Formula 1 Aero

[browney]

Hey guys,
I wanted to start a thread to discuss a couple of things about F1 aerodynamics.

1) What are the rules in F1 about 'ground effects'? The cars have diffusers and front wings both wich run in 'ground effect' so what do people reffer to as being banned? does the rest of the car underbody have to be flat? Are they allowed to have side skirts?

2) People seem to talk about 'ground effects' as being better for cars following close together, is this because the diffuser creates less of an upwash for the same amount of downforce than wings?

3) The FIA raised the front wings to reduce downforce, I assume this was to increase the ability for the cars to follow each other closer but thinking about it, wouldn't this move the wing more into the car infronts upwash?

4) Would it be possible to help the cars to follow each other closly by making a rule that did not allow any surface (including the chord on a cambered wing) on the car to exceed a certain angle from horizontal?

Anyway, some things to discuss.....

[Locost47]

Bit of a geeky pub discussion, but an intriguing one nonethless!

1/ I think their intention is to ban full body-length diffusers and accompanying flexible side-skirts sealing the underbody to the ground. You can get astronomical levels of downforce from this but the drag penalty is only a small fraction of what you'd have to pay if you'd just used normal wings. As i understand it, in F1 the underside of the car has to be flat, between certain specified points. Skirts aren't allowed because there were cases of them falling off or whatever and the change in grip was even greater than when a car loses it's rear wing. Big crashes result...

2/ Referring back to the thread in the racing tech forum, the advantage that underbody downforce has over wing-based downforce is that much of it comes from the constriction of the airflow under the car, as well as the fundamental turning of the air upwards around a convex surface. 'Dirty air' may cause a diffuser to stall, in the same way as a wing, but the drop in overall downforce won't be as large a percentage. There is also potentially less upwash for the following car, as you say.

3/ When they first raised the wings some drivers complained that it did indeed make it harder to follow others closely and, at a guess, i'd say it's due to the combined effect of an increased effective angle of attack for the front wing due to its location in the upstream car's wake and the supply of 'dirty air'. Makes it much more likely to stall.

4/ One option would be to move to Indycar-style venturis under the sidepods. They could be made very efficient even without dubious side-skirts and would be less sensitive when following another car. You could still have single-element front & rear wings for balance & sponsorship opportunities. The main downside could be that they'd have lots of grip and not so much drag so safety would be a concern.

Surely anything's got to be better than the ugly beats we have on the grid nowadays?

[stephen_c]

Originally Posted by Locost47

-cut- Surely anything's got to be better than the ugly beats we have on the grid nowadays?

You can say that again. F1 cars used to be so pretty. Nowadays, they look like Japanese Transformers. (Nothing wrong with Japanese Transformers by themselves though. I used to own a couple)

[sonic]

yeah, they look weird from certain angles. that said I think the cars look a hulllava lot better now they are in proportion.

when they went to that narrow track and semi slicks they looked ridiculous. all tall and big.

at least they look low, thin and racy again.

dumbed that hi tech aero talk down pretty quickly eh? ;P

[stephen_c]

^
Sorry, don't want to get in trouble for going off topic.
I like option number 4, Indycar-style venturis under the sidepods.

[Bononi]

Originally Posted by browney

Hey guys,
I wanted to start a thread to discuss a couple of things about F1 aerodynamics.

1) What are the rules in F1 about 'ground effects'? The cars have diffusers and front wings both wich run in 'ground effect' so what do people reffer to as being banned? does the rest of the car underbody have to be flat? Are they allowed to have side skirts?

2) People seem to talk about 'ground effects' as being better for cars following close together, is this because the diffuser creates less of an upwash for the same amount of downforce than wings?

3) The FIA raised the front wings to reduce downforce, I assume this was to increase the ability for the cars to follow each other closer but thinking about it, wouldn't this move the wing more into the car infronts upwash?

4) Would it be possible to help the cars to follow each other closly by making a rule that did not allow any surface (including the chord on a cambered wing) on the car to exceed a certain angle from horizontal?

Anyway, some things to discuss.....

Hi browney, maybe here : Racing Technology, you'll find our members that have more knowledge on tech matters, though I'll leave this one here as we can always discuss without going too much into tech stuff.

[Bononi]

Originally Posted by stephen_c

You can say that again. F1 cars used to be so pretty. Nowadays, they look like Japanese Transformers. (Nothing wrong with Japanese Transformers by themselves though. I used to own a couple)

Transformers ? Now this is really tech stuff !

[Greenback]

Originally Posted by Bononi

Transformers ? Now this is really tech stuff !

The FW26 it probably the most mighty transformers off all.

[MRJUCY]

Not paying attention to liveries the FW28 is in my opinion tho the prettiest car for several years.

[Knowlesy]

What, the McLaren MP4/20 painted blue you mean?

[b1ackcr0w]

As an addition to the reply to question 1). I was lucky enough to get a factory tour with a leading F1 aerodynamasist a few years ago. And his view of ground effects was roughly as follows.

Although the most obvious and powerful way of causing ground effect has been banned (IE stating minimum ride hights and banning side skirts), the aero guys still intensionally cause ground effects and always will because no rule can ban a central law of physics. Many years after the main measures to limit ground effects came in, the aero guys in most teams found other more subtle ways of causing ground effects by stealth. The biggest step forward they made in this area was to start having a moving road underneath the wind tunnel models in order to properly simulate ground effect as well as the effect of air moving over the top of the car. Even in modern "non gorund effect" cars, GE still provides a significant proportion of the car's aero package.

[stephen_c]

^
Sure, anytime you have a difference in air pressure between top and bottom the result is either lift or downforce. It doesn't have to look like a wing.

[browney]

If the rules mandating a flat underbody were removed and side skirts allowed with modern technoligy, would the safety issue still be as concerning? Allowing more downforce to be created by the underbody seems like one solution to the 'dirty air' problem, surley the FIA should be looking into it?

2) I'm not sure if I'm right, but I guess that downforce made from the underbody wouldn't be significantly affected by a car in front, because I would guess that vorticies would be created in the air passing under the car by the cars front wing anyway.

[Locost47]

You don't necessarily need solid skirts anymore. As b1ackcr0w mentioned, you can get a similar effect of sealing the underbody by being cunning with the lower edges of the sidepods, particularly if you can cut away the bodywork immediately above the edge, as many teams are doing. Not quite as effective as a solid seal but not bad at all.

Underbody aero is a lto less likely to be affected by 'dirty air'. A lot of work goes into deliberately generating small vortices from various bits of the front wing and barge boards which are then directed under the car. Vortices have very low pressure cores which you can imagine being like little tubes which then get squashed under the car. This reduces the pressure under there even more for not that much of a drag penalty.

I say reduce the wings to 1 element each front & rear and take the bulk of the downforce generation from the main body. It *should* be safer, allow closer racing and still allow the marketing people somewhere to put their logos. What do you think?

[Pingguest]

Originally Posted by Locost47

You don't necessarily need solid skirts anymore. As b1ackcr0w mentioned, you can get a similar effect of sealing the underbody by being cunning with the lower edges of the sidepods, particularly if you can cut away the bodywork immediately above the edge, as many teams are doing. Not quite as effective as a solid seal but not bad at all.

Yep, GP2 uses this kind of "skirts" as well.

[Pingguest]

Yesterday I read the technical regulations for LMP1-cars. And they have something interesting:

To join up with the bodywork, the lateral parts :
- may be curved upwards with a maximum radius of 50 mm rearward of the front wheels and forward of the rear
wheels (see area 1 of drawing n°1).

Formula 1 could start with a similar rule. Allow teams to make curves with a maximum radius of 5 cm.

[browney]

Without sideskirts wouldn't the higher pressure air outside be sucked under the car, I would imagine this reducing the efectiveness of the underbody at producing downforce quite significantly. Plus, the diffuser needs to be pretty close to the ground for the maximum effect.

Perhaps one of the reasons that the FIA are not keen on using 'ground effects' for downforce would be that less drag is created by using underbody downforce, in fact a good diffuser will reduce drag. The FIA seem keen to limit straight line speed.

I'm not sure if you could ban the 'winglets', because it would be hard to define these in the rules. That is why I thought a better way of reducing downforce from wings would be to set a maximum angle for body work with respect to the horizontal.

[browney]

How fast does a vehicle with a well designed underbody & diffuser need to be traveling before the downforce is enough to be noticeable. Is around 50km/hr fast enough, or do you need greater speeds for more mass flow to get a low enough pressure under the car to be usefull.

[Locost47]

Some of the Group C cars were reported to be achieving CL's of between -3 and -4.

At a CL of -3 you're only looking at about 60kg of downforce at 50kph but that rockets up to ~630kg at 100mph and ~1430kg at 150mph.

Current F1 cars can apparently achieve similar values even with the highly-restrictive aero regs. Only difference is a Group C car had a CD of about 0.6 or less whereas an F1 can be as high as 1.2, which is almost identical to that of a brick wall, funnily enough.

A diffuser that's producing any significant amount of downforce won't reduce drag though. A gentle one will do, but once you start generating forces either up or down you don't get away without paying a penalty in the streamwise direction.

The underbody and sides of a current LMP car are mandated by the regs to have radiussed edges as part of the measures to reduce the likelihood of them flipping over. Alternatively they could have just dropped this crazy 'flat floor' business and allowed the designers to generate downforce in a less insanely pitch-sensitive way, though perhaps there's more to it than that.

[Obi Offiah]

Originally Posted by Locost47

The underbody and sides of a current LMP car are mandated by the regs to have radiussed edges as part of the measures to reduce the likelihood of them flipping over. Alternatively they could have just dropped this crazy 'flat floor' business and allowed the designers to generate downforce in a less insanely pitch-sensitive way, though perhaps there's more to it than that.

Hi Locost47

This is what I couldn't understand. I only started watching sportscar races in 2000, so I don't know much about cars prior to the flat-bottom regulations flipping a-la Mercedes CLR style. From the little I've gathered flips in the ground effects Group C era were down to accidents, collisions, mechanical/tyre failures.

As for F1 I think they should re-introduced tunnels, albeit in a more restricted format, such that they generate 70-80% of the total downforce. The rear wing should produce 15-20% of downforce and the front wing 5-10%. If the interaction between a lower tier rear wing and tunnel diffuser creates substantial upwash, the regulations such be modified to ban lower tier wings.

Obi