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saade
02-18-2010, 04:44 AM
HI
Can any1 tell me how to get the frequency spectrum from wind profiles? are there any records available? I knw this sounds like a strange question but i have a problem that im trying to wrap my head around.. how wud u go about makin a mechanical structure less susceptible to wind induced vibrations.. I knw that modes of vibration for my structure just don't knw if they wud correspond to the frequency of wind induced vibrations... What is the general range of frequency spectrum of wind?

Any help would be most appriciated Thanks

Bill O
02-18-2010, 07:27 AM
Is that you Stephen Hawking? Crashing our forums again.

JimS
02-18-2010, 04:21 PM
HI
Can any1 tell me how to get the frequency spectrum from wind profiles? are there any records available? I knw this sounds like a strange question but i have a problem that im trying to wrap my head around.. how wud u go about makin a mechanical structure less susceptible to wind induced vibrations.. I knw that modes of vibration for my structure just don't knw if they wud correspond to the frequency of wind induced vibrations... What is the general range of frequency spectrum of wind?

Any help would be most appriciated Thanks

I don't really understand the question, I'm sorry, can you break that down a bit more for us?!

Knapper
02-19-2010, 09:58 AM
I am also a bit confused as to what kind of records you are looking for. I haven't even heard of what a wind profile frequency spectrum is. I agree with JimS, maybe with a clearer explanation, I might be able to point you in the right direction. The only thing I can suggest in the meantime is looking over the data at NCDC (http://www.ncdc.noaa.gov/oa/ncdc.html). Anything and everything weather record wise is there from the US and an ever growing world database. Sorry I can't be more helpful.

Bill O
02-19-2010, 11:14 PM
I am also a bit confused as to what kind of records you are looking for. I haven't even heard of what a wind profile frequency spectrum is....

Few, I was worried I fell asleep during that class. Good to know I wasn't the only one.

Lawson
02-20-2010, 10:21 AM
Is this the property/kind of phenomenon you're talking about (aeroelastic flutter): http://www.youtube.com/watch?v=HxTZ446tbzE

If so... super cool.:cool:

I believe it depends on the materials you're using as well as the geometry of your structure. In which case, you'll need to look up the physical properties (namely the "aeroelastic coefficient," me thinks) of those specific materials, and/or consult your local wind-tunnel facilities (probably not very realistic, though). A quick consultation with Google leads me to believe that most of the research out there focuses on bridge-deck, wind-turbine, and aeroplane materials. This literature is fairly specific or slightly tangential, but might help (?):

http://books.google.com/books?id=TuJ76UrfMUcC&pg=PR7&lpg=PR7&dq=principles+of+aeroelasticity&source=bl&ots=pO3Lu_Z6pg&sig=JFjDpugDdzryGSv4Gh8v2cecnQQ&hl=en&ei=w_5_S8OVJIaXtgeX5_igBw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CBkQ6AEwAg#v=onepage&q=&f=false

http://74.125.47.132/search?q=cache:L995DKwJIEUJ:citeseerx.ist.psu.edu/viewdoc/download%3Fdoi%3D10.1.1.81.1881%26rep%3Drep1%26typ e%3Dpdf+aeroelastic+coefficients&cd=7&hl=en&ct=clnk&gl=us

http://iris.lib.neu.edu/civil_eng_theses/5/

http://www3.interscience.wiley.com/journal/112224729/abstract?CRETRY=1&SRETRY=0


Hope some of that helped.

Bill O
02-22-2010, 08:04 PM
It seems like the best way to reduce vibration would be to add some irregularities to the object. It would disrupt the airflow and reduce the likelihood of resonance.

A good example was when I strapped my surfboard to the roof of my car. The webbing I used was lying perfectly parallel to the direction of the wind and at highway speeds it flapped so violently it sounded like a tire was coming off. The simple fix was to just put a half twist in the webbing.