Question: What is aerodynamics and how important are they to a racecar?
Answer: Aerodynamics - - - or the dynamic or active effect of air as it moves over a surface of an object - - in the case of a racecar as the object moves through the air -- there is an interaction - - A simple illustration of aerodynamic force is when you put you hand out the window of a vehicle while it is moving, you can feel the force of the air against your hand - - as the vehicle increases in speed the force against you hand increases and if you move your hand around the forces will push your hand in different directions depending on the relative direction of the air over the surface of your hand.
Aerodynamics is what allows birds to fly, aircraft to fly, golf balls to fly etc. etc. - - - the principal is quite simple if you make something smooth and pointed at the front it will penetrate the air with less resistance after the front part if you make the object smooth shaped the air will flow over the mid section more easily and if you make the object pointed again at the rear then the air molecules can easily flow back together - - This same pointy at each end slip through the molecules principal is used in the design of sailboat hulls - - Air actually behaves like water or any other fluid as it flows over the surface of an object -- This smooth shape stuff is all aimed at reducing the resistance to movement and in air terms is called streamlining - - In nature the model for the best streamlined shape is the rain drop - it is naturally shaped by the air as it falls through the air on its way to deposit the dust and acids contained within all over your freshly polished paint work - this natural shape is called teardrop.
We are partially there in our discussion - - The air that doesn't flow easily over the surface and gets all churned up by the shape of the object going through it, is called drag -- Drag enhances the resistance to movement and is generally thought of as a bad thing but it is a fact of life - - The thing to do is try and minimize drag by making air flow over the vehicle as easily as possible. The measurement of drag is referred to as the drag coefficient.
Even the most efficient shapes still have a drag coefficient because no matter how smooth and teardropped the object is it still creates a disturbance in the air when it moves through it. Some of the shapes that are seen on racecars are not the perfect teardrop shape but are shapes that research has shown will help the air bend and flow around the body shape more easily and therefore reduce the effect of drag. If you look at historical racecars most of the early stuff all had some sort of egg shape or primitive teardrop shape - - you also have to remember that even though a particular shape is perhaps ideal it is not always attainable because of the packaging constraints that occur when you are trying to fit all the mechanical components plus a driver and controls into a length and width that is defined by some rule committee that controls the series that you are running the racecar in. There is one other factor too and that is that the larger the vehicle the larger the displacement through the air - - the larger the air displacement (frontal area) the more horsepower necessary to push the vehicle through the air the more horsepower the larger the power plant - - the larger that everything gets means the heavier it gets which also then effects the operating parameters of the vehicle such as braking and ability to negotiate corners - so figuring out the optimum formula or collection of compromises is the real trick - - these dimensional constraints that have been discovered over time have more or less helped develop the formulae that are now dictated by these sanctioning bodies that control the race series So formulae 1 then is based roughly on the best over all packaging compromises to produce the most high tech and fastest cars for a given size to propel a single individual around any one circuit at the highest rate of speed.
If we go a step further and try to convince the air to flow over a surface in a particular fashion we can create the phenomena of LIFT - - by taking advantage of the way that the air molecules basically want to exist in a uniform group we shove a shape like a wing through the molecules of air like your hand out the car window we reduce the drag by the basic teardrop shape of the wing- - but by angling the broad flat surface of the wing in a slightly opposing angle to the relative air flow we build pressure under this same surface and a less pressure on the surface away from the relative air flow - - now if we also modify our basic teardrop shape to convince or make it easier for the air to follow this modified shape we minimize the turbulence created by the air flowing around the shape and reduce the drag but we maintain the pressure differential that we have created on the upper and lower surface of the shape - - the relative air flow then pushed the shape in the direction of the lower pressure - - if you are building an airplane then you want the high pressure on the bottom of the wing pushing up - - if you are building a racecar you want the high pressure on the top pushing down to help hold the car on the track.
When talking about wings and their lift properties we also talk about the wings drag properties - - most wings have a lift to drag ratio of about 3 units of lift to 1 unit of drag. So even though we put wings on the vehicle to help hold it onto the track there is a penalty of more drag that means that it takes more horsepower to push the car through the air - - everything is a compromise- - and racecar builders look at the net gain - - after all everything is aimed at getting around the track in a shorter time than your competitor. One thing we haven't mentioned yet is that as the speed through air increases the effects of the air also increase at a very rapid rate - actually the increase is exponential - so if it takes 100 hp to go 100 mph it may take for example 150 hp to go 120 mph these of course are bogus numbers but you get the point. The reason we mention this is that now we have another phenomenon to deal with - - different wings and different aerodynamic shapes work better at different speeds i.e. Indy cars running at a high bank oval trace at a sustained 200 + mph will run a different wing than when they go to the Molson Indy race through the streets of Toronto where the average speed is less - - just as a plane built to fly in the bush in the north country that needs lots of lift at relatively low speeds will use a totally different wing shape than the F18 Hornet flying miles above the north country bush at a speed that are in the what dreams are made of category.
Now one more huge factor that we haven't discussed is an aerodynamic effect called ground effect. Literally the effect of the air between the moving vehicle and the ground - - it has been known for along time that any aircraft flying close to the ground experiences different flight characteristics - - the theory was that the wings sort of trap the air between the wings and the ground and you get additional lift on the wings from this air cushion under the wings - - thinking back to our earlier discussion on how the wings fly by creating a pressure differential above and below the wing, it stands to reason that if you create more pressure under the wing the lift will go up - - the aircraft is said to be flying in ground effect. When everyone in racing had pretty much caught onto the idea of bolting on an upside down aircraft style wing on to there racecar to create higher speed capabilities especially in corners, the next step was trying to take advantage of ground effect. The early attempts were all based on angling the car floor lower at the front and higher at the rear to try and create a vacuum as the vehicles flat bottom moved along at speed - eventually there were even articulating skirts around the peripheral edges of the body to try and seal of the edges to the ground by letting the skirts rub on the road surfaces to create this seal - - - This worked amazingly well and racecars developed some incredible cornering capabilities - - in stepped the sanctioning body and skirts were banned - under the guise of it's a safety issue.
One of the most innovative individuals ever to get involved in racing and car development was a man called Colin Chapman founder of Lotus Cars -- Chapman figured out that instead of just trying to vacate the air from under the vehicle if he could take advantage of the air flowing under the vehicle in a different way there might be a big pay off. There is a characteristic of flow called a venturi effect. The basic idea is that when air is flowing along in a tube and you squeeze the tube down to a smaller diameter for a short section the air has to accelerate in order to fit through the restricted area in order to get to the larger area on the other side. The venturi effect is that the pressure on the walls of the tube in the restricted area is reduced - - carburetors have venturi sections in the throat - - what happens in the carburetor is that a small hole is drilled in the low pressure section of the
venturi, this small hole is connected to a mini reservoir of fuel called the carburetor bowl and the low pressure sucks fuel from the bowl as it passes through the venturi - the fuel mixes with the air in a ratio that makes it ideal for burning when it gets inside the engine - - This has nothing directly to do with the aerodynamic shape of cars it's just proof of the existence of the venturi effect -- - -- - back to Colin Chapman - he figured out that if you shaped the front of the car in such a manor as to jam air under the front of the body by providing a larger gap rather than a smaller gap then force the air to go through a smaller gap under the car the expand into a larger gap again he could create a venturi effect under the car and create more down force than ever before - - he was right!! Lotus won the formula 1 championship that year and started a whole new development phase - - - the shape of racecars aerodynamically today are all based on the research and development done on the basic principal that Chapman came up with - - - the big advantage to the underwing type car is that the ground effects have a lift to drag production ratio that is twice what a normal wing can produce - - most modern racecars that employ this technology produce a downforce that is higher than the weight of the car and conceivably could drive on the ceiling up side down if a race track was ever constructed in such a fashion.
In a nut shell aerodynamics has a very high level of importance in racing today and you never know what theory from the past will be played out in the future to the advantage of more speed.