Red Bull RB18

[Juzh]

Max's wing does 340km/h when the DRS is open. It doesn't get much quicker than that for these cars.

The sims are probably telling them Max's wing is the quicker one in qualifying, which is why they are bothering at all.

340 kmh is spa wing level.

Yes. And that is the wing that Max has on his car this weekend.

Italian language got me there. Thought is was the other way around. Just did a quick glance.

[Vanja #66]

@Vanya#66. I agree with you for the most part, except for your representation of Redbull's floor concept. Newey has put a lot of effort into distributing the downforce generated by the floor of the RB18. Peak downforce is evenly spaced between the floor kick at the back and tunnel expansion, levelled. That's why they're less affected by air flow disturbances that can lead to porpoising. They don't lack downforce. Sure, peak downforce may be lower, but they're able to sustain higher downforce levels.

You sure about this? Could you explain the physics behind this explanation?

[organic]

[VacuousFlamboyant]

@Vanya#66. I agree with you for the most part, except for your representation of Redbull's floor concept. Newey has put a lot of effort into distributing the downforce generated by the floor of the RB18. Peak downforce is evenly spaced between the floor kick at the back and tunnel expansion, levelled. That's why they're less affected by air flow disturbances that can lead to porpoising. They don't lack downforce. Sure, peak downforce may be lower, but they're able to sustain higher downforce levels.

You sure about this? Could you explain the physics behind this explanation?

Given the teardrop shape of the reference plane the viscous medium passing alongside its edge (transition area) becomes thinner at its center, this in turns increases air velocity. Instead, the RB18 floor height is bigger at the center, reducing pressure. The catch are both the turning vanes and the humps at the front of the reference plane.

The hamps produce capillary ripples that reduce surface tension around the middle of the reference plane edges, they act as vortex generators that prompt the transition to the back of the floor, preventing back-flow in that area. The vortexes energize the flow to the sides while reducing the friction factor, which is important because of the stress at the wall at a larger surface (parabolic compared to a flat tunnel). The shape of the first vane suggests he put a lot of emphasis as to have minimal disturbance between the two (guesswork). The vanes, plus the cut in the sidepod pressurizing the upperfloor flow and the humps are of paramount importance as to why I think pressure distribution of the underfloor is somewhat the same accross that section of the main plane.

The key to me is keeping the flow as steady as possible. Newey might have make extensive use the Hagen–Poiseuille equation and Darcy–Weisbach equation to make pressure distribution as even as possible. Optimising ground effect as to not have an axis point that could shift pressure distribution as downforce builds up. That's why when the RB18 hits the ground it's still levelled.

[Vanja #66]

Given the teardrop shape of the reference plane the viscous medium passing alongside its edge (transition area) becomes thinner at its center, this in turns increases air velocity. Instead, the RB18 floor height is bigger at the center, reducing pressure. The catch are both the turning vanes and the humps at the front of the reference plane.

Increasing tunnel height reduces pressure? Brings it further down? You sure about this?

The hamps produce capillary ripples that reduce surface tension around the middle of the reference plane edges, they act as vortex generators that prompt the transition to the back of the floor, preventing back-flow in that area. The vortexes energize the flow to the sides while reducing the friction factor, which is important because of the stress at the wall at a larger surface (parabolic compared to a flat tunnel). The shape of the first vane suggests he put a lot of emphasis as to have minimal disturbance between the two (guesswork). The vanes, plus the cut in the sidepod pressurizing the upperfloor flow and the humps are of paramount importance as to why I think pressure distribution of the underfloor is somewhat the same accross that section of the main plane.

I'm really not able comment back on this, not sure where to start with so much guesswork...

The key to me is keeping the flow as steady as possible. Newey might have make extensive use the Hagen–Poiseuille equation and Darcy–Weisbach equation to make pressure distribution as even as possible. Optimising ground effect as to not have an axis point that could shift pressure distribution as downforce builds up. That's why when the RB18 hits the ground it's still levelled.

What would pipe flow equations have to do with external flow conditions around a car?

[vorticism]

If the continuous front arm is acting as a transverse leaf spring then it would allow them to make the pullrods slightly thinner.

[PlatinumZealot]

Its has springyness but it's not acting as a spring there.

It's a continuous flexture for fatigue reasons (so it last longer) and perhaps for additional dampening of high frequency judders.

It's too lon and far away a lever arm to really be of any great influence spring wise. Look how it is when the car is on jack stands to get an idea of how stiff it is.

[vorticism]

It would have some effect, the question is how much. Is it supporting 0.005% of the front axle weight or 50%?

By comparison here is a composite spring supporting 500-600 kg on the rear axle of a C3 corvette. The front axle of current F1 cars should be ~300 kg. Connecting the inside of each wheel, so it is a similar overall span. Halve the weight supported, replace the GRP with CF, then factor in % front axle still supported on the torsion bars. All told, the longbow wouldn't have to be such a great size to have some major effect on the other suspension components, like downsizing pullrod and rockers, f.e.



Or a C5 example:



Halve it in thickness and depth and you'd end up with something that could fit within an aero shroud while supporting a significant percentage of the front axle weight.

[Henk_v]

As a European, I'm not sure how stiff a Corvette is sprung, but I'd bet an F1 car is a significantly stiffer sprung car.

Maybe you're overcomplicating. My guess is that is is just far lighter to mount it this way.

A discontinouous arm would need two mounting points, each capable of absorbing the forces of whatever the force of a tyre is on that point. The RB longbow way, you have also two mounting points, but each capable of absorbing half of the above force.

Lets say hitting a curbstone at 250kph is the "limit case" these suspension are designed towards. If one wheel hits the curbstone, resulting in a compressive force in the arm, it will be absorbed by both mounting points in more or less equal share. If both wheels hit the curbstone, there is just compression in the arm and little force on the mounts as both forces counteract. In a discontinouous arm solution, you'd need two mounts that can fully absorb the force ánd you need that part of the chassis to be able to take the full compressive load between the mounting points.

So I think it's just smart engineering.

An additional benefit is that if it turns out the forces were underestimated, you just use a beefier longbow. No need to beef up the chassis and go through the hassle of homologating it. This allows for taking a bit more risk designwise.

It could also be that , as this area of the chassis does not have to be as strong and stiff, it's more effective in a crashtest.

[vorticism]

Yes it may only be about lightening the mounting points. However the spring rate of the flexure remains unknown. A 1,5 cm solid round bar of CF (unidirectional) should be able to support around 100 kg with less than 2 cm deflection across 0,5 m. Very rough calculation. The cross section, layup, and material properties are guesswork for us at this point. What is the value of more lightweight pullrods, rockers, springs and bearings?

[VacuousFlamboyant]

Increasing tunnel height reduces pressure? Brings it further down? You sure about this?

I'm really not able comment back on this, not sure where to start with so much guesswork...

What would pipe flow equations have to do with external flow conditions around a car?

To each their guesswork...

Aerodynamics and hydrodynamics are subdisciplines of fluid mechanics. Newey could've derived the equations to account for the pressure of a "semicircle", like the underfloor's concave tunnel. He obviously would not use the equations as they are. Look up the influence of compressibility of the airflow on lift and drag.

Where I said pressure, read negative pressure. We want downforce, not lift. I was thinking about the pressure difference over that surface, induced drag in the boundary layer, not overall pressure. The overall pressure in the area will decrease as the volume increases, so will air speed. As a side effect, that would vastly reduce parasitic drag. And the vortexes are important to seal the boundary layer and retain downforce, otherwise flow separation would occur. This would explain why the RB18 less sensitive to ride height.

What I'm trying to convey is that Newey conceived that floor with the idea of using that "steady" turbulent flow through the tunnel section to keep air velocity as constant as possible. The floor tunnel height gets bigger as the reference plane widens.

[Vanja #66]

To each their guesswork...

Aerodynamics and hydrodynamics are subdisciplines of fluid mechanics. Newey could've derived the equations to account for the pressure of a "semicircle", like the underfloor's concave tunnel. He obviously would not use the equations as they are. Look up the influence of compressibility of the airflow on lift and drag.

Where I said pressure, read negative pressure. We want downforce, not lift. I was thinking about the pressure difference over that surface, induced drag in the boundary layer, not overall pressure. The overall pressure in the area will decrease as the volume increases, so will air speed. As a side effect, that would vastly reduce parasitic drag. And the vortexes are important to seal the boundary layer and retain downforce, otherwise flow separation would occur. This would explain why the RB18 less sensitive to ride height.

What I'm trying to convey is that Newey conceived that floor with the idea of using that "steady" turbulent flow through the tunnel section to keep air velocity as constant as possible. The floor tunnel height gets bigger as the reference plane widens.

Experience and knowledge leave you with educated guesses, which can be a real benefit actually... Speeds things up quite a lot, adds value and yields good hourly rates. For instance, when I said this

What RB did is very different, they emphasized the curvature around diffuser kink (mandated by rules) and they opened up the diffuser side wall to let the air from the top of the floor enter there to feed and energize the vortex. This makes the floor work more like classical flat-floor with diffuser, as it doesn't rely on ground proximity for optimal performance. Energizing the vortex reduces the pressure in diffuser, which in turn also drives the front of the floor and reduces overall pressure under the floor.



This is just a general outline of their floor philosophy. This is why RB never had any problems with bouncing, but why they also lacked overall downforce compared to Ferrari.

I didn't guess out of my rear, I know which geometries are at play and how those influence floor design in practice. Like this quick floor profile CFD demonstrates:



RB floor is by far the most complex out there, it uses a lot of additional features to negate the pressure increase that comes with greater tunnel height (not decrease, as you seem to think), including tub profile, vanes, lots of small geometry changes etc. They made a very small throat height and created a strong, but quite small downforce area around it. Only they know how the rest of the floor pressure distribution looks like, especially at the front where all the fun geometry is. Take a look at this thread to see a glimpse of how inconsistent the pressure distribution at the front is:

viewtopic.php?p=879079#p879079

This is very far from what typical ground effect floor pressure distribution looks like and the rear end is practically the same as previous generation diffuser floors. You can be sure that other teams, with conventional ground effect floor design, have a very, very different pressure distribution, far more even as opposed to RB peaky downforce design.

Seeing how strongly this design will be affected by increasing floor throat and edge height in 2023, I can understand why Horner was so much against it. Other than the change playing right to Mercedes' hand...

[VacuousFlamboyant]

To each their guesswork...

Aerodynamics and hydrodynamics are subdisciplines of fluid mechanics. Newey could've derived the equations to account for the pressure of a "semicircle", like the underfloor's concave tunnel. He obviously would not use the equations as they are. Look up the influence of compressibility of the airflow on lift and drag.

Where I said pressure, read negative pressure. We want downforce, not lift. I was thinking about the pressure difference over that surface, induced drag in the boundary layer, not overall pressure. The overall pressure in the area will decrease as the volume increases, so will air speed. As a side effect, that would vastly reduce parasitic drag. And the vortexes are important to seal the boundary layer and retain downforce, otherwise flow separation would occur. This would explain why the RB18 less sensitive to ride height.

What I'm trying to convey is that Newey conceived that floor with the idea of using that "steady" turbulent flow through the tunnel section to keep air velocity as constant as possible. The floor tunnel height gets bigger as the reference plane widens.

Experience and knowledge leave you with educated guesses, which can be a real benefit actually... Speeds things up quite a lot, adds value and yields good hourly rates. For instance, when I said this

What RB did is very different, they emphasized the curvature around diffuser kink (mandated by rules) and they opened up the diffuser side wall to let the air from the top of the floor enter there to feed and energize the vortex. This makes the floor work more like classical flat-floor with diffuser, as it doesn't rely on ground proximity for optimal performance. Energizing the vortex reduces the pressure in diffuser, which in turn also drives the front of the floor and reduces overall pressure under the floor.

https://i.ibb.co/2dWCbvp/iBwWx4U.jpg

This is just a general outline of their floor philosophy. This is why RB never had any problems with bouncing, but why they also lacked overall downforce compared to Ferrari.

I didn't guess out of my rear, I know which geometries are at play and how those influence floor design in practice. Like this quick floor profile CFD demonstrates:

https://i.ibb.co/44dsV89/rb-floor.jpg

RB floor is by far the most complex out there, it uses a lot of additional features to negate the pressure increase that comes with greater tunnel height (not decrease, as you seem to think), including tub profile, vanes, lots of small geometry changes etc. They made a very small throat height and created a strong, but quite small downforce area around it. Only they know how the rest of the floor pressure distribution looks like, especially at the front where all the fun geometry is. Take a look at this thread to see a glimpse of how inconsistent the pressure distribution at the front is:

viewtopic.php?p=879079#p879079

This is very far from what typical ground effect floor pressure distribution looks like and the rear end is practically the same as previous generation diffuser floors. You can be sure that other teams, with conventional ground effect floor design, have a very, very different pressure distribution, far more even as opposed to RB peaky downforce design.

Seeing how strongly this design will be affected by increasing floor throat and edge height in 2023, I can understand why Horner was so much against it. Other than the change playing right to Mercedes' hand...

I was specifically talking about the transition area when I first talked about air pressure, which is the name given to the side of the main plane. I think I've been pretty clear pointing that the downforce increase that comes within the pressure acting on the boundary layer and the airflow pressure within the gap with all those vortexes are two separate things. You misunderstood what i said.

I don't know what you're trying to demonstrate with that oversimplified CFD as pressure distribution shown in the figure isn't the same thing as air pressure accross that gap. You're acting like air pressure stays the same within the whole area, from boundary layer to the ground. It doesn't. The plots from Vyssion in the thread you linked show exactly that. The Software you're using is limiting your potential.

You think the shape of the floor is much flatter at the front, much like a conventional floor from previous regulations. I'd say height difference is much more pronounced, with the sculpted concave area in the middle being of greater importance. Therefore, as explained before, I don't think Redbull's floor concept is as sensible to ride height. You can doubt me, but the results on tracks like Spa and the word from F1 team principals back this statement. What will hurt them in 2023 is the prohibition of the ice skates, but Perez wasn't too far off without them in FP.

[AR3-GP]

What will hurt them in 2023 is the prohibition of the ice skates, but Perez wasn't too far off without them in FP.

When did Perez test without ice skates?

[Vanja #66]

I was specifically talking about the transition area when I first talked about air pressure, which is the name given to the side of the main plane. I think I've been pretty clear pointing that the downforce increase that comes within the pressure acting on the boundary layer and the airflow pressure within the gap with all those vortexes are two separate things. You misunderstood what i said.

Mate, you can't use terms of opposite meaning interchangeably, there's either pressure increase or decrease... There's no negative pressure, anywhere, absolute vacuum has a pressure of 0 Pa - which is not negative pressure. If we talk about sub- or above-ambient pressure, we can use terms such as suction side and pressure side (of an aerofoil, e.g.), we can talk about positive and negative pressure coefficient, but not about positive or negative pressure on its own.

I honestly can't understand what you wrote, again, but it doesn't matter.

I don't know what you're trying to demonstrate with that oversimplified CFD as pressure distribution shown in the figure isn't the same thing as air pressure accross that gap. You're acting like air pressure stays the same within the whole area, from boundary layer to the ground. It doesn't. The plots from Vyssion in the thread you linked show exactly that. The Software you're using is limiting your potential.

Let me first remind you what you wrote:

Newey has put a lot of effort into distributing the downforce generated by the floor of the RB18. Peak downforce is evenly spaced between the floor kick at the back and tunnel expansion, levelled.

I've asked you to give an explanation, you gave some guesswork and I gave you a floor profile simulation to demonstrate what I explained earlier. Since this was the only purpose of the simulation, it's complexity is exactly right. You are free to model RB18, use OpenFOAM for free and demonstrate your own CFD results to prove your point. I'd honestly love to see those, since I can't figure what you're trying to say.

As for software limitation, it's been validated and correlated to 1% error with several complex WT race-car models. If we've had the right measuring equipment, we could have gone bellow 1%, but it would've cost too much time and money. Don't compare these results to Vyssion and jjn9128's results, we don't use the same scale and coefficient plots. When you leave out vortex generators, the pressure between the floor and the ground stays mostly the same, since there is no geometry in 30-40mm of space to influence the pressure distribution.

I have to ask - what does boundary layer have to do in all of this? I'm sure you know there is no (significant) pressure gradient in boundary layer and that pressure acts on surface, not boundary layer.

You think the shape of the floor is much flatter at the front, much like a conventional floor from previous regulations. I'd say height difference is much more pronounced, with the sculpted concave area in the middle being of greater importance.

I honestly have no desire and no means to study RB18 floor to get all it's details. I noticed this distinct profile (similar on Sauber as well), I offered an explanation of profile's influence and I demonstrated what I explained. That's all...