Aerodynamic Discussion Thread
 

I wanted a place to put mixed info about all Race Car Aero, not just Miata's but Ideas. Yes I know there is Treads currently about "Miata DIY Aero", "New Wing toTest" and some Miata under body Aero from ThePass and me. I was going to put some ideas and questions up on my "Miata Underbody Aero" but that would be off topic and can not share what your ideas are. And maybe "plucas" can share what he is thinking of since he has the knowledge and programming with data to give us.

The one of the things that I was looking at that brought up the idea of this thread was this found on the Nissan GTR GT1 race car. What is the function of this vent? or what is it?

https://www.miataturbo.net/attachmen...ine=1359012179

I like the idea for the thread, although with such a broad subject of discussion, I expect it will wander around a lot!

I love "under the skin" pics of race cars, they can be very inspiring.

As for the duct in that pic, there's what looks most likely to be an oil line at the base of it - and I would put my top bet on that being for a differential oil cooler. Looks like the duct supplies air to it, and it looks like the duct then takes the exiting the cooler and sends it off to the side - I would also bet that that air is evacuated over the top of the rear diffuser somewhere...

I can't embed the photo here because it's copyrighted, but the pic in this link shows the duct opening in the trunk. It's an interesting location...:

Nissan GTR R35 FIA-GT1 | Flickr - Photo Sharing!

Id have thought that would be a low pressure area there?

Dann

Most probably depends on the roof/trunk, and the exists can be placed in an even lower pressure area.
That exact solution might not work that well on a Miata with OEM-style hardtop, but you might be able to fetch air from below and dump it op there instead. Or fetch air from around the diff, pass it though a cooler and exit in the number plate area. I'm not completely sure what panel area in the rear is best suited for exiting air (low pressure and not disturbing diffusor and/or wing). Quarter panels, just in front of the rear lights?

Trying to apply Aero solutions from other racecars can be interesting, you never know what you will learn (about your car, the original car or the restricting regulations that have "inspired" the solution).
Pike Peaks and Time Attach series are some of the few areas where the Aero is free, and the focus is to make it go faster, many others are restricting in one way or another (or travels at speeds where we will never dare to go).

Any thoughts on the fenders autokenexion is working on?

http://clubroadster.net/vb_forum/att...erofender3.jpg

They're cheap (kevlar is only like $650!), light (kevlar is ~3 pounds!), supposedly fit well, and clear 275's on 10's I'm not sure what else you really need to justify buying them. Of if you're a cheap bastard fiberglass are like $270 and weigh around 9 pounds, that is cheaper than you will be able to make them.

And some more aero food for thought.
Nerd's Eye View: The MCA Suspensions "Hammerhead" Silvia S13

I kinda working on the same thing (waiting until I get almost done with the design, Top Secret). I just picked up a fender from a local Pcola Junkyard, but I TDY (sent to another state for Military business) here so I don't have tools. I will be making mine 30mm wider and will allow the air to be removed from the front fender. I am making a mould so if anyone else wants one I can make them. It will be made out of prepreg carbon (about 11 ounces each). Mine will more or less copy the Lotus 300RR, but will also have anti-lift vents on top of the wheel arches.

A friend built vented fender on his VW Golf and the problem he ran into was the pinch weld in the wheel well didn't allow the air to move smoothly out.

I like to see The MCA Suspensions "Hammerhead" Silvia S13 on a wind tunnel because I dont think its as efficient as the think.

Pre-preg? How do you have access to an autoclave big enough to do fenders? Lucky bastard.

Anyone can do it, we don't need a pressurized oven. The oven just needs to be big enough to run the parts and be stable enough using ramp up schedule.

Regarding the duct in the OP, it might actually be a decent place on the miata, judging by the below picture (shamelessly stolen from a post by plucas in the flat underbody thread)

There appears to be a high pressure zone right where the top meets the trunk. The air could come in there and vent where the license plate is, or just above a diffuser. The question is, who'll be the first to try it and report back?!?

Attachment 185655

Dump it into the diffuser where the air is already "straightened" and moving.

Use the high pressure zone to bring air to differential?

This is used on F1 cars, active aero with no moving parts. Just like when you have the A/C on and when we take a corner quickly moves to the opposite way that we are turning.

Question: Why is the airflow in the Acc/Decell module follow the G-force and in the Left/Right module moves against the G-force?
Or is there any other phenomena that steers the airflow?

Autokonexion fenders:

I did custom fenders just like these and have run them for the past few years. Works pretty well. Eventually though, I was dissatisfied with how the vent only addresses about 1/3 of the wheel well, so I designed new ones. For an off-the-shelf option though, I think those are pretty good.

Trunk duct topic:

That pic courtesy of Plucas does show a small high pressure area at the rear base of the hardtop, but look at its position and remember that miatas have a 4" or so panel behind the base of the hardtop before it becomes trunk, which means that a trunk duct would be further back than where the high pressure is. In the pic of the GTR GT1, you can see they don't have that problem - the duct is right at the base where the rear window slope hits the horizontal trunk surface.

-Ryan

After know what I wanted to do as far a fender design, I looked up it on google to see what I'm picturing and this is the closes thing. So know I have junkyard parts sitting in my hotel for the next 2 months lol.

https://www.miataturbo.net/attachmen...ine=1359069075

I saw an article on this. I think Braun GP (Ross Braun, the man himself) originally came up with this system. Anyway, it is actually an aero device that through virtue of its profile multiplies the incoming angle of attack at the port. If the air enters the incoming slot at say 2 degrees (from a turn maneuver) then it leaves the slot at say 10 degrees in a focused stream. This is used to direct the airflow into a series of ports behind the slot (like mailbox cubby holes) that through a series of duct tubes direct the flow into the flaps and out through bleed ports in a manner that augments the downforce for cornering or straights. Nothing moves in the wing, all fixed, yet the airflow gets redirected passively depending on which way the car is turning. It is a fantastic example of how innovative F1 aero can be when working around the rules for an advantage. Genius.

:jerkit:

The only F1 team with air channels in the front wing is Mercedes for its double DRS that even if they werent banning it for next season said that they wouldn't do it again for next season because it takes too much damn money, work, and time to iterate a new wing. And, with out doors to change which outputs are open. Air just doesnt magically move like that from inertia or any other bullshit quasi physics.

Oookay I guess tell us all about Aerodynamics Mr. Adrian Newey

Sorry, but F1 teams don't scrap ideas because it's too complex to make the part. If anything, expect new ideas to be more complex and expensive to make, not less. And rules won't stop that - they'll just come up with a new crazy way to go faster while working around the rules.

On a slightly related note, the RedBull cars have been running rubber noses that flex as a unit so that at speed they get closer to the ground. Cool.

They're not rubber noses, they are still some sort of carbon kevlar composite, the noses are just designed to flex at an amount of force higher than the testing force from the FIA. And this effect seems to have been reduced in the past season with the ugly noses. And speaking of the ugly noses, only redbull has an air inlet in anywhere close to the "correct" position shown in this video. An F1 team will scrap an idea. F1 teams go through an entire truck load of wings testing them, if they wing is so complex that they can only afford to make a few within the time constraints they have for testing and the budget caps set by the FIA they will likely scrap an idea, unless it shows itself to be worth it.

So you two are either trolling, and sucking at it, or need to go do some research. Either way, this topic offshoot needs to stop.

When did these come into effect?

Think about it... G-forces (lateral and/or longitudinal acceleration) will change the trajectory of anything with mass that is not directly tied to the frame of reference. The trajectory of the air (which has mass) is changed relative to the direction of travel of the car. It's not bullshit quasi physics, just physics.

For those not used to free body diagrams and dynamics, let me illustrate. Attach a water hose in the center of your dash firing straight back along the centerline of the car. Take a corner and the stream of water's trajectory shifts in the opposite direction away from the centerline of the car. The harder you turn, the harder it shifts. Lateral trajectory shift due to lateral acceleration. The same thing would happen if you directed the stream sideways, and slammed on the brakes. It's not voodoo, it's a cool idea.

I'm not talking about double DRS, this is something different.

It would be a cool idea, if air had enough mass for that to work. Air flowing through a box is going to take the path of least resistance, also know as the path with the greatest pressure differential, and no matter how violently you accelerate it side to side you will not change that. The air will flow through all the holes and the volume flow distribution will be directly proportional to the pressure differentials. Now with a fluid with a significantly higher density, like water, the acceleration would actually change the the pressure profile side to side in that box which would change the rate. That pretty cfd in that video, go try to repeat that with the assumptions you're making, the cfd is 100% faked.

If you make air travel fast enough (and don't slow it down too much when "touching" it) it will behave less like air in confined spaces (i.e. compressed air to tools etc). But to do that in "ducts" and trough "porous material" sounds fishy.

Like trying to make power in a running stream, you can make some with propellers/wheels etc, but to create static pressure you have to build a dam.

But if the speed where it might be feasible is 100mph or supersonic, I don't know (how many Gs are needed to divert airflow at all, it's not like you notice a change in HVAC air when you take a corner in your DD).
I assume it's not AutoX-speed at least, where barn-door sized aero is needed to get any effect (and not by flow over wing, but rather creating pressure by diverting air).

The Trunk-high-pressure-usage: If the high pressure zone is short and wide, just make the opening/ducts the same shape, as with any air intake in front of the windshield.

I like how someone is calling bullshit on all the top F1 aero designers... just saying, there's a reason they have their jobs, and a reason the cars get faster every year. They know their field better than we do, and it would be foolish and pompous to claim otherwise. Not saying it's bad to question things - but accept that there may be things you don't understand well enough.

Agreed with Mr Pass. Assuming the vid is not fake, if teams use anything like that this year, then it'll be because it works. We'll find out in a few months, I guess.

The concept of path of least resistance is an oversimplification that is frequently overused when explaining the flow of water, air, electricity, forces, loads, sewage, whatever. It is true in its basic premise. But, anyone who understands engineering or physics knows in a system that it is not absolute, is much greyer, and depends on a lot of factors.

I agree, I would really do my homework before I called bullshit on something any of the renowned F1 aero designers are trying/doing. Aerodynamics (at least until recently with the new engine formula) is where most of the advances are in F1 and where most of the R&D money is spent. Some of the best and brightest are working in that area. Sure they are fallible, but it's more likely they are right than any one of us relative amateurs.

I for one, wasn't calling bullshit on any aero or other devices actually used in formula 1.

Ok when I get back home I am going to finish my under car aero and one thing I wanted to discuss was front diffusers.

I get something like this where it is solving two purposes. Helping move air into the brake region and help accel the air under the splitter.

https://www.miataturbo.net/attachmen...ine=1359285382

But I don't get this. Why do you want the air to accelerate then slow down with turbulence, then find its way out to go to the underbody.

https://www.miataturbo.net/attachmen...ine=1359285382

I wanted to do this for a long time, to build a fan car. It would be interesting if motorsport could use this again.

1970 Chaparral 2J

https://www.miataturbo.net/attachmen...ine=1359286024

1977 Brabham BT46B

https://www.miataturbo.net/attachmen...ine=1359286024

Cheaparral Champion Corvette

around 3:40 they show the car running and you can see the plume of debris it throws up. I wouldn't want to run behind that car on a track.



Thomas

IIRC the main issues they had with the mechanical bits to make the F1 fan car work:
1) They had to seal the car down, and seal meant to run skirts that wore themselves on the track.
2) The one race they were able to run at , there was a seam where old/new pavement met that was ripping the skirts off till they figured a way to make it ramp up onto the pavement better. (I believe the driver said that the jump when it hit that seam they were losing all suction, but it was on a straight, so they were not worried about it.
3) The fan at the time, it got thru the rules as it “sucked air thru the radiator” Later testing iirc it pulled around 35-38% of the air thru the radiator.
4) The materials for the fan, when the car was made I am sure they were using the most high-tech of stuff possible, but something with the gyroscopic forces and its RPM, at the end of the one race, its bearings were shot, and they were surprised it did not explode on the track. Their testing their fan kept blowing up, so they one race the fan lasted just long enough
If I can remember when I get home I have the story about this car in a book, there was something about their straightaway speed was slower than all the other cars (10-20 mph), but did not have to slow down at all for the corners, (like a 30-50mph difference)

That vid, I would more concerned with having that fan right beside you spinning at high RPM. I have seen some nasty pictures of exploding flywheels on drag cars before, that shroud does not look safe. I would have mounted it behind the driver and made some kind of barrier made of steel to guard in case it exploded and deflect it (and the air) away from the driver.

My guess is that it's out of necessity - they can't get enough of the air out of the hood (or don't want to - street car that they don't want a big extractor hood on or something), and so the air leaving the radiator must exit out the bottom of the car. This is how all of our cars expel that air as well, after all, except that we don't have any fancy ducting routing it out nicely, it's just a turbulent mess flowing out from the oil pan/bell housing area. I would think that guiding it, like in that pic, at least improves the way the air joins the air already passing under the car better than no guidance. Of course, if you can send all the air exiting the radiator up and out the hood, that's better, but not every setup has "maximum performance" as the one and only priority.

That's all just my own conjecture on that subject though.

Interestingly, the F50 has something kinda similar - the center section of the bumper is basically a splitter/horizontal fin, and the air going over that is then channeled down and under the car. But, the airflow for the coolers are on either side of that center tunnel, and the air for those is all exited out the hood:

http://www.driveaccord.net/forums/at...1&d=1257452450

And that brings me to something else I will be doing for another car of mine. Im going to wait until after my LS swap this summer or I am going to get ancy and build one now. I was thinking about the LS intake and how it is right in the way. So I am going to separate the ducts with the exits in the hood right about where the DTM cars do.

AMS Time Attack Evo X
https://www.miataturbo.net/attachmen...ine=1359312956

https://www.miataturbo.net/attachmen...ine=1359312956


2012 Audi ultra A5 DTM Hood Vent

https://www.miataturbo.net/attachmen...ine=1359312956

http://i526.photobucket.com/albums/c...psd64f8cd1.jpg

Yeah with that last picture you can really see the wicker just before the opening to really get that low pressure zone there.

Since I didn't see anyone answer though I would like to speculate on the matter it looks to be a cooler of some sort. With out doing any research on the car Idk if it's a diff cooler, inter cooler or what but you can see a line going in to the side.

If you do a quick google on chris griswold mustang you'll see that guy does that with a rear mount IC

^ Covered that in post #2 of the thread ;)

yup, guess you got it. I must have glanced over it and not seen it. and damn the second post too. :bang:

In other news while reading the thread the 2012 Audi ultra A5 DTM Hood Vent pics make me moist.

I finally got my fluid dynamics book in the mail to start reading up on aero stuff and can't wait to dabble on my own, those hood vents look so sexy though

Naturally the Audi DTM has a much more elegant wickerbill/gurney flap, but here's the crude one I just added to my hood vent:

https://www.miataturbo.net/attachmen...ine=1359363174

Seeing your hood I think has made me change my mind. I was planning on cutout out the front vents like you have an placing a Gurney flap in front of them. After seeing your drop vent I think I'll make that instead. How far down is vent?

What do you mean by how far down?

I'm guessing he means how large is the opening.

Never mind, I went back to your CR.net build thread. I didn't remember seeing the pics of the revised hood vent.

I was thinking of playing with a speed brake that would be about 50"x4". It would sit under the wing, extend 3" and be flush with the trunk lid. During braking a linear actuator will push the speed brake up (to about 60-80 deg) and once the car gets under 15 mph the brake will go down.

I also found this video

Would be cooler if it was two piece and you could also use it to help you turn, ala the Pagani Huayra. If you're going to make your car illegal in practically every class, you might as well do it right.

Like this

I wish some racing classes would allow to use Active Aerodynamics

Or the sucker car this is funny and alot of weight

I remember back a few years ago that Vic Sias was developing one on his SM M3. He showed up to the Solo Nationals with it, but it was disallowed (he had to run it in a fixed position). People where saying it would be too expensive to run, but IIRC the pricing was less than what Eric Strelniks is rumored to paid for is dual element carbon wing.

There may have been a chicken or egg problem here. The elements that I saw vic testing in 2007/2008 in SFR region weren't very big and didn't have a large effect at solo speeds.

Because anything like that would quickly be protested away, nobody has taken the time to develop a big, multielement version at an affordable price. Because there isn't an affordable one, nobody is petitiong the SEB to allow them. Back to chicken.

donour

Well part of the problem is that the rules state you can only have 2 wing elements. His wing was considered 2 elements. He was also within the maximum size allowance. I think he tried to stay within the rules of the time. I think now its written in that active aero is expressing prohibited.

I remember noticing that they explicitly banned movable side skirts in the SSM rules... at the time I wondered if someone was awesome enough to have made a sucker car. Good to know :D

I posted an article of the building of that car earlier in the thread.

Does QLD's "Lightning Composites" have anything to do with an Aussie member of ours with a similar name? The one building CF race Miatas?

Unrelated: I'm also wondering a bit about the wisdom of dumping air into the diffuser. I think it'd be better to dump it into the wake above the diffuser.

Are you talking about Lightyear

That's it. I thought maybe his name was Lightning but I couldn't remember for sure, and that didn't sound right.

Lightyear lives in a state one the opposite side of the country.

Good thread. What's the highest downforce Miata we know of right now? Just wondering.

2,045,070 newton meters.