Author(s): Kazunori Noguchi; Iehisa Nezu; Tomohiro Nakajima
Linked Author(s): Iehisa Nezu
Keywords: No Keywords
Abstract: The dune shapes of the riverbed influence various significant impacts on the flows, such as the lifting-up phenomena of sediment particles, energy loss and friction law in rivers. In the developing stages of sand dunes from a flat bed, turbulence structure is dramatically changed when the reverse flow area occurs behind the dune crest, i.e., a separation bubble zone appears. Then the turbulence intensities are enhanced as compared with the data before the reverse-flow area occurs. This indicates that the generation of the reverse flow makes significant influences to sediment transport mechanism over sand dunes. Therefore, the sediment flux over the developing dunes and fully-developed dunes was measured experimentally and compared in this study. As the results, the turbulence structure is drastically changed between the case of still-developing dune and that of fully-developed case in boil area, because of the occurrence of the reverse flow area. In addition, it was found that the kolk-boil vortex has a great effect to the lift up of the sediment in the boil area.
Year: 2009