Aerodynamics of a bug

[aartjan]

Originally Posted by Wally

Imo, when the air hits the nose, the part that goes over the front bumper splits in a part that goes over the bumper and bonnet and part goes downwards and under the car.
I think you want as much air over the car and not go under it.
My undertray may just help draw air from behind the bumper and downwards through the underside of the car.

I think part of the effect of the bumper cover might be attributed to another phenomena. The high pressure of the stagnation at the front of the car (where the flow splits, velocity=0) is used to press on top of the cover and thus forcing the car down. That's just another way of saying that the bumper is a large splitter. However, the bumper itself does also have stagnation in front of it. Maybe slightly lowering the bumper might give some additional benefit of stagnation at the front bonnet when using a cover?