when i got home today after driveing trough the rain i noticeds some strange flow patterns on the cars roof. these where very clearly defined, but unfortunately where wiped out by the rain before i could take some pictures
for the most part the car is covered in small doplets of water and relatively dry given the amount of rain (wich accumulates quicky when the car is stopped) but halfway the roof untill the seem of the rear hatch there where some distinctive water streaks that started earlier near the center than the sides and they formed continuous parallel lines from the center of the roof until the seem of the hatch. after the seem there where doplets again.
what could this indicate? is this an indication of attached flow or just the opposite?
what i also notice when it's raining or when the car is wet, is at relative high speeds the drops will stay on the bonnet but they will fly of the leading edge/frontal part of the car, and strangely, seem to shoot up and over the car.
at higher speeds the rear windshield will stay clear and receive no additional raindrops (wich made the rear wiper pretty much obsolete) but existing drops will stay in place for as far as i can see.
i noticed most panels on my car seem fish scaled with the leading panel ending a little higher than the trailing panel.
even though the rear hatch slops down very gently this step, combined with the big seem might be enough to have the air separate again at that point, thus leading to the end of the stripes
my car has a pretty low 0.29 Cd so i think most of the angles where pretty well considered, so what's going on?
is the front shaped such that most of the airflow is deflected over the bonnet and windshield and reattaches somewhere at the center of the roof? given that the roofs gently slopes down from that point it would create a pretty teardrop profile?
any thoughts on this?
for reference here's a profile picture of my car, the streaks started somewhere between the doors
