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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Abstract
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 |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| 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: | 0022-1120 |
| 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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