A

TECHNICAL SEMINAR REPORT

ON

“RECENT DEVELOPMENTS IN THE FIELD OF AUTOMOTIVE AERODYNAMICS”Submitted in partial fulfillment of the requirement for the award of degree of

BACHELOR OF TECHNOLOGY

IN

AUTOMOBILE ENGINEERING

(VALLURUPALLI NAGESWARA RAO VIGNANA JYOTHI

INSTITUTE OF ENGINEERING & TECHNOLOGY)

Submitted by

Roney Mathew (11071A2437)

Under The Esteemed Guidance Of

M.Venkat Ramana, Associate Professor

DEPARTMENT OF AUTOMOBILE ENGINEERING

VALLURUPALLI NAGESWARA RAO VIGNANA JYOTHI

INSTITUTE OF ENGINEERING & TECHNOLOGY

BACHUPALLY, NIZAMPET (S.O), HYDERABAD – 500 090,

DEPARTMENT OF AUTOMOBILE ENGINEERING

VALLURUPALLI NAGESWARA RAO VIGNANA JYOTHI

INSTITUTE OF ENGINEERING & TECHNOLOGY

BACHUPALLY, NIZAMPET (S.O), HYDERABAD – 500 090.

CERTIFICATE

This is to certify that the technical seminar report on “RECENT DEVELOPMENTS IN THE FIELD OF AUTOMOTIVE AERODYNAMICS” Submitted by Roney Mathew (11071A2437) in the partial fulfillment for the requirement of the degree of Bachelor of Technology. JNTUH, Hyderabad. This is a technical seminar report in the academic session 2014-2015.

INTERNAL GUIDE H.O.D

PRINCIPAL

Contents

1. Introduction

2. Introduction to Aerodynamics

3. Automotive Aerodynamics

4. Aerodynamic forces on a body

5. Important terms of Aerodynamics

6. Principles of Aerodynamics

7. History and evolution of Aerodynamics

8. Aerodynamics in F1

9. Advancements in Aerodynamic devices

9.1 Front Wing analysis

9.2 Ram effect

9.3 Canards and vortex generators

9.4 Diffuser

9.5 F-duct

9.6 Blown Air diffusers

9.7 Gurney Flaps

10. Future scope

11. References

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, whereas 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 depending 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.

INTRODUCTION TO AERODYNAMICS

In fluid mechanical terms, road vehicle are bluff bodies in very close proximity to the

ground. Their detailed geometry is extremely complex. Internal and recessed cavities which

communicate freely with the external flow (i.e. engine compartment and wheel wells,

respectively) and rotating wheels add to their geometrical and fluid mechanical complexity. The

flow over a vehicle is fully three-dimensional. Boundary layers are turbulent. Flow separation is

common and may be followed by reattachment. Large turbulent wakes are formed at the rear and

in many cases contain longitudinal trailing vortices.

As is typical for bluff bodies, drag (which is a key issue for most road vehicle but far

from the only one) is mainly pressure drag. This is in contrast to aircraft and ships, which suffer

primarily from friction drag. The avoidance of separation or if this is not possible, its control are

among the main objective of vehicle aerodynamics.

With regard to their geometry, road vehicle comprise a large variety of configuration.

Passenger cars, vans and buses are closed, single bodies. Trucks and race cars can be of more

than one body. Motorcycles and some race cars have open drive compartments. With the race car

being the only exception, the shape of a road vehicle is not primarily determined by the need to

generate specific aerodynamic effects as, for instance, an airplane is designed to produce lift.

To the contrary, a road vehicle’s shape is primarily determined by functional, economic

and last but not least, aesthetic arguments. The aerodynamic characteristics are not usually

generated intentionally they are the consequences of but not the reason for the shape. Their

“other than aerodynamic” consideration place severe constraints on vehicle aerodynamicists. For

example, there are good reasons for the length of a vehicle being a given. Length for a passenger

car is a measure of its size, and thus its class. To place a car in a specific market niche means

recognizing length as an invariant in design. Furthermore, mass and cost are proportional to

length.

6

In the same sense all the other main dimensions of a vehicle, such as width

Fig 1.1: Road Vehicle Shapes

and height (which define frontal area), are frozen very early in the design process. Even the

details of a car’s proportions are prescribed to close limits for reasons of packing and aesthetics.

Of course, some manoeuvring room must be left to the aerodynamicists. Otherwise, they would

do no more than just measure the aerodynamic characteristics of configuration designed by

others.

Depending on the specific purpose of each type of vehicle, the objectives of aerodynamic

differ widely. While low drag is desirable for all road vehicles, other aerodynamic properties are

also significant. Negative lift is decisive for the cornering capability of race cars, but is of no

importance for trucks are not.

8

Wind noise should be low for cars and buses, but is of no significance for race cars.

Fig 1.2: Frozen Dimensions

There is no question, however, that aerodynamic does influence design. The high trunk

typical of notch back cars with low drag is the most striking example. Despite the fact that it

tends to look “bulky,” it had to be accepted by designer because of its favourable effects on drag

and the extra luggage space it provides. Today’s cars are streamlined more than ever and an

“aero-look” has become a styling feature of its own.

AUTOMOTIVE AERODYNAMICS

Automotive aerodynamics is the study of the aerodynamics of road vehicles. The main concerns

of automotive aerodynamics are reducing drag (though drag by wide wheels is dominating most

cars), reducing wind noise, minimizing noise emission, and preventing undesired lift forces and

other causes of aerodynamic instability at high speeds. For some classes of racing vehicles, it

may also be important to produce desirable downwards aerodynamic forces to improve traction

and thus cornering abilities.An aerodynamic automobile will integrate the wheel arcs and lights

in its shape to have a small surface. It will be streamlined, for example it does not have sharp

edges crossing the wind stream above the windshield and will feature a sort of tail called a

fastback or Kammback or liftback. Note that the Aptera 2e, the Loremo, and the Volkswagen 1-

litre car try to reduce the area of their back. It will have a flat and smooth floor to support the

Venturi effect and produce desirable downwards aerodynamic forces. The air that rams into the

engine bay, is used for cooling, combustion, and for passengers, then reaccelerated by a nozzle

and then ejected under the floor. For mid and rear engines air is decelerated and pressurized in a

diffuser, loses some pressure as it passes the engine bay, and fills the slipstream. These cars need

a seal between the low pressure region around the wheels and the high pressure around the

gearbox. They all have a closed engine bay floor. The suspension is either streamlined (Aptera)

or retracted. Door handles, the antenna, and roof rails can have a streamlined shape. The side

mirror can only have a round fairing as a nose. Air flow through the wheel-bays is said to

increase drag (German source) though race cars need it for brake cooling and a lot of cars emit

the air from the radiator into the wheel bay.Automotive aerodynamics differs from aircraft

aerodynamics in several ways. First, the characteristic shape of a road vehicle is much less

streamlined compared to an aircraft. Second, the vehicle operates very close to the ground, rather

than in free air. Third, the operating speeds are lower (and aerodynamic drag varies as the square

of speed). Fourth, a ground vehicle has fewer degrees of freedom than an aircraft, and its motion

is less affected by aerodynamic forces. Fifth, passenger and commercial ground vehicles have

very specific design constraints such as their intended purpose, high safety standards (requiring,

for example, more 'dead' structural space to act as crumple zones), and certain regulations. Roads

are also much worse (smoothness, debris) than the average airstrip. Lastly, car drivers are vastly

undertrained compared to pilots, and usually will not drive to maximize efficiency.Automotive

aerodynamics is studied using both computer modelling and wind tunnel testing. For the most

accurate results from a wind tunnel test, the tunnel is sometimes equipped with a rolling road.

This is a movable floor for the working section, which moves at the same speed as the air flow.

This prevents a boundary layer forming on the floor of the working section and affecting the

results. An example of such a rolling road wind tunnel is Wind Shear's Full Scale, Rolling Road,

Automotive Wind Tunnel built in 2008 in Concord, North Carolina.

Relationship to velocity

The frictional force of aerodynamic drag increases significantly with vehicle speed. As early as

the 1920s engineers began to consider automobile shape in reducing aerodynamic drag at higher

speeds. By the 1950s German and British automotive engineers were systematically analyzing

the effects of automotive drag for the higher performance vehicles. By the late 1960s scientists

also became aware of the significant increase in sound levels emitted by automobiles at high

speed. These effects were understood to increase the intensity of sound levels for adjacent land

uses at a non-linear rate. Soon highway engineers began to design roadways to consider the

speed effects of aerodynamic drag produced sound levels, and automobile manufacturers

considered the same factors in vehicle design.

Downforce

Downforce describes the downward pressure created by the aerodynamic characteristics of a car

that allows it to travel faster through a corner by holding the car to the track or road surface.

Some elements to increase vehicle downforce will also increase drag. It is very important to

produce a good downward aerodynamic force because it affects the car’s speed and traction.

AERODYNAMIC FORCES ON A BODY

LIFTIt 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 aero foil and a high pressure region is formed below the aero foil, it is this difference in pressure that creates the object to riseF= (1/2) CLdV2AWhere:CL= Coefficient of Lift, dependent on the specific geometry of the object,Determined experimentallyd= Density of airV=Velocity of object relative to air, A=Cross-sectional area of object, parallel to wind.

DRAGIt 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.

THRUSTWhen 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.

IMPORTANT TERMS OF AERODYNAMICS

FLUID: Webster defines a fluid as "a substance” tending to flow or to conform to the shape of its container. “This means simply that a fluid is any substance which has little internal friction-i.e., one that will easily yield to pressure. All liquids and all gasses are fluid at any temperature or pressure that interests us. For sure air is a fluid and must inexorably obey all of the laws of fluid mechanics. Just because the internal friction between the particles which comprise the air that we breathe and through which we force our race cars is very low does not mean that there is no pressure present or that the air will behave in the way that we want it to. It will behave in accordance with the laws of fluid mechanics and in no other way. So we had best achieve a basic understanding of those laws.

STATIC PRESSURE is defined as the ambient pressure present within a certain space and is expressed in units of mass related to units of area as in pounds persquare inch (psi).

DYNAMIC PRESSURE is defined as one half of the product of the mass density of a fluid times fluid velocity squared. We don't have to know that. We do have to know that the dynamic pressure of a fluid is proportional to the difference between the undisturbed static pressure present ahead of a body moving through a fluid and the local pressure of the fluid at the point along the body where we are taking the measurement. Dynamic pressure is directly proportional to the local momentum of fluid particles.

STREAMLINE: If a small cross-sectional area of a fluid in motion is colored with something visible (colored smoke in a wind tunnel or dye in a liquid), a single line becomes visible in side elevation. This line is called a streamline and allows visual study of fluid flow. Bodies are miscalled streamlined when they are so shaped that most streamlines passing around the body will do so without crossing each other and without becoming disrupted or dissolved.

LAMINAR FLOW is that state of fluid flow in which the various fluid sheets or streams do not mix with each other. In laminar flow all of the streamlines remain essentially parallel and the relative velocities of the various sheets or streamlines remain steady-although the fluid velocity may be either increasing or decreasing. Laminar flow is what we are always trying to achieve.

TURBULENT FLOW is that state of fluid flow in which the various fluid sheets or streamlines exhibit erratic variations in velocity and do not remain parallel but mix and eddy together. Turbulent flow causes drag. A common example of laminar and turbulent flow is the behavior of a plume of cigarette smoke in still air. At first the plume will rise smoothly and the smoke will remain in ' streamlines. Sooner or later the plume gets tired, becomes' unstable, and turbulence becomes visible as the streamlines cross and become disrupted.

THE BOUNDARY LAYER is a comparatively thin layer of decelerated fluid adjacent to the surface of a body in motion through a fluid. Friction between the body and the fluid slows the fluid flow from its full external value to effectively zero at the surface of the body. The flow within the boundary layer can be either laminar or turbulent and the layer can be either thin or thick. At the front of a reasonably well shaped body, as the fluid starts to move out of the way, the boundary layer will normally be thin and the flow will be laminar. Internal fluid friction and the friction between the fluid and the body dissipate some of the energy in the fluid and, as the flow moves rearward over the body, the boundary layer will normally thicken and become unstable. If it becomes thick enough, or turbulent enough, or if it must flow into a region of increased pressure, the boundary layer will separate from the body.

PRESSURE DIFFERENTIAL is the local pressure at a given point along the surface of a body less the static pressure ahead of the body. Variation of the pressure differential along the surface of a body is referred to as the pressure gradient. A positive pressure gradient-one in which the pressure differential increases in the direction of flow-is termed an adverse pressure gradient and can lead to flow separation.

TOTAL PRESSURE AND THE LAW OF CONSTANTPRESSURE: Bernoulli assures us that, under steady and non-viscous conditions, the sum of static pressure and dynamic pressure will remain constant. This explains the generation of pressure induced drag. Both the velocity and the pressure of fluid particles approaching a body reduce. Therefore the static pressure immediately ahead of a body in motion is increased-by the "bow wave," as it were -the fluid is getting ready to get out of the way. In the perfect or ideal condition, a corresponding exchange between static and dynamic pressure would take place at the rear of the body; equilibrium would exist and there would be no pressure induced drag. In the real world, viscous friction, boundary layer deceleration and separation do exist and so the flow pattern around a body in motion is modified from the ideal state. The deceleration of the fluid particles upon reaching the rear of the body and the corresponding pressure recovery are not complete. The resultant of the increased static pressure ahead of the body and decreased pressure behind it is pressure induced drag.

FLOW SEPARATION originates within the boundary layer and results in a bulk separation of the flow. In simple terms the fluid flow is not able to follow the shape of the body. Boundary layer separation takes place when the frictional shearing forces between the sheets of the boundary layer become too great for the layer to remain attached. This occurs when there is too steep an adverse pressure gradient, too much turbulence within the layer, a rapid change in body shape or when the boundary layer "trips" over a skin joint or a protuberance. It is possible for a boundary layer that has separated to become reattached at some point downstream of the separation point. Examples of bulk flow separation are wing stall and the large turbulent wake at the rear of blunt bodies. Whenever the flow separates, a notable increase in drag is instantlyrealized. In the case of wings, stall also produces a dramatic decrease in lift force.

ATTACHED FLOW is the opposite condition to detached flow and is much to be preferred. It is possible for fluid flow to be turbulent but to remain attached. In fact, a laminar boundary layer may separate sooner in an adverse pressure gradient than will a turbulent boundary layer.

DRAG is the retarding force which acts on anybody in motion through a fluid. Its action is always parallel to and in the opposite direction from the direction of motion. Drag is due to the transfer of momentum between the body and the fluid and is caused by displacement of the fluid by the body and by friction between the fluid and the body.

PRESSURE DRAG, or PROFILE DRAG is that drag force caused by the displacement of a fluid by a body in motion through that fluid. Fluid arriving at the leading edge of a body causes a positive pressure at the leading edge which resists the motion of the body. As the fluid flow progresses past the leading edge, the pressure rapidly decreases, may become negative for a time, and then slowly increases until flow separation occurs. The pressure in a region of separated flow will be negative and will pull against the forward motion of the body just as the high pressure at the leading edge pushes against it. The sum of these two retarding forces is pressure induced drag and is the major component of total drag for unstreamlined or semi-streamlined bodies-which happen to be the sort of bodies that we will be discussing (with the exception of ourwings, which we hope will be more efficient shapes). With streamlined bodies, skin friction drag is normally greater than pressure drag. Even with streamlined bodies, we cannot entirely eliminate pressure drag.

INDUCED DRAG: Induced drag is the drag force produced by a lifting surface as a result of the lift. A wing, in order to produce lift, will necessarily impart momentum to the fluid. This momentum is not recovered and appears as drag. The lift doesn't come free and the greater the lift, the greater the induced drag. We can only hope to induce the minimum amount of drag per unit of lift generated by appropriate design of the lifting surface. The most effective way of minimizing the induced drag of a wing is to increase its span. Nature understands this and has given all of her efficient soaring bird’s wings of great span. Our sanctioning bodies must also understand since they have decreed that racing car wings be small in span. As a result, the induced drag of racing car wings is their major drag component.

PARASITE DRAG is the drag produced by the friction and pressure caused by the various protuberances on the body such as fasteners, heat exchangers, mirrors, air scoops and the like.

Most studies treat skin friction drag as a portion of parasite drag. We will consider it to be separate.

SKIN FRICTION DRAG is the drag force caused by friction between the surface of a body and the fluid through which it moves. Its magnitude is a function of surface finish and of surface area. Strangely enough, skin friction drag is not terribly important in the case of the racing car-but it is really easy to do something about it.

MOMENTUM, defined as mass time’s velocity, is an indication of the amount of energy that a body in motion can release if it is stopped. Momentum is constantly transferred from a body in motion to the fluid through which it moves-by displacement of fluid in order for the body to pass and by the heat of friction between the body and the fluid. Momentum transferred per unit time is equal to drag. In order for a body to continue moving through a fluid at a constant speed, the lost momentum must be constantly replenished by a power source. In order for the body to accelerate, the power source must produce more thrust than is lost by the transfer of momentum. Otherwise a vehicle will decelerate or an aircraft will lose either velocity or altitude. Momentum is transferred from a body to a fluid by:(I) the displacement of a certain volume of fluid in thedirection of motion and of more fluid in a direction perpendicular to the direction of motion.(2) The placement of a certain volume of fluid into turbulence or irregular motion.(3) The containment of a certain volume of fluid in a system of regular vortices.(4) The generation of heat by friction between the fluid and the body and between fluid sheets moving at differing relative velocities.

VISCOSITY is the molecular resistance which fluid particles exhibit against lisplacement in relation to each other and with respect to the surface of a body. Most directly this type of resistance presents itself in the form of frictional drag-as a tangental force when fluid moves past the surface of a body. This tangental force is skin friction drag and increases with viscosity. The viscosity of air is, for our purposes, independent of pressure and although it decreases with rising temperature, we shall consider it to be constant.COMPRESSIBILITY is the quality of a gaseous fluid of reducing in volume as static pressure is increased. In practical terms, liquids are not compressible and gasses are-which is why bubbles in the braking system cause a spongy brake pedal. At vehicle speeds we do not approach incompressible airflow, so we will not worry about it.

REYNOLDS NUMBER is a dimensionless quantity which varies directly with air speed and size of the body in motion and inversely as fluid density and viscosity. Its chief value lies in enabling fluid mechanicists to predict full scale results from model tests. It has limited practical application within the scope of this chapter.

THE COEFFICIENT OF DRAG is a dimensionless quantity used to compare the drag caused bodies of different shapes It is abbreviated to CD and is obtained by measuring the drag force and dividing it by the dynamic pressure and the reference area.

THE COEFFICIENT OF LIFT is another dimensionless quantity which compares the lift generated by different

shapes. It is normally abbreviated C I and is obtained by measuring the lift force and dividing it by the dynamic pressure and the reference area.

Blockage Usually referred to as a percentage, this is the ratio of the frontal area of the

vehicle being tested to the cross-sectional area of the wind tunnel. For a solid

tunnel 4-5% would be a typical “good” value.  Higher numbers would begin to

require significant blockage correction.

Blockage Correction Forces directly measured on a wind tunnel model are often “corrected” to allow

for the effects on forces caused by the (close proximity of the) walls of the wind

tunnel. Typically this will involve reductions in both the drag and lift values with

different corrections for each. The “correction” factors are typically derived

from standard bluff bodies tested at many blockages.

Boundary Layer As air passes over a stationary surface, the air nearer the surface moves more

slowly than air further away. Over time and distance, this layer of slow-moving

air builds up. This is the boundary layer.

Contact Patch The point where the tire touches the road. Being flexible, the tire is squashed

locally creating a contact patch, which increases as the vertical load on the tire

increases. Simplified you could imagine that the tire is cut by the plane of the

road.

Double Diffuser A diffuser is limited in size by regulation and creates downforce by creating a

pressure differential, with low pressure beneath and higher pressure

above. Clever interpretation of the rules regarding holes in the floor and

continuous surfaces led to the openings that allowed double diffusers.

Effectively the step formed two separate, but individually continuous, surfaces

allowing airflow to pass up above the step plane into the upper deck of the

diffuser. This rule was clarified for 2011 and now a single continuous surface

must be formed under the floor.

Double DRS (DRD) (See DRS below).  Active systems (eg Mercedes system where air was

channelled through an opening in the rear-wing endplate when the DRS was

activated and then fed through the car to help stall the front wing) banned for

2013 and beyond. Passive systems (sometimes known as Drag Reduction

Devices [DRDs]) with no moving parts other than the airflow through them are

still allowed.

Downforce For the purist, this should be referred to as “negative lift”, since most

aerodynamic devices were invented for aircraft and were designed to lift them

into the air. It is the vertical part of the aerodynamic force generated by the car

as it moves through the air.

Drag This is the horizontal part of the aerodynamic force generated by the car as it

moves through the air. This force is so great on a F1 racing car that, when the

driver comes off the throttle at maximum speed, the car slows down at least as

briskly as a road car can brake at maximum effort.

Drag Coefficient Usually shown as Cd or Cx. Changes as a function of the shape of the body. 

Drag force changes as a function of Cd or Cx and flow direction, fluid/air density

and viscosity, object position and size, and speed; and is proportional to the

density of the fluid/air and to the square of the relative speed between the

fluid/air and the object.

DRS - Drag Reduction

System

An overtaking aid which allows the driver to make an adjustment to the rear

wing from the steering wheel and deactivated when the driver brakes. Can only

be used in DRS zones (designated areas of the track) in qualifying and, during

the race, if the following car is within one second of the car in front at the DRS

detection points. Race Director may decide to suspend use in adverse weather

conditions or in a yellow-flag zone. The rear wing flap must be at least 10mm

from the main plane when closed and no more than 65mm when open.

Exhaust Effect The exhaust from a F1 engine exits the tailpipe at high speed (was

approximately 1100 kph/700 mph in 2013) depending on exhaust pipe

diameter and temperature. This exhaust gas can, in certain circumstances, be

used to reduce drag or increase downforce. In other circumstances, it can do

quite a bit of damage, due to its extremely high temperature, severely damage

the car mechanically (such as melting the wings). For 2014 exhaust diameters

have been increased (which then reduces speed in the pipes) and moved to an

area where less (aero-wise) can be achieved.

F-Duct McLaren were the first to use. They managed to redirect airflow over the rear

wing, allowing the flap to stall and increasing top speed by a few kph, and

controlled by a vent in the cockpit which could be blocked by the driver’s leg.

The rules were then clarified and, from 2011, any system, device or procedure

which uses driver movement as a means of altering the aerodynamic

characteristics of the car is prohibited.

Ground Effect A curved aerodynamic surface influences the airflow even a long way from that

surface, bending the airflow in such a way that flow adjacent to the surface

follows that surface almost perfectly. The further away from the surface you go,

the straighter the flow becomes. When an aerodynamic surface is placed close

to the ground, the presence of the ground determines where the flow becomes

straight. This has the effect of speeding up the airflow between the surface and

the ground, increasing the aerodynamic effect of the surface.

Pitch When the front and rear ride heights are different to one another; the car is

said to be pitched. Pitch can be expressed as an angle or as a difference

between the front and rear ride heights.

Reynolds Number Ratio of speed, length and air density to fluid/air viscosity. At low levels of

Reynolds Number (ie equal to or below 2300) flow is laminar, at higher levels

(ie above 4000) is turbulent and, in between, is in transition.

Ride Height Height or average height of the car to the ground.  Each team has its own plane

or point of reference for ride height.

Roll This is the difference in ride height left to right and is usually expressed as an

angle to the ground.

Stall When an aerodynamic surface curves too quickly for the air particles to follow

the shape of the surface, the airflow is said to be stalled.

Steer Turning the steering wheels (front in F1) at an angle to the vehicle.  Just like the

effect of turning the steering wheel in a road car.

Subsonic Literally, below the speed of sound.  The reason this is important in

aerodynamics is that there is a dramatic, almost switch-like, change in the way

air behaves when the speed of sound is reached.

Supersonic Above the speed of sound.  At supersonic speeds, airflow sometimes appears

as a shock wave and seems to move in straight lines.

Vortex Swirling flow of air.  A vortex would occur at the tip of a wing where the air

passing around the wing is deflected just beside air that does not touch the

wing.  The sudden change in flow angularity created by the meeting of these

two different flow directions creates the swirling mass of air.  Rear-wing

vortices can be seen on racing cars in damp conditions.  Sometimes vortices

are generated on purpose to control airflow such as the small angled rectangles

that protrude above many aircraft wings.  F1 teams are investigating vortex

generators to push the limits of aerodynamic downforce further than they now

can.

Yaw A car is said to be in yaw when it corners with a sliding (usually tail-out)

attitude.  In other words, the car is cornering sideways.

PRINCIPLES OF AERODYNAMICS

Coanda EffectA moving stream of fluid in contact with a curved surface will tend to follow the curvature of the surface rather than continue traveling in a straight line. One of the most widely used applications of Bernoulli's principle is in the airplane wing. Wings are shaped so that the top side of the wing is curved while the bottom side is relatively flat. In motion, the front edge of the wing hits the air, and some of the air moves downward below the wing, while some moves upward over the top. Since the top of the wing is curved, the air above the wing must move up and down to follow the curve around the wing and stay attached to it (Coanda effect), while the air below the wing moves very little. The air moving on the top of the curved wing must travel farther before it reaches the back of the wing; consequently it must travel faster than the air moving under the wing, to reach the back edge at the same time. The air pressure on the top of the wing is therefore less than that on the bottom of the wing, according to Bernoulli’s principle. The higher pressure air on the bottom of the wing pushes up on the wing with more force than the lower pressure air above the wing pushes down. This result in a net force acting upwards called lift. Lift pushes the wings upwards and keeps the airplane in the air. Though Bernoulli's principle is a major source of lift in an aircraft wing, Coanda effect plays an even larger role in producing lift. If the wing is curved, the airflow will follow the curvature of the wing. In order to use this to produce lift, we need to understand something called angle of attack. This gives the angle between the wing and

the direction of the air flow, as shown in the following picture. The angle of attack indicates how tilted the wing is with respect to the oncoming air. In order to produce lift, or downforce acting on the wing, Newton's third law says that there must be equal force acting in the opposite direction. If we can exert a force on the air so that it is directed down, the air will exert an upward force back on the wing.

This diagram shows that increasing the angle of attack increases how much the air is deflected downwards. If the angle of attack is too high, the air flow will no longer follow the curve of the wing (Coanda effect is losing the power). As shown in the bottom of the diagram, this creates a small vacuum just behind the wing. We can say that wing is stalled. As the air rushes in to fill this space, called cavitations’, it causes heavy vibrations on the wing and greatly decreases the efficiency of the wing. For this reason, aircraft wings are generally angled like the middle wing in the diagram. This wing efficiently directs the airflow downward, which in turn pushes up on the wing, producing lift. If you turn this wings on upper picture upside down, you get formula 1 or any wing in use in auto sport. This configuration of the wing, with longer lower part ofthe wing will produce opposite force, called downforce. But we can apply same rules. To get around air stream separation problem in airplane wing construction and in Formula 1, and increase the Coanda effect on wings, dual or more element or slot-gap wings are used, these allow for some of the high pressure flow from (in Formula 1 case) the upper surface of the wing to bleed to the lower surface of the next flap energizing the flow. This increases the speed of the flow under the wing, increasing downforce and reducing the boundary flow separation. If you look at a F1 rear wing few years ago on picture above, you can see this concept taken to the extreme, with multi-element wings creating huge amounts of downforce and little air stream separation even on the flaps with extremely high angle of attack. The Coanda effect has important applications in various high-lift or high downforce devices on aircraft, or in our area of interest, on the racing car wing, where air moving over the wing can be "bent" using flaps over

the curved surface of the top of the wing. The bending of the flow results in its acceleration and as a result of Bernoulli's principle pressure is decreased; aerodynamic lift or downforce is increased. Notice how unlikely is to have a wing in flight with air flow only on one side. The Coanda effect only works in specific conditions where an isolated jet of fluid (or air) flows across a surface, a situation which is usually man-made. You don't find it much in nature. Just so you know, there is no Coanda lift on an airfoil. Coanda effect helps airstream to stay attached to the wing surface, but Bernoulli principle and difference in pressures are the reason why we have a lift or downforce. Coanda effect is a balancing act between many factors, among them speed of fluids stream, pressure, molecular attraction, and a centrifugal effect if the surface is curved. Main trouble of the Coanda effect is the airstream becoming turbulent and detaching from the surface, that's how a wing stalls. Pull of surrounding air causes turbulence, drag from the surface and from the ambient air. It's a goal to pull as much as possible ambient air into the airstream, but the drag caused by the difference in velocity between the airstream and the surface is just a loss of energy. If the airstream gets turbulent and stops following the curved surface, there's no more low air pressure, no more thrust. Since all applications of a Coanda effect involve a fluid object flowing over a solid one, the science behind this effect is known as fluid dynamics. Fluid dynamics represents and study the motion of liquids or gases. Studying this science can lead to many consequential discoveries like the Coanda effect.

Ground effectGround effect is term applied to a series of aerodynamic effects used in car design, which has been exploited to create downforce, particularly in racing cars. TheoryIn racing cars, a designer's aim is for increased downforce, increasing grip and allowing for greater cornering speeds. (Starting in the mid 1960s 'wings', or inverted airfoils, were routinely used in the design of racing cars to increase downforce, but this is not ground effect.) Substantial further downforce is available by understanding the ground to be part of the aerodynamic system in question. This kind of ground effect is easily illustrated by taking a tarpaulin out on a windy day and holding it close to the ground: it can be observed that when close enough to the ground the tarp will suddenly be sucked towards the ground. This is due to Bernoulli's principle; as the tarp gets closer to the ground, the cross sectional area available for the air passing between it and the ground shrinks. This causes the air to accelerate and as a result pressure under the tarp drops while the pressure on top is basically unaffected, and together this results in a net downward force. The same principles apply to cars. The Bernoulli principle is not the only mechanic in generating ground effect downforce. A very large part of ground effect performance comes from taking advantage of viscosity. In the tarp example above neither the tarp nor the ground is moving. The boundary layer between the two surfaces works to slow down the air between them which lessens the Bernoulli Effect. However when a car moves over the ground the boundary layer on the ground becomes helpful. In the reference frame of the car, the ground is moving backwards at some speed. As the ground moves, it pulls on the air above it and causes it to move faster. This enhances the Bernoulli effect and increases downforce. It is an example of Couette flow.

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 were 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.

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.

AERODYNAMICS IN F1

Ask any engineer in the pit lane and they’ll tell you that the most important consideration in F1 car design - the difference between designing a championship-challenging machine or a tail ender - is aerodynamics.

In simple terms, F1 aerodynamicists have two primary concerns: the creation of downforce, to

help push the car's tyres onto the track and improve cornering forces; and the minimisation of

drag, a product of air resistance which acts to slow the car down.

Although always important in race car design, aerodynamics became a truly serious proposition

in the late 1960s when several teams started to experiment with the now familiar wings. Race car

wings - or aerofoils as they are sometimes known - operate on exactly the same principle as

aircraft wings, only in reverse. Air flows at different speeds over the two sides of the wing (by

having to travel different distances over its contours) and this creates a difference in pressure, a

physical rule known as Bernoulli's Principle. As this pressure tries to balance, the wing tries to

move in the direction of the low pressure. Planes use their wings to create lift, race cars use theirs

to create negative lift, better known as downforce. A modern Formula One car is capable of

developing 3.5 g lateral cornering force (three and a half times its own weight) thanks to

aerodynamic downforce. That means that, theoretically, at high speeds they could drive upside

down.

Early experiments with movable wings and high mountings led to some spectacular accidents,

and for the 1970 season regulations were introduced to limit the size and location of wings.

Evolved over time, those rules still hold largely true today. 

Front wings typically have multiple elements and highly complex designs to manage airflow

By the mid-1970s 'ground effect' downforce had been discovered. Lotus engineers found out that

by cleverly designing the underside of the car, the entire chassis could be made to act like one

giant wing which sucked the car to the road. The ultimate example of this thinking was the

Brabham BT46B, designed by Gordon Murray, which actually used a cooling fan to extract air

from a sealed area under the car, creating enormous downforce. After technical challenges from

other teams it was withdrawn after a single race. Soon after rule changes followed to limit the

benefits of 'ground effects' - firstly a ban on the skirts used to contain the low pressure area, then

later a requirement for a 'stepped floor'.

In the years that have followed aerodynamic development has been more linear, though ever

increasing speeds and various other factors have led the sport’s regulators to tweak and tighten

the regulations on several occasions. 

As a result, today’s aerodynamicists have considerably less freedom than their counterparts from

the past, with strict rules dictating the height, width and location of bodywork. However, with

every additional kilogram of downforce equating to several milliseconds of lap time saved, the

teams still invest considerable amounts of time and money into wind tunnel programmes and

computational fluid dynamics (CFD) – the two main forms of aerodynamic research. 

The most obvious aerodynamic devices on a Formula One car are the front and rear wings,

which together account for around 60 percent of overall downforce (with the floor responsible

for the majority of the rest). These wings are fitted with different profiles depending on the

downforce requirements of a particular track. Tight, slow circuits like Monaco require very

aggressive wing profiles to maximise downforce, whilst at high-speed circuits like Monza the

amount of wing is minimised to reduce drag and increa se speed on the long

straights. 

Every single surface of a modern Formula One car, from the shape of the suspension links to that

of the driver's helmet - has its aerodynamic effects considered. This is because disrupted air,

where the flow 'separates' from the body, creates turbulence which in turn creates drag and slows

the car down. In fact, if you look closely at a modern car you will see that almost as much effort

has been spent reducing drag and managing airflow as increasing downforce - from the vertical

endplates fitted to wings to prevent vortices forming to the diffuser mounted low at the rear,

which helps to re-equalise pressure of the faster-flowing air that has passed under the car and

would otherwise create a low-pressure 'balloon' dragging at the back. But despite this, designers

can't make their cars too 'slippery', as a good supply of airflow has to be ensured to help cool the

various parts of the power unit.

The ingenuity of F1 engineers means that every now and then a loophole will be found in the

regulations and a clever aerodynamic solution will be introduced. More often than not these

devices, such as double diffusers, F-ducts and exhaust-blown diffusers, will be swiftly banned,

but one innovation that has been actively endorsed is the DRS (Drag Reduction System) rear

wing. This device, which was introduced to encourage more overtaking, allows drivers to adjust

the angle of the main plane of the rear wing to reduce drag and increase straight-line speed,

though it may only be used on specific parts of the track and when a driver is within one second

of the car ahead in a race.

Advancements in Aerodynamic Devices

Front wing analysis:

Endplates

In the months before any 2014 car was launched, it became clear teams would have a challenge with getting air around the wheel, avoiding drag and turbulent airflow coming from the wheel wake, because of a reduction of 75mm on both sides of the front wing. Many, including myself, believed teams would choose to sacrifice even more front wing area to create endplates that bended more aggressively to get air away from the wheel.

Surprisingly, most teams chose not to. This is because they converged, throughout the years, to an “endplate-less” design. They for fill the mandatory bodywork that makes up the endplate, but actually let the front wing itself do most of the work in getting air around the tire. Still, since the endplate has to be there, teams utilize it to help the front wing in this aspect.Mercedes’ solution actually goes way back to its 2009 predecessor Brawn team. Just getting started with radical aero rules changes, they came up with a unique solution of 2 smaller endplates partly overlapping each other. That year included, Mercedes actually kept that very same design for 3 years, with only very subtle changes. Such was the efficiency of its design. Coming into 2012, they made changes to it, resembling more closely its current iteration:

Being remarkably simple, it does have a few functions. Air coming from the lower wing elements gets leaked out in the gap in between the 2 endplates. The latter endplate meets up with the last 3 front wing elements, bleeding off more high pressure at that point. The endplates bend subtly outwards, just enough to direct air away from the wheel. Interestingly, Mercedes copied a solution from Lotus F1, adding a small flap to the latter endplate:

Lotus came up with this solution, albeit in a slightly different form, at Spain 2013. Its purpose isn’t completely clear, but I believe it tries to keep the faster moving air coming from the outer edges of the first wing elements, close to the footplate, not interrupting with the slower moving air coming from the latter wing elements, which have a higher angle of attack. That way the higher pressure air doesn’t get sucked in the lower pressure air and avoids contact with the wheel wake. A vortex will probably also be created at its tip, further separating the 2 flows. It’ll probably create a little bit of lift and drag, but it should overall have a beneficial effect.

Plain WingThe front wing itself is also a clear evolution from last year. They kept the same amount of elements, 5, but while only the upper element had a slot through and through, this year the 2

upper elements are just that.

More elements and longer slots keep the wing from stalling at high angles of attack. While technically they can use that for higher angles of attack, I believe it’s more a solution to the turbulent air from the rotating wheel, which normally messes up the airflow beneath the wing. Bleeding off cleaner airflow to underneath the wing will help in keeping airflow underneath the wing attached, preventing sudden downforce loss.The endplate-less design becomes very apparent with the other parts removed. The outer edges of the elements try to roll up the airflow into a powerful vortex, accelerating air into an outwards bending flow. The upper element has its highest AoA nearer the edges, with a very interesting setup around it.

First of all Mercedes added a small inverted gurney flap right on top of the element (highlighted in light blue) and also right in front of the tire. Air underneath it gets blocked, creating a rotating flow structure. This will push the rest of the air much higher, again to ensure minimal interference from the tire. They aid this process with what must be the most twisted carbon fiber piece on the grid (yellow). This piece spans over the 2 uppermost elements and together with the endplate boxes in airflow in the path of the tire, separating it completely from the other airflow. While this solution isn’t beneficial for downforce creation, it does help significantly in reducing wheel drag, and also creates a low pressure field behind it, sucking in air coming from underneath the front wing. Also note that the twisted vane is integrated in the wing flap adjuster, which curls back down to the middle element. Clearly a lot of effort has been put into this.

The 2 elements that have slots through and through create a vortex at their tips. Last year Mercedes only choose to do so at the uppermost element, but this year they saw it needed to have 2 tips creating a single stronger vortex. This vortex passes along the Y250 line, a critical area for airflow moving to the splitter and floor.

Cascades

This part has been largely overhauled since last year, yet also keeping some trademark solutions. First of all, Mercedes dropped the r-winglet, which created a bit of downforce. Since downforce levels have been reduced, that winglet is less needed. The R-winglet also created another vortex along the Y250-line, but Mercedes felt a stronger vortex at the wing tips could do the job as well. We’ll see if the r-winglet pops back up during the season.

Mercedes expanded the cascade attached to the endplate, added a J-part (yellow), added a small vertical turning vane (blue) and twisted all vertical pieces outwards, in an aggressive attempt to get again air away from the tires. Also note they kept the small flick at the middle plate of the cascade (red circle) (this was the inner endplate of the cascade in 2013), as well as the IR sensor (green).

Complete Picture

. The mounting pillar of the cascades for instance is placed right in the path of the flap adjuster piece, directing air from the second it touches the wing. Vortices coming off the vanes and plates of the cascade set up airflow structures that close off even more the ‘boxed-in’ airflow ahead of the tire. The Y250 vortex will also meet up with the turning vanes underneath the chassis further down the road. And air between the endplates and wing elements gets nicely guided towards the last element which bends the airflow very aggressively away from -yet again- the tire.

It also shows that modern front wings are just way more than downforce-production devices, acting as complex flow conditioners to both set up airflow patterns across the car and minimizing wheel drag.

All in all this a very detailed front wing to start the year with. I don’t see any major overhauls coming just yet. However, with the team bound to recuperate more and more rear downforce across the season, they will have to gain the same amount out of the front wing. Changing the angle of attack isn’t as convenient as in the past, influencing airflow, forcing perhaps at one point to completely overhaul the front wing. However, for now they clearly have a strong base to build on.

Engine Air Intake - Airbox, ScoopSucking warm air in from the engine bay is a great way to lose power. Getting enough fresh, cold air into the cylinders is a challenge on normally aspirated cars, but even harder on forced air vehicles that use a turbocharger or a supercharger, since these devices raise the air temperature as they raise the air pressure. Consequently you often see intercoolers (sometimes called aftercoolers) and big scoops. Make sure you have a cold air feed pipe to get cool air from outside of the engine bay - cold air carries more oxygen. Motorcyclists and car enthusiasts use the term airbox for what might more properly be described as an air intake chamber. Older engines drew air directly from the surroundings into each individual carburetor. Modern engines instead draw air into an airbox (an air intake chamber), which is connected by individual hoses to each carburetor, or directly to the intake ports in fuel-injected engines. This allows the use of one air filter instead of many, and allows the designers to exploit the properties of air to improve performance. The standard mods include a Cold Air Intake box, which replaces the stock air filter box and panel filter with an airbox that seals against the bonnet, or has a sealed top, and opens to the rear cowl to get air from the cowl opening in front of the windshield for example. Airboxes do slow the air down. That converts the kinetic energy of the air into static pressure. A good airbox is shaped like a diffuser 'bent' round a corner. A bad one isn't... If you assume incompressibility so Bernoulli's equation is valid, you can easily calculate the effect.Refreshing myself on my old college physics text, I can now understand that Bernoulli's equation tells us that the pressure increases because the air slows down.Ram-air intake is any intake design which uses the dynamic air pressure created by vehicle motion to increase the static air pressure inside of the intake manifold on an engine, thus allowing a greater mass flow through the cylinder intake valve and hence increasing engine power. Naturally aspirated Formula 1 racing engines have tuned intake systems and can now achieve volumetric efficiencies in excess of 175% and peak engine speeds in excess of 18,000 rev/min. Engines designed for single seater racing commonly dispense with the intake manifold and its convoluted and restricting flow path preferring single lengths of pipe feeding each cylinder separately from only one chamber. An investigation into the intake process on a single cylinder racing engine has shown that inertial ram effects make a strong contribution to the intake process at high engine speeds whereas acoustic resonance effects are more important to the rather weak wave action that occurs at low engine speeds. An acoustic model of the resonant wave action has proved useful in distinguishing between these two effects.Ram TheorySir Isaac Newton created three "law's of motion".More commonly known as the "law of inertia", the first law of motion says:"An object at rest tends to stay at rest" and"An object in motion tends to stay in motion".This law is the foundation for Ram Induction. Visualize the intake cycle of the engine as air flowing through the intake manifold runner, past the intake valve, and into the cylinder. Everything is fine until the intake valve shuts. Here is where the law of inertia comes to play - because the air was in motion, it wants to stay in motion. But the air can't go anywhere because the valve is shut so it piles up against the valve like a chain accident on the freeway. With one piece of air piling up on the next piece of air on the next on the next, the air becomes compressed. This compressed air has to go somewhere so it turns around and flows back through the intake manifold runner in the form of a pressure wave. This pressure wave bounces back and forth in the runner and if it arrives back at the intake valve when the valve opens (proper arrival

time), it is drawn into the engine. This bouncing pressure wave of air and the proper arrival time at the intake valve creates a form of supercharging. In order to create this supercharging, all of the variables have to be aligned perfectly so the pressure wave arrives at the intake valve at the right time. This combination of synchronized events is known as 'resonant conditions'.The following parameters affect the arrival of our pressure wave at the intake valve:Engine speedThe number of crank rotation degrees the intake valve is closed.Length of the intake runner tube. If these parameters are not balanced properly, ram induction doesn't work. RAM Induction didn't die with the letter cars. In fact, RAM induction is so common today that almost every new engine design incorporates the concept. When you look at those snake-like intake manifolds in the new 300M, Ferraris or the V-10 Viper, you are looking at ram induction. Normally, but not always, RAM air intake going together with air scoop. A bonnet or roof scoop is an upraised component on the hood or roof of a car that allows a flow of air to directly enter the engine compartment. It has one opening only and is closed on all other sides. Its main function is to allow a direct flow of air to the engine, hence the need for it to be upraised so as to effectively channel air to the engine compartment. It may be closed, and thus purely decorative, or serve to enhance performance in several possible ways. At higher road speeds, a properly designed hood scoop can increase the speed and pressure with which air enters the engine's intake, creating a resonance supercharging effect. Such effects are typically only felt at very high speeds, making RAM air primarily useful for racing, not street performance. Pontiac used the trade name Ram Air to describe its engines equipped with functional scoops. Despite the name, most of these systems only provided cool air, with little or no supercharging effect. The RAM air intake works by reducing the intake air velocity by increasing the cross sectional area of the intake ducting. When air velocity goes down the dynamic pressure is reduced while the static pressure is increased. The increased static pressure in the plenum chamber has a positive effect on engine power, both because of the pressure itself and the increased air density this higher pressure gives. Ram-air systems are used on high performance vehicles, most often on motorcycles and race cars. Ram-air has been a feature on some cars since the late sixties, but fell out of favor in the seventies, and has only recently made a comeback. At low speeds increases in static pressure are however limited to a few percent. Given that the air velocity is reduced to zero without losses the pressure increase can be calculated according. The lack of losses also means without heating the air. Thus a ram-air intake also is a cold air intake. It should be noted that in some cars the intake is placed behind the radiator, where not only the air is hot, but the pressure is below ambient pressure. Modern parachutes use a ram-air system to pressurize a series of cells to provide the aerofoil shape.

Canards and vortex generatorsAlso known as dive planes or dive plates, they are small triangle wings attached to the front spoiler of a car for the purposes of modifying the aerodynamic characteristics of the car in a modest way. Canards help generate downforce in two different ways. First, the canard redirects the oncoming air's momentum upwards, which causes a downward force on the canard. This is only moderate, since the velocity near the skin of the car is significantly slower than in the free stream because of boundary layer effect. In addition, canards, together with vortex generators, generate strong vortices that travel down the sides of the car and act as a barrier. If the canards

are positioned correctly, these strong vortices act to keep high-pressure air around the car from entering the low-pressure underbody region, thus maintaining more downforce. If air was allowed to enter the underside, the pressure would inevitably rise, reducing downforce. Therefore, these strong vortices act like a virtual curtain or dam, restricting higher-pressure air around the car's sides from entering the underbody region. Unfortunately, canards are not very efficient, since the strong vortices and position of canards create a significant amount of drag. They are more useful for fine-tuning aerodynamic balance. The bumper canards, once installed, provide additional small amount of downforce at the front of the vehicle, adjusting the balance of traction and thus improving the handling characteristics of the car. Very often, front bumper canards are fitted together with vortex generators. Vortex generators are smaller triangle winglets fitted few centimeters higher of the bigger canards. Vortex generators help to guide the air flow on cars with very steep drop-off angles between the roof and the rear window. Air flow has a tendency to become turbulent as it separates from the surface of the car in this region. This turbulent air causes drag and reduces the effectiveness of a rear wing. They help to reduce drag and improve the effectiveness of the rear wing by delaying the air flow separation and reducing turbulence. In addition, vortex generators generate strong vortices that travel down the sides of the car and act as a barrier explained before, but only if positioned correctly. As a result, the low pressure under the car is maintained and downforce is maximized. In high performance racing, bumper canards and vortex generators are most likely to be installed on racing vehicles which are based on conventional road cars such as Stock Cars, Touring Cars and GT Cars where the car's essentially stock bodies (designed for road-use) have not already been designed to provide optimum aerodynamic characteristics for track use. But they are used in Formula 1, LeMan series, DTM racing and now I am seeing them even on NASCAR cars. Basic aerodynamic principles dictate that the downforce created by air pressure on a surface increases exponentially with speed, thus, as with many aerodynamic modifications the bumper canards are best suited to the high speed of motor racing. Due to strength and weight considerations, bumper canards designed for race use were originally fabricated from carbon fiber reinforced plastic. The high strength to weight ratio and desirable appearance of this material ensures that bumper canards currently sold for road-going cars are often also made from this material. Bumper canards and vortex generators are generally made either as a flat sheet 'triangles' with additional edging strips (for mounting and directing airflow) or as a bespoke molded component utilizing the strength of the material and sophisticated match tooling to integrate the necessary upturns and curvature into a single piece of carbon fiber. Bumper canards are relatively simple to install and are often available with slightly different curvature to match the shape of the front spoiler of the vehicle to which they will be fitted. They are most commonly installed in sets of four, a larger canard and a smaller vortex generator on each side of the bumper with the larger canard at the bottom. Commercially available bumper canards include a 'mounting kit'. There is a set of high quality bolts which fasten through holes drilled in the front bumper to accommodate the canards.Canards should be installed with the large face at the front and aligned such that they do not protrude outside the existing outer line of the car body (so as to avoid creating a safety hazard). This ensures that the main area of wing surface is as far forward on the vehicle as possible in the clean air stream. Whether bumper canards installed on road-going cars are a genuine performance enhancement or simply a cosmetic modification? How do you know if they work? How can you measure the lift they are reducing? Also is there any science behind the shape and attack angles? First of all, on street cars traveling at legal or even near legal speeds such devices would make only a very tiny difference, if any, and if you are traveling in such a manner that this

tiny difference has any effect on your ability to control the vehicle, then you should stop this practice. The amount of down force generated is related to the speed of air passing over/under the wing. Faster speeds mean more down force. Racing vehicles that use this technology are traveling two to three times faster than any street legal vehicle should be traveling, and they are dealing in hundredths of seconds for victories worth millions of dollars. People who are attaching these wings to street legal vehicles are either using them only for decoration, or are modifying their vehicle with the intention of using it for racing. In some rare cases they are built into the design of a street legal sports car. Of course those vehicles are designed from the start to be street legal, but fully capable of competing in races right from the factory. Many manufacturers however are looking at the shape of the underside of their vehicles either to maximize down force, or to minimize fuel consumption. The real racer will work on this area first before attaching tiny wings to the front of his car. If after reading this you still want to know exactly how much downforce the canard will generate, then either the packaging should say, or the manufacturer's website should say. If they don't say, then assume it is only for decorative purposes, and will actually increase drag without improving performance.

DiffuserOnce the potential of using aerodynamic downforce to win races was realized, designers began experimenting with methods other than simply attaching inverted wings. The diffuser is an area of bodywork at the rear of the car, although the term "Diffuser" is technically incorrect, it is the most popular term applied to this part of the car. The air flowing below the car, exits through the diffuser on the rear of the car. The diffuser is usually find on each side of the central engine and gearbox fairings and is, by the rules, located behind the rear axle line. Although wings and diffusers work similarly, they are based under different concepts. A diffuser serves to eject air out from the underside of the car. This pulling action decreases the velocity of the air below the car, so that the more slowly moving air above the car will push the car into the ground. The suction effect is a result of Bernoulli's equation, which states that where speed of the fluid is higher, pressure must be lower. Therefore the pressure below the racecar must be lower than the pressure at the outlet since the speed of the air below the racecar will be higher than the speed of the air at the outlet. The diffuser in itself doesn't produce a reduction in pressure. Its main function is to decrease the flow's velocity from inlet to outlet (so that at the outlet the flow velocity is similar to the free stream velocity), with a corresponding increase in static pressure. This pressure rise can be used to increase the flow rate through a system, as was known even in Roman times. The diffuser can be considered to have "pumped-down" the underbody, inducing a component of downward force on the vehicle. The pressure rise in the diffuser drives this process, so it is the pressure-recovery behavior of the diffuser that governs the influence on an automobile. This pressure rise is a function of the ratio of the areas at the outlet and the inlet diffuser, where this area ratio is set by the diffuser angle and the vehicle ride height. Its design includes vertical fences, some of which are curved, some stepped, and some angled, but all are developed through constant tweaking and evolution in the wind tunnel. The basic job of these fences is to keep apart the many different types of air flows found at the rear end of a racing car - areas of low pressure air due to the rear wheels, and the rear wing, and the air coming under the floor. All these different air flows have different energy levels and different speeds, and their separation makes them easier to deal with. Showing precious little of the secretive diffuser, F1 rules prohibit under-car shaping or venturis, and mandate a minimum ride height enforced by a

relatively low-tech wear plank or skidblock attached underneath the car. However, there is still scope to shape the area directly under and behind the rear axle line.

F-Duct or Rear Blown WingFirst we need to look at some basic aerodynamic theory regarding wing profiles and lift/drag ratios. At the simplest level a wing generates downforce due to its profile accelerating airflow on its lower surface in relation to the flow over the top surface. If flow is accelerated pressure drops, with the result being a pressure differential between the upper and lower surface of the wing and thus a net downward force. If the angle of attack of a wing is increased it can ultimately 'stall' due to flow separation along the trailing edge, with a resultant loss in downforce and consequently aerodynamic grip.

To get around this problem, dual element or slot-gap wings are used, these allow for some of the high pressure flow from the top surface of the wing to bleed to the lower surface of the next flap energizing the flow. This increases the speed of the flow under the wing, increasing downforce and reducing the boundary flow separation.

If you look at a F1 rear wing few years ago, you can see this concept taken to the extreme,with multi-element wings creating huge amounts of downforce. The downside being a significant drag penalty. However if the flow over the 'flap' section of the wing can be stalled, the lift/drag ratio worsens, but the overall result is a massive drop in the coefficient of downforce, resulting in a net reduction in drag, and the big benefits in relation to top speed. It should however be noted that it is only stalling the trailing edge flow that is beneficial as opposed to stalling the entire wing.F-DuctModern F1 wing with proper and attached air stream around itFor an F1 car the rear wing creates around a third of the cars downforce. But running at high speed the drag from the rear wing is tremendous. Anything that reduces the drag of the rear wing will aid top speed. If this can be done in a nonlinear way (ON/OFF), that is; high downforce/drag at lower speeds increasing towards top speed and then less drag only at speeds where car is in a

straight line and doesn't need downforce, then lap times will show an improvement.

Modern F1 wing with air stream detached and stalled due to high angle of attack As airflows over the surface of a wing increase, or angle of attack is bigger, it has a tendency to slow down and separate from the wing. Particularly underneath the wing which runs at a lower pressure than the top surface. This separation initially reduces efficiency by adding drag to the wing, before the airflow totally breaks up and the wing stalls. What is very important in F-duct case is that when a wing stalls the wing loses most of its downforce and most importantly the drag. The steeper a wings angle, the greater chance of separation.

To combat this, aerodynamicists need to speed up and energize the flow near the wings lover surface. To do this they split the wing into separate elements (flaps) and this creates a slot. Through the slot they send high pressure air from above the wing to the area underneath the flap which then speeds and energize the local flow underneath the wing. The more slots the steeper the wing can run. When the driver places his knee over the 'hole' the flow is diverted from cockpit "cooling" into the rest of the duct and this feeds the slot on the rear wing flap. There is enough airflow and pressure through the

Convoluted duct to disrupt the airflow under the rear of the wing, effectively breaking up then flow around the wing. This is what F1 aerodynamicists term a 'stalled' condition, although this is different to the term 'stall' used in aeronautical aerodynamics.In this 'stalled' state, the strong spiraling flows coming off the wing, that lead to the huge drag penalty at highly loaded F1 wing incurs, break up. Without these flows and their resulting drag penalty, the car is able to get to a higher top speed, by around 3-7kmh.When the driver is ready to brake for the next corner, he releases knee from the hole and the airflow passes back into the cockpit and the rear wing flow reattaches, creating downforce and its attendant drag. In this configuration the car can lap normally with its wings delivering maximum downforce.

Gurney FlapFlap, from aerodynamic point of view is hinged or fixed device at the trailing edge of the wing, which can be, in majority of the cases, lowered to increase lift of the wing. The device basically operates by increasing pressure on the pressure side of the wing, decreasing pressure on the suction side, and helping the boundary layer flow stay attached all the way to the trailing edge on the suction side of the airfoil. At the same time, a long wake downstream of the flap containing a pair of counter-rotating vortices can delay or eliminate the flow separation near the trailing edge on the upper surface (aircraft wing) or lower surface (racing car wing).

Correspondingly, the total suction on the airfoil is increased.For the Gurney flap to be effective, it should be mounted at the trailing edge perpendicular to the chord line of airfoil or wing. The flap height must be of the order of local boundary layer thickness. The first picture shows a racing car wing which generates downforce or negative lift as it moves through the air. The air has to accelerate to go around the lower side of the wing and

loses pressure when it speeds up. Remember Bernoulli? The slower air on top is at a higher pressure and presses down on the wing surface. The force a wing produces depends on the airfoil shape, the area of the wing, and the square of its speed through the air.On the second picture is a racing car wing at a high angle of attack. At high angles of attack, air is unable to follow the contour of the lower wing surface and can detach (stall), lowering the efficiency (downforce) of the wing and adding drag.

A small lip on the trailing edge, shown in the third picture, causes a lower pressure just behind it which

Sucks the lower flow back up to the wing surface. The Gurney flap causes some extra drag, but the wing can be run at a higher angle of attack and produces more downforce. Designers can only use limited amount of the wing on a racecar because of rules limiting the number and dimensions of wings. Sidepods and tires get in the way and they just can't be left out. A designer has to get all the downforce possible out of the wing

surfaces used. With Gurney flaps you can get more downforce from the allowable wings because you can run them at higher angles of attack.

FUTURE SCOPE

If you can reduce the drag of the car you will go faster on the straights. If you can use the shape of the car to generate some downward pressure (usually called downforce)

onto the tires, then the car will go faster around the corners. Research into aerodynamics has allowed cornering speeds in “high speed” corners to be much higher than that which is possible without the use of aerodynamic aids, although it has reduced

ultimate top speeds. Track lap times have improved significantly.

The aerodynamics of F1 cars is intensively researched and annual 5% - 10% downforce increases have been possible if rules don’t change too much between seasons. Due to the nature of the vehicles, the aerodynamics of F1 cars are quite different to that of

road cars – with drag coefficients of between 0.7 and 1.0 (it used to be even higher but rules restrict how much area can be used for aerodynamic devices) – this is between

about 2 and 4 times as much as a good modern road car. This is partly due to the rules (running exposed wheels is part of the definition of an open-wheeled racing car) and

partly because downforce is usually much more important than drag.

REFERENCES:

1. Tune to win by Caroll Smith2. Race Car Vehicle Dynamics by Milliken and Milliken3. ‘Inside F1’ – www.formulaone.com4. ‘Aerodynamics’ www.f1technical.net 5. www.wikipedia.com