33 replies to this topic

[Kvothe]

This is a discussion that started off in the Lewis v Jenson thread, and thrown up a lot of questions that no one seems to have any scientific answers for. I've decided to start a new topic, because while I would like to discuss dirty air, I would like to do so outside of the emotive context of the Lewis v Jenson scorecard thread. I feel the topic itself warrants greater forum inclusion, then a select group of fans with a vested interest.

engel made an interesting point.

If dirty air was a panacea then nobody would ever catch up to the driver ahead on the road

Just some questions that the discussion prompted in my mind and to get the topic started.

Firstly dirty air seems to have less of an effect the faster the car behind is. Why?

Secondly the effect of dirty air increases in intensity the closer the car behind is. Why?

Thirdly what is the range of dirty air?

Fourthly are all cars affected the same? For example If the car behind is identical, and so has identical characteristics, are they affected more then a car not identical?

Fifthly what is the effect of turbolent air on a car running at identical pace behind, and when does such an effect end?

While of course the discussion is open to everyone, and opinions are always welcome, if anyone is able to provide any technical information, links to F1teams take on the situation ect then that would be extremely helpful.

[jrg19]

Well i remember Alonso getting a penalty for this in 2006 i guess massa was in the "dirty" air.

[dau]

Dirty air means the front wing is less effective than in normal flow conditions, so the car behind can't stay close through corners because of heavy understeering, forcing them to leave some space to the car ahead. Which then means they are not close enough on the following straights, so they can't catch up to attack in the next braking zone.

It has no negative effect on straights or on cars which don't rely as much on FW downforce. Dirty air is more severe the closer you are to the car ahead. If the car behind is faster, it will have much more downforce anyway, so even when they're losing some, they can still afford to stay close to the slower car in front.

Edited by dau, 22 March 2012 - 11:55.

[Peat]

It become's an issue when spelt incorrectly.

[Kvothe]

It become's an issue when spelt incorrectly.

Ouch I hope the mods will be kind enough to change it for me.

[windtravels]

Well i remember Alonso getting a penalty for this in 2006 i guess massa was in the "dirty" air.

Wow its amazing alonso got a penalty for that, can barely see him in the video, hes so far ahead of massa.

Edited by windtravels, 22 March 2012 - 11:55.

[Kvothe]

Well i remember Alonso getting a penalty for this in 2006 i guess massa was in the "dirty" air.

Can't tell if you're throwing this out as sarcastic commentary or as an actual point?

Edited by Kvothe, 22 March 2012 - 11:58.

[dau]

It become's an issue when spelt incorrectly.

Like becomes?

[jrg19]

Can't tell if you're throwing this out as sarcastic commentary or as an actual point?

Well if the FIA deem this kind of distance to cause a disruption to the airflow to the car behind, it must be horrific the whole race to everyone who isn't 1st.

[KOMORI]

Like becomes?

Touché

[Kvothe]

Like becomes?

[amppatel]

OK here is my attempt at explaining it:

When you are running in clear air the air is undisturbed i.e it has no velocity and is at uniform density. When F1 cars are designed and tested (in CFD/wind tunnel - blows out uniform non turbulent air) they are trying to maximize the down-force when running in uniform density (clean) air - as they assume that they will be running in clean air most of the time.

But when any object passes through air it will disturb it - leaving in its wake high/low pressure zones which in turn create moving flows of air which means the air is no longer uniform. This effect is greater when the car has lots of aerodynamic parts (F1 cars) - each wing disturbs the air more and more. The dirty air effect is reduced if the following car is at a large distance because the air (after the first car has passed) has enough time to re-reach equilibrium which is uniform density at which the following F1 car likes!

Turbulence is what aerodynamicists call the flows when they simply don't know what is going on - but this is not completely true behind a car - they can calculate roughly what the air is doing after the rear wing. In theory they could even design front wings to take advantage of the high/low pressure zones and then the traditional clean air would become the dirty air!

Generally the air directly behind the car in front will be a low pressure zone so the density of air is much lower - meaning less down-force (and so drag) for the car behind - good in straights - bad in corners!

[Peat]

Like becomes?

hoisted by my own petard!

[Kvothe]

hoisted by my own petard!

Those who live by the sword....

[Dunder]

Firstly dirty air seems to have less of an effect the faster the car behind is. Why?

Not quite sure that this observation is valid but it could be that the faster car behind just has superior mechanical grip.

Secondly the effect of dirty air increases in intensity the closer the car behind is. Why?

This isn't true. The exact size and shape of the turbulent wake depends on many thing things but with the current generation of F1 cars the area/volume of minimum pressure will be 3 or 4 metres behind the leading car.

Thirdly what is the range of dirty air?

All air is dirty to some extent. So even a car 5 seconds behind will be affected to a small extent. In terms of making a tangible difference to the following cars' handling characteristics 1.5 seconds is a decent guesstimate.

Fourthly are all cars affected the same? For example If the car behind is identical, and so has identical characteristics, are they affected more then a car not identical?

All cars are affected slightly differently but whether the leading car is identical is not a factor.

Fifthly what is the effect of turbolent air on a car running at identical pace behind, and when does such an effect end?

This is essentially the same question as 'thirdly'. The main effect in F1 terms is the air enveloping the FW is at much lower pressure which results in a loss of front downforce and a tendency understeer.

Edited by Dunder, 22 March 2012 - 12:22.

[Kvothe]

OK here is my attempt at explaining it:

When you are running in clear air the air is undisturbed i.e it has no velocity and is at uniform density. When F1 cars are designed and tested (in CFD/wind tunnel - blows out uniform non turbulent air) they are trying to maximize the down-force when running in uniform density (clean) air - as they assume that they will be running in clean air most of the time.

But when any object passes through air it will disturb it - leaving in its wake high/low pressure zones which in turn create moving flows of air which means the air is no longer uniform. This effect is greater when the car has lots of aerodynamic parts (F1 cars) - each wing disturbs the air more and more. The dirty air effect is reduced if the following car is at a large distance because the air (after the first car has passed) has enough time to re-reach equilibrium which is uniform density at which the following F1 car likes!

Turbulence is what aerodynamicists call the flows when they simply don't know what is going on - but this is not completely true behind a car - they can calculate roughly what the air is doing after the rear wing. In theory they could even design front wings to take advantage of the high/low pressure zones and then the traditional clean air would become the dirty air!

Generally the air directly behind the car in front will be a low pressure zone so the density of air is much lower - meaning less down-force (and so drag) for the car behind - good in straights - bad in corners!

Thanks for the information.

Can the effect of dirty air be quantified i.e. tenths lost? Although I know that this would change depending on proximity to the vehicle ahead.

So the range of the effect of dirty air is dependent on how long it takes for the air to re-reach equilibrium. Have there been any studies on or is it known, how long this would take?

Edited by Kvothe, 22 March 2012 - 12:26.

[Kvothe]

@Dunder, very informative thanks

Edited by Kvothe, 22 March 2012 - 12:32.

[amppatel]

Thanks for the information.

Can the effect of dirty air be quantified?

So the range of the effect of dirty air is dependent on how long it takes for the air to re-reach equilibrium. Have there been any studies on or is it known, how long this would take?

The problem with this effect is that it depends heavily on the car in front and the car behind, as I said before if the car behind was designed differently it could take advantage of the car in front! But I suppose you could take 2 cars into a wind tunnel/ CFD and measure the drag and down force ratio - then compare it with only one car. But even if the ratio is similar the car still needs down force in corners and the lower drag won't really help.




Dunder - I don't agree with your answer to the secondly question! I think the closer you are the worse the effect - lowest pressure is directly behind the car....

[argiriano]

Dirty air means the front wing is less effective than in normal flow conditions, so the car behind can't stay close through corners because of heavy understeering, forcing them to leave some space to the car ahead. Which then means they are not close enough on the following straights, so they can't catch up to attack in the next braking zone.

It has no negative effect on straights or on cars which don't rely as much on FW downforce. Dirty air is more severe the closer you are to the car ahead. If the car behind is faster, it will have much more downforce anyway, so even when they're losing some, they can still afford to stay close to the slower car in front.

I absolutelly agree without the last part because that`s not always the case.
In last couple of seasons we saw couple of mistakes from Vettel in the rare cases he was behind chasing. I give him as an example because RBR was the undoubtably the car with most downforce on the grid. The loss of front downforce from closer chase sometimes unbalanced the car and mistakes are almost inevitable because it leads to unpredictable behaviour.

It was the same last week in Australia when Vettel get closer to Michael - the former lost front downforce and made the first corner wide. I can`t call that usual driver mistake because it`s from unpredicted behaviour. Drivers just don`t know if this is going to happen or not so they still pushing.

[Faupa]

This is a discussion that started off in the Lewis v Jenson thread, and thrown up a lot of questions that no one seems to have any scientific answers for. I've decided to start a new topic, because while I would like to discuss dirty air, I would like to do so outside of the emotive context of the Lewis v Jenson scorecard thread. I feel the topic itself warrants greater forum inclusion, then a select group of fans with a vested interest.

engel made an interesting point.



Just some questions that the discussion prompted in my mind and to get the topic started.

Firstly dirty air seems to have less of an effect the faster the car behind is. Why?

Secondly the effect of dirty air increases in intensity the closer the car behind is. Why?

Thirdly what is the range of dirty air?

Fourthly are all cars affected the same? For example If the car behind is identical, and so has identical characteristics, are they affected more then a car not identical?

Fifthly what is the effect of turbolent air on a car running at identical pace behind, and when does such an effect end?

While of course the discussion is open to everyone, and opinions are always welcome, if anyone is able to provide any technical information, links to F1teams take on the situation ect then that would be extremely helpful.

Lets start with 5 . As Hamilton will invaribly be following Button this year it is impossible to say how much turbulence from one Maclaren will effect another or if Massa, who it appears may not be there that much longer is in front of Alonso under the current rules Massa may be directed to make room for Alonso.

The "turbulance factor" seems to be relevant at a range of 30 metres becoming proportionally more intense ( closer distance means more aerodynamic disturbance) which means passing using DRS and KERS is still a very risky proposition. To obtain an aerodynamic tow and then pass using DRS ( and or KERS) needs huge commitment as downforce is dimished the closer the driver approches the car in front, therefore grip is diminished, engine,airflow, ( airbox and radiator) is less dense and more turbulent so horsepower diminishes.

So the critics of DRS ( and some of those of KERS) have not really appreciated what a commitment an F1 driver has to pass a car under race conditions

[Dunder]

Dunder - I don't agree with your answer to the secondly question! I think the closer you are the worse the effect - lowest pressure is directly behind the car....

Technically speaking you are correct but in practical/racing terms the area of minimum pressure immediately behind the diffuser isn't an issue.

I did have more detailed info on this for the high/narrow wings introduced in 2009 but the below image is still a decent approximation

Edited by Dunder, 22 March 2012 - 12:47.

[Zava]

it is only an issue if Hamilton suffers the turbulent air.

[zack1994]

Well i remember Alonso getting a penalty for this in 2006 i guess massa was in the "dirty" air.

Most thought this incident was BS form the FIA, renault/pat symonds said that massa was actually getting a toe from alonso not dirty air.

[jrg19]

Most thought this incident was BS form the FIA, renault/pat symonds said that massa was actually getting a toe from alonso not dirty air.

I didn't relies the FIA could make such decisions.

[Kraken]

The effect varies as well depending on how the car in front works the air. I remember a few seasons ago a lot of the drivers saying that it was very hard to follow the Renault because the air coming off of it was so dirty.

[Kraken]

Most thought this incident was BS form the FIA, renault/pat symonds said that massa was actually getting a toe from alonso not dirty air.

But what does Alonso feet have to do with anything?

[Kvothe]

Technically speaking you are correct but in practical/racing terms the area of minimum pressure immediately behind the diffuser isn't an issue.

I did have more detailed info on this for the high/narrow wings introduced in 2009 but the below image is still a decent approximation

On the image you've posted, why is it that the level of energy doesn't progressively go from low to full as time progresses and the air re-reaches equilibrium but instead seems to vacillate between low and full before gradually becoming full.?

Edited by Kvothe, 22 March 2012 - 13:08.

[Risil]

Worth pointing out that Alonso wasn't on a flying lap when he "impeded" Massa; he was driving a much quicker than usual out-lap because of a mistake by his team. Still, it was all politics. I don't think there's been a similar penalty before or since.

[amppatel]

Technically speaking you are correct but in practical/racing terms the area of minimum pressure immediately behind the diffuser isn't an issue.

I did have more detailed info on this for the high/narrow wings introduced in 2009 but the below image is still a decent approximation

OK - thanks for the pic!

[Risil]

On the image you've posted, why is it that the level of energy doesn't progressively go from low to full as time progresses and the air re-reaches equilibrium but instead seems to vacillate before settling down?

Now that's a question for the Tech Forum.

[amppatel]

On the image you've posted, why is it that the level of energy doesn't progressively go from low to full as time progresses and the air re-reaches equilibrium but instead seems to vacillate between low and full before gradually becoming full.?

So the image is a steady state CFD simulation - it shows the air behind the car when the car is at constant speed - it doesn't give any information of how that changes with time. The air will gradually go back to normal as low and high pressures equalize.

[Dunder]

On the image you've posted, why is it that the level of energy doesn't progressively go from low to full as time progresses and the air re-reaches equilibrium but instead seems to vacillate between low and full before gradually becoming full.?

In simple terms the separate wakes left by different parts of the leading car (diffuser, RW, wheels etc) interfere with each other and the wake left by any object moving at high speed is subject to a vortex (spiralling) effect.

You are now approaching an area of extreme geekiness - turn back now before it is too late!

[Kvothe]

So the image is a steady state CFD simulation - it shows the air behind the car when the car is at constant speed - it doesn't give any information of how that changes with time. The air will gradually go back to normal as low and high pressures equalize.

So that's a steady state CFD simulation, ok got it thanks.

In simple terms the separate wakes left by different parts of the leading car (diffuser, RW, wheels etc) interfere with each other and the wake left by any object moving at high speed is subject to a vortex (spiralling) effect.

You are now approaching an area of extreme geekiness - turn back now before it is too late!

That makes complete sense.

There is no turning back;), but seriously very fascinating and one of the most interesting discussions I've had on this board for a long time, I may actually read up more on this when I have time.

Thanks to everyone who has contributed so far.

[zack1994]

But what does Alonso feet have to do with anything?