A comparison of turbulent pipe, channel and boundary layer flows

TLDR

The extent or existence of similarities between fully developed turbulent pipes and channels, and in zero‑pressure‑gradient turbulent boundary layers has come into question in recent years, contrasting the traditionally accepted view that, upon appropriate normalization, all three flows can be regarded as the same in the near‑wall region. The authors aim to clarify this issue by measuring streamwise velocity in pipes, channels, and boundary layers with matched Reynolds numbers and resolution. They conduct streamwise velocity measurements in the three flows, carefully matching Reynolds number and measurement resolution. Mean statistics in the near‑wall region collapse well, but premultiplied energy spectra of streamwise velocity fluctuations reveal marked structural differences that cannot be explained by scaling arguments, indicating that similarities exist only with caution even near the wall.

Abstract

The extent or existence of similarities between fully developed turbulent pipes and channels, and in zero-pressure-gradient turbulent boundary layers has come into question in recent years. This is in contrast to the traditionally accepted view that, upon appropriate normalization, all three flows can be regarded as the same in the near-wall region. In this paper, the authors aim to provide clarification of this issue through streamwise velocity measurements in these three flows with carefully matched Reynolds number and measurement resolution. Results show that mean statistics in the near-wall region collapse well. However, the premultiplied energy spectra of streamwise velocity fluctuations show marked structural differences that cannot be explained by scaling arguments. It is concluded that, while similarities exist at these Reynolds numbers, one should exercise caution when drawing comparisons between the three shear flows, even near the wall.