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Article

Experimental Analysis of Incipient Motion for Uniform and Graded Sediments

1
Department of Watershed Management Engineering, Ferdowsi University of Mashhad, Mashhad 9177948974, Iran
2
School of the Built Environment, Heriot-Watt University, Edinburgh EH14 4AS, UK
3
School of Geography, University of Lincoln, Lincoln LN6 7TS, UK
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Centre for Water Security and Environmental Sustainability, School of Engineering, The University of Newcastle, Callaghan, NSW 2308, Australia
5
School of Engineering, University of Guelph, Guelph, ON N1G 2W1, Canada
*
Authors to whom correspondence should be addressed.
Academic Editor: Michele La Rocca
Water 2021, 13(13), 1874; https://doi.org/10.3390/w13131874
Received: 30 May 2021 / Revised: 23 June 2021 / Accepted: 25 June 2021 / Published: 5 July 2021
So far, few studies have focused on the concept of critical flow velocity rather than bed shear stress for incipient sediment motion. Moreover, few studies have focused on sediment mixtures (graded sediment) and shape rather than uniform sediment for incipient motion condition. Different experiments were conducted at a hydraulic laboratory at the University of Guilan in 2015 to determine hydraulic parameters on the incipient motion condition. The aim of this study is to conduct a comparison between uniform and graded sediments, and a comparison between round and angular sediments. Experiments included rounded uniform bed sediments of 5.17, 10.35, 14 and 20.7 mm, angular uniform sediment of 10.35 mm, and graded sediment. Results demonstrated that angular sediment has a higher critical shear velocity than rounded sediment for incipient motion. Results also showed that for a given bed sediment, although critical shield stress and relative roughness increased with the bed slope, the particle Froude number (based on critical velocity) decreased. In terms of the sediment mixture, the critical shear stress (Vc*) was higher for the graded sediment than for the three finer uniform sediment sizes. The finer fractions of the mixture have a higher particle Froude number than their corresponding uniform sediment value, while the coarser fractions of the mixture showed a lower stability than their corresponding uniform sediment value. Results demonstrated that the reduction in the particle Froude number was more evident in lower relative roughness conditions. The current study provides a clearer insight into the interaction between initial sediment transport and flow characteristic, especially particle Froude number for incipient motion in natural rivers where stream beds have different gravel size distribution. View Full-Text
Keywords: incipient motion; graded sediment; uniform sediment; critical flow velocity; relative roughness incipient motion; graded sediment; uniform sediment; critical flow velocity; relative roughness
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MDPI and ACS Style

Khosravi, K.; Chegini, A.H.N.; Mao, L.; Rodriguez, J.F.; Saco, P.M.; Binns, A.D. Experimental Analysis of Incipient Motion for Uniform and Graded Sediments. Water 2021, 13, 1874. https://doi.org/10.3390/w13131874

AMA Style

Khosravi K, Chegini AHN, Mao L, Rodriguez JF, Saco PM, Binns AD. Experimental Analysis of Incipient Motion for Uniform and Graded Sediments. Water. 2021; 13(13):1874. https://doi.org/10.3390/w13131874

Chicago/Turabian Style

Khosravi, Khabat, Amir H.N. Chegini, Luca Mao, Jose F. Rodriguez, Patricia M. Saco, and Andrew D. Binns 2021. "Experimental Analysis of Incipient Motion for Uniform and Graded Sediments" Water 13, no. 13: 1874. https://doi.org/10.3390/w13131874

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