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Theoretical velocity distributions downstream of non-uniform single and multiple smoothing screens

Published online by Cambridge University Press:  04 July 2016

N. A. Jackson
N. A. Jackson*
Affiliation:
Marchwood Engineering Laboratories, Central Electricity Generating Board
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Extract

Smoothing screens are frequently used in wind tunnels and other ducts to minimise irregularities in velocity profiles and reduce turbulence.

There is an optimum value for the screen pressure drop coefficient which, for wire gauzes, corresponds to an open area ratio less than 0·5 if only one screen is used. However, screens with open area ratios of about 0·5 or lower, produce lateral non-uniformities in the downstream flow due to jet coalescence. To avoid coalescence, two or more relatively open screens may be used in succession, either so close as to behave more or less as a single screen or more spaced out with each screen operating independently. It is the latter situation which is considered in detail in this note.

Because of inevitable manufacturing tolerances there will always be errors in the characteristic screen parameters, which will make the screen impose its own irregularities on the downstream flow.

Type
Technical Notes
Information
The Aeronautical Journal , Volume 76 , Issue 736 , April 1972 , pp. 251 - 255
Copyright
Copyright © Royal Aeronautical Society 1972 

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