Mclaren Mercedes MP4-25

A place to discuss the characteristics of the cars in Formula One, both current as well as historical. Laptimes, driver worshipping and team chatter do not belong here.
SZ
SZ
0
Joined: 21 May 2007, 11:29

Re: Vodafone Mclaren Mercedes MP4/25

Post

Pup wrote:We may be on the same page already - adding a stream of air to the underside of the wing to keep the boundary layer attached (which could possibly be controlled to a degree). But I'm not sure I'd call that air 'disruptive'. Still thinking.
I'm thinking the other way...

thestig84
thestig84
10
Joined: 19 Nov 2009, 13:09

Re: Vodafone Mclaren Mercedes MP4/25

Post

segedunum wrote:
thestig84 wrote:Or your quite happy with the base line of the car and you know now is the only time to gather this data.
You don't do that at the expense of other things you need to do in the tests.
Your right...you do it at the same time as other things, like they did. According to the Mclaren web site Button was still using the time to familiarize himself with the car while

"The dry start to the day permitted aerodynamic measurements of the car to be taken as planned. This included short runs with instrumentation on the car to gauge flow structures."

segedunum
segedunum
0
Joined: 03 Apr 2007, 13:49

Re: Vodafone Mclaren Mercedes MP4/25

Post

thestig84 wrote:According to the Mclaren web site Button was still using the time to familiarize himself with the car...
Good for him, but that doesn't amount to actually doing anything useful.
"The dry start to the day permitted aerodynamic measurements of the car to be taken as planned. This included short runs with instrumentation on the car to gauge flow structures."
They weren't getting much else done then.

User avatar
Fil
0
Joined: 15 Jan 2007, 14:54
Location: Melbourne, Aus.

Re: Vodafone Mclaren Mercedes MP4/25

Post

SZ wrote:
Pup wrote:We may be on the same page already - adding a stream of air to the underside of the wing to keep the boundary layer attached (which could possibly be controlled to a degree). But I'm not sure I'd call that air 'disruptive'. Still thinking.
I'm thinking the other way...
You're thinking they're purposely attempting to further disrupt airflow behind the car to impede closely-following cars..?

:shock: my god you're sinister!
Any post(s) made by this user are (semi-)educated opinion(s), based on random fact(s) blurred by the smudges of time.
Any fact(s) claimed by this user will be supplemented by a link to the original source of said fact(s).

SZ
SZ
0
Joined: 21 May 2007, 11:29

Re: Vodafone Mclaren Mercedes MP4/25

Post

segedunum wrote: They weren't getting much else done then.
You don't build a rig like this overnight. This was planned a long time ago.

You're making a lot out of something that's really quite easy to explain - very likely they're validating the effects of the new size front tyres.
Fil wrote:You're thinking they're purposely attempting to further disrupt airflow behind the car...
Yes...
Fil wrote:...to further disrupt airflow behind the car to impede closely-following cars..?
NO. But very close. Think of what happens when you disrupt the airflow on a certain part of a wing that isn't the high pressure side... VERY NEARLY THERE PEOPLE.
Fil wrote::shock: my god you're sinister!
Yes :wink:.

Raptor22
Raptor22
26
Joined: 07 Apr 2009, 22:48

Re: Vodafone Mclaren Mercedes MP4/25

Post

SZ wrote:
newbie wrote:some of the explanations here for that wake array have been simply rediculous. thanks for the laughs!!! :lol:

As some have suggested, it is a pitot array for measuring the front wheel wake...possibly THE most important characteristic of an F1 car as it's position and behavior has a knock-on effect on floor and diffuser performance.
Thank God someone's thinking - it's just a bloody wake rake, used in aero testing all the time. You use these in a tunnel to interrogate flow, e.g. in F1 you'd use it to measure performance against CFD. Flow around a rotating wheel is highly unstable and very, very difficult to get right in CFD. The interactions between wheel and front wind endplate are very significant also (a few good papers on this floating out) so all in all there's a lot going on in this region and it's important to understand what's what.

They'll probably have chosen a few steady state positions (straight ahead, full lock turning, etc) and are simply mapping the flow behind the front wheel to see what's what. It's possible they're also very smart and are using it to look at transient behaviours e.g. as the car moves from straight ahead to yaw, as the front wheel turns, etc.

You can pick up the steady state positions in a wind tunnel no problem but there are always scaling effects.

You can't pick up the transient stuff in a wind tunnel as you can't reposition a model quickly enough (not at >=50% scale).

It's a pain in the ass having a full grid of pitot tubes as that's quite intrusive and the channel count is very high, much easier to manufacture a single row and then just traverse that. They're probably sampling very, very quickly.

Given that the rake alone takes an age to make, I don't think this is a sign of desperation from McLaren, they'd have looked at building this a long time ago as getting some decent data out of a slow day or similar.

n smikle, you do it in a wind tunnel as easily as you would on track either with a similar rake, usually with one fixed to the tunnel. The device that you traverse doesn't necessarily have to be a pitot tube, it can be any device used to interrogate flow. This is pretty standard in aero testing for anything.

***
Tyre temperature is measured with infra red pyrometers generally and there's only three of them used (inner, middle, outer). How people might think these sensors - that run far wide of the width of the tyre - are measure tyre temperature is beyond me.

***
Mr G, Raptor 22, that cannot be what McLaren's doing with their rear wing. The pipe losses in such a duct would be huge. That alone gives me a clue as to what they might be up to, which is potentially far more sinister than what you've presented here.

Think about it.

***
Whoever pulled up that flow viz pic of last year's car, the distribution of paint looks normal. It'll blow off where the air is faster and it's fastest on the underside of a big wing in clean flow. I'd suggest they've applied it everywhere evenly.

I'd also suggest that that pic was taken when McLaren had no idea what the car was doing and were getting desperate, or you'd have no need to do the entire rear end.

Ok I'm completely sold on the wake measurement tool now. Good stuff guys.


re Mr G.'s concept, its loosely correct. The exact detail of their "flapblowing" I don't know. I've suggested that they could bleed off exhaust gases to a pressure chamber if they are using exhaust gas recirculation but I'm not even sure if that would work because exhaust gas can't provide much over pressure for long or you start to get back pressure on the engine. I know one team has looked into making EGR work for fuel economy purposes because theres quite a bit of unburned fuel exiting the rear of the car.
So any theories would make for interesting discussion.

SZ
SZ
0
Joined: 21 May 2007, 11:29

Re: Vodafone Mclaren Mercedes MP4/25

Post

Raptor22 wrote:re Mr G.'s concept, its loosely correct.
It's correct in that air goes from one place to another, but what it's intended to do there is completely misunderstood.

If I'm halfway near right and they've done a 'visible' flow viz of their rear wing, it'd make for an interesting diversion from what's possibly, really going on. Which would be highly contentious.

Nearly there, people...

manchild
manchild
12
Joined: 03 Jun 2005, 10:54

Re: Vodafone Mclaren Mercedes MP4/25

Post

Mr.G wrote:Hi All,

Whad do you think about this idea, is it possible? Sorry I do not go trough all 66 pages :(
Ciro's topic, item number 6.

http://www.f1technical.net.vs03001.virt ... 96d336fe04

Unfortunately, there's a mistake in description. It's been at least 3 or 4 years since I've drawn that. My idea was to have full width "nozzle" at the edge of the wing blade, trough which air could flow out. Depending on CFD, I though that it could either serve as an virtual "extension" of the wing @ 180°, or as a virual gurney flap @ 90°.

Image

Crabbia
Crabbia
9
Joined: 13 Jun 2006, 22:39
Location: ZA

Re: Vodafone Mclaren Mercedes MP4/25

Post

i'm not really that jacked up as far as aero is concerned, i mean i know my bernoulli's but who on this forum doesn't and applying bernoulli's to some of the finer details here is like trying to do surgery with an angle grinder, so i can only look at the oustide concepts.

i dont think mclaren are desperate. ppl have not mentioned the loss of the wheel rims in the new regs. the wheel rims enable the teams to control and understand the flow of air around the tires to an extent. this meant they could design a front wing or front wing end plates and then design wheel fairings to re-enforce or work with the flow that these wings created in the wheel area.

with the new regs, the situation is a one 180. now they have to understand what the tire is really doing to have effective flow around it. they can't use the wheel rims as a crutch anymore.

as SZ has said it is incredibly hard to model all the dynamic conditions is a wind tunnel, especially when scaling, but one thing they will never know for sure is how the new tyre characteristics affect the flow. and not just the new size, there will be a new construction of tyre due to the increased weight of the cars. this means different spring rates of the tyre, which again is impossible to model in a wind tunnel.

this is not like last year. mclaren probably poured the money they had allocated to the design and construction of wheel fairing into these pitot tube rakes as a means of continuing development in this area.
A wise man once told me you cant polish a turd...

Darknight
Darknight
0
Joined: 11 Feb 2010, 09:21
Location: Bahrain

Re: Vodafone Mclaren Mercedes MP4/25

Post

Would make sense if you could stall the wind for higher top speed. Or if at all possible for have a sort of ram air effect to get more power out of the engine.

SZ
SZ
0
Joined: 21 May 2007, 11:29

Re: Vodafone Mclaren Mercedes MP4/25

Post

Darknight wrote:Would make sense if you could stall the wind for higher top speed.
If you mean 'wing' not 'wind', then TEN POINTS TO THE DARK KNIGHT.

Then there's working out what's sinister about it... halfway there guys!
Crabbia wrote:as SZ has said it is incredibly hard to model all the dynamic conditions is a wind tunnel, especially when scaling, but one thing they will never know for sure is how the new tyre characteristics affect the flow. and not just the new size, there will be a new construction of tyre due to the increased weight of the cars. this means different spring rates of the tyre, which again is impossible to model in a wind tunnel.

this is not like last year. mclaren probably poured the money they had allocated to the design and construction of wheel fairing into these pitot tube rakes as a means of continuing development in this area.
Crabbia, most wind tunnel facilities worth their salt keep pitot rakes on hand. It's as fundamental a tool in an aerodynamicists' arsenal as flow viz paint, wool tufts, force balances, a manometer, etc. There is very little outlay in manufacturing them. It's a bunch of tubes on a take, and you can mount that in turn on some sort of traverse if you like. There are more complicated variations on the theme but if someone claims to know your way around basic aerodynamics and thinks that a pitot rake is exoctic... back to school - in any aero introductory text it's the first device mentioned right after Bernoulli's law gets an introduction.

I would contend that a likely scenario runs a bit like this: certain aspects of the flow field between the wing and endplate which end up going around the wheel are highly sensitive to the wheel dimensions (which are new, and subject to scaling effects). Certain aspects of that much are probably sensitive to tyre deformation also. I'd bet the tyres used on the car and those scale model tyres in the wind tunnel probably don't correlate exactly in terms of this aspect of performance, and McLaren simply wants to look to see if there's any difference. Some other teams might have done this differently. McLaren might be looking at aspects a little more advanced than average pressures (something often done in road car development where rotating wheels are concerned).

The usual idiot fanboy pitlane pundits (and I'm talking about those that call themselves 'professionals', not the fans on this board) would probably gain more from having a look at when the rake moves to get an idea of what conditions they're assessing than to wonder what sort of latest take on an unobtanium flux capacitor it might (not) be. Other teams will probably be looking at when the rake moves - e.g. are they looking at tyre wake when it's straight ahead running, turning, etc to assess what information they might be missing out on or what information McLaren might have missed in development.

Crabbia
Crabbia
9
Joined: 13 Jun 2006, 22:39
Location: ZA

Re: Vodafone Mclaren Mercedes MP4/25

Post

SZ wrote:There are more complicated variations on the theme but if someone claims to know your way around basic aerodynamics and thinks that a pitot rake is exoctic... back to school - in any aero introductory text it's the first device mentioned right after Bernoulli's law gets an introduction.
i understand wake rakes are a basic piece of kit, but the wake rake in question can hardly be considered a basic piece of kit can it?

and i dont mean soley in the construstion and implementation of the tool itself, i mean what area's are understudy and the mathematical tools to interpret them. the wake rake itself, while it is a complicated variation on the theme with the attachment to the car, is nothing compared to the maths needed to treat the real world situations mclaren are exploring.
A wise man once told me you cant polish a turd...

SZ
SZ
0
Joined: 21 May 2007, 11:29

Re: Vodafone Mclaren Mercedes MP4/25

Post

That wake rake is REALLY simple.

The area under study is a known PITA to simulate for any open-wheel racer - be it CFD or in the tunnel at scale.

The maths is actually really simple. Any competent motorsports DAQ package usually has the calculations built in, and even if not, they're pretty simple to get out. I could go into what's involved for the more advanced stuff if you like, but simply CP (coefficient of pressure normalised against some reference, in this case probably wheel speed) is dead simple.

Writing a tool to rip out only the relevant bits of, say, a lap of data is something a good third year engineering student can do without breaking a sweat.

Darknight
Darknight
0
Joined: 11 Feb 2010, 09:21
Location: Bahrain

Re: Vodafone Mclaren Mercedes MP4/25

Post

SZ wrote:
Darknight wrote:Would make sense if you could stall the wind for higher top speed.
If you mean 'wing' not 'wind', then TEN POINTS TO THE DARK KNIGHT.

Then there's working out what's sinister about it... halfway there guys!
Yes i meant wing sorry.. was typing before running to a meeting.

Right so we establish that the purpose is to stall the wing at speed. We also know that stalling the wing was done before with the flexiwings. I have a feeling though that the what SZ is alluding to as being sinister is an effect of this channelled air and not the fact that the wing is stalled. Are we 3/4 ways there?

SZ
SZ
0
Joined: 21 May 2007, 11:29

Re: Vodafone Mclaren Mercedes MP4/25

Post

You are.

Consider that you could theoretically stall the wing with some well-directed air, and that it'd be useful at speed.

Consider that there are times when you'd certainly not want this to happen either.

How does the system change between the two?

If this is potentially how it works, this is where it's potentially sinister... go on!