Nils Rüther

Three-dimensional (3D) modeling of non-uniform sediment transport in a channel bend with unsteady flow

A fully three-dimensional non-hydrostatic model was applied to compute the water flow and morphodynamic processes in a laboratory flume. The experiments provided data for bed deformation and grain sorting processes in a 180? channel bend. The data were used to investigate the performance of different sediment transport approaches. The original van Rijn formula for uniform sediments was compared with two advanced nonuniform sediment formulas that considered the interaction between individual grain sizes by defining hiding-exposure approaches. The results showed that the default configuration of the model was able to predict bed deformations and grain sorting processes with satisfying magnitude and trend. However, the default approach considerably overestimated the bar evolution. The computed results improved significantly when applying any of the introduced hidingexposure approaches, representing better the physical mechanisms of the hiding-exposure effect. This study shows that the present numerical model is able to predict the morphodynamic bed changes in a flume of nonuniform sediments with good agreement if appropriate sediment formulations are used.

Reynolds-Averaged Navier-Stokes Modeling of Submerged Ogee Weirs

AbstractThe present study documents the successful application of a Reynolds-averaged Navier-Stokes model with conventional turbulence closure to calculate discharge coefficients for submerged flow...