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Modelling cross-shore intensive sand transport and changes of bed grain size distribution versus field data [An article from: Coastal Engineering]
Description
This digital document is a journal article from Coastal Engineering, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.
Description:
The study is focused on the cross-shore transport of size-graded sediment under combined wave-current flow in the intensive flow regime. The mathematical method for the description of hydrodynamic processes and sediment transport is adapted from the approach of Kaczmarek and Ostrowski [Coast. Eng. 45 (2002) 1] for non-graded sediment. The theoretical model of vertical structure of sediment concentration, as well as vertical mixing and sorting, is presented. The model of transport of graded sediment accounts for two-directional cross-shore sand flux. The first component of this flux is directed onshore and results from wave asymmetry effects, while the second one is directed seawards and is caused by undertow. The vertical structure of this two-directional sediment flux and its variability along a cross-shore profile is a reason for segregation of grains in a horizontal direction. This horizontal sorting of sand is theoretically modelled using the present approach. A concept of the ''carpet'' of sorted sediments is implemented to reproduce the segregation of sediment in time and to assess the influence of grain size changes on short-term evolution of the cross-shore profile. The results of computations are compared with the large-scale laboratory data from the literature and with field measurements carried out by the authors. The agreement between the model results and the experimental data is found to be very good. Particularly, it has been theoretically shown that the observed in situ bimodal grain size distributions result from two-directional sediment fluxes on the cross-shore profile.
Description:
The study is focused on the cross-shore transport of size-graded sediment under combined wave-current flow in the intensive flow regime. The mathematical method for the description of hydrodynamic processes and sediment transport is adapted from the approach of Kaczmarek and Ostrowski [Coast. Eng. 45 (2002) 1] for non-graded sediment. The theoretical model of vertical structure of sediment concentration, as well as vertical mixing and sorting, is presented. The model of transport of graded sediment accounts for two-directional cross-shore sand flux. The first component of this flux is directed onshore and results from wave asymmetry effects, while the second one is directed seawards and is caused by undertow. The vertical structure of this two-directional sediment flux and its variability along a cross-shore profile is a reason for segregation of grains in a horizontal direction. This horizontal sorting of sand is theoretically modelled using the present approach. A concept of the ''carpet'' of sorted sediments is implemented to reproduce the segregation of sediment in time and to assess the influence of grain size changes on short-term evolution of the cross-shore profile. The results of computations are compared with the large-scale laboratory data from the literature and with field measurements carried out by the authors. The agreement between the model results and the experimental data is found to be very good. Particularly, it has been theoretically shown that the observed in situ bimodal grain size distributions result from two-directional sediment fluxes on the cross-shore profile.
