General aero discussions

[godlameroso]

Thread created to have general aero discussions. This started in the Haas 2023 car threads and its speculation thread, but it is generic F1 aero. So it does not belong in the car threads.

This looks like a suitable place for such debates.

Please, so not have large conversations about general aero in the individual car threads, quickly no one can find anything in any of them. General aero here. Thanks.

Here's what I mean. Notice how the wing starts tapering off inboard of the front tire? The front wing accelerates air underneath it. The Winglet at the bottom of the front wheel assembly, catches that energized front wing air, and pulls it behind the front wheel. Then the bargeboard is also there creating outwash.







The yellow represents the vortex that gets formed behind the wheel. What this does in effect is it somewhat organizes the wake behind the wheel into a vortex. The benefit of this is that the wake becomes confined to said vortex and then becomes a predictable flow structure. It becomes easier to manage a vortex wake, than a turbulent wake. There's more to it than that, like how do you manage said wake, but that's a topic for another day.



Some evidence to support my theory.

Basically, teams figured this out last season, and now they're going to apply this knowledge to the diffuser and the front end, because it reduces tire squirt massively. Which in turn makes the floor work much better. Then they can make all sorts of intricate shapes with the tunnels and whatnot, and not have to worry about tire squirt breaking up all the fancy flow structures.

[Vanja #66]

Here's what I mean. Notice how the wing starts tapering off inboard of the front tire? The front wing accelerates air underneath it. The Winglet at the bottom of the front wheel assembly, catches that energized front wing air, and pulls it behind the front wheel. Then the bargeboard is also there creating outwash.

https://files.catbox.moe/f9gq63.png

https://files.catbox.moe/wsslcf.jpg

https://files.catbox.moe/f4rr3p.png

The yellow represents the vortex that gets formed behind the wheel. What this does in effect is it somewhat organizes the wake behind the wheel into a vortex. The benefit of this is that the wake becomes confined to said vortex and then becomes a predictable flow structure. It becomes easier to manage a vortex wake, than a turbulent wake. There's more to it than that, like how do you manage said wake, but that's a topic for another day.

https://files.catbox.moe/09zvom.jpeg

Some evidence to support my theory.

Basically, teams figured this out last season, and now they're going to apply this knowledge to the diffuser and the front end, because it reduces tire squirt massively. Which in turn makes the floor work much better. Then they can make all sorts of intricate shapes with the tunnels and whatnot, and not have to worry about tire squirt breaking up all the fancy flow structures.

Air under the front wings is de-energised after generating downforce, the upper (pressure) side is the one energised. That's why slots are directing air from suction to pressure side. Examples

Wheels generate 6 separate vortices, counter rotating. Example

Wheels are never nearly as much in yaw. When the car is steering, front wheels are almost aligned to the airflow. Example

Teams are trying to reduce front tyre squirt for decades, 2018 wings were so complex (allowed by rules to be) to form vortices that hit the front tyre, reduce pressure difference and tyre squirt as a result. With these rules, all teams can do is induce some outwash to hit the front tyre and use front wheel cake tin bodywork (very regulated) to manage tyre squirt.

[trinidefender]

Here's what I mean. Notice how the wing starts tapering off inboard of the front tire? The front wing accelerates air underneath it. The Winglet at the bottom of the front wheel assembly, catches that energized front wing air, and pulls it behind the front wheel. Then the bargeboard is also there creating outwash.

https://files.catbox.moe/f9gq63.png

https://files.catbox.moe/wsslcf.jpg

https://files.catbox.moe/f4rr3p.png

The yellow represents the vortex that gets formed behind the wheel. What this does in effect is it somewhat organizes the wake behind the wheel into a vortex. The benefit of this is that the wake becomes confined to said vortex and then becomes a predictable flow structure. It becomes easier to manage a vortex wake, than a turbulent wake. There's more to it than that, like how do you manage said wake, but that's a topic for another day.

https://files.catbox.moe/09zvom.jpeg

Some evidence to support my theory.

Basically, teams figured this out last season, and now they're going to apply this knowledge to the diffuser and the front end, because it reduces tire squirt massively. Which in turn makes the floor work much better. Then they can make all sorts of intricate shapes with the tunnels and whatnot, and not have to worry about tire squirt breaking up all the fancy flow structures.

Vortex wake is turbulent wake

The way you talk it's as if you know all of this before the teams do.

[godlameroso]

Here's what I mean. Notice how the wing starts tapering off inboard of the front tire? The front wing accelerates air underneath it. The Winglet at the bottom of the front wheel assembly, catches that energized front wing air, and pulls it behind the front wheel. Then the bargeboard is also there creating outwash.

https://files.catbox.moe/f9gq63.png

https://files.catbox.moe/wsslcf.jpg

https://files.catbox.moe/f4rr3p.png

The yellow represents the vortex that gets formed behind the wheel. What this does in effect is it somewhat organizes the wake behind the wheel into a vortex. The benefit of this is that the wake becomes confined to said vortex and then becomes a predictable flow structure. It becomes easier to manage a vortex wake, than a turbulent wake. There's more to it than that, like how do you manage said wake, but that's a topic for another day.

https://files.catbox.moe/09zvom.jpeg

Some evidence to support my theory.

Basically, teams figured this out last season, and now they're going to apply this knowledge to the diffuser and the front end, because it reduces tire squirt massively. Which in turn makes the floor work much better. Then they can make all sorts of intricate shapes with the tunnels and whatnot, and not have to worry about tire squirt breaking up all the fancy flow structures.

Air under the front wings is de-energised after generating downforce, the upper (pressure) side is the one energised. That's why slots are directing air from suction to pressure side. Examples

Wheels generate 6 separate vortices, counter rotating. Example

Wheels are never nearly as much in yaw. When the car is steering, front wheels are almost aligned to the airflow. Example

Teams are trying to reduce front tyre squirt for decades, 2018 wings were so complex (allowed by rules to be) to form vortices that hit the front tyre, reduce pressure difference and tyre squirt as a result. With these rules, all teams can do is induce some outwash to hit the front tyre and use front wheel cake tin bodywork (very regulated) to manage tyre squirt.

They merge into 4 large ones particularly when airflow is oblique to the direction of the tire.

[godlameroso]

Here's what I mean. Notice how the wing starts tapering off inboard of the front tire? The front wing accelerates air underneath it. The Winglet at the bottom of the front wheel assembly, catches that energized front wing air, and pulls it behind the front wheel. Then the bargeboard is also there creating outwash.

https://files.catbox.moe/f9gq63.png

https://files.catbox.moe/wsslcf.jpg

https://files.catbox.moe/f4rr3p.png

The yellow represents the vortex that gets formed behind the wheel. What this does in effect is it somewhat organizes the wake behind the wheel into a vortex. The benefit of this is that the wake becomes confined to said vortex and then becomes a predictable flow structure. It becomes easier to manage a vortex wake, than a turbulent wake. There's more to it than that, like how do you manage said wake, but that's a topic for another day.

https://files.catbox.moe/09zvom.jpeg

Some evidence to support my theory.

Basically, teams figured this out last season, and now they're going to apply this knowledge to the diffuser and the front end, because it reduces tire squirt massively. Which in turn makes the floor work much better. Then they can make all sorts of intricate shapes with the tunnels and whatnot, and not have to worry about tire squirt breaking up all the fancy flow structures.

Air under the front wings is de-energised after generating downforce, the upper (pressure) side is the one energised. That's why slots are directing air from suction to pressure side. Examples

Wheels generate 6 separate vortices, counter rotating. Example

Wheels are never nearly as much in yaw. When the car is steering, front wheels are almost aligned to the airflow. Example

Teams are trying to reduce front tyre squirt for decades, 2018 wings were so complex (allowed by rules to be) to form vortices that hit the front tyre, reduce pressure difference and tyre squirt as a result. With these rules, all teams can do is induce some outwash to hit the front tyre and use front wheel cake tin bodywork (very regulated) to manage tyre squirt.

Can you explain this a bit more? This seems to contradict basic understanding of pressure and how it relates to air velocity. Typically higher velocity, indicates lower pressure, on aircraft the air goes faster on the suction side, it shouldn't be any different here in F1, particularly since the wing is in ground effect. If the wing is generating downforce, then the pressure side has higher pressure, as the name implies, higher pressure implies slower moving air.





These streamlines tend to agree with my reasoning, as they show higher velocity and lower pressure.

[Vanja #66]

Can you explain this a bit more? This seems to contradict basic understanding of pressure and how it relates to air velocity. Typically higher velocity, indicates lower pressure, on aircraft the air goes faster on the suction side, it shouldn't be any different here in F1, particularly since the wing is in ground effect. If the wing is generating downforce, then the pressure side has higher pressure, as the name implies, higher pressure implies slower moving air.

Yeah, it is a bit counter intuitive. Convex surfaces (suction side) speed up the fluid flow over them, concave surfaces (pressure side) slow it down. However, speeding up the fluid without increasing the upstream pressure (i.e. having a pump and cranking it up) takes away the energy from the fluid - fluid is working hard to stay attached and curvature is simply speeding it up. Free stream airflow obviously does not have an increase in upstream pressure, so the Total Pressure (static + dynamic) available is constant. Contrary to suction side, pressure side does not take away energy from the fluid in practice (unless the surface is very rough and uneven), since the geometry leads to pressure building up and fluid slowing down. There are losses in terms of boundary layer, but this is present on all geometries obviously.



Here's a Cp_T plot from Toet. The upper limit on Total Pressure plots is usually the stagnation pressure (ambient + dynamic pressure, p_0+0.5rho*V^2) since this is the actual limit in free stream flow. You can see the yellow colour under the front wing, this indicates some loss of energy. You can also see a tiny bit of orange after the slot - this is the slot energising the flow from pressure to suction side.

You can also see the losses on longer surfaces which shows the boundary layer at work. This simply means the increase in dynamic pressure (generated by fluid speeding up) is less than decrease in static pressure (which generates fluid dynamic forces), meaning there is an energy loss.

Separation generates huge losses and separation on wings can only happen on suction side (unless there are local areas with extreme convex geometry, for whatever reason). Separation is caused by boundary layer separation, which happens a lot faster on high-gradient convex surfaces than on a flat surface of same length - because the fluid is losing energy over convex surfaces. Hope I managed to make it clear enough...

[godlameroso]

Can you explain this a bit more? This seems to contradict basic understanding of pressure and how it relates to air velocity. Typically higher velocity, indicates lower pressure, on aircraft the air goes faster on the suction side, it shouldn't be any different here in F1, particularly since the wing is in ground effect. If the wing is generating downforce, then the pressure side has higher pressure, as the name implies, higher pressure implies slower moving air.

Yeah, it is a bit counter intuitive. Convex surfaces (suction side) speed up the fluid flow over them, concave surfaces (pressure side) slow it down. However, speeding up the fluid without increasing the upstream pressure (i.e. having a pump and cranking it up) takes away the energy from the fluid - fluid is working hard to stay attached and curvature is simply speeding it up. Free stream airflow obviously does not have an increase in upstream pressure, so the Total Pressure (static + dynamic) available is constant. Contrary to suction side, pressure side does not take away energy from the fluid in practice (unless the surface is very rough and uneven), since the geometry leads to pressure building up and fluid slowing down. There are losses in terms of boundary layer, but this is present on all geometries obviously.

https://www.racetechmag.com/wp-content/ ... tY0000.jpg

Here's a Cp_T plot from Toet. The upper limit on Total Pressure plots is usually the stagnation pressure (ambient + dynamic pressure, p_0+0.5rho*V^2) since this is the actual limit in free stream flow. You can see the yellow colour under the front wing, this indicates some loss of energy. You can also see a tiny bit of orange after the slot - this is the slot energising the flow from pressure to suction side.

You can also see the losses on longer surfaces which shows the boundary layer at work. This simply means the increase in dynamic pressure (generated by fluid speeding up) is less than decrease in static pressure (which generates fluid dynamic forces), meaning there is an energy loss.

Separation generates huge losses and separation on wings can only happen on suction side (unless there are local areas with extreme convex geometry, for whatever reason). Separation is caused by boundary layer separation, which happens a lot faster on high-gradient convex surfaces than on a flat surface of same length - because the fluid is losing energy over convex surfaces. Hope I managed to make it clear enough...

29. This longitudinal cross section shows CpT (total pressure = energy in the flow relative to the car). With this type of plot, you can get an initial idea about how effectively aerodynamically important items have been places. If you put something into a blue (very little energy) area, you cannot expect it to do much. So a plot like this can tell you where you still have high energy air to play with.

He says that the orange color air is high energy, whereas the blue is low energy. Wouldn't that imply the air behind the wing is high energy? Any time you redirect flow, you're taking away some energy, this is true, but the energy doesn't go to zero. If it doesn't separate, the losses are kept to a minimum.

[Vanja #66]

He says that the orange color air is high energy, whereas the blue is low energy. Wouldn't that imply the air behind the wing is high energy? Any time you redirect flow, you're taking away some energy, this is true, but the energy doesn't go to zero. If it doesn't separate, the losses are kept to a minimum.

It depends a lot on what the plot distribution is. If it's [+1,0] then orange is high energy. If it's [+1,-1] then not so much... Also, I'd say he is trying to make an unambiguous statement, to make sure there is no confusion.

In practice, if Cp_T in the zone is 0.1 or lower, then you can't do much with that air. I've literally placed wing cascades in such zones to try and add some downforce, but the pressure difference was ridiculously low...

[godlameroso]

Can you explain this a bit more? This seems to contradict basic understanding of pressure and how it relates to air velocity. Typically higher velocity, indicates lower pressure, on aircraft the air goes faster on the suction side, it shouldn't be any different here in F1, particularly since the wing is in ground effect. If the wing is generating downforce, then the pressure side has higher pressure, as the name implies, higher pressure implies slower moving air.

Yeah, it is a bit counter intuitive. Convex surfaces (suction side) speed up the fluid flow over them, concave surfaces (pressure side) slow it down. However, speeding up the fluid without increasing the upstream pressure (i.e. having a pump and cranking it up) takes away the energy from the fluid - fluid is working hard to stay attached and curvature is simply speeding it up. Free stream airflow obviously does not have an increase in upstream pressure, so the Total Pressure (static + dynamic) available is constant. Contrary to suction side, pressure side does not take away energy from the fluid in practice (unless the surface is very rough and uneven), since the geometry leads to pressure building up and fluid slowing down. There are losses in terms of boundary layer, but this is present on all geometries obviously.

https://www.racetechmag.com/wp-content/ ... tY0000.jpg

Here's a Cp_T plot from Toet. The upper limit on Total Pressure plots is usually the stagnation pressure (ambient + dynamic pressure, p_0+0.5rho*V^2) since this is the actual limit in free stream flow. You can see the yellow colour under the front wing, this indicates some loss of energy. You can also see a tiny bit of orange after the slot - this is the slot energising the flow from pressure to suction side.

You can also see the losses on longer surfaces which shows the boundary layer at work. This simply means the increase in dynamic pressure (generated by fluid speeding up) is less than decrease in static pressure (which generates fluid dynamic forces), meaning there is an energy loss.

Separation generates huge losses and separation on wings can only happen on suction side (unless there are local areas with extreme convex geometry, for whatever reason). Separation is caused by boundary layer separation, which happens a lot faster on high-gradient convex surfaces than on a flat surface of same length - because the fluid is losing energy over convex surfaces. Hope I managed to make it clear enough...

Free stream airflow obviously does not have an increase in upstream pressure, so the Total Pressure (static + dynamic) available is constant.

Cp_T is dependent on car velocity, as that determines dynamic pressure. Also, the main loss seems to be at the boundary layer.

[Vanja #66]

Cp_T is independant of velocity, that's why that plot is used. It's Total pressure divided by dynamic pressure.

If suction side loss is about boundary layer, same thing would happen with pressure side. Even worse, since boundary layer grows when velocity drops. Obviously, it doesn't.

I can't really get why you feel the need to constantly find holes when people try to explain the basics of fluid mechanics. I'm not pulling this out of my rear, I heard about energy loss and use of total pressure plots to find where the energy is lost from Toet, a guy who designed actual F1 cars, a whole crapload of them...

[n_anirudh]

Also, you will have losses when you have viscous walls - due to the boundary layer effect - even if its a flat plate, but these are negligible compared to the separation

Plot Po/Po_infinity and the losses can be visualised as well.

[johnny comelately]

Also, you will have losses when you have viscous walls - due to the boundary layer effect - even if its a flat plate, but these are negligible compared to the separation

Plot Po/Po_infinity and the losses can be visualised as well.

Is there a chance you could put up a graph/picture of this please (aero for dummies )

[godlameroso]

Cp_T is independant of velocity, that's why that plot is used. It's Total pressure divided by dynamic pressure.

If suction side loss is about boundary layer, same thing would happen with pressure side. Even worse, since boundary layer grows when velocity drops. Obviously, it doesn't.

I can't really get why you feel the need to constantly find holes when people try to explain the basics of fluid mechanics. I'm not pulling this out of my rear, I heard about energy loss and use of total pressure plots to find where the energy is lost from Toet, a guy who designed actual F1 cars, a whole crapload of them...

I'm just trying to understand where you're coming from, I simply seek accuracy for my benefit and those reading this. Feel free to ask direct questions which help you find holes in my understanding.

You say the front wing has used up energy from the airflow to generate downforce, and as a result can't do much else, yet in the same breath contradict yourself by mentioning that they used the front wing to condition air in the previous generation cars. So by logical conclusion, one would wonder why in one instance you can use the front wing to condition air, but in another it has lost its energy and ability to condition airflow downstream.

Do the wings in the current generation use a different fluid medium than the previous generation that would prevent them from being able to condition airflow downstream?

If suction side loss is about boundary layer, same thing would happen with pressure side. Even worse, since boundary layer grows when velocity drops. Obviously, it doesn't.

Can you explain this? If there's a boundary layer, then there exists a no slip condition, the resulting shear forces are losses. Losses when turning air is a given, it's going to happen(to say nothing of secondary flows), the only way it won't is if you don't turn the air. Even then, if you have a surface to channel air, you get losses. The fewer the losses you impart on the air when you turn it, the more energy is going to be left over in it to do stuff downstream. This applies to both bodywork and engines.

[Vanja #66]

I'm just trying to understand where you're coming from, I simply seek accuracy for my benefit and those reading this. Feel free to ask direct questions which help you find holes in my understanding.

You say the front wing has used up energy from the airflow to generate downforce, and as a result can't do much else, yet in the same breath contradict yourself by mentioning that they used the front wing to condition air in the previous generation cars. So by logical conclusion, one would wonder why in one instance you can use the front wing to condition air, but in another it has lost its energy and ability to condition airflow downstream.

Do the wings in the current generation use a different fluid medium than the previous generation that would prevent them from being able to condition airflow downstream?

Let's just go back to what you said about air going under the wing being high-energy, I just wanted to correct this for you and other members. It's a used up air, but not 100% used up.

2009-2018 cars had rules that allowed those famous arches and lots of vanes. Arches and vanes helped form lots of vortices that were aimed at the bottom part of front tyre front surface. Vortex cores are low-energy and low pressure, so having a big core and a few smaller ones hit the tyre helped threefold. Cores reduced pressure in that lower part of the tyre, reducing lift, drag and tyre squirt. Pages 10 and 11 of this paper have some good plots, this plot is also somewhat useful - even if this is far from an optimised design:

Can you explain this? If there's a boundary layer, then there exists a no slip condition, the resulting shear forces are losses. Losses when turning air is a given, it's going to happen(to say nothing of secondary flows), the only way it won't is if you don't turn the air. Even then, if you have a surface to channel air, you get losses. The fewer the losses you impart on the air when you turn it, the more energy is going to be left over in it to do stuff downstream. This applies to both bodywork and engines.

I was saying what I said - if losses on suction side are only from boundary layer as you said, then same thing would happen on pressure side. As the CpT plots show - it doesn't.

[n_anirudh]

Also, you will have losses when you have viscous walls - due to the boundary layer effect - even if its a flat plate, but these are negligible compared to the separation

Plot Po/Po_infinity and the losses can be visualised as well.

Is there a chance you could put up a graph/picture of this please (aero for dummies )

You can see this in any aero engine intake flows/distorted regions of flow. Dont have an automotive aero pic