2017-2020 Aerodynamic Regulations Thread

[Big Tea]

Is it ok to ask a question in this section?. If not please scrub it.

What I wanted to know is what is the effect on the overtaking car when the front wing gets the full effect of the vortices's?

I know it is disturbed air and it 'upsets' the car, but does it only make it loose on the front, on one corner or does it 'steer' in or out?

[Tommy Cookers]

the leading car at 200 mph is doing work at 200 mph on still air
the following car is meeting air moving at eg 20 mph so is doing work at 180 mph on the air
its DF is 19% less than the leading car's DF

the front wing (of the following car) will only meet one tip's worth of vortices

[Big Tea]

the leading car at 200 mph is doing work at 200 mph on still air
the following car is meeting air moving at eg 20 mph so is doing work at 180 mph on the air
its DF is 19% less than the leading car's DF

the front wing (of the following car) will only meet one tip's worth of vortices

But what is the effect on the car as the driver sees (feels) it? Just (!) loss of grip, or unbalance in other ways, like steer to/from the other car?

I assume this tumble would continue on to other components along the car too? I just wonder what it feels like to the driver. Is it like on the motorway behind a flatbed truck or is it 'directional'? I can not explain properly what I am asking as I have never experienced it, but as a motorcyclist I know there are several different effects of passing vehicles with turbulence.

[jjn9128]

the leading car at 200 mph is doing work at 200 mph on still air
the following car is meeting air moving at eg 20 mph so is doing work at 180 mph on the air
its DF is 19% less than the leading car's DF

the front wing (of the following car) will only meet one tip's worth of vortices

But what is the effect on the car as the driver sees (feels) it? Just (!) loss of grip, or unbalance in other ways, like steer to/from the other car?

I assume this tumble would continue on to other components along the car too? I just wonder what it feels like to the driver. Is it like on the motorway behind a flatbed truck or is it 'directional'? I can not explain properly what I am asking as I have never experienced it, but as a motorcyclist I know there are several different effects of passing vehicles with turbulence.

That's a good explanation of what's going on from Tommy! I approve! It's not really about the vortices, more about the air having momentum because of the lead car. I've been trying to write something about the Azerbaijan GP and wind effects on aero for a while which may never see the light of day (too boring even for something I've written), but the effect of wind can be a substantial loss (tail) or gain (head) of downforce/drag for the same reason.

As for the driver - a general loss of downforce will reduce the peak lateral load in cornering, so they can't corner at the same speed as they would in free air. So the car won't feel as good to them anyway - we know from team radio how prima Donna-ish they can be if ERS isn't performing at full potential "NO POWER, NO POWER!!!!!" Then there's the fact that the front surfaces lose more than the rear - the wake is stronger closer to the lead car - which has an effect of inducing understeer, so the car will feel lazy to them.

There won't be any steer or anything, the cars are too heavy, but there may well be an increase of buffeting that the driver will feel - especially on their helmet - from the turbulence in the wake.

[Big Tea]

Cheers both, thanks for humoring me . I just like to know things.

[jjn9128]

Cheers both, thanks for humoring me . I just like to know things.

You can read my phd thesis on wakes here fair warning - it. is. long!
http://etheses.dur.ac.uk/12051/

[Big Tea]

Cheers both, thanks for humoring me . I just like to know things.

You can read my phd thesis on wakes here fair warning - it. is. long!
http://etheses.dur.ac.uk/12051/

Thanks, thats excellent, but will take me a wile to get through. Just finished ' CHAPTER 1. INTRODUCTION ' and realised I need to read it again as I now follow things I did not really understand earlier

Thanks again but it will take me a while to 'get it'

[M840TR]

The final simplification appears to be a limit on the number of elements allowed in the front wing volume - a rule already enforced for the rear wing. The number of elements is not a means of generating more downforce, but will instead affect how the wing behaves as it moves closer or further from the ground. The low position of the front wing means it's ground clearance is significantly altered by small changes in ride height, which can stall the front wing when the car pitches forwards under braking - when the car needs front grip the most. This could lead to a lower rake (flatter attitude) philosophy than pioneered by Red Bull and copied by most teams on the grid in the last few years - to move the front wing further from the ground.

How does the number of elements (I'm guessing flaps) manipulate the wing behavior in relation to the distance from ground? Or is it the height that's being reduced?

[jjn9128]

The final simplification appears to be a limit on the number of elements allowed in the front wing volume - a rule already enforced for the rear wing. The number of elements is not a means of generating more downforce, but will instead affect how the wing behaves as it moves closer or further from the ground. The low position of the front wing means it's ground clearance is significantly altered by small changes in ride height, which can stall the front wing when the car pitches forwards under braking - when the car needs front grip the most. This could lead to a lower rake (flatter attitude) philosophy than pioneered by Red Bull and copied by most teams on the grid in the last few years - to move the front wing further from the ground.

How does the number of elements (I'm guessing flaps) manipulate the wing behavior in relation to the distance from ground? Or is it the height that's being reduced?

A very simple description of a wing with a flap is it allows the lower surface to be worked harder before stalling. There are a number of mechanisms at work but the simplest is that it jets some high velocity air into a region where the air attached to the surface is starting to lose momentum - and could possibly separate. The way a front wing is different to a conventional wing is that it is so close to the ground, so the air underneath is accelerated by the proximity to the ground - as the car pitches forward under braking the front wing gets closer - as it squats under acceleration the front wing gets higher. This can significantly alter the speed of the air flowing under the wing - such that you get huge changes in pressure - where you get a spike of low pressure you get something called an adverse pressure gradient. The adverse pressure gradient is where you can get flow separating - so if you jet high speed air (low pressure) into the adverse pressure gradient and you reduce the likelihood of the flow separating. Ergo 9 element front wings.

[djos]

Interesting comments regarding the removal of rake, I'd have thought teams like RedBull and Ferrari would be forced to abandon rake in their cars due to the loss of the out wash turning vanes and front Axel blowing. Without these tools I'd have thought they'd no longer be able to seal the sides of the floor and that would be the reason to abandon rake?

[Vyssion]

The final simplification appears to be a limit on the number of elements allowed in the front wing volume - a rule already enforced for the rear wing. The number of elements is not a means of generating more downforce, but will instead affect how the wing behaves as it moves closer or further from the ground. The low position of the front wing means it's ground clearance is significantly altered by small changes in ride height, which can stall the front wing when the car pitches forwards under braking - when the car needs front grip the most. This could lead to a lower rake (flatter attitude) philosophy than pioneered by Red Bull and copied by most teams on the grid in the last few years - to move the front wing further from the ground.

How does the number of elements (I'm guessing flaps) manipulate the wing behavior in relation to the distance from ground? Or is it the height that's being reduced?

A very simple description of a wing with a flap is it allows the lower surface to be worked harder before stalling. There are a number of mechanisms at work but the simplest is that it jets some high velocity air into a region where the air attached to the surface is starting to lose momentum - and could possibly separate. The way a front wing is different to a conventional wing is that it is so close to the ground, so the air underneath is accelerated by the proximity to the ground - as the car pitches forward under braking the front wing gets closer - as it squats under acceleration the front wing gets higher. This can significantly alter the speed of the air flowing under the wing - such that you get huge changes in pressure - where you get a spike of low pressure you get something called an adverse pressure gradient. The adverse pressure gradient is where you can get flow separating - so if you jet high speed air (low pressure) into the adverse pressure gradient and you reduce the likelihood of the flow separating. Ergo 9 element front wings.

I just want to expand on this point by jjn and actually tell you the physics going on in a little more detail.

Firstly, there are 5 effects in play here:


Slat Effect

In the vicinity of the leading edge of a flap element, the velocities due to the circulation on a main element run counter to the velocities on the flap element and so reduce pressure peaks on the downstream element. Essentially, pressure recovery is reduced and so higher angles of attack can be run because it acts to slow the velocity over the nose of the flap element


Circulation Effect

In turn, the flap element causes the trailing edge of the main element to be in a region of high velocity that is inclined to the average line at the rear of the main element.
Such flow inclination induces considerably greater circulation on the main element. The trailing edge is effectively at a higher angle of attack due to the "turning" of the flow in that local region.


Dumping Effect

Because the trailing edge of the maiun element is in a region of velocity which is appreciably higher than the freestream velocity, the boundary layer on the main element "dumps" off the surface at a high velocity.
This relieves the pressure rise impressed on the boundary layer which helps to reduce the chance of separation problems occuring.
Not only does the "Circulation Effect" occur, the tangential velocity at that point is also increased by the flap element. More load can therefore be sustained without increasing the likelihood of stalling the wing.


Off-The-Surface Pressure Recovery

The boundary layer from the forward elements is "dumped" at velocities which are appreciably higher than the freestream around it. Because of this, the final decelleration back to whatever the freestream velocity is, happens in a more efficient manner because the wake region is reverting out of contact with any aerodynamic surface. This is more efficient than the best possible recovery when you are in contact with a wall.


Fresh Boundary Layer Effect

Each new element starts out with a fresh boundary layer at it's leading edge. And so because of this, the boundary layer is effectively kept "thinner" for a larger proportion of the total distance of your wing assembly. Thin boundary layers are more able to withstand adverse pressure gradients, which again, helps with pressure recovery and minimizing the chances of flow separation.

Those are the 5 main effects present when you add a flap to an aerofoil, and I will say again that pressure recovery is much more efficient in the wake region than on/in the attached boundary layer. So it is beneficial to increase the velocity at the trailing edges of an element as much as possible.

In summary,

The finite suction at the trailing edge of the main element results in a less severe pressure recovery from the suction peak (damping effect). Large regions of separated flow can be seen when you incline a single element to a similar position as the flap element is. For double-element wings, separation is not as widespread and the main element produces more downforce due to the presence of the flap element (circulation effect).
For the majority of cases, the flow remains attached to teh trailing edge of the main element. The increase in downforce as the ground is moved closer to is significantly smaller for the flap element than the main element due to being located at a higher position than the main one.
As the height of the wing is changed, the flap is farther from the ground and therefore less sensitive to changes in ride height than the main element.
There is a more significant reduction in downforce at the lowest height for a high flap angle, which is caused by the boundary layer separating over the flap. The lower circulation imparted by the flap on the main element can be seen as represented by the lower suction on the main element suction-surface for the lowest height.



This has turned into a bit of a longer post than I thought... I pulled out my "CFD Bible" and found some of my additional notes on this topic Hope it helps, and any questions, please do ask.

[turbof1]

This has turned into a bit of a longer post than I thought... I pulled out my "CFD Bible" and found some of my additional notes on this topic Hope it helps, and any questions, please do ask.

"Thou shall sucketh thine main plane with a less severe recovery, for thou shall not invoke the wrath of thine CFD Lord!"

[Just_a_fan]

As well as the general "simple" ground effect from the front wing running close to the ground, current wings work like a diffuser at the outer end utilising vortices to both generate downforce (nice low pressure area below the wing) and help with tyre wake control. (The Y250 area does the same, of course, and helps to generate the Y250 vortex and work the neutral section to generate downforce). The proposed wings appear to be intended to do away with this aspect although doubtless the teams will find a way to do it or something with a similar effective.

[henry]

If the objective is to inject high velocity air into the stream on the underside of the previous element are the slots between the element convergent? Or have I failed at my first real attempt to understand what’s happening with these slotted wings?

[jjn9128]

If the objective is to inject high velocity air into the stream on the underside of the previous element are the slots between the element convergent? Or have I failed at my first real attempt to understand what’s happening with these slotted wings?

Wing slot gaps are convergent yes. Somewhere between 8-15mm at the minimum for the front wing, a slot between 10 and 15mm is enforced on the rear wing.