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Influence of vertical motion on initiation of sediment movement

Journal Article


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Abstract


  • This paper makes an attempt to answer why the observed critical Shields stress for incipient sediment

    motion deviates from the Shields curve. The measured dataset collected from literature

    show that the critical Shields stress widely deviates from the Shields diagram’s prediction. This

    paper has re-examined the possible mechanisms responsible for the validity of Shields’ diagram

    and found that, among many factors, the vertical velocity in the sediment layer plays a leading role

    for the invalidity of Shield’s prediction. A closer look of the positive/negative deviation reveals

    that they correspond to the up/downward vertical velocity, and the Shields diagram is valid only

    when flow is uniform. Therefore, this diagram needs to be modified to account for hydraulic environments

    when near bed vertical velocities are significant. A new theory for critical shear stress

    has been developed and a unified critical Shields stress for sediment transport has been established,

    which is valid to predict the critical shear stress of sediment in both uniform and nonuniform

    flows.

Publication Date


  • 2014

Citation


  • Alfadhli, I., Yang, S. & Sivakumar, M. (2014). Influence of vertical motion on initiation of sediment movement. Journal of Water Resource and Protection, 6 1666-1681.

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=4171&context=eispapers

Ro Metadata Url


  • http://ro.uow.edu.au/eispapers/3155

Number Of Pages


  • 15

Start Page


  • 1666

End Page


  • 1681

Volume


  • 6

Place Of Publication


  • United States

Abstract


  • This paper makes an attempt to answer why the observed critical Shields stress for incipient sediment

    motion deviates from the Shields curve. The measured dataset collected from literature

    show that the critical Shields stress widely deviates from the Shields diagram’s prediction. This

    paper has re-examined the possible mechanisms responsible for the validity of Shields’ diagram

    and found that, among many factors, the vertical velocity in the sediment layer plays a leading role

    for the invalidity of Shield’s prediction. A closer look of the positive/negative deviation reveals

    that they correspond to the up/downward vertical velocity, and the Shields diagram is valid only

    when flow is uniform. Therefore, this diagram needs to be modified to account for hydraulic environments

    when near bed vertical velocities are significant. A new theory for critical shear stress

    has been developed and a unified critical Shields stress for sediment transport has been established,

    which is valid to predict the critical shear stress of sediment in both uniform and nonuniform

    flows.

Publication Date


  • 2014

Citation


  • Alfadhli, I., Yang, S. & Sivakumar, M. (2014). Influence of vertical motion on initiation of sediment movement. Journal of Water Resource and Protection, 6 1666-1681.

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=4171&context=eispapers

Ro Metadata Url


  • http://ro.uow.edu.au/eispapers/3155

Number Of Pages


  • 15

Start Page


  • 1666

End Page


  • 1681

Volume


  • 6

Place Of Publication


  • United States