Rule Interpretation - Double deck diffusers

[Just_a_fan]

Renault had openings in the floor like that too but they blanked them (in accordance with the rules) with aero profiles. You can see them through the rear of the bodywork thanks to the extinguisher that was fire around the rear of the car.

https://i.redd.it/5y8c29jrku401.jpg

Interesting that there is another section that opens up above the beam wing. Not sure if that was from the below or above the floor, or just exhaust gases?

I think it was all part of drawing air from below the car. The exhaust pipes and cooling exhaust from the sidepods are visible at the top of the photo.

[Slo Poke]

Can anyone explain to me the working principle of the double diffuser? As it seems, judging from everything I have read in this thread, I don’t have a clue!

[jjn9128]

Can anyone explain to me the working principle of the double diffuser? As it seems, judging from everything I have read in this thread, I don’t have a clue!

Increase flow expansion, lower pressure under the car, move centre of pressure forward.

[SiLo]

Can anyone explain to me the working principle of the double diffuser? As it seems, judging from everything I have read in this thread, I don’t have a clue!

Increase flow expansion, lower pressure under the car, move centre of pressure forward.

Further to this, not only does a diffuser expand the area the air can move into, creating a negative pressure on the underside of the body, having the holes there is a better way to increase the expansion area/rate, and decrease the pressure underneath the car further.

[Slo Poke]

Can anyone explain to me the working principle of the double diffuser? As it seems, judging from everything I have read in this thread, I don’t have a clue!

Increase flow expansion, lower pressure under the car, move centre of pressure forward.

JJN9128:
I can’t express how Pleased I am that it’s you, that has chosen to help me out. That isn’t flattery, I mean it sincerely.
Consider the racing car below to be a high rake car.
I would like to take what you’ve written and refer it back to you in small easy to grasp/understand pieces or chunks. Don’t worry, this should not take long. I catch on quite quickly.
Increase flow expansion.
Consider me a particle of air. I’m lingering in what’s considered to be the boundary layer very close to the macadam and there’s a racing car coming towards me. As the front wings pass over me I’m lifted into free air where I’m caught up in a vortex but somehow I break free and now I have been channeled beneath the car. As the tea tray flew by me I felt okay but now I’m in an area of low pressure because there are now a lot of minuscule gaps opening up between me and my counterpart particles. There’s nothing to worry about as yet however because we are many and there’s only one car above us but if the multitude of gaps keep increasing in distance the car above us is going to find itself with a serious problem.
That is what I know as mid car downforce and from what I’ve read elsewhere, from books and the like, it’s the area of a racing car that’s most dominant.
Lower pressure under the car.
Well that we already have! Although as the car continues its progress over and above me the countless gaps all around me begin to become smaller, until that is, there’s a sudden reversal in the ongoings caused by the above passage of an extremely violent expansion field.
Move centre of pressure forward.
I have no idea what you mean by that, as the car has done and dusted me.
Where am I wrong?
Thank you.

[Slo Poke]

Can anyone explain to me the working principle of the double diffuser? As it seems, judging from everything I have read in this thread, I don’t have a clue!

Increase flow expansion, lower pressure under the car, move centre of pressure forward.

Further to this, not only does a diffuser expand the area the air can move into, creating a negative pressure on the underside of the body, having the holes there is a better way to increase the expansion area/rate, and decrease the pressure underneath the car further.

Thanks for the reply SiLo but let’s just wait a wee while to see what JJN9128 does with the comment below your’s. I’m a thicko see and Slo Poke likes his cornerstones set right. No disrespect intended mind you but JJ’s a Phd what an’ all.

[Just_a_fan]

Move centre of pressure forward.
I have no idea what you mean by that, as the car has done and dusted me.
Where am I wrong?
Thank you.

The centre of pressure is similar to centre of gravity/mass. It's the point through which all of the aerodynamic loads can be treated as a single resultant, just as the centre of mass is the resultant through which the mass of the object is considered to act.

If you look at the image below, you will see a blue blob in the middle of the car. This blob is the centre of pressure. If there is more downforce at the front of the car, the blue blob will be nearer the front of the car, if more downforce at the rear, the blue blob will be nearer the rear.

http://www.formula1-dictionary.net/Images/aerogrip.jpg

The relationship between the centre of pressure and the centre of mass is important to the stability of the car. If the centre of pressure is behind the centre of mass, the car will be stable - think of a dart and you'll see the centre of mass at the front thanks to the big bit of metal, the centre of pressure is at the rear thanks to the very light flights.


If a car's centre of pressure is in front of the centre of mass, the car will want to turn so that the centre of pressure is behind the centre of mass. Obviously, if they are close together then the effect is small. If the centre of pressure was on the front wing and the centre of mass on the rear wing, the car would just flip around as soon as it could.

As the wheelbase of the cars has increased, the centre of mass has moved forward. It is important to ensure the centre of pressure moves forward too in order to prevent the cars being too stable.

The centre of pressure naturally moves forward when a car brakes and the body pitches down at the front. This is why many sports cars have active rear spoilers that lift up when the car brakes- it moves the centre of pressure back behind the centre of mass and so helps the car to be stable under braking.

[Slo Poke]

Move centre of pressure forward.
I have no idea what you mean by that, as the car has done and dusted me.
Where am I wrong?
Thank you.

The centre of pressure is similar to centre of gravity/mass. It's the point through which all of the aerodynamic loads can be treated as a single resultant, just as the centre of mass is the resultant through which the mass of the object is considered to act.

If you look at the image below, you will see a blue blob in the middle of the car. This blob is the centre of pressure. If there is more downforce at the front of the car, the blue blob will be nearer the front of the car, if more downforce at the rear, the blue blob will be nearer the rear.

http://www.formula1-dictionary.net/Images/aerogrip.jpg

The relationship between the centre of pressure and the centre of mass is important to the stability of the car. If the centre of pressure is behind the centre of mass, the car will be stable - think of a dart and you'll see the centre of mass at the front thanks to the big bit of metal, the centre of pressure is at the rear thanks to the very light flights.
https://www.clipartmax.com/png/middle/1 ... -arrow.png

If a car's centre of pressure is in front of the centre of mass, the car will want to turn so that the centre of pressure is behind the centre of mass. Obviously, if they are close together then the effect is small. If the centre of pressure was on the front wing and the centre of mass on the rear wing, the car would just flip around as soon as it could.

As the wheelbase of the cars has increased, the centre of mass has moved forward. It is important to ensure the centre of pressure moves forward too in order to prevent the cars being too stable.

The centre of pressure naturally moves forward when a car brakes and the body pitches down at the front. This is why many sports cars have active rear spoilers that lift up when the car brakes- it moves the centre of pressure back behind the centre of mass and so helps the car to be stable under braking.

Just a Fan:
Thanks for the help Just a Fan but I sorta kinda, or at least kinda sorta have my head around the balancing aspect of f1 tweakery but I’ll thank you for the time you devoted.
Move centre of pressure forward.
I have no idea what you mean by that as the car has done and dusted me.
How am I as a singular particle of air, admittedly surrounded by countless other particles, going to Move a centre of pressure forwards or anywhere else after I have exited the rear of the diffuser? Or even before I even end-up anywhere near the throat of the diffuser, especially when I’m betwixt and between the most dominant area of downforce generation and an oncoming diffuser, singular or double. Which incidentally, is or was the item of instruction I set out have explained to me.
Thanks again Just a Fan.
As an aside, I was darn good at darts in my day you know. Well.... until the incident!

[jjn9128]

Where am I wrong?
Thank you.

Forgive me I'm a little confused by the narrative of the little air particle that could

On the subject of centre of pressure:
Centre of pressure is often referred to as aero-balance - it's basically the balance point of the downforce acting on the car. You want the COP behind the centre of mass for a slight understeer balance - because that's more controllable for the drivers. Depending on circuit layout the ideal COP changes, so for Monaco you want maybe 45% of the downforce on the front axle, for Monza closer to 35%.

This is what's called an x-ray plot of downforce, i.e. the downforce projected onto a 2d slice, more blue to purple means more downforce. You can see the main downforce is produced at either extreme of the car. The rules in 2009 were basically what's called rear limited, so with very small diffusers and narrow rear wings. So they couldn't use the front wing to capacity because the car would be "oversteery" around most circuits.



They couldn't really add much more rear downforce, as the rules were intended, but if they could it would mean the front wing had to be worked more - to maintain the handling balance. However, using more front wing annoyingly takes away rear downforce - as it "uses" the potential of the air. But if you can move the downforce produced by the floor forwards then the front wing downforce doesn't have to be increased so much because the centre of pressure of the car hasn't been moved rearwards.

So imagine a strip of purple around where the "batman logo" of the double-deck entrance is, and more blue behind.

[RZS10]

Kinda like this (?) ... put the picture of the DDD over your image

[jjn9128]

Kinda like this (?) ... put the picture of the DDD over your image
https://i.imgur.com/LgIOiU8.png

Indeedly doodly

[bartez1000]

This rebirth of the topic inspires me to ask a question I pondered for some time.
Was the double-diffuser only possible due to the 2009 rules changes, or did it only just became viable due to new diffuser shape limitations? Even with the strange, 1994-2008 diffusers with big center section and small side sections, the increase to flow expansion and lowered pressure under the car might be beneficial, right?
Were some teams aware of the loophole, and just mothballed it until a big regulation change occurred?

[jjn9128]

This rebirth of the topic inspires me to ask a question I pondered for some time.
Was the double-diffuser only possible due to the 2009 rules changes, or did it only just became viable due to new diffuser shape limitations? Even with the strange, 1994-2008 diffusers with big center section and small side sections, the increase to flow expansion and lowered pressure under the car might be beneficial, right?
Were some teams aware of the loophole, and just mothballed it until a big regulation change occurred?

The loophole in the step-reference transition was technically possible, I think... I don't think the wording was much different. What made it desirable to exploit was the diffuser being made smaller, and the kick being moved rearwards, basically they wanted more downforce.