sound barrier
Submitted: Saturday, Jan 15, 2011 at 22:11
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Member - MUZBRY(Vic)
Good evening
I was just wondering how many RPM your fan would have to do to break the sound barrier and what is the equation ?
Murray
Reply By: dereki - Saturday, Jan 15, 2011 at 22:53
Saturday, Jan 15, 2011 at 22:53
I just tried a rough calculation and got about 15000rpm based on a 44cm diameter fan which is about what my car has.
But I have probably buggered my calcs up somewhere.
Speed of sound at ground level at 20degC is 343 meters/sec (Wikipedia)
Thats 20580 meters per minute.
Pi x Diameter of fan = circumference of the fan. ie distance travelled per revolution.
RPM revs per minute x 3.14 x Fan diameter = meters/minute
RPM x 3.14 x Fan Diameter = 20580m/min
RPM = 6554 / Fan diameter in meters
RPM = 6554 / 0.44
RPM = 14895
That would give a speed at
the tip of the blade at the sound barrier.
Please correct me if I have made a mistake.
D
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Follow Up By: Member - MUZBRY(Vic) - Saturday, Jan 15, 2011 at 22:59
Saturday, Jan 15, 2011 at 22:59
Gday Mr D
Thanks , i will do the math when I am at work next. Imagine the racket at 14000 + rpm down the main street at mid night . It would be like a screaming banshee.
Murray
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