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Aeronautical Engineering/sieve factor for wind load calculations

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Question
Paul
I design tensile fabric structures with knitted fabric that is quite porous (permeable to wind and rain +/_ 35%) but am forced to use it in  calculations as a 100% solid membrane. Is there a ASTM test already available for testing the sieve factor of fabric . ( I have tried and could not find any). but have to ask . Do you a facility in mind that can test the wind pass through,or sieve factor of a fabric mesh .
Thank you in anticipation
Dennis

Answer
Dennis - This is a little outside my experience, but I found in my Fluid-Dynamic Drag book by S. Hoerner a couple of sections discussing the drag and pressure drop of both 1) porous materials such as screens and fabrics mounted across ducts and 2) porous parachutes. He gives theoretical equations and experimental data acquired in various wind tunnels. Almost any wind tunnel should be capable of measuring what you want, but I suspect it is much cheaper to use small test rigs such as are described in ASTM spec D737-96. I didn't buy that spec, so I don't know what the test rig looks like. I also found links to various test labs by googling 'testing labs for porous material' (using Duck Duck Go search engine). The lab at Porous Materials Inc in New York looks promising. Good luck.

Paul

Aeronautical Engineering

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Paul Soderman

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Aeronautics, Aerodynamics, Fluid Mechanics, Aeroacoustics, Noise Control, Muffler Design, Wind Tunnel Research.... I know nothing about India - do not ask about schools, jobs, application requirements, career choices, etc. for India. Please, no text message verbiage; I prefer full words in full sentences. Thanks.

Experience

38 years as research engineer at NASA

Publications
AIAA, NASA

Education/Credentials
B.S. and M.S. Aeronautical Engineering - U. of Washington, Graduate work Standford U.

Awards and Honors
AIAA Associate Fellow (American Institute of Aeronautics and Astronautics)

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