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On the Use of the Preston Tube in Concentric Annuli

Published online by Cambridge University Press:  04 July 2016

H. G. Lyall*
Affiliation:
Central Electricity Generating Board, Berkeley Nuclear Laboratories

Extract

In his technical note in the January 1967 JOURNAL, Quarmby (pp 47-49) concludes that because he was able to predict the axial pressure gradient in a concentric smooth annulus by using Preston tubes to measure the inner and outer wall shear stress, then the Preston tubes are giving correct values for the wall shear stresses. I cannot agree that this is a valid conclusion to draw. A Preston tube can only give wall shear stress correctly if the dimensionless velocity in the wall region is the same as that for which the tube was calibrated.

Type
Technical Notes
Copyright
Copyright © Royal Aeronautical Society 1967

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References

1.Patel, V. C.Calibration of the Preston Tube and Limitations on its Use in Pressure Gradients. Jnl Fluid Mech, Vol 23, p 1, 1965.Google Scholar
2.MacMillan, F. A. Experiments on Pitot-Tubes in Shear Flow. ARC R and M No 3028, 1957.Google Scholar
3.Quarmby, A.An Experimental Study of Turbulent Flow through Concentric Annuli. Int J Mech Sci, Vol 9, p 205, 1967.CrossRefGoogle Scholar