Reynolds and dispersive shear stress contributions above highly skewed roughness

Jelly, T. O. and Busse, A. (2018) Reynolds and dispersive shear stress contributions above highly skewed roughness. Journal of Fluid Mechanics, 852, pp. 710-724. (doi: 10.1017/jfm.2018.541)

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The roughness functions induced by irregular peak- and/or pit-dominated surfaces in a fully-developed turbulent channel flow are studied by direct numerical simulation. A surface generation algorithm is used to synthesise an irregular Gaussian heightmap with periodic boundaries. The Gaussian heightmap is decomposed into “pits-only" and “peaks-only" components which produces two additional surfaces with similar statistical properties, with the exception of skewness, which is equal and opposite (S=±1.6). While the peaks-only surface yields a roughness function comparable to that of the Gaussian surface, the pits-only surface exhibits a far weaker roughness effect. Analysis of results is aided by deriving an equation for the roughness function which quantitatively identifies the mechanisms of momentum loss and/or gain. The statistical contributions of “form-induced" and stochastic fluid motions to the roughness function are examined in further detail using quadrant analyses. Above the Gaussian and peaks-only surfaces, the contributions of dispersive and Reynolds shear stresses show a compensating effect, whereas, above the pits-only surface, an additive effect is observed. Overall, the results emphasise the sensitivity of the near-wall ow with respect to higher-order topographical parameters, which can, in turn, induce significant differences in the roughness function above a peak- and/or pit-dominated surface.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Busse, Dr Angela and Jelly, Mr Thomas
Authors: Jelly, T. O., and Busse, A.
College/School:College of Science and Engineering > School of Engineering
College of Science and Engineering > School of Engineering > Autonomous Systems and Connectivity
Journal Name:Journal of Fluid Mechanics
Publisher:Cambridge University Press
ISSN (Online):1469-7645
Published Online:14 August 2018
Copyright Holders:Copyright © 2018 Cambridge University Press
First Published:First published in Journal of Fluid Mechanics 852: 710-724
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
712071Fluid dynamic properties of irregular, multi-scale rough surfacesAngela BusseEngineering and Physical Sciences Research Council (EPSRC)EP/P004687/1ENG - AEROSPACE SCIENCES