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Article

Direct Measurements of Bed Shear Stress under Swash Flows on Steep Laboratory Slopes at Medium to Prototype Scales

1
Water Research Laboratory, School of Civil and Environmental Engineering, UNSW Sydney, Sydney, NSW 2052, Australia
2
Water, Environment and Infrastructure Resilience Research Unit, Department of Architecture and Civil Engineering, University of Bath, Bath BA2 7AY, UK
3
School of Civil Engineering, University of Queensland, St Lucia, QLD 4072, Australia
4
Center for Applied Coastal Research, University of Delaware, Newark, DE 19716, USA
*
Author to whom correspondence should be addressed.
J. Mar. Sci. Eng. 2019, 7(10), 358; https://doi.org/10.3390/jmse7100358
Received: 27 August 2019 / Revised: 2 October 2019 / Accepted: 4 October 2019 / Published: 9 October 2019
(This article belongs to the Special Issue Dynamics of the Coastal Zone)
Robust measurements of bed shear stress under wave runup flows are necessary to inform beachface sediment transport modelling. In this study, direct measurements of swash zone bed shear stress were obtained in medium and prototype-scale laboratory experiments on steep slopes. Peak shear stresses coincided with the arrival of uprush swash fronts and high-resolution measurement of swash surface profiles indicated a consistently seaward sloping swash surface with minimal evidence of a landward sloping swash front. The quadratic stress law was applied to back-calculate time-varying friction factors, which were observed to decrease with increasing Reynolds number on smooth slopes, consistent with theory for steady flows. Additionally, friction factors remained relatively constant throughout the swash cycle (except around flow reversal), with a variation of approximately ±20% from the mean value and with only small differences between uprush and backwash. Measured friction factors were observed to be larger than expected when plotted on the Moody or wave friction diagram for a given Reynolds number and relative roughness, consistent with previous field and laboratory studies at various scales. View Full-Text
Keywords: swash; runup; bed shear stress; friction coefficient; shear plate swash; runup; bed shear stress; friction coefficient; shear plate
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MDPI and ACS Style

Howe, D.; Blenkinsopp, C.E.; Turner, I.L.; Baldock, T.E.; Puleo, J.A. Direct Measurements of Bed Shear Stress under Swash Flows on Steep Laboratory Slopes at Medium to Prototype Scales. J. Mar. Sci. Eng. 2019, 7, 358. https://doi.org/10.3390/jmse7100358

AMA Style

Howe D, Blenkinsopp CE, Turner IL, Baldock TE, Puleo JA. Direct Measurements of Bed Shear Stress under Swash Flows on Steep Laboratory Slopes at Medium to Prototype Scales. Journal of Marine Science and Engineering. 2019; 7(10):358. https://doi.org/10.3390/jmse7100358

Chicago/Turabian Style

Howe, Daniel, Chris E. Blenkinsopp, Ian L. Turner, Tom E. Baldock, and Jack A. Puleo. 2019. "Direct Measurements of Bed Shear Stress under Swash Flows on Steep Laboratory Slopes at Medium to Prototype Scales" Journal of Marine Science and Engineering 7, no. 10: 358. https://doi.org/10.3390/jmse7100358

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