## Formula 1 Aerodynamics - article series and general discussion

Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum.
Just_a_fan
Just_a_fan
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### Re: Formula 1 Aerodynamics - article series and general discussion

godlameroso wrote:
Tue Apr 13, 2021 1:33 am
Outside of the core the pressure is higher or the vortex would lose integrity, you can't have a vortex without high pressure air rushing to fill low pressure. Wing tip vortecies exist precisely because high pressure air is trying to fill the low pressure on the other side of the wing.
The vortex does lose integrity. That's why it has a finite length. Remember that the vortex only looks long because the car is travelling quickly and we look at it from the perspective of the car. In reality, the air is disturbed and rotates strongly where it is (approximately) for a short period of time - only a matter of seconds - before it loses energy and the vorticity breaks down (in to ever smaller vortices). The teams use those few short seconds of its existence to make use of it.

The vorticity is created by the pressure difference across a physical surface - wing tip, VG, etc., and then starts to run down as soon as it leaves the creating environment. It has to as there is no more energy being added to the air. Energy is given to it by the car (that's what drag is - energy given to the air by the car) and then once the air has left the surface of the car, it starts to lose rotational energy. The vortex gets wider as time passes as the energy disperses in to the surrounding air. Eventually you are left with a whole load of ever smaller vortices spread through a large volume of air - turbulence behind the car.
Turbo says "Dumpster sounds so much more classy. It's the diamond of the cesspools." oh, and "The Dutch fans are drunk. Maybe"

godlameroso
305
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Location: Miami FL

### Re: Formula 1 Aerodynamics - article series and general discussion

Just_a_fan wrote:
Tue Apr 13, 2021 9:24 am
godlameroso wrote:
Tue Apr 13, 2021 1:33 am
Outside of the core the pressure is higher or the vortex would lose integrity, you can't have a vortex without high pressure air rushing to fill low pressure. Wing tip vortecies exist precisely because high pressure air is trying to fill the low pressure on the other side of the wing.
The vortex does lose integrity. That's why it has a finite length. Remember that the vortex only looks long because the car is travelling quickly and we look at it from the perspective of the car. In reality, the air is disturbed and rotates strongly where it is (approximately) for a short period of time - only a matter of seconds - before it loses energy and the vorticity breaks down (in to ever smaller vortices). The teams use those few short seconds of its existence to make use of it.

The vorticity is created by the pressure difference across a physical surface - wing tip, VG, etc., and then starts to run down as soon as it leaves the creating environment. It has to as there is no more energy being added to the air. Energy is given to it by the car (that's what drag is - energy given to the air by the car) and then once the air has left the surface of the car, it starts to lose rotational energy. The vortex gets wider as time passes as the energy disperses in to the surrounding air. Eventually you are left with a whole load of ever smaller vortices spread through a large volume of air - turbulence behind the car.
Vortecies can create others and merge. The length of the vortex is affected by many things, helicity of two or more vortecies can extend their lifespan as well as length. So called "vortex braiding".

"Theoretical results for turbulence have shown that flow structures of high helicity are associated with low dissipation of kinetic energy, making them candidates for coherent structures that can persist longer than others in the flow field."

https://journals.aps.org/prfluids/abstr ... s.5.062601
Saishū kōnā

Just_a_fan
Just_a_fan
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Joined: Sun Jan 31, 2010 7:37 pm

### Re: Formula 1 Aerodynamics - article series and general discussion

godlameroso wrote:
Tue Apr 13, 2021 3:01 pm
Just_a_fan wrote:
Tue Apr 13, 2021 9:24 am
godlameroso wrote:
Tue Apr 13, 2021 1:33 am
Outside of the core the pressure is higher or the vortex would lose integrity, you can't have a vortex without high pressure air rushing to fill low pressure. Wing tip vortecies exist precisely because high pressure air is trying to fill the low pressure on the other side of the wing.
The vortex does lose integrity. That's why it has a finite length. Remember that the vortex only looks long because the car is travelling quickly and we look at it from the perspective of the car. In reality, the air is disturbed and rotates strongly where it is (approximately) for a short period of time - only a matter of seconds - before it loses energy and the vorticity breaks down (in to ever smaller vortices). The teams use those few short seconds of its existence to make use of it.

The vorticity is created by the pressure difference across a physical surface - wing tip, VG, etc., and then starts to run down as soon as it leaves the creating environment. It has to as there is no more energy being added to the air. Energy is given to it by the car (that's what drag is - energy given to the air by the car) and then once the air has left the surface of the car, it starts to lose rotational energy. The vortex gets wider as time passes as the energy disperses in to the surrounding air. Eventually you are left with a whole load of ever smaller vortices spread through a large volume of air - turbulence behind the car.
Vortecies can create others and merge. The length of the vortex is affected by many things, helicity of two or more vortecies can extend their lifespan as well as length. So called "vortex braiding".

"Theoretical results for turbulence have shown that flow structures of high helicity are associated with low dissipation of kinetic energy, making them candidates for coherent structures that can persist longer than others in the flow field."

https://journals.aps.org/prfluids/abstr ... s.5.062601
The timescales required are less than a second. The slowest corner on the calendar is taken at approx.13m/s, most are taken at speeds in excess of 40 - 50 m/s. That means any rotating bit of air is interacting with the car, at most, for less than 0.5s, with much of the time that being less than 0.1s. So the vortex doesn't need a long life, nor is it a long structure as the car is a few metres long with many of the bits that interact much closer together than that. There is video of Y250 vortex cores that burst before they get to the front of the sidepod suggesting they exist for a metre or two at most or the air is "in" the vortex for 1/50s - 1/25s at 50m/s car speed. So the energy of the air within the vortex gets dispersed very quickly. Sure, you can get vortices that last for long periods - hence the wake turbulence spacings between aircraft at airports, but those are much stronger structures developed by much more powerful devices.
Turbo says "Dumpster sounds so much more classy. It's the diamond of the cesspools." oh, and "The Dutch fans are drunk. Maybe"

Tommy Cookers
Tommy Cookers
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### Re: Formula 1 Aerodynamics - article series and general discussion

Just_a_fan wrote:
Tue Apr 13, 2021 4:18 pm
.... So the energy of the air within the vortex gets dispersed very quickly. Sure, you can get vortices that last for long periods - hence the wake turbulence spacings between aircraft at airports, but those are much stronger structures developed by much more powerful devices.
light aircraft vortices persist for at least a minute if produced by eg 3g's worth of manoeuvre - so are comparable to F1
it's almost normal to hit a vortex of one's own (ie a minute after generating it) eg in a continuous hard turn or in a loop
Last edited by Tommy Cookers on Tue Apr 13, 2021 7:53 pm, edited 1 time in total.

Zynerji
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Joined: Wed Jan 27, 2016 3:14 pm

### Re: Formula 1 Aerodynamics - article series and general discussion

I'd love to work with a modeler on here to try out a Relamimator front/rear wing concept. Especially with the MVRC cars and the home CFD setups, I think the data would be worth paying to see visualized.

Anyone interested in making some CashApp?

godlameroso
305
Joined: Sat Jan 16, 2010 8:27 pm
Location: Miami FL

### Re: Formula 1 Aerodynamics - article series and general discussion

Just_a_fan wrote:
Tue Apr 13, 2021 4:18 pm
godlameroso wrote:
Tue Apr 13, 2021 3:01 pm
Just_a_fan wrote:
Tue Apr 13, 2021 9:24 am

The vortex does lose integrity. That's why it has a finite length. Remember that the vortex only looks long because the car is travelling quickly and we look at it from the perspective of the car. In reality, the air is disturbed and rotates strongly where it is (approximately) for a short period of time - only a matter of seconds - before it loses energy and the vorticity breaks down (in to ever smaller vortices). The teams use those few short seconds of its existence to make use of it.

The vorticity is created by the pressure difference across a physical surface - wing tip, VG, etc., and then starts to run down as soon as it leaves the creating environment. It has to as there is no more energy being added to the air. Energy is given to it by the car (that's what drag is - energy given to the air by the car) and then once the air has left the surface of the car, it starts to lose rotational energy. The vortex gets wider as time passes as the energy disperses in to the surrounding air. Eventually you are left with a whole load of ever smaller vortices spread through a large volume of air - turbulence behind the car.
Vortecies can create others and merge. The length of the vortex is affected by many things, helicity of two or more vortecies can extend their lifespan as well as length. So called "vortex braiding".

"Theoretical results for turbulence have shown that flow structures of high helicity are associated with low dissipation of kinetic energy, making them candidates for coherent structures that can persist longer than others in the flow field."

https://journals.aps.org/prfluids/abstr ... s.5.062601
The timescales required are less than a second. The slowest corner on the calendar is taken at approx.13m/s, most are taken at speeds in excess of 40 - 50 m/s. That means any rotating bit of air is interacting with the car, at most, for less than 0.5s, with much of the time that being less than 0.1s. So the vortex doesn't need a long life, nor is it a long structure as the car is a few metres long with many of the bits that interact much closer together than that. There is video of Y250 vortex cores that burst before they get to the front of the sidepod suggesting they exist for a metre or two at most or the air is "in" the vortex for 1/50s - 1/25s at 50m/s car speed. So the energy of the air within the vortex gets dispersed very quickly. Sure, you can get vortices that last for long periods - hence the wake turbulence spacings between aircraft at airports, but those are much stronger structures developed by much more powerful devices.
That doesn't make sense, the car never comes to a complete standstill, the car's speed is such that vortecies are relatively constant, particularly above 160kph.

If we reduce this to only yaw conditions then the vortecies shift through entry, mid, and exit phases. However as long as the car is moving, it is displacing air and creating a pressure difference. Only when the car is stationary does what you say make sense. F1 cars continue moving thus they continue energizing the fluid they displace.

Often we hear that the car creates an aero disturbance as far as 5 seconds ahead.
Saishū kōnā

Just_a_fan
Just_a_fan
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### Re: Formula 1 Aerodynamics - article series and general discussion

godlameroso wrote:
Tue Apr 13, 2021 8:42 pm
Just_a_fan wrote:
Tue Apr 13, 2021 4:18 pm
godlameroso wrote:
Tue Apr 13, 2021 3:01 pm

Vortecies can create others and merge. The length of the vortex is affected by many things, helicity of two or more vortecies can extend their lifespan as well as length. So called "vortex braiding".

"Theoretical results for turbulence have shown that flow structures of high helicity are associated with low dissipation of kinetic energy, making them candidates for coherent structures that can persist longer than others in the flow field."

https://journals.aps.org/prfluids/abstr ... s.5.062601
The timescales required are less than a second. The slowest corner on the calendar is taken at approx.13m/s, most are taken at speeds in excess of 40 - 50 m/s. That means any rotating bit of air is interacting with the car, at most, for less than 0.5s, with much of the time that being less than 0.1s. So the vortex doesn't need a long life, nor is it a long structure as the car is a few metres long with many of the bits that interact much closer together than that. There is video of Y250 vortex cores that burst before they get to the front of the sidepod suggesting they exist for a metre or two at most or the air is "in" the vortex for 1/50s - 1/25s at 50m/s car speed. So the energy of the air within the vortex gets dispersed very quickly. Sure, you can get vortices that last for long periods - hence the wake turbulence spacings between aircraft at airports, but those are much stronger structures developed by much more powerful devices.
That doesn't make sense, the car never comes to a complete standstill, the car's speed is such that vortecies are relatively constant, particularly above 160kph.

If we reduce this to only yaw conditions then the vortecies shift through entry, mid, and exit phases. However as long as the car is moving, it is displacing air and creating a pressure difference. Only when the car is stationary does what you say make sense. F1 cars continue moving thus they continue energizing the fluid they displace.

Often we hear that the car creates an aero disturbance as far as 5 seconds ahead.
Yes, they energise new bits of air as they move through the air. The air in the vortex is constantly moving relative to the car and is spinning for a short period of time. It's not a fixed thing, it's a conveyor belt where air molecules are in and out of the vortex in a quick time.

The effect of the car on following cars is partly due to the break down of the car's vortices (turbulence), and partly/mostly caused by the car pulling the air along behind it - that reduces the apparent air speed over the following car. That reduced air speed reduces the following car's down force. That reduction in apparent air speed over the following car is also what creates the tow effect.
Turbo says "Dumpster sounds so much more classy. It's the diamond of the cesspools." oh, and "The Dutch fans are drunk. Maybe"

hecti
hecti
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Location: Montreal, QC

### Re: Formula 1 Aerodynamics - article series and general discussion

Saw this on another thread, this guy put the 2021 williams in CFD, take a look at the rear tire squirt vortex and how far it penetrates into the center of the diffuser, its pretty remarkable, even if the leaked model I believe isn't that great

https://media-exp1.licdn.com/dms/image/ ... sSr6mHa2HY

DP_CFD
DP_CFD
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### Re: Formula 1 Aerodynamics - article series and general discussion

hecti wrote:
Wed Apr 14, 2021 2:11 pm
Saw this on another thread, this guy put the 2021 williams in CFD, take a look at the rear tire squirt vortex and how far it penetrates into the center of the diffuser, its pretty remarkable, even if the leaked model I believe isn't that great

https://i.imgur.com/KMBG7VA.png

https://media-exp1.licdn.com/dms/image/ ... sSr6mHa2HY
I would exercise heavy caution on reading too far into this without knowing anything about the mesh, or how the contact patch and tire deformation is modelled.
aka David Penner

jjn9128
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Joined: Tue May 02, 2017 10:53 pm

### Re: Formula 1 Aerodynamics - article series and general discussion

hecti wrote:
Wed Apr 14, 2021 2:11 pm
Saw this on another thread, this guy put the 2021 williams in CFD, take a look at the rear tire squirt vortex and how far it penetrates into the center of the diffuser, its pretty remarkable, even if the leaked model I believe isn't that great

https://i.imgur.com/KMBG7VA.png

https://media-exp1.licdn.com/dms/image/ ... sSr6mHa2HY
Leaked model doesn't have diffuser strakes which will help to some extent.
#aerogandalf
"There is one big friend. It is downforce. And once you have this it’s a big mate and it’s helping a lot." Robert Kubica

Just_a_fan
Just_a_fan
561
Joined: Sun Jan 31, 2010 7:37 pm

### Re: Formula 1 Aerodynamics - article series and general discussion

jjn9128 wrote:
Wed Apr 14, 2021 3:27 pm
hecti wrote:
Wed Apr 14, 2021 2:11 pm
Saw this on another thread, this guy put the 2021 williams in CFD, take a look at the rear tire squirt vortex and how far it penetrates into the center of the diffuser, its pretty remarkable, even if the leaked model I believe isn't that great

https://i.imgur.com/KMBG7VA.png

https://media-exp1.licdn.com/dms/image/ ... sSr6mHa2HY
Leaked model doesn't have diffuser strakes which will help to some extent.
Interesting to see the floor edge appearing to create a vortex that then follows the floor's edge and goes between the rear wheel and the diffuser. This would appear to be "sealing" the floor's edge from lateral flow/the tyre wake. Surprised that's not being pulled across towards the centre of the car. Although, as the tyre squirt is going across below it, presumably other unwanted general lateral flow occurs below that edge vortex too.
Turbo says "Dumpster sounds so much more classy. It's the diamond of the cesspools." oh, and "The Dutch fans are drunk. Maybe"

godlameroso
305
Joined: Sat Jan 16, 2010 8:27 pm
Location: Miami FL

### Re: Formula 1 Aerodynamics - article series and general discussion

jjn9128 wrote:
Wed Apr 14, 2021 3:27 pm
hecti wrote:
Wed Apr 14, 2021 2:11 pm
Saw this on another thread, this guy put the 2021 williams in CFD, take a look at the rear tire squirt vortex and how far it penetrates into the center of the diffuser, its pretty remarkable, even if the leaked model I believe isn't that great

https://i.imgur.com/KMBG7VA.png

https://media-exp1.licdn.com/dms/image/ ... sSr6mHa2HY
Leaked model doesn't have diffuser strakes which will help to some extent.
To a large extent! This image is fantastic, we see that the way the strakes are shaped are creating high pressure towards the outside of the diffuser. This also validates a lot of theories I have regarding why high rake cars are less affected. Also what can be done with the current floor to improve performance, but I'm sure the smart cookies at the teams already figured it out and are scrambling to test and manufacture new floors.
Saishū kōnā

godlameroso
305
Joined: Sat Jan 16, 2010 8:27 pm
Location: Miami FL

### Re: Formula 1 Aerodynamics - article series and general discussion

Just_a_fan wrote:
Wed Apr 14, 2021 4:01 pm
jjn9128 wrote:
Wed Apr 14, 2021 3:27 pm
hecti wrote:
Wed Apr 14, 2021 2:11 pm
Saw this on another thread, this guy put the 2021 williams in CFD, take a look at the rear tire squirt vortex and how far it penetrates into the center of the diffuser, its pretty remarkable, even if the leaked model I believe isn't that great

https://i.imgur.com/KMBG7VA.png

https://media-exp1.licdn.com/dms/image/ ... sSr6mHa2HY
Leaked model doesn't have diffuser strakes which will help to some extent.
Interesting to see the floor edge appearing to create a vortex that then follows the floor's edge and goes between the rear wheel and the diffuser. This would appear to be "sealing" the floor's edge from lateral flow/the tyre wake. Surprised that's not being pulled across towards the center of the car. Although, as the tyre squirt is going across below it, presumably other unwanted general lateral flow occurs below that edge vortex too.
If your car has less rake it would be closer to that tire squirt wouldn't it? Tire squirt turbulence is drawn to low pressure, either behind the tire, or the diffuser. Think about what happens if the car were turning, would those vortices under the car still be there or would they shift? What about the tire squirt, if it migrates more inboard, then it would be more likely to fill the low in the diffuser. So how do you keep the squirt from migrating to the diffuser under yaw, which is what causes the rear instability?

If the car rolls the loaded side will get even closer to the ground making the diffuser interact with the tire squirt even more, so the solution is to have tons of roll stiffness, or aero tricks to make sure the tire squirt stays closer to the tire.
Saishū kōnā

godlameroso
305
Joined: Sat Jan 16, 2010 8:27 pm
Location: Miami FL

### Re: Formula 1 Aerodynamics - article series and general discussion

So what aero tricks can you do to keep the tire squirt close to the tire under yaw? We already know why it happens, high pressure at the front of the tire, low pressure at the rear, the high pressure air spills along the ground and rushes to the low pressure behind the car.

The floor itself creates a nice vortex, and the current philosophy intends to increase the vorticity ahead of the rear tire, the boundary layer of the vortex acts as a high pressure barrier to the high pressure tire squirt, and delays it from interacting with the diffuser.

Currently the floor tapers inward, but some of the floor still covers the rear tire. Teams have flick ups in front of the tire to encourage vorticity and helicity to form ahead of the rear tire. However I feel this may be a bit counter productive, and the tire is too powerful at breaking it up.

Like the falcon shows us, perhaps it's more effective to make the floor even narrower, and focus on strengthening the vortex that forms inboard of the wheels. Use the whole length of the floor. Then the vortices that you induce travel inboard of the tire instead of smacking into it. Then you have a vortex acting as a buffer for the tire squirt even under yaw.
Saishū kōnā

jjn9128
752
Joined: Tue May 02, 2017 10:53 pm

### Re: Formula 1 Aerodynamics - article series and general discussion

godlameroso wrote:
Wed Apr 14, 2021 4:25 pm
To a large extent!
Typical British understatement
#aerogandalf
"There is one big friend. It is downforce. And once you have this it’s a big mate and it’s helping a lot." Robert Kubica