The minimal channel: A fast and direct method for characterising roughness

Michael Macdonald, Daniel Chung, Nicholas Hutchins, Leon Zen Hsien Chan, Andrew Ooi, Ricardo García-Mayoral

Research output: Contribution to journalConference article

2 Citations (Scopus)

Abstract

Roughness only alters the near-wall region of turbulent flow and leaves the outer-layer unaffected, making it a prime candidate for the minimal-span channel framework which only captures the near-wall flow. Recently, Chung et al. (J. Fluid Mech., vol. 773, 2015, pp. 418-431) showed that the minimal-span channel can accurately characterise the hydraulic behaviour of roughness. Following on from this, we aim to further optimise the minimal-span channel framework by primarily noting that the outer layer it produces is inherently incorrect, and as such modifications to this region can be made to improve performance. Firstly, a half-height channel with slip wall is shown to reproduce the near-wall behaviour seen in a standard channel, but with half the number of grid points. Next, a forcing model is introduced into the outer layer of a half-height channel. This reduces the high streamwise velocity associated with the minimal channel and allows for a larger computational time step. The streamwise length of the channel is also investigated independent of the previous improvements, and suggests the minimum length should be at least 3 times the spanwise width and also 1000 viscous-units long, whichever is longer. Finally, an investigation is conducted to see if varying the roughness Reynolds number with time is a feasible method for obtaining the full hydraulic behaviour of a rough surface, instead of running multiple simulations at fixed roughness Reynolds numbers.

Original languageEnglish
Article number012010
JournalJournal of Physics: Conference Series
Volume708
Issue number1
DOIs
Publication statusPublished - 29 Apr 2016
Event2nd Multiflow Summer School on Turbulence - Madrid, Spain
Duration: 25 May 201526 Jun 2015

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roughness
hydraulics
Reynolds number
wall flow
turbulent flow
leaves
slip
grids
fluids
simulation

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

Macdonald, Michael ; Chung, Daniel ; Hutchins, Nicholas ; Chan, Leon Zen Hsien ; Ooi, Andrew ; García-Mayoral, Ricardo. / The minimal channel : A fast and direct method for characterising roughness. In: Journal of Physics: Conference Series. 2016 ; Vol. 708, No. 1.
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The minimal channel : A fast and direct method for characterising roughness. / Macdonald, Michael; Chung, Daniel; Hutchins, Nicholas; Chan, Leon Zen Hsien; Ooi, Andrew; García-Mayoral, Ricardo.

In: Journal of Physics: Conference Series, Vol. 708, No. 1, 012010, 29.04.2016.

Research output: Contribution to journalConference article

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