Natural Frequency Equation
Natural Frequency Equation
(OP)
I'm analyzing a flag pole for wind loads and wanted to see what the critical wind speed was for vortex shedding. I'm using Vc = fd/s where f=natural freq, d=diameter of pole, and s=Strouhal number. I'm assuming the pole could be modeled as a cantilevered beam with fixed end? Also, I've found a few equations for f, all of which differ slightly. Can anyone tell me if the following sounds correct:
w (or f) = (1.875)^2 sqrt[EI/mL^4]
Since the mass is just the mass of the pole can you just use that? Most of the examples I've seen have an object serving as the mass, being acted by springs, and dampers, etc...
Thanks in advance!
w (or f) = (1.875)^2 sqrt[EI/mL^4]
Since the mass is just the mass of the pole can you just use that? Most of the examples I've seen have an object serving as the mass, being acted by springs, and dampers, etc...
Thanks in advance!






RE: Natural Frequency Equation
Look at this website and use the first formula case. the formula looks slightly different but you could compare answers,
htt
desertfox
RE: Natural Frequency Equation
RE: Natural Frequency Equation
your welcome
desertfox
RE: Natural Frequency Equation
RE: Natural Frequency Equation
Good point, however I assume your just after the natural frequency of the beam, if thats things going to vibrate then its going to do so because of wind or some other tranverse load, in that circumstance (wind loading) it would be loaded just like a beam.
desertfox
RE: Natural Frequency Equation
RE: Natural Frequency Equation
have a look at this report on lamp poles it also refers to some standards which might be relevant:-
http
desertfox
RE: Natural Frequency Equation
foundation is soft so your calculated frequency is wrong.
Pole is stiff enough that the aero forces are not significant.
pole material is damped.
flag damps pole motion.
flag halyards act as a vortex suppressor (bit of a long shot)
luck.
Cheers
Greg Locock
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