Quote:
Originally Posted by Cd
Yes, yes - nevermind the smudges.
I was concentrating on the clean area behind the rivets that showed the airflow.
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That's the separation bubble. There's a captured volume of turbulence traveling behind the rivets. Air is of such a low mass, that is can enter and leave this region, however the mass of the water and entrained road debris particulates prevents their following. The inertia of the water and entrained solids are just too great to allow them to follow a trajectory like that. They 'overshoot.'
If the rivet heads were a perfect hemisphere, you'd see the separation at around 115-degrees from the forward stagnation point, like a PGA, Regulation golf ball. If a 'clock face', and air hit at 3:00 o'clock, separation would be at 5-seconds after 12- Noon. At 22-degrees of downslope.