Is there any "real", schooled, aerodynamicists on this BB (no offense, Mr. A) that could explain to me what impact the stepped bottom plane, rear diffuser, low three-section rear wings and so on does to the air behind the car?
The reason why I ask off course has to do with overtaking in F1. Don't give me all this about the cars need less downforce and more mechanical grip, I have heard it millions of times before. And I don't buy the explanation that everything has to do with the "dirty air" that takes downforce off the following car's front wing. Today, even if a car is right up the gearbox (OK, it doesn't happen very often, probably because of the "Dirty air", but you do see it every now and then) when entering a long straight, it can't pass. There has got to be an aerodynamic explanation why the current design of the cars simply won't allow slipstreaming. Today's cars can't even lap lower power cars on the long straight.
What I want to know is how the aerodynamic design has changed during the 90's, and what impact it has on the slipstreaming environment behind the car. My guess is that it's got to have something to do with the stepped bottom plane, and the large amount of (low pressure) air that passes through the rear diffuser. But I'm no aerodynamic expert, just a simple telecom-engineer.
/// JQ
Aerodynamics
Started by
Tipha
, Jun 08 1999 07:16
28 replies to this topic
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#2
MrAerodynamicist
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Posted 08 June 1999 - 16:13
No offense taken, although if you're in no hurry for an answer, I can give you them in 3 years once I've finished my uni course 
MrA
MrA
#3
Janne
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Posted 08 June 1999 - 18:40
Enzo Ferrari once said: Aerodynamics is for those who cannot manufacture good engines.
#4
Tipha
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Posted 08 June 1999 - 07:16
Why don't you think 'dirty air' hinders the following car? I'm guessing, but I would think that downforce is more important than drag when going round corners, and if the car is in the turbulance of the car in front, its wings will not be able to generate as much downforce. (On the straights I guess then drag is more important than downforce -> flexible wings)
Im a few years ahead of Mr.A so maybe I could help, but I don't know what the 'stepped bottom plane, rear diffuser, low three-section rear wings' are!
T
Im a few years ahead of Mr.A so maybe I could help, but I don't know what the 'stepped bottom plane, rear diffuser, low three-section rear wings' are!
T
#5
Joakim Quensel
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Posted 08 June 1999 - 20:10
(excuse me if my English, especially when it comes to difficult technical terms, may not be that good)
It seems to be two major aerodynamic problems that make it difficult for today's F1 cars to overtake:
1) Dirty air, i.e. turbulence that reduces away downforce on the following car's front wing
2) The area behind the car where drag (for the following car) is reduced seems to be shorter
The reduced mechanical grip may make the problem worse, because the cars get more dependent on aerodynamic grip, but I don't think that this is the core question here.
All the aerodynamic discussions I have seen so far have been about 1). I would like to focus at least just as much on 2). My guess is that 1) and 2) are very correlated though. The question is how do we get rid of these problems. In order to come up with a qualified guess, you must know what causes these problems. I certainly don't, even if I have some ideas:
Something have obviously happened during the 90's. Apart from various aerodynamic development, which basically is to increase downforce with a minimum amount of drag, we have seen changes in the undertray (the plank and the two stepped plane introduced 1995), and a lower rear wing which have several sections. I can think of a whole lot of ideas how to get improve overtaking in F1. I don't know if they are any good though, because I lack the aerodynamic knowledge necessary to estimate the aerodynamic effects.
Cars tend to be longer, and together with compact engines, gearboxes and clever design on the exhaust system and cooling systems, there is more aerodynamic freedom for the designers. As I understand it, most of the downforce, other than from the wings, come from the rear diffuser. The regulations is such that 33 cm in front of the rear axis, the two stepped flat bottom ends, and the undertray slopes upwards (this is the rear diffuser). The air slows down, the pressure becomes lower and the downforce is generated. From what I understand, the rear diffuser also help to redirect the air that passes above the chassis to increase the efficiency of the rear wings. What about changing the regulations for example so that the two-stepped plane has to reach all the way back to the car, i.e get rid of the rear diffuser. What would the effect be? Seems logical that this would cause a longer area with reduced drag behind the car, as well as reduce overall downforce, but I don't know
The two step plane reduces downforce. The question is, what effect did it have on the aerodynamic environment behind the car? A lot more air passes under the car, out through the rear diffuser. Is that good or bad?
What about increasing the maximum height for the rear wing. Will give more downforce (otherwise the designers wouldn't place them at maximum height), but maybe it will also contribute to a better slipstreaming environment behind the car. I don't know...
As you can see, there are a lot of things I don't know, but it interests me and I'd be happy too hear from someone who does understand these things.
It seems to be two major aerodynamic problems that make it difficult for today's F1 cars to overtake:
1) Dirty air, i.e. turbulence that reduces away downforce on the following car's front wing
2) The area behind the car where drag (for the following car) is reduced seems to be shorter
The reduced mechanical grip may make the problem worse, because the cars get more dependent on aerodynamic grip, but I don't think that this is the core question here.
All the aerodynamic discussions I have seen so far have been about 1). I would like to focus at least just as much on 2). My guess is that 1) and 2) are very correlated though. The question is how do we get rid of these problems. In order to come up with a qualified guess, you must know what causes these problems. I certainly don't, even if I have some ideas:
Something have obviously happened during the 90's. Apart from various aerodynamic development, which basically is to increase downforce with a minimum amount of drag, we have seen changes in the undertray (the plank and the two stepped plane introduced 1995), and a lower rear wing which have several sections. I can think of a whole lot of ideas how to get improve overtaking in F1. I don't know if they are any good though, because I lack the aerodynamic knowledge necessary to estimate the aerodynamic effects.
Cars tend to be longer, and together with compact engines, gearboxes and clever design on the exhaust system and cooling systems, there is more aerodynamic freedom for the designers. As I understand it, most of the downforce, other than from the wings, come from the rear diffuser. The regulations is such that 33 cm in front of the rear axis, the two stepped flat bottom ends, and the undertray slopes upwards (this is the rear diffuser). The air slows down, the pressure becomes lower and the downforce is generated. From what I understand, the rear diffuser also help to redirect the air that passes above the chassis to increase the efficiency of the rear wings. What about changing the regulations for example so that the two-stepped plane has to reach all the way back to the car, i.e get rid of the rear diffuser. What would the effect be? Seems logical that this would cause a longer area with reduced drag behind the car, as well as reduce overall downforce, but I don't know
The two step plane reduces downforce. The question is, what effect did it have on the aerodynamic environment behind the car? A lot more air passes under the car, out through the rear diffuser. Is that good or bad?
What about increasing the maximum height for the rear wing. Will give more downforce (otherwise the designers wouldn't place them at maximum height), but maybe it will also contribute to a better slipstreaming environment behind the car. I don't know...
As you can see, there are a lot of things I don't know, but it interests me and I'd be happy too hear from someone who does understand these things.
#6
MrAerodynamicist
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Posted 09 June 1999 - 00:58
But it would be much harder to increase the 'tow' distance than it would be to decrease the downforce.
MrA
MrA
#7
SlowDrivr
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Posted 09 June 1999 - 03:23
I don't think increasing the height of the rear wing will help. The reason its at the maximum height is so that its in the cleanest air, away from the body of the car. Making it higher could help it make more downforce. But...
The problem is that the front wing, being closer to the ground and closer to the car in front, gets dirty air and so lowers the downforce on it. Since the front downforce is lower but the rear downforce is about the same, the balance of the car is screwed up and you get bad understeer. A taller rear wing would only make it worse.
I think you have the part about the rear diffuser backwards- when it slopes up and the air slows down, the pressure increases, not decreases. The downforce is generated where the underside is closest to the road, before the diffuser.
I don't know if drafting is part of the problem of not being able to pass or not. I know that F1/CART cars have large Cd (drag coefficients), which would imply that the air behind them is moving forward which would help with drafting. If the long straight is followed by a medium-high speed turn, then the imbalance comes into play- when they try and pass at the end of the straight, they understeer a lot and have to back off. If the straight is followed by a low speed turn, then I'd think they should be able to pass more easily.
If you were to get rid of wings, the designers would focus on lowering Cd, that would allow a car to be close behind another car without messing up its balance. However, it wouldn't be able to use a draft much because of the very good Cd of the car in front of it. I think overall this configuration would make it easier to pass.
The problem is that the front wing, being closer to the ground and closer to the car in front, gets dirty air and so lowers the downforce on it. Since the front downforce is lower but the rear downforce is about the same, the balance of the car is screwed up and you get bad understeer. A taller rear wing would only make it worse.
I think you have the part about the rear diffuser backwards- when it slopes up and the air slows down, the pressure increases, not decreases. The downforce is generated where the underside is closest to the road, before the diffuser.
I don't know if drafting is part of the problem of not being able to pass or not. I know that F1/CART cars have large Cd (drag coefficients), which would imply that the air behind them is moving forward which would help with drafting. If the long straight is followed by a medium-high speed turn, then the imbalance comes into play- when they try and pass at the end of the straight, they understeer a lot and have to back off. If the straight is followed by a low speed turn, then I'd think they should be able to pass more easily.
If you were to get rid of wings, the designers would focus on lowering Cd, that would allow a car to be close behind another car without messing up its balance. However, it wouldn't be able to use a draft much because of the very good Cd of the car in front of it. I think overall this configuration would make it easier to pass.
#8
MrAerodynamicist
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Posted 09 June 1999 - 03:48
Appprently they've made big steps in Cd's over the last few years and now they're quite low.
MrA
MrA
#9
IAM
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Posted 09 June 1999 - 05:30
Rear wings higher, to get into clean air was tried yonks ago, but they broke off and caused tremendous accidents so were banned.
Ian
Ian
#10
Pascal
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Posted 09 June 1999 - 06:09
Maybe Don Capps has this in store: cars during the free practices of the Monaco Grand-Prix 1969. The mother of all wings...
#11
The RedBaron
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Posted 09 June 1999 - 07:02
Interesting topic, learnt something new. I'm just wondering whether the reduction in the width of the car plus the decrease in mechanical grip ie tyres plays a part in all this, or is a combination of various other aspects?
#12
SlowDrivr
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Posted 09 June 1999 - 07:23
Mr A- My statement about Cd's is based on a book I have "Aerodynamics for Racing and Performance Cars" by Aird. It was published recently (1997). It stated that the Cd's for F1 cars was about 0.7 to 1.4, depending on setup (low or high downforce, etc). So it might be slightly out of date but I wouldn't think by much.
#13
Pascal
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Posted 09 June 1999 - 07:49
How about THAT for high wings?
#14
tak
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Posted 09 June 1999 - 08:57
This is a complicated subject--if someone here is qualified to answer it, they would probably be working for one of the teams!
Some real fundamental fluid mechanics do apply here. For a car (or aeroplane), there are two numbers that describe drag. The first is frontal area, the second is the coefficient of drag. Regardless of other changes to the car, this decade has seen the cars get narrower and shorter. The wings don't stick up as much, and they have smaller tires. All of this means a considerably smaller frontal area. The smaller frontal area means the current cars punch a smaller hole in the air--this is (partly) why cars don't get a good tow anymore.
Someone also asked about "dirty air" and why is affect the car behind. I'm sure we've all seen pieces of paper or other debris cought in the wake of a race car--notice how it follows the car? This is a good indication that some air is also following the car. Picture a clear straight on a track. two cars (nose to tail) on that straight are going 250 kph. The first car is seing air going over and around it at 250 kph. Some of that air gets momentum and "follows" the car. The result is that the second car sees air traveling at less than 250kph, even though the cars true ground speed is 250 kph. Aerodynamic load (lift or drag) go as a function of velocity squared. If the second car sees air traveling at 90% of free stream velocity, the second car will only have (.9 x .9) 81% of the downforce of the first car. The change from free stream velocity is a function of how close the two cars are--the closer together, the higher the change.
It's not much, but I hope it helps!
Some real fundamental fluid mechanics do apply here. For a car (or aeroplane), there are two numbers that describe drag. The first is frontal area, the second is the coefficient of drag. Regardless of other changes to the car, this decade has seen the cars get narrower and shorter. The wings don't stick up as much, and they have smaller tires. All of this means a considerably smaller frontal area. The smaller frontal area means the current cars punch a smaller hole in the air--this is (partly) why cars don't get a good tow anymore.
Someone also asked about "dirty air" and why is affect the car behind. I'm sure we've all seen pieces of paper or other debris cought in the wake of a race car--notice how it follows the car? This is a good indication that some air is also following the car. Picture a clear straight on a track. two cars (nose to tail) on that straight are going 250 kph. The first car is seing air going over and around it at 250 kph. Some of that air gets momentum and "follows" the car. The result is that the second car sees air traveling at less than 250kph, even though the cars true ground speed is 250 kph. Aerodynamic load (lift or drag) go as a function of velocity squared. If the second car sees air traveling at 90% of free stream velocity, the second car will only have (.9 x .9) 81% of the downforce of the first car. The change from free stream velocity is a function of how close the two cars are--the closer together, the higher the change.
It's not much, but I hope it helps!
#15
Joakim Quensel
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Posted 09 June 1999 - 15:27
About the rear diffuser:
If we compare the undertray and the rear diffuser to a flat horn, into which you blow air, where only one side (facing upwards) slopes up, and the bottom is flat. What happens to the air at the wide section of the horn? The air slows down for sure, but how is actually the downforce creeated?
What does the turbulence behind the horn look like? Will it "suck down" air from above and decrease the length of the tow? Does it decrease the air pressure close to the ground ("dirty air")?
If you compare the stepped bottom undertray (introduced 1995) by increasing the narrow end of the horn, and blow more air into it, how is the airflow behind the horn affected?
Less downforce? Shorter tow? More/less turbulence?
If you "regulate away" the rear diffuser, and you can compare it to replacing the horn with a square tunnel. Will this take away most of the downforce? Do we get less turbulence and longer tow?
If we compare the undertray and the rear diffuser to a flat horn, into which you blow air, where only one side (facing upwards) slopes up, and the bottom is flat. What happens to the air at the wide section of the horn? The air slows down for sure, but how is actually the downforce creeated?
What does the turbulence behind the horn look like? Will it "suck down" air from above and decrease the length of the tow? Does it decrease the air pressure close to the ground ("dirty air")?
If you compare the stepped bottom undertray (introduced 1995) by increasing the narrow end of the horn, and blow more air into it, how is the airflow behind the horn affected?
Less downforce? Shorter tow? More/less turbulence?
If you "regulate away" the rear diffuser, and you can compare it to replacing the horn with a square tunnel. Will this take away most of the downforce? Do we get less turbulence and longer tow?
#16
DLH
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Posted 09 June 1999 - 07:06
Tak,
very interesting, but on a straight that reduction in downforce shouldn't matter. It's only when a corner is reached! But the second car is facing air not at 250kph, and thus should be able to gain an extra kph or 5 allowing momentum to overtake. But this 'never' happens between similarly powered cars (because the following car is never close enough to benefit from this)
And as for dirty air - why do you think planes can drop a 1000 ft in seconds if they hit turbulence? Wings, of any description be it sails, car wings or plane wings, only develop power/lift if smooth air passes over them. The moment they pass through turbulent air they lose it. Almost too obvious to post.
Cheers
David
very interesting, but on a straight that reduction in downforce shouldn't matter. It's only when a corner is reached! But the second car is facing air not at 250kph, and thus should be able to gain an extra kph or 5 allowing momentum to overtake. But this 'never' happens between similarly powered cars (because the following car is never close enough to benefit from this)
And as for dirty air - why do you think planes can drop a 1000 ft in seconds if they hit turbulence? Wings, of any description be it sails, car wings or plane wings, only develop power/lift if smooth air passes over them. The moment they pass through turbulent air they lose it. Almost too obvious to post.
Cheers
David
#17
Christiaan
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Posted 09 June 1999 - 07:16
JQ, remember that the objective is to have as much air passing on the undertray as possible so that you create a low pressure zone in accordance to Bernoullis principle.
I have asked myself a lot of aerodynamics questions with regard to F1. I did not know that the Cd's were so high. I have now realised that the complexity in F1 aerodynamics is great. The reason being that active aero~ are not allowed thus the designer has to produce a car for all seasons. The race leader will benefit from one setup and the second man will benefit from another. As is several airflow patterns are not enough the designer also has to come up with design for a very wide bad of speeds. This is why we started seeing flexible wings and also exhaust systems like Ferraris (which Mclaren is rumoured to be currently trying to clone)
I am only speculating here but I also think that the reason its getting harder to overtake on the straights is that there might be a very wide wake of turbelent streams behing a car. That would indeed slow down a car in over-taking position.
I have asked myself a lot of aerodynamics questions with regard to F1. I did not know that the Cd's were so high. I have now realised that the complexity in F1 aerodynamics is great. The reason being that active aero~ are not allowed thus the designer has to produce a car for all seasons. The race leader will benefit from one setup and the second man will benefit from another. As is several airflow patterns are not enough the designer also has to come up with design for a very wide bad of speeds. This is why we started seeing flexible wings and also exhaust systems like Ferraris (which Mclaren is rumoured to be currently trying to clone)
I am only speculating here but I also think that the reason its getting harder to overtake on the straights is that there might be a very wide wake of turbelent streams behing a car. That would indeed slow down a car in over-taking position.
#18
SlowDrivr
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Posted 10 June 1999 - 03:02
I was also surprised at how high the Cd is for F1 cars also. There are two reasons why-
1) The wheels sticking out. If they could be covered up like a street car that would lower the amount of drag they create.
2) The wings. It seems to be a law that whenever you create lift or downforce you also create drag. Of course the designers try to get the best downforce/drag ratio possible, but with 4000lbs of downforce there will be quite a bit of drag coming with it.
That's why I said getting rid of the wings would lower the Cd a lot. Then the wheels would be the dominant source of Cd for the cars.
1) The wheels sticking out. If they could be covered up like a street car that would lower the amount of drag they create.
2) The wings. It seems to be a law that whenever you create lift or downforce you also create drag. Of course the designers try to get the best downforce/drag ratio possible, but with 4000lbs of downforce there will be quite a bit of drag coming with it.
That's why I said getting rid of the wings would lower the Cd a lot. Then the wheels would be the dominant source of Cd for the cars.
#19
MrAerodynamicist
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Posted 10 June 1999 - 03:36
If oyu look closely at the picture, they've got the wings connected directly onto the suspension arms, something thats now illegal.
SlowDrivr, you're correct in that you can't have lift without drag. I'm not going to attempt to really explain it cause I'm not too sure myself and I'd only confuse you. Half-knowledge can be a dangerous thing. Simply, one of the process by which drag is created is the same process that lift is created. [Just don't hold me to that]
MrA
SlowDrivr, you're correct in that you can't have lift without drag. I'm not going to attempt to really explain it cause I'm not too sure myself and I'd only confuse you. Half-knowledge can be a dangerous thing. Simply, one of the process by which drag is created is the same process that lift is created. [Just don't hold me to that
]MrA
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#20
tak
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Posted 10 June 1999 - 08:11
DLH--wings do work in turbulent air--just not as well! Remember that the turbulence encountered by aircraft is a much larger phenominon. It is usually columns of air hundreds of meters accross that are moving up or down, that involves wind shear, local temperature, and density variations. Something F1 don't have to deal with. You are correct that the loss of downforce doesn't matter on the straight, but as soon as the road turns, it does. My example is easier to understand when presented in a straight line.
#21
MrAerodynamicist
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Posted 10 June 1999 - 16:01
tak, what sort of engineer are you?
MrA
MrA
#22
Tipha
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Posted 10 June 1999 - 07:43
Well I still don't know what most of the terms are, but what the hey!
It seems that the downforce/drag problems are mutually exclusive. The way regulations have been going, reduction in tyre sizes and grooves reduces the grip, which must be made up with aerodynamics. Increasing the downforce (whatever the method), causes drag, which helps in the towing effect, but reduces the grip of the following car to a greater effect.
So I would submit that the regulations help in overtaking on the straights, but hinder overtaking in the corners. And it seems that it doesn't help enough on the straights, and stops almost all overtaking in the corners.
So the way to help towing without hindering cornering is to increase drag without increasing downforce. So increase tyre sizes (maybe put more grooves in), make rear wings straight, bigger helmets, parachutes, you get the idea...
T <-- tried for a job at MacLaren, but they wouldnt have me. Wonder why?
It seems that the downforce/drag problems are mutually exclusive. The way regulations have been going, reduction in tyre sizes and grooves reduces the grip, which must be made up with aerodynamics. Increasing the downforce (whatever the method), causes drag, which helps in the towing effect, but reduces the grip of the following car to a greater effect.
So I would submit that the regulations help in overtaking on the straights, but hinder overtaking in the corners. And it seems that it doesn't help enough on the straights, and stops almost all overtaking in the corners.
So the way to help towing without hindering cornering is to increase drag without increasing downforce. So increase tyre sizes (maybe put more grooves in), make rear wings straight, bigger helmets, parachutes, you get the idea...
T <-- tried for a job at MacLaren, but they wouldnt have me. Wonder why?
#23
Joakim Quensel
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Posted 10 June 1999 - 20:57
I read that up to 33% of an F1's car's total downforce come from the rear wing, up to 25% form the front wing. This means that 42% (more on "low wing" tracks) of the downforce come from something other than the wings.
As I understand it, most of this downforce come from the undertray/rear diffuser, that cause a simple form of venturi tunnel (I found some info on www.powerup.com.au/~philmak/GP2MAN/GndEffec.htm ). Am I right about this? What else causes downforce on a F1 car?
And isn't it also so that downforce from wings creates more drag than that from the undertray/rear diffuser? If the goal is to increase drag and reduce downforce, why not just go for a flat undertray, without a up-loping rear diffuser (because this would get rid of the downforce created under the car, right???). Maybe a flat bottom, all the way to the rear end of the car, will also get rid of a lot of the turbulence. I'm not sure about this, but it seems logical that whatever creates downforce is likely to cause turbulence.
As I see it, "the roth of all evil" in F1 is the rear diffuser. I'm not sure at all about this, but that's my conclusion and I would like to hear som arguments why this is not likely to be true.
Regarding drag, the Cd coefficient would be easy to estimate if someone took a picture of a F1 car, taken straight forward, and estimate the frontal area. We pretty much know the topspeed for different tracks, and the relation between power and Cd is:
Power = constant * Cd * area * speed*speed*speed
I don't know the constant (I guess it also depends on the air density but we can assume normal airpressure at sealevel), but I'm sure someone else does.
The large difference in Cd (0.7 - 1.4) seems reasonable. If Cd=0.7 is Hockenheim and 360 km/h, a car with Monaco-setup and Cd=1.4 would do 285 km/h (on a long enough straight). Well, maybe the difference is a little too large, I think tha "Monaco-car" would do a few more km/h.
Does anybody have downforce figures (kg) for F1 cars? Figures per aerodynamic device would be very interesting...
Or good links to pages about race-car aerodynamics? Or books (preferably that you can order by mail)?
Eddie Jordan said that 80% of the F1 development is aerodynamics, so if I want to be technical updated with F1, I guess I have to start learning more about this subject.
As I understand it, most of this downforce come from the undertray/rear diffuser, that cause a simple form of venturi tunnel (I found some info on www.powerup.com.au/~philmak/GP2MAN/GndEffec.htm ). Am I right about this? What else causes downforce on a F1 car?
And isn't it also so that downforce from wings creates more drag than that from the undertray/rear diffuser? If the goal is to increase drag and reduce downforce, why not just go for a flat undertray, without a up-loping rear diffuser (because this would get rid of the downforce created under the car, right???). Maybe a flat bottom, all the way to the rear end of the car, will also get rid of a lot of the turbulence. I'm not sure about this, but it seems logical that whatever creates downforce is likely to cause turbulence.
As I see it, "the roth of all evil" in F1 is the rear diffuser. I'm not sure at all about this, but that's my conclusion and I would like to hear som arguments why this is not likely to be true.
Regarding drag, the Cd coefficient would be easy to estimate if someone took a picture of a F1 car, taken straight forward, and estimate the frontal area. We pretty much know the topspeed for different tracks, and the relation between power and Cd is:
Power = constant * Cd * area * speed*speed*speed
I don't know the constant (I guess it also depends on the air density but we can assume normal airpressure at sealevel), but I'm sure someone else does.
The large difference in Cd (0.7 - 1.4) seems reasonable. If Cd=0.7 is Hockenheim and 360 km/h, a car with Monaco-setup and Cd=1.4 would do 285 km/h (on a long enough straight). Well, maybe the difference is a little too large, I think tha "Monaco-car" would do a few more km/h.
Does anybody have downforce figures (kg) for F1 cars? Figures per aerodynamic device would be very interesting...
Or good links to pages about race-car aerodynamics? Or books (preferably that you can order by mail)?
Eddie Jordan said that 80% of the F1 development is aerodynamics, so if I want to be technical updated with F1, I guess I have to start learning more about this subject.
#24
MrAerodynamicist
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Posted 10 June 1999 - 21:26
Had a quick flick though this weeks autosport in the shop earlier. Apprently the front wing can lose around 33% of it's downforce when following another car. It's this which gives the massive understeer and thus makes it hard to follow the car.
The full equation should be:
Power = 0.5 * air density * Cl * S * (V^3)
MrA
The full equation should be:
Power = 0.5 * air density * Cl * S * (V^3)
MrA
#25
Joakim Quensel
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Posted 10 June 1999 - 21:39
And the airdensity is...
Cl=Cd?
S=Frontal area?
[This message has been edited by Joakim Quensel (edited 06-10-99).]
Cl=Cd?
S=Frontal area?
[This message has been edited by Joakim Quensel (edited 06-10-99).]
#26
Yelnats
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- 2,026 posts
- Joined: May 99
Member
Posted 10 June 1999 - 23:13
First lets review the factors that have changed since 1997 Hungary, when 3 cars were able to pass Micheal Schumacher's Ferrari in as many laps.
These changes can be resolved to two catagories, TOW and GRIP.
TOW- 1999 F1 cars provide less tow on the straights due to;
i) reduced over all car width
ii) narrower tires
both conspiring to reduce width and length of the hole punched in the air-stream to provide a tow for a following car.
GRIP- Less mechanical grip on the corners and more dependance on aerodynamic down-force due due to;
1. Reduced tire contact patch. (Harder rubber required)
2. Less competition between tire manufactures to produce sticky tires. (Harder rubber supplied)
Thus the 1999 F1 cars rely more heavily on aerodynamic down-force than the 1997 car so they cannot drive as far into the zone of disturbed air behind a car on a corner without lossing their all important down-force and running wide.
In Hungary 1997 cars could be observed following as closely as .3 seconds whereas in Barcelona 1999 this spaceing was increased to about .7 seconds. So with the reduced tow zone and increased car spacing it proved impossible to latch onto a tow in Barcelona and slingshot by a car on the straight.
I will leave it to someone like Adrian Newey to explain the nuances of venturi and turbulance effects but the rule changes in 1998/99 have killed on-track passing and surprised the rule makers while dissapointing the fans. More grip and more drag makes for more passing so get with it FIA and lets see some bigger softer tires next year and less pit stops and on-track psssing will return.
[This message has been edited by Yelnats (edited 06-10-99).]
These changes can be resolved to two catagories, TOW and GRIP.
TOW- 1999 F1 cars provide less tow on the straights due to;
i) reduced over all car width
ii) narrower tires
both conspiring to reduce width and length of the hole punched in the air-stream to provide a tow for a following car.
GRIP- Less mechanical grip on the corners and more dependance on aerodynamic down-force due due to;
1. Reduced tire contact patch. (Harder rubber required)
2. Less competition between tire manufactures to produce sticky tires. (Harder rubber supplied)
Thus the 1999 F1 cars rely more heavily on aerodynamic down-force than the 1997 car so they cannot drive as far into the zone of disturbed air behind a car on a corner without lossing their all important down-force and running wide.
In Hungary 1997 cars could be observed following as closely as .3 seconds whereas in Barcelona 1999 this spaceing was increased to about .7 seconds. So with the reduced tow zone and increased car spacing it proved impossible to latch onto a tow in Barcelona and slingshot by a car on the straight.
I will leave it to someone like Adrian Newey to explain the nuances of venturi and turbulance effects but the rule changes in 1998/99 have killed on-track passing and surprised the rule makers while dissapointing the fans. More grip and more drag makes for more passing so get with it FIA and lets see some bigger softer tires next year and less pit stops and on-track psssing will return.
[This message has been edited by Yelnats (edited 06-10-99).]
#27
MrAerodynamicist
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- 14,226 posts
- Joined: March 99
Member
Posted 10 June 1999 - 23:23
density could be taken as 1.225Kg/M^3
Sorry, I meant Cd but put down Cl [coefficent of lift] instead. Whoops
MrA
Sorry, I meant Cd but put down Cl [coefficent of lift] instead. Whoops
MrA
#28
Christiaan
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- 1,834 posts
- Joined: May 99
Tech Forum Host
Posted 11 June 1999 - 23:04
I have always thought that a flat undertray would greatly change F1. There might be problems with the fact that a flat undertray would mean that the aerodynamic force distribution curve along the length of the car would be very very different. As I understand it Rubens was carrying a ballast box in the middle of his car, and this was officially banned by FIA. It would become nesceassary to have a large amount of weight in the middle of the car just to keep it balanced.
If the undertray accounts for almost 30% of the total downforce then that would mean a substantial amout of grip gone, an effect similar to banning wings. Of course wings would have to be made with deeper attack angles and that could elevate downforce to previous levels but also create a huge amount of drag. I do not know how feasible it is to rule flat undertrays, but I think there might be too big a trade off.
When a car crashes, have you seen how hard they try to keep the wreck horizontal? The design of the undertray is one of a teams closely guarded secrets.
To answer one of JQ's qtns - in Super Speedway, Andretti said that an F1 car generates enough downforce at full speed to support itself upside down, that means the force is in the order of +6kN.
If the undertray accounts for almost 30% of the total downforce then that would mean a substantial amout of grip gone, an effect similar to banning wings. Of course wings would have to be made with deeper attack angles and that could elevate downforce to previous levels but also create a huge amount of drag. I do not know how feasible it is to rule flat undertrays, but I think there might be too big a trade off.
When a car crashes, have you seen how hard they try to keep the wreck horizontal? The design of the undertray is one of a teams closely guarded secrets.
To answer one of JQ's qtns - in Super Speedway, Andretti said that an F1 car generates enough downforce at full speed to support itself upside down, that means the force is in the order of +6kN.
#29
Senna4ever
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- 349 posts
- Joined: February 99
Member
Posted 12 June 1999 - 14:51
I thought the Autosport article was interesting.
It seems that both Max's ideas for F1 were barking up the wrong tree...
He chose groved tyres - mathematically proven to be the wrong choice.
He chose narrower cars (he reasoned, if I remember, that the lack of overtaking previously was because of lack of space on the track thus making the cars narrower would increase the space and hence offer more overtaking opportunities).
Making the cars narrower, has severly reduced the size of the "hole" made in the air by the car in front, which means that the car behind gets almost no "tow" down the straights. Put that together with the over-reliance on aerodynamics caused by the teams trying to overcome the lack of grip due to the tyres, and it is almost impossible to get close enough through a corner to get a tow down the straights.
We need greater mechanical grip for the corners, and a greater "hole" in the air for "tow". Overtaking should occur with much greater frequency if we achieve that.
It seems that both Max's ideas for F1 were barking up the wrong tree...
He chose groved tyres - mathematically proven to be the wrong choice.
He chose narrower cars (he reasoned, if I remember, that the lack of overtaking previously was because of lack of space on the track thus making the cars narrower would increase the space and hence offer more overtaking opportunities).
Making the cars narrower, has severly reduced the size of the "hole" made in the air by the car in front, which means that the car behind gets almost no "tow" down the straights. Put that together with the over-reliance on aerodynamics caused by the teams trying to overcome the lack of grip due to the tyres, and it is almost impossible to get close enough through a corner to get a tow down the straights.
We need greater mechanical grip for the corners, and a greater "hole" in the air for "tow". Overtaking should occur with much greater frequency if we achieve that.
