抄録
The simulation with 2-D (Two-dimensional) model and 3-D (Three-dimensional) model is a popular method to study open channel flows because it is very effective from the aspects of economy and efficienty. However, the applications of 2-D models sometimes cause serious discrepancies between the computational results and real phenomena. Recently, Nanson (2010) measured the velocity profile in a natural meandering river and discovered that, a secondary flow can be weak even though in a sharply curved and deep channel. The study related to weak secondary flow is unfamiliar in this field and the applicability of simulation models on such flows is not known well. In this study, we thus deal with both 2-D and 3-D numerical models to clarify the flow structures related to the secondary flows at a sharply curved meandering channels. We considered two different types of sharp bends in rivers, one is relatively wide and extremely shallow bend, and the other is relatively narrow and deep bend. In those two bends, it has been reported that the secondary flow is relatively weak. We apply both models to the two bends and clarify the different mechanisms of flow structures as well as the applicability of each model.
