Aerodynamics and you, why we use wings and splitters Options

[playr158]

Ok in light of recent dicsussions I see the need to bring in another informational topic about something i enjoy very much.

Aerodynamics.

what is it?
how does it work?
why do we need it?

a) What is/are aerodynamics?
"Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object" wiki
"the branch of mechanics that deals with the motion of air and other gases and with the effects of such motion on bodies in the medium." dictionary


b) How does it work?!

I'm going to talk about how aerodynamics works in relation to our application and very simplified.

Downforce (and for that lift as well) are caused by the effects of air pressure on two sides of an object. The direction of pressure is from high to low. High pressure is caused by lower velocity of air on one side of the object and low pressure is from higher velocity of air on the opposite.

Where do we want these pressures to be?

• low pressure zones - under the car's body, under a wing and just outside the front wheels
  
• high pressure zones - over the car body, over the top of a wing

Why?

[1] The car body - means there is a directional air pressure push downward overall on the car. This creates more traction and thus more speed.
[2] The wing - again high pressure pushing downwards on the wing.
[3] Outside front wheels- this low pressure zone creates a vacuum pulling air out of the engine bay. Pulling air out from under the hood, means low pressure zone inside the engine bay, means frontal downforce from the high pressure zone above the hood.

Since its the "hot topic" Wings

The rear spoiler produces two effects at the same time. It provides aero downforce generated from low pressure on the underside as well as aero drag, which creates a cantilever effect that redistributes some of the weight of the car from the front to the rear. Many racers mistake this effect for downforce because it tightens a loose car by adding more weight to the rear of the car.

If we put the car on a set of scales and have four guys pull straight back on the rear spoiler to simulate drag, we would see a change in the front-to-rear percentage of total weight distribution. This is what drag from the spoiler does. If we need the car to turn well (and who doesn't?), then the creation of a high drag effect cannot be in our best interest.

It has been found that the optimum angle for the rear spoiler is between 55 and 60 degrees from horizontal, depending on the type of racetrack. The longer and faster the track, the less spoiler angle we need to run.

ok and now for the pictoral section of this lesson

THIS PICTURE IS FOR UPFORCE - IF YOU FLIP THE PICTURE UPSIDE DOWN, THAT IS HOW IT WORKS ON A CAR
"The wing on an airplane provides lift by causing the air passing over the top of the structure to travel farther and faster than the air moving underneath. Because of the increased speed, the air on top is under less pressure than the air under the wing. The higher pressure under the wing pushes up on the structure, and this provides lift to enable the airplane to fly. We use differential pressure in a similar way to achieve downforce in a car."



"Because the air under the hood is at a lower atmospheric pressure than the air above it, a force much like the one on the airplane wing is created in reverse. We refer to this as downforce. By making changes to the shape of the front nose, fenders, and wheelwells, we can greatly increase the amount of low pressure and the overall downforce effect."




"As the car travels through the air, some of the airflow is directed around the nose and to the sides of the front fenders and wheelwells. If the sides of the nose are angled from a top view, the air will flow out and away from the wheelwells, creating a low-pressure area just outside the wheels. The air under the hood is mostly stationary, and some of that air rushes to the wheelwells to fill the void created by this suction. This creates a low-pressure area under the hood, and the pressure differential between the top and bottom creates the downforce needed to provide more grip in the front of the car."


"A slightly angled nose tends to cut the air more cleanly, and more is directed up and around the nose with a smoother flow."




So.... Aerodynamics are all over our car and effect how it works. But does everything we put on the outside transfer to a change we can feel or even function?!
The answer is no.
you cannot grab any wing or spoiler and slap it to the back of your car and assume you are making downforce. 99% of the time you are making DRAG which is NON-beneficial.
Wings need the correct shape, angle and height in order to be effective.


some learning places:
http://www.sportcompactcarweb.com/features...erms/index.html
http://www.circletrack.com/techarticles/ct...orce/index.html

This post has been edited by playr158: Dec 5, 2008 - 10:38 AM

[richee3]

I just thought of a question. Now that I know that front splitters serve a higher purpose than just sitting there looking good, do rear splitters serve a similar purpose? Do they also deflect air away from under the car or are they there just for the sole purpose of completing the lines you've started on your car by adding the front splitters and skirts? I ask because I wouldn't imagine too much air is flowing behind your tires. I would think (notice I said I would just think- I'm no expert on this subject I'm here to learn!!!) that since the front splitters, front tire, skirts, and rear tire have already cut through the air by the time your rear tires come around that most of the air has been deflected away from the rear splitters.

This post has been edited by richee3: Dec 5, 2008 - 4:59 PM