Skip to main content

Research Repository

Advanced Search

Hydrodynamic efficiency in sharks: the combined role of riblets and denticles

Lloyd, Charlie J.; Peakall, Jeffrey; Burns, Alan; Keevil, Gareth; Dorrell, Robert M.; Wignall, Paul; Fletcher, Thomas


Jeffrey Peakall

Alan Burns

Gareth Keevil

Paul Wignall

Thomas Fletcher


We investigate the influence of smooth and ribletted shark skin on a turbulent boundary layer flow. Through Laser Doppler Anemometry the role of riblets in combination with the shark skin denticle is established for the first time. Our results show that smooth denticles behave like a typical rough surface when exposed to an attached boundary layer. Drag is increased for the full range of tested dimensionless denticle widths, w+ ≈ 25-80, where w+ is the denticle width, w, scaled by the friction velocity, uτ, and the kinematic viscosity, ν. However, when riblets are added to the denticle crown we demonstrate there is a significant reduction in drag, relative to the smooth denticles. We obtain a modest maximum drag reduction of 2 % for the ribletted denticles when compared to the flat plate, but when compared to the smooth denticles the difference in drag is in excess of 20 % for w+ ≈ 80. This study enables a new conclusion that riblets have evolved as a mechanism to reduce or eliminate the skin friction increase due to the presence of scales (denticles). The combination of scales and riblets is hydrodynamically efficient in terms of skin-friction drag, while also acting to maintain flow attachment, and providing the other advantages associated with scales, e.g. anti-fouling, abrasion resistance, and defence against parasites.


Lloyd, C. J., Peakall, J., Burns, A., Keevil, G., Dorrell, R. M., Wignall, P., & Fletcher, T. (2021). Hydrodynamic efficiency in sharks: the combined role of riblets and denticles. Bioinspiration&biomimetics, 16(4), Article 046008.

Journal Article Type Article
Acceptance Date Mar 30, 2021
Online Publication Date Jun 4, 2021
Publication Date Jun 4, 2021
Deposit Date May 17, 2021
Publicly Available Date Oct 27, 2022
Journal Bioinspiration & biomimetics
Electronic ISSN 1748-3190
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 16
Issue 4
Article Number 046008
Keywords Biotechnology; Biophysics; Molecular Medicine; Engineering (miscellaneous); Biochemistry
Public URL


Published article (5.7 Mb)

Publisher Licence URL

Copyright Statement
© 2021 The Author(s). Published by IOP Publishing Ltd.<br /> Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

You might also like

Downloadable Citations