Idea for avoiding dirty air

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Post Tue May 20, 2008 6:08 pm

I was watching Mythbusters and they made a wind tunnel. They used some kind of buffer made of soda straws to achieve laminar flow in the tunnel.

I wonder if something similar could be used at the exit of the diffussor to minimize dirty air. It is possible?
Ciro
Ciro Pabón
 
Joined: 10 May 2005

Post Tue May 20, 2008 6:57 pm

I always though the problem was not that the air was dirty/turbulent but that the regulations year on year dictated shorter and steeper diffusers in order to curb underbody downforce levels, until eventually they reached the level today, where the air is departing at a very steep (vertical) angle compared to a deep, shallow diffuser or a tunnel underbody.
zac510
 
Joined: 24 Jan 2006
Location: London

Post Tue May 20, 2008 10:18 pm

zac510 wrote:I always though the problem was not that the air was dirty/turbulent but that the regulations year on year dictated shorter and steeper diffusers in order to curb underbody downforce levels, until eventually they reached the level today, where the air is departing at a very steep (vertical) angle compared to a deep, shallow diffuser or a tunnel underbody.


Well if that is the reason things are going to get even worse next year as the diffuser is going to be even steeper and shorter (I believe starting at the rear wheel's centre-line rather than the front of the wheel and rising to a max height of 17cm than 12.5cm).

Oops again FIA :roll:
Powertrain Cooling Engineer
Scotracer
 
Joined: 22 Apr 2008
Location: Edinburgh, Scotland, UK

Post Tue May 20, 2008 10:50 pm

I'm happy to be corrected. Maybe in 2009's case the overall volume of air will decrease (by the changes all over the car) and the change will be justified.
zac510
 
Joined: 24 Jan 2006
Location: London

Post Wed May 21, 2008 9:37 am

Are you sure they made them steeper and steeper?

In any case the FIA made them shorter and lower too. So any steep angle increase was very nullified.

Next year the steeper angle will allow for less extension of the upwash, which is one of the main reason of decreased downforce, and the coupling with rear wing being less, the rate of flow will surely be less i think.

Any way, turbulences are a problem but if you want slipstream you need them, so laminar flow is not a good idea.

Or you can try to shape the wake like what the CDG was supposed to do, that is having less turbulence in a downwash toward front wing while having re-circulation on the higher and side parts of the car (thus giving less drag).

But the rear wing suffers then...Well that's a complex thing.
Ogami musashi
 
Joined: 13 Jun 2007

Post Wed May 21, 2008 10:07 am

Scotracer wrote:
zac510 wrote:I always though the problem was not that the air was dirty/turbulent but that the regulations year on year dictated shorter and steeper diffusers in order to curb underbody downforce levels, until eventually they reached the level today, where the air is departing at a very steep (vertical) angle compared to a deep, shallow diffuser or a tunnel underbody.


Well if that is the reason things are going to get even worse next year as the diffuser is going to be even steeper and shorter (I believe starting at the rear wheel's centre-line rather than the front of the wheel and rising to a max height of 17cm than 12.5cm).

Oops again FIA :roll:


this is again one of the examples where the FIA makes an effort of intensive consultation, a team expert group proposes a solution, the teams vote in favor and the FIA codifies the whole thing. the moment someone perceives a problem the responsibility is entirely on the FIA instead of the other participants who have contributed to the rule. when will this nonsense stop to blame the governing body for everything that is perceived as negative. they surely could not have acted more responsible in this particular case!!! :roll: [-X #-o
Formula One's fundamental ethos is about success coming to those with the most ingenious engineering and best .............................. organization, not to those with the biggest budget. (Dave Richards)
WhiteBlue
 
Joined: 14 Apr 2008
Location: WhiteBlue Country

Post Wed May 21, 2008 10:43 am

Ogami musashi wrote:Are you sure they made them steeper and steeper?

In any case the FIA made them shorter and lower too. So any steep angle increase was very nullified.


I can't be sure, but shortening it makes it steeper automatically.
zac510
 
Joined: 24 Jan 2006
Location: London

Post Wed May 21, 2008 11:06 am

I don't know Ciro - but I think you have the right sort of idea (is it mainly the diffuser that cause the problem 'tho?)

When these discussions come up - often slipsteaming and over-taking get mixed in the same conversation. I think it can confuse the issue.

Sure - getting a tow helps overtaking. But it's not essential.

Giving cars the ability to follow each other as the chose and as close as they like would help overtaking (without needing a slipstream). We see cars with a significant laptime advantage being unable to get past a slower car these days. Because their speed advantage in corners is negated by the car in front. If they could hold that corning advantage, they would get into the next straight at a higher speed and have much more chance of making the pass stick.

OK - my racing experience is limited to Sim racing - but the tactics still work. Jamming yourself up someones arse rarely achieves anything other than contact and you getting slowed down; hanging back a touch before a crucial corner and getting a clean fast drive off that corner often sets you up for a pass at the end of the next straight (as if you had an overtake button ;)). Of course the opportunist pass can happen, but the do in F1 too - but are rare and rely on a mistake from the other guy.

So, cleaning up the wake is surely more important than allowing slipstreaming.

A slight aside - seeing top speed figures in the F1 races may not be an indication of engine power or low downforce, it might be an indication of a car that leaves the last corner with more speed than it's rivals - I guess a chart showing the accleration to top speed would be a better indicator.
RH1300S
 
Joined: 6 Jun 2005

Post Wed May 21, 2008 11:07 am

zac:Why?
Last edited by Ogami musashi on Wed May 21, 2008 11:08 am, edited 1 time in total.
Ogami musashi
 
Joined: 13 Jun 2007

Post Wed May 21, 2008 11:20 am

RH1300S wrote:I don't know Ciro - but I think you have the right sort of idea (is it mainly the diffuser that cause the problem 'tho?)

When these discussions come up - often slipsteaming and over-taking get mixed in the same conversation. I think it can confuse the issue.

Sure - getting a tow helps overtaking. But it's not essential.

Giving cars the ability to follow each other as the chose and as close as they like would help overtaking (without needing a slipstream). We see cars with a significant laptime advantage being unable to get past a slower car these days. Because their speed advantage in corners is negated by the car in front. If they could hold that corning advantage, they would get into the next straight at a higher speed and have much more chance of making the pass stick.

OK - may racing experience is limited to Sim racing - but the tactics still work. Jamming yourself up someones arse rarely achieves anything other than contact and you getting slowed down; hanging back a touch before a crucial corner and getting a clean fast drive off that corner often sets you up for a pass at the end of the next straight (as if you had an overtake button ;)). Of course the opportunist pass can happen, but the do in F1 too - but are rare and rely on a mistake from the other guy.

So, cleaning up the wake is surely more important than allowing slipstreaming.

A slight aside - seeing top speed figures in the F1 races may not be an indication of engine power or low downforce, it might be an indication of a car that leaves the last corner with more speed than it's rivals - I guess a chart showing the accleration to top speed would be a better indicator.


i disagree. The field is so tight and performance between cars so close than not allowing slipstream would be a severe limitation.

Not allowing slipstream would restrict overtakings to straight lines.
If you want to overtake in a corner you need to go offline that means you need to take a longer line, if you don't enjoy a better acceleration out of the corner you can't overtake.

I Think one great thing in the rare occasions of overtaking in F1 is that the moves are quite not classical many times occuring in portions were other series running can't do that.

There're many in-corner overtaking in F1, and the last thing i want to see is the classical outbrake-straight line passes only. I love when the track overtaking possibilities are increased by your car possibilities.


Slipstream and cornering are opposed. Slipstream means loss of downforce.
But actually in F1 we are in a situation where we don't even have slipstream to significant extent, and yet you lose downforce...so we have the worst of both worlds.

If slipstream was present and turbulent wake sufficiently weakened, the downforce loss caused by slipstream would be bearable because restricted.

You actually have to go as close as half a car lenght at 250km/h to lose 20% of drag, while you lose about 45% of your downforce!

With the rev limiter the small size of the slipstream is even more a problem.


As of final note, the diffuser's turbulences are not a problem and they decay very fast. The problem is the turbulences of the rear wing that because of the coupling with the diffuser are strengthened and extend far away from the car to mix with the upwash.

Now the upwash is a problem and needs to be carefully shaped.

Well a simple solution would be small venturi channels..I don't understand why F1 is so afraid of that; Not entering into the "whole grip generated by ground effects" we could use GP2 like package (venturi+wings) and that works fine..
Ogami musashi
 
Joined: 13 Jun 2007

Post Wed May 21, 2008 11:28 am

I tend to agree that wings and diffusers are now forced to be too steep and aggressive leading partially (but primarily) to the problem of following other cars. To get Df out of the current wings and floor the devices have to set very steep with aggressive steps in the floor. The cascade of the floor, rear wishbone, beam wing and finally upper wing all conspire to end up with this near vertical spiralling exit flow.

You will see from looking closely at a F1 cars aero:-
• RW flap set almost vertical
• Side diffuser channels start with a steep stepped incline
• Side channel exit aided by driveshaft\toe link fairing
• Centre diffuser tunnel set very tall with steep exit

I would suggest larger longer-chord lower-AOA wings\diffusers, may be with wings having a deep section to incur drag. Additionally restricting profile changes across the span.

Plus limiting wishbone\pushrod\driveshaft profiles to smaller and fixed cross sections.
scarbs
 
Joined: 8 Oct 2003
Location: Hertfordshire, UK

Post Wed May 21, 2008 11:36 am

Ogami musashi wrote:zac:Why?


I'm assuming they'll always build it to the maximum height allowable at its rear-most point.
zac510
 
Joined: 24 Jan 2006
Location: London

Post Wed May 21, 2008 11:43 am

Wings are set at too much AOA that is clear.

About diffuser i think the spiraling is due to rear wing turbulence mixing and that's because of the coupling, so i don't think the steep angle is a problem.

It may be a problem of english, but i don't understand how current diffuser can be steeper and steeper?

The lenght is limited but the height too so all in one you're in the same steep angles isn't it?

About next year i think the rate of flow will be lower (because of shortened diffuser and reduced coupling with rear wing) but the steeper angle will enable for faster pressure recovery so the upwash will be smaller i think.
Ogami musashi
 
Joined: 13 Jun 2007

Post Thu May 22, 2008 2:15 am

Ogami musashi wrote:Are you sure they made them steeper and steeper?

In any case the FIA made them shorter and lower too. So any steep angle increase was very nullified.


Not really . . . I did the diffuser for a 2009 drafting study I'm solving in CFD and under the rules one could easily do a diffuser just as steep as before. Because of the smaller, further rear wing though, I've had to crank the angle down 2 degrees lower than before from 2007 for the center section. But the rules allow a steeper section, and I am sure some team will figure out a way to pull on that diffuser hard. But past 250mm from the centerline I've actually increased the angle with positive results. AND you can go even further behind the car when within 250 and 150mm of the centerline than before, so I am sure teams will be taking advantage of that to pull some magic out the diffuser.

Let's not even get into the mesh the wider rear tires create in terms of wake characteristics . . .

Quite frankly the 2009 rules are rubbish. They are NOT keeping the same levels of drag, they are NOT cutting downforce by 50% and they are NOT cleaning up the wake as much as the FIA make it sound like. And this is not on an optimzed car, either, so I bet there's even more downforce to be made, legally.

I will ask about getting permission to post the results here so we can see what garbage the 2009 rules really are.
AeroGT3
 
Joined: 29 Mar 2006

Post Thu May 22, 2008 3:45 am

scarbs wrote:I would suggest larger longer-chord lower-AOA wings\diffusers, may be with wings having a deep section to incur drag. Additionally restricting profile changes across the span.

Plus limiting wishbone\pushrod\driveshaft profiles to smaller and fixed cross sections.


I've long held

that restricting the AoAs of any shapes along the longitudinal axis of the vehicle could make for an easier time of following another F1 car. Of course, this is based on preferences the motivations of which can and will be found lacking and/or possibly aerodynamically irrelevant on closer examination. The way Ogami describes things, also shortening the diffuser sufficiently seems to have the potential to produce a steep, but less energised and more localised, i.e. short and unremarkable, "wave" of turbulence. I'm not entirely clear on whether the level of the energy or the span of the "disturbance" are the main "problems" currently - there could also be something else to the predictability, method of decay and distribution of the turbulent wake - something more easily managed by less aggressive shapes than todays'.

The attention to detail in shaping suspension elements to flow, albeit dictated by its contemporarily induced realities, is also a faint echo from the "lost opportunities" of coupling the flows to the solids in motorsport to me. Like the first wing struts being attached directly to uprights, or the Lotus 88 double chassis construction. Now that adaptable aero is coming into focus, albeit tentatively, I've entertained visions of doing away with "traditional" wings and merging the functions of suspension elements and airfoils into physically integrated entities. In so relating the movement of the sprung part and steering input to downforce might lead into thus far less meaningful setup variables becoming important - and could present a new challenge in mathematical modelling as well.

Or so I'd presume without having attained or providing tangible evidence to this effect; and having to admit that this line of thought is also steered by a desire to seek out novel ways to "unclutter" the cars.

AeroGT3 wrote:Quite frankly the 2009 rules are rubbish. They are NOT keeping the same levels of drag, they are NOT cutting downforce by 50% and they are NOT cleaning up the wake as much as the FIA make it sound like. And this is not on an optimzed car, either, so I bet there's even more downforce to be made, legally.

I will ask about getting permission to post the results here so we can see what garbage the 2009 rules really are.


Not that it'd be among my favourite pastimes to discover more reasons why all the different facets of F1's self-governance have gone astray, I'd still be interested to see the actual observations behind your statement. My main concern isn't so much whether the promises and predictions were wrong (it's the nature of F1 to use rules changes to unexpected effects), as the scale of the misappraisals. I'm not too worried in the sense that within such discrepancies, positive and negative effects tend to be evenly distributed anyhow. Not to mention that these future experiences will morph into another gleefully quixotic efforts soon enough.
"In theory there's no difference between theory and practice. In practice, there is." - Yogi Berra
checkered
 
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