In the last few decades, both theoretical and experimental investigations have been devoted to understand the physics of the formation of large-scale migrating bed forms, called alternate bars. The effect of sediment heterogeneity over uniform size was experimented in the flume tests. Physical or mathematical models developed often for the prediction of morphology have neglected the influence of sediment heterogeneity. In the present research, 2-D numerical modelling with spatial variations of grain size has been carried out. The main objective is to establish the effect of sediment heterogeneity on the formation of alternate bars in laboratory flumes. Mainly two models have been developed for the formation of the bars. In one model, the grain size field is functional to the space co-ordinates. In the numerical computation, it is demonstrated that with this model, it is not possible to replicate what happens in nature and in flume tests. The effect of grain sorting could not be reproduced. In the other model, the grain size field is functional to the local velocity based on a simplified idea of grain sorting. With this model, the effect of grain sorting in bar formation was successfully computed. Due to sediment heterogeneity, the bar height dams out appreciably and the wave length tends to increase with respect to uniform grain size. The numerical computation in this model is in good agreement with theoretical analysis and with flume test results. To provide input to the above models, a pre-processing tool is developed. The tool generates the variations of spatial grain size as input to the above models. The research aimed to make application of the above models in real life. The river Meuse at Roosteren in the Netherlands was selected for the case study. The computation has been carried out on a curvilinear orthogonal grids. The application has been limited to the development of a hydrodynamic model due to time constraint. However, it is recommended to apply the flow module for graded sediment transports.
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