 0,307739 0,685727 0

1 21 0,294764 0,666578 0

1 22 0,281505 0,646875 0

1 23 0,268003 0,626669 0

1 24 0,254304 0,606012 0

1 25 0,240451 0,584956 0

1 26 0,226492 0,563555 0

1 27 0,212472 0,541862 0

1 28 0,19844 0,519933 0

1 29 0,184443 0,497823 0

1 30 0,170529 0,475586 0

1 31 0,156747 0,453278 0

1 32 0,143146 0,430955 0

1 33 0,129774 0,408671 0

1 34 0,116678 0,386482 0

1 35 0,103905 0,364443 0

1 36 0,0915 0,342609 0

1 37 0,079507 0,321034 0

1 38 0,067969 0,299773 0

1 39 0,056924 0,278879 0

1 40 0,046412 0,258406 0

1 41 0,036465 0,238407 0

1 42 0,027117 0,218933 0

1 43 0,018396 0,200037 0

40 | P A G E

1 44 0,010328 0,18177 0

1 45 0,002738 0,162788 0

1 46 -0,00381 0,144838 0

1 47 -0,00938 0,127434 0

1 48 -0,01392 0,110693 0

1 49 -0,01739 0,094741 0

1 50 -0,0198 0,079705 0

1 51 -0,02118 0,065709 0

1 52 -0,02159 0,052868 0

1 53 -0,02112 0,041283 0

1 54 -0,01984 0,031038 0

1 55 -0,01785 0,0222 0

1 56 -0,01523 0,014812 0

1 57 -0,01208 0,008902 0

1 58 -8,45E-03 0,004475 0

1 59 0 0 0

1 60 0,009472 0,001154 0

1 61 0,014428 0,003718 0

1 62 0,01955 0,007513 0

1 63 0,024866 0,012466 0

1 64 0,030409 0,018506 0

1 65 0,036219 0,025567 0

1 66 0,04234 0,033591 0

1 67 0,048817 0,042535 0

1 68 0,055696 0,052367 0

1 69 0,063022 0,063072 0

1 70 0,070835 0,074652 0

1 71 0,079169 0,087124 0

1 72 0,088047 0,100517 0

1 73 0,097477 0,114872 0

1 74 0,10704 0,129772 0

1 75 0,117829 0,146576 0

1 76 0,128782 0,164272 0

1 77 0,139871 0,182809 0

1 78 0,151068 0,202136 0

1 79 0,162349 0,222197 0

1 80 0,173687 0,242932 0

1 81 0,185059 0,264283 0

1 82 0,196443 0,286185 0

1 83 0,207815 0,308575 0

1 84 0,219155 0,331384 0

1 85 0,230442 0,354546 0

1 86 0,241656 0,37799 0

1 87 0,252777 0,401647 0

1 88 0,263785 0,425446 0

1 89 0,274661 0,449316 0

41 | P A G E

1 90 0,285385 0,473186 0

1 91 0,295939 0,496986 0

1 92 0,306303 0,520644 0

1 93 0,316456 0,544091 0

1 94 0,326381 0,567259 0

1 95 0,336058 0,590079 0

1 96 0,345467 0,612485 0

1 97 0,35459 0,634412 0

1 98 0,363409 0,655796 0

1 99 0,371905 0,676575 0

1 100 0,380061 0,696689 0

1 101 0,387862 0,71608 0

1 102 0,395291 0,734691 0

1 103 0,402333 0,752468 0

1 104 0,408976 0,76936 0

1 105 0,415207 0,785316 0

1 106 0,421015 0,800291 0

1 107 0,426389 0,81424 0

1 108 0,431321 0,827121 0

1 109 0,435803 0,838896 0

1 110 0,439828 0,84953 0

1 111 0,443391 0,85899 0

1 112 0,446488 0,867249 0

1 113 0,449114 0,87428 0

1 114 0,451266 0,880063 0

1 115 0,452942 0,884579 0

1 116 0,454141 0,887815 0

1 117 0,45486 0,889761 0

1 0 0,4551 0,89041 0 Table 8: NACA23012 aerofoil profile coordinates

42 | P A G E

Appendix III: Comparison of different NACA aerofoil designs (14, 18, 23, 34)

Figure 33: Different aerofoil comparison scanned figure copies (25).

43 | P A G E

Appendix IV: Detailed Drawing of F14 Modified Prototype race car

44 | P A G E

Appendix V: 3D Domain Geometry Dimensions

Figure 34: Detailed domain geometry for 3D analysis of a F14 prototype race car.

45 | P A G E

Appendix VI: Angle of Attack 2D Results

Experimental CFD Theoretical

Angle of attack (degrees) Cd Cl Cl/Cd Cd Cl

0 0.009377 -0.02805 -2.9916884 0.0082 0

1 0.009148 -0.11435 -12.5 0.008 -0.1

2 0.009486 -0.21183 -22.330781 0.0094 -0.2

3 0.014719 -0.32885 -22.342231 0.0125 -0.3

4 0.017721 -0.42505 -23.985758 0.0175 -0.4

5 0.023354 -0.52886 -22.644985 0.02 -0.5

6 0.026468 -0.63221 -23.885788 0.023 -0.6

7 0.030704 -0.75643 -24.636093 0.03 -0.7

8 0.039167 -0.84456 -21.563269 0.038 -0.8

9 0.048841 -0.95525 -19.55843 0.047 -0.9

10 0.053491 -1.06884 -19.981739 0.051 -1

11 0.060576 -1.15884 -19.130435 0.0575 -1.1

12 0.072331 -1.27269 -17.595308 0.0682 -1.2

Table 9: Results of experimental (CFD) and theoretical studies (34) of 2D NACA 23012 aerofoil.

46 | P A G E

Cd Cl Cl/Cd

0.005508 -0.02811 5.103502

0.005575 -0.0313 5.614529

0.005535 -0.02995 5.411618

0.005662 -0.04129 7.292533

0.006382 -0.08466 13.26434

0.009995 -0.20489 20.49886

Cd Cl Cl/Cd

0.007138 -0.08599 12.04717

0.007273 -0.09138 12.56434

0.007293 -0.09739 13.35253

0.007702 -0.11067 14.3686

0.009316 -0.17223 18.48838

0.014531 -0.26574 18.2879

Cd Cl Cl/Cd

0.008219 -0.10614 12.91393

0.008428 -0.11153 13.23402

0.008448 -0.11754 13.91287

0.008582 -0.13027 15.17865

0.01084 -0.19541 18.02657

0.015686 -0.31972 20.38255

Cd Cl Cl/Cd

0.009632 -0.12178 12.64358

0.00984 -0.12517 12.7202

0.00988 -0.13717 13.8832

0.009995 -0.1499 14.99828

0.012031 -0.21494 17.86543

0.018642 -0.33646 18.04861

Cd Cl Cl/Cd

0.011246 -0.14475 12.87109

0.011462 -0.15066 13.14477

0.011487 -0.15599 13.57959

0.011678 -0.1759 15.06195

0.014616 -0.243 16.62602

0.018225 -0.4169 22.87499

Cd Cl Cl/Cd

0.013117 -0.16261 12.3976

0.012985 -0.17048 13.12861

0.013564 -0.17771 13.10149

0.014064 -0.19985 14.20945

0.017173 -0.27046 15.74948

0.02522 -0.3649 14.46829

12.5

10

7.5

5

2.5

1.25

7.5

5

2.5

1.25

Inverted aerofoil at 7 degrees Ground clearance (cm)

2.5

1.25

Inverted aerofoil at 6 degrees Ground clearance (cm)

12.5

10

Inverted aerofoil at 5 degrees Ground clearance (cm)

12.5

10

7.5

5

12.5

10

7.5

5

2.5

1.25

7.5

5

2.5

1.25

Inverted aerofoil at 4 degrees Ground clearance (cm)

2.5

1.25

Inverted aerofoil at 3 degrees Ground clearance (cm)

12.5

10

Inverted aerofoil at 0 degrees Ground clearance (cm)

12.5

10

7.5

5

Appendix VII: Ground Effect 2D Results

Table 10: Ground clearance study of 2D NACA 23012 aerofoil for different angle of attack.

47 | P A G E

Appendix VIII: 3D Results Visualisation - Pressure

Visualisation type

Baseline Baseline + final wing design

Total Pressure (front)

Total Pressure

(side)

Table 11: Pressure plots on F14 race car prototype.

48 | P A G E

Appendix IX: 3D Results Visualisation - Streamlines

Visualisation type

Baseline Baseline + final wing design

Streamlines (Top)

Streamlines (Top)

Streamlines (Top)

Table 12: Streamline plots around the F14 race car prototype.

49 | P A G E

Appendix X: Gurney Flap Height Variation 3D Results

Gurney Flap Height Drag Force

Drag Coefficient

Lift Force

Lift Coefficient

Lift/Drag Ratio

2mm 134,4328 0,48818376 -103,002 -0,37404584 -0,766199

3mm 134,9263 0,48997968 -109,909 -0,39912943 -0,814584

4mm 134,1944 0,48731813 -99,041 -0,35966028 -0,738040 Table 13: Gurney flap height variation in 3D for the simple front wing design.

Figure 35: Gurney Flap Height variation efficiency comparison.

190.00%

200.00%

210.00%

220.00%

230.00%

240.00%

250.00%

Cl/

Cd

rat

io e

ffic

ien

cy

Gurney Flap Height Variation

2mm 3mm 4mm

50 | P A G E

7. References

1. SELJAK, G. Race Car Aerodynamics. In: Department of Theoretical Physics (F-1), 2008

2. KATZ, J. Aerodynamics of race cars. In: Annual Review of Fluid Mechanics. Palo Alto:

Annual Reviews, 2006, pp.27-63.

3. WORDLEY, S. and J. SAUNDERS. Aerodynamics for Formula SAE: Initial Design and

Performance Prediction. In. SAE International (2006-01-0806), 2006.

4. SAE. 2013 Formula SAE® Rules [online]. 2012. [Accessed 20 December 2012]. Available

from: http://students.sae.org/competitions/formulaseries/rules/2013fsaerules.pdf.

5. Ibid. p.6.

6. Penn State University. NACA 5 Digits Series [online]. 2009. [Accessed 15 November

2012]. Available from: http://www.ppart.de/aerodynamics/profiles/NACA5.html

7. MCKAY, N.J. and GOPALARATHNAM, A. The Effects of Wing Aerodynamics on Race

Vehicle Performance. In: SAE International (2002-01-3294), 2002.

8. NASA Glenn Research Centre. Inclination Effects on Lift [online]. 2010. [Accessed 20

November 2012]. Available from: http://www.grc.nasa.gov/WWW/k-

12/airplane/incline.html

9. GALVÃO, F.L. Wing Aerofoil Simplified Design and Analysis. In: SAE International (2005-

01-3974), 2005.

10. MAHON, S.A. and ZHANG, X. Computational analysis of pressure and wake

characteristics of an aerofoil in ground effect. In: Journal of Fluids Engineering, 2005.

11. ARIZONA STATE UNIVERSITY. Fluid Mechanics [online]. 2011. [Accessed 20 December

2012]. Available from:

http://www.asu.edu/courses/kin335/documents/Fluid%20mechanics.pdf

12. FIRST FLIGHT, OPEN UNIVERSITY. Aerofoil Forces [online]. 2012. [Accessed 27 December

2012]. Available

from: http://firstflight.open.ac.uk/pages/aerodynamics/how_planes_fly/forces/media/l

d_forces.gif

13. CORNELL RACING. About FSAE [online]. 2012. [Accessed 25 December 2012]. Available

from: www.cornellfsae.coam

51 | P A G E

14. Aerospaceweb.org. NACA Aerofoil Series [online]. 2001. [Accessed 25 December 2012].

Available from: http://www.aerospaceweb.org/question/aerofoils/q0041.shtml

15. WELTNER, K. A comparison of explanations of the aerodynamic lifting force. In: Am. J.

Phys. 55(1), 1987, p.52.

16. ANDERSON, D. Introduction to Flight (5th ed.), McGraw-Hill, 2004, pp. 257–261.

17. PLATT, R. Aerodynamic characteristics of NACA 23012 and 23021 aerofoils with 20-

percent-chord external-aerofoil flaps of NACA 23012 section. In: NACA Technical Report

573, 2011.

18. HARRIS, T. Wind-tunnel investigation of NACA 23012, 23021, and 23030 aerofoils

equipped with 40-percent-chord double slotted flaps. In: UNT Digital, 1941.

19. HANEY, P. Angle of Attack, In: Inside Racing Technology, 2000.

20. ComputerWeekly.com, Renault F1 aerodynamics and design [online]. 2009. [Accessed

23 October 2012]. Available from:

http://www.computerweekly.com/photostory/2240107861/Photos-Renault-F1-

aerodynamics-and-design-for-2009/4/Renault-F1-Front-wing-design

21. The Official F1 Website, Brawn BGP001 - new front wing [online]. 2009. [Accessed 10

February 2013]. Available from:

http://www.formula1.com/wi/full/ta_article/ta_article_665.jpg

22. Leeds Formula Student Race Team, Undergraduate FSAE team [online]. 2010. [Accessed

22 February 2013]. Available from:

http://www.engineering.leeds.ac.uk/images/520x198/Mechanical/formula%20student.j

pg

23. NEWMAN, D. Evolution of Airfoils. In: University of Alaska-Fairbanks Physics

Department Turbulence research paper, 2008.

24. MONTGOMERY, R. B. Viscosity and Thermal conductivity of air and diffusivity of water

vapour in air, In: Woods Hole Oceanographic Manuscript, 1947.

25. ABBOTT, I. H. Summary of Airfoil Data. In: NACA REPORT No. 824, 1945.

52 | P A G E

26. UIUC Airfoil Coordinates Database, NACA23012.dat [online]. 2011. [Accessed 5

November 2012]. Available from: http://www.ae.illinois.edu/m-

selig/ads/coord_database.html

27. ANSYS Inc. Turbulence modelling In: ANSYS FLUENT 14.0 User’s Guide, 2011.

28. ANSYS Inc. Local Mesh Controls In: ANSYS Meshing User’s Guide 13.0, 2010.

29. LANFRIT, M. Best practice guidelines for handling. In: Automotive External Aerodynamics

with FLUENT, 2005.

30. BARDINA, J.E., HUANG, P.G. and COAKLEY, T.J. Turbulence Modelling Validation Testing

and Development. In: NASA Technical Memorandum 110446, 1997.

31. KEATING, M. Accelerating CFD Solutions. In: ANSYS Advantage Volume V, Issue 1, 2011.

32. BROWN, L., FILIPPONE, A. Theoretical background of Gurney Flap. In: Aerofoil at low

speeds with Gurney Flaps, 2003.

33. MOKHTAR, W. A., Aerodynamics of High-Lift Wings with Ground Effect for Racecars. In:

Vehicle Aerodynamics (SP-2151), 2008.

34. EASTMAN, N. J., WILLIAM C. C., Characteristics of the N.A.C.A. 23012 Airfoil from tests in

full-scale and variable-density tunnels, In: Report No. 530 of NACA, 1935.

53 | P A G E

Project DVD