Well, you can't do that with these tools. That's a limitation of the 2D methods. They assume an infinitely long wing. They usually assume a free field as well, although if you can do multiple wings then you can do a reflecting ground plane.

Best you can do with a 2D tool for a wing that varies its spanwise geometry is to take slices of it along the span and run those separately. Then try to merge the results.

But really, you want a 3D tool for this. I don't have one or know where to point you to one. If I need a 3D analysis done, I go down three floors and ask the Aero guys to do it for me. Of course, it has to be Boeing business....

Datalogger probably is the best way. However, if you have an idea of what is actually happening then it really helps your interpretation of the datalogger results.

 

If you want to try to get scientific about aero on a grassroots budget, there are a few ways you could go about it:

1. tape bright colored threads to different parts of the wing and use a couple small vid cameras to record what the strings do at speed.

2. Either use a suspension travel sensor or video camera to record ride height at speed. Lower ride height corresponds to greater downforce. Might be hard to get a good measurement here because we're probably talking about 150 lbs of downforce at the most and on a car that probably has 500+ lb/in springs. Even with a 0.8 correction factor for wheel rate relative to spring rate, that still means that 150 lbs of downforce would only cause about a 1/6 of an inch of droop if the force was applied only to the two rear wheels. 500 lb/in * 0.8 (to correct for the wheel rate being less than spring rate) = 400 lb/in. at each wheel. 400 lb/in * 2 rear wheels = 800 lb/in. (150 lb) / (800 lb/in) = 0.1875 in. Soften your shocks all the way to minimize their impact on this.

3. Rig up some kind of smoke system and a video camera pointed at the wing. Probably only want to try this one on a day with no wind and if you can use a source of smoke that puts out a lot of smoke without the source being big enough to disrupt airflow too much. I got no suggestion for what would make that much smoke without having a big object on the surface of the car messing up the airflow.

 

There's a pic of the thread idea in a wind tunnel.

BTW, this is TOTALLY OT, but a really cool idea that I believe has come up a few times (and been banned from F1) is to have all aero pieces be suspension-mounted instead of chassis-mounted. Anyway, just think of all the advantages...

 

Make the smoke inside the car and pipe it outside via a tube through the window, taped in place to the roof.

But I've done smoke experiments. Even in wind tunnels they are hard to set up and hard to interpret. You are unlikely to get any useful result while driving on a track.

 

good thread - sounds like the datalogger would be the easiest/most accurate guesstimate for us.

mike- too bad they don't let you use the boeing software/computers for personal purposes

 

That was the original design of the first successful winged race car (the Chaparral). It was promptly banned. In fact, that's where the ban on "movable aero devices" comes from.