A Paper on

AERODYNAMICS IN ACTION

FORMULA ONE CARS

Presented at TECHNOFEST-2010

Organized by VRSEC

Presented by

Krishna Kanth KVSS

Ph No-9553794862

Department of Mechanical Engineering

Jawaharlal Nehru Technological University

Kakinada

East Godavari

Andhra Pradesh -533 003

India

Index

Aerodynamics in Action-Formula One cars

-Abstract

-Introduction

-Earlier Developments

-F1 configuration

-Streamlining the body

-Downforce

-Base Design

-Front wing

-Rear wing

-The high nose

-Diffuser

-Angle of attack

-Conclusion

-References

Aerodynamics In Action

Formula One Car

Abstract

Aerodynamics in Formula One racing is often described as a black art, the real secret to success on the track .In the tough struggle for crucial seconds in Formula 1, aerodynamics play a fundamental role .Small impact make the difference between success and failure. A small change in aerodynamic structure can make the difference. A modern formula one car is a technical master piece. Aerodynamics in formula one deals with how effectively we utilize the air, in favor of requirement of us and not considering it as a frictionally force .Any person driving his/her car at 120-150 KMPH finds it very difficult to control it. But any one has ever imagined how difficult it is to control a car at 300-350 KMPH on road. Practically not possible, but it is all made to work by aerodynamics. With the available technology it is not difficult to manufacture an engine which can run at speed on par with the speed of sound or even greater, but the thing is how effectively a driver controls it on the road. There the role of aerodynamics comes into play. In a sport obsessed with attention to detail, the aerodynamicists are more obsessive than most. The teams invest up to 20% of their total budget in the science of the winds, making their cars even faster with innovative aerodynamic designs. Meticulous precision work is undertaken down to the last millimeter, according to the motto; races are won in the wind tunnel and lost on the track.

INTRODUCTION

First and foremost, aerodynamics is the science of manipulating and making use of airflow. Put simply, aerodynamics deals with the flow of air and how it reacts with bodies in motion. A windmill and an aero plane are both examples of aerodynamics in action. In Formula One racing, high speeds means the air is a formidable force presenting an obstacle to speed but it can be used to the car’s advantage as well. The following deals with different parts of the formula one car aerodynamically streamlined so as to get maximum performance on the track. The paper entirely revolves around the downforce developed on the car

Early Development

In the 1960's the use of soft rubber compounds and wider tyres , demonstrated that good road adhesion and hence cornering ability, was just as important as raw engine power in producing fast lap times. The tyre width factor came as something of a surprise. In simple school experiments on sliding friction between hard surfaces, the friction resistance force is found to be independent of the contact area. It came as a similar surprise to find that the friction could be greater than the contact force between the two surfaces, apparently giving a coefficient greater than one. The desire to further increase the tyre adhesion led the major revolution in racing car design, the introduction of inverted wings, which produce negative lift or 'down force'. Since the tyres lateral adhesion is roughly proportional to the downloading on it, or the friction between tyre and road, adding aerodynamic down force to the weight component improves the adhesion.

F1 configuration

F1 can be considered to be canard configurations in the sense that the front and back wings are on opposite sides of the centre of gravity and both are "lifting" (strongly) in the same direction, in this case down. The car should be considered in (at least) 3 parts; front wing, body and rear wing. Each of these parts should be optimized for down force (i.e. "lifting" down) and low drag, with the accent very definitely on down force. This down force can be likened to a "virtual" increase in weight, pressing the car down onto the road and increasing the available frictional force between the car and the road, therefore enabling higher cornering speeds. This allows today's formula-1-cars to withstand centrifugal forces from 4G as to where a passenger car with sport chassis begins to slip at 1G.

Streamlining the body

An important aspect of aerodynamics is the drag, or resistance, acting on solid bodies moving through air. The drag forces exerted by the air flowing over the car must be overcome by the thrust force developed by the engine. These drag forces can be significantly reduced by streamlining the body.

A streamlined shape is one with a contour that is itself a streamline (such as the airfoil below), or its shape is such that its resistance to the flow of air, water, or another fluid past it is minimized. So when we talk about streamlining a body, we are trying to smooth out the external contours of the shape to create a streamlined flow over it and reduce the flow's resistance to that motion. This resistance is what we call drag, and this particular kind of drag is referred to as form drag. For bodies that are not fully streamlined, the drag force increases approximately with the square of the speed as they move rapidly through the air. The power required, for example, to drive an automobile steadily at medium or high speed is primarily absorbed in overcoming air resistance. The more streamline a vehicle is, the less power it needs to obtain high speeds, and therefore is more economical.

Downforce

Aero foils in motorsports are often called wings, referring to aircraft wings. In fact they are very similar. F1 wings and winglets aim to generate high downforce, by having a high angle of attack, thus also increasing the drag of the aerofoil. The evolution of an airfoil to what it is now is mainly thanks to Bernoulli and Newton, who initially had totally different views on generating downforce. When a gas flows over an object (or when an object moves through a gas), the molecules of the gas are free to move around. They are not closely bound to one another as in a solid. Because the molecules move, there is a velocity (speed plus direction) associated with the gas. Within the gas, the velocity can have very different values at different places near the object. Bernoulli's equation relates the pressure on the object to the local velocity; so as the velocity changes around the object, the pressure changes as well, in the opposite way.

Bernoulli / Newton / Today

Now adding up the velocity variation around the object instead of the pressure variation also determines the aerodynamic force. The integrated velocity variation around the object produces a net turning of the gas flow. From Newton's third law of motion, a turning action of the flow will result in a re-action (aerodynamic force) on the object. So both "Bernoulli" and "Newton" are correct. Integrating the effects of either the pressure or the velocity determines the aerodynamic force on an object. These two equations have lead to the current airfoils used and make optimal use of both theories.

Base Design

Formula One reverses the principles behind an aeroplane wing.In simple terms, an F1 wing is designed so that air flows more rapidly over its lower surface than the upper. This creates an increase in pressure on the top surface compared to the bottom. The resulting pressure difference creates a downward pressure, which we call downforce.This relatively simple concept is made more complex by the relationship between downforce and drag. A wing is so designed that air flows more rapidly over its upper surface than its lower one, leading to a decrease in pressure on the top surface as compared to the bottom. The resulting pressure difference provides the lift that sustains the aircraft in flight. If the wing is turned upside-down, the resultant force is downwards. This explains how performance cars corner at such high speed

The 'downforce' produced pushes the tyre into the road giving more grip.This down force helps the car to firmly grip to the ground. During the turnings of the car the down force compensate to the high centrifugal force on the car giving it high stability. This makes the car to achieve high speed. A modern Formula one car when travelling at high speed can produce a down force which is sufficient for the car to go upside down on the roof of a construction.

Front Wing

The front wing is vital to the entire car, as it is the first part to come in contact with the air, and must be able to leave it relatively undisturbed, whilst producing sufficient downforce for grip on the front tyres . It affects the airflow down the full length of the car and even tiny changes can have huge effects on the overall performance. The front wing accounts for approximately 33% of the total car downforce. The front wing end plates reduce drag and also direct air over the front wheels in attempt to reduce the drag.

The front wing is shaped to direct air to the underside of the car and ultimately feed the undertray. Shaping is also employed to allow air to cool the brakes and radiators. The front wing is a compromise between producing downforce and directing air to other areas of the car.The front wing of a Formula One car is held by two vertical connectors, which also act to shape the airflow underneath the car. The front wing consists of either two or three components, all of which are Shaped and angled to produce the most downforce with the least amount of drag. Each component is adjustable, such that its angle of attack can be altered to suit different circuits, or even during a race in order to deal with understeer or oversteer. Whilst covers over the wheels which sit on either end of the front wing, styled to direct airflow over the wheels such that there is less turbulence as it travels over the rest of the car. Modern endplates often have smaller wings protruding from the outside, producing a small amount of extra downforce and aiding the correction of airflow.

Rear wing

The rear wing helps glue the rear wheels to the track, but it also hugely increases drag. This means designers are constantly working to use as little angle of incidence on the rear wing as possible without harming overall performance.The basic principle of a formula one wing is exactly the same as with a common aircraft. The greatest difference is the direction air is pressed and how that aerodynamic force is generated. Knowing that an aircraft wing does the opposite of an F1 wing, the formula one wing is explained. With a single wing, we do not have to think about turbulence that is generated by the car itself (the engine cover mainly), neither do we have to take in account the direction and speed of outside wind. It is obvious that both these factors decrease the efficiency of an aerofoil. As you can see in the picture above, air flows onto the rear wing with a straight direction (which is often called clean air) at the speed of the car. The white flaps push the air up. Following Newton's law, an action causes a reaction, which is why the aerofoil is being pushed towards the ground by the air. Having in mind that air flowing onto the flaps is pushed upwards, and underflowing air keeps going its own way, a low pressure area (nearing a vacuum at very high speeds) is created right behind the horizontal aerofoils. This 'vacuum' causes a suck up of the air passing under that flap. The underpassing air on the other hand again flows faster in an attempt to equalize pressure on both sides of the aeleron, and thereby increasing the total wing efficiency. Because of the car's speed this is impossible, which is why the effect is maintained. The force that is created by this type of wing, so that the car is pressed onto the ground, is called downforce.

The high nose

The nose cone of formula one car is similar to the nose cone of a modern aircraft .The main advantages of a higher nose need some thinking and knowledge of the complete car to see. At first sight the higher nose is equal to less downforce as by itself it pushes less air up over the nose. Surprisingly the nose is not aimed to push air up, but instead small at the front to allow air flow aside of the nose. The air that passes the nose forms the basic concept of a high nose cone. Having such a nose allows air to go straight through under the nose instead of having to bend around it. While it reduces drag for sure, the front wing planes can span the complete width of the car which in fact allows more downforce to be generated at the front. All air that passed under the nose is then guided under the car or split to either side of the car by the splitter located just in front of the sidepods. But the sky is not all blue as there are also some disadvantages to it. The nose itself of course does not generate much downforce; in fact the higher the nose point the less downforce by itself (this does not include any downforce generated by front wing or floor). Another disadvantage for the highest noses may be visibility from the driver's point of view