Quote:
Originally Posted by Hawiian Cadder
I actually thought about this a bit more after posting, I think the best soulution would be a 37 inch diameter fan pointed up and toward the key. With all the power in the KOP motors you could achieve about 3-4 times as much power as a large gym fan. This would almost certainly deflect any shots enough to miss.
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The air wall was tried in 2006. Early testing indicated that it was useless against any robot shots--range, 60" shooting air at a target about 8' up. (More like 6.5' up if on the ramp.) For a dropping shot this year, you'd need to add some height to that. Hover the ball that year, yep. Add velocity, though, and in the goal every time.
Think about it this way: You need to generate enough drag force on the ball that gravity can take over, or that it will move in a different direction. There are a couple of possible estimates for the drag coefficient of a sphere, namely 0.5 (laminar flow) and 0.2 (turbulent flow). You have an area (pi*D^2)/4, a known air density (1.204 kg/m^3 for 20C), and you can estimate the drag force needed to deflect the ball.
Now, you plug into the equation Fd=Cd*A*density*(V^2)/2, and solve for the velocity needed. Now that you know how fast the air needs to move, you can figure out how big of a fan you'll need, or how much you need to apply a nozzle to get the air moving that fast, using one of several possible methods.
Power in the motors in the KOP has to translate to a fan, and thus to the air. That is where you run into trouble (in addition to keeping most of the air column generated together instead of going off into eddies in the surrounding air--you're probably best off using the turbulent flow analysis for that part of the equation).
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... nah. - dlavery [more] 
21-04-2012, 20:04
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