New 818 Configurations Windtunnel Tested

[Mechie3]

Would it be possible to get a photo of just the center grill section all by itself? I can't quite make out the center styling with the stuff behind it. Also wondering what I need to work around to make a new hinge.

[Bob_n_Cincy]

Would it be possible to get a photo of just the center grill section all by itself? I can't quite make out the center styling with the stuff behind it. Also wondering what I need to work around to make a new hinge.

Craig,
There is a builder here in Cincy that just got a coupe with the new nose. I need to stop by and visit him. Are you over this way any time soon?
Bob

[Rasmus]

On the matter of a the roll-bar, if you try to "wing-it" (yuk-yuk-yuk), then you might run afoul of the tech inspectors. But that's not the proposal Rasmus (and I) are suggesting. I'm going to build a fairing around it so that it extends into the body. This is no different than what you see on a Radical (or Honda del Sol). The objective is to simply clean up the body and stop the turbulence and you don't need an airfoil to do that - just about any simple ovoid shape is going to greatly diminish turbulence.

That's exactly what I was thinking. And by calling it a "fairing" I think I could convince a tech inspector that it is body work and not a wing intended to produce down force in between the front and rear wheels.

Even though


the Eppler 862, and


the NACA 63+520m

are both airfoils and when made 3d with fluid flowing around them become wings. Their purposes are entirely different.

[Bob_n_Cincy]

Rasmus
Here is some FAIRINGS use on ultralights.
streamlinedfairing.jpg

http://www.ultralightnews.ca/streamlinedfairings/1.html

Bob

[Mulry]

Nice find Bob. That's sweet.

[C.Plavan]

This thread escalated quickly.

[Jim Schenck]

frontgrill.JPG

This is one with all the openings cut out. They will come shipped with just the upper opening cut and be able to be opened up as needed.

[Sgt.Gator]

If the roll bar is faired in like this it would look great and have no tech issues:
Subaru Radical 4.jpg

This might be a problem:




BTW, this Radical is Subaru powered. Here's how they solved the intercooler problem:

Subaru Radical 1.jpg.......Subaru Radical 2.jpg......Subaru Radical 3.jpg

[Santiago]

Damn, I'm having trouble viewing all but one of Gator's images. Any direct links?

Best,
-j

[Canadian818]

Damn, I'm having trouble viewing all but one of Gator's images. Any direct links?

Best,
-j

I don't see them either

[Mulry]

I don't see them either

They were showing up earlier today, but now none of the ones of the Radical are showing up, just the Chaparral.

[Sgt.Gator]

They were showing up earlier today, but now none of the ones of the Radical are showing up, just the Chaparral.

I think I was over the size limit. I reduced the size and compressed the images more, you should be seeing them now. Let me know if your not.

[Sgt.Gator]

The latest Radical has a dip in the top of the fairing, directly above the intake scoop. I'm wondering if that helps channel air to the scoop? They say this one has the best aero yet.


radical-sr8-rsx-03-1 sm.jpg

[Mulry]

I think I was over the size limit. I reduced the size and compressed the images more, you should be seeing them now. Let me know if your not.

Still not appearing. Not even the new one.

[Santiago]

Ditto, can't see them...

But here's a sweet SR3 (showing off the basic concept)



And the street version of the SR8 is pretty enticing (think, wider bar fairing to accommodate both 818 engine cover humps):

[Scargo]

Here's one link for a yellow Radical with a Subaru motor.
John, from looking at the Radicals I'm puzzled. Puzzled because wind tunnel testing by FFR has not found the Radical's scoop position to be clean air area in the 818. With helmets in the way I am surprised the Radical's design is efficient and effective.
The Radicals intake is similar to a concept I have where I might want to modify the roll bar brace location. Also, with the link you see a front-mounted turbo. Also a plan of mine by using the gas tank area but staying low and exiting the side.

[Mulry]

Depending on the power output goal of the Radical, the necessary efficiency (thus effectiveness) of the Radical scoop may be lower than that which Jim is looking for on the 475hp motor they have in that test mule. A stock+ level tune may be able to make use of the over-engine location with reduced airflow whereas a really boosted motor might need more air to cool the A2A in that location. Just a thought.

I wonder if one were to bring the forward plane of an A2A rear deck scoop flush (or near flush) with the vertical plane of the roll hoop if that wouldn't improve airflow a bit by avoiding the turbulence of the roll bar. Fairing in the entire roll structure is probably the best way to go though, but not easy.

[Sgt.Gator]

Here's one link for a yellow Radical with a Subaru motor.
John, from looking at the Radicals I'm puzzled. Puzzled because wind tunnel testing by FFR has not found the Radical's scoop position to be clean air area in the 818. With helmets in the way I am surprised the Radical's design is efficient and effective.
The Radicals intake is similar to a concept I have where I might want to modify the roll bar brace location. Also, with the link you see a front-mounted turbo. Also a plan of mine by using the gas tank area but staying low and exiting the side.

Great link Scargo!

I don't know why my images quit working as links from my Google Photos cloud file. It's always worked in other threads. And I can see the images here! There must be a security/privacy/sharing setting on my photo file I need to change.
So I've uploaded them.

[Mulry]

Here's one difference between the Radical scoop and using one on the 818. Look at the airflow off the front of the Radical in this photo:

RadicalSR8 airflow.jpg

Versus what the airflow testing was indicating in the recent video from FFR:

818R Airflow.JPG

I wonder what is the effect of the location of the radiator exit duct on pushing the airflow up. There's a real difference between the Radical and the FFR on that score. We've been playing with this in SolidWorks but nothing conclusive yet.

[Hindsight]

Back to engines......

So the new Ford Focus RS is 2.3L, and makes 350 ft/lbs of torque at only 3200 RPMs. By contrast, the WRX STI has only 290 ft lbs of torque, and it's all the way up at 4,000RPMs, and that's with 2.5L of displacement. The Focus also makes 350HP.

With those kinds of numbers, I'm really curious as to how it's making so much torque so low in the RPM band, and still pulling hard up top. On pump fuel, I don't think I've seen a WRX do anything similar.

[Mulry]

The Focus RS uses a twin-scroll turbocharger. Don't know if it's variable geometry, but that would be another way to expand the range of useful boost.

[Sgt.Gator]

It's also a Direct Injection engine. "Engine technology supplier Bosch says that direct injection can return a 15 percent gain in fuel economy while boosting low-end torque as much as 50 percent."

[Hindsight]

That ecoboost option keeps looking more and more attractive.

[DanielsDM]

Direct injection allows for a higher compression ratio too (9.5:1 on the 2.3L ecoboost) because there is better control of the combustion process.

[AZPete]

"Back to engines" Huh?

[DanielsDM]

Here's one difference between the Radical scoop and using one on the 818. Look at the airflow off the front of the Radical in this photo:

RadicalSR8 airflow.jpg

Versus what the airflow testing was indicating in the recent video from FFR:

818R Airflow.JPG

I wonder what is the effect of the location of the radiator exit duct on pushing the airflow up. There's a real difference between the Radical and the FFR on that score. We've been playing with this in SolidWorks but nothing conclusive yet.

Do you have a SW model of the 818?

[Mulry]

Do you have a SW model of the 818?

This one:

http://www.turbosquid.com/3d-models/...8-model/752174

[Santiago]

Back to airflow! [We can do a Bud Light commercial later...]

Those are great comparison pictures Mulry. There are a number of differences in the Radical set up that could account for why they are getting better flow sufficient for their application, not the least of which are (a) lower driver position, (b) smaller cockpit area in general, (c) properly radiused intake scoop entry, and (d) a very different hood strategy. The bar placement is different, the fairings are smoothing airflow aft of the intake (which can actually have a beneficial effect forward of the intake), the scoop itself is higher, etc. Just a lot of differences here that can add up to significant differences in flow. Look at this head-on perspective:

Radical-SR3.jpg

It's a different beastie.

[Santiago]

This one:

http://www.turbosquid.com/3d-models/...8-model/752174

Mulry, I have that file as well but I wasn't able to get solid surfaces out of it. I must be doing something seriously wrong with the wizard. If you're willing to help a brother out, PM me.

Best,
-j

[Mulry]

I'd love to help, I'm not the one doing the work. Hell, I'm struggling to learn to do 3D CAD so that I can start printing brackets with the 3D printer. I had a 2D program that I used to use but it's useless in 3D. Different thought pattern required.

Anyway, Roland is doing that. He took that model and then ran wind tunnel simulations in Autodesk Flow Design. Don't know if there was an interim step. I'll check.

[Santiago]

Ah-that may be it. I was setting up to do the CFD analysis in Solidworks, but the turbosquid file options weren't importing well. You need to take the mesh files and convert them into solid surfaces. There's a wizard to help do it, but the automated results were...well, catastrophic.

[07FIREBLADE]

My 15 WRX puts that power out after being tuned on 91. It's my high boost map though, stock turbo just an intake and turbo back. It's a direct injected motor that's light years newer in tech when compared to the old EJ in the STI that's with 2.0l instead of 2.5 or 2.3l ecoboost. This fact right here was one of the selling points for me not to buy the sti when I got my 15.

Back to engines......

So the new Ford Focus RS is 2.3L, and makes 350 ft/lbs of torque at only 3200 RPMs. By contrast, the WRX STI has only 290 ft lbs of torque, and it's all the way up at 4,000RPMs, and that's with 2.5L of displacement. The Focus also makes 350HP.

With those kinds of numbers, I'm really curious as to how it's making so much torque so low in the RPM band, and still pulling hard up top. On pump fuel, I don't think I've seen a WRX do anything similar.

[Mechie3]

I have the turbosquid models as well. I can import them as surfaces but not as solids. Using the medium or high density point clouds kills my computer.

[nkw8181]

What wizard did you use? I have access to NX but not solid works anymore and it doesn't appear to support obj or 3ds

[Mechie3]

ScanTo3D plugin

[ssssly]

Do the turbosquid models treat the whole car as 1 object or as a series of parts that can be disassembled?

If when the model was scanned (I'm assuming they 3d scanned an 818) it wasn't intended to be treated as a solid, the mesh will not likely be manifold.

One thing you could try is converting the .obj to .stl. There are several web apps that will repair a non-manifold .stl. Some of them will however also then render it as a series of triangles instead of discrete surfaces. Which could cause issues once you compile it for an autodesk fluid simulation. Since an object created with triangles can't have a truly smooth surface.

Once it is manifold though, you might be able to mitigate that be converting it back and texture wrapping it.

Also from looking at the photos, it seems that they rendered all the vents (front grill, side and top) as solid extensions of body panels. So they would need to be removed and the interior paths recreated somehow.

I've been debating getting that model, but $150 seemed a bit much when I could just 3d scan mine as separate parts and have a better model to work from. Unfortunately I have been indisposed and haven't gotten around to scanning it yet.

[DodgyTim]

Older thread on the turbosquid model, developed from photo's?
http://thefactoryfiveforum.com/showt...ght=turbosquid

[LowEndTheory]

Roland here: I am no expert at this but, I am able to run wind tunnel simulations on the TurboSquid model (*.3ds and *.obj) in Autodesk Flow Design. Flow Design meshes the model automatically.

The original model was made in Autodesk 3DS Max, which is more for 3D animations (Avatar!) than accurate CAD or CFD work. It can be taken apart and modified, but there are no vent openings and the grills are just bitmaps. Looks great though.

Since the model is basically solid, I've been mostly using it to observe surface pressures and airflow around areas of the car. I am tweaking the model in 3DS Max by opening up the vents to test intercooler locations, but I am learning this as I go. It can be exported to AutoCAD (and others) and might be a good starting point for you hardcore CAD/CFD people.

[Santiago]

Welcome Roland!

I wish I were a hardcore CFD person. I just have a hardcore program.
Most of the CFD work I've done is just testing different things (wings, wings in ground-effect, tube profiles, wheels, and one full-car w/rolling ground) to get comfortable with SW Flow Simulation program.

I tried using the same plugin Mechie used, but SW flow simulation requires solids not merely surfaces. I was going to bite the bullet and just start recreating the body in SW using the imported model as a template, but I'm kind of dreading that process (and as ssssly so aptly put it, I've been indisposed as well).

The TurboSquid model is nicely detailed, and for your money you do get quite a few different file formats, but as mentioned, they're mostly graphic related. My computer can handle the medium density files, but the resulting solids I'm getting are still a mess (think of something that looks like a microscopic spore; it's a geometric mess). I've got a low density .obj file in a google.doc if anyone is interested in playing around with it (PM me).

Best,
-j

[LowEndTheory]

I learned that I can look for manifold errors in 3DS Max.

Short version:
If your CFD program is sensitive to this sort of thing, the TurboSquid model isn't going to work without A LOT of work.

Long version:
Each wheel has 7232 open edge errors and the body has 8092. I stopped checking there. Autodesk positions Flow Design as a tool to look at preliminary designs which I guess is why it can afford to ignore/extrapolate these errors during meshing. From their forums:

"If you are looking to examine rough designs/dirty cad (study the what if's) and you don't have time to prepare to use in Simulation CFD then Flow Design is great to get an idea of what is going on."
"If you are looking to really study a wind tunnel analysis in depth with more accuracy and more ability to extract quantitative vs. qualitative data then I would suggest Simulation CFD."

I bet if I try use this model in Autodesk Simulation CFD it would fail as spectacularly as it does in SolidWorks.