Bargeboards and its complex design

[effuno]

Looking through all the new cars(and the previous cars) I came across lots of complex shapes in bargeboards, but similar on all cars. Could someone shed some light on what exactly those pieces does to the bargeboard functioning other than conditioning flow to sidepods and around it ?

by 'pieces' I was refering to the shapes on top of bargeboard which are cut into a stepped shape and those horizontal pieces on the bottom ?

Are they trying to seal the air flowing in and out of the underbody in some way by these designs ? And does the curved(in plan view) stepped shape not create vortices(into the underbody flow and to sidepod regions) and thereby more drag ?

[Ogami musashi]

The steps are vortex generators.
The main direction in which they aim is the underfloor to accelerate flows under the car improving the effect of the diffuser.

They are stepped in cascade to have a good lateral repartition and having multiple layers.

[effuno]

The steps are vortex generators.
The main direction in which they aim is the underfloor to accelerate flows under the car improving the effect of the diffuser.

They are stepped in cascade to have a good lateral repartition and having multiple layers.

Thanks ogami for the reply. I was thinking on the same lines, but does this not have too many negatives ?
to list some thoughts :

1) the vortex flow has a higher drag than laminar flow

2) the thickness(diameter?) of the vortices will be difficult to control, especially since this region is hugely influenced by the flow over wheels ? (bargeboards condition the wheel flow, but, I guess, only to an extend and not completely, as the bargeboard sizes are restricted by other design parameters involving flow in and around sidepods, undertray flow etc )

3) the chances for a vortex breakdown are too high, again as it is difficult to control being in the wake of wheel flow and this in turn could make the car too sensitive to the ride height changes (through suspension travel, bumps and kerbs in track)



And i guess you were mentioning to the horizontal plates as vortex generators. So, What does the stepped profile on the top part of bargeboards do to the flow ? Again, it has to generate vortices, i guess, but this time the flow goes into or around the sidepods ? I was under the impression that the sidepods were designed for laminar flow to reduce drag, though turbulent flow does give better mixing.

[Ogami musashi]

The steps are vortex generators.
The main direction in which they aim is the underfloor to accelerate flows under the car improving the effect of the diffuser.

They are stepped in cascade to have a good lateral repartition and having multiple layers.

Thanks ogami for the reply. I was thinking on the same lines, but does this not have too many negatives ?
to list some thoughts :

1) the vortex flow has a higher drag than laminar flow

No, a turbulent (a turbulent may have vortex, but not necessary, a vortex is a turbulent flow) has higher skin friction drag but well managed provide less pressure drag.
On an F1 the vast majority of drag is pressure drag.

2) the thickness(diameter?) of the vortices will be difficult to control, especially since this region is hugely influenced by the flow over wheels ?

The bargeboards benefit from the flow coming from the undersize of the nose, the flow coming out of the wheel are directed appart by end plates on the front wing, suspension aerodynamic covers etc..
however the profile of the barge board slows down the flow before transition to a vortex.

3) the chances for a vortex breakdown are too high, again as it is difficult to control being in the wake of wheel flow and this in turn could make the car too sensitive to the ride height changes (through suspension travel, bumps and kerbs in track)

That's precisely why you have that staged profile, by the way i think you misunderstood my point (or i wasn't clear enough):

And i guess you were mentioning to the horizontal plates as vortex generators. So, What does the stepped profile on the top part of bargeboards do to the flow ? Again, it has to generate vortices, i guess, but this time the flow goes into or around the sidepods ? I was under the impression that the sidepods were designed for laminar flow to reduce drag, though turbulent flow does give better mixing.

No i don't talk about the horizontal plates i talk about the squared (stepped) lines at the end of the barge board. the squared lines force the "laminar-turbulent" transition.

By making a sharp line, it forces the particles to stay attached to attain an infinite velocity which is impossible of course so they morph into a vortex behavior.

The multiple stage profile is comprised of one big vortex, then small vortex.
This gives a huge vortex scale with a lot of inertia thus minimizing the vortex breakdown possibility.

[effuno]

No, a turbulent (a turbulent may have vortex, but not necessary, a vortex is a turbulent flow) has higher skin friction drag but well managed provide less pressure drag.
On an F1 the vast majority of drag is pressure drag.

I do agree.. but i was talking of a scenario without flow separation... I thought the flow through the diffuser was kept laminar, to the point such that it just avoids separation ! sorry if i am wrong.

The bargeboards benefit from the flow coming from the undersize of the nose, the flow coming out of the wheel are directed appart by end plates on the front wing, suspension aerodynamic covers etc..
however the profile of the barge board slows down the flow before transition to a vortex.

That confuses me. Endplates does redirect some flow from hitting the wheel, but I wonder if it has anything to do directly with the flow that has already gone over the rotating wheel. The suspension components too doesnt seem to affect the after-wheel flow much, though it might work on the flow that spills from the sides(top, should I say) of the wheel.

That's precisely why you have that staged profile, by the way i think you misunderstood my point (or i wasn't clear enough)

I am not sure. Maybe I did not read that properly. I have understood some things better when I read it for a second time, in another session...i'll read through that again tomorow...Right now I am a bit busy with work .. Sorry..


Between, whats the function of the horizontal plates ?:)

[Ogami musashi]

I do agree.. but i was talking of a scenario without flow separation... I thought the flow through the diffuser was kept laminar, to the point such that it just avoids separation ! sorry if i am wrong.

I think you confuse "attached" and "laminar". A turbulent flow with vortex can be attached without any problem.
That's the whole interest of low turbulent flows, they stay attached with ease and the expense of the skin friction drag but overall provide more efficiency.

So in the case of the diffuser, you can have a turbulent flow condition that allows for a steeper diffuser for example.

That confuses me. Endplates does redirect some flow from hitting the wheel, but I wonder if it has anything to do directly with the flow that has already gone over the rotating wheel. The suspension components too doesnt seem to affect the after-wheel flow much, though it might work on the flow that spills from the sides(top, should I say) of the wheel.

The first object air encounters is the front wing. The end plates modify the nearby layers by making them turbulent.
As turbulent flows "poison" the adjacent flows, those flows are also redirected away from the wheel.
Okay of course not all the particles are deviated away from the wheel, but compared to a no end plates situation, the barge board is much more effective then.
The suspension coverings (i don't find the right word, i would say the streamlining of suspension arms) also redirect air and prevent for parasite drag peaks around the side pods so this include the barge board section.

The whole deal of nowadays F1 cars and why the loose so much downforce when following someone, is to reduce parasite drag which is pressure drag mainly.

I am not sure. Maybe I did not read that properly. I have understood some things better when I read it for a second time, in another session...i'll read through that again tomorow...Right now I am a bit busy with work .. Sorry..


Between, whats the function of the horizontal plates ?:)

No problem, in all honesty, despite the fact that i know from sources that barge board shapes are vortex generators and my knowledge in fundamentals of aerodynamics, F1 cars now are so advanced as far as applied aerodynamics are concerned that i can't tell with 100%.
A competitor team's aerodynamist may not even know the purpose of one car's aerodynamic device, and sometimes even the group that developed the device doesn't know what are the flow physics behind that.

So i know barge boards are vortex generators because i heard/read it from team engineers, i also know that such a shape will for sure develop vortex, i also know from aerospace example (of which i'm sure) that multiple vortex generators are quite the hype if you want to be a killer aerodynamist and also know a bit about the physics behind (but still need to learn so much as turbulence is definitely another level in aerodynamics) so i presume i may be correct, however...

[effuno]

I do agree.. but i was talking of a scenario without flow separation...

I think you confuse "attached" and "laminar". A turbulent flow with vortex can be attached without any problem.

i did mean to say separation, just that i did not express it clearly.. i'll try again.. : I do realise that tubulent stays attached better than laminar.. What I refering to by saying ' without flow separation' is about a situation where flow does not have any tendency to separate when it is laminar and therefore does not neccesitate the need for transition...I thought thats the state of flow in diffuser.... Hope that conveys it better.. Sorry.. My mistake. !
Thanks for the info..You will surely have better info on these than me as the sources you quote are more reliable than mine.

That confuses me. Endplates does redirect some flow from hitting the wheel, but I wonder if it has anything to do directly with the flow that has already gone over the rotating wheel. The suspension components too doesnt seem to affect the after-wheel flow much, though it might work on the flow that spills from the sides(top, should I say) of the wheel.

The first object air encounters is the front wing. The end plates modify the nearby layers by making them turbulent.
As turbulent flows "poison" the adjacent flows, those flows are also redirected away from the wheel.
Okay of course not all the particles are deviated away from the wheel, but compared to a no end plates situation, the barge board is much more effective then.
The suspension coverings (i don't find the right word, i would say the streamlining of suspension arms) also redirect air and prevent for parasite drag peaks around the side pods so this include the barge board section.

I dont think i have any disagreement with this... What I said was that the endplates and suspension elements cant do anything about the flow once it has gone over the wheel, though they do put all their best effort before the flow hits the wheels.. ..!

[Ogami musashi]

did mean to say separation, just that i did not express it clearly.. i'll try again.. : I do realise that tubulent stays attached better than laminar.. What I refering to by saying ' without flow separation' is about a situation where flow does not have any tendency to separate when it is laminar and therefore does not neccesitate the need for transition...I thought thats the state of flow in diffuser.... Hope that conveys it better.. Sorry.. My mistake. !

No problems, i do myself have difficulties to express myself with the correct words in english sometimes.

By the way,many times, especially with F1 bodies (which are now streamlined but because of wheels and suspension arms are still considered bluff)it is not possible to keep a laminar flow and in the case of an aggressive diffuser this is the case.
In those cases it is better to have what we call an early transition to make use of turbulent flow's proprieties to stay attached.

I'll digress a bit to show you a very relevant consequence of that:
The regulations reduced the steep angle of the diffuser, the minimum height of the front wing and the height of the rear wing.
Those regulations gave very aggressive profiles (as you can see a typical medium downforce front wing angle is already big) that make laminar condition impossible on the vast majority of the chord, this precisely why you see so many appendices all over the cars now.

Those vortex generators are so important in the overall efficiency of the car, if one of them fails to induce a steady vortex in the good direction you may loose 10% of the total downforce.

That's why they're so important.

My digression is that, in 2009, since those vortex generators are so sensible (so when following a car you loose a lot of downforce because they're not efficient anymore), many of them will be banned.
To make of for the loss of downforce, wings and diffuser will be changed.
For the diffuser it may still use vortex generators (but the vortex generators will be standard) as the steep angle will be greater, but for the wings they will be larger and closer to the ground, for the front, and higher for the rear.
In this case a more laminar flow condition is to be expected.

I dont think i have any disagreement with this... What I said was that the endplates and suspension elements cant do anything about the flow once it has gone over the wheel, though they do put all their best effort before the flow hits the wheels.. ..!

Well that's what i wanted to say, the air is shaped before the wheels so basically we try to make the air that comes to the wing going outside when it leaves the wheels, so the barge board is not so disrupted.
Suspension streamlined arms are of the concept, the goal is to make the air past them cleaner.

Of course a total clean condition is not possible yet.

[Conceptual]

Ogami,

Since you are so into this stuff, what designs have YOU come up with? I have a friend that has 6 degrees in engineering, and when I brought up vortex physics, he almost blew up!

Is it possible to make a front wing shape that would literally make a vortex induced 'vacuum' that the tub would actually move within? Maybe have the vortex tails drive into the rear wing?

That is what it seems like these cars are doing already.

What do you think?

Chris

[Belatti]

Chris, please tell me where do they give degrees away!
I mean, 6 degrees in engineering! What kind of degrees?

Here I´m fighting hard to get just one! We were 800 in 1st year and now we are just 20 in the 5th! Engineering is not for anyone.

[PNSD]

Chris, please tell me where do they give degrees away!
I mean, 6 degrees in engineering! What kind of degrees?

Here I´m fighting hard to get just one! We were 800 in 1st year and now we are just 20 in the 5th! Engineering is not for anyone.

It may be easily one of the most interesting areas of science, but yeah its damn hard.

[effuno]

I have a friend that has 6 degrees in engineering, and when I brought up vortex physics, he almost blew up!

Half an year or so ago I would have reacted the same way..I did not know much about vortex generators.. but quite recently i've learned more about turbulence, transition, separation , vortex generators etc..! So, i do understand the theories ..now its about learning different applications which, I believe, will come with experiece(this.. ).


Thanks ogami.. I was under the impression that the undertray did not use much of vortex flows, except for the endplates at the diffusers which creates edge vortices..!Thought the vortex generators on bargeboards were more useful in sealing the flow from moving underneath the car(more like skirts)...But a closer look at it made me realise that it had to go underneath, the way its designed, and got me a bit confused.. Thanks for correcting me..!

We were 800 in 1st year and now we are just 20 in the 5th!

A 4 year engineering course, I guess..

[checkered]

By the way,many times, especially with F1 bodies (which are now streamlined but because of wheels and suspension arms are still considered bluff)it is not possible to keep a laminar flow and in the case of an aggressive diffuser this is the case. In those cases it is better to have what we call an early transition to make use of turbulent flow's proprieties to stay attached.

From an aerodynamical

standpoint this is exactly what I was talking about quite some time ago in the "Franework (sic) For Discussion - F1 2011 Aero Regs (* see quote below)", inspired by the illustrations of the new Formula Nippon chassis by Swift. The bluffness is a very fundamental contradiction between the sleek image and the functioning of a "Formula" type open wheel car, a basic shape carried over from days when computational fluid dynamics were constrained within academic circles and racecar designers went mostly by intuition, trial and error. I'm a bit troubled by this and keep thinking that it's not unlike a situation where the track width of European railroads can be traced back to a Roman legions' chariot standard ... With examples like the "box fish" Mercedes prototype (with a Cd of 0.19) is it conceivable to an aerodynamicist that there could be a much more intelligent way of shaping open wheel racecars, unconventional but still in keeping with logical traditions? I'm also wondering whether, given the chance, the OWG has remained only on a functional level or have they perhaps addressed issues that go somewhat deeper into the philosophy of F1 engineering ...

My digression is that, in 2009, since those vortex generators are so sensible (so when following a car you loose a lot of downforce because they're not efficient anymore), many of them will be banned. To make of for the loss of downforce, wings and diffuser will be changed. For the diffuser it may still use vortex generators (but the vortex generators will be standard) as the steep angle will be greater, but for the wings they will be larger and closer to the ground, for the front, and higher for the rear. In this case a more laminar flow condition is to be expected.

In this regard I don't quite follow the OWG's logic. If I'm not completely off my rocker (always a possibility), if an aerodynamicist raised the rear end of the diffuser and wanted to make it more efficient and produce a predictable wake, wouldn't he also lengthen it considerably so as perhaps not to have problems with the separation of a laminar flow? Or is it completely impossible from the outset to make an efficient laminar diffuser in F1, no matter what? For all I know a steep and short section might suit the variety of conditions in F1 best but right at this moment I can't quite imagine why that'd be.

There are a few things about the basic geometry that instictively bother me nonetheless. The general interaction between the bodywork and the wheels doesn’t seem very well articulated, but one hardly sees any other approach in the larger formulae these days. The wings extend half way in front of the tyres – not completely, nor not at all. To me this “half way” approach seems like an almost completely meaningless compromise and complication. It may be merely a stylistic preference on my part, but I want that the interaction between the chassis, wings and wheels is either very direct or very minimal.

[Ogami musashi]

From an aerodynamical

standpoint this is exactly what I was talking about quite some time ago in the "Franework (sic) For Discussion - F1 2011 Aero Regs (* see quote below)", inspired by the illustrations of the new Formula Nippon chassis by Swift. The bluffness is a very fundamental contradiction between the sleek image and the functioning of a "Formula" type open wheel car, a basic shape carried over from days when computational fluid dynamics were constrained within academic circles and racecar designers went mostly by intuition, trial and error. I'm a bit troubled by this and keep thinking that it's not unlike a situation where the track width of European railroads can be traced back to a Roman legions' chariot standard ... With examples like the "box fish" Mercedes prototype (with a Cd of 0.19) is it conceivable to an aerodynamicist that there could be a much more intelligent way of shaping open wheel racecars, unconventional but still in keeping with logical traditions? I'm also wondering whether, given the chance, the OWG has remained only on a functional level or have they perhaps addressed issues that go somewhat deeper into the philosophy of F1 engineering ...

The "bluff" designation is given by the wheels alone.
If the wheels where not here to disrupt air (even when they are covered) a car, especially a F1 car would be more towards the streamlined.

But this is an open wheeler so..


In regard to your quote on the 2011 topic, the front wing width has been reduced over the year by regulations in a attempt to decrease their efficiency thus increasing the drag...which didn't work at all since end plates now divert flows quite efficiently while providing good induced drag specs.

Any way, in 2009 the front will come back to its more conventional width 180 instead of 140 (of course the max width of the car will be 2meters).

It will require less aggressive end plates.

The OWG, IMHO is to tackle tasks at once, 2009 is a rare change in F1 that we haven't see since long time, they will look at future regs but only there's a "less drag" FIA boosted way of development.
The way to do that is up to the teams then.

In this regard I don't quite follow the OWG's logic. If I'm not completely off my rocker (always a possibility), if an aerodynamicist raised the rear end of the diffuser and wanted to make it more efficient and produce a predictable wake, wouldn't he also lengthen it considerably so as perhaps not to have problems with the separation of a laminar flow? Or is it completely impossible from the outset to make an efficient laminar diffuser in F1, no matter what? For all I know a steep and short section might suit the variety of conditions in F1 best but right at this moment I can't quite imagine why that'd be.

The problem with "laminar" is that is it a very weak situation, if the gradient of pressure become near adverse there's already risks of separation.
Also please bear in mind that a steeper curve of a diffuser is not such a problem since the vortex direction will be above the the following car (that is why the rear wing is increased in height too).

But most, the problem with today's F1 is not really the "dirty air" as described, if you follow a nascar stock car you'll experience vortex all the way. Sure they'll have less strong pressure variations but by definition a slipstream condition is a low total pressure condition so that's not a clean condition.

The problem is really into the sensitivity of wing and more of the vortex generators.
They are small and generally have aggressive profile to induce strong vortex.
Because of that any change in yaw or pitch angle with the freestream will affect their performance quite a lot.
Nowadays, they're so important on the overall efficiency that just one pair of vortex generators failing to entertain a boundary layer create a lot of drag and a big fall of downforce.


That's why the OWG wants to reduce the number of vortex generators, make primary surfaces less sensitive and having a standard middle of front wing so that vortex generation on the underfloor is not so sensible.



While i'm affraid we could loose quite a bit of technological advance with this measure (look at the middle sections of wings that year, some of them are really complex),i trust the OWG.

By the way on this subject, many caution to take, as said, the rules are still under debate and it is not until early march that something clear will emerge and it depends a lot of the budget cap idea success or not.

[effuno]

is it not better to trip the flow at a point slightly upstream of the point where the separation occurs, rather than induce vorticity as early as from the bargeboards ? This would result in less drag....!

With all the wind tunnel data at their disposal it doesnt seem to be a tough task to find the separation point at different speeds and attitudes..! and then leave some vortex generators on the surface of diffusers ..!!

Or, is it because the higher speed, and thus, the lower pressure, of vortices is more desirable ? i guess, the efficieny will drop a little with these vortices in the underbody, though downforce might increase !

edit : And also, does laminar flow not have long-er lasting momentum than a vortex flow ? .. I mean..vortices tend to die down whereas laminar flow moves with the same(almost) momentum (until separation). the reattatching of vortices is due to its momentum in y and z direction( to use coordinate system), and initially has more momentum in x direction as well but tends to die down ...!!

Frankly, am not sure my assumptions are right, as F1 teams wouldn't have put vortex generators on bargeboards without reason