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Wind speed calculation from a pressure setting

  1. Aug 24, 2012 #1
    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.

  2. jcsd
  3. Aug 25, 2012 #2


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    Perhaps see..


    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?
  4. Aug 27, 2012 #3
    Thanks, I'll try that.
    As far as defining "protection", under 1cfm of air permeability is generally considered insensible for windchill.
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