Author(s): Supapap Patsinghasanee; Ichiro Kimura; Yasuyuki Shimizu; Kazuyoshi Hasegawa
Linked Author(s): Ichiro Kimura, Yasuyuki Shimizu
Keywords: Bank erosion; Two-dimensional depth-averaged model; Homogeneous condition; Heterogeneous condition
Abstract: Many river engineering problems were caused by bed deformation and bank erosion in all alluvial channels. Therefore, the effective prediction of bed deformation and bank erosion is an urgent issue to understand the complicated alluvial channel mechanisms. This paper focuses on computational modelling of bed deformation and bank erosion under unsteady flow by using a two-dimensional shallow-water model on a curvilinear boundary-fitted coordinate system, an equilibrium sediment transport model, and a simplified bank failure model for homogeneous and heterogeneous conditions. The computational conditions are similar with those used in the existing experimental flume conditions in the both grain size conditions. The computational models under homogeneous and heterogeneous conditions can reproduce the experimental results by using an appropriate angle of repose of 35o and a suitable transversal grid size of 1 cm. The temporal changes in cross-sectional profile averaged over longitudinal direction, resulted from the homogeneous condition, are in a relatively good agreement with the experimental data and can be seen that one point divides the region into deposition and scour zone, which is relatively common behavior for channel in a homogeneous condition. However, dunes observed in the exiting homogeneous experiment data are not reproduced and alternate bars are not well generated in computational results, respectively. In heterogeneous condition, the comparison results between the computational results and the experimental data are satisfactory. However, the agreement of the bed deformation are not satisfactory. The difference in bed deformations caused an overprediction in the dimensionless shear stress exceeding the critical values over the whole range of bed channel and the static armoring layer is fully developed to protect bank erosion on the top of bank toe, with an average grain size of 3-5 mm.