Derivation of Pitot corrections for the Zagarola & Smits Superpipe data and their composite fit
Abstract
The original turbulent pipe flow experiments in the Princeton "Superpipe" by Zagarola & Smits (1997, 1998) at unprecedented laboratory Reynolds numbers have started an ongoing vigorous debate on the logarithmic law in the mean velocity profile and the intimately related question of Pitot probe corrections for mean shear, viscous effects and turbulence level. Considering that the Pitot probe diameter exceeded 7000 wall units at the highest Reynolds number, the various \textcolor{black}{traditional Pitot} corrections had to be extended into uncharted territory \textcolor{black}{where they may no longer be additive}. In this note, the inverse approach is adopted, where the net result of all the corrections is assumed to be compatible with the model for developed by \cite{Monk17}. The latter has an inner part which is, up to higher order corrections, identical to the zero pressure gradient turbulent boundary layer profile and switches around to a logarithmic overlap layer with a K\'arm\'an "parameter" \textcolor{black}{that depends on pressure gradient and possibly on other flow parameters}. The simplicity of the resulting global Pitot correction proportional to , with only two fitting parameters, indirectly supports this model. \textcolor{black}{Based on the required equality of the overlap and centerline 's, it is furthermore shown that must be a constant.} \textcolor{black}{Finally,} the outer "wake" part of the profile is argued to be asymptotically linear between the wall and about half the pipe radius. This gives rise to a linear higher order tail in the logarithmic overlap layer, which has been \textcolor{black}{the subject} of asymptotic analysis over the last decades.
Keywords
Cite
@article{arxiv.1902.03829,
title = {Derivation of Pitot corrections for the Zagarola & Smits Superpipe data and their composite fit},
author = {Peter A. Monkewitz},
journal= {arXiv preprint arXiv:1902.03829},
year = {2019}
}
Comments
11 pages, 6 figures