W06 Influenced CFD Study

[bhall II]

[...]

The r28 is the renault f1 of 2008 from which i posted a cfd picture. You can see that they purposely (dented ramped endplate) design the endplate to direct a vortex on top of the tire.

I'll wait until you can expand on that first bit before I comment on it.

However, I will say I highly doubt Renault intentionally shed vortices over the wheels. That creates lift.

With a 50% scale 580mm front wing-span (relevant to pre-2009 F1 regulations), van den Berg identified that the top edge front-wing vortex passes over the crown of the wheel at high ride-heights, but passes inside the wheel at low ride-heights. At high ride-heights this vortex over the crown keeps the flow attached for longer, increasing the lift of the wheel, and creating a zone of re-circulation behind the wheel, which increases the wheel drag:

Those cutouts (dents) had the exact opposite effect...



Think of it this way: a front end plate cutout is the bastard son of a rear end plate cutout.

[chuckdanny]

OK! i had completly forgotten this tremendous study, very good thanks for puting me back on rail!

For the R28 that's what the picture suggest

Well its not completly on the tread side (crown) neither on the inside, in between. It could explain why it was so bad

And so i was asking myself out loud the reason why ? I thought it may create a bit of lift but reshaped favorably the tire wake to avoid the inside tire trailing edge vortex going under the carpet. But clearly it creates lift, drag and even reinforce this bad worm!

So that point to the solution it seems, the lower edge vortex (feature “C”) of this study being replaced by the gutter(sorry) vortex of my model no ?
i refer to this

it can be seen that both the bow wave to the inboard side of the wheel, and the inside leg of the counter-rotating vortex pair in the wheel wake, have been replaced by the vortex generated by the bottom-edge of the front-wing, which is strengthened in ground-effect.

So the worm is kept at bay in the process. inside bow merging with the gutter vortex, flowing into the brake duct turning vane (i think permanently, whatever the wheel angle is) and merging with this trailing worm.

And of course the turning winglet vortex passes exactly were i thought it was on inside part captured by the top brake duct fairing pincer :

[bhall II]

So that point to the solution it seems, the lower edge vortex (feature “C”) of this study being replaced by the gutter(sorry) vortex...

...inside bow merging with the gutter vortex, flowing into the brake duct turning vane (i think permanently, whatever the wheel angle is) and merging with this trailing worm.

And of course the turning winglet vortex passes exactly were i thought it was on inside part captured by the top brake duct fairing pincer.

There's no mystery about vortical flow from the turning vanes, because we know exactly what's happening:



But, maybe I confused the issue when I disagreed with the assertion that such flow might reduce the adverse pressure gradient. While it's directed toward the same spot, the idea is to increase the dynamic pressure of air flow over the wing in order to create a stronger vortex when it merges with air flow from under the wing.

Your model doesn't reflect that because the wheel is too small, too far back, and it's not spinning.



(I'll get to the rest later.)

[chuckdanny]

I've applied a local tangential velocity condition to the wheel.
I tested closer wheel-wing gap, it doesn't change the overall picture much just impede the gutter vortex from flowing inside.
Is the top edge endplate vortex going over the crown of the R28? Is it a fake?

[bhall II]

I can't speak to the R28 CFD, because I don't know. But, I can't think of any good reasons to direct vortical flow over the wheel.

I also can't think of anything else to say on the overall subject that's not just me repeating myself.

[chuckdanny]

The turning winglet of the E22 was sloted while the one from the w06 is not. The butterfly goes on the high pressure side while the vortex form on the low pressure side, behind the winglet.

That's what i mean talking about 1st and 2nd floor


The bottom of footplate and strakes define the start of 2nd floor, 1st floor is the inwash part.
If your a butterfly, want to experience the intricacies of the complete inside wheel aerodynamics take the 1st floor, to get away from this beast take 2nd floor, thank you!

[chuckdanny]

What happend to the butterfly on the lotus gif may not be representative of the airflow. Particules trajectories in a flow is not the same as air streamlines because of inertia for exemple. Pushed or pulled by both winglets vortices it follows the tangent path.

[Just_a_fan]

I've applied a local tangential velocity condition to the wheel.
I tested closer wheel-wing gap, it doesn't change the overall picture much just impede the gutter vortex from flowing inside.

I'd have thought that impeding the vortex from flowing inside was a big change as it will alter flow elsewhere too. Add a spinning wheel, moving road and suspension/brake ducts acting as flow conditioners and the picture will likely be different again.

[chuckdanny]

You've been misled for some times now by a little butterfly!
You've learn something there, even what we see in aerodynamics is false! Well what we deduce from it.
Is it this the butterfly effect ?

I think that again paradoxically the turning vane are not turning the flow as such to outwash in an horizontal plane but it is the streamwise rotation that enhance this outwash above the wing. With the old wing design it may have led to those vortices shifting outboard like the gutter bend inboard or at least not being very stable and changing position with regard to the tire. I still think that this new design is there to stop this (not exclusively), it is clearly visible on the streamlines. The Gordon mccabe article shows how they harness the trailing vortex of the tire with the flank vortex also.

Turning vane vortices have opposite sens hence outwash over the wing while gutter and arches vortices inwash under.
Those movement would seem antagonist except that being placed above each other like gearing it is cumulative.

I must say that this Van Gogh animated painting is mesmerizing


Be carefull of the snake though


Maybe this front wing pulls the car! and the vortices help spinning the wheels!!


Hmmm... no! no no no no !

[bhall II]

You've been misled for some times now by a little butterfly!

It's probably not a great idea to be overly critical of the source for someone's point of view when the source for your point of view is an incomplete, visibly flawed model that's not been simulated under real-world conditions and has been buttressed by an article taken out of context.

Just sayin'.

The difference between a considered opinion here and what your model represents is that the opinion attempts to incorporate everything; your model conspicuously does not.

Moreover...

One note of caution should be sounded here: the Figures reproduced above are obtained from steady-state simulations, whereas the actual flow in the wheel-wake tends to flap about in an unsteady manner, as close observation of the water droplets shed by the wheel in wet-weather conditions reveals. Flow features which appear to exist in a steady simulation are sometimes completely absent in the instantaneous flow fields of an unsteady simulation.

And...



You've done some excellent work here, and I really mean that. But, I also think you're reading way too much into the results.

[chuckdanny]

Bhall! i'm just joking, i don't take it too seriously. I'm also taking other sources as biased confirmation
But by curiosity i just attended the nicolas Perinn conference and quit some nice informations there.
The arches vortex calibration (should not be too strong and wide instead of a nervous thin snake, and burst at the tire tread, like mine to reduce stagnation pressure hence drag), they design different vortex states.
they use exactly the same section cut as me and Van gogh convolution representation to analyse flow structure and as you said its surprisingly compelling.

They also said that steady state and transient were very close in term of simulation.

[bhall II]

Yeah, I imagine modeling transients is more or less as straightforward as modeling steady-state interactions; it's just time-consuming. But, with enough runs to model each step, I'm sure you can build a decent picture.

The difficulty is modeling unsteady features like turbulence caused by wheel wake. As I understand it, that takes up the bulk of the team's CFD/wind tunnel time. Almost like quantum mechanics, I guess they just have to look for averages and probabilities in order to to account for unsteady events. (I don't know.)

I'm not exactly sure what you mean with the rest of your statement. But, if the idea is that the "arches" reduce "stagnation pressure" in front of the wheels, I think that's a horrendous waste of wingspan.



I can't imagine why a team would give up so much real estate for such a small gain during an era in which downforce is at a premium.

One thing has become clear, though, and it's that we have very different ideas about what's going on here. So, at this point, I'm content to agree to disagree. But, I do hope you keep working on your model. Accuracy can only help.

[eyalynf1]

Yeah, I imagine modeling transients is more or less as straightforward as modeling steady-state interactions; it's just time-consuming. But, with enough runs to model each step, I'm sure you can build a decent picture.

The difficulty is modeling unsteady features like turbulence caused by wheel wake. As I understand it, that takes up the bulk of the team's CFD/wind tunnel time. Almost like quantum mechanics, I guess they just have to look for averages and probabilities in order to to account for unsteady events. (I don't know.)

I'm not exactly sure what you mean with the rest of your statement. But, if the idea is that the "arches" reduce "stagnation pressure" in front of the wheels, I think that's a horrendous waste of wingspan.

http://i.imgur.com/JzxchIf.jpg

I can't imagine why a team would give up so much real estate for such a small gain during an era in which downforce is at a premium.

One thing has become clear, though, and it's that we have very different ideas about what's going on here. So, at this point, I'm content to agree to disagree. But, I do hope you keep working on your model. Accuracy can only help.

I would guess that frontend downforce has not been at a premium since the systematic neutering of the rearend post 2008. Narrower rear wings, shallower diffusers...did they also change tire dimensions? Now, you can trade front end down force for flow structure optimization because you need less front end to have better overall balance. Yes?

[bhall II]

I don't think there are any hard and fast rules; everything is a compromise. In fact, my theory for the revised end plate design is that it trades peak downforce for consistent downforce. That makes sense to me, and F1 history is filled with examples in which teams have made the same trade.

For instance, exhaust blown diffusers were initially abandoned because their effect on downforce was very inconsistent. It wasn't until the advent of off-throttle blowing that they made a comeback.



But, would I trade downforce to reduce stagnation pressure in front of the wheels? Or for this...?

What do you think of the idea that the v-section might control the positioning of the turning winglets vortices?

Never. Even if the goals made sense, the benefits would still be small.

[chuckdanny]

I'm correcting the flaws of my model, learning more about CAD in the process and this history based feature modeling does strange things sometimes, wonder if my version is not buggy in some areas... In a way the endplate vertical component being too much inboard is the occasion to correct my footplate gutter/slots transitions.
I thank turbof1 and Ric85 (neutral template) for they usefull criticism.

Bhall, this venturi twister is highly optimised, they have a parametric model as opposed to mine (i would have to be paid for that ) and maybe you can get both caracteristics right, a quickly bursting vortex still producing very low pressure. This thing convert venturi in ground effect plus pressure over the wing in streamwise rotational speed.



The worm seems, despite the actual flaws, traited like in the study above, no more twin trailing vortices repelling each others but one going straight and not toward the ground