Computational modelling of bed morphodynamics in curved channels

Most natural rivers tend to meander and develop curved channels. The spiral flow in a bend has important effects on the bed morphology, not only by generating a cross-stream slope, but also by affecting the bedforms (e.g. oblique dunes). The generated bedforms, in their turn, specify the form drag and hence, the water stage. Here, we studied this phenomenon numerically by employing a detailed three-dimensional numerical model using large-eddy simulation. The flow model was combined with a sediment model. The sediments are considered as spherical particles, and they are calculated in a Lagrangian framework. The bed morphodynamics is the result of pick-up and deposition of those particles. We simulated the bed morphodynamics in a curved channel and compared the results with previously published experimental measurements. The model successfully generated the scouring area in the vicinity of the outer bank. Moreover, the sediment was deposited close to the inner bank. The model successfully replicated the bed features and it showed a good agreement with the experimental data.