Direct numerical simulations of turbulent channel flow over ratchet roughness

Busse, A. and Zhdanov, O. (2022) Direct numerical simulations of turbulent channel flow over ratchet roughness. Flow, Turbulence and Combustion, 109(4), pp. 1195-1213. (doi: 10.1007/s10494-022-00352-8)

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Abstract

The influence of the orientation of ratchet-type rough surfaces on their fluid dynamic roughness effect is investigated using direct numerical simulations of turbulent channel flow at Reτ= 395. The ratchet length-to-height ratio is varied from ℓ/ k= 2 to 16 for a fixed ratchet height of k/ δ= 0.1 where δ is the mean channel half-height. The results show that both roughness function and mean flow and turbulence statistics strongly depend on the ratchet orientation. Existing empirical formulae, which estimate the roughness function Δ U+ or the equivalent sand-grain roughness ks based on surface-slope related parameters such as the effective slope or the Sigal-Danberg parameter, fail to accurately predict the differences between ratchet surfaces with high windward slopes and ratchet surfaces with high leeward slopes.

Item Type:Articles
Additional Information:We gratefully acknowledge support by the Engineering and Physical Sciences Research Council under grant numbers EP/V002066/1 and EP/P009875/1, and access to the HPC facility Cirrus hosted by EPCC Edinburgh under the ‘Access to HPC’ scheme. A.B. gratefully acknowledges support via a Leverhulme Trust Research Fellowship.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Busse, Dr Angela and Zhdanov, Dr Oleksandr
Authors: Busse, A., and Zhdanov, O.
College/School:College of Science and Engineering > School of Engineering > Autonomous Systems and Connectivity
Journal Name:Flow, Turbulence and Combustion
Publisher:Springer
ISSN:1386-6184
ISSN (Online):1573-1987
Published Online:09 August 2022
Copyright Holders:Copyright © 2022 The Authors
First Published:First published in Flow, Turbulence and Combustion 109(4): 1195-1213
Publisher Policy:Reproduced under a Creative Commons License
Data DOI:10.5525/gla.researchdata.1318

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
309558Secondary currents in turbulent flows over rough wallsAngela BusseEngineering and Physical Sciences Research Council (EPSRC)EP/V002066/1ENG - Autonomous Systems & Connectivity
173614Surface-specific Moody diagram: A new paradigm to predict drag penalty of realistic rough surfaces with applications to maritime transportAngela BusseEngineering and Physical Sciences Research Council (EPSRC)EP/P009875/1ENG - Autonomous Systems & Connectivity