MKII Airflow / Pressure Rendering / 2D Model

Will do. I'm going to have to be making some changes to the shape file, I need to remove the wheels and fix a few glitched points. Also need to figure out how to get my shape file to the BOTTOM of the wind tunnel. Right now the damn thing is smack dab in the middle, even though I'm selecting "Ground Effect"

Thanks for the offer of help. Right now I'm dual Booting to Ubuntu on my Desktop & Laptop. I'm just wanting to get as much rendering done on the laptop before the demo expires. Although I'm thinking of using WINE in Linux to install a Window App (MicroCFD) and then I won't have to worry about the damn "trial period" expiring. Sure it'll be a pain to get it properly config'd but I know I can do it I might get some of your help if you know a bit about WINE when it comes to that.

RESULTS!!! I can haz them!

Unfortunately I've yet to figure out how to get MicroCFD to test @ speeds LESS than .8 Mach... which if you do the math is a stupid, we'll-never-see-it 608.9 MPH ... which is a bit fast. SO we can very crudely infer slower speeds from the first few frames.

Right now I have work to do on the wifes Supra, however I'll eventually post up links to the SWF flash files.

If anyone wants the AI outlines, Shape files, Slides, Test result files, LMK.















I'll be doing processing on ONLY the front bumper, hood, windshield and roof next.

pimptrizkit said:

so whats the pressure wave look like when a mk2 hit's the sound barrier?

Click to expand...

Well pretty close to the second animation I posted. It was @ .8 Mach which is 608 MPH. I DID figure out how to change the speed of the wind tunnel test. I'm currently RE-running the test @ .1 Mach (76.1 MPH) which should give us a much more accurate rendering of the air flow, and pressure zones created from normal driving.

Just waiting for the number crunching to finish. My poor laptop has been running full tilt for the last 4 or 5 days doing nothing but wind tunnel testing. Thank god I don't need it for anything else. It's so CPU intesive the rest of the laptop pretty much grinds to a halt. Even on my 64-bit dual core AMD desktop it was using 100 CPU and choking it down (of course it was getting done a lot faster... but still).

Anyways looking forward to getting some real data on the MKII airflow/streamlines.

Thanks guys. Next I hope to run tests with larger scales of the shape file. IE. The Supra bigger so we could get a better picture of air flow over the front half (Bumper, Hood, Windshield), however that's for another day.

Of note. @ 76 MPH the air under the car is moving a WHOPPING 118 or so MPH. That's nucking futs. Really. I never knew it moved that fast. It's obvious our cars can benefit from underbody side skirts. I had been thinking about making some from 1" L aluminum angle iron as a bracket, and then bolting thick rubber belting (1/4" -> 3/8") to the vertical bit of the L aluminum. That way the skirt will still be flexible enough to not get destroyed over the occasional speed bump but still stiff enough to do its purpose.

No wonder Mercedes makes a big deal about their cars being as aerodynamic UNDERbody as well as Overbody.

All of the above would help. From what I've seen in these, a front chin splitter would help (I'm thinking approx a 3 to 4" lip, but I'm sure less would help as well). Also it would work better if it was NOT just a lip but continued up under the front portion of the engine bay as well. The side skirts will help contain the high-speed low pressure area that starts right behind where the front wheel hubs are and continues all the way back to about where the rear control arms are.

A wing is dependant on what speeds will be run, but more downforce up front would be well matched with more rear downforce. Even something as simple as adding a Gurney Flap can make a big help, and they're stupid simple. It would be pretty easy to add one to the stock MKII 84/85 wing. Though it WOULD permanantly put holes in an otherwise okay FG hatch wing.

All of the things you mmentioned will help the car stick to the ground better. Although they are in 2 different categories. The splitter/spoiler, skirts, undertray tunnels, and diffuser all promote low pressure zones, and stabilize them based off of air that's already flowing under the car. I don't see drag increasing by much with the addition of these, if anything I see it lowering (lower drag). The Wing on the other hand will increase drag, however it also greatly increases downforce, and also drag. The amount of downforce/drag is a trade off. More DF=More drag... can result in slower times, however if the power is there and the track isn't fast enough for the the drag to hurt times, then use it. It's one of those things that would need to be dialed in.


I'll put this in perspective. I know of a Miata that races Auto-X. This dude has a Lexan wing/spoiler. It's attached to the trunk lid, it's about 18" TALL, and it's the FULL WIDTH of the car. (Of course the underside is braced with aluminum strapping). But for him the amount of DF he sees at Auto-X speeds is offset by the amount of drag it creats. Obviously above 45mph that thing would almost positively get ripped off, or slow the car like a drag chute (not that much but you get the idea).

So yes, all of the above.

I think the easiest things to implement are the front chin splitter, side skirts, and a Gurney Flap on the rear stock 84/85 hatch wing.

The next step would be re-inforced sheets of FG under the car to smooth airflow with a mild inverted airfoil shape to create even MORE downforce. Added to that removal of the stock wing and a race wing added. Wing to be chosen based off of track speeds. Higher speeds can use a smaller wing. Though if you have HUGE HP you can get away with a huge wing and huge DF.

The last step would be continuing the underbody streamlining from around the rear sub-frame and adding a diffuser. This would promote a stable exit of undercar air and probably yield a top-speed increase of a few mph.

Personally I may be over zealous for suggesting it but I think vortex generators are pretty cool and don't see when more high-end exotics use them.






Along the header panel, as well as right in front of back window (like on the Mitsu EVO) perhaps on the rear 1/2's of the fender flares (or a few inches behind them) might promote better airflow.