Ground Effect - Bring It Back

[djos]

What makes you think that's correct?

How else are they able to run the current level of rake? The vorticies are there to seal the floor and effectively make the diffuser larger.

[Andres125sx]

Basically what I´m trying to say is a proper venturi tunnel will cause less dirty air than two wings working as a venturi tunnel. Dirty air will always exist, but much reduced, so overtaking would be easier with proper venturi tunnels and reduced or removed wings. How much easier is difficult to say, but it will be easier for sure.

Wings are not necessary today, aerodynamics have evolved enough to create enough DF without wings. Wings create a lot of downforce but also a lot of dirty air, too much IMO, there are better options to produce DF.

Yes, I understand what you're trying to say; I just don't understand why you're trying to say it.

Then it´s reciprocal, because I really don´t understand the reason you insist talking about front wing vortices when nobody questioned them, nobody questioned they´re used to improve GE, nobody questioned current cars use GE, but you insist repeating the same again and again....

https://www.youtube.com/watch?v=Wokswr_KHXQ

http://i.imgur.com/usOEKuv.jpg
(Click to enlarge)

They are functionally identical, as current front wings are not freestream airfoils. Any similarities between them are 99.9% cosmetic.

[...]

The difference between this...

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

...and this...

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

...is superficial.

Does it make sense now? (I had no idea this was the point of contention.)

So the rules forcing to use flat floor between wheels do not limit GE, the rules banning double diffusers do not limit GE, all the rules limiting floor design do not limit GE, GE used today are the same they would be if engineers will be allowed to design proper venturi tunnels with freedom

You can´t be serious bhall

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...

[rjsa]

I can see where bhaII is coming from. There's that paper one page back claiming downforce is generated by vortex suction. just_a_fan mentioned something like that too.

While I can see how much effort is placed in controlling vortexes, I'm still not convinced it's for any reason other than sealing & shaping the wake downstream. Vortexes are the result of suction on the low pressure side, not the cause of it.



There are high speed/low pressure areas alright, but those are not in place to generate downforce.

This is from Jonathan Pegrum's work: https://spiral.imperial.ac.uk/bitstream ... Thesis.pdf

[timbo]

While I can see how much effort is placed in controlling vortexes, I'm still not convinced it's for any reason other than sealing & shaping the wake downstream. Vortexes are the result of suction on the low pressure side, not the cause of it.

Well, look at airplines where LERX are used to improve the lift of the main plane at high AoA


PS https://en.wikipedia.org/wiki/Vortex_lift

[rjsa]

http://www.lerx.net/Arbre/Lerx/Lerx_anglais.html

Indeed, the LERX generate powerful swirls of air or Vortex which increase the air velocity on the roots of wings and around tails. This makes it possible to keep the control of the plane at angles superiors of 30˚. These Vortices when are intenses are particularly visible, materialized by the condensation of the moisture of air.

On vortex lift:

Vortex lift works by capturing vortices generated from the sharply swept leading edge of the wing. The vortex, formed roughly parallel to the leading edge of the wing, is trapped by the airflow and remains fixed to the upper surface of the wing. As the air flows around the leading edge, it flows over the trapped vortex and is pulled in and down to generate the lift.

...

The major advantage of vortex lift is that it allows angles of attack that would stall a normal wing. Since it does not require camber to generate lift, but does require significant sweep back, vortex lift is utilized by most supersonic aircraft for landing; the characteristic bending nose of the commercial Concorde was built to allow the pilots to see over the nose during landing, when the aircraft was at a very high angle of attack.

Emphasis mine, I guess it doesn't apply here, whatever it is.

By my 20th century knowledge it was about delaying stall and allowing higher AOA on slim profile wings.

[bhall II]

How else are they able to run the current level of rake? The vorticies are there to seal the floor and effectively make the diffuser larger.

Why do you think a higher diffuser is better? Please explain to me the details of the various aerodynamic phenomena that have led you to draw such a conclusion.

So the rules forcing to use flat floor between wheels do not limit GE, the rules banning double diffusers do not limit GE, all the rules limiting floor design do not limit GE, GE used today are the same they would be if engineers will be allowed to design proper venturi tunnels with freedom

You can´t be serious bhall

Frankly, I'm not at all surprised you think that's what I've said here. You've managed to successfully evade any comprehension of the subject matter in question, so it's only natural that correctly identifying my point of view would prove equally improbable.

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.

By my 20th century knowledge it was about delaying stall and allowing higher AOA on slim profile wings.

Why do you often reference aircraft? What similarities beyond the obvious -- "they both have wings" -- make it relevant?

[rjsa]

By my 20th century knowledge it was about delaying stall and allowing higher AOA on slim profile wings.

Why do you often reference aircraft? What similarities beyond the obvious -- "they both have wings" -- make it relevant?

I was rebutting a reference to aircraft. And saying it doesn't matter here.

[rjsa]

How else are they able to run the current level of rake? The vorticies are there to seal the floor and effectively make the diffuser larger.

Why do you think a higher diffuser is better? Please explain to me the details of the various aerodynamic phenomena that have led you to draw such a conclusion.

So the rules forcing to use flat floor between wheels do not limit GE, the rules banning double diffusers do not limit GE, all the rules limiting floor design do not limit GE, GE used today are the same they would be if engineers will be allowed to design proper venturi tunnels with freedom

You can´t be serious bhall

Frankly, I'm not at all surprised you think that's what I've said here. You've managed to successfully evade any comprehension of the subject matter in question, so it's only natural that correctly identifying my point of view would prove equally improbable.

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.

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

By my 20th century knowledge it was about delaying stall and allowing higher AOA on slim profile wings.

Why do you often reference aircraft? What similarities beyond the obvious -- "they both have wings" -- make it relevant?

Not all of the front wing is about downforce, from Pegrum:

1.2 Front Wing Aerodynamics
As discussed above, the performance of a race-car can be greatly enhanced by the
production of downforce. As such, the main design objective for a front wing is to
generate as much downforce as possible. However, as a consequence of its location
as the most upstream aerodynamic component, it is extremely important that the
production of negative lift by the front wing is not at the detriment of other compo-
nents downstream (Wright (2001) and Zhang, Toet, & Zerihan (2006)). Moreover,
due to the distance of the front wing from the cars centre of pressure, the downforce
produced by the front wing is a major parameter in setting the aerodynamic balance
of the car and hence its handling characteristics.

1.3 Project Motivation

The wake downstream of a Formula 1 front wing consists of a trailing vortex system
originating from the endplates. This system usually consists of several co-rotating
vortical structures which after having been shed from the endplate, immediately
encounter the presence of the front wheels (see Figure 1.3). One of the governing
rules of Formula 1 dictates that the car must have four large exposed wheels. The
aerodynamics of the °ow about these wheels is complicated, and not only must the
vortices navigate about these large blu® bodies, but they must also encounter the
strong cross-°ows which further complicate the °ow in this region (Agathangelou &
Gascoyne (1998) and Wright (2001)).
All of these factors contribute to a complicated °ow structure inboard and down-
stream of the front wheel. These structures can result in an undesirable region of
energy loss, which may a®ect the performance of the car.
Therefore, the behaviour of the front wing wake inboard and downstream of
the wheel, provides the main motivation for this experimental project. By gaining
further knowledge about how the vortex system behaves and interacts with the °ow
about the wheel, then hopefully performance gains can be made in the future.
In the next chapter the literature relevant to this problem will be reviewed and
the speci¯c aims and objectives of the project will be presented.

[timbo]

By my 20th century knowledge it was about delaying stall and allowing higher AOA on slim profile wings.

Yep, now apply this to an underfloor at high rake. And the important question is how -- how do vortices allow hight AoA without stall.

BTW, another use for vortices on aircraft is maintaining the rudder efficiency at high AoA, the relatively forward position of rudders on Su-27 aircraft was implemented so as to allow vortice provide enough flow to the rudder to maintain performance. Compare Su-27 to its prototype T-10 to see this.

[rjsa]

By my 20th century knowledge it was about delaying stall and allowing higher AOA on slim profile wings.

Yep, now apply this to an underfloor at high rake. And the important question is how -- how do vortices allow hight AoA without stall.

Re-attaching the flow.

But see, I'm fighting the notion that the low pressure area in the vortex core generates downforce under the front wing, not that it enables the generation of downforce downstream of said wing.

[Andres125sx]

So the rules forcing to use flat floor between wheels do not limit GE, the rules banning double diffusers do not limit GE, all the rules limiting floor design do not limit GE, GE used today are the same they would be if engineers will be allowed to design proper venturi tunnels with freedom

You can´t be serious bhall

Frankly, I'm not at all surprised you think that's what I've said here. You've managed to successfully evade any comprehension of the subject matter in question, so it's only natural that correctly identifying my point of view would prove equally improbable.

Sorry to be so dumb, it seems like I need further explanation about what did you mean with this:

The difference between this...



...and this...



...is superficial.

Does it make sense now? (I had no idea this was the point of contention.)

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.

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

What´s the relevance to the thread?

It´s you who is trying to prove front wings and current aero design are the same as true venturi tunnels so venturi tunnels wouldn´t be any advantage over current design regarding dirty air.

Actually all your previous explanations prove how different they are. Front wing vortices are used to improve GE, ok, but you´re ignoring those vortices, once they left the car (or the car pass through them), are dirty air for the car behind. A proper venturi tunnel does not need vortices from the front wing to work as a venturi tunnel, so it wouldn´t create as much dirty air for the car behind.

IMO that´s the point of the thread while you keep repeating current cars already use GE, front wings are designed to let the floor work as a venturi tunnel, etc. Nobody questioned that, the question is if different rules with more freedom for floor design AND reducing wings camber and size would reduce dirty air.

In other words, 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?

[timbo]

By my 20th century knowledge it was about delaying stall and allowing higher AOA on slim profile wings.

Yep, now apply this to an underfloor at high rake. And the important question is how -- how do vortices allow hight AoA without stall.

Re-attaching the flow.

But see, I'm fighting the notion that the low pressure area in the vortex core generates downforce under the front wing, not that it enables the generation of downforce downstream of said wing.

Ah, yeah, on that I agree.

[Tommy Cookers]

vortices that disappear 1m or even 5 m behind their point of origin are probably associated with efficiently-obtained DF
clearly there is little disturbance of the wake

aircraft vortices that disappear eg 1 - 5 km behind their point of origin ......
(be assured that even a light aircraft will eg at max turn performance continuously generate vortices that persist for 1 - 2 km)
are not associated with an efficient source of lift
and there is much disturbance of the wake

so - determining the persistence (range) of our F1 vortices with GE and with the current rules should settle the controversy ??

[timbo]

vortices that disappear 1m or even 5 m behind their point of origin are probably associated with efficiently-obtained DF
clearly there is little disturbance of the wake

aircraft vortices that disappear eg 1 - 5 km behind their point of origin ......
(be assured that even a light aircraft will eg at max turn performance continuously generate vortices that persist for 1 - 2 km)
are not associated with an efficient source of lift
and there is much disturbance of the wake

so - determining the persistence (range) of our F1 vortices with GE and with the current rules should settle the controversy ??

I would not consider any vortex generation as efficient way of producing lift/DF. Note how it is again to follow another cars. Basically all those fins pre-2009 cars had get replaced by vortices.
It's just that there's no other way to get that much DF with the current regs.
Actually, same with airplanes. Noone runs LERX or vortex generators (maybe with the exception of tiny ones actually designed to interfere and break up vortices!) on airliners and gliders -- the most efficient planes there is. The winglets on wingtips are designed to break up vortices as well. 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.

[bhall II]

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. I'm looking for another way to identify the flaw.

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...



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. So, it's identical to a Formula One wing in all but appearance and scope. Where the F1 wing has a large convergent and a small throat, the IndyCar wing has a smaller convergent and a larger throat (and a positively gigantic diffuser).

I hope seeing it in exaggerated form will make that more clear, because...

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."

A front wing's sensitivity to "dirty air" is no different to that of an underbody venturi. If anything, it could actually be less sensitive, because the elements that constitute the convergent will have a stabilizing effect on turbulent flow.

Now, I recognize you have concerns about the front wing's role in creating "dirty air" and about overall underbody efficiency. We'll get there. Let's just take this one step at a time, all right?