Most pec...bizarre aerodynamics thread.

Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum.
Manoah2u
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Re: Most pec...bizarre aerodynamics thread.

Post by Manoah2u » Sat Dec 13, 2014 9:51 pm

moar moar moar

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perhaps this ain't technically bizarre aero rather than bizarre design, but

I'm going to go crazy here and admit i think this car is absolutely gorgeous and stunning. It's so extravagant and strange
that it has something amazing over it. Apart from that, i'd never really want it because it's actually a Honda NSX which has been characteristically raped (the original Honda NSX is so good that almost any adjustment would be .......violating....this piece of art), and the price tag is crazy.

It is amazing though.

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btw, this one is tuned, there is a more.....'basic' version of it :lol:

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anyway, moar

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would this count btw? :)

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Dumpster sounds so much more classy. It's the diamond of the cesspools.

Sombrero
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Re: Most pec...bizarre aerodynamics thread.

Post by Sombrero » Sun Dec 14, 2014 8:50 am


NoDivergence
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Re: Most pec...bizarre aerodynamics thread.

Post by NoDivergence » Sun Dec 14, 2014 4:33 pm

MadMatt wrote:
NoDivergence wrote:What do you mean go fast enough? It's one of the fastest time attack cars in the world. Same laptime as a Formula 3 car, despite being on road legal tires.

That Car has the most aero downforce of any car ever made. That includes Group C
Do you know how much air flow velocity and amount you need to fill a tunnel that big? I ? My experience tells me that he will have flow separation in the diffuser itself and that this air flow will not be pretty to watch in CFD with streamlines.

In the following video (couldn't find a more recent one with speed displayed) he is not exceeding 265km/h:

https://www.youtube.com/watch?v=bNFXg_IO_wA

Not enough to fill that diffuser. Have you got downforce and drag numbers to add? I have those of some of the group C machines.
First off, you do know that underbody flow at the entrance to diffuser is definitely not at freestream velocity, right? And that a lot of volume actually comes from the side of the vehicle? This S15 is very very wide. Floor area is huge. Also, the region of low pressure behind the car is huge.

Andrew Brilliant has a lot more experience than you do. There are lots and lots of tricks, but looking at MCA hammerhead S13, Nemo Evo, and the Scorch Racing S15, there's an obvious trend arising.

Nemo Evo downforce was 5400 lbf at 150 mph, and this was measured and confirmed on track. The S15 has much, much more.

Here's some streamlines for you from 2013. You can definitely see that even more pressure recovery is needed.
https://scontent-a-pao.xx.fbcdn.net/hph ... 4742_o.jpg

He is definitely getting the kind of upwash that you would expect from downforce of that level.

https://www.facebook.com/video.php?v=10 ... =2&theater

MadMatt
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Re: Most pec...bizarre aerodynamics thread.

Post by MadMatt » Mon Dec 15, 2014 9:31 am

NoDivergence wrote:First off, you do know that underbody flow at the entrance to diffuser is definitely not at freestream velocity, right? And that a lot of volume actually comes from the side of the vehicle? This S15 is very very wide. Floor area is huge. Also, the region of low pressure behind the car is huge.
Of course, I never said otherwise. Although I do not really agree with your second sentence regarding the flow coming from the side. This will depend on a lot of factors (car geometry and aero setup). Not to mention some guys will use side skirts to block the flow from entering from the side, so what you say is not always right and you will only know once you've seen CFD or wind tunnel experiment.
NoDivergence wrote:Andrew Brilliant has a lot more experience than you do. There are lots and lots of tricks, but looking at MCA hammerhead S13, Nemo Evo, and the Scorch Racing S15, there's an obvious trend arising.
Why the critisism? I never claimed to be better than X so why are you doing it? You have no idea of who I am or what experience I have. Also experience doesn't mean you are good at something, it just means you have been doing it for a long time. Andrew didn't invent anything, he just used what Katz, Hucho, and what others discovered and applied these concepts to the car. He did it well since the results are there, but give this amount of cash to some people on this forum and they will also produce some good machines.
NoDivergence wrote:Nemo Evo downforce was 5400 lbf at 150 mph, and this was measured and confirmed on track. The S15 has much, much more.
24kN then. Some group C cars had that amount of downforce (Allard J2X for example), but achieved that WITH regulations. Also you say this was measured and confirmed, do you actually have evidence of this? This is the engineer talking, I would love to get a hot lap data that I can analyze (Motec format, PI, excel, whatever).
NoDivergence wrote:Here's some streamlines for you from 2013. You can definitely see that even more pressure recovery is needed.
https://scontent-a-pao.xx.fbcdn.net/hph ... 4742_o.jpg

He is definitely getting the kind of upwash that you would expect from downforce of that level.

https://www.facebook.com/video.php?v=10 ... =2&theater
That streamline thing doesn't show anything, it is more of a commercial picture than else, so I will not comment on this. As for quantify downforce by looking at the upwash, well, I have no words. With your 2 last arguments, you just showed me that you don't know much and that talking about this car (or its aero designer) will just create a fanboy rant so I will leave it here. Are you related to him by the way?

EDIT: I dug in my folders and I found experiments I did on a Cooper body. I had a small wind tunnel where I experimented with ride height and diffuser angle changes, and did the same in CFD. I was able to see that there is a tipping point in the diffuser angle where you start loosing downforce (in my case 20° was the best, 25° nearly as good, but 30° a big loss). It will of course vary with speed, the shape, and tons more parameters, but more diffuser angle is not always better, that's the point I was trying to make by posting the picture.

Pieoter
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Re: Most pec...bizarre aerodynamics thread.

Post by Pieoter » Mon Dec 15, 2014 12:32 pm

MadMatt wrote:
NoDivergence wrote:What do you mean go fast enough? It's one of the fastest time attack cars in the world. Same laptime as a Formula 3 car, despite being on road legal tires.

That Car has the most aero downforce of any car ever made. That includes Group C
Do you know how much air flow velocity and amount you need to fill a tunnel that big? I ? My experience tells me that he will have flow separation in the diffuser itself and that this air flow will not be pretty to watch in CFD with streamlines.

In the following video (couldn't find a more recent one with speed displayed) he is not exceeding 265km/h:

https://www.youtube.com/watch?v=bNFXg_IO_wA

Not enough to fill that diffuser. Have you got downforce and drag numbers to add? I have those of some of the group C machines.
Don't have numbers but aero on that car was done by http://www.amb-aero.com/

xpensive
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Re: Most pec...bizarre aerodynamics thread.

Post by xpensive » Tue Dec 23, 2014 4:42 pm

The 1980 Brabham BT49, running with front wing positive lift to balance the enormous ground-effect from the venturis;

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"I spent most of my money on wine and women...I wasted the rest"

Sebp
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Re: Most pec...bizarre aerodynamics thread.

Post by Sebp » Tue Dec 23, 2014 8:08 pm

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TurboLag
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Re: Most pec...bizarre aerodynamics thread.

Post by TurboLag » Wed Dec 24, 2014 12:23 pm

MadMatt wrote:<"lots of aero discussion finishing with:">
..diffuser angle where you start loosing downforce (in my case 20° was the best, 25° nearly as good, but 30° a big loss). It will of course vary with speed, the shape, and tons more parameters, but more diffuser angle is not always better, that's the point I was trying to make by posting the picture.
I have a question for you MM, since you seem to have a good grasp of aero :)
Couldn't we get a big expansion like this by just increasing the length of the diffuser/tunnels? This WOULD give us a geometry that would leave a huge diffuser exit/mouth without having crazy angles, and wouldn't this give us a good expansion if we could avoid too much flow separation? I know AMB used a combination of a blade spoiler and the rear wing here for Nemo..
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Merry christmas btw :)

MadMatt
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Re: Most pec...bizarre aerodynamics thread.

Post by MadMatt » Thu Dec 25, 2014 12:23 am

Yes if you can, start the tunnel as far up front as possible. This will shift your CoP forward, always a good thing on these cars, as you can easily get lots of downforce at the rear with silly wings and nothing to balance it at the front unless you are using big splitters. There was a subject with convex VS concave diffusers here on the forum, and even CFD tests with both, unfortunately the pictures are gone: http://www.f1technical.net/forum/viewto ... =6&t=10943

The problem with having a long long tunnel is that your friction drag increases proportionally, as does the boundary layer thickness, which is something you don't really want. It all depends on the car you have, the space you have for the diffuser, the speed you are travelling at, and so on.

Another interesting small study here also shows that bigger angle is not always better as I was saying few messages ago: http://consultkeithyoung.com/content/cf ... user-angle

What I found is that having massive tunnels is not always a good thing, since you will have space for vortices and big recirculation areas to form inside them, helped by the low pressure area just behind the car. You then end up having just a small portion of the diffuser working, with the rest being a big airflow mess. I haven't really investigated the use of strake design to help in this matter but hopefully soon I will have things to say about this! :)

xpensive
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Re: Most pec...bizarre aerodynamics thread.

Post by xpensive » Thu Dec 25, 2014 9:25 am

MadMatt wrote:Yes if you can, start the tunnel as far up front as possible.
...
In other words, don't make the venturis this short, Ralph Bellamy's 1979 Fittipaldi F6, thinking that you can move CoP rearwards;

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This car was soon replaced with the F6A, see the difference?;

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"I spent most of my money on wine and women...I wasted the rest"

Manoah2u
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Re: Most pec...bizarre aerodynamics thread.

Post by Manoah2u » Thu Dec 25, 2014 5:16 pm

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1938 Dubonnet Hispanio Suiza H6C Xenia - Gorgeous and amazing in every sense of the word

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1930 Henderson KJ Streamline Motorcycle
Dumpster sounds so much more classy. It's the diamond of the cesspools.

NoDivergence
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Re: Most pec...bizarre aerodynamics thread.

Post by NoDivergence » Thu Dec 25, 2014 7:17 pm

Circulation is directly proportional to lift and drag. You can get a general idea of how much downforce a car is making just by looking at the upwash.

Andrew has a lot of tricks, things that haven't been used on racecars for decades and he has plenty of his own ideas. With every car, the cooling is different, and that can directly affect how the underbody is implemented. And yes, the diffuser starts well forward of the rear axle line, so the angle is actually not that steep. 20 degrees is not that aggressive if you can use vortices coming in from the edge of the diffuser. Essentially working like a low aspect ratio wing at high AOA.

Yes you will have significant boundary layer growth along the length of the diffuser. You will also have significant spanwise 3D effects. It is a tradeoff.

Also remember that the suspension arms are also in the diffuser. The lower the pressure and size of the region behind the car, the more you can do pressure recovery.

For many cars, you actually do not want to seal the side of the car. You can hear it yourself from one of the masters of grounds effects. You can utilize this

https://www.youtube.com/watch?v=PZxC-knQmkM

Also, the S15 has much much more downforce than the Nemo Evo. Nemo was relatively early development compared to what has been done to the S15. We're talking well over 10000 lbf downforce @ 200 mph

Really, if you compare directly, the tunnels on the S15 really aren't that much bigger than on many Group C cars

Crucial_Xtreme
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Re: Most pec...bizarre aerodynamics thread.

Post by Crucial_Xtreme » Fri Dec 26, 2014 12:49 am

J.A.W. wrote:Kawasaki shows 'teaser' vid of aero-winglets on pending new road bike..

http://www.youtube.com/watch?v=oGmjysEyhmU

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SectorOne
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Re: Most pec...bizarre aerodynamics thread.

Post by SectorOne » Sat Jan 03, 2015 10:50 am

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Sebp
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Re: Most pec...bizarre aerodynamics thread.

Post by Sebp » Thu Jan 08, 2015 3:23 pm

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