Internal Body Aerodynamics

[rtj]

[ame]https://www.youtube.com/watch?v=GccHDULm4cc[/ame]

Just uploaded.

 

[rtj]

Thought this was interesting, especially when he stood on the splitter.

[ame]https://www.youtube.com/watch?v=yTd-Dum6ASE[/ame]

 

[rtj]

[ame]https://www.youtube.com/watch?v=iVB9h9pGxEE[/ame]

 

[rtj]

A few neat aero details. But, really great vid overall.

[ame]https://www.youtube.com/watch?v=mc1JMuyqh_Y[/ame]

 

[rtj]

Another super car ($$$$), but lots of aero treatments, so ....

[ame]https://www.youtube.com/watch?v=iuuC2NHurfc[/ame]

 

[rtj]

At 1:00 you can see just how big the duct is putting air out over the front wheel. Again at 1:11.

[ame]https://www.youtube.com/watch?v=PnXLl2ca7IE[/ame]

 

[rtj]

[ame]https://www.youtube.com/watch?v=7xBMDmaLy5o&t=355s[/ame]

Discusses front end charges to reduce flow underneath.

Pretty pictures:

[ame]https://www.youtube.com/watch?v=LYNliMcHd1U[/ame]

I think the GTM needing a Porsche trans really hurt them. Maybe as c8 wrecks accumulate, they’ll revise the GTM for that power train (GTM-8 ).

 

[rtj]

All the neat aero developments are $$$.

[ame]https://www.youtube.com/watch?v=XCEkOo5yVK8&app=desktop&persist_app=1[/ame]


Couple of neat things in this one, aerodynamic supercharging and the wind tunnel at Mercedes with the rolling tires.

[ame]https://www.youtube.com/watch?v=KU9XxC7-3NE[/ame]

 

[mfain]

Canard Aero

Here is something interesting. It looks like the front canards are creating a low pressure area at the top of the fender well causing air to be pulled out. Also note the angle of the airflow out of the fender vents. Looks like providing an airflow exit further back behind the wheel could help reduce pressure in the wheel well which would help downforce.

 

[rtj]

Nice. Driving on wet pavement acts like flow visualization.

 

[phantomjock]

Pappy -

Nice pic with a lot to digest, so I'll guess...(or bloviate)

I'm thinking that the dual canards are acting as "vanes" and not only creating downforce (vectoring the flow), but also making an "air curtain" to blanket flow just outside the wheel. Yep, that would create a low pressure area. And, I'll bet that the reason we don't see flow further forward on the wheel is because it has all been exhausted over the top of wheel and also out the louvers. That would be a good thing - more low pressure in the wheel well forward of the tire. [Need a magnehelic gauge and some pressure taps to do some analysis.]

I'm disappointed we see no flow out the side exits. They're open - right?

There is some interesting disturbed area between the F/R wheels, and it looks like it may be wrapping around and under. A skirt could fix that - or sharp edge. Curves are nice looking, but judicious use of sharp edges can be useful too.

Just curious - any DAQ onboard? AEM/MOTEC/RT/Harry's Laptimer?

(What do I know - I'm waiting on some bits to complete that damn suspension!)

Cheers - Jim

 

[rtj]

The YouTube guy is pretty critical, might be in over his head on this one.


https://m.youtube.com/watch?pbjreload=101&v=bwVbklHHE4w

 

[rtj]

The manufacturer video.

At 10:30 he sits in the car and fires it up, the smile on his face says it all

https://m.youtube.com/watch?pbjreload=101&v=ShJ0i8xIUzI

 

[phantomjock]

The YouTube guy is pretty critical, might be in over his head on this one.

https://m.youtube.com/watch?pbjreload=101&v=bwVbklHHE4w

Hmmm... I'm pretty much "in-gee" with 99% of his observations. I too am puzzled at their choice of nomenclature for Cd. Also, a bit disappointed Kyle didn't use a bit of CAD to get a more accurate frontal area. Although no good shots of the new car I guess.

His notes on the diffuser are spot on I'd say - and I bet they went with the easy build (straight vanes) after all the other complex work. Sad though.

Cheers - Jim

FWIW - He is putting together an on-line Aero course, but won't be cheap I bet.

 

[rtj]

My guess is they (Bugatti) have done cfd and wind tunnel testing. He doesn’t know what is going on before the exit of the diffuser, with all that internal flow through the doors etc, it may have been used in the diffuser to control bl. So, the exit shapes would not be conventional.

He’s also very critical of the dimples. Again, Bugatti isn’t divulging much, my guess is they put some work in there. Kyle wants to add material instead of the dimples, but that will impact the wing.

He’s also critical of the front splitter, but they move a lot of air internally so that might result in a non conventional design.

Notice the factory doesn’t go into a lot of aero detail other than their coefficient info, no cfd plots of any kind.

I like Kyle’s vids, he just seem too negative on this one.

I would like to be able to afford one, but that won’t happen anytime soon

 

[rtj]

Here are some great close up shots.

https://m.youtube.com/watch?pbjreload=101&v=tsFyPOzLofg

 

[rtj]

My new favorite YouTuber!

Just kidding, but her enthusiasm is contagious.

https://m.youtube.com/watch?pbjreload=101&v=_SB7h2kB6Eg

 

[rtj]

At 3:40 this guy claims big drag reduction from the dimples. 10% for the entire car or 10% for the scoop drag? He is vague.


[ame]https://www.youtube.com/watch?v=OfvmjXAzUfE[/ame]

 

[phantomjock]

My bet - the Scoop.

WHY?
The camber of the scoop is pretty radical, as compared to what Kyle was suggesting as a smoother transition in the previous video. The flow is highly likely to separate anyway, and have a region of high skin friction before the separation region.
The Dimples, surface roughness (like maybe a vinyl top recall the "drama" Mark D. + Penske NASCAR?), a trip wire, or even VGs could be used to "turbulate*" the boundary layer as well. That would reduce skin friction and by re-energizing the near-field flow help fill the region behind the scoop. Yes, I'd really like to see some CFD here. And, I bet they are using the dimples to tailor the separation zone.

Yes/No? Just one guy's opinion.

But - on the other hand - it is a cool idea (the others could work too), and the dimples on the scoop make for real cool marketing ploy and heaps of armchair aero-discussions.

I'll admit - I haven't caught the video - just yet, so these observations may be subject to "recall." OK - Watched it. He is glossing over the 10% --I'll still stick with the scoop.

Cheers - Jim

OK -- I did a bit of figuring;

So what is 10%? Is it the whole car Cd?
The Chiron drag data is available and I'll use it for similitude (a cool term- eh?).

In low drag the Chiron Cd is 0.38.in drive around mode, in handling mode up to 0.40, and then drops to 0.35 in top speed mode.
Handling mode is going to have some induce drag from wing downforce increases, and the dimples only function in High Speed Mode, so I'll only use Top Speed Mode Cd.

If the Chiron had Dimples which came into function at the high speed range, And, if the Dimples reduced the whole car Cd - that would be 0.315.

WOW! That would be SIGNIFICANT.

Now to the Bolide:
Using Kyle's estimate of the Bolide low drag configuration of 0.3522. With DIMPLES it would be 0.317 (whole car) using Kyle's Cd estimate. Since the Bolide is only moderately faster than the Chiron (again, it has no dimples), I suggest the 10 percent reduction in drag on the Bolide is just the scoop. Else, there would be a much larger difference in the top speeds.

Lastly, I'll also suggest his Cd is pretty close to what we might expect on the Bolide. We must wait for further details.

I love saying this, "Class Dismissed..."

* Please not the Urban Dictionary Definition!

Cheers - Jim

 

[rtj]

10 % of the total seems like a lot, but if the scoop had an issue in one region (or regions) and messed up the rear wing aero, I guess that would make sense.

The dimples seem like a lot of work, so they must have their reasons.

With those wheel fans, that thing is sort of like a vacuum cleaner ( for lack of a better description).

At $10M each, they will be able to afford lots of R&D.

 

[mfain]

Take a look at the aero on this Subaru.
http://www.thebaynet.com/articles/1220/pastrana-stunt-video-heats-up-the-internet.html
Active aero includes a spoiler on the rear wing that appears to be activated by the button on the top of the rear brake handle. He uses the spoiler (increased rear downforce) to control the car's pitch attitude during the long over-water jump. Equally impressive is Kirby Chambliss's ability to put the Red Bull aircraft in nearly 90 degrees of pitch - and probably 60+ degrees AOA - in less than 100' of altitude from initial takeoff. Both guys have great control of their respective machines. On another aero note, take a look at Brian Faessler's Mustang that won this years Ultimate Track Car Challenge at VIR, beating some exotic stuff like tube chassis Challengers with NASCAR motors and a couple of the Hendrick's Track Attack cars. It has a lexan strip horizontally across the hood just forward of the radiator "chimney" air outlets. The supports for the lexan strip also appear to be vortex generators that influence air that passes below the strip. Reminds me very much of the same type strips used on the old C-1 (1961-62) road race cars. The strip deflected the airflow over the hood so it did not hit the windshield at such a sharp angle - drag reduction. Also, on Faessler's car, the strip probably causes a low pressure area behind it and above the radiator chimney, probably increasing airflow through the radiator. He has a very small 17"X14"X2" radiator, but manages to cool a turbo, flat-crank, 600+ whp motor. He reached 181 mph at VIR! You can probably find info/videos regarding the car on the Grassroots Motorsports website. This stuff is a little more real world than a $10M, one-off supercar.

Pappy

 

[rtj]

Good stuff mfain. More links would be great too. I remember when every farmer had a bug deflector on their truck hood. The windshield would have a line showing where the air hit.

But, the high dollar cars show a lot of cutting edge stuff. Ideas that can be adapted.

Just trying to keep a discussion going when I see something that interests me. And, once you start watching a particular kind of video YouTube keeps offering them up.

It seems this site gets slower and slower. Which is too bad, there was always lots of good info before.

 

[COLE SWEAT]

Can any of this be applied to the c3?
Canards maybe? In front of the front wheels.

 

[rtj]

Wheel discs like on that Porsche a few pages back would likely work on grand sport rims.

Looks like cutting out the quarter panels is popular, but making it looks look good would take some effort.

Rear view cameras instead of mirrors.

Splitters work.

I’m seeing C7 widebody kits with the back of the flare cut out. It might be cosmetic, but some of these high end cars show that. So, could do that on a C3.

69427 has body panels under his car.

Yes, canards might even look good.

I guess it depends on how far you want to go.

Here is an example of the c7 widebody with the fender flares cut out. There is a better vid, just can’t find it.

[ame]https://www.youtube.com/watch?v=6-lDxscVgyo[/ame]


Am I going to do it ? Probably not, but I am interested in the topic.

 

[mfain]

Here are a couple of thoughts based on what others in the racing community are doing. A front splitter with diffuser tunnels produces good downforce. Air ducted into a narrow slot in the front fender well front lip creates a low pressure area outside of the front wheel (air curtain) for better brake cooling and promotes more laminar airflow down the side of the car. You see this on everything from late model Corvettes, Camaros, Vipers to pick-ups. Canards are pretty draggy, but if they are used to create a vortex outside of the front wheel they have the same brake cooling and airflow advantages as the "air curtain" described above. One of the best drag reducers is evacuating air from the front fender well. The Viper and Porsche GT2R have fender vents, and some like GSpeed with their C5 track car cut out the body panel behind the front tire. On a C-3, cleaning up the "parachute" at the back of the car with an effective, properly designed (not just cosmetic) diffuser helps a lot, as does a belly pan to clean up airflow under the car. Side skirts keep air from rolling under the car and causing lift. One of the best cooling/downforce aids is to route exhausted radiator air up through the hood (sometimes called a chimney) to reduce front drag and create better airflow up and around the cockpit. A lot of the design concepts rtj has been posting are all about managing airflow through the car, not just around it. In effect, they are reducing drag by reducing frontal cross-sectional area - creating areas where the air flows through the car without impacting blunt surfaces. They often use this "flow-through" air to interact with downforce devices or for cooling functions ala Formula 1.

Pappy

 

[phantomjock]

I'll second what Pappy said. And as I often do, add a few comments;
Splitter with Diffuser - these are awesome. By do that (as pappy described) you can effectively double the effectiveness of the splitter. So you can cut it back some - keep inside the "design box" constraints and garner heaps of DF.


Regarding air curtains - they are an easy build and can be effective in putting the flow where you want it. These two direct flow to the tunnels in the side pods of my SR. Garden-variety edging - literally. It bends easily enough and you can not worry about getting curb rash.

Hood and fender louvers - easy enough - and you can still get the fiberglass ones I bet from Ecklers (etc). But the best hood louvers I've seen are on Aaron's ride (Plastic-Fantastic). Add some smarts to them (and a motor) and - wow what an option. Work engine bay temps and flow through the hood.
Yes getting the radiator exhaust out the hood is the way to go. The Corvette team has demonstrated that a number of years - and with a setup like Arron has, could almost look stock when parked. Note - if you can do it to isolate the engine bay at the same time there would be a heap of drag saved - we've been over that before - but I need to repeat so I don't forget (getting to build again soon.)


Regarding side skirts. First there are a lot of "odd things" you could see/say about this car. But he's got the radiator exit on hood, side exits ahead of front wheels, cut out front fenders, side splitter, etc.


He has the side skirts figured out, I believe. Sharp corners tend to not let air wrap around and get back underneath the car. Also if you are not concerned with sanctioning rules, or ride height restrictions, you could add PVC verticals reaching to almost ground level. They will make the car ride like on rails when matched with a full belly pan. I ran that on the SR (illegal in my class - then pulled to race) and the difference was night and day. Wish I had the data to prove it - we bought the data boxes later that season.

Here is pic from a guy I spent some time chatting with about some interesting areo approaches (as he had done some tunnel testing full scale during his build). For his radiators:
he split them; left and right and exhausted outside in front of the tires. Got 2 biirds with one stone. He runs/ran in SPO and set several track records in NE. Car sometimes on RacingJunk - still for sale. (Not a Corvette--but may be a useful approach.)

Not a vette - but a few ideas here from my SR:

The hood exhaust the laydown radiator that is augmented with 2 fans. The louvers were pulled to baseline the DF without louvers, then with. The tire diffuser/spoiler/spats cover the wheels that are "exposed" when turning, but the aft wheel cut out is a do-able mod in a C3 (I think). I'll try a CAD look on a C3 this weekend - time permitting.

Mirrors will remain draggy until sanctioning bodies let cameras do that job.

ENOUGH! I hear you say.
I say, Cheers - Jim

 

[rtj]

Good stuff mfain, Phantomjock.

Another C3 option is the Greenwood trick, running a convertible hardtop. Just an hour or two with the sawzall if you have a hardtop.

The silver C3 from Europe posted at the beginning of the thread has some aero. Those photos were 10 years ago. I think racers started the technique of supporting the rear wing on the top/pressure surface more recently, it is possible that would benefit a c3 wing (same downforce less drag as the suction surface isn’t disturbed).

Found this looking for the silver C3.



Not for me, but it worked on the Dodge. Probably would work best on a big rear window car (78).

 

[rtj]

This shows the cutouts on the back of the flares better. Not sure if they did any testing, but there are other cars with that feature.

[ame]https://www.youtube.com/watch?v=Kaj4RUp5xPo[/ame]

 

[rtj]

[ame]https://www.youtube.com/watch?v=DdZIkFSz0iI[/ame]

YouTube picks these, this one was worth sharing.

 

[mfain]

These Time Attack Cars take things to the extreme, but if you look through the photos you will see examples of some of the things we have been discussing - waterfall hood openings, cut-outs behind the front and rear tires, extreme side skirts, etc.

https://www.bing.com/images/search?...13730D&selectedIndex=6&FORM=IRPRST&ajaxhist=0

In rtj's video above - smart guy! Interesting concern for "wheel wake".