W06 Front Wing Discussion

[monsi]

So if I am understanding BHall's argument correctly, when the car is as shown there will be a surge of additional downforce on the right hand side of the picture [left side of the car] as the central part of the wing has less adverse pressure gradient to contend with, as the wheel is effectively further back from this than when driving straight ahead. The inside wheel in a corner will thus be pressed into the ground to increase reaction and enable higher friction. Clearly it would be undesirable to have a one sided effect as the suspension of the car would not be able to compensate for all of this. I imagine that on the other side it would be desirable that the outside of the wing would be similarly triggered into action to create a surge of downforce when the wheels are as shown. However as far as I can see there are no wing elements that would be substantially freed from an adverse pressure gradient on this side by the wheel moving further away from them, excepting that tiny bit on the outside of the end plate. Instead we have this very prominent tunnel structure. Can I presume that the intent is to switch on a vortex to move as much air as possible outside the wheel when it is in this orientation, giving a more general adverse pressure reduction in front of the wheel ? Have I got this even remotely right ?

[bhall II]

[...]

The inside wheel in a corner will thus be pressed into the ground to increase reaction and enable higher friction. Clearly it would be undesirable to have a one sided effect as the suspension of the car would not be able to compensate for all of this...

I''m not so sure that uneven loading of the wing is especially harmful, because downforce is applied to both wheels through the wing pylons, nose, and the chassis, all of which are more or less situated about the car's center line.

That said...

Could a blown front axle reduce the amount of air passing on the inside of the wheel?

I mean, they take air from the brake duct and blow it out on the outside, effectively reducing flow between the wheel and the nose/body.

I considered that possibility as well, and it seems unlikely. On the other hand, there might be a benefit to doing something along those lines.

For instance, the orientation of the brake duct scoops on the SF15-T suggests it could be possible to use the effects of the car's blown axles, which are fed by those scoops, to somehow pull air flow over any section of the wing that lies directly in front of them. If so, the areas of the wing influenced by such an effect would change concurrently with any changes to steering angle, and it would include both end plates.



The question mark is the pressure within the ducts. If it's lower than static pressure under the wing, I can't think of any reason why it wouldn't work. If it's too high, though, it'll form a high-pressure blockage just like the wheels. The hypothetical system's ability to vent air flow as quickly as it's drawn in would make the difference.

But...it might benefit the wing's response to transients, regardless.

F1 cars have absurdly high yaw rates, i.e. the time it takes for a car to respond to steering changes. For a very, very, very, very brief moment after steering lock is initially applied, the car continues in the direction it was traveling before the change was made. Think of it as that initial "bite" upon turn-in, and it is the state of the car for which downforce is never more important and thus the primary focus for virtually all aerodynamic layouts.

If the brake duct scoops can accommodate any flow at all from the wing during this transient period, no matter how briefly, it should increase the wing's efficiency by some degree, no matter how small.

[...]
However as far as I can see there are no wing elements that would be substantially freed from an adverse pressure gradient on this side by the wheel moving further away from them, excepting that tiny bit on the outside of the end plate. Instead we have this very prominent tunnel structure. Can I presume that the intent is to switch on a vortex to move as much air as possible outside the wheel when it is in this orientation, giving a more general adverse pressure reduction in front of the wheel ? Have I got this even remotely right ?

If I correctly understand the question, I think you've made a solid presumption.

The goal of outwash designs isn't necessarily to "drive" air flow over the end plates; it's to remove, or at least mitigate, the downstream blockage of the end plates caused by the wheels, and to do so in a way that doesn't effect underbody aerodynamic efficiency. The end plates "drive" themselves.

(For the record, my speculations should be taken with a healthy dose of salt, because they are highly theoretical, and I'll never be able to either prove or disprove them empirically.)

[bhall II]

Frankly, there's absolutely nothing you can do to accurately model these interactions. Without a precise representation of all variables and components, a picture drawn with crayons would be just as valid as the results.

That's just how it be, yanno?

[chuckdanny]

You always say that pressure wants to flow (to use your own words) from high to low pressure, so how do you explain pressure build up in the bow of the tire?
AIr from the high static pressure in front of tire is flowing right (or left)?
So must be some flow going in this area from somewhere right, otherwise it would disappear? but wait a minute, this is the highest static pressure area in the neighborhood ? It must come from lower static pressure area then, ---!
Do you know the basics? dynamic pressure converting into static pressure ?
It's a dynamic equilibrium thing, there is forcing going on. It's pretty simple though, by reducing dynamic pressure in front of the tire you reduce bow static pressure build up hence the so called adverse pressure gradient (which maybe not so adverse where it is placed that is relatively low).
It's pretty unatural for flow to keep with the stiff ramp behind, under the wing, maybe this bow high static pressure area could help? to be used like a ramp ? You see ? instead of blocking, bending the flow, fluid dynamic.
Something else, because of the high rotation of the wheel, flow condition on top is very low static pressure, high velocity, could this help? We see that flow is squeezed between endplate and the arches area like a venturi, do you really get the picture? the physic ? I still think those are first order flow physics that can qualitatively be represented at low resolution.
It's not a question of --- it's a question of resolution (and time). Sometimes a butterfly can trigger hurricane, sometimes not.

[bhall II]

You always say that pressure wants to flow (to use your own words) from high to low pressure, so how do you explain pressure build up in the bow of the tire?

[...]

I even linked to the article...

Not surprisingly, the results of the LES simulations, confirmed by the PIV measurements, illustrate that unsteadiness, large-scale separation, and longitudinal vortical structures dominate the turbulent airflow behind the tire. The flow is very unstable and has the tendency to fluctuate from side to side. The results also show that there is a region of separated flow close to the back of the tire where air particles recirculate and travel forward faster than the car moves. Finally, the simulations show that a system of counter-rotating vortices overwhelms the wake of the isolated tire very far downstream. Additional simulations and experiments also confirmed the fundamental effect of tire rotation; specifically, the presence of a very strong downwash in the wake of a stationary tire which leads to only limited recirculation and thus to airflow that is not representative of realistic racecar conditions.

EDIT: You simply cannot do this accurately without all of the the details. I don't know why that's so difficult to grasp.

Or am I just weird for thinking accuracy is important? Given the pushback, I might be willing to accept that it's actually me who's crazy.

[chuckdanny]

That's very good! If They don't understand themself some part of the flow physics then they can't design taking thoses phenomenon into account so that we can understand what there intent is regardless of the true result

[Just_a_fan]

EDIT: You simply cannot do this accurately without all of the the details. I don't know why that's so difficult to grasp.

Or am I just weird for thinking accuracy is important? Given the pushback, I might be willing to accept that it's actually me who's crazy.

No, you're not alone. I made a similar position in another thread where a particular item on the W06 was being modelled. Without the rest of the flow, both upstream and downstream, being modelled correctly the results are meaningless. They're interesting in themselves but they don't give a proper view of what is going on in the case being discussed.

Without a millimetre-accurate model of the front wing, the under-nose turning vanes, the suspension, brakes ducts and rotating tyre the results from this study will only give the broadest feeling of a result. It certainly won't be a "here, this is what the front wing does" answer - anyone who says that just doesn't understand the limitations of the model.

For one thing, I think that the way that the front wing turns the flow around the front wheel is helped by the turning vanes below the nose. I also think that the batwing device behind the turning vanes is there to help regain control of the flow and direct it to the front of the floor/sidepod region. These devices will help to reduce front tyre induced drag, increase underbody downforce and also front wing downforce by scavenging flow from the front wing. It's a very powerful combination of devices working together - remove any one of them and I think the system would be much less effective.

I think it's interesting that people focus on one item - I remember back when Brawn brought out their double diffuser car. The other teams and the media were focussing on the diffuser - that was, as far as they were concerned, where the performance of the car was. Even then, Brawn was saying that people were looking in the wrong place and at the wrong end of the car. The Brawn had one of the first successful outflow front wing endplates. We see these on all of the cars now. The endplate's interaction with the flows around the front wheel and how that determines the rest of the aero map of the car means that you need to understand the interaction. To understand it you need to model it correctly. A partial model will give worse-than-useless results - it will give incorrect results.

Having said all of that, I applaud the effort that people are putting in to this topic. I hope we can pick out some useful answers from it although I'm cautious of doing so.

[SectorOne]

Sent him a tweet, maybe he can lay down some knowledge, in the meantime, have a tweet.

(OLD WING) https://twitter.com/F1_Aero/status/581132071319539713 Hopefully he will respond about the new wing.


Edit: to me, as an ignorant donkey it seems to me the new wing is designed to improve flow inside the tire.
Or in some way spread the flow out and above the tire as opposed to trying to force it all outside the tire.

[chuckdanny]

Your posts are useless, where did you read that there will be no rotating wheel.

Can you argue instead on your claims on the batwing and nose, you see the flow, you have a special brain ? What make your unargumented guesswork better than our ridiculous cfd?

I don't need your advices, useless.

[turbof1]

Common people calm down. We have a good debate going on here, please let's not squander it.

It's a matter of being cautious and tampering expectations. We'll always be guessing, whether we create a cfd analysis or we try to reach to academic research. We should look pass that. We can't simulate fully the true real life conditions, but we can try to get some insight from various concepts the team use. On broader terms: when did we have such a discussion and analysis, cfd or not, on post-2013 wings? After years we finally got to a point where we started to scratch the surface concerning the post-2008 wings, but we barely have seen any deep studying in relative public confinents about these newer wings. This is a good oppertunity.

I get there's friction. It's balancing being cautious and trying to discover, to learn more. That'sthe essence both parties in this story are respectively telling. So instead of pulling eachother's pukes out, telling "the cfd is useless" "the guesswork is useless" etc, try to cooperate.

[bhall II]

From the first time I ignored my better judgment...

The following is excerpted from a paper entitled Ground Effect Aerodynamics of Race Cars written, in part, by the most recent head of aerodynamics at Sauber, Willem Toet. (The full paper can be found here.)

Everything beyond the suction peak is, by definition, an adverse pressure gradient. Otherwise, there would be no flow separation.

Because they constitute downstream blockages that inevitably slow down upstream flow, i.e. increase static pressure, the front wheels contribute to the separation of the vortices by pushing the suction peak forward, which reduces the efficiency of the wing.

It is my contention that the application of steering lock more or less removes those blockages to at least some degree, allowing the suction peak to travel aft as air flow accelerates. This increases the efficiency of the wing.

I think that enhancing this transient property is the whole point of the updated wing. I also think it's next to impossible to model this transient property without data we will almost certainly never see.

And this is giving me an ulcer.

[Just_a_fan]

No one is saying "don't do it", we're just trying to ensure people don't take any output as being gospel. It's going to be nothing more than an interesting exercise. I'm looking forward to the results but I won't be expecting "the truth".

[Just_a_fan]

What make your unargumented guesswork better than our ridiculous cfd?

It's not better; it's the same. That's rather the point we've been making. =D>

[bhall II]

Eh, I'm not always particularly clear when it comes to explaining myself. Plus, this kind of conversation lends itself to confusion, anyway.

I'm just glad I'm not losing my mind, because I thought I was for a moment or two, and I don't have too many more neurons left to spare.

[chuckdanny]

Your post are long and well documented, i don't always spend the time needed to get what you try to explain i must admit.
And sometimes i'm pretty stubborn and stop reading because i'm fealing that one part of the argument is wrong.
But unlike the computer we can live with a certain amount of error leaving some kind of slack.