Ok, this is my first post to this brutally informative forum, so go easy on me. I've lurked around for a while trying to understand what most of you are typing so I'm no aerodynamicist by any means.
I had a question that came up again while reading about BAR's aerodynamics woes at Australia this past weekend:
"Jenson was able to get close to people but couldn’t find enough grip to pass." -Nick Fry
Why is it that every other form of motorsports relies so heavily on drafting and slingshotting out of it to pass? Are F1 cars so aerodynamically efficient (read: reliant) that they are compromised in the slipstream? I've read about some drivers camping farther behind a car to stay out of "dirty air", but how the heck would they expect to pass the car generating it?
Would it be possible to design an aerodynamics package that would actually excel in the turbulent airflow behind another car? Would that package compromise performance when lapping without traffic? How would the car react while transitioning from the "dirty" air to the "clean" air when pulling out to overtake?
Now I don't expect explicit answers to any of these questions, but any insight would help.
Last edited by ruf4play on 10 Mar 2005, 21:46, edited 1 time in total.
Cars are aerodynamically built to run on a clean stream of air. Hence when drafting the downforce isn't really there, although the drag certainly decreases. A good course would be the Circuit de Catalunya, where most of the turns are high speed/medium downforce. W/o the downforce, you can't take the corner at high speed, which will happen when one car is drafting behind another.
As for designing a car to operate in another's wake... I'm sure it's possible. But for the front running teams it's not really a concern...
Bring back wider rear wings, V10s, and tobacco advertisements
Down the straights, it should be possible to overtake using drafting to get close enough to the car infront of you. However, if you stay behind the car, they will have better braking and more downforce for the corner due to more downforce. In otherforms of motorsport, the braking and corning advantage that the lead car has isn't as great compard to the car behind so it could be possible to overtake since the second car has a higher velocity when they pull out from behind the lead car.
West wrote:As for designing a car to operate in another's wake... I'm sure it's possible.
I'm not that positive about this. Downforce generation relies on aerodynamic effects. In the slipstream of another car, the mass of air is, besides more turbulent, effectivelly less (that's why the cars get more speed in the slipstream: lower drag, because of less air). So less air flow around the car = less downforce.
Even if a car would be optimized to run in a turbulent environment, that would reduce its efficience in free flow, which is the closest condition to the situation a F1 works most of the time...
when you see a F1 car go past, there is a massive wake behind the car, that air is moving around with lots of eddies and vorticites disipating the energy in the air.
A fluid that has a velocity has a lower pressure compared to air that is not moving (Bernoulli) and it has a lower pressure due to viscous losses as the first car went through. So the air has a lower pressure behind the vehicle. That is why slipstreaming is effective, when there is less drag to a lower pressure behind the leading car.
Wings use a pressure difference between the top edge and bottom edge to create lift or in this case, downforce. The larger the difference in pressure from the top and bottom surface, the greater the force exerted on the wing.
So since the pressure is lower behind the leading car, the pressure difference across the wing will be less along with the effects of early separation on the undersides of the wings due to adverse pressure gradients. As a result, there is less downforce on the wings.
I guess in theory, you could put bigger wings on the car to make up for the loss in downforce. But, then in the free stream, there would be to much downforce and more importantly, more drag
In a slipsteaming position we should also not forget to mention,that the dirty air from the leading car changes the angle of attack for the front wing of the back car which is not designed for this.
Variable with the distance to the leading car downforce losses also chang.When half car length away,the following car looses appr.53% of the downforce on the front wheels and appr.39% on the rear wheelsSo there is not only a loss in downforce but also very significant change in the aerodynamic balance moving more to the rear of the following car. Less important but also noteable is the bow-effect . When at 1/2 car length away from the front runner the rear car causes this effect which results in a downforce loss of appr.5% on the rear wheels of the leading car. From this is is understandable that the aerodynamic balance of the front car moves more to the front of the leading car.
Losses are not only wing losses but also undertray and diffuser losses.
(Source:Advantage CFD)
For me the best visible point for downforce loss/gain in a race are helicam shots of two following cars racing from a long straight to a low speed corner.
If the following (faster) car closes the gap on the straight, it struggles to go quicker and to overtake just the last edge before the turn when downforce is needed more than ever.
Also when cornering the front car extends again the gap while its wings
are in clean air.The following car struggles to find the same grip level and when it has again a competitable grip level the leading car is already a few car lengths away.
Considering above said I also would say that due to current techregs
the design of a car operating in another's wake is not possible.
So I take it that the consensus is that it would be impossible to design an aero package that takes advantage of the turbulent airstream. I thought it would be complex, but not impossible. Forgive my ignorance, but would there be any way to take advantage of the "directionality" of the vortices generated?
ruf4play wrote:So I take it that the consensus is that it would be impossible to design an aero package that takes advantage of the turbulent airstream. I thought it would be complex, but not impossible. Forgive my ignorance, but would there be any way to take advantage of the "directionality" of the vortices generated?
ruf4play ,I am not an expert but I do remember that I read somewhere
that turbulent airstream is of use for radiator cooling .
Another discussion I do remember was about thoughts of designing a car which effects the front runners vehicle so much that it looses more than the a.m. 5% downforce . In other words to increase the bow-effect .
I do not know if such a design is possible without increasing the drag figure.
The effectiveness of drafting in racing is directly related with the time spent at top speed.
Look at the bikes, 125 cc vs MotoGp, no downforce to blame there.
In 125 cc slipstreaming is fundamental, in many races you have a group of riders very close each other until the end of the race and rarely the winner is the guy exiting first from the last corner.
In MotoGp slipstreaming is almost ineffective but in the very last part of the straight line and the guy exiting first from the last corner wins the race.
That’s because the 125 cc bikes, having little power, do reach the top speed on the first part of the straight line, the leader is at the top speed while the others, exploiting the wake, are still accelerating and this allows them to overtake, also requiring a relatively short space.
MotoGp bikes having lot more power do accelerate quite deeply in the straight line, even if drafting allows the bikes behind to gain a few km/h, the advantage is drastically reduced, furthermore at 330+ km/h, compared with the 220-230 km/h of 125 cc, you need lot more space to close the same gap with the same speed advantage.
Result is that in the same straight line where you see 3 or even 4 overtakes in 125 class, MotoGp bikes are unable to overtake.
Same applies to cars.
F1 cars, even worse than MotoGp bikes, do accelerate for almost all the straight line and only in the last part the acceleration is low enough to allow the car behind to take, theoretically, advantage from the slipstreaming.
Unfortunately when this happens usually the gap is too large, the effect is reduced and it’s hard to get close. But the important thing to notice is that the gap is so large not because of aerodynamics, it is so large simply because of Physics : the same time gap correspond to different distance at different speed, space = time * speed, you know...
So out of slow speed corners, even if the following car is very close to the leading car, it will lose lot of space simply because of the acceleration, even if both cars accelerate at the same rate. Since F1 cars do accelerate at a very high rate the gap builds up very rapidly.
Then at high speed, even if the following car has a speed advantage, it needs lot of space to close the gap, more often than not the straight line is too short to allow it.
At the end, in braking for a very slow corner, exactly for the same physical reason, a gap that at low speed of the corner would be less than a car length (theoretically allowing the car behind to take the inner line and pass) at high speed is large enough for the leading car to close the door, and the driver of the car behind is forced to brake earlier.
Aero disturbance does exist but it’s definitively overrated as cause of lack of overtakes, especially because most of people with zero knowledge of the argument point at it just as it was witch hunting suggesting the most stupid solution for the problem.
The simple truth is that F1 are too fast to see plenty of overtakes on the current circuits and the recent modifications to the tracks made it worse.
I believe that this concept you are talking about is referred to as the "rubber band" effect. On the tighter corners, I would think that braking is most effected due to the lack of downforce on the front wheels on the trailing car. Therefore, the leading car should be able to brake much later preventing an attack. From my brief career sucking at motorcycle racing, most of my passing attacks came from outbraking someone into a corner, and/or braking less and carrying more corner speed. Rarely were you able to really pass with power unless the leader lost traction. Now on the long sweepers, I could definitely see LOSING time due to lack of front downforce for steering and rear downforce for drive, so there I'm trying to think of a way to minimize the losses. Hopefully that would let you stay in touch close enough to the leader to outbrake him thanks to your newly developed front aerodynamics that give you comparable braking performance while in his wake or just on the edge of it as you pull out. Then it becomes a contest of balls and skill instead of a disadvantaged banzai manuever. Keep dreaming I know...
I figured that the aero modelling would be complex, but not impossible. Guess I was wrong.
I dont think that speed or lack of speed(for the trailing vehicle) is the reason for lack of overtaking manouvers.
Straight speeds did not change a lot during the last 20 years of formula 1.
Cornering speed,acceleration and braking distances have changed.
So this is certainly not the reason.
Also permanent drafting at very high speeds with more equal matched vehicles at the IRL ovals undermines this .
It is the aerodynamics of the current F1 cars.
I dunno, that toyota-williams battle on sunday proved overtaking and battling were still possible. If you are talking about downforce, its the smaller teams who don't have it and therefore can't keep up, imo.
Bring back wider rear wings, V10s, and tobacco advertisements
The Toyota-Williams battle in Sepang is imo not relevant for drafting.
As West says,overtaking is still possible as long as a frontrunner makes a mistake and misses a turn and the dynamic ability /speed of the following car is higher.As it was in the fight between R.Sch., M.W. and N.H.
But overtaking manouvers such as between R.Sch.,M.W. and later between M.W.,G.F. at the end of the long back straight failed or ended in a crash despite straight line speed differences between Toyota/Williams and Renault/Williams.
As R.Sch. said after the race (RTL): "Overtaking is not possible and when I thought its now or never..it was never"
Incident between him and Mark Webber after which R.Sch. had to pit unscheduled and get the nose of his car changed.
