Ground Effect - Bring It Back

[djos]

So bhall but no one else agrees with your assertions.

[bhall II]

So bhall but no one else agrees with your assertions.

And I find that extremely troubling, because they're not really my assertions.

Like most people, I don't own a wind tunnel. So, I have to learn through study, and the information I've presented here has been gleaned from research undertaken and/or compiled by highly respected individuals.

Among others, whoever disagrees with me actually disagrees with...

Xin Zhang, BSc, PhD, CEng, AFAIAA, FRAeS,
Airbus Professor of Aircraft Engineering at the University of Southampton

Willem Toet
former Head of Aerodynamics at Sauber, BMWSauber, BAR Honda, Ferrari,
engineer at Benetton

Jonathan Zerihan, PhD
aerodynamacist Team Leader at Mercedes AMG Petronas, Brawn GP, Honda Racing, BAR Honda

The blatant disregard for documentation in this thread has been absolutely --- astonishing!

[djos]

So bhall but no one else agrees with your assertions.

And I find that extremely troubling, because they're not really my assertions.

Like most people, I don't own a wind tunnel. So, I have to learn through study, and the information I've presented here has been gleaned from research undertaken and/or compiled by highly respected individuals.

Among others, whoever disagrees with me actually disagrees with...

Xin Zhang, BSc, PhD, CEng, AFAIAA, FRAeS,
Airbus Professor of Aircraft Engineering at the University of Southampton

Willem Toet
former Head of Aerodynamics at Sauber, BMWSauber, BAR Honda, Ferrari,
engineer at Benetton

Jonathan Zerihan, PhD
aerodynamacist Team Leader at Mercedes AMG Petronas, Brawn GP, Honda Racing, BAR Honda

The blatant disregard for documentation in this thread has been absolutely --- astonishing!

Sorry mate but I still think you are putting your own interpretation on what you are presenting and it isn't always imo valid. I'm not saying you a 100% wrong, just your spin on certain items doesn't seem to stack up. Admittedly my knowledge is limited, however I believe the arguments put forth by others are more logical.

Btw if you really believe you are fully correct, why don't you invite turbo in here to provide his expertise? He's well respected by all and I'm not sure many posters around here have a better understanding of aero in F1 than he does.

[Just_a_fan]

If replaced with a pair of venturi tunnels, it would have zero impact on frontal area, because that's defined by the tires and the chassis.

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.

[Just_a_fan]

On fighter jets OTOH there's an excess of thrust and they are designed to be able to produce maximum lift ( =g-force for maneuver) and keep being controlled at highest AoAs.

Which can be written as:
"On F1 cars OTOH there's an excess of power and they are designed to be able to produce maximum downforce ( =g-force for cornering) and keep being controlled at highest cornering speeds"

You can see how similar they are.

[Just_a_fan]

So bhall but no one else agrees with your assertions.

Not strictly true.

[bhall II]

Admittedly my knowledge is limited, however I believe the arguments put forth by others are more logical.

Priceless.

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]

If you'll recall the beginning of this discussion when I said that a tightly-regulated series can get away with simpler, more robust aerodynamic solutions, because they have little reason to fear runaway development, this is the embodiment of that reality...

http://i.imgur.com/miN5gOI.jpg

Good post.

It makes sense that the vortices are high velocity and therefore create a low pressure area around them.

It makes sense that the teams will exploit this effect when they want to use vortices to seal the edges of the underbody anyway.

The picture of the jet demonstrates the theory in action.

It would also help to explain why Newey can say that the RB6 had the most downforce of any F1 car ever.

However I query whether relocating the source of the majority of the downforce nearer to the centre of the car would help the cars be less sensitive to dirty air, i.e. the dirty air would reduce the overall downforce but should maintain the overall balance. Overall though I think that active aero would be the best solution and would allow F1 cars to catch up with supercar technology..

[bhall II]

It makes sense that the teams will exploit this effect when they want to use vortices to seal the edges of the underbody anyway.

[...]

However I query whether relocating the source of the majority of the downforce nearer to the centre of the car would help the cars be less sensitive to dirty air, i.e. the dirty air would reduce the overall downforce but should maintain the overall balance. Overall though I think that active aero would be the best solution and would allow F1 cars to catch up with supercar technology..

Vortices shed from the front wing end plates don't "seal" anything. They spin the wrong way for that.

And if we can ever get this discussion focused on the physical realm that actually exists, I have answers for you about underbody efficiency.

[Andres125sx]

To get us back on the same page, will you please use as many details as possible to describe for me the various flow patterns around the front wing that create downforce? Let's see if we can avoid future misunderstandings.

What´s the relevance to the thread?

A fundamental misconception of ground effect aerodynamics has become an impassable bottleneck to this discussion. In fairness, it's not just you. But, we cannot proceed any further until it's rectified, and my onslaught of well-documented and illustrated explanations has apparently had zero impact in that regard.

As Djos said, nobody questioned those explanations and documentation, we´ve questioned your interpretation applied to current F1

If you'll recall the beginning of this discussion when I said that a tightly-regulated series can get away with simpler, more robust aerodynamic solutions, because they have little reason to fear runaway development, this is the embodiment of that reality...

http://i.imgur.com/miN5gOI.jpg

Just like a modern F1 wing, Honda's IndyCar wing is incapable of producing a force by way of anything other than the Venturi effect.

Can you assert this without any doubt?

Multi flaps are not working as wings?

No DF is created by the high AOA of all those flaps?


Probably that´s the point of discussion. I´ve never questioned front wing work as a venturi tunnel, but I think it also work as a wing while you reject or ignore this. It´s not posible for the wing to work both ways?

A venturi tunnel work with air only below it, while a wing also use air from the upper side. It wouldn´t make too much sense to ignore that air moving at the top side. If they can use air below to create DF but also the air above, why not? That has always been a wing, can´t see any reason to stop using it as a wing.

Just like a modern F1 wing, Honda's IndyCar wing...

is different, it´s easy to see it´s been designed to work as a venturi tunnel with no flaps, or if those are called flaps too, they do not have the high AOA F1 flaps have.

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.

Front wing vortices are used to improve GE...

...it's imperative for us to acknowledge that current F1 front wings are functionally identical to underbody venturis. They do not use vortices to "improve" ground effect; they use vortices, because that is ground effect. Until that's crystal clear to us all, there will continue to be a tendency to greatly overestimate the impact of "dirty air."

No vortices mean no GE?

True venturi tunnels also create vortices?

[Andres125sx]

Anycase you didn´t reply a question I did some posts back, wich IMO is very relevant to the thread...

..imagine if multi element wings are banned, max camber is limited, and to compensate that more freedom for floor design is allowed so true venturi tunnels can be used without the need of using front wing vortices to seal the floor and produce lift. Would that reduce dirty air?

I think aero has evolved too much to keep same direction. When DF was initially used, it was thanks to wings. Then GE were used... and banned, so rules tried to keep wings as main DF generators. But aero has evolved so much now they use wings, specially front one, in many different ways, but only as rules allow it

GE currently is the main DF generator. Then, why continue using those wings? For balance you don´t need them that size and complexity. Without any extensive knownledge about the subject, I think aero would be way more efficient if rules would be written considering the reality, DF is created by GE not wings. Instead of using wings to create GE, use proper VT to create GE. As you will need to limit the DF they create, you could even use those limits to also limit dirty air.

[Andres125sx]

If replaced with a pair of venturi tunnels, it would have zero impact on frontal area, because that's defined by the tires and the chassis.

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


And this


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

[bhall II]

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.

[timbo]

Vortices shed from the front wing end plates don't "seal" anything. They spin the wrong way for that.

Is the discussion only limited to the endplates? There's much more in play.
And IMO current endplates are all about managing the wake of front tyres. Not so much about DF. I can see compromises made to the wing efficiency to improve the wake management. All IMO of course.

[djos]

So bhall but no one else agrees with your assertions.

Not strictly true.

I just meant in some areas, not everything.