# Wind speed calculation from a pressure setting

## Main Question or Discussion Point

I have been out of school a long time, so please go easy on me. If the answer is an equation with symbols or letters, could you please help define them for me?

I am trying to calculate the windspeed flowing through a tube with circular opening that is 38cm2 when the vacuum creating the wind is set at a 125pa pressure. I have the ability to change the pressure setting and am wondering if different pressures equate to different windspeeds.
The machine that creates these conditions is a Textest FX3300 Air Permeability tester. It is intended for the use of putting a fabric over the top of tube (38cm2 area opening) and measuring the air permeability of the fabric. The output measurement at these settings is in cfm.
I'm am looking for a way to equate lab results with wind speed,, is there a way to say how much wind protection a particular fabric will give you. For instance, if a fabric has 0cfm airpermeability at the above settings, is it blocking a 15mph wind?, a 30mph wind?

I do understand that in the real world, wind does not only go through your clothing , the majority of it probably goes around your body like a cylander, but it seems like that would mean a straight calculation is erring on the conservative side which would be ok.

thanks

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CWatters
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Perhaps see..

http://www.knmi.nl/samenw/hydra/faq/press.html

That will give you a rough guide to the wind pressure for a given wind speed but how do you define "protection"?

Presumably there is a figure for the air leakage above which you consider "protection" has been lost?

Thanks, I'll try that.
As far as defining "protection", under 1cfm of air permeability is generally considered insensible for windchill.