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On the Use of the Preston Tube in Concentric Annuli

Published online by Cambridge University Press:  04 July 2016

V. C. Patel*
Affiliation:
Engineering Department, Cambridge University

Extract

In a recent discussion on measurements made by Quarmby in fully-developed turbulent flow in concentric annuli, Quarmby has made several statements which are incorrect and need to be clarified.

Quarmby states that the pitot displacement corrections measured by MacMillan are those solely due to the shear and that they do not take account of the effect due to the presence of the wall. This is not so. Fig. 9 of MacMillan's original paper shows the total displacement effect. It is this total displacement effect which was used in my paper on the calibration of Preston tubes to relate the calibration curve to the inner-law velocity distribution. It is quite obvious that a Preston tube will be influenced both by shear as well as the wall and it would have been pointless to attempt to correlate its calibration with the velocity distribution using pitot displacement corrections unless these corrections included the rather important influence of the wall.

Type
Technical Notes
Copyright
Copyright © Royal Aeronautical Society 1969 

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References

1. Quarmby, A. On the Use of the Preston Tube in Concentric annuli. Journal of the Royal Aeronautical Society, Vol 71, p 47, January 1967.Google Scholar
2. Quarmby, A. An Experimental Study of Turbulent Flow through Concentric Annuli. Int J Mech Sci, Vol 9, p 205, 1967.Google Scholar
3. Quarmby, A. On the Use of the Preston Tube in Con centric Annuli. Reply to a Comment by Lyall, H. G.. Journal of the Royal Aeronautical Society, Vol 71, p 865, December 1967.Google Scholar
4. Macmillan, F. A. Experiments on Pitot Tubes in Shear Flow. ARC R & M 3028, 1957.Google Scholar
5. Patel, V. C. Calibration of the Preston Tube and Limitations on its Use in Pressure Gradients. J Fluid Mech, Vol 23. p 1, 1965.Google Scholar