Alternative interpretation of the Superpipe data and motivation for CICLoPE: the effect of a decreasing viscous length scale

Authors: Vinuesa, R., Duncan, R.D., Nagib, H.M.
Document Type: Article
Pubstate: Published
Journal: European Journal of Mechanics - B/Fluids
Volume: 58   109-116
Year: 2016


Pressurization and cryogenic conditions have been used in some experiments to change the kinematic viscosity of the flowing gas by many orders of magnitude in order to achieve high Reynolds number conditions in facilities of limited size. This leads to a substantial reduction of the viscous length scale l*=nu/ut, as in the so-called Princeton “Superpipe” experiments. We demonstrate that the limited dimensions of the facilities and probes can lead to inaccuracies in the near-wall measurements for increasing Reynolds number. Specifically, a lack of accurate wall-normal probe positioning is simulated using three different datasets of wall-bounded turbulent flows. Relatively large errors in the overlap region parameters are observed for position errors of small physical magnitude that become greatly amplified in wall units as l* is reduced. This offers an alternative interpretation to some of the key findings reported by the Superpipe team, such as the increasing lower limit of the logarithmic region y+log;min, the existence of a power law region between the wall and the logarithmic layer, and the “mixing transition” phenomenon in wall-bounded turbulence.