Comparison of three roughness function determination methods

Comparison of three roughness function determination methods Three methods have been used to experimentally determine the roughness function (ΔU +) for several rough surfaces. These include the rotating disk, the towed plate, and the velocity profile methods. The first two are indirect methods in as much as they rely on measurements of overall torque or resistance and boundary layer similarity laws to obtain ΔU +, whereas the velocity profile method provides a direct measurement of ΔU +. The present results indicate good agreement between the towed plate and the velocity profile methods for all of the surfaces tested. Tests for the rotating disk were carried out at much higher unit Reynolds numbers. Using this method, the results for sandpaper rough surfaces agree within their uncertainty with a Nikuradse-type roughness function in the fully rough regime, while a spray painted surface agrees with a Colebrook-type roughness function. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Comparison of three roughness function determination methods

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Publisher
Springer-Verlag
Copyright
Copyright © 2003 by Springer-Verlag
Subject
Engineering
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-003-0686-x
Publisher site
See Article on Publisher Site

Abstract

Three methods have been used to experimentally determine the roughness function (ΔU +) for several rough surfaces. These include the rotating disk, the towed plate, and the velocity profile methods. The first two are indirect methods in as much as they rely on measurements of overall torque or resistance and boundary layer similarity laws to obtain ΔU +, whereas the velocity profile method provides a direct measurement of ΔU +. The present results indicate good agreement between the towed plate and the velocity profile methods for all of the surfaces tested. Tests for the rotating disk were carried out at much higher unit Reynolds numbers. Using this method, the results for sandpaper rough surfaces agree within their uncertainty with a Nikuradse-type roughness function in the fully rough regime, while a spray painted surface agrees with a Colebrook-type roughness function.

Journal

Experiments in FluidsSpringer Journals

Published: Aug 23, 2003

References

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