Belly pan NACA duct to reduce low pressure draft...?

[wungun]

Have a look at my car this morning...



The rear center bumper, you can clearly see how the snow clings to it because
, I'm assuming, that part of the cars aero has a large low pressure zone from boundary separation...and being a hatch back, somewhat worse than your average sedan...

I was thinking, if I had a belly pan from the rear axle to the bottom of the bumper, with a NACA duct or even a scoop hanging down, to pickup air underneath the car and plumb it to a grill opening, maybe 20" wide, in the center of the bumper where the colored part meets the matte black plastic, I could cancel out some of the low pressure void and replace it with ambient pressure air...
Does a racecar like diffuser do something similar, or is that more or less to create low pressure under the rear of the car for aero grip?

Of course, if would have to be equal diameter thruout so as to not create low or high pressure inside the ducting...
(restricting the diameter would create low pressure venturi effect)

Also thinking of a modified spoiler to grab some of the clean air over the roof and direct it downward over the glass area. I remember some of the early minivans used something similar to keep the rear glass free of dirt/snow...?

As for the snow clinging to the car after the rear wheels...? I'm not entirely sure I can explain that. Maybe the air coming off the trailing edge of the wheel? Another low pressure area?

[Frank Lee]

Ah, the old duct theory. Search EM for "duct".

[wungun]

So, a lot of modders on here using (gasp) duct tape...
Didn't see anything of much use...

[Frank Lee]

http://ecomodder.com/forum/showthrea...ube-16788.html

http://ecomodder.com/forum/showthrea...ces-15156.html

http://ecomodder.com/forum/showthrea...flow-3498.html

http://ecomodder.com/forum/showthrea...fun-18339.html

[wungun]

I think the small amount of drag over a small duct opening and a short lengthed duct would be more than made up for with reducing, even a small amount, the "wake" left behind my speeding car....?

I'm not trying to replace the air (vacuum) at the back of my car with an enormous duct, but just try to reduce the negative pressure back there, which I think would reap easy benefits in increased aero.

[nbleak21]

Originally Posted by wungun

I was thinking, if I had a belly pan from the rear axle to the bottom of the bumper, with a NACA duct or even a scoop hanging down, to pickup air underneath the car and plumb it to a grill opening, maybe 20" wide, in the center of the bumper where the colored part meets the matte black plastic, I could cancel out some of the low pressure void and replace it with ambient pressure air...

Sounds completely reasonable to me.

Also thinking of a modified spoiler to grab some of the clean air over the roof and direct it downward over the glass area. I remember some of the early minivans used something similar to keep the rear glass free of dirt/snow...?

I feel that if this were something that were effective aero-wise, that we would be seeing it more on vehicles then we do. If your purpose is just solely to keep the snow off the rear, then it will probably help.

As for the snow clinging to the car after the rear wheels...? I'm not entirely sure I can explain that. Maybe the air coming off the trailing edge of the wheel? Another low pressure area?

Low Pressure area would be my guess as well.