Quadruple decomposition of current-dominated pulsatile rough-wall turbulent pipe flow
Date
2018
Authors
Jelly, T.
Chin, R.
Illingworth, S.
Monty, J.
Marusic, I.
Ooi, A.
Editors
Lau, T.
Kelso, R.
Kelso, R.
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Conference paper
Citation
21st Australasian Fluid Mechanics Conference, 2018 / Lau, T., Kelso, R. (ed./s), pp.1-4
Statement of Responsibility
T. O. Jelly, R. C. Chin, S. J. Illingworth, J. P. Monty, L. Marusic and A. S. H. Ooi
Conference Name
Australasian Fluid Mechanics Conference (10 Dec 2018 - 13 Dec 2018 : Adelaide, Australia)
Abstract
The physics of pulsatile rough-wall turbulent pipe flow is investigated using data from direct numerical simulation (DNS). Three geometrically-scaled sinusoidal roughness topographies are considered — the amplitude and wavelength of each surface are systematically varied whilst holding their amplitude-towavelength ratio constant. Pulsation is achieved by imposing a time-harmonic axial pressure gradient. The resulting flow-field is triple phase-averaged (in two spatial directions and also in time) which permits a quadruple decomposition of the instantaneous field variables to be invoked. The four components of the quadruple decomposition are: (i) a global-averaged mean component; (ii) a steady roughness-induced fluctuation; (iii) an unsteady pulsation-induced fluctuation and (iv) the remaining turbulent fluctuation. We compare statistics of (i)-(iv) against their non-pulsatile counterpart using past results from related work [1, 2]. Whilst the pulsatile and non-pulsatile data collapse well in the outer region, clear differences are observed in the near-roughness region. In particular, profiles of the mean axial velocity, roughness-induced stress and turbulence-induced stress exhibit consistently lower magnitudes below the roughness crests under pulsatile conditions.
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