A direct comparison of pulsatile and non-pulsatile rough-wall turbulent pipe flow. (25th July 2020)

• Record Type: Journal Article
• Authors: Jelly, T. O.; Chin, R. C.; Illingworth, S. J.; Monty, J. P.; Marusic, I.; Ooi, A.
• Is Part Of: Journal of fluid mechanics. Volume 895(2020)
• Publication Date: 2020-07-25
• Subjects: shear layer turbulence, -- turbulence simulation, -- pipe flow boundary layer; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2020.337
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract : Abstract : Pulsatile rough-wall turbulent pipe flow is compared against its non-pulsatile counterpart using data obtained from direct numerical simulation. Results are presented at a mean friction Reynolds number of 540 for a set of three geometrically scaled roughness topographies at a single forcing condition, which, based on existing classifications, falls into the current-dominated very-high-frequency regime. By comparing the pulsatile data against an equivalent non-pulsatile dataset (Chan et al., J. Fluid Mech., vol. 854, 2018, pp. 5–33), the key differences (and similarities) between the forced and unforced configurations are identified. A major finding of this study is that the flow in the outer region retains its self-similar functional form under pulsatile rough-wall conditions, and, as a result, Townsend's outer-layer similarity hypothesis holds for the roughness-forcing combinations considered here. On the other hand, the unsteady cases exhibit a rich array of flow physics in the region beneath the roughness crests not observed in the steady case. These differences are examined using a Moody chart, which encapsulates how the hydraulic properties of pulsatile rough-wall pipe flow differ from their non-pulsatile counterpart.