Corrado physics question.

[Henny 0]

Volkswagen used to claim that the rear spoiler increased downforce by around 30% at 100kph when deployed. Although it's not a big spoiler, it elevates into an airstream area immediately behind the car where a "swirl" is pushing down just above the tailgate.

 

Oh god, not this old gem again! :roll:

 

VW NEVER said that the spoiler increased downforce...

 

It's a spolier, not a wing! You're right about the swirl, but it DECREASES the lift effect by around 30% by spoiling (hence the name "spoiler"!) the airflow over the rear of the car which slows the air over the top of the car reducing the lift effect caused by the shape of the car passing through air.

 

No downforce is produced by the wing... have a look at the mounting brackets and tell me that they'd take enough force pressing down on them to make any difference when driving the car before they broke off... ;) :lol:

 

This is exactly the same reasons the TT had to be recalled and have that nasty little spoiler bolted on... too many of them span off at high speeds due to the rear end getting light due to the lift effect... the spoiler spoilt that lift and made the rear end more stable at speed stopping costly law suits...

 

 

p.s. John, not a dig at you mate, it's a topic that's cropped up quite a few times and is a common mis-conception about the effect of the spoiler which just happens to bug me... LOTS... ;)

[craigowl 0]

OT, but worth remembering that Howard Hughes did not want every bump in this world smoothed down.

Jane Russell's chest had to have engineering expertise applied so that she looked her best in HUghes' western "The Outlaw".

Hughes apparently spent a lot of time on this. What normal red blooded male wouldn't, given the opportunity!

[Yandards 0]

I did mention that Henny but not as directly as you have ;)

[dinkus 10]

Should I point out to Henny that VW didn't make the Corrado? :lol:

[dr_mat 0]

so in conclusion - the red one ! is more aerodynamic

 

I beg to differ, Purple ones are clearly faster!!!

 

In fact the fastest car would be one where incident light radiation was absorbed at the front of the car and bounced off at the rear of the car. So that means black front, white rear .... ;)

 

And the Corrado is hardly known for it's aerodynamics. The Calibra pisses all over it from a great height for Coefficient of drag...

[Trig 0]

Yeh I seem to remember having it explained to me that a Corrado is the same shape as a wing itself (air travels faster over the top than underneath) so it naturally wants to 'take-off'. The spoiler spoils it by slightly changing the shape of the car so it's less 'winglike'.

[GIXXERUK 0]

so in conclusion - the red one ! is more aerodynamic

 

I beg to differ, Purple ones are clearly faster!!!

 

In fact the fastest car would be one where incident light radiation was absorbed at the front of the car and bounced off at the rear of the car. So that means black front, white rear .... ;)

 

And the Corrado is hardly known for it's aerodynamics. The Calibra pisses all over it from a great height for Coefficient of drag...

 

aye i remember vx bragging about that ,was it 0.32 dc or something ?, calibra on a desert wasteland flying along in the background

[Dec 1]

Well if by any miracle someone has a 2d or 3d CAD model of a Corrado, I have all the aerodynamic/CFD software and access to a large multi processor computer here to do a full analysis on it and settle this once and for all! :lol: :lol:

[Crispy 0]

.....

[Crispy 0]

Volkswagen used to claim that the rear spoiler increased downforce by around 30% at 100kph when deployed. Although it's not a big spoiler, it elevates into an airstream area immediately behind the car where a "swirl" is pushing down just above the tailgate.

 

Oh god, not this old gem again! :roll:

 

VW NEVER said that the spoiler increased downforce...

 

It's a spolier, not a wing! You're right about the swirl, but it DECREASES the lift effect by around 30% by spoiling (hence the name "spoiler"!) the airflow over the rear of the car which slows the air over the top of the car reducing the lift effect caused by the shape of the car passing through air.

 

No downforce is produced by the wing... have a look at the mounting brackets and tell me that they'd take enough force pressing down on them to make any difference when driving the car before they broke off... ;) :lol:

 

This is exactly the same reasons the TT had to be recalled and have that nasty little spoiler bolted on... too many of them span off at high speeds due to the rear end getting light due to the lift effect... the spoiler spoilt that lift and made the rear end more stable at speed stopping costly law suits...

 

 

p.s. John, not a dig at you mate, it's a topic that's cropped up quite a few times and is a common mis-conception about the effect of the spoiler which just happens to bug me... LOTS... ;)

 

Just to stir it up a bit - surely by decreasing lift, there is a subsequent increase in downforce? :wink: Or is that just poor terminology....

[craigowl 0]

There was me thinking it was just to keep the rear window clean and pose. :roll:

[Storm Monkey 0]

Nah, its there to stop the lights on the car behind from dazzling you!

[vr6storm 0]

jeez 3 pages and no one has a Fruckin clue...........never mind spoilers and colour the most aerodynamic,lightest and fastest Corrado will be the one with the rear seats folded flat :geek: just ask any Corsa driver

[dr_mat 0]

Just to stir it up a bit - surely by decreasing lift, there is a subsequent increase in downforce? :wink: Or is that just poor terminology....

 

Not "poor terminology", just "utter bullshit". ;)

[Jim 2]

Volkswagen used to claim that the rear spoiler increased downforce by around 30% at 100kph when deployed. Although it's not a big spoiler, it elevates into an airstream area immediately behind the car where a "swirl" is pushing down just above the tailgate.

 

John

 

Hm.. that probably explains why the Corrado suffers particularly badly with getting a filthy back / rear bumper when the rest of the car remains relatively clean! I never thought about it from aerodynamics and airflow point of view but if there is moisture in that flow then guess it has to go somewhere!

 

With regards the actual topic in hand, I would argue that the higher car is probably more aerodynamic. I believe that with aerodynamics you can liken a lot of the effects of drag, etc to boats and the way that they cut through water. If your car is decked to the floor, air cannot flow underneath it as easily..?

 

Of course I know nothing about aerodynamics so this is just guess work.. but there is no harm in at least trying to contribute :)

[Dec 1]

Just to stir it up a bit - surely by decreasing lift, there is a subsequent increase in downforce? :wink: Or is that just poor terminology....

 

Not "poor terminology", just "utter ****". ;)

 

ehh...it's actually more or less right!... lift coefficient = negative downforce coefficient. Car produces lift (neg df) at speed. The spolier is designed to "spoil" or reduce the lift coeff, therefore decreasing the negative downforce (lift) produced!

 

It's the same term...just the opposite sense!....so saying the spolier increases downforce isn't actually "wrong"

[dr_mat 0]

IIRC the Calibra had a Cd of about 0.28. Not sure what the Corrado's was, but maybe it's crapness is one of the reasons VW never touted it in the advertising... The Corrado achieved high speed simply by brute force. That's one of the reasons it wasn't as fuel efficient as the Calibra.

But it's a lot less GAY.

[dr_mat 0]

It's the same term...just the opposite sense!....so saying the spolier increases downforce isn't actually "wrong"

 

Of course it's wrong. The only downforce in action here is GRAVITY. All else is a reduction in lift.

 

It's like saying that NOT punching someone is an increase in benevolence?!

[Dec 1]

Well gravity has no bearing on aerodynamics whatsoever (unless you are analysing a particulate flow) so doesn't affect the lift coeff at all!!

 

Caling lift 'negative downforce' is correct in practice...just not termed very well!

 

:-P

[dr_mat 0]

Well gravity has no bearing on aerodynamics whatsoever (unless you are analysing a particulate flow) so doesn't affect the lift coeff at all!!

 

Exactly my point. Gravity is the only downforce, so it has nothing whatsoever to do with the lift. And we're talking about lift!

If it were a wing, and it produced downforce, which acts against lift, I would be happy to see it described as "increasing downforce", even if overall the car still had a tendency to lift.

But it's not. It's a spoiler, it decreases lift, but does *not* generated downforce.

[Dec 1]

Ok...I see what you're saying.

 

But, gravity still has nothing to do with aerodynamics though (lift/drag/downforce)

 

If I was to model the rear spolier on its own in a simulated 30m/s windtunnel it will produce downforce!

 

It's just the fact that the body of the car will produce a lot more lift than the amount of downforce generated by the spoiler. So, the spoiler will reduce the lift produced by the car due to the downforce it creates, but obviously not generate enough downforce to completely counteract it.

 

The spolier is effectively altering the shape of the car to reduce the lift it produces. But analysed on its own it is a downforce producing element, no question about it!

 

The computers in here aren't really being used a whole lot as it's coming up to Xmas, so I'll run a few cfd simulations over the next few days to illustrate what I'm on about! :wink:

[Guest]

quite correct Doc_mat.

 

just because it doesn't create a force, doesn't mean it is creating an opposiing force.

 

And I'm with Rodders, over inflate the tyres, drive with 5 quids worth of fuel in it, polish it, and fold the seats down "its like crawling across a frozen pond" :lol:

(what a w*nker that guy was, was thinking the other day I wished I'd copy/pasted those posts)

[dr_mat 0]

The spolier is effectively altering the shape of the car to reduce the lift it produces. But analysed on its own it is a downforce producing element, no question about it!

 

But it's not operating on it's own in this context, it's operating as part of the car to "flip" the air flow up at the rear and create turbulence behind the car (hence "spoiler").

This breaks up the stable flow and reduces the lift that the car generates as the air flows around it.

You simply cannot consider the spoiler on it's own, because it doesn't act on it's own. If it did, it would be called a "wing"..

 

But anyway ... anyone seen any snow yet? Anywhere?

[Jim 2]

No. No snow :(

[Dec 1]

lol...no snow here either!

 

I'll setup the simulations later with a generic, corrado'ish 2d profile.

 

It's not truly acting as part of the cars body, because it has flow both above and below it though!

 

And breaking up the 'stable' flow and increasing turbulence doesn't necessarlily reduce lift at all!!....the project I'm currently working on (I'm an aerodynamicist) is tripping laminar flow to turbulence to Increase lift!