NUMERICAL SIMULATION OF BED DEGRADATION AND BED ARMOURING

摘要

In order to simulate successful bed degradation process in alluvial channels it isrnnecessary to take into account the non-uniformity of the grains and the evolution ofrnbed armouring. The critical point is how to predict the change of grain size distributionrnduring the degradation process and the final composition of the “armour” layer. In thisrnpaper a procedure to simulate the evolution of bed armouring and degradationrnprocess in a straight channel is proposed. The variation of the bed is evaluated inrnfunction of friction factor, that reflects not only the variation of the hydraulicsrncharacteristics of the flow, but also the variation of the grain size distribution curve ofrnsediments on the bed and, thus, of median sediment diameter during the process.rnThe variation of the dimensions of bed forms is also considered.