aerodynamics in cars

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Seminar Report ’05 Aerodynamics In Cars ACKNOWLEDGEMENT I express my deep gratitude to God-Almighty, for bestowing his blessings upon me in my entire endeavor. I would like to express my sincere gratitude and profound obligation to Dr.T.C.Peter, Head of the department of Mechanical Engineering and Mr. Alex Bernad V K, staff in charge who gave his full support for my seminar. I also would like to thank all the staff of Mechanical Engineering Department for their whole hearted cooperation. Last but not the least I would like to express my gratitude to my family, especially my friends who gave me moral support and helped me bring this seminar to success. Dept of Mechanical Engg MESCE Kuttipuram 1

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Page 1: Aerodynamics in cars

Seminar Report ’05 Aerodynamics In Cars

ACKNOWLEDGEMENT

I express my deep gratitude to God-Almighty, for bestowing

his blessings upon me in my entire endeavor.

I would like to express my sincere gratitude and profound

obligation to Dr.T.C.Peter, Head of the department of Mechanical Engineering and Mr.

Alex Bernad V K, staff in charge who gave his full support for my seminar. I also

would like to thank all the staff of Mechanical Engineering Department for their whole

hearted cooperation.

Last but not the least I would like to express my gratitude to my family, especially my friends who gave me moral support and helped me bring this seminar to success.

Dept of Mechanical Engg MESCE Kuttipuram1

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Seminar Report ’05 Aerodynamics In Cars

ABSTRACT

When objects move through air, forces are generated by the relative

motion between the air and surfaces of the object. Aerodynamics is the study of these

forces, generated by the motion of air, usually aerodynamics are categorized according to

the type of flow as subsonic, hypersonic, supersonic etc.

It is essential that aerodynamics be taken in to account during the

design of cars as an improved aerodynamics in car would attain higher speeds and more

fuel efficiency. For attaining this aerodynamic design the cars are designed lower to the

ground and are usually sleek in design and almost all corners are rounded off, to ensure

smooth passage of air through the body , in addition to it a number of enhancements like

spoilers, wings are also attached to the cars for improving aerodynamics. Wind tunnels

are used for analyzing the aerodynamics of cars , besides this a number of software’s are

also available now days to ensure the optimal aerodynamic design.

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CONTENTS

Acknowledgement

Abstract

Contents

List of figures

1. Introduction

2. Aerodynamic forces on a body

a) Lift

b) Weight

c) Drag

d) Thrust

3. History and evolution of aerodynamics

4. Study of Aerodynamic forces on cars

a) Drag

b) Lift or Downforce

5. Aerodynamic devices

6. Drag Coefficiant

7. Methods for evaluating Aerodynamics in cars

a) Wind tunnels

b) Softwares

8. Aerodynamic Design tips

9. conclusions

10. References

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INTRODUCTION

When objects move through air, forces are generated by the

relative motion between air and surfaces of the body, study of these forces generated by

air is called aerodynamics. Based on the flow environment it can be classified in to

external aerodynamics and internal aerodynamics; external aerodynamics is the flow

around solid objects of various shapes, where as internal aerodynamics is the flow

through passages in solid objects, for e.g. the flow through jet engine air conditioning

pipe etc. The behavior of air flow changes depends on the ratio of the flow to the speed

of sound. This ratio is called Mach number, based on this mach number the aerodynamic

problems can be classified as subsonic if the speed of flow is less than that of sound,

transonic if speeds both below and above speed of sound are present, supersonic if

characteristics of flow is greater than that of sound and hypersonic if flow is very much

greater than that of sound. Aerodynamics have wide range of applications mainly in

aerospace engineering ,then in the design of automobiles, prediction of forces and

moments in ships and sails, in the field of civil engineering as in the design of bridges

and other buildings, where they help to calculate wind loads in design of large buildings.

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AERODYNAMIC FORCES ON A BODY

Fig 1

LIFT

It is the sum of all fluid dynamic forces on a body normal to the direction

of external flow around the body. Lift is caused by Bernoulli’s effect which states that air

must flow over a long path in order to cover the same displacement in the same amount

of time. This creates a low pressure area over the long edge of object as a result a low

pressure region is formed over the aerofoil and a high pressure region is formed below

the aerofoil, it is this difference in pressure that creates the object to rise

F=(1/2)CLdV2A

Where :

CL= Coefficient of Lift, dependent on the specific geometry of the object,

determined experimentally

d= Density of air

V=Velocity of object relative to air, A=Cross-sectional area of object, parallel to wind

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DRAG

It is the sum of all external forces in the direction of fluid flow, so it acts

opposite to the direction of the object. In other words drag can be explained as the force

caused by turbulent airflow around an object that opposes the forward motion of the

object through a gas or fluid.

F=(1/2)CDdV2A

where: CD= Coefficient of Drag, dependent on the specific geometry of the object,

determined experimentally.

d= Density of air.

V=Velocity of object relative to air.

A= cross section of frontal area.

Since drag is dependent on square of velocity it is most predominant

when object is traveling at very high speeds. It is the most important aerodynamic force

to study because it limits both fuel economy of a vehicle and the maximum speed at

which a vehicle can travel.

WEIGHT

It is actually just the weight of the object that is in motion.i.e. the mass of the

object multiplied by the magnitude of gravitational field.This weight has a significant

effect on the acceleration of the object.

THRUST

When a body is in motion a drag force is created which opposes the motion of

the object so thrust can be the force produce in opposite direction to drag that is higher

than that of drag so that the body can move through the fluid. Thrust is a reaction force

explained by Newton’s second and third laws, The total force experienced by a system

accelerating in mass “m” is equal and opposite to mass “m” times the acceleration

experienced by that mass.

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HISTORY & EVOLUTION OF AERODYNAMICS

Ever since the first car was manufactured in early 20 th century the

attempt has been to travel at faster speeds, in the earlier times aerodynamics was not a

factor as the cars where traveling at very slow speeds there were not any aerodynamic

problems but with increase of speeds the necessity for cars to become more streamlined

resulted in structural invention such as the introduction of the windscreen, incorporation

of wheels into the body and the insetting of the headlamps into the front of the car. This

was probably the fastest developing time in automobiles history as the majority of the

work was to try and reduce the aerodynamic drag. This happened up to the early 1950’s,

where by this time the aerodynamic dray had been cut by about 45% from the early cars

such as the Silver Ghost. However, after this the levels of drag found on cars began to

slowly increase. This was due to the way that the designing was thought about.

Before1950, designers were trying to make cars as streamlined as possible to make it

easier for the engine, yet they were restricting the layout of the interior for the car. After

1950, the levels of aerodynamic drag went up because cars were becoming more family

friendly and so as a consequence the shapes available to choose were more limited and

so it was not possible to keep the low level of aerodynamic drag. The rectangular shape

made cars more purposeful for the family and so it is fair to say that after 1950 the

designing of cars was to aid the lifestyle of larger families.

Although this was a good thing for families, it didn’t take long before

the issue of aerodynamics came back into the picture in the form of fuel economy.

During the 1970’s there was a fuel crisis and so the demand for more economical cars

became greater, which led to changes in car aerodynamics. During the 1970’s there was

a fuel crisis and so the demand for more economical cars became greater, which led to

changes in car aerodynamics. If a car has poor aerodynamics then the engine has to do

more work to go the same distance as a car with better aerodynamics, so if the engine is

working harder it is going to need more fuel to allow the engine to do the work, and

therefore the car with the better aerodynamics uses less fuel than the other car. This

quickly led to a public demand for cars with a lower aerodynamic drag in order to be

more economical for the family.

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This diagram below shows the typical use of cars energy that it gets,

Fig 2

Only about 15% of the energy from the fuel you put in your tank gets

used to move your car down the road or run useful accessories, such as air conditioning.

The rest of the energy is lost to engine and driveline inefficiencies and idling. Therefore,

the potential to improve fuel efficiency with advanced technologies is enormous.

Now a days almost all cars are manufactured aerodynamically , one

misconception that everyone has is aerodynamics is all about going faster, in a way it is

true but it is not all about speed, by designing the car aerodynamically we can reduce the

friction that it encounters and there by power needed to overcome would be less thus fuel

can be saved; In the modern era where our fuel resources are fast depleting all the efforts

are to find alternate sources of energy or to save our current resources or minimize the

use of current resources like fuels, so now a days aerodynamics are given very much

importance as everyone like to have a good looking , stylish and fuel efficient car.

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STUDY OF AERODYNAMICS OF CARS

In order to improve the aerodynamics we must first know how the flow of air

past a car, if we visualize a car moving through the air. As we all know, it takes some

energy to move the car through the air, and this energy is used to overcome a force called

Drag.

DRAG

A simple definition of aerodynamics is the study of the flow of air around and

through a vehicle, primarily if it is in motion. To understand this flow, you can visualize

a car moving through the air. As we all know, it takes some energy to move the car

through the air, and this energy is used to overcome a force called Drag.

Drag, in vehicle aerodynamics, is comprised primarily of two forces. Frontal pressure

and rear vaccum.

DRAG FORCE AT LOW SPEEDS

The total drag force decreases, meaning that a car with a low drag force will be

able to accelerate and travel faster than one with a high drag force. This means a smaller

engine is required to drive such a car, which means less consumption of fuel.

CAR WEIGHT

As with the parts inside the engine, when the entire car is made lighter, through

the use of lighter materials or better designs, less force is required to move the car. This

is based on F=MA or more accurately, A=F/M, so as mass of the car decreases, the

acceleration increases, or less force is required to accelerate the lighter car.

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FRONT END

Fig 3

Frontal pressure is caused by the air attempting to flow around the front of the

car. As millions of air molecules approach the front grill of the car, they begin to

compress, and in doing so raise the air pressure in front of the car. At the same time, the

air molecules traveling along the sides of the car are at atmospheric pressure, a lower

pressure compared to the molecules at the front of the car. The compressed molecules of

air naturally seek a way out of the high pressure zone in front of the car, and they find it

around the sides, top and bottom of the car. Improvements at the front can be made by

ensuring the ‘front end is made as a smooth, continuous curve originating from the line

of the front bumper’. Making the screen more raked (ie. not as upright) ‘tends to reduce

the pressure at the base of the screen, and to lower the drag’. However, much of this

improvement arrives because a more sloped screen means a softer angle at the top where

it meets the roof, keeping flow attached. Similar results can be achieved through a

suitably curved roofs.

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This graph clearly shows that drag force is directly proportional to frontal area.(results of

wind tunnel tests)

Fig 4REAR END

Rear vacuum (a non-technical term, but very descriptive) is caused by the "hole"

left in the air as the car passes through it. To visualize this, imagine a bus driving down a

road. The blocky shape of the bus punches a big hole in the air, with the air rushing

around the body, as mentioned above. At speeds above a crawl, the space directly behind

the bus is "empty" or like a vacuum. This empty area is a result of the air molecules not

being able to fill the hole as quickly as the bus can make it. The air molecules attempt to

fill in to this area, but the bus is always one step ahead, and as a result, a continuous

vacuum sucks in the opposite direction of the bus. This inability to fill the hole left by

the bus is technically called Flow detachment .At the rear of vehicles, the ideal format is

a long and gradual slope. As this is not practical, it has been found that ‘raising and/or

lengthening the boot generally reduces the drag”. In plan view, rounding corners and ‘all

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forward facing elements’ will reduce drag. Increases in curvature of the entire vehicle in

plan will usually decrease drag provided that frontal area is not increased. ‘Tapering the

rear in plan view’, usually from the rear wheel arch backwards, ‘can produce a

significant reduction in drag’. Under the vehicle, a smooth surface is desirable as it can

reduce both vehicle drag and surface friction drag. ‘For a body in moderate proximity to

the ground, the ideal shape would have some curvature on the underside.’

Fig 5

Flow detachment applies only to the "rear vacuum" portion of the drag equation,

and it is really about giving the air molecules time to follow the contours of a car's

bodywork, and to fill the hole left by the vehicle, The reason keeping flow attachment is

so important is that the force created by the vacuum far exceeds that created by frontal

pressure, and this can be attributed to the Turbulence created by the detachment.

Fig 6

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LIFT OR DOWNFORCE

One term very often heard in race car circles is Down force. Down force is the

same as the lift experienced by airplane wings, only it acts to press down, instead of

lifting up. Every object traveling through air creates either a lifting or down force

situation. Race cars, of course use things like inverted wings to force the car down onto

the track, increasing traction. The average street car however tends to create lift. This is

because the car body shape itself generates a low pressure area above itself.

For a given volume of air, the higher the speed the air molecules are traveling,

the lower the pressure becomes. Likewise, for a given volume of air, the lower the speed

of the air molecules, the higher the pressure becomes. This of course only applies to air

in motion across a still body, or to a vehicle in motion, moving through still air.

When we discussed Frontal Pressure, above that the air pressure was high as the air

rammed into the front grill of the car. What is really happening is that the air slows down

as it approaches the front of the car, and as a result more molecules are packed into a

smaller space. Once the air Stagnates at the point in front of the car, it seeks a lower

pressure area, such as the sides, top and bottom of the car.

Now, as the air flows over the hood of the car, it's loses pressure, but when it

reaches the windscreen, it again comes up against a barrier, and briefly reaches a higher

pressure. The lower pressure area above the hood of the car creates a small lifting force

that acts upon the area of the hood (Sort of like trying to suck the hood off the car). The

higher pressure area in front of the windscreen creates a small (or not so small) down

force. This is akin to pressing down on the windshield.

Where most road cars get into trouble is the fact that there is a large surface area

on top of the car's roof. As the higher pressure air in front of the wind screen travels over

the windscreen, it accelerates, causing the pressure to drop. This lower pressure literally

lifts on the car's roof as the air passes over it. Worse still, once the air makes it's way to

the rear window, the notch created by the window dropping down to the trunk leaves a

vacuum, or low pressure space that the air is not able to fill properly. The flow is said to

detach and the resulting lower pressure creates lift that then acts upon the surface area of

the trunk.

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Fig 7

Not to be forgotten, the underside of the car is also responsible for creating lift or down

force. If a car's front end is lower than the rear end, then the widening gap between the

underside and the road creates a vacuum, or low pressure area, and therefore "suction"

that equates to down force. The lower front of the car effectively restricts the air flow

under the car. So, as you can see, the airflow over a car is filled with high and low

pressure areas, the sum of which indicate that the car body either naturally creates lift or

down force.

Fig 8

WINGS & SPOILERS

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What this wings or spoilers does is it prevents the separation of flow and

there by preventing the formation of vortices or helps to fill the vaccum in the rear end

more effectively thus reducing drag. So what actually this wings does is that, The wing

works by differentiating pressure on the top and bottom surface of the wing. As

mentioned previously, the higher the speed of a given volume of air, the lower the

pressure of that air, and vice-versa. What a wing does is make the air passing under it

travel a larger distance than the air passing over it (in race car applications). Because air

molecules approaching the leading edge of the wing are forced to separate, some going

over the top of the wing, and some going under the bottom, they are forced to travel

differing distances in order to "Meet up" again at the trailing edge of the wing. This is

part of Bernoulli's theory. What happens is that the lower pressure area under the wing

allows the higher pressure area above the wing to "push" down on the wing, and hence

the car it's mounted to.

The way a real, shaped wing works is essentially the same as an airplane wing,

but it's inverted. An airplane wing produces lift, a car wing produces negative lift or in

other words what we call us, downforce. That lift is generated by a difference in pressure

on both sides of the wing. .

But how is the difference in pressure generated? Well, if you look closely at the

drawings, you'll see that the upper side of the wing is relatively straight, but the bottom

side is curved. This means that the air that goes above the wing travels a relatively

straight path, which is short. The air under the wing has to follow the curve, and hence

travel a greater distance. Now there's Bernoulli's law, which basically states that the total

amount of energy in a volume of fluid has to remain constant. (Unless you heat it or

expose an enclosed volume of it to some form of mechanical work) If you assume the air

doesn't move up and down too much, it boils down to this: if air (or any fluid, for that

matter) speeds up, its pressure drops. From an energetic point of view, this makes sense:

if more energy is needed to maintain the speed of the particles, there's less energy left do

do work by applying pressure to the surfaces.

In short: on the underside, air has to travel further in the same amount of time,

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which means it has to speed up, which means its pressure drops. More pressure on top of

the wing and less on the underside results in a net downward force called downforce.

AERODYNAMIC DEVICES

SCOOPS

Fig 9

Scoops, or positive pressure intakes, are useful when high volume air flow is

desirable and almost every type of race car makes use of these devices. They work on the

principle that the air flow compresses inside an "air box", when subjected to a constant

flow of air. The air box has an opening that permits an adequate volume of air to enter,

and the expanding air box itself slows the air flow to increase the pressure inside the box.

See the diagram below:

Fig 10

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NACA Ducts

NACA stands for "National Advisory Committee for Aeronautics". NACA is

one of the predecessors of NASA. In the early days of aircraft design, NACA would

mathematically define airfoils (example: NACA 071) .

Fig 11

The purpose of a NACA duct is to increase the flowrate of air through it while

not disturbing the boundary layer. When the cross-sectional flow area of the duct is

increased, you decrease the static pressure and make the duct into a vacuum cleaner, but

without the drag effects of a plain scoop. The reason why the duct is narrow, then

suddenly widens in a graceful arc is to increase the cross-sectional area slowly so that

airflow does separate and cause turbulence (and drag).

NACA ducts are useful when air needs to be drawn into an area which isn't

exposed to the direct air flow the scoop has access to. Quite often you will see NACA

ducts along the sides of a car. The NACA duct takes advantage of the Boundary layer, a

layer of slow moving air that "clings" to the bodywork of the car, especially where the

bodywork flattens, or does not accelerate or decelerate the air flow. Areas like the roof

and side body panels are good examples. The longer the roof or body panels, the thicker

the layer becomes (a source of drag that grows as the layer thickens too). Anyway, the

NACA duct scavenges this slower moving area by means of a specially shaped intake.

The intake shape, shown below, drops in toward the inside of the bodywork, and this

draws the slow moving air into the opening at the end of the NACA duct. Vortices are

also generated by the "walls" of the duct shape, aiding in the

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scavenging. The shape and depth change of the duct are critical for proper operation.

Fig 12

SPOILERS

Spoilers are used primarily on sedan-type race cars. They act like barriers to air

flow, in order to build up higher air pressure in front of the spoiler. This is useful,

because as mentioned previously, a sedan car tends to become "Light" in the rear end as

the low pressure area above the trunk lifts the rear end of the car. See the diagram below:

Fig 13

Front air dams are also a form of spoiler, only their purpose is to restrict the air flow

from going under the car.

WINGS

Probably the most popular form of aerodynamic aid is the wing. Wings perform

very efficiently, generating lots of down force for a small penalty in drag. Spoiler are not

nearly as efficient, but because of their practicality and simplicity, spoilers are used a lot

on sedans.

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The wing works by differentiating pressure on the top and bottom surface of the wing.

As mentioned previously, the higher the speed of a given volume of air, the lower the

pressure of that air, and vice-versa. What a wing does is make the air passing under it

travel a larger distance than the air passing over it (in race car applications). Because air

molecules approaching the leading edge of the wing are forced to separate, some going

over the top of the wing, and some going under the bottom, they are forced to travel

differing distances in order to "Meet up" again at the trailing edge of the wing. This is

part of Bernoulli's theory.

What happens is that the lower pressure area under the wing allows the higher pressure

area above the wing to "push" down on the wing, and hence the car it's mounted to. See

the diagram below:

Fig 14

Wings, by their design require that there be no obstruction between the bottom of the wing and the road surface, for them to be most effective. So mounting a wing above a trunk lid limits the effectiveness.

DRAG COEFFICIANT

To calculate the aerodynamic drag force on an object, the following formula can be used:

F = ½ CDAV²

Where:F - Aerodynamic drag forceC - Coefficient of dragD - Density of airA - Frontal areaV - Velocity of object

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In this system, D as air density is expressed in kg/m³. The frontal area is the surface of

the object viewed from a point that object is going to. It's expressed in m³. The

better(lower) the number is the easier it is for air to pass around a car

Fig 15

It is the measure of the aerodynamic efficiency of the car .

.

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METHODS FOR EVALUATING AERODYNAMCIS OF CARS

WIND TUNNELS

A wind tunnel is a research tool developed to assist with studying the effects

of air moving over or around solid objects. Air is blown or sucked through a duct

equipped with a viewing port and instrumentation where models or geometrical shapes

are mounted for study. Various techniques are then used to study the actual airflow

around the geometry and compare it with theoretical results, which must also take into

account the Reynolds number and Mach number for the regime of operation. Threads

can be attached to the surface of study objects to detect flow direction and relative speed

of air flow.

Dye or smoke can be injected upstream into the airstream and the streamlines that dye

particles follow photographed as the experiment proceeds.

Traditionally, wind tunnel testing was a sizeable trial and error process, ongoing

throughout the development of a vehicle. Today, with the high level of CAD prediction

and pre-production evaluation, coupled with a greater human understanding of

aerodynamics, wind tunnel testing often comes into the design process later. The wind

tunnel is the proving ground for the vehicle's form and allows engineers to obtain

considerable amounts of advanced information within a controlled environment.

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Fig 16

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Now a days the aerodynamic studies are not constrained to the flow of air past

cars but also a number of other factors like new methods are developed to provide a

greater level of detailed information. Special pressure sensitive paint is now used in the

wind tunnel to graphically show levels of air pressure on a vehicle how it is done is

that ,Two different images are obtained, one at normal room air pressure (wind-off) and

a second in which the wind tunnel is running (wind-on) at a desired test speed. These

differences in color, from wind-off to wind-on, are used to calculate surface pressure.

A bank of blue lights illuminate the car to be tested that has pressure-sensitive

paint applied on the driver's side window. The car and lights are in a wind tunnel at Ford

Motor Company's Dearborn Proving Ground. Ford researchers have developed a

computerized, pressure-sensitive paint technique that measures airflow over cars,

shaving weeks off current testing methods. A digital camera near the blue lights captures

this information and feeds it into a computer, which displays the varying pressure as

dramatically different colors on a monitor.

The images obtained from tests in the wind tunnel are captured on computer.

They can then be used to study air flow patterns across a vehicle, highlighting areas of

possible refinement or improvement. Additionally, actual data from a production ready

model can be compared with pre-production computer predictions which can in turn help

improve the accuracy of the early design stages.

SOFTWARES

Now a days a large number of software’s are developed for the analysis and

optimization of aerodynamics in automobiles. Earlier times the cars were worked

directly on wind tunnels where they prepared different shapes or cross sections and

tested upon the cars, during those times it was not possible to test the for small areas that

is for a small part of front area etc there testing were made for the entire cross sections,

But with the introduction of computational fluid dynamics i.e. the use of computers to

analyze fluid flows where the entire area is divided in to grids and each grid is analyzed

and suitable algorithms are developed to solve the equations of motion.Based on CFD

large number of software’s are developed for the design and analyzing aerodynamics the

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most commonly used software’s are ANSYS,CATIA.

Here are some of the features of commonly used software Alias surface studio

ALIAS SURFACE AND AUTO STUDIO

Alias Surface Studio is a technical surfacing product designed for the

development surfaces. It offers advanced modeling and reverse engineering tools, real-

time diagnostics and scan data processing technology. Surface Studio is comprised of a

complete suite of tools for creating surface models to meet the high levels of quality,

accuracy and precision required in automotive styling.

This software performs all the basics of design right from the sketching to

evaluation.

Features:

1)User Interaction

A user interface that enables creativity and efficiency

2) Sketching

A complete set of tools for 2D design work tightly integrated into a 3D modeling

environment

3)2D / 3D Integration

Take advantage of your sketching skills throughout the design process. Add details

and explore ideas quickly by sketching over 3D forms before taking the time to model

them.

4) Modeling

Industry-leading, NURBS-based surface modeler.

5) Advanced Automotive Surfacing Tools

Surface creation tools that maintain positional, tangent or curvature continuity

between surfaces - for high quality, manufacturability results.

6) Reverse Engineering

Tools for importing and configuring cloud data sets from scanners for visualizing,

as well as extracting feature lines and building surfaces based on cloud data.

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7) Evaluation Tools

Tools to analyze and evaluate the styling and physical properties of curves and

surfaces interactively, while creating and editing geometry.

8)Rendering

Create photorealistic images using textures, colours, highlights, shadows,

reflections and backgrounds.

9)Animation

Animations can be used for high quality design presentations, design analysis of

mechanisms, motion and ergonomic studies, manufacturing or assembly simulation.

10)DataIntegration

Support for industry-standard data formats and a wide range of peripheral

devices.These software’s are now commonly in use as wind tunnel testing is an

expensive process as compared to this software’s where we get more accurate and easily

the test results.

AERODYNAMIC DESIGN TIPS

.) Keep the vehicle low to the ground, with a low nose, and pay attention to

the angle of wind shield.

.) Cover the wheel wells, Open wheels create a great deal of drag and air flow turbulence

.) Enclose the under carriage (avoid open areas-convertibles, etc.)

.) Make corners round instead of sharp

.) The underbody should be as smooth and continuous as possible, and should sweep out

slightly at rear.

.) There should be no sharp angles (except where it is necessary to avoid crosswind

instability ).

.) The front end should start at a low stagnation line, and curve up in a continuous line.

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.) The front screen should be raked as much as is practical.

. ) All body panels should have a minimal gap.

.) Glazing should be flush with the surface as much as possible.

.) All details such as door handles should be smoothly integrated within the contours.

.) Minor items such as wheel trims and wing mirrors should be optimized using wind

tunnel testing.

.) Using spoilers or wings.

FOR A VEHICLE YOU ALREADY OWN

• Keep your vehicle washed and waxed. This reduces skin friction.

• Remove mud flaps from behind the wheels.

• Add a spoiler to the front fender or the rear of the car. Having it on the front fender

reduces air flow beneath the car, while having it behind will decrease the low pressure

behind the car and reduce drag.

• Close your windows, put your top up, and close your sun roof. All at once!

• Avoid having roof-racks and carriers on your car.

• For pickups: cover the back, take the gate off, or at least leave the gate open. Air gets

trapped in the bed and causes major drag.

• Place your license plate out of the air flow

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CONCLUSION

Earlier cars were poorly designed with heavy engines , protruding parts

and rectangular Shapes due to which they consumed large quantities of fuel and and

became unaffordable all theses factors lead to the development and need of

aerodynamics in the design of cars now it would be fair to say that all most all cars are

tested for getting the optimum aerodynamic configuration.

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REFERENCES

BOOKS 1) Road Vehicle Aerodynamic Design , Barnard R.H.2) Introduction to Aerodynamics by Anderson.

WEBSITES1) www.wikipedia.com 2) www.cardesignonline.com

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