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The Effect of Biofilms on Turbulent Flow over Permeable Beds

Kazemifar, F.; Blois, G.; Aybar, M.; Calleja, P.P.; Nerenberg, R.; Sinha, S.; Hardy, R.J.; Best, J.; Sambrook Smith, G.H.; Christensen, K.T.

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F. Kazemifar

G. Blois

M. Aybar

P.P. Calleja

R. Nerenberg

S. Sinha

J. Best

G.H. Sambrook Smith

K.T. Christensen


Despite an increasingly large body of work advancing our understanding of flow interactions occurring at the interface of a turbulent flow overlying a permeable bed, little is known concerning how such flow may be affected by the presence of biofilms, which exist in nearly all aquatic environments. This paper quantifies the effects on flow exerted by biofilms grown over experimental laboratory permeable beds until biofilm detachment, and then compares this to the residual effects after its detachment. The investigation is conducted in a flow channel by immersing two‐dimensional permeable beds with idealized geometry and different porosities in order to explore different bed permeabilities. Sequences of increasingly higher flow velocity conditions followed by lower flow, were considered to explore the effect of detachment. Measurements were performed using particle image velocimetry. The total wall shear stress and friction velocity were found to increase in the presence of pre‐grown biofilm, and decrease after biofilm detachment, when compared at the same pump frequency. The dimensionless Reynolds stresses, at constant pump frequency, collapsed for different bed configurations in the outer layer, while for the inner layer, the presence of biofilm led to a decrease in dimensionless Reynolds stress. Quadrant analysis shows that this decrease was primarily due to a reduction in strong Q2 contributions. These results suggest that models for flow and transport over permeable media in aquatic environments cannot neglect the role of biofilms in modifying turbulence.


Kazemifar, F., Blois, G., Aybar, M., Calleja, P., Nerenberg, R., Sinha, S., …Christensen, K. (2021). The Effect of Biofilms on Turbulent Flow over Permeable Beds. Water Resources Research, 57(2), Article e2019WR026032.

Journal Article Type Article
Acceptance Date Dec 8, 2020
Online Publication Date Dec 14, 2020
Publication Date 2021-02
Deposit Date Jan 19, 2021
Publicly Available Date Dec 14, 2021
Journal Water Resources Research
Print ISSN 0043-1397
Electronic ISSN 1944-7973
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 57
Issue 2
Article Number e2019WR026032


Accepted Journal Article (8.9 Mb)

Copyright Statement
This is the peer reviewed version of the following article: Kazemifar, F., Blois, G., Aybar, M., Calleja, P. P., Nerenberg, R., Sinha, S., et al. (2020). The Effect of Biofilms on Turbulent Flow over Permeable Beds. Water Resources Research, 56, e2019WR026032., which has been published in final form at This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

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