Formula One - How Does the Diffuser Create Downforce?

Do you know why airplanes can fly?

as the air goes over it the air is fored to flow up thus pressing down on the rear of the car.

essentialy as lyn said the opposite of flying

http://www.nas.nasa.gov/About/Education/Racecar/physics.html

http://en.wikipedia.org/wiki/Downforce

http://www.superhachi.com/theory/airfoils/

Semantics strikes again. I mistook diffuser for wing.

So, would you call that the inverse of the Bernoulli effect?

how does the vaccum created can increase downforce???

the vacume is between the car and the road or the under belly of the car and the road, Sucking the car down so as well as the weight of the car and the aerofoil you now have the suction all contributing to hold the car down.

why To make cornering faster without the car lifting or sliding off the track.

the downside is on the straight as all that extra down ward force slows the car a little, But if you can go round the corners faster than your competitor then you have the edge

what you explaine is about aerfoil and that to be working of rear wing ???? i want about diffuser

the vacume is between the car and the road or the under belly of the car and the road, Sucking the car down

now have the suction all contributing to hold the car down.

why To make cornering faster without the car lifting or sliding off the track.

the downside is on the straight as all that extra down ward force slows the car a little, But if you can go round the corners faster than your competitor then you have the edge

the above is caused by the defuser creating suction under the car

If you have a flat board and you have positive pressure above it and negative relative pressure under it, the board will be pushed down.

The same is for the car. More atmospheric pressure above the chassis and less on the bottom pushes the tail of the car down.

A wing is a different story and the description as to how a wing works on a car is another thing that everyone has wrong!

The airfoil does not contribute much if anything to the downward force of a wing. Does anyone here know why? Challenge question. :)

"A wing is a different story and the description as to how a wing works on a car is another thing that everyone has wrong!

The airfoil does not contribute much if anything to the downward force of a wing." Does anyone here know why? Challenge question. :)

WRONG Anony mouse.

Please read the following

Wings

The front and rear wings account for the

majority of the overall downforce (approximately 66%) on an F1 car.

Typically, multi-element airfoil sections optimized for relatively low-speed airflow (at least by aerospace standards) are employed with end plates to minimize induced drag.

Front Wing

Front Wing on Formula 1 CarThe 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 an attempt to reduce drag. The front wing is shaped to direct air to the underside of the car and ultimately feed the undertray (described later). 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.

Rear Wing

Rear Wing on Formula 1 CarThe upper portion of the rear wing is a traditional multi-element airfoil (similar to those deployed on aircraft during landing) with end plates, and generates approximately 33% of the total car downforce. The lower portion of the rear wing, usually a single airfoil, 'pulls' or drives air from the undertray.

Ah! Are you sure?

Sorry, the airfoil is not the primary cause of lift and it has nothing to do with Bernoulli. It is something everyone was taught in school, but is wrong. I thought so to when I first took flight lessons.

Yes, wings are designed to reduce drag and lift, but the only way you get lift is by something called angle of attack.

Think I am wrong? Look at an aerobatic plane. The wing profile is symmetrical. They fly just as easily upside down as they do right side up. The reason is angle of attack (AOA), which is the relative angle of the wing to the direction of forward motion.

I can go to the hardware store and buy a piece of plywood and make a wing and it will fly if the AOA is correct or it can supply downforce if the AOA is correct.

So, why make an airfoil for wing? Drag, mostly. An airfoil is much more slippery than plywood, however, go look at a few race cars and you will see some pretty poor airfoils, yet they work just fine.

Again, the contribution of the airfoil is small compared to the AOA of the wing. The wing lift is not due to the Bernoulli effect. Do you know why?

Now that the lecture is complete and I have turned your thinking on its ear, how about a lab to see why?

Go to the kitchen and get a spoon. Turn on the kitchen spout on so that you get a steady stream of water. It should not be turbulent, just a nice flow.

Lightly grasp the spoon at the very end of the handle so that it can rock in your fingers with the curved end hanging down. Now back the convex side of the spoon so that it just contacts the stream of water.

Before you do that, predict what will happen. What will the spoon do when it contacts the water?

Now watch what happens. Can you explain why the spoon does what it does?

Whos talking about Lift ? i am talking about down force and according to the figures the down force is quite considrable from both areo foils.

and yes i know why the aero foils on a race car are shaped the way they are to reduce drag whilst applying down force

"Again, the contribution of the airfoil is small compared to the AOA of the wing. The wing lift is not due to the Bernoulli effect. Do you know why?"

here you appear to be talking about a wing, Where did that come from ? i was talking about aero foils on a car to apply downward force.

sorry cant be arsed to go play in kitchen and whats a spoon got to do with racing cars.

would it have anything to do with coanda ? same as a tea spout ?

re the wing i know angel of attack is imporatant but why are wings on normal aircraft not stunt planes shaped the way they are ? ie large curve on top small curve on bottom.

.

But whats that got to do with a car ?

Airfoils wings, same principles, same thing! Read about it here:

What does a spoon have to do with it? Have you lost all curiosity and is your mind made up on the subject?

I am trying to impart a lesson here, don't get stuck on something else.

All wings (aerofoils, airfoils) work on the same principle. Many people believe it is Bernoulli that explains the effect, but it is Newtonian physics at work.

"... would it have anything to do with coanda ? "

You are getting warm!

"but why are wings on normal aircraft not stunt planes shaped the way they are ?"

Reduced drag and economy.

"But whats that got to do with a car ?"

Great question. They are the same thing, but instead of trying to lift the car up, you are trying to fly into the ground. So, it is an upside down wing. The amount of downforce is a function of the negative angle of attack.

The wing on my car is adjustable so that I can set the AOA to suit the particular track and the course on that track. On the street it is dialed in less aggressively so that I get better fuel economy and there is little need for going 170 mph on the street. ;-)

Anyway, the only reason we diverted to wings was that the first two posts assumed that the diffuser was a wing, but we know now that it isn't. Then I pointed out that the way a wing actually functions is contrary to what most people have been taught. So, it was a side diversion from the original topic.

Are you saying that an asymmetric air foil will generate no lift at 0 angle of attack?

No, but the amount of lift from an airfoil is not the primary component for lift in a wing.

Again, Bernoulli is not why wings produce lift. If it was, symmetrical wings would not fly.

Peter suggested the Coandă effect, which is where a fluid (or air in this case) tends to stick to a surface (wing) and follow the surface's contour.

This is actually how an airfoil works and produces a change in momentum]/i] of the air that imparts lift on a wing, not a rarefaction of air above the top surface. At least not so much.

Angle of Attack is where the heavy lifting comes from in a wing (up or down). Just take your hand and stick it out the window of a moving car and you can see/feel that effect.

Wow that spoon thing is awesome!

Why does it do that?

Take a look at the links

http://en.wikipedia.org/wiki/Coand%C4%83_effect

http://www.google.co.uk/search?q=coanda+effect&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7DKUK_en-GB&redir_esc=&ei=zeX3S7_2NqOI4gazosAI

A common misconception is that Coandă effect is demonstrated when a stream of tap water flows over the back of a spoon held lightly in the stream and the spoon is pulled into the stream. While the flow looks very similar to the air flow over the ping pong ball above (if one could see the air flow), the cause is not really the Coandă effect. Here, because it is a flow of water into air, there is no entrainment of the surrounding fluid (the air) into the jet (the stream of water). This particular demonstration is dominated by surface tension.

Another demonstration is to direct the air flow from, e.g., a vacuum cleaner operating in reverse, tangentially past a round cylinder. A waste basket works well. The air flow seems to "wrap around" the cylinder and can be detected at more than 180° from the incoming flow. Under the right conditions, flow rate, weight of the cylinder, smoothness of the surface it sits on, the cylinder will actually move. Note that the cylinder will not move directly into the flow as a misapplication of the Bernoulli effect would predict, but at a diagonal.

The effect can also be seen by placing a can in front of a lit candle. If one blows directly at the can, the air will bend around it and extinguish the candle.

If two lit candles are placed side-by-side, the heated air from each candle rises and entrains surrounding air. Since both "jets" are trying to entrain common air from the space between the two streams, they are drawn towards one another. This is more apparent if the candles are making a little smoke. This is a demonstration of the Coandă effect without the presence of any surface. In some sense, the plane of symmetry between the two flows can be thought of as the surface.

Having grown up on an Air Force base that had B-52's, I noticed that they take off nose down. When looked at close up the wing does have an positive angle of attack when the plane is on the ground, but as it fly's on take off the wing looks as if it has a neutral AOA. I was always told that was the Bernoulli effect in action. Now since the airfoil is not the primary means of lift how does the B-52 gain lift enough to fly? (Maybe it is like the bumble bee, it was never told it wasn't suppose to be able to fly, sorry just a bad joke.) Is the AOA of the wing positive, but small enough not to be able to see it without being too close to the aircraft? I really like this topic; F-1 and Airplanes too of mans coolest creations!

Thanks

how does the lower pressure induced by the expansion creates vaccum effect and also how that vaccum create downforce

http://charismapro.co.uk/images/F109/F12009/F1%20GUIDE/F1%20Car%20Setup%20-%20How%20to%20adjust%20your%20car%20for%20the%20right%20conditions.htm

3 quarters of a ton down force on front wing at speed

http://www.youtube.com/watch?v=TJZ7agPHbzs&feature=fvw

It looks like Peter is a real fan of F1 with all the great links.

Let me try to answer your question.

The diffuser rarifies the air by taking the volume of air at the front of the car and expanding it to a larger volume. This creates a pressure drop compared to the surrounding air above the car. Any time there is more pressure on one side of a surface than the other that surface will be pushed toward the side that has lower pressure.

A spit ball in a soda straw works this way, your vacuum cleaner works this way, filling a ballon works that way, too.

By diffusing the air underneath the car you create a pressure gradient between the bottom of the car and the top of the car. In this case it is biased at the tail of the car, but the effect is the same, the car experiences greater air pressure on the top than the bottom.

Take a playing card and hold it lightly at one end so it is horizontal. Blow on the top of the card, it will bend down. Take your vacuum cleaner nozzle and place it under the card and it will be pushed (some people say sucked, but it really is pushed) into the nozzle.

Does that help?

http://www.symscape.com/blog/f1_aero

http://gleez.com/articles/did-you-know/some-interesting-info-about-f1-cars

hope it all helps