General aero discussions

[Henk_v]

Those who state that the DF comes from the floor need to brush up their understanding if downforce. Downforce is the pressure difference between the underside of the floor and what goes on above. For sure, the floors are developed to get as much underpressure as possible, but that must always be considered in relation to the pressure above the floor.

[Vaexa]

I don't know why a transparent PR statement like "sidepods don't matter" is even taken seriously on a technical forum. If they didn't matter, why did 10 teams turn up with 10 different interpretations of it last year? Why did several teams toss theirs to copy another?

They're not the sole differentiator but Mercedes' insistence that they don't matter to performance is just a way to divert criticism from their technical team, nothing more, nothing less. It shouldn't be taken seriously in any serious technical discussion.

People are far too invested in the zeropod, halfpod, whatever you want to call it thing, like some weird point of personal pride. We all know working the beam wing and diffuser roof is important, in both this aero formula and last (well, more diffuser roof); we all know floor edge interaction is important to diffuser and floor performance; we all know the airflow that eventually goes to both does, in fact, encounter the sidepods before it ever encounters the diffuser/beam wing. Why would Mercedes have bothered changing the things otherwise, over the winter? If it was just a floor and suspension fix, save some money under the budget cap by running the old W13 bodywork. They didn't. Why does a technical thread periodically devolve into bizarre semantics slapfights over sidepod volume, sidepods mattering/not mattering to overall aero performance and that sort of thing?

Anyway, to be a little bit more topical, this was posted in the team thread but I feel it has relevance here as well:

https://www.formu1a.uno/riunione-merced ... m-elliott/

Google translated relevant part that isn't just a Bahrain GP recap:

There will be a change of philosophy with more conventional bellies , what the current generation of cars needs to make up for the lack of the (old) bargeboard area. An area that served to move the turbulent wake of the front tires, a function that is now also partly performed by the sidepods. “We have a different bodywork in the works, which will not be the same as that of the others, nor the one we have now. It will just be different.” said DT Mike Elliott. Remembering that Mercedes uses a 'single' frame , i.e. flared at the sides to be able to insert the radiators which are thus moved along the longitudinal axis of the car.“The new bellies are part of the planned development on the W14. It takes time to bring it because we need to produce new parts and we need to change some parts that are underneath the bodywork to be able to assemble it. It will debut we will bring as soon as possible."

There was a going theory that it would be easier for Mercedes to change their sidepods around as their engine packaging is more compact (at least in terms of width lower down) which seems not to be the case, if this change entails moving things around.

[mechanoit]

Those who state that the DF comes from the floor need to brush up their understanding if downforce. Downforce is the pressure difference between the underside of the floor and what goes on above. For sure, the floors are developed to get as much underpressure as possible, but that must always be considered in relation to the pressure above the floor.

Even if you passed no air flow above the floor, and only under the floor, the higher volume throat of the front of the floor, then going into the small volume lowest part of the floor, then exiting out of the higher volume diffuser, you still create a pressure differential to the top of the floor which is simply at atmosphere.

Mercedes is trying to use the flow around the side pods to energise the diffuser too. But majority of the downforce is coming from the floor design.

[Vanja #66]

Those who state that the DF comes from the floor need to brush up their understanding if downforce. Downforce is the pressure difference between the underside of the floor and what goes on above. For sure, the floors are developed to get as much underpressure as possible, but that must always be considered in relation to the pressure above the floor.

While not untrue, this is misleading and fairly incorrect. In a free stream, you can only reach Cp of +1, you can't build up the pressure more than the stagnation pressure. In practice, going for anything above 0.2-0.3 (and 0.3 is likely way too much in any case) on top of the floor will ruin the flow for the rear end completely.

On the other hand, the underfloor can easily reach peaks of -4 and bellow, so the underside is the important side in practice.

[atanatizante]

So it`s commonly understood that they need to keep the front tyre wake out to not mess with the clean airflow towards the diffuser but in order to achieve that how about they build some bulky but hollow bodywork above the existing side pods, which has an air intake/entrance at both ends?

Obviously, the back-end outlet will guide the airflow towards the diffuser. Something like some teams is doing with the roll hoop engine air intake by splitting the airflow with special ducting towards specific car`s hardware and engine plenum.

What are the disadvantages and had they outweigh the advantages?

[SiLo]

There was a going theory that it would be easier for Mercedes to change their sidepods around as their engine packaging is more compact (at least in terms of width lower down) which seems not to be the case, if this change entails moving things around.

I assume people thought that they could add extra to the sidepods easily without changing anything internally, but the internals are already compromised to fit the zeropod ideology. So maybe they figured moving things back nets them other benefits elsewhere while still fitting nicely into a new sidepod design.

[Henk_v]

Those who state that the DF comes from the floor need to brush up their understanding if downforce. Downforce is the pressure difference between the underside of the floor and what goes on above. For sure, the floors are developed to get as much underpressure as possible, but that must always be considered in relation to the pressure above the floor.

While not untrue, this is misleading and fairly incorrect. In a free stream, you can only reach Cp of +1, you can't build up the pressure more than the stagnation pressure. In practice, going for anything above 0.2-0.3 (and 0.3 is likely way too much in any case) on top of the floor will ruin the flow for the rear end completely.

On the other hand, the underfloor can easily reach peaks of -4 and bellow, so the underside is the important side in practice.

I'm not sure what you mean. Accelerating air above the floor will lower the dynamic pressure. Sure there are other things to consider, but downforce is still the result of the difference beween the dynamic pressure above and below the floor. The floor cant be considered in isolation. Gains can be made below and above.
Less displacement of air above the floor=slower air above the floor=higher dynamica pressure. That must be the key (imagined) advandage of the zeropod.

[Vanja #66]

I'm not sure what you mean. Accelerating air above the floor will lower the dynamic pressure. Sure there are other things to consider, but downforce is still the result of the difference beween the dynamic pressure above and below the floor. The floor cant be considered in isolation. Gains can be made below and above.
Less displacement of air above the floor=slower air above the floor=higher dynamica pressure. That must be the key (imagined) advandage of the zeropod.

I'm sure it was lapsus linguae, but any aerodynamic force is a result of static pressure difference.

Yes, you can make minor gains on top of the floor (since rules don't allow a lot of variation other than the floor edge region) and with these gains you'd ruin the flow to the rear end completely. This is way teams wouldn't place air dams on the floor even if they were allowed - you could make much bigger gains by feeding the diffuser with undisturbed, high energy air and further reduce the pressure under the floor.

Internal flow excluded, the pressure difference from under the floor is partially compared to pressure on top of sidepods obviously, maybe this is what you were thinking of? However, the same caveat applies there, you don't want to mess the flow on the sides since you'd ruin the flow towards rear and beam wings. Not that the rules would allow you to, but still...

[chrisc90]

I'm sure it was lapsus linguae, but any aerodynamic force is a result of static pressure difference.

Yes, you can make minor gains on top of the floor (since rules don't allow a lot of variation other than the floor edge region) and with these gains you'd ruin the flow to the rear end completely. This is way teams wouldn't place air dams on the floor even if they were allowed - you could make much bigger gains by feeding the diffuser with undisturbed, high energy air and further reduce the pressure under the floor.

Internal flow excluded, the pressure difference from under the floor is partially compared to pressure on top of sidepods obviously, maybe this is what you were thinking of? However, the same caveat applies there, you don't want to mess the flow on the sides since you'd ruin the flow towards rear and beam wings. Not that the rules would allow you to, but still...

Pulled this quote out the W14 thread as I have a question for those who understand aero.

Obviously we get faster airflow under the floor which makes a higher pressure area above the floor. What then happens if you have a sidepod on top of that airflow where air can pass over that too, AND use the air above the floor.

What effects does a side pod have on the air passive between the two surfaces? Is it possible that one will neutralise the other or even accelerate it further? Is there any effects on the downforce that could have under the floor too?

I know its probably not the best worded question out there, but my knowledge isnt good enough to write the question well enough.

[Henk_v]

[quote="Vanja #66" post_id=1122418 t
I'm sure it was lapsus linguae, but any aerodynamic force is a result of static pressure difference.

[/quote]

Well if that's the new rule, put on your hardhats as planes will fall from the sky and dig up mr. Venturi to tell him he messed up science.


I never set the top of the floor, but above the floor. There's a big difference.

[Vanja #66]

Well if that's the new rule, put on your hardhats as planes will fall from the sky and dig up mr. Venturi to tell him he messed up science.

So what is the value of a dynamic pressure on the surface? Don't forget the boundary layer and velocity distribution

[mzso]

Its probably not really any of the upper body work that is behind the performance delta. I think that its a difference in front end, the suspensions here are probably the key differentiator, that and the floor interaction with the front wing/wheel wake.

It's a combination of things. The underfloor isn't as efficient and the small pod / midwing don't help the airflow over the body and around the tyres. Lewis said with the smaller rear wing that he had no grip which just goes to show how ineffective the Mercedes underfloor is and so just replacing the small pods won't by themselves sort out all there issues.

Ironically I think the initial W13 Barcelona test sidepods would probably work a hell of a lot better if they don't want to go full Red Bull / Ferrari.

It could be, however I dont think its the sidepods at all.. I think its a red herring, and the most visible difference so ppl point to it. Issues with the interactions from the Front Suspension (the kinematics, not necessarily the aerofoil/blade profile of the arms), Front Wing, and Floor Entrance (Strake Geometry) - Just think that the upper body work accounts for a small percentage of overall DF and Performance, in this era. I could be wrong, but this is where I think the gap to the front is.

Well, the upper bodywork, particularly the side-pod guides the unwanted air away from the diffuser and the wanted air towards the diffuser exit. So it seems a tad relevant.

[Vanja #66]

Pulled this quote out the W14 thread as I have a question for those who understand aero.

Obviously we get faster airflow under the floor which makes a higher pressure area above the floor. What then happens if you have a sidepod on top of that airflow where air can pass over that too, AND use the air above the floor.

What effects does a side pod have on the air passive between the two surfaces? Is it possible that one will neutralise the other or even accelerate it further? Is there any effects on the downforce that could have under the floor too?

I know its probably not the best worded question out there, but my knowledge isnt good enough to write the question well enough.

Well, I hope I got it. First of all, the air above the floor (so exposed top of the floor) is basically ambient/atmosphere pressure area. Some parts are slightly above ambient, some slightly bellow. It's not really a high pressure area like the top surface of the wings.

What I understood from the question is if the sidepod can influence airflow on top and also under the floor? In both cases, yes. Specifically, with outlaw of bargeboards, sidepods got even more important for airflow management and making sure the diffuser and floor work as best as possible. The topic is very complex and we are discussing this area more than all others because it's visible and different on all cars. It's as complex as any other area of an F1 car aero and it turned out some teams are struggling with proper sidepod design for more than a year already...

[chrisc90]

You understood the question fine, Thanks.

So I guess it is entirely possible for the sidepod to have faster air flowing under it (above the floor) whilst there is also air flowing quickly under the floor. I guess this can neutralise the downforce made by the floor.

Agree it will be a very aero sensitive area, just like the rest of the car

[TimW]

From many years back when I raced sailing boats, you tend to reduce the angle of attack at the top of the sail so as to reduce the lateral force and hence tipping force the sail produces. You make more power from further down the sail and there's usually plenty to use - any more and you often have trouble keeping the boat from tipping over.

It is not only that, also because of the gradient in wind speed, which increases with distance from the earth's surface. Therefore the angle of attack of the apparent wind changes with height, and the twist in the sail profile can account for that.