JCB Dieselmax aero
 

I find myself thinking about this undertray quite often:

http://i202.photobucket.com/albums/a...ews-1280x9.jpg

JCB DIESELMAX photos - Google Search

It's interesting that it is not entirely flat. The way it channels out air after the front tires and slopes up back towards the rear wheels seems unusual, just comparing to other aero-undercarriages. *shrugs* Whatever works I guess...

The slope towards the rear is to reduce wake size, no? Mehbe the front bit helps with the disturbance caused by the front wheels?

The driver of that streamliner, Andy Green, is a real interesting, smart and likeable guy. I talked with him for half an hour at the Bonneville World Finals about 5 years ago. Land Speed Racing (LSR) isn't just a bunch of backyard hacks with wheel driven junk anymore...

There is a forum for LSR racers worth looking at, that also has a technical section (areodynamics are a hot topic) like eccomodder. For those here who don't see anything useful coming from racing, let me say there's more crossover information than you'd expect.

Landracing.com - Index

I don't know much about fluid dynamics, but my guess would be that the sloped rear is to create a low pressure zone, keeping (or helping to) the "car's" butt on the ground.

Maybe the front recessed areas are for the same purpose, since they seem deeper toward the back/side.

I'd have to agree with Jeece; those vents open up as they direct air away from the underside of the vehicle. Isn't that the principle of a venturi? I'll bet they create quite a lot of downforce at the speeds this thing is capable of.

aero
 

A full ground-effect vehicle.We can't do that.The full-length skirts must skim very close to ,if not actually touching the ground,for the entire length of the vehicle.Low base pressure from the wake can communicate forward,underneath the vehicle,via the tunnel,effectively vacuuming the vehicle to the ground.JCB is at speeds where "flight" must be considered,especially if the car loses traction and begins to yaw.You end up like Ed Tradup in "Danny Boy",off the salt,and in the air.Ground-effects downforce helps avoid wheelspin and fish-tailing,to maintain straight down course attitude.If they still manage to get sideways,the drag chutes are the only thing left to the driver to keep the car straight and on the ground.Spooky!