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Joined: 28/03/2016(UTC) Posts: 6 Location: Munich
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Hi, i calculated the Reynoldsnumber where i need the revolutions per minute. What struck me was the conversion from rpm to 1/s -> 60rpm = 1 rps = 1 s^-1. According to smath 60rpm = 6,28 s^-1. Is there a bug or are i'm doing the math wrong? thanks a lot!
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Rank: Advanced Member Groups: Registered, Advanced Member Joined: 13/01/2012(UTC) Posts: 2,647 Location: Italy Was thanked: 1329 time(s) in 875 post(s)
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please read here (SS-2395) (you can vote and comment it), here or here (and other...) base unit of a revolution is coded as 2pi radians (not 1), hence the multiplication factor. |
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1 user thanked Davide Carpi for this useful post.
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Rank: Advanced Member Groups: Registered
Joined: 23/03/2016(UTC) Posts: 276 Was thanked: 91 time(s) in 57 post(s)
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This is because the standard unit in SMath for rotation is radian = 2*pi which is ~6.28. If you look at the definition of rpm it is pi/30 1/s or 2*pi/60. In order to get the right result you need to divide by 2*pi. What i would suggest is creating your own unit for RPMs as done in the attached. rpm.sm (3kb) downloaded 46 time(s).Edit: Davide beat me to it. |
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Joined: 04/07/2015(UTC) Posts: 6,866 Was thanked: 981 time(s) in 809 post(s)
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Originally Posted by: alyles This is because the standard unit in SMath for rotation is radian = 2*π ... and this is because trig functions are numerically approximated in radian. Those functions are native in Microsoft, used by math software as is.
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Rank: Newbie
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Joined: 28/03/2016(UTC) Posts: 6 Location: Munich
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thanks a lot for your quick reply, good to know
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