Slipstream effect of 2021 cars

[raymondu999]

Hi guys.

So generally slipstream is of course correlated with dirty air from the turbulence of a car's downforce. Generally speaking a car with more downforce/drag (generalising a bit for argument simplicity's sake) should mean a bigger tow slipstream which rivals can steal.

With the 2021 cars, current estimates claim that while the 2019 cars will suffer around 45-55% loss of downforce at 1 car's length behind another car, the 2021 simulations reportedly are claiming 10-14% loss of downforce at 1 car's length behind another car.

While that bodes well for following cars closely in cornering conditions, what would this do with the slipstream? Would it suffer a proportionate loss? I'm no aero engineer, please be kind

[marmer]

I suspect the effect would be reduced marginally as in you would have to be slightly nearer the car in front to get a tow. this shouldn't be a huge effect and it only comes into play on an actual overtake. if the new regs work as they should cars should be able to get much nearer the car infront without needing such a huge pace advantage plus with drs on most straights slipsteam is less important.

would be interesting if a slow midfield car was very fast in a straight line if that causes trains to build up as they get caught in the corners but can't get past on the straights due to less slipstream.

[GPR-A]

The one big parameter that has hurt the racing with regards to following a car, is the tyres. With the exception of this year, the tyres have shown enarmous thermal degradation in the past year when the cars get closer, due to which they lose the grip and a chasing car starts to slide a lot. That hurt the racing and a chasing car almost always had to, either back off to cool the tyres OR slow down in corners while chasing, more than they needed to AND not just because they were losing downforce due to the wake of the leading car.

Pirelli has improved the tyres this year and they have a target of improving it further for 2020. For 2021, with the 18 inch wheels and much less rubber, Pirelli should have less headache in manufacturing better tyres that can provide consistent cornering performance while chasing a car.

The numbers that FIA has put out, with regards to reduced wake and increased downforce in the chasing condition, I am not sure if they include the tyre performance OR is it only the aerodynamic changes. If the tyres provide a great deal of grip through cornering and are less susceptible for thermal influence of the wake, then we can have great racing and slipstreaming effect should be better.

Pirelli should work a little better to reduce the tyre pressure for 2020 and for 2021 as the current pressures are absolutely absurd. Pirelli's apprehension about the security of the tyres and the obsession to higher tyre pressures has also hurt the car performance. The tyres pressures should be back under 20 PSI.

[Polite]

The one big parameter that has hurt the racing with regards to following a car, is the tyres. With the exception of this year, the tyres have shown enarmous thermal degradation in the past year when the cars get closer, due to which they lose the grip and a chasing car starts to slide a lot. That hurt the racing and a chasing car almost always had to, either back off to cool the tyres OR slow down in corners while chasing, more than they needed to AND not just because they were losing downforce due to the wake of the leading car.

Pirelli has improved the tyres this year and they have a target of improving it further for 2020. For 2021, with the 18 inch wheels and much less rubber, Pirelli should have less headache in manufacturing better tyres that can provide consistent cornering performance while chasing a car.

The numbers that FIA has put out, with regards to reduced wake and increased downforce in the chasing condition, I am not sure if they include the tyre performance OR is it only the aerodynamic changes. If the tyres provide a great deal of grip through cornering and are less susceptible for thermal influence of the wake, then we can have great racing and slipstreaming effect should be better.

Pirelli should work a little better to reduce the tyre pressure for 2020 and for 2021 as the current pressures are absolutely absurd. Pirelli's apprehension about the security of the tyres and the obsession to higher tyre pressures has also hurt the car performance. The tyres pressures should be back under 20 PSI.

Agree for all till here: ``The tyres pressures should be back under 20 PSI.``

Higher pressures are needed first of all due to the weight of the cars. 800+ kg s produce a lot of stress, this not only produces security problems but also temperature control problems which affect performance.

[Tommy Cookers]

won't the tyre pressure (for the required compliance ie contact patch area) be ? .....
proportionately greater as the aspect ratio has become smaller

[NL_Fer]

Isn’t the tow effect caused by lower pressure behind the front car? Because the air is pushed to the sides?

Then the lower pressure causes the air the return and this movement is turbulence disturbing the following car’s aero.

Two different things?

[jjn9128]

Isn’t the tow effect caused by lower pressure behind the front car? Because the air is pushed to the sides?

Then the lower pressure causes the air the return and this movement is turbulence disturbing the following car’s aero.

Two different things?

I've always hated 'turbulence' as a means to describe the wake effect. A wake is lots of things, velocity deficit, total pressure deficit, low static pressure, rotational flow, as well as turbulence. The main one affecting cars is velocity/dynamic pressure deficit (which is proportional to velocity squared) this reduces the static pressure on the surface of the following car which aids slipstreaming but also causes the loss of downforce. Upwash/downwash will affect relative incidence of wings which affects downforce/drag, but the effect is very small. The low static pressure will help slipstreaming. At the intensity and length scales of F1 wakes the turbulence will have a destabilizing effect, but isn't responsible for any downforce change.

[EDIT: I think the slipstream effect will be smaller, but if they can follow 6/7 car lengths closer through corners for the same downforce loss, they're closer by the end of the straight anyway.]

[NL_Fer]

But loss of static pressure was always been there in the old days and those cars could still follow and overtake.

It is the increased complexity of the modern aerodynamic design, which is more sensititive to wake effects. Especially turbulence.

[Just_a_fan]

Isn’t the tow effect caused by lower pressure behind the front car? Because the air is pushed to the sides?

Then the lower pressure causes the air the return and this movement is turbulence disturbing the following car’s aero.

Two different things?

The tow is caused by the leading car "pulling" the air with it. As the leading car passes through the air, the air will move with the car - you can see this in normal life by seeing leaves on the road moving in the direction of the car as it passes. This means the following car is moving in to air that is moving in the same direction as it - the effect is that the car "sees" a lower air speed, hence drag is reduced. The car then goes faster until it is hitting the air at the same speed as the leading car. The speed the air is moving forwards is basically equal to the speed increase in the tow.

There is also some loss of downforce caused by this air movement as the following car "sees" slower air and so generates less downforce (what with downforce being proportional to the square of the air velocity, a small reduction in apparent speed will have a noticeable effect on on downforce). The "turbulence" has a similar effect because turbulent air doesn't have the same total velocity (some of the air in the eddies is moving with the car, some sideways, some against the car).

[mzso]

Wouldn't all the upwash mean that the slipstream is better? All the turbulent air is diverted upwards, doesn't mean it's leaving more of a void behind?

[raymondu999]

Wouldn't all the upwash mean that the slipstream is better? All the turbulent air is diverted upwards, doesn't mean it's leaving more of a void behind?

disclaimer - I'm no aero engineer

However, if there is more of a void behind then cars would definitely be losing a lot more downforce closer. The whole thing with there being more downforce for the following car means there is less of a void

[marmer]

Question regarding the us gp.

Does bad turbulent air become greater at higher speeds as more air per second is disturbed.
Which leads to the track layout at Austin
Straight into turn one allows for cars to slipstream up but not necessarily pass as the corners leading up to the start finish are too high speed. While sector 1 is too high speed after turn 1 which makes passing difficult into the hairpin but allows for cars to get close /overtake on the back straight. Combined with the slower corners following allowing for more close action.

[turbof1]

Question regarding the us gp.

Does bad turbulent air become greater at higher speeds as more air per second is disturbed.
Which leads to the track layout at Austin
Straight into turn one allows for cars to slipstream up but not necessarily pass as the corners leading up to the start finish are too high speed. While sector 1 is too high speed after turn 1 which makes passing difficult into the hairpin but allows for cars to get close /overtake on the back straight. Combined with the slower corners following allowing for more close action.

As jjn9128 said, the biggest contributor velocity/dynamic pressure deficit, is proportional to the velocity squared. Meaning that indeed the issue becomes bigger at higher speeds. However, cars might still generate enough downforce to take high speed corners.

[strad]

Isn't the tow created by the size of the hole punched in the air? If that is so isn't there less tow/slipstream ability from a more aerodynamic lead car? Isn't the new car supposed to be more slippery/aerodynamic and therefor supply less of a hole punched in the air?

[raymondu999]

Isn't the tow created by the size of the hole punched in the air? If that is so isn't there less tow/slipstream ability from a more aerodynamic lead car? Isn't the new car supposed to be more slippery/aerodynamic and therefor supply less of a hole punched in the air?

Ya that was what I was wondering (sort of) when I started this thread