While writing a physics report, I obtained a data that
for balls of rough surfaces, there is a higher drag force and thus
the ball can stay stable at a much smaller angle when put up in an airstream.
However, while analyzing this result, I found out that the drag coefficient is not always
bigger for rough spheres : it depends on the reynolds number of the flow.
I would really like to know whether the flow past a sphere
(in my experiment, styrofoam balls) is attached flow (Stokes flow) and steady separated flow, separated unsteady flow, separated unsteady flow with a laminar boundary layer at the upstream side, or post-critical separated flow, with a turbulent boundary layer.
Put simply, what is the reynolds number of the air coming out of an air supply?
For further information, the air supply used in our lab was SF-9216, PASCO.
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 After discussion with an intimate physics professor, we reached contradicting results: like in the case of golf balls, the rough surface can make air pockets, or when the air meets a certain condition (some sort of Reynolds number boundaries) the drag coefficient is bigger for rougher spheres. Also, we concluded that the air flow from the supply is turbulent. Could you please help us out? Thank you!
 Recognitions: Homework Help In the case of dimpled golf balls, the flow tends to stay attached longer producing less drag at speeds between 55 mph == 88 kph and 300 mph == 480 kph. Below 55 mph drag is about the same. Above 300 mph a smooth ball has less drag. Links to articles: golf_ball_aerodynamics.aspx wiki_golf_ball_aerodynamics.htm