Ground Effect - Bring It Back

[bhall II]

Is the discussion only limited to the endplates?

Not at all. Context just made it seem like a reference to front wing end plate vortices.

[Just_a_fan]

Stupid teams, you should tell them they can save the effort of using specific wings for Monza, as they don´t reduce drag because frontal area is defined by the tyres and chasis...

The front wing is generally considered to be drag free in this regard because it is shadowed, in frontal area terms, by the vehicle behind. At Monza, where downforce is reduced because the trade off with straight line speed is more important, the rear wing is trimmed down to give a much smaller frontal area and thus drag. This works because the rear wing is mostly on its own in terms of frontal area. If you remove rear wing performance you must balance that with reduced front wing downforce or you have a very unbalanced car.

It really is quite simple.

This
http://elpreciodelafruta.es/wp-content/ ... utobus.jpg

And this
http://estaticos.elmundo.es/assets/mult ... 748909.jpg

Both have very similar frontal areas, but you can bet an arm drag is completely different

Drag depend on many more things than frontal area. It is not that simple

The bus has likely got a less good Cd than the train. Hence less drag for the same frontal area.

The front wing on an F1 isn't seen separately from the rest of the car in frontal view so its drag is "hidden" within the drag from the rest of the structures that make up that frontal area. If you reduce the front wing angle, you will reduce the drag slightly because the downforce is reduced. If you took off the front wing the overall drag of the car wouldn't drop massively. You'd probably notice more of an effect caused by the lack of flow conditioning that the front wing provides to the rest of the car.

The rear wing is a separate item. Its frontal area is "seen" by the air flow. Reduce the frontal area, you reduce the drag. That you also reduce the downforce by reducing the frontal area also reduces the drag further. If take off the rear wing, the car's overall drag would reduce by a large amount. The rear wing is like a parachute as far as drag is concerned. That's why the spend a lot of time fiddling with the endplates to reduce vortices and hence drag. Reduce the drag that's not from the lifting surfaces of the wing and you gain an improved L/D.

[Aesto]

From what I can tell, ground effect (i.e. through a shaped/skirted floor) would aid overtaking in three ways:

1. Currently, downforce generation depends on a lot of knock-on effects, as the front wing, front tires, cameras, front suspension, bargeboards, T-cam, sidepods, etc. all interact with the airflow in a concerted way. Thus, if the airflow is disturbed through ''dirty air'', so is their interaction with one another. And since most of an F1 car's downforce is produced at the rear, the air doesn't arrive there as intended, hence the loss of downforce. However, in the case of shaped floors, the airflow doesn't have to travel over the sidepods and everything behind them, hence the problem of the disturbed interaction effect is reduced. That being said, I do agree with bhall in the sense that people overestimate the ability of shaped floors to overcome this problem, because most of the interacting components are still at the front of the car.

2. Downforce generated via ground effect has a better downforce/drag ratio than downforce generated via conventional means. Experience shows that series in which cars have lower amounts of drag (i.e. F1 >20 years ago, Indy Car, GP2, GP3, etc.) produce more overtakes.

That being said, I can already see what the counter-argument is going to be here

3. Downforce generated via ground effect is inherently more unstable because it depends on the distance of the floor to the ground, which changes constantly. This has two repercussions:

a) it's harder to study in moving belt wind tunnels, ergo it will take teams longer to master it. Experience shows (and bhall has repeated this ad nauseum in this thread) that there are more overtakes when aerodynamics aren't as optimized.
b) the cars are harder to drive, because aerodynamic grip is more ''peaky'' and can be lowered drastically in an instant. Hence more mistakes, hence more opportunities for overtakes. Niki Lauda (probably the most technically-minded driver of the ground effect era) also made this exact point when explaining why he thought reintroducing ground effect would be a good idea. Unfortunately I cant find the quote right now


On a sidenote: does anyone have a good picture of the shaped floor of a current GP2 car?

[rjsa]

On a sidenote: does anyone have a good picture of the shaped floor of a current GP2 car?

I've been searching for a while. Can't find Indy either.

[Just_a_fan]

Indy:

[Andres125sx]

IMO that´s a difference relevant to my previous explanation/question. That wing only work as a venturi tunnel, while F1 front wings also work as a wing.

Can you or can you not explain the basis for your opinion? Simply restating a thesis is not an explanation.

Can you explain the contrary?

It´s logical, they´re wings so, what´s the reason to stop using downforce created by wings-bernoulli effect? Teams spend millions looking for ways to improve DF, it would be absurd to not use front wing as a wing.

Also, all those flaps, if they´d be intended only to act as a venturi tunnel, would be more slippery at the top side to reduce drag. If they´re that stepped what causes drag, it must be because they also produce DF


No reply to any of my questions?

[Andres125sx]

If you reduce the front wing angle, you will reduce the drag slightly because the downforce is reduced. If you took off the front wing the overall drag of the car wouldn't drop massively.

Obviously, I never tried to say it would drop massively, only that drag depends on more things than just frontal area.

The rear wing is a separate item. Its frontal area is "seen" by the air flow. Reduce the frontal area, you reduce the drag. That you also reduce the downforce by reducing the frontal area also reduces the drag further. If take off the rear wing, the car's overall drag would reduce by a large amount. The rear wing is like a parachute as far as drag is concerned.

And parachutes causes a lot of turbulences and dirty air. That´s the reason I think wings are antiquated. There are better ways to produce DF than wings..... or to be more precise, for the amount of DF rules will ever admit (to limit cornering speed as we all agree more than 5-6G would be too dangerous on most tracks) I´m sure it would be possible to create that amount of DF with less dirty air.

A front wing and a flat floor to produce GEs, combined with a high cambered rear wing can´t be the most efficient way

[Andres125sx]

Indy:
http://grandepremio.blob.core.windows.n ... 204_DR.jpg

OMG impressive picture, makes you wonder how the driver coped with the crash...

[rjsa]

IMO that´s a difference relevant to my previous explanation/question. That wing only work as a venturi tunnel, while F1 front wings also work as a wing.

Can you or can you not explain the basis for your opinion? Simply restating a thesis is not an explanation.

There is no such thing as a multi element venturi. Injecting more high pressure/low speed air into the extracting cone kills the sucking effect downstream of the injection.

Multi element WINGS allow for more camber and AOA by keeping the flow attached on the low pressure side, that otherwise would stall.

[bhall II]

Can you explain the contrary?

My mistake is that I kept trying to bridge the gap even after you "corrected" someone who I strongly suspect is a formally trained aeronautical engineer simply because "[you] fly RC planes, and [you] like experimenting."

Since you're the expert, I trust this will explain itself...

There is no such thing as a multi element venturi. Injecting more high pressure/low speed air into the extracting cone kills the sucking effect downstream of the injection.

Multi element WINGS allow for more camber and AOA by keeping the flow attached on the low pressure side, that otherwise would stall.

And I'm convinced that the one or two times you've made even vaguely insightful comments were the result of sheer luck, because the rest of your Google-logic has had absolutely no relevance whatsoever to this discussion, and you're completely oblivious to it...

Wing tip vortex is a bad thing. It's pressure leakage and results in an reduction of the effective wingspan and increased drag.

To understand front-wing ground effect, it's worth revisiting some research performed by Zhang, Zerihan, Ruhrmann and Deviese in the early noughties, Tip Vortices Generated By A Wing In Ground Effect. This examined a single-element wing in isolation from rotating wheels and other downstream appendages, but the results are still very relevant.

The principal point is that front-wing ground-effect depends upon two mechanisms: firstly, as the wing gets closer to the ground, a type of venturi effect occurs, accelerating the air between the ground and the wing to generate greater downforce. But in addition, a vortex forms underneath the end of the wing, close to the junction between the wing and the endplate, and this both produces downforce and keeps the boundary layer of the wing attached at a higher angle-of-attack.





The diagrams above show how this underwing vortex intensifies as the wing gets closer to the ground. In this regime, the downforce increases exponentially as the height of the wing is reduced. Beneath a certain critical height, however, the strength of the vortex reduces. Beneath this height, the downforce will continue to increase due to the venturi effect, but the rate of increase will be more linear. Eventually, at a very low height above the ground, the vortex bursts, the boundary layer separates from the suction surface, and the downforce actually reduces.

So, for a wing in isolation, the ground effect is fairly well understood.

[mrluke]

From the above I suspect that the purpose of the rubber skirts seen on the GE cars was as much to create these vortices as to stop the high pressure air leaking into the underfloor area. The rubber skirts are in effect the end plates of the underbody "wing"

[Tommy Cookers]

McCabe is saying 6 times over (as if these aspects were independent) only the basic nature of wings as known these last 110 years
(what does he think happens in every landing of a low-wing airoplane ?)
not something new and of unique sugnificance
btw 'exponentially increasing' sounds good but doesn't mean what most people think it means

tip vortices and lifti at surfaces are like chickens and eggs - they are inseperable, neither is the cause of the other
but the detached vortices (excapt insofar as their use eg by geese in formation or F1 bottoms) are an equivalence of inefficient lift


@ mrluke - at this moment fwiw I disagree with your point (let's see where it takes the thread)
the flexible skirt (in combonation with the track surface) is doing in full what the wing endplate onlyl does in small part ....
prevent detached vortices

[bhall II]

The McCabe piece is just a brief, accessible summary of a study by Zhang et al., in 2002: http://citeseerx.ist.psu.edu/viewdoc/do ... 1&type=pdf

The point is not to say it's a new phenomenon. It's just an investigation of it.

[Andres125sx]

^ They said wing? OMG

Can you explain the contrary?

My mistake is that I kept trying to bridge the gap even after you "corrected" someone who I strongly suspect is a formally trained aeronautical engineer simply because "[you] fly RC planes, and [you] like experimenting."

Since you're the expert, I trust this will explain itself...

http://i.imgur.com/6sXAEww.jpg

I´m tired of your patronising attitude Bhall, specially since you ignore most questions related to the thread and keep repeating the same again and again and again and again... your real knownledge is miles away from what you think it is... People with real knownledge reply questions, you ignore the most crucial to the discussion, how would true venturi tunnels with reduced wings compare to current design with big wings and flat floor, regarding dirty air.

Otherwise please reply my questions. I don´t try to assert anything, if you read my replies you´ll notice from my very first to the last I never try to say how things are, I´m constantly making questions so someone with real knownlege may reply.

BTW, you should learn reading with a bit more attention. What I said there is NOT contradictory to what Tommy Cookers said, he talked about decreased L/D ratio with no significant increase in lift ratio, what means it increases a bit but a lot less than drag, and that´s exactly what I also said, so I didn´t correct him. Please stop saying BS trying to prove how smart you are and how dumb we all the rest are.

And yes, I think any aeronautical engineer should fly RC planes. Aeronautic laws don´t care if the plane is 1:1 or 1:5 scale, they´re the same and the plane must comply with same rules, so it´s real world experimenting wich is really useful, specially since there´s nobody inside so you can do a lot of tests you would never do on a 1:1 plane


Now you can continue posting pics of the bottom side of front wings, ignoring they´re wings even if they work as venturi tunnels, ignoring the questions regarding true venturi tunnels compared to current design, and trying to show how smart you are. Bye

[rjsa]

There is no such thing as a multi element venturi. Injecting more high pressure/low speed air into the extracting cone kills the sucking effect downstream of the injection.

Multi element WINGS allow for more camber and AOA by keeping the flow attached on the low pressure side, that otherwise would stall.

And I'm convinced that the one or two times you've made even vaguely insightful comments were the result of sheer luck, because the rest of your Google-logic has had absolutely no relevance whatsoever to this discussion, and you're completely oblivious to it...

Engineering, naval architecture, in a time we weren't allowed a calculator in finals. So I know my math and my fluid mechanics.

Now I'll just pick Andres125s's cue and leave you to your ranting.

Maybe this becomes your toy thread, like Feliks has one. It might even get as cute. Good luck with that =D>