| AERO BASICS |
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| The same principles that make a plane fly, apply to generating downforce on our cars. Fundamentally speaking, the generation of downforce was arguably the single greatest discovery in the world of racing. |
| If you haven't read the sections on Tires feel free to look them over. If you have read up on tires and consulted the 'Tire Performance Curve' you'll recall that as we increase weight on the tires (load), we increase grip. Increased grip elevates our tires' ability to accelerate in a straight line, and generate more cornering force when we turn. |
| A heavier vehicle will load the tires more, and as such, increase their grip on the road surface. But increasing vehicle weight is the exact opposite of what our goals are as race car tuners. Heavier vehicles are slower, require more power to overcome the laws of inertia, and generate a whole host of other problems, all of which are bad for turning the fastest laps possible. |
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| BERNOULLI'S PRINCIPLE |
| Let's get into a little history, not that it's necessarily applicable in regard to being able to tune our aero bits in Forza Motorsport 3, but it's really cool to know, nonetheless. |
| First of all, in regard to aero, we need to make a differentiation between a 'liquid' and a 'fluid'. When we hear the term fluid, the average person thinks of something wet. But this isn't the case. Carroll Smith has a good definition of the term: |
| '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.' |
| Carroll Smith - Tune To Win - pg. 78 |
| Okay, so you've gathered that air is in fact a fluid. |
| In fluid dynamics, Bernoulli's principle states, in a nutshell, that an increase in the speed of the fluid occurs simultaneously with a decrease in pressure. Bernoulli's principle is named after the mathematician Daniel Bernoulli, who published his principle in his book Hydrodynamica in 1738. |
| This means that the faster air travels, the lower its pressure is. In regard to flight, the airplane wing is designed to split air as it travels through it, and adjust the air speed above and below the wing so that there's low pressure on the top of the wing's surface, and higher pressure on the bottom. This variance in air speed and pressure generates lift. If you take a plane wing and turn it upside down it generates downforce. |
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| In the diagram above, the laws of fluid mechanics state that the two air particles (as represented by the blue and red dots) that start in the same location at the leading edge of the wing, must arrive at the trailing edge at the same time. Since the red dot must travel a greater distance (due to the shape of the wing) than the blue dot, in order for them to arrive at the back of the wing simultaneously, the red dot must travel faster. The accelerated air speed at the bottom of the wing is what causes a variance in air pressure between the top and bottom surfaces, and because it's lower pressure air, we get downforce. |
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