Quote:
Originally Posted by Ian Curtis
I knew someone would bring up the drag crisis, that's what I get for keeping it simple I suppose...
To remain at the low spot requires pretty spectacular attention to surface roughness. We tunnel tested several models as part of one of my aero labs, and indistinguishable (by fingers) differences in surface roughness will knock you out of the crisis. Seeing as these are low quality foam balls produced in the thousands by robots, I don't think there is much to worry about.
(Where did that chart come from? I've never seen Cd v. Re with how the drag crisis moves as a function of roughness before, that's a nice chart!)
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The chart is in A Brief Introduction to Fluid Mechanics. I'm really not sure if drag is entirely predictable just because robots may rough them up a bit. Unfortunately, drag might be a real issue too. At 5 m/s, the drag force is right at around 1 N (and weight is 3.1 N). That's pretty non-negligible.