Air Flow Disruption

[Max Mosley 2]

I liked the article. One thing should be pointed out, I think: the drag coefficient of a football varies only when the air is made turbulent from increased velocity, right? F1 cars, unlike footballs, are designed to smooth out the turbulent air.

Yeah I think you're right: the drag coefficient of a football varies most when the air is made very turbulent, which perhaps happens quite suddenly, but it does change a (very) little over all speeds too. (I think you can see this on their graphs.) F1 cars are designed to smooth out air, as you say, but they also must do other things, like provide downforce in the corners etc. These conflicting aims mean that in practice the air may well be quite turbulent behind an F1 car - I think this is one reason why so much downforce is lost behind another car. Racing cars tend to have surprisingly high drag coefficients, which is what makes me think their slipstream may be quite turbulent. Higher velocity normally leads to higher turbulence for a given geometry too, I think. But yeah, you're basically right that a football is not a very good example here! I would like to find some decent articles about the physics of F1 but haven't managed to find anything that interesting (yet).

I'll sum up what I was trying to say with this: BAN THE GREEBLIES!!!!111!one!

Yep!

[Yoda McFly 1]

Yeah I think you're right: the drag coefficient of a football varies most when the air is made very turbulent, which perhaps happens quite suddenly, but it does change a (very) little over all speeds too. (I think you can see this on their graphs.) F1 cars are designed to smooth out air, as you say, but they also must do other things, like provide downforce in the corners etc. These conflicting aims mean that in practice the air may well be quite turbulent behind an F1 car - I think this is one reason why so much downforce is lost behind another car. Racing cars tend to have surprisingly high drag coefficients, which is what makes me think their slipstream may be quite turbulent. Higher velocity normally leads to higher turbulence for a given geometry too, I think. But yeah, you're basically right that a football is not a very good example here! I would like to find some decent articles about the physics of F1 but haven't managed to find anything that interesting (yet).

In truth, the area intrigues me. Most of my aero knowledge relates to aircraft and ballistics...

With sailplanes, the big deal is maximizing lift while minimizing drag ... Seems like similar, but somewhat reversed, goals, although the shapes and speeds are drastically different.

I'd agree with you on the turbulent slipstream; what graphs/plots of CFD runs I've seen seem to confirm this as well.

Here's a tangential (bordering on OT for the thread) question, then: with the design of the new ChampCar, much attention was paid to the design of the undertray/venturis/underwing to increase its downforce contribution, thereby allowing for less contribution to be made by the wings, all with the stated goal of reducing turbulence effects on the trailing car, and hopefully allowing for more overtaking. We're only three races into that season, and I managed to miss the latest race (Houston) entirely, but based on Vegas and Long Beach, they might be on to something. So, on to the question, should F1 consider this instead of bizarre-looking split rear wings as a turbulence-reducer? I can't seem to remember why F1 mandates a flat bottom, and I'm too tired and in too much pain to look it up right now. Maybe I will later this evening, after the beer and vicodin kick in. (Still recovering from elbow surgery. ) (And discussion of whether Panoz builds cars that are inherently bad for a driver's back is definitely OT for this thread. )

[Max Mosley 2]

Interesting point Yoda! I thought the reason ground effects were banned in F1 was because they are very sensitive to the height from the ground. So if a driver goes over a bump and bounces slightly he can lose half his downforce, which could be very dangerous in a corner of course. I wonder how they overcome this in ChampCar. Although I'm a little skeptical of some of the driving talent in ChampCar, F1 could learn a lot from the way they run the series. Frankly imho F1 is a big joke sometimes - it's like Bernie wants to see how bad he can make it and still get us to watch.

And I hope your elbow gets better! No tennis for a while then.

[Autumnpuma 0]

Interesting point Yoda! I thought the reason ground effects were banned in F1 was because they are very sensitive to the height from the ground. So if a driver goes over a bump and bounces slightly he can lose half his downforce, which could be very dangerous in a corner of course. I wonder how they overcome this in ChampCar.

ChampCar limits the amount of aero-created downforce in favor of more mechanical grip. This makes the car more forgiving when it goes over a bump. More aero (as in current F1) actually enables the car go faster than the traction circle would normally allow, so the loss of any downforce is more dangerous than a ChampCar. ChampCar drivers are running closer to the limits of the traction circle by relying on mechanical grip more than aero grip.

And I hope your elbow gets better! No tennis for a while then.

Fencing, not tennis.

[Yoda McFly 1]

Interesting point Yoda! I thought the reason ground effects were banned in F1 was because they are very sensitive to the height from the ground. So if a driver goes over a bump and bounces slightly he can lose half his downforce, which could be very dangerous in a corner of course. I wonder how they overcome this in ChampCar. Although I'm a little skeptical of some of the driving talent in ChampCar, F1 could learn a lot from the way they run the series. Frankly imho F1 is a big joke sometimes - it's like Bernie wants to see how bad he can make it and still get us to watch.

And I hope your elbow gets better! No tennis for a while then.

In general, I agree ... Specifically, as it relates to the sliding skirts, Brabham's fan, etc ... From watching ChampCars (CART, IndyCars) for as long as I've been watching F1 (I'm 30-cough, and have been involved in racing since I was a kid), though, if that's what F1/FIA/FOM is concerned about, then they just need to pop a Xanax or drink a beer, and let it go. The downforce generated by the tunnels/venturis on a ChampCar chassis (Sitting here, I can pull definitive memories back as far as '92 ...) don't really get that far out of shape with bumps, kerbs, etc ... They do generate a bunch of downforce, and the cars definitely get squirrely, but nothing more than a good open-wheel driver should be able to handle. Nothing at all like what would happen with a true ground-effects car when something failed there ... Anyone remember the Chapparals with the wings mounted directly to the wheel hubs?

ChampCar limits the amount of aero-created downforce in favor of more mechanical grip. This makes the car more forgiving when it goes over a bump. More aero (as in current F1) actually enables the car go faster than the traction circle would normally allow, so the loss of any downforce is more dangerous than a ChampCar. ChampCar drivers are running closer to the limits of the traction circle by relying on mechanical grip more than aero grip.

This, I believe, is the real rub of the situation. Over the last 10-odd years, 'most everything F1 has done has been to reduce the mechanical grip of the car. How can that possibly be good? Bring back slicks, bring back pre-99 (98??, hell, I can't remember) wide-track .... Allow the cars to have real mechanical grip, and I'd be willing to lay serious odds that the overall downforce levels would go way down, because of the attached reduction in drag.. Suddenly, with tonnes of mechanical grip and none of that obnoxious "dirty air" to deal with, and having your nose under someone's rear wing going into La Source would not just be "do-able", but the best way to go ...

Just my $0.02. I might not be sober enough, though. . Who knows.

And I hope your elbow gets better! No tennis for a while then.

Thanks. Yeah, as mIke pointed out above, it's actually due to too much fencing. I've actually taken the last year or so off from fencing to get the elbow fixed. Now that the surgery is finally done, I hope/intend to start working footwork again within the next week or two, and actually be able to bout inside the next month ... After over a year off, it should be interesting.

Thanks ...

[DOF_power 0]

Interesting point Yoda! I thought the reason ground effects were banned in F1 was because they are very sensitive to the height from the ground. So if a driver goes over a bump and bounces slightly he can lose half his downforce, which could be very dangerous in a corner of course. I wonder how they overcome this in ChampCar. Although I'm a little skeptical of some of the driving talent in ChampCar, F1 could learn a lot from the way they run the series. Frankly imho F1 is a big joke sometimes - it's like Bernie wants to see how bad he can make it and still get us to watch.

And I hope your elbow gets better! No tennis for a while then.

You're comfusing the types of ground effects.

The cars that were creating problems were the mini-skirt wingless ground effects cars.

The are other forms of ground effects like the initial inverted-wing ground-effects car.

a] A (inverted-)wing ground-effects car (Lotus 78) is one where the sidepods (of a single seater) or the undertray (of a sportscar) is shaped as an inverted wing. Distance of wing section from ground is not critical for generation of downforce. The first generation of "wing car/ground effect" cars were wing cars, as the Lotus 78 (note the "brushes" that Colin Chapman used to keep the fast, low speed air under the car).

b] A "ground effect" skirt car (or wingless car; Lotus 80) is one where the profile of the sidepod or of the undertray is not the one of an inverted wing, but it operates accelerating the air under the car and then extracting at its rear as fastly as possible. In this case, the distance (low height) from ground is very important to generate downforce.

(these were the ones causing the big problems, due to their ride height and dependence on the fragile mini-skirts)

(The Lotus 79 was sort of hybrid between a/Lotus 78 and b/Lotus 80)

c] Today's flat bottom F1 single seaters of today are also partially ground-effects cars. As the combination of flat-bottom + rear diffuser (introduced in 87 I belive) achieves the trick to a limited extent.

(Inverted) Wing ground-effects cars - and not mini-skirts/wingless nor today's flat-bottoms - could make racing safer and better.

By using inverted-wing shaped sidepods/undertrays the overall downforce generated by the single-seater becomes less dependent on the front and rear wing.

So the system may act as a "safety harness" in case the front is lost and/or the car goes over a crest following the tow given by another.

The shape and profile of the floor can be easily regulated by using templates (as the Nascar body inspection technique). Besides safety, wing cars can also be used to spice up racing.

Cars become less dependent on the front wing, so they are more able to follow another one through disturbed air (turbulent air) and not become quite tough to handle in these circumstances.

So it would be easier (and safer) to a car to follow another one up close and then pull an overtaking move.

This would only solve part of the problem, as the suspensions and tires are the other ones.

The suspensions of today don't follow the track properly (as they're actually transversal suspensions not vertical). So we need a new type of suspensions either passive (hydropneumatic, hydragas) or active that can follow the road properly.

Next stop would be slick tires.