Modelling the flow and morphology in groyne fields

摘要

Experiments have been conducted in a mobile-bed flume for a straight river with groynes on one side to study the morphological interaction between the groyne fields and the main channel. The flume had a geometrical scale of 1:100 based on typical dimensions of the River Waal. The bed material has been scaled to have bed load as well as suspended sediment transport. In this paper a numerical simulation of an emerged case of the laboratory experiment is presented. The sediment exchange between the main channel and the groyne field are of special interest. The simulation has been carried out using the DELFT3D-FLOW system coupled with Horizontal Large Eddy Simulation (HLES). For the morphological computations, the Online-sediment module was used; it calculates the sediment concentration, the sediment transport, and the bed level changes simultaneously with the flow. The model was calibrated against data from the experiment. The results of the hydrodynamic computations show the typical turbulent structures in emerged groyne fields, which have also been observed in previous experiments and described by several authors. With a sensitivity analysis, the influence of some input parameters on the computed flow field was studied. From this analysis, the effect of some physical parameters was investigated. The results of the morphological computation showed a qualitative accordance with the measured bed levels. In conclusion, we can state that Delft3D computes the morphological pattern in the vicinity of groynes qualitatively well.