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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal,Volume 3, Issue 1, January 2013)

236

Analysis of NACA 2412 for Automobile Rear Spoiler UsingComposite Material

A. Sunanda1,M. Siva Nayak21Asst. prof, Department of Mechanical Engg., SNIST,Ghatkesar, Hyderabad.

2Asst Prof, Mechanical Engineering Department, Rise Groups Of Institution, Ongole.

Abstract-- The NACA 4digit series aerofoil shapes are

universally accepted standard designs generally used for wind

turbine blades, helicopter rotor blades and car spoilers. The

Design and Simulation of these complex shapes is a

challenging task for the manufacturing engineers. These

components need to be made of materials having high specific

strength and better fatigue properties. The composites with

sandwich construction fulfill the above requirements.

The main aim of the present investigation is to select the

best fiber orientation for the fabrication of automotive rear

spoiler. The Design FOIL software provides different shapes

of aerofoil from which NACA 2412 has been selected. The

spoiler is modeled using CATIA software and is analyzed for

the static deflection as well as harmonic analysis has been

done by using ANSYS for various orientations of the fiber.

The designed model has been compared with the values

obtained from the simulation values. This confirms the design

feasibility and software adoptability for the design of

sandwich aerofoil shapes.

Keywords-- Automobile Rear Spoiler, CATIA, Composite

Material, NACA, air foil

I.

INTRODUCTION

A car spoiler is a wing like accessory that is usually

attached to the rear end of the cars, or normally mounted on

top of a car's trunk or positioned under the front bumper.

While the rear spoiler is sometimes called 'wing', the

frontal car spoilers are also called 'air dam'. Car spoiler

dynamically improves the external beauty of the car

making the car stand out in a crowd, making it more trendy

and sporty. In automobile parlance, a spoiler is an

aerodynamic device that is attached to an automobile. The

intended function of this device is to 'spoil' unfavorable air

movement across a body of vehicle of some kind in motion.It is customary for racing and other high performance

sports cars to be fitted with spoilers. Nowadays-even

passenger vehicles use spoiler very commonly. To put it

more succinctly, a car spoiler improves the performance of

the car and even sometimes stimulates its resale value of

the car.

The next area for development was to manage the

airflow underneath the car; firstly this was done by using

suction fans in the 1970s, once again by Chevrolet -

Chaparral.

However this car was banned as the cornering speed

reached, up to 1.7g, were thought too dangerous. This wa

taken on by Lotus when in 1978 the Lotus 79 had a fully

shaped underbody to channel the airflow, this car was also

banned. Modern day Formula One cars can now reach

cornering speeds of up to 5g, even though there are very

strict restrictions in the guidelines. This shows how faautomotive aerodynamics have been improved.

The introduction of the car spoiler begins in the 1960s

when NASCAR automobiles still looked like what you

drove on the street. In 1966, the Dodge Charger had

flatter nose and a long, sloping roofline that seemed to

make the car unstable and lift at higher speeds. NASCAR

was petitioned and they allowed the Dodge teams to a piec

of metal about one-half to two inches high to the rea

decklid. This trapped air on the decklid and created dow

force to stabilize the car. It did not make the Dodge

standout car, but other manufacturers did see th

aerodynamic perk of adding something to the back of th

car to increase down force.

II.

BASIC FUNCTION OF SPOILER

The main function of a spoiler is diffusing the airflow

passing over and around a moving vehicle as it passes ove

the vehicle. This diffusion is accomplished by increasing

amounts of turbulence flowing over the shape, spoilin

the laminar flow and providing a cushion for the lamina

boundary layer often spoilers are added solely fo

appearance with no thought towards practical purpose.

An important principle in aerodynamics is Danie

Bernoulli's principle. It is this principle that says that wher

there is an increase in flow velocity of a gas there is a

decrease in pressure for a fixed volume. This is due toNewton, as he said that energy cannot be created o

destroyed. This theory is used extensively in aeronautica

applications. The shape of an aircraft wing causes the air t

flow faster over the top surface than the bottom one

Bernoullis principle says that this means there is a lowe

pressure on the top surface compared to the bottom surfac

and so this creates lift.

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However if the wing were turned upside down then the

resultant force would be downwards, this is called downforce and is useful in car design as it pushes the tires onto

the road giving more grip. The diagram below illustrates

the Bernoulli principle on an aircraft wing.

Fig 1 How Lift is created on an aircraft wing

Fig.2 Air foil

Over the whole of a cars body there are many different

areas of lift and down force created. When explaining drag

it was said that the air molecules slowed when approaching

the front grill and then accelerated over the top and sides of

the car. This means that when the air flows over the bonnet

of the car it will be accelerating and so at a lower pressure,

therefore a lift force is felt over the bonnet. The air then

meets the windscreen and this acts like a barrier, similar to

the front grill and so a small down force will be createdhere. The air then once again accelerates to create lift over

the roof of the car. For some vehicles the roof has a large

surface area and so a large lift force can be created. There

may also be down force created as the air flows underneath

the vehicle, if there is a narrow gap between the road and

the car the air is constricted and so has to accelerate,

creating suction to the road surface. These forces are

shown on the diagram below.

Fig.3 Forces created by airflow over a car body

III.

BENEFITS OF CAR SPOILERS

A spoiler is a flattish, slightly curved appendage on th

rear of the vehicle. Spoilers are found on racing cars an

high performance sports cars. They primarily reduce th

amounts of lift and drag a vehicle experiences and at highespeed the force of the wind pushes down on the spoile

adding additional traction for the tires. While most stoc

spoilers usually add no discernable performance, a racing

spoiler that is usually larger in size and more aerodynami

can add performance- especially at higher speeds.

Apart from contributing to the external appearance of the

car, the spoiler is very useful in making the car more fuel

efficient. This mechanical accessory can make the ca

stable on roads. Spoiler improves vehicle stability by

decreasing lift or decreasing drag that may caus

unpredictable handling in a car speed. Spoiler disrupts th

airflow going over a moving car thereby reducing th

amount of life naturally generated by the shape of the car

Spoiler accomplishes this feat by increasing the turbulence

flowing over the shape 'spoiling' the laminar flow an

providing a cushion for the laminar boundary layer.

Most of the time, the car spoiler is a styled piece o

fiberglass, which enhances the aerodynamics of the car

Due to increase in traction a car in motion brakes, turns an

accelerates with more stability. Drag increases as the spee

of the car increases. It can be seen that some spoilers ar

effective at very low speeds often generating excessiv

drag while some other spoilers can work pretty well at high

speeds. Some passenger cars can be seen equipped with

both front and rear spoilers. Front spoilers which are found

beneath the bumper are used to direct airflow away from

the tires to the under body. Rear spoilers help to modify thtransition in shape between the roof and the rear and the

trunk and the rear. This minimizes the turbulence at the rea

of the vehicle. Some rear spoilers come with a warning

brake light built into the spoiler.

IV.

CAR SPOILER TYPES

Spoiler wings come in various shapes and sizes and in

numerous designs. They could be high hopped, Supr

styled, Lip spoiler or wings wrest spoilers.

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Most of the car spoilers come made of polyurethane.

Spoilers are also made of lightweight steel while others offiberglass. These lightweight spoilers are found to be

extremely durable and do not crack, separate or sag.

Sometimes spoilers can be made of a combination of

two or three dissimilar substances. Car spoilers made of

'high impact resin' display high density with extreme

temperature resistance. They are super impact resistant.

Generally, spoilers are purchased unpainted to facilitate the

buyer paint it on an accurate color match with the car.

Mention should be made of the fact that most of the time

a car spoiler is incorrectly confused with 'wings'. While

automotive wings are devices whose intended design is to

actually generate down force as air passes around them, the

function of a car spoiler is to disrupt existing airflowpatterns.

V. COMPOSITE MATERIALS

A composite is a structural material that consists of two

or more combined constituents that are combined at a

macroscopic level and are not soluble in each other. One

constituent is called reinforcing phase and the one in which

it is embedded is called the matrix. The reinforcing phase

material may be in the form of fibers, particles, or flakes.

The matrix phase materials are generally continuous. In this

form, both fibers and matrix retain their physical and

chemical identities, yet they produce a combination of

properties that cannot be achieved with either of theconstituents acting alone. In general, fibers are the principal

load carrying members, while the surrounding matrix keeps

them, and protects them from environmental damages due

to elevated temperatures and humidity.

The composite materials have the following properties:

High specific strength

High specific stiffness

More thermal stability

More corrosion and wear resistance

High fatigue life

VI. FORMULATION OF PROBLEM AND ANALYS IS

The main aim of the present work is to investigation the

better orientation of the glass fiber in the spoiler

manufacturing. As composite material have tailoring

properties i.e., based on the users requirement material

properties of the component can be obtained by stacking

the different or similar oriented fiber together.

Design of Fiber Reinforced polymer composit

components require extensive study of material propertiebefore selecting the material to be used to make th

product. Design approach used for metallic materials could

not be utilized for polymer composite materials, since thes

materials are orthotropic in nature. Design of composit

materials is based on the classical laminate theory. Th

cumbersome mathematical solutions may be performed to

estimate the tailored material properties to be estimated by

software tools.

The design of the FRP components requires a definit

approach with consensus of discussion depending on th

functional requirements. The complex nature of failur

behavior of fiber-reinforced composites makes the desig

approach complex. In view of developing user-friendlyapproaches for design of commercial FRP products th

present work provides a pathway towards establishin

simple methods for required class of products.

Typical Aerofoil shapes have been found in a differen

NACA series from that a NACA 2412 four digit model ha

been taken for the simulation.

In the present work the Design FOIL workshop is used

to export the coordinates for geometric molding and to

estimated the lift and drag coefficients. Based on the lif

and drag coefficients the lift and drag forces are calculated

based on the below mentioned formulae:

Lift force L= *V2*S*ClDrag force D = *V2*S*Cd

To avoid the laborious processes laminate design

software is developed as a first experimental work.

The coordinates obtained form the Design FOILworkshop software are fed into CATIA sketcher and then

extruded up to one meter, this gives the foam part and then

the same coordinates are used to form the skin by giving

thickness as 3mm and then extruding up to 1m.

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Fig.4 Assembled Aerofoil Model

VII.

RESULTS

The assembled model then is imported into ANSYS.

Meshing has been done using mesh option as shown in

figure.

Fig.5 Meshed Model

The finite element modeling and analysis is used to

study the deflections and stress variation at different

locations of the spoiler and also the deflection at various

ends. The figure shows all the deflection stresses and

harmonic Analysis at different orientations of fibers.

Fig.6 Model in Workbench

Results for Aluminium material

Fig.7 Deflection For Aluminium

Fig.8 Equivalent stress For Aluminium

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Fig.9 Frequency Vs Amplitude for aluminum

Results for 00orientation

Fig.10 Deflection at 00orientation

Fig.11 Equivalent stress 00orientation

Fig.12 Frequency Vs Amplitude (00)


Fig.13 Deflection at 45oorientation

Fig.14 Equivalent stress 450

orientation

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VIII.

CONCLUSION1.

The simulation results are that [45o] orientation of

the fiber is the best orientation for the fabrication of

the spoiler.

2.

[45o] orientation of the fiber with foam gives best

result when compared the same [45o] orientation of

the fiber without foam

3.

The fabrication of the spoiler has been done with

sandwich construction..

4.The theoretical calculation and the simulation resultsdiffer i.e., due to localized buckling effect in the

sandwich construction.

IX.

SCOPE FOR FUTURE WORK

Having successfully proven that the manufacturing

concept is feasible in basic engineering terms, work i

currently in progress on Spoiler design and analysis

Although flat panel structures are relatively simple to

model for FEA, it is necessary to quantify the mechan icaproperties of the bonded joints, and to represent these in th

model efficiently.

In the current situation of limited resources, th

following aspects are recognized as being oconsiderable importance, but must wait furthefunding:

Manufacturing of different composite materials lik

Kevlar/epoxy, Boran/epoxy, Carbon/epoxy

Selection of sandwich panel component material

(skins and core) for ease and consistency o

manufacture, performance and recycling.

Optimization of adhesive for cure cycle and long term

properties.

Crashworthiness testing.

Production plant layout, process monitoring an

quality systems.

Operational considerations (e.g. thermal, acoustic and

dynamic characteristics).

Funding and in-kind support is actively being sough

from various bodies (e.g. materials suppliers

manufacturers and potential customers) to carry the projecforward.

REFERENCES

[1 ]

W.J. Cantwell et al. A comparative study of the mechanica

properties of sandwich materials for nautical construction. SAMP

Jnl., 30 (4), 45-51 (1994).

[2 ]

K. Lowe. Automotive steels. Engineering, Feb. 1995, 20-21.

[3 ] http://www.fibermaxcomposites.com/index.files/manufacturingtech

iques.htm

[4 ]

http://www.dreesecode.com

[5 ]

http://www.en.wikipedia.com

MaterialDeflection

(mm)

Von-

misses

Stress

N/mm2

Peak

frequency

(Hz)

foam 9.057 141.49 1400

Without

foam15.946 186.98 400

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