Stan Stockton wrote:
> Seems like there is some factor for round tubing instead of square -
> like 2/3 or something?
>
> Stan, K5GO
Depends on the speed of the wind, or more properly the Reynolds number
(Re). This size/speed range is an area where the drag coefficient
varies a lot with the Reynolds number (as in a 3:1 variation).. If you
want to be conservative, take 1.2 times projected area (because that's
about as big as the Cd can get).
I use projected area as a rule of thumb (i.e. Cd=1), but mostly for
computational convenience.
If your design is so close to ragged edge of failure that your estimate
of the Cd of the tubes makes a difference, then maybe there are bigger
design issues that need to be addressed?
Jim
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