W06 Influenced CFD Study

[chuckdanny]

You don't understand the differences between flow structures, trends which is what is looked for when they do qualitative analyses and flow mesurement which is quantitative. Your excerp of the workshop is misleading because they clearly says that for the conceptual design phase steady simulation is what they use and of course it doesn't give the fluctuations in time because it is steady and turbulence is inherently unsteady so they don't incorporate everything. They trade absolute quantitative mesurement for qualitative flow structure, trend design. He didn't say also that for that purpose steady simulation was close enough to unsteady?
You didn't hear that or you just want to pick what is suitable for your point of view ?
You can stop with your allegation that i'm unable to understand the necessity to have the full car, its trivial, simple, obvious, everybody knows that! But to infer from that it would completly change some really strongly determined flow structures like the turning vane vortices... I know you will now say that we need yaw angle, but can't we talk about a specific case that is in a straight or do we need to incorporate everything everytime? Did you think about earth rotation? quantum mecanic ? And what about the thermal effect of the near ground thermal layer?

Analysis from bhall amount to do exactly the opposite, incorporate everything, the memory of the air!
Yes air has memory, it knows what will happen at the next corner so it prepares for it, did you think about that ?

From the thesis you pointed out :

The interaction of the many elements present in a formula one car is very complex and to increase our understanding of their behaviour, these elements have been studied in isolation

It seems that they gain some understanding in doing so while you claim from the beginning that it has no sense at all because we must incorporate everything!

In a way the w06 wing achieve the same as this

But in a more efficient way with pressure release that feeds the underside vortices that create downforce on their own.

[bhall II]

You didn't hear that or you just want to pick what is suitable for your point of view ?

Read the whole thing. It's from a different Q&A.

Another excerpt:

...from my experience, in the correlation or what we call correlation (which is how close the CFD is to the real car or to the wind tunnel car) you can find differences. But in localized area, and mainly on the contact patch of the tire on the ground and things like that...

To put that in context, you're mostly relying on the most unreliable part.

From the thesis you pointed out :

The interaction of the many elements present in a formula one car is very complex and to increase our understanding of their behaviour, these elements have been studied in isolation

It seems that they gain some understanding in doing so while you claim from the beginning that it has no sense at all because we must incorporate everything!

Yeah, and that study trialed a generic wing in three different states: complete isolation, with a static wheel, and with a spinning wheel. Comparing the three can be useful; looking at only one is not.

The study also made no specific claims about any real-world designs.

Context is everything.

I think it's clear you know enough about aerodynamics to get yourself into trouble, but not enough to recognize it when that happens. It's something I've previously likened to so-called "medical students' disease":

“Medical students’ disease” refers to the phenomenon in which medical students notice something innocuous about their health and then attach to it exaggerated significance. It often corresponds to a disease they have recently learned about in lectures or encountered on the wards.

This isn't meant to patronize you, nor is it to claim I'm some sort of expert. But, I can identify limits (especially my own).

Try not to take the jokes personally; that's just how I vent, and it probably means it's time for me to move on. The frustrated version of me has even less value than the one that fires on all cylinders (worthless ≠ priceless). So, if I don't respond to anything else, that's why.

And in all seriousness, I do appreciate your contribution here. It has forced me to develop a more thorough understanding of my own ideas, and I can respect that you've not just blindly accepted them as fact. Keep it up, as the capacity for independent thought is the most valuable commodity one can possess.

That said, I strongly urge you to advance and bolster your thoughts with academic study. Practical application can only get you so far without an understanding of what it all really means. Absent a proper foundation, it will likely continue to be difficult for you to discern between possibilities that should be considered and those that should be ignored.

In other words, you have to be your own technical director.

[chuckdanny]

Context is everything

Yes ! thats because under 0.3 Mach the pressure waves travels fast enough to inform, correct, have an impact on the whole flow field.
The flow field is non local. Interference drag refer to waves.
THe tire contact patch is changing quit a lot like the tremendous documents shows and its like an endplate/wing junction that would change by quit a large margin which would affect the whole wing that's true!
But it is not of the fluid/structure interaction kind because the flow doesn't move the wheel, that's why i wonder if it can't be modeled with the overset mesh technic!

Oh no, no, no!! more and more trouble...
Bhall! F1 is both technical and entertainment industry where getting into trouble produces laugh! What is bad for one part of this industry is good for the other !! Watt an efficiency !

[chuckdanny]

My model despite all the discrepancies has already shown some very plausible features, one that i talk about since the beginning and that is surprisingly confirmed by the workshop which Bhall doubted* is that the arches vortex bursting at the tire tread reduces wheel drag (40% of total drag).
The inflow pattern while still questionnable is also confirmed by the workshop.
I'm pretty sure that turning vane are treating the upper part of the wheel with vortices enhanced upwash.

I don't understand why you are putting all in the bin like that.
Concerning the tire contact patch that is extremely challenging to model even for them, needing transient etc, it maybe precisely why they direct vortex in the inside bottom flank area of the tire to circumvent the flow unstabilities (biased confirmation).


*

chuckdanny wrote:
Like justafan says one of the purpose of this venturi twister must be to reduce adverse pressure gradient...

Bhall wrote:
Why? I don't see a need for it. The adverse pressure gradient is resolved when steering angle changes. Otherwise, it's favorable because cars don't need downforce on straights.

They don't need drag either...

[bhall II]

I don't understand why you are putting all in the bin like that.

Oh, I think that goes without saying.

...the plenum behavior of the slotted footplate upper path would make sens (thanks bhall for the vocabulary i didn't know the word) feeding arches, turning vanes and upper endplate edge contra rotating vortices, the surplus leaking outside and feeding the outside winglet vortex flowing along the outside tire bottom flank interacting etc...

First and perhaps foremost: anyone who can enable the "arches" to contain any sort of positive pressure should be worshiped as a deity, because it's impossible for everyone else. In fact, it might be easier to walk on water than it is to coax a structure that's roughly 3/5 empty space to hold anything.

Hold a fork in front of your face. Blow on it. How much air is contained?



Second, even if this was possible, it wouldn't reduce drag; it would just relocate the source.


What's the difference?

Lastly, at some point, you absolutely must recognize that you are not testing a representative model.

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.

(Life's a whole lot easier when it's not spent chasing phantoms.)

[chuckdanny]

I know it can't be totally representative.

You forget that the spinning vanes are changing the incidence of the flow, they bring outward momentum toward the endplate and throw the air against the inside arches faces that is turning so with an angle.
The rear wing slot is not less open and i don't think that the pressure equalize ?

Relocate the source? of course because the new source of drag also produces downforce as opposed to the old one, the tire which as an aerodynamic device is pretty inefficient .
How? first the spinning vane in doing there job also produce downforce changing the flow incidence on the wing part of the wing (light contribution) if i may say as opposed to the endplate part which begins at the v-section, providing more air inside the tire channel but over the wing this time and feeding the arches hence increasing the vortex which together with the gutter one produces suction. This mechanism get rid of the wheel blocage and work the air sideways. The strakes then define where to stop this because the wing part doesn't work sideways.

I'm beginning to read the last study on sunny day not to fall asleep, joking that's a fantastic source, and i'm making progress toward a more representative spinning tire, understanding better why i didn't have the top arche vortex, now with a tread flank discontinuity plus a rim the difference with a stationary tire start to show up !

Edit 29/06 :
you forget that there is a tire behind, the reason why there maybe a plenum effect building pressure at the vortex periphery which further reinforce vorticity into the arches.
I'm not saying there is positive pressure into the arches but just on entry. If there is a vortex of such a state that it spins fast but burst fast into the tire, we have to imagine that the streamwise flow into the arches slot somehow transform into vortex wise that is arches wise (tangentially) which should necessitate 1st a slowdown hence a pressure building and second a pressure blowing spinning wise.

[bhall II]

Relocate the source? of course because the new source of drag also produces downforce as opposed to the old one, the tire which as an aerodynamic device is pretty inefficient .

Slow down, chief. We can't just glaze over the reality that it's impossible for the "arches" to contain positive pressure as you've theorized. That's the alpha and the omega for this thing, and anything beyond it is a moot point.

For the sake of conversation, though, if by some miracle the "arches" were able to act as a plenum, the adverse pressure gradient between the wing and the wheels would still exist, and it would still cause flow separation. That means heavily compromised efficiency, which means you're back to square one.

The "arches" form an end plate that behaves like every other end plate; it's not sorcery. I don't know why that's so difficult to see.

[bhall II]

Edit 29/06 :
you forget that there is a tire behind, the reason why there maybe a plenum effect building pressure at the vortex periphery which further reinforce vorticity into the arches.
I'm not saying there is positive pressure into the arches but just on entry. If there is a vortex of such a state that it spins fast but burst fast into the tire, we have to imagine that the streamwise flow into the arches slot somehow transform into vortex wise that is arches wise (tangentially) which should necessitate 1st a slowdown hence a pressure building and second a pressure blowing spinning wise.

You forget that the adverse pressure gradient between the wing and the wheels causes the wing's point of peak suction/separation point to move forward until the opposing pressure streams reach equilibrium. Thus, there's zero "pressure building."

Ever.

It's like you're going 'round and 'round in circles here, looking for every conceivable answer except the one I've put forward.

This is so --- easy.



Everyone knows that an inverted wing in ground effect relies on vortices for efficiency.

Everyone knows that an adverse pressure gradient causes vortical separation.

Everyone knows that placing a spinning wheel behind a wing creates an adverse pressure gradient.

Everyone knows that an adverse pressure gradient can be addressed by removing pathline blockages.

When putting these things together, at what point does it all become Sanskrit?

[toraabe]

According to this article http://www1.skysports.com/f1/news/12433 ... alty-rules

" 'A new set of regulations aimed at achieving faster and more aggressive looking cars for 2017, to include wider cars and wheels, new wings and floor shape and significantly increased aerodynamic downforce has been outlined and is currently being assessed by the teams."

is what I undestand a return to groundeffect (like indy) and less frontwing and so on ..