Under floor flow & diffusers

[chuckdanny]

As expected louvers reduce tip vortex strength (if i can trust my low res experiments of course) at top speed which in turn kind of stall the flap.

without louvers


With louvers


And... the vortex systems generated by the endplate strakes



It seems to shield the exit of the rear wing from tire wake and virtually extend the endplate to further constrained the flow.
Maybe it is beneficial in yaw also preventing asymetrical flow structures from developing. It is joined by the diffuser side exit vortices also.
Next thing to work out are the slats...

[turbof1]

I didn't know the downforce levels would be reduced by that much when applying louvres.

Does you program has the ability to calculate the speeds of stalling, and how much drag and downforce that sheds? I think that your downforce levels on the flap are not factoring in stalling. The louvres do diminish the vortex strength hence total drag, but l/d figures are actually better when the louvres are not present, making louvres quite an inefficent solution if you look it that way.

Again however, the biggest purpose of them is to keep airflow attached, hence why I believe that in reality we are never going to get to see such numbers.

[chuckdanny]

There is no stall indeed, that's why i said "kind of", in fact the louvers create a pressure release at the inlet hence there is less momemtum on the extrados of flap so greater static pressure but no flow separation.

Of course i don't trust the numbers, i'm more confident in the trends.

L/D is better but that's maybe the problem, at the top speed range it's easy to generate downforce, so you better bet on a configuration which despite being very inefficient (that is create more drag for a given amount of downforce) create so much less downforce that it produces also less drag.

That's why they stall there efficient device no? Because even stalled the backpressure is still greater than when not.

In general, aerodynamics device should be movable, there problem is to create downforce when needed maybe in the range of 90 to 200 but above there problem is they have to much uneccessary downforce hence drag. So maybe they design louvers so that it "kicks in" in the right range, in that case it would be a stalling device (note: i had corrected this one, not a stalling but pressure releasing device).
I "designed" mine perpendicular to the streamlines that were feeding the wing tip vortex covering almost all the endplate and with a quit big opening but if you look at there design it is less protruding and sometimes even horizontal.
I assume one way of controling the "kick in" moment is how far from flap leading edge and direction of those louvers.

[turbof1]

Ok. Great work Chuck! My comment was by no means intended as criticism, just a thing I felt had to be highlighted.

Very interested to see you keep building up the flow mechanisms. We will get a clearer picture when the diffuser is added. Personally I believe that the endplate strake vortices will merge much quicker due the diffuser upwash, probably also enhancing rear wing performance.

Are you also perhaps going to try red bull's solution from last year?
http://somersf1.blogspot.be/2014/03/bit ... 1.html?m=1

[chuckdanny]

Ok, no problem, i was not clear enough and constructive criticism are welcome.

Yes i will try those redbull reverse opening(from outside to inside). Interesting article while i don't know where he gets his informations from, are they hints from f1 insiders? For exemple the purpose of those openings is to stabilize the flow, what does it mean? to better recover the normal working after the closing of drs ?
I observed that main plane tends to stall from the tips hence the reason while the leading edge of main plane work the air harder at the leading tip and sometimes the trailing tip is a bit lower. So it remembers the blowing that occures on certain wings to delay separation, is it what he means by stability?
We observe an interesting bump also in this area that follow the curvature of main plane...
Another point, testing the wing/flap without endplate, while it is inefficient because of outwash and even stall for real this time, vortices that occures at the trailing tip of main plane seems to be of interest though... And it disapear with the endplate. Thoses that occures are forming outside and when we observe somes vapour feed rear wing f1real images, it seems that this vortex comes from inside... hm hm..

Louvers being parallel to the flow are not forcing the air to get outside, i have to investigate this thing

And correct me if i'm wrong but he seems to say the opposite of you concerning the efficiency of the wing with the louvers, quote :
" Usually you'll find a set of louvres placed in the upper front section of the endplate (see lower left inset). Their job is to allow pressure to move either side of the endplate which in turn maximizes the efficiency of the Wing (more downforce, less drag)"

[chuckdanny]

This picture:
http://i.imgur.com/XAuzDHc.jpg

But especially this one:
http://i260.photobucket.com/albums/ii14 ... ces_01.jpg
The vortex seems to come from inside, the low pressure vane.
I don't know if in this case we can call this a wing, it's a wall!

In the w06 case, it seems that the wing tip vortex is behind the almost flat smoking vortex sheet that is clearly coming from inside.

[chuckdanny]

So to sum up and believing my numbers what are those numerical experiments telling me?

=============================================================
Without louvers, we have :

1514 N of downforce coming from the flap
4163 N main plane(wing)
Hence 5677 N of total downforce
937 N of drag => flap
621 N => wing
and 1558 N of total drag

A lift/drag ratio of : 3.64
=============================================================
With louvers, we have :
980 N of downwforce => flap
4202 N => wing
Hence 5182 N of total downforce
602 N of drag => flap
655 N of drag => wing
and 1257 N of total drag

A lift/drag ratio of : 4.12

So!
According to those numbers, while louvers affected wing are more efficient they create less downforce at the speed of 320km/h but also less drag, around 19% less.

Why is that ? Where does this increase of efficiency comes from?
A decrease in drag ok, but why also a decrease in downforce?

[hollus]

Downforce is partly from high pressure air "trapped" above the wing's planes. Incoming air was being trapped above the wing with no option but to push against it to deflect upwards. With louvres you are giving the air an alternative path and allowing some of it to diffuse away. By reducing the high pressure above the wing you are directly reducing downforce.
Another way to look at it, you added end plates to increase downforce. With louvres, you simply have less endplate.

[chuckdanny]

Very good!
Simple enough isn't it? And no need of vortices in the explanation.

And why is the efficiency increasing ?

[hollus]

The change is mostly coming from your flap. Its angle of attack is so large, close to 45 degrees, that any aero pressure acting on it is pointing backwards (drag) almost as much as downwards. The efficiency of your flap has a lift/drag in the order of 1.6, so when you make it work less hard, the overall efficiency increases. Not much has changed for the main plane, according to your own numbers.

[chuckdanny]

So efficiency should be compared at the same level of downforce or drag depending on the goal of the device, otherwise it makes no sense, no pain no gain

They could achieve the same with a different wing/flap design, less steep. But you would need a dedicated wing/flap design on every track. It must be a cheap way to adjust a given flap/wing configuration for a set of similar tracks, and because depending on the condition or opposition, there qualifying, if they need to overtake etc...they need to quickly adjust on site.
The range of allowable set up is maybe tighter when adjusting flap without degrading the proper operating mode of the wing/flap system.
Especially with drs

[chuckdanny]

F1 art

A mercedes like nose vortex system!


It seems designed to triumph in china


I wonder if by adjusting the elements we could better assemble this tubulair chassis?
To make a system that james dyson would be so proud of

[hardingfv32]

Can you post a illustration or photo of the wing to match the test data?

Thanks
Brian

[chuckdanny]

Well yes, but it's not a wing it's a.... well i don't know (raikkonen style)



If you ask me what it is used for, i have no clue. I thought it could reduce the lift of the nose which is quit hard to get rid of i found but i didn't test to many design, a more frontal one like redbull.
Maybe it stabilizes the flow under yaw like the endplate did with the 2d case. It's not the right word i mean it keeps the flow symetrical.
The link between nose and so called neutral part of wing is wrong, there shouldn't be vortices there outside behind the nose tip.

[chuckdanny]

When i say i have no clue it's not totally true

Those facing multi element winglet with footplate that are endplate depending on your point of view create there fair share of low pressure under the nose.
It could well be in fact that better designed and better aligned with the angry bird, that this bird help this device work harder and at least decrease the lift from the nose which would allow less dragy front wing.