Downforce question

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adam2007
adam2007
0
Joined: 30 Mar 2009, 14:34

Downforce question

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what things do formula one use for downforce
i know

wings,diffusers, but what else do they use, vortex generators? more...

plus, on a plane wing air over the top travels longer than the air on bottom due to the shape so presure underneath is high and low on top, is that the oppsiste on formula one?

thank you

DaveKillens
DaveKillens
34
Joined: 20 Jan 2005, 04:02

Re: downforce question

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Welcome to THE forum, adam2007. You have the basic concept correct. Basically, every millimeter of the car's aero design is to 1) channel airflow into and out of inlets for cooling or engine air supply. 2) provide downforce while generating minimal drag.

I suggest you read this. The topic covers a different car type, but the rules are similar.
http://www.nas.nasa.gov/About/Education/Racecar/
Racing should be decided on the track, not the court room.

Scotracer
Scotracer
3
Joined: 22 Apr 2008, 17:09
Location: Edinburgh, Scotland, UK

Re: downforce question

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F1 wings are aircraft wings flipped over.

An F1 rear wing in cross section looks a lot like a airliner during take off (but upside down obviously!):

Image

Image

That is the reason F1 cars produce so much drag. They are going for as much downforce as possible whereas a jet wants the least amount of drag to keep them up in the air. They are looking for an equilibrium whereas F1 is all about pushing into the road at all times.

And yes, they do use vortex generators but they have been severely restricted this year in an effort to clean up the air flow.
Powertrain Cooling Engineer

adam2007
adam2007
0
Joined: 30 Mar 2009, 14:34

Re: downforce question

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sorry another question, this was from massa today on the site

"we ran too low on the downforce and should have run with more rear wing, because as the temperature rises, the grip from the tyres went down and we needed to compensate for that. As the temperature gradually got higher, our cars were running slower and slower in the first sector of the track; the one where you need the most downforce. In other words, the problem we had was related to the way we worked, rather than any specific fault on the car."

I though when track temperature rises the tyres provides more grip, hes saying it doesnt???

Jersey Tom
Jersey Tom
166
Joined: 29 May 2006, 20:49
Location: Huntersville, NC

Re: downforce question

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adam2007 wrote:I though when track temperature rises the tyres provides more grip, hes saying it doesnt???
Nope. It depends. Track temp of 70F will certainly have more tire grip than track temp of 20F.. but when the track gets hot grip often goes down. Sometimes tire temps go down as well (with it hotter out)!

As I am fond of saying, heat is not always good for race tires. It is often bad.

More importantly though Massa is making the comment about downforce. As ambient temp comes up, downforce goes down. The effect isn't trivial.
Grip is a four letter word. All opinions are my own and not those of current or previous employers.

Scotracer
Scotracer
3
Joined: 22 Apr 2008, 17:09
Location: Edinburgh, Scotland, UK

Re: downforce question

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It depends on the rubber compound - they all have an operating window. In general though, the hotter the temperature on track (particularly if it's an unexpectedly high temp) the less grip you get. Also you get less engine power and less downforce. You go slower.
Powertrain Cooling Engineer

The Thorn
The Thorn
0
Joined: 13 Apr 2009, 22:01

Re: downforce question

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About temperatures:

I know somebody who has raced Formula Ford here in Holland. He told me one time that he lapped faster in the beginning and the end of the season, then in high summer, because he got more grip and more power when it was colder. The higher power can be related to the higher airpressure when it is cold.

About grip of tyres. I only have a little advanced knowledge about racing technology, but I think that when the ambient and track temperatures gets higher, you will need to select a tyre compound that is best suited for the situation. A tyre that is too soft will overheat faster, so that is mostly used on slower tracks or when it is colder, with less load on the tyre or less temperature build, and harder tyres are are used on tracks that demand more from the tyre, where wear is a problem, or when it gets hotter.
Every compound has a optimal operating temperature. The best choise of compound is that what gets near optimal temperatures in the given situation.
But when it gets hotter, you will need to use a harder compound, which will give less grip, but does give the most optimal grip compaired to the other compounds.

So my state of thinking says that the hotter it gets, the harder compound you need to use, the less grip you will have. Is this anywere true, or am I missing on something important?

F1 regulations now are somewhat weird for me. There are 2 compounds used in a raceweekend, and those 2 compounds are the same for every team. But every car has other characteristics, and use the tyre in little different ways, because of balanse and suspension geometry. I think this is why some teams sometimes have problems getting grip.

One thing about aerodynamics:
untill last year, we saw the "Indy-flip-up's" on the side of the cars, in front of the rear wheel. It is only said that these were there to guide auir over the tyres, but I also think they generated a pretty good load of downforce. but these parts were not classed as wings. So this might also be some thing on the cars that had 2 reasons to be on the cars.

Jersey Tom
Jersey Tom
166
Joined: 29 May 2006, 20:49
Location: Huntersville, NC

Re: downforce question

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Hardness, grip level, and temperature range are all quasi independent, but related.

It's a very, very, very involved subject.

And specifics are a secret.
Grip is a four letter word. All opinions are my own and not those of current or previous employers.

ubrben
ubrben
29
Joined: 28 Feb 2009, 22:31

Re: downforce question

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In terms of tyre compounds the main factors are compound properties, track surface and temperature.

The two main things you characterise a compound by are dynamic modulus and damping. For a given strength more damping generally means more dynamic stiffness. Changing the relationship between stiffness, damping and strength is what compounds do

The surface comes into things because the dynamic stiffness you need is related to the roughness. Rougher = less stiff compound (using the word soft in this context just confuses things). If it gets hotter you might be able to run a stiffer compound and recover some grip because it might have more damping.

If you have a smooth surface and it's hot you can often run a very high level of damping without the increased stiffness being an issue.

Ben

riff_raff
riff_raff
132
Joined: 24 Dec 2004, 10:18

Re: downforce question

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More specifically, the tread surface temperature at any given instant is what ultimately matters. The tread surface temperature will determine how the tread rubber compound produces grip and how quickly it wears away. Racing tires are designed to be very light, so they have very little structural mass and the absolute minimum amount of rubber in the tread. If the tire has less/greater than optimum inflation pressure during a run, then it won't wear well. The inflation pressure at any given point on the track can vary due to things like local track surface temps, how much the tires are sliding or spinning due to cornering, acceleration or braking, or what inflation pressures were used initially for that tire.

Most of the race tire suppliers now use very sophisticated non-linear FEA models to analyze how their tires will respond during a race.

As for recycling tires, the vulcanized rubber and synthetic fiber belts of a race tire are not really recyclable for anything. They are normally burned as fuel.
"Q: How do you make a small fortune in racing?
A: Start with a large one!"

Belatti
Belatti
33
Joined: 10 Jul 2007, 21:48
Location: Argentina

Re: downforce question

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ubrben wrote:In terms of tyre compounds the main factors are compound properties, track surface and temperature.

The two main things you characterise a compound by are dynamic modulus and damping. For a given strength more damping generally means more dynamic stiffness. Changing the relationship between stiffness, damping and strength is what compounds do

The surface comes into things because the dynamic stiffness you need is related to the roughness. Rougher = less stiff compound (using the word soft in this context just confuses things). If it gets hotter you might be able to run a stiffer compound and recover some grip because it might have more damping.

If you have a smooth surface and it's hot you can often run a very high level of damping without the increased stiffness being an issue.

Ben
I would have thought that stiffness and damping were due to tyre construction/wall thickness rather than compound, but thinking about it a little while and after your comment, I see the thing is wat more complex... as it always is :lol:
"You need great passion, because everything you do with great pleasure, you do well." -Juan Manuel Fangio

"I have no idols. I admire work, dedication and competence." -Ayrton Senna

speedsense
speedsense
13
Joined: 31 May 2009, 19:11
Location: California, USA

Re: downforce question

Post

adam2007 wrote:sorry another question, this was from massa today on the site

"we ran too low on the downforce and should have run with more rear wing, because as the temperature rises, the grip from the tyres went down and we needed to compensate for that. As the temperature gradually got higher, our cars were running slower and slower in the first sector of the track; the one where you need the most downforce. In other words, the problem we had was related to the way we worked, rather than any specific fault on the car."

I though when track temperature rises the tyres provides more grip, hes saying it doesnt???
IMHO- Massa is speaking of the downforce availiable. As the temp went up the downforce went down for the same wing angles. Just like a jet needs higher speed and more flaps to take off if it's a hot day, a race car has the same problem, and needs more wing angle to achieve the same downforce numbers...
"Driving a car as fast as possible (in a race) is all about maintaining the highest possible acceleration level in the appropriate direction." Peter Wright,Techical Director, Team Lotus