Recent Comments by zomgg • VideoSift: Online Video *Quality Control

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Stupid driver or attempted murder? - “he was probably trying to run over that obnoxious squawking bird he seemed to have pinned down” read more by rottenseed

Recent Comments by zomgg

Wind turbine self destructs

These types of videos make me kinda sad, the destruction of something so beautiful and useful is a little depressing.

>> ^budzos:
I heard it's a challenge to keep the blade tips on these huge windmills from creating sonic booms.

To check this we can look at the velocity of the tips of a blade, and compare with the speed of sound to see if a sonic boom will occur. According to Wikipedia, common modern wind turbines have a blade radius of 20 to 40 m. Taking an average of 30 m:

velocity = rate of rotation x radius
speed of sound = 343 m/s
radius = 30 m

rate of rotation where the tips are approaching the speed of sound = 109 rpm
This is much greater than the common operating parameter of 10-22 rpm

For the worlds biggest turbine (according to Wikipedia), r = 63 m
rate of rotation where the tips are approaching the speed of sound = 52 rpm

So it does pose a problem for really big turbines, but in general can be avoided for average turbines. Also, note that with any wind speed the required rotation rate will be slightly lower, since the velocity at the tips will be the combination of the wind and the rotating speed.

The more you know!

src: http://en.wikipedia.org/wiki/Wind_turbine

written by zomgg | 1 day 2 hours 50 minutes ago | CH

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Do boomerangs work in space?

The point of science is to question everything, no matter how obvious. The interesting wrinkle here is that without gravity a boomerang would actually stop eventually due to energy losses from viscous dissipation (you can see it slowing down by the end of the turn). While this is easy to show analytically, having a guy who is already up there doing all kinds of experiments throw a boomerang a couple of times proves expected theory elegantly and with a small cost ($2 boomerang).

written by zomgg | 2 weeks ago | CH

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