Flow question

[pmiulian]

Hello. I`ve been reading a lot the aerodynamics forums and I am very interested in tuning my car for better FE. I have a 2005 sedan Hyundai Accent.

This morning I had some snow on my car and I noticed something interesting about the aerodynamic flow. As I got to about 50 mph, a V-shaped snow trail formed above my trunk. No turbulences, just two easily curved lines that started on the C pilars and would unite somewhere above the trunk - just above the edge.

I`m not sure how to interpret this - I`m guessing that this is attached flow, and is a good thing.

[Old Tele man]

...a picture would help.

[pmiulian]

I`m sorry. I have no pictures. I just saw it in the rear view mirror. I can post a picture of the car - but that is just an accent sedan '03-'05 model.

[kach22i]

When ever two planes (roof and side) of air intersect (at corners), there is a meeting of "pressure differences". One pressure plane is bound to be more than the other, and moves or gets sucked into the lesser one. This movement of converging/meeting air is constrained by the flow of air passing all around it, and tends to funnel or contain it. This funnel of air is called a Vortex.

The example below is my own pick up truck, I suggest doing a Google image search for an image more matching your own vehicle.

S10 4x4 Pick Up pictures by kach22i - Photobucket

[Sven7]

I might add that having vortexes like that is bad. A remedy would be fabricating a partial kammback (below). The air you saw was not attached because it was not against the surface. It detached at your C Pillar and went on to pull on the back of your car, creating drag.

Good luck!