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)

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, Professor 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

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
309558		Secondary currents in turbulent flows over rough walls	Angela Busse	Engineering and Physical Sciences Research Council (EPSRC)	EP/V002066/1	ENG - Autonomous Systems & Connectivity
173614		Surface-specific Moody diagram: A new paradigm to predict drag penalty of realistic rough surfaces with applications to maritime transport	Angela Busse	Engineering and Physical Sciences Research Council (EPSRC)	EP/P009875/1	ENG - Autonomous Systems & Connectivity